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Selection and Advantages of Refractory Materials for Cement Rotary Kiln Preheater
In modern cement production process, rotary kiln preheater plays a key role. Its internal working conditions are extremely complex and harsh. Therefore, the rational selection of refractory materials has become one of the core elements to ensure the efficient and stable operation of preheater.
The function of preheater is to use the preheating of rotary kiln and grate cooler to preheat cement raw material. In this system, preheater generally has 4-6 levels (the highest level is the first level). The cement raw material that has been homogenized and prepared enters the preheater from the highest level through the material pipe step by step to complete dehydration and preheating. The tertiary air duct introduces the cooling air preheating into the last level preheater. The logistics flows downward and the hot air is discharged upward. Heat exchange is carried out step by step to realize the preheating process of cement raw material.
Since both preheater and decomposition furnace are stationary equipment, a larger equipment shell can be used to accommodate more refractory materials. Therefore, insulation materials with lower thermal conductivity are selected to reduce the temperature of the equipment shell and achieve energy saving.
Some preheaters and decomposition furnaces have complex shapes, and refractory castables with more flexible molding can be selected.
The upper area of the preheater usually has a temperature range of 400-700℃, which is relatively low compared to the entire preheater system. However, the content of harmful components such as alkali, chlorine, and sulfur in the air flow in this area is relatively high. Under this working condition, high-aluminum refractory materials are the first choice. High-aluminum refractory materials contain a high proportion of alumina (Al₂O₃), and their crystal structure gives the material good thermal shock stability, which can withstand rapid changes in temperature without cracking. At the same time, its chemical composition makes it resistant to harmful components such as alkali, chlorine, and sulfur, effectively preventing the material from peeling off due to chemical erosion, thereby effectively ensuring the structural integrity of the preheater. Moreover, from the perspective of economic cost, the price of high-aluminum refractory materials is relatively moderate. While meeting production needs, it has a high cost-effectiveness and reduces production cost investment for enterprises.
As the preheater moves downward, the temperature gradually increases in the middle and lower areas, reaching 800-1000℃ or even higher. At this time, more stringent requirements are placed on the high temperature resistance of refractory materials. Anti-stripping high-alumina bricks stand out and become the ideal material for the working conditions in this area. Anti-stripping high-alumina bricks are made on the basis of traditional high-alumina bricks through special process treatment and formula optimization. Its internal structure is more dense and uniform, and the adhesion between the brick body and the kiln body is significantly enhanced. During the operation of the preheater, even in the face of frequent temperature fluctuations, the thermal stress generated is unlikely to cause the material to spall. This not only reduces the number of equipment repairs and downtime caused by refractory damage, reduces maintenance costs and production losses, but also ensures the long-term stable operation of the preheater and extends the overall service life of the equipment. This ensures the continuity and stability of the cement production process, laying a solid foundation for enterprises to stabilize production, improve production efficiency and create better economic benefits.
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