The roasting process is actually a process in which the green body is carbonized into a binder coke through heat treatment. That is, the pressed green body is placed in a roasting furnace, and the air is isolated for heating. The binder undergoes a series of physical and chemical reactions at a certain temperature to form a certain thickness of coke film on the surface of the carbon aggregate. Through the binder coke, the carbon powder particles and the particles are connected into a whole with certain mechanical strength and physical and chemical properties.
Its purpose is:
(1) Obtain bonded coke, so that the dispersed carbon particles can become an organic whole, that is, the bonding agent can complete the carbonization process.
(2) The product structure tends to be more uniform, and there are no defects such as internal and external cracks, voids and pores.
(3) Make the product have a certain geometric size, shape, mechanical strength and performance. The mechanical strength and performance of calcined products depend on the amount of coke converted from binder into binder during baking, and the mechanical performance is directly related to the coking value.
The heating speed is a very important factor affecting the roasting process. The heating speed first determines the temperature distribution of the product and the temperature distribution of the product in the entire furnace chamber. Because the temperature of each part of the product is different, they have different pyrolysis reactions at the same time, which causes uneven volume shrinkage of the product, and also produces harmful internal stress. This internal stress can cause plastic deformation at low temperatures; when the product hardens and becomes brittle at a higher temperature, this internal stress will cause the product to crack. The heating speed also has a great influence on the coke yield of the binder. As the heating speed becomes slower, the coke yield always increases. It has been proved that as the coke yield increases during roasting, the strength and density of the product increase. However, a slower firing curve will cause a reduction in furnace productivity. Therefore, the roasting curve should be optimized, it should not only ensure the process requirements, but also meet the economic benefits of the roasting process.
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