How to extend the life of refractory materials

refractory materials

How to extend the life of refractory materials. Generally divided into kiln kiln is divided into four bands, namely, decomposition zone, transition zone, firing zone and cooling zone. Four belt, firing with kiln lining the most critical, at home and abroad in the pre-decomposition kiln burning with the main use of alkaline refractory brick.
Thermal, mechanical and chemical factors contribute to the stress in the kiln lining and cause damage. With the kiln, operation and kiln lining in the kiln position of the different factors of the damage is also different. Which decisive role is the flame, kiln and kiln body deformation, they make the kiln bearing a variety of different stress.
For alkaline tiles, there are eight kinds of destructive factors, namely clinker melt infiltration, agglomeration of volatile components, reduction or reduction - oxidation, overheating, thermal shock, thermal fatigue, extrusion and grinding. However, these eight factors have different effects on the damage of different refractory brick lining in kiln, and the mechanism of damage to alkaline brick is described in this paper.
1, clinker melt infiltration:
Clinker melt mainly from the kiln and fuel, infiltration phase is mainly C2S, C4AF. The infiltration of C2S and C4AF in the metamorphic layer strongly dissolves magnesia and chrome ore in magnesia carbon bricks, precipitates secondary silicates such as CMS and magnesium rose pyroxene (C3MS2), and sometimes even precipitates potassium Stone; and the melt will be filled with brick lining pores, so that part of the brick layer of dense and embrittlement; combined with thermal stress and mechanical stress dual role, resulting in easy cracking refractory brick peeling. Due to C2S, C4AF above 550 ℃ began to form, and pre-decomposition kiln into the kiln material temperature has reached 800 ℃ ~ 860 ℃, so clinker melt penetration throughout the pre-decomposition kiln, the clinker melt on the pre-decomposition Kiln lining with a certain infiltration into the erosion effect.
2, the condensation of volatile components:
Pre-decomposition kiln, alkaline sulphate and chloride and other components volatile agglomeration, repeated circulation, resulting in the accumulation of these components in raw materials. By the production practice, the R2O, SO3 and CI- contents of the raw material in the warmest preheater of the kiln are often increased to 5 times, 3 to 5 times and 80 to 100 times respectively higher than that of the raw material. When the hot material enters the third part of the kiln cylinder (800 ° C to 1200 ° C), the volatile components in the material will aggregate in all the brick and brick layers, And the erosion of the adjacent components other than magnesite, resulting in brick thermal penetration stability of the infiltration layer is significantly reduced, the formation of expansion of potassium nepheline, garnet, the refractory brick lime damage, and thermal - mechanical stress Under the combined action of peeling off. The more the depth of the kiln lining is affected by the alkali salt, Selection.
3, reduction or reduction - oxidation reaction:
When the thermal system in the kiln is unstable, it is easy to produce the reduction flame or the incomplete combustion, so that the Fe3 + reduction or Fe2 + in the magnesia-chrome brick shrinks, and the migration and diffusion of Fe2 + in the magnesite crystal is stronger than Fe3 + More, which further exacerbated the volume shrinkage effect, so that the brick hole, the structure weakened, the intensity decreased. At the same time, the reduction of the kiln gas and the alternating atmosphere of the oxidation of the shrinkage and expansion of the volume effect occurs repeatedly, the brick will produce chemical fatigue. This process mainly occurs in the absence of kiln protection of magnesium chrome brick.
4, overheating:
When the kiln heat load is too high, so that the brick surface for a long time to lose the protection of the kiln, the hot surface layer of the matrix at high temperature melting and moving to the cold layer direction, leaving the brick lining layer of dense, hot surface layer is loose Porous (generally easy to occur in the firing area of ​​the firing zone), which is not resistant to abrasion, shock, vibration and thermal fatigue, easy to damage.
5, thermal shock:
When the kiln is not working properly or kiln leather is unstable, the alkaline tiles are susceptible to thermal shock. Kiln of the sudden collapse of the brick surface temperature caused by a sudden surge (or even up to thousands of degrees), leaving the brick to produce a lot of thermal stress. In addition, the frequent opening and closing of the kiln to produce alternating alternating heat within the brick. When the thermal stress, once beyond the structural strength of the brick lining, the brick suddenly cracks, and along the structure of the weakening of the Department continue to deepen the deepening, and finally the brick fragmentation. When the kiln skin falls, the broken brick in the hot surface layer is taken to keep the brick from damage. The thermal shock phenomenon can easily occur in the transition zone near the kiln.
6, thermal fatigue:
In the kiln operation, when the brick lining is not in the material layer, the surface temperature is lowered, and when the brick lining is exposed to the flame, the surface temperature is increased. Kiln each turn a week, brick lining surface temperature rise and fall range of up to 150 ℃ ~ 230 ℃, the impact of depth 15mm ~ 20mm. Such as pre-decomposition kiln speed of 3r / min, this periodic temperature rise and fall of up to 130,000 times per month. This repeated temperature rise and fall causes the thermal fatigue of the surface layer of the alkaline brick to accelerate the peeling of the brick.
7, squeeze:
Rotary kiln operation, the kiln refractory lining material by the pressure, tension, torque and shear mechanical stress, such as the combined effect. Among them, the rotation of the kiln, the oval of the kiln and the kiln fall, the bricks are subjected to the dynamic load; the weight of the refractory brick and the kiln and the thermal expansion of the brick itself make the brick bear the static load. In addition, between the lining brick and the kiln body, the relative movement between the brick lining and the brick lining, and the welds on the retaining ring and the kiln body, will cause the brick lining to withstand various mechanical stresses. When all these stresses exceed the structural strength of the brick, the brick is cracked. This phenomenon occurs in the kiln lining of the precalciner kiln.
8, wear:
Pre-decomposition kiln kiln discharge area without kiln leather protection, and clinker and large kiln leather and hard, will be on the part of the brick lining, resulting in more serious impact and abrasion damage.
In short, the impact of kiln lining consumption of more factors, but also more complex, and only continue to explore, the use of new technologies, new materials, improve the operation and management level, in order to achieve both reduce consumption, but also the kiln system balanced and stable operation.
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Principle of Selection of Refractories for Cement Kiln

refractory material

Preheat zone and decomposition zone
The temperature of these two places is relatively low,  refractory material requiring brick lining of the thermal conductivity is small, good wear resistance, in this area from raw materials, fuel sulfuric acid base and chlorinated alkali began to evaporate, in the kiln condensation and enrichment, and infiltration brick internal. Ordinary clay brick and alkali reaction to form kaolinite and garnet, so that the brick surface crisp, brick body expansion caused by cracking peeling. And containing Al2O3 25% ~ 28% and SiO2 65% ~ 70% of the alkali-resistant or alkali-resistant insulation brick at a certain temperature and alkali reaction, the brick surface immediately formed a layer of high viscosity glaze layer, to prevent the Peeling, but this brick can not resist the use of more than 1200 ℃ temperature. So the preheating zone is generally combined with high alumina refractory bricks, anti-peeling high alumina bricks or resistant to alkali brick.
Decomposition with the general use of anti-peeling good high alumina brick, silicon brick in the performance is better than the anti-peeling good high alumina brick, life than peeling off the high alumina brick about twice as high, but the price is higher, kiln The tail feed should be made of anti-crusted silicon carbide castable.
Transition zone and firing zone
Transition zone kiln leather is unstable, require kiln lining resistance to climate change ability, good thermal shock resistance, thermal conductivity is small, wear. Foreign recommended magnesium aluminum spinel brick, but the thermal conductivity of the brick, the cylinder temperature is high, the relative heat consumption is large, is not conducive to reducing energy consumption. Domestic silicon Mo brick thermal conductivity is small, wear, its performance to a certain extent, comparable with imported materials.
Burning zone with high temperature, intense chemical reaction, requiring brick lining anti-clinker erosion, anti-SO3, CO2 capacity. Foreign generally use magnesium aluminum spinel brick, but the brick hanging kiln skin is more difficult, and dolomite brick thermal shock resistance is not good, easy to hydrate; foreign magnesium iron spinel brick in the hanging kiln skin effect is better , But the cost is too high. The use of new low-chromium perovskite composite spinel brick use is better.
Cooling belt and kiln mouth
Cooling zone and kiln temperature as high as 1400 ℃ or so, the temperature fluctuations, clinker grinding and air erosion are very serious. Requirements of brick lining of the thermal conductivity is small, wear resistance, thermal shock resistance; good thermal shock resistance of alkaline bricks, such as spinel brick or high alumina brick for cooling zone. Foreign generally recommended the use of spinel brick, but the spinel brick thermal conductivity, and wear resistance is not good. Most of the domestic use in recent years, silicon-resistant brick and anti-peeling good wear-resistant brick.
Kiln parts of the use of good resistance to thermal shock castable. Such as: wear-resistant heat-resistant high-alumina brick or steel fiber toughened castables and low-cement high-alumina refractory castable, but the kiln temperature is very high in the large kiln is the use of ordinary, or steel fiber toughening Of the corundum castable.
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Refractory materials for coke ovens

Refractory materials

Coke oven is the technical equipment of coking plant, is a complex and continuous production of thermal equipment, mainly by the combustion chamber, carbonization room, regenerative, roof, chute, small flue and other components. Its purpose is in the isolated air conditions, the coal heated to 950 ~ 1100 ℃, after dry distillation to obtain coke and other by-products.
At present, the life of a coke oven is generally 25 to 30 years, the use of refractories mainly silica brick, clay brick, high alumina refractory bricks. The environmental conditions of the various parts of the coke oven and the requirements for refractory materials are as follows:
Carbonization chamber and partition wall of combustion chamber
The partition wall acts to heat the heat and isolate the furnace gas and support the load. Coke coking temperature is generally 950 ~ 1050 ℃, in order to ensure coking, coke oven wall carbonization chamber side of the surface temperature should be heated to 1100 ~ 1450 ℃; carbonization chamber side of the wall to be thrusting wear; due to coal dry distillation, coking The process in the isolated air conditions, the requirements of the wall air tightness, high temperature airtight, does not occur shrinkage deformation, product shape regular, accurate size to ensure that the small cracks and not cause cracks in the cracks; carbonization chamber in the coking process There is water discharge, the combustion of indoor combustion products contain a small amount of water, and because of coal salt chemical erosion and gas decomposition and carbon deposition, may damage the walls of the organization and performance, strength decreased.
Based on the above characteristics, carbonization chamber and combustion chamber with refractory materials, the world's coke oven almost all use silicon brick. Silica brick compared with other refractories, in the range of 700 ~ 1450 ℃ within the product changes and thermal conductivity of the small changes in its high temperature strength is high, the load softening temperature and its similarity (1620 ~ 1660 ℃), wear resistance, It is not easy to hydrate. With the large-scale coke oven and strengthen the production needs, can also be used thermal conductivity, volume stability, high temperature strength are high silicon carbide refractories. But the price is expensive, in the oxidative atmosphere easily oxidized damage, so the curtain wall is rarely used. And the incorporation of metal oxide high-density high thermal conductivity of silicon brick, wall thickness can be reduced, the intensity of heat transfer, improve the productivity of coke oven, but also improve the furnace life.

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Refractory materials for iron and steel smelting

Refractory materials

Blast furnace refractories:
The development of blast furnace ceramic cups is becoming more and more common, but the need for high corrosion resistance refractory applications to ensure the extension of its service life. In addition to changes in design, refractory material also has a great change, such as micro-porous carbon refractory brick instead of the past, ordinary carbon block to reduce the penetration of molten iron. Used clay refractory bricks as raw materials can better meet the requirements of the use of iron mouth guns. The use of grouting method to repair the blast furnace backing can effectively prevent the erosion of the hot air flow, thereby extending the life of blast furnace lining.
Refractory for converter:
In the aspect of converter steelmaking, a water cooling technology and suspension system are respectively applied in the upper cone and lower barrel parts of the converter shell, thereby reducing the deformation of the converter furnace, prolonging the life of the converter lining and improving the converter productivity. The application of these new technologies has had a certain impact on the use of refractories. So that the converter furnace age increased to an average of 4000 furnace or more, combined with the spray, high lime and dolomite applications and slag splashing furnace technology applications, furnace age more than 10,000 times is not a problem. It is worth the attention of refractory producers to the direction of development.
Continuous submerged nozzle:
Due to the development of the continuous casting system, the tundish has changed from the past transit station to the present metallurgical container which affects the quality of cast steel and improves the productivity of cast steel. Therefore, many functional materials are gradually used in tundish, such as slag weir, impact plate, filter, blowing argon breathable plug and so on.
Immersion nozzle as an important function of continuous casting refractory material, the research carried out mainly in two aspects, one is to improve the slag line parts of the anti-erosion, the second is to reduce the wall of Al2O3 adhesion. The measures to increase the ZrO2 content to 88% and to optimize the particle size distribution can reduce the thermal expansion and porosity of the product and improve the density to improve the slag resistance.
In addition, we should pay close attention to the technological progress of the user industry, such as the recent years of the emergence of direct reduction of iron, and DC arc furnace steel and other new technology on the new requirements of refractories.

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Furnace with the overall refractory

Furnace with the overall refractory

Rolling furnace is the main business of iron and steel enterprises thermal equipment, its performance directly affect the performance of the enterprise's production and economic benefits, for the majority of thermal workers to improve the performance of the furnace and operating conditions, reduce energy consumption, improve Furnace life, extended overhaul cycle, gallbladder, and achieved encouraging results. In recent years with the mechanical and electrical, refractory materials and other new technologies and materials continue to develop, there have been different design of the regenerative heating furnace, the technical indicators compared with the traditional heating furnace has greatly improved. In the case of
At present, I am in the provision of complete sets of furnace refractories, has accumulated a wealth of practical experience, according to the user's actual use requirements, to provide a reasonable combination of refractory products, the furnace for comprehensive furnace, supporting the use of lower Cost, improve life.
To provide high quality and efficient products, and constantly develop new products, good after-sales technical services, and users work closely with the new product applications to solve the technical problems, so that the new refractory products have been successfully applied, and create economic benefits for users, we Consistent work policy; also my company's purpose.
Some of the products are listed below:
Gravity castable
In addition to the characteristics of high-performance refractory castable, its outstanding advantages are excellent construction performance, construction without vibration, can automatically flow, degassing and dense, the construction of time-saving, effort , High efficiency, to ensure the integrity of the construction body, uniformity and air tightness, in particular, to adapt to the complex structure, high quality requirements of the site, once available by the user's wide welcome. Series of self-flow castables of the technical indicators:
Chrome corundum platform refractory brick, slide brick, brick tiles
The furnace trough and tapping platform mechanical wear serious, the temperature fluctuations, high temperature, slag erosion serious, the use of the conditions are extremely harsh, often because of the material wear and tear was forced to stop production maintenance. Where the use of steel fiber reinforced castables, fused mullite tiles, water-cooled cast iron, etc., although achieved good results, but with the increase in production capacity and maintenance cycle to extend the material on the higher The request.
Platform brick, slide brick, refractory brick tiles with high strength, excellent wear resistance and anti-slag erosion strong, long life (up to 1 to 2 years) and so on.

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Refractory materials for industrial furnaces

Refractory materials for industrial furnaces

Refractory materials for industrial furnaces:
High-strength lightweight clay high alumina brick, high-aluminum foam brick, poly light brick, light mullite insulation brick, heavy carburizing refractory brick, diatomaceous earth insulation brick, pearlite refractory bricks. All kinds of pit furnace, box furnace, carburizing furnace, trolley furnace, vibration furnace, steel chain plate furnace, mesh belt furnace, crucible furnace, push burning furnace, vacuum furnace, salt bath furnace with light, Heavy standard fire bricks, shaped bricks. Electric corundum furnace tube, silicon carbide furnace tube, high alumina furnace tube.
Electric radiant tube with corundum, high aluminum insulator, plug cover clip.
Electric furnace furnace with corundum silicon carbide brick, radiant furnace floor. Textile machinery singeing machine with a variety of specifications of silicon carbide fire bricks, honeycomb panels, masonry with a variety of high temperature adhesives.
Fire mud, anti-carburized mud, aluminum silicate fiber cotton, aluminum silicate fiber felt, aluminum silicate fiber board.

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Characteristic Refractory Material Mud Mixing Method

Characteristics of refractory material mud mixture method is to produce special refractory products, in particular the use of gypsum injection molding, casting and injection molding molding of the mud slurry f operation method is the ingredients of various refractory raw materials, enhancers, Suspending agent, admixture and 30 ~ 40% of the clean water, while adding a wear-resistant lining in the ball mill (mixing mill), after a certain period of mixing fine grinding, made for the production of mud slurry. In the process of making mud, according to the characteristics of materials and mud pouring their own requirements, to control the density and pH of the mud.
Mud mixing method used by the main equipment are ball mill, air compressor, wet iron, mud pump, vacuum degasser and so on.
Paraffin and resin-based binder, at room temperature for the solid refractory materials (or into a sticky), at room temperature, especially law mixture, must be used to increase the method of heating.
The use of hot casting process, the use of paraffin as a binder. Due to the melting point of paraffin in the 60-80 <€, in the first paraffin heated to 100T or more and have good mobility, and then the fine powder raw materials added to the liquid paraffin, the mixing after mixing, made of slurry Wax cake for hot die casting.
The main mixing equipment for heating the mixture is a heated mixing mixer.