Lightweight insulating bricks refer to shaped refractory bricks with a porous structure inside, with low bulk density, high porosity, and excellent thermal insulation and high temperature properties. They can also be called lightweight refractory bricks or lightweight insulating bricks. According to the different raw materials used, it is divided into many kinds, such as light clay bricks, light silica bricks and light high alumina bricks made of clay, siliceous and high alumina materials. The composition characteristics, operating temperature and uses of lightweight thermal insulation bricks are as follows:
Lightweight clay insulation brick: refers to the lightweight firebrick with aluminum content of 30%-46%. It is produced by combustible material method with clay clinker or light clinker and plastic clay as the main raw materials. The bulk density is 0.75-1.20g/cm3, the compressive strength is 2.0-5.9MPa, the thermal conductivity is 0.221-0.442W (m.k), and the operating temperature is 1200-1400℃. It is used in various industrial kilns without contact with the molten material. and insulating material without the effect of erosive gases.
Lightweight high-alumina thermal insulation brick: refers to the lightweight refractory brick with an AL2O3 content of more than 46%. Bricks made of natural high-alumina bauxite clinker are called ordinary light-weight high-alumina bricks; those made of fused or sintered alumina are called light-weight corundum bricks, and the main crystal phase is corundum. Lightweight high-alumina bricks are usually produced by the foam method, with a bulk density of 0.4-1.35g/cm3, a porosity of 66%-75%, a compressive strength of 1.3-8.1MPa, and a thermal conductivity of 0.291-0.582W (m.k) . The operating temperature of ordinary lightweight high-alumina bricks is 1350-1500 ℃, which is suitable for kilns with hydrogen, CO and other gases as protective atmosphere. The temperature of the light corundum brick reaches 1650-1800 ℃, and it can directly contact the lining of the kiln with the flame, but it is not suitable for the part that is eroded by the slag.
Mullite light insulation brick: refers to the lightweight refractory brick with AL2O3 content of 50%-85%, high-quality insulation material with mullite as the main crystal phase and combined phase. The main features are: high structural strength at high temperature, low creep at high temperature, small coefficient of thermal expansion, strong resistance to tidbits, and excellent thermal shock resistance. According to the difference of aluminum content and bulk density, the working temperature of the furnace is 1350-1700℃, and the working layer lining of the kiln can directly contact the flame.
Silica thermal insulation refractory brick: refers to the thermal insulation siliceous refractory brick with SIO2 content above 90% and bulk density less than 1.2g/cm3. The bulk density is 0.9-1.1g/cm3, the compressive strength is 2.0-5.9MPa, the thermal conductivity is 0.35-0.42W (m.k), and the operating temperature is 1200-1500℃. It is suitable for high temperature kilns without contact with slag It is used, such as the thermal insulation material of the high temperature hot blast furnace silica brick lining of the large blast furnace and the thermal insulation of the glass kiln silica brick masonry.
Anorthite light insulation brick: mainly divided into two types, one is made of anorthite as the main raw material, and the other is made of anorthite combined with light mullite. Bricks (need to add kyanite raw materials) are characterized by low bulk density, low thermal conductivity, good thermal shock resistance, and strong anti-reducing atmosphere. The operating temperature is 1100-1300℃, suitable for thermal insulation linings of hot blast furnaces, soaking furnaces, heating furnaces in the iron and steel industry, and thermal insulation linings of various catalytic cracking furnaces in the petroleum industry.
In addition to the above commonly used lightweight refractory bricks, there are also lightweight refractory bricks suitable for alkali erosion, such as magnesia heat insulating bricks, magnesia chrome heat insulating bricks, chrome magnesia heat insulating bricks, and zirconia insulating bricks. Hot bricks, silicon carbide lightweight insulation bricks, etc.