The Study Of Theory And Technology Of Recovery Of Co, Ni And Cu From Nickel Converter Slag

Valuable metals, such as Co, Ni and Cu are present in converter slagof the nickel smelter, it is very important for economy and environmentalprotection to recover these valuable metals. In order to enrich, separateand extract these valuable metals, the theory was studied in detail inmineralogy, thermodynamics and so on in this paper, a flowsheet torecover cobalt, nickel and copper in slag was presented, which is"Enriching Co and Ni by reduction and sulfurization—Selectiveleaching matte—Effective refining solution of leaching—Separatingand extracting cobalt and nickel", and abbreviated and enlargedexperiments of the flowsheet were completed. The main points andcontent of the paper are indicated as following:(1) Producing cobalt matte by carbothermal reduction and pyritesulfuration of nickel converter slag at high temperatureA mineralogical study of coverter slag shows that the most of cobaltand nickel exist in fayalite of a kind of silicate minerals as a form ofoxide and the rest of cobalt and nickel and most of copper in slag assulphide. Reducing agent carbon reduces oxide of cobalt, nickel and iron,and sulfuring agent Fe₂S forms trickles of matte at high temperature, inthe process of assembling and settling of trickles of matte slag is washed,reduced metals of iron, cobalt and nickel and sulphide in slag are enrichedin the matte to form cobalt matte and be separated from slag due to theirintimity to the matte, washing of the matte and their settling.(2) The theory and technology of selective leaching cobalt matte atatmospheric pressureThe cobalt matte is mainly made of of metals of Fe, Co, Ni andtheir sulphides and CuS. The study of thermodynamics of cobalt matteshows that iron mainly exists as form of Fe²⁺ when pH is less than 1.78,cobalt and nickel mainly exists as CoS and NiS as pH is up 0.63 andthere is enough H₂S in the solution, and copper exists in the leachingresidue as form CuS all through in the process of acid leaching.So the cobalt matte can be leached by steps, at first the end of pH ofleaching solution is kept in the range of 0.63 to 1.78, and there is enough H₂S in the solution to selectively leach Fe of the cobalt matte andsulfur and precipitate Co and Ni of the solution at the same time, thenthe leaching residue containing Co and Ni is leached in acid, copper iskept in the end residue. The process of three-step countercurrentleaching is presented, in the first leaching step Fe as leading impurity inthe matte is leached priorly, Co and Ni are enriched in the residue of thefirst step and then are leached in the second leaching step with a lowconcentration acid, the residue from the second step containing hardleaching Fe, Co and Ni are leached with a high concentration sulfuricacid in the third step, and Cu stays in the final resude, the leachate of thethird leaching step is diluted and divided into two parts as the leachantsto the first and second leaching step.(3) Refining and separating of the leaching solutionThe leaching solution is refined by two steps, Fe is removed with themethod of amarillite in the first step, P204 is applied to extract in thesecond step, and then the refined solution is extracted and separated withP507.(4) The technology and application of the recovery of Ni, Co, Cuand Fe from coverter slagA flowsheet to recover Co, Ni and Cu from converter slag ispresented, which is "Enriching Co, Ni and Cu from a slag by reductionand sulfurization—Selective leaching cobalt matte—Effective refiningsolution of leaching—Separating and extracting cobalt andnickel products". Abbreviated and enlarged experiments of theflowsheet were accomplished, there are products of CoC₂O₄·2H₂O,NiSO₄, FeSO₄·7H₂O and the residue of Cu, recoveries of Co, Ni and Cuare 84.43%, 85.48%, 89.17% respectively.