The principle of muffle furnace calcination is as follows:
Calcination: At a certain temperature, heat treatment is carried out in air or inert gas stream, which is called calcination or roasting.
Calcination is the process of thermal dissociation or crystal transformation of natural or man-made compounds; At this point, the compound is dissociated by heat into a simpler composition compound or a crystal shape transition occurs. The thermal dissociation of carbonates is called roasting.
Calcination operations can be used to directly process mineral raw materials to suit subsequent process requirements, and can also be used for chemical beneficiation post-treatment to produce chemical concentrates to meet the requirements of users for products.
The main physical and chemical changes that occur in the calcination process are:
(1) Thermal decomposition. In addition to volatile impurities such as chemically bound water, CO2, and NOx, at higher temperatures, solid phase reactions may also occur in the oxide to form an active combined state.
(2) Recrystallization, a certain crystal shape, crystal size, pore structure and specific surface can be obtained.
(3) Microcrystallites are properly sintered to improve mechanical strength.
The main factors affecting the calcination process:
(1) Calcination temperature, gas phase composition, thermal stability of compounds, etc. Therefore, the thermal stability varies according to various compounds (such as carbonates, oxides, hydroxide monosulfides, oxygenates, etc.).
(2) By controlling the calcination temperature and gas phase composition, the composition of certain compounds can be selectively changed or the crystal shape transformation can be changed, and then treated by corresponding methods can achieve the purpose of removing impurities and separating and enriching useful groups.
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