What is calcination + leaching?
Calcination is a process of thermal or crystal transformation of a natural compound or an artificial compound; at this time, 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:
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 enriching the useful components.
Leaching is the process of adding a solid material to a solvent to selectively dissolve the solvent into certain components of the mineral feedstock. Therefore, the task of leaching is to select a suitable solvent to transfer the target component into the solution, and the leaching itself is the extraction and separation process of the target component.
The reagent for leaching is called a leaching agent, the solution obtained by leaching is called a leaching solution, and the residue after leaching is called leaching slag. In practice, the leaching rate is measured by the leaching rate of useful components or impurity components, the selectivity of the leaching process, and the reagent consumption. The leaching rate of a component is the percentage of the component transferred into the solution and its total amount in the raw material under leaching conditions, ie
Where ε - the leaching rate of the target component, %; Q - the dry weight of the material, tons; a - the grade of the target component, %; V - the volume of the leachate, meters. ; C - the concentration of the target component in the leachate, t / m 3; m - dry weight of the dross, tons; δ - slag grade, %.
Therefore, the leaching rate essentially refers to the percentage of the target component that is leached by the solvent. This is an important indicator, which reflects whether the leaching process is technically reasonable and reflects the degree of utilization of resources. The leaching operation should be obtained as much as possible. The highest leaching rate of the target component.
There are many common leaching methods, and there are various classification methods. See Table 7-1 for classification of leaching reagents.
Table 7-1 Leaching method and its application range
According to the movement mode of the material in the leaching process, it can be divided into percolation leaching and stirring leaching. The diafiltration leaching process is a leaching process of the leaching reagent from top to bottom or under pressure by the fixed material layer under the action of gravity, and is further divided into in-situ percolation leaching, heap leaching and tank leaching. Stirring leaching is a leaching process in which the ground material and the leaching reagent are vigorously stirred in a stirred tank.
According to the temperature and pressure conditions of leaching, it can be divided into high temperature and high pressure leaching and normal temperature and atmospheric pressure leaching. At present, atmospheric pressure leaching is more common, but high temperature and high pressure leaching can accelerate the leaching process and improve leaching efficiency, which is a promising leaching method.
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