The Study For Extract Of Nickel In Serpentine From Huili By Reduction-Ammonia Leaching

Having good mechanical strength, ductility, and high chemical satiability, nickel is widely used as an important strategic metal, and65%of nickel is used for stainless steel. Nickel is smelted from sulfide ore all over the world. However, the nickel sulfide ore could not provide enough raw materials for the long time being for its shortage. In this situation, nickel oxide ore is utilized adequately for nickel metallurgy, because it is relatively abundant and occupies more than half of nickel ore. It has been surveyed that the contents of nickel in serpentine which is reserved in Huili Sichuan province of China are to0.6～0.8%. However, the utilizations of nickel in serpentine are still at the primary stage. Therefore, the researches of extracting nickel from serpentine have big important significances.The properties of serpentine raw material were characterized and analyzed in this paper. In this case, the technological processes for nickel extraction were studied systematically by reduction roasting, ammonia leaching and hydrogen reduction. The correlative factors in nickel extraction processes were also confirmed. What have been carried out and obtained are as follows.(1) On the bases of the reduction roasting of handled serpentine, the temperature ranges for reduction roasting and thermal decomposition of serpentine were obtained by TG-DTA curve, thermodynamic analysis and XRD analysis. The influences of the amount of pyrite as additive agent and activated carbon as reductive agent, the roasting temperature and reduction time on leaching rates of nickel were gained in the processes of reduction roasting. On the optimization reaction conditions that the amounts of pyrite are4%, the roasting temperature is at700℃, activated carbon are needed at5%and reduction time is120minutes, can we get the leaching rates for nickel at52.32%.(2) The ammonia leaching experiments for deoxygenated nickel calcine experiment were conducted in the air. The nickel calcine was grinded with a little of ammonia water in a mortar, and the ammonia leaching solution is a mixture of ammonia and ammonium carbonate. The influences of temperature, ratios of ammonia solution, leaching time and air flow on leaching rates of nickel were investigated. The optimization reaction conditions show as follows: leaching temperature for50℃, the ratios of NH3and CO2at90:60, liquid-solid ratios at15:1, leaching time for4hours and air flow for0.4L·min-1, on that conditions can the leaching rates for nickel reach56.42%. If the processes above-mentioned were done twice, the leaching rates for nickel could reach59.81%.(3) The ammonia leaching solution was conducted by ammonia distillation, calcination, and then deoxygenated by hydrogen at atmospheric. The weightlessness rates were used to express the levels of the nickel reduction. The influences of reduction temperature, reduction time and flow rates of hydrogen on weightlessness rates were also investigated. The weightlessness rates reached to18.56%, and the reduction rates for nickel were52%at the temperature of400℃for30minutes with the hydrogen flow rates of0.4L·min-1.