Calcination is a process of thermal dissociation or crystal transformation of a natural compound or an artificial compound; in this case, the compound is thermally dissociated into a simpler compound or undergoes a crystal transformation. Thermal dissociation of carbonate is referred to as baking. Calcination can be used to directly process mineral raw materials to suit subsequent process requirements, and chemical concentrates can be used to prepare chemical concentrates to meet user requirements.
The chemical reaction of the calcination process can be expressed as:
MCO 3 ==== MO+CO 2
MSO 4 ==== MO+SO 2 + â€”â€”O 2
MS 2 ==== MS + â€”â€” S 2
(NH 4 ) 2 WO 4 ==== WO 3 + 2NH 3 +H 2 O
The main factors affecting the calcination process are: calcination temperature, gas phase composition, thermal stability of the compound, and the like. Therefore, depending on the thermal stability of various compounds (such as carbonates, oxides, hydroxides-sulfides, oxyacid salts, etc.), certain compounds can be selectively changed by controlling the calcination temperature and the gas phase composition. The composition or the transformation of the crystal form, and then treated by the corresponding method, can achieve the purpose of removing impurities and separating and enriching the useful group.
Industrial example of calcination:
Example 1 calcined ore siderite - siderite magnetic chemical composition of FeCO 3, pure mineral containing Fe48.2%, equivalent Fe062%, C0 2 38%; siderite is weakly magnetic minerals, neutral or weak Under oxidizing atmosphere, it is heated to above 570 Â°C to convert the siderite into ferromagnetic Fe 3 0 4 ; and then recovered by magnetic separation.
Example 2 calcined apatite - Lin digested phosphorus-containing mineral resources is not high grade ore, should not be directly used to produce phosphate fertilizer, especially gangue minerals dolomite, limestone-based carbonate minerals, because the production of fertilizer In the process, a large amount of sulfuric acid is consumed. The general physical beneficiation method is difficult to separate these gangues, and the calcination-digestion process can effectively remove carbonate impurities and improve the homogenization grade.
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