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Application of Lightweight Mullite Refractory Castable on Heating Furnace

2021-04-09 by globalrefractory

Furnace materials are mainly refractory bricks, heavy fireclay castables, or high-alumina castables. Due to the large material capacity, large heat capacity, and large thermal conductivity, the heat storage and heat dissipation losses of the furnace body are relatively serious. Moreover, due to the large heat capacity of the material, it takes a long time for the oven and the shutdown to cool down, which limits the energy-saving and efficient operation of the heating furnace. In order to save energy and improve operating efficiency, the use of lightweight castables with light bulk density, low heat capacity, and low thermal conductivity is an effective method. However, most lightweight castables at present are difficult to meet the requirements of high temperature and flame erosion in the heating furnace due to the low use temperature. Lightweight composite furnace lining is used, that is, the heavy castable (contact fire filling) in the inner layer is covered with lightweight castable (heat preservation and energy saving). The construction process is complicated and the effect is not ideal. Due to the different expansion coefficients of lightweight castables, they will also cause greater shear stress to the hanging bricks and increase the risk of furnace roof collapse. This has been confirmed in practice.

Lightweight Mullite Refractory Castable and Its Application Advantages

The key raw material of lightweight castables is lightweight refractory aggregates that can make the bulk density of the castables lighter. Lightweight aggregates generally account for 50% to 70% of the total pouring, and the volume ratio can reach more than 90%. Therefore, the performance of castables also mainly depends on the performance of lightweight aggregates. In the past, the reason why the use temperature of lightweight castables was low was that the use temperature of its aggregates was low.

In order to use castables with a long-term use temperature of 1400 to 1500°C, lightweight mullite aggregates have been successfully used. Mullite is a refractory mineral with good mechanics and high-temperature properties. Its melting point can reach 1910°C, with high hardness and low creep. Refractory products with mullite as the main mineral phase have higher fire resistance.

Lightweight mullite refractory castables are prepared by using lightweight mullite aggregates. This castable has refractoriness of more than 1710°C, has the characteristics of small bulk density and high temperature, and can be used for a long time at an ambient temperature of 1500°C.

For example, the heating furnace in the 500 steel rolling workshop of a steelmaking plant is used to heat 325kg of steel ingots. The heating conditions are harsh, and the maximum temperature of the furnace is 1450°C. Adopt liquid slagging. The original furnace roof is made of high-aluminum castables, and the spalling is more serious in the high-temperature section, and the service life is less than one year. At the same time, due to the high thermal conductivity of high-aluminum castables, the heat dissipation of the furnace body is greater. In April 1992, the heating furnace used lightweight mullite refractory castables. By the time the furnace was shut down in October 1992, it had been in operation for nearly 6 months. The furnace top has no cracks, and the inner surface has no peeling, smooth as before.

The use of lightweight mullite refractory castables not only improves the life of the furnace top and reduces heat loss, but also because of the high porosity of the lightweight materials, the baking is simple, which can achieve rapid baking, rapid heating, and save maintenance time. This is unmatched by heavy castables. At the same time, because the flexible castable has good resistance to rapid cold and rapid heat, its peeling resistance is also much better than that of heavy castables.

When the 500 billet heating furnace was repaired and shut down, the inner surface of the furnace roof was only slightly peeled off after one year, and the furnace roof was still in good condition.

The successful application of the lightweight mullite castable in the 500 billet heating furnace has established a model for other heating furnaces, and the castable has been quickly promoted in other heating furnaces.

Lightweight Mullite Insulating Refractory Castable

Why Choose Lightweight Mullite Refractory Castable?

(1) Lightweight mullite castable is a high-temperature, lightweight castable with light bulk density, low thermal conductivity, and high operating temperature. It can be used for a long time under high temperature and direct flame environment, and it is extremely suitable for steel rolling heating furnace as furnace wall and furnace roof material.

(2) Because the lightweight castable has high porosity and small heat capacity, it can achieve rapid baking, rapid heating, and cooling. Save maintenance time and improve productivity.

(3) The application of light-weight mullite refractory castable has an obvious effect on heat preservation and energy saving.

(4) The castable has good resistance to rapid cold and heat and peeling resistance.

(5) After using the castable, the original light and heavy composite structures are canceled. On the one hand, it eliminates the shear stress caused by the different expansion coefficients of the light and heavy castables on the hanging bricks. On the other hand, it also reduces the load of hanging bricks and steel structures, greatly increasing the safety factor of the furnace roof and furnace wall.

Rongsheng Refractory Manufacturer

Rongsheng is a refractory manufacturer with rich experience in refractory production and sales. Its refractory materials have been sold to more than 60 countries around the world. For example, Russia, South Africa, Kazakhstan, Philippines, Chile, Malaysia, Uzbekistan, Indonesia, Vietnam, Kuwait, Turkey, Zambia, Peru, Mexico, Qatar, etc. And received unanimous praise from customers. High customer return rate. Moreover, Rongsheng‘s newly established advanced environment-friendly and fully automatic unshaped refractory production line have an annual output of 80,000 tons. It provides a reliable guarantee for the normal operation of the refractory lining of various thermal furnace equipment. Our high-quality lightweight mullite refractory castables can also provide better insulation for the lining of your kiln equipment so that your equipment can achieve the best energy-saving state during normal operation and save production costs.

What is Alumina Bubble Brick for Gasifier?

2021-03-22 by globalrefractory

Alumina bubble brick for gasifier is a new type of high-temperature insulation material. It is made by smelting and blowing industrial alumina in an electric furnace, and the crystal type is a-Al2O3 microcrystals. The content of AL2O3 in the alumina bubble brick of the gasifier is not less than 98%, the content of SiO2 is not more than 0.5%, and the content of Fe2O3 is not more than 0.2%. The bulk density is 1.3～1.4g/cm3, the apparent porosity is 60%～70%, and the compressive strength is not less than 9.8MPa. The load (0.2MPa) softening temperature is not less than 1700°C, and the thermal conductivity is 0.7～0.8 W/(m.k).

Alumina Bubble Brick - Rongsheng Refractory — Alumina Bubble Brick

Alumina hollow sphere brick for gasifier is mainly made of alumina hollow spheres, which can be made into products of various shapes, with a maximum operating temperature of 1800°C. The product has high mechanical strength, several times that of general lightweight products, and the bulk density is only one-half of corundum products. It is widely used in high temperature and ultra-high temperature furnaces such as petrochemical industry gasifiers, carbon black industrial reaction furnaces, metallurgical industry induction furnaces, and so on. And achieved a very satisfactory energy-saving effect.

The manufacturing method of alumina bubble brick. First, the alumina raw material is put into the dump-type electric furnace and melted into a liquid state. Then the furnace is poured at a certain angle so that the solution flows out of the casting trough at a certain speed. The liquid flow is blown away by a flat nozzle 60°～90° with the flow stream with a high-speed airflow with a pressure of 0.6-0.8 MPa to form a hollow alumina ball. Then, the alumina hollow spheres, the sintered alumina fine powder, and the binder are compounded in a certain proportion, formed, dried, and fired to obtain alumina hollow sphere bricks.

Alumina bubble brick for gasifier has the following characteristics:

High temperature and good thermal stability. The reheating line has a small change rate and can be used for longer.
Optimize the structure to reduce the weight of the furnace body. The alumina bubble brick is only 1.1~1.5g/cm. For the same volume of one cubic meter, the use of alumina bubble bricks can reduce the weight of 1.1-1.9 tons.
Save materials. To reach the same operating temperature, if alumina bubble bricks are used, 1.1-1.9 tons of heavy bricks can be saved per cubic meter, and 80% of refractory insulation materials can be saved.
Save energy. Alumina hollow spheres have obvious thermal insulation properties, low thermal conductivity, and can play a very good thermal insulation effect. Reduce heat dissipation and improve thermal efficiency, thereby saving energy.

FAQ1: Will the alumina bubble brick melt at 1700 ℃?

The alumina bubble brick will not melt at 1700 ℃. Alumina hollow sphere is a new type of high-temperature insulation material, which is made by smelting and blowing industrial alumina in an electric furnace, and the crystal type is a-Al2O3 microcrystals. With alumina hollow sphere as the main body, it can be made into products of various shapes, and the maximum use temperature is 1800℃. The product has high mechanical strength, several times that of general lightweight products, and the bulk density is only one-half of corundum products.

FAQ2: What is the general volume ruler of alumina bubble brick?

The high-temperature-resistant materials currently used are heavy bricks with a bulk density of 2.3-3.0g/cm³. The alumina bubble brick is only 1.3~1.5g/cm. For the same volume of one cubic meter, the use of alumina bubble bricks can reduce the weight of 1.1-1.9 tons. The size of alumina bubble brick is generally 230×114×65mm (T3 brick).

If you have a demand for alumina bubble bricks for gasifiers, please contact us. We will provide you with high-quality refractory materials and considerate service.

How are Alumina Bubble Bricks Prepared?

2021-03-04 by globalrefractory

Alumina Bubble Bricks and its products are a kind of light refractory material with excellent high-temperature resistance and energy saving, and it is very stable to use in various atmospheres. Especially it is used in the high-temperature kiln at 1800℃. Alumina hollow spheres can also be used as high-temperature and ultra-high-temperature insulation fillers, high-temperature refractory concrete lightweight aggregates, high-temperature castables, etc. Alumina hollow ball bricks can be used for high-temperature energy-saving (>30%) inverted flame kilns, shuttle kilns, molybdenum wire furnaces, tungsten rod furnaces, induction furnaces, nitriding furnaces, etc. Obvious effects will be achieved for reducing the weight of the furnace body, transforming the structure, saving materials, and saving energy.

Forming and Firing of Alumina Bubble Bricks

Molding methods include manual molding, vibration molding, and press molding. According to the size and complex shape of Alumina Bubble Bricks, the ingredients and forming methods are selected. Manual molding should be stratified and rammed, and the addition of each layer should not exceed 50mm. The vibration molding time is generally 2 minutes. The molding pressure of press molding is generally 50-80MPa. For molds processed by various molding methods, there is no need to add a ruler. After the semi-finished product is fully dried, the residual moisture should be less than 0.5%. Alumina hollow ball bricks are fired in a high-temperature kiln, the firing temperature is generally 1800-1850℃, and the heat preservation is 4-6h. Generally, it is to prevent Alumina Bubble Bricks from cracking during firing. When installing the kiln, consider that Alumina Bubble Bricks should not be directly impacted by the flame as much as possible. Add emulsified paraffin wax 0.5%-1.0%, plasticizer 4%-6%, high-efficiency dispersant 1%, and water generally 40%-45%. The slurry is made in a high-speed mixer, and the slurry is sent into the spray drying tower through a nozzle with a diaphragm pump for spray granulation drying. The inlet temperature of the drying tower is generally 420-440°C, and the outlet temperature is generally 120-130°C.

At the time of firing, the temperature is about 1680°C, the Alumina Bubble Brick has begun to sinter, and the bulk density and compressive strength are both high. The compressive strength is measured to reach 317.3MPa. Insulation materials are generally used to reduce heat accumulation and heat dissipation on the walls of the kiln, so as to reduce the energy consumption of the kiln. With the advancement of science and technology, many new refractory and thermal insulation materials with high-temperature resistance and high strength have emerged in recent years. The performance of Alumina Bubble Bricks is generally determined by the chemical composition, followed by the production process of alumina hollow ball bricks. Factors such as particle ratio, molding pressure, and firing temperature are also important.

Related Product Introduction

Alumina Bubble Bricks and zirconia hollow ball bricks are both heat-insulating refractory materials, also known as lightweight refractories. They are characterized by high porosity, which can generally reach 40%-85%. The bulk density is low, generally lower than 1.5g/cm3. The thermal conductivity is low, generally lower than 1.0W (m·K). Hollow ball bricks are used as heat insulation and refractory materials for industrial furnaces, which can effectively reduce the heat loss of the furnace and save energy. And because the body density is small, the weight of thermal equipment can be effectively reduced.

Regarding the alumina hollow ball brick, I will introduce it here, and I hope it will be helpful to everyone. Rongsheng refractory materials manufacturers provide customers with samples of various refractory bricks and insulation bricks, such as Alumina Bubble Bricks, mullite insulation bricks, etc., for free. As an experienced refractory manufacturer, Rongsheng Refractories not only pays attention to the expansion of its own scale but more importantly, always takes a long-term development perspective and continuously develops new refractory materials. The purpose is to continuously meet the more stringent market demand and conform to the trend of the times. Rongsheng refractory material manufacturer specializes in the production of various high alumina bricks, silica refractory bricks, magnesia bricks, magnesia carbon bricks, clay bricks, castables, and other products. Welcome customers to visit the factory and establish long-term cooperative relations.

Why are High Alumina Castables So Popular?

2021-02-07 by globalrefractory

The high-aluminum castable is based on the traditional ratio, adjusted the particle gradation, and added different additives to reduce the amount of cement and improve the performance. Improve the medium temperature strength and load softening temperature, reduce the thermal conductivity, and have good thermal stability. High-alumina castables are resistant to penetration, erosion, impact, and abrasion. Good mechanical properties, strong integrity of the furnace body structure, and better air-tightness than brick furnaces. Extend the furnace life, save the cost of repairing the furnace, and have the characteristics of high aluminum castables with significant economic benefits.

High Alumina Castable Refractory - Rongsheng Company — High Alumina Castable Refractory

The Effect of Adding High Alumina Cement to Refractory Castable

The high alumina cement is added to the refractory castable for binding.

According to the content of alumina, alumina, and calcium oxide in high alumina cement, there are CA-50, CA-70, and CA-80. CA-50 high alumina cement is yellow cement, and its raw materials are bauxite and limestone. CA-70 high-alumina cement has fewer impurities and has better setting characteristics and refractoriness than CA-50 refractory cement. The binder used in the preparation of low cement refractory castables. The aluminum content of CA-80 high-alumina cement is 80%, and it contains α-AL2O3 fine powder, which is used as a binder in high-grade refractory castables. Because CA-70 and CA-80 have high aluminum content in cement, they can improve the weak links of the setting-speed and medium temperature strength of refractory castables. And because of the low calcium content, the later strength of the refractory castable has a longer service life.

The higher the alumina content, the higher the refractoriness; the lower the alumina content, the higher the calcium oxide content. Add high-alumina cement as a binder to demould the refractory castable within 24 hours. High alumina cement will affect the fluidity, construction time, and demoulding time of refractory castables. If used improperly, it will have a great impact on the construction of refractory castables.

The use of high alumina cement is divided into three stages: dissolution, nucleation, and precipitation. For example, CA-50 high alumina cement is generally used in medium and low-grade refractory castables. CA-50 cement has the weakest strength at 800℃. Therefore, if the temperature of the furnace lining is 800℃, it is also the most embarrassing temperature. The temperature is not high, instead of using general refractory castables, low cement castables must be used. Low-cement castables have low calcium content, good strength at medium temperature, and good strength in later use.

CA-70 and CA-80 high-alumina cement have high aluminum content and a low addition ratio. Therefore, it is used in low cement refractory castables, which not only enhances the strength of the refractory castable but also reduces the calcium content of the refractory castable. It can also improve the use of medium temperature strength.

Therefore, adding high-alumina cement to refractory castables not only depends on the combination but also pays attention to the use temperature to determine whether to add CA-50 high-alumina cement or CA-70 and CA-80 high-alumina cement.

Is there a difference between high-alumina castable and high-alumina low-cement castable?

There is a difference between high-aluminum castables and high-alumina low-cement castables.

The high-aluminum castable refractory cement is added in 12%, which is convenient for construction and fast in the early stage, but the calcium content is high, and the later use strength is not as good as the low cement castable. High-aluminum low-cement castable refractory cement is added in 6%, low calcium content, and good strength in later use.

If used for chimney lining, it is better to use high aluminum castable. Because of a large amount of refractory cement added, the chimney lining will encounter the impact of smoke and water mist. Due to a large amount of cement on the surface of high-aluminum castables, the construction speed is fast and the surface is smooth. Therefore, in this case, high-aluminum castables are more suitable.

High-aluminum low-cement castables have a small amount of refractory cement binder added, and a small amount of water added during construction. It is easy to bake and has good strength in later use and high-temperature resistance. In addition, the raw materials and binders of high-alumina and low-cement castables are better than those of general high-alumina castables, and the refractory cement is also relatively different in grades. The price is also relatively higher than that of high-aluminum castables.

High-alumina and low-cement castables are relatively used in high-temperature parts. It has a better effect than high aluminum castable. The material matrix used is also different than the high-aluminum castable. So these two castables are different.

Rongsheng Refractory Material Manufacturer and Sales Factory

Rongsheng is a refractory castable manufacturer with rich production and sales experience. Rongsheng’s advanced environment-friendly and fully automatic unshaped refractory production line have an annual output of tons. If you need to buy high-quality high-aluminum refractory castables and high-alumina low-cement refractory castables, please contact us. We will provide you with refractory products that best suit your production needs according to your specific production needs.

The Best Proportion of Non-Stick Aluminum Castable for Aluminum Melting Pool

2021-01-06 by globalrefractory

The aluminum melting furnace is an important piece of equipment in the aluminum processing industry, and the refractory lining, especially the non-stick aluminum castable used in the aluminum melting pool, plays a vital role in its normal operation at high temperatures. Liquid aluminum is lively and has a low viscosity. Therefore, the refractory materials in the molten pool that are in direct contact with molten aluminum are most severely damaged by molten aluminum erosion. Its quality and life will directly affect the quality of the product and the life of the aluminum melting furnace. So What’s the Best Proportion of Non-Stick Aluminum Castable for Aluminum Melting Pool?

The Best Proportion of Non-Stick Aluminum Castable for Aluminum Melting Pool

Recently, it is time to repair the aluminum melting furnace and purchase refractory lining materials. Among them, in order to prepare non-stick aluminum castable for an aluminum melting pool with excellent resistance to aluminum melt corrosion. High alumina bauxite (8~5, 5~3, 3~1, and ≤1mm) is often used as aggregate, and fine mullite powder, α-AL2O3 powder, silica fume, barium sulfate, and high alumina cement are used as powder materials. After many times of running-in between refractory manufacturers and customers, The Best Proportion of Non-Stick Aluminum Castable for Aluminum Melting Pool. the best ratio of powder was finally obtained. The content of silica fume, anti-erosion agent, barium sulfate, and cement are 3%, 3%, 4%, and 4% respectively.

Analysis of the Influence of Fine Powder on the Corrosion Resistance of Castables for Molten Aluminum Pool

The erosion of the non-stick aluminum castable by the aluminum melt first occurs in the matrix. Therefore, in order to improve the corrosion resistance of non-stick aluminum castable for the aluminum melting furnace. In this experiment, in addition to using high alumina bauxite as aggregate, the influence of fine powder in the matrix composition on the corrosion resistance of the castable for the aluminum melting pool was also studied.

The raw material in the experiment is high alumina bauxite (8~5, 5~3, 3~1, and ≤1mm). The fine powder includes mullite fine powder (≤0.088mm), barium sulfate fine powder (≤0.045mm), α-AL2O3 fine powder (d=5μm), silica fume (≤1μm), high alumina cement, and anti-erosion agent. The basic ratio of the main raw materials is 71.71% high alumina bauxite, 5.29%-19.29% mullite fine powder, 5% α-AL2O3 powder, and the remaining matrix materials are silica fume, anti-erosion agent, barium sulfate, and cement. The anti-erosion performance of the materials after the ratio is analyzed as follows.

(1) With the addition of silica fume and the increase of its addition, the corrosion resistance of the sample gradually improves. This is because the particle size of silica fume is extremely small and can be filled in the voids formed by the coarse aggregate to densify the sample. As a result, the apparent porosity of the sample is reduced, and the passage of aluminum melt into the sample is reduced. In addition, the high proportion of silica fume has high reactivity, and it can promote the sintering of the sample matrix material at high temperatures so that the sample is densified and the strength of the sample is improved. The strength of the sample affects the ability of the castable to resist the stress caused by the metamorphic layer, and the stress change makes the corrosion caused by the appearance of cracks and cracks propagation intensified. It can be seen that the incorporation of silica fume can increase the strength of the non-stick aluminum castable while also improving the corrosion resistance of the sample.

(2) When the mixing amount of barium sulfate is 2%, the corrosion resistance of the sample can be increased from scratch to nearly double, and the corrosion resistance becomes excellent. It shows that the addition of barium sulfate can significantly improve the corrosion resistance of aluminum melt.

(3) With the increase of cement content, the corrosion resistance of aluminum melt of the sample has a tendency to decrease first and then increase. This is because the cement hydration increases the water requirement of the sample, and the dehydration of the hydration product at high temperature causes the internal structure of the sample to become loose, which weakens the structure and reduces the corrosion resistance of the sample. When the cement content continues to increase by more than 6%, the introduction of CaO into the matrix increases the amount of liquid phase at high temperatures. The surface tension of the liquid phase shortens the distance between the particles and promotes the internal densification of the sample. Thereby improving the aluminum melt corrosion resistance of the sample.

Summary: Non-stick aluminum castables are used for molten aluminum pools based on materials such as silica fume, corrosion inhibitor, barium sulfate and cement. The main factor that has an obvious influence on the corrosion performance of aluminum alloy melt is barium sulfate, and as the content increases, the corrosion resistance improves. Within a certain range, with the increase of the amount of silica fume incorporated, the corrosion resistance of the castable is improved. However, if the added amount of anti-corrosion agent and cement is controlled within a certain range, it can play a better anti-melt erosion effect.

Rongsheng High-Quality Unshaped Refractory Materials Manufacturer

Rongsheng is an experienced refractory material manufacturer and sales company. Rongsheng’s monolithic refractory production line has an annual output of 80,000 tons. Customers who purchase monolithic refractories from Rongsheng manufacturers each year have both new turnkey projects and furnace refractory lining repair projects. From the customer’s purchasing experience, they have not only experienced experiments with high-priced unsuitable refractory lining products, but also low-priced refractory lining materials that are not well used. Through various searches, the Rongsheng refractory manufacturer was finally selected. The product quality is qualified and the customer service is good. Formally because of this, Rongsheng continues to accumulate experience in the matching of customer projects and refractory materials, striving to provide customers with high-quality refractory products. Save production costs for customers and improve economic benefits. To choose high-quality refractory castables products, such as non-stick aluminum castables for aluminum melting furnaces, please contact us. We will provide you with unshaped refractory products that best suit your production needs according to your specific project needs.

Why are Alumina Bubble Bricks Widely Used?

2020-12-23 by globalrefractory

Alumina Bubble Bricks belongs to a kind of ultra-high temperature material energy-saving insulation material. It uses alumina hollow spheres and alumina powder as the main raw materials, combined with other binders, and fired at a high temperature of 1750 degrees. As a refractory manufacturer, why are alumina hollow ball bricks widely used? Why recommend alumina hollow ball bricks to customers? This will start with the performance of Alumina Bubble Bricks.

The Manufacturing Process of Alumina Bubble Bricks

Alumina Bubble Brick is a new type of high-temperature insulation material, which is made by smelting and blowing industrial alumina in an electric furnace. With alumina hollow spheres as the main body, it can be made into products of various shapes, with a higher use temperature of 1800°C. The mechanical strength of the product is high, which is several times that of the general lightweight product, and the bulk density is only one-half of the corundum product. Among them, the alumina powder is produced by using reliable industrial alumina as the raw material, using a new high-temperature inverted flame kiln and a scientific calcination process. Manual selection, clear classification, fewer impurities, high conversion rate, stable shrinkage rate, and good consistency.

High-Quality Alumina Bubble Bricks for Sale

The Performance of Alumina Bubble Bricks

Alumina hollow ball and its products are a kind of light refractory material with excellent high-temperature resistance and energy saving, and it is very stable to use in various atmospheres. Especially it is used in the high-temperature furnace at 1800℃. Hollow balls can be used as high-temperature, ultra-high-temperature insulation fillers, high-temperature refractory concrete lightweight aggregates, high-temperature castables, etc. Hollow ball bricks can be used for high-temperature energy-saving (>30%) inverted flame kilns, shuttle kilns, molybdenum wire furnaces, tungsten rod furnaces, induction furnaces, nitriding furnaces, etc. Obvious effects will be achieved for reducing the weight of the furnace body, transforming the structure, saving materials, and saving energy.

The specific advantages of alumina bubble bricks are as follows.

The operating temperature is high, up to 1750 degrees. Good thermal stability, the small change rate of the re-burning line, longer use.
Optimize the structure and reduce the weight of the furnace body. The high-temperature-resistant materials currently used are heavy bricks with a bulk density of 2.6-3.0g/cm. The alumina hollow ball brick is only 1.1~1.5g/cm, the same volume of one cubic meter, the use of alumina hollow ball brick can reduce the weight of 1.1-1.9 tons.
Save materials. To reach the same operating temperature, the price of heavy bricks is equivalent to that of Alumina Bubble Bricks, and considerable refractory materials are required for insulation. If alumina hollow ball bricks are used, 1.1-1.9 tons of heavy bricks can be saved per cubic meter, and 80% of refractory insulation materials can be saved.
Save energy. Alumina hollow spheres have obvious thermal insulation properties, low thermal conductivity, and can play a very good thermal insulation effect. Reduce heat dissipation and improve thermal efficiency, thereby saving energy. The energy-saving effect can reach more than 30%.

Obviously, the excellent energy-saving effect of alumina hollow spheres makes it more competitive as a lightweight refractory material. Buyers of kiln lining materials will definitely prefer such superior refractory products. Therefore, not only refractory manufacturers recommend everyone to buy Alumina Bubble Bricks, but also its own advantages that make it so widely used. Alumina Bubble Bricks are widely used, for example, in high temperature and ultra-high temperature furnaces such as petrochemical industrial gasifiers, carbon black industrial reactors, metallurgical industrial induction furnaces. And they have achieved very good energy-saving effects.

For more refractory materials products, please contact us: inquiry@global-refractory.com.

Non-stick Aluminum Castable for Aluminum Melting Furnace

2020-12-03 by globalrefractory

Non-stick aluminum castables need to be suitable for different aluminum alloy series in the aluminum melting furnace. The working temperature of the aluminum melting furnace is generally 700～1200℃, and the highest temperature of the upper part of the molten aluminum can reach 1200℃. The aluminum, magnesium, and other components in the aluminum alloy can easily react with some components of the refractory lining to form a reaction layer, and the copper, manganese, and zinc in the aluminum alloy can penetrate into the refractory castable through the pores to form a modified layer.

Why must refractory castable for aluminum melting furnace use non-stick aluminum castable?

With the continuous development of the metal smelting industry, aluminum products have been applied to various industries, and the thermal kilns used in aluminum smelting are collectively referred to as aluminum melting furnaces. The melting point of aluminum is 660°C, which is relatively low among many metals. However, aluminum is highly active and has a very strong penetration ability, which can easily corrode the refractory castable lining and change its performance, causing cracks and peeling. Therefore, it is very important to choose the material of refractory castable.

Reasons for damage of aluminum melting furnace lining

During the operation of the aluminum melting furnace, the non-stick aluminum castable can resist the falling off of the reaction layer and the deteriorated layer formed by the aluminum solution. On the one hand, it does not pollute the aluminum alloy, and on the other hand, it increases the service life of the lining of the aluminum melting furnace. In the current common aluminum alloy series on the market, because the types and contents of the alloys in each series of aluminum alloys are different, the alloy components in the aluminum alloys have different damage to the non-stick aluminum castable. In summary, there are three main reasons for the damage of the aluminum melting furnace lining.

1) Although the temperature of the molten aluminum in the furnace is not high, it is very penetrating. The very active aluminum melt slowly penetrates into the furnace lining through the pores and fine lines of the furnace lining, physically and chemically react with the furnace lining, and slowly loosens and peels off the furnace lining. The cracks of the furnace lining increase and fall off.
2) The aluminum melt in the furnace reacts chemically with the furnace lining to form adhesion. Long-term adhesion increases, forming nodules and causing damage to the furnace lining.
3) During the process of adding raw materials or slagging, bauxite or aluminum slag will cause a certain degree of impact and wear on the furnace lining, causing physical loss of the furnace lining.

Characteristics of Non-Stick Aluminum Refractory Castable

Non-stick aluminum refractory castables are made of special grade high alumina bauxite, brown corundum, kyanite, alumina powder, calcium aluminate cement, silica powder, and special additives, which are mixed in strict proportions. It is a low cement refractory castable specially developed according to the use requirements of an aluminum melting furnace. It has the performance characteristics of low impurity content, high density, high strength, high corrosion resistance, high permeability resistance, and no infiltration by molten aluminum. Table 1 shows the performance indexes of non-stick aluminum refractory castables.

Table 1 Properties of non-stick aluminum refractory castable

Items		High-Strength Non-Stick Aluminum Castable
Al₂O_{3 +}SiO₂ (%)		86
Bulk Density (g/cm³)	110℃ × 24h	2.7
Flexural Strength (MPa)	110℃ × 24h	9
Flexural Strength (MPa)	1200℃ × 3h	11
Crushing Strength (MPa)	110℃ × 24h	45
Crushing Strength (MPa)	1200℃ × 3h	83
Linear Change (%)	1200℃ × 3h	±0.4

Application of Non-Stick Aluminum Refractory Castable

Non-stick aluminum refractory castables can be used for aluminum melting furnace bottoms, lower furnace walls, slagging slopes, chutes, aluminum ladle, and other severely corroded parts due to their superior aluminum corrosion resistance. After use, the erosion and nodulation of molten aluminum are largely controlled and delayed.

Rongsheng Refractory Manufacturers

Non-stick aluminum refractory castable, as a tailor-made lining material for aluminum melting furnaces, has been applied to the construction of aluminum melting furnaces in many large aluminum factories and aluminum alloy processing enterprises. At present, user feedback has been good. Its superior performance effectively prolongs the life cycle of the aluminum melting furnace for more than 10 months. Rongsheng refractory material manufacturer, advanced automatic unshaped refractory material production line, with an annual output of 80,000 tons. Customers in more than 60 countries all over the world, for example, Russia, South Africa, Kazakhstan, Philippines, Chile, Malaysia, Uzbekistan, Indonesia, Vietnam, Kuwait, Turkey, Zambia, Peru, Mexico, Qatar, etc. Rongsheng’s high-strength refractory castables, refractory plastics, and non-stick aluminum castable products on Rongsheng’s production line have a high frequency of orders and customers’ return orders. If you are interested in our Rongsheng refractory manufacturer or want to purchase indefinite refractory products, please contact us. We will provide you with services according to your specific needs.

Why do Cracks Appear after the High Alumina Castable Lining is Baked?

2020-11-26 by globalrefractory

The oven-drying is a vital link after construction and before the operation of high alumina castable. The oven-drying directly determines the future service life of the kiln. When the high-aluminum castable is in the oven-drying, the oven-drying should be prepared, the oven-drying time must be controlled, and the furnace heating curve, etc., all need to be operated under strict conditions. Irregular operation of the oven-drying may cause engineering quality accidents such as cracks in the castable.

Is it normal for the castable to have cracks after the oven-drying? What are the reasons?

Under normal circumstances, after the oven-drying is finished, the kiln can operate normally after passing the project acceptance, and the castable can reach its own performance within the use temperature range. There are three main reasons for the cracks in the castable after the oven-drying.

The amount of water added is not well controlled when the high-aluminum castable is wet mixed and stirred. Adding too much water leads to insufficient bonding of the castable, which causes the castable to fall off. Adding too little water will greatly weaken the performance of the castable. Therefore, the amount of water added must be added in proportion and strictly in accordance with the instructions on the instructions.
When curing high-aluminum castables, the curing time is not enough, resulting in the failure of the strength of the formed castables. Under normal circumstances, when the temperature is higher, the curing time of the castable is 24 hours. In colder winters, the curing time of castables is 48 hours. Due to the low temperature, a small amount of coagulant will be added to speed up the setting speed of the castable.
When the castable is in the oven-drying, the temperature rises too fast. When the castable is in the oven-drying, the boiler heating curve must be controlled. When drying the furnace, the construction personnel will often formulate the furnace curve according to the boiler situation. In the oven-drying, strictly control the heating temperature to avoid the phenomenon of rapid heating and rapid cooling.

After baking, if the cracks in the castable are not obvious or serious, it needs to be checked in time and repaired with the same castable. If the crack is large or the castable falls off, the construction personnel need to make a solution to the problem. And it needs to be repaired with new castable.

The oven-drying after the construction of the high-aluminum castable is a very important factor. Similarly, when purchasing castables, how to purchase high-quality high-aluminum castables is also very important.

High Alumina Castable - Rongsheng Supplier — Rongsheng High Alumina Castable for Sale

How to distinguish the quality grade of high aluminum castable?

High-alumina castable is the most used castable among refractory castables. The quality grades of high-aluminum castables produced from different raw materials are not the same.

How to distinguish the quality grade of high aluminum castable? By the manufacturer, there are many methods, the most important of which is to distinguish from the aspects of aluminum content, body density, porosity, compressive strength, and load softening temperature.

First, it is the index of aluminum content. The higher the aluminum content of the high-aluminum castable, the higher the quality level of the castable. The high aluminum content indicates that the raw materials used have high purity and low impurities.

Body density is also an important indicator of the quality of high alumina castables. The higher the volume density, the higher the density of the high-aluminum castable, the higher the wear resistance and erosion resistance. The bulk density and porosity of high-alumina castables are also closely related to the composition of the raw materials.

The flexural strength at room temperature is the ability of high-aluminum castables to withstand bending. Moreover, flexural resistance plays a decisive role in high-temperature strength. The higher the purity of the raw material, the higher the bending resistance and the higher the temperature it can withstand. Therefore, the flexural strength is also a way to distinguish the priority of castables.

The compressive strength at room temperature can also indirectly show the wear resistance and impact resistance of high-aluminum castables. The higher the strength, the better the abrasion resistance, erosion resistance, and erosion resistance. The load softening temperature of high aluminum castables is also an item that cannot be ignored. The higher the load softening temperature, the lower the probability of deformation of the castable. The high softening temperature under load is sufficient to prove the structural strength of the castable under the conditions of use.

The performance indexes of aluminum content, bulk density, and load softening of high-aluminum castables are the best way to distinguish castables. When selecting high-aluminum castables, different grades of castables should be determined according to the use temperature and the degree of acid-base corrosion. This makes the best use of it, and also reduces costs reasonably.

Acid-Resistant Bricks and Refractory Castables for Chimney Masonry

2020-11-24 by globalrefractory

When buying refractory materials for chimney masonry, is it better to choose acid-resistant bricks or acid-resistant castables? If the purchaser does not have a very clear demand, they will generally wander between the two. Chimney acid-resistant bricks belong to shaped refractory materials, refractory bricks. It has good acid resistance and flue gas erosion resistance. Its structure is compact, the surface is smooth and clean, and it has excellent acid resistance. However, it is brittle, poor in impact resistance, low thermal stability, and easy to crack when exposed to sudden cold and sudden heat. Some manufacturers of refractory materials have made a summary of the refractory materials for chimneys, which are rough as follows.

Question: Is it better to use acid-resistant bricks or acid-resistant castables for chimney masonry?

Which is better for the boiler chimney castable or acid-resistant brick? Castables and acid-resistant bricks have their own advantages. The refractory manufacturer recommends that you read the following in detail so that you can clearly know what kind of product is more suitable for the boiler chimney. Is it better to use castables for boiler chimneys or acid-resistant bricks?

The choice of chimney lining has an important influence on the construction conditions of the chimney. For example, the construction period, local environment, and other conditions affect the choice of lining materials. How to complete the project within the specified construction period? This needs to choose the lining material according to the local environment, temperature, construction conditions, and economy.

Generally speaking, when the height of the chimney is higher than 100 meters, acid-resistant castable is used as the lining, and when the height of the chimney is lower than 100 meters, the acid-resistant brick is used as the lining. No matter what kind of lining, the cylinder construction adopts a single slip form scheme, with an average of 2~3m/d and the slip form is completed in 60 days. After the cylinder sliding form is completed, the lining masonry will not affect the construction of surrounding buildings. Acid-resistant bricks are more complex than acid-resistant castables, so there will be no material returning to alkali after masonry.

When using acid-resistant castables, the castable must be baked in time to drain the free water in the castable. Before the alkali metal and alkaline earth metal substances are converted into hydroxides and migrate, they will react with each other to form stable compounds, thereby preventing the phenomenon of back alkali.

Acid proof brick — Acid-Resistant Bricks for Chimney Masonry

Choose castable or acid-resistant brick for the lining of the boiler chimney?

The traditional chimney project is lined with acid-resistant bricks. In order to reduce the cost and investment, the project plans to use refractory castables as the lining. Refractory castables are characterized by their low bulk density (1/3 of acid-resistant bricks), reducing the amount of chimney wall concrete and foundation steel bars, and low thermal conductivity (castables are 0112W/m·k, acid-resistant bricks are 019W/m·k). There is no need to add a heat insulation layer, which is more economical in design than acid-resistant bricks. Moreover, the performance of the castable is similar to that of the concrete. By combining the embedded steel bar and the concrete, the overall force performance is better. Compared with the economic investment of acid-resistant bricks and refractory castables, the price of refractory castables can save tens of thousands to hundreds of thousands based on the price of acid-resistant bricks. And the running time is long, so it is recommended to use boiler chimney castable as the lining body.

How to choose the lining of the power station boiler chimney?

As the flue gas discharged from the power station boiler chimney is saturated with water after wet deacidification, the flue gas temperature drops to between 50°C and 70°C, and it also contains a small amount of corrosive media such as sulfuric acid and entrained chloride. Due to the strong permeability of low-concentration sulfuric acid and chloride, the corrosion and damage to the inner wall of concrete are stronger than that of high-concentration sulfuric acid solution. Therefore, higher requirements are put forward for the anti-corrosion performance of the chimney lining after wet flue gas desulfurization in coal-fired power plants. The castable for the boiler chimney of the power plant produced by the Rongsheng refractory material manufacturer can be directly poured into the inner layer of the chimney to play a role in heat preservation, heat insulation, acid resistance, and corrosion resistance. And it has the advantages of relatively high compressive strength, which replaces the original traditional light bricks and acid-resistant bricks, and is convenient for construction.

Construction plan for stacking chimney with chimney lined with acid-resistant bricks

The construction plan for stacking chimneys with acid-resistant bricks lining the chimney introduced by the acid-resistant brick manufacturer, I hope will help the one which is looking for the solutions for the construction for the chimney’s lining masonry.

First, clean the inner wall of the chimney with a high-pressure water gun. If the old chimney has been preserved before, the damaged area needs to be cleaned up, and the intact part only needs to be cleaned. Then use special acid-resistant cement to make putty and repair the surface until the application is smooth and smooth. Then the surface of the acid-resistant clay is completely and thoroughly treated with corrosion protection. Using the traditional hoop bucket principle, the hoop ceramic lining with a thickness of 5mm is made outside the anti-corrosion layer, and the ceramic hoop ceramic lining is filled with low-temperature enamel and the surface is enameled.

According to this method, the ceramic-lined chimney is made of a chimney lining with acid-resistant bricks. The inner wall is smooth and beautiful, with four layers of anti-corrosion and excellent corrosion resistance. This should be the first choice for chimney corrosion protection in power generation companies.

The Development of Alumina Silicate Refractories

2020-11-19 by globalrefractory

Alumina Silicate refractory materials can be divided into the following three types according to the alumina content. Semi-silica (15%-30% alumina), clay (30%-48% alumina), and high alumina (alumina greater than 48%). In addition to making fired bricks or unfired bricks, it can also make molten cast products, as well as various grades of ramming materials, castables, refractory coatings, and other unshaped refractory materials.

Advantages of Alumina Silicate Refractories

Alumina Silicate refractories have the advantages of a lightweight, high-temperature resistance, thermal stability, low thermal conductivity, small heat capacity, good mechanical vibration, good heating and heat preservation performance, and good expansion. Aluminum silicate fiberboard, aluminum silicate fiber felt, and aluminum silicate fiber blanket products made by special treatment. Model sealing materials have the characteristics of low thermal conductivity, high-temperature resistance, lightweight, long service life, high tensile strength, good elasticity, and non-toxicity. It is a new type of material to replace asbestos and is widely used in thermal insulation in metallurgy, electric power, machinery, chemical, and other industries.

The Development of Alumina Silicate Refractories

Alumina Silicate refractory materials have a long history, and aluminum silicate refractory materials have been used in the bronze period about 1700 BC. Later, due to the rise of iron smelting and silicate industries, aluminum silicate refractories changed from natural raw materials to products such as saggers, crucibles, and blocks. After the nineteenth century, Alumina Silicate refractories became the main material for various furnace linings.

Since the 1960s, aluminosilicate refractories have developed into high-quality, high-purity, and indeterminate varieties. Since the founding of the People’s Republic of China, my country has manufactured many high-quality products of the world’s advanced level and has gained rich experience in the production of Alumina Silicate refractories. Refractory materials are mainly aluminum silicate, accounting for more than 85% of the total refractory materials, and high-aluminum and amorphous refractories are also increasing year by year. Since the 1980s, products in the steel industry have continued to emerge. Up to now, the lining of steel drums still uses aluminum silicate. The ladle used by Anshan Iron and Steel is lined with A120, which is more than 45%. Clay or high-alumina bricks are also used for steel. Many high-alumina bricks are used in the United States and Japan, which have been used more than 100 times. The life span of my country’s primary-fired high alumina bricks is 31-47 times. Clay bricks for coke ovens are of similar quality to similar products in Japan. Our homemade mullite slabs are better than non-fired high alumina bricks, such as corrosion resistance, no cracks, smoothness, and non-sticky slag. The mullite bricks used in torpedo bags developed by our country exceed the Japanese standards. Mullite plug bricks can be used in steel mills for more than four hours.

In the past 20 years, silicate aluminum refractories have moved towards high quality and high efficiency. Clay bricks are decreasing year by year, and high-alumina products are increasing year by year. Although the total amount of ordinary clay bricks has a downward trend, their role in industrial kilns and thermal equipment has not decreased. In the iron and steel industry, mullite or corundum bricks are widely used in the hearth, waist, and belly of the steel industry. Ordinary clay bricks or high-alumina bricks are generally still used on the main part of the blast furnace. The aluminum oxide of fireclay bricks used in Japanese blast furnaces has increased from 38% to more than 42%, the apparent porosity has been reduced from 20% to 10%, and the compressive strength has more than doubled. The high-density clay bricks or kaolin bricks used in the Soviet Union have a life span of more than 10 years. The walls of medium-sized blast furnaces in the United States are still using dense clay or high alumina bricks. Clay bricks and high alumina bricks are also used in blast furnaces in West Germany, France, the United States, and Italy.

Most hot blast stoves in various countries use alumina silicate firebrick materials. When the air temperature is lower than 900 ℃, ordinary clay bricks are generally used. When the wind temperature is 900-1100℃, high alumina bricks, mullite bricks, or sillimanite bricks are used for furnace lining and checker bricks. When the wind temperature is as high as 1100℃, high alumina bricks and mullite bricks are generally used as furnace lining and checker bricks. There are semi-silica, clay, high alumina bricks, and mullite bricks in American hot blast stoves.

The Development Trend of Alumina Silicate Refractories

In order to adapt to the development of modern technology, refractories are also facing a new development. This requires refractory materials to use raw materials with high chemical purity to make the products dense and resistant to sudden temperature changes. It can withstand the corrosion of molten metal in a vacuum and various atmospheres, and has high mechanical strength at high temperatures, and can resist creep and other properties.

The basis for the development of high-quality Alumina Silicate refractory materials is high-quality Alumina Silicate refractory raw materials. In recent years, foreign countries have kept improving the quality requirements of aluminum silicate refractories. A lot of research has been done in the aspects of beneficiation, purification, synthesis process, and calcination technology. The purity of raw materials is improved, the degree of sintering is improved, the composition structure is uniform, and the performance is stable, which provides a foundation for the development of high-quality, high-purity, and high-efficiency products. The research and development of new lightweight Alumina Silicate refractories and amorphous aluminum silicate refractories is a focus of future development of aluminum silicate refractories. In recent decades, the rapid development of monolithic aluminum silicate refractories and the expansion of their use range is a major breakthrough in the production of Alumina Silicate refractories. This material is characterized by a simplified production process, a simple firing process, energy-saving, easy construction, and can adapt to various complex furnace body structure requirements.

Rongsheng‘s new fully automatic monolithic refractory castable production line will provide high-quality monolithic refractory products for the lining of your kiln equipment. Provide better solutions for your furnace repair. For more detailed information, please contact us.