During the production process of cement rotary kiln, due to its harsh working environment such as high temperature, chemical corrosion and physical wear, a variety of refractory materials are needed to protect the kiln body and extend its service life. At present, the composition of cement rotary kiln is mainly composed of preheater, decomposition furnace, tertiary air duct, rotary kiln, kiln door cover, cooler and other parts, and the rotary kiln is composed of front kiln mouth, rear kiln mouth, safety belt, upper transition zone, lower transition zone, burning zone and other parts. The refractory materials required for different working environments of each part are also different.
1. Preheater
The preheater of cement rotary kiln is a key equipment in the cement production process. Its function is to use the waste heat of rotary kiln and grate cooler to cool cement clinker to preheat cement raw material, so as to improve production efficiency and energy saving. At present, the commonly used refractory materials for preheater are mainly alkali-resistant castables and alkali-resistant bricks to resist the erosion of alkaline materials on preheater.
2. Decomposition furnace
The function of the decomposition furnace of the cement rotary kiln is to pre-decompose the calcium carbonate in the preheated raw material to generate calcium oxide and carbon dioxide, preparing for the subsequent clinker calcination process. The working conditions of the decomposition furnace are relatively harsh, so there are specific requirements for the selection of refractory materials. Refractory materials such as anti-stripping high-alumina bricks, alkali-resistant bricks, and alkali-resistant castables are usually selected.
3. Tertiary air duct
The tertiary air duct of the cement rotary kiln is an important part of the cooler and hot air duct connecting the rotary kiln system. It plays a key role in combustion support and stability, high-temperature preheating, material transfer and carrying, and heat recovery in cement production. The tertiary air duct needs to withstand high temperature, high-speed airflow, and wear of carrying clinker particles, so alkali-resistant bricks and alkali-resistant castables are usually used to resist high temperature erosion.
4. Rotary kiln
Front and rear kiln mouth
The front and rear kiln mouths of cement rotary kiln are the weak links of kiln lining, especially the front kiln mouth, because they need to withstand the impact of rapid cooling and rapid heating air flow, the wear of high-temperature clinker, and the alkali corrosion of high-temperature harmful gases, so steel fiber reinforced refractory castables are usually used.
Upper and lower transition zones
The upper and lower transition zones of cement rotary kiln are areas with complex working environment in the kiln. The temperature in these areas fluctuates greatly, the kiln skin is not easy to stabilize, and the refractory materials are exposed to high temperature environment for a long time, and are impacted and worn by clinker. Therefore, the thermal shock stability and chemical erosion resistance of refractory materials are required to be high. Therefore, magnesium-aluminum spinel bricks, silicon-molybdenum wear-resistant bricks, anti-stripping high-aluminum bricks, magnesium-aluminum-chrome bricks, phosphate-bonded high-aluminum wear-resistant bricks, phosphate-bonded high-aluminum bricks and special phosphate-bonded high-aluminum bricks are usually selected.
Safety belt
The safety belt of cement rotary kiln refers to a specific area in the kiln. This area is usually located in the middle of the kiln, where the material begins to react chemically and burn. Usually, anti-stripping high-alumina bricks, phosphate-bonded high-alumina wear-resistant bricks, phosphate-bonded high-alumina bricks or steel fiber reinforced refractory castables are mainly selected.
Firing zone
The firing zone of the cement rotary kiln is the part with the worst working environment in the whole system. It is directly related to the quality and output of cement clinker. Therefore, the requirements for refractory materials are extremely strict. The working temperature is usually 1300~1450℃, so direct-bonded magnesia-alumina bricks, magnesia-alumina-chrome bricks, magnesia-alumina spinel bricks, anti-stripping high-alumina bricks, direct-bonded magnesia-chrome bricks and semi-direct-bonded magnesia-chrome bricks are usually used.
5. Kiln door cover
The kiln door cover of the cement rotary kiln is located at the kiln head of the rotary kiln. Its main function is to protect the kiln head from high temperature and chemical corrosion. It also seals the kiln head to prevent heat loss and leakage of harmful gases. Therefore, in the selection of refractory materials, anti-stripping high-alumina bricks or 75% high-alumina bricks are usually used for masonry.
6. Cooler
The cooler of cement rotary kiln is a quenching cooling equipment, which is mainly used for rapid cooling, transportation and heat recovery of high temperature clinker. Usually, the choice of refractory materials is mainly anti-stripping high-alumina bricks, special phosphate-bonded high-alumina bricks, or phosphate-bonded high-alumina wear-resistant bricks.