Main Functions of Kiln Bricks
The kiln brick is a layer of refractory filled in the inner part of the rotary kiln. The main functions of kiln bricks are as follows:
1. Reduce the chemical erosion and mechanical wear of the cylinder by high-temperature gas and material, and protect the kiln shell.
2. Kiln bricks as heat transfer medium can absorb part of heat from gas and transmit it to materials in different ways of conduction and radiation.
3. Kiln bricks can also be insulated to reduce the heat loss of the kiln body.
According to the different parts of refractories used in kilns, the main requirements for kiln bricks in the rotary kiln are as follows:
1. High-temperature resistance. No matter the firing condition of the inner tube is good or bad, the temperature in the kiln is above 1000 C, which requires refractory bricks not to melt at high temperature, but to maintain a certain strength under the melting point.
2. The stability of thermal vibration is good, that is, the ability to resist the drastic change of kiln temperature without being destroyed is good. Under the unstable conditions of kiln shutdown, kiln opening and rotary kiln operation, the temperature changes in kiln are relatively large, which requires that kiln bricks should not be cracked or peeled when the temperature changes dramatically.
3. Strong resistance to chemical erosion. When fired in a rotary kiln, ash, slag and steam formed will cause great erosion to kiln bricks.
4. Good wear resistance and mechanical strength. Sliding of feed in kiln and friction of dust in airflow will cause great wear and tear of kiln bricks, especially in the early stage of kiln opening. Kiln bricks also bear the stress caused by expansion stress at high temperature and elliptical deformation of kiln shell. Kiln bricks are required to have certain mechanical strength.
5. Good performance of hanging kiln skin. Kiln skin has a great protective effect on kiln bricks. Kiln bricks should have good performance and durability of kiln skin.
6. Porosity should be low. If the porosity is high, the corrosive kiln gas will permeate into kiln bricks and condensate, destroying kiln bricks, especially alkaline gas.
7. The stability of thermal expansion is good. Although the coefficient of thermal expansion of kiln shell is larger than that of rotatry kiln brick, the temperature of kiln shell is generally around 280-450 C, while the temperature of kiln brick is generally above 800 C, and the temperature of kiln brick is more than 1300 C in the firing zone. In this way, the expansion degree of kiln bricks is still larger than that of kiln shell, and kiln bricks are liable to be peeled by compressible stress.