Mullite lightweight bricks are used in insulation layers to play a role in heat preservation and energy conservation. However, in furnace linings with low corrosiveness, they can be used in the working layer (the area directly in contact with the flame).
For neutral furnace linings, JM23, JM26, JM28, JM30, JM32 can all be used directly in contact with flames. Especially the bricks of JM30 and JM32, like alumina hollow sphere bricks, can be used in high temperatures. Currently, the bricks which used in the insulation layer on the market also have clay lightweight bricks and high alumina lightweight bricks. The mostly used insulation layer brick is clay lightweight brick. Since the thermal conductivity of clay lightweight bricks and polymeric lightweight mullite bricks is not significantly different, it is only necessary to select lightweight bricks of the appropriate material density at the right temperature.
Polymeric lightweight mullite bricks are high-end insulation materials. Moreover, when the furnace temperature is high, choosing polymeric lightweight mullite bricks with different bulk densities and different service temperatures can all play a role in insulation and energy conservation. In some special furnace linings, especially the outside temperature of the furnace is low, mullite lightweight bricks can be selected for both the insulation layer and the working layer.
However, for some strong acid and strong alkali furnace linings, the working layer is not suitable for using lightweight bricks. That's because when the corrosiveness is high, the strength of lightweight bricks is not strong, and the corrosive slag will erode through the lightweight bricks. But if alumina hollow sphere bricks are used, they can also be used.
Based on the current market usage, mullite lightweight bricks are mostly used in insulation layers. Under conditions where the temperature outside the furnace shell is required to be low and the temperature and environment are suitable, mullite lightweight bricks can be selected. They can also be built in multiple layers. JM23 can be used for areas close to the furnace shell, and JM28, JM30, and JM32 can all be chosen for flame usage. It is segmented and itself serves as an insulator. It's lightweight type and the performs even better when used in light-duty kilns.