Refractory Castables Archives - Rongsheng Refractory Castable Cement for Sale Manufacturer and Supplier

24 Kinds of Refractory Raw Materials Commonly Used in Unshaped Refractory Castables (2)

April 5, 2024 by rsrefractorycastable

In recent years, the output of unshaped refractory products has become higher and higher, and their application range has become wider and wider. Refractory castables do not need to be fired at high temperatures and can be used directly after being baked during construction. It is a new refractory material with a simple production process, saving energy and labor, mechanized construction, good integrity, easy repair, and long life.

Refractory castables are a type of refractory material that is mixed with a certain grade of refractory aggregates and powdery materials, binders, and admixtures and is used directly without going through the molding and firing processes.

According to the combination of raw materials, refractory castables can be divided into oxide refractory castables, non-oxide refractory castables, and composite refractory castables. Oxide refractory castables can be subdivided into non-alkaline refractory castables and alkaline refractory castables. Therefore, the performance of refractory castables mainly depends on the raw materials used in the formulation. In order to improve the performance of refractory castables, most manufacturers have used high-purity raw materials, homogeneous materials, electrofusion materials, synthetic materials, transformation materials, and ultra-fine powders as main raw materials. Let’s talk about the 24 raw materials that are often used in the formula of refractory castables.

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The Main Raw Material of Refractory Castables (13-24)

(13) Magnesite.

Magnesite is a natural alkaline mineral raw material with magnesium carbonate (MgCO3) as the main component. Our country is rich in magnesite resources, with high quality and large reserves. Magnesite is mainly distributed in Liaoning Province. Magnesite is mainly used to produce sintered magnesia, fused magnesia, and raw materials for the production of alkaline refractory materials.

(14) Sintered magnesia.

Sintered magnesia is a product obtained by fully sintering magnesite at 1600~1900℃. The main mineral is periclase. The MgO content of high-quality magnesia is generally above 95%, the particle volume density is not less than 3.30g/cm3, and it has excellent resistance to alkaline slag erosion. Sintered magnesia is one of the main raw materials for the production of alkaline refractory materials.

(15) Fused magnesia.

Fused magnesia is made by melting selected magnesite or sintered magnesite at a high temperature of 2500°C in an electric arc furnace. Compared with sintered magnesia, the main crystal phase periclase grains are coarse and in direct contact, with high purity, dense structure, strong resistance to alkaline slag, and good thermal shock stability. It is a good raw material for high-grade carbon-containing unburned bricks and amorphous refractory materials.

(16) Silicon carbide.

Silicon carbide is usually made from a mixture of coke and silica sand as the main raw materials through high-temperature smelting in an electric furnace. β-SiC (cubic crystal) is generated at a temperature of 1400-1800°C, and α-SiC (hexagonal crystal) is generated when the temperature is higher than 1800°C. Silicon carbide has high hardness, high thermal conductivity, low thermal expansion rate and excellent resistance to neutral and acidic slag. The composition range of commercial silicon carbide is 90%~99.5% SiC. Refractory castables, gunning materials, ramming materials and plastics often use silicon carbide with higher purity.

(17) Silica fume.

Silica fume is a by-product of the production of ferrosilicon and silicon products. Appearance: white to dark gray fine powder with round particles. The particle diameter is generally 0.02~0.45μm, the specific surface area is about 15~25m2/g, and the volume density is 0.15~0.25g/cm3. In recent years, some silica fume has become the leading product and is no longer a by-product. It has high purity, white color and stable ingredients. Shows good rheology when used in self-flowing castables.

(18) Graphite.

Graphite is divided into artificial graphite and natural graphite. Artificial graphite is made by sintering petroleum coke (heating to above 2800°C) or using graphite electrodes. Natural graphite crystal is a hexagonal crystal system with rhombohedral symmetry. There are usually three forms: amorphous, flake graphite and pure crystalline. Amorphous graphite (no form) and artificial graphite have better fluidity than flake graphite and crystalline graphite in castable applications.

(19)Asphalt.

Coal tar pitch has a higher residual carbon content than petroleum pitch, and both can effectively provide carbon components to refractory materials. According to the formula design requirements of the material, it can be used in the form of fine powder or granules. The use of bitumen is preferred over other forms of carbon (such as graphite) in amorphous refractory applications. Because asphalt has a low melting temperature, it can coat particles and thus provide a good protective layer against slag erosion.

(20) Calcium aluminate cement.

The main method for producing high alumina cement is the sintering method. Pureer limestone is the calcium oxide raw material from which all calcium aluminate cements are produced. Sintered alumina is used to produce high-grade calcium aluminate cement, while low-iron, low-silica bauxite is used as alumina raw material for mid-grade and low-grade high-alumina cement. Pure calcium aluminate cement or high alumina cement is the most important hydraulic cement used in the binding phase of refractory castables and shotcrete. During the construction of the refractory castable lining, the water temperature, water addition amount, mixing intensity and time, temperature and heating rate must be strictly controlled. Among them, temperature is the most important parameter, which significantly affects the generation of cement binding phase and the discharge of water in the early stage of heating.

(21) Silica sol.

Silica sol is a water-containing colloid with dispersed silica particles. It is a milky white liquid that is slightly sticky to the touch and has a high specific surface area. Silica sol can be cemented by dehydration, changing the pH value, adding salt or water-miscible organic solvents. When drying, silicon-oxygen (Si-0-Si) bonds are formed on the surface of the particles through rapid dehydration, resulting in polymerization and internal bonding. Silica sol is converted from solution into solid, commonly known as cementation. Commonly used in coatings, castables, pumped materials, ramming materials and gunning materials.

(22) Sodium silicate.

Commonly used silicates are sodium silicate (Na₂O·mSiO·nH₂O), potassium silicate and lithium silicate. The dehydrated product of sodium silicate is usually as transparent as glass and soluble in water, so it is also called water glass. The molar ratio of SiO₂/N₂O (called the modulus of water glass) in industrial products is between 0.5 and 4.0, and the molar ratio of sodium silicate for refractory materials is 2.2 and 3.35. The viscosity of sodium silicate aqueous solution is affected by its molar ratio and concentration, and changes significantly with temperature. Sodium silicate hydrates in aqueous solution, and the solution becomes alkaline. The smaller the molar ratio, the more obvious the hydration of sodium silicate is, and the pH value decreases as the molar ratio decreases. Sodium silicate with a high molar ratio reacts slowly. The choice of curing agent for sodium silicate combined refractory materials needs to be determined based on the application of the refractory materials. Commonly used curing agents include sodium fluorosilicate, polyaluminum chloride, phosphoric acid, sodium phosphate, polyaluminum phosphate, polymagnesium phosphate, ammonium pentaborate, glyoxal, citric acid, tartaric acid, ethyl acetate, etc.

(23) Phosphoric acid and phosphate.

Orthophosphoric acid itself has no binding properties. When it comes into contact with refractory materials, the two react quickly to form phosphate, which makes it show good adhesion. Different forms of phosphates can be used as binding agents. The salt most commonly used in refractory materials is aluminum phosphate. As a binding agent, aluminum dihydrogen phosphate is known for its solubility in water, binding strength and stability. Sodium phosphate is mainly used in refractory materials for cohesion, depolymerization and as a binding agent for alkaline gunning materials. Sodium polyphosphate is often used as a water reducing agent in castables. In addition, sodium phosphate can react with alkaline earth metal compounds (such as CaO and MgO), resulting in agglomeration. It is based on this performance of sodium phosphate that it is used in magnesia alkaline gunning materials.

(24)ρ-Al₂O₃

ρ-Al₂O₃ is a kind of activated alumina. It is different from other crystalline Al₂O₃ and is the worst crystallized Al₂O₃ variant. Among the various crystal states of Al₂O₃, only ρ-Al₂O₃ has a spontaneous hydration reaction at room temperature. The gibbsite and boehmite sol generated by hydration can play a cementing and hardening role. ρ-Al₂O₃ is eventually transformed into α-Al₂O₃ (corundum), an excellent refractory material at high temperatures. Therefore, this ρ-Al₂O₃ combined castable can be regarded as a self-bonding castable of refractory materials, which also acts as a binder. It itself is a high-grade refractory oxide with obvious excellent properties.

(THE END)

By selecting different raw materials as the main raw materials of refractory castables, castables with different properties, operating temperatures, and ranges can be made. Of course, only the main raw materials are not enough. Binders, admixtures, and some special additives are also needed. These are all to improve the performance of refractory castables. Rongsheng Unshaped Refractory Castables Manufacturer is a powerful manufacturer and seller of refractory castables. Our environmentally friendly, fully-automatic unshaped refractory material production line provides high-quality customized refractory lining materials for high-temperature industrial furnaces. Contact us to get a free refractory lining solution and quote.

24 Kinds of Refractory Raw Materials Commonly Used in Unshaped Refractory Castables (1)

March 29, 2024 by rsrefractorycastable

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The Main Raw Material of Refractory Castables (1-12)

(1) Sintered corundum.

Sintered corundum, also known as sintered alumina or semi-fused alumina. It is a refractory clinker made from calcined alumina or industrial alumina as raw material, ground into balls or green bodies, and sintered at a high temperature of 1750~1900℃. Sintered alumina containing more than 99% of aluminum oxide is mostly made of uniform fine-grained corundum directly combined. The gas appearance rate is less than 3.0%, and the volume density reaches 3.60%/m³. The refractoriness is close to the melting point of corundum, and it has good volume stability and chemical stability at high temperatures. It is not corroded by reducing atmosphere, molten glass and molten metal, and has good mechanical strength and wear resistance at room temperature and high temperature.

(2) Fused corundum.

Fused corundum is artificial corundum made by melting pure alumina powder in a high-temperature electric furnace. It has the characteristics of high melting point, high mechanical strength, good thermal shock resistance, strong corrosion resistance and small linear expansion coefficient. Fused corundum is a raw material for manufacturing high-grade special refractory materials. Mainly include fused white corundum, fused brown corundum, sub-white corundum, etc.

(3) Fused white corundum.

Fused white corundum is made from pure alumina powder and smelted at high temperature. It is white in color. The smelting process of white corundum is basically a process of melting and recrystallization of industrial alumina powder, and there is no reduction process. The Al₂O₃ content is not less than 9%, and the impurity content is very small. The hardness is slightly smaller than brown corundum and the toughness is slightly lower. Often used to make abrasive tools, special ceramics and advanced refractory materials.

(4) Fused brown corundum.

Fused brown corundum is made from high-alumina bauxite as the main raw material and mixed with coke (anthracite), and is smelted in a high-temperature electric furnace at temperatures above 2000°C. The main chemical components are Al₂O₃, TiO₂ and contain a small amount of SiO₂ and Fe₂O₃. Fused brown corundum has a dense texture and high hardness and is often used in ceramics, precision castings and advanced refractory materials.

(5) Sub-white corundum.

Subwhite corundum is produced by electromelting special grade or first grade bauxite under reducing atmosphere and controlled conditions. When melting, add reducing agent (carbon), settling agent (iron filings) and decarburizing agent (iron scale). Because its chemical composition and physical properties are close to white corundum, it is called sub-white corundum. Its bulk density is above 3.80g/cm3 and its apparent porosity is less than 4%. It is an ideal material for manufacturing advanced refractory materials and wear-resistant materials.

(6) Mullite.

Mullite is a refractory raw material with 3Al₂O₃·2SiO₂ as the main crystal phase. Natural mullite is very rare and is usually synthesized artificially by sintering or electrofusion. Mullite has the characteristics of uniform expansion, good thermal shock stability, high load softening point, small high-temperature creep value, high hardness, and good chemical corrosion resistance.

(7) Zirconium corundum mullite.

Zirconium corundum mullite is made of industrial alumina, kaolin, and zircon as its main raw materials. It is synthesized by fine grinding, uniform mixing, semi-dry briquetting, and high-temperature calcination at 1600~1700℃. Increasing the zircon content will increase the sintering temperature, reduce the total shrinkage, and increase the closed pores. These reactions give sintered zirconium corundum mullite higher density and strength as well as better thermal shock resistance and slag resistance.

(8) Magnesia-aluminum spinel.

Magnesia-aluminum spinel is synthesized from industrial alumina and light-burned magnesium oxide through high-temperature sintering or electric fusion. The chemical formula of magnesia-aluminum spinel is MgO·Al₂O₃, in which the MgO content is 28.2% and the Al₂O₃ content is 71.8%. It has the advantages of high-temperature resistance, wear resistance, corrosion resistance, high melting point, small thermal expansion, low thermal stress, good thermal shock stability, strong resistance to alkaline slag erosion, and good electrical insulation properties.

(9) Sillimanite, andalusite, and kyanite.

The chemical formula is Al₂O₃·SiO₂, and the theoretical composition is Al₂O₃63.1% and SiO₂36.9%. After heating, they are irreversibly converted into mullite and cristobalite, which have the advantages of good slag corrosion resistance, good thermal shock stability, and high load softening point. Kyanite mineral products are high-quality raw materials for amorphous refractory materials. Because sillimanite and andalusite change little in volume when heated, they can be directly made into bricks or used as refractory aggregates. Kyanite expands greatly when heated and can be used directly as an expansion agent for amorphous refractory materials.

(10) High alumina bauxite.

my country’s high-alumina bauxite resources are mainly distributed in Shanxi, Henan, Guangxi and Guizhou. High-alumina bauxite clinker calcined at high temperature is mainly used for high-aluminum refractory materials, and can also be used to make fused brown corundum and sub-white corundum. In recent years, the homogenized alumina clinker produced in my country has been developed due to its low absorption rate and stable performance. The application in unshaped refractory materials has achieved good results.

(11) Soft clay.

The mineral composition of soft clay is mainly kaolinite or halloysite, mixed with other impurity minerals. The Al₂O₃ content can range from 22% to 38%, and the average refractoriness is around 1600℃. Soft clay is mostly earth-like, with fine particles, easily dispersed in water, and has strong plasticity and cohesiveness. It is widely used in plastics, ramming materials, gunning materials, refractory mud, and medium and low-grade refractory materials.

(12) Clay clinker.

Refractory clay clinker can be divided into two types according to the raw materials used and production methods. One type is obtained by calcining hard clay blocks directly in a kiln. The other type is made of kaolin or hard clay, which is finely ground, homogenized, filtered, dehydrated, dried, and finally burned in a kiln. It is a high-quality clay clinker. The main mineral phase of hard clay clinker is mullite, accounting for 35% to 55%. Followed by glass phase and cristobalite. Clay clinker is the main raw material of ordinary aluminum silicate refractory materials.

(To be continued. Since the article is too long, I will post it in two parts.)

By selecting different raw materials as the main raw materials of refractory castables, castables with different properties, operating temperatures and ranges can be made. Of course, only the main raw materials are not enough. Binders, admixtures and some special additives are also needed. These are all to improve the performance of refractory castables. Rongsheng Unshaped Refractory Castables Manufacturer is a powerful manufacturer and seller of refractory castables. Our environmentally friendly, fully-automatic unshaped refractory material production line provides high-quality customized refractory lining materials for high-temperature industrial furnaces. Contact us to get a free refractory lining solution and quote.

Refractory Castables Materials for Rotary Kiln Insulation

March 18, 2023 by rsrefractorycastable

Due to the structure and working characteristics of the rotary kiln, as well as the diversity and complexity of the materials it handles, the requirements for the temperature of the outer wall of the rotary kiln are also different. From the perspective of environmental protection and energy saving, reducing the temperature of the outer wall of the rotary kiln as much as possible, doing a good job in the insulation layer of the rotary kiln, and the configuration of the refractory lining material of the rotary kiln are all the enterprises that operate the rotary kiln expect. Rongsheng monolithic refractory manufacturer has rich experience in the production, sales, and application of monolithic refractory materials. We have served various types of rotary kilns, which can help you solve the problem of rotary kiln insulation lining. Get pricing information for free.

Lightweight High-Strength Castable for Steel Ladle — Lightweight High-Strength Castable Refractory

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There are also various designs for the thermal insulation lining of the rotary kiln, and the types of refractory materials used are also various. According to the specific needs of customers, we can provide customers with insulating castables, lightweight castables, lightweight plastics, dense refractory plastics, heavy wear-resistant castables, phosphate-bonded composite insulation bricks, ceramic fiber products, etc.

Working Layer and Thermal Insulation Layer of the Rotary Kiln Lining

When the rotary kiln lining refractory material is selected, the next step is to evaluate the heat loss of the rotary kiln body.

When we realize that the working temperature in the rotary kiln is high, and the material has serious erosion and wear on the inner lining, then the inner lining design must consider the double-layer inner lining, and the two inner linings are respectively called the working layer and the thermal insulation layer.

The working layer is made of heavy refractory materials to meet the resistance to high-temperature flames and material erosion and wear; the heat insulation layer is made of light refractory materials to improve the thermal insulation performance of the inner lining and reduce the heat loss of the rotary kiln body.

The inner lining of the rotary kiln has a thermal insulation layer, which can effectively reduce the heat loss of the rotary kiln and also help protect the rotary kiln shell and other shell components.

Generally speaking, the rotary kiln lining with a thermal insulation layer is often used for rotary kilns with high operating temperatures. The refractories of the inner lining of the thermal insulation layer and the inner lining of the working layer have similar chemical compositions, and the difference between Rongsheng refractory materials lies in their respective strength and thermal conductivity. The refractory material lining the thermal insulation layer has a low density and low strength, but its thermal resistance is relatively large, which can effectively reduce the heat loss of the rotary kiln body.

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What Refractory Castables are Used for Each Part of the Cement Rotary Kiln?

Refractory castables are used as the main insulation material for the new dry-process rotary kiln. If it is properly configured, it can protect the normal operation of production equipment at high temperatures and effectively reduce system energy consumption.

Cement Rotary Kiln Refractory Castable

Kiln mouth with refractory castables. At the kiln mouth in front of the rotary kiln, the clinker outlet temperature is around 1400°C, and the temperature of the secondary air entering the kiln changes frequently due to kiln conditions. With the expansion of the scale of the cement plant, the amount of clinker at the kiln mouth is also increasing, and the thermal stress and mechanical stress on the refractory castable at the kiln mouth increase accordingly. For this reason, the kiln mouth refractory castable should have sufficient refractoriness, mechanical strength, thermal shock stability, and alkali resistance under high-temperature environments. It is recommended to use high-performance kiln mouth special refractory castable or improved kiln mouth special refractory castable. The product has excellent anti-stripping performance, high temperature and alkali resistance, and cement clinker erosion resistance.
Refractory castables for burners. The working environment of the burner is about 1400°C, the flame temperature is about 2000°C, and it works in an alkaline atmosphere for a long time. Compared with the front kiln mouth, the temperature changes more frequently and the temperature difference is larger. Therefore, the requirements for its thermal shock resistance are higher. The front end of the burner is always scoured by the high-temperature airflow entrained with clinker dust, especially the lower part is more severely scoured. Therefore, burner refractory castables need sufficient wear resistance. It is recommended to use special castables for burners or special refractory castables for improved burners. The product has excellent spalling resistance and thermal shock stability.
Refractory castables for kiln hood and grate cooler. For some large rotary kilns, the heat load on the lower part of the kiln hood is relatively high. If the general high-alumina refractory castable is not well controlled for curing and temperature rise, it is prone to bursting and falling off. The top of the kiln hood is close to the tertiary air duct, and the erosion of the dusty airflow is relatively serious, and the construction of the top castable is relatively difficult, and the requirements for the fluidity and early strength of the material are relatively high. The working temperature at the top of the front end of the grate cooler is high, and the temperature changes greatly. The low walls on both sides of the front end have been worn by the high-temperature clinker coming down through the kiln mouth for a long time, and they are also damaged by certain mechanical stress and thermal stress. It is recommended that these two parts use high-strength wear-resistant castables with good high-temperature performance, strong thermal shock resistance, and wear resistance.
Refractory castables for tertiary air pipe elbows and air valves. This part has a large change in heat and cold and is washed by high-temperature clinker particles. The castable is prone to loosening and peeling, and it is the most prone to wear and tear during the operation of the cement plant. It is recommended to use wear-resistant refractory castables.
Refractory castables for C4 and C5 cones and their discharge pipes, calciner cones, and smoke chambers. These areas are prone to crusting and are difficult to remove. Cleaning needs to be done manually with iron tools, which will inevitably cause mechanical damage to the refractory castable. Once severe skinning occurs, the kiln needs to be stopped for treatment. It is recommended to use high-strength anti-skinning silicon carbide castables.
Refractory castables are used for other parts of the cement rotary kiln. It is recommended to use high-strength alkali-resistant castables for C1~C3, high-temperature high-strength alkali-resistant castables for C4 and C5 (except for the cone), and high-strength wear-resistant castables for the decomposition furnace.

Rongsheng Insulation Castable Manufacturer

The application and development of refractory and insulating castable refractory should conform to the concept of environmental protection and circular economy. Reasonable selection of thermal insulation castables can prolong the service life of the rotary kiln castable lining, effectively protect equipment, reduce system heat loss, reduce system crust blockage, reduce kiln shutdown times and maintenance time, and improve system operation rate. To achieve the purpose of stable production, high production, and low energy consumption of the kiln system. For a case study on the configuration of thermal insulation and refractory materials for the rotary kiln project, please contact us. We will provide you with the most suitable thermal insulation refractory solutions for your production needs according to your working conditions.

How Much Water Should be Added During the Construction of Refractory Castables?

January 3, 2023 by rsrefractorycastable

The amount of water added to the refractory castable is very important, and directly affects the service performance and service life of the castable. How much water should be added during the construction of refractory castables? Different binders are used in castables, and the prepared refractory castables are also different. Even the same kind of refractory cement can be used as a binder to prepare various refractory castables. The amount of water added to the castable is also different during construction. The strength and service life of castables are inseparable from water consumption.

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During the construction of castables, the increase in water consumption will generally lead to a large decline in various properties. When the amount of water is large, the water will escape after heating, and the pores will increase accordingly, forming a loose structure, resulting in an overall decline in the performance of the castable and affecting the service life of the castable. Therefore, during the construction of castables, it is necessary to minimize the amount of water used during mixing.

According to the current use of castables, basically, the amount of cement is increasing, and the amount of cement added is basically canceled. Because the amount of low-cement castable high-alumina cement added is small, the amount of water added during construction is also small, and the situation of low medium-temperature strength is also overcome. If the amount of water added to the castable is too large, it is not only a coagulation problem, but the biggest reason is to affect the later use strength.

When the ratio of refractory castables and the production process are basically the same, water consumption has the best value. Generally, after the castable is produced, the manufacturer will make a sample block and do certain chemical and physical tests. Then, according to different situations, determine the optimal value of water consumption for each pouring material. Sometimes it is necessary to do certain tests or equip some binders according to the temperature on the spot during construction so that the water consumption of different castables during construction can be used at different temperatures.

Therefore, when making cement-bonded refractory castables, they should be mixed to the best fluidity. Then, according to the size of the normal temperature strength, determine the optimal amount of water.

The main points of adding water during the construction of refractory castables

Refractory castables are divided into neutral, alkaline, and acidic. The materials are divided into high aluminum, magnesium, acid, light series, and so on. Regardless of the series, the amount of water added is different for different models and materials.

Mixing of Refractory Castables Water Addition

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During the construction of refractory castables, drinking water with pH = 6-7.5 must be used. In general, the water content of the high aluminum series is 10-15%, the water content of the low cement series is 6-8%, and the water content of the wear-resistant series is controlled at 5.5-6.5%. The amount of water added to the spray paint is 10-15%, and the amount of water added to the corundum series is 5-6%. If it is the refractory mud for brick matching, the water addition is 20-25%, and the water added for the light series is 20-25%. Be sure not to add too much water. Adding too much water will prolong the setting time of the castable and affect the strength of use.

The amount of water added to the refractory castable also has a great influence on the internal structure. If you add too much water, the internal performance will gradually decline. As the amount of water added increases, the strength decreases, the porosity increases, and the anti-scouring ability also decrease, which seriously affects the service life.

During the construction of refractory castables, the amount of water added is determined according to the particle gradation and the ratio of the binder. The castable does not have a large amount of water and good performance. If too much water is added, the aggregate will be separated from the base material, which will affect its performance and reduce its density and corrosion resistance.

However, the amount of water added is insufficient, the fluidity cannot be achieved, the air bubbles cannot be discharged, and the internal structure cannot form density accumulation, which will still affect various performances.

Therefore, in the construction, it is necessary to follow the instructions provided by the manufacturer, add water and stir the construction reasonably, so that the performance of the refractory castable can be fully utilized.

How to judge the appropriate amount of water added to monolithic refractory castables?

Why do castables that add water in strict accordance with the construction instructions still have problems? This problem is often encountered in actual use. Most people will say that I added water strictly according to the construction instructions, why is it still too wet (too dry)? In fact, the amount of water added in the construction instructions is only a theoretical reference, and the specific amount of water added should be determined according to actual construction needs.

After determining the raw materials of castables, qualified refractory castables are produced after a series of processes. Users can use it by adding water and stirring it, but it is precisely the step of adding water that stumps many construction workers. Either the mixing is too dry, or it is too wet. I have summed up a method in many times of practices, which can well control the amount of water added so that the performance of the castable can be better exerted.

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the appropriate amount of water added to monolithic refractory castables

The reference water content of general refractory castables is 8%-10%. When actually adding water, you can add water according to the principle of “small amount and many times”. Control the time well, and the mixing time of the pouring material should not be too long. After the mixing is finished, grab a handful of castables with your hands and hold them into balls (balls). If the dough disperses immediately after holding the ball, it means that the amount of water added is too small. If the spherical castable flows down from the fingers after holding the ball, it means that the amount of water added is too large. The amount of water added is appropriate only if the spherical castable does not disperse or flow out.

The amount of water to be added to the castable during construction is not only related to the raw materials, but also factors such as the construction site environment, dryness and humidity, and seasons. Only by controlling the amount of water added can the performance of the castable be maximized.

Low Cement Refractory Castable for Cement Kiln Lining

September 30, 2022 by rsrefractorycastable

With the continuous progress of the production and use technology of monolithic refractories, especially the development of low-cement refractory castables, self-flowing castables, and wet injection technology. The refractory lining used in the new dry-process cement kiln system has gradually developed into a castable-based lining structure.

Multifunctional refractory castables have many functions such as high early strength, high thermal strength, alkali resistance, wear resistance, and heat insulation. For the vulnerable parts in the new dry process cement kiln system. Such as the kiln mouth, the top of the kiln door cover and the blanking slope, the low wall of the grate cooler, and the high-temperature area on the top of the grate cooler. Coal injection pipe, tertiary air pipe elbow, and other parts. Various refractory castables have different damage mechanisms under different conditions of use parts. Because the vulnerable parts in the new dry-process cement kiln system are in harsh environments such as high temperature, cement clinker erosion, abrasion, rapid cooling, rapid heating, etc. And it is located in special parts of the port, and the service cycle of these parts seriously restricts the life of the kiln lining of the whole kiln. According to the specific use characteristics of each part of the kiln, the development trend of refractory castables for the cement industry is as follows.

Improve the wear resistance of wear-resistant castables.
Improve the thermal shock resistance of wear-resistant castables.
Reduce Fe2O3 content.
Reduce the bulk density of the castable. Reducing the load on the equipment Reduce the bulk density of the castable on the premise of ensuring wear resistance and thermal shock resistance.

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Low Cement Refractory Castable for Cement Kiln Lining

Low cement refractory castables for cement kilns mainly include high alumina, mullite, and corundum refractory castables. This series of products has the characteristics of high strength, erosion resistance, wear resistance, and excellent performance. At the same time, the material can be made into a quick-baking explosion-proof castable according to the user’s baking time requirements.

Rongsheng monolithic refractory castables are the first to produce low-cement products with reliable quality and stable performance. It is widely used in blast furnace tap ditch, cast iron furnace tap trough, integral powder spray gun for molten iron pretreatment, high-temperature burner lining, heating furnace water cooling tube wrapping lining, etc.

Corundum and chromium-containing corundum low-cement castables are used for the lining of some parts of the refining device outside the molten steel furnace. It is also used in the lining of power frequency induction furnaces, the high-temperature wear-resistant lining of the petrochemical catalytic cracking reactor, etc. The low-cement refractory castable has the properties of high strength, alkali resistance, and wear resistance, which is obvious to all who have used it.

Corundum Self-flowing Wear-resistant Castable

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Index of low cement refractory castable for cement kiln

There are three common low-cement refractory castables, where low refers to less cement content in the product. The cement content of castables is as high as 10-30%, and the cement content of low-cement castables is between 3%-8%, so there are also 1% of ultra-low cement castables.

How to cure and bake low cement castable in the rotary kiln?

Low cement castables are widely used in new dry process cement rotary kilns. It is mainly used in the rear kiln mouth, kiln door, decomposition furnace, cooler and other parts. As we all know, the construction of refractory castable is mainly composed of three links, namely mixing, pouring, and curing. So how to maintain and bake it?

Maintenance

The tools that low-cement castables need to use in the curing process are polyethylene plastic film, straw bags, etc.

Ambient temperature requirements and controls. The curing temperature of the casting body is preferably between 15-35 ℃. Outside this temperature range, corresponding heating or cooling measures should be taken. Otherwise, the performance of the product will be degraded.

conservation. After the castable is hardened, the surface of the construction body must be covered with polyethylene plastic film immediately. A wet straw bag is added on top to prevent water evaporation and promote cement activation. After hardening, it is forbidden to beat and vibrate within one day. According to the hardening situation, the mold can be removed after 24-30 hours of hardening, or it can be removed in 3 days. After de-molding, continue curing for 2 days. Continue to cover with polyethylene film and wet straw bags during maintenance. After 3 days of curing, remove the polyethylene plastic film and a wet straw bag. Let the cast body dry naturally in the air for 1 day before baking.

Baking

One of the most critical aspects when using castables during baking. Because the casting body is relatively thick and dense, the water is not easy to discharge. Therefore, it is absolutely forbidden to heat up too fast during baking, otherwise, it will cause the casting body to crack.

Two Questions and Answers about Refractory Castables Used in Furnace Lining

June 16, 2021June 10, 2021 by rsrefractorycastable

With the increase in the use temperature and service life of various high-temperature kilns and thermal equipment, refractory castables are widely used in production and use as unshaped refractory materials. In the modern era of rapid industrial technology, there are many types of refractory castables. Compared with refractory bricks, the advantages of using refractory castables are simple to process, energy-saving, low cost, and easy mechanized construction. It has been widely used in various types of thermal equipment such as cement, steel, glass, and electric power. As a result, the use of refractory castables in high-temperature kilns often encounters some problems. Experienced unshaped refractory castable manufacturers will take you to understand these problems and provide you with the most suitable refractory castable lining solution for your production needs.

Question 1: The operating temperature of the kiln is 1500℃, what refractory castable should be used?

When the temperature of the working part of the kiln is 1500℃, corundum castable should be selected according to the use temperature of the refractory castable. Many users do not understand but think that the price is high, so they choose general high-aluminum castables.

However, if the direct use temperature is 1500°C, the general high-aluminum castable is not acceptable. The brown corundum castable must be selected to meet the application requirements. There are also users who propose to use steel fiber castables, which is not acceptable. Because steel fibers begin to melt at temperatures above 1300°C. Therefore, steel fiber castables cannot be used.

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However, some customers choose to use stainless steel. The answer given by refractory manufacturers is still no. Because the stainless steel used for the lining only serves as an anchor, it cannot resist high temperature and corrosion. The characteristics of corundum castable are the highest bulk density, lowest apparent porosity, high-temperature resistance, corrosion resistance, and thermal shock resistance. And at 1500℃, the characteristics of corundum castable can be fully reflected. If steel fiber castable is used, it cannot withstand the high temperature of 1500℃. The general high-aluminum castables can be used at a temperature of 1300℃-1400℃.

Refractory castable manufacturers pointed out that if it is a different kiln, the working atmosphere inside the kiln is different and the degree of erosion is different, corundum wear-resistant castable or high-strength wear-resistant castable can also be selected. In this way, it is resistant to both high temperature and corrosion. For example, waste incinerators have low temperatures, but strong corrosion, sometimes with acid and alkali corrosion. At this time, the choice of corundum castable is not acceptable, the temperature is not high, and the corundum cannot be fully used. Wear-resistant castables with clean raw materials can be used to resist acid or alkali corrosion. Moreover, the price is lower than that of corundum castable, and it is also suitable for the special use of incinerators.

In short, no matter what kind of refractory castable is selected, the appropriate refractory castable must be selected according to different kilns, different temperatures, and different degrees of erosion.

Question 2: How much is a ton of corundum steel fiber refractory castable for the rotary kiln?

Corundum steel fiber refractory castable is a high-quality refractory castable. It uses special grade bauxite clinker and sintered corundum as refractory aggregates and admixtures, and calcium aluminate cement as a binder. Unshaped refractory material mixed with a small amount of water reducing agent and a certain proportion of wear-resistant and heat-resistant steel fibers of different sizes and diameters using micro-powder technology. It is castable with good fluidity, high strength, good wear resistance, and good thermal shock resistance.

Steel Fiber Reinforced Castable — Steel Fiber Castable

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The corundum steel fiber refractory castable has a good effect. Corundum steel fiber castables with different physical and chemical indicators are used in different industrial furnaces, such as steel-making electric furnaces, tundishes, heating furnaces, rotary kilns, and other thermal equipment. So, how much is a ton of corundum steel fiber refractory castable for the rotary kiln?

Generally, the price of corundum steel fiber castable is about 6,500 yuan per ton. However, there are many factors affecting the price of castables, and the details need to be determined based on the actual kiln situation and the use of castables.

The price of corundum steel fiber castable is a reference factor when customers purchase. But what you pay for is what you pay for. Refractory castables are different from other refractory products. Its quality is not only about the price, but also about the application. The better the effect of the application in high-temperature kilns, the more expensive it is. When purchasing high-quality corundum steel fiber refractory castables, it is best to provide refractory castable manufacturers with the working conditions of the furnace, such as operating temperature and service life. Then the refractory manufacturer will have a technical team to provide corresponding castable solutions to ensure the use of corundum steel fiber castables and calculate the cost of purchasing refractory castables.

To learn more about refractory castables for furnace refractory linings, please continue to follow our blog. For the price of high-quality refractory castables, please contact us.

How to Solve the Phenomenon on the Surface of Refractory Castables Preforms

June 16, 2021March 9, 2021 by rsrefractorycastable

Unshaped refractory castables and castable preforms have been widely used by more and more high-temperature industrial kilns due to their advantages of convenient, fast construction and low labor intensity. However, many enterprise users have found that refractory castables or preforms have found some abnormal phenomena during storage or maintenance, such as chalking, white hairs, and so on. So, how to solve the white hair and chalking on the surface of refractory castables preforms?

Firstly, let’s understand how these phenomena are formed.

In fact, these are caused by the contact of high-alumina cement hydration products in refractory castables with acid gases in the atmosphere. As the moisture in the castable evaporates, salt substances continue to migrate and precipitate to the surface, and then slowly aggravate the damage process of the refractory castable. We will analyze these phenomena today. Pulverization occurs during the storage of preforms made of cement-containing refractory castables. Some of them grow “white hair” on the surface, commonly known as white alkali, which causes the pulverization of the surface of the castable. In severe cases, the strength of the castable decreases.

White-Hair and Chalking on the Surface of Refractory Castables and Preforms — White-Hair and Chalking on the Surface of Refractory Castables Preforms

Several Phenomena on the Surface of Refractory Castables after Construction

Carbonation of Castables

Carbonation of high-alumina refractory castables is often considered to be one of the main reasons that lead to the decrease of castable structure and spalling. The high-alumina cement-bonded refractory castable is exposed to the air, and the hydration products therein react with the CO2 gas in the air to undergo a carbonation reaction. In addition, refractory castables are more likely to undergo carbonation under high humidity conditions and compared with dense castables, lightweight castables with high water content are easier to pulverize. This shows that in the presence of water, the hydration product interacts with the CO2 acid gas, and the PH value of the liquid in the single pore of the phase drops sharply, which makes all the new hydration organisms in the refractory castable become unstable.

Sulfation of Castables

Compared with the carbonation of high-alumina cement hydration products, the sulfation phenomenon has not attracted enough attention from the construction party and the user. In the atmosphere, in addition to the CO2 acid gas, there are also SO2, H2S, and other gases, which also have a strong corrosive effect on the hydration products of the matrix part of the high alumina cement castable. Eventually, this lead to powdering and peeling of the castable.

In addition to being sulphated by SO2 and H2S in the air, high-alumina cement hydrate may also interact with SO42- or H+ in the water source. As the activity and acidity of the two increase, the stability of the three high-alumina cement hydration products also decreases sharply.

Salt Precipitation Phenomenon of Castable

The salt precipitation phenomenon on the surface of refractory castables is another important factor that aggravates the structural damage of the castables. During the curing or natural drying process of refractory castable, some soluble carbonate, sulfate, chloride, phosphate, and other salt compounds will focus on the surface of refractory castable and crystallize with the evaporation of water. This phenomenon is often called salting out.

As the water evaporates from the surface of the refractory castable, these ions migrate and aggregate with the water molecules from the inside to the surface of the castable, or react with acid gases in the air on the surface of the castable. The salts formed after the hydrate reaction are focused on the surface. Finally, these salt compounds crystallized out due to exceeding the solubility in water.

In fact, all soluble salts containing crystal water include chloride, sulfate, carbonate, and so on. These salts all have the process of removing the crystal water, accompanied by the change of crystal form and volume change. These are some of the reasons that aggravate the pulverization, peeling, and lumps of the surface structure when the castable is cured in the air.

Solutions to the Phenomenon after the Construction of Refractory Castables and Preforms

(1) Dry the castable as soon as possible after construction to remove water and eliminate the carrier of sodium salt in the cast, so that the alkali stays in the construction body and no longer migrates to the surface.
(2) If the construction conditions cannot be dried in time, the pouring material should be sealed and the surface should be covered with plastic film to prevent moisture from migrating to the surface with alkali.
(3) The refractory castable is made of refractory raw materials with low alkali content to increase the viscosity and fast hardening of the refractory castable. It can reduce the migration speed of sodium salt, strengthen quality management, and strictly control the amount of water added to the construction.

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Rongsheng Refractory Castable Manufacturer

Rongsheng is a refractory manufacturer with an environmentally-friendly and advanced unshaped refractory production line. Rongsheng’s unshaped refractory production line has an annual output of 80,000 tons. Our refractory products have been sold to more than 60 countries and regions all over the world. Our customers of refractory castables have a high degree of recognition of our product quality and a high rate of return orders. Our monolithic refractory products can be customized according to the customer’s specific furnace requirements. We have rich experience in the field of wear-resistant refractory castables and refractory plastic products. In addition, he has rich experience in prefabricated refractory castables on the roof of the furnace. For more information about monolithic refractories, please contact us.

What are the Lining of the Heating Furnace?

June 16, 2021September 27, 2020 by rsrefractorycastable

The heating furnace is divided into furnace, fuel system, air supply system, smoke exhaust system, and cooling system. The furnace is a space composed of the furnace wall, the furnace top, and the furnace bottom, and different pouring materials are used for each part. Let us understand the refractory materials used in the lining of the heating furnace.

Refractory Lining of the Heating Furnace

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Low-cement castables are used to wrap the structure of water beam-columns. The column tube and the lower part of the supporting beam in the furnace are all made of low cement castables. Low-cement castables are also used in the low-temperature zone of the heating furnace, flue parts, and furnace body parts that do not exceed 1300°C.
Self-leveling castables are used in the heating furnace where the structure is complicated and cannot be vibrated manually. The use temperature is 1500℃, which is characterized by good thermal shock resistance, high refractoriness, easy construction, and almost no need for vibration.
Phosphate castables are suitable for heating furnace bottoms and other parts that are severely affected by material friction and hot air erosion. The operating temperature is between 1000-1600°C. It is a castable with phosphoric acid or phosphate as the binder and aluminum calcium cement and magnesia as the accelerator.
Mullite castable. Because mullite refractory castable has high thermal shock resistance, erosion resistance, good erosion resistance, good volume stability, and high service temperature. It is generally used in key parts such as furnace walls, furnace roofs, and press beams.
Anti-dry slag castable, suitable for the bottom of the heating furnace, and the place where iron oxide slag is deposited. The use temperature can reach 1600℃. Its main characteristics are high refractoriness, good thermal shock resistance, and good resistance to the corrosion of iron oxide slag in the heating furnace.
Lightweight castable, suitable for heat insulation layer of the furnace wall, furnace roof, flue, etc. High-strength lightweight castables can also be used as working linings for smoke exhaust systems and hot air ducts. It is characterized by low bulk density, good thermal stability, low thermal conductivity, and certain refractoriness.
Bauxite cement castable is a castable produced by mixing various refractory aggregates and powders in a certain proportion with aluminate cement as a cementing agent. It has the characteristics of fast solidification, high strength, thermal shock resistance, and slag resistance. It not only meets the refractory performance of the heating furnace body but also improves the construction performance of the furnace body.
The advantage of fire-resistant plastic is that there are no gaps in the overall construction and good airtightness. The furnace lining uses a large number of plastic materials instead of castables and is mainly used for the top of the furnace.

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What is the Meaning of the Refractory Castables Grades?

The various castables used for the lining of the heating furnace have been introduced above. How to make a specific distinction between them? This introduces the definition of refractory castable grades. What is the meaning of refractory castable grades? It is usually used in combination with numbers and pinyin letters to distinguish the material, performance, and purpose of the castable. Refractory castable grades have refractory standards and the settings of different castable manufacturers. Next, we will learn about the types and grades of common refractory castables.

Classification of Refractory Castables

1. Classified by material, silicon castable, clay castable, high alumina castable, mullite castable, corundum castable, aluminum-magnesium castable, etc.

2. According to the purpose, it can be divided into several types of castables for industrial furnaces, such as castables for steel rolling furnaces, castables for tapping channels, castables for mixing furnaces, and castables for cement kilns.

3. According to the bulk density, it can be divided into light castable and heavy castable.

4. According to its characteristics, it can be divided into refractory steel fiber reinforced castable, anti-skinning castable, low cement castable, high-strength castable, etc.

Mullite castable price — Mullite Refractory Castable with High-Quality

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Grades of Refractory Castables

1. Brands of silicon castables: rsg-70, rsg-60, rsg-50, etc. Among them, rs is the manufacturer of Rongsheng castables, G is the main material selected for castables is silicon, and the quantity is the silicon content.

2. Brand of castable clay: nn-45. Among them, the first n is clay as the binder, and the second n is the main material selected for the clay castable. The number is the main component content of the clay castable)

3. Grades of high-aluminum castables: nl-70, nl-60. Among them, n is clay as a binder, l is the main material selected for the castable is high aluminum material, and the quantity is the aluminum content of the high aluminum castable.

4, aluminum-magnesium castable grades: amc-70, amc-80, etc. Among them, a, m, and C are the English initials of alumina, magnesia, and castable. The number is the content of the main raw materials selected for aluminum-magnesium castables.

Castable grades for steel rolling heating furnace: zj-42, zj-60, zjs-65, etc. Among them, Z is the steel rolling heating furnace, J is the castable, and s is a part of the water-cooled tube of the heating furnace. The number is the main material content selected for the castable of the steel rolling heating furnace.

6. Grades of castable for iron ditch: Asc-1, Asc-2, Asc-3. Among them, a, s, and C are the English initials of alumina, silicon carbide, and carbon. The number is only used to distinguish the castable grade.

The above is the introduction of a refractory castable brand. Hope you can understand the meaning of the casting brand after reading it. There are many brands of refractory castables, some are set by the castable manufacturers themselves, and some are set in accordance with refractory standards. No matter what way the refractory castable is named, it is to distinguish the material, grade, performance, and purpose of the refractory castable.

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Rongsheng Refractory Castables Manufacturer

Rongsheng refractory castable manufacturer has an advanced and fully automatic unshaped refractory castable production line with an annual output of 80,000 tons. Rongsheng has provided high-quality refractory castables, mullite castables, self-flowing refractory castables, wear-resistant refractory plastics, corundum mullite refractory plastics, etc. for many turnkey projects. For more information about the refractory castables Lining of the Heating Furnace, Rongsheng’s monolithic refractory products, and Rongsheng refractory manufacturers, please contact us. We will provide you with services according to your specific needs.