Research On Sulfation Roasting Nickel Laterite Ore Using Ammonium Bisulfate

Nickel laterite is an important resource, and its metallurgical processes have attracted more and more attentions. Aimed at the shortages of traditional sulfation roasting process, such as high energy consumption and equipment corrosion, circulating process by using the roasting agent ammonium bisulfate was presented which can efficiently prepare hydroxides and oxides of metals from nickel laterite.Taking nickel laterite ores from Philippines as raw material, the roasting mechanism and thermodynamics process were analyzed. Major low temperature roasting products were the ammonium sulfate (NH4)2Mg2SO4and (NH4)3Fe(SO4)3. The increase of low temperature roasting temperature and decrease of NH3and H2O partial pressure can be beneficial to increase the leaching recoveries of nickel and cobalt.Influencing factors of leaching rate including sulfation agent dosage, low temperature roasting temperature, low temperature roasting time, feed types, high temperature roasting temperature and high temperature roasting time were discussed. The results indicated that about92%Ni,84%Co,86%Mn,66%Mg and10%Fe were extracted under the optimal conditions.The effect of adding Na2SO4into sulfation roasting process was studied. It showed no obvious impact when add Na2SO4to garnierite during sulfation process. But Na2SO4plays a significant role in the sulfation process of limonitic nickel laterite. The influencing mechanism of Na2SO4was analyzed. Na2SO4promote the extractions of Ni and Co by increasing HSO4-contents and reactive activity of sulfation agent during low temperature roasting process and favoring the reaction of SO3by the formation of sodium pyrosulphate Na2S2O7during elevated roasting process.Ammonia concentration during leaching process was discussed. The extraction of Fe can be reduced by means of regulating the ammonia concentration of the leach liquor during leaching process of low temperature roasting clinker. However, it’s more suitable to reduce the ammonia concentration of the leach liquor during leaching process of elevated roasting clinker.Removing impurity and separating valuable metals for leaching solution were preliminary studied. Using ammonia method, precipitation processes when pH values were4.0,8.0and9.5were conducted in order to effectively separate Fe, Ni and Mg, respectively.With the chief advantages of high Ni and Co extraction, closed circulation and good environment compatible, the process is an effective method for the treatment of nickel laterite especially saprolitic laterite, and it is of significant importance to exploitation and utilization of low grade nickel laterite ore.