What are silica bricks?
Silica bricks refer to refractory products with a SiO2 content of more than 93%. Zhengzhou Kewei Refractory Silica Bricks are made of silica with a SiO2 content of not less than 96% as raw material, with mineralizers (such as iron scale, lime milk) and binders (such as sulfite pulp waste liquid) added, and are made through mixing, molding, drying, and firing. The higher the SiO2 content in the silica raw material, the higher the refractoriness of the product. Impurity components such as K2O and Na2O are harmful and will seriously reduce the refractoriness of refractory products. Impurities such as Fe2O3, CaO, and MgO act as flux. The raw materials of high-grade silica bricks need to be specially treated to remove impurities.
Characteristics of silica bricks
1 Refractoriness and load softening temperature
The refractoriness of silica bricks is generally between 1690 and 1730°C, and the load softening temperature of silica bricks is relatively high, about 1650°C. The load softening temperature and refractoriness of silica bricks are close, which is mainly due to the fact that the main crystal phase of silica bricks is a network structure formed by tridymite with spearhead twins and a glass phase with high viscosity as the matrix.
2 Slag resistance
Silicon bricks are acidic refractory materials and have strong resistance to acidic and weakly acidic slags and corrosive gases.
3 High temperature volume stability
During the heating process, in addition to a certain amount of thermal expansion, silica bricks also undergo crystal transformation and volume expansion. If there is untransformed residual quartz in the brick, it will continue to become tridymite or cristobalite at high temperatures, which will produce a large volume expansion.
4 Thermal shock stability
The thermal shock resistance of silica bricks is poor, and water cooling at 850°C is only 1 to 2 times. The reason is that during the high-temperature rapid cooling process, the silica brick will undergo a crystal transformation, which will cause a large volume change. This is a major weakness of silica bricks.
Silica bricks are acidic refractory materials with strong resistance to acidic slag or acidic melt erosion, but poor resistance to alkaline substances. They are easily destroyed by oxides such as Al2O3, K2O, and Na2O, and have good resistance to oxides such as CaO, FeO, and Fe2O3.
Therefore, silica bricks are mainly used to build the carbonization chamber, combustion chamber, and partition walls of coke ovens (about 73% of the refractory materials for a coke oven are silica bricks), glass tank kilns and kiln roofs, tank walls, high-temperature load-bearing parts of hot blast furnaces, carbon roasting furnaces and other thermal kilns. In order to improve the production capacity of modern large coke ovens, it is necessary to thin the carbonization chamber, combustion chamber, and partition walls of coke ovens, so it is required to use high-density and high-thermal conductivity silica bricks. There are many varieties of silica bricks, which are divided into silica bricks for coke ovens, silica bricks for hot blast furnaces, silica bricks for electric furnaces, silica bricks for glass kilns, etc. according to their uses. According to the complexity of the brick type, it is divided into standard bricks, general bricks, special-shaped bricks, and special bricks.
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