Lime Kiln Introduction
Refractory for Lime Kiln. Lime kilns are generally divided into two categories: rotary kilns and vertical kilns.
For rotary kiln and shaft kiln, it is generally believed that the rotary kiln has good quality and is suitable for large-scale production, but it covers a large area, high investment and high heat consumption, so it is suitable for calcining small particle lime;
The quality of lime produced by shaft kiln is slightly lower than that of rotary kiln, but it has the advantages of small floor area, low investment and low heat consumption.
Lime Kiln Refractory Requirements
The refractory lining of lime kiln is affected by high temperature thermal shock, mechanical wear, structural stress and chemical erosion. In view of the harsh service conditions, it is required that the refractory must have good chemical erosion resistance, excellent high-temperature volume stability, integrity of masonry, good thermal shock resistance, good mechanical erosion resistance and wear resistance.
The requirements for refractory materials used in each section of lime rotary kiln are as follows:
1. Preheater Zone
The preheater is in front of the preheater, and limestone is heated in the preheater first. The heat source is the waste flue gas from the cooling section. The particle size of raw materials is 10-30mm, and the temperature entering the preheating section is 1000-1-50 ℃. The requirements for materials are mainly high strength, good wear resistance and certain thermal shock resistance. Dense clay brick or high-quality clay brick are used in this stage, and permanent layer is generally not used during masonry, The furnace shell temperature shall be controlled not higher than 350 ℃. Wet masonry with refractory mud.
2. Transition zone
The temperature of this section is 1200-1300 ℃, which is the transition stage from limestone to firing zone. In this stage, the temperature changes greatly, and some limestone has begun to react. It is required that the thermal shock stability and material strength of the materials at this stage are good. Generally, three-level high alumina bricks are selected. At the same time, in this stage, in order to make the materials evenly distributed and heated, During masonry, left and right raised lifting belts are generally added in the length direction to drive the turnover of raw materials. The raised materials are generally prefabricated blocks of the same material. During the masonry of this section, grade III bricks and refractory mud are used directly, and there may be no permanent layer.
3. High Temperature Zone
The high temperature zone is close to the firing zone, and the service temperature is 1300-1400 ℃. The temperature changes frequently. The material in this section is required to have a high load softening starting point and high volume stability (micro expansibility). Generally, 70 high alumina bricks and refractory mud are used for masonry without permanent layer.
4. Firing Belt
The firing zone is the final reaction stage of lime. In this stage, a large burner is used for heating, and the temperature is 1400-1500 ℃. The higher the activity requirements of lime, the higher the firing temperature. Therefore, the permanent thermal insulation layer is adopted in this section, and the thermal insulation material is required to have considerable strength to prevent it from being worn and powdered by the working layer. This section is made of magnesia alumina spinel or super grade phosphate brick, which is dry masonry without fireclay, and a locking steel plate is added between the brick and the brick. At high temperature, the steel plate is combined with the material and firmly bonded together.
5. Cooling Belt
The cooling zone is very short, with only a few ring bricks or castables, and the temperature is 1300-1400 ℃. Generally, 70 content high aluminum bricks are used for masonry.
6. Cooler Zone
This equipment is the cooling equipment for finished lime, which is cooled by blower. The temperature of cooled lime in this section is required to be lower than 100 ℃. The cooled lime enters the silo through the belt. The temperature of hot air after heat exchange is about 600 ℃, which enters the rotary kiln as combustion supporting air for mixed combustion with gas. This section is constructed with clay bricks and refractory mud wet masonry.
7. Refractory Mud
Since most of the masonry in each stage of lime rotary kiln needs to be built with refractory mud, there are special requirements for refractory mud. Generally, the appropriate refractory mud shall be selected according to the temperature and requirements of each part to prevent the simple pursuit of high material quality of refractory mud from matching with the temperature and materials in this stage, affecting the overall operation of the kiln.
Refractory for Lime Kiln Summary
For refractory materials used in lime kiln, the lining refractory bricks and refractory castables should be selected according to the combustion mechanism, wear mechanism of the kiln itself and the corrosion resistance of raw materials under high temperature reaction.
In short, the appropriate furnace lining can create high-efficiency production capacity.