Rotary kiln skin formation causes and prevention measures

Rotary kiln skin formation causes and prevention measures
1. Pre-decomposition zone Causes of skin formation::
The fusion bonding under the surface tension of the wet liquid film, the surface bonding caused by the suction force acting on the surface, and the adhesion caused by the interweaving of fibers or net-like substances.
As the alkali, chlorine, sulfur and other harmful components in the kiln gas condense in the kiln tail, preheater and decomposition furnace, the minimum eutectic temperature is reduced, so when the alkali, chlorine, sulfur, etc. in the kiln gas condense, It will precipitate in the molten state and enter the kiln together with the materials, and form a viscous substance together with the materials and dust. The viscous film on the raw meal particles will hinder the flow of the raw meal particles, causing skinning or even blockage. The factors that cause skin formation in the precalcining kiln are as follows:
(1) Circulating enrichment of harmful components (alkali, chlorine, sulfur, etc.) in the gas, which is an important factor leading to the formation of crust mesophase in the kiln.
(2) The local temperature is too high, which is a key factor for the formation of crusts. This is the key factor causing skin formation.
There are at least the following reasons for local high temperature:
1) Incomplete combustion of pulverized coal.
2) The feed rate is unstable, which easily disturbs the normal operation of the preheater and decomposition furnace.
3) Due to the small amount of ash returned, it is not easy to mix uniformly in the raw meal homogenization warehouse, resulting in fluctuations in the raw meal composition.
4) When the preheater leaks cold air into contact with hot materials, it is easy to cause the hot materials to condense and adhere to the system wall and cause skinning.
2. The source of volatile components. The exhaust gas of the kiln system contains a lot of volatile components, mainly alkali, chlorine and sulfur.
1) The source of alkali. Alkali mainly comes from raw materials, especially clay.
2) The source of sulfur. Most of them come from fuel, and coal is the most used.
3) The source of chlorine. Chlorine mainly comes from water-soluble alkali metal chlorides, and the raw materials usually exist in the form of KCl and NaCl.