Refractory materials for cement kilns

refractory brick

1,cement kiln working environment and the requirements of refractory
The new dry cement kiln is a large system. From raw materials preheating, decomposition, to high temperature calcination to produce clinker, until the cooling out of the material, before and after the total length of several hundred meters. And this is only the main system, there are a large auxiliary system, such as ventilation systems, waste heat power generation systems, are at high temperatures, need to protect the refractory material. However, such a large main and auxiliary system in addition to the work in a serious chemical erosive atmosphere, the other conditions are different, the temperature is not only different levels, there are varying degrees of variation and frequency. Force situation is different, have been washed by the air, there are raw clinker wear, there are mechanical stress. The air erosion strength, wear and mechanical stress and the size of the different, the situation is very complex. Therefore, the performance requirements for refractory materials is also very complex. It is not possible to use only one material to meet all requirements. Must use a series of refractory materials. In view of the above situation, cement kiln refractory use environment although vary widely, but in general there are a few common, that is: a serious chemical erosive atmosphere; greater mechanical stress and wear, strong thermal stress. The difference is mainly due to the difference in temperature. The main requirements for refractory materials are: resistance to chemical attack, high strength, wear resistance, thermal shock resistance, different parts of the refractoriness are quite different. If combined with the actual cement company repair work, it is best to early hardening easy early sintering high strength, it would be better.
2,several commonly used refractory performance comparison
Cement kiln refractory castables are the following: Alkaline castables, high-silicon castables, high-alumina castables.
Alkaline castable refers to the magnesium, magnesium aluminum spinel material based on a class of castables. This material is particularly alkaline resistance, the inadequacies of the thermal expansion coefficient is greater, less thermal shock resistance, such as to solve the thermal shock problem, the application effect in the cement kiln is also good.
High siliceous material refers to the alumina content of less than 30% of the aluminum siliceous material, such materials at a certain temperature and kiln materials and kiln gas in the alkali compounds in the surface of the material quickly formed a closed dense protective glaze Layer, to prevent the continued infiltration of alkali, so as to protect the material inside the alkali is no longer continue to attack, the formation of good resistance to alkaline. However, the weakness of such materials is that the soft temperature is low, low strength, poor wear resistance.
Performance of Alkaline Castables for Kiln Kiln
High alumina refractory brick refers to the formation of a class of alumina-based materials. Mainly including a variety of corundum mullite and so on. The common characteristics of these materials are high hardness, high wear resistance, the inadequacies are not alkali, because the alumina and (K, Na) 2O reaction can form β-alumina, resulting in volume expansion, destruction of material structure, when there is Silica material in the presence of nepheline can form, not only volume expansion, and the lower melting point, the use of a significant decline in performance.
3,Analysis of Damage Mechanism of Refractories for Cement Kiln
1: Alkaline peeling
2: Thermal shock cracks and mechanical stress damage
3: wear air erosion material wear
4: damage caused by non-material properties
Construction defects: construction caused by poor performance of the material caused by defects, poor mobility, material segregation, construction cracks, etc.
Maintenance did not meet the process requirements: baking, no sintering strength low auxiliary equipment: mixing machine, tire mold, vibration anchor welding, bandage, structure, set the size of each location
4, high strength and high wear resistance castable performance analysis
1: high strength and high wear resistance analysis: performance from the nature of the material itself. The cast material is made of high-alumina corundum material, corundum we all know that high hardness and high strength of the material, wear resistance is yes. But in the castable only grain wear is useless, but also must be binding agent and the same part of the matrix wear-resistant Caixing. In the matrix is ??added with corundum homogeneous material @ -AL2O3 powder, so the castable overall wear resistance is very good.
2: thermal shock resistance analysis: pure corundum material wear resistance is good, but the thermal shock is poor, but also part of the sio2, to produce part of the mullite, mullite thermal expansion coefficient of only magnesia three One by one, corundum half, coupled with the thermal expansion coefficient of corundum caused by the micro-cracks toughening effect, which improves the thermal shock resistance of the material.
3: alkali-resistant problem solving: If the corundum is also barely alkaline resistance in the past, mullite in alkaline conditions is very unstable. So ordinary high-alumina materials used in the cement kiln is certainly not work. But the high strength and high wear-resistant castable due to the formation of anti-alkaline protective film can be formed on the material, the corundum mullite from the protective effect, so the corundum mullite to maintain its excellent characteristics, but also have a very good Alkali resistance. Therefore, the full satisfaction of the cement kiln on the requirements of refractories.


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Refractory materials for induction furnaces

Refractory materials

Refractory materials for induction furnaces:
The furnace lining is usually made of clay brick or ternary high alumina brick masonry. The bottom of the furnace is sometimes the first high-alumina refractory castable watering grass, and then in the high aluminum brick. When the induction furnace capacity is less than 10t, the lining can be made of high alumina refractory castable or refractory ramming material with about Al2O3 content of about 75%. It can also be made of corundum refractory castable or dry vibration material. Stove sensor coil around the lining, the general use of corundum refractory castable as a whole watering or vibration with dry vibration compact. As the type of raw materials and operating conditions are different, the furnace life is also different, the general furnace age of 0.5 to 4 years. In the use of the coil around the coil and other vulnerable parts should be carried out 1 to 5 times minor repair.
Insulation materials for holding furnaces and aluminum tanks:
Aluminum insulation furnace is divided into slot induction furnace, resistance heating pool furnace and gas furnace furnace. The working temperature of such equipment due to lower operating temperature, generally with clay refractory brick and other materials for the lining, also obtained a higher service life.
Refractory material for rotary drums:
The non-working layer of the drum is made of clay or heat-resistant brick or floating brick masonry, and can also be made of lightweight refractory castable with a bulk density of 1.0g / cm3 or made of prefabricated masonry. The working layer is made of dense clay refractory bricks or Al2O3 content of more than 55% of high alumina refractory masonry. Rotor furnace furnace age is generally 300 ~ 500 furnace times. When the addition of salt solvent smelting aluminum, due to increased chemical erosion, the furnace age has decreased.

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Advantages and disadvantages of refractory bricks

refractory bricks

Refractory materials are generally divided into two types, unshaped refractories and shaped refractories. The most widely used refractory bricks are as follows:
1. Dolomite brick
Dolomite brick has good hanging kiln skin performance, good resistance to erosion, but it is easy to hydration and difficult to transport and custody.
2. Magnesia chrome brick
Magnesia chrome brick’s hanging kiln skin performace is good, it is used for firing belt. And its disadvantage is that magnesia chrome refractory brick manufacturers performs not quite well in thermal shock resistance.
3. Phosphate brick
Phosphate brick’s refractoriness is low, but it has high strength and high thermal shock resistance, it is usually used for kiln hood and so on.
4. Silicon carbide brick
Silicon carbide brick has good resistance to high temperature (1800 degrees centigrade, load softening temperature 1620-1640 degrees centigrade). Its thermal expansion coefficient is small, and silicon carbide brick has good resistance to acute cold and hot, good abrasion resistance. Silicon carbide brick is suitable for furnace cooling zone and kiln mouth.
5. Silicon mullite brick
Silicon mullite brick has good thermal shock resistance, high strength and good abrasion resistance. Silicon mullite brick is suitable for furnace transition zone.
6. Spinel brick
Spinel brick is mainly used for transition zone. It has good thermal shock resistance, good anti-reducibility, but its refractoriness is a little low.
7. High alumina brick
High alumina brick’s Al2O3 content is more than 75%, its refractoriness is higher than that of clay brick for sale. High alumina brick has good anti-acid and alkali erosion, it is suitable for cement kiln burning belt, etc. High alumina brick’s using life is long but its price is a little high.
8. Anti-peeling brick
Anti-peeling brick contains a small amount of ZrO. It has excellent resistance to alkaline, good anti-peeling performace and good slag resistance.

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Advantages and disadvantages of refractory bricks
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