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Chemical composition and fire resistance of silica
Jan 24, 2018

The presence of Al2O3, in addition to increasing the tendency of silica to form liquids at elevated temperatures, also slows down the decomposition of silica. The Al2O3 content will decrease the load softening point of brick, the Al2O3 is 2%, the load softening point decreases 125°c;al2o3 6%, then the 275°c is reduced. Therefore, the general control of al2o3<1.3%, the production of high-quality silica brick requires 0.5%. Na2O, K2O is a very strong flux, on the one hand it is a significant reduction of the refractory silica, on the other hand they can promote the transformation of quartz, the requirements of the NA2O+K2O is generally not more than 0.2%~0.4%. The effects of impurities such as Fe2O3, CaO and MgO on the quality of silica rock are not as large as K2O, Na2O and Al2O3, and if they are dispersed, they can be considered as beneficial components. TiO2 does not affect the conversion of quartz, but the study shows that the addition of rutile (TIO2) reduces the porosity of silica brick, enhances the bulk density, promotes sintering, thus enhances the thermal conductivity of silica brick and improves thermal shock stability, which is particularly useful for coke oven silica bricks. It is proved that the effect of adding 1.5% rutile is better. If the chemical composition and fire resistance to determine the quality of silica stone, it is not enough, but also must consider its structure, calcination properties and other factors. Some silica raw materials, such as pulse quartz, chemical composition is very pure, fire resistance is very high, but not the ideal raw materials for the manufacture of silica, because of its crystalline particles, high swelling, quartz difficult to convert, and sintering easy to crack.

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