Overview and basic principles of nickel smelting

(I. Overview
Is made of copper matte smelting, an important step of nickel, cobalt pyro metallurgical process, the main metal sulfides and iron sulfides to prepare a co-melt sulfonium called named. Because the main metal content of the sulfide concentrate is not high enough, in addition to the gangue, it is often accompanied by a large amount of iron sulfide, the amount of which is super hard to fight the main metal, and the crude metal is directly refined from the concentrate by the fire method. There are certain difficulties, such as: 1 metal with large slag loss; 2 high melting point of Fe 3 O 4, affecting the normal operation; 3 crude metal product quality often does not meet the requirements. Therefore, the affinity of copper, nickel and cobalt for sulfur in production is similar to that of iron, and the affinity for oxygen is much smaller than that of iron. In the process of smelting smelting with different degrees of oxidation, the sulfide of iron is continuously oxidized in stages. The oxide is subsequently removed from the gangue. After the main metal enters the 锍 phase through these processes, it is enriched and the grade is gradually improved. The smelting smelting can be realized in a reverberatory furnace, a blast furnace, an electric furnace, a flash furnace, and various smelting furnaces. The smelting smelting of nickel sulphide concentrate is the same as smelting smelting like copper sulphide concentrate. Nickel oxide ore can also be used in the presence of a vulcanizing agent (such as pyrite), first formed into a mass or sintered into a block, and then added to the blast furnace to smelt, the coke rate is 20% - 30%, is a reducing, so it is also called reduction sulfurization smelting .
The smelting materials mainly include sulfide concentrates or fluxes for minerals and slag formation. For the smelting and melting of nickel, the smelting materials include nickel sulfide concentrate or copper sulphide nickel concentrate slag solvent, coke powder, return material, etc., and produce nickel bismuth or copper nickel bismuth, slag, smoke, smoke and the like.
(2) The basis of nickel smelting
1. The main physicochemical changes in the smelting process are smelting and smelting. The smelting furnace is filled with copper-nickel sulphide ore, such as nickel pyrite [(Ni,Fe) 9 S 8 ], containing nickel. Pyrrhotite [(Ni,Fe) 7 S 8 ], pyrite nickel ore (3NiS.FeS 2 ) and pyrrhotite (Fe 7 S 8 ) associated with nickel sulfide ore, chalcopyrite (CuFeS 2 ) , Gong iron ore (FeS 2 ) and Fe 2 O 3 , SiO 2 , MgO, CaO, Al 2 O 3 and other gangue oxides.
These materials undergo a series of physicochemical reactions in the furnace, eventually forming mutually immiscible nickel or copper nickel bismuth and slag. The main chemical reactions are as follows:
1) High-priced sulfides decompose when they are not yet in full contact with oxygen, for example:
Fe 7 S 8 =7FeS+1/2S 2 (gas)
2CuFeS 2 =Cu 2 S+2FeS+1/2S 2 (gas)
3NiS.FeS 2 =Ni 3 S 2 +FeS+S 2 (gas)
(Ni,Fe) 9 S 8 =2Ni 3 S 2 +3FeS+1/2S 2 (gas)
3NiS=Ni 3 S 2 +1/2S 2 (gas) [next]
Decomposition of high-priced sulfides results in the most stable low-valent sulfides at high temperatures of smelting, which have lower melting points, such as nickel sulphide Ni 3 S 2 ( melting point 79 ° C), cuprous sulfide Cu 2 S ( melting point 1135) °C) and ferrous sulfide FeS (melting point 1190 ° C), these low-valent sulfides are not compounds in which metal atoms and sulfur atoms are covalently bonded, and they dissolve in a molten state to form corresponding nickel iridium (NI 3 ) S 2 -FeS), copper bismuth (Cu 2 S-FeS) and nickel bismuth (Cu 2 S-Ni 3 S 2 -FeS), and thus FeO and SiO 2 , CaO, MgO, AI 2 O 3 which have been oxidized The slag formed by the gangue oxide is separated, which is the basis for smelting and melting in copper and nickel pyrometallurgy.
Under neutral or reducing atmosphere, the elemental sulfur released by the above decomposition reaction is a gaseous molecule (sulfur melting point 112.8 ° C, boiling point 444.6 ° C), sulfur vapor encounters oxygen in the furnace gas, it is easy to ignite and burn to generate SO 2 gas .
In modern fortified smelting furnaces, the charge often enters a high temperature and strong oxidizing atmosphere, so high-priced sulphide will be directly oxidized in addition to iron reaction, such as:
2CuFeS 2 +5/2O 2 =Cu 2 S.FeS+FeO+2SO 2
3FeS 2 +8O2=Fe 3 O 4 +16SO 2
2Fe 7 S 8 +53/2O 2 =7Fe 2 O 3 +16SO 2
2Cu 2 S+3O 2 =2Cu 2 O+2SO 2
Ni 3 S 2 +7/2O 2 =3NiO+2SO 2
2FeS+3O 2 =2FeO+2SO 2
3) slagging reaction The FeO produced by the oxidation reaction will form slag in the presence of SiO 2 according to the following reaction:
2FeO+SiO 2 =2FeO.SiO 2
2. △G Θ T -T diagram of smelting related reactions The pyrometallurgical process of nickel sulphide concentrate is similar to copper sulphide concentrate. In essence, iron and sulfur are removed by selective oxidation and slagging through a smelting process. Sulfur can also be removed by calcination. The direction and limits of the relevant reactions can be understood by means of the ΔG Θ T -TT diagram of the phase reaction [see Figures 2-1 (a) and 2-1 (b)]. It is seen from the ΔG Θ T -TT diagram that the affinity of copper and nickel for sulfur and the iron phase continue to oxidize to Fe 3 O 4 , but Fe 3 O 4 is easily reduced to Fe by C at high temperature. At a relatively low temperature (1200-1300 ° C), Cu 2 S is oxidized to obtain metallic copper, and in the same process, a high temperature of 1600 ° C or higher is required for nickel. For nickel smelting, the product of smelting and blowing is a low-iron (0.5%--3%), sulfur-containing (10%--22%) converter nickel crucible instead of crude nickel.

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