Ferronickel Alloy Research Articles

Effects of Reducing Parameters on the Size of Ferronickel Particles in the Reduced Laterite Nickel Ores

Crude ferronickel alloy can be produced by the carbothermal reduction of laterite ore-coal composite. The size of ferronickel particles in semi-molten state is crucial for the subsequent magnetic separation between the ferronickel and slag. Aimed to better understand the effects of reducing parameters on the size of ferronickel particles in the reduced laterite nickel ores, a series of carbothermal reduction experiments of laterite ore-coal composite in tall pellets bed was carried out. The experimental results indicated that, higher reducing temperature, longer reducing time and more CaO additive were beneficial for the aggregation and growth of ferronickel particles. Temperature (1400 °C) is the most important parameter. Less CaO additive needs longer reducing time, more CaO additive needs shorter reducing time. Excessive CaO amount (CaO = 10 pct) may prevent ferronickel particles from aggregation and growth due to its rapid melting. The importance ranking of these parameters should be temperature > time > CaO additive. The optimum reduction parameters were “1400 °C, 45 minutes, CaO = 0 pct” and “1400 °C, 30 minutes, CaO = 5 pct”. Under these conditions, all the ferronickel particles in 4 layers were clear and bigger. The percentages of + 50 μm of particles were about 65 and 59 pct respectively, and the recovery rates of Ni were about 88 and 85 pct. The findings from this work may provide guidelines for the improvement of ferronickel alloy production by laterite nickel ores.

Optimum Treatment Time for Solid-State Extraction of Nickel from Nickel Sulfide Concentrates at 1073 K

Solid-state thermal treatment of Ni sulfide concentrates in an inert or reducing atmosphere, and the presence of metallic Fe is proposed as a feasible route to produce ferronickel (FeNi) alloy while retaining S in iron sulfides. The present work investigated the effects of temperature and amount of Fe addition via a thermodynamic analysis, giving a suitable temperature of 973 K to 1173 K and metallic Fe to Ni concentrates mass ratio of 0.5 to 2. The minimum time required for Ni extraction at 1073 K was investigated via thermal treatment experiments of various durations, and it was determined to be 30 minutes. Under the tested experimental conditions, average Ni concentration in the resulting sulfides and the generated FeNi was found to be 0.5 ± 0.2 mass pct and 16 to 18 mass pct, respectively, and in good agreement with the thermodynamic predictions. The maximum Ni recovery to FeNi was approximately 97 pct and the characteristic particle sizes d10 and d80 of FeNi were 14 and 45 µm, respectively. During 360 minutes of the thermal treatment, only 0.7 mass pct of S in the concentrates was released to the off gas as SO2.

Separation and recovery of iron and nickel from low-grade laterite nickel ore by microwave carbothermic reduction roasting

An effective strategy to achieve separation and recovery of iron and nickel from low-grade laterite ore via microwave carbothermic reduction roasting is reported. In this work, we determined the underlying reason for the poor separation of iron and nickel during the magnetic separation process. The effect of operating variables on the recovery and separation of nickel and iron from low-grade laterite ore was initially investigated during microwave carbothermic reduction roasting to reveal the underlying reason for their poor separation. Then, the phase transformation and interfacial reduction of fayalite Fe2SiO4 and hortonolite Fe2−xMgxSiO4 in the mineral composition of laterite were systemically investigated via SEM/EDS and XRD analysis to determine the influence of CaO and MgO on the stepwise reduction behavior of Fe2SiO4. Phase transformation during the microwave carbothermic reduction roasting process by microwave irradiation heating occurred according to the following steps: (Fe,Ni)2SiO4 (x=0) and Mgx(Fe,Ni)2−xSiO4 (0≤x≤2)→MgxCay(Fe,Ni)2−x−ySiO4 (0≤x+y≤2)→MgxCa2−xSiO4. Finally, the substituted iron and nickel ions were found to reduce to ferronickel alloy under a reductive atmosphere. The ferronickel alloy with a nickel grade of 7.05wt.% and an iron grade of 71.70wt.% was produced successfully from low-grade laterite ores in which the recovery ratios of nickel and iron were 92.44% and 91.17%, respectively. Furthermore, these methods could be extended to the reduction behavior and interfacial reaction of silicates in other ores.

Solid State Extraction of Nickel from Nickel Sulfide Concentrates

The conventional smelting and refining of Ni sulfide concentrates is an effective strategy for extracting Ni from sulfide ores. However, during the smelting process, sulfur is oxidized to sulfur dioxide (SO2), which poses a significant environmental hazard. The present work investigates the feasibility of an alternative process to recover Ni as a ferronickel (FeNi) alloy while retaining the bulk of the sulfur in a solid phase (FeS), mitigating potential SO2 emissions. A Ni concentrate blended with iron was treated at 950 °C under an Ar atmosphere for 2 h, yielding a FeNi containing ∼22 wt% Ni and a residual iron sulfide containing <2.2 wt% Ni. The composition of these FeNi alloy particles is in good agreement with thermodynamic predictions.

An innovative process for extracting scandium from nickeliferous laterite ore: Carbothermic reduction followed by NaOH cracking

Laterite ores account for >60% of the world's nickel resources. This ore contains considerable amount of scandium, a strategic material in increasingly high demand in various industries. Here, an innovative two-step process was developed in which scandium is first concentrated in a slag phase using carbothermic reduction and then is leached using NaOH cracking process. The byproduct of the first step is metallic iron enriched with nickel and cobalt (ferronickel alloy). The carbothermic reduction process was performed at 1400–1600 °C using lignite as a reductant and calcia and/or silica as a fluxing reagent. A systematic study was carried out using a fractional factorial design methodology to investigate the quantitative effect of four variables. Utilizing the results, an empirical model was built to optimize the process for maximizing scandium concentration. Under the optimum conditions, scandium was successfully concentrated in the slag phase >14 times compared with that in the feed material, while at the same time a high-grade ferronickel alloy was produced. Furthermore, fundamental investigations were performed to elucidate the carbothermic reduction reaction mechanism. For NaOH cracking process, the investigated operating parameters were baking temperature, NaOH-to-slag ratio, baking time, and liquid-to-slag ratio. After optimization, 88% of scandium was recovered, indicating the predictability of the empirical model for scandium recovery.

Thermal Upgrading of Nickeliferous Pyrrhotite Tailings for the Recovery of Nickel in the Form of Ferronickel Alloy

Production of ferronickel alloy by thermal treatment of nickeliferous pyrrhotite (Pyrr) tailings was studied by both thermodynamic assessment and experimentation. It was demonstrated that Ni can be extracted from Pyrr by increasing the Fe/S ratio of the material, which was achieved by either partial oxidation of Pyrr followed by H2 reduction or in situ generation of metallic Fe from the reduction of magnetite by petroleum coke pre-mixed with Pyrr. Examination of the samples produced from thermal treatment at 1173 K demonstrated that both approaches were effective in generating ferronickel, although the size of the particles was suboptimal for subsequent separation. Increasing the ferronickel particle size could be achieved by a smelting step at 1473 K, forming a sulfur-deficient molten matte. Slow cooling of the molten matte resulted in precipitation, settling, and growth of ferronickel alloy particles.

Durability and Microstructure Properties of Low-Carbon Concrete Incorporating Ferronickel Slag Sand and Fly Ash

AbstractFerronickel slag (FNS) which is also known as electric arc furnace slag is a byproduct of the production of ferronickel alloy. The production of FNS at Societe Le Nickel (SLN) in New Caledo...

Characteristic and behavior of an electrodeposited chromium (III) oxide/silicon carbide composite coating under hydrogen plasma environment

Hydrogen permeation barriers play a crucial role in reducing the risk of hydrogen permeation and radioactive leakage during the service of a fusion reactor. In this work, a chromium (III) oxide/silicon carbide (Cr2O3/SiC) composite coating was proposed to improve the hydrogen permeation resistance of ferronickel alloy. At first, the Cr/SiC composite coating was prepared by pulse electrodeposition in a trivalent chromium plating bath containing suspended SiC nanoparticles, and then oxidized it under 500 °C at a pressure of 100 Pa. The surface morphology, phase structure, surface chemical states, thickness, and the integrity of the composite coating were analyzed and compared. In particular, the effects of hydrogen permeation of the composite coatings were investigated. As a result, the composite coating showed huge potential in improving hydrogen permeation resistance, which provides a promising application for fusion reactors.

Thermal upgrading of nickeliferous pyrrhotite tailings: Formation mechanism of ferronickel alloy

Current practices of handling pyrrhotite (Pyrr) tailings pose the risk of acid mine drainage (AMD), which is a significant environmental problem. A thermal upgrading process by which nickel value can be recovered in the form of ferronickel alloy is a possible alternative to treat nickeliferous pyrrhotite tailings analyzing 0.5–1.5% Ni. The basis of this process is that the formation of ferronickel alloy from Pyrr is possible at kinetically favorable temperatures once the Fe/S ratio of Pyrr is shifted to stoichiometric or near stoichiometric FeS (troilite) with the addition of iron and/or removal of sulfur under non-oxidizing atmosphere. In this study, the formation mechanism of ferronickel alloy was investigated by treating diffusion couples at 850 °C to better understand the transport phenomena of sulfur, iron and nickel. When a compact of Pyrr powder was coupled with metallic Fe, the ferronickel alloy was found: (1) in the newly-formed sulfide layer adjacent to the remaining metallic Fe; (2) at the outer edge of the remaining metallic Fe; and (3) within the sulfide away from the metal/sulfide interface. The formation mechanism of ferronickel particles in different locations within the diffusion couple was linked to the various mass transport phenomena involved.

A new process of smelting laterite by lowtemperature reduction and microwave irradiation

A new smelting process for the reduction of laterite with a relatively high yield of Ni has been presented in this paper; particularly, this process has been underwent industrialized experiment in China. This new process was based on the following fundamental research results. (1) Since nickel oxide can be reduced more easily than iron oxide, the nickel content of the produced ferronickel alloy increases significantly when the quantity of coal that is mixed with laterite ore is optimized, leading to a right oxygen potential of gas for reduction reaction. (2) When laterite is reduced at 1150°C, only 75% of the reduced ferronickel product can be magnetically separated from slag, although more than 95% Ni has been reduced from laterite. (3) The key technology is to realize a fast carburization at 1300°C by microwave irradiation, which causes ferronickel fines grow to a large size in the semi-melting state so that they can be separated magnetically with a high efficiency. The first demonstration production line with an annual capacity of 100 kt green balls has been established in China. The Ni content reaches 13.5%, moreover, both P and S contents are also within the expected range.

Separation and Recovery of Iron and Nickel from Low-Grade Laterite Nickel Ore Using Reduction Roasting at Rotary Kiln Followed by Magnetic Separation Technique

The low-grade nickel laterite ore used in this study was successfully upgraded through selective reduction by industrialized rotary kilns followed by magnetic separation. The results indicated that both iron metallization extent and nickel metallization extent showed obvious linear correlation. In addition, rational roasting temperature and prolonged grinding time could enhance the overall fineness level of reduced laterite nickel ore. The moderate roasting temperature at a range of 1100–1150 °C should be suitable enough to a conversion of total nickel to metallic nickel and partly inhibited the conversion of total iron. Ultimately, the obtained ferronickel alloy with a nickel content of 7.32% and an iron content of 84.15% was prepared successfully from the low-grade nickel laterite ore containing a nickel content of 1.92%. Nickel and iron recoveries were 96.72 and 89.08% respectively, which achieved the highly efficient recovery and utilization of iron and nickel from low-grade laterite nickel ore.

Recovery of Rare Earth (i.e., La, Ce, Nd, and Pr) Oxides from End-of-Life Ni-MH Battery via Thermal Isolation

In this study, rare earth elements (REEs, i.e., La, Ce, Nd, and Pr) were thermally isolated in oxide form, from Ni-metal hydride (Ni-MH) batteries via an oxidation–reduction process. The anode part of the batteries (metal hydride anode, MHA) (with chemical composition of 54 wt % Ni, 23.7 wt % La, 6.7 wt % Ce, 5.4 wt % Co, 3.6 wt % Nd, and 3.4 wt % Mn) sourced from e-waste was subjected to an oxidation process in air at 1000 °C for 60 min followed by reduction at 1550 °C for 90 min using waste developer kit (>99 wt % Fe) as a reducing agent. Oxides of nickel and cobalt were reduced and diffused into metallic iron, resulting in the formation of ferronickel alloy. In a separate process, pure hematite was mixed with the MHA as oxidizing agent, and the resulting mixture underwent a 90 min heat treatment at 1550 °C. Both processes resulted in a successful separation of Fe-based metal (ferronickel) and rare earth oxide (REO) phases. The mechanism of thermal isolation of REEs in both processes is explained in thi...

Constraints and opportunities for the recycling of growing ferronickel slag in China

Ferronickel slag is a by-product of nickel production. The discharge of ferronickel slag has gradually increased with the expansion of the scale of smelting for ferronickel alloys in China, which is a huge challenge for environmental protection. Ferronickel slag recycling has good economic and social benefits. In this perspective, in accordance with the inherent physical and chemical properties of ferronickel slag, we explain the factors restricting ferronickel slag recycling and propose the potential pathways for ferronickel slag recycling. We also point out that the technical and environmental standards related to ferronickel slag recycling should be formulated. This perspective can provide an important reference for the sustainable development of the industry focused on ferronickel production in the future.

Thermodynamic modelling of the reduction of a saprolitic laterite ore by methane

The recovery of nickel from the sulphide deposits is becoming more expensive and thus increasing attention is being paid to the nickeliferous laterite ores. One option being considered for the extraction of nickel would be the production of a concentrate by reduction and magnetic separation of the ferronickel alloy. The utilization of methane as a reducing agent offers some environmental benefits when compared to carbon. In this paper, thermodynamic modelling has been used to investigate the pyrometallurgical reduction of a saprolitic laterite ore by methane. The effects of methane additions, temperature, and ore composition on the nickel grade and nickel recovery were determined. It was found that nickel recoveries of 90% could be achieved at about 1000 °C with nickel grades of about 60%. The majority of the reduction was due to the carbon in the methane.

Pilot-scale plant study on solid-state metalized reduction–magnetic separation for magnesium-rich nickel oxide ores

An innovative technology named solid-state metalized reduction–magnetic separation (SSMRMS) was developed to produce ferronickel concentrates from magnesium-rich nickel oxide ores. A pilot-scale plant with a daily processing capacity of 500kg of dry ores was assembled and tested. SSMRMS involves four steps: feed preparation, solid-state metalized reduction, quenching and ball milling, and magnetic separation. After 40days of continuous tests, the operational stability of the proposed technology was good, and accretion did not form in a rotary kiln. Results revealed that (i) an appropriate positive pressure in the kiln terminal was beneficial to metallization; (ii) the overall recoveries of nickel and iron could reach 91.3% and 73.8%, respectively, whereas the nickel and iron grades of the produced ferronickel concentrate could be 7.4% and 69.6%, respectively; (iii) residual nickel to tailings was 0.16%; and (iv) the return ratio of dusts was approximately 8%. Notably, nickel could be released and sufficiently metalized at an appropriate temperature once the structures of the Ni-bearing silicates were destroyed in the presence of fluorite. The metalized nickel aggregated with the metalized iron surrounding the margins of the minerals. Therefore, fluorite could promote the generation and growth of ferronickel alloy particles, thereby increasing the recoveries of nickel and iron. Preliminary calculation showed that the electricity consumption of the solid-state metalized process was 52.5kWh/t-ore. Hence, SSMRMS is a competitive strategy for the processing of magnesium-rich nickel oxide ores.

Preparing Ferro-Nickel Alloy from Low-Grade Laterite Nickel Ore Based on Metallized Reduction–Magnetic Separation

Nickel, a valued metal, mainly exists as nickel oxide in laterite nickel ore. Furthermore, a large part of the laterite nickel ore is low-grade saprolitic ore. In this paper, a research on preparing ferro-nickel alloy from low-grade saprolitic laterite nickel ore using metallized reduction-magnetic separation was studied. In the research, the carbothermic reductions of iron oxide and nickel oxide were analyzed in terms of thermodynamics. The influences of reduction temperature, reduction time, carbon ratio, and CaO addition on the recoveries and grades of iron and nickel were experimentally investigated. To analyze and clarify the related mechanism, the microstructure of ferro-nickel alloy was observed by optical microscope (OM) and scanning electron microscope/energy dispersive spectrometer (SEM/EDS). Accordingly, the results showed that, increasing reduction temperature can improve the grades and recoveries of nickel and iron; appropriate reduction time, carbon ratio and CaO addition can favor aggregation and growing up of the ferro-nickel particles, improving the grades and recoveries of nickel and iron. The optimal process parameters obtained were a reduction temperature of 1350 °C, reduction time of 2 h, carbon ratio of 1.2, and CaO addition of 10%. In this case, the ferro-nickel alloy with nickel grade 7.90% and iron grade 77.32% was prepared successfully from the low-grade saprolitic ore with nickel content 1.82%. The nickel and iron recoveries were 89.36% and 95.87% respectively, which achieved the highly efficient recovery and utilization of iron and nickel of low-grade laterite nickel ore.

Exergy assessment of a rotary kiln-electric furnace smelting of ferronickel alloy

The main objective of this paper is to assess the thermal performance of the RKEF process based on the actual operational data by using exergy analysis method. To identify the factors affecting exergy efficiency loss, exergy destruction caused by the main chemical reactions (fuel combustion, reduction reaction, decomposition reaction and slagging reaction) is investigated in detail. The results show that the energy efficiency of the RKEF process is 53.3% whereas the exergy efficiency is 15.7%, indicating a great potential for energy-saving. The overall exergy destruction accounts for 46.4% of the total exergy input, in which 24.8% is caused by chemical reactions. Moreover, the exergy destruction due to chemical reactions of rotary dryer, rotary kiln and electric furnace is 20.4%, 27.1% and 5.1%, respectively. It is also found that combustion is the dominant factor for the efficiency loss of rotary dryer and rotary kiln and slag with high temperature contributes most for the efficiency loss of electric furnace. Several suggestions for improving the thermal performance of RKEF system are proposed. The present work should do helpful effort for further improvement of the RKEF process.

Two-stage reduction for the preparation of ferronickel alloy from nickel laterite ore with low Co and high MgO contents

The preparation of ferronickel alloy from the nickel laterite ore with low Co and high MgO contents was studied by using a pre-reduction–smelting method. The effects of reduction time, calcination temperature, quantity of reductant and calcium oxide (CaO), and pellet diameter on the reduction ratio of Fe and on the pellet strength were investigated. The results show that, for a roasting temperature >800 °C, a roasting time >30 min, 1.5wt% added anthracite coal, 5wt% added CaO, and a pellet size of ~10 mm, the reduction ratio of Fe exceeds 70% and the compressive strength of the pellets exceeds 10 kg per pellet. Reduction smelting experiments were performed by varying the smelting time, temperature, quantity of reductant and CaO, and reduction ratio of Fe in the pellets. Optimal conditions for the reduction smelting process are as follows: smelting time, 30–45 min; smelting temperature, 1550°C; quantity of reductant, 4wt%–5wt%; and quantity of CaO, 5wt%; leading to an Fe reduction ratio of 75% in the pellets. In addition, the mineral composition of the raw ore and that during the reduction process were investigated by process mineralogy.

Ferronickel particle formation during the carbothermic reduction of a limonitic laterite ore

Attempts to economically extract nickel from the nickeliferous laterite ores face a number of challenges, including a limited ability to beneficiate the ore prior to processing. One method to address this issue would be to reduce the ore at moderate temperatures to form a ferronickel alloy, which could then be selectively recovered to form a nickel concentrate. The current work explores the effects of varying coal, elemental sulphur and pyrite additions and temperatures in the range of 1000–1200°C on the formation of ferronickel alloy particles in a limonitic ore. It was observed that a small sulphur addition (⩽4%) yielded a significant increase in the average size of the ferronickel particles formed during reduction. A decrease in the average nickel grade of the ferronickel particles, resulting from the increased metallization of iron, was also observed in the presence of sulphur. The ferronickel particle morphology and distribution of sulphur in the reduced ore are consistent with a liquid-phase growth mechanism driven by the FeFeS eutectic at 988°C.

Efficient Utilization of Nickel Laterite to Produce Master Alloy

To lower the smelting temperature associated with the carbothermic reduction processing of laterite, the optimization of slag and alloy systems was investigated to enable the reduction of laterite ore in the molten state at 1723 K. The master Fe-Ni-Mo alloy was successfully produced at a lower temperature (1723 K). The liquidus of the slag decreased with the addition of oxide flux (Fe2O3 and CaO) and that of the ferronickel alloy decreased with the addition of Mo/MoO3. More effective metal–slag separation was achieved at 1723 K, which reduces the smelting temperature by 100 K compared with the current electric furnace process. A small addition of Mo/MoO3 not only decreased the melting point of ferronickel alloys but also served as a collector to aggregate the ferronickel sponges allowing them to grow larger. The FeO concentration in the slag and the nickel grade of the alloy decreased with increasing graphite reductant addition.