The lightweight silica heat insulating brick is an insulating refractory product made of silica as a main raw material and having a SiO2 content of not less than 91%. The lightweight silica brick has a bulk density of 0.9~1.1g/cm3, and the thermal conductivity is only half of that of ordinary silica brick. It has good thermal shock resistance, and its softening start temperature under load can reach 1600°C, which is much higher than clay insulation bricks. Therefore, the maximum temperature of the silica insulation brick can reach 1550 °C. Does not shrink at high temperatures. It even has a slight expansion.
Lightweight silica bricks generally use crystalline quartzite as raw material, and flammable substances such as coke, anthracite, sawdust, etc. are added to the batch. Or using gas foaming method to form a porous structure. Similar to the production of ordinary silica bricks, some mineralizers (CaO, Fe2O3) are added to promote the conversion of quartz, and the pulp waste liquid is used as a binder to make the bricks have a certain strength. When coke or anthracite is used as combustibles, since ash will bring in Fe2O3 and Al2O3, no additional iron and phosphorus will be added to the ingredients. When the lightweight silica brick is fired, a strong oxidizing flame should be maintained before 1200 °C, so that the additive is completely burned out.
Generally, the lightweight silica brick has a compressive strength of 2.0 to 9.5 MPa and a thermal conductivity of 0.35 to 0.42 W/(m·K). Lightweight silica bricks have excellent fire resistance. The softening temperature under load is above 1620 °C close to that of dense silica bricks , and its thermal stability is better than that of dense silica bricks. Therefore, the lightweight silica brick can be used for a long time under high temperature conditions at 1500 to 1550 °C which are not in contact with the slag.
