Smelting methods: Modern methods for producing nickel mainly include fire method and wet method. According to the world's two main types of nickel-containing minerals (nickel-containing sulfide ore and oxidized ore), smelting treatment methods vary. Nickel sulfide ore mainly pyrometallurgical process, by reflection concentrate roasting furnace (electric furnace or a blast furnace) copper and nickel smelting sulfur-bearing nickel concentrate blowing electrolytic metal to give a nickel. The oxidized ore is mainly nickel-containing laterite ore, which has low grade and is suitable for wet treatment; the main methods are ammonia leaching method and sulfuric acid method. Pyrogenic process is a nickel iron oxide ore method.
Process operation: Pyrometallurgical smelting of nickel sulfide concentrate
Its main process features are as follows:
(1) Melting. After the nickel concentrate is desulphurized, it is sent to an electric furnace (or blast furnace) for melting. The purpose is to convert the copper-nickel oxide into a sulfide, and produce low-ice nickel (copper-nickel-bismuth), while the gangue is slag-forming. In the obtained low-ice nickel, the total content of nickel and copper is 8% to 25% (generally 13% to 17%), and the sulfur content is 25%.
(2) Blowing of low ice nickel. The purpose of the blowing is to remove iron and a portion of the sulfur to obtain high ice nickel (nickel high sulfur) containing 70% to 75% of copper and nickel instead of metallic nickel. The converter smelting temperature is higher than 1230 ° C. Due to the low grade of low ice nickel, the blowing time is generally longer.
(3) grinding and floating. Nickel matte fine grinding, after crushing, magnetic separation and flotation, to give 67% -68% nickel-containing nickel concentrate, while the copper-nickel alloy and copper concentrate selected separately recovered copper and platinum group metals. The nickel concentrate is melted in a reverberatory furnace to obtain nickel sulfide, which is then sent to electrolytic refining or reduced by electric furnace (or reverberatory furnace) to obtain crude nickel for electrorefining.
(4) Electrolytic refining. In addition to copper and diamond, crude nickel also contains gold, silver and platinum group elements, which require electrolytic refining and recovery. Unlike copper electrolysis, a diaphragm electrolyzer is used here. The crude nickel is used as the anode, the cathode is the nickel starting piece, and the electrolyte is mixed with the sulfate solution of the sulfate and the chloride. After electrification, nickel is precipitated from the cathode, and the platinum group element enters the anode mud and is separately recovered. The product nickel purity is 99.85%-99.99%.
Treatment of nickel oxide by pyrometallurgy to obtain nickel iron and metal nickel silicate oxidized ore can be smelted by fire smelting, and reduced, melted and refined to obtain nickel. In the reduction, it is necessary to strive to completely change the nickel oxide into metallic nickel. When melting, the rumor that ferronickel will separate from the lighter slag. The nickel content of ferronickel depends on the ability to select a partial reduction process. Coke is used as a reducing agent, and ferrosilicon can also be used as a reducing agent. In order to remove impurities such as carbon, sulfur, phosphorus and chromium in the crude ferronickel, refining must be carried out. Directly partial reduction of ferronickel with carbon in an electric furnace The ore is reduced to ferronickel by a carbothermal method in a submerged arc furnace, followed by refining.
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