How are the high alumina bricks fired?
According to the quality requirements of different grades of high alumina brick, choose different grades of bauxite raw materials, it is conducive to rational use, fine materials, fine distribution, as far as possible not to use mixed grade severe raw materials. The quality of the clinker depends on the calcination temperature, calcination temperature, sintering temperature should be generally reached or slightly higher than that of alumina clinker sintering, to ensure the full and possible high volume density, and the two secondary Mullitization and sintering shrinkage effect in calcination process. Lightweight high alumina brick, also known as high aluminum insulation brick (high-aluminium heat insulating brick). A lightweight refractory consisting of mullite and glass phases or corundum in excess of 48%. The volume density is 0.4 ~ 1.35g/cm3. The porosity is 66% ~ 73%, and the compressive strength is 1 ~ 8MPa. Better thermal shock resistance.
Generally, the high alumina bauxite is added with a small amount of clay. After being ground, the gas is injected and shaped in the form of slurry by the way of gas attack or foam, and it is burnt at 1300~1500 DEG C. Sometimes industrial alumina can be used to replace part of bauxite clinker. Used for lining and thermal insulation of masonry kilns, as well as for areas where there is no high temperature, high melting material erosion and erosion effects. When touching the flame directly, the touch temperature shall not be higher than 1350 degrees.
Light and high alumina bricks are usually fired in a weak oxidizing atmosphere. In light and high alumina bricks firing, they are often rich in impurities such as R2O, RO, Fe2O3 and so on. They react with Al2O3 and SiO2 at high temperature to produce liquid phase. In the Al2O3 - SiO2 - R2O system, the growth rate of liquid phase increases with the increase of temperature at high temperature. So, because the increase of sintering temperature brings a lot of liquid phase, the decrease of liquid viscosity will lead to the deformation of brick and the decline of brick high temperature function. Therefore, the lower sintering temperature and longer holding time should be adopted in the sintering process dominated by liquid phase sintering. The production practice shows that the same firing temperature can be used for the high grade aluminum bricks. When fired in an inverted flame kiln, it is usually 1430 degrees centigrade and insulated by 40H. The high alumina bricks such as Ill are 1390~1420 degrees centigrade. When the tunnel kiln is fired, they are 1550 and 1450~1500 degrees centigrade respectively. High alumina brick is usually made of weak oxidizing atmosphere.
