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Mar 18 2026
Refractory Materials for Aacid Slag-Based Electric Arc Furnace Linings

In the high-temperature smelting process of an electric arc furnace with intense charge movement, the refractory lining of the furnace is an essential guarantee for the normal operation of the process. Based on the type of slag and the properties of the refractory materials used, electric arc furnaces can be divided into acidic slag electric arc furnaces and basic slag electric arc furnaces. Most of the aforementioned electric arc furnaces used in steelmaking are basic slag electric arc furnaces, with a slag basicity greater than 1. Since acidic slag does not have desulfurization and dephosphorization effects, the application of acidic slag electric arc furnaces is currently limited in my country. Currently, the furnace linings mostly use basic refractories with good resistance to basic slag, such as magnesia-carbon bricks and magnesia-chrome bricks. Therefore, my country produces a very large amount of basic slag as a byproduct each year. It is estimated that in 2019, the slag produced in my country’s electric arc furnace steelmaking production was approximately 0.2 billion tons. Such a large accumulation of slag, if not properly handled, could cause environmental pollution due to the heavy metals such as chromium, lead, and cadmium it contains, posing a significant potential threat to biological health and the balance of the ecological environment.

Refractory Materials for Aacid Slag-Based Electric Arc Furnace Linings
Refractory Materials for Electric Arc Furnace

Refractory Materials for Lining Acidic Slag-Based Electric Arc Furnaces

The slag in acidic slag-based electric arc furnaces is acidic, and the lining uses acidic or neutral refractory materials. Compared to basic slag, acidic slag is more environmentally friendly. When the SiO2 content in acidic slag is high, it forms acidic silicate slag with a microstructure similar to glass. This is an amorphous, non-crystallizing material that cools slowly, i.e., glassy slag (hereinafter referred to as “glass slag”). Some studies suggest that when amorphous silicate materials are corroded in an acidic environment, the inconsistent dissolution of oxides causes the silicate surface to form a silicon-rich protective layer. This fixes harmful metals in the slag, and the higher the degree of vitrification (amorphous material content), the better the fixation effect. This significantly reduces the risk of environmental pollution and harm to animal and plant health. Based on this characteristic, many industrial waste treatment processes, such as leather industry waste treatment and waste incineration fly ash treatment, are suitable for this high-temperature vitrification process, which is an effective method for fixing metal pollutants. Meanwhile, this glass slag can also be reused as a raw material for preparing microcrystalline glass. The vitrification process of acidic slag has been proven to be a successful example of the harmless treatment and reuse of waste resources.

Acidic slag-based electric arc furnace smelting can be used for the recovery and harmless treatment of valuable metals in secondary resources. One very important smelting process is the electric arc furnace smelting of waste automotive exhaust purification catalysts. Waste automotive exhaust purification catalysts mainly consist of a carrier component (composed of oxides such as γ-Al₂O₃ or cordierite) and an active component (composed of three precious metals: platinum, palladium, and rhodium). After crushing and finely grinding the catalyst, it is mixed with trapping metals, flux, and a small amount of coke, granulated, and then smelted in an electric arc furnace. This utilizes the principle that trapping metals such as iron or copper have a strong affinity for platinum group metals in the catalyst at high temperatures (above 1420 °C). This process enriches the precious metal active components in the catalyst within the molten metal, while the catalyst support components, along with added fluxes such as SiO2 and CaO, form slag that enters the glass slag, achieving efficient and harmless recovery of valuable metal resources. Depending on the attractant and flux composition, the electric arc furnace operates at varying temperatures, reaching up to 1600 °C. At this temperature, the scouring motion of the furnace charge on the refractory material is quite intense. Furthermore, carbon is added during smelting to reduce the oxides of the target metal, creating a reducing atmosphere in the furnace, thus placing high performance requirements on the furnace lining refractory material of the electric arc furnace. Existing refractory materials have a short service life in the aforementioned electric arc furnaces; in pilot-scale small electric arc furnaces, the lining needs to be replaced approximately every two months, limiting the industrial application of this process. This paper addresses the problem of short lining service life in electric arc furnace smelting of acidic slag-based refractory materials, analyzing the mechanism of acidic glass slag corrosion of refractory materials. It also reviews the development and research of refractory materials suitable for high-temperature acidic slag-based electric arc furnaces both domestically and internationally in recent years. The feasibility of these materials in high-temperature acidic slag-based electric arc furnaces was analyzed, and the future development trend of refractory materials for acidic slag-based smelting furnaces was prospected.

The Corrosion Mechanism of Acidic Glass Slag on Refractory Materials

The corrosion of refractory materials by molten slag is a complex process involving many influencing factors. These include the chemical composition and pH of the molten slag and refractory materials, the viscosity and surface properties of the molten slag, the melting atmosphere, the physical properties of the refractory materials (porosity, high-temperature flexural strength, etc.), and the solubility limits of their components in the molten slag (i.e., the concentration of refractory components in the molten slag at saturation). Furthermore, unlike other melting furnaces, electric arc furnaces use a high-temperature electric arc to heat the furnace charge, and the resulting electromagnetic field significantly affects the properties of the molten slag. For example, it alters the wettability and penetration kinetics of the molten slag on refractory materials, influencing the formation and distribution of different phases, thus affecting the erosion of refractory materials by the molten slag. Currently, there is little research, both domestically and internationally, on the influence of the electromagnetic field of electric arc furnaces on the erosion of refractory materials by acidic glassy molten slag. The erosion of refractory materials by glass slag can be divided into two types: penetration erosion and chemical corrosion.

Current Status of Research on Refractory Materials for Acidic Slag-Based Electric Arc Furnaces

Currently, research on the slag erosion resistance of refractory materials largely relies on high-temperature erosion resistance tests to simulate the erosion of refractory materials by molten slag during industrial production, in addition to using refractory materials that have failed in actual industrial production. The quality of refractory material’s slag resistance is evaluated using indicators such as the rate of mass change before and after the test, the erosion rate of the molten slag, and the penetration rate. High-temperature erosion resistance tests can be divided into two types: static and dynamic methods. The difference lies in whether an external force is applied to keep the molten slag flowing relative to the refractory material. The most widely used static method is the static crucible method. This method requires simpler equipment and operation, and the molten slag only statically penetrates and dissolves the refractory material. It is suitable for refractory materials whose erosion is mainly caused by the dissolution of components in the molten slag. Dynamic erosion resistance tests are more suitable for refractory materials with more complex erosion processes.

Application of Refractory Materials in High-Temperature Acidic Slag-Based Electric Arc Furnaces (1600 ℃)

Based on the corrosion mechanism of acidic glassy molten slag (glass slag) on ​​refractory materials, and assuming their potential application in acidic slag-based electric arc furnaces, this paper reviews the research results on the resistance of several refractory materials (Al2O3-SiO2 materials, Al2O3-SiO2-ZrO2 composite materials, chromium-containing materials, densified zirconium (chromium)-containing materials, carbonaceous and carbide materials) to glass slag corrosion, summarizing their advantages and disadvantages. The feasibility of applying these refractory materials in high-temperature acidic slag-based electric arc furnaces (1600 ℃) was discussed, and the following conclusions were drawn:

  • (1) Al2O3-SiO2 refractory materials have poor high-temperature corrosion resistance and are not suitable for high-temperature acidic slag-based electric arc furnaces.
  • (2) Chromium-containing refractory materials have excellent resistance to glass slag corrosion, but due to the toxicity of Cr, which can easily cause environmental hazards, their use should not be expanded.
  • (3) Carbonaceous and carbide refractories have high thermal conductivity and poor insulation performance, which can lead to a significant increase in energy consumption of electric arc furnaces.
  • (4) Al2O3-SiO2-ZrO2 composite refractories have good resistance to glass slag corrosion, and the densification process further enhances their corrosion resistance. In addition, the feasibility of using 41# (containing 41% ZrO2) fused cast zirconia-corundum bricks in high-temperature acidic slag-based electric arc furnaces (1600 ℃) has been preliminarily demonstrated.

Currently, with the gradual increase in public awareness of environmental protection and the strict implementation of national environmental protection policies, researchers will focus on improving and developing environmentally friendly and energy-saving refractory materials without affecting service life. The structure and properties of the slag in high-temperature acidic slag-based electric arc furnaces are similar to those of the glass melt in glass melting furnaces and other vitrification furnaces. The development of refractory materials for high-temperature acidic slag-based electric arc furnaces can fully draw on the industrial application experience of both. It is foreseeable that, represented by 41# fused cast zirconium corundum refractory, densified zirconium-containing materials with excellent resistance to glass melt corrosion will become a widely used furnace lining material for high-temperature acidic slag-based electric arc furnaces.

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Mar 3 2026
Rongsheng Well Block Refractory Material – Quality Guaranteed

A seat brick is a refractory brick installed at the bottom of a steel ladle to fix the nozzle brick. The well block refractory brick is square in shape, hence also called a square brick. Its functions are to fix the nozzle position, facilitate nozzle removal and installation, support the lower end of the stopper rod during pouring, and ensure that the stopper rod slides along the curved surface towards the nozzle after pouring to cut off the flow.

Rongsheng Well Block Manufacturer
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    Application and Classification of Well Block Refractory Bricks

    Well block refractory bricks are mainly used in conjunction with nozzles in continuous casting tundishes. They are mostly used at the bottom of the ladle and tundish to protect the internal nozzles and permeable bricks. Well block refractory bricks have high corrosion resistance and are used in conjunction with zirconium sizing nozzles.

    Initially, well block refractory bricks could be made of clay, high-alumina, or unfired high-alumina materials. Later, well block refractory bricks were classified according to changes in the usage environment and the materials used:

    • (1) Al2O3-Cr2O3 well block refractory bricks. Original high-alumina well block refractory bricks had poor heat spalling resistance. Using corundum as the main raw material, adding appropriate amounts of alumina, spinel, chromium oxide, etc. to the matrix can produce Al2O3-Cr2O3 well block refractory bricks with good heat spalling resistance and strong corrosion resistance. This material has a long service life and can be used synchronously with the ladle. Currently, most well block refractory bricks used are Al2O3-Cr2O3 well block refractory bricks.
    • (2) Magnesia well block refractory bricks. Precast well block refractory bricks were prepared by adding fused corundum powder (below 1μm) and magnesium oxide to the original alumina base material. Because the material is an alumina castable containing magnesium oxide, the cement content is extremely low, increasing the service life by 40%. The main reasons are: the fine corundum powder containing magnesium oxide densifies the matrix, improving erosion resistance; the matrix density and low cement content increase the material’s high-temperature strength, enhancing its resistance to thermal shock and mechanical spalling; and the magnesium oxide and alumina in the matrix largely form spinel at high temperatures, thus inhibiting slag penetration and improving erosion resistance. The magnesia base bricks are precast, reducing brick joints and simplifying construction.
    Nozzle Well Block Refractory Bricks
    Nozzle Well Block Refractory Bricks

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      Characteristics of Nozzle Well Block Refractory Bricks

      1. High-Temperature Corrosion Resistance: Refining steel ladles requires extremely strict temperature and time control, often exceeding 1750℃.
      2. High-Temperature Abrasion Resistance: Forced stirring is used in various ladle refining methods, which severely impacts the high-temperature abrasion resistance of the well block refractory bricks.

      Well Block Refractory Bricks Installation

      Before installing the well block refractory bricks at the taphole, the bottom should be leveled with ramming material to ensure the taphole cylinder and the masonry layer are on the same plane. When laying separate well block refractory bricks, the mating surfaces of each brick must be evenly coated with mortar. The inner holes of the well block refractory bricks must be uniform; on-site correction is necessary if required to ensure proper installation of the taphole tube bricks. Considering that the well block refractory bricks consist of multiple pieces, ramming material should be filled from both sides simultaneously around the taphole well block refractory bricks to prevent rotation.

      Main Components of  Permeable Bricks, Nozzle Well Block Refractory Bricks, and Castables

      In the steelmaking industry, steelmakers commonly use refractory materials such as permeable bricks, nozzle well block refractory bricks, electric furnace covers, castables, guide sand, and magnesia-carbon bricks in their ladles and refining furnaces. These refractory materials differ significantly in their main components and additives. Chemically, refractory materials are composed of minerals, such as corundum, mullite, and magnesia. Their main components include alumina and magnesia.

      The main components of refractory materials are the matrix components that constitute their refractory properties and form the basis of their characteristics, directly determining the properties of the finished refractory product. For example, permeable bricks require high-quality ore and are manufactured through strict and reasonable processes to ensure that the service life of the permeable bricks used by steelmakers meets requirements. The main components of refractory materials can be oxides (alumina and magnesia, etc.) or elements or non-oxide compounds (carbon, silicon carbide, etc.).

      Based on the properties of their main components, refractory materials can be classified into three categories: acidic, neutral, and basic. Acidic refractories mainly contain acidic oxides such as silicon dioxide, with silicic acid or aluminum silicate as the primary components. They will form salts under high temperatures and alkaline conditions. Basic refractories mainly contain magnesium oxide and calcium oxide. Common refractory products include guide sand and ladle slide plates. Neutral refractories are strictly speaking carbonaceous and chromium-based refractories. High-alumina refractories (alumina content greater than 45%) tend towards acidic neutrality. Chromium-based refractories are alkaline but tend towards neutrality. Common high-alumina refractories include permeable bricks, nozzle well block refractory bricks, and electric furnace covers.

      Rongsheng Refractory Materials Factory researches, develops, produces, and sells permeable bricks, nozzle well block refractory bricks, castables, and other refractory materials. With patented formulas, unique designs, and strict adherence to every process standard, we provide high-quality refractory lining materials for high-temperature industrial furnaces. Contact Rongsheng to get free samples and quotes.

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        Feb 16 2026
        Causes and Preventive Measures for Cracking in Glass Kiln Lip Bricks

        Glass Kiln Lip Bricks are a relatively special type of irregularly shaped refractory material. Their service life is affected by every aspect, including the raw material composition, forming and manufacturing process, and assembly. Especially during the hammering and ignition processes, the bricks must withstand temperature differences of hundreds of degrees Celsius. Therefore, whether using a single brick or combining several lip bricks, cracking is a potential problem. The causes of cracking in lip bricks and preventative measures are listed below.

        Refractory Bricks for Glass Furnaces
        Refractory Bricks for Glass Furnaces

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          • ① The brick material itself has low compressive strength, poor thermal stability, and a high coefficient of thermal expansion. When subjected to thermal shock, the tensile strength of the brick is less than the expansion thermal stress, causing it to break. To eliminate this factor, in addition to designing a good formula and selecting good materials, the contact surfaces between the fixing screws and the retaining iron used to fix the lip brick and the lip brick should be padded with flexible material, and the iron parts should not directly contact the brick body.
          • ② The firing temperature is low, and the dehydration stage of crystal water is short. During the high-temperature dehydration process of the crystal water inside the brick body, the original structure is destroyed and new minerals are generated. To avoid this situation, in addition to avoiding components with a large amount of mineral structural water when determining the lip brick formula, the brick blank must be fully dried after casting before being fired in the kiln. Furthermore, the heat preservation time should be increased in the dehydration temperature range of crystal water according to the mineral composition.
          • ③ The lip brick is backed by the tail brick, and there are fixing screws on the front and sides acting on the brick body. When heated, forces from four directions act on the local area of ​​the brick body. The fixing screws restrict the expansion and movement of the brick body, but they can also easily cause the brick body to crack under external forces. Preventive Measures: After the lip brick is fixed to the overflow port support, secure the support with jacking screws and bolts, but do not tighten it completely; leave an expansion gap. Then, heat it with fire, slowly raising the temperature to above 700℃ to allow the lip brick to fully expand. Tighten the jacking screws again before the lead-in.
          • ④ Insufficient pre-use baking time prevents the removal of free water from the brick. To eliminate this factor, place the lip brick in a high-temperature environment before use to fully remove free water, or preheat the kiln during on-site construction.
          • ⑤ Using deformed lip brick supports may cause cracks or even breakage of the lip brick. Therefore, deformed lip brick supports, especially those with deformed contact surfaces with the lip brick, should not be used.

          Lip Brick Replacement

          After a period of operation in a rolled glass production line, if defects appear in the glass due to erosion or wear of the lip brick, it needs to be replaced.

          Before replacing the lip brick, it must be baked at a high temperature for at least 72 hours to remove free water remaining in the brick due to processing, transportation, or other reasons. Baking can be done using a natural drying method: the brick is placed next to the kiln, relying on the heat emitted by the kiln for baking. Because it is natural baking, it requires a long time and can only remove some free water, so the baking is not thorough. Alternatively, a preheating furnace baking method can be used. A kiln is built with refractory materials, and the lip brick is heated according to a heating curve, baked at 200-300℃ for 24 hours, and then assembled to the overflow port. After the calender is positioned and installed, the temperature is further increased to 1100℃ for the lead-in operation. This method requires specialized hoisting and installation tools. It is also more difficult to operate at high temperatures, but it ensures that the lip brick will not crack. Online baking can also be used: after the lip brick and calender are positioned and installed at the forming port, they are baked using a spray gun. This method uses gradual heating, allowing sufficient time for the free water and crystal water in the lip brick to be fully drained. This method reduces the probability of the lip brick cracking or even shattering.

          Before replacing the lip brick, prepare the following tools: pipe wrench, Allen wrench, wrench, pliers, level, measuring tape, 1-3mm sheet metal, square timber, mullite fiber paper, etc.

          When removing the lip brick from the calender, first use a sledgehammer and pneumatic hammer to remove the old lip brick. Then, use an electric scraper to clean the tail brick thoroughly, ensuring there is no residual glass or unevenness on the surface. After applying a 3-5mm thick layer of high-temperature mullite fiber paper to the contact surface of the tail brick, assemble the lip brick on the lip brick support as required, or install the lip brick already assembled on the support at the tail brick location. Finally, push the calender into position, check for any problems, and then slowly heat the lip brick to the guide plate with a spray gun to complete the replacement operation.

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            Feb 1 2026
            Splicing of Glass Kiln Lip Bricks

            Glass Kiln Lip Bricks used in rolled glass forming can be made from a single piece or from several bricks joined together. The choice between a single brick and several bricks depends on many subjective and objective factors, such as brick quality, brick cost, production cycle, glass specifications, and operator skill level. The basic principle is to ensure product quality, prevent defects during use, and guarantee durability.

            Glass Kiln Lip Bricks
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              Solid Lid Brick

              The length of the solid lip brick is determined by the length of the calendering roll. The advantages of using a solid lip brick are:

              1. Not limited by glass specifications, meeting the cutting needs of various glass sizes;
              2. Good stability during operation, with virtually no displacement or tilting;
              3. Compact, stable, and robust assembly with the support structure.

              The disadvantages are: It is prone to breakage, with severe cases showing 4-5 cracks. The brick is relatively long and heavy, and assembly and transportation are inconvenient due to space constraints.

              Two Lip Bricks Joined Together

              A set of lip bricks consists of two pieces joined together, each piece being half the length of the calendering roll.

              The advantages of using two pieces are:

              1. It distributes the various forces acting on the lip brick, reducing the probability of cracking;
              2. Each brick is lighter, making assembly, transportation, and movement easier.

              However, using two pieces together has many disadvantages, including:

              1. It is difficult to guarantee the quality of the assembly, mainly due to larger joints between the bricks and the tendency for misalignment to occur on the upper surface of the lip brick, resulting in overall unevenness;
              2. During operation, the brick joints often widen, tilt, shift, or even misalign;
              3. The assembly process is time-consuming and labor-intensive.

              There are three methods for splicing two lip bricks together:

              • Method 1: Make semi-circular grooves downwards on both sides of the splicing surface of the lip bricks, 10mm from the top plane of the lip. After splicing the two bricks, the semi-circular grooves on both sides will form a circular hole. Fill the hole with mortar, ensuring it is completely filled. After fixing both sides, place it near the kiln and bake at high temperature for a period of time. At this point, the refractory mortar inside the hole will have dried and solidified. If the bricks expand when heated, the resulting cylindrical refractory material will not fall off, sealing the joint between the two bricks. Therefore, no air enters, reducing the release of air bubbles and minimizing the impact on the temperature of the surrounding molten glass.
              • Method 2: Soak ceramic fiber paper (<1mm thick) in molten glass, then apply it to one side of the lip brick, and then align them together. After completion, bake it near the kiln.
              • Method 3: Dry splicing. Join two well-fitting lip bricks together, ensuring the gap between them is less than 1mm, and then tighten them with screws on both sides before use.

              Three-Piece Lip Brick Assembly

              A set of lip bricks consists of three pieces joined together. The middle piece is 2-2.2m long, and each of the two ends has a lip brick joint of 250-350mm.

              Advantages:

              1. The two joints release more of the compressive force generated by the expansion of the lip bricks, reducing the probability of cracking.
              2. The length of the middle brick can meet the production needs of various glass sizes.

              Disadvantages:

              1. The structure is unstable, making it difficult to guarantee the quality of the splicing. Misalignment on the upper surface of the lip bricks at the joints can make expansion and contraction of the glass difficult.
              2. There is a possibility of tilting or displacement during operation.
              3. More fastener installation work is required during online assembly, resulting in a longer cycle time.

              Whether used as a single piece or in combination of multiple lip bricks, the lip bricks must be assembled, installed, and fixed to a support frame. Production lines using brick-making calenders initially employed online assembly. However, after a period of trial and error, it was found that online assembly was neither convenient nor guaranteed in terms of quality. Therefore, many companies now use offline assembly, where the assembled bricks are transported to the overflow port by a mobile trolley and installed at the outlet. Production lines using integrated brick-making calenders also use offline assembly, where the lip bricks are assembled and fixed to a support frame outside the production line, and then hoisted and installed as a whole onto the calender frame.

              When assembling lip bricks, the upper flat working surface serves as the reference horizontal plane. By processing the brick material or adding leveling shims at the bottom, the lip brick is ensured to be horizontal, with its contact surface with the tail brick perpendicular to the horizontal surface. The joint between lip bricks must be straight and as small as possible, less than 1mm after assembly. There should be no misalignment of the lip brick tips; the tips should be kept in a straight line along the tangent direction. The curved surfaces of the assembled bricks must be on the same plane, without any misalignment or stepped formations. Mullite fiber paper must be used to separate the lip brick from the tail brick, the lip brick from the edge brick, and the lip brick from the support. The center longitudinal direction of the lip brick should be aligned with the production line, the tangent direction parallel to the edge, and the normal direction perpendicular to the top plane of the lip brick.

              Online assembly of lip bricks involves high-temperature operation in a confined area. Besides the long operation time (approximately 1-2 hours), the assembly quality of the lip bricks and supports, and the supports and calenders, is inferior to offline assembly. It also negatively impacts the kiln temperature regime.

              Offline assembly offers a better working environment, lower labor intensity for workers, and doesn’t interfere with brick-changing time. It allows ample time and space for assembly, enabling precise positioning of the lip brick’s front-to-back and left-to-right spacing with the rollers. If bricks or steel components are unsuitable, they can be processed offline, ensuring the assembly quality of the lip bricks and supports, and the supports and calenders, saving brick loading time. Brick changing can be completed quickly with minimal kiln temperature changes, facilitating rapid production recovery. However, once the integrated brick-making calender is positioned, the relative position of the tail brick cannot be moved, lacking a means to handle defects. In actual production, damage can occur on both sides during the lead-in operation, especially for those accustomed to using a pull-in lead-in system. Once the edge is damaged, the machine must be replaced, and the tail brick must be replaced along with the lead-in brick. Separating the lip brick and tail brick involves long working hours, a poor working environment, and high labor intensity. The heat-resistant steel lip brick support integrated with the brick machine has poor deformation resistance, is prone to bending at high temperatures, and is difficult to restore for reuse after deformation, resulting in waste.

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                Jan 17 2026
                Lip Bricks for Rolled Glass Production

                Lid bricks used in rolled glass production are classified into various types based on their material, including low-porosity clay, zircon mullite, α-β corundum, sillimanite, and fused silica. Currently, most solar rolled glass production lines use lip bricks made of zircon mullite, sillimanite, and α-β corundum.

                Rongsheng Zircon Mullite Bricks
                Rongsheng Zircon Mullite Bricks

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                  Zircon-Mullite Lip Bricks

                  The main components of zircon-mullite lip bricks are ZrO₂≥6%, Al₂O₃≥75%, SiO₂≤18%, and Fe₂O₃≤0.5%. They are made from industrial alumina (or high-alumina bauxite) and zircon as raw materials, mixed, shaped, dried, and then fired at high temperatures in a shuttle kiln using a reaction sintering process. Zircon-mullite lip bricks possess a dense crystal structure, high mechanical strength at high temperatures, good wear resistance, good thermal shock stability, low reheat shrinkage and high-temperature creep, and extremely high chemical stability and resistance to alkaline media erosion. Their room temperature compressive strength is ≥100MPa, load softening start temperature is ≥1670℃, bulk density is 2.8g/cm³, and air cooling performance is ≥10 cycles. Due to their good wear resistance, long service life, short debubbling time, and minimal impact on the forming after lip wear, zircon-mullite lip bricks offer high cost-effectiveness. Therefore, it is increasingly used in solar rolled glass production lines.

                  Rongsheng Sillimanite Bricks for Glass Kilns
                  Rongsheng Sillimanite Bricks for Glass Kilns

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                    Sillimanite Lid Bricks

                    Sillimanite, with the molecular formula Al₂O₃·SiO₂, has a theoretical chemical composition of 62.93% Al₂O₃ and 37.07% SiO₂. Typically, sillimanite’s mineral composition contains ≥55% Al₂O₃, ≤37% SiO₂, and ≤5% Fe₂O₃, TiO₂, CaO, MgO, Na₂O, K₂O, etc., making it a high-quality, high-alumina raw material. Sillimanite undergoes irreversible transformation into 83.96% mullite (3Al₂O₃·2SiO₂) and 16.04% silicate glass phase during high-temperature sintering at 1500–1750℃, a process known as sillimanization. Mullite-treated sillimanite can be used to prepare high-density clinker with a porosity of less than 3%. This clinker, after being pulverized, can be used to make refractory materials, including lip bricks. Lid bricks made of sillimanite can be used in high-temperature operations up to 1650℃, and have advantages such as high high-temperature strength, low porosity, good volume stability and thermal shock resistance, and resistance to molten glass corrosion. Therefore, sillimanite lip bricks are also used in solar rolled glass production lines.

                    α-β Alumina Bricks
                    α-β Corundum Bricks

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                      α-β Corundum Lip Bricks

                      Corundum lip bricks are made from raw materials containing ≥94% alumina, ≤1.2% Na₂O, and ≤0.02% Fe₂O₃, through high-temperature alumina melting and casting in an electric arc furnace at temperatures above 2000℃. α-β corundum products consist of α-alumina and β-alumina, with their interlocking crystals forming a very dense microstructure, exhibiting excellent alkali resistance. In temperature ranges below 1350℃, its resistance to glass melt erosion and scouring is better than that of zirconia corundum bricks, possessing excellent mechanical strength and a long service life. Because it contains almost no impurities such as Fe₂O₃ and TiO₂, the matrix glass phase is extremely low, with a porosity ≤2% and a bulk density of 3.4 g/cm³. It produces very few bubbles or other foreign matter when in contact with molten glass, making it the best material for producing lip bricks. However, α-β corundum lip bricks suffer from poor thermal stability, are prone to cracking, and are expensive, limiting their widespread use in solar rolled glass production lines.

                      Regardless of the lip brick material, its appearance quality must meet the following requirements: the upper surface must be smooth and flat, free of molten holes. The lip brick edge must not have cracks, not gaps, or defects. The working surface and all contact surfaces must be finely ground to a precision of ±0.5mm, and the lip brick’s curvature must be consistent.

                      Processing Before Lip Brick Assembly

                      After the lip bricks arrive at the rolled glass manufacturing plant, if their length exceeds the required length or their surface is not smooth, they need to be processed to the required size using a cutting machine or ground.

                      • ① First, cut the lower edge of the lip brick. This should be done gradually and repeatedly to ensure a smooth, flat surface with good curvature.
                      • ② When processing the upper surface of the lip brick, it should also be done gradually and repeatedly to ensure a smooth, flat surface.
                      • ③ The bottom of each lip brick must be flat to maintain the stability of the lip brick and the brick frame support.
                      • ④ After pre-assembling the lip bricks, ensure that the contact area between the lip brick tips is less than 1mm. If the connection is not tight, grinding is required. The back of the lip brick should be as tight as possible while ensuring a tight fit, requiring a gap of less than 1.5mm.
                      • ⑤ Ensure that the inner dimensional tolerance of the lip brick is no greater than 5mm.
                      • ⑥ Based on the condition of the lip brick, use an aluminum alloy ruler and ink lines to clearly mark the areas where the lip brick tips will be processed. ⑦ Place the processed lip bricks near the kiln and bake for at least 72 hours.
                      • ⑧ Secure the baked lip bricks with clamps on a lip brick support, install the edge bricks, and fix them in place.
                      • ⑨ Precautions for processing lip bricks:
                        1. When cutting lip bricks, leave approximately 5mm of length for processing.
                        2. Use a pneumatic brick grinder for rough processing, and an electric angle grinder with a diamond wheel for fine processing.
                        3. When processing the contact surface of the lip brick, repeated up-and-down finishing is required. Be careful to control the force applied; do not use excessive force.
                        4. When high precision is required for the contact surface of the lip brick, it must be manually ground with a whetstone; do not use an electric angle grinder.
                        5. When using a pneumatic angle grinder, pay attention to the orientation of the lip brick to prevent small brick pieces and dust from directly hitting your face. Wear protective gear to prevent facial injury.
                        6. Handle lip bricks gently, ensuring the lip tip does not touch the ground. Lay cardboard on the ground to prevent damage.
                        7. Because lip brick processing is delicate work, it takes one to two days. Therefore, the processing of lip bricks must be carried out in a timely manner so that they can be installed and used immediately once the calendering machine is replaced.

                      Buy high-quality glass kiln lip bricks, such as zircon mullite bricks, sillimanite bricks, α-β Corundum Bricks, etc. Fused AZS Bricks for glass kiln, please feel free to contact Rongsheng Refractory Factory now!

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                        aluminabricks 0 Comments
                        Jan 2 2026
                        Production Process of Mullite-Sillimanite Bricks

                        Rongsheng Refractory Factory lists several production processes, formulas, and molding techniques for mullite refractory brick products. (For reference only)

                        Mullite-Sillimanite Bricks

                        Using Shandong calcined shale as aggregate, sillimanite, high-alumina bauxite, and binding clay as fine powders, and sulfite pulp waste liquor as a binder, mullite-sillimanite ceramic kiln furniture can be manufactured.

                        The raw material composition is as follows: 55% calcined shale clinker particles <3mm; 45% finely ground sillimanite, high-alumina bauxite clinker, and binding clay (<0.088mm). (Of which: 10% sillimanite, 22% high-alumina bauxite, 13% clay); 3% water; 1% sulfite pulp waste liquor (density 1.2g/cm3).

                        Particle size distribution (%): >5mm, 3; 5~2mm, 25; 2~0.5mm, 24; 0.5~0.088mm, 9.5; <0.088mm, 38.5; Moisture 9.0.

                        The order of adding materials for clay mixing is: granular material, binder and water, then fine powder. Mixing time is 10 minutes.

                        After drying, the green body is fired in a downdraft kiln at 1370℃.

                        The physicochemical properties of the product are as follows: Al₂O₃ 51.9%, SiO₂ 43.9%. Apparent porosity 23%, bulk density 2.27 g/cm³. Compressive strength 38.2 MPa, load softening temperature 1520℃. Thermal shock resistance (1100℃, water cooling) > 20 cycles.

                        Mullite-sillimanite bricks, used as pusher bricks in a ceramic pusher kiln, show no deformation or wear after approximately 25 uses.

                        Sillimanite Bricks
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                          Sillimanite Bricks

                          Sillimanite bricks can be manufactured using synthetic mullite, high-alumina bauxite clinker, and coke clinker as aggregates, with Jixi sillimanite as the matrix, employing equipment and processes used for clay brick production.

                          The raw material proportions are as follows: sillimanite 45-50%, mullite + coke clinker + Grade II high-alumina bauxite 35-50%, Grade I high-alumina bauxite 5-10%, and clay 5-10%. The above raw materials are weighed according to the proportions and mixed in a mixer. Granular materials are added first, followed by the binder, and after thorough mixing, fine powder is added and mixed for 10 minutes. The moisture content of the clay is controlled at 3-3.5%.

                          Sillimanite bricks are formed using a friction brick press with a capacity of 300t or higher, with the green body density controlled at 2.53g/cm³ or higher. The formed green bodies are then dried in a tunnel drying kiln. The drying kiln inlet temperature is 40-50℃, and the outlet temperature is 150-200℃. Drying time is 8-10 hours, with residual moisture not exceeding 0.5%. The firing temperature of the sillimanite bricks is 1350-1400℃, with a holding time of 8-10 hours.

                          The main physicochemical properties of the sillimanite bricks are as follows: Al₂O₃ 61.45%; SiO₂ 35.15%. Apparent porosity 15.3%; bulk density 2.58 g/cm³. Compressive strength at room temperature 123.4 MPa; linear change after reheating at 1500℃ for 2 hours +0.17%; creep rate at 1450℃ for 50 hours 0.72%; thermal shock resistance (1100℃ to water cooling) greater than 15 cycles.

                          Sillimanite Rotary Tube

                          The rotary tube is the main working component of a glass tube drawing machine. Its working conditions are harsh; it must withstand the erosion and scouring of molten glass at 1150℃, and it must also operate while rotating. Therefore, the product must possess strong resistance to molten glass corrosion.

                          Sillimanite rotary tubes can be manufactured using Shandong premium grade coke as aggregate, and Jixi sillimanite and purple clay as fine powders.

                          The ingredient ratio is as follows: coke 60-65%, sillimanite 20-30%, clay 5-10%, plus 1.5% sulfite pulp waste liquor and 4% water.

                          The mixture is kneaded in a wet mill, with the following order of addition: coke, water, sulfite pulp waste liquor, clay, and sillimanite. The kneading time is 10 minutes. Clay particle size (%): >0.84mm 13-18, 0.84-0.50mm 15-20, 0.50-0.08mm 20-25, <0.08mm 40, Moisture 6%.

                          Formed by pneumatic hammer tamping, with a working air pressure of 0.39-0.49 MPa. After drying, the residual moisture content of the green body is <1%. The product is fired in a down-draft kiln at a maximum firing temperature of 1370℃ for 48 hours.

                          The physicochemical properties of the product are as follows: Al₂O₃ 49%, SiO₂ 47%. Apparent porosity 15.7%, load softening temperature 1550℃. Room temperature compressive strength 149.7 MPa. The product is ready for use after polishing.

                          Sillimanite Bowl

                          The bowl is the main working component at the bottom of the clarification tank of a glass melting furnace, used for the outlet of molten glass used to produce bottles and jars. Sillimanite bowls can be manufactured using sillimanite concentrate and clay as raw materials.

                          The raw material ratio is as follows: sillimanite concentrate 3-0.5mm 30-40%, 0.5-0.088mm 20-30%, <0.088mm 20-30%; clay 8-12%, plus 3% sulfite pulp waste liquor.

                          Mixing is carried out in a mixing mill. According to the clay ratio, first add granular materials and dry mix for 1 minute, then add binder and mix for 3 minutes, then add fine powder and mix for 4-6 minutes. The clay moisture content is controlled at 3-3.5%. The green body is formed under a pressure of 14.7 MPa, dried at 40-60℃ for 3-4 days, and fired at 1450℃.

                          The main physical properties of the product are as follows: apparent porosity 22.5%, bulk density 2.07 g/cm³, room temperature compressive strength 83 MPa, load softening temperature 1320℃, and thermal shock resistance (1100℃, water cooling) 18 cycles.

                          Sillimanite Balls

                          Sillimanite filler balls for blast furnace hot blast stoves can be manufactured using high-alumina bauxite clinker and Jixi sillimanite concentrate as raw materials, and soft clay and sulfite pulp powder as binders.

                          The raw material ratio is as follows: high-alumina bauxite clinker particles, 0.9-0.5mm, 55%; high-alumina bauxite clinker fine powder, <0.074mm, 15%; sillimanite fine powder, <0.045mm, 20%; binder clay fine powder, <0.074mm, 10%; and added pulp powder, <0.28mm, 5%.

                          The sillimanite fine powder, high-alumina bauxite clinker fine powder, and clay fine powder are ground together in a vibratory mill for 10-15 minutes according to the ratio. Mixing is carried out in a wet mill. First, add the high-alumina bauxite clinker, then add an appropriate amount of water, mix for 2-3 minutes, and then add the pulp powder. After mixing for 1 minute, add the fine powder and mix for another 7-10 minutes, maintaining a moisture content of 5-17%. Dry the shaped green body at 60-80℃ for 8-10 hours, ensuring residual moisture is <2%. Firing temperature is 1500℃, held for 10-12 hours.

                          Main physical properties of the product: Apparent porosity 25.41%, bulk density 2.45 g/cm³, room temperature compressive strength 54 MPa, softening temperature under load 1450℃, thermal shock resistance (water cooling at 1100℃) >30 cycles.

                          Rongsheng Andalusite Bricks Supplier
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                            Andalusite Bricks

                            Andalusite bricks, made from andalusite as aggregate and high-alumina bauxite clinker, sillimanite, and fine clay powder as matrix, can be used to manufacture torpedo iron ladles.

                            Andalusite is crushed and graded for later use. High-alumina bauxite clinker and clay are mixed and ground finely in a vibrating ball mill. The raw material ratio is as follows: andalusite 50-55%, sillimanite 15-25%, high-alumina bauxite 15-20%, and clay 5-10%. The mixture is kneaded using a roller mill, adding large and medium particles first and dry-mixing for 2-3 minutes, then adding the binder and co-ground powder, with a total kneading time of 15 minutes.

                            The particle size distribution of the clay is: 3-2mm 25%, 2-1mm 15%, 1-0.5mm 6.5%, 0.5-0.088mm 10.5%, <0.088mm 43%. After being conditioned for 25 hours, the clay was formed using a 630t friction brick press, resulting in bricks with a density of 2.65-2.75 g/cm³. The finished bricks were dried and then fired in a tunnel kiln at a maximum firing temperature of 1350℃ for 8 hours.

                            The main physical properties of the finished bricks are: bulk density 2.48 g/cm³, apparent porosity 13.7%, room temperature compressive strength 110.8 MPa, load softening temperature 1560℃, creep rate (1350℃, 50h) 15%, reheat linear change (1450℃, 2h) 0.07%, and thermal shock stability (1100℃ water cooling) >30 cycles.

                            Sillimanite-Silicon Carbide Shelving Bricks

                            Sillimanite-silicon carbide shelving bricks can be manufactured using silicon carbide sand as aggregate, sillimanite and clay as matrix, and sulfite pulp waste liquor as binder. The formula is as follows: silicon carbide (grade 1) 50-65%, sillimanite 15-35%, clay 10-15%. The particle size distribution of the clay is as follows: 3-2mm 12-20%, 2-1mm 15-24%, 1-0.5mm 10-12%, 0.5-0.088mm 20-25%, <0.088mm 30-35%.

                            The clay is mixed in a mixing mill. The feeding sequence is: first add silicon carbide particles, then add sulfite pulp waste liquor, mix evenly, and then add the mixed fine powder. Continue mixing for 10 minutes before discharging. The moisture content of the clay should be controlled at 3-4%.

                            The molding process is carried out on a 500t hydraulic press, with a green body density of not less than 2.65 g/cm³. The green body is dried at 40℃ for 3 days, with residual moisture content less than 1%. Firing can be carried out in a down-draft kiln at 1430℃, with a holding time of 8-16 hours and a total firing time of 90 hours.

                            The physical properties of the sillimanite-silicon carbide kiln floor bricks are as follows: apparent porosity <21%, bulk density 2.30-2.35 g/cm³, compressive strength >35.2 MPa, load softening temperature >1520℃, and thermal shock resistance (1100℃, water cooling) >8 cycles.

                            This product can be used as floor bricks in ceramic tunnel kilns fired at 1370℃. It exhibits good thermal conductivity, thermal shock resistance, oxidation resistance, simple production process, and low cost, and can replace high-alumina floor bricks.

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                              aluminabricks 0 Comments
                              Dec 18 2025
                              High-Purity Electrofused Mullite Castable Precast Refractory for Steel Rolling Heating Furnaces

                              The working conditions of certain critical components of industrial kilns, such as high-temperature burner bricks, burner brick upper crossbeams, and the furnace bottom of steel rolling mills, are extremely harsh. The working temperatures of burner bricks and burner brick upper crossbeams often exceed 1500℃, subjecting them not only to high-temperature melting damage but also to the impact of high-speed flame gas flow, their own weight, and the load-bearing capacity. The erosion of iron oxide scale and molten slag mainly damages the furnace bottom of steel rolling mills. In industrial furnaces with frequent start-ups and shutdowns, these components are subjected to stress damage caused by rapid heating and cooling.

                              Only refractory materials that are both resistant to high temperatures and possess excellent thermal shock stability can meet these requirements. Phosphate castables, high-alumina cement castables, and refractory plastics failed to achieve the desired results. After repeated experiments, high-purity electrofused mullite castable precast refractory achieved satisfactory results.

                              Theoretical Basis for Material Selection of Precast Refractory Castables in Steel Rolling Heating Furnaces

                              Why is high-purity electrofused mullite chosen as the main raw material? This is determined by the properties of mullite. Mullite is the only stable compound in the Al₂O₃-SiO₂ binary system. From the Al₂O₃-SiO₂ phase equilibrium, it can be seen that the composition of mullite is between 3Al₂O₃·2SiO₂ and 2Al₂O₃·SiO₂. The composition (by weight) of mullite (A₃S₂) itself is 72.8% Al₂O₃ and 28.2% SiO₂. The composition of the saturated solid solution is 78% Al₂O₃ and 22% SiO₂. That is, the mullite solid solution can contain up to 6% Al₂O₃. Compare the properties of solid solutions in this range below, and the typical composition of mullite 3Al₂O₃·2SiO₂. It has a high melting point (1910℃), high hardness, low high-temperature creep value, and good resistance to chemical corrosion.

                              Sources of Mullite Raw Materials

                              Natural mullite is rare among natural minerals. Only extremely small quantities of β-mullite and γ-mullite have been found, and their production is far from meeting the large-scale needs of production. Furthermore, the veins are generally very thin, difficult to mine, and the purity is often insufficient, making them rarely usable.

                              Fused Mullite Refractory Raw Material
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                                There are two methods for the artificial synthesis of mullite: ① sintering method; ② electrofusion method.

                                The sintering method involves finely grinding the raw materials required for mullite synthesis, forming them into pellets, and then calcining them at high temperatures in a kiln. Impurities inevitably enter during the production process, and it is difficult to reach the ideal high temperature during calcination, resulting in incomplete reactions, poor crystallization, and poor high-temperature stability.

                                The electrofusion method for producing mullite involves strictly mixing raw materials such as industrial alumina, sintered high-quality bauxite, high-purity silica, and silica in a specific ratio, then loading them into an electric arc furnace. After melting at temperatures above 1850℃, the mixture is slowly cooled and crystallized. Because an electric arc is used as the heat source, very few impurities are introduced during the electrofusion process. As long as the purity of the raw materials is controlled, the product quality is relatively easy to manage, and high-purity electrofused mullite can be produced. The quality of high-purity electrofused mullite raw materials is the guarantee of the quality of the finished product.

                                Performance of High-Purity Electrofused Mullite Castable Precast Refractory

                                The main characteristic of high-purity electrofused mullite castable Precast Refractory is its excellent thermal shock resistance. Their thermal shock resistance is significantly better than that of other refractory materials. However, their compressive strength is not high, reaching only 51 MPa, while their thermal shock resistance is several times that of other refractory materials. This may be because the mullite crystal phase forms primary bonds at 850℃, producing a needle-like interstitial layer, which blocks the fracture layer that occurs within the Precast Refractory during surface water cooling tests. Therefore, high-purity electrofused mullite castable Precast Refractory can withstand thermal shock damage when used in steel rolling furnaces.

                                How to Improve Thermal Shock Resistance in Corundum-Mullite Castables?

                                Corundum-mullite castables are characterized by high load softening temperature and good creep resistance among high-temperature refractory materials. However, pure corundum products have a relatively large coefficient of thermal expansion, resulting in less than ideal thermal shock resistance. Pure mullite products, on the other hand, have a smaller coefficient of thermal expansion and better thermal shock resistance.

                                Rongsheng Corundum Mullite Refractory Castable
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                                  Corundum-mullite castables are composed of mullite and corundum phases. When the mass ratio of mullite to corundum is 75:25, it coincides with the eutectic melting point at 1840℃ in the SiO2-Al2O3 phase. Therefore, a mullite to corundum ratio of 75:25 is optimal for improving thermal shock resistance. This is because mullite has a lower coefficient of thermal expansion than corundum, and the coefficient of thermal expansion in composite materials is always greater for the former than the latter. The thermal expansion mismatch between mullite and corundum within the composite material leads to microcracks, increasing the material’s fracture absorption energy and thus improving the castable’s thermal shock resistance.

                                  Using a low eutectic point aggregate composition can negatively impact the creep resistance of castables, as the creep rate is minimized at this point. When the mullite to corundum ratio is approximately 75:25, the aggregate significantly affects the product’s coefficient of thermal expansion and thermal expansion mismatch. When microcracks develop in the castable, they propagate under thermal shock stress, simultaneously causing transgranular fracture of the aggregate and consuming a large amount of energy. This inhibits the propagation of the main crack and also affects the thermal shock stability of the corundum-mullite castable.

                                  Of course, corundum castables also exhibit good thermal shock resistance. This is because the different aggregate-to-binder ratios lead to variations in thermal shock stability. The coefficient of thermal expansion of corundum-mullite castables significantly impacts thermal shock stability; microcracks caused by thermal expansion mismatch can actually improve the castable’s thermal shock resistance.

                                  In summary, a mullite-to-corundum ratio of 75:25 in the process mix provides the best thermal shock stability. An apparent porosity of around 20% is highly beneficial for the thermal shock stability of castables. Therefore, controlling the apparent porosity of corundum-mullite castables to around 20% further enhances thermal shock stability.

                                  Rongsheng Refractory Materials Manufacturer offers environmentally friendly, professional, fully automated monolithic refractory material production lines, specializing in the production of integral refractory castable linings for high-temperature industrial furnaces. Our newly commissioned factory also specializes in producing various precast refractory components. If your industrial furnace requires lining material replacement or lining repair, Rongsheng’s professional technical team can customize a lining material solution based on the actual operating conditions of your industrial furnace. Contact Rongsheng for a free quote and solution.

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                                    aluminabricks 0 Comments
                                    Dec 5 2025
                                    Refractory Configuration and Optimization for a 5000t/d Clinker Line (3)

                                    Refractory materials are developing towards environmental friendliness, strong adaptability, and long service life. Rongsheng Refractory Materials Factory supplies refractory materials for kilns used in 5,000 t/d clinker production lines. Rongsheng Refractory Materials Manufacturer leverages its innovative capabilities in refractory castables while focusing on customer needs, aiming to provide high-quality, long-life refractory lining materials for high-temperature industrial furnaces. Contact Rongsheng for free solutions.

                                    Refractory Lining Configuration for a 5,000 t/d Cement Clinker Production Line

                                    This article focuses on the refractory configuration for a 5,000 t/d cement clinker production line. The cement firing system involves a complex chemical process from raw meal to clinker, going through stages such as preheating in the preheater, decomposition in the calciner, high-temperature calcination, and cooling. The refractory materials used in each stage must be adapted to this process.

                                    Analysis of Certain Defects in the Current Configuration and Improvement Plans

                                    (1) Preheater System

                                    1. Severe scaling at the smoke chamber and precalciner necking, impacting ventilation.
                                      • Cause: The production line was designed to produce 5,000 tons per day, but actual production typically reached 5,500 tons, resulting in an overload of over 10%. This increased the kiln’s thermal load and the likelihood of scaling at the kiln tail. Furthermore, the increased use of anthracite and low-quality coal resulted in less than ideal combustion, increasing the likelihood of incomplete combustion and the rate of scaling. In short, scaling can be caused by a variety of factors, including operational factors, fuel, and raw material issues. In severe cases, it can lead to the cessation of rotary kiln operation.
                                      • Improvement Plan: In actual production, scaling at the kiln tail is not limited to the smoke chamber, but can sometimes extend to the precalciner necking and the fifth-stage drum discharge chute. Therefore, it is recommended to expand the scope of anti-scaling castables, such as using anti-scaling castables throughout the entire section below the fifth-stage drum discharge chute.
                                    Anti-Scaling Refractory Castable
                                    Anti-Scaling Refractory Castable

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                                      1. The castables on the top of the cyclone and decomposition furnace are prone to falling off, posing a production safety hazard.
                                        • Causes: Poor anchorage and welding quality, design flaws, and excessively rapid cooling can all cause the top castables to fall off, resulting in numerous fatalities on the production line.
                                        • Improvement Solution: Correct the design flaws, eliminate the calcium silicate board interposition, and use only lightweight castables. Use ceramic anchors and anchor bricks, etc.
                                      1. The kiln tail tongue is prone to damage.
                                        • Cause: Due to the erosion of high-temperature materials and corrosion from the kiln tail flue gas, the steel plate under the kiln tail tongue is easily damaged, which in turn damages the kiln tail tongue, significantly impacting kiln operation.
                                        • Improvement Solution: Use prefabricated components and eliminate the bottom steel plate to extend service life.
                                      1. Small-scale repairs are labor-intensive and time-consuming.
                                        • Cause: After two years of operation in a new kiln, some refractory materials in the preheater system may be partially damaged. Because the preheater is hollow, scaffolding must be erected during construction, which reduces maintenance time.
                                        • Improvement plan: Using spray paint for construction can save time and energy, and should be promoted vigorously.

                                      (2) Rotary Kiln System

                                      1. The kiln mouth castable is easily damaged, resulting in a long construction time.
                                        • Cause: Because the kiln mouth is prone to deformation, the castable is currently cast as a single piece. However, the casting cycle is long, and the baking time may be insufficient. As a result, the kiln mouth refractory cycle is significantly lower than that of other parts of the kiln.
                                        • Improvement: Using plastic castables eliminates the need for formwork, saving construction time. Curing and baking are unnecessary, making it suitable for routine maintenance.
                                      Magnesia Aluminum Spinel Bricks
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                                        1. Firing zone magnesia-chrome bricks does not meet environmental requirements.
                                          • Cause: Magnesia-chrome bricks react easily with sulfur in cement rotary kilns, generating some toxic hexavalent chromium ions, which can cause water pollution. Consequently, European countries have imposed very strict restrictions on the production and use of magnesia-chrome bricks.
                                          • Improvement: Using dolomite bricks, magnesia-iron spinel bricks, and magnesia-alumina spinel bricks.
                                        1. Spinel bricks have a large thermal conductivity, causing the kiln body temperature to rise.
                                          • Cause: Spinel bricks are currently used near the No. 2 wheel rim and have a good service life. However, their main drawback is their high thermal conductivity, which increases the drum temperature and poses a risk to kiln operation. This also results in significant heat loss.
                                          • Improvement: Use high-quality silica-molybdenum bricks.
                                        Rongsheng Silicon Carbide Mullite Bricks
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                                          (3) Short Burner Head Life

                                            • Cause: Due to the harsh operating environment of the coal injection pipe, such as large temperature differences, a thin refractory layer, a strong reducing atmosphere, and high-temperature radiation, the head has a short service life.
                                            • Improvement: The head is prefabricated and manufactured in advance, with adequate curing and baking, for optimal performance.

                                          (4) The top castable of the kiln hood is prone to partial detachment

                                          Cause: See the top of the preheater.

                                          (5) Cooler System

                                          1. Susceptible Wear of the Low Wall
                                            • Cause: The high-temperature clinker exiting the rotary kiln is directly rubbed against the low wall during cooling, and the alternating contact between hot and cold air causes rapid wear of the low wall.
                                            • Improvement: Use highly wear-resistant castables.
                                          1. Susceptible detachment of the top castable
                                            • Cause: See the top of the preheater.

                                          (6) Tertiary air duct bends are prone to wear.

                                            • Cause: The hot air from the kiln head cooler contains a large amount of clinker particles, which rub against the castable at the bend. Typically, castables only last three months.
                                            • Improvement: Use highly wear-resistant castables.

                                           

                                          (The end)

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                                            Nov 20 2025
                                            Refractory Configuration and Optimization for a 5000t/d Clinker Line (2)

                                            Refractory materials are developing towards environmental friendliness, strong adaptability, and long service life. Rongsheng Refractory Materials Factory supplies refractory materials for kilns used in 5,000 t/d clinker production lines. Rongsheng Refractory Materials Manufacturer leverages its innovative capabilities in refractory castables while focusing on customer needs, aiming to provide high-quality, long-life refractory lining materials for high-temperature industrial furnaces. Contact Rongsheng for free solutions.

                                            Refractory Lining Configuration for a 5,000 t/d Cement Clinker Production Line

                                            This article focuses on the refractory configuration for a 5,000 t/d cement clinker production line. The cement firing system involves a complex chemical process from raw meal to clinker, going through stages such as preheating in the preheater, decomposition in the calciner, high-temperature calcination, and cooling. The refractory materials used in each stage must be adapted to this process.

                                            (3) Kiln Head Hood

                                            The kiln head hood connects the rotary kiln to the cooler and serves as the inlet for kiln air and tertiary air. Air pressure is extremely unstable, making positive pressure a common feature of the entire kiln system. Gas temperatures range from 800-1300°C, with significant temperature fluctuations. Furthermore, the impact of clinker particles is intense, making the top and inlet areas susceptible to damage. Therefore, thermal shock resistance and wear resistance should be considered when selecting materials.

                                            1. High-Alumina High-Strength Wear-Resistant Castable

                                            Amount: 180 tons

                                            Technical Performance:

                                            Application Location: Round top

                                            1. Calcium Silicate Board

                                            Amount: 7.2 tons

                                            Technical Performance: See above

                                            Application Location: All refractory linings

                                            (4) Burner

                                            Because the burner is located in the high-temperature gas between the kiln mouth and the cooler, and the pulverized coal burns near the burner head, it is significantly affected by the high-temperature radiation and reducing atmosphere. The chemical composition of coal significantly influences combustion, making the burner head plate susceptible to damage. The refractory material used in this area requires high refractoriness and wear resistance, as well as enhanced thermal shock stability and spalling resistance.

                                            RS Mullite Castable Manufacturer
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                                              1. Mullite Castable

                                              Quantity: 5 tons

                                              Technical Performance:

                                              Application Area: Burner head hood where it enters the kiln

                                              (5) Rotary Kiln

                                              As a rotating drum that calcines raw materials into clinker at high temperatures, the lifespan of its refractory materials often determines the production cycle, making it a key and challenging aspect of refractory material management in cement plants. After preheating and approximately 90% decomposition, the raw material enters the kiln from the kiln outlet, where its temperature gradually rises to over 1450°C, completing the calcination process and entering the cooler. A 74-meter rotary kiln can be broadly divided into five thermal stages. Because the refractory materials within the rotary kiln must be fixed to the continuously rotating drum, the strength of the refractory bricks must not fall below a certain threshold due to the following factors:

                                              1. There is a certain degree of slippage or sliding tendency between the refractory bricks and the shell, generating friction. The refractory bricks must possess a certain strength to resist damage from this friction.
                                              2. A rotary kiln is not an absolutely rigid structure when viewed axially. Because the rotary kiln drum has a certain curvature between its support points, it experiences periodic bending in sync with its rotation during operation. Because the three-roller rotary kiln utilizes a statically indeterminate structure, the different expansion rates of each roller group due to temperature differences can cause deviations in the kiln shell’s coaxiality, generating significant additional loads. Furthermore, the 4% inclination of the kiln shell also generates downward stress during rotation.
                                              3. The shell is not a perfect circle in the radial direction, but rather an elliptical shape. Deformation is greatest at the wheel belts, and this deformation places additional pressure on the refractory bricks. Due to the kiln’s own weight and rotation, the kiln undergoes periodic elliptical deformation, synchronized with the rotation, placing alternating loads on the refractory bricks. When this deformation or elliptical deformation reaches a certain value, it can exceed the internal stresses in the refractory bricks, causing premature failure. Therefore, refractory materials with insufficient strength must be used in rotary kilns; they must meet basic strength requirements.
                                              4. In addition to the aforementioned mechanical stresses, the refractory materials within the kiln are also subject to the effects of high-temperature gases and liquid clinker. It can be roughly divided into five or six working zones, which require different refractory materials for laying.

                                              Refractory Configuration for a 5,000-ton Rotary Kiln:

                                              1. Mullite Castable

                                              Usage: 15 tons

                                              Technical Performance: See above (RT-70MC)

                                              Applicable Area: 0-0.6 m

                                              1. High-Abrasion-Resistant Bricks

                                              Usage: 8 tons

                                              Technical Performance:

                                              Applicable Area: 0.6-1.6 m

                                              RS Direct Bonded Magnesia Chrome Bricks
                                              RS Direct Bonded Magnesia Chrome Bricks

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                                                1. Direct-Bonded Magnesia-Chrome Bricks

                                                Usage: 340 tons

                                                Technical Performance:

                                                Applicable Area: 1.6-25 m/35-45 m

                                                Spinel Refractory Bricks
                                                Spinel Refractory Bricks

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                                                  1. Spinel Bricks

                                                  Usage: 99 tons

                                                  Applicable Area: 25-35 m

                                                  1. Anti-Spalling Bricks

                                                  Usage: 242 tons

                                                  Applicable Area: 45-73.2 m

                                                  1. High-Alumina Castables

                                                  Usage: 8.5 tons

                                                  Technical Performance: See above

                                                  Applicable Area: 73.2-74 m

                                                  (6) Cooler

                                                  The cooler uses air to cool the hot clinker leaving the kiln from 1400°C to below 80°C. Due to the large temperature difference between the front and rear sections, the most vulnerable parts are concentrated in the front wall and the lower wall. Furthermore, the overhanging beams at the interface with the kiln head are also susceptible to premature damage due to the erosion of high-temperature gases.

                                                  Grate coolers are stationary relative to the refractory shell, so insulation materials with low strength but low thermal conductivity can be used on the outer layer. The cooler’s inner surface must withstand thermal erosion and high-temperature abrasion caused by contact with high-temperature clinker at 300-1450°C, so the selected refractory materials must have strong wear resistance. Furthermore, the first stage cooler must also withstand high thermal loads.

                                                  Because the grate cooler has large vertical walls, the use of special anchoring refractory bricks is crucial when constructing the refractory brickwork to strengthen the connection between the bricks and the shell to prevent collapse of the vertical walls.

                                                  Currently, the most commonly used refractory castables are:

                                                  1. High-strength alkali-resistant castable

                                                  Usage: 20 tons

                                                  Technical properties: See above (RT-13NL)

                                                  Application: Section 3 and top

                                                  1. High-alumina castable

                                                  Usage: 106 tons

                                                  Technical properties: See above (RT-16)

                                                  Application: Section 2 and 3 side walls and parapet

                                                  1. High-heat high-alumina castable

                                                  Usage: 183 tons

                                                  Application: Cooler front wall and Section 1 parapet

                                                   

                                                  (To be continued…3)

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                                                    Nov 5 2025
                                                    Refractory Configuration and Optimization for a 5000t/d Clinker Line (1)

                                                    Refractory materials are developing towards environmental friendliness, strong adaptability, and long service life. Rongsheng Refractory Materials Factory supplies refractory materials for kilns used in 5,000 t/d clinker production lines. Rongsheng Refractory Materials Manufacturer leverages its innovative capabilities in refractory castables while focusing on customer needs, aiming to provide high-quality, long-life refractory lining materials for high-temperature industrial furnaces. Contact Rongsheng for free solutions.

                                                    Refractory Lining Configuration for a 5,000 t/d Cement Clinker Production Line

                                                    This article focuses on the refractory configuration for a 5,000 t/d cement clinker production line. The cement firing system involves a complex chemical process from raw meal to clinker, going through stages such as preheating in the preheater, decomposition in the calciner, high-temperature calcination, and cooling. The refractory materials used in each stage must be adapted to this process.

                                                    (1) Preheater System

                                                    This system utilizes kiln exhaust gas to gradually heat the raw meal from ambient temperature in a suspended state to above 750°C before entering the precalciner system for decomposition. The amount of refractory material used in this system accounts for nearly two-thirds of the total refractory material used. Its thermal characteristics are:

                                                    1. 60% of the fuel and the preheated raw meal are thoroughly mixed in the precalciner for flameless combustion. Wall and flue gas temperatures are generally controlled below 1000°C. The temperatures of the other cyclones, from the first to the fifth stage, are not higher than 450°C, 650°C, 750°C, 900°C, 1000°C, and 1100°C, respectively.
                                                    2. The preheater system calcines the material with virtually no liquid phase, resulting in minimal agglomeration and sintering, and therefore requires less refractoriness. Furthermore, the overall system temperature is relatively stable, requiring less thermal shock resistance from the refractory material.
                                                    3. The preheater system is a stationary device, but its size is relatively large, requiring insulation materials with low thermal conductivity to reduce the outer shell temperature.
                                                    4. Due to the complex shape of the preheater system, including cones, cyclone inlet and outlet diameter changes, thin feed pipes, and numerous measuring holes, it is more convenient to use on-site formed refractory castables in these areas.
                                                    5. When using raw materials and fuels with high alkali content, the refractory materials in the preheater must withstand not only high-temperature corrosion but also chemical attack from alkali metal oxides.

                                                    The aforementioned thermal environment generally determines the configuration of refractory materials for each stage of the preheater, and the following principles should be followed:

                                                    1. Refractory materials with low thermal conductivity, good insulation, and a working surface with sufficient strength and resistance to alkali corrosion should be used.
                                                    2. Castables should be used for sections with complex shapes and a large number of thin pipes, while alkali-resistant bricks should be used for straight tubes and regular sections.
                                                    3. Different materials should be designed for different sections based on the different temperatures of the cyclones and to save costs. For example, for the first and second stage cyclones, a combination of refractory and insulation considerations can be considered, and clay-based alkali-resistant refractory materials can be selected. For preheaters below the third stage, alkali-resistant materials capable of temperatures exceeding 1100°C should be used.
                                                    4. Anti-scaling castables should be used for the refractory castables from the fifth stage to the smoke chamber and below the calciner, as the surface is prone to scaling.

                                                    The following is a brief introduction to the selection and dosage of refractory materials for the preheater of a 5000t/d production line:

                                                    Alkali Resistant Bricks for Rotary Kiln
                                                    Alkali-Resistant Bricks for Rotary Kiln

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                                                      1. RK-H High-Strength Alkali-Resistant Bricks

                                                      Quantity: 569 tons

                                                      Performance:

                                                      Application Areas: Vertical ascending flues, cyclone tubes, and cones

                                                      High-Strength Alkali Resistant Castable
                                                      High-Strength Alkali-Resistant Castable

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                                                        1. High-strength alkali-resistant castable

                                                        Usage: 850 tons

                                                        Performance:

                                                        Construction method:

                                                        Application: Tops of preheater stages 1-4, irregular shapes, etc.

                                                        RS High-Alumina Low-Cement Castable
                                                        RS High-Alumina Low-Cement Castable

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                                                          1. High-alumina low-cement castable

                                                          Usage: 200 tons

                                                          Performance:

                                                          Application: Precalciner, fifth-stage drum

                                                          1. Anti-scaling castable

                                                          Usage: 112 tons

                                                          Performance:

                                                          Application Area: Kiln tail flue chamber

                                                          1. Calcium Silicate Board

                                                          Consumables: 156 tons

                                                          Performance:

                                                          Application area: All refractory linings

                                                          (2) Tertiary Air Ducts

                                                          Tertiary air ducts utilize high-temperature, oxygen-rich gases from the kiln head to guide the ducting channels of the precalciner. At temperatures of 800-900°C, these gases contain a large amount of clinker particles, which can severely erode and wear the refractory materials at the bends. Therefore, the system’s alkali resistance and wear resistance must be considered. High-strength alkali-resistant bricks and calcium silicate board are used in the straight sections, while high-wear-resistant castables and calcium silicate board are used in the irregular sections.

                                                          Currently, two types of tertiary air ducts are used: parallel ducts and V-shaped ducts. Parallel ducts are arranged almost parallel to the kiln, while V-shaped ducts are V-shaped, with a settling chamber and discharge gate valve located at the lower end of the duct.

                                                          Parallel ducts are simple in design, aesthetically pleasing, and require minimal investment. However, to prevent clinker particles from settling in the tertiary duct, higher operating air velocities are required, resulting in greater resistance in the tertiary duct. This higher air velocity also requires higher wear resistance from the refractory materials. The V-type duct is more complicated and requires a large investment. It also requires regular dust discharge from the discharge gate valve. However, the V-type duct can adopt a lower operating wind speed, so the system resistance is low, and the wind speed wear is small.

                                                          The refractory material usage and performance requirements are as follows:

                                                          1. RK-H High-Strength Alkali-Resistant Bricks

                                                          Usage: 140 tons

                                                          Performance: See above

                                                          Application: Straight sections of air ducts

                                                          1. Ultra-High-Strength Wear-Resistant Castable

                                                          Usage: 70 tons

                                                          Performance:

                                                          Application Area: Tertiary duct bends and gates

                                                          1. Calcium Silicate Board

                                                          Consumables: 17 tons

                                                          Performance: See above

                                                          Application Area: All refractory linings

                                                           

                                                          ( To be continued…2)

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