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Selection of Refractory Aggregate and Powder for Ultra-Low Cement Castables for Iron Troughs

2024-11-152024-11-08 by globalrefractory

In the preparation process of ultra-low cement refractory castables for the blast furnace tapping channel, the selection of refractory aggregates and refractory powders is very important. Only by selecting suitable refractory aggregates and powders, reasonably preparing them, and using them in proper amounts can they play their greatest role. Rongsheng refractory material manufacturer, an advanced fully automatic amorphous refractory castable factory, specializes in providing long-life refractory castable products for high-temperature industrial furnaces. Contact Rongsheng to get a free quote for ultra-low cement castables for tapping channels.

Selection and grading of refractory aggregates for ultra-low cement castables for iron trenches

In ultra-low cement refractory materials, the amount of refractory aggregate is generally 68% to 72%, which acts as a skeleton and can significantly affect the performance of the refractory castable lining. The thickness of the lining and the construction and production methods are different, and the critical particle size of the refractory aggregate is also different. At present, the critical particle size of refractory aggregates tends to decrease, and 8mm or 5mm is generally used. The preparation of iron ditch refractory castables usually adopts three-level gradation or four-level gradation. The particle gradation is as follows: 8~5mm 40%~60%, 5~1.2mm 10%~30%, 1.2~0.15mm 20%~40%. Or 5~3mm 40%~60%, 3~1mm 20%~30%, 1~0.15mm 15%~25%. Different types of refractory aggregates have different properties of the prepared ultra-low cement castables.

Ultra Low-Cement Castable Precast Shapes for Iron Trough

The influence of aggregate type and quality on the properties of castables. Different types of refractory aggregates have different drying compressive strengths of castables. That is, the quality of refractory aggregate directly affects its performance. Because good aggregate has low porosity and low water absorption, the castable requires less water and its performance can be improved.

Preparation of refractory powder for iron ditch castables

Refractory powder is the matrix material of amorphous refractory materials, which plays the role of filling aggregate gaps and improving construction and workability.

Refractory powder for iron ditch castables includes fused corundum powder, SiC powder, and carbon materials, among which the amount of fused corundum powder is 5% to 10%. The amount of ultrafine powder should be determined according to the experience of its variety, generally 5% to 15%. Among them, the appropriate amount of active SiO2 ultrafine powder is 5% to 7%, and the amount of other ultrafine powders is 7% to 10%.

Use of active SiO2 ultrafine powder and α-Al2O3 ultrafine powder

In ultra-low cement refractory castables, the basic mechanism of action of ultrafine powder is filling. In ultra-low cement refractory castables, various ultrafine powders can form colloidal particles in water. When a dispersant is present, the double electric layer formed on the surface of the particles overlaps to generate electrostatic repulsion, which prevents adsorption and flocculation between particles. At the same time, the dispersant is adsorbed around the particles to form a solvent layer, thereby increasing the fluidity of the castable.

The ultrafine powders used in Tiegou refractory castables mainly include active SiO2 powder and α-Al2O3 powder. The content of their components is 93.2% and >90%, respectively, and the particle size distribution <1.0μm should be >70%.

There are two types of SiO2 ultrafine powder. One is made of high-purity silica, and the other is a by-product of producing metallic silicon or ferrosilicon. The former is granular and inactive, while the latter is hollow spherical and active, does not agglomerate, and has good dispersibility and filling properties. It reacts with volcanic ash at room temperature and reacts with Al2O3 to form mullite at high temperature, which is beneficial to improving the strength of the castable.

α-Al2O3 ultrafine powder is made by calcining industrial alumina. Its characteristics are good dispersibility, small particles, easy sintering at high temperature and small volume effect.

Active SiO2 is added to ultra-low cement refractory castables. When the temperature is higher than 900°C, it reacts with Al2O3 in powder or cement. Mullitization is gradually formed, producing a volume effect, offsetting part of the volume shrinkage of the refractory castable, and promoting the improvement of strength. Adding α-Al2O3 ultrafine powder can cause calcium aluminate to form more calcium hexaaluminate (CA6) at high temperatures, as well as a small amount of mullite, anorthite, etc. The molar volumes of these minerals are relatively large, which prevents their volume from shrinking. Microscopic observation confirmed that the main crystal phase CA6 is a small columnar and needle-shaped crystal, and the anorthite is a small columnar crystal, which together form a small columnar and needle-shaped cross-skeleton structure, which is relatively strong and dense. Therefore, the strength of the castable can be significantly increased.

As the amount of ultrafine powder increases, the effect of cohesion and bonding increases, the strength increases, the volume density increases, and the apparent porosity decreases. However, increasing the dosage of SiO2 ultrafine powder will reduce the Al2O3 content in the castable. At the same time, the increase of free quartz will inevitably lead to a decrease in the slag resistance of the castable. Experiments have proven that when the dosage of SiO2 ultrafine powder is about 5%, the slag resistance is the best. In addition, adding more ultrafine powder will cause uneven shrinkage of the castable after high-temperature sintering, resulting in a significant decrease in strength.

Effect of ultrafine powder on the flexural strength of ultra-low cement castables. The ultrafine powder mixed with equal amounts of active SiO2 and α-Al2O3 has the highest strength. In fact, in ultra-low cement refractory castables, not only the fineness of the ultra-fine powder plays a role, but also its shape and activity. For example, SiO2 powder is silica fume, which is spherical and active, although slightly thicker. However, its filling and water-reducing properties are better than granular inactive α-Al2O3. Therefore, the dosage of active SiO2 ultrafine powder can also be less.

Effect of ultrafine powder dosage on the compressive strength of castables. As the amount of ultrafine powder increases, the compressive strength increases after sintering at 1600°C. When the dosage of SiO2 ultrafine powder is about 5%, the dosage of Al2O3 ultrafine powder is about 7%. At this time, the compressive strength is high and other properties are also excellent.

Use of silicon carbide and carbon materials

SiC and carbon materials should be added to the iron trench refractory castable to improve its slag resistance and thermal shock stability. Tests and use have shown that the grade and amount of SiC and carbon materials have a great influence on the performance of the castable. The grade and amount should be reasonably selected according to the size of the blast furnace and the different parts of use.

In the iron trench refractory castable, silicon carbide plays a filling role and forms the matrix of the iron trench material. Therefore, the particle size should be <3.4mm, of which <0.15mm should account for more than 60%. The particle size of the carbon material should also be less than 0.3mm.

Due to the addition of SiC and carbon materials, the oxidation resistance of the castable is reduced. To improve the oxidation resistance of the castable, metal aluminum powder and metal silicon powder can be added at the same time. In this way, metal silicon and aluminum react with carbon at high temperatures to generate SiC and Al4C3. The castable’s structure and surface are made denser, its oxidation resistance is improved, and the castable’s strength is also improved.

Factors Affecting the Performance of Refractory Castables

2024-10-25 by globalrefractory

There are many varieties of refractory castables, with different mix proportions, different performances, different construction methods, and different maintenance systems. Rongsheng Refractory Material Factory has found that there are many factors that affect the performance of refractory castables based on their production and sales experience over the years. The specific ones are as follows.

Application Fields of Refractory Castables

Amount of cement

Cement is one of the important components of refractory castables. It is an important material that determines strength and also affects other properties. Different types of cement and their dosage have different effects on performance. For example, CA-50 cement high-alumina refractory castables, refractory aggregates and powders are both secondary alumina clinker, and the amount of water added is 10%. With the increase of cement dosage, the compressive strength at room temperature will increase. The compressive strength after burning at 1200℃ is 40%~65% lower than the drying compressive strength. The refractoriness and load softening temperature continue to decrease, and the linear shrinkage after burning also increases. This is because CA-50 cement has a high impurity content and low refractoriness. When the dosage increases, the amount of liquid phase in the heating process of the castable is large, resulting in a decrease in performance. Therefore, under the condition of ensuring the strength at room temperature, the amount of CA-50 cement should be minimized to improve the high-temperature performance of the refractory castable. When the amount of cement is reduced, the refractory powder should be appropriately increased so that the combined amount of cement and powder can fully wrap the refractory aggregate and the refractory castable can achieve the maximum density. The commonly used cement dosage is 10%~15%.

Water addition

Different types of aluminate cement can produce different refractory castables. The same type of cement can also be used to make multiple types of refractory castables. When the mix ratio and process conditions of refractory castables are the same, the influence of water dosage on the performance of refractory castables is basically the same. Taking CA-50 cement high-alumina refractory castable as an example, the influence of water dosage on the performance of castables is that refractory aggregate and powder are both secondary alumina clinker, aggregate is 70% of the total material <15mm, powder and cement are 15% each. After the initial setting of the molding, the mold is removed after wet curing for 1d, and then standard curing is carried out for 2d to test various properties. As the amount of water used in the castable increases, various properties generally decrease significantly. The compressive strength at room temperature decreases by 27%~35%, the drying compressive strength decreases to 19.1MPa, the compressive strength after burning decreases by about 40%, and the high temperature compressive strength decreases by about 57%. The load softening temperature dropped from 1400℃ to 1250℃, and the post-firing line change dropped from -0.38% to -0.96%. The apparent porosity increased from 19% to 23%, and the bulk density dropped from 2.29g/cm3 to 2.17g/cm3. That is to say, the selection of water dosage (or water-cement ratio) is very important when preparing aluminate cement refractory castables. When the amount of water is large, after heating, the water escapes, the pores increase, the structure becomes loose, and various properties are reduced comprehensively. Therefore, under the condition of ensuring its construction and workability, the amount of water in the mixture should be minimized. Under the premise of not adding water reducing agent, the appropriate water dosage of aluminate cement refractory castable is 10%~13%.

It should be pointed out that when the mix ratio and production process of refractory castables are basically the same, there is an optimal value for its water dosage. Therefore, when constructing and making aluminate cement refractory castables, they should be tried and mixed first to select the best fluidity. Compare the strength at room temperature and determine the optimal amount of water before production and construction can begin.

Refractory powder

Refractory castables are generally mixed with appropriate refractory powder. Its functions: (1) Reduce cement consumption, reduce costs and increase operating temperature. (2) Refractory powder can play a role in infertility, and can participate in reactions at high temperatures to form high-temperature resistant minerals to improve refractory performance. (3) The addition of refractory oxide ultrafine powder can reduce the amount of water, form high-temperature resistant minerals at high temperatures or enhance sintering properties, so it can improve the performance of castables. The type, fineness and dosage of refractory powder are important factors affecting the performance of castables.

The fineness of refractory powder directly affects the strength, bulk density and apparent porosity of refractory castables. Generally speaking, the finer the refractory powder, the better the performance of the refractory castable. When ultrafine powder is used to replace part of the refractory powder, its bulk density increases, its apparent porosity is low, and its strength is significantly improved.

Refractory Aggregate

Refractory aggregate is one of the important components of refractory castables. Its variety, grade, maximum particle size and particle grading are the main factors affecting performance. The influence of refractory aggregate variety on the performance of refractory castables. In addition, the grade, impurity content and sintering quality of refractory aggregate also affect its performance. For example, when alumina clinker is used as refractory aggregate, as the Al2O3 content increases, that is, the grade improves, the refractoriness and load softening temperature of the castable increase, and the linear change after burning decreases. When the material is under-burned or has a high impurity content, its refractoriness and load softening temperature decrease, and the linear shrinkage after burning is large. Therefore, only by selecting suitable refractory aggregates with good sintering and high purity can high-performance refractory castables be prepared.

The more irregular the shape of the refractory aggregate particles, the better, and try not to use long flake materials. Its maximum particle size should be determined according to the thickness of the lining. Once the maximum particle size of the refractory aggregate is determined, its particle grading has a significant impact on the performance of the refractory castable.

Additives

Common additives used in refractory castables are generally divided into water reducers, setting accelerators and setting retarders. In addition, sintering agents and expansion agents are also added. It should be noted that the refractory cement used in refractory castables is different, and the selected additives and their dosage are also different, which should generally be determined by experiment.

Maintenance system

Maintenance systems are divided into standard maintenance, natural maintenance, wet maintenance, steam maintenance, water maintenance and dry maintenance.

The technical team of Rongsheng manufacturer reminds that when constructing amorphous refractory castables, they must be constructed strictly in accordance with the construction instructions. Strictly control the amount of water added. Choose experienced construction workers. To ensure the efficient construction quality. If there are any problems with the construction of refractory castables, technical formula adjustment, etc., please let us know. We can customize refractory lining material solutions according to your actual working conditions.

What is the Difference between Low Cement Castable and Ordinary Refractory Castable?

2024-10-11 by globalrefractory

The low cement series refractory castables are developed on the basis of clay-combined refractory castables. According to their content characteristics, they are mainly divided into low cement refractory castables, ultra-low cement refractory castables, and cement-free refractory castables.

The main characteristics of low cement series refractory castables are high volume density, low porosity, high compressive strength, good wear resistance, good thermal shock resistance and strong erosion resistance. In terms of construction, the advantages of low cement refractory castables are strong volume stability and low water consumption in construction. Because of these, low cement refractory castables are widely used.

Classification of Low-Cement Series Refractory Castables

There is no national standard or industry standard for this product in the industry. Therefore, manufacturers have many names for this type of product, some are called dense high-strength refractory castables, some are called low-porosity refractory castables, and some are called low-moisture refractory castables based on the characteristic of low water addition during construction. In foreign countries, the United States classifies low-cement series products according to the calcium oxide content in the castable. Traditional cement castables (calcium oxide content greater than 2.5), low-cement castables (calcium oxide content between 1.0 and 2.5), ultra-low cement castables (calcium oxide content between 0.2 and 1.0), cement-free or ultra-fine powder castables (calcium oxide content less than 0.2).

According to the material of its main raw materials, it is divided into mullite low cement castable, corundum low cement castable, spinel low cement castable, aluminum silicate low cement castable, high aluminum low cement castable, etc.

According to its scope of use, it is divided into ladle refractory castable, iron ditch refractory castable, etc. Different parts of use can directly name the low cement refractory castable.

Compared with traditional aluminate cement castables, low cement refractory castables have a lower cement content. Generally, the cement content of low cement series products is less than 4%, and the water content is less than 11%.

Low-Cement Steel Fiber Reinforced Castable

What are the Differences between Low-Cement Castables and Ordinary Refractory Castables?

Low-cement castables have the characteristics of high density, low porosity, high strength, low wear, thermal shock resistance and erosion resistance. They are mainly used in metallurgy, electric power, petroleum, chemical industry and various silicate kilns. Such as some components of off-furnace refining devices, off-furnace refining bag covers, electric furnace top linings, heating furnace soaking furnace linings, annealing furnace linings, tundish linings, steel tapping troughs, high-temperature burners and blast furnace iron tapping ditch covers, iron ladle linings, etc.

Low-cement castables have high fluidity. They are used as industrial furnace linings. On-site pouring, smearing and ramming construction methods can be used.

Low cement castables are similar to ordinary refractory castables. They are all composed of refractory aggregates, refractory fine powders and binders. The difference is that in the matrix composed of refractory fine powders and binders, fine powders are used to replace part or all of the alumina cement. A small amount of dispersant is added to evenly disperse the fine powders between the aggregate particles and fill them in the submicron-level gaps, thus forming a uniform and dense organizational structure. The key to this type of castable is the introduction of fine powders and their dispersion technology. In the field of amorphous refractory materials, ordinary cement castables have low medium-temperature strength and poor spalling resistance. The clay-bonded castables introduced in the early 1970s, although the medium-temperature strength has been improved, the room-temperature strength is much lower than that of ordinary cement castables. They cannot meet the needs of industrial furnaces and thermal equipment for refractory materials. In order to change this situation, low-cement high-strength refractory castables have been developed at home and abroad in recent years.

The main uses and advantages of low-cement castables. The use temperature of low cement castables and ultra-low cement castables is higher than that of ordinary refractory castables of the same material. The use temperature of low cement castables and ultra-low cement castables is higher than that of ordinary refractory castables of the same material.

Rongsheng Refractory Material Factory, environmentally friendly fully automatic monolithic refractory material production line, specializes in providing high-quality monolithic refractory material lining for high-temperature industrial furnace lining. Low cement castables, ultra-low or no cement castables, use micro powders with the same or similar chemical composition as the main material to replace most or all cement. Scientifically optimize factors such as particle grading, micro powder, particle morphology, etc., and add a small amount of dispersant (water reducer) and appropriate amount of retarder and other composite admixtures. Contact Rongsheng for free samples and quotes.

RS Low-Cement Castable Refractory Factory

Physical and Chemical Properties of Ultra-Low Cement Castables

Ultra-low cement castables are a common category of refractory castables for cement kilns. Due to the continuous updating of technology in recent years, the problems of slow setting, hardening and low dry strength have been solved, and the problem of excessive strength after burning has been solved. Ultra-low cement refractory castables with excellent performance have been developed. The physical and chemical performance indicators of ultra-low cement castables made with the introduction of 0.5% CaO are as follows.

The flexural strength of ultra-low cement refractory castables after drying at 110°C is 9.8MPa and the compressive strength is 78MPa. After sintering at 1100°C, the flexural strength is 21MPa and the compressive strength is 155MPa. After sintering at 1500°C, the flexural strength is 18MPa, the compressive strength is 149MPa, and the line change after burning is 0.02%. These properties fully meet the requirements of cement companies. This ultra-low cement refractory castable is made of active calcium aluminate cement. If ordinary pure calcium aluminate cement is used with silica sol or diluted chain sol as an auxiliary binder, ultra-low cement refractory castables with similar properties can also be produced.

Magnesia Refractory Castable in Rongsheng Refractory Manufacturer

2024-09-27 by globalrefractory

Magnesia refractory castable is a castable refractory material with magnesium oxide (MgO) as the main component. According to the material, it can be divided into: alkaline castables such as magnesia, alumina-magnesia, spinel, magnesium-chromium, magnesia-silica and magnesia-carbon. Magnesite (periclase) refractory castables are prepared from fused magnesia or sintered magnesia aggregates and fine powder.

High-Quality Alumina Magnesia Refractory Castable

Magnesium Refractory Castables with Different Properties

The magnesia refractory castable combined with high alumina cement has the advantages of high purity, small linear change rate after burning, and high load softening temperature. However, as the heat treatment temperature increases, especially between 400 and 1200°C, the magnesium hydroxide generated by the hydration of magnesia loses its cementing effect due to dehydration, and the combination of refractory aggregate and powder becomes loose and peels off.

The magnesia refractory castable combined with water glass has the advantages of high strength and strong resistance to alkali and sodium salt molten corrosion. However, due to the use of water glass as a binding agent, a large amount of Na2O (or K2O) and SiO2 are brought in, which greatly reduces the fire resistance and load softening temperature of magnesia refractory castables. This limits the maximum service temperature of water glass bonded castables.

The magnesia refractory castable combined with polyphosphate has the advantages of high strength after burning, small decrease in strength as the heat treatment temperature increases, high softening temperature under load, and good thermal shock resistance. However, at high temperatures (above 1400°C), the strength of magnesia castables decreases due to the large amount of P2O3 volatilization. Generally speaking, sodium polyphosphate is used as the binder for magnesium castables.

Commonly used ones include sodium tripolyphosphate, sodium hexametaphosphate, etc. The degree of polymerization of polyphosphate and the content of P2O3 have a great influence on the strength of castables. When the average polymerization degree of polyphosphate is 24, the castable has the greatest strength. In addition, in order to improve the high-temperature strength of magnesia refractory castables, add an appropriate amount of calcium-containing materials (such as calcium carbonate, etc.). In order to generate the Na2O·2CaO·P2O5 phase with high collective strength and stable existence at high temperature.

However, no matter which of the above-mentioned binders is used, it is difficult to overcome the problem of easy hydration of magnesia refractory castables, and cracks are prone to occur during the drying process. Adding an appropriate amount of silica ultrafine powder can overcome hydration problems.

Advantages of Ultrafine Powder Combined Magnesium Refractory Castables

Ultrafine powder combined with magnesium refractory castables were successfully developed around 1990. They have good resistance to slag erosion, less pollution to molten steel and have a purification effect. However, due to the presence of magnesium oxide, the resistance to slag permeability and thermal shock resistance is reduced. At the same time, the low medium temperature strength and easy water absorption and powderization affect the promotion and use of castables.

In recent years, a lot of effective work has been done in the research and improvement of the varieties and performance of ultrafine powder combined with magnesium refractory castables. Its varieties have increased and its defects have been improved. It has also been used in thermal equipment such as ladle slag line, tundish working lining and slag weir, non-ferrous metallurgical Ausmelt furnace and slag depletion furnace, with good results.

The varieties of superfine powder combined with magnesia refractory castables include magnesia, magnesia chromium, magnesia spinel and magnesia calcium. The first three castables developed earlier, faster and more practical, and the latter magnesia calcium refractory castable is under development. The key is to solve problems such as hydration.

The refractory aggregates of superfine powder combined with magnesia refractory castables include fused or high-purity magnesia, high-quality magnesia, brick-making magnesia and metallurgical magnesia. Refractory powders include magnesia powder, chromite powder, aluminum magnesium spinel powder, Cr2O3 and a-Al2O3 and other superfine powders, and uf-SiO2 powder is used as a binder, and admixtures and explosion-proof agents are added.

Magnesium Castable Refractory in Rongsheng Company

Magnesia Cement Refractory Castables

Magnesia cement mainly includes periclase cement and periclase-spinel cement, which are made by grinding highly recrystallized sintered magnesia sand. Its setting and hardening mechanism is mainly the hydration reaction of magnesium oxide and the crystallization of magnesium hydroxide. The reaction formula of cement is:

MgO+H2O——Mg(OH)2

However, the hydration rate of periclase cement is slow. Therefore, tempering agents such as magnesium chloride, magnesium sulfate and magnesium nitrate should be added to promote its hydration and crystallization. It is well known that the solubility of magnesium hydroxide in water is very small, and its gel is difficult to crystallize into large particles. When the tempering agent is added, the boiling point of the tempering water is increased, the solubility of magnesium hydroxide is increased, and the crystallization and growth of magnesium hydroxide gel are accelerated. This needle-shaped brucite crystal cross-grows, which makes the magnesia cement refractory castable gain strength. The effect of magnesium chloride as a blending agent is better than that of magnesium sulfate and other blending agents because magnesium chloride as a blending agent also generates magnesium oxychloride which gradually crystallizes and promotes the coagulation and hardening of cement.

This type of refractory castable is air-hardening and should be naturally cured after molding without watering.

For example, the mix ratio of refractory castables combined with magnesia cement is that the refractory aggregate is metallurgical magnesia sand aggregate, chromium slag and cement, iron powder, and magnesium chloride solution and magnesium sulfate solution are added with iron powder to act as mineralizers or sintering agents.

The drying strength of periclase cement refractory castable is relatively high. However. At about 400℃, the strength begins to decrease due to the decomposition of magnesium hydroxide. As the heating temperature increases, the organizational structure becomes loose and the strength continues to decrease. When the temperature reaches 1000~1200℃, it has not yet been sintered, and the strength is reduced to the lowest point, only 2.5-9.3MPa. When it exceeds 1200℃, the strength rises slightly due to the recrystallization of magnesium oxide. At about 1400℃, solid phase reaction begins, and the strength increases, which is about 25% of the drying strength. When iron powder and chromium slag are added, the sintering of periclase can be promoted, and the medium-temperature strength is improved.

To purchase high-quality magnesium refractory castables, please choose Rongsheng Refractory Material Factory. The product quality is reliable and the performance is guaranteed.

Improvement of Lime Kiln Burner Brick Material

2024-09-142024-09-13 by globalrefractory

The magnesia refractory bricks used in the burners of general sleeve lime kilns are prone to breakage within more than one year of use. This makes the service life of the burner bricks inconsistent with the life of the kiln body. One-third of the burner bricks of the sleeve lime kiln broke within less than one year of use, while the service life of the lime kiln is more than 3 years. Therefore, the service life of the burner bricks is inconsistent with the life of the kiln body. Although the breakage of the burner bricks does not affect the use of the lime kiln, it has a certain negative impact on the calcination process.

The Reason Why Burner Bricks are Easy to Break

The reason why burner bricks are easy to break is that the material used for burner bricks is magnesia refractory bricks. In addition to having excellent high temperature resistance and anti-lime reactivity, this alkaline material has the following unfavorable factors, which lead to premature breakage.

1: Magnesium refractory materials have large thermal expansion and poor thermal shock resistance. The burner bricks are washed by the hot air flow of the flame, and the thermal shock environment they endure is harsh, which makes them prone to cracks caused by thermal shock.
2: Due to the large thermal expansion coefficient, the thermal stress of magnesium refractory materials is high. When there is local stress concentration, it is easy to break.
3: Magnesium refractory materials are easy to hydrate, resulting in bulging and cracking. They are greatly affected by environmental conditions during construction. Improper baking is also prone to cracking, resulting in falling blocks. In cold and humid weather, the moisture in the fire mud is not easy to remove, and it is easier for the bricks to hydrate. Therefore, the construction environment conditions and baking requirements are strict
4: Magnesium refractory materials have low hot strength and are prone to creep under thermal stress.

Corundum-Mullite Burner Brick

Improvement of burner brick material The choice of corundum-mullite refractory castables to make burner brick prefabricated parts has the following advantages:

1: The main crystal phases of corundum-mullite refractory castables are corundum and mullite. The former has a high melting point of 2050℃, hardness and strength, can resist high temperature and airflow erosion, and has excellent high temperature wear resistance. The melting point of mullite is also relatively high at 1840℃, and its characteristic is a small thermal expansion coefficient. The crystal has a needle-column mosaic structure and has good thermal shock resistance. The composite refractory castable of corundum phase and mullite phase has the advantages of both, which can effectively resist the erosion of burner bricks by flame hot air flow. It can withstand harsh thermal shock environments and prevent burner bricks from breaking.
2: There is no hydration problem with corundum mullite refractory castables, and the construction is less affected by the environment. The construction conditions are not demanding, and the pouring, curing and heat treatment can be carried out at the material supplier, so the quality is easy to be guaranteed. It will not hydrate and crack during construction and baking.
3: The burner brick is a special-shaped brick, which is not easy to be machine-pressed. The pouring method is easy to achieve integral or split forming, and realize precise control of shape and size. The critical particle size of machine-pressed bricks is limited, generally 5 mm, while the critical particle size of castables can be as large as about 20 mm, which is conducive to the stability of the structure and improves the resistance to thermal shock.
4: When the burner brick is in use, the gas (or fuel oil) is sprayed into the furnace, and the CaO dust in the furnace is not easy to adhere to the burner cavity, and the reaction of CaO and Al2O3-SiO2 materials will not occur. Even if a small amount of CaO adheres to the burner brick, the Al2O3 content in the burner brick is high (greater than 75%), while the content of SiO2 and CaO is relatively low. According to the A12O3-SiO2-CaO ternary phase diagram, the temperature of the reaction is about 1500℃. It can be considered that the solid phase reaction of Al2O3-SiO2-CaO is not easy to occur at the working temperature of the lime kiln.

The magnesia refractory bricks used in the burners of general sleeve lime kilns are prone to fracture after more than a year of use, which makes the service life of the burner bricks out of sync with the life of the kiln body. That is, the burner of the sleeve kiln is prone to fracture. By analyzing the cause and reproducing the prefabricated burner bricks made of corundum mullite refractory castables suitable for the burner of the sleeve kiln according to the combustion process of the lime kiln calcining zone and the structure of the lining refractory material, the problem of burner brick fracture is effectively solved. And practice shows that the service life of the corundum mullite burner bricks is synchronized with the life of the kiln body.

Performance of High-Purity Mullite Refractory Bricks for Lime Kilns

High-purity mullite refractory bricks for lime kilns have important application value in the field of refractory materials. High-purity mullite refractory bricks for lime kilns are a type of refractory material specifically used in the lime kiln industry. It is made of high-purity mullite as the main raw material and sintered at high temperature. High-purity mullite refractory bricks for lime kilns have good wear resistance, high temperature resistance, shock resistance and corrosion resistance, and are an indispensable and important material in lime kiln production.

First of all, lime kiln high purity mullite refractory bricks have excellent refractory performance. This refractory performance advantage ensures the reliability of lime kiln high purity mullite refractory bricks during long-term use.
Secondly, lime kiln high purity mullite refractory bricks have excellent wear resistance. High purity mullite refractory bricks have high hardness and wear resistance, which can effectively resist the wear of materials and extend service life.
Next, lime kiln high purity mullite refractory bricks also have good seismic resistance. Lime kiln high purity mullite refractory bricks have good seismic resistance, which can effectively resist the influence of vibration on its structure and performance, and ensure long-term stable operation of equipment.
In addition, lime kiln high purity mullite refractory bricks also have good corrosion resistance. Lime kiln high purity mullite refractory bricks can resist the erosion of chemical substances and maintain their stable performance.

In short, lime kiln high purity mullite refractory bricks have excellent refractory performance, wear resistance, seismic resistance and corrosion resistance. Suitable for the production environment of various types of lime kilns. Its application can improve the working efficiency of the lime kiln, extend the life of the equipment, and reduce production costs. It is an indispensable and important material in the lime kiln industry.

Lightly-Burned Dolomite Double Chamber Kiln (Double C Structure) Kiln Refractory Lining Material

2024-09-142024-08-30 by globalrefractory

Double-chamber kiln is widely used in the production of metallurgical lime due to its advantages such as low heat consumption, high degree of automation, easy-to-adjust production, parallel flow heat storage, less refractory material usage, less floor space, stable product quality, etc. A project uses this kiln to produce and supply light-burned dolomite. Rongsheng Refractory Material Manufacturer supplies refractory lining materials for double-chamber kiln double C structure kiln of light-burned dolomite.

Double-Chamber Kiln Refractory Lining Structure

The construction of a double-chamber kiln of a light-burned dolomite manufacturer adopts a domestic double-chamber kiln with a “double C structure”. Its internal refractory masonry structure is shown in Figure 1. The double-chamber kiln lining structure is divided into cooling zone, calcining zone, and preheating zone from bottom to top. They are built with refractory materials with good high-temperature resistance, wear resistance, and thermal insulation performance. The two kiln chambers are constructed with an intermediate channel and 8 cooling pillars. The outer ring bricklayer of the kiln is counted from the bottom of the kiln chamber, a total of 194 layers.

Figure 1 Refractory masonry structure inside double-chamber kiln

The cooling belt and the bottom of the steel structure are leveled with low cement castables, and then the cooling belt is laid. From the 1st to the 40th floor, from the steel shell structure outward, coating material, two layers of fiberboard, insulation bricks, and high-strength clay bricks are used in sequence. The thickness of the fiberboard is 30mm, the thickness of the insulation brick is 230mm, and the thickness of the high-strength clay brick is 260mm. When laying each layer of bricks, expansion joints are reserved in the circular ring of the kiln brick layer at a certain distance.

From the 41st to the 82nd floor, as the kiln height gradually approaches the calcining zone area, the working temperature increases accordingly, and the brick lining working layer is changed to high-alumina refractory bricks.

The middle channel is equipped with a fire door. It is used to observe the ash accumulation during the kiln shutdown, and a template is required during masonry.

The calcining zone has the highest temperature, which can reach 1100℃. Considering the calcination characteristics and temperature, the working layer of the 83rd to 161st layers of bricks on the outer ring of the kiln is built with mullite refractory bricks. From the steel shell structure to the outside, it is built with coating material, two layers of fiberboard, insulation bricks, and mullite bricks in sequence.

Anchors are welded on the bottom of the steel structure and the supporting structure inside the kiln, and castables are used for masonry. At the same time, thermocouples are evenly arranged in the inner and outer ring areas of each kiln chamber to detect the calcination of the kiln.

The 162nd to 194th brick lining working layer is built with high-strength clay bricks as part of the preheating zone.

The entire kiln structure should be strictly symmetrical. In order to ensure the construction period, the masonry of the two kiln chambers can be carried out at the same time. During the masonry process, overlapping of brick joints should be avoided, and the mortar should be applied in sufficient and uniform amounts.

Problems with the Lining of the Double-C Structure Lime Kiln

After the double C structure lime kiln was in production for a period of time, two high-temperature spots were found on the surface of the furnace shell, and it was forced to be emptied for inspection. It was found that the refractory bricks in the working layer at about 700mm from the bottom of the kiln spray gun were burned, and the refractory bricks in the insulation layer were molten (see Figure 2). In order to avoid the recurrence of this phenomenon, it is necessary to analyze the cause of the burning of refractory bricks. The project team conducted a comprehensive analysis of the aspects of design, process operation, raw material structure, equipment installation structure, etc. Find the cause and optimize and rectify it.

Figure 2 Burning condition of refractory material in kiln shell at high-temperature point — Figure 2 Burning condition of refractory material in kiln shell at a high-temperature point

After investigation and inspection, it was found that the coal powder spraying gun was not installed correctly, and the flame directly washed the furnace wall, which was the direct cause of the burning of the refractory materials. The coal powder conveying fan was not a variable frequency fan, the wind pressure was too high, and the flow rate was too fast. The coal powder guide pipe was worn in less than one month, and the coal powder conveying of the spray gun increased, which was another reason for the aggravation of the burning of the refractory materials.

Rectification of the Lining of the Double-C Structure Lime Kiln

The construction and maintenance team was required to strictly follow the drawings to ensure that the spray gun was vertically parallel and downward and to ensure the distance between the spray gun and the furnace wall. This reduced the burning of refractory materials.

At the same time, the pulverized coal conveying fan was retrofitted with frequency conversion, and the fan operation program was updated. That is, the fan operating frequency was reduced during the reversing period, and the fan speed was adjusted according to the kiln conditions during the combustion period. This ensured the transportation of pulverized coal while reducing power consumption. The double-chamber kiln after the rectification had a good operating effect, and no corresponding refractory material burning occurred.

How to Improve the Service Life of the Kiln Refractory Lining?

After the double C structure kiln refractory bricks were overhauled and the conveying fan frequency conversion was modified, the entire kiln no longer had refractory material burning. This fully proves that the rectification effect is good.

(1) The abnormal damage of the furnace wall in the high-temperature section of the lime kiln causes the furnace shell to turn red. The main reason is that the mullite bricks in the working layer are corroded and melted at high temperatures during the production process.
(2) Alkali metals such as K₂O and Na₂O react with mullite bricks at high temperatures to form low-melting products such as feldspar. The mullite bricks are continuously corroded, and the furnace wall becomes thinner after melting, which causes the furnace shell to turn red at high temperatures.
(3) The source of alkali metal oxides in the lime kiln is mainly the ash of the mixed coal. Due to the double C structure of the kiln type, abnormal installation of the spray gun will also cause ash to adhere near the end wall and corrode the furnace wall.
(4) The frequency conversion of the conveying fan is conducive to reducing power consumption, stabilizing the kiln condition, reducing the erosion of the coal powder guide pipe, and increasing its service life.

Rongsheng Refractory Material Production and Sales Manufacturers is a powerful refractory material production and sales manufacturer. Rongsheng Refractory Manufacturer can customize the construction and maintenance plan of refractory lining according to the actual working conditions of high-temperature industrial furnaces. For high-quality refractory bricks and amorphous refractory products, contact us for free samples and quotes.

Advantages of Tunnel Kiln Lightweight Mullite Bricks Hang Roof Bricks

2024-08-02 by globalrefractory

Hanging roof tiles are generally made of mullite, so they are often called Mullite Hang Roof Bricks, or roof anchor bricks. The composition of mullite hanging bricks and mullite lightweight bricks is similar, and the general alumina content is between 65% and 75%. In addition to mullite, the mineral composition contains low alumina and a small amount of glass phase and cristobalite. Those with higher alumina content also contain a small amount of corundum.

Characteristics of Hang Roof Bricks

Low thermal conductivity and good thermal insulation effect.
Low heat capacity. RS insulation bricks store very little heat energy and have obvious energy-saving effects during intermittent operation.
Low impurity content, with very low oxide content such as iron and alkali metals. Therefore, the refractoriness is high, and the high aluminum content allows it to maintain good performance under reducing atmosphere.
High hot compressive strength.
Standard appearance and dimensions. Speeding up the masonry construction and reducing the amount of refractory slurry ensures the strength and stability of the masonry.

Lightweight Mullite Bricks Hang Roof Bricks

Performance Indicators of Hang Roof Brick Mullite

Fire resistance temperature: 1350-1550. Volume density: 800-1000kg/m3. Thermal conductivity (800℃): 0.35 w/n.k. Strength: 4-5Mpa.

Packing form: pallet. Product category: Mullite products.

Specifications: 230*230*65mm; 250*230*97.

Rongsheng Refractory Materials Manufacturer can customize the dimensions and specifications of Hang roof brick Mullite for enterprises according to the different sizes of various types of industrial kilns. Each company can also send us drawings, and we will customize the size specifications for the company based on the company’s design drawings.

Hang Roof Brick Mullite Uses

Various industrial kilns, such as bell furnaces, heating furnaces, cracking furnaces, heat treatment furnaces, shuttle kilns, tunnel kilns, roller kilns, enamel kilns, ceramic kiln roofs and walls, and thermal insulation lining materials.

Advantages of Tunnel Kiln Lightweight Mullite Brick Hang Roof Bricks

Tunnel kiln mullite Hang Roof, which includes multiple mullite groups. Each mullite set consists of two mullite Hang Roof Bricks, mullite T-shaped pendants, and metal hooks. The mullite T-shaped pendant as shown in the figure includes a plug-in board, a connecting block is provided on the plug-in board, and a metal hook is provided on the connecting block. Moreover, the mullite Hang Roof tiles are square in shape, and one side of the mullite Hang Roof Bricks is provided with a mullite T-shaped slot. Mullite T-shaped slots provided on the two mullite Hang Roof tiles of each group of mullite groups are respectively located at both ends of the insert plate. It has the advantages of lightweight, easy installation, disassembly and replacement, having good heat resistance, and the metal hook is not easy to be corroded and damaged.

Tunnel kiln mullite Hang Roof tiles include multiple mullite groups. Each mullite group consists of two mullite Hang Roof Bricks, mullite T-shaped pendants, and metal hooks.

Tunnel kiln mullite Hang Roof bricks are made of high-quality and high-purity refractory powder, and organic composite fillers are added according to the required proportion of the product. Lightweight mullite products are formed by vacuum extrusion and high-temperature sintering.

Advantages of tunnel kiln mullite Hang Roof Bricks: low thermal conductivity and low heat capacity. High purity and low impurity content. Resistant to high temperatures and can be in direct contact with flames. High strength and excellent thermal shock resistance. Can be cut at will.

Advantages of Kyanite Lightweight Mullite Refractory Bricks

As a raw material for refractory materials, kyanite has been used in a variety of products. The ideal chemical composition of kyanite is AL2O3·SiO2, which is a homogeneous multi-phase variant with the same composition as andalusite and sillimanite. Kyanite is denser than andalusite and sillimanite. This high density is in a metastable state under normal pressure and can spontaneously decompose into a low-density mineral combination, namely mullite-quartz, at a certain temperature.

Lightweight mullite bricks are used for high-temperature kiln linings that are not in contact with the melt. Not only high operating temperature is required, but also low thermal conductivity is required. For general lightweight refractory materials, they are not only required to have a high operating temperature but also need to have a low thermal conductivity. For lightweight refractory materials, the smaller the gap size within a certain range, the lower the thermal conductivity. Therefore, the micropores formed by the decomposition and expansion of kyanite are favorable conditions for improving the thermal insulation performance of lightweight mullite bricks.

Lightweight mullite refractory bricks have the characteristics of high operating temperature, low heat capacity, low thermal conductivity, high strength, and good thermal shock resistance. The AL2O3 content of lightweight mullite bricks synthesized from kyanite and industrial alumina powder is 67.1%, which is significantly higher than that in foreign countries.

Buy high quality Hang roof brick Mullite, Hang roof brick High aluminum poly-light brick. Rongsheng refractory materials manufacturer can customize the shape, size, specifications, etc. of hanging bricks for customers. Contact us for a free quote.

Refractory Materials for Reactors Producing Sulfur from H2S

2024-07-26 by globalrefractory

In the sulfur reactor, the H2S combustion furnace has a higher operating temperature and is one of the single equipment with the highest design temperature. In its design, in order to improve the recovery rate of sulfur, the method of preheating the raw gas and air is generally used to increase the furnace temperature. At present, the operating temperature of the reactor has been increased from 1050°C to 1450°C. Coupled with the combustion support of alkane gas, the furnace temperature may reach 1600°C. Therefore, it is a great challenge to the refractory materials built in the furnace.

The production of sulfur currently uses the Claus process to recover sulfur from acid gas containing H2S. This production process is common in coal gasification or petrochemical industries, because H2S is the main by-product in the production of such industries. The process principle is to use the partial combustion method in the sulfur recovery device, that is, introduce all the acid gas into the combustion furnace, and distribute the air according to the complete combustion of hydrocarbons and the complete combustion of 1/3 H2S to generate SO2. For H2S, the reaction results in that about 65% (mass fraction) of H2S in the furnace is converted into S vapor, 1/3 of the remaining 35% (mass fraction) of H2S is burned into SO2, and 2/3 remains unchanged. Among them, 65% of the S vapor generated by the reaction is condensed and captured in the waste heat boiler, while the remaining H2S and SO2 reacted in the furnace react under the action of the catalyst in the converter to further generate S. In order to react uniformly and prevent impact on the hot end of the waste heat boiler, a flower wall is built in the middle of the furnace. The main medium in the furnace is H2S + SO2 + high-temperature gas containing S vapor. The operating pressure is not greater than 0.05MPa, and the operating temperature is not greater than 1450°C. Made of refractory materials, thickness 400mm.

Difficulties in Selecting Refractory Materials for Masonry Reactors Producing Sulfur

(1) The furnace temperature is high. The working temperature is 1100~1450℃, which is a furnace with a higher working temperature. Under occasional operating conditions, the furnace temperature may reach 1600°C or higher.
(2) There are various corrosive components such as H2O, H2S, SO3, SO2 and S vapor in the furnace. H2S has reducing properties. As a result, there are strict restrictions on certain impurity components in furnace lining materials.
(3) Acid gas combustion furnace has no heating surface inside the furnace. Any large fluctuation during combustion means a thermal shock to the furnace lining, which requires the furnace lining to have good thermal shock resistance.
(4) The combustion furnace has strict requirements on wall temperature and requires the furnace lining material to have good thermal conductivity.

Selection of Several Domestic Mainstream Refractory Materials

2.1 Corundum castable material material

At the earliest, corundum castable linings were commonly used as lining materials for acid gas reactors in sulfur recovery units at home and abroad. The reason is that the corundum castable lining not only has a higher fire resistance temperature but also has better wear resistance. However, due to its poor thermal shock resistance, problems such as peeling and falling off may occur within a short period of time, and it will be gradually eliminated over time.

2.2 High alumina brick + corundum brick material

The lining material of the original acid gas combustion furnace is high alumina brick + corundum brick. The brick joints are one of the weakest links. Damage to the brick joints often leads to overall deformation and collapse of the masonry. On the other hand, high alumina bricks and corundum bricks are difficult to process and manufacture, difficult to fit into some special-shaped parts, and the cost is also high.

2.3 Steel fiber castable material

Steel fiber castables have achieved good results in catalytic converters and other applications due to their good fire resistance. However, in the case of acid gas combustion furnace, this material is prone to problems such as agglomeration and deep cracks.

2.4 Combined material of castable and ramming material

Castable combined with ramming makes a very good high-temperature-resistant lining. The composition (mass fraction) of ramming material is 85% AL2O3+15%SiO2. Has the following salient features:

①High temperature resistance (up to 1800℃) and high strength.
②The furnace wall support is hanging type, which is not easy to deform or fall off.
③The insulation layer is constructed by pouring, and the working layer is constructed by pounding. It can be made into any shape (especially in special shapes) and is easy to construct. Its combined structure is dense and solid, with no gaps in the walls.
④When the lining is supported by anchors, the furnace wall can withstand peeling and protrusion, making maintenance easy.
⑤The lining material has good peeling resistance and will not embed foreign matter.
⑥Short oven time, fast and economical construction

To purchase high-quality refractory lining materials, please contact us. We can provide high-quality refractory products and customer service.

Furnace Lining Refractory Materials for Sulfur Making Furnaces

2024-07-19 by globalrefractory

The sulfur-making combustion furnace is one of the core equipment of the sulfur recovery unit, where 60%-70% of the hydrogen sulfide is converted into elemental sulfur. It controls the process of converting 1/3 of hydrogen sulfide into sulfur dioxide and complete combustion with ammonia and hydrocarbons. It can be said to be the heart of the combined device. Therefore, the operation of the sulfur combustion furnace directly affects the sulfur recovery rate and sulfur dioxide emissions. One of the most direct factors affecting the performance of a sulfur furnace is the refractory lining of the furnace. The originally designed refractory layer was made of large corundum mullite bricks, and the thermal insulation layer was made of lightweight insulating castables. However, in the early stages of operation, the outer walls of the sulfur furnaces experienced varying degrees of over-temperature and even red heat.

The sulfur recovery and sulfur production system adopts the partial combustion method to introduce all the raw gas into the sulfur production combustion furnace. In the sulfur-making furnace, the air distribution ratio is strictly controlled according to the amount of oxygen required for complete combustion of 1/3 of hydrogen sulfide, ammonia, and hydrocarbons. The amount of sulfur dioxide generated after hydrogen sulfide is burned satisfies H2S/SO2 to be close to 2. About 60% to 70% of hydrogen sulfide and sulfur dioxide react at high temperatures in the furnace to form gaseous sulfur. The operation of the sulfur-making combustion furnace directly determines the sulfur recovery rate of the entire sulfur-making system and whether the exhaust emissions meet the standards. The components of raw sour gas are relatively complex, including H2S, CO2, H20, NH3, H2 hydrocarbons, etc. The chemical reactions that occur in the furnace are also relatively complex.

Refractory Materials for Sulfur Making Furnaces

Conditions that Lining Refractory Materials Should Meet when Designing Sulfur Furnaces

Conditions that lining refractory materials should meet when designing sulfur furnaces. Able to withstand higher temperatures, the operating temperature of the sulfur furnace furnace is 1250~1400℃, which may reach 1600℃ under abnormal conditions. Since the supply of raw materials is unstable and most of them are corrosive, they must have strong corrosion resistance. There is no heating surface in the furnace, and the lining must have stable thermal shock resistance. It has stable thermal conductivity and the furnace wall temperature can be controlled to ≤300℃. For furnaces with excessively large diameters, the lining should have good high-temperature stability. It has a long service life and meets the requirements of full load and long-cycle operation. Has good volume stability. Masonry is convenient and the construction period is short.

Thickness of Refractory Material Lining Sulfur Furnace

The total thickness of the lining refractory material of the sulfur-making combustion furnace is designed to be 400mm. The refractory lining in the upper 1/2 part of the front cone section adopts a double-layer lining structure, 200mm alumina hollow ball castable + 200mm corundum refractory plastic. The acid gas inlet distribution ring bricks have a four-layer lining structure, namely 100mm lightweight insulating castable + 150mm corundum castable + 150 corundum mullite bricks + acid gas inlet distribution ring bricks. The rest of the structure is a double-layer lining structure, that is, 220mm corundum refractory plastic + 180mm lightweight heat-insulating castable. The anchoring system consists of anchor bricks with C-shaped hooks and V-shaped nails. The flower wall tiles, annular channel ring tiles, and acid gas inlet distribution ring tiles are all made of corundum mullite bricks. The anchor bricks are arranged on 2/3 of the furnace, and the center distance between adjacent anchor bricks is 400mm.

Construction of Lining Refractory Materials for Sulfur-Making Combustion Furnace

Construction method: The insulation layer is constructed by manual pounding. Use a forced mixer to mix the materials, and add water in strict accordance with the mix ratio. The mixing time is generally about 3 minutes, subject to uniform color. The mixed materials should be used within 10 minutes. It is strictly forbidden to add water to the hardened materials for reuse. The construction joints of the two layers of insulation should be staggered by more than 100mm. The insulation layer should be maintained in moisture, and the second layer of insulation or refractory plastic can be constructed only after at least 24 hours. When the entire ramming construction is completed, remove the formwork and trim the lining surface to the designed thickness. The expansion joint should be cut according to the drawing requirements, generally 60mm deep and 2-3mm wide. Horizontal and vertical expansion joints should be left at the junction of the furnace roof and furnace wall, and the joints should be filled with fiber cotton. After the lining has been trimmed, vent holes should be punched to allow moisture in the material to escape. Before and during the drying process, steam, water, oil and other impurities are not allowed to corrode the plastic. Corundum bricks should be cured naturally after being laid wet, and contact with water is strictly prohibited. The original expansion joint is widened to about 3mm, and then filled with zirconium-containing fiber blankets. The flower wall tiles and acid gas inlet distribution ring bricks are laid wet, with staggered joints, and the mortar fullness is greater than 90%. Refractory plastic is a pre-mixed and pre-pressed blank material. When using it, you only need to pound it tightly without stirring or adding binders. The construction is simple and the on-site operating conditions are good. At the same time, because plastic is a gas-thermohard material, no maintenance is required. The construction period is short and suitable for rapid repair operations of the lining. The lining structure has good thermal shock resistance and resistance to thermal stress. However, the continuity and consistency of construction must be ensured.

To purchase high-quality refractory lining products, please choose a competent manufacturer and seller of refractory materials. For example, Rongsheng Refractory Material Manufacturer. Rongsheng’s refractory products have been sold to more than 100 countries and regions around the world. Our refractory products have reliable product quality and our comprehensive customer service ensures the long life and efficient operation of the refractory lining. Contact us for a free quote.

Refractory Ceramic Balls High Strength – Refractory Ceramic Heat Storage Balls

2024-07-12 by globalrefractory

Refractory ceramic balls and refractory balls are made of industrial alumina and refractory kaolin as the main raw materials, through scientific formula, shaping, and high-temperature calcination. it has:

High mechanical strength and long service life.
It has good chemical stability and does not react chemically with materials.
Good high-temperature resistance, the heat resistance temperature of refractory porcelain balls can reach 1900 degrees Celsius.

It is especially suitable for high and low-temperature conversion furnaces, reforming furnaces, hydroconverters, desulfurization tanks, and methanation furnaces in fertilizer plants. It plays the role of dispersing gas and liquid, and supporting, covering and protecting the catalyst. Refractory ceramic balls can also be used in hot blast furnaces and heating conversion equipment in the steel industry.

Classification of refractory balls: Refractory porcelain balls are divided into ordinary refractory balls and high-aluminum refractory balls. Ordinary refractory balls are suitable for converters and conversion furnaces in the sulfuric acid and fertilizer industries. High-aluminum refractory balls are suitable for hot blast furnaces, heating conversion furnaces, and other equipment in urea, steel and other industries.

Refractory Ceramic Heat Storage Balls

Heat storage ball is an excellent refractory material. It has significant characteristics such as low shrinkage of the refired line, high softening temperature under high temperature load, corrosion resistance, high strength, large heat storage and release, good thermal shock stability, good thermal conductivity, and small thermal expansion coefficient. By double preheating gas (blast furnace, converter) and air (combustion air single heat storage method is used for oil, high calorific value gas, etc.), the regenerative heating furnace can reduce the smoke exhaust volume by 20-50%. The exhaust gas temperature drops to less than 150 degrees, and the output increases by 15-20%. The billet heating time is shortened by 50%, and the oxidation and burning loss is reduced by 30-50%, which is an environmentally friendly and energy-saving effect.

1) The specific surface area of heat storage balls can reach 240m2/m3.
2) Numerous small balls divide the air flow into small streams. When the air flows through the heat storage body, it forms strong turbulence, which effectively breaks through the boundary layer on the surface of the heat storage body. And because of the small ball diameter, small conduction radius, small thermal resistance, high density, and good thermal conductivity, it can meet the frequent and rapid reversal requirements of regenerative burners.
3) The regenerator can use 20 to 30 reversals per hour. After the high-temperature flue gas flows through the regenerator bed, the flue gas can be reduced to about 130°C and then emitted.
4) When high-temperature gas and air flow through the regenerator in the same path, they can be preheated to only about 100°C lower than the flue gas temperature. The temperature efficiency is as high as over 90%.
5) Because the heat storage body is very small in size and the small pebble bed has strong circulation capacity, even if the resistance increases after dust accumulation, the heat exchange index will not be affected.
6) Thermal storage balls have the characteristics of strong resistance to oxidation and slag.
7) The ceramic ball is very convenient to replace and clean, and can be reused.

What are the Functions of Refractory Balls

Refractory ball is a kind of sphere made of industrial alumina and refractory kaolin as the main raw materials, and calcined at high temperature through scientific formula. It is mainly divided into high-aluminum refractory balls, silica refractory balls, magnesium-aluminum refractory balls, porcelain balls, etc. Converters and shift furnaces for the sulfuric acid and fertilizer industries. High-aluminum refractory balls are suitable for hot blast furnaces, heating conversion furnaces and other equipment in urea, steel and other industries.

The main role of refractory balls in actual use is due to their good high-temperature resistance and high hardness. Putting the refractory balls evenly into the heating furnace can evenly distribute the gas. Evenly dispersed gas can reduce the effect on the catalyst and extend the service life of the catalyst. At the same time, it has high hardness, so it can play a supporting role in heating objects in the heating furnace.

The working principle of refractory balls is to divide the air flow into small streams by dividing many small balls. The airflow flows through the heat storage body, forming intense turbulence, which effectively breaks through the boundary layer on the surface of the heat storage body. And because the ball diameter is small, the conduction radius is small, the density is high, and the thermal conductivity is good. Therefore, the requirement of frequent and rapid reversal of the regenerative burner can be realized.

High-aluminum refractory balls are often used during use. Although high-aluminum refractory balls are very hard, they become very brittle after high temperatures. Dry grinding can easily cause cracks in the ball stones and pits on the surface of the ball stones, resulting in very high wear. Therefore, we must pick out the spheres with high cracking and wear during actual use.