After the fuel injected from the rotary kiln outlet with material of volatile is in combustion, it produces high temperature in the furnace. Furnace temperature presents a certain distribution state, which can be roughly divided into the following three temperature zones:

Preheating zone is the beginning of the rotary kiln inlet.The material preheater into the feeding tube above the kiln inlet in this interval is through the combustion gas preheating and drying. The temperature of the preheater is generally 800-900 ℃.

Calcining zone is in the central area of the kiln body of rotary kiln, which accounts for about l / 2 the total length of the kiln. Calcining zone is the key calcination area to material by high temperature, and the material in this area is heated to 1200-1350 ℃.

From calcining zone end to the kiln outlet it is called cooling zone.Material is cooled in the cooling zone, the temperature gradually decreases to 800 ℃- 900 ℃, and then is fell into the furnace cooling. The rotary kiln with the length of 30 m long has only about five-meter-long cooling zone.

To improve the quality of material calcined and production, you must raise the temperature and the length of calcining zone as much as possible. Because the higher the temperature is, the longer the calcining zone will be, and the more material calcining is , the better the quality is .