The performance and use requirements of refractory materials are different for different types, sizes and structures of kilns for producing glass. The shaped refractory materials used in the glass industry, especially float glass kilns, mainly include three categories: fused cast refractory materials, silica bricks and magnesia refractory materials.
Silica bricks are traditional products of refractory materials for glass kilns, which refer to refractory products with SiO2 content ≥93%. Silica bricks are made of silica with SiO2 content ≥96% as raw materials, added with mineralizers and binders, 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.
Silica bricks are acidic refractory materials with strong resistance to acid erosion. Silica bricks have the characteristics of high load softening temperature, low density and low price. They are widely used in thermal equipment such as carbonization chambers, combustion chambers and partitions of coke ovens, glass tank kilns and kiln roofs, tank walls, high-temperature load-bearing parts of hot blast furnaces, and carbon roasting furnaces.
Silica bricks for glass tank furnaces are mainly used for the large arch of the melting furnace and part of the flame space. The quality of silica bricks is related to the normal operation and life of the melting furnace. Silica bricks have gone through three generations of development since their advent.
1. The first generation of silica bricks is the traditional ordinary silica bricks, and the second generation is advanced silica bricks. Compared with ordinary silica bricks, it has the characteristics of "three highs and three lows". "Three highs" refers to high purity (SiO2 content> 96%), high load softening temperature (> 1685℃), high content of scale quartz and cristobalite (high scale quartz and cristobalite content> 90%); "three lows" refers to low impurity content (Al2O3+2R2O≤0.5%), low true density (≤2.34g/cm3), and low residual quartz (≤3%).
2. The third generation is an improved brick of the second generation. The CaO content is reduced from the original 2%~3% to below 1%, the alkali metal oxide content is further reduced than 0.5%, the FeO content is below 0.2%, and the apparent porosity is reduced from 20%~22% of the second generation to 16%~18%.
The production technology of silica bricks in my country is relatively mature, but the product quality varies. With the development and promotion of full oxygen combustion technology in glass kilns, the silica bricks used tend to require lower apparent porosity and lower melting index. At the same time, in order to reduce the rat holes generated when used in glass melting furnaces, the prepared materials are required to have fewer structural defects and dense bonding of fire mud between expansion joints.
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