Paper Details
Click any entry in the programme grid to jump here.
Ferrochrome’s Future in South Africa: Decline, Disruption, or Renewal?
↑ to programmeS. Swanepoel (Samancor Chrome, 🇿🇦)PLENARY
Pyrometallurgy | Ferrochrome | Industry outlook
South Africa’s ferrochrome industry, once the crown jewel of global stainless steel supply, now faces an existential crisis. Rising energy costs, infrastructure fragility, and global market realignments have challenged an industry that was built on world-class ore, pioneering technology, and bold industrial vision. This address reflects on the historical forces that shaped South Africa’s ferrochrome sector, from the early days of state-backed smelting development and technology transfer, to the hard-won operational excellence that made local producers world leaders in energy efficiency and technology. Against this backdrop, the presentation explores the structural and policy challenges that threaten competitiveness today, and how the ferrochrome industry’s evolution provides lessons for a new era of resilience and reinvention. The presentation will examine whether ferrochrome has indeed “lost its shine” or whether a new phase of transformation can strike a new arc to reignite the glow that ferrochrome once had. It calls for pragmatic collaboration between industry, government, and research institutions to rebuild the foundations of competitiveness and ensure that ferrochrome remains central to South Africa’s pyrometallurgical future.
South Africa's local beneficiation outlook for 2026 and subsequent impacts
↑ to programmeN. Bester (FAPA, 🇿🇦)
Pyrometallurgy | Ferrochrome | Industry outlook
The future of coal in South Africa's power generation sector
↑ to programmeV. Bayoglu (Menar, 🇿🇦)INVITED
Pyrometallurgy | Other Commodities | Industry outlook
Over the past two decades, unreliable power supply and high electricity costs have gradually eroded South Africa’s industrial capacity, leading to the demise of its ferroalloy and steel sectors. An estimated 4,596 direct jobs and 16,900 indirect jobs in SA’s smelting industry have been impacted across 10 operations between 2014 and 2024, according to the Ferro Alloy Producers Association. The steel industry is also affected, with the closure of ArcelorMittal SA’s long-steel operations putting 3,500 jobs at risk. Meanwhile, the country also braces for a data centre boom, which is expected to further strain the national grid and increase the demand for steel amid steep declines in the domestic alloys sector. The discussion will look at these challenges and implications of recent energy policy decisions contained in the 2025 Integrated Resource Plan, which excludes the construction of new coal-fired power stations. Furthermore, it will explore potential opportunities that can be unlocked through the development of a viable energy scheme to revive key sectors and reindustrialise SA.
W.J.vdM. Steyn (UP, 🇿🇦)KEYNOTE
Pyrometallurgy | Commodity-agnostic | Industry outlook
Co-reduction of chromite using hydrogen and silicon carbide
↑ to programmeS. P. du Preez, D. Coertzen, D. G. Bessarabov (HySA Infrastructure…, 🇿🇦)
Pyrometallurgy | Ferrochrome | Green processing & environment
Ferrochrome (FeCr) is produced from chromite ore by means of carbothermic reduction. During this process (Reaction 1), significant quantities of carbon monoxide (CO) gas are released to the atmosphere. FeCr2O4 + 4C → Fe + 2Cr + 4CO(g), Reaction 1 As alternative to C, a combination of hydrogen (H2) gas and silicon carbide is considered as reductants, to be employed in a sequential manner. For instance, H2 is intended to reduce the iron (Fe) oxides at lower temperatures (Reaction 2), while SiC reduced chromium (Cr) oxides at relatively higher temperatures (Reaction 3). FeCr2O4 + H2(g) → Cr2O3 + Fe + H2O(g), Reaction 2 Cr2O3 + SiC → 2Cr + SiO2 + CO(g), Reaction 3 By doing so, 1 mol CO(g) is generated as appose to 4 mol. Theoretically, C emissions can be reduced by 75%. In this study, chromite pellets were prepared containing 16 wt% SiC. Pellets were firstly reduced at 1100 °C in H2, at 1300 °C in N2 (for SiC reduction), or sequentially. During H2 reduction, Fe metallization was ~95%. For SiC reduction, Fe and Cr metallization was ~49 and ~10%, respectively. Sequential reduction yielded Fe and Cr metallization of 68 and 66%, respectively. It was shown that pre-reduction using H2 reduced the majority of Fe-oxides, allowing SiC to reduce Cr2O3. It was found that Fe metallization was lower during sequential reduction than during H2-only reduction. This phenomenon was likely due to Fe reoxidation in the formed acidic slag phase. As SiC reacts with chromite, SiO2 is ejected to the slag phase, decreasing the basicity index of the slag. X-ray diffraction (XRD) analysis showed that during H2 reduction, metallic Fe and a sesquioxide phase formed. SiC reduction yielded Fe and Cr carbides, and a cordierite phase, i.e., slag. Moreover, metallic Fe formed during H2 reduction was converted to Fe carbide. Scanning electron microscopy (SEM) showed that during SiC reduction, metallic phases, encompassing Fe and Cr, were encapsulated within the slag phase. Various partially reacted chromite particles were also observed, showing an intermediate Fe-stripped phase, containing mainly Cr-, Mg-, and Al-oxides. SEM further showed that the pellets densified, resulting in adverse process gas diffusivity. From this study, it was proposed that FeCr smelters using closed submerged arc furnaces (SAFs) employ CO-rich off-gas as an energy source, instead of flaring it, to produce SiC from undersized quartz and anthracite on-site. By doing so, the chemical energy associated with the CO-rich off-gas can be stored as SiC, which can be utilized during chromite smelting.
Unlocking a competitive pyrometallurgy industry in South Africa
↑ to programmeE. Matinde (Mintek, 🇿🇦)INVITED
Pyrometallurgy | Commodity-agnostic | Industry outlook
How will technology advances affect the production of Ferroalloys in the future?
↑ to programmeE. Ringdalen (SINTEF, 🇳🇴)KEYNOTE
Pyrometallurgy | Ferrochrome | Industry outlook
Products from Ferroalloy industry are crucial for our daily life and their importance is increasing. The industry is facing several challenges that need to be solved. Technological advance is, as is the tradition in this industry, expected to be a main contributor to overcome these. Important challenges are to ensure sustainable production with net zero CO2 emission and low environmental footprint, economic feasibility with increasing energy scarcity and cost, and also to meet the expected changes in raw material quality and availability and political aims to be self sufficient with critical raw materials within own regions as for instance Europe. This is expected to trigger developments of completely new processes and technologies, new technologies for preprocessing and postprocessing and developments in furnace technologies as well as competence to improve existing production processes. Developments are often necessarily, alloy specific and related to the conditions for producing a specific alloy or related to high temperature processes at reducing conditions which is the case for most of metal production. At the same time there is a rapid technological development within other metal producers and other sectors that the ferroalloy industry can benefit from. Ferroalloy furnaces are to some extent like a “black box” with limited possibility to measure conditions inside. Expected advances within sensor technologies have thus a potential to improve existing processes and increase feasibility of new processes. A prerequisite to benefit from this, is that new data from the sensors are coupled to and used to increase process competence. This can be followed by better simulations of the process and use of AI tools. Changes in raw material qualities is an example of a challenges that is expected to generate to and benefit from technological advances. Raw material with lower content of valuable element must be upgraded before use giving raw materials with finer particle size. Technologies where furnaces or reactors can be fed with fines instead of lump materials and technologies for production of agglomerates will thus probably be developed within several branches. Use of composite agglomerates and adaption of furnace design and process operation is a natural part of this. Technological advances are expected both within raw materials, furnace technologies, sensor and others. Examples of different combinations of challenges and possible technological advances, and how they can contribute to developments in the ferroalloy industry will be presented and discussed.
Choosing to compete: South Africa's pyrometallurgy sector in a shifting world
↑ to programmeC. Hattingh (Centre for Risk Anal…, 🇿🇦)KEYNOTE
Pyrometallurgy | Commodity-agnostic | Industry outlook
South Africa's pyrometallurgy sector sits at an inflection point; endowed with an unrivalled mineral resource base yet constrained by energy costs, logistics bottlenecks, and a decade of industrial attrition. This presentation argues that the path forward is not primarily a function of policy relief or commodity cycles, but of deliberate choice: how industry, researchers, and government choose to engage with each other, with the economy, and with emerging opportunity. Drawing on sector data and observations from international engagements across the United States and beyond, it makes the case for measured optimism - noting that while Europe and China face a difficult decade of demographic and energy constraints, the global environment is, for the first time in years, shifting in South Africa's favour. The question before this industry is not whether it can compete, but whether it will choose to.
Digital Solutions for Competitive and Sustainable Pyrometallurgy - Towards Industry 5.0
↑ to programmeJ. H. Zietsman (Ex Mente Technologie…, 🇿🇦)KEYNOTE
Pyrometallurgy | Commodity-agnostic | Industry outlook
The pyrometallurgical industry is under pressure to boost efficiency, sustainability, and competitiveness in a rapidly changing global landscape. This presentation explores how advanced digital solutions address these challenges, using a chromite sintering simulator and DRI smelting furnace process models as key examples. We demonstrate a progression from training tools to operational support systems, soft sensors, and closed-loop control, driving operational excellence and environmental stewardship. Through case studies in chromite sintering and smelting, PGM smelting, and green ironmaking, we showcase practical impacts - enhanced process understanding, accelerated technology development, optimized performance, and reduced environmental footprints. These applications leverage digital frameworks for material descriptions, material behaviour analysis, and process modelling, supporting the technology lifecycle from conceptualization to sustainable and profitable operation. Looking ahead, we envision integrating these modelling infrastructures with model context protocol APIs, enabling seamless data access for humans, systems, and artificial intelligence tools like large language models. This fosters innovation, empowers engineers through training, and enhances knowledge capture and utilization, aligning with Industry 5.0’s human-centric, AI-enabled, technology-driven, and knowledge-rich future. By bridging current capabilities with forward-looking possibilities, this talk underscores how digital solutions build foundations for a competitive, sustainable pyrometallurgical industry, supporting the conference theme of long-term success.
Influence of oxidative sintering on the hydrogen reduction of industrially produced pellets
↑ to programmeD. Coertzen, D. G. Bessarabov, S. P. du Preez (HySA Infrastructure…, 🇿🇦)
Pyrometallurgy | Ferrochrome | Green processing & environment
Chromite is an important mineral that is used in the production of ferrochrome (FeCr). FeCr, in turn, is mainly consumed by the stainless-steel industry. The production of FeCr is a highly carbothermic and energy-intensive process. Carbon (C) is used as a reductant, which results in large amounts of C emissions. To lower the C emissions of this process, hydrogen is proposed as a pre-reductant (Reactions 1 for C and 2 for hydrogen). Using hydrogen, H2O(g) is produced as a by-product along with Cr2O3, which is then reduced during smelting to chromium (Cr) metal. The reduction of chromite using C and hydrogen is as follows: FeCr2O4 + 4C → Fe + 2Cr + 4CO(g), ΔH° = 1015.96 kJ Reaction 1 FeCr2O4 + H2(g) → Cr2O3 + Fe + H2O(g), ΔH° = 81.60 kJ Reaction 2 The majority of SA chromite requires agglomeration, of which the Outotec process is mainly used. It has been shown that oxidatively sintered pellets require ~200 kWh/ton FeCr less energy to be smelted when compared to raw ore. This is due to the liberation of Fe from the chromite spinel, yielding Fe3+ as a semi-segregated phase. This segregated phase, though occurring in a higher oxidation state, is more susceptible to reduction than its spinel-bound counterpart. This study investigated the use of hydrogen as a pre-reductant for oxidatively sintered chromite pellets obtained from industry. Pellets from four Sinter Plants (SP 1 – 4) were used, all employing the Outotec process. Pellets were reduced using hydrogen at 1100°C for up to 120 min, achieving Fe metallization of 48.1 – 69.2%, while Cr metallization remained limited. XRD indicated the presence of a sesquioxide phase in varying degrees for each of the SPs. The sesquioxide phase is present in a so-called Widmanstätten pattern, which was used to semi-quantitatively determine the presence and extent of oxidation. It was found that the various SPs have very dissimilar degrees of oxidation, suggesting that SPs employing similar technology yielded pellets with dissimilar degrees of oxidation. SEM indicated that SP 3 and 1 had the highest degree of oxidation, seen as the Widmanstätten pattern occurring throughout the pellets, correlating with higher metallization (69.3 and 63.7% respectively). The opposite was true for SP 4 pellets (Fe metallization of 48.1%), whereas the SP 2 pellets showed an intermediate degree of oxidation and metallization (61.4%). As the Outotec process is used to create mechanically strong pellets, pellet break strength testing showed that hydrogen reduction adversely affected pellet mechanical integrity. However, the obtained break strength was still sufficient for smelting. A preliminary cost analysis showed a reduced cost increase from 75.65 ZAR (smelting using anthracite) to 262.83 ZAR (pre-reduction with hydrogen followed by smelting with anthracite) to process 1 kmol (224 kg) of chromite. Such a decrease corresponds to an estimated reduction of 566,280 – 809 640 t CO2/annum and carbon tax savings of 67.9 – 97.2 million ZAR.
Opportunities for the Iron and Steel Industry in South Africa in a Changing World
↑ to programmeV. J. Karplus, P. C. Pistorius (Carnegie Mellon Univ…, 🇺🇸)INVITED
Pyrometallurgy | Commodity-agnostic | Industry outlook
While a number of technology pathways to support deep decarbonization of the iron and steel industry have been proposed, it is often unclear under what conditions regions and plants should adopt them. In our presentation, we will combine insights from an open-source tool, the decarbSTEEL (the Decarbonizing Steelmaking TechnoEconomic EvaLuation) Tool Version 5, and a machine-learning based model of the global iron and steel industry to consider opportunities for the industry in South Africa. Interpretation of our analysis will be informed by observations from a eight-day study tour of the iron and steel industry in South Africa and Namibia during May 10-18, 2026. Our remarks are intended as a starting point for further customizing analysis to help answer major questions the industry is currently facing.
N. J. Sweeten, S. Ritchie, M. Sidawi, K. Marais, K. Joubarani, W. Marshall, K. Chomyn (Hatch Africa Pty Ltd, 🇿🇦)
Pyrometallurgy | Commodity-agnostic | Equipment & design
The global metallurgical industry faces many challenges, providing ample opportunities for engineering innovation with exciting new projects, whether it involves extracting critical minerals, promoting circularity, shifting to green metals production or simply improving efficiency to increase profitability. Wasmund et al (2011) and others have demonstrated that well-executed piloting is essential for de-risking new technologies and ensuring successful project outcomes. A key outcome of piloting should be metallurgical understanding; however, it is also important that the pilot program is designed to provide information required to enable the scale up and design of practical and affordable equipment. This paper outlines the execution of a cutting-edge pyrometallurgical test campaign—from problem definition to the design of the furnace and monitoring systems, through to test execution and data analysis. The campaign employed advanced monitoring techniques, including real-time off-gas analysis and high-temperature bath video, to gain novel insights into process behaviour. The paper will also show how a computational model, developed in parallel with the test work and validated against experimental results, can be further used to support process and equipment scale-up.
Industrial Validation and Process Modeling of Biocarbon-Chromite Briquettes for Fossil CO2 Mitigation in FeCr Production
↑ to programmeE. Mousa, K. Manu, A. Tomy, J. Orre, A. Papadopoulos, L. Ånnhagen, G. Hauri, G. G. Aktan, N. Tiraani (¹ Swerim AB, Aronsto…, 🇸🇪)
Pyrometallurgy | Ferrochrome | Green processing & environment
Ferrochromium (FeCr) alloy production, a critical input for stainless and specialty steels, is characterized by a high fossil carbon footprint stemming from its reliance on coke in the Submerged Arc Furnace (SAF). This study investigates a direct and sustainable pathway to decarbonization through the industrial application and quantified performance of biocarbon-chromite ore briquettes. On a technical scale, briquettes were developed using vibro-press (up to 10% biocarbon) and roller-press (up to 20% biocarbon) techniques. To maximize resource efficiency and circularity between the specialty steel and FeCr sectors, mill scale was integrated into the briquettes as an iron carrier. The material development phase, focused on achieving adequate cold and hot mechanical strength, was systematically followed by successful pre-industrial trials. The resulting biocarbon-mill scale-chromite briquettes was then subjected to a full industrial campaign and charged into a commercial SAF at Vargön Alloys. The campaign, which was accompanied by online dust collection and gas measurement, confirmed the briquettes' structural integrity and demonstrated acceptable operational performance under the industrial conditions, validating their viability for partial replacement of fossil coke in the FeCr production. To provide quantitative evidence of the process shift, a detailed heat and mass balance analysis was executed using the HSC thermochemical software model. The combined industrial operational data and thermodynamic modeling results definitively confirm an improved overall process efficiency within the SAF. Crucially, the analysis precisely determined the significant mitigation of fossil CO2 emissions achieved by partial substituting coke with biocarbon, providing a direct, measurable environmental benefit for the ferroalloys sector. This research validates an innovative, industrially mature, and measurable pathway toward the decarbonization of the FeCr industry. This work is part of the FEMOST project, conducted in collaboration with Swerim, Vargön Alloys, Future Eco, Ovako, Uddeholms, and RISE, and financed by the Vinnova funding agency in Sweden.
A method of determining and optimising the capacity of individual equipment for improved utilisation of the asset.
↑ to programmeD. B. Grant (DC Connections, 🇿🇦)INVITED
Pyrometallurgy | Commodity-agnostic | Operations
Sustainable competitiveness in pyrometallurgical operations increasingly depends on maximising the effective capacity of existing assets rather than large-scale capital expansion. This paper examines how the true productive capacity of smelting and refining plants evolves from the initial design intent to the “as-built” and “as-aged” states, highlighting how capacity creep and operational pressures drive plants to operate beyond nameplate limits. A structured framework and utilisation modelling tool have been developed to quantify plant capacity at equipment and component levels. The approach combines operational data analysis with reliability and control-system assessments to distinguish real from perceived constraints. Case studies demonstrate how the method identifies bottlenecks, supports decision-making on maintenance intervals, control-loop upgrades, and equipment retrofits, and quantifies the effect of such interventions on overall plant utilisation. The paper further discusses practical strategies for aligning Key Performance Indicators (KPIs) with continuous improvement goals, ensuring that sustainability, safety, and availability targets are balanced with production objectives. The findings illustrate how a data-driven understanding of plant capacity can guide incremental improvements that collectively deliver significant performance gains without major capital investment. This contribution offers a pragmatic roadmap for engineers and managers to achieve higher utilisation and sustainability in modern pyrometallurgical plants.
Coupling Thermochemistry and Multiphysics Models for Simulation of Pyrometallurgical Processes
↑ to programmeA. E. J. Bogaers, W. A. Roos, M. Rajh, J. H. Zietsman (Ex Mente Technologie…, 🇿🇦)
Pyrometallurgy | Commodity-agnostic | Fundamentals
Incorporating thermochemical equilibrium calculations into process and multiphysics models can provide significant insights into industry-relevant processes that current modelling or measurements cannot. By including phase stability as well as composition- and temperature-dependent material properties, these models can more accurately describe phenomena observed in pyrometallurgy such as melting, smelting, solidification, chemical reactions, dissolution, and gas evolution. In this work, we present an integrated modelling framework developed for OpenFOAM that couples detailed thermochemical equilibrium calculations with multi-phase flow, heat transfer, and mass transport. To demonstrate the developed framework, two representative case studies are presented: (1) carbon dissolution into molten alloy, highlighting the interplay between interfacial kinetics, thermal gradients, and local thermochemical equilibrium; and (2) slag freeze lining formation, demonstrating the ability to capture phase transitions and evolving material properties at the slag–refractory interface. Beyond these examples, this approach will enable coupling thermochemical equilibrium calculations with process and multiphysics models which will provide new insights into process and furnace behaviour. It also establishes a foundation for developing digital twins and soft-sensor frameworks, linking fundamental thermodynamics with plant-scale data for improved process understanding and operational decision-making.
T. Ntloko, E. Matinde, X. Goso (Mintek, 🇿🇦)
Pyrometallurgy | Ferrochrome | Fundamentals
Alloys of ferrochrome (FeCr) are mainly used in the production of stainless steel. It imparts corrosion-resistant properties. The production of FeCr, however, results in significant amounts of waste slag, most of it discarded in landfilled or stockpiled in slag dumps. Slag dumps are generally costly to maintain and occupy otherwise valuable land. The slag is also an environmental hazard as it contains hexavalent chromium (Cr6+). This study determines the phase equilibria of multicomponent ferrochrome slag with a view to influence the formation of the usable and recoverable species, such as the spinel phases. Phases were identified by the classical quenching technique after different compositions of slag and gas in contact, were brought to equilibrium. Five slag systems with variable FeO-Cr2O3 and CaO-MgO ratios in a Pt crucible were studied in an atmosphere (pO2 = 0.21) at temperatures from 1180 to 1650°C. The compositions of the phases was measured by inductively coupled plasma optical emission spectroscopy (ICP-OES) and electron probe micro analysis (EPMA). The phases were predicted in FactSage 8.2. FactSage predicted that, for the slag systems with variable Feo-Cr2O3 ratios in the temperature range of 1200-1350°C, the phases at equilibrium would be a liquid slag, spine, orthopyroxene, olivine and cordierite. Tests confirmed the presence of liquid slag, spinel, orthopyroxene, olivine and cordierite. For the same slags in the temperature range 1600-1650°C, FactSage and empirical test showed liquid slag and spinel at equilibrium. For the slag system with variable CaO-MgO ratios at temperatures in the range 1110-1350°C, FactSage predicted liquid slag, spinel, anorthite, cordierite, mellilite, orthopyroxene and olivine. The empirical tests under the same conditions showed liquid slag, spinel, cordierite, anorthite, pyroxenes, cordierite and olivine. For the same slags at higher temperatures 1600-1650°C FactSage showed that liquid slag, spinel and cordierite would form, yet only liquid slag and spinel were observed in empirical tests. By large, empirical tests matched the predictions of FactSage. Both the simulation studies and empirical tests results showed that is possible to engineer the formation of species such as the spinel for possible recovery by mineral processing techniques and re-usable less hazardous slag.
KPI trees - a structured method to break down blind targets
↑ to programmeH. Kotze (Tronox, 🇿🇦)INVITED
Pyrometallurgy | Commodity-agnostic | Operations
Escalating costs and top-down targets can enforce commitment to blind targets: commitment without knowing how to. The key performance indicator (KPI) tree is not a new technique, but it does shine in highlighting opportunities and pitfalls when challenged with untangling the how-to of a blind target. In this paper ilmenite smelting is used to demonstrate how a well-constructed KPI tree can highlight drivers, their relative impacts on the desired outcome, and the improvement opportunities each hold. The KPI tree links inter-dependencies between drivers and outcomes and serves to challenge perceived limitations. It has a crucial role in aggregating the benefits from several projects: checking unrealistic benefit commitments in the planning phase, and measuring success in the implementation phase. It sets the basis for cost-benefit analyses, especially when venturing into new and perceived risky concepts and technologies. This paper demonstrates these concepts with three examples: how a KPI tree can be used to untangle a blind target, its use in enforcing realistic promises, and breaking through perceived limitations. The KPI tree will not necessarily provide the how-to answer of a blind target, but it does show which door(s) to knock on.
Beyond the Numbers: Material Properties Insights as the Hidden Foundation of Furnace Performance
↑ to programmeM. Zhu, S. Koning, H. Muire, W. Roos, J. H. Zietsman (Ex Mente Technologie…, 🇿🇦)
Pyrometallurgy | Commodity-agnostic | Fundamentals
South African pyrometallurgical industries are facing increasing challenges from escalating production costs and the urgent demand for industrial transformation. To remain competitive in the global market, it is therefore more important to tackle challenges like furnace lining lifetime, slag management, energy efficiency and overall sustainability. While these challenges are often addressed from design or operational perspectives, their root causes frequently lie deeper in the limited understanding and uncertain quantification of material properties. In fact, uncertainties in fundamental properties such as slag density, viscosity, thermal conductivity, and electrical conductivity propagate through every level of furnace design and operation, ultimately shaping plant performance, efficiency, and profitability. In reality, metallurgists often operate within a multidimensional compositional and property landscape, where each composition and property is intricately coupled with others. Modifying a single variable such as slag basicity inevitably alters other variables like viscosity, thermal conductivity, metal bath temperature, alloy composition, refractory corrosion rate, and energy losses simultaneously. This elaborate interdependence demands a systemic and quantitative understanding of material behaviour. This is also to say, to operate a furnace right the first time, we must design right the first time, and to design right, we must understand material properties right. Otherwise, engineers are forced to accommodate wide margins of uncertainty that cost both efficiency and capital. Unfortunately, most existing material property models are empirical and often extrapolated beyond their calibration range, lacking a consistent physical foundation. Consequently, estimations of material behaviour can vary widely, leading to inconsistent design inputs. In practice, even widely used models for slag thermal conductivity may differ by nearly an order of magnitude, leading to markedly different estimations of heat flux and furnace throughput. Such discrepancies illustrate how uncertainties in material property data can cascade into significant process-level variability. Ex Mente advances this challenge by deepening its understanding of material behaviour and integrating materials science with process and multiphysics modelling. Recent developments have focused on furthering the investigation of slag composition-structure-property-performance relationships and conducting comprehensive sensitivity analyses of key parameters. In addition, recently released digital tools such as auxi-mpp, an open-source Python library for slag–alloy–gas physical properties, are facilitating integrated and reproducible modelling workflows. Together, these efforts demonstrate how rigorous material property knowledge forms the unseen, unsung, yet underpinning foundation of sustainable furnace performance.
Technology evolution in the Southern African Ni-Cu-PGM smelting industry
↑ to programmeR. J. Hundermark, G. Marsden, R. Snodgrass, K. van der Merwe (Valterra Platinum, 🇿🇦)PLENARY
Pyrometallurgy | PGMs | Industry outlook
The Southern African Ni-Cu-PGM smelting industry has evolved significantly from 1937 to the current day. As the demand for PGMs has increased, the commensurate expansion in metals extraction from the various ore bodies prevalent in Southern Africa has required scale up of the smelting and converting furnaces. Consequently, smelting technology development has been closely linked to the need for greater metal output, but also to the changing chemistry and mineralogy of the concentrates from the various PGM-containing reef types. Early technologies relied on blast furnaces and Great Falls converters, but from the late 1960s, electric furnaces and Peirce Smith converters took their place. In the early 1990s, the introduction of water-cooled copper plate coolers into the slag zones of the primary smelting furnaces enabled greater power intensity and throughput, with further intensification from the early 2000s with the introduction of deep cooled copper coolers. Converting technology was also modernised to include a top submerged lance converter in one instance. Approaches to slag cleaning have evolved from recycling slag to the primary furnaces, to milling and flotation or electric furnace slag cleaning as the Cr2O3 content in slags has increased. The shift in the 1990s from concentrates derived from predominantly Merensky ores to those from UG2 ores had a significant impact on the process design considerations for the primary smelting furnaces, with UG2 concentrates having lower matte falls and higher Cr2O3 levels. Conversely, concentrates derived from Platreef and Great Dyke ores, with high matte falls and lower Cr2O3 levels have introduced other challenges. Furnace designs and operating philosophies have been incrementally improved to better handle these ranges of concentrate compositions, resulting slags and superheated mattes, the containment of which is non-trivial. The smelting of non-roasted concentrates in the primary furnaces gave rise to rapid corrosion of the copper coolers, and triggered development of corrosion mitigation strategies. Advances in environmental emission control of SO2 primarily has evolved from very limited capture, to the introduction of single contact sulfuric acid plants in the 1970s, to the adoption of double contact acid plants, tailgas and dual-alkali scrubbing in the early 2000s. Low SO2 strength offgas streams from primary smelting furnaces are abated in some cases with technologies such as the Sulfacid process introduced from the early 2000s and the Wet-gas Sulfuric Acid process from the early 2020s. With the technology advances, process intensification, increase in operating temperatures and throughputs, and use of water cooling, risks have increased and consequences of failures have become more severe. Water leaks into the molten material environment, primary furnace containment and slag granulation have been particularly challenging. Technologies, operating and maintenance philosophies have been developed for prevention and mitigation of failures, and the adoption of Process Safety Management approaches has yielded systematic benefits. With the outlook in demand for PGMs changing as a function of automotive requirements, it is clear that smelting technology will need to evolve for further enhancement of safety and environmental protection, reduced costs and greater efficiencies.
Safe and efficient PGM smelting operations in a high-chrome, low matte fall environment
↑ to programmeM. van der Merwe (Northam Platinum Lim…, 🇿🇦)INVITED
Pyrometallurgy | PGMs | Operations
Over a period of 5 years, Northam Platinum increased PGM production through its processing facility from approximately 460 000 ounces PGE 4E to one million-ounces PGE 4E per year. To operate at this throughput, operational discipline and meticulous control of furnace process conditions is of non-negotiable importance. The concentrates smelted by Northam tend to be high in chrome with a low matte-fall, creating unique smelting challenges. The presentation at the Pyrometallurgy International Conference will focus on the principles that Northam followed to maintain furnace stability and crucible lining integrity. To ensure sustainable furnace operations whilst in a challenging operating environment, the operational teams had to be committed, focused and had to be confident in what they were doing. This journey will also be presented to the conference.
Process Optimization of a PCB Smelting Process via improved Slag Design
↑ to programmeE. Bantjes, A. Filzwieser (Mettop GmbH, 🇦🇹)
Pyrometallurgy | Other Commodities | Operations
The pyrometallurgical processing of PCB based electronic waste represents a key route for recovering copper and precious metals from PCB scrap. In this work, a comprehensive optimization program was carried out on an existing PCB smelter by combining thermodynamic process simulation, targeted slag engineering and industrial scale validation. A technical evaluation indicated that the existing process reduces metal recovery and limited the potential for downstream refining technologies. Thermodynamic calculations were used to redesign the slag composition and to define improved operating windows for smelting. The thermodynamic calculations were applied on site at the smelter, where the revised slag operating regime was implemented and validated. These on-site trials demonstrated that an adjusted slag practice can significantly improve metal recovery and overall process stability. The new slag formulation exhibited a lower viscosity and a more favorable phase composition, which led to significantly improved slag–metal separation, reduced energy demand and more stable furnace performance. Following this optimization, the process chain will be expanded by installing the Mettop Mini Smelter technology to convert the produced black copper into raw copper. This step enabled the generation of a stable and consistent copper quality suitable for electrolytic refining. In addition, an electrolytic refinery and a precious metals plant are being implemented, allowing the onsite production of high purity gold, silver and platinum group metals.
G. Tranell (NTNU, 🇳🇴)INVITED
Pyrometallurgy | Other Commodities | Green processing & environment
Both production of metals and waste end-of-life management typically comes with environmental burdens such as slags, sludges/dust and fugitive emissions. An increased focus on resource efficiency and lowering the specific carbon footprint for common and critical metals, has led to new and innovative technologies for recovery and production of metals. In the current talk, the focus will be on experiences and results from both EU projects and Norwegian programs. Examples such silicon and manganese production from slags and drosses, extraction of manganese from off-gas wet scrubbing sludges, as well as recovery of Cu and Zn from municipal waste incineration ashes will be described.
Smelting of dead-roasted sulfide concentrate into a Ni/Cu-based alloy for PGM Recovery
↑ to programmeA. Nyembwe (University of Witwat…, 🇿🇦)
Pyrometallurgy | PGMs | Fundamentals
The increasing demand for platinum group metals (PGMs) highlights the need for more efficient and environmentally sustainable recovery methods. Conventional PGM recovery processes face challenges due to the high chromite and low base metal content in South Africa's UG2 ore, leading to operational inefficiencies. In addition to these technical challenges, there is a growing need to recycle PGMs to support sustainable practices and reduce the environmental footprint of PGM production. Alternative PGM smelting processes have the potential to overcome these issues and facilitate the processing of secondary sources, such as revert tailings and spent automotive catalysts. Previous research has focussed on producing PGM-enriched iron alloys through the ConRoast process, however, the high iron content in these alloys complicates the downstream PGM recovery in the existing Base Metal Refinery (BMR) processes. This study aims to address these challenges by conducting a thermodynamic analysis of alternative base metals, such as copper and nickel, that can be used to collect PGMs. This research will simulate interactions between PGMs and base metals using FactSage software to identify stable phases, optimal smelting temperatures, and metal-slag partitioning conditions. In addition, experiments will be conducted to validate the results from the thermodynamic study. Key objectives include assessing the solubility of PGMs in different base metals to determine the most effective collector metals to maximise PGM recovery. The resulting PGM-enriched base metals will then be integrated into the conventional BMR (Base Metals Refining) process to improve overall efficiency and sustainability.
Mechanical conveying and crushing of waste heat boiler dust
↑ to programmeE. Lehtilä, H. Talvensaari (Kopar Oy, 🇫🇮)
Pyrometallurgy | Commodity-agnostic | Equipment & design
This study addresses the optimisation of drag chain conveyors utilised in Waste Heat Boiler (WHB) systems, focusing on enhancing operational reliability under high-temperature conditions. The research combines material science, thermal analysis, and mechanical design principles to mitigate wear and failure risks in demanding metallurgical environments. The investigation examines the influence of Waste Heat Boiler (WHB) design parameters on thermal profiles and particulate flow dynamics within the drag chain conveyor, the connection between the WHB and conveyor system, and the optimisation of material selection for conveyor components under high-temperature and abrasive conditions. Computational Fluid Dynamics (CFD) simulations complement these findings by modelling heat distribution and airflow patterns within the WHB, enabling accurate prediction of thermal stresses on conveyor components. The findings highlight the importance of optimized grate structures to ensure uniform load distribution, integrating expansion allowances to counteract thermal elongation, and adopting advanced surface treatments to minimise abrasive wear. Furthermore, the study emphasises the importance of predictive maintenance supported by real-time monitoring of temperature and mechanical loads. The proposed optimisation framework demonstrates significant potential for extending equipment lifespan, reducing unplanned downtime, and improving overall energy efficiency in smelting operations. By aligning empirical data with simulation-driven insights, this research provides a comprehensive approach to conveyor design under extreme thermal conditions, contributing to sustainable and cost-effective plant performance. Keywords: copper, smelter, waste heat boiler, dust handling, conveying, crushing
K. E. Zitha (University of Johann…, 🇿🇦)
Pyrometallurgy | Other Commodities | Fundamentals
The recovery of zinc and germanium from copper slag has not been extensively studied. This research project investigated the recovery of these elements from copper slag using the reduction roasting method. Coke was employed as the reductant to extract germanium and zinc from copper slag obtained from the Gécamines copper smelter plant in Lubumbashi, Katanga Province, Democratic Republic of Congo (DRC). The experimental results showed that 6.4% recovery of germanium was achieved, whereas zinc recovery was limited to only 0.04%. In the slag, germanium was present as germanium dioxide (GeO₂) and zinc as zinc oxide (ZnO). Germanium dioxide, which has a boiling point of ~1200 °C, can be reduced in the presence of coke to germanium monoxide (GeO) at ~600 °C. GeO sublimates at 710 °C, enabling fuming and subsequent recovery of germanium during roasting. In contrast, although metallic zinc boils at 907 °C, zinc oxide has a significantly higher boiling point of 2360 °C, which explains the very low recovery of zinc under the roasting conditions (working temperature of 1200 °C). Furthermore, chemical analysis revealed that zinc was not significantly reduced from the raw slag (8% Zn) to the secondary slag, indicating that much of the zinc remained trapped. This retention is attributed to the complexation of zinc with other elements in the slag matrix, potentially forming stable alloys that resist reduction and volatilization under the applied conditions. The study was conducted on a laboratory scale and provides insight into the different behaviors of germanium and zinc during reduction roasting. The findings suggest that while germanium can be effectively recovered by volatilization as GeO, zinc recovery requires alternative approaches or higher temperature/chemical conditions to overcome its thermodynamic stability in oxide or alloyed form.
Optimising Specific Energy Consumption in a PGM Smelting Case Study
↑ to programmeM. Sitefane (Hatch, 🇿🇦)
Pyrometallurgy | PGMs | Operations
Specific Energy Consumption (SEC) is a key performance indicator for evaluating the operational efficiency of pyrometallurgical processes. In the context of rising energy costs, increasing concerns over energy supply reliability, and the anticipated financial impact of carbon taxation, energy efficiency has become a critical lever for enhancing smelter profitability and ensuring long-term sustainability. A structured framework for SEC optimisation, using Zimplats’ Furnace 2 as a case study following its commissioning and ramp-up, is presented in this paper. The study integrates theoretical modelling, plant data analysis, and sensitivity analysis across key operational parameters, including bath chemistry and related reaction energy required, recycle stream contributions, infiltration air volumes, temperatures of matte, slag, and off-gas, as well as crucible heat losses. SEC can vary significantly depending on the interplay of these factors. However, with a robust SEC optimisation framework aiming to support efficient energy use, the operational costs for a smelter can be significantly reduced. Furthermore, digital integration for SEC optimisation is identified as the next strategic step toward unlocking deeper, long-term cost competitiveness and operational resilience.
Smelter Off-Gas Systems: Evolving Practices, Design Strategies and Operational Enhancements from Recent Projects
↑ to programmeJ. Bezuidenhout, G. Mulder (Hatch, 🇿🇦)
Pyrometallurgy | Commodity-agnostic | Equipment & design
Off-gas handling systems represent a significant portion of a smelter’s infrastructure and capital investment. Such systems and their objectives have become increasingly complex due to evolving environmental regulations, sustainability targets, complex feeds and pressured economics. These factors demand continuous improvement in the design of new plants, modernization of existing off-gas handling systems and implementation of emissions abatement projects. This paper explores the current state of off-gas system design by drawing on recent project experience to highlight emerging best practices and evolving philosophies.
A. Kotze, E. Nagels, S. Arnout (Inspyro, 🇧🇪)
Pyrometallurgy | Other Commodities | Green processing & environment
The Dust2Value project demonstrates the feasibility of decarbonizing the state-of-the-art Waelz process for recovering zinc from steelmaking waste, specifically Electric Arc Furnace Dust (EAFD). The novel process utilizes hydrogen to reduce zinc oxide to zinc vapor. This is followed by in-situ reoxidation with water vapor, forming fine zinc oxide particles that exit with the off-gas stream. A valuable co-product is secondary-grade Direct Reduced Iron (DRI), which is reusable in EAF steelmaking. To support process development, various simulations were employed: - Thermodynamic modelling established the critical operational window for the kiln. A coupled kiln model (mass and energy balance) iteratively balanced the three-way interactions among temperature, reaction kinetics, and endothermic reduction heat. This yielded the estimated gas and solid temperature profiles, along with the progress of zinc and iron reduction over the kiln's length. Key outcomes include evaluating the effect of different feed compositions on efficiency and determining hydrogen need and efficiency. - Computational Fluid Dynamics (CFD) This provided detailed engineering insights, including a temperature map, heat losses, and heat transfer estimates for critical components like the kiln. CFD visualizations of the gas flow trajectory were essential for optimizing the gas heating system design. Simulations will remain crucial during future development and pilot plant operations through the deployment of a digital twin.
J. P. van Dyk, T. Porretta (ECSA, 🇿🇦)
Pyrometallurgy | PGMs | Equipment & design
Hatch provided full EPCM services to Zimplats for the US$ 400 million Smelter Expansion and SO2 Abatement Project at the Selous Metallurgical Complex, South-West of Harare, Zimbabwe. The smelter expansion scope included the installation of a new electric furnace, two new Peirce-Smith converters and primary and secondary off-gas systems to serve the new furnace and converters. Implementation of an acid plant to convert the SO2 gas that is generated during the PGM smelting and converting processes is integral to the SO2 abatement system to ensure that the client’s facility adheres to the governing environmental regulations. To minimize the capital and operational cost it is required that the acid plant receive high purity SO2 gas and run an autothermal process. The inlet temperature and maximum amount of dilution air that is drawn into the primary off gas system need to be controlled. The capture efficiency of the converter off gas system needs to be maximized and adhere to the emission limits. A combination of a close sealing water cooled converter primary hood, spray cooler and converter secondary hood was required. An integrated system approach to gas capture efficiency and mechanical design of the converter hoods was adapted. All aspects of the off gas capturing and heat transfer process were simulated using Computational Fluid Dynamics (CFD). Equipment profiles were developed to ensure that the capture efficiency, dilution air ratio and thermal characteristics were achieved. The CFD off gas models included the converter geometry where the off gas originates, converter and primary hood interface, secondary hood, primary hood gas flow channel, spray cooler inlet duct and spray cooler. Heat transfer from the gas to the water-cooled primary hood, inlet duct and spray cooler was incorporated in the CFD analysis to ensure that the required gas outlet temperature is achieved, minimum surface temperatures to prevent acid condensation and identify any hot spots or areas with irregular flow. The spray cooler profile and nozzle layout was optimized to ensure that the water spray evaporates fully before exiting the spray cooler or impinging on the spray cooler inside surface. The temperature profiles of the primary hood, spray cooler inlet duct and spray cooler were transferred to Finite Element Analysis (FEA) software as input to the structural design of the equipment. Previous failures guided the detailed analysis of specific areas of the primary hood panels. Material selection was based on the process requirements, thermal properties and strength characteristics. Capital budget limitations required the spray cooler design to adopt lower cost 3CR12 stainless steel which is not refractory lined or fully insulated. Fabrication process improvements included stud welding methods opposed to manual fillet welding of approximately 8000 studs and varying levels of non-destructive testing of critical and less critical areas. Construction planning was incorporated during the design, considering preassembly of the off-gas equipment as far as possible and ensuring that appropriate lifting points were included for the assembled sections. The building design was adapted to facilitate for future removal and replacement of the large pieces of equipment.
Cost-Effective Emission Control Strategies for a Changing Pyrometallurgical Landscape
↑ to programmeT. Post, L. de Witt (About Air Pollution, 🇿🇦)
Pyrometallurgy | Commodity-agnostic | Green processing & environment
For the pyrometallurgical industry, cost-effective emission control strategies are no longer optional but essential to manage rising regulatory and financial risks. The Department of Mineral Resources and Energy released the Draft Mineral Resources Development Bill (2025), which highlights stronger regulatory alignment between resource development and environmental management (DMRE, 2025). Although air emissions remain formally governed by the National Environmental Management: Air Quality Act (2004), the Bill underscores government’s growing focus on sustainability and compliance. This evolving framework places additional pressure on pyrometallurgical operations to demonstrate reliable emission control and environmental performance. At the same time, the industry faces increasing economic pressure from the carbon tax regime. The carbon tax has escalated rapidly, rising from R159/ton CO2 in 2023 to R190/ton CO2 in 2024, and further to R236/ton CO2 as of January 2025 (National Treasury , 2024). Under phase 2 of the regime, starting in 2026, the basic tax-free allowance will be cut from 60% to 30%, with additional annual reductions of 2.5%, sharply increasing effective tax liabilities for heavy emitters such as smelters and furnaces (National Treasury , 2024). Traditional emission abatement systems are costly to install, energy-intensive, and often inflexible under varying process conditions. According to Schubert & Gottschling (2011), electricity consumption remains one of the major cost drivers in the metallurgical industry, making energy efficiency a critical design consideration. Recent research has highlighted opportunities to leverage the energy content of off-gas streams to improve system efficiency. Drawing on the co-generation approach described by Schubert & Gottschling (2011), off-gas can be utilized as a supplementary fuel source for internal combustion engines, supplying power to abatement equipment or offsetting furnace energy demand. In parallel, the potential to generate carbon credits offers a pathway to extend the value of abatement infrastructure. While conventional systems are designed primarily to meet compliance limits, linking them to carbon markets could transform abatement from a pure cost center into a revenue-generating opportunity. Among emerging strategies, co-generation and carbon capture show particular promise. A key challenge lies in integrating these into pyrometallurgical operations, where off-gas characteristics must meet strict requirements. For co-generation, particulate concentrations must remain below 5 to protect turbines and downstream equipment . For carbon capture, the concentration of in the off-gas largely determines whether removal technologies can be deployed cost-effectively within the abatement train. Within carbon markets, three categories of credits exist: avoidance, reduction, and removal. Carbon removal credits are the most relevant in this context, as captured can be utilized in long-lived products. Verification requires continuous monitoring of emissions before and after the abatement system to ensure transparent quantification of reductions. Integrating co-generating and carbon capture into abatement systems enhances their economic feasibility and broadens their appeal to industry stakeholders. Such innovations could accelerate compliance with national emission standards while positioning the pyrometallurgical sector to align more closely with emerging international benchmarks. By reframing emission abatement systems as platforms for both compliance and value generation, this approach opens new pathways for the pyrometallurgical industry. Integrating co-generating and carbon capture has the potential to convert unavoidable emissions into measurable assets while ensuring cleaner, standards but also enables participation in carbon markets, strengthening the industry’s long-term sustainability and competitiveness.
Fluidized Bed Reactor Tests of Oxidized Senegalese Ilmenite with Varying Temperatures and Water Vapor Content Studying Kinetics and Morphology
↑ to programmeT. P. M. van Kaam, B. Taferner, M. Tangstad, J. Eisbacher-Lubensky (NTNU, 🇳🇴)
Pyrometallurgy | Other Commodities | Fundamentals
Ilmenite pre-reduction occurs today using carbon materials, emitting carbon dioxide. Moving closer to Norway’s 2025 carbon neutral goal forces changes of today’s processes. One way to drastically decrease emissions is switching carbon materials out with hydrogen gas during pre-reduction. Taking inspiration from Direct iron reduction (DRI), a fluidized bed reactor (FBR) can be used. A lab-scale FBR was used to conduct 15 reduction experiments in hydrogen/nitrogen, and hydrogen/water vapor/nitrogen atmosphere. A Senegalese ilmenite ore was oxidized in a muffle furnace, then reduced at temperatures varying from 625 to 1000 °C. Water vapor content was varied from 0-10 vol%. From the experiments it was found that pseudobrookite reduction to ilmenite occurs un-affected by water vapor in the system. For temperatures 625 and 700 °C a significant drop in reaction rate occurs. Ilmenite reduction to metallic iron and rutile was found to be very dependent on both water vapor content and temperature. The ilmenite reduction rate decreases with an increase in water vapor content and/or a decrease in temperature. Distance form equilibrium partial pressures correlated to the driving force for the reaction, Collision factor (k0) and activation energies (Ea) were calculated for both reduction steps. Reduction of pesudobrookite, the activation energy was 30.6 [kj/mol] with a k0 of 2.19 [1/s]. The low activation energy signifies a diffusion dependency. The second reduction step had a activation energy of 39.8 [kj/mol] and a k0 value of 0.796 [1/s]. A similar activation energy as the first step, but with a lower reaction rate. This approach was found to cover temperatures 775, 850, and 925 °C best. The lowest temperatures of 625 and 700 were seen as outliers with a different mechanism governing the reaction.
A case study of risk-based prioritisation of spare parts for a PGM smelter
↑ to programmeM. von Delft, A. Irvine, F. Hannemann, D. Naidoo, R. Hocking, B. Ferrer (Hatch Africa, 🇿🇦)
Pyrometallurgy | PGMs | Operations
This paper aims to discuss a method for optimising the purchase of spares, to allow for staggered spares purchasing, to ease cashflow pressures. This method is explored via a case study of a spares priorisiation exercise done for a PGM furnace, designed and built by Hatch in a previous project phase. By applying operational experience as the OEM, within a capital-constrained environment, we were able to help the client manage cashflow at an acceptable risk level, by not tying up budget by holding spares not immediately critical to their operation. Multi-component localised failure is more common in PGM furnaces; thus a “systems” approach to spares prioritisation is needed, and so component-by-component criticality evaluation methods are not suitable. Due to our understanding of the client’s budget and time constraints, we decided to focus on a simplified method to help support the client’s needs. Additionally, not enough data on failures on this site was available to complete a full FMECA. However, based on our unique position as the OEM, with previous experience with furnace failures and access to benchmarking data, it was possible to properly assess the criticality of spares. The focus was on developing an accessible and efficient method to reliably prioritise spares purchases, and stagger capital expenditure for the client. The approach was tailored to a PGM smelting furnace in Zimbabwe, however the versatility of the approach is evident. The primary limitation of the approach is its reliance on the involvement of PGM furnace subject-matter experts (SMEs), however, this approach could be used for other asset types if the relevant SMEs were engaged.
Competitive and Sustainable SO2 Abatement with the WSA Process in Pyrometallurgy industry
↑ to programmeC. Frandsen (Topsoe, 🇩🇰)
Pyrometallurgy | Commodity-agnostic | Green processing & environment
The metallurgically industry faces increasing pressure to reduce SO2 emissions. While treating strong SO2 gases is standard, handling lean and fluctuating SO2 off-gases is a future challenge. These gases, which can have both low SO2 concentrations and be highly fluctuating, present both operational challenges and opportunities. This presentation explores the sources of these gases from furnaces and smelters and specific obstacles that may arise when these are to be handled. The presentation focuses on efficient methods for dealing with sulfurous off-gases and examines innovative solutions like the Wet Gas Sulfuric Acid (WSA) process to enhance sulfur abatement, energy efficiency, and regulatory compliance. As regulatory authorities tighten emissions standards for the metallurgically industry—such as the stringent SO2 emission requirements implemented in South Africa recently — there is increasing pressure to improve SO2 capture across plant operations while maintaining both sulfur recovery and energy efficiency. The drive to reduce greenhouse gas emissions and increase circularity further emphasizes the need for innovative solutions to SO2 control. In the typical off-gas from the furnaces and smelters there is a wide range of off-gases containing varying amounts of SO2, with concentrations ranging from low level to several percentage points. High-concentration SO2 gases are routed to gas cleaning systems and sulfuric acid production units to minimize emissions and recover sulfur. However, Lower concentration SO2 gases are either released into the atmosphere or treated with scrubbers. Using a scrubber to handle large volumes of low-concentration SO2 is perhaps the simplest solution, given the lower number of equipment required. However, this leads to sulfur being captured in a by-product of lower value compared to commercial-grade sulfuric acid. Additionally, the chemicals used in this process add significant operating costs, as does the transportation of chemicals and by-products, further complicating the operation. The WSA process represents a viable solution, allowing plant operators to recover sulfur from leaner gas streams while maintaining high energy efficiency and reducing the need for additional chemicals or external energy input. This approach not only enhances plant performance but also supports the metallurgically industry’s long-term sustainability goals.
Demolition Techniques Applied to the Palabora Mining Company Smelter Converter Stack of 107 Meters Tall
↑ to programmeC. Coetzee, S. Ledwaba, P. Junius, R. T. Rathogwa, R. B. Khumalo, F. K. Mulenga, T. Habib (Palabora, 🇿🇦)
Pyrometallurgy | Other Commodities | Operations
In June 2025, Draco Group demolished a 107-metre converter stack at Palabora Mining Company after a survey confirmed severe instability. Commissioned in 1960, the stack underwent a single significant refurbishment in the late 1980s. This was the last major intervention before the stack was demolished. By the time the project began, the concrete shell and internal reinforcement of the stack had deteriorated to the point where its stability could no longer be guaranteed. Survey results by Knight Piésold, a company specialising in geotechnical engineering showed the stack leaned 6 with a corresponding 600 mm deflection from the centre lin. This exceeded the SANS 10160 serviceability limits by 22%. The location of the stack within an active smelter and close proximity to the Kruger National Park meant that the geotechnical risk of the infrastructure extended beyond industrial operations to environmental protection. Top-down dismantling and crane-assisted removal were assessed and rejected due to the degree of instability and restricted access to the stack. Instead, a controlled toppling strategy was developed, combining precision blasting with structural engineering measurements. More than 400 blast holes were drilled to form a failure plane. A hinge was formed using a diamond rope cut to guide the fall, and additional masonry and steel supports were installed to deal with voids left from earlier alterations to the stack base. Collapse modelling drew on more than 1,000 reflectorless survey data points, while thermal drone surveys provided additional information on structural stress. This was done to verify that the exclusion zone was clear of people and wildlife. As the surrounding infrastructure occupied nearly the entire perimeter, only a narrow 20-degree corridor could be used as the fall zone. Within this strip lay three active railway lines, which were taken up before demolition and rebuilt within two days after demolition to allow production to continue. A 300-metre exclusion boundary was set around the site and actively monitored. Environmental controls were an integral part of the demolition plan. They included continuous water spraying to suppress dust, careful containment and transportation of debris to a licensed disposal area, and the separation of reinforcing steel for recycling. The stack was brought down safely within the planned zone, landing with a deviation of less than 20 metres. No damage occurred to adjacent infrastructure, and no safety incidents were recorded. Smelter operations resumed within 48-hours, following the reinstatement of the rail lines. Draco Group’s achievement as a technical service company sets a new benchmark for specialist demolition across Africa. It showcases how engineering excellence, environmental care, and stakeholder collaboration can align to solve complex problems safely, responsibly, and memorably. At its core, the project was about more than toppling a stack; it was about protecting lives, safeguarding critical infrastructure, and leaving a legacy of world-class execution in extremely challenging environments. The approach provides a clear framework for future high-risk demolitions where conventional dismantling methods are not applicable.
Developing Process Safety Management (PSM) Key Performance Indicators (KPIs) for Smelting Operations
↑ to programmeM. Ndlovu, K. L. Heins, J. Maharaj, N. Dubazana (Valterra Platinum, 🇿🇦)
Pyrometallurgy | PGMs | Operations
The introduction of Process Safety Management across the mining value chain is relatively novel and offers an opportunity to manage high consequence, low frequency events associated with the release of energy from fires, explosions and hazardous materials. Safety data has typically emphasized lagging occupational safety indicators such as lost time injury frequency rates (LTIFR) and total recordable case frequency (TRCF). While these metrics are important, they fail to adequately elevate process safety risk around catastrophic incidents. Specifically, the smelting industry, despite its high-temperature processes, hazardous materials, and complex operations, has fallen outside the scope of traditional process safety management. This paper presents an approach to developing Process Safety Management (PSM) key performance indicators (KPIs) with a focus on pyrometallurgical operations. The KPI’s are tailored to smelting operations, with the objective of advancing PSM dialogue to the benefit of safety in the sector. The methodology begins with a review of established process safety management systems and metrics applied in the oil and gas industries as guided by American Petroleum Industry Recommend Practice (API RP) 754 to identify possible extrapolation into pyrometallurgical operations. This is compared with more established mining risk management processes such as Operational Risk Management (ORM) to focus on Process Safety Unwanted Events around molten metal processes to identify both existing and new process safety leading indicators. These established pyrometallurgical risks include challenges such as molten material containment, refractory degradation, fuel system failures and corrosive or flammable gas handling systems. The paper concludes by proposing a KPI dashboard to represent leading and lagging indicators for generic benchmarking of Process Safety performance to support vigilance and continuous improvement. By doing so, pyrometallurgical operations can supplement a reactive stance centered on personal safety with a proactive culture that anticipates and prevents process safety failures, thereby safeguarding people, assets, business, and the environment.
Predicting flue gas conditions from bio-based Si production for carbon capture implementation
↑ to programmeM. K. Windfeldt, G. Tranell, V. Andersen (NTNU, 🇳🇴)
Pyrometallurgy | Ferroalloys + Silicon | Green processing & environment
Increased use of biogenic carbon materials and implementation of carbon capture are both recognised as necessary steps in the transition to zero emissions ferroalloy production. In the production of silicon and ferrosilicon metal, low flue gas CO2 concentration has been a barrier for the latter, as this has an adverse effect on both capital and operational costs. The primary strategy for increasing the concentration will be reducing the furnace air intake, but this is expected to have several secondary effects on both furnace operation and flue gas handling that must be identified and addressed. In particular, the temperature of the flue gas and concentration of key components such as SO2, PAHs, moisture and troublesome trace elements should be kept under control. As a first step, the composition and energy content of the flue gas after combustion at the charge surface will in this work be predicted using model-based mass- and energy balances. Proximate and ultimate analyses of various carbon materials from literature will form the basis, along with distribution coefficients between the metal/slag, particulate, and gas phases for each element of interest. For various carbon material mixes, ranging from mostly coal and coke to fully biogenic material, the impact of reducing the air intake will be studied. Key operational parameters such as silicon yield and carbon loss will also be included as inputs. Initial results indicate that a significantly reduced air intake is required for the CO2 concentration to reach above 5 vol%. Increased amounts of biocarbon makes it slightly more difficult as well, but has the positive side effect of significantly reducing the SO2 concentration, even at very low air amounts. The opposite is expected with regards to some unwanted trace elements, particularly alkalis and phosphorous. Flue gas temperatures increase predictably as the air intake is reduced but also show a dependence on the carbon mix, and specifically on the level of moisture and combustible volatiles it contains. The intent behind the model presented in this work is to highlight gaps in the knowledge on Si flue gas conditions with significance for carbon capture, in the context of increasing biocarbon use. This will inform future experimental work
Three-stage Approach in Rehabilitation Work of the Smelter Hyperbolic Cooling Tower at Palabora Mining Company
↑ to programmeR. Van Rensburg, P. J. Junius, R. R. Rathogwa, S. Ledwaba, S. W. Ngobeni, R. B. Khumalo, F. K. Mulenga (Palabora, 🇿🇦)
Pyrometallurgy | Other Commodities | Equipment & design
The smelter power plant at Palabora Mining Company (PMC) was commissioned in 1964. This plant incorporates a hyperbolic cooling tower that is essential for dissipating heat from the cooling water system. The cooling tower serves key equipment, including the turbine generator condenser and blowers. The structural integrity of the hyperbolic cooling tower is so critical to the continued operation of the smelter that, a series of engineering assessments have been carried out to address its progressive deterioration. A stability study done in 2009 formed the first rehabilitation approach that identified wind-induced stresses on the ageing shell as the main contributor to loss of structural integrity. As a result of this, stiffening rings were installed to enhance resistance against wind shear. The second rehabilitation approach happened in 2017, where further investigation revealed significant deterioration of the concrete support columns, and a reinforcement design incorporating steel beams was implemented. A comprehensive structural assessment in 2023 was the third rehabilitation approach which concluded that all compromised concrete columns required replacement with steel beams. Now in this last approach, rehabilitation measures included enlargement of plinths to accommodate steel base plate knuckles, reinforcement of the lower shell with 100 mm of additional concrete and steel mesh, thickening and protective coating of the outer wall, and repair and coating of all internal columns. Following these interventions, the cooling tower is now fully supported by steel columns, with all weakened concrete supports removed. The three-stage rehabilitation approach programme has restored structural stability and extended the operational lifespan of the cooling tower beyond the current life of mine. Scheduled routine maintenance of the cooling tower will continue while, the involvement of the external parties will be arranged at certain intervals as and when required.
L. R. Nelson (Independent Consulta…, 🇿🇦)PLENARY
Furnace Tapping | Furnace Tapping | Operations
Basic Operating Principles of Furnace Tapping Equipment
↑ to programmeE. J. Grant (Dango and Dienenthal…, 🇿🇦)
Furnace Tapping | Furnace Tapping | Equipment & design
The furnace taphole and the related tapping activities are a key component of the successful and safe operation of a smelting operation. By taking advantage of the advancements present in the modern tapping equipment, operator safety, taphole lifespan, tapping consistency, and furnace availability can all be optimized. In order to make the most of the equipment available to the operation it is key for all parties involved in the operation, maintenance, and adoption of the equipment to understand both the makeup of the equipment as well as the necessary steps and procedures involved with the operation of said equipment. By addressing the functionality and operation of the equipment in a "back to basics approach", this paper aims to assist all parties in the operation and optimization of their furnace tapping equipment, with a focus on taphole management and extension of taphole life.
Accelerating Green Ironmaking: Emerging R&D Methods, Progress, and Challenges
↑ to programmeY. Shen (University of New So…, 🇦🇺)INVITED
Pyrometallurgy | Steel | Green processing & environment
Process design and control play a crucial role in the development of green ironmaking technology. Most processes and reactors are very complex, remaining as black boxes for centuries, as they usually involve not only multiphase flows but also heat and mass transfers related to chemical reactions and their interactions – the so-called reacting flow. The operations must be redesigned and/or optimised in order to be competitive and sustainable, particularly for low-cost ironmaking decarbonisation. This will need continuous innovative research and development. Computer simulation and modelling, supported by data and experiments, have emerged as an indispensable adjunct to the traditional modes of investigations for the design and optimization of processes and reactors for green ironmaking, including blast furnace innovation using renewable injections (including biochar and hydrogen-rich gas) and sustainable burdens (including ferro-coke, bio-coke and bio-iron ore products), shaft furnace, electric smelting furnace, and fluidization ironmaking. In this presentation, Prof. Shen will report his core research on process modelling of reacting flows and its applications to a range of green ironmaking processes and reactors, followed by a review of challenges. Several examples of industry applications will be used for demonstration. The modelling works are indeed helpful to understand fundamentals and optimize & develop new, cleaner, and more efficient green ironmaking technologies with measurable industrial outcomes.
Reduction of vanadium titanomagnetite (VTM) using hydrogen gas
↑ to programmeL. Otto, S. P. du Preez, E. L. J. Kleynhans (Metix (Pty) Ltd, SMS…, 🇿🇦)
Pyrometallurgy | Other Commodities | Fundamentals
Vanadium titanomagnetite (VTM) is a valuable polymetallic iron ore containing appreciable amounts of iron, vanadium, and titanium, along with minor elements such as chromium, nickel, and cobalt. Global reserves of VTM exceed 40 billion tons, with significant deposits located in China, Russia, South Africa, the United States, Canada, Norway, Finland, India, and Sweden. These ores are of considerable industrial relevance, serving not only as a source of iron for steelmaking but also as a primary feedstock for vanadium and titanium extraction. Typically, VTM ores undergo beneficiation to produce concentrates enriched in vanadium and titanium, which are subsequently processed according to their specific elemental compositions. This study explores the hydrogen (H₂) gas-based reduction of as-received South African VTM ore, aiming to demonstrate a promising low-carbon process route for industrial application. The reduction pathway involves a series of thermochemical reactions: Hematite (Fe 3+ ) is first reduced to magnetite. 3Fe 2 O 3 + H 2 = 2Fe 3 O 4 + H 2 O, ∆H ° = 1.52 kJ Magnetite is then reduced to wüstite (Fe 2+ ). Fe 3 O 4 + H 2 = 3FeO + H 2 O, ∆H ° = 78.6 kJ Wüstite is reduced to metallic iron. FeO + H 2 = Fe + H 2 O, ∆H ° = 23.2 kJ Ilmenite (FeTiO 3 ) commonly occurs as a secondary phase in VTM ores and is reduced to metallic iron together with titanium oxides: FeO.TiO 2 + H 2 = TiO 2 + Fe + H 2 O, ∆H ° = 45.4 kJ Following iron oxide reduction, the hydrogen-treated VTM can be further beneficiated to recover titanium and vanadium oxides for downstream processing. In this investigation, VTM ore lumps were selected to evaluate the effectiveness of hydrogen penetration and reduction within dense ore structures. Particular attention was given to intra-lump gas diffusivity (for H₂ and H₂O) and the extent of decrepitation during reduction. Experiments were conducted at 900 °C, 1000 °C, and 1100 °C for durations of 5, 15, and 60 minutes using pure hydrogen gas. The reduction progression and phase transformations were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), and wet chemical analysis to determine metallization. Metallization degrees and associated mass losses were quantified to assess the efficiency of hydrogen reduction under varying thermal and temporal conditions. The findings provide valuable insights into the reduction kinetics of untreated VTM ore and establish a foundation for evaluating its suitability in hydrogen-based direct reduction technologies aimed at sustainable iron and steel production.
Development of a blister copper taphole for flash furnace operation
↑ to programmeG. F. Marx (Tenova Pyromet, 🇿🇦)
Furnace Tapping | Other Commodities | Equipment & design
Taphole operations are critical to the safe and efficient performance of flash furnaces. Their success depends on the integration and optimization of several factors, including taphole design, component fabrication, installation, process conditions, tapping practices, and maintenance strategies. This paper presents the development and implementation of a blister copper taphole design tailored for a direct-to-blister flash furnace. The design prioritizes operational safety, process compatibility, structural and thermal integrity, maintainability, and monitoring, while supporting increased throughput. The taphole was engineered to cope with high thermal and mechanical stresses while maintaining compatibility with existing furnace interfaces. Key design features include optimized geometry, enhanced cooling strategies, and robust material selection. Installation and maintenance procedures were refined through iterative feedback from operational data, resulting in improved campaign longevity and safety. Real-time monitoring and site-specific performance metrics were used to validate the design and guide procedural adjustments. Insights from several years of site operation have informed ongoing improvements. The paper concludes with key lessons learned and recommendations for future development, contributing to the broader understanding of taphole optimization in high-intensity copper smelting environments.
Advancing Sustainable Ironmaking: Design and TRL Development of a Containerized Hydrogen Plasma Smelting Reduction Furnace
↑ to programmeE. L. J. Kleynhans, T. K. Wickham, A. Laubscher, M. Ramagadza, S. Louw (Metix (Pty) Ltd, SMS…, 🇿🇦)
Pyrometallurgy | Steel | Green processing & environment
The global iron and steel industry faces mounting pressure to decarbonize, with hydrogen-based technologies emerging as a promising pathway toward low-carbon production. Among these, Hydrogen Plasma Smelting Reduction (HPSR) offers a direct and carbon-free alternative to traditional ironmaking routes by replacing carbon-based reductants with hydrogen plasma. This paper presents the design, modelling, and Technology Readiness Level (TRL) development of a containerized, 100 kVA bench-scale HPSR furnace, engineered to simulate industrial conditions and support continuous smelting operations. The unit is designed to process pre-reduced iron ore at feed rates of 18–20 kg/h, with batch tapping capabilities of 60–80 kg. A dynamic simulation model was developed to perform mass and energy balance calculations, incorporating time-dependent heat loss estimations based on furnace geometry and operating parameters. The model enables real-time assessment of furnace performance and informed key design decisions, including slag chemistry, feed strategies, and arc stability. The simulation results show strong correlation with experimental data and provide insights into specific energy requirements (SER), hydrogen utilization, and degree of reduction (DOR) under various operating scenarios. Key findings include the identification of off-gas recycling as a critical strategy for reducing SER and improving overall hydrogen efficiency. Sensitivity analyses revealed that feed distribution and ore pre-reduction are dominant variables influencing process efficiency. The furnace design accommodates multiple feed configurations—through the hollow electrode, peripheral arc zone, and sidewall slag bath—allowing for comparative studies on feed methodology and its impact on reduction kinetics. The unit also integrates advanced instrumentation and safety systems, including ATEX-compliant components, hydrogen concentration monitoring, and remote operation via PLC and HMI interfaces. The off-gas handling system includes a slip-gap and baghouse for dust removal, with provisions for synthetic syngas testing to evaluate alternative hydrogen sources. This containerized HPSR test unit represents a significant step in progressing the TRL of hydrogen-based ironmaking technologies from laboratory-scale (TRL 4) toward pilot-scale (TRL 5–6). By enabling controlled, repeatable, and scalable experimentation under near-industrial conditions, the unit provides a platform for validating process models, optimizing operating parameters, and informing future scale-up strategies. In alignment with the conference theme “Foundations of Competitiveness and Sustainability”, this work demonstrates how collaborative research, innovative furnace design, and dynamic modelling can accelerate the transition to sustainable pyrometallurgical practices. The insights gained will support the development of green steelmaking routes and contribute to the broader decarbonization goals of the metallurgical industry.
Upgrading of low-grade manganese ores by hydrogen-rich reduction for the ferroalloy industry
↑ to programmeD. A. Barrett, M. Tadie, B. von der Heyden, R. Cromarty (Stellenbosch Univers…, 🇿🇦)
Pyrometallurgy | Ferroalloys + Silicon | Green processing & environment
Manganese is a key global resource primarily used in the steel industry for ferroalloy production. South Africa has the world’s largest reserve of manganese, found in the Kalahari Manganese Field. Fines (D50 = 193 µm) from the Nchwaning mine, previously considered subeconomic, contain recoverable manganese but are penalised by elevated and complex iron content. To be used as high-quality ferroalloy feedstock, iron needs to be separated to achieve the target grade of 44 wt. % Mn and a Mn/Fe ratio of at least 7.5. The fines contain 44 wt. % Mn and have a Mn/Fe ratio of 2.6 (wt. %/wt. %). Therefore, the manganese content is acceptable, but the iron content poses the primary challenge. There is a high degree of mineralogical variability found in the fines. Iron is present both as discrete hematite and in solid solution within manganese minerals such as bixbyite, braunite, and braunite II. The mineralogical distribution influences process response during beneficiation. The solid solution of Fe in Mn minerals, in particular, complicates separation, as it has been shown to lead to the formation of mixed (Mn, Fe)O phases during conventional carbothermic roasting. This study employed reductive roasting between 650 C – 1 050 C in a hydrogen-rich atmosphere, followed by magnetic separation. Hydrogen has a low carbon footprint and is sufficiently reducing to produce metallic iron that can be separated magnetically. Lime and silica additives were investigated to determine their influence on Fe reduction kinetics and globule formation, which impacts the separability of Fe and Mn. A central composite design was employed in laboratory-scale experiments to optimise key response variables such as Mn grade, Mn/Fe ratio, and Mn recovery while minimising the number of experimental runs. Optical microscopy and SEM analysis of the reduced material revealed distinct metallurgical behaviour between iron liberated from hematite—forming larger globules (50-600 µm)—and iron reduced from Mn-hosted phases, which formed smaller globules (0.1-2 m). CaO and SiO2 additives were not found to have a significant influence on the reduction behaviour, however, both additives diluted the non-magnetic product stream, decreasing the Mn grade and Mn/Fe ratio. Mild reducing conditions resulted in the best separation between Mn and Fe as the conditions were strongly reducing enough to fully reduce free hematite into large metallic Fe globules that are easily separable, while not reducing the Fe in solid solution in Mn minerals enough to form small magnetic Fe globules. These globules are not fully liberated after crushing and result in the associated manganosite to report to the wrong stream. Mild reducing conditions achieved the highest Mn/Fe ratio of 4.52 and an Mn grade of 57 wt. %. While below the desired target specification, this can still be met by blending the product stream with other low-grade ores that lack Mn but also contain minimal Fe.
M. Tangstad (NTNU, 🇳🇴)KEYNOTE
Furnace Tapping | Ferroalloys + Silicon | Fundamentals
Slag in Mn-ferroalloy furnaces is an important part of the process, as the main part of the oxidic raw materials will produce a primary slag when reaching high temperatures. The liquid slag will be reduced, and metal will be formed. In the Si-ferroalloy process, the process is different. In this process the Si-raw materials are quite pure, and only percentages of trace elements will be present. In the molten SiO2, the trace elements will be enriched in mass as the SiO2 is reduced, and at a certain stage this will also be a slag containing mainly SiO2-CaO-Al2O3. The main aspect is the reduction reaction to metal, which for FeMn slags are determined by the solid MnO phase. For SiMn and Si-ferroalloy slags the slag is completely liquid. The reduction from Si-ferroalloy slags needs however more than 1800°C while SiMn can be produced around 1600 °C. The reduction rate is also very dependent on the carbon materials, and it is seen that for SiMn production charcoal gives a lower reaction rate due to less S content. The slag flow is also important for the operation. In the reduction zone the slag must be able to flow through the coke bed. In other parts of the furnace, the slag will be forming inactive zones, and examples of that are SiO2-CaO-Al2O3 slags at the walls and bottom of the Si-ferroalloys furnaces, and the MnO layer in Mn-ferroalloy furnaces. Both found during industrial excavations. Lastly oxidic materials can be accumulated in the furnace if not dissolved in the slag, like quartz particle both in SiMn and in Si-ferroalloy furnaces. Slag in Mn- and Si-ferroalloy operation has been studied in the Recursive project with the Norwegian ferroalloy industry, and this paper will discuss the work done in these topics.
Competitive production of green steel and ferroalloys with the ground-breaking SmeltDirect technology.
↑ to programmeP. H. F. Bouwer (African Rainbow Mine…, 🇿🇦)KEYNOTE
Pyrometallurgy | Steel | Green processing & environment
In response to Europe’s push to phase out CO₂-intensive blast furnace technologies, hydrogen has emerged as a proposed solution for decarbonizing the steel and ferroalloys industry. However, producers are increasingly recognizing that hydrogen-based reduction entails prohibitively high production costs and is ineffective for metallizing chromium (Cr) and manganese (Mn) oxides. As a result, hydrogen is unsuitable for producing ferrochrome, ferromanganese, and stainless steel. To address these limitations, African Rainbow Minerals has developed the ground-breaking SmeltDirect technology over more than a decade of research and refinement. This breakthrough enables the smelting of ores, previously restricted to solid-state pre-treatment, using combusted hot gases. The process achieves exceptional energy efficiency by utilising nearly all the chemical energy typically lost in conventional methods. SmeltDirect presents a cost-effective and sustainable alternative, leveraging biocarbon and recycled carbon as reductants. This positions it as a compelling solution for green steel and ferroalloys.
R. T. Jones (Pyro Consulting, 🇿🇦)KEYNOTE
Pyrometallurgy | Commodity-agnostic | Industry outlook
South Africa's large-scale mining industry began with diamonds in 1867, and gold in 1886. This required large amounts of electrical power. Plentiful and cheap electricity made it possible to establish smelters for iron and steel, and ferro-alloys in the early 1900s. This was later extended to the smelting of platinum group metals, as well as ilmenite. More recently, the lack of inexpensive electrical power has hugely constrained the South African smelting industry.
Innovative Solutions for Slag Tapping Control and Safety
↑ to programmeG. de Villiers, D. Bezuidenhout, H. Joubert (Tenova Pyromet, 🇿🇦)
Furnace Tapping | Furnace Tapping | Operations
Tenova's SlagFlo® device represents a significant advancement in the control and management of slag tapping operations within metallurgical processes. Designed to precisely regulate the slag flow rate, SlagFlo® enables optimal performance for downstream processes such as spinner-based mineral wool manufacture and slag granulation. The device is engineered to provide both controlled closure during regular taphole operations and rapid emergency closure in the event of tapping equipment failure, ensuring continuous safety and operational integrity. SlagFlo® features seamless integration with the slag taphole faceplate and incorporates a robust construction that delivers exceptional durability and long campaign life, even under demanding thermal conditions. The system can be operated via hydraulic or electromechanical drives, allowing adaptation to the specific requirements of each installation. With its application-optimised design philosophy, SlagFlo® offers metallurgical plants enhanced flexibility, reliability, and process control. This paper details the device—s technical characteristics, operational benefits, and the impact of its deployment across various slag handling scenarios.
Impact of EAF Slag Composition Variability on the Slag Valorisation Furnace Design
↑ to programmeR. K. Dantu, M. Kalenga, S. Louw, E. Kleynhans, I. Geldenhuys (Metix (Pty) Ltd, SMS…, 🇿🇦)
Pyrometallurgy | Steel | Fundamentals
Slags generated in the electric arc furnace (EAF) and ladle furnace (LF) contain significant quantities of unrecovered iron alongside oxide phases that, if suitably stabilised, can be reused in cement manufacture. The concept of a slag valorisation furnace is therefore twofold: to recover Fe-units that would otherwise be lost to waste, and to produce a secondary slag of consistent quality for the cement industry. The main obstacle to realising this potential lies in the large compositional variability of steelmaking slags, which strongly influences furnace performance and product suitability. EAF and LF slags typically contain CaO, SiO₂, Al₂O₃, FeO, and MgO as principal constituents. The relative proportions of these oxides vary with feedstock quality and operating practice, leading to marked differences in viscosity, liquidus temperature, and reduction potential. Minor components such as MnO and Cr₂O₃, though present at lower levels, further complicate behaviour. MnO alters slag basicity and affects sulphur partitioning, while Cr₂O₃ promotes the formation of spinel phases that increase viscosity and accelerate refractory wear. These factors directly impact both the efficiency of iron recovery and the chemical stability of the residual slag intended for clinker substitution. Thermodynamic modelling of representative slag compositions highlights the sensitivity of liquid fraction, melting temperature, and reduction equilibria to relatively small compositional shifts. High-FeO slags, for example, increase energy demand and refractory attack, while Cr₂O₃-rich slags restrict flowability and hinder tapping operations. At the same time, the Ca/Si ratio and residual Fe content must be carefully managed to produce a secondary slag compatible with cement chemistry. Failure to control these variables can result in material that is unsuitable for clinker blending or requires costly downstream adjustment. The study demonstrates that furnace design must be based not on an average slag composition, but on an operational envelope that accounts for the extremes encountered in practice. Flexible power input, refractory systems resistant to chemically aggressive slags, and operating measures such as staged reduction and controlled flux addition are essential to maintaining stable performance. By linking compositional variability to furnace design and operation, this work outlines an approach that ensures robust Fe-unit recovery while delivering a consistent secondary slag for cement applications
Large-scale dual-electrode dc arc furnace technology for the ferro-alloy industry
↑ to programmeR. Greyling (GLPS, 🇿🇦)INVITED
Pyrometallurgy | Ferroalloys + Silicon | Equipment & design
The dual-electrode direct current (DC) arc furnace has emerged as a transformative advancement in ferro-alloy production, offering a scalable and efficient alternative to conventional furnace designs. This technology surpasses established configurations—including single- and twin-electrode DC, three-electrode AC, and 6-in-line furnaces—by enabling power levels beyond 140 MW. A key innovation is the integration of external electromagnetic arc compensation, which effectively mitigates arc flaring toward furnace sidewalls, enhancing operational stability. Utilizing a conventional non-conductive hearth, the system retains proven design benefits while unlocking new performance capabilities. Building on theoretical and pilot-scale validation, the authors successfully converted two industrial-scale FeNi DC furnaces to the dual-electrode configuration. These units now operate reliably above 100 MW each, demonstrating the technology’s potential for widespread industrial adoption. This development marks a significant leap forward in furnace design, promising improved efficiency, reliability, and scalability for the ferro-alloy industry.
D. Rotthoff (Tapping Measuring Te…, 🇩🇪)
Furnace Tapping | Furnace Tapping | Operations
Tapfloor operations in blast furnaces, non-ferrous smelters, and ferroalloy smelters remain among the most hazardous areas of heavy industry. On the tapfloor, operators are exposed to molten metal, sparks, fumes, high thermal loads, and repetitive physical strain. Despite strict safety protocols and personal protective equipment, incidents still occur, highlighting the limits of conventional safety management. A new paradigm is required: —If there is nobody on the tapfloor, nobody can be injured." This paper outlines a structured pathway toward zero accidents through progressive automation of tapfloor operations. Three implementation levels have been defined. Level 1: Installation of Tapping Machines. The mechanization of tap-hole opening and closing removes direct human exposure from the most dangerous tasks while process repeatability and consistency improve. This milestone has already been successfully implemented at bigger smelters. Customers report both safety and process benefits. Level 2: Advanced Tapping Automation. Building upon the use of tapping machines, the next step involves video-assisted and fully automated tapping procedures. Operators supervise operations remotely from a control room with cameras and monitoring systems, eliminating the need for close proximity to molten metal. This reduces accident risks, lowers stress, and improves working conditions, making tapfloor work more attractive for skilled staff. Automation also minimizes variation in operator behaviour, leading to longer maintenance intervals of machines and a more predictable tapping process. Customer feedback confirms significant safety improvements and higher operator satisfaction. Level 3: Auxiliary Work Automation. Beyond tapping itself, auxiliary activities such as rod changing, clay loading also carry risks. In addition oxygen lancing cannot be avoided in all cases. To address this, compact automated devices have been developed which can be integrated into existing layouts. Automated lancing unit has been successfully tested and can be installed as add-on or standalone solutions. By shifting these operations from tapfloor to the control room, operators spend less time in hazardous environments. A further dimension is the use of digital twin training platforms, which allow personnel to practice procedures virtually, building competence without exposure to risk. Results and Experience. Field implementations in blast furnaces, non-ferrous smelters, and ferroalloy smelters demonstrate tangible results: accidents and near-misses are significantly reduced, process stability improves, and overall operational satisfaction rises. Benefits include consistency, efficiency, workforce well-being, and adaptability. Conclusion. The vision of zero accidents on the tapfloor is no longer utopian. Progressive automation—from tapping machines to automated auxiliary tools and digital twin training—shows that safety and productivity can reinforce each other. By systematically reducing operator exposure, smelters move toward safer workplaces while securing operational reliability and competitiveness. The pathway is clear: through automation, every operator is exposed to less risks to return home safely after every shift.
Kinetic modelling and simulation of hydrogen reduction of iron from low-grade tailings
↑ to programmeI. C. Kohitlhetse (Clean Technology and…, 🇿🇦)
Pyrometallurgy | Steel | Fundamentals
This work develops and validates a kinetic model for the hydrogen reduction of iron oxides contained in low-grade tailings, enabling simulation from thermogravimetric to reactor scales. Low-grade tailings (hematite–goethite with 35–45 wt% Fe and siliceous gangue were pelletized (Ø 6–10 mm) and reduced in flowing H2 (0.2–1.0 atm) at 600–900 °C. Time-resolved mass loss and off-gas H2/H2O were recorded by TGA–MS, while XRD, SEM-EDS quantified phase evolution and porosity. A porous-pellet grain model was formulated in additive-reaction-time form for sequential Fe2O3→Fe3O4→FeO→Fe steps, incorporating mixed bulk/Knudsen diffusion, evolving tortuosity, and sintering-induced pore closure. Heat effects were included through an energy balance with effective thermal conductivity. Global rate expressions first order in H2 with product-gas inhibition captured the data; apparent activation energies were 45±5, 65±5, and 80±8 kJ·mol⁻¹ for the three steps, respectively. At ≤700 °C, kinetics followed surface-controlled reaction mechanism; at ≥800 °C, sintering shifted control to concur with the intra-pellet diffusion during FeO→Fe, limiting metallization. The model matched independent TGA experiments within ±5% conversion and reproduced H2/H2O transients, confirming correct water-gas balance and oxygen removal. Packed-bed simulations (1-Dimension pseudo-homogeneous with effective properties from the pellet model) revealed strong heat and mass transfer coupling and steep reduction fronts. For 10-mm pellets at 0.6 atm H2 and superficial gas velocity 0.2 m·s⁻¹, >90% metallization was reached in 14–18 min at 800 °C; lowering PH2 to 0.3 atm or raising SiO2+Al2O3 above 50 wt% lengthened characteristic time by 30–50% via reduced reactive surface and higher tortuosity. Sensitivity analysis identified an operating window of 775–825 °C and hydrogen utilization up to 80% with inlet dew point slightly less than 20 °C to suppress reoxidation. Small CaO additions (1–3 wt%) increased porosity and improved final metallization by 5%. The study provides physically grounded parameters for scale-up of hydrogen-based retreatment of iron ore tailings, predicting pellet size limits, hydrogen demand, and reactor temperature profiles, and make a room for digitized optimization, process control and automation.
Devolatilization of charcoal and interaction of volatiles with manganese ore
↑ to programmeT. L. Schanche, A. A. Lindholm, F. Vollan, H. Gaertner, E. Ringdalen, V. Canaguier, M. Ksiazek (SINTEF, 🇳🇴)
Pyrometallurgy | Ferroalloys + Silicon | Fundamentals
Charcoal is considered as an alternative reductant in manganese ferroalloy production to replace metallurgical coke, thereby reducing fossil-based CO₂ emissions. However, charcoal differs from metallurgical coke in both chemical and physical properties. Its higher CO₂ reactivity may lead to increased carbon and energy losses via the Boudouard reaction. Additionally, its lower mechanical strength can result in excessive fines within the furnace, negatively affecting permeability. Charcoal also contains a higher proportion of volatile compounds compared to coke. Previous studies have shown that gases such as hydrogen, carbon monoxide, carbon dioxide, and methane are released from charcoal when temperatures reach 400–500 °C. Increased volatiles content may introduce challenges in the off-gas handling due to increased gas-flow. On the other hand, if these volatile species interact with manganese ores in the furnace, they may enhance the prereduction process, potentially lowering the specific carbon and energy consumption during production. In this study, the devolatilization behaviour of industrial charcoal and the effect of its volatile species on the prereduction of manganese ores were investigated.
Technical Application of Process Safety in Smelting: A Qualitative Roadmap from HAZID to Inherently Safer Design
↑ to programmeJ. Maharaj (Valterra Platinum, 🇿🇦)
Furnace Tapping | PGMs | Operations
This study applies Process Safety Management (PSM) principles to smelting operations that run high energy processes yet lack a structured, risk-based programme owing to limited process safety information and an over-reliance on legacy occupational health and safety systems. A qualitative toolkit, including smelter-specific HAZID to seed Bowtie analyses of barrier effectiveness, alongside Inherently Safer Design (ISD), was utilised. This toolkit drew on a flowsheet with a broad hazard envelope, historical incident data, and a focused review of smelter technology. The analysis revealed three concentrated risk clusters: steam explosions from molten material – water contact (the most frequent severe outcome), molten material runouts driven by refractory failure, and flammable furnace atmospheres arising from mismanaged firing and electrode breaks. Bowtie mapping indicated a heavy dependence, around 60%, on administrative barriers. Mechanical integrity failures of cooling elements, refractories, and off-gas components dominated initiating and escalation paths. Water, pervasive in cooling and quench systems, was the principal escalation vector. Risk is concentrated at transitional operations (tapping, molten material handling, feed changes, and start-up) within tightly coupled operating envelopes that narrow the window for stable control. Residual risk identified through HAZID informed the risk reduction themes. Priority was given to removing or minimising hazards where practicable (via inherently safer design); and where elimination was not feasible, preventive and mitigative measures were defined and strengthened.
Swelling and lump iron ore breakage in hydrogen gas reduction
↑ to programmeS. S. Mkhize, R. Cromarty (University of Pretor…, 🇿🇦)
Pyrometallurgy | Steel | Fundamentals
The transition to hydrogen based direct reduction of iron ore is one of the critical alternatives to decarbonizing the steelmaking industry. It has the potential to reduce carbon emissions significantly compared to the conventional blast furnace operations. However, the implementation of hydrogen direct reduction (HyDR) is challenged by lump iron ore decrepitation, the fragmentation and breakdown of ore during thermal treatment and reduction. Decrepitation poses sever operational risks including poor shaft furnace permeability, increase fines generation, flow blockages and compromised product quality. It is significantly important to understand the underlying mechanisms of decrepitation as the HyDR scales up to meet global decarbonization targets. This study employs an in-situ monitoring approach using a linear variable differential transducer (LVDT) displacement sensor coupled with a precision analytical balance system integrated within a controlled atmosphere induction furnace. The LVDT system, positioned to monitor the uniaxial displacement of the lump iron ore sample, provides continuous real-time measurements of the swelling behavior. Concurrently, the balance system tracks the mass changes associated with volatile and oxygen release, allowing for the calculation and correlation with physical degradation. LVDT and balance was directly in contact with the iron ore sample by fused silica rods at the top and bottom, respectively. A gas-based sealing component was designed and installed on the furnace to create a frictionless movement of the fused silica rod. The experimental setup enables simultaneous real-time measurements of the volumetric swelling and mass loss during reduction process under varying hydrogen concentrations and temperature profiles The observed trends in lump iron ore reduction at 800 °C, under varying hydrogen concentrations elucidate critical mechanisms for decrepitation, integrating swelling, mass loss and phase transformations. LVDT data reveal initial expansion (peaking at 4-6% normalized height), driven by volatile impurity decomposition and hematite to magnetite transitions. Sample contractions follow due to densification of iron from wüstite, promoted by higher hydrogen increasing the kinetics. Mass loss, reflecting oxygen removal, stabilizes post-reduction. Higher reduction degree is observed at higher hydrogen concentrations and incomplete reduction at lower hydrogen mixtures. The trends inform the decrepitation models, where reduction kinetics predict conversion, as validated by the mass loss as a proxy. Swelling and contraction behaviors parameterize pore volume changes, linking initial porosity to stress induced fragmentation. Dimensional changes quantify expansion or contraction thresholds for decrepitation risks. This model-based framework provides predictive assessment for mineralogical based decrepitation through optimized iron ore selection and operational parameters. This research addresses a critical knowledge gap in HyDR by providing a quantitative understanding of the decrepitation mechanisms and their dependence on process conditions. The in-situ monitoring method developed offers a robust experimental design for evaluating ore quality and optimizing process parameters. The findings will contribute to the development of predictive models for ore behavior in HyDR processes, supporting industrial implementation of low-carbon steelmaking technologies.
SmeltDirect: Ground-breaking smelting of ores, including lower grades and fines, with hot gasses generated from available chemical energy
↑ to programmeP. H. F. Bouwer (African Rainbow Mine…, 🇿🇦)
Pyrometallurgy | Ferroalloys + Silicon | Operations
Ore smelting at high temperatures like chrome ore have been deemed to require drawing an electric arc of a few thousand degrees as essential to smelt the ore. Pre-treatment of ores have been limited to the solid state as equipment like kilns cannot handle the burden as soon as melting phases are generated at high temperatures.
This step change enables the smelting of ores, previously restricted to solid-state pre-treatment, using hot gases. The process achieves exceptional energy efficiency by utilising nearly all the chemical energy typically lost in conventional methods. Low grade and fine ores, reductants and fluxes can be smelted cost efficiently. Molten product from the Packed Bed Reactor flows into a Slag Cleaning Furnace where metal recovery is improved, approaching thermodynamic limits, which is substantially higher than conventional processes.
SmeltDirect technology has been fully developed by African Rainbow Metal Technologies (ARMeT) over a period of 13 years and enables the production of chrome and manganese alloys at the bottom of the cost curve. SmeltDirect is also well placed to produce competitive green steel and alloys.
Is understanding drainage through a tap hole a trip down a rabbit hole?
↑ to programmeJ. E. Olsen (SINTEF, 🇳🇴)KEYNOTE
Furnace Tapping | Furnace Tapping | Fundamentals
M. Guo, S. Huang, A. Malfliet, P. T. Jones (KU Leuven, 🇧🇪)KEYNOTE
Pyrometallurgy | Steel | Fundamentals
Worldwide, approximately 400 million tons of steel slags—including Basic Oxygen Furnace (BOF), Electric Arc Furnace (EAF), and Secondary Refining (SR) slags—are produced each year. However, most of these slags are not yet recycled or reutilized due to inherent instability issues, such as volume expansion and heavy-metal leaching. The recycling and valorization of steel slags into value-added applications are therefore key to improving the sustainability of the steel industry. For over two decades, the HiTemp group at KU Leuven has been dedicated to the study of steel slag stabilization, with the ultimate goal of achieving “zero waste” in steel production. The group’s research activities span a wide range of slag chemistries and processes, including: (1) stabilization of the C₂S phase in stainless steel and ladle slags; (2) stabilization of free CaO and MgO in BOF slags; and (3) stabilization of chromium in ferro-alloy and stainless steel slags. In this lecture, the authors discuss the various aspects of slag instability, pinpoint the underlying physicochemical mechanisms responsible for volume instability and heavy-metal leaching, and provide a framework to distinguish between these phenomena. Possible solutions to address slag instability in its broadest sense are discussed and proposed through innovations in hot-stage slag engineering, including modifications of slag chemical composition, optimization of slag cooling, and control of gas–slag reactions (e.g., slag carbonation). These approaches contribute to enhancing the sustainability of the steel industry while significantly alleviating its environmental burden.
Foundations of Competitiveness and Sustainability in Mn Ferro-Alloy Production
↑ to programmeK. Sutherland (Transalloys, 🇿🇦)KEYNOTE
Pyrometallurgy | Ferroalloys + Silicon | Industry outlook
Thermal dependence of material properties in furnace tapping models
↑ to programmeQ. G. Reynolds, J. E. Olsen, O. F. Oxtoby, M. W. Erwee (Mintek, 🇿🇦)
Furnace Tapping | Furnace Tapping | Fundamentals
The pyrometallurgical production of ferroalloys such as chromium and manganese is a large industry worldwide. These materials are used in the manufacturing of specialised steels and many other products, and feature on the critical minerals lists of many countries. At present most ferroalloy production is performed using submerged-arc furnaces, a type of electric furnace with a cylindrical crucible and three vertically mounted self-baking graphite electrodes. Alternating current is passed between the electrodes to provide power by resistive heating of the solid charge and molten slag and alloy baths. The charge fed to the furnace builds up to form a porous bed of solid material — the burden — which is continuously consumed by melting and chemical reaction in the hot zones around the electrode tips. Slag and alloy produced by the reactions accumulate in the furnace as a molten bath and must be removed periodically by tapping the furnace. This involves opening a dedicated tap-hole channel in the furnace sidewall, removing a quantity of the molten material through it, and resealing the tap-hole to continue operations. Tapping is one of the most challenging furnace operations for man and machine, and any unexpected inconsistencies in the furnace tapping process can be detrimental to plant safety as well as causing supply disruptions to downstream processes. While the furnace tap-hole is open, several physical phenomena are of importance. These include multiphase fluid flow of the immiscible slag and alloy phases, flow through porous media in the burden, and heat transfer as the hot molten material moves through the furnace toward the tap-hole. In particular the dependence of material properties of the slag and alloy on temperature needs to be understood, as local variations in properties such as density and viscosity may significantly alter the pattern of flow in the vicinity of the tap-hole inside the furnace. In the present work, the authors make use of computational multiphysics models of the fluid flow and heat transfer during furnace tapping to assess the importance of accounting for the temperature dependence of slag and alloy properties, with the ferromanganese process selected as an example case study. Material properties are estimated using thermochemical simulation tools, and the coupled multiphysics models are validated against simple analytical and reduced-order calculations to verify the methods used. Results from multiphysics models using constant properties are compared to models including heat transfer and temperature-dependence effects, to identify similarities and differences.
Pilot and bench scale test work for comparative carburization of Hot Metal produced in a DRI smelting process
↑ to programmeT. Ndwandwe, E. Kleynhans, E. Rex (Metix (Pty) Ltd, SMS…, 🇿🇦)
Pyrometallurgy | Steel | Fundamentals
Metix and the SMS Group has developed a novel solution for a decarbonized steel production route, incorporating an Open Bath Furnace (OBF) for the reductive smelting of highly metallized, blast furnace grade Direct Reduced Iron (DRI). An OBF pilot test campaign was conducted for technology demonstration on a custom-built test furnace, successfully tapping hot metal (HM) and achieving carbon levels above 4 wt-%. This was achieved by charging reductant as part of the raw material feed mixture to the furnace in combination with a deep bath carbon injection system that pneumatically injected a high-quality carburization agent. Additional test work was conducted on bench scale to evaluate three commercial carburization agents to increase the carbon content of the HM from 2.6 wt-% to the required target specification. The carburization agents used were calcined Low Sulphur Pet Coke (LSPC),Gas Calcined Anthracite (GCA), and Raw Hard Coal (RHC). These carburizers were precisely dosed, based on a mass balance, to target a final metal carbon content of 4.5 wt-%. Tests were executed by combining 100 g of granulated metal with each carburizer in an alumina crucible within a 60 kW induction furnace at 1500 ˚C under an Argon atmosphere. Test durations ranged from 10 to 40 minutes. The LSPC demonstrated a significantly superior ability to carburize the metal and achieve the target specification. After 40 minutes, LSPC reached an average carbon content of 4.39 wt-%, nearly reaching the 4.5 wt-% target which was more effective than the GCA (3.60 wt-%) and RHC (3.13 wt-%), respectively. The LSPC's superior carburization rate was consistently confirmed across all tests. These findings validate the LSPC as the optimal, fast-acting carbon source for high-efficiency operation, providing essential process confidence for achieving required carbon content in the HM.
Combined hydrogen and aluminothermic reduction of Mn ores in HAlMan process; thermochemistry, products qualities, and sustainability
↑ to programmeJ. Safarian (NTNU, 🇳🇴)INVITED
Pyrometallurgy | Ferroalloys + Silicon | Green processing & environment
In the new HAlMan integrated process, hydrogen gas and aluminium scrap/dross are used to produce manganese ferroalloys with low energy consumption and carbon footprint. In this process, hydrogen gas is used to pre-reduce manganese ores which contains metallic iron and MnO. The MnO content of this intermediate is further reduced at elevated temperatures by aluminium in a smelting-aluminothermic reduction process, yielding high-Mn alloy and a calcium-aluminate slag. The metal product of the process is manganese, new Mn-Al alloy, ferromanganese, or silicomanganese, depending on the process adjustments. The thermochemistry of the HAlMan process is evaluated in comparison with the state-of-the-art carbothermic process in Submerged Arc Furnace (SAF). Experimental results of the HAlMan process are presented, and the effect of ore type and process conditions on the quality of the metal and slag products are discussed. It is shown that that the process is flexible to produce a variety of metallic products, and a consumable/valuable slag byproduct. Mass and energy balances calculations are presented, and it is shown that the energy consumption for the process is significantly lower than the SAF process. It is shown that ferromanganese production by this process prevents significantly CO2 emission in a more robust approach with less challenges than the current low-carbon ferromanganese production technology. The implementation of the HAlMan process in pilot scale through HAlMan EU project is presented, and it is shown how the process products can be used to make commercial metal products such as commercial grades of steels and aluminium alloys.
Novel PAH-Free Carbon-Based Taphole Material for Ferroalloy Furnaces: Performance, Repairability, and Workability
↑ to programmeP. Brito, T. Reis, L. Smemo, M. Bryntesen, I. Cameron, A. de Pretto (Elkem Carbon Solutio…, 🇳🇴)
Furnace Tapping | Furnace Tapping | Equipment & design
Taphole clays and repair pastes play a critical role in sealing and maintaining the integrity of the tapholes of ferroalloy furnaces. While conventional oxide-based clays are effective for basic taphole closure, the overall performance in taphole repair and refractoriness may be limited, especially during extended campaigns. This can lead to increased frequency of maintenance and a shorter operational lifespan of the taphole. To address these challenges, Elkem has developed ELTAP® G THL a carbon-based taphole material that is free from polycyclic aromatic hydrocarbons (PAHs). This paper seeks to evaluate lab-scale methods for measurement of tap hole pastes and clays properties such as extrudability through Marshall extrusion test and comparing that to results from parallel plate viscosimeter test, as currently there exists no standardized methods to quantitatively measure in-furnace performance of tap hole pastes and clays. These results from these lab tests are correlated with operational observations of taphole materials and how they perform in an industrial setting. A secondary goal of this work is to compare the rheological properties of the ELTAP® G-THL versus an industrial traditional material and highlight the stable viscosity and reliable flow of the paste, that makes it a durable, efficient, and safer alternative to traditional oxide-based clays for demanding ferroalloy furnace conditions.
Gasification of coke in a hydrogen-enriched blast furnace atmosphere
↑ to programmeR. B. Kgohlo, A. Garbers-Craig (University of Pretor…, 🇿🇦)
Pyrometallurgy | Steel | Fundamentals
The steelmaking industry is among the leading contributors to carbon dioxide (CO2) emissions, and as a result, faces substantial pressure to reduce its environmental impact. The majority of the world's steel is produced from virgin iron ore via the blast furnace (BF) – basic oxygen furnace (BOF) route, a practice that is expected to remain dominant through 2050. The BF utilises coke both as a fuel and as a reductant. Since the coke generates CO2, reducing CO2 emissions depends on lowering coke consumption. Although coke has been partially substituted with alternative fuels, complete replacement remains a challenge because coke is the only fuel capable of providing both burden support and permeability in the BF. Hydrogen (H2) has been proposed as an alternative reductant to coke, as it produces water (H2O) instead of CO2. Hydrogen injections in the range of 5 -15% have already been successfully implemented. The gasification reaction of coke results in significant coke degradation within the BF. This research employed thermogravimetric analysis (TGA) to examine the kinetics of gasification using both the volumetric model (VM) and the grain model (GM) under conditions of 100% CO2 and a mixture of 85% CO2–15% H2O at 1100 ºC. In addition, critical coke properties associated with gasification, including the coke reactivity index (%CRI) and the coke strength after reaction (%CSR), were evaluated. Alkali recirculation in the BF, primarily from potassium (K) and sodium (Na) vapours, poses a major challenge as it catalyzes the gasification reaction. Therefore, this research also investigated the impact of potassium on coke properties. As efforts to reduce coke consumption in the BF progresses, optimising coke properties becomes increasingly important. Consequently, this study also explored the use of boric acid (H3BO3) as a potential additive to enhance coke performance by lowering %CRI and improving %CSR. A comparative study was conducted on four types of coke: as-received coke, coke impregnated with H3BO3 (B-coke), coke impregnated with potasium (K-coke) and coke impregnated with both potassium and H3BO3 (KB-coke). It was found that the gasification rate in H2O surpasses that in CO2, except in K-coke, where potassium reacts with H2O, thereby decreasing the amount of H2O available to react with the coke surface. H3BO3 decreases the reaction rate under both conditions, whereas potassium enhances it. The VM provides a better fit to the data than the GM, indicating that gasification is limited by the chemical reactions occurring on the coke surface. As expected, %CRI and %CSR showed an inverse relationship: %CRI is higher in H2O except in K-coke, because K reacts with H2O; conversely, CSR is lower in H2O and higher in CO2, except for K-coke. H3BO3 improves the properties of coke, except in K-coke in H2O, where %CRI increases. Potassium acts as a catalyst for gasification, with %CRI in K-coke being higher than that of the as-received coke. Keywords: Coke, Gasification reaction, Volumetric model, Grain model, Coke Reactivity Index (CRI), Coke Strength after Reaction (CSR)
Hydrogen pre-reduction of different manganese ores in a vertical retort toward demonstration of the HAlMan process
↑ to programmeM. Mampuru, S. Tsebe, D. Mchabe, E. Matinde (Mintek, 🇿🇦)
Pyrometallurgy | Ferroalloys + Silicon | Green processing & environment
The HAlMan process is a zero-waste flowsheet for the production of manganese alloys using hydrogen gas and aluminium metal as carbon-free reductants. The process focuses on treating primary and secondary raw materials in a sustainable manner while pursuing decarbonisation of industrial metal production and recycling of by-products for secondary application. The hydrogen pre-reduction step of the process can be undertaken in vessels of different designs including vertical retorts, rotary furnaces, shaft furnaces, and fluidised bed reactors. The current study investigated hydrogen pre-reduction of 2 different manganese ores in a pilot scale vertical retort. The retort was externally electrically heated, and the hydrogen gas was introduced at the bottom of the retort through a distribution plenum to percolate through a packed bed of coarse particulates. The study evaluated the pre-reduction of Nchwaning and UMK ore, screened to a size class of +6 mm –20 mm, with 100% hydrogen gas under different reaction temperatures and residence times. The paper will present a detailed account of the characterisation of the manganese ores, experimental equipment and methods adopted, and discuss the experimental results obtained with respect to the extent of reduction achieved for each type of manganese ore.
Transition from Tar/Resin-Bonded to Synthetic Binder Taphole Clays
↑ to programmeJ. Krog, T. Makosa, G. Newall, M. Rösch, J. Vilakazi (Refraline, 🇿🇦)
Furnace Tapping | Furnace Tapping | Equipment & design
Reduction and carburisation of iron ore pellets using methanol and glycerol
↑ to programmeE. E. Kemp, R. Cromarty (University of Pretor…, 🇿🇦)
Pyrometallurgy | Steel | Green processing & environment
The steel industry is under increasing pressure to reduce carbon emissions while maintaining high production efficiency. This study investigates the reduction and carburisation iron ore pellets using thermally decomposed methanol and glycerol as alternative carbon sources. The objective is to evaluate whether these agents are efficient reducing and carburising agents for DRI production. Pelletised iron ore samples underwent reduction, and carburisation in a vertical retort shaft furnace at 950°C under controlled gas composition conditions. Methanol was decomposed inside the retort furnace, while glycerol was decomposed externally at 950°C and was then fed to the retort furnace. The gas entering the retort furnace is rich in CO and H2. Initial and final material characterisation was performed using X-ray Diffraction (XRD), Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM-EDS), optical light microscopy and LECO carbon combustion analysis. All samples were completely reduced during experiments; only limited carburisation took place. When compared to industrial DRI, methanol and glycerol have a too low carbon content. The carbon content needs to be above 1%. DRI produced using methanol had an average carbon content of 0.94%, where one test had a carbon content of 1.02% which is in the industrial standard range. DRI produced using glycerol had an average carbon content of 0.1%. This low carbon content is due to carbon soot forming during glycerol decomposition, which reduces the amount of carbon going into the reduction process.
Hydrogen reduction of iron- and manganese-oxides in ferroalloy ores
↑ to programmeM. S. Ernst (NTNU, 🇳🇴)
Pyrometallurgy | Ferroalloys + Silicon | Fundamentals
Manganese (Mn) ferroalloys are indispensable in steelmaking, yet their conventional production in submerged arc furnaces is highly carbon-intensive, with CO2 emissions arising from both smelting and pre-reduction. Replacing carbon monoxide with hydrogen (H2) as a reductant offers a pathway to decarbonization, producing water vapor as the sole by-product. While thermodynamic studies confirm the feasibility of Mn ore reduction with H2, challenges remain in understanding kinetic behaviour under industrially relevant conditions, particularly in the presence of water vapor and temperature gradients. This study investigates the non-isothermal reduction of Assmang Mn ore in H2/H2O atmospheres up to 1100 °C. Ore particles of three size fractions (2–4 mm, 6.3–8 mm, and 10–14 mm) were reduced in gas mixtures of 100%H2, 95%H2/5%H2O, 90%H2/10%H2O, and 80%H2/20%H2O. Mass loss was continuously monitored using a thermogravimetric setup with a suspended, gas-tight crucible, enabling precise quantification of reduction rates and extents. Complementary characterization was employed to link chemical and structural evolution to reduction behaviour. These findings will provide new insight into Mn ore reduction mechanisms under dynamic H2/H2O conditions, advancing the knowledge base required for hydrogen integration in low-carbon Mn ferroalloy production.
J. D. Steenkamp (Independent Consulta…, 🇨🇦)KEYNOTE
Furnace Tapping | Furnace Tapping | Industry outlook
Analysis of Carbon Emission Reduction Opportunities in an Integrated Steel Plant for Environmental and Business Sustainability
↑ to programmeM. Estabrooks, N. Aubry, M. Sukhram (Hatch Ltd., 🇨🇦)
Pyrometallurgy | Steel | Green processing & environment
The steel industry is a major contributor to global greenhouse gas emissions, with a large portion of emissions coming from the integrated steel mill production route. For this reason, the steel industry is facing increasing pressure to reduce carbon emissions in response to global sustainability initiatives, with specific focus on the blast furnace-basic oxygen furnace route. As the industry pursues sustainable steelmaking to achieve carbon neutrality by 2050, several step wise changes will be required, covering all key areas of the plant. This includes operation and technological changes, along with raw material improvements in areas such as the coke plant, sinter plant, blast furnaces, and power plant. This paper investigates numerous carbon emission reduction opportunities that can be implemented in the integrated steel mill and compares them to a representative base case to highlight the site wide emission reductions that can be achieved. The specific emission reduction opportunities this paper investigates include equipment and operational improvements such as pulverized coal injection increases and burden distribution improvements, raw material changes, digital improvements for better process monitoring, and green energy production and substitution. The challenges associated with emission reduction and the corresponding reduction in power production is discussed with various methods to overcome these challenges. Financial sustainability is a critical aspect to maintaining competitiveness in the industry in addition to carbon emission reduction and environmental sustainability. This paper also analyses the operating cost impacts of the suggested emission reduction opportunities and outlines the expected cost constraints.
M. Folstad, M. Tangstad (NTNU, 🇳🇴)
Pyrometallurgy | Ferroalloys + Silicon | Fundamentals
Metallurgical silicon is industrially produced in submerged arc furnaces through carbothermic reduction of quartz. In addition to the raw materials, oxide impurities are present in the furnace and will react and interact with the charge. Presence of accumulated slag in the furnace leads to dissolution of SiO2 into the slag. To ensure an optimal furnace operation it is important to minimize the loss of SiO2 to the slag so that SiO2 can react according to the production process. The dissolution rate of silica into different compositions of SiO2-CaO-Al2O3 slags was studied at temperature 1500 °C and 1550 °C under an inert atmosphere of argon. The results show that the dissolution process is controlled by mass transfer of SiO2 in the slag. The experimental results were used to calculate the dissolution rate, which was found to increase with increasing CaO/Al2O3 ratios as well as with increasing temperature. Furthermore, a model was made based on Fick’s second law of diffusion to describe the dissolution kinetics. The model showed good agreement with the experimental values. The diffusion coefficient and the activation energy for the reaction were estimated from the model and experimental data, and both were found to be within the range of values reported in the literature.
Graphite Electrode Manufacturing and Its Impact on Electric Arc Furnace Efficiency and Sustainability: A Review of Process Innovations and Performance Metrics
↑ to programmeB. Yari, S. Kashani (Hatch Ltd., 🇨🇦)
Pyrometallurgy | Steel | Equipment & design
Graphite electrodes are critical components in electric arc furnace (EAF) steelmaking, directly influencing energy efficiency, process stability, and sustainability outcomes. This literature review examines recent innovations in graphite electrode manufacturing, including raw material selection, impregnation techniques, and joint design, and evaluates their impact on electrode performance and lifecycle. The review also explores the role of high-performance electrodes in optimizing EAF operations, reducing energy consumption, and minimizing carbon emissions. Lifecycle assessments and recycling strategies are discussed to highlight environmental considerations. The paper concludes with recommendations for future research and industrial adoption of advanced electrode technologies to enhance competitiveness and sustainability in steelmaking.
Production of Si alloy by aluminothermic reduction with Al dross
↑ to programmeL. Meistad, L. Smemo, G. Tranell (NTNU, 🇳🇴)
Pyrometallurgy | Ferroalloys + Silicon | Green processing & environment
Solar panels are becoming an increasingly important method of producing electricity, but over time they tend to become less effective and are therefore typically decommissioned after 20 years. These panels are mechanically separated and crushed producing among other things glass from the encasing protecting the wafers. As a relatively homogenous waste material in significant quantities, this crushed glass presents itself as a potential raw material for Si production. In combination with Al dross, a byproduct of Al production with significant metallic content, this can become the basis for a Si production process without the need for new raw recourses. The metallic Al in the dross can react with the silica in the glass waste to produce Si metal, while the alumina in the dross and other oxides from the glass form a slag phase. The main reaction of this process is shown below: This study aims to investigate whether end-of-life solar glass is a viable Si source, and what alloy quality can be produced with aluminothermic reduction. Additionally, this study aims to evaluate the impact of different Al sources. Experiments were conducted with Three Al sources, namely pure Al, 1.25-5mm, and 5-10mm. 2000g of glass was used, while the dross was added in half the stoichiometric amount according to the equation above to ensure full utilization of the dross. The glass, dross, and flux were combined in a crucible and held at 1500 C for 60 minutes, after which the metal and slag phase were cast separately and analysed by electron probe microanalysis. Two experiments were conducted for each dross fraction, and thermodynamical simulations were conducted with FactSage 8.3 for comparison. The experiments produced a high-purity silicon alloy with more than 95% Si by weight and small amounts of Fe. Results were similar across all six experiments, with less than 5% deviation between the lowest and highest Si amount, showing both reproducibility of the experiments as well as robustness in regard to the Al source used. The slag contained 30-40% alumina, 25-35% silica, and 20-25% calcia, with smaller amounts of Sodium oxides and magnesia. These results were in line with the FactSage simulations, which predicted a slightly lower Si content in the metal phase of 90%. This work shows a potential way forward for producing Si without needing to mine new raw materials, while also utilizing a waste source that will become increasingly abundant as the increase in solar panels being built over time translates into more decommissions.
Informing Slag Management Policy through Modeling: A Multi-dimensional Approach to Predict Cr(VI) Water Emissions for Robust Life Cycle Assessment
↑ to programmeS. J. Baumgartner, A. V. Cherkaev, J. Pettersen, G. Tranell (NTNU, 🇳🇴)
Furnace Tapping | Ferrochrome | Operations
Life cycle assessment (LCA) is a well-established methodology for evaluating environmental impacts, providing a holistic foundation for decision making and enabling comparison and assessment, whether by industry players, policy makers or researchers. However, to ensure the validity of these assessments, particularly for impact categories determined from heavy metals emissions in particulate matter and slag, significant improvements are needed in inventory determination to quantify the human toxicity and ecotoxicity of metal production. Acquiring emissions data for heavy metals is often hindered by the fact that data is frequently proprietary within industry, measurements are limited to fixed conditions, and the number of measurements is small. This makes the data statistically questionable and limits its availability and reliability for research, and to support environmental policy. This work investigates three key aspects to address this gap. First, it evaluates the environmental impacts of an industrial ferrochrome smelting complex using real-world operational data, which is the core of the analysis. Delineated from this, the second aspect focuses on determining heavy metal air emissions; in which measured off-gas particulate matter analyses is substituted with thermodynamic modelled values. This approach offers an alternative to conventional methods relying on isokinetic testing, which is conducted under ideal, stable conditions, and often unavailable to researchers. Furthermore, for slag, industry predominantly relies on static leaching tests to predict heavy metal release. These tests are limited because they fail to represent the true dynamic conditions of an environment, often leading to exaggerated inventory inputs for LCA and inaccurate impact assessment results. To provide a more realistic prediction for slag, the third aspect involves the development of a foundational numerical model using time-dependent modelling to predict long-term heavy metal leaching, which would be used to substitute the emissions values typically acquired via static leaching tests. The value in investigating these methods of determining water and air emissions is that it creates a more robust, systematic and scientifically defendable framework for LCA, particularly in metal production in the absence of industrially measured data for these facets. Furthermore, these methods can be applied to different furnace conditions and operational parameters. While the methods developed and studied provide a foundation for determining heavy metal emissions, they represent an initial step. Further verification through experimental studies is required to validate, refine, and confirm their accuracy and practical application in real-world scenarios.
Feed Pile Behaviour in DRI Smelting Furnaces – Analysis and Modelling Methods
↑ to programmeR. C. Bosman, A. E. J. Bogaers, J. H. Zietsman (University of Pretor…, 🇿🇦)
Pyrometallurgy | Steel | Fundamentals
Granular systems are common in pyrometallurgy — from submerged-arc furnace burden to rotary kiln feed — and will be central to the DRI smelting furnaces (DSFs) expected to replace the blast furnace.
DSFs will likely use two simultaneous feeding regimes: feeding at the electrodes for throughput, and feeding at the walls to protect the furnace lining. In both cases, particle melting behaviour will be governed by their interaction with the bath and with each other. Particles fed at the electrodes encounter a concentrated energy source and should melt quickly with limited inter-particle interaction. Wall-fed particles interact closely with their neighbours in colder process regions, and melt more slowly.
This work focuses on wall feed piles. The interaction between the piles and the bath, together with the internal dynamics of the piles, determines the melting rate and therefore whether the feed pile adequately protects the wall. Modelling these feed piles is essential for designing the first generation of DSFs.
The primary obstacle is capturing the discrete nature of the feed pile and its interaction with the bath. Discrete methods such as CFD-DEM can represent this, but are computationally demanding — impractical for the rapid design iterations required. The alternative is to treat the feed pile as a continuum, modelled with the conservation equations for mass, momentum, and energy. We describe the key phenomena that drive feed pile behaviour and how we intend to represent them in a proposed computational model.
Quo Vadis – Refractory Management in Peirce Smith Converters
↑ to programmeD. M. Brazier (RM Solution, 🇿🇦)PLENARY
Refractory Materials | Refractories | Operations
The Peirce Smith Converter (PSC) remains a cornerstone of copper smelting operations, yet its refractory systems face mounting challenges in the pursuit of efficiency, longevity, and cost-effectiveness. This presentation explores the evolving landscape of PSC refractory performance, emphasizing the shift from traditional corrosion-centric assessments to a more nuanced understanding of thermal mechanical wear mechanisms. Drawing on field data, campaign analysis, and experimental insights, it highlights the critical role of operational practices—temperature control, slag chemistry, and tuyere management—in influencing refractory life. As the industry confronts higher throughput demands and fluctuating commodity cycles, the question —Quo Vadis — Refractories— invites a strategic reflection: Where must refractory technology go to meet tomorrow—s metallurgical realities. The answer lies in tailored material selection, predictive maintenance strategies, and design innovations that address site-specific stressors. The presentation advocates for a data-driven, proactive approach to refractory management, moving beyond reactive repairs toward integrated solutions that enhance converter reliability and profitability. Ultimately, the future of PSC refractories will be shaped not only by material science but by the operational intelligence applied in their use. This talk provides a roadmap for navigating that future—one built on insight, innovation, and informed decision-making.
A. Malfliet (KU Leuven, 🇧🇪)KEYNOTE
Refractory Materials | Refractories | Fundamentals
Development of thermodynamic database for V oxide containing slag systems and application to pyrometallurgical process
↑ to programmeI.-H. Jung, J. Nam (SNU, 🇰🇷)KEYNOTE
Pyrometallurgy | Other Commodities | Fundamentals
Accurate thermodynamic database for the CaO-MgO-Al2O3-SiO2-FeO-Fe2O3-VOx system was developed based on the critical evaluation of available literature data and new phase diagram experiments. In particular, the multiple oxidation states of V (V3+, V4+ and V5+) in the oxide system were well taken into account in the modeling to cover the phase equilibria under both oxidizing and reducing condition. In this study, the key phase diagram experiments and thermodynamic modeling results for several important ternary systems will be overviewed, and the applications of the thermodynamic database for the Fe-V production process will be presented.
Ferroalloys furnace lining management - guideline for operators to extend furnace lifetime and maximize profitability
↑ to programmeC. Coetzee, S. Arjun, M. Erwee, S. Swanepoel, C. Briedenhann, R. Webb (Intocast South Afric…, 🇿🇦)
Refractory Materials | Refractories | Operations
Due to the existing market downturn of commodities and cost pressures on ferroalloys producers, extending refractory lining lifetime, postponing complete relines and preventing furnace run outs are major economic and safety drivers. Furnaces are run at maximum capacity until they reach the end of lifetime. Furnace relines are not only costly but having multiple furnaces offline results in less production and directly impacts profitability. In this competitive, cost driven market, the role of lining monitoring and management is becoming increasingly important. Lining management requires a comprehensive understanding of furnace design criteria, engineering principles and thermal modeling (heat transfer and heat flux calculations) of a particular furnace. Lining monitoring is so much more than just thermocouple readings. There is direct correlation between refractory wear, sidewall and hearth cooling, operational and metallurgical factors, tap hole management, maintenance and original furnace design criteria. Some furnaces are installed with designated lining management systems (LMS). LMS requires a significant number of thermocouples on the hearth and sidewall, heat flux calculations and algorithms linked to a SCADA/PLC to provide an actual wear profile of the furnace lining. Thermocouples are damaged by lining and shell movement, refractory wear and being subject to proximity of metal and slag. On older furnaces especially the accuracy/validity of thermocouple readings can be questionable. The aim of this paper is to review all on-site methods operators can use to monitor and improve furnace lining lifetime in combination with establishing a basic understanding of furnace engineering principles.
G. Mulder, W. Steinberg (Hatch, 🇿🇦)
Pyrometallurgy | Other Commodities | Operations
This paper elaborates on the advances in vanadium processing to increase productivity, reduce operating costs and enhance process stability. Additionally, it is known that environmental compliance is becoming more stringent with more focus placed on energy utilisation and integration. This paper explores the developments required within the vanadium landscape to ensure a low-cost, efficient processing facility, that is also considered an environmentally sound solution. Published Highveld Steel processing information has been considered as the basis for this evaluation and compared to the modelled improvements with kiln operating configuration, furnace crucible design considerations, process control systems, slag processing considerations and energy optimisation considerations detailed accordingly.
S. C. Louw (METIX, 🇿🇦)KEYNOTE
Refractory Materials | Refractories | Equipment & design
Impact of feed mixture control on arc behaviour in DC arc furnace smelting of chromite - a modelling study
↑ to programmeQ. G. Reynolds, M. W. Erwee, S. Swanepoel, R. Fourie (Mintek, 🇿🇦)KEYNOTE
Pyrometallurgy | Ferrochrome | Fundamentals
Chromium is a critical mineral in South Africa, which harbours most of the world’s known ore reserves. It is used primarily as an alloying agent in the manufacture of stainless steel and other specialised metal products. The majority of the chromium supply worldwide is produced as a ferrochromium alloy by reductive smelting of chromite ore in electric furnaces, which are of alternating current submerged-arc or direct current (DC) plasma arc design. DC furnace technology is particularly well-suited to chromite smelting due to its ability to handle fine feed materials and high temperatures. DC furnaces consist of a closed cylindrical crucible which contains the process material, and one or more graphite electrodes entering through the vessel roof. An electric arc is formed between the electrode tip and the surface of the molten bath below it. The arc is a high-velocity, high-temperature jet of ionised gas converting electrical energy into thermal and mechanical energy, which in turn drive the thermochemistry of the reduction process. Chromite ore and carbonaceous reductants such as metallurgical coke are fed to the furnace together with fluxes and chemical modifiers, producing a waste slag and the product alloy. For optimal performance, electrical control of DC furnaces is important to ensure open arc operation and correct power input to the process is maintained at all times. This is generally accomplished by a series of nested control loops, the outermost of which moves the electrode hoist up or down to meet a desired furnace voltage or resistance setpoint. Even with such tight control measures excursions in hoist position are sometimes observed on furnace plants, and would seem to indicate sudden changes in the electrical properties of the arc. In the present paper the authors apply an integrated arc modelling workflow comprising thermochemistry simulations, plasma property calculations, and computational multiphysics models of the plasma arc to explore this problem. The impact on the arc’s behaviour of over- or under-feeding reductant for a given feed mixture is presented as a case study for a representative industrial-scale DC furnace, and evaluated as a possible explanation for hoist excursion events.
Extension of ferrochrome furnace lifetime — Technical dig-outs to repair furnace hearths and clovers leaving sidewall brickwork refractories intact
↑ to programmeP. Pienaar, M. Erwee, S. Swanepoel, S. Arjun (Intocast South Afric…, 🇿🇦)
Refractory Materials | Ferrochrome | Operations
South Africa's ferrochrome production is facing significant cost pressures with these factors leading to reduced production, smelter closures and a shift towards chrome ore exports instead of ferrochrome. Key cost pressures include high electricity cost, global price competition, rising ore and reductant costs, logistics costs and ageing infrastructure. In this cut-throat environment the aim for survival is preserving cash flow and cost saving initiatives. Ferrochrome producers do not have the luxury to spend millions on spare linings for every furnace in their fleet. Producers are increasingly looking at new innovative type of repairs to extend furnace and refractory lifetime. Complete furnace relines including demolition, possibly civils, new steel shells/grillage beams and installation can take up to 3-4 months. With large ageing fleets, producers also cannot afford to take multiple furnaces offline for reline at the same time. In this cost-conscious environment producers also cannot take furnaces offline to do “textbook” dig-outs which would require significant cool down periods, expensive demolition to identify reaction zones, sampling and detailed technical analysis and interpretation of results. A novel approach to extend freeze lining lifetime without reline has been developed by South African producers and Intocast South Africa. This approach includes fast high-level demolition to keep refractory sidewalls intact to get to problem areas at the clovers, tap holes and furnace hearths. This approach can be summarized as “Dig-outs with the aim to repair furnace refractories, gather as much information as possible on reaction zones and metallurgy and cost saving”. This approach is not “demolition to destruct furnace refractories as what is done prior to relines”. Changes in ores and reductants and running furnaces beyond reline dates also lead to the main wear areas on ferrochrome furnaces now being much deeper into the hearths with resultant damage on bottom plate steelwork. This paper will give an overview of dig-outs done globally on furnaces and discuss the main considerations for demolition and installation leaving sidewall brickwork intact. An overview of steel work considerations will also be provided to elaborate on steel work observations seen such as bottom plate lifting, separation of sidewall shell from the bottom plate and steel work integrity.
Reduced order model for isothermal pre-reduction of chromite pellets with hydrogen
↑ to programmeM. Khama (Mintek, 🇿🇦)
Pyrometallurgy | Ferrochrome | Green processing & environment
Full scale models such as 3D Computational Fluid Dynamics (CFD) models are often used to investigate the multi-scale flow physics in heterogeneous reactors. However, these models impose prohibitive computational expense in the modelling of heterogeneous reacting flow systems. The high computational expense prevents the use of high dimensional systems in real time control and online optimization of reacting flow systems. In order to facilitate incorporation of predictive models in the heterogenous reacting flow systems control loop, computationally efficient reduced order models are required. Owing to these requirements, a reduced order model for pre-reduction of chromite with hydrogen was developed with the view to rapidly predict the performance indicators for pre-reduction of chromite with hydrogen. Thiele modulus method was used to develop the reduced order model, and the model results were compared to isothermal pre-reduction experimental results at a range of pre-reduction temperatures from 1200oC to 1400oC. The model predicts the degree of reduction, diffusion of gases through the product layer, unreacted core radius of the grain radius, local and global conversion. The findings indicate that the reduced order model results agree closely with experimental results for all the investigated temperature range.
Tenova's Composite Copper-Graphite Cooler Design for Enhanced PGM Furnace Performance
↑ to programmeH. Joubert, G. de Villiers (Tenova Pyromet, 🇿🇦)
Refractory Materials | PGMs | Equipment & design
Tenova's innovative composite copper-graphite cooler design addresses the unique challenge of sulphidation corrosion encountered in platinum group metal (PGM) smelting furnaces in South Africa. The design features graphite sheathing over all copper surfaces vulnerable to labile sulphur, effectively inhibiting the onset of sulphidation—a corrosion mechanism particularly prevalent in local PGM operations. Central to the cooler's safe operation is the incorporation of shallow cooling water channels within the copper elements, significantly mitigating the risk of water leaks into the furnace environment. Extensive test work preceded implementation, rigorously validating both constructability and cooling performance under extreme service conditions. Following successful deployment in an industrial PGM furnace, operating data and performance metrics confirmed reliable functionality and robust cooling efficiency. After 29 months of continuous operation, select coolers above the matte tapholes were extracted for comprehensive evaluation, including visual and dimensional inspection, full dismantling to assess sulphidation corrosion, and analysis of the copper-graphite bond integrity. Laboratory investigations encompassed conductivity measurements of the copper, elemental analysis of the graphite to detect any compositional shifts, and assessment of the graphite—s cold crushing strength, bulk density, and apparent porosity. Results demonstrated sustained material integrity and performance, validating the cooler's long-term reliability. Insights from the post-operational evaluation informed subsequent design refinements, further enhancing constructability and operational safety. This paper presents the design philosophy, test methodologies, performance results, and lessons learned from the extended service of Tenova's composite copper-graphite coolers, offering a robust solution to the persistent challenge of sulphidation in PGM smelting applications.
Effect of Pellet Size on The Reduction Behaviour of Chromite Pellets Using Gaseous Hydrogen as Reducing Agent
↑ to programmeA. H. Wicaksono, V.-V. Visuri, T. Fabritius (University of Oulu, 🇫🇮)
Pyrometallurgy | Ferrochrome | Fundamentals
Conventional ferrochrome production relies on carbothermic reduction of chromite pellets in Submerged Arc Furnaces (SAF). The SAF process involves melting step which largely diminishes the influence of pellet size on its reduction behaviour. However, this production route generates substantial carbon dioxide (CO2) emission which is not compatible with the decarbonisation goals. Due to this concern, hydrogen gas (H2(g)) has been explored as reducing agent in metals production including ferrochrome industry. Unlike carbothermic reduction, H2(g) reduction process proceeds in the solid state. This condition puts the gas diffusion and particle geometry as decisive factors in the mechanism. Since every bulk material, including industrial chromite pellets, are produced with certain size distribution rather than a uniform size, understanding the effect of size is important for evaluating the reduction behaviour of this low-carbon alternative process. In this paper, chromite pellets of different average diameters were reduced with H2(g) at two constant holding temperatures and 4 hours holding time. In addition, the reduction degree (RD) was also recorded. The results show that smaller pellets achieve higher reduction degrees compared to larger pellets. At 1400oC, the RD of iron and chromium for smallest pellet (14.00 mm in diameter) reaches 70.26%, while the biggest pellet with 17.81 mm has 54.24% RD. The similar trend is also shown in 1200oC experiment. The RD of 15.98 mm pellet reaches 42.65% while the RD of 17.41 mm pellet is 37.82%. Kinetic modelling also confirmed the influence of pellet size on the reduction rate. This behaviour is attributed to shorter diffusion paths and it improved gas–solid interactions in smaller pellets. Therefore, these findings implies that pellet size becomes important parameter in the H2-based reduction process.
Testing of refractory materials. An overview of how it assists in assessing suitability of a material for the intended application.
↑ to programmeA. T. Shonhiwa (Cermalab CC, 🇿🇦)
Refractory Materials | Refractories | Fundamentals
Cost of refractory materials constitute a significant fraction of any pyrometallurgical process. Using the right refractory materials comes with many advantages, including increased equipment durability and lifespan, improved energy efficiency, and enhanced safety. All these benefits translate into lower operating costs by reducing fuel consumption, minimizing repairs, and decreasing down-time. Assessing the suitability of a refractory material for its intended application involves evaluating its chemical, mechanical, and thermal properties in relation to the proposed application. Key properties include its chemical and mineralogical composition, refractoriness, resistance to thermal shock, as well as its density, porosity, and dimensional stability under high temperatures. Proper selection of a refractory material depends on matching these properties to the operating conditions, such as temperature and chemical environment. This paper will give an overview of the testing services offered by Cermalab CC in as far as testing of refractory materials is concerned and how the test results can assist refractory users in selecting the right material for any application.
A Novel Cooling Liquid for Pyrometallurgical Applications: Metix's Solution and TRL Validation
↑ to programmeS. de Beer, R. Dantu, E. Kleynhans (Metix (Pty) Limited, 🇿🇦)
Pyrometallurgy | Commodity-agnostic | Equipment & design
Addressing the critical safety risks of water-based furnace cooling, this invention presents a novel, intrinsically safe heat transfer fluid. The fluid was rigorously evaluated using Metix’s comprehensive de-risking strategy, combining precise lab-scale testing with advanced computational fluid dynamics (CFD) modelling to analyse its thermal and fluid dynamic properties, as well as its behaviour in molten materials. This project successfully developed a commercially viable and safer alternative, marking a substantial step forward for industrial safety and heat transfer technology.
M. B. Berger (🇿🇦)
Refractory Materials | Refractories | Fundamentals
Refractories are used for demanding conditions and need to be sound, robust and capable. Users of refractories need to understand this family of materials better so as to ensure the quality of their applications. This presentation discusses: • forms of silica • types of refractories • effects of hydration • thermal expansion and linear change • thermal conductivity • chemical and mineralogical composition • density & porosity • strength at room and elevated temperatures • slag resistance • refractory applications • all measurements to ensure the quality of refractory materials.
ILTEC: Safe, Water-Free Pyrometallurgical Furnace Cooling with Ionic Liquid
↑ to programmeE. Bantjes, A. Filzwieser (Mettop GmbH, 🇦🇹)
Pyrometallurgy | Commodity-agnostic | Equipment & design
Steam and hydrogen explosions caused by water entering high-temperature zones remain one of the most severe safety risks in pyrometallurgy. When water contacts molten metal, extreme volumetric expansion and hydrogen formation can trigger violent reactions, limiting safe operating windows and constraining furnace design. A non-flammable, water-free cooling medium fundamentally changes these boundary conditions and enables new levels of operational safety. The patented ILTEC technology employs a specially engineered ionic liquid that is entirely non-flammable and no explosive upon contact with molten copper, steel or slag. Unlike conventional organic heat-transfer oils, which can ignite once their flash point is exceeded, the ionic liquid does not burn and does not sustain combustion. When introduced into a melt, it exhibits only minor degassing and a characteristic greenish flame, eliminating the risk of steam or hydrogen explosions observed with water. This safety profile opens cooling applications that were previously impossible or prohibited due to explosion hazards. Industrial implementations already demonstrate the capability of the technology: sub-bath cooling elements in copper metallurgy, tap-hole cooling in slag-cleaning and smelting units, near-surface lance cooling for improved bath penetration, as well as controlled thermal management of hot-dip galvanizing baths including Zn and Zn–Mg systems. The medium’s high thermal stability and sufficient heat capacity enable reliable heat extraction, while built-in leak detection, redundant pump systems and nitrogen blanketing ensure robust operational safety. By eliminating both the explosion risks of water and the flammability hazards of organic coolants, ILTEC represents a transformative step in furnace cooling. It allows safer, more efficient and more flexible process operation, setting a new standard for modern high-temperature metallurgical systems.
Composition of refractory materials. An overview of bulk chemical analysis (XRF/ICP) and phase analysis (XRD) of refractory materials with reference to the Al2O3 – SiO2 system.
↑ to programmeA. Shonhiwa (Cermalab CC, 🇿🇦)
Refractory Materials | Refractories | Fundamentals
Selection of a refractory material for a particular application is mainly done based on chemical composition. However, 2 or more materials with same bulk chemical composition might end up exhibiting different refractory properties and therefore recommended for different applications due to them existing as different polymorphs / crystal structures. This paper gives a general overview of bulk chemical analysis (XRF & ICP) and phase analysis (XRD) of ceramic/ refractory materials with reference to the Al2O3-SiO2 system and how these 2 techniques can used to compliment each other in order to have a better understanding of the behaviour, application and phase transformation of refractory/ceramic materials.
Fundamental Principles of Electric Furnace Start-ups: Theory, Applications, and Case Study
↑ to programmeC. Strong, T. Koehler, F. Stober, S. Southall, R. Veenstra (Hatch, 🇨🇦)
Pyrometallurgy | Commodity-agnostic | Operations
Start-up is a critical phase during any electric furnace project that requires careful planning as they are challenging and very different from normal operations. To ensure a successful furnace start-up that maintains long term furnace integrity requires a clear understanding and a strict adherence to fundamental start-up principles and philosophy. This paper presents and discusses fundamental start-up principles for the various stages of an electric furnace start-up. A variety of topics are discussed for each stage: Start-up Preparation (commissioning, initial charge, instrumentation) Dry-out/Curing (freeboard target temperature and rise rates) Pre-heating (refractory temperature rise rates and hearth gap closure) Slag Pool Formation (pool formation and growth) Feed Addition (ramp-up to tapping). These start-up principles can be applied to a variety of commodities (ferronickel, platinum group metals, etc.), furnace types (AC vs. DC electric furnace) and start-up types (green hearth with pool formation via solid slag, green hearth with bath formation via molten slag charge, frozen heel reheats after sidewall rebuilds, etc.). This paper discusses at a high-level how fundamental start-up principles were adapted and applied in recent start-ups performed by Hatch to ensure successful start-ups. The paper also presents a detailed case study of the recent start-up of a PGM electric furnace. Data from the start-up is presented and analyzed and lessons learned are summarized.
Protecting a newly installed refractory lining through automated heat-up control
↑ to programmeM. Rajh, W. A. Roos, A. E. J. Bogaers, J. H. Zietsman (Ex Mente Technologie…, 🇿🇦)
Refractory Materials | Commodity-agnostic | Operations
The installation of a new refractory lining in a DC smelting furnace represents an investment of tens of millions of rands. The heat-up of this lining is a critical period: thermal shock must be avoided, and keying, the closure of gaps between bricks through thermal expansion, must be complete before any molten material exists in the furnace. Refractory suppliers prescribe heat-up schedules designed to achieve this safely, but operational reality, including power failures, unplanned stoppages, and equipment limitations, makes faithful manual execution of these schedules difficult. When the process is proceeding according to plan, a human operator can manage effectively. When disruptions occur, however, the dynamic thermal response of the lining exceeds what any operator can carry cognitively, and decisions made without adequate information risk reducing lining lifespan by years.
This paper presents a model-based approach to furnace lining heat-up management. A thermal model of the furnace lining, built using measured refractory material properties, primarily thermal conductivity as a function of temperature and thermal expansion, simulates the heat-up process and provides visibility into quantities that cannot be directly measured: the degree of keying, hot-face temperatures, and heat flux through the lining. A concept is demonstrated in which the model guides heat-up control through operational disruptions, adjusting power input to protect the lining and providing the operator with the information needed to make sound decisions throughout the process.
The approach also enables heat-up schedules and recovery strategies to be tested computationally before starting the furnace, and supports evaluation of different startup burden configurations. Results are presented for a circular DC furnace with a Radex-S type refractory lining, demonstrating the capability for ferrochrome and ilmenite smelting applications. The same principles are directly applicable to 6-in-line furnaces used in PGM smelting, and to circular AC furnaces used in ferromanganese production. The approach depends on reliable thermal property data from the refractory characterisation community, and would benefit from advances in structural mechanics measurements, including damage characteristics and high-temperature mechanical properties, to enable quantification of stress states within the lining as a function of heat-up rate and thermal expansion.
Investigating Pore Structure Development of Biocarbon Sources at High Temperature
↑ to programmeN. Palamutcu (NTNU, 🇳🇴)
Pyrometallurgy | Commodity-agnostic | Fundamentals
Biocarbon derived from renewable biomass sources represents a promising carbonaceous reductant for advancing sustainable production in metallurgical industries. A comprehensive understanding of the physicochemical behavior and structural evolution of biocarbon under industrially relevant conditions is crucial for its effective integration into metallurgical processes. To address this need, the present study examined the reactivity of various biocarbon types using a Macro TGA furnace operated at 1100 °C under different gas atmospheres, namely pure argon, an argon–CO/CO₂ mixture, and a CO/CO₂ mixture. Structural and chemical transformations of the biocarbon samples were characterized through Brunauer–Emmett–Teller (BET) analysis, scanning electron microscopy (SEM), and computed tomography (CT). Particular attention was given to surface modifications and pore volume evolution. The results were interpreted in comparison with those obtained from fossil coke, which was employed as a reference carbon source.
PGM Furnace Continuous Hearth Growth — A Computational Study
↑ to programmeG. S. Kambewa, J. H. Zietsman, W. Roos, R. Hundermark (Valterra Platinum, U…, 🇿🇦)
Refractory Materials | PGMs | Fundamentals
Continuous hearth growth in platinum group metals (PGM) smelting furnaces has emerged as a critical operational challenge, reducing effective furnace volume, altering heat transfer, and shortening campaign life. Despite extensive operational experience, the underlying mechanisms remain poorly defined. This study applies computational modelling to interrogate the phenomenon by integrating electrical, thermal, and mechanical analyses of the furnace hearth. The work begins with problem definition, linking operational observations of accelerated hearth growth to furnace start-ups following extended stoppages. An electrical model was developed to capture current distribution and Joule heating behaviour within the molten bath, highlighting localised current density as a driver of thermal gradients at the matte–refractory interface. Simplified transient thermal models were then constructed using finite element analysis to simulate furnace start-up conditions. The models, incorporating realistic hearth geometries and a matte layer, predicted isotherm locations in the hearth layers, with specific focus on the 690 °C matte solidus contour. Results show that start-up thermal cycles promote isotherm penetration into the hearth, creating conditions favourable for new growth. Finally, a stress–strain model assessed thermo-mechanical responses of the hearth. Refractory expansion, contraction, and associated stresses were shown to contribute to cracking and potential matte penetration, compounding the thermal drivers of hearth growth. The findings suggest that electrical distribution, start-up transients, and refractory stress all act in concert to drive continuous hearth growth. These insights provide a foundation for predictive modelling and highlight the importance of furnace operation, refractory design, and start-up procedures in mitigating hearth growth.
PGM Smelting Furnace Throughput vs Concentrate Quality – A Multiphysics Modelling Analysis
↑ to programmeW. A. Roos, M. Rajh, A. E. J. Bogaers, J. H. Zietsman (Ex Mente Technologie…, 🇿🇦)
Pyrometallurgy | PGMs | Fundamentals
PGM concentrate composition is changing significantly. Future blends will contain less base metal and sulphur and more chromium — and smelter operators need to know whether their furnaces can still deliver the required throughput.
To answer this, we built a multiphysics model of a circular AC PGM smelting furnace, validated against operating data for power input, heat losses, temperatures, and throughput. The model covers the slag bath, matte bath, black top, freeboard, refractories, and electrodes, solving for fluid flow, radiation, thermal conduction, and electromagnetic heating. A dedicated throughput sub-model uses computational thermochemistry to estimate the energy required to melt the concentrate through the black top — the critical zone where most energy is absorbed.
We used the model to run a large parametric study, varying slag properties, bath depths, operating temperatures, resistance set-points, and concentrate composition. The results quantify how throughput responds to changes in concentrate quality and identify the dominant sensitivities.
The current model operates at the macro scale. Micro-scale phenomena — matte droplet coalescence, localised phase transformations in the black top, and the transient interaction between the black top and the slag — are not yet captured. Resolving these, through finer-scale models and targeted experiments, is the next step toward more accurate throughput estimation.
ECO Tab® - a new alumina aggregate for steel ladle lining
↑ to programmeD. van Garsel, S. Klaus, A. Buhr, H.-L. Groß, D. Schmidtmeier, W. Zwijnenburg, J. Dutton (Almatis GmbH, 🇩🇪)
Refractory Materials | Refractories | Equipment & design
ECO-TAB® is a new alumina refractory aggregate with lower density when compared to the globally produced Tabular Alumina T60/T64 (3.3 vs. 3.55 g/cm³). The business case for the development of this new aggregate is based on its application in a steel ladle wear lining. Two factors are relevant here. The heat capacity and the thermal conductivity of the wear lining material are important for reducing the thermal losses of steel into the refractory lining during the thermal cycling of the ladle whilst in use. With lower heat capacity and thermal conductivity of the lining, the heat losses while the ladle is empty can be reduced and accordingly the heat losses from the steel to the refractory lining later. In addition, a lower density and weight of the refractory lining enables lower materials demand and higher tapping weight of steel into the ladle when the maximum crane weight in the steel works becomes the limiting factor during the ladle campaign. Firstly, the volume is the limiting factor but with increasing refractory wear, the crane weight then becomes the new limiting factor. ECO-TAB® contributes to energy saving, capacity improvement, and reduced material consumption through lower weight of the refractory lining. The paper discusses material properties and application tests, as well as experiences with ECO-TAB® used in steel ladle refractory linings at European steel plants.
Physicochemical Phenomena Occurring During PGM Smelting: Microstructural Evolution of the Black Top and its Transition to a Slag-Matte Dispersion
↑ to programmeM. Bhebhe, R. Cromarty (University of Pretor…, 🇿🇦)
Pyrometallurgy | PGMs | Fundamentals
In platinum group metal (PGM) smelting, material behaviour in the higher regions of the furnace strongly affects matte recoveries. Yet the concentrate layer (“black top”) and its interaction with slag remain poorly understood. Its role in controlling how sulfides and gangue report to bulk slag has mostly been inferred empirically, leaving key mechanisms unresolved. This study addresses this gap by experimentally reproducing black top buildup and examining its transition into molten slag. A laboratory-scale smelting setup was developed to replicate industrial temperature gradients and dynamic concentrate melting. Bushveld Complex concentrate and primary smelter slag from the Northern Limb were processed in a magnesia–chromite crucible using an induction furnace and a graphite susceptor to supply heat. Concentrate was gradually added onto molten slag, ensuring heating was primarily via slag-concentrate heat transfer, consistent with industrial practice. After sufficient buildup, samples were naturally cooled and analysed using SEM–EDS and XRD to map material evolution across the black top and slag interface. In the black top, low-temperature phenomena are dominated by sulfide decomposition and melting. Molten sulfides form spherical and globular particles and interact with gangue in diverse ways, ranging from attachment to single gangue grains to pools where sulfides spread across multiple particles in a matrix. Simultaneously, gangue minerals undergo dehydroxylation and liquid-state sintering. Sintering produces small pores that progressively merge into larger voids, which act as sites for sulfide collection, coalescence, and the development of more homogeneous matte-like compositions. The interface between concentrate and slag was not a sharp boundary but a progression from sintered concentrate into molten slag. Initially, sulfide interaction is governed by shrinkage of the gangue matrix with limited drainage. As sintering advances and the liquid fraction of gangue increases, sulfides become larger, more spherical, and more homogeneous, indicating the onset of liquid-phase settling and coalescence. Within the reactive zone, large pores provide evidence of bubble formation in the slag. Molten sulfide interactions are prominent here, but no flotation was observed, and no correlation was found between sulfide morphology and bubble size or shape, suggesting bubble effects are subtle. The presence of unreacted powdered concentrate beneath the liquid surface further highlights the dynamic and partially unstable nature of this transition region. This study provides the systematic characterization of microstructural evolution and phase interactions within the black top and its transition into slag and attempts to directly emulate a primary smelter. The findings highlight the importance of early sintering, pore development, and sulfide coalescence in governing how phases report to the bulk slag. These insights form a foundation for predictive models of furnace behaviour and open pathways for improving PGM smelting efficiency and reducing matte losses.
Inhibition of hexavalent chromium in refractory castables : the role of Elkem silica products
↑ to programmeH. Liu, S. Song, I. Cameron, A. Garbers-Craig (The School of Metall…, 🇨🇳)
Refractory Materials | Refractories | Green processing & environment
Chromium-containing refractory castables remain indispensable in severe service conditions—such as intense slag corrosion, thermal shock, and cyclic redox environments—across steelmaking, non-ferrous smelting, and waste-to-energy units, owing to their outstanding chemical stability and structural integrity. However, Cr2O3-based systems can undergo excessive oxidation in the presence of alkaline oxides and free alkali during heat treatment or high-temperature service, leading to the formation of hexavalent chromium (Cr(VI)). Cr(VI) is highly water-soluble and acutely toxic, thereby posing significant environmental and occupational health risks. Balancing performance retention with reliable mitigation of leachable Cr(VI) therefore remains a central refractory material design challenge. The present study introduced a novel no-cement binder system (SioxX®-Zero) together with Elkem Microsilica® 971U into the castable matrix formulation. The effects of these additives on the formation and leachability of Cr(VI) were systematically examined across different temperatures. Preliminary results indicate that at the lower temperature (500 °C), neither SioxX®-Zero or Microsilica 971U effectively suppressed Cr(VI) formation; leaching tests detected measurable, albeit minor, amounts. Moreover, increasing the SioxX®-Zero dosage at 500 °C tended to increase Cr(VI) formation, likely due to its specific binder characteristics and the associated local chemical environment. However, the amount of hexavalent chromium formed at this temperature appears limited, and extending the holding time did not lead to a further increase in Cr(VI) formation. At higher temperatures (900 and 1300 °C), both Microsilica 971U and SioxX®-Zero were more reactive than Cr2O3 (eskolaite) toward CAC-related phases, promoting the formation of Ca2Al2SiO7 (gehlenite) and CaAl2Si2O8 (anorthite). These reactions correlated with a marked reduction of Cr(VI)-bearing species, lowering leachable Cr(VI) to trace levels. After high-temperature, and soaking for prolonged periods, storage at lower temperatures did not lead to the reappearance of Cr(VI) within the observation temperature window. Overall, matrix composition containing SioxX®-Zero and Elkem Microsilica®971U—particularly the partial substitution of CAC with SioxX®-Zero—shows promise for enabling greener, regulation-compliant chromium-containing castables without sacrificing service-critical performance. The findings also delineate a low-temperature risk window (~500 °C) in which Cr(VI) formation can occur, requiring careful control of SioxX®-Zero dosage. These insights provide practical guidance for optimizing castable formulations and preparation strategies. (This work was supported by the Hubei Provincial Regional Innovation Program for International S&T Cooperation [Grant No. 2024EHA004], project title: Development of Chromium-Containing Refractory Materials for Waste-to-Energy.)
Coalescence of sulfides under simulated PGM smelter conditions
↑ to programmeL. S. Maphalala, A. Garbers-Craig (University of Pretor…, 🇿🇦)
Pyrometallurgy | PGMs | Fundamentals
The coalescence and subsequent settling of sulfide matte droplets through the blacktop and slag layers in an electric furnace constitute the primary mechanism of matte separation and collection during platinum-group metal (PGM) concentrate smelting. This study investigated the coalescence behaviour of sulfide matte droplets under laboratory-simulated PGM smelter conditions, focusing on the effects of total sulfide content, sulfide mineral composition, silicate mineral composition and the presence of chromite in concentrate feed blends used. Two blends of Platreef, UG2 and Great Dyke-type concentrates, and a pure Great Dyke-type concentrate were isothermally heated at 1300°C, 1400°C and 1480°C for two hours in silica crucibles sealed in steel capsules under an argon atmosphere, followed by rapid quenching to preserve the high-temperature phase composition. After quenching, the crucibles were sectioned in half: one half was used for the preparation of polished sections for microstructural, phase and chemical composition analyses, while the other half was used for high-voltage pulsed power (HVPP) comminution. Matte droplet size distributions were analysed at the top, middle, and bottom regions of the crucibles using optical microscopy and ImageJ software. Additional characterization techniques included micro-XRF imaging, scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS), and thermochemical modelling using FactSage 8.3. These methods provided comprehensive insights into how variations in sulfide content, sulfide composition, and chromite concentration influence matte coalescence. SEM was used to analyse microstructures, while EDS analysis was used to determine phase compositions and interactions. Micro-XRF imaging was applied to map elemental distributions of Fe, Cu, Ni, Cr, S and Si to track sulfide coalescence and settling. HVPP comminution, conducted with a SelFrag Lab S2.1 unit, enabled the separation of matte droplets from the silicate slag, and allowed for 3D visualization of the formed matte droplets. FactSage 8.3 was used to predict the liquidus and solidus temperatures of the concentrate samples, the compositions of the liquid silicate phases (LP), and their viscosities at the three working temperatures. Slag and matte physical properties (viscosity, surface tension and density) were estimated using published empirical models.
LCA as a tool for assessing the environmental impact of ferroalloy production – past and future
↑ to programmeY. Ma, S. J. Baumgartner, J. B. Pettersen, G. M. Tranell (NTNU, 🇳🇴)
Refractory Materials | Refractories | Green processing & environment
Life Cycle Assessment (LCA) is a standardized environmental management tool for quantifying the potential impacts of products, processes, or activities across their entire life cycle. It systematically evaluates environmental burdens from raw material extraction through production, use, and end-of-life management, thereby identifying stages or processes with the greatest contribution to environmental impacts. Ferroalloys are iron-based alloys containing substantial amounts of one or more alloying elements, such as manganese, chromium, or silicon. Their primary application lies in steelmaking, where they serve as alloying additions to improve mechanical properties. Industrial production of ferroalloys is predominantly conducted via carbothermic reduction of oxidic ores or concentrates, typically employing carbon in the form of coke or coal as the reducing agent. In the context of global efforts to achieve net-zero carbon dioxide emissions by 2050, decarbonization of ferroalloy production has become a critical challenge. The substitution of fossil carbon with biocarbon, a carbon-neutral reductant, represents a promising approach to reducing greenhouse gas emissions in metallurgical processes. Meanwhile, metallothermic reduction using silicon or aluminium as reductants which avoids direct carbon dioxide emissions offers another alternative production route. LCA has been employed to evaluate the environmental performance of these production routes. Despite the importance of the ferroalloy industry, only a limited number of LCA studies have been reported, some of which focus primarily on energy consumption and associated greenhouse gas emissions. This review aims to synthesize and critically evaluate the existing LCA literatures on ferroalloy production, comparing methodological approaches, system boundaries, and impact categories. By highlighting current knowledge gaps and methodological limitations, the review provides insights into how LCA can serve as a multi-criteria decision-making tool for assessing trade-offs among environmental and economic indicators in ferroalloy production. The findings offer guidance for future LCA studies and underscore opportunities to enhance sustainability, resource efficiency, and emissions reduction in the ferroalloy industry.
M. Mabunda, R. Cromarty (University of Pretor…, 🇿🇦)
Pyrometallurgy | PGMs | Fundamentals
The pyrometallurgical processing of platinum group metal (PGM) concentrate involves smelting and converting. During the converting process, nickel, copper and cobalt are lost to the slag as oxides. These base metals can subsequently be recovered in a slag cleaning furnace (SCF) as a possible treatment route in which reductant (typically coke) is added to reduce these metal oxides, and a sulfur source (typically concentrate), which collects the base metals in a matte phase. The use of coke is associated with the generation of greenhouse gas emissions. This study therefore aimed to identify alternative reductants and optimal conditions that maximize base metal and matte recovery while minimizing greenhouse gas emissions, thereby contributing to sustainable PGM processing. To align with circular economy principles and reduce reliance on fossil fuels, sustainable alternatives to coke were investigated—specifically, aluminium dross, silicon carbide bricks from spent refractories, and biochars derived from black wattle and macadamia nut shells. The study commenced with a detailed characterization of the chemical and phase compositions of the SCF feed materials and the alternative reductants. Converter slag and concentrate were analyzed using X-ray fluorescence (XRF), X-ray diffraction (XRD), and scanning electron microscopy (SEM), coupled with energy dispersive spectrometry (EDS). Coke and biochars underwent proximate analysis to quantify moisture, volatile matter, fixed carbon, and ash content. Silicon carbide bricks were characterized using XRF, XRD, and SEM-EDS to confirm composition and identify impurities. Aluminium dross was processed by melting to separate metallic aluminium from oxides; the aluminium was then leached in citric acid, the leachate evaporated, and the resulting powder analyzed by XRF to determine impurities. FactSage thermochemical software was used to predict equilibrium phases. Baseline tests, replicating industrial SCF operation with coke, were compared with tests using the alternative reductants —aluminium powder, silicon carbide powder, and biochar. The reductants were added in stoichiometric amounts based on the nickel oxide content in the converter slag. Reactants were blended, placed in magnesia crucibles, and sealed in argon-purged, welded steel capsules to prevent oxidation and sulfur loss from the charge. Experiments will be conducted at three temperatures (1380°C, 1430°C, and 1480°C) covering typical furnace operating ranges, with reductant additions varied by ±10% to assess the influence of temperature and dosage on reduction efficiency and matte formation. After establishing the behaviour of pure reductants, tests were performed using the actual alternative reductants from secondary sources to evaluate the impact of their impurities on the process. Each test was held at the target temperature for two hours, followed by quenching to preserve high-temperature phases. Quenched samples were analyzed using SEM-EDS to identify phase morphology and the elemental distribution of nickel, coper, cobalt and iron. High-voltage pulsed power (HVPP) fragmentation, using a Selfrag Lab S2.1 unit, was employed to separate matte and slag for quantitative analysis. Results were compared to FactSage predictions.
