Refractory bricks are refractory ceramic blocks used for lining furnaces, kilns, fireboxes, and fireplaces. Refractory bricks are mainly designed to withstand high temperatures, but usually should also have low thermal conductivity to save energy. Dense bricks are typically used in applications with extreme mechanical, chemical, or thermal stress, such as the interior of wood burning kilns or furnaces, where they are subject to wear and tear from wood, melting of ash or slag, and high temperatures. Dense firebricks have a high thermal quality, which is sometimes a useful feature because they can retain heat, such as when the fire is extinguished in a pizza oven.
Kiln bricks are made by firing clay based compositions in the kiln until they partially vitrify and can also be glazed for special purposes. Refractory bricks typically contain 30-40% alumina, with the main raw materials typically being clinker and other materials. The high usage temperature increases with the increase of alumina content, and kiln bricks with alumina content of 80% or above can be produced. Low density refractory bricks are a good choice in other less demanding situations, such as natural gas kilns, where porous bricks are commonly referred to as insulation bricks.
They are weaker, but lighter, easier to form, and have better insulation than dense bricks. In this case, their thermal mass is low and therefore cannot be used to store heat. Insulating bricks have better thermal shock resistance than dense refractory bricks, but the main drawback is their low strength. The thermal insulation properties of these bricks usually come from perlite or vermiculite. Like dense refractory bricks, there are a series of grades corresponding to different usage temperatures. The common one is Grade 23-1260 ° C.
