Damage reason of refractory

According to the specific conditions of various furnaces and thermal equipment, proper selection and application of refractory material is very necessary. It is to improve the service life of the kiln and thermo technical equipment, reduce maintenance time, reducing the consumption of refractory material and energy, improve furnace production and guarantee the quality of the products and reduce the cost of production plays an important role.

As is known to all, there will be some damage reasons for different kinds of kilns or thermal equipment under different working conditions. Even in different parts of the same furnace or thermal equipment. There are many factors that affect the damage of refractory materials:

(1) The use of the temperature is too high, exceeding the limit temperature of the refractory;

(2) The temperature changes in temperature, refractory material damage in blast crisis;

(3) The refractories by slag furnace, mechanical shock or friction and wear serious the damage;

(4) The refractory material is damaged by the high temperature physical and chemical erosion and penetration of the molten metal, slag and furnace gas;

(5) The thermal stress and the weight of the heat generated by the heat of the refractory material cause damage to the stress concentration and the volume effect.

The above factors are not isolated, only to find out the main influencing factors in order to correct selection of refractory materials.

Insulation materials used in power plant

Thermal insulation refractory material in the electric power industry especially thermal power plants, such as coal-fired power plants occupies an important position. It has energy saving, reduce heat loss, to meet the requirements of the power plant production process, ensure theequipment, production and personal safety, improve the environment, improve the economic benefit, is an important part of the construction of power plants. So the power plant is commonly used in the refractory material is light heat insulation brick. According to the present and future development, electric power industry of insulating refractory material demand quantity big, more varieties, high quality requirements, which the fiber insulation refractoriness demand maximum, followed by hard material, and is lightweight materials and thermal insulation coating.

One, according to the various parts of the heat preservation refractory materials of the insulation requirements of choice

(1) The medium temperature of the equipment and the pipeline at 350~600 is chosen to use calcium silicate products, aluminum silicate composite insulation;

(2) with rock, mineral wool products such as insulation equipment and piping medium temperature less than 350 DEG c;

(3) The valve, elbow and other special-shaped pieces of light insulation material or heat preservation coating insulation;

(4) The use of ordinary aluminum silicate fiber rope insulation is less than 38mm;

(5) The low temperature equipment and piping in the wet environment are chosen for the insulation of the hydrophobic insulation material

High alumina refractory brick for hot blast furnace

Hot air furnace is insulation and withstand high temperature load, so to determine the various parts of the furnace lining refractory brick material and thickness of, should according to the requirements of masonry bearing temperature, load and heat insulation and flue gas of masonry of physical and chemical action condition and decide.

The has good resistance to creep and corrosion resistance, domestic use of high aluminum brick containing Al2O3 with greater than 65% is adopted abroad of SiO2 94~96% siliceous refractory brick is with or containing Al2O3 72%~76% mullite refractory brick using high temperature zone of the upper 30% to 40% of the height of hot air furnace lining refractory bricks. According to the experiment, under the condition of 0.2MPa, 1550 and 50h, the former is 0%~0.5%, the latter is 0.1%~0.3%, and so the creep resistance is good. The brick arch with the thermal shock resistance is better, so as to avoid peeling and cracking. For the middle and lower part of the refractory brick should be considered to the compressive strength, the general use of clay brick and high alumina brick. Selection of heat insulation material should pay special attention to the work of the hot surface temperature should not be higher than the allowable temperature. Insulation wall and the upper part of the vault generally use diatomite refractory brick or lightweight clay brick.

Refractory materials for aluminium melting furnace

The main equipment for thermal melting aluminum has calcinations sintering furnace, melting furnace and electrolytic cell. The rotary kiln firing with a lining of high aluminum brick masonry are commonly used, other parts available clay brick as a liner, insulation layer close to the furnace shell at laying a layer of refractory fiber felts and masonry a layer of light brick or light weight castable refractory pouring.

The most common aluminum smelting equipment is a reflective furnace. The lining of the molten aluminum contact. In general, the Al2O3 content is 80% ~ 85% of the high aluminum brick masonry, melting high purity aluminum metal, are advised to the mullite brick and corundum mullite brick. Some factories in hearth slope and scrap aluminum material, easy erosion and wear parts, the use of silicon nitride bonded silicon carbide brick masonry. Flow aluminum groove and an opening of the aluminum and other parts, aluminum melt erosion heavier, the general use of self bonding or silicon nitride combined silicon carbide brick masonry, and also useful zircon brick lining. The effect of the refractory fiber cone is better than that of the aluminum outlet. The lining does not contact the molten aluminum, using clay brick, fireclay refractory castable refractory material such as plastic or masonry. In order to speed up the melting speed and save energy, light brick, light refractory and refractory fiber products are widely used in the present work.

Aluminum smelting induction crucible furnace is more commonly used equipment, its lining generally use Al2O3 content is 70% ~ 80% of high alumina castable refractory ramming material production, but also useful for just corundum brick concrete lining of.

Aluminum molten liquid from the furnace outlet, the flow of aluminum trough. The slot liner generally adopts silicon carbide brick, useful also fused silica foam perform. Such as the use of precast block for tank lining, the surface should be coated fused silica or as protective layer with high alumina cement electric fused silica foam refractory castable.

Easy damaged part and common refractory for steelmaking electric arc furnace

The current commonly used arc furnace, furnace wall and bottom furnace, the hot spot is the weak link of electric arc furnace.

Reasons for damage of the refractory at the top of the one is splashes, furnace dust erosion; second is due to the high around the electrode temperature, top temperature difference larger
caused by melt erosion and thermal shock. Commonly used in the refractory with high aluminum brick, magnesia chrome brick, dolomite brick, silica and other and relevant material of refractory pouring material or ramming material, and some also used prefabricated pieces of the roof of the furnace.

Hot parts of furnace wall lining easy erosion, the reason is high temperature, molten steel and slag erosion, charging the impact.Refractory material is mainly used all kinds of basic refractories, the prevailing magnesia carbon brick.

The damage of the bottom is mainly due to chemical erosion and mechanical Chong, commonly used alkaline refractory ramming material or castable lining, the dry vibration material effect is good.

The overall development trend of the steelmaking electric arc furnace is the large-scale, two is the power unceasing enhancement, and three is the additional enhancement smelting measure. The steelmaking arc furnace of new technology: strengthening smelting enriched pulverized coal injection, bottom blowing stirring, eccentric bottom tapping, DC electric arc furnace.

The new technology adopted, both positive and negative influences to the refractory material, overall negative effect on refractory larger, such as ultra high power, oxygen enriched intensified smelting, bottom blowing stirring the refractory material of the more demanding conditions of use. Eccentric bottom tapping and DC arc furnaces are the conditions for the use of refractory material of furnace wall relative improvement, but conditions of use of certain parts of refractory become demanding, especially for DC arc furnace bottom lining. Therefore, the refractory industry must develop new varieties to meet the need of new technology for steelmaking arc furnace.

Properties of clay refractory

(1) Fire resistance. The low degree of fire resistance of clay refractory products is lower, and the increase of three aluminum oxide content in clay brick is improved… Generally 1580 for ~1750;

(2) Load softening temperature. Fireclay refractory load softening temperature is low; refractoriness under load was usually less than 1300 degrees.

(3) Thermal shock stability. Fireclay refractory thermal shock stability is better, the main reason is mullite crystals are surrounded by glass phase, mullite itself smaller coefficient of expansion, when heated does not produce stress concentration, so the stability of thermal shock resistance is good.

The main factors that affect the thermal shock stability of clay refractory are the physical properties of raw materials and the structure of clay brick… Therefore, the thermal stability of the clay brick can be improved by increasing the proportion of clinker and adopting reasonable brick making process…

(4) Slag resistance. The main chemical constituents of the clay refractory are silica and threealumina, and the former is more than the latter, and the clay brick is obviously weak acidity… Therefore, the ability of acid slag erosion ability than the strong anti alkaline slag.

Increase the density of two aluminum oxide and clay brick, increase the content of clinker, decrease porosity and decrease the impurity content of clay brick, and increase slag resistance of clay brick…

(5) The change of heavy firing line. For the clay refractory, the shrinkage of the residual shrinkage is no more than l%. Increasing tile clinker proportion, an appropriate increase in firing temperature and reasonable insulation, can make clay brick volume stability improvement, that reheating linear change decreases.

Why coke oven must use silica bricks

Silica brick belongs to acidic refractory  material, has good acid resistance erosion ability, its good thermal conductivity, high refractoriness under load, general in 1620 DEG C above, only than the low refractoriness of 70 to 80 DEG C. Brick thermal conductivity increases with theincrease of temperature, no residual shrinkage, in the baking process, the volume of the brick with the increase of temperature increases. Therefore, silica is coke oven ideal refractory products, modern large and medium coke important parts (such as the combustion chamber, ramps and regenerator with brick masonry.

In the baking process, silica brick maximum expansion occurred in the 100 to 300 DEG C, 300 DEG C before the expansion is about 70% to 75% of the total amount of expansion. The reason is SiO2 in baking process appear 117 degrees, 163 DEG, 180 to 270 DEG C and 573 DEG C four crystal transition points, including 180 to 270 DEG C, caused by cristobalite volume maximum swelling.

Thermal stability of silica brick quality is the key to true density and the size of the true density is to determine the important symbol of the transformation of the quartz. The true density ofsilicon is smaller, the lime into more completely and the residual in the oven in the process of expansion is small.

In the brick, tridymite crystal true density minimum and linear expansion rate, good thermal stability such as quartz and quartz, slag corrosion resistance strong, good thermal conductivity, high refractoriness under load is quartz volume is the most stable form. Burnt better silica brick, tridymite content was the highest, accounting for 50% ~ 80%; cristobalite times accounted for only 10% ~ 30%; and quartz and glass phase content fluctuation in 5% ~ 15%.

When the working temperature is lower than 600 DEG C, brick volume changes larger, anti sudden cold and hot performance is poor, the thermal stability is not good. If the coke oven is working at this temperature, the masonry is easily cracked and damaged…