Silica (SiO2) content of not less than 93% of the refractory products.
Silica seven variants and a crystalline amorphous variants. These variants can be divided into two categories: the first variant of quartz, tridymite and cristobalite, and their crystal structure is very different from each other into very slow; second variant is the variant subspecies -αβ and gamma type, their structural similarity between rapid transformation. In theory, the transition between them is shown in Figure 1.
Silica brick
The raw material for the manufacture of silica brick silica. The higher the silica SiO2 content of the raw materials, the higher refractoriness. The most harmful impurities is Al2O3, K2O, Na2O, which can seriously degrade the refractoriness of the refractory products. As raw material, silica brick silica SiO2 content of not less than 96% of the mineralizing agent (such as iron scales, milk of lime) and binder (such as molasses, sulfite pulp waste), mixing, forming, drying, burning into other processes in the system.
Silica bricks are acidic refractories having a good acid resistance of the slag erosion ability, softening temperature under load of up to 1640 to 1670 ° C, the volume of long-term use at high temperatures is relatively stable.
Silica brick mine mainly composed of tridymite and cristobalite, as well as a small amount of quartz and glassy. Tridymite, cristobalite and residual quartz polymorph changes at low temperatures due to the volume of large changes the silica brick poor thermal stability at low temperatures. The use of the process, at 800 ° C or less for slow heating and cooling, in order to avoid cracks. So should not be below 800 ° C use thermal shock furnace. The microscopic structure of the silica bricks of the coke oven shown in Figure 2.
Silica brick
The nature of the silica bricks and the process the polymorph transformation is closely related with the SiO2, therefore, the true specific gravity of the silica brick is an important quality indicators. General requirements, high-quality silica brick 2.35 2.38. True specific gravity is small, the number of tridymite and cristobalite reflect brick, a small amount of residual quartz, and thus the residual linear expansion, use intensity decreased less.
Silica brick is mainly used for masonry carbonization chamber of coke oven and the wall of the combustion chamber, the kiln top of the glass tank furnaces, pool walls, silicate products, firing kiln. Modern large-scale coke oven, in order to improve the production capacity of the coke oven carbonization chamber and the combustion chamber of the furnace wall thinning, and therefore requires the use of a high density, high thermal conductivity silica brick.
