Introduction of three stages in the combustion process of pulverized coal in cement rotary kiln

The cement rotary kiln is the main equipment in the production line of the cement plant. The fuel used for calcining clinker is generally coal. It is understood that it takes about 200-300kg of coal to burn one ton of clinker. The coal powder is sent to the cement rotary kiln. Before internal calcination, it is firstly ground into pulverized coal that meets the requirements, and is blown into the cement rotary kiln by a high-pressure blower for combustion. Here is an introduction to the three stages of the combustion process of pulverized coal in the cement rotary kiln.

1. Drying preheating stage

The main purpose of pulverized coal combustion in the cement rotary kiln is to evaporate and dry the water contained in the pulverized coal, which generally takes 0.03 to 0.05 seconds. However, in the case of coarse and wet pulverized coal, the required time will be extended accordingly. The length of this time determines the length of the black flame of the cement rotary kiln.

2. Fractionation and combustion stage

This is the second stage of the combustion of pulverized coal in the cement rotary kiln, which generally takes about 0.01 to 0.03 seconds. As the temperature of the dried pulverized coal increases, the volatile matter begins to fractionate, and the fractionated gas is surrounded by the pulverized coal particles to form a thin film of volatile matter gas, which is in contact with the oxygen in the air entering the cement rotary kiln and burns. , Before the combustion is completed, the carbon particles are isolated by the film, cannot contact with oxygen, cannot be burned, and can only be coked. The length of the volatile matter burning time is related to the amount of volatile matter content, the gas flow rate, and the temperature. The less volatile matter content, the faster the gas flow rate and the higher the temperature, the shorter the burning time.

3. Coke combustion stage

It takes about 0-0.4 seconds for pulverized coal to burn in the cement rotary kiln at this stage. The main function of this stage is to burn the residual coke, and its speed determines the length of the cement rotary kiln flame. The combustion time of coke is related to the coal powder particles, carbon content, air temperature and air volume.

The above are the three stages of the combustion process of pulverized coal in the cement rotary kiln, which is actually related to the quality of the clinker of the entire cement plant production line.