The high-temperature flue gas at the tail of the cement kiln enters the calciner through the kiln tail smoke chamber, and most of the preheated cement raw materials enter the calciner from the preheater (the remaining part directly enters the discharge chute from the discharge pipe of the fifth-stage preheater) , Most of the calcium carbonate in the cement raw meal is initially decomposed here to generate calcium oxide and carbon dioxide, and the temperature gradually rises to about 1000-1200 °C.
Same as the preheater, the calciner also needs to consider the problem of heat loss, so it is necessary to paste calcium silicate boards for heat preservation. The difference from the preheater is that the temperature of the calciner has increased, so the early dry rotary kiln was born out of In consideration of cost, high-strength alkali-resistant bricks are mostly used as kiln lining.
In recent years, in order to increase the output of cement enterprises, the temperature of the calciner has been increased to above 1200°C. At the same time, with the trend of large-scale cement kilns, the height and diameter of the calciner are also increasing. Low, long-term use will produce shrinkage, and the wear performance of high-strength alkali-resistant bricks under high temperature conditions can no longer meet the use requirements. Therefore, most of the current calciners use anti-flaking high-alumina bricks as the kiln lining, and high-alumina castables are used for pouring construction at the shrinkage and gooseneck positions.
After passing through the calciner, the cement raw meal has completed part of the pre-decomposition process, and then enters the kiln tail smoke chamber through the material pipe, and enters the rotary kiln through the feeding slope.
The kiln tail smoke chamber is an independent sealed structure connecting the rotary kiln with the calciner and the preheater. The material enters the rotary kiln from here, and the flue gas generated in the rotary kiln gathers here, the temperature is relatively high, and the material is severely washed out. The temperature point is just around the condensation temperature range (800-1100°C) of the low-melting point sulfur-chlor-alkali salt in the flue gas. The low-melting point sulfur-chlor-alkali salt in the flue gas is easy to condense. When the alkali content reaches a certain amount and gradually enriches, it is combined with cement The small particles and fine powder in the raw meal are attached to the kiln lining refractory to form a crust, which blocks the feeding pipe, smoke chamber and smoke pipe.
In the process of cement production, once the crust is formed, the material of the rotary kiln will be blocked and production will be stopped. Therefore, when the crust is formed, it must be removed manually or mechanically. In the process of removing the crust, if the crust is very firmly bonded, It will easily cause the refractory material to peel off together.
In order to solve this problem, it is necessary to use anti-skinning castables for masonry in the kiln tail smoke chamber and the attached feeding pipes and smoke pipes that are prone to skinning.