Unshaped Refractory Materials for Preheaters, Coolers, Smoke Chambers, Transfer Chutes, Kiln Hoods, Etc.

(2-3%heat resistant steel fiber can be added to the castables according to the use environment and temperature)

The rotary kiln is composed of a cylinder, a kiln head with a burner, a cooler, a dust collector and a transmission device. Its production process is as follows: cement raw materials are fed from the kiln tail (i.e., the cold end or high end), and the fuel and required air are sprayed from the kiln head. The two move in opposite directions and exchange heat; due to the rotation of the cylinder, the material gradually rolls toward the kiln head, and is heated and completes its physical and chemical changes at the same time. Qualified products fall into the cooler from the discharge port, and the temperature is reduced to below 200°C. That is to say, the rotary kiln is generally produced continuously and can be divided into a preheating zone, a decomposition zone, a burning zone and a cooling zone. The operating temperatures are 300-1000°C, 1000-1300°C, 1300-1500-1300°C and 1300-800°C respectively. That is, when the product is about 800°C, it enters the cooler for cooling.

 

There are many types of rotary kilns, which can be classified from different perspectives. The following is a brief description:

1) According to the purpose, it can be divided into cement rotary kiln, bauxite clinker rotary kiln and dolomite rotary kiln, etc.;

4) According to the geometric shape of the cylinder, heating method and clinker cooling method, it can be divided into straight cylinder kiln, dumbbell kiln, internal heat kiln and multi-cylinder cooler kiln, etc.;

5) According to the different types of preheating devices and decomposition furnaces installed outside the kiln tail, it can be divided into two categories: suspension preheating kiln and pre-decomposition kiln.

The so-called suspension preheating kiln (taking NP type kiln as an example) is a suspension preheater composed of several cyclones installed outside the rotary kiln tail, which can preheat the material and decompose 40-50% of the carbonate, and then send it into the rotary kiln for calcination. This kind of kiln can improve production efficiency and extend the service life of the kiln lining.

The use temperature of the preheating zone and decomposition zone of the rotary kiln is about 1300℃. Lightweight refractory materials can be used as insulation layers to reduce the carcass temperature, reduce the energy consumption of kiln rotation and improve working conditions.

In international cement rotary kilns, high-strength lightweight bricks or lightweight refractory castables are mainly used as insulation layers, which have achieved good results. For example, the UK uses lightweight bricks with an A12O3 content of 34-54% as insulation layers in the preheating zone, which are connected to the working layer with wedge pins or bonded with adhesives to strengthen the integrity of the kiln lining; the insulation layers of rotary kilns in countries such as Japan and West Germany are mainly castables, which have high strength, good integrity and significant energy-saving effects.

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