Abstract
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.
Highlights
Nickel, an important strategic metal resource with the properties of anticorrosion, antiabrasion, and thermostability, has been widely used in stainless steel, special alloy steel, and other areas [1,2].Nickel ore is divided into 30% nickel sulfide ore and 70% nickel oxide ore, but almost 60% of nickel products come from nickel sulfide ore at present [3,4,5,6]
In limonitic laterite nickel ore, the contents of iron and cobalt are high, while that of silicon, magnesium, and nickel are low, which is appropriately beneficiated by hydrometallurgical processes, such as reducing roasting-ammoniac leaching, high pressure acid leaching (HPAL), and heap leaching
In saprolitic laterite nickel ore, the contents of silicon, magnesium and nickel are high, while that of iron and cobalt are low, which is appropriately treated by pyrometallurgical processes, such as rotary kiln-electric furnace process (RKEF) and blast furnace processes
Summary
An important strategic metal resource with the properties of anticorrosion, antiabrasion, and thermostability, has been widely used in stainless steel, special alloy steel, and other areas [1,2]. In saprolitic laterite nickel ore, the contents of silicon, magnesium and nickel are high, while that of iron and cobalt are low, which is appropriately treated by pyrometallurgical processes, such as rotary kiln-electric furnace process (RKEF) and blast furnace processes. The first rotary kiln reduction-magnetic separation process, the Krupp-Renn process, was used to produce luppen (iron particle) in the 1930s This process used coal as reductant instead of coke or electric energy, significantly saving production cost. Many researches of metallized reduction-magnetic separation to deal with laterite nickel ore have been done currently, there is little referenced data available for producing and applying ferro-nickel alloy in China because some pivotal parameters are not given due to the commercially confidential information. A metallized reduction-magnetic separation process based on hot briquetting was proposed to treat low-grade saprolitic ore in this paper. The paper provides a reference for the research and utilization of low-grade saprolitic laterite nickel ore
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