On the one hand, the rotary kiln is a combustion device, in which pulverized coal is burned to generate heat; at the same time, it is also a heat transfer device, the raw material absorbs the heat of the gas for calcination; and the conveying device transports the raw material from the feed end to the discharge end. The fuel combustion, heat transfer and raw material movement must be properly coordinated, so that the heat generated by the fuel combustion can be transferred to the raw materials in time during the passage of the raw materials, which has achieved the goal of high yield, high quality and low consumption.
The various thermal zones of the rotary kiln distributed along the axial direction are the rear kiln opening, the decomposition zone, the upper transition zone, the firing zone, the lower transition zone and the front kiln opening.
The maximum temperature of flue gas in the rotary kiln can reach above 1800, and the temperature fluctuation of kiln material and clinker is above 900~1400.
The post-kiln mouth continuous preheater system (including the decomposition furnace) is washed by the raw material falling from the preheater, and at the same time withstands the high alkali content in the flue gas and the crust erosion of the alkali sulfur compound, requiring the refractory material to have good mechanical strength and alkali resistance. Sex.
The temperature of the flue gas in the decomposition zone is lower than 1300, and the temperature of the clinker is less than 1000. The lining body is subjected to the high alkali content in the flue gas and the crust erosion of the alkali sulfur compound.
The temperature of the upper transition zone is generally less than 1700. Due to the influence of fuel combustion, the temperature of the flue gas changes frequently. When the kiln skin is hung, the lining body directly contacts the flue gas and clinker. The thermal stress undergoes frequent changes and is susceptible to ripening. Abrasion, as well as erosion of high temperature flue gas and alkali sulfide in clinker, and elliptical stress in the barrel of the wheel.
The firing zone is located at the highest temperature of the kiln, the flame temperature is up to 1800~2000, and the temperature of the kiln material is from 1350~1400 clinker forming temperature. The part must form a stable kiln skin to protect the lining brick. In addition, the thermochemical attack of a large amount of alkali sulfur compounds in the kiln material also needs to withstand the thermal shock stress caused by the kiln skin collapse.
The lower transition zone and the front kiln lining are subjected to high temperature air and thermal stress of clinker above 1400, and are more resistant to high temperature dusty airflow and solidification of clinker and dissolution of solution and sulfur alkali compound solution and sulfur alkali compound in clinker. Body and gas erosion, high temperature cylinder deformation and elliptic stress at the belt.
Rotary kiln requirements for refractory materials
(1) Front kiln mouth requirements Wear resistance is good; chemical erosion ability; thermal shock resistance stability is strong.
(2) Requirements for firing zone Thermal shock resistance; corrosion resistance; thermal mechanical strength; performance of hanging kiln skin
(3) Transition zone requires high temperature thermal shock; hot mechanical strength; smaller elastic mode
(4) Decomposition zone requires the connection with the pre-tropical zone. Due to the small thermal stress and chemical erosion, various quality clay bricks and aluminum bricks can be used; the joint with the transition zone is important; blast furnace brick, ordinary magnesium Chrome brick, spinel brick
(5) The requirements of the rear kiln mouth are good for alkali resistance and heat insulation.