What are the advantages of choosing silica molybdenum bricks for cement rotary kiln?
  • Time:Feb 03, 2023
  • Views: 1

      Silica brick, which has the homonym of "wear-resistant brick", was once called HMS high wear-resistant brick, and its wear resistance coefficient is more than five times higher than that of phosphate-bonded high-alumina bricks. In terms of its phase composition, it is a silicon carbide-mullite product, referred to as silicon mollite brick. In recent years, silica molybdenum bricks have been widely used in cement rotary kilns, especially with the emergence and large-scale of new dry process kilns, the speed of kiln and the intensity of thermal stress in the kiln have been greatly improved, and new requirements have been put forward for the material and physical and chemical properties of refractory materials. higher requirements. Therefore, except that the firing zone of the cement rotary kiln is still using magnesia-chrome bricks under the protection of the kiln skin, the effect of the secondary firing zone, transition zone, and cooling zone is obviously better than that of magnesia-chrome bricks after switching to silica-molybdenum bricks. brick.

1. The product has compact structure and good wear resistance

      The main crystal phase of silica-molybrick is composed of high hardness mineral corundum (Mohs hardness 9.0~9.2), silicon carbide (Mohs hardness 9.0~9.5), and mullite (Mohs hardness 7.0~7.5). The structure of the product is dense, and the bulk density is generally 2.7~3.0g/cm³. The normal temperature wear resistance of refractory materials depends on its strength and compactness of structure. Materials with high strength and density have better wear resistance. The lining of cement rotary kiln is subject to the rolling friction of materials for a long time, and wear is one of the main reasons for the damage of refractory lining.

      Silica bricks have a good effect in the secondary firing zone and filter zone of cement rotary kiln. It can be said that good wear resistance plays a very important role.

2. High softening temperature under load, good high temperature performance

      The load softening temperature of silica bricks is above 1450°C, and the highest is above 1650°C. Different brands of products have different softening temperatures under load. Different parts of the cement rotary kiln lining have different temperature on the brick surface. HMS-1680 grade can be selected for the secondary firing zone and the front transition zone, and the lower temperature parts such as the rear transition zone and cooling zone. HMS-1650, HMS-1550 and other brands can be selected.

      The load softening temperature indicators of these bricks are also higher than the commonly used anti-stripping high-alumina bricks and phosphate high-alumina bricks (the load softening temperature is 1300~1520°C).

      Silica bricks have a compact structure, especially the surface of silica bricks forms a continuous SiO2 dense layer, which infiltrates molten substances, and Al2O3, SiC, CO2 and other gases react violently and do not chemically react with cement materials, so the corrosion resistance is relatively low. powerful.

      Secondly, silica bricks have good thermal shock stability. Since silica bricks contain a certain amount of SiC, it is well known that SiC has high thermal conductivity and relatively small thermal expansion coefficient, which significantly improves the thermal shock stability of the product. The 1100°C water cooling test is more than 10 times, up to 46 times, so Silica bricks for cement rotary kiln do not peel off or break, and can significantly increase the service life.

3. Reduce the temperature of the kiln body and have good heat insulation performance

      The thermal conductivity of silica bricks [2.3~2.5W/(m·K)] is lower than that of alkaline products [2.69~2.74W/(m·K)], so the heat insulation effect of silica bricks is better. Silica bricks are used in the secondary firing zone, transition zone, preheating zone, kiln tail, tertiary air duct, calciner and other parts of large rotary kilns. Compared with alkaline bricks, the surface temperature of the cylinder body can be reduced by more than 100 °C.

      The silicon molybdenum bricks produced by ZHENJIN REFRACTORIES use high-quality silicon carbide and high-purity bauxite clinker as the main raw materials. A dense glaze film is formed on the lower surface, which prevents the refractory lining from reacting with the material, delays the rate of penetration and erosion, and makes the product have high resistance to chemical erosion and excellent wear resistance, and the product has good thermal shock resistance. It is widely used in rotary kiln.


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