Technologies built on the leaching of nickel compounds from its products find wider use in a nickel metal than copper metallurgy. In both cases the use of hydrometallurgical processes, precious metal extraction is regulated during the processing of raw ferrous metals. In this regard, the processing of oxidized nickel ores, hydrometallurgical methods are more common than in the metal processing of copper or copper-nickel ores. But now more and more attention is paid to the intermediate products hydrometallurgy of copper-nickel production — processing of copper-nickel nis. Almost all of the technology based on non-ferrous metals leaching from oxidized nickel ores, pyrrhotite concentrates, intermediate products using sulfuric acid, ammonia and hydrochloric acid solutions.
Leaching is carried out at atmospheric and elevated pressure at relatively high temperatures in special sealed devices — autoclaves. High temperature and pressure can accelerate the speed and completeness of chemical reactions. Such processes are called autoclave.
For processing oxidized nickel ores are known ammonia technology. The oxidized nickel ore is subjected to reductive roasting when the iron is reduced to magnetite, and nickel and cobalt to metals. The cooled calcine is leached with a solution containing 7.5% ammonia and 6.4% CO, with a turboaeratorah pnevmoperemeshivaniem. The chemistry of the process is as follows:
Ni + 6NH3 + CO2 + ½ O2 = Ni (NH3) 6 CO3
Nickel goes into solution in the form of iron hydroxide and most of the cobalt is in the tails leaching. leaching solutions were subjected to thermal decomposition by heating with steaming. In this form insoluble compounds of nickel and cobalt. The pellet was calcined in tube furnaces, which leads to the formation of nickel oxide containing 88% Ni and 0.7% Co. Extraction of nickel from the ore is 75% and the recovery of cobalt — 20%.
Known technique of ammonia leaching of copper and nickel in the four-chamber autoclaves kotsentratov volume of 120 m³. Processing concentrates ammoniacal solution is carried out at temperatures of 77−82 ° C, a pressure of about 700 MPa. The solution passes nickel, cobalt, copper, and iron is oxidized and precipitates. as gdrooksida. Copper is released from solution by heating do110 ° C in the form of copper sulfide. Nickel is reduced with hydrogen to the metallic state. After separation of cobalt, nickel from solution by precipitation with hydrogen sulfide released in the form sudfida. From the residual liquid by crystallization of ammonium sulfate is released. The main disadvantage is the complexity of the technology of ammonia utilization of ammonium sulfate, ammonium as a major participant in the technological schemes of conditions of the Arctic.
According to the sulfuric acid leaching oxidized nickel ore is treated with sulfuric acid solution at a pressure of 0.4−0.5 MPa in the vertical autoclaves at temperatures of 240−250 ° C. The solution was transferred to 95% nickel, cobalt and a small amount of iron. the leach solution is purified by conventional techniques for iron, neutralized and treated with hydrogen sulfide. This yields a sulfide concentrate containing 55−60% nickel and 6.5% cobalt. The final extraction of metals from ores is about 90%.
In use NMSC POX technology solutions of sulfuric acid for processing pyrrhotite concentrates containing up to 4% Ni, up to 3,5% Co, 54% Fe, and 30% S. The leaching is carried out using oxygen in the autoclave 100 m³ at 108 ° C. Non-ferrous metals into solution. As a result of autoclave processing iron goes into solution in the form of hydroxides and sulphate is reduced to elemental sulfur.
Autoclaves exiting pulp enters reactor with mechanical stirring. When processing solution in the slurry reactors metallized iron ore pellets reaction proceeds
MeSO4 + Fe + S ° = MeS + FeSO4,
where Me — non-ferrous metal -nikel, copper, cobalt.
The sulfides formed by the reaction of copper, nickel and cobalt, which are allocated in the sediment. Serosulfidnaya pulp is fed to the flotation separation of sulfur from the concentrate and tailings waste rock and iron hydroxide. Serosulfidny resulting concentrate is sent to a second flotation to produce a sulfide concentrate and sulfur concentrate. Sulphide concentrates of nonferrous metals melted in a pyrometallurgical technology to matte. Of the sulfur concentrate obtained sulfur commodity to the consumer. Due to the fact that the production of sulfuric acid in the Norilsk region unprofitable due to its transport to the mainland enterprises, transport of sulfur does not cause such difficulties. Further processing of sulfur to sulfuric acid may be carried out under any conditions.