The requirements of refractory materials for shaft kilns

refractory brick

① high temperature heat loss: refractoriness of not less than 1580 ℃ inorganic non-metallic materials and products called refractory materials. In the kiln under high temperature, do not soften, insoluble; in normal or abnormal circumstances, can maintain a certain structural strength and bulk density stability. This kind of refractory masonry lining of the kiln in order to maintain the normal operation and production.
② anti-acid and alkali chemical erosion: the material in the kiln of the calcination process, to go through a series of complex physical and chemical reactions, different parts of the acid gas or alkaline slag will erode the kiln lining. Especially in the firing zone, the reaction material in the high temperature liquid phase, the chemical effect of refractory material is more intense. So the material can not participate in chemical reactions, does not appear sticky phenomenon.
③ anti-material movement wear: shaft kiln calcination process, the material from top to bottom, from low temperature to high temperature, to the low temperature kept moving. The lining of the inner wall of the kiln body is always subjected to the movement of the material, especially the clinker formed after calcination is stronger and the wear of the lining is more serious. Therefore, masonry in the kiln body of the refractory material must have a strong anti-wear ability.
④ specifications of the size: refractory masonry quality of the kiln calcination process has an important impact. Shaft kiln is not round, calcined easily lead to "partial fire" phenomenon; brick surface uneven, contact is not close, in the kiln bottom position is unstable, due to thermal shock phenomenon will occur loose lining, reduce service life and kiln heat loss Increase and so on. Therefore, the shape and shape of the refractory brick must be standardized and accurate, which is to ensure the quality of the most basic conditions of masonry.

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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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Other refractory materials for industrial furnaces

refractory materials

Other industrial furnaces include boilers, gas stoves, heating furnaces. Building materials industry, the use of refractories furnace up, such as calcined cement industrial furnace and glass melting furnace.
Calcined cement rotary kiln working temperature in the firing zone for the 1450 ~ 1500 ℃, masonry subjected to high temperature and alkali erosion, the production of frequent rotation caused by masonry vibration, while the wear and impact of sports load, masonry Laying layer to make the brick temperature fluctuations, so the use of cement masonry with high refractoriness, good alkali resistance, high compressive strength, good thermal stability of refractories. Generally in the firing zone with the use of magnesia bricks or magnesia-alumina bricks, the calcining belt uses good quality high alumina bricks or phosphates high alumina bricks, and other places use clay tiles.
Glass kiln masonry suffered 1600 ~ 1700 ℃ high temperature role, with the material and glass chemical erosion and mechanical action, as well as dust, air erosion and so on. So the refractory material must have the ideal anti-erosion performance, and should avoid the glass in the stones, stripes, bubbles and other defects. According to this requirement glass melting furnace generally use high-quality silica brick, fused zirconia corundum brick, fused α-β corundum brick, thermal storage room using magnesia or magnesia chrome brick. Refractory industrial kiln, according to the calcined raw materials and firing products, common shaft kiln, rotary kiln, inverted flame kiln and tunnel kiln and so on. Shaft kiln masonry is subjected to high temperature and abrasive wear. Therefore, the refractory used should have substantially the same chemical properties as the calcined raw material, the refractoriness suitable for the calcination temperature of the raw material, and the good high temperature volumetric stability, mechanical strength and slag resistance. For example, calcined limestone and clay clinker can be used in clay kiln lining, calcined magnesite and dolomite shaft kiln lining magnesium, calcined bauxite with high alumina brick or high alumina brick.
Rotary kiln masonry due to rotation leaving the masonry vibration, while the movement of the charge also wear and impact masonry, masonry in addition to meet the requirements of the production process, but also should have high strength and wear resistance.
The flame-resistant kiln is affected by the high temperature effect and the scouring effect of the combustion air flow and the abrupt change in the temperature of the kiln cooling. Therefore, the refractory used has high refractoriness and mechanical strength as well as good thermal stability and high temperature volumetric stability Wait. Masonry use of refractory materials and firing products should be consistent, such as firing high-alumina refractory bricks and magnesia brick masonry using high alumina brick, magnesia brick and silicon brick.
Tunnel kiln due to the high temperature of the firing zone, masonry quality requirements. Therefore, the masonry should be used refractory, fire resistance, mechanical strength and load softening temperature are high, high temperature stability and good dimensional dimensions of the refractory material. At the same time the performance of masonry and firing performance should be adapted.

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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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