Process Steps for Producing Alumina Bricks by Molding

Most simple, thick alumina bricks are manufactured using a molding process. Molding (also known as semi-dry pressing) involves placing a blank containing a small amount of binder, with a relatively coarse particle to fine powder ratio, into a metal mold and pressing it into shape on a press.

Rongsheng High Alumina Bricks

For brick products, i.e., molding, why is it important to emphasize a combination of coarse, medium, and fine particle sizes in the clay? This needs to be explained in detail here. At the same time, the precautions in the molding process for alumina bricks become clear.

1. First, crushing the raw material to a certain fineness aims to increase the contact surface between particles, which is beneficial for solid-phase reaction and sintering. However, this is not entirely true for molding. Because the finer the powder particles, the larger their specific surface area, and the larger the loose volume of the powder. This makes it difficult to achieve a dense compaction during molding and easily leads to delamination. Conversely, if the clay material consists entirely of coarse particles, it is equally difficult to compact. Furthermore, the reduced contact area between particles and increased distance between particle centers hinder sufficient solid-phase reaction. Therefore, a mix of coarse and fine particles is required in the batching process.
2. Second, when using particles of the same size for packing, the porosity is 26%–47.6%. To achieve the maximum packing density, a mix of particles of different sizes must be used, allowing smaller particles to fill the gaps between larger particles.
3. Third, an appropriate particle size distribution can reduce green body shrinkage, which is beneficial for controlling the green body's dimensions.

Of course, when forming green bodies with very small dimensions, the above three points are not necessarily overemphasized.

Coarse particles used in compression molding are mostly made by adding a binder to finely ground powder to create coarse particles with good flowability. These coarse particles are conventionally called pseudo-granules. The methods for producing pseudo-granules, or granulation, are as follows:

• (1) Ordinary method: An appropriate amount of binder aqueous solution is added to the powder, mixed, and then passed through a coarse sieve. The binder's agglomerative effect yields relatively uniform granules.
• (2) Pressurization method: The powder mixed with the binder is first pressed into blocks, then crushed and sieved into coarse particles. This method has high density and mechanical strength and is commonly used in industrial production.
• (3) Light calcination method: Finely ground powder is mixed with a small amount of water to form mud balls, calcined at a low temperature, and then crushed and passed through a coarse sieve.
• (4) Spray drying method: The powder is mixed with a binder to form a slurry, which is then sprayed into a granulation tower for atomization. The droplets are dried by the hot air inside the tower to form granules. 

The compression molding process can be summarized as follows:

• (1) First, process the raw materials into fine powder and pseudo-granules.
• (2) Then, according to the requirements of the blank, perform particle size distribution.
• (3) Additives, lubricants, binders, etc., are added and mixed evenly to form a blank (or clay material).
• (4) Finally, weigh and pour into the mold, and shape under pressure on a press.

Rongsheng Refractory Materials Manufacturer specializes in producing various alumina refractory bricks and refractory castables. Contact us for free samples and quotations.

Principles of Refractory Material Configuration for Glass Furnaces

The selection of refractory materials for glass kilns directly affects the kiln's lifespan, glass product quality, and production costs. Because the working environments of different parts of the kiln (temperature, molten glass erosion, alkaline vapor erosion, mechanical scouring, etc.) vary, the selection of refractory materials must be "reasonably matched and synchronized with the kiln's lifespan."

Glass Furnace Refractory Material

Selection of Refractory Materials for Glass Melting Furnaces

The selection and configuration of refractory materials for glass melting furnaces should follow these basic principles:

① Select and configure refractory materials of appropriate quality based on the operating environment (temperature, atmosphere, raw material composition and state, and fuel, etc.) of each part of the furnace and the causes of refractory material damage.

② Select and configure bricks with appropriate physical and chemical properties and dimensions based on the furnace's planned lifespan and the damage rate of refractory materials in each part, ensuring that the lifespan of the refractory materials in each part matches the furnace's lifespan.

③ Avoid using refractory materials that will chemically react at the operating temperature. If this is unavoidable, a transition brick or transition layer should be used between the two types of bricks.

④ Minimize transverse brick joints in the pool wall areas in contact with molten glass to prevent upward drilling erosion that could exacerbate brick erosion.

⑤ When refractory mortar is required, it must be of the same properties as the bricks being laid. Refractory bricks and refractory mortars of different materials must not be mixed.

⑥ During cold repairs of the melting furnace, improvements should be made to address the causes of refractory material damage in the weak points that led to the shutdown.

⑦ The selection and configuration of refractory materials for the melting furnace should also consider the economic rationality of the total cost of the refractory materials. Based on current refractory material production levels and practical experience, the recommended material combinations for various structural components of a glass furnace are as follows.

Refractory Bricks Used in the Melting Pool of a Horseshoe Flame Glass Furnace

The specific selection of refractory materials for the melting pool of a horseshoe flame glass furnace (for bottles, jars, utensils, light bulbs, and fluorescent lamps) is as follows:

Melting Pool:

Pool Wall: For operating temperatures of 1400-1600℃, AZS-33 brick TC is selected. Selection criteria: Good corrosion resistance and thermal shock resistance to molten glass.

Lower Temperature Sections of the Pool Wall: For operating temperatures <1400℃, fused zirconia-mullite bricks are selected. Selection criteria: Good corrosion resistance and thermal shock resistance to molten glass.

Pool Bottom Paving Bricks: For operating temperatures of 1300-1500℃, fused AZS-33# brick D.C.L is selected. Selection criteria: Good corrosion resistance and thermal shock resistance to molten glass.

Pool Bottom: For operating temperatures <1400℃, clay bricks or high-alumina bricks are selected.

Feed port: Operating temperature 1400-1500℃, use either fused AZS-36# R.V or fused AZS-41# R.V. Selection criteria: Extremely strong resistance to glass corrosion.

Bubble section: Operating temperature 1400-1500℃, use fused AZS-41# D.C.L. Selection criteria: This brick is suitable for the most corrosive areas.

Electrode section: Operating temperature 1400-1600℃, use fused AZS-41# RD.C.L.

Upper Structure of the Melting Pool:

Charging Port Upper Part: Operating temperature 1400-1500℃, fused AZS-36# R.C. bricks selected. Selection criteria: Resistant to flying debris and possesses high resistance to flame impact and thermal shock.

Burner: Operating temperature 1500-1650℃, fused AZS-31# or 41# R.C. bricks selected. Selection criteria: Resistant to flying debris and flame impact.

Small Furnace Passage (Top and Side Walls): Operating temperature 1450-1600℃, fused β-Al₂O₃ or high-quality silica bricks selected. Selection criteria: Prevents the adhesion of flying debris and offers good resistance to alkaline vapor corrosion.

Lattice Wall: Operating temperature 1400-1600℃, fused α-Al₂O₃ bricks or fused AZS bricks selected.

Large arch of melting pool: Operating temperature 1300-1650℃, use high-density silica bricks or electrofused AZS bricks.

Hook bricks and nozzle bricks: Operating temperature 1500-1650℃, use electrofused AZS bricks.

Characteristics of Cordierite Bricks and Kiln Furniture Cordierite Bricks

Cordierite bricks and kiln furniture: Cordierite bricks are a type of refractory material with cordierite (2MgO·2Al2O3·5SiO2) as its main component. Pure cordierite contains 13.7% magnesium oxide (MgO) and has the following characteristics: a low coefficient of thermal expansion of 3×10⁻⁶/℃. Due to its low coefficient of thermal expansion, cordierite materials generally exhibit excellent thermal shock resistance.

Pure cordierite is an expensive material, so lower purity semi-cordierite materials are often used as substitutes. Semi-cordierite materials also exhibit a low coefficient of thermal expansion.

Semi-cordierite materials are frequently used as kiln furniture, kiln car fixing blocks, and ceramic components in ceramic kilns. In some cases, alumina-silicate materials are also used for the same product applications. Table 7 lists the characteristics of some semi-cordierite products used for kiln furniture/kiln blocks. The maximum service temperature of these products is typically 1200℃ or higher.

Table 7 shows the relationship between magnesium oxide content and the coefficient of thermal expansion. When the magnesium oxide content is very low, the coefficient of thermal expansion is close to that of clay bricks or mullite [approximately 6 × 10⁻⁶/℃]. Figures 5 and 6 show the microstructure of such typical products.

Figure 5: Microstructure of hemicordierite extruded into pyrophyllite

Figure 6: Microstructure of clay-based hemicordie bricks

The microstructure of cordierite exhibits "crack-like" pores, a typical characteristic of extruded clay products (Figure 5). The large size of the pyrophyllite aggregate particles, sometimes approaching 3 to 4 mm, is not clearly visible in this micrograph. In contrast, the microstructure of pressed cordierite shows that the refractory aggregate particles are surrounded by a sintered clay matrix, with predominantly circular pores (Figure 6). Many experts believe that the presence of fine circular pores improves thermal shock resistance. Therefore, pressed products with approximately 0.9% MgO content (Table 7) may have similar properties to extruded products with 3.0% MgO content.

A typical impurity in cordierite bricks is quartz, which is converted from "free" silica (SiO2) or quartz in the raw materials when the refractory is fired at a temperature of at least 1300°C. By referring to the MgO-Al2O3-SiO2 phase equilibrium diagram (not shown), it can be seen that free cristobalite is an equilibrium phase unless the product composition is exactly the same as pure cordierite. Excessive cristobalite content can lead to "caking" and reduce the lifespan of kiln furniture/kiln blocks. Crizobalite can be conveniently determined using X-ray diffraction (XRD) or thermal analysis (TA) techniques.

Requirements for Refractory Castables in Various Parts of CFB Circulating Fluidized Bed Boilers

Circulating fluidized bed boilers are currently the most widely used and relatively environmentally friendly waste heat boilers in China. They are primarily used in the power industry, petrochemical industry, waste incineration industry, and other sectors. While their applications vary, their structure is largely the same. During boiler operation, high-temperature gases and solid particles in the gases cause severe wear on the refractory linings in various areas, including the furnace and circulation system. Therefore, the wear protection and thermal insulation requirements of these linings are critical to boiler operation. Taking power plant boilers as an example, the operating environment of various boiler components and the requirements for the refractory castable lining are as follows.

Lower Furnace

The dense phase area in the lower furnace is a highly wear-prone area in circulating fluidized bed boilers. The material within this area is coarse, highly concentrated, and fluidized at high speeds. The combustion atmosphere is somewhat corrosive. The wear-resistant refractory castable used in this area must be wear-resistant, have good thermal conductivity, and exhibit excellent resistance to thermal cracking and thermal shock. Steel fiber wear-resistant refractory castables are recommended.

Separator Inlet Flue Duct

The separator inlet flue duct experiences a change in airflow direction, resulting in fine ash particles and a high concentration. The airflow velocity is generally 4.5-6.0 m/s, and the temperature is 850-950°C. The combustion atmosphere is oxidizing, resulting in severe wear and erosion. The castable must exhibit excellent wear resistance, thermal cracking, and thermal shock resistance. Steel fiber wear-resistant refractory castables are recommended.

Cyclone Separator

The high airflow velocity within the cyclone separator causes centrifugal force, causing coarse particles in the airflow to collide with the wall and separate. This results in severe wear at the separator inlet and on the inner wall of the separator. The operating temperature within the separator is less than 1000°C, and the refractory and wear-resistant layer is relatively thick. The atmosphere is oxidizing. The castable must be lightweight, dense, wear-resistant, and have excellent thermal insulation (for adiabatic separators), as well as good resistance to thermal cracking and thermal shock. High-strength, wear-resistant, and refractory castables or wear-resistant, refractory plastics are recommended.

Return Material Transfer Unit

The return material transfer unit transports ash separated by the separator into the furnace for recirculating combustion. The return material transfer unit features a fluidized bed on one side of the furnace and a moving bed on the other. It is a fluidized, sealed ash conveying device. The fluidization velocity is less than 1 m/s, and the material inside is fine and highly concentrated. The operating temperature is approximately 900°C. Compared to other parts, the return material transfer unit's operating environment is not particularly adverse, but construction is challenging. Since combustion does not occur within the return material transfer unit, the castable must possess excellent thermal insulation, thermal cracking, and thermal shock resistance. High-strength, wear-resistant, and refractory castables are recommended.

Platenose Heating Surfaces

Power plant boiler furnaces feature platenose heating surfaces (water-cooled platen and superheater). The lower elbow of the platen is subject to wear and tear from ash particles. This requires the castable to exhibit excellent wear resistance and thermal conductivity. High-strength, wear-resistant, and refractory castables are recommended.

Precautions for High-Strength Wear-Resistant Castable Construction

The quality of high-strength wear-resistant castable construction directly determines its wear resistance and service life. Key considerations lie in controlling the water-cement ratio, ensuring density, and maintaining proper maintenance to prevent cracking and shedding caused by improper construction. Specific precautions can be divided into four key stages:

Refractory Castables in Various Parts of CFB Circulating Fluidized Bed Boilers

1. Pre-construction Preparation: Clean the base surface to remove oil, dust, and loose debris. Sandblast and roughen as necessary. Install anchors according to design requirements, ensuring uniform spacing (usually 150-200mm). Secure with welds and apply anti-rust paint.

2. Mixing: Use a forced mixer. First, add the dry castable and mix for 2-3 minutes. Then, strictly control the amount of water added according to the instructions (generally a water-cement ratio of 0.10-0.14). Mix until a uniform, lump-free paste forms. The mixing time should be minimal (5-8 minutes total). Avoid initial setting.

3. Casting Process: Use an inserted vibrator (30-50mm diameter) to vibrate the lining layer by layer, with each layer no thicker than 300mm. Vibrate until the slurry is smooth and free of bubbles, avoiding missed or over-vibration. Casting should be continuous, with the interval between each layer no longer than the initial setting time to prevent cold joints.

4. Curing and Baking: Cover with plastic sheeting or wet burlap for 12 hours after casting, maintaining an ambient temperature of 5-35°C for at least 7 days. After curing, bake slowly according to a heating curve to remove moisture and avoid cracking caused by rapid heating. Baking time varies depending on the thickness of the lining and generally takes 3-7 days.

Effect of α-Al2O3 on the Properties of Aluminum-Chrome Bricks Made of Chromium-Containing Slag

Aluminum-chrome bricks containing chromium slag. The aluminum-chrome bricks with an aluminum-chrome slag addition amount (wt) of 30% were used as reference samples, and the formula was set as the basic formula. On this basis, 1wt%, 2wt%, 3wt%, and 4wt% of α-Al2O3 were added respectively, and the increased amount replaced the brown corundum fine powder, keeping the Cr2O3 content unchanged, and exploring the effect of α-Al2O3 on the performance of aluminum-chrome bricks containing chromium slag.

Performance of Aluminum-Chrome Bricks

After the raw aggregates were dry-mixed in a small wet mill for 3 minutes, about 3% of the binder (aluminum dihydrogen phosphate solution) was added. After mixing for 1 minute, the machine was stopped, and fine powder was added to continue mixing. Continue to add binder until the mud is suitable, and the total amount of binder added is about 3.5%. After fully mixing, the material is discharged and loaded into a woven bag lined with a plastic bag. Then the trapped material was sealed for 12 hours and formed on a 630-ton electric press. The molded blank sample is a standard brick (230×114×65mm). The formed wet bricks enter the tunnel drying kiln and are kept warm and dried at 110℃~120℃ (>12 hours). After drying, they are loaded with the loading method with the width direction as the pressure direction. They are heat treated in a 111m long ultra-high temperature tunnel kiln fueled by natural gas. The firing system is 1600℃×4.5h.

According to relevant standards, the bulk density, apparent porosity, compressive strength, linear change rate after firing, load softening temperature and thermal shock stability (1100℃ water cooling) of the samples are tested, and the performance indicators of each experimental brick are tested.

Effect of α-Al2O3 on the performance of aluminum-chrome bricks containing chromium slag

The effect of α-Al2O3 micropowder addition (wt.%) on the volume density, apparent porosity, compressive strength and post-firing linear change rate of aluminum-chrome bricks containing aluminum-chrome slag. With the increase of α-Al2O3 micropowder addition, the apparent porosity decreased, the volume density increased, but the amplitude was not large; the compressive strength tended to increase, but the amplitude was not large. The post-firing linear change rate is gradually decreasing, and the comprehensive effect is better when the α-Al2O3 micropowder is added at 3wt%. This is because the basic mechanism of micropowder is ST filling. Appropriate micropowder is filled in the micropores of refractory aggregate and fine powder, which can increase its volume density and reduce apparent porosity. In corundum products, adding α-Al2O3 micropowder can promote sintering and reduce the sintering temperature.

Since the brown corundum and aluminum-chromium slag used in the raw materials are both electro-melting materials, and the South African chromium ore are both raw materials with high volume density and low apparent porosity, the change rate of the product during the sintering process is very limited. Although the addition of α-Al2O3 micropowder has a certain improvement on the conventional performance, the impact is relatively small. When the addition amount is 3wt%, the filling effect is more obvious, and the performance will be reduced if the addition amount is further increased. This has a certain relationship with the overall particle grading of the product.

Effect of α-Al2O3 on load softening temperature. The addition amount of α-Al2O3 micropowder has almost no effect on the load softening temperature, which is due to the high grade of the raw materials of the product itself. The load softening temperature of the reference sample itself is ≥1700℃. The addition of α-Al2O3 micropowder has the effect of promoting sintering. After sintering, it mainly forms high-melting-point mineral phases such as corundum or aluminum-chromium solid solution. Therefore, it will not reduce the load softening temperature of the product.

Effect of α-Al2O3 addition amount (wt.%) on thermal shock stability As the amount of α-Al2O3 powder added increases, the thermal shock stability of the product is not greatly affected. However, when the amount added is 4wt%, the thermal shock stability decreases. This is because as the volume density of the product increases, the apparent porosity decreases, and the denser structure reduces the thermal shock stability of the product. Therefore, it is more appropriate to add α-Al2O3 powder within 3wt%.

What are the Main Products of Corundum Brick Shaping?

Corundum refractory products, Al2O3 98% or more, self-bonded solid phase sintered high-purity corundum brick products, the bonding phase is mainly corundum, and there is a small amount of mullite, etc. Mainly used in petrochemical industry gasification furnace, carbon black reactor, gasification furnace, ammonia decomposition furnace, two-stage reforming furnace, high temperature and ultra-high temperature kiln in refractory ceramic industry, blast furnace in metallurgical industry, etc.

Rongsheng Corundum Bricks

Corundum Bricks Shaped Products

Modified high alumina bricks

①Low creep high alumina bricks: For high alumina bricks with a creep temperature of 1500℃-1550℃, adding some fused corundum and silica raw materials can produce low creep rate high alumina bricks.

②Phosphate bonded high alumina bricks: Special-grade or first-grade high alumina bauxite clinker is used as the main raw material, and phosphoric acid solution or aluminum phosphate solution is used as the binder. A small amount of fused corundum, mullite, etc. is added to strengthen the matrix. Chemically bonded refractory products made by heat treatment at 400-600℃. Mainly used in ironmaking hot blast furnaces, cement kilns, electric furnace tops, ladles, etc.

Corundum mullite bricks

Use fused white corundum, plate-shaped corundum, fused mullite and other raw materials. After batching, mixing, high-pressure molding, and firing in a high-temperature kiln. The main crystal phase of corundum mullite brick products is corundum, and the bonding phase is mullite. Corundum mullite bricks are mainly used in high-temperature firing kilns and kiln tools such as push plates and firing plates in the ceramic industry.

Plate-shaped corundum mullite brick

Plate-shaped corundum mullite brick is made of plate-shaped corundum as the main raw material and mullite as the auxiliary raw material. It is made by adding appropriate amounts of high-purity alumina, ultrafine silicon oxide powder and additives. It is strongly pressed and formed by a 300t friction press and fired at high temperature in an oxidizing atmosphere. Plate-shaped corundum mullite brick can be used for a long time in a high temperature environment of 1700 degrees. Characteristics of plate-shaped corundum mullite brick:

(1) The Al2O3 of plate-shaped corundum mullite brick is ≥82%, which has good high temperature resistance, high refractory temperature, and load softening temperature as high as 1700 degrees.

(2) Resistant to chemical erosion, with strong resistance to acidic solutions or slag.

(3) The Fe2O3 content in plate-shaped corundum mullite brick is ≤0.5%, which is resistant to oxidation. It is not easy to react chemically with gases such as O2, H2, and CO.

(4) Good thermal stability, high temperature volume stability, and not easy to expand or shrink.

(5) Good thermal shock resistance, 1100℃ water cooling ≥30 times, resistant to rapid cooling and heating, not easy to peel off.

(6) High compressive strength at room temperature, ≥ 85 MPa, not easy to wear during transportation or unloading.

Physical and chemical indicators of plate-shaped corundum mullite bricks

Project indicators Al2O3, %≥82Fe2O3, %≤0.5Load softening temperature, ℃1700 (0 deformation) Thermal shock stability, times, 1100℃ water cooling ≥30 Normal temperature compressive strength, MPa≥85 Creep rate, %, 1450℃×50h-0.05 High temperature flexural strength, MPa, 1450℃×0.5h≥10

Application of plate-shaped corundum mullite bricks

Plate-shaped corundum mullite bricks can directly contact flames, resist peeling, and resist high temperatures. It can be used as the thermal insulation lining of high-temperature industrial furnaces and as the working layer of other industrial high-temperature kilns. It is mainly used in petrochemical industry, large and medium-sized synthetic ammonia gasification furnaces and magnetic material gas furnace materials, high-temperature industrial kiln supporting facilities materials, etc. Rongsheng Refractory can customize refractory bricks and products of various materials and shapes according to the customer's high-temperature equipment requirements.

Advantages and Disadvantages of Silicon Carbide Refractory Castables

Rongsheng Refractory Manufacturer, solutions for high temperature industrial furnace lining refractory materials. Advantages and disadvantages of silicon carbide refractory castables. In the field of amorphous refractory materials, silicon carbide refractory castables have always been a product that has attracted much attention. Whether from raw materials to research and development, or from production to use, it is a product that users love and hate. Understanding the advantages, disadvantages and why silicon carbide refractory castables can resist slag erosion can help companies make better choices.

Advantages and disadvantages of silicon carbide refractory castable products

The biggest advantage of silicon carbide refractory castable is that it has high thermal conductivity, low thermal expansion, and does not react with slag. It has been used in kiln parts with severe slag reaction and high-temperature spalling since a long time ago.

Rongsheng Silicon Carbide Refractory Castables

The biggest disadvantage is that the chemical properties are very unstable in certain atmospheres. It is easily corroded in oxidizing gases such as (oxygen, water vapor, carbon monoxide, carbon dioxide), iron oxide, etc., and easily oxidized and decomposed in molten iron and vacuum. Another disadvantage is that silicon carbide refractory castables have poor water solubility. In water-based amorphous refractory materials such as castables, the poor fluidity sometimes causes the poor density of silicon carbide refractory castables. The third disadvantage is the lack of sintering and difficulty in obtaining high strength, but sometimes it is difficult to produce over-sintering and shrinkage, which is a strength in amorphous refractory materials.

Why is silicon carbide refractory castable resistant to slag erosion?

When considering the slag resistance and slag resistance of silicon carbide refractory castable, the following aspects must be considered comprehensively: (1) wettability to slag (contact angle) (2) slag invasion (3) reactivity with slag (4) melting point and viscosity of reaction products. Considering these four aspects, although alumina refractory materials are materials that easily react with slag, as raw materials of refractory materials, they are not materials with poor slag resistance. This is because there are not many low-melting point compounds generated by reaction with slag.

The reason why silicon carbide refractory castable is difficult to be wetted by slag is because of the material of silicon carbide itself. SiC has two crystal forms, α and β, and the crystal structure of β-SiC. Among them, α-SiC has about 120 polymorphs such as 4H, 15R and 6H, among which 6H polymorph is the most widely used in industry. In 6H-SiC, Si and C are stacked alternately in layers, the distance between Si layers or C layers is 2.5Å, and the atomic distance between Si-C is about 1.9Å. There is a certain thermal stability relationship between the various forms of SiC, and the α β crystal forms also transform into each other. When the temperature is below 1600℃, SiC exists in the form of β-SiC. When the temperature is higher than 1600℃, β-SiC slowly transforms into various deformation forms of α-SiC (4H, 15R, 6H, etc.) by recrystallization. For α-β transformation, higher pressure is required, while for β-α transformation, only lower pressure is required. The transformation between various types of silicon carbide does not produce volume effect. SiC is a compound with strong covalent bonds. It still maintains high bonding strength at high temperatures, so SiC has high hardness, large elastic modulus, excellent wear resistance, and will not be corroded by most acid and alkali solutions. For the intrusion of slag and the melting point generated after reaction with slag, when compared with oxides, the slag resistance is significantly better.

When using silicon carbide refractory castables in monolithic refractory materials, the advantages, disadvantages, and prices of use should be considered. Only after the use site is determined can the lining material be used more accurately. However, in the actual use environment of monolithic refractory castables, these favorable and unfavorable environments for silicon carbide are mostly mixed. The evaluation of many environments currently used is often inconsistent with the actual use environment.

Lightweight High-Strength Thermal Insulation Castable

Lightweight high-strength castable is a new type of refractory material newly developed by Rongsheng Refractory Material Manufacturer. Rongsheng Lightweight High-Strength Thermal Insulation Castable combines the advantages of lightweight materials and high-strength characteristics and is widely used in high-temperature industrial equipment. This material not only has good thermal insulation performance but also is comparable to heavy refractory bricks in strength. Contact Rongsheng for more information.

Lightweight High-Strength Insulation Castable

Basic Characteristics of Lightweight High-Strength Castables

Lightweight high-strength castables are composed of refractory aggregates (such as lightweight particles), binders, and additives (such as reinforcing materials). Its main characteristics include:

• Lightweight: The castable contains lightweight aggregates (such as lightweight bauxite, expanded perlite, lightweight silicates, etc.), which makes the overall weight of the material lighter and has a lower density.
• High strength: Although it is a lightweight material, after special formula design and process treatment, it can achieve strength similar to that of traditional heavy refractory bricks, and can withstand large mechanical loads and structural stresses at high temperatures.
• Thermal insulation: Due to the special structure of its lightweight aggregate, lightweight high-strength castables have excellent thermal insulation properties, which help to reduce heat loss and improve energy efficiency.
• High refractoriness: This type of castable is usually composed of refractory aggregates and binders, has high refractoriness, and can work stably in high-temperature environments.
• Thermal shock resistance: Due to its certain elasticity and toughness, lightweight and high-strength castables have good thermal shock resistance and can cope with working environments with large temperature changes.

Advantages of Lightweight High-Strength Castables

(1) Thermal insulation performance

Reduced heat loss: The lightweight aggregate of lightweight high-strength castables makes it have lower thermal conductivity, which can effectively reduce the conduction and loss of heat. This is of great significance for equipment that needs to maintain high temperatures for a long time (such as blast furnaces, hot blast furnaces, smelting furnaces, etc.), and can reduce energy consumption.

Lightweight High-Strength Castables

Improved temperature control: Good thermal insulation effect makes the temperature distribution in the equipment more uniform, avoids excessive temperature fluctuations, and reduces the occurrence of thermal shock.

(2) High strength

Withstand greater mechanical stress: The high-strength design enables lightweight high-strength castables to withstand greater mechanical stress and impact, especially in some areas affected by high temperature and pressure (such as the inner wall of the furnace, the bottom of the furnace, etc.), and can maintain stability.

Comparable to heavy refractory bricks: Traditional heavy refractory bricks have higher strength, but are often heavier and are not suitable for occasions where a lower dead weight is required. The strength of lightweight high-strength castables has been optimized to be comparable to that of heavy refractory bricks, while having a lower density.

(3) Convenient construction

Quick forming: Castables are constructed by pouring, vibrating or spraying, which is particularly suitable for irregular shapes and difficult-to-brick parts. This construction method not only saves time and manpower, but also avoids the existence of bricklaying joints during the construction process, improving the construction quality.

Adaptable to complex structures: Since the material is in a cast state, it is suitable for use in furnace bodies, furnace walls, furnace bottoms and other parts with complex shapes or difficult to cut and splice.

(4) Good thermal shock resistance

Lightweight and high-strength castables can better adapt to working environments with large temperature fluctuations due to the structural characteristics of their lightweight aggregates, avoiding thermal stress and cracks caused by drastic temperature changes. This enables it to effectively improve durability and stability in equipment such as hot blast furnaces and blast furnaces.

(5) Energy saving and maintenance reduction

Due to its excellent thermal insulation performance, lightweight high-strength castables help improve the energy efficiency of the equipment. It reduces energy waste and enables equipment to operate at a higher thermal efficiency, reducing operating costs.

Its good thermal shock resistance, high-temperature resistance, and strength also extend the service life of the refractory lining, thereby reducing the frequency of maintenance and replacement and reducing overall operating costs.

Rongsheng Refractory Castable Manufacturer

Rongsheng's lightweight high-strength castable is a refractory material that combines light weight, high strength, excellent thermal insulation and thermal shock resistance. It can provide good performance in high-temperature metallurgical equipment. Compared with traditional refractory bricks, it can provide similar or even stronger strength. And due to its lightweight structure, it has better thermal isolation effect, helping to improve the energy efficiency of equipment and reduce repair and maintenance costs. It is especially suitable for metallurgical equipment that requires high strength, good thermal insulation and high temperature resistance and thermal shock resistance. Such as blast furnaces, hot blast furnaces, coke ovens, steelmaking furnaces, etc.

Quality Requirements for Checker Bricks in Coke Oven Regenerators

The quality requirements of the checker bricks in the heat storage chamber are mainly as follows:

1. In order to reduce the friction resistance of the gas flowing in the checker bricks and make the resistance in each heat storage chamber consistent, it is convenient to master the heating system, and the holes of the upper and lower layers of the checker bricks are required to be aligned as much as possible.

2. Keep the checker bricks clean to avoid blockage of the brick holes and reduce the number of cleaning times during production to improve heating efficiency.

3. The bricklayer should be laid smoothly and have a good staggered width.

4. Maintain necessary expansion joints. The gas flow space at the top of the heat storage chamber should maintain a certain cross-sectional area according to the design to prevent vortexes from being generated when the gas is distributed at the top of the heat storage chamber.

Rongsheng Checker Bricks

Rongsheng Refractory Manufacturer, Regenerator Checker Brick, Magnesia Checker Brick. Contact Rongsheng for more information.

Construction of checker bricks

The laying time of checker bricks is divided into two construction methods according to the width of the regenerator: laying at the same time as the regenerator furnace wall (first laying) and laying after the entire furnace body is built and cleaned (latter laying). According to construction experience, when the net width of the regenerator is less than 310 mm (such as Otto coke oven), the construction method of laying checker bricks first should generally be adopted. This is because it is more difficult to lay checker bricks later in a narrow regenerator.

The construction method of laying checker bricks first has several advantages: First, because the workers are standing on the wall of the regenerator to lay checker bricks, the operating conditions are better, and it is easy to check after laying. Therefore, it can ensure that each checker brick hole is connected from top to bottom and has good staggered joints. However, due to the addition of many processes - cleaning protection and cleaning work, the construction progress is slow and it is more difficult to ensure cleaning.

The construction method of laying checker bricks is as follows: checker bricks can be laid in sections, that is, according to the convenience of construction, they can be laid in two sections on the entire height of the heat storage chamber, that is, divided into upper and lower sections according to the height of the replacement handrail. After the first section of the main wall is built, all the cleaning and brick joint finishing work on the wall surface is completed, and the grate bricks are cleaned, and the row numbers of the grate bricks are checked once, and then the first layer of checker bricks is placed on the grate foot platform according to the designed position, and the expansion joints on the four sides and the staggered joint width between the checker bricks and the grate foot platform are checked. Make sure that the checker bricks can be firmly placed on the grate foot platform, and finally lay each layer of checker bricks from the center partition wall to both sides according to the designed position.

During construction, the checker bricks are placed on the brick pad. The hook of the checker brick is inserted into the hole of the checker brick to place the checker brick in the heat storage chamber. Then use a long wooden stick to adjust its position. When storing, it can be laid from the center to the furnace head in a stepped shape, or it can be laid layer by layer. The heat storage chamber sealing wall is built after the checker bricks of this section are laid.

After the first section of checker bricks is laid, the checker bricks are covered with a checker brick protection board to prevent waste such as mortar from falling into the checker bricks. Then continue to build the heat storage chamber wall. When it reaches the top of the heat storage chamber, lay the second section of checker bricks and build the second section of sealing wall.

Lime Kiln Refractory Bricks - Refractory Materials for Kilns

Limekiln refractory brick is a kind of refractory material used in a lime kiln, usually made of high alumina, clay, or corundum. Because lime kiln has the characteristics of high temperature and strong corrosion, the performance requirements of refractory materials are relatively high, and lime kiln refractory brick is designed to meet these requirements.

Lime Kiln Refractory Brick Lining

Characteristics of lime kiln refractory bricks

1. High temperature performance. Limekiln refractory bricks can withstand high temperatures, have high thermal stability, and can be used in environments up to 1300°C or above.

2. Corrosion resistance. Since the gases and materials in the lime kiln are corrosive, lime kiln refractory bricks need to have good corrosion resistance.

3. Good thermal insulation performance. Lime kiln refractory bricks can insulate, reduce heat transfer, and improve energy utilization.

4. Wear resistance. In harsh environments such as high temperatures and corrosion, lime kiln refractory bricks need to have good wear resistance to ensure their service life.

Application of lime kiln refractory bricks

Lime kiln refractory bricks are widely used in various types of lime kilns, including vertical kilns, rotary kilns, etc. During use, it is necessary to select appropriate refractory brick models and specifications according to different furnace types and use environments. At the same time, the following points should be noted during use:

• 1. During installation, it should be carried out according to the drawings provided by the manufacturer to ensure the installation quality and service life.
• 2. Avoid collision and extrusion during use to avoid damage.
• 3. Regularly inspect and maintain, discover and solve problems in time, and ensure the normal operation of the lime kiln.

Rongsheng Refractory Brick Manufacturer

Lime kiln refractory bricks are an indispensable part of the lime kiln furnace. Their performance and service life are directly related to the normal operation and production efficiency of the lime kiln. With the continuous development and progress of technology, lime kiln refractory bricks will continue to innovate and develop, providing better support and guarantee for the development of the lime industry.

When choosing suitable lime kiln rotary kiln refractory bricks, we need to analyze the characteristics of different types of refractory bricks in detail. According to the production process and the actual situation of the lime kiln rotary kiln, Rongsheng refractory brick manufacturer can customize refractory lining bricks. For example, for high temperature and high pressure environments, we can choose high alumina refractory bricks or magnesium-alumina refractory bricks. For occasions that require corrosion resistance, we can choose silicate refractory bricks. In the selection process, we need to consider a variety of factors, such as refractoriness, stability, durability, and cost. Contact Rongsheng for free solutions and quotes.

Magnesia Spinel Refractory Brick Manufacturer

In the vast land of China, there is a powerful manufacturer and seller of refractory materials, Rongsheng Refractory Material Factory. Rongsheng Factory has its own unique concept, high-quality products and comprehensive customer service in the field of refractory materials. Magnesia refractory brick, magnesium spinel refractory brick manufacturer. Contact us for free samples and quotes.

RS Magnesia Spinel Refractory Brick Manufacturer

Magnesia Alumina Spinel Brick

Magnesium-aluminum spinel has a series of excellent properties such as high melting point, good thermal shock stability, and resistance to slag erosion. It has been widely used in refractory materials and other industrial fields.

At present, the most common method for preparing magnesium-aluminum spinel is solid-phase reaction synthesis. That is, oxides, chloride oxides or carbonates are used as raw materials, and the raw materials are mixed and pressed into billets and then reacted at high temperature (greater than 1400°C) to prepare spinel. The electric melting method is another commonly used method for synthesizing spinel in industry, which also has disadvantages such as high energy consumption. Although wet chemical methods such as sol-gel method and hydrothermal method can synthesize spinel at a lower temperature, their operation process is complicated, the equipment required is expensive, and the cost is too high to meet the needs of large-scale industrial production.

Magnesium-aluminum spinel bricks produced with magnesia sand and magnesium-aluminum spinel sand as raw materials are usually called magnesium-aluminum (periclite-spinel bricks). The magnesia sand raw material used to produce periclase spinel bricks is required to have as low an impurity content as possible (especially CaO).

Domestic sintered magnesia MS95, MS97, MS97.5, and DMS97 are widely used. Spinel sand is used as granular material, and magnesia sand is used as fine powder and part of the granular material. According to the mixing, forming, and firing process of high-grade magnesia-alumina bricks, products with good high-temperature performance and high thermal shock stability can be produced.

Magnesia-alumina spinel bricks are often used in cement rotary kilns, glass kiln lattices, mixed iron furnaces, and refractory kilns with large temperature changes.

Magnesium Aluminum Chrome Spinel Brick

The magnesium aluminum chrome spinel brick system is the periclase/magnesium aluminum chrome spinel system: MgO-R2O3 (Cr2O3, Al2O3) system. In order to facilitate the comparison of the production of magnesium aluminum chrome products, Cr2O3 is introduced into MgO in the form of chromite, and the manufacturing process often accompanies the appearance of sesquioxides such as Cr2O3, Al2O3, and Fe2O3.

First of all, from the perspective of high temperature resistance and slag resistance, the MgO-MgO·Cr2O3 system has advantages in the MgO-R2O3 system. In addition to its high eutectic temperature (2350℃), it also lies in the low solubility of Cr2O3 in the silicate liquid phase.

As we all know, lower solubility should have stronger crystallization ability. It can effectively reduce the intercrystalline interface energy, so that the silicate liquid phase tends to move into the intergranular gap in an isolated state. It is easy to achieve direct bonding between periclase grains or through magnesium chrome spinel bridges, which can effectively improve high temperature strength and inhibit slag penetration, and improve slag resistance. However, Cr2O3 is highly volatile and has poor stability at high temperatures, especially under vacuum conditions.

Secondly, from the perspective of thermal shock resistance, the MgO-MgO·Al2O3 system is more superior. Because the solid solution-peptization effect of MgO·Al2O3 or Al2O3 in MgO at high temperature is much weaker than that of MgO·Cr2O3 or Cr2O3, especially MgO·Fe2O3 or Fe2O3, and the high-temperature vapor pressure of MgO·Al2O3 above 1600℃ is also lower than that of MgO·Cr2O3. Therefore, the MgO-MgO·Al2O3 system material is more stable when the temperature fluctuates and has good thermal shock resistance.

When the MgO/R2O3 ratio is constant, the MgO-MgO·Al2O3 and MgO-MgO·Cr2O3 systems are compared. It can be inferred that in the molten MgO-MgO·Al2O3 system material, there are fewer precipitated spinels in the periclase grains, and more spinels between the grains. MgO-MgO·Cr2O3 system materials have more intracrystalline precipitated spinel and less intercrystalline spinel. Obviously, changing the proportion of each component in R2O3 can adjust the distribution of spinel phase and change the microstructure.

Magnesium Iron Aluminum Spinel Brick

Magnesia-alumina spinel bricks are mainly used in cement kiln firing zones. Traditional refractory materials used in cement kiln firing zones are mainly magnesia-chrome refractory materials. The highly toxic hexavalent chromium that can be dissolved in water in magnesia-chrome bricks after use will cause serious environmental pollution. Finding chromium-free alternative products for cement kilns has been recognized by experts. Magnesia-alumina spinel bricks were proposed by RHI in the 1990s. It is a mixture of magnesia sand and pre-synthesized alumina spinel, and fired at high temperature under certain processes. It has now been widely used in the lining of cement rotary kilns to replace magnesia-chrome bricks.

The microstructural characteristics of magnesia-alumina spinel are relatively complex, mainly a combination of magnesia sand microstructure and alumina spinel microstructure. The interface between magnesia sand and alumina spinel is closely combined through the mutual diffusion of Mg2+, Al3+, and Fe2+ ions, realizing direct bonding of materials.

Please contact us to purchase high-quality refractory products. Refractory lining materials, refractory services, and furnace lining materials for sale.

Unshaped Refractory Lining Materials for Cupola Linings

Different from the traditional cupola ladle lining, the two types of ladles built with refractory ramming material or refractory castable material can greatly increase the working life of the ladle lining and reduce the number of spare ladles. What are the specific material choices for the two new types of ladle linings?

High-Alumina Refractory Ramming Materials

Refractory Ramming Material Lining

Ramming material is a general term for plastic refractory materials composed of refractory aggregate, binder, and moisture. The mineral composition of refractory aggregate coated with ramming material is generally bauxite, corundum, quartz sand, and quartz powder. The chemical composition is mainly composed of alumina (Al2O3) and silicon oxide (SiO2) two parts. Due to the different mineral compositions and particle sizes, various suppliers have developed a variety of packaging ramming material specifications. At present, the chemical composition of the lining ramming material, among which the higher the alumina content, the higher the use temperature, the greater the drying density, the stronger the thermal conductivity of the lining, and the longer the life of the lining.

Bauxite, corundum, quartz sand, and quartz powder in the lining ramming material are materials with high thermal conductivity. In addition, due to the size grading of refractory materials, the compaction density of ramming materials is larger. Therefore, the thermal conductivity of the lining ramming material is higher. If the ramming material is used completely to build the lining, the heat conduction of the lining causes the temperature of the iron liquid to drop more. Therefore, before using the lining ramming material to build the lining, a heat insulation layer of a certain thickness should be designed inside the cladding.

The ramming die must be prepared in advance to build the packing lining with ramming material. The ramming die is specially designed according to the ladle structure and lining to be located, and either has a certain inclination or has the performance of split disassembly. When building the lining, first use the ramming material layer by layer, ramming the bottom to a certain thickness. Then, the ramming mold is placed in the shell, and the ramming material is filled layer by layer to the mouth of the bag. Finally, pull out or remove the ramming die, and brush the surface of the lining with graphite powder coating.

The construction quality of ramming material lining has a decisive influence on the life of the lining, and the difference in construction quality may make the same material have different life. When building the lining with ramming material, it should be rammed tightly. The ramming compactness must conform to the drying compactness range of the lining material. The drying and roasting temperature and time of the packaging should also meet the technical requirements of the relevant products.

SiC Refractory Castable Lining

Refractory Castable Lining

Refractory castable is a class of amorphous refractory materials with cement as binder. The mineral composition of the refractory aggregate is the same as that of the refractory aggregate used for lining ramming. Calcium oxide (CaO) is an essential component of cement as the binder lining cement castable is high alumina cement. Therefore, the calcium oxide content can indirectly represent the cement content in the castable. Cement-lined castable can be divided into general cement castable, low cement castable and ultra-low cement castable. The lower the cement content, the higher the refractoriness of the material. Chemical composition range of coated low cement and ultra low cement castables. Among them, the higher the Al2O3 and the lower the CaO, the higher the refractoriness and the longer the life of the lining.

Before building the lining with refractory castable, it is necessary to make the casting mold with thin steel plate in advance, and the casting mold needs a certain taper to facilitate smooth pulling out after pouring. A certain thickness of heat insulation layer is set in the interior of the cladding to improve the heat preservation property of the ladle before constructing the cladding with cement castable. During construction, the bottom is covered with castable to the required thickness. After vibrating with a vibrator commonly used in concrete construction, the casting mold is fixed in the cladding. The castable is then filled layer by layer between the insulation layer and the casting mold. At the same time, vibrator is used to vibrate to the envelope, and the casting mold is pulled out in time after the initial solidification of the castable. Finally, the coating surface is coated with graphite powder.

Using low cement or ultra-low cement castable to build the lining is short in construction time, less in physical exertion, and easy to ensure the construction quality. At the same time, the lining can be repaired after partial damage. Therefore, the lining life is long and the consumption of tons of liquid iron refractory is low.

Unshaped Refractory Lining Materials for Cupola

Selection of Amorphous Refractory Castable for Cupola Lining

Cupola is subjected to high temperature and chemical erosion during melting. The melting time of cupola is 6~10 hours, the furnace lining erosion is large, and the furnace condition is unstable.

The corrosive atmosphere of furnace lining has a high requirement on the selection of refractory castable. It is better to use refractory castable with 70%~80% aluminum content in the feeding area and flow channel. Because of the high aluminum content, the high temperature strength and wear resistance and thermal shock performance are good, and the resistance to alternating hot and cold shock is strong.

The main parts of the cupola are hearth, bridge and slag separator. These parts have slag contact, chemical erosion is serious. Refractory castables with high aluminum content, due to the purity of the substrate itself, less impurities, strong resistance to iron wash, and very good oxidation resistance.

When selecting castable material for cupola lining, the slag composition should be considered, because there is a certain proportion of limestone in the burned material. Limestone has an alkaline composition, so the refractory castable used should have the ability to resist alkali erosion. That is, there should be a silicon carbide component in the castable, silicon carbide wear resistance and slag erosion resistance.

If it is alkaline erosion, magnesium or spinel are good choices. If spinel and silicon carbide are added to the castable, then this composite material is the most ideal material. However, silicon carbide and spinel should be added in different proportions according to the different slag composition.

If the top of the furnace lining can also be selected plastic, so easy to construction. Plastic should also consider the composition of ceramic combination, it is best to use phosphoric acid combination of plastic, do not use water glass combination. Because phosphate bonded plastic, strength and high temperature resistance are good. If castable is selected, plastic is still used for daily repair, which can shorten the maintenance time.

It should also be noted that in the furnace production process if the coke does this cupola melting heat source. It is necessary to control the quality of coke to stabilize the use of furnace lining.

In the final analysis, the refractory castable selected for the lining is still a refractory castable with high aluminum content. Because the pure castable has good wear resistance, the castable with silicon carbide or spinel composition has better corrosion resistance.

Are There Any Lightweight Spraying Refractory Coatings?

During the construction process of refractory spray paint material, the material is compacted by repeated and continuous impact of the sprayed material. Therefore, the sprayed coating has a better density and mechanical strength. Refractory spray paint can be used in hot blast duct systems, blast furnace throats, furnace tops and gas outlet pipe systems, furnace bottom foundations, and blast furnace and hot blast furnace linings.

RS Spraying Refractory Coatings for Sale

What is Refractory Coating?

The construction of spray refractory coating actually combines transportation, pouring, or tamping into one process. It does not require or only requires a single-sided formwork. The process is simple, highly efficient, and has good adaptability. During the construction process of refractory spray coating, the repeated and continuous impact of cement, aggregate, and other constituent materials causes the sprayed materials to be compacted, so the spray coating has better density and mechanical strength.

Are There Any Lightweight Spraying Refractory Coatings?

High-temperature refractory coatings and spray coatings are unshaped materials among refractory materials. Therefore, there are also light, heavy, and semi-heavy ones.

Heavy refractory spray paint is relative to light refractory spray paint. Light spray paint refers to a density of 0.5-1.3g/cm3, and medium-heavy spray paint refers to a density of 1.3-1.8g/cm3. Then the density of heavy spray paint is the largest, and its volume density is greater than 1.8g/cm3. Lightweight spray coatings are used as thermal insulation and thermal insulation linings, while medium and heavy spray coatings can be used as both thermal insulation linings and working linings for low and medium-temperature atmosphere furnaces. Heavy spray coatings are mainly used as high-temperature service linings.

Lightweight Spraying Refractory Coating

Applications of High-Temperature Refractory Coating Products

Refractory spray paint is mainly used as a sealing material for the lining of thermal equipment in industrial furnaces. It can be used in hot blast duct systems, blast furnace throats, furnace tops and gas outlet pipe systems, furnace bottom foundations, and blast furnace and hot blast furnace linings.

The lightweight spray coating plays the role of thermal insulation, while the semi-heavy spray coating not only plays the role of thermal insulation, but also can be used as a working layer in furnace linings, chimneys, and pipes where the temperature does not exceed 1000°C.

Heavy refractory spray coatings are generally used for lining hot blast furnaces and blast furnaces and are also used for emergency repairs in lime kiln linings. At present, some domestic manufacturers also spray directly on the lining of the white ash shaft kiln as the working layer. The advantage of refractory spray paint is that it can be applied quickly.

Semi-heavy spray paint is used for flue and chimney linings because the temperature of the flue and chimney linings is not high and there cannot be adequate lining materials. Therefore, many manufacturers choose semi-heavy spray coatings for both thermal insulation and working layers. In this way, the inner diameter space is saved, and it can also prevent wind and smoke erosion.

The lightweight spray paint is used as a thermal insulation layer, and when used, if the area to be used is small, it can also be applied directly. Because the construction time of lightweight spray paint is short, in general, it is convenient and quick to use lightweight spray paint when the usage is large. Because hundreds of tons of spray paint will be sprayed within a few hours.

However, spray coatings have a rebound rate, and the national standard is 20%. However, the rebound rate of spray coatings currently on the market is around 8-10%. During construction, professionals must cooperate with the sprayer for normal use. A small amount can also be applied manually, and just use putty when applying.

Spray coatings are divided into neutral, acidic, and alkaline materials. When using, select the material suitable for the furnace lining for spraying according to the atmosphere of the furnace lining. Because the furnace lining atmosphere and materials are in the same atmosphere, the furnace lining atmosphere is good and the service life is long.

Rongsheng Refractory Materials Manufacturer is a powerful manufacturer and seller of refractory materials. Our environmentally friendly, fully automatic unshaped refractory material production line provides high-quality refractory lining materials for various industrial kilns. Product quality is guaranteed, and the spray refractory coating formula can be customized. The professional technical and construction team provides pre-sales technology and after-sales construction services for refractory lining solutions. Contact us to get free samples and quotes.

Rongsheng Refractory Plastic Manufacturer

Refractory plastic is composed of refractory (bauxite) aggregate and refractory powder, mixed in proportion, adding binders such as plastic white mud or clay and an appropriate amount of plasticizer. It is an unshaped refractory material that is in the form of bulk material or paste and maintains high plasticity for a long time.

Classification of refractory plastics: According to the types of refractory aggregates, they are divided into clay, high alumina, mullite corundum, chromium, silicon carbide, and zirconium. According to the type of binder, it is divided into composite binders such as raw clay and aluminum sulfate, phosphoric acid, phosphate, water glass, and resin. According to the normal temperature hardening properties, it is divided into air-hardening and thermosetting refractory plastics.

RS High Alumina Plastic Refractory

Refractory Plastic Properties

To ensure normal use at high temperatures and smooth construction, refractory plastics should have the following basic characteristics:

1. It has a shelf life of construction time to ensure that the molding performance remains unchanged during the specified storage period.

2. It has good plasticity for easy construction.

3. It has good strength after curing at room temperature so that the frame can be dismantled after construction.

4. It has good high-temperature volume stability to prevent damage to the furnace lining structure due to excessive deformation.

Applications of Refractory Plastics

Refractory plastics are mainly used in the linings and maintenance of furnaces, cyclones, superheaters, flues, etc. of various power station boilers, and in the linings of heating furnace roofs, water-cooled walls, etc. Materials can be divided into high aluminum, clay, corundum, corundum silicon carbide, silicon, magnesia, chromium, etc. According to the classification of binders, there are white mud binders, aluminum phosphate binders, water glass binders, sulfate binders, aluminate binders, etc.

Advantages of Rongsheng Refractory Plastics

Application Advantages of Rongsheng Refractory Plastics

The characteristic of refractory plastic is that it can be constructed into any shape and the construction period is short. It can be constructed by ramming, or it can be repaired according to the damaged location. Moreover, it can be put into use directly according to the furnace temperature without baking. It is a good repair material.

Fire-resistant plastic has good wear resistance, strong plasticity, and good bonding properties. It is mostly used in circulating fluidized bed boilers or heating furnaces. Plastics can be produced in many forms during the production process. If the construction is to be put into use immediately, one-third of the cementing material can be added during production. Trapped materials first, go to the construction site and add the other two-thirds of the PA80 glue, and then the construction can be started. You can also add all the glue into the material, but the packaging must be scientific. Open the plastic packaging at the construction site and put it into use.

The raw material of refractory plastic can be corundum, burnt gemstone, or high-aluminum aggregate. It can be made into plastics of different grades and qualities. However, the cementing material used must be PA80 glue. Glue is made by boiling aluminum dihydrogen phosphate and phosphoric acid. It can be added first or on-site. If it is added on-site, there still needs to be a process of trapping the material to achieve the best results.

Different grades of refractory plastics are determined according to the furnace lining atmosphere, temperature, and wear resistance of the used parts. If the temperature is low, materials suitable for the temperature can be made and produced, and the price is relatively cheap. If the temperature is high or too high, corundum or even zirconium corundum must be used to make it meet the needs of the furnace lining.

The function of refractory plastic is that it has strong plasticity and can be used on the stovetop. It can also be used for pounding on the furnace wall.

To purchase high-quality refractory materials and refractory plastic products, please contact us. Get free samples and quotes.

High Performance Lightweight High Aluminum Castable

To improve the energy-saving effect of thermal kilns, the number and scope of applications of lightweight castables are gradually expanding. From the permanent layer, the insulation layer to the working layer, it extends from the medium and low-temperature areas to the medium and high-temperature areas and transitions from a low-load environment to a high-load environment. At present, the technical performance of lightweight high-aluminum castables used in working layers at medium-low temperatures (<1 200°C) and high temperatures (>1 500°C) has been basically mature. However, the performance of lightweight castables used in the medium and high-temperature range (1 200 ~ 1 500 ℃) needs to be improved. To meet the new requirements for the use of lightweight high-aluminum castables, it is first necessary to understand the impact of the selection and configuration of lightweight aggregates on their performance. RS refractory material manufacturer can provide high-quality refractory lining products for high-temperature industrial furnace linings.

Lightweight High Aluminum Castable

The raw material configuration of traditional lightweight high-aluminum castables mainly uses lightweight aggregates and heavy fine powders. The lightweight aggregate used has larger pore diameters and lower strength, so the thermal conductivity of the lightweight castable is higher. At the same time, the low strength of the aggregate affects the overall strength of the lightweight castable, limiting its use at higher temperatures. Therefore, microporous aggregates and high-strength aggregates are used. The raw materials used mainly include microporous lightweight mullite and complex-phase hollow spheres. High alumina bauxite, floating beads, kyanite, silica micro powder, alumina micro powder, pure calcium aluminate cement, raw bauxite powder, andalusite, pore-forming agent D, pore-forming agent C, etc.

The Choice of Lightweight Aggregates

To meet the construction and high-temperature performance of lightweight castables, lightweight mullite, and complex-phase hollow balls are selected as lightweight aggregates. Multiphase hollow spheres were used to gradually replace lightweight mullite to study the effect on the properties of the castables. The wall thickness of the multiphase hollow spheres is 0.3~0.5 mm, the particle size is 3~7 mm, and its packing density is 0.60 g/cm3. The packing density of microporous mullite is 0.80 g/cm3.

Effect of adding amount of multi-phase hollow spheres on the volume density of castables

When the amount of multiphase hollow spheres increased from 0 to 40%, the bulk density of the sample dropped from 1.86 g/cm3 to 1.68 g/cm3 after baking at 110 °C × 24 h. The bulk density also shows the same trend after high-temperature firing. Since the packing density of the composite hollow spheres is smaller than that of the lightweight mullite aggregate, the bulk density of the castables shows a downward trend as its addition amount increases. That is, the effect of complex-phase hollow balls on reducing the volume density of castables is greater than that of lightweight mullite.

Effect of the Adding Amount of Complex Phase Hollow Balls on the Normal Temperature Compressive Strength of Castables

The changing trend of normal temperature compressive strength of castables after adding different proportions of multi-phase hollow spheres. As the amount of composite hollow balls increases, the normal temperature compressive strength of the castables after baking and high-temperature firing shows an upward trend. Since the strength of the composite hollow sphere, aggregate is higher than that of the lightweight mullite aggregate, and the surface of the composite hollow sphere is dense, its water absorption rate is lower than that of the lightweight mullite aggregate. At the same time, the spherical aggregate is beneficial to improving the fluidity of the castable, reducing the amount of water added to the castable, and is also beneficial to improving the strength of the sample. Therefore, the reinforcing effect of complex hollow spheres on castables is greater than that of light mullite.

Effect of the Adding Amount of Complex Phase Hollow Spheres on Thermal Conductivity of Castables

As the amount of multiphase hollow spheres increases, the thermal conductivity of the sample shows a downward trend. Since the complex-phase hollow balls have a hollow structure, the air is enclosed in the holes, which has a good heat insulation effect. Therefore, the thermal conductivity of the castable decreases after adding complex-phase hollow balls. Since the pore diameter of the multi-phase hollow sphere is larger, the effect of convective heat transfer will increase at high temperatures. As a result, the effect of reducing the thermal conductivity of the castable at 1000°C is not as obvious as that at 700°C.

Microporous lightweight mullite aggregate is beneficial to reducing the thermal conductivity of castables, but its strength is low. Complex-phase hollow spheres are beneficial to improving the strength of castables, but their effect on reducing thermal conductivity is limited. Due to the low density of composite hollow spheres, taking into account the uniform dispersion of different aggregates and taking into account various properties, the appropriate addition amount of both aggregates is 20% to 30%.

To purchase high-quality lightweight high-aluminum castables, please contact Rongsheng Refractory Materials Manufacturer. Our refractory products are of reliable quality and our after-sales service is guaranteed.