Search Results (85)

Limonitic nickel laterite is difficult to sinter because of its high loss on ignition, high combined-water content, and complex refractory mineral composition, which often result in poor sinter strength and high solid fuel consumption. In this study, a pellet-sintering process was adopted to improve the sintering performance of limonitic nickel laterite. Pot sintering tests were carried out to investigate the effects of key process parameters—including moisture content, solid fuel dosage, return fines dosage, and drying–holding regime—on yield, tumble index, productivity index, and solid fuel consumption. The selected conditions were determined as follows: moisture content of 21%, solid fuel dosage of 5.8%, return fines dosage of 25%, drying at 450 °C for 5 min, and holding at 1000 °C for 10 min, under a fixed basicity of 1.5 and a bed height of 850 mm. Under these conditions, the yield, tumble index, productivity index, and solid fuel consumption reached 70.19%, 57.87%, 1.37 t·m⁻²·h⁻¹, and 95.86 kg·t⁻¹, respectively. Compared with conventional sintering, pellet sintering increased the yield, tumble index, and productivity index by 24.05%, 35.56%, and 31.73%, respectively, while reducing solid fuel consumption by 22.87%. XRD, OM, quantitative image analysis, and SEM–EDS analyses showed that pellet sintering reduced the average two-dimensional pore area fraction from 33.29% to 18.05% and the large-pore area fraction from 22.25% to 11.61%, while promoting a more continuous bonding structure characterized by a spinel-rich mineral framework, spinel–olivine eutectic-type composite bonding phases, and SFCA-type bonding phases. These results demonstrate that pellet sintering is a feasible route for improving the sintering performance and consolidation behavior of limonitic nickel laterite. Full article

The transition towards climate-neutral metallurgical production requires a broader transformation than the simple substitution of fossil-fuel combustion with electrical heating. While process electrification is a fundamental step towards reducing greenhouse gas emissions, achieving truly sustainable high-temperature processing also depends on the ability to maintain tightly controlled reaction environments, minimise thermal losses, and maximise the efficient use of process gases. These factors become increasingly important as the industry moves towards hydrogen-assisted processing routes and greater integration of renewable energy sources. By controlling heat transfer and gas composition, a stable processing environment can be maintained in which temperature, and gases’ partial pressure, can be accurately regulated throughout the treatment cycle. This study introduces the engineering concept of an airtight electrified indirect-fired rotary furnace, developed as a new process for efficient calcination, and also, hydrogen-based reduction processes. To assess the applicability of the proposed reactor concept, a bench-scale experimental campaign was carried out using two representative metallurgical processes: magnesite calcination and hydrogen-assisted reduction of lateritic ores. Throughout the testing campaign, the reactor maintained stable thermal conditions and a well-controlled process atmosphere, while the integrated monitoring system enabled continuous observation of temperature evolution and gas composition. The calcination trials achieved conversion efficiencies above 98%, whereas the hydrogen-reduction experiments successfully promoted the transformation of iron and nickel oxide phases into their metallic state. The results demonstrate that the integration of indirect electrical heating with airtight reactor operation provides a robust platform for hydrogen-assisted thermal processing. The proposed architecture improves atmosphere control and process efficiency while offering a scalable solution for the future implementation of electrified, low-carbon metallurgical technologies. Full article

Cobalt has emerged as a strategic critical metal due to its essential role in rechargeable batteries, high-performance alloys, catalysts, and clean energy technologies. However, its supply chain remains heavily dependent on cobalt produced as a by-product of copper and nickel mining and is geographically concentrated, particularly in the Democratic Republic of Congo. This review provides a comprehensive assessment of cobalt geology, mineralogy, global reserves, market trends, primary extraction routes, and emerging secondary recovery strategies. Unlike previous reviews that address these topics separately, this work integrates geological occurrence, mineralogical characteristics, extraction technologies, and resource circularity within a unified framework aimed at evaluating future cobalt supply resilience. The main cobalt-bearing deposit types of sediment-hosted Cu–Co deposits, Ni–Co laterites, and magmatic Ni–Cu–Co sulphide deposits are compared in terms of their mineralogical characteristics and processing requirements. Hydrometallurgy is identified as the dominant industrial route, typically combining high-pressure acid leaching (HPAL) with downstream purification and recovery processes such as solvent extraction and electrowinning (SX–EW). Emphasis is placed on the relationship between ore mineralogy and process selection, as well as on the growing integration of secondary resources, including tailings, slags, and spent batteries, into existing cobalt production chains. Despite promising recovery rates at laboratory scale, challenges remain in impurity control, economic scalability, and integration into established refining infrastructure. This review demonstrates that secondary resources are evolving from supplementary feedstocks to strategically important contributors to cobalt supply. Future supply security will depend on feedstock diversification, more flexible refining systems, improved impurity management, and the implementation of sustainable circular-economy strategies. Full article

The demand for metallic nickel has been growing steadily. Laterite nickel ore, as an oxide mineral, contains a higher nickel content than sulfide ores, enabling more economical smelting in the nickel extraction process. However, an extremely thick slag layer generated during side-blown smelting of laterite nickel ore alters the bath circulation characteristic of conventional smelting processes. To address this, this study employs a validated Multi-Fluid VOF model to analyze the flow field characteristics of the side-blown furnace bath under varying slag layer thicknesses. Within the slag thickness range of 1.5–2.5 m, the ascending air plume shifts horizontally along the furnace wall with increasing slag thickness, entraining matte into the slag and promoting its diffusion toward the settling zone. Matte diffusion is governed by bath circulation: backflow from the settling zone dominates at lower slag thickness, while vertical kinetic energy from splashed melt reflux dominates at higher thickness. This reflux-induced circulation is blocked by the dense matte layer, causing no disturbance to the bottom matte and thus favoring slag–matte separation. Increasing slag thickness raises the near-wall circulation zone and plume entry point, reducing gas holdup near the tuyere and weakening oxygen–matte contact. Full article

This study investigates the production behavior of Fe–Ni–S matte from synthetic nickel ore designed to simulate low-grade saprolitic laterite. The synthetic feed was formulated based on XRF and XRD analyses of magnetically upgraded laterite concentrate. Thermodynamic modeling, including phase stability analysis, Ellingham evaluation, viscosity prediction, and sulfidation equilibria, was employed to define optimal smelting conditions. Carbothermic reduction at 1550 °C enabled selective reduction in NiO and FeO, leading to the formation of Fe–Ni alloy droplets, which subsequently reacted with FeS to produce Fe–Ni–S matte. The carbon ratio played a critical role in controlling FeO content in slag, thereby influencing slag basicity and viscosity. An optimal carbon ratio of 0.2–0.4 mol maintained slag viscosity within the industrially favorable range (2–5 poise) and minimized crucible dissolution. Thermodynamic analysis confirmed that FeS is the only stable sulfide phase at high temperature and dissolves into the Fe–Ni melt, promoting stable matte formation. Under optimized carbon and FeS addition conditions, a maximum nickel recovery of approximately 88% was achieved, attributed to improved slag composition, controlled viscosity, and enhanced matte–slag separation. These results demonstrate that simultaneous carbothermic reduction and sulfidation is an effective route for Fe–Ni–S matte production from saprolite-derived oxide feed. Control of carbon ratio, FeS addition, and Al₂O₃ flux is essential for achieving stable matte formation and efficient metal–slag separation. Full article

Lateritic nickel deposits exhibit complex weathering-driven geometries, strong vertical variability, and complex multivariate geochemical relationships. These characteristics challenge conventional deterministic resource modeling. This paper presents a unified probabilistic workflow for lateritic nickel mineral resource modeling that integrates lithology and grade simulation within a consistent geostatistical framework. The methodology combines unfolding, plurigaussian simulation, multivariate imputation of incomplete datasets, projection pursuit multivariate transformation (PPMT) for decorrelation, and conditional simulation using the Turning Bands algorithm. Application to an Indonesian lateritic nickel deposit demonstrates reproduction of lithological proportions, spatial continuity, marginal distributions, and complex multivariate relationships. The proposed workflow enables explicit quantification of geological and grade uncertainty, providing a basis for uncertainty assessment in recoverable resource estimation and supporting downstream applications such as resource classification and drillhole spacing analysis. Full article

Ring formation in rotary kilns is a major operational problem in the ferronickel dry smelting process, in which nickel laterite ore undergoes drying, calcination, and partial reduction. Excessive ring accretion reduces thermal efficiency and disrupts stable kiln operation. In this study, the mechanism of ring formation was investigated through a combined approach integrating laboratory-scale experiments and long-term operational data obtained from a large-scale industrial rotary kiln. The effects of ore composition, particle size, and temperature on melting and sintering behavior were examined, and their correlations with operating variables such as fuel input and kiln rotational speed were analyzed. The results show that ring formation is governed by the selective melting and adhesion of low-melting constituents, particularly in ores with low basicity (MgO/SiO₂ < 0.55) and high Fe content (>14 wt.%). A high fraction of fine particles (<75 μm) further promotes adhesion due to their lower melting temperature and enhanced mechanical retention on the refractory surface. In industrial operation, localized overheating near the burner zone and low kiln rotational speeds (0.9–1.1 rpm) significantly accelerate ring growth. These findings provide a mechanistic understanding of ring formation and suggest that appropriate ore blending and optimized control of fuel input and kiln rotation are effective strategies for mitigating ring accretion in commercial ferronickel rotary kilns. Full article

Processing of nickel ores is a key aspect of modern metallurgy due to the growing demand for nickel in stainless steel, battery production, and advanced materials. The depletion of high-grade sulfide ores has shifted attention toward oxidized (lateritic) nickel ores, which are characterized by complex mineralogy and low metal content. This study presents a comparative review of major processing technologies, including pyrometallurgical, hydrometallurgical, and hybrid approaches, with particular emphasis on their applicability to Kazakhstan’s limonitic laterites with high iron and low nickel content. The analysis shows that the most suitable processing routes for such ores include atmospheric acid leaching (AL), high-pressure acid leaching (HPAL), metallothermic reduction, and combined flowsheets integrating thermal and leaching stages. Among these, AL and hybrid approaches are identified as the most promising under resource-constrained conditions. Despite recent technological progress, challenges remain related to energy consumption, economic feasibility, and environmental impact. The study highlights the importance of developing energy-efficient and low-carbon technologies, including hydrogen-based reduction, and provides practical recommendations for selecting and adapting processing methods for Kazakhstan. Full article

Limonitic laterites typically contain low Ni and Co contents and significant impurities, making the development of technical and economically feasible processes challenging. To address this challenge, this study investigates and evaluates an integrated hydrometallurgical process comprising sulfation roasting, water leaching, and solvent extraction (SX) for the selective recovery of Ni and Co from limonite-type laterite. Response Surface Methodology coupled with a Central Composite Design (RSM-CCD) was employed as a statistical experimental design tool to efficiently optimize the sulfation roasting conditions. Under the optimal sulfation roasting conditions (temperature 703 °C), selective leaching efficiencies of 87.2% for Ni and 96.6% for Co were achieved, with only 3.8% Fe co-leaching. A multi-stage SX scheme was subsequently applied to purify the pregnant leach solution (PLS) of water leaching. In the first SX step, D2EHPA at pH 2.8 selectively removed more than 95% of the impurities, including Mn, Zn, Al, Ca, and Fe. In the second SX step, Cyanex 272 at pH 5.8 enabled the extraction of more than 99.9% of Co and 86.0% of Mg into the organic phase, and Ni remained in the raffinate. Subsequent stripping with H₂SO₄ enabled the recovery of 99.9% of both Co and Mg from the loaded organic phase. Finally, selective carbonate precipitation is proposed as a potential downstream recovery method for Ni after enrichment. This approach is considered relatively less energy-intensive than sulfate crystallization. The process developed in this study was benchmarked against similar processes reported in the literature, and a conceptual flowsheet for the selective extraction and separation of Ni and Co from limonitic laterite was proposed. Findings demonstrated the feasibility of the integrated sulfation roasting-water leaching, solvent extraction process for treating impurity-rich laterite leach solutions. Full article

The depletion of global reserves of high-quality sulfide nickel deposits, coupled with the steady growth of nickel demand, has led to increased interest in the processing of oxidized (lateritic) nickel ores, including deposits with significant resource potential in the Republic of Kazakhstan. This paper provides an overview of global nickel ore reserves and their distribution, as well as the major nickel deposits in Kazakhstan, which are primarily located in the Aktobe, East Kazakhstan, Kostanay, and Pavlodar regions. Pyrometallurgical processing routes for lateritic nickel ores are also considered. Conventional production technologies, including the Rotary Kiln–Electric Furnace (RKEF), Krupp–Renn process, blast furnace smelting, Vaniukov process, and ISASMELT process, are reviewed, and their process flow diagrams are presented. These methods typically process lateritic nickel ores containing more than 1.2% Ni, whereas Kazakhstan ores are characterized by lower nickel grades, generally in the range of 0.75–1.1%. The advantages and limitations of conventional processing routes are analyzed, and the factors limiting the effective beneficiation of lateritic nickel ores using traditional methods are identified. The present study substantiates the feasibility of producing nickel-containing alloys from lateritic nickel ores using a metallothermic reduction approach. This method is based on the reduction of nickel and iron oxides using metallic reductants, which enables more selective extraction of target components and the formation of alloys with controlled composition. Metallothermic reduction is of particular interest for the processing of low-grade lateritic ores, as it allows the production of nickel-containing alloys without prior beneficiation, at lower energy consumption, and with reduced sensitivity to variations in the chemical and mineralogical composition of the raw materials. Therefore, this approach is considered a promising direction for the processing of lateritic nickel ores in Kazakhstan. Full article

The accelerating transition to low carbon energy systems has intensified the demand for nickel and cobalt from low-grade (<1.5 wt.%) refractory lateritic ores. These low-grade laterites are however not amenable to conventional beneficiation due to their complex mineralogy, eclectic physicochemical properties, and fine Ni–Co dissemination. This review examines recent advances made in the extraction of nickel and cobalt from complex low-grade lateritic ores, emphasizing the interplay between ore mineralogy, chemistry, beneficiation, pretreatment, and processing route selection. Developments in selective ore comminution–classification have led to the generation of Ni-rich fine fractions (undersize) and Co-rich coarse fractions (oversize), enabling differentiated extraction strategies that improve resource utilization, frugal energy use, and process efficiency. Mechanical activation via stirred media milling, thermal calcination-induced structural disorder, and dehydroxylate goethite products, are shown to significantly enhance Ni–Co leaching kinetics under both atmospheric and heap leaching conditions. A critical comparison of pyrometallurgical (rotary-kiln electric furnace) and hydrometallurgical (HPAL, EPAL, heap, atmospheric, bioleaching) routes demonstrates that ore-specific optimization is essential to balance recovery, acid consumption, and greenhouse gas emissions. The novel resin in moist mix (RIMM) process, which integrates ambient leaching and in situ ion exchange selective recovery, is shown to offer potential for sustainable values extraction from sub-economic resources. Furthermore, the review highlights the key innovation challenges and concomitant opportunities for enhanced critical battery metal recovery from complex laterite ores. Full article

Determining nickel extraction during the roasting–reduction stage of the Caron process is an essential tool for controlling the metallurgical efficiency of the technology. This study evaluated the performance of a new semi-empirical kinetic model for predicting nickel extraction during the reduction of lateritic ores predominantly composed of iron oxides and oxyhydroxides in multiple-hearth furnaces. To achieve this, the lateritic ore was characterised by scanning electron microscopy (SEM) before and after the reduction process. The temperature in hearth six was varied between 495 and 780 °C by adjusting the post-combustion air supply. The proposed model demonstrated high predictive accuracy for nickel extraction, with absolute and residual errors below 1.70% and 1.15%, respectively. The findings emphasise the importance of controlling metallurgical efficiency through mathematical models that incorporate key technological variables and the kinetic behaviour of the process. Full article

Owing to the superior reduction kinetics of limonite and goethite relative to silicates, coupled with the poor beneficiation performance of saprolite-type laterite, the direct carbothermal reduction of saprolite-type laterite exhibits limited nickel selectivity. This study leverages the selective oxidation effect of CO-CO₂ atmosphere on the metallic iron of pre-reduced minerals, as well as its suppression of Fe²⁺ reduction, to promote iron migration from oxides to the silicate phase, achieving homogenization and thereby negating its kinetic advantage in reduction. Parameter optimization experiments revealed that treating pre-reduced minerals with a 30 vol% CO atmosphere at 1200 °C for 20 min achieves complete iron homogenization within the silicate phase. Compared with the nickel–iron alloy (containing less than 10 wt% Ni) obtained via the RKEF process, the combination of pre-reduction, CO-CO₂ treatment, and the melting reduction process yielded nickel–iron alloys with nickel contents of 52.1 wt% (FeNi50 alloy) and 64.2 wt% at carbon consumptions of 4.0 wt% and 3.83 wt%, respectively, accompanied by nickel recovery rates of 95.5% and 91.2%. Furthermore, the enrichment of Fe²⁺ in the slag significantly reduces its melting point to approximately 1450 °C, enabling complete slag–metal separation after smelting at 1550 °C for 10 min. Full article

Given the importance of nickel in lithium-ion batteries and the expectation of the growth in electric vehicles and electrical devices, the demand for nickel in battery production is expected to increase dramatically. Nickel is primarily sourced from laterite saprolite ore, and there is now substantial interest in moving from ferronickel smelting technology to nickel matte technology in its processing to produce high-grade nickel. This research involved a thermodynamic modelling and lab–scale experiment on the smelting of nickel matte. Nickel concentrate from laterite saprolite was used, and CaS, produced from commercially available gypsum, was employed as a sulfurizing agent. The matte smelting experiment was conducted at 1500 °C to optimize CaS and C consumption. During smelting with CaS, matte particles form, although sufficient reduction of nickel and iron from the concentrate is not achieved. By consuming carbon, the reduction potential of iron is increased, and this process, along with enriching the matte with iron, aids in the transportation of nickel. At a nickel grade in the matte with a Ni/Fe ratio of approximately 1, the nickel recovery only reached 63%. Upon achieving a nickel recovery exceeding 93%, the Ni/Fe ratio reached 0.44, corresponding to a nickel grade reduction to 22.78%. By employing analytical techniques and thermodynamic modelling, we have successfully determined the sulfidizing of nickel, identified the ideal CaS and C additions, and characterized the structure and quality of the slag produced during nickel matte smelting, supplying vital technological data necessary for practical application. Full article

Martensitic stainless steel is a commonly used stainless steel, and is widely used in daily production and life, but its high content of alloy elements increases its cost. This study aimed to develop low-cost martensitic stainless steel with excellent seawater corrosion resistance by using Zr-Ti combined deoxidation with molten iron from low-priced laterite nickel ore as raw material, taking advantage of the corrosion-resistant elements Cr and Ni, abundant in laterite nickel ore. The characteristics of corrosion-active inclusions in steel, such as their density and electrostatic potential saturation-current density, were observed and studied using scanning electron microscopy and electrochemical testing methods. The intentionally added composite deoxidizing elements (Zr, Ti) form highly stable oxide particles at high temperatures. During the solidification of the molten steel and subsequent solid-state phase transformation, the highly corrosion-active MnS nucleates and disperses on the oxide particles already formed in the liquid phase, while TiN continues to precipitate and coat the MnS particles. This significantly reduces the saturation-current density of locally corrosion-active inclusions, resulting in a marked improvement in seawater corrosion resistance. Full article