Limestone calcination temperature
The calcination rate of limestone has a great relationship with the temperature. Under normal pressure, the decomposition temperature of limestone is 898℃, and it will decompose rapidly when the temperature is higher than 925℃. When the calcination temperature is 900°C, the decomposition rate of limestone is 3.3mm/h; 1000°C is 6.6mm/h; 1100°C is 14mm/h. It can be seen that increasing the calcination temperature can accelerate the decomposition of limestone. However, when the calcination temperature is greater than 1100 °C, over-burning is likely to occur, the lime grains increase rapidly, the lime activity becomes poor, the digestion time increases, and the product quality decreases. Therefore, in actual production, the calcination temperature should be controlled at about 1050 °C.
Limestone particle size, shape
The calcination speed of limestone depends on the particle size of limestone, the larger the particle size, the slower the calcination speed. The decomposition of calcium carbonate in limestone is promoted layer by layer from the surface to the inside. The thermal conductivity of quicklime is smaller than that of limestone. The thicker the lime layer, the worse the thermal conductivity and the longer the heat transfer time; and the more difficult it is to decompose CO2 inward. Escape, resulting in the formation of lime that is in a high temperature state for a long time, causing the CaO crystals to gradually increase and the decomposition rate to decrease. It can be seen that the decomposition time of limestone with large particle size is longer than that of small particle size, and the calcination is more difficult.
Fuel particle size, proportioning ratio
In the process of limestone combustion, the proportion of fuel is the key to affect the calcination and decomposition of limestone. If the ratio is too low, the temperature cannot meet the requirements, the calcination is not sufficient, and the lime burns seriously; on the contrary, if the ratio is too large, it is easy to cause nodules. Therefore, the combustion ratio should be appropriate, and the operation measurement should be accurate. In actual production, the proportion should be adjusted timely and reasonably according to the limestone particle size, fuel particle size, water content, kiln shutdown time, lime quality and output changes. Usually, the proportion of anthracite is 2% higher than that of coke.
Air supply volume
In general, the control of air volume is expressed by pressure, that is, air supply pressure. When the fuel ratio is appropriate, the size of the wind pressure will affect the upward or downward movement of the calcination zone in the lime kiln, and at the same time affect the change of the kiln gas during the calcination process. The main components of kiln gas are: CO2, CO, O2, respectively, should control ϕ(CO2)=40～42%, ϕ(CO)＜0.4, ϕ(O2)≤1.0.
