Kinetics of Reduction of Low-Grade Nickel Laterite Ore Using Carbon Monoxide
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NICKEL is a critical metal widely used in production of stainless steel, batteries, catalysts, and high-temperature alloys.[1] Laterite ores, which contain approximately 70 pct of the nickel resources, account for 40 pct of the world’s nickel production.[2] Sulfide ores are still the dominant source of nickel but as a result of their depletion and more costly mining, the trend is shifting towards a greater reliance on nickel laterite ores.[3–5] Globally, nickel laterite ores are widely distributed in Australia, New Caledonia, Cuba, the Philippines, Indonesia, Americas, Caribbean, and Africa.[6] Coal-based reduction followed by magnetic separation has been widely used for the recovery of nickel and iron from nickel laterite ores.[7,8] In this approach, nickel and iron minerals in laterite ore are directly reduced by
BO LI, ZHIGUANG DING, YONGGANG WEI, and HUA WANG are with the State Key Laboratory of Complex Nonferrous Metal Resources Clean Utilization, Kunming University of Science and Technology, Kunming, 650093, China. Contact e-mail: [email protected] YINDONG YANG and MANSOOR BARATI are with the Department of Material Science and Engineering, University of Toronto, Toronto, ON M5S 3E4, Canada. Manuscript submitted March 20, 2018.
METALLURGICAL AND MATERIALS TRANSACTIONS B
coal to metallic nickel and iron, forming a Fe-Ni alloy. Compared with the coal-based reductants, the reduction of nickel laterite ore using gas as reductant decreases the operating temperature and it can potentially save energy. Several studies have been carried out on the kinetics and mechanism of reduction of nickel oxide. Abdel-halim et al.[9] studied the carbothermic reduction of nanoscale Fe2O3-NiO composites for the formation of Fe-Ni alloy. The compacts made of pure Fe2O3 and Fe2O3-26 pct NiO were reduced at 800 C to 1100 C and Fe-Ni alloys with different compositions were obtained. In another study, the same group[10] investigated the isothermal reduction behavior of nanoscale NiFe2O4 powder in pure hydrogen at 800 C to 1100 C and obtained nanocrystalline Fe-Ni alloy (Fe0.64Ni0.36). The reduction rate increased with increasing the temperature in both the initial and final reduction stages. Grain growth and coalescence of the formed Fe0.64Ni0.36 grains took place by increasing the reduction temperature. Yu et al.[11] investigated the kinetics of hydrogen reduction of an iron-nickel oxide using TGA and found that effective reduction of the oxide could only be achieved at temperatures greater than approximately 350 C. The rate-controlling step shifted from chemical reactions to gas diffusion when the temperature increased from 600 C to 1200 C. Nasr et al.[12] studied the isothermal reduction behavior of iron oxide mixed
with different amounts of NiO at 900 C to 1100 C. It was found that the rate of reduction in both earlier and final stages increased with the increase of NiO content at all reduction temperatures. This was attributed to the formation of nickel ferrite (NiFe2O4) phase and the consequent increase in the total porosity
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