Study On Ni-Fe Enrichment By Coal-Based Direct Reduction And Magnetic With Laterite Nickel Ore

Due to the rapid development of iron and steel industry in China, the demand of nickel increases greatly. For a long time, nickel sulfide is the major source of nickel raw resources in our country. With long term mined, nickel sulfide ore reserves have a sharp decline. Therefore, it becomes very necessary to research and develop laterite. Laterite ores can be approximately divided into two categories:the limonite type and humus soil type. The former with lower Ni content and higher Fe content is suitable for higher pressure acid leaching.The latter with lower Fe content, higher Ni content, and higher Mg content, is subjected to electric furnace reduction smelting.Wet process brings serious environmental pollution and pyro metallurgical process leads to high energy consumption. A process-the laterite nickel ore is directly reduced by coal and then nickel-iron is concentrated by magnetic separation from the reduction materials-was put forward in this paper:First, Ni and Fe in laterite is reduced to the metal, and then processed by magnetic separation. The laterite (Nil.73%, TFe24.56%) is from Indonesia. Through laterite basic reduction test, the effect of temperature, time, C/O ratio and CaO addition content on grade and recovery rate of Ni and Fe was studied, and the basic reduction parameters was obtained. Then by conducting converter dynamic reduction test to simulate the charge movement state in the rotary kiln, the effect of different process conditions on the reduction effectiveness was researched.The main conclusions obtained in this paper are as follows:(1)Temperature, time, carbon amount and CaO amount are important factors of reduction process. When reduction time is constant, temperature is the most important factor, carbon amount is the second important, and CaO amount affects the minimum. Increasing temperature, the grade and recovery rate of Ni and Fe will increase significantly. Whether the temperature is high or not, the size of nickel-iron particles is affected significantly. When the temperature is too high, the slag and metal phase can melt, nickel-iron particles will adhesion. Increasing carbon content is also good to the reduction and gather of nickel-iron particles. At the same time, ash and the remaining carbon in the pulverized coal affect the magnetic effect. Before C/O ratio is over1.3, the more CaO, the more recovery rate of Ni and Fe. As the temperature is higher, the excess of CaO can reduce the slag melting point more. So there is more liquid, which leading to reduction dynamics condition deteriorated and metal particles and slag sticking together. As a result, the recovery of Ni decreases.(2) After magnetic separation,Ni in the concentrate exists in the form of iron-nickel alloy (Fe, Ni),and enstatite (MgSiO3),((Fe,Mg)SiO3) and forsterite (Mg2Si04) and other silicate is mainly in the tailings. The separation from nickel-iron and gangue is obvious.(3)The appropriate reduction parameters of laterite basic reduction roasting test are as follows:temperature is from1275℃to1300℃, C/O ratio does not exceed1.3, and CaO amount is7.5%. During exploration test, dynamics conditions is improved because of the charge continuous turning in the rotary furnace, so the temperature of1300℃is slightly higher. The final temperature was controlled from1250℃to1275℃.(4)In rotary furnace test, the temperature is more, enrichment of Ni and Fe is better.This is similar to the basic test.At the temperature of1250℃, as CaO quantity increases from7.5%to10%, the grade and recovery rate of Fe is increased, but the grade and recovery rate of Ni is dropped. At1275℃, as CaO increases, the recovery rate of Fe and Ni decline a little, the grade of Fe almost has no change,but the grade of Ni increases.Because when the temperature is1275℃,temperature plays a dominant role. With particle size of original ore and fuel increasing, the recovery rate of Fe and Ni increase, but the grade of Ni and Fe decline. The size is not conducive to separate metal from slag. While particle size is larger, the reduction material bonds into chunks.