Silica has seven crystallization type variation and an amorphous type variant.These variations can be divided into two categories: the first kind of variation is quartz, scales, quartz and cristobalite vary their crystal structure, transformation between each other slowly,The second variation is the variation of subspecies ─ ─ alpha, beta, and gamma type their structure similar to that of mutual transformation between faster.In theory, the mutual transformation relationship between them is shown in figure 1.
Silica brick
Raw materials for manufacturing of silica brick of silica.Silica raw materials of SiO2 content is higher, the higher refractoriness.The most harmful impurity is Al2O3, K2O and Na2O, they severely reduce refractoriness of refractory products.Silica brick with SiO2 content not less than 96% of silica as raw material, adding mineralizer (such as iron scales, lime milk) and bond (e.g., molasses, sulfite pulp waste liquid), the mixing, molding, drying and firing practice etc.
Silica acid refractory material, has good resistance to the ability of acid slag erosion, refractoriness under load is as high as 1640 ~ 1670 ℃, long-term use of volume is stable at high temperatures.
Composed mainly of silica scales, quartz and cristobalite and a small amount of quartz and glass.Scale quartz, stones and residual quartz for crystal structure change in low temperature, the volume has great change, so the silica brick under the low temperature thermal stability is very poor.In use process, under 800 ℃ to slow heating and cooling, so as to avoid cracks.So should not be under 800 ℃ temperature leaps of kiln.The microstructure of coke oven silica brick as shown in figure 2.
Silica brick
Processes on the properties of silica brick and crystal transformation has close relationship with SiO2, therefore, true proportion of silica is an important quality index.General requirements under 2.38, the high quality silica brick should be below 2.35.Is the proportion of small, reflected in the brick scale number, quartz and cristobalite small amount of residual quartz and residual small linear expansion, thus less use of strength.
Silica brick is mainly used for laying the partition of the coke oven of coking chamber and combustion chamber, glass tank furnace kiln top, pool wall, calcining kiln of silicate products.Modern large-scale coke oven, in order to improve the production capacity, need thinning coke oven of coking chamber and combustion chamber wall, thus requiring the use of high density and high thermal conductivity silica brick.