Refractory for rotary kiln

At present, the production process of alumina in China mostly adopts sintering method and joint method due to raw materials. The drying, calcination and roasting of bauxite are mostly made in rotary kilns. In recent years, the fluidized roasting device introduced has been widely used, but it still occupies a large proportion in some old factories.

Rotary kiln is a sinter kiln for alumina clinker. In the production of alumina, the first proportion of bauxite and soda ash and lime into the rotary kiln, after calcining 1200~1300℃ out of the kiln, and then after proper treatment into aluminum hydroxide and mother liquor; Aluminum hydroxide is put into a rotary kiln and calcined at 1200℃. The calcination process in the rotary kiln is as follows: the high temperature flame and the heated material do reverse motion in the furnace. Alkaline bauxite raw material slurry (40% water) or aluminum hydroxide (12%~18% water) is added at the end of the kiln. After low temperature drying, dehydration, heating and high temperature calcining, the material is discharged from the kiln head, and the high temperature gas flows from the kiln head to the kiln tail. Therefore, the kilns are divided into pre-tropical and high-temperature calcining zones. In order to prevent paste from bonding kiln lining and enhancing heat transfer in the heating and calcination process, a chain is also installed in the refractory masonry to continuously strike materials and lining bricks during the rotary movement of kiln body, which has a certain impact on the service life of kiln lining.

In alumina production, the rotary kiln body is welded steel plate, lined with refractory materials. Refractories work in a harsh environment and harsh conditions. It should have the following characteristics: strong resistance to alkali corrosion; It can work under high temperature of 1200~1300℃ for a long time without damage. Can withstand the impact of dynamic load; Resistant to charge erosion; Able to withstand high temperature erosion by air flow. The refractory materials used in the rotary kiln are mainly high-alumina bricks and magnesia-chrome bricks, while the low-temperature drying kiln USES clay bricks as the lining.

At present, amorphous refractory has been widely used in aluminum industry. The kiln mouth of rotary kiln is easy to be deformed and damaged due to high temperature wear of materials and thermal shock stress. In the transition zone of alumina clinker kiln, the ambient temperature is 400~1000℃, and the lining often falls off due to alkali erosion and mechanical damage (vibration and distortion).