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Modern new dry process cement production line, system equipment continues to be large-scale, unit product energy consumption and system operation rate is an important index to judge whether the enterprise production is advanced. As the main insulation material of new dry process cement production line, the reasonable configuration of refractory castable can not only protect the normal operation of production equipment under high temperature, but also effectively reduce the energy consumption of the system.
Problems in application of refractory castables
The rotary kiln and preheating decomposition system of the new dry process cement production line are operated under high temperature and high dust, and some parts are very worn. The main problems exposed in the use of refractory castables are as follows:
1. The service life of refractories used in front of cement kiln and coal injection pipe is short. The service life of refractory castables used in front of cement kiln is generally 4-8 months. The common problems are: the castables are exfoliated, chipped and poor alkali resistance. The service cycle of refractory castable for coal injection pipe is generally 3-5 months. Due to frequent changes and large temperature difference in use, the castable at 1m in front of burner is easy to crack and peel off.
2. The cone, discharge pipe, precalciner cone and flue gas chamber of No.4 and No.5 cyclone are easy to be skinned, which affects the normal production
The calcination of low-grade raw materials, anthracite, inferior coal and solid waste increases the content of alkali, sulfur, chlorine and other harmful components in the whole kiln system. It is easy to skin in the cone of No.4 and No.5 cyclone, discharge pipe, calciner cone and flue gas chamber, which leads to frequent use of air gun and water gun. It is not only unsafe, but also affects the normal production and reduces the system operation rate.
3. The elbow and valve of the tertiary air pipe are worn seriously and the service cycle is short
Under normal conditions, the temperature of the tertiary air containing dust is 750 ℃ - 950 ℃, and the wind speed is above 20m / s. The hardness of clinker particles in the tertiary air is high, and the refractory lining in the tertiary air valve and other parts is seriously worn. The service cycle is short, only 2-3 months, and only about 6 months. Once the refractory lining in the elbow of the tertiary air pipe or the tertiary air valve is worn off, the elbow or the tertiary air valve plate will be worn through, and the kiln has to be shut down for treatment.
Reasonable selection of refractory castables
Different parts of the new dry process cement production line have different requirements for refractory castables, so the corresponding varieties must be selected in the design. In view of the above problems in the use of refractory castables in new dry process cement production line, this paper puts forward some opinions on the refractory castables used in different parts of medium and large dry process cement kiln system
1. Refractory castables for kiln entrance
In front of the rotary kiln, the temperature of the clinker outlet reaches about 1400 ℃, and the temperature of the tertiary air entering the kiln changes frequently due to the kiln conditions. With the expansion of the scale of the cement plant, the kiln diameter becomes larger and larger, the kiln speed becomes higher and higher, and the amount of clinker at the corresponding kiln outlet becomes larger and larger, which aggravates the thermal stress and mechanical stress of the refractory castables at the kiln outlet. Therefore, the refractory castable of kiln mouth should have enough fire resistance, mechanical strength, thermal shock stability and alkali resistance under high temperature environment. Combined with the operation characteristics of this part, it is suggested to use high-performance refractory castable or improved refractory castable. The product has excellent spalling resistance, high temperature alkali resistance and cement clinker corrosion resistance.
2. Refractory castable for coal injection pipe
The working environment temperature of the burner is about 1400 ℃ and its flame temperature is about 2000 ℃. When the burner works in alkaline atmosphere for a long time, the temperature changes more frequently and the temperature difference is larger than that of the front kiln. Therefore, the requirement for its thermal shock is higher. The front section of the burner is always scoured by air flow in the kiln, especially the lower part, and the air flow entrains the clinker in the kiln Therefore, the refractory castable of burner needs enough wear resistance. Combined with the operation characteristics of this part, it is suggested to use special refractory castable for coal injection pipe or improved refractory castable for coal injection pipe. The product has excellent spalling resistance and thermal shock stability.
3. Refractory castables for kiln hood and grate cooler
The refractory castables at the lower part of the kiln head cover are impacted by the rebound heat of the high-temperature clinker from the kiln mouth. For some large cement kilns, the daily clinker output is large, and the heating load is relatively high. If the maintenance and temperature rise of the general high alumina refractory castables are not well controlled, they are prone to burst and fall. The top of the kiln head cover is close to the tertiary air duct, and the dust airflow erosion is relatively serious, so the pouring is difficult The wear resistance of the castable at high temperature is better, and the construction of the top castable is more difficult, which requires higher fluidity and early strength of the material. The top of the front section of the grate cooler is impacted by the rebound heat of the clinker, and its working stability is relatively high, with great changes; the low walls on both sides of the front section are worn by the high temperature clinker coming down through the kiln mouth for a long time, and also bear certain mechanical stress and thermal stress damage.
Combined with the operation characteristics of this part, it is suggested to use high-strength wear-resistant castable with good high temperature performance, strong thermal shock resistance and wear resistance.
4. Refractory castables for elbow and valve of tertiary air duct
It is easy for the castables to loose and peel off, which is the most easily worn place in the operation of cement plant. Combined with the operation characteristics of this part, it is suggested to use wear-resistant refractory castable.
5. Refractory castables for cone of No.4 and No.5 cyclone, discharge pipe of cyclone, Cone of calciner and flue gas chamber
The above parts are easy to be skinned, and it is difficult to clean them. When cleaning the skinning, iron tools are needed to clean it manually, which will inevitably cause mechanical damage to the refractory. Once serious crusting occurs, the kiln needs to be shut down for treatment, which is not only unsafe, but also affects the operation rate of the kiln. Combined with the operation characteristics of this part, it is suggested to use high strength anti caking silicon carbide castable. The product has excellent alkali resistance, crust resistance and wear resistance.
6. Refractory castables for other parts
High strength and alkali resistant castable is recommended for No.1, No.2 and No.3 cyclone, high temperature and high strength and alkali resistant castable is recommended for No.4 and No.5 cyclone (except cone part), and high strength and wear-resistant castable is recommended for calciner.