Carbind and Nitride Composite Brick, Silica Mullite Refractory Brick

The main crystalline phase of silica brick is composed of high hardness mineral corundum (Mohs hardness 9.0~9.2), silicon carbide (Mohs hardness 9.0~9.5), mullite (Mohs hardness 7.0~7.5). The product structure causes high density, and the bulk density is generally 2.7~3.0g/cm³. The wear resistance of the refractory at room temperature depends on its strength and the density of the structure, and the material with high strength and density has better wear resistance. The lining of cement rotary kiln is subjected to rolling friction of materials for a long time, and wear is one of the main reasons for the damage of refractory lining. The density, strength and wear resistance of Silmo refractory brick are better than those of high alumina brick and magnesia alumina spinel brick. Silmo refractory brick in cement rotary kiln secondary firing belt, filter belt and other parts of the use effect is good, it can be said that good wear resistance plays a very important role.

The load softening temperature of silica brick is above 1450ºC. Different brands of products have certain differences in softening temperature under load. The surface temperature of refractory brick in different parts of the cement rotary kiln lining is different, and the temperature of the secondary firing zone and the former transition zone is about 1400ºC, which is higher than the surface temperature of refractory brick in the firing zone (because the firing is protected by the kiln skin, the surface temperature of refractory brick is 900~1000 ºC). The load softening temperature index of these bricks is also higher than that of frequently used high alumina brick and phosphate high alumina refractory brick (load softening temperature of 1300~1520 ºC).

Compared with the sintering zone, the transition zone is easy to be affected by reducing atmosphere and thermal load due to the lack of kiln skin protection, and its service life has always been the bottleneck problem of cement rotary kiln, so some cement factories use magnesia-aluminum spinel products in the transition zone. According to the study of MG-Al spinel brick used in transition zone of a 5000 t/d large-scale cement rotary kiln in a factory, MG-Al spinel brick used in transition zone basically has no erosion, but the structure is densified due to alkali deposition in the opening porosity, resulting in the formation of different sections of the same refractory brick, and the hot surface of the refractory brick is spalled and cracks are produced, resulting in the lining damage. The silica refractory brick due to its dense structure, especially the formation of a continuous SiO2 dense layer on the refractory brick surface, prevent the penetration of molten substances, coupled with Al2O3, SiC, SiO2 chemical properties are stable, do not react violently with SO2, O2, CO2 and other gases produced in the kiln, do not produce chemical reactions with cement materials, so the corrosion resistance is strong. Secondly, the thermal shock stability of silicon Mo brick is good. Because silica brick contains a certain amount of SiC, as we all know, SiC thermal conductivity is high, thermal expansion coefficient is relatively small, so that the thermal shock stability of the product is significantly improved, 1100ºC water cooling test is more than 10 times, the peak can reach 46 times, so the cement rotary kiln silica brick does not flake, do not break, can significantly improve the service life.

Application of Silica mullite brick in cement rotary kiln:

The brick surface temperature of the transition zone of cement rotary kiln is about 1400ºC, the temperature of the pre-heat zone, cooling zone and other parts is lower than the transition zone, that is, the burning zone is protected by the kiln skin, the brick surface temperature is not high, the load softening temperature of silica brick is above 1500ºC, especially the product structure is dense, composed of high hardness minerals, corundum, silicon carbide, mullite, etc. Wear resistance is particularly good, is the ideal brick for the transition zone. The compressive strength and load softening temperature are significantly higher than that of high-alumina brick, and its thermal shock stability, corrosion resistance, good wear resistance, and thermal conductivity are not high, which are exactly the requirements of the post-transition zone process characteristics, and the service life is 1.5 to 2 times that of anti-peeling brick. Good wear resistance is more suitable for cooling belts, and the service life can reach more than two years, which is 3 to 5 times the life of high aluminum bricks. Now according to the use conditions of different sections of the rotary kiln, different grades of silicon Mo bricks with different properties have been applied.