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Rongsheng Precast Refractory Materials for Cement Kilns

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In cement production, the refractory materials used in parts such as the grate cooler’s low wall, throat, tertiary air duct bends, and gate valves suffer severe wear and short service life due to the scouring effect of high-speed airflow containing cement clinker particles and the erosion of alkali. Users frequently experience premature wear, seriously affecting the normal operation of the cement kiln. Rongsheng Refractory Precast Refractory for Cement Kilns addresses this issue by using precast refractory components. Pre-fabricated refractory materials are pre-formed at the refractory material manufacturer, shortening the time required for refractory construction, curing, and baking. After on-site installation, they can be put into immediate use.

Rongsheng Precast Refractory for Cement Kilns
Rongsheng Precast Refractory for Cement Kilns

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    Precast Refractory for Cement Kilns

    Standardized manufacturing of monolithic refractory materials for special parts of cement kilns has been developed, offering the following advantages:

    1. No on-site casting or formwork required, reducing labor intensity and material costs.
    2. No need for heat-resistant anchors, eliminating material and installation costs.
    3. Precast refractory components have completed casting, curing, drying, and baking processes upon delivery, saving significant construction time.
    4. Unaffected by environmental or climatic conditions, solving the problem of on-site construction under natural conditions during extreme heat and winter.
    5. Can be manufactured into various sizes and shapes for specific applications, such as refractory materials for grate cooler walls, tertiary air duct elbows, lifting gate valves, kiln tail flue, pulverized coal injection pipes, and kiln inlets.
    6. Easy to replace during maintenance, minimizing waste and saving labor and time.

    Precast Refractory for Tertiary Air Duct Valve Plates

    Tertiary air valves primarily withstand the erosion and wear of high-speed airflow carrying dust, as well as the corrosion of alkali. Precast tertiary air valve components offer good integrity, facilitating installation, maintenance, and replacement. Prefabrication and on-site installation ensure high-quality construction. It is recommended to use corundum-mullite high-strength wear-resistant precast refractory components.

    1. Materials Used: Corundum, Mullite, Silicon Carbide.
    2. Service Life: 1.5-3 years.
    3. Product Features: The main feature of this precast component is the tight bonding between the valve body mold and heat-resistant steel reinforcement and refractory castable, forming a unified whole. Pre-baking ensures good overall integrity. The lining incorporates corundum, fused mullite, premium bauxite aggregate, and special wear-resistant materials, along with a certain proportion of special additives, and is formed by tamping and vibration. Therefore, the product boasts high strength, wear resistance, corrosion resistance, good mechanical impact resistance, and excellent thermal shock resistance. It has excellent resistance to spalling and cracking, a long service life, and is easy and safe to construct, greatly shortening the construction period.

    Precast Refractory for Tri-duct Elbow Components

    This section primarily withstands the erosion and wear of high-speed airflow carrying dust, as well as the corrosion of alkalis. Precast refractory components ensure construction quality, are pre-baked, and are high-strength, wear-resistant, erosion-resistant, and corrosion-resistant. They offer good integrity, facilitating construction, maintenance, and replacement. High-strength, wear-resistant mullite precast components are recommended.

    1. Materials Used: Corundum, mullite, silicon carbide.
    2. Service Life: 1.5-2 years.
    3. Product Characteristics: High strength, high temperature resistance, wear resistance, corrosion resistance, stable performance, excellent anti-stripping and erosion resistance, and long service life. Furthermore, the original heat-resistant steel anchors and castable refractory are eliminated, replaced by direct precast component construction, making construction and maintenance convenient, safe, and reliable, significantly shortening the construction period. The elimination of heat-resistant steel anchors also reduces material costs to varying degrees, improving overall economic efficiency.

    Precast Refractory Components for the Low Wall of the Grate Cooler

    The refractory material in this area is primarily subject to wear and tear from cement clinker, requiring frequent replacement. After the castable refractory is poured, it is difficult to bake and prone to cracking. Precast refractory components offer convenient installation and easy replacement. They require no curing or baking, saving time. It is recommended to use corundum-mullite high-strength steel fiber wear-resistant precast components.

    1. Materials Used: High alumina, corundum, mullite, silicon carbide.
    2. Service Life: 1.5-3 years.
    3. Product Characteristics: High strength, wear-resistant, thermal shock resistant, corrosion resistant.

    The low wall of the grate cooler eliminates the need for traditional heat-resistant steel anchors and castable refractory, replacing them with precast components directly laid in masonry. This facilitates construction and maintenance, ensures safety and reliability, and significantly shortens the construction period. It also facilitates future replacement of the grate cooler blind flange, and the elimination of heat-resistant steel anchors reduces material costs to varying degrees, improving overall economic efficiency.

    Precast Refractory Components for Straight and Sloping Walls of the Smoke Chamber

    This area primarily bears the erosion and wear of cement raw materials, as well as the corrosion of dust containing alkali and sulfur, making it prone to crusting. Using silicon carbide anti-scabbing precast refractory components largely solves these problems. It extends the service life of the refractory material in this area, shortens the kiln downtime for cleaning crusts, and improves the rotary kiln’s operating rate. Most importantly, it avoids the safety issues caused by crust detachment from the performer or cyclone due to vibrations from vibrators and pneumatic drills during castable refractory construction. It is recommended to use silicon carbide anti-scabbing, high-strength, high-wear-resistant precast components.

    1. Materials Used: Silicon carbide, mullite.
    2. Service Life: 1.5-3 years or more.
    3. Product Characteristics: The precast components are baked, resulting in high strength, anti-scabbing, alkali-resistant, high-temperature resistant, and wear-resistant properties, with excellent anti-stripping and erosion resistance. The product has good integrity, is easy to construct, and is convenient to maintain.

    Precast Refractory Components for the Throat of a Grate Cooler

    The service life of refractory materials in this area is short, mainly due to the high dust content in the flue gas, the high hardness of the particles, and the high wind speed, which severely erodes the materials. Simultaneously, the flue gas composition is complex, making the materials highly susceptible to acid and alkali corrosion. Therefore, the selection of refractory material and the construction method are particularly critical for this area. Due to the complex structure of this area, the construction of castable refractory materials is very difficult, resulting in inconsistent construction quality, difficulty in baking, and a tendency to crack. Using precast refractory components for the throat of a grate cooler can completely solve these problems. It is recommended to use high-strength mullite precast components specifically designed for grate cooler throats.

    1. Materials used: Mullite, silicon carbide.
    2. Service life: 3-5 years.
    3. Product features: High strength, high temperature resistance, wear resistance, good corrosion resistance, excellent thermal shock resistance, and superior anti-stripping properties.

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      Rongsheng Low-Cement Refractory Castable Manufacturer

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      Rongsheng, as one of the low-cement castable manufacturers, produces castable refractory castables with low cement content that rely on the addition of micro-powders or sols to achieve cohesion and bonding. Rongsheng low-cement refractory castables use oxide or synthetic compound micro-powders or sols with the same chemical composition as the main castable material as the binder, resulting in low impurity content. Without reducing the castable’s refractoriness and resistance to slag erosion, it can self-bond during long-term use, effectively improving the high-temperature structural strength.

      Rongsheng Low Cement Castable Materials
      Rongsheng Low-Cement Castable Materials

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        Bonding Mechanism of Low-Cement Refractory Castables

        There are various bonding methods for low-cement refractory castables. Currently, common methods include silica micropowder (dust silica) bonding, clay bonding, silica sol bonding, and silica-alumina sol bonding. Manufacturers can also choose bonding methods suitable for customer requirements. The setting and hardening mechanism of Rongsheng low-cement castables is as follows: The castable, when mixed with water, first achieves a certain degree of fluidity (or thixotropy) through the addition of dispersants (deflocculants or anti-flocculators) and delayed-acting accelerators. After self-flowing or vibration molding, the castable sets and hardens due to the delayed-acting accelerators.

        Low-cement castables can use oxide micropowders alone as binders, or silica sols and alumina sols as binders, or a combination of oxide micropowders and sols as binders. The choice of binder depends on the chemical composition of the aggregates used. For example, corundum castables should use reactive alumina, or alumina micropowder combined with silica micropowder as binders. Aluminosilicate castables can use silica micro powder or silica sol as binders.

        Hardening of Low-Cement Refractory Castables

        The hardening of low-cement refractory castables requires the addition of a delayed-setting accelerator. This accelerator is a type of agent that slowly hydrolyzes and ionizes in water, releasing counterions with the opposite charge to the surface charge of the micro-powder or colloidal particles. When the adsorbed counterions on the particle surface reach the “isoelectric point,” the particles aggregate and harden through drying.

        Performance Characteristics of Low-Cement Refractory Castables

        Compared to calcium aluminate cement-bonded castables, low-cement refractory castables have a slower setting and hardening rate, and slightly lower strength after room temperature curing. They are suitable for direct casting into monolithic linings on-site. Their long-term operating temperature is higher than that of sol-bonded castables of the same material. Low-cement castables can be used as linings for high-temperature vessels under more demanding operating conditions, such as monolithic linings for induction furnaces and steel ladles.

        Low Cement Castable Directly from Factory
        Low-Cement Castable Directly from Rongsheng Factory

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          Analysis Report on Thermal Shock-Resistant Low-Cement Castables

          This experiment utilized ultrafine silica fume and high-efficiency water-reducing agent technology to reduce the amount of cement in refractory castables. This resulted in a dense structure with low porosity, improved mid-temperature strength, and excellent erosion and abrasion resistance. Adding SiC micron powder to low-cement castables already incorporating silica fume significantly impacted the material’s strength and thermal shock resistance.

          To investigate the effect of SiC micron powder on the performance of low-cement castables already incorporating silica fume, samples A, B, C, and D were prepared. All four samples used the same aggregate material, dosage, and particle size distribution, with a total fine powder (including micron powder) content of 30%. The fine powder in sample A has a chemical composition of CaO/11.12%, Al2O3/60.16%, and SiO2/28.72%, and is composed of high-alumina cement, grade I bauxite clinker powder, and silica fume. Other samples B, C, and D, while maintaining the same total amount of fine powder, gradually replaced the fine powder in sample A with 325-mesh SiC micro-powder; the specific composition is shown in Table 1. Different amounts of high-efficiency water-reducing agent were added to each sample to ensure the same amount of water was used during molding. Each sample was made into a 4cm × 4cm × 16cm specimen, vibrated, and cured at 40℃ for 24 hours. The number of thermal shock tests after firing at 1450℃ was then measured. The results were compared by directly immersing each sample from 1450℃ to 20℃ cold water without cracking. The experiment also measured the apparent porosity, bulk density, and linear change rate of each sample after calcination at 1450 ℃ for 4 h, and compared the fine powder of each sample.

          SiC has good thermal conductivity, and its introduction into low-cement, high-alumina castables is beneficial for improving thermal stability. However, the amount of SiC micropowder added is not large enough to be the main reason for a significant improvement in thermal shock resistance. The thermal shock resistance of a material largely depends on its microstructure. The oxidation of SiC micropowder in the samples increases the porosity of the material. Since the SiC micropowder is uniformly dispersed in the fine powder, the pore distribution formed in the material matrix during calcination is also uniform, which is equivalent to a large number of microcracks uniformly distributed in the matrix. The Hasseman theory states that the more microcracks there are, the shorter the final length reached by crack propagation under the critical temperature difference, and smaller cracks can propagate in a quasi-static manner, avoiding catastrophic fracture. Therefore, the addition of SiC micro powder to the fine powder improves the thermal stability of the castable matrix, which in turn greatly enhances the overall thermal shock resistance of the material.

          Rongsheng Low-Cement Castable Manufacturer

          The simultaneous addition of SiC micropowder to low-cement high-alumina castables containing silica fume and high-efficiency water-reducing agents significantly improves the material’s thermal shock resistance due to the oxidation of SiC, which causes the fine powder portion of the castable to form a microstructure beneficial to thermal stability at high temperatures. However, the increased porosity delays the sintering process, resulting in a slight decrease in the compressive strength of the SiC-doped samples after firing at 1450 °C. The formation of more needle-like mullite somewhat compensates for this strength reduction.

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            High Heat Furnace Cement’s Application and Functional Characteristics

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            High-heat furnace cement, also known as aluminate cement, is a refractory building material specifically designed for high-temperature applications. In many industrial sectors and specialized engineering projects, the requirements for materials at high temperatures are quite stringent. Rongsheng Unshaped Refractory Castable Manufacturer will delve into the application of high-temperature furnace cement in high-temperature environments and its functional characteristics.

            High Heat Furnace Cement
            High Heat Furnace Cement

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              Applications of High-Heat Furnace Cement

              Due to its unique functional characteristics, high-heat furnace cement has been widely used in many industrial fields.

              1. Metallurgy

              High-temperature refractory cement plays a vital role in the metallurgical industry. The corrosive effects of high temperatures, alkaline substances, and acids during smelting place high demands on materials. The application of high-temperature refractory cement can effectively resist high-temperature corrosion of the furnace and the erosion of alkaline substances, extending the service life of equipment.

              1. Chemical Industry

              In chemical enterprises, many processes require high-temperature conditions, which places higher demands on the high-temperature resistance of building materials. The application of high-temperature refractory cement can effectively prevent corrosion and erosion by chemical substances, playing an important role in ensuring the safe operation of equipment.

              1. Glass and Ceramics Industry

              High-temperature kilns are indispensable equipment in the glass and ceramics industry. High-temperature refractory cement is widely used in the glass and ceramics firing process, able to withstand high-temperature corrosion and thermal stress, ensuring the normal operation of the kiln and product quality.

              1. Construction Industry

              Due to limitations imposed by the external environment and internal usage conditions, some special construction projects, such as high-rise buildings and large bridges, require building materials capable of withstanding high temperatures. In these projects, high-temperature refractory cement plays a vital role in ensuring the safety and stability of building structures.

              Functional Characteristics of High Heat Furnace Cement

              High heat furnace cement possesses many unique functional characteristics, making it an ideal material for high-temperature environments.

              1. Excellent High-Temperature Resistance

              High-temperature refractory cement maintains stability under extremely high temperatures, resisting softening, burning, and failure. It can withstand thermal stress and thermal shock at high temperatures, ensuring the normal operation and service life of equipment.

              1. Excellent Chemical Resistance

              High-temperature refractory cement is resistant to chemical corrosion, acids, and alkaline substances. This makes it widely used in metallurgy, chemical industry, and other specialized industrial fields.

              1. Excellent Mechanical Strength and Abrasion Resistance

              High-temperature refractory cement exhibits excellent mechanical strength and abrasion resistance, enabling it to withstand significant external forces and pressures under high temperature and pressure. Its high strength and abrasion resistance demonstrate excellent performance at high temperatures.

              High-temperature refractory cement is an ideal high-temperature material. Its widespread application plays a crucial role in ensuring the normal operation of equipment and product quality in many industrial fields. In the construction and industrial sectors, high-temperature refractory cement possesses excellent functional properties and is an indispensable material.

              Furnace Refractory Cement
              Furnace Refractory Cement

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                The Difference Between Refractory Mortar and Refractory Cement

                Many customers are confused about the differences between refractory mortar and refractory cement. Rongsheng Refractory Materials Manufacturer will explain the differences between the two for you.

                When constructing kilns, a binder called refractory mortar or jointing material (mixed with water to form refractory mortar) is used. It is a major auxiliary material in kiln construction and serves as the joint filler for bonding refractory bricks, ensuring a strong initial bond and preventing detachment.

                Refractory mortar should be selected according to the material of the refractory bricks used and should not be mixed. Refractory mortar is classified according to its material into: clay-based, high-alumina, silica-based, magnesia-based, carbonaceous, corundum-based, and mullite-based pre-made binders. For example, high-alumina refractory mortar is used for high-alumina bricks, magnesia refractory mortar for magnesia bricks, and silica refractory mortar for silica bricks, etc.

                Refractory mortar is supplied in dry powder form. When using it, a liquid binder is added and mixed thoroughly to form a slurry of suitable viscosity. This type of slurry is collectively referred to as high-temperature refractory mortar, high-temperature refractory slurry, or high-temperature binder. Based on the bonding method of the liquid binder, it is classified into: water glass-bonded refractory mortar, phosphate-bonded refractory mortar, aluminum phosphate-bonded refractory mortar, etc.

                Refractory mortar is composed of refractory powder and additives. Almost all refractory raw materials can be made into powders used to formulate refractory mortar. Refractory mortar made by adding appropriate binders to refractory clinker powder is called ordinary refractory mortar; its strength at room temperature is relatively low, and it only achieves higher strength at high temperatures through the formation of a ceramic bond. Refractory mortar using air-hardening or heat-hardening binders is called chemically bonded refractory mortar; it hardens through a chemical reaction before reaching the temperature required to form a ceramic bond.

                The particle size of refractory mortar varies depending on the application requirements; its limiting particle size is generally less than 1 mm, and some are less than 0.5 mm or even finer. The material of the refractory mortar should be chosen to be consistent with that of the refractory products used in the masonry. Besides being used as a jointing material, refractory mortar can also be applied as a protective coating for the lining using a coating or spraying method.

                Main characteristics: Good plasticity, convenient construction, high bonding strength, and strong corrosion resistance. Based on chemical properties, it is classified into acidic refractory mortar, neutral refractory mortar, and alkaline refractory mortar. In addition, there are refractory mortars for special applications.

                Refractory cement, also called aluminate cement or high-alumina cement, is a hydraulic cementitious material made from bauxite and limestone through calcination. It is a clinker with calcium aluminate as the main component and an alumina content of approximately 50%, which is then ground.

                Aluminate cement is usually yellow or brown, but can also be gray. The main minerals are monocalcium aluminate (CaO·Al₂O₃, abbreviated CA) and other aluminates, as well as small amounts of dicalcium silicate (2CaO·SiO₂). It is used to bind various refractory aggregates (such as corundum, calcined high-alumina bauxite, etc.) to make refractory mortar or concrete, used as linings for industrial kilns.

                The biggest difference between refractory mortar and refractory cement is that one is used as a mortar for building refractory bricks (mixed with water or other liquids), while refractory cement is used as a binder for various refractory aggregates and is used as a material for refractory castables for kiln linings.

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                  Hydration Process of Adding Refractory Cement to Refractory Castable

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                  The setting of refractory castables is closely related to the hydration of refractory cement. When a certain proportion of refractory cement is added to a refractory castable, the hydration, setting, and hardening process begins with the raw materials and binder coming into contact with water. First, the refractory cement undergoes a hydration reaction on the surface of the particles. The first step in hydration is the formation of crystal nuclei. As the nuclei enlarge, they adhere to the hydration products. During the curing process, the hydration products grow and agglomerate into particles. Then, the refractory castable begins to set and harden further, eventually reaching the required strength.

                  Refractory cement
                  Refractory Cement to Refractory Castable

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                    The Hydration Process of Castable Refractory Cement

                    The water reaction process differs among different grades of refractory cement, and hydration varies with temperature and time. After hydration for a certain period, the free water and crystal water that have not yet participated in the hydration reaction separate out with increasing temperature.

                    When refractory cement is added to refractory castables, and then a certain proportion of water is added during construction, the refractory cement begins to dissolve. As the refractory cement forms crystal nuclei, cement hydrates precipitate out after nucleation. After a hydration dormancy period and heat release, the hydration of the refractory cement reaches its peak as the temperature rises. This is the setting time of refractory cement hydration. Different refractory cements have different setting times and hydration rates.

                    During on-site casting of refractory castables, the hydration process has a significant impact on the setting and demolding of the refractory castable. After mixing with water, the refractory castable will initially set within 4 hours, and demolding typically occurs after 24 hours.

                    The curing process after casting is also crucial. It solidifies only after hydration. However, free water can be drained, while the water of crystallization must be slowly baked at 600℃ to achieve sufficient strength.

                    Castable Refractory Cement

                    Castable refractory cement is a type of refractory cement used in the production of refractory castables. It can be used as a binder, additive, and other ingredients. Due to its stable performance and good application results, castable cement is an indispensable refractory raw material.

                    Castable refractory cement is a type of cement with a refractoriness of not less than 1580℃, made from bauxite and lime as raw materials. The raw materials are mixed in a certain proportion to form appropriate amounts of raw meal, which is then sintered to obtain clinker with aluminate as the main component. This clinker is then ground into a fine powder to produce a hydraulic cementitious material with refractory properties. It is a type of refractory clinker that can be directly added to the production of castables. Depending on the raw materials and composition, it can be classified into aluminate refractory cement, low-calcium aluminate refractory cement, calcium-magnesium aluminate cement, and dolomite refractory cement, etc.

                    Applications of Castable Refractory Cement
                    Castable Refractory Cement

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                      Applications of Castable Refractory Cement

                      1. Refractory cement can be used to bind various refractory aggregates (such as corundum, calcined high-alumina bauxite, etc.) to produce refractory mortar or concrete for use as linings in cement rotary kilns and other industrial kilns.
                      2. It can be mixed with lightweight aggregates to produce insulating and heat-resistant concrete.
                      3. It can be mixed with asbestos to produce asbestos cement products with insulating and heat-resistant properties.

                      Technical Requirements for Refractory Cement

                      1. Fineness of Refractory Cement: The finer the cement particles, the larger the specific surface area, the faster and more complete the hydration reaction, and the higher the early and later strength. National regulations stipulate that the specific surface area should be greater than 300 square meters per kilogram; otherwise, it is considered unqualified.
                      2. Setting Time of Refractory Cement: To ensure sufficient time for mixing, transportation, molding, and other processes during construction, the initial setting time of the cement should not be too short. After construction, it is desirable for the cement to harden and develop strength as quickly as possible, so the final setting time should not be too long. The initial setting time of refractory cement shall not be earlier than 45 minutes, and the final setting time shall not be later than 390 minutes.
                      3. Volume stability of refractory cement: The uniformity of volume change of cement paste during the setting and hardening process is called the volume stability of cement. If the volume change is uneven, i.e., the volume stability is poor, warping and cracking are likely to occur, reducing project quality and even causing accidents.

                      Precautions for Using Refractory Cement

                      Refractory castable cement, when used, is mixed with an appropriate amount of water to form a paste. It hardens in air or, even better, in water, and effectively binds other aggregates and powders in the refractory castable together.

                      Refractory cement is characterized by rapid hardening, high bond strength, strong plasticity, and convenient construction. Unlike ordinary cement, refractory cement acts as a binder in castables at high temperatures, rapidly hardening and exhibiting excellent bonding performance, thus improving the high-temperature performance of refractory castables. While refractory cement has a wide range of applications, its use in the refractory materials industry is primarily as a binder in the production of refractory castables.

                      Construction of Castables of Different Grades

                      • Ordinary cement-bonded castables have a relatively high tolerance for construction errors, but their high-temperature performance and erosion resistance are limited.
                      • Low-cement/ultra-low-cement castables are highly sensitive to water addition and vibration. Excessive water or segregation significantly reduces their high-temperature strength and thermal shock resistance.
                      • Cement-free/sol-based castables rely heavily on strict construction and kiln drying procedures, making them more suitable for skilled teams and high-end projects.

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                        Applications of Several Wear-Resistant Refractory Plastics

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                        Rongsheng Refractory Materials Manufacturer specializes in the research, development, and production of shaped and unshaped refractories, providing comprehensive life-cycle services for thermal kiln linings, including refractory material configuration, furnace lining optimization, engineering construction, and technical services. Rongsheng also boasts an environmentally friendly, fully automated production line for unshaped refractories, professionally producing various types. Among unshaped refractories, abrasion resistant refractory, those with common refractory and wear-resistant properties include the following:

                        Ordinary Wear-Resistant Plastic

                        Ordinary wear-resistant plastic is a high-alumina, corundum-based granular product. Compared with traditional refractory plastics, it has excellent properties such as easy construction, high efficiency, good molding, and high strength. abrasion resistant refractory. This material is composed of adhesive, refractory aggregate, and hardening accelerator. Adding a certain proportion of PA adhesive forms a plastic refractory mortar, facilitating construction in various complex areas. It is an air-hardening material with low-temperature hardening properties, ensuring the wear resistance required for circulating fluidized bed boilers. However, its wear resistance is relatively poor.

                        • 1) Application Method: Use a forced mixer to stir the material, adding the accelerator evenly during stirring. After dry stirring for 1 minute, add 4-5% of the adhesive and stir for another 3 minutes. Once the material reaches a certain plasticity, it can be unloaded and used.
                        • 2) Applicable Areas: Suitable for high-temperature areas with low friction, such as the boiler bottom air chamber, primary air duct, return riser (material leg), return feeder, return pipe, tail flue furnace wall, slag cooler, and filling of various furnace doors in the tail flue. 3) Storage method. Generally, store in a cool, dark place. Shelf life is about 2 to 3 months.
                        Micro-Expansion Wear-Resistant Plastic Refractory
                        Wear-Resistant Plastic Refractory

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                          Wear-Resistant Refractory Plastic

                          Abrasion-resistant refractory plastics are made from high-alumina bauxite clinker, corundum, mullite, and silicon carbide as aggregates. They possess excellent wear resistance, strong adhesion, and a high service temperature. Formulated with different binders and additives, they are refractory materials with high strength and wear resistance. They offer advantages such as easy construction, good plasticity, and excellent wear resistance. The applied wear-resistant layer has high strength and wear resistance, fully meeting the performance requirements of wear-resistant refractory materials for boilers.

                          • 1) Application Method: The materials and binder are mixed evenly with phosphoric acid before use. Construction is typically carried out using a ramming process.
                          • 2) Applicable Areas
                            • Suitable for construction in thin-thickness areas such as furnace water-cooled walls, mainly used in the dense phase zone of the furnace and in steam-cooled and water-cooled cyclone separators. In this area, the wear-resistant refractory material is designed as a single-layer rammed structure, fixed with wear-resistant pins, and its design thickness is relatively thin, directly applied to the construction surface.
                            • In the repair of circulating fluidized bed cyclone separators, its superior bonding properties allow for the repair of any irregular wear areas without the need for steel templates or molds. Ignition can be performed immediately after construction, requiring no special curing, thus shortening the construction cycle and saving costs.
                          • 3) Storage method. Avoid open-air storage and direct sunlight. Store in a cool, damp place in summer and protect from freezing in winter.

                          Corundum Wear-Resistant Refractory Plastic

                          This material belongs to the field of high-temperature wear-resistant refractory materials. The raw materials consist of high-alumina homogeneous material, alumina micropowder, silica micropowder, clay, phosphoric acid, aluminum dihydrogen phosphate solution, and pure calcium aluminate cement. Its key feature is the use of low-water-absorption, low-porosity, and highly uniform synthetic homogeneous materials to replace traditional high-water-absorption, high-porosity, and poorly uniform sintered bauxite clinker natural raw materials or corundum composite raw material systems, producing a homogeneous, high-strength, wear-resistant corundum plastic.

                          • 1) Application Method: This material is applied using a tamping process, suitable for thin-thickness applications such as furnace water-cooled walls. The resulting wear-resistant layer exhibits high strength and wear resistance. Unlike castables, this plastic does not require molds and can be applied directly using a smearing and tamping method. The refractory plastic material has good workability, high strength, and good wear resistance, resulting in optimal performance in the field. It helps extend the service life of furnace linings and improve the utilization efficiency of high-temperature kilns.
                          • 2) Applicable Areas. It is mainly used in the dense phase zone of the furnace and in steam-cooled/water-cooled/insulated cyclone separators. The wear-resistant refractory material in this area is designed as a single-layer rammed structure and fixed with wear-resistant pins. Its thickness varies, generally 40-60mm (steam-cooled/water-cooled) and 320-350mm (insulated), and it can be directly laid on the construction surface.
                          Corundum Silicon Carbide Wear Resistant Refractory Plastic
                          Corundum Silicon Carbide Wear-Resistant Refractory Plastic

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                            Silicon Carbide Corundum Wear-Resistant Refractory Plastic

                            Silicon carbide corundum wear-resistant refractory plastic is a high-grade refractory material. It possesses excellent wear resistance, strong adhesion, and a high service temperature. It is also renowned for its simple construction process, short construction period, and the superior characteristic of not requiring furnace drying after construction. In practice, its service life is significantly longer than other wear-resistant refractory materials, and it is widely used in industries such as power, metallurgy, steel, and ceramics.

                            • 1) Application Method: This material is applied using a smearing and tamping method. Before application, rigid anchor pins should be fixed to the required locations, with a mesh spacing of approximately 120-150mm (maximum not exceeding 200mm). During application, the plastic is laid evenly on the required areas. The thickness of the smear can be determined according to the design requirements of different furnace types.
                            • 2) Applicable Areas: Silicon carbide wear-resistant refractory plastic can be widely used in cyclone separators, thermal radiation materials, and other applications where refractory materials are used. It possesses superior adhesive properties, allowing for easy application and application to any irregular, worn areas, significantly reducing wear. No steel templates or molds are required; it can be ignited immediately after application without special curing, thus shortening the construction cycle and saving costs.
                            • 3) Storage Method. Avoid open-air storage and direct sunlight. In summer, store in a cool, damp place; in winter, protect from freezing. The shelf life of the plastic is generally one year, and the accelerator should be replaced after 4-6 months of unused use (if used after one year of storage, the material must be re-cured).

                            High-Strength Wear-Resistant Refractory Plastics

                            Rongsheng’s high-strength wear-resistant refractory plastics belong to the high-strength wear-resistant series of refractory plastics. Their materials include high-alumina, corundum, silicon carbide, chromium, and zircon.

                            High-strength wear-resistant refractory plastics possess strong plasticity and wear resistance. They can be tamped into any shape using the tamping method, making them a quick-repairing material for kiln linings.

                            High-strength wear-resistant refractory plastics are refractory plastics composed of the above-mentioned materials as the main raw materials, with the addition of binders and additives (shrinkage inhibitors, preservatives, and antifreeze agents).

                            Commonly used castables include: corundum wear-resistant refractory castables, wear-resistant refractory plastics, non-stick alumina castables, low-cement refractory castables, adjustable-mouth castables, high-strength impermeable low-cement castables, lightweight refractory insulating castables, and steel fiber refractory castables.

                            Applications of High-Strength Wear-Resistant Plastics:

                            1. In the power generation industry: coal unloading trenches, coal hoppers, coal storage bins, dry coal grids, tippers, slag removers, water treatment, etc.
                            2. In the chemical industry: corrosion-resistant flooring, pump foundations, etc.
                            3. In the coal industry: wear-resistant linings for grinding bins, medium tanks, scraper conveyors, bucket elevators, chutes, underscreen hoppers, etc.; in the steel industry: blast furnace mixing bins, sintering bins, feeders, pelletizing machines, etc.

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                              Lightweight Insulating Castable for Nitrogen Purification Equipment

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                              High-purity nitrogen is a crucial protective gas required for cold-rolled sheet, hot-dip galvanizing, and silicon steel production lines. The purity of nitrogen significantly impacts product quality. Excessive oxygen content leads to surface oxidation of steel sheets, causing surface elements to react with oxygen and affecting steel quality, resulting in problems such as bare spots in galvanized sheets. Cryogenic air separation units produce nitrogen as a byproduct; due to its relatively low purity and unstable oxygen content, this nitrogen is often referred to as “dirty nitrogen.” Chinese steel mills possess abundant “dirty nitrogen” resources, but due to purity and stability issues, this nitrogen cannot be directly used in cold-rolling production and must be purified before use. Even imported air separation units experience fluctuations in gas production and potential cross-contamination of instrument air. Therefore, imported production lines typically employ terminal purification devices to ensure nitrogen purity and stability. Currently, these nitrogen purification devices commonly use ceramic fiber as an insulation material. However, ceramic fiber has drawbacks, including a short lifespan requiring replacement every two years, difficulty in installation as required, inability to achieve a 1/2 compression ratio, significant environmental hazards, and health risks to construction workers.

                              Lightweight Insulating Castable
                              Rongsheng Lightweight Insulating Castable

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                                Lightweight Insulating Castable Refractories for Nitrogen Purification Units

                                Vermiculite is a group of hydrous mica (usually biotite or phlogopite) formed through alteration and weathering in hot aqueous solutions. It is a secondary metamorphic mineral containing magnesium and iron silicates. When raw vermiculite ore or beneficiated ore is heated to above 300℃, it becomes a highly efficient insulating material. The resulting expanded vermiculite possesses properties such as low density, thermal insulation, sound insulation, earthquake resistance, fire resistance, and freeze resistance. Furthermore, since vermiculite is environmentally friendly, it is also an important environmentally friendly material. To address the drawbacks of using ceramic fibers as insulation materials, this paper develops a lightweight insulating refractory castable refractories using vermiculite and calcium aluminate cement as the main raw materials, based on the operating conditions and requirements of nitrogen purification units, aiming to meet the insulation material requirements of nitrogen purification units.

                                Based on the experimental results, the developed lightweight insulating castable was used as an external insulation material in a field test on two nitrogen purification units at the gas plant of a steel plate company. The results showed that the lightweight insulating castable performed well as the external insulation material for the nitrogen purification units, with no damage observed. Furthermore, the use of this lightweight insulating castable reduced the external temperature of the nitrogen purification units. In actual use, the external temperature remained below 40℃, achieving the goals of reducing heat loss from thermal equipment, improving thermal efficiency, reducing energy consumption, and achieving energy conservation and emission reduction.

                                In conclusion, the lightweight insulating castable can replace ceramic fiber as the external insulation material for nitrogen purification units, demonstrating excellent performance. It reduces the external temperature of the nitrogen purification units, achieving the goals of reducing heat loss from thermal equipment, improving thermal efficiency, reducing energy consumption, and achieving energy conservation and emission reduction.

                                Lightweight Insulating Castable

                                Lightweight insulating castable is an unshaped material with lightweight aggregates and a specific binder as its core, possessing both fire resistance and high-efficiency thermal insulation properties. It is also known as lightweight insulating castable. Aggregates, depending on the service temperature, can include expanded vermiculite, expanded perlite, ceramsite, porous clay particles, corundum, high-alumina mullite, etc. Binders include ordinary silicate cement, alum cement, calcium aluminate cement, dialuminate phosphate, silica sol, alumina sol, etc. It is usually supplied in dry powder or slurry form, and is mixed with water or liquid binder on-site before being applied by pouring, vibration, tamping, etc.

                                Characteristics of Lightweight Insulating Castable: Lightweight insulation with low bulk density and low thermal conductivity, effectively reducing heat loss. High strength, with certain flexural and compressive strength. Good corrosion resistance; some products are resistant to acidic gas corrosion and can be used in harsh chemical environments. Construction is convenient; it can be cast into various shapes and made into precast blocks as needed, making construction relatively easy. It is suitable for kiln insulation layers, reducing kiln load and improving thermal efficiency, such as kilns in the metallurgical and building materials industries, and acid-resistant pools and tanks in the petroleum, chemical, and non-ferrous metallurgical industries. It is also an ideal material for high-temperature flue ducts and air duct linings in chimneys, effectively improving the airtightness and corrosion resistance of the lining.

                                Ultra-Lightweight Insulating Castable Series
                                Ultra-Lightweight Insulating Castable Series

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                                  Optimization of Low Thermal Conductivity Castable Technology

                                  Low thermal conductivity castables are not simply an extension of the ordinary “lightweight” concept, but rather achieve “three lows and one high” simultaneously under high-temperature service conditions—low bulk density, low thermal conductivity, low linear shrinkage rate, and high refractory strength. This performance combination breaks the traditional rule of “temperature increase → simultaneous increase in bulk density,” enabling simultaneous reduction of equipment weight and strengthening of furnace lining insulation, providing a material basis for further energy saving and consumption reduction in industrial kilns.

                                  Performance Characteristics of Low Thermal Conductivity Castables

                                  1. Lightweight and High Strength: At the same service temperature level, the bulk density can be lower than that of conventional lightweight insulating castables, while the compressive strength remains at the same or higher level.
                                  2. Stable Thermal Conductivity: In the 1000 ℃ high-temperature range, the thermal conductivity remains ≤0.35 W·(m·K)⁻¹, significantly reducing heat loss from the furnace wall. 3. Excellent integrity and high plasticity: The material has a uniform porous network structure, allowing for on-site casting, tamping, spraying, or prefabrication. Complex irregular furnace linings can be formed in one piece, and subsequent local repairs do not require furnace shutdown for cooling.
                                  3. Thermal shock resistance and spalling resistance: The introduction of composite micro-powder and fiber synergistic toughening ensures no through-cracks after more than 50 rapid cooling and heating cycles, extending service life by 1.5 to 2 times.

                                  Raw Materials and Processes for Low Thermal Conductivity Castables

                                  1. Lightweight Aggregate Selection: Low-iron, high-alumina porous homogeneous aggregates are used, requiring a bulk density ≤1.2 g·cm⁻³ and a compressive strength ≥8 MPa, ensuring “lightweight yet not loose” from the source.
                                  2. Composite Additives: Expandable minerals are introduced to offset high-temperature sintering shrinkage; reducing water addition while increasing filling rate.
                                  3. Particle Size Distribution Redesign: The upper limit of critical particle size is relaxed to enhance the aggregate “skeleton” effect, balancing construction flowability and surface smoothness.
                                  4. Standardized Testing Methods: A “dual-indicator” admission system is established to address regional differences in aggregate testing—measuring both the intrinsic properties of the lightweight aggregate and its high-temperature linear change and thermal conductivity after coupling with additives, ensuring batch stability.

                                  Construction Advantages of Low Thermal Conductivity Castables

                                  After mixing with water, the material has a flow value ≥180 mm, self-leveling with vibration, and can be poured within 30 minutes; initial setting time is 2.5 hours, final setting time is 4 hours, and the baking curve is shortened by 20% compared to traditional materials; no harmful gases are emitted, and there is no corrosion to the furnace shell steel structure.

                                  Energy Saving and Economic Benefits

                                  Field measurements in metallurgical heating furnaces, mechanical heat treatment furnaces, electric circulating fluidized bed furnaces, chemical cracking furnaces, and petrochemical reforming furnaces show that: the average temperature of the furnace lining outer wall decreases by 40-60℃, and heat loss is reduced by 20%-25%. The furnace heating rate increases by 15%, the production cycle is shortened, and the unit consumption of gas or electricity decreases by 8%-12%. Furnace temperature uniformity is improved, the product qualification rate increases by 2-3 percentage points, and the material price difference can be recovered within one year of comprehensive operating costs. Industry Application Differences

                                  Petrochemical kilns, due to their harsh operating conditions (large temperature differences, high permeability of light oils), require low thermal conductivity castables with even lower bulk density and higher chemical stability. Corresponding products require high-purity matrices and special sealants, resulting in prices approximately 20%–30% higher than similar materials used in the metallurgical industry. However, their service life can be extended by more than 3 years, and their total life-cycle cost is still superior to ordinary light materials.

                                  With the continuous advancement of raw material purification and composite modification technologies, the application boundaries of low thermal conductivity castables will further expand from traditional kilns to higher temperatures, more complex, and more demanding extreme operating conditions.

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                                    Formulation and Properties of Corundum and High-Alumina Refractory Mortar

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                                    Refractory mortar is an unshaped refractory material composed of powdered materials and binders, used for preparing slurries. The powdered materials are made from fully sintered clinker (such as high-alumina clinker, calcined silica, magnesia, etc.) or other volume-stable refractory raw materials (such as silica, wax stone).

                                    Rongsheng Refractory Mortar Manufacturer

                                    The powder used to make refractory mortar can be fully sintered clinker and other volume-stable refractory raw materials. The particle size of the powder depends on the application requirements, with a generally limited particle size of less than 1mm, and sometimes less than 0.5mm or even finer. A reasonable particle composition has a significant impact on ensuring the mortar’s workability, as do the binders and admixtures. Ordinary refractory mortars use bonded clay as the binder. However, chemical binders are increasingly widely used. Adding various admixtures to refractory mortar can improve its workability. For example, adding water-retaining agents to extend the water loss time and ensure construction quality; adding plasticizers, even in small amounts, can increase the mortar’s plasticity; adding dispersants to improve the mortar’s fluidity, etc.

                                    Refractory mortars can be classified into hydraulic, thermohardening, and air-hardening refractory mortars based on their binder setting and hardening characteristics. Hydraulic refractory mortars use cement as a binder and can be used at room temperature or in places where they may frequently come into contact with water or moisture. Thermosetting refractory mortars are commonly made with thermosetting binders such as phosphoric acid or phosphates. After hardening, these mortars exhibit high strength at various temperatures, low shrinkage, tight joints, and strong erosion resistance. Air-hardening refractory mortars commonly use air-hardening binders such as sodium silicate. These mortars ensure tight joints in masonry.

                                    Depending on the material of the refractory powder used, commonly used refractory mortars can be classified as: clay-based, silica-based, high-alumina-based, magnesia-based, and insulating. Refractory mortar is mainly used as a contact and surface coating for refractory brick masonry. When used as a jointing material, its quality has a significant impact on the lifespan of the masonry. It can adjust dimensional errors and irregular shapes of bricks, making the masonry neat and load-bearing. It also helps the masonry form a strong and tight whole, resisting external damage and preventing the infiltration of molten metal.

                                    Rongsheng Corundum Refractory Mortar
                                    Rongsheng Corundum Refractory Mortar

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                                      Corundum Refractory Mortar

                                      The formulation of corundum refractory mortar mainly uses sintered corundum clinker or fused alumina with a diameter of 0.5-0.63 mm and finer. Fused alumina with a diameter of 5-7 μm or industrial alumina with a diameter of less than 5 μm is used as a binder. To ensure the shrinkage of the refractory clay during air and firing, the industrial alumina content in the formulation should not exceed 15%-20%, while the content of ultrafine fused alumina powder should reach 40%-50%. 10% of the refractory mortar is introduced with orthophosphoric acid (density 1.72 g/cm³).

                                      Using corundum clinker and introducing less than 0.1% fermented alcohol waste liquid can improve the plasticity of the slurry and reduce its water content. This refractory mortar has a normal moisture content of less than 19%, a weight loss of 1.8% when heated to 110°C, and an apparent porosity of 26%. As shown in Table 1, the refractory clay has sufficient shear bond strength after firing at 1000-1500°C.

                                      Properties of Corundum Refractory Mortar
                                      Properties of Corundum Refractory Mortar

                                      Note: Component 1 is a refractory mortar primarily composed of sintered corundum, with particles smaller than 0.5 mm, 10% phosphoric acid, and 0.1% fermented alcohol waste liquid. Component 2 is a refractory mortar primarily composed of industrial alumina, with particles smaller than 30 μm, 5.5% polyphosphoric acid, and 0.1% fermented alcohol waste liquid. Component 3 is a refractory mortar primarily composed of light-burned alumina, bonded with sodium pyrophosphate. Component 4 is a refractory mortar primarily composed of high-alumina clinker, 10% clay, 0.1% fermented alcohol waste liquid, and 0.15% sodium carbonate.

                                      According to Table 1, the shear bond strength of the refractory mortar is related to the final porosity; as porosity increases, the shear bond strength tends to decrease. To maintain the uniformity of the moisture content of the corundum refractory mortar at 2.5%, some dust needs to be removed, and 2.5% CaCl2 needs to be introduced. This increases the moisture content of the slurry to 24%–27%, without reducing the cohesive strength between the refractory mortar and the corundum refractory material. The shear bond strength after firing at 1000°C is 1.4–2.0 MPa, and reaches 10 MPa after firing at 1500°C.

                                      Phosphate-bonded corundum refractory mortar can withstand 40 cycles of repeated water exchange at 1300°C without cracking. Corundum refractory mortar containing approximately 96% alumina has a refractoriness of 2000°C. Reducing the alumina content in the refractory mortar to 90%–91% slightly decreases the refractoriness, and the deformation initiation temperature under a 0.2 MPa load drops to 1580°C.

                                      High Alumina Mortar Material Can Be Used to Fill up Seam
                                      High Alumina Mortar Material of Rongsheng

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                                        High-Alumina Refractory Mortar

                                        The technical properties of high-alumina refractory mortar are shown in Table 2.

                                        Properties of High-Alumina Refractory Mortar
                                        Table 2: Properties of High-Alumina Refractory Mortar

                                        Storage and Usage Principles of High-Alumina Mortar

                                        High-alumina mortar is the jointing material for high-alumina refractory bricks, mainly used for bonding bricks. Its storage time affects its performance, and its continued usability can be determined.

                                        Judging the Storage Condition of the Binder

                                        1. Check the Binder Packaging

                                        First, check if there is a separately packaged binder in the high-alumina refractory mortar. If there is a separately packaged binder, and the storage time exceeds 6 months, it cannot be used and needs to be replaced.

                                        If there is no separately packaged binder, take a small amount of refractory mortar and smell it. If there is an odor, it means that the binder was added to the refractory powder during production; if there is no odor, it means that the binder was not added.

                                        1. Advantages of No Added Binder

                                        High-alumina mortar without added binder is in its optimal state. It can be remixed with binder and used again, thus ensuring its bonding performance.

                                        Judgment of Refractory Mortar with Added Binder

                                        If the high-alumina refractory mortar has had a binder added directly during production and has been stored for more than 6 months, the following test is required to determine its usability:

                                        1. Test Preparation

                                        Weigh 1 kg of refractory powder, add 20%-25% drinking water, and stir to form a slurry. Prepare two refractory bricks of the same material.

                                        1. Test Procedure

                                        Take a portion of the refractory mortar and evenly spread it on one refractory brick, smooth it out, and place the second refractory brick on top. Rub the two refractory bricks back and forth approximately 15 times.

                                        1. Result Judgment

                                        If the two refractory bricks can bond together, the high-alumina refractory mortar is still usable. If the refractory bricks cannot bond, add an appropriate amount of binder in a reasonable proportion and repeat the above test. If the refractory bricks bond successfully, they can be put into use.

                                        Summary of High-Alumina Refractory Mortar Usage

                                        The binder in high-alumina refractory mortar primarily promotes the adhesion of the mortar. However, the binder will disappear after high-temperature baking. Therefore, high-alumina mortar that has been stored for a long time needs to be assessed for its continued usability using the methods described above. By checking the storage condition of the binder and conducting simple tests, the feasibility of using high-alumina refractory mortar can be effectively determined, avoiding the impact of material issues on the bonding effect and construction quality of refractory bricks.

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                                          Preparation and Properties of Porous Spherical Mullite Castables

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                                          In high-temperature industries such as iron and steel metallurgy, the poor insulation and rapid heat loss of refractory materials used in industrial kiln linings lead to excessively high kiln surface temperatures, resulting in increased energy consumption during ironmaking and steelmaking processes. This not only hinders the lifespan of refractory materials but also affects production schedules and endangers the safety of production personnel.

                                          Low Thermal Conductivity Refractory Materials for High-Temperature Kilns

                                          For example, the high thermal conductivity of refractory materials used in steel ladles leads to accelerated heat loss, which triggers a series of chain reactions during steelmaking:

                                          1. Rapid heat loss causes excessively high ladle shell temperatures, resulting in severe deformation;
                                          2. Rapid cooling of molten steel leads to cold forming, nodule formation, and even ladle flow interruption and final pouring.

                                          Therefore, developing low thermal conductivity refractory materials for high-temperature kilns has become an urgent need for major steel mills. The high porosity and low thermal conductivity of lightweight materials offer new insights into the preparation of insulating refractory materials for high-temperature kiln linings. However, the preparation of lightweight refractories is often achieved by changing process conditions or adding additives, which suffers from poor controllability of pore size distribution. Consequently, functionalized refractory raw materials have rapidly developed, such as lightweight mullite, alumina hollow spheres, and gel powder. These raw materials facilitate the preparation of lightweight thermal insulation refractory materials. However, their excessively light weight and high price also limit their industrial application.

                                          Meanwhile, with increasing production requirements, lightweight, high-strength refractory materials suitable for higher temperatures have gradually become the focus. Using microporous lightweight mullite, multiphase hollow spheres, high-alumina bauxite, silica, and alumina micropowder as main raw materials, the effects of lightweight aggregate composition, micropowder composition, bonding system, and pore-forming agent on the performance and structure of lightweight high-alumina castables were studied, and a lightweight high-alumina castable with good high-temperature performance was developed. Using mullite microspheres, α-Al₂O₃ micropowder, and silica micropowder as raw materials, and AlF₃·3H₂O and V₂O₅ as additives, a lightweight, high-strength mullite microsphere thermal insulation refractory material was prepared. Lightweight, high-strength, and highly thermally shock resistant corundum-mullite refractory materials were prepared by using alumina hollow spheres as pore-forming agents and AlF3·3H2O as additives to control the pore characteristics of corundum-mullite and the in-situ formation of mullite whiskers.

                                          Rongsheng Mullite Refractory Castable Manufacturer
                                          Rongsheng Mullite Refractory Castable Manufacturer

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                                            Preparation and Properties of Porous Spherical Mullite Castables

                                            Existing research shows that recent studies on the performance of aluminosilicate materials have largely focused on aggregate substitution or the use of additives. Alumina, a commonly used and relatively inexpensive raw material in aluminosilicate materials, has had its impact on aluminosilicate castables rarely reported.

                                            • To prepare a high-temperature kiln insulating refractory material with excellent thermal insulation and mechanical properties, porous spherical mullite-based castables were prepared using porous spherical mullite, fine alumina powder, α-Al₂O₃ micropowder, silica powder, and Secar 71 cement as the main raw materials.
                                            • The effects of fine alumina powder content on the mechanical properties, thermal conductivity, erosion resistance, and thermal shock resistance of the porous spherical mullite-based castables were investigated.

                                            The results show that changing the content of fine alumina powder can improve the thermal insulation, thermal shock resistance, and erosion resistance of the porous spherical mullite-based castables while maintaining high mechanical properties.

                                            With increasing bauxite powder content, the mechanical properties of porous spherical mullite-based castables did not change significantly. However, the thermal conductivity decreased slightly, and the erosion resistance showed considerable differences, with thermal shock stability initially increasing and then decreasing. When the bauxite powder content was 28% (mass fraction), the porous spherical mullite-based castable exhibited good mechanical properties, thermal shock stability, and erosion resistance. The thermal conductivity at 1000℃ was 0.905 W·m⁻¹·K⁻¹. The high-temperature flexural strengths of the porous spherical mullite-based castable at 1100℃ and 1400℃ were 22 MPa and 5 MPa, respectively, indicating good thermal insulation performance, high flexural strength, and a certain degree of resistance to ladle slag erosion.

                                            The thermal conductivity of the porous spherical mullite-based castable is lower than that of high-alumina castables used in tundish and ladle permanent layers, making it a viable alternative to high-alumina castables used in tundish and ladle permanent layers to reduce heat loss.

                                            Mullite refractory castable price
                                            Mullite refractory castable price

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                                              Application Effects of Lightweight Mullite Castables

                                              Lightweight mullite castables are primarily used as integral linings for regenerators in heating furnaces. This working layer operates continuously at a high temperature of 1350℃, enduring temperature fluctuations within the kiln and the erosion and wear of high-temperature gases. During construction, the casting thickness is 300-400mm, with a water content of 18%-19%. In practical applications, this castable demonstrates advantages such as high workability, high-temperature strength, low thermal conductivity, good insulation, and good thermal shock resistance. Furthermore, its low-cement, micro-powder composite bonding allows for direct contact with the flame.

                                              Energy-saving and environmentally friendly lightweight mullite castables, with their superior workability and high-temperature performance, have become ideal refractory linings for regenerators in heating furnaces. In addition, their application in thermal kilns such as aluminum melting furnaces, fluidized bed boilers, and gasifiers has also seen widespread development.

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                                                The Importance of Water Addition in the Fabrication of Precast Refractory Shapes

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                                                Precast Refractory Shapes are products made according to the shape of the application area to facilitate on-site construction. They are produced by pouring the refractory castable into a mold and vibrating it into various shapes after the refractory castable is produced.

                                                Rongsheng Precast Refractory Shapes
                                                Rongsheng Precast Refractory Shapes

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                                                  Water Addition in Precast Refractory Shapes Manufacturing

                                                  The amount of water added during the manufacturing process of Precast Refractory Shapes is crucial. Excessive water leads to a sparse particle size, affecting the strength and performance of the finished product. Insufficient water results in a lack of fluidity, making it impossible to form. The water addition amount for each type of precast refractory castable is determined based on the raw materials and binders used in the mixing process.

                                                  If the binder, such as high-alumina cement, is used in large quantities, resulting in a high calcium content, the water addition amount will also increase. Currently, most castable products utilize low-cement technology to reduce water addition, shorten drainage time, and enhance product strength. A moderate water addition improves product fluidity and facilitates construction. Furthermore, reduced drainage time results in higher product strength, lower porosity, and consequently, a longer service life for the Precast Refractory Shapes.

                                                  Excessive water addition fails to enhance the fluidity of the castable. Moreover, during the manufacturing process, the use of a vibrator can cause water to splash out, quickly rising to the surface while large aggregates sink to the bottom. This also generates a large number of water bubbles, meaning excessive and large pores. This prolongs the demolding cycle of Precast Refractory Shapes, and even if demolding is successful, the product’s strength and usability will suffer from cracking and eventual detachment during use.

                                                  The appropriate amount of water added depends on the different raw material matrixes. During mixing, aggregates should be added first, followed by fine powders, then the binder, and finally the appropriate proportion of water. This simplifies the manufacturing process, reduces drainage, increases product strength, and lowers porosity.

                                                  Therefore, the amount of water added during the pre-fired Precast Refractory Shapes manufacturing process is crucial and cannot be arbitrarily increased. The principle is to add less rather than more, which enhances the product’s performance and facilitates faster and more convenient construction.

                                                  Rongsheng Precast Refractory Shapes Manufacturer
                                                  Rongsheng Precast Refractory Shapes Manufacturer

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                                                    Can Precast Refractory Shapes be Used Without Baking?

                                                    Yes, Precast Refractory Shapes can be used without baking at a certain temperature. However, this requires the addition of explosion-proof fibers to the pre-made process mix to ensure sufficient drainage of crystal water. Alternatively, a long natural drying time can also allow them to be used without baking.

                                                    Precast Refractory Shapes are an extension of refractory castables. They are made by mixing raw material granules and powders, binders, and water to form a castable. This mixture is then poured into pre-made molds and undergoes dehydration, baking, and drainage processes before use. Comparatively, precast refractory components that have been baked at 300℃ have a better service life and safety than those that haven’t been baked.

                                                    However, if the quantity of precast refractory components used is large and the operating conditions are not demanding, adding explosion-proof materials during production and ensuring sufficient drainage of moisture allows them to be used during the industrial furnace lining baking process as the furnace temperature gradually increases. Unbaked pre-fired refractory precast components, while possessing higher strength, are more prone to breakage during transportation, handling, and construction.

                                                    Currently, the proportion of unbaked Precast Refractory Shapes used in the market is higher than that of baked ones. This is due to lower costs, coupled with improvements in castable technology, resulting in performance comparable to products from earlier technologically advanced periods.

                                                    However, under harsh operating conditions, such as excessively high furnace lining temperatures and the need for emergency repairs, where the furnace lining temperature rises rapidly, unbaked Precast Refractory Shapes, even those unbaked, offer better performance and a longer service life. Baked precast refractory components, on the other hand, have higher strength, better thermal shock resistance, and are less likely to crack during use.

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                                                      Basis for Selecting Castable Refractory for Flue Lining

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                                                      The most important consideration for flue lining is the erosion and corrosion caused by acidic gases. Acidic gases necessitate the use of acid-resistant castables or acid-resistant bricks for the lining. However, flues can be vertical or horizontal; for vertical flues, weight must be considered. If they are too heavy or the chimney is too tall, installation and assembly will be extremely difficult.

                                                      Flue Lining Acid Castable Refractory
                                                      Flue Lining Acid Castable Refractory

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                                                        Flue Lining Using Castable Refractory

                                                        Flue temperatures are not high, but the gas pressure is high, and the flue gas volume is large. The lining is susceptible to acid erosion and water erosion due to the generation of water vapor. Therefore, careful consideration is needed when choosing castable refractory or refractory bricks for the lining.

                                                        For example, roasting furnace flues can be vertical or horizontal, and the vertical and horizontal structures are often connected. Therefore, when selecting materials for the lining, both weight and erosion must be considered. If acid bricks are used, the mortar joints will result in poor airtightness. If heavy acid-resistant castable refractory is used, it will be too heavy. If lightweight acid-resistant castable refractory is used, its erosion and scouring resistance is insufficient, which is not suitable for flue lining applications. Furthermore, since the flue lining temperature is not high, insulation is generally not required.

                                                        Therefore, semi-heavy acid-resistant castable refractory should be considered. Semi-heavy refractory has a bulk density of around 1.5, which provides resistance to erosion and scouring while also offering some insulation. Another reason is that the weight issue is also alleviated. Currently, considering market conditions and chimney characteristics, semi-heavy acid-resistant castable is an ideal material for flue linings. It is particularly suitable for use in large-diameter flues.

                                                        What is the thickness of the castable lining for a chimney?

                                                        Fluid ducts typically have small inner diameters. If acid-resistant castable lining is used, the thickness is generally less than 100mm, resulting in a significant weight reduction. However, the small diameter of the lining can cause unnecessary difficulties during construction. For flues with a diameter of less than 2 meters, using a coating material is a better alternative, as semi-heavy coating materials can be 30-50mm thick. This reduces the weight by approximately 50% compared to castable lining. For vertical flues, this further reduces the potential for excessive weight. It also facilitates construction in small-diameter flues. Therefore, semi-heavy acid-resistant coating materials are an ideal choice for small-diameter flues.

                                                        Construction of Flue Lining Refractory
                                                        Construction of Flue Lining Refractory

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                                                          Construction of Flue Lining with Castable Refractory

                                                          The construction of flue lining with castable refractory can be carried out after installation or after the lining is installed. When constructing the flue lining with castable refractory, a 3mm gap should be left between each cast section for expansion joints. The process involves applying sealant to adjacent sections of the castable refractory before pouring the next section.

                                                          Construction of Flue Lining with Castable Refractory Before Installation

                                                          Constructing the lining after installation is generally preferable. Large-diameter flue linings are easier to construct with castable refractory. However, if the large-diameter pipe is heavy, lining before installation will significantly increase the pipe’s weight, increasing installation risk and making component welding difficult. Large-diameter flue linings are best constructed after installation.

                                                          The construction of flue lining with castable refractory before installation is suitable for small-diameter flue linings due to its lighter weight. Pre-installation construction reduces the difficulty of high-altitude operations, as the refractory lining is poured on the ground, resulting in lower labor intensity and higher construction efficiency. The disadvantage is that the lining construction cannot be carried out continuously, and expansion joints are difficult to handle.

                                                          Safety is the primary concern during construction.

                                                          The primary concern in constructing flue linings using refractory lining is safety, followed by the welding of anchors and the refractory pouring method. For large-diameter flues, the anchor nails are welded first, and then the anchors are painted before proceeding with the construction in sections. Sectioning involves constructing two sections within a 180° radius, then rotating the pipe 180° to construct the third and fourth sections. If there is an insulation layer, the insulation refractory lining is constructed first, followed by the working layer of the wear-resistant refractory lining. Additionally, if two types of refractory lining are used, the construction must also be carried out in four sections. However, a 12-hour break must be observed after each section is completed before proceeding to the next section. The lower half is poured first, and then the flue is rotated on the ground to pour the remaining half.

                                                          Lining Construction on the Ground

                                                          If lining construction is carried out on the ground, pipe openings must be straightened and anti-deformation measures implemented. This is to prevent pipe opening deformation due to weight differences during construction and rotation. Areas prone to deformation during refractory lining construction should not be constructed initially; lining should be applied to these areas after other parts are completed.

                                                          For pipe bends, expansion joints, and valves, refractory lining should be applied in sections, with expansion joints reserved in both horizontal and vertical directions. For lower-lying areas, inclined formwork can be used for refractory lining, followed by vibration to ensure compaction, and excess material should be removed tangentially. In areas with limited space or high construction joints, refractory lining should be applied using a flat butt joint, with a 3mm high-temperature resistant ceramic fiber felt sandwiched within the joint before welding.

                                                          What Type of Refractory Castable is Best for a Kiln Operating at 1500℃?

                                                          When the operating temperature of a kiln is 1500℃, corundum castable should be selected based on the temperature. However, many users don’t understand this and think that because it’s expensive, they should choose general high-alumina castable.

                                                          However, if the operating temperature is directly at 1500℃, general high-alumina castable is not suitable. Brown corundum castable is required to meet the requirements. Some users have suggested using steel fiber castable. However, this is also not an option because steel fibers begin to melt above 1300℃. Therefore, steel fiber castable cannot be used.

                                                          However, some users suggest using stainless steel, but this is also not suitable. Because the lining only uses rust as an anchor, it does not provide high-temperature resistance or corrosion resistance. Corundum castable is characterized by the highest bulk density, the lowest apparent porosity, and good high-temperature resistance, corrosion resistance, and thermal shock resistance. Moreover, the characteristics of corundum castable are fully realized at 1500℃. If steel fiber castable is used, it cannot withstand temperatures up to 1500°C. General high-alumina castables, however, can be used at temperatures of 1300°C-1400°C.

                                                          However, for different kilns with varying gas fields and degrees of corrosion, corundum wear-resistant castables or high-strength wear-resistant castables can be selected. This provides both high-temperature resistance and corrosion resistance. For example, in waste incinerators, the temperature is not high, but the degree of corrosion is strong, sometimes involving both acid and alkali corrosion. In such cases, corundum castable is unsuitable because the temperature is too low for the corundum to be fully utilized. Using clean, wear-resistant castables can resist acid or alkali corrosion. Moreover, they are cheaper than corundum castables, making them cost-effective and suitable for the special conditions of incinerators.

                                                          In short, regardless of the material of the refractory castable chosen, it is essential to select the appropriate refractory castable based on the specific kiln, temperature, and degree of corrosion.

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