Nickel refinery process


Since nickel ores and concentrates with a low-grade, complex composition, much associated gangue, belonging the refractory materials and other characteristics, therefore the production method of nickel is more complex. According to the different types of ore grade and user requirements, can produce a variety of different forms products, usually has pure nickel class, such as: electrolytic nickel, nickel block, nickel ingots, nickel powder; non pure nickel categories: sintered nickel oxide and nickel-iron and so on. The past 30 years , mainly in non- pure nickel dominated. International non-pure nickel consumption is account for more than 30% of total consumption.

Since high nickel matte contains nickel and sulfur, except that also contains a considerable quantity of copper, and the enrichment of the raw material metals, precious metals and cobalt, therefore high nickel matte copper-nickel separation and refining of the outstanding problems in the nickel smelting process, also the production key of handling sulfide ore for many years. In the early stages of the development of nickel metallurgy, usually use four ways to deal with high nickel matte, namely layered melting method, the beneficiation grinding floating separation, selective leaching and low-pressure-based method.

The basic theory of layered melting method is: mixed melted high nickel matte and sodium sulphide, in the molten state, copper sulfide is highly soluble in Na2S, and nickel sulfide is difficult to dissolve in Na2S. The density of copper sulfide and nickel sulfide is 5300-5800kg/m3, and the density of Na2S is only 1900kg/m3. High nickel matte and Na2S mixed melting copper sulfide Na2S within floating on the top floor of their density, while nickel sulfide stay at the bottom of its density.

When the temperature drops to freezing temperature, the two are separated more completely, it is easy to separate the top and bottom layers after solidification. In order for the copper sulfide and nickel sulfide better separation, the top and bottom were respectively layered melting again, regain copper sulfide and nickel sulfide until meet process requirements.

Since this method processes complex, poor working conditions and high production costs, In addition to individual factories still in use after the revamped, basically been eliminated now.

Use grinding float separating copper and nickel – the soluble anode electrolytic traditional process, ie: blowing to high nickel matte – translate slag furnace depleted – high nickel matte grinding float separation – anode melting – electrolysis.

The disadvantage of this process is the low production efficiency, high sulfur content of the flue gases discharged into the atmosphere, the large power consumption , the losses of the polyvalent metal.

Wet selective leaching due to its copper-nickel extraction method different can be broadly divided into five categories: sulfuric acid selective leaching electrical product method; the selective leaching sulfate hydrogen reduction; pressurized ammonia leaching-hydrogen reduction; hydrochloric acid leaching; chlorine leaching method. Carbonyl method of production belong to the method of gasification metallurgy. Its high nickel matte component is (%): Ni62, Cu14, S2.0, Fe2, CO1, in the rotating converter with oxygen blown to S 0.2% – 4%, at 180°C, 7.2MPa pressure carbonylation to produce high purity nickel powder and Ni – Fe powder, copper and precious metal enrich in the residue. This method’s efficiency is higher than mond method, but unlike mond method requires raw materials can not contain sulfur and copper.

Though the efficiency of high-pressure method is higher than medium-voltage method, but the process requires in 200 ℃, 18-20MPa pressure, the requirements of mid-pressure method to sulfur and nickel-copper content in the raw material is strictly than the high-pressure method.

From the separation and refining process of the high nickel matte development point of view, the general trend is the separation and refining closely integrated, gradually streamline the processes. But the specific conditions of various methods used are not the same, the reason is related to the ingredients of various methods and the products form requirements are different, on the other hand also shows high nickel matte separation and refining processes to be further research and development.