China Henan Rongsheng Xinwei New Materials Research Institute Co., Ltd Company News

1.Introduction Ceramic fiber products are increasingly favored in construction due to their unique properties. These fibers are crafted from alumina-silicate materials through various production techniques, providing solutions for modern engineering challenges.   2.Advantages of Ceramic Fiber Products Thermal Insulation Ceramic fibers excel in high-temperature environments, maintaining stability and performance even under extreme conditions. This makes them ideal for insulation in industrial furnaces and kilns. Energy Efficiency By minimizing heat loss, ceramic fiber products contribute to energy conservation, reducing the overall operational costs in buildings and industrial processes. Lightweight and High Strength Despite their lightweight nature, ceramic fibers possess remarkable strength, ensuring ease of installation and long-term durability. This characteristic also allows for innovative architectural designs and structural solutions. Chemical Resistance These fibers exhibit excellent resistance to chemical attacks, making them suitable for environments exposed to corrosive substances, thus prolonging the lifespan of the construction materials. Sound Absorption With inherent sound-absorbing properties, ceramic fiber products contribute to acoustic management in buildings, creating quieter and more comfortable living and working spaces.   3.Applications in Construction and Engineering Building Insulation Ceramic fiber products are used extensively for insulating walls, roofs, and floors, enhancing thermal efficiency and comfort in residential and commercial buildings. Industrial Uses In industries such as petrochemical, steel, and glass manufacturing, these fibers are utilized in high-temperature insulation, furnace linings, and fire protection systems. Sustainable Construction The eco-friendly nature of ceramic fibers aligns with sustainable construction practices, as they are often manufactured from recycled materials and contribute to reduced energy consumption. 4.Future Prospects As construction and engineering industries continue to evolve, the adoption of ceramic fiber products is expected to rise, driven by the demand for high-performance, energy-efficient, and sustainable building materials. Continuous advancements in material science will further enhance the properties and applications of these versatile fibers.   Ceramic fiber products are set to play a crucial role in the future of construction and engineering, offering solutions that meet the demands of modern infrastructure while promoting sustainability and efficiency.

Refractory raw materials are essential in many industrial processes because they maintain stability at high temperatures. Here, we will detail the five classification methods to help you better understand these materials. Refractory raw materials come in various types, and there are multiple ways to classify them. Overall, there are six classification methods. PART 01: Classification by Chemical Composition Refractory raw materials can be divided into oxide and non-oxide materials. With modern scientific and technological advancements, some organic compounds have become precursor materials or auxiliary raw materials for high-performance refractories. PART 02: Classification by Chemical Properties According to their chemical properties, refractory raw materials can be divided into: Acidic Refractory Raw Materials: Examples include silica and zircon. Neutral Refractory Raw Materials: Examples include corundum, bauxite (slightly acidic), mullite (slightly acidic), chromite (slightly alkaline), and graphite. Basic Refractory Raw Materials: Examples include magnesia, dolomite, and magnesia-calcium sand. PART 03: Classification by Production Process Role Based on their role in the production process of refractories, raw materials can be classified as primary or auxiliary materials. Primary Raw Materials: These form the main body of the refractory materials. Auxiliary Raw Materials: These can be further divided into binders and additives. Binders: Used to provide sufficient strength during production and use. Common binders include sulfite pulp waste liquid, pitch, phenolic resin, aluminate cement, water glass, phosphoric acid and phosphates, and sulfates. Some primary raw materials also act as binders, such as binding clay. Additives: Used to improve production or construction processes or to enhance certain properties of refractory materials, such as stabilizers, water reducers, inhibitors, plasticizers, foaming agents, dispersants, expansion agents, and antioxidants. PART 04: Classification by Acidity and Alkalinity Refractory raw materials can be classified into five main categories based on their acidity and alkalinity. Acidic Materials: Mainly silica-based materials, such as quartz, cristobalite, tridymite, chalcedony, flint, opal, quartzite, and diatomaceous earth. These materials contain at least 90% silicon dioxide (SiO2), with some pure materials having over 99% SiO2. They react chemically with metal oxides to form fusible silicates. Semi-Acidic Materials: Primarily refractory clays, which have lower free silica content compared to purely silica-based materials. Refractory clays contain 30-45% alumina, often combined with silica to form kaolinite. At high temperatures, they decompose into free silica and alumina, which further react to form mullite. Therefore, clays have weaker acidic properties than pure silica. Neutral Materials: These include chromite, graphite, and synthetic silicon carbide, which do not react with either acidic or basic slags at any temperature. Natural neutral materials include chromite and graphite. Basic Materials: These include magnesite (magnesium carbonate), dolomite, lime, olivine, serpentine, and high alumina materials. These materials resist basic slags but react with acidic slags to form salts. Special Refractory Materials: These include zirconia, titania, beryllia, ceria, thoria, and yttria. These materials have varying degrees of resistance to different slags but are limited in availability and used only in special applications. PART 05: Classification by Raw Material Origin Based on their origin, refractory raw materials can be classified into natural and synthetic categories.   Natural Refractory Raw Materials: These still form the bulk of refractory materials. Natural minerals are abundant, with the main elements being oxygen, silicon, and aluminum. Major natural refractory raw materials include silica, quartz, diatomaceous earth, clay, bauxite, kyanite, magnesite, dolomite, limestone, olivine, serpentine, talc, chlorite, zircon, and natural graphite. Most natural raw materials require purification, grading, or calcination to meet the production standards of refractory materials. Synthetic Refractory Raw Materials: These are designed to meet specific requirements for high-quality and high-tech refractory materials. Synthetic materials can have predetermined chemical compositions and structures, providing stable quality and suitability for advanced refractory products. Major synthetic refractory raw materials include magnesia-alumina spinel, synthetic mullite, seawater magnesia, synthetic magnesium silicate, sintered alumina, aluminum titanate, and silicon carbide. These materials have seen significant development in the past two decades.

Introduction Refractory materials are essential in numerous high-temperature industrial processes. With the increasing demand for high-performance and energy-efficient materials, the refractory industry is poised for significant advancements. Growing Demand for High-Temperature Applications Industries such as steel, cement, glass, and non-ferrous metals are expanding, leading to a surge in the need for materials that can withstand extreme temperatures. This growing demand drives innovation in refractory materials to meet the specific requirements of these industries. Emphasis on Energy Efficiency With a global focus on sustainability, the refractory industry is increasingly prioritizing energy efficiency. Developing energy-saving refractory materials, such as lightweight insulating bricks and high-temperature insulation wool, is crucial. These materials help reduce energy consumption, thereby contributing to environmental sustainability. Shift Towards Monolithic Refractories There is a noticeable shift from traditional shaped refractories to monolithic (unshaped) refractories. Monolithic refractories offer several advantages, including easier installation and reduced labor costs. Their versatility and ease of use make them increasingly popular in various applications. Custom Solutions and Services As industries become more specialized, the demand for custom refractory solutions grows. Companies are now offering tailored products and professional guidance to meet the unique needs of different applications. This trend underscores the importance of providing bespoke solutions to optimize performance and efficiency. Conclusion The future of the refractory material industry is shaped by the need for high-temperature resilience, energy efficiency, and customized solutions. By focusing on these areas, the industry can help reduce production costs, enhance energy efficiency, and minimize environmental impact, ensuring sustainable growth and innovation in high-temperature applications. These developments will significantly impact the industry's ability to meet evolving industrial demands while promoting sustainability and efficiency. As the industry advances, continued innovation and adaptation will be key to maintaining its critical role in various high-temperature processes.

In the field of refractory materials, refractory aggregate is a crucial component. Not only does it possess excellent refractory properties, but it also plays a key role in various high-temperature industrial environments. This article delves into the definition, classification, and applications of refractory aggregate in different fields.   PART 01 Refractory Aggregate As a core component in the field of refractory materials, refractory aggregate plays a key role in providing structural support. These aggregates are made from various refractory raw materials, such as high alumina bauxite, through stringent high-temperature calcination, fine crushing processes, or meticulous artificial synthesis techniques. Their particle size is greater than 0.088mm, exhibiting granular material characteristics.   In monolithic refractories, refractory aggregates hold a significant position, typically comprising 60%-75% of the total material composition. Consequently, the names of monolithic refractories often reflect the type of aggregate used. For instance, if high alumina bauxite clinker is used as the aggregate, the resulting refractory castable or ramming mix is correspondingly named high alumina castable or high alumina ramming mix. This naming convention highlights the decisive role of refractory aggregates in determining material properties.   The specialized manufacturing process of refractory aggregates and their substantial proportion in monolithic refractories underscore their outstanding performance in refractory properties. Whether protecting high-temperature industrial environments or producing various refractory products, refractory aggregates are indispensable, ensuring the stability and durability of the entire refractory material system.   PART 02 Classification of Refractory Aggregates Refractory aggregates, as core materials in high-temperature industries, have a professional and detailed classification system. First, from a material perspective, refractory aggregates include various types such as clay-based, high alumina, corundum, silica, magnesia, and magnesia-alumina spinel. Each type of material imparts unique high-temperature stability and chemical corrosion resistance to the aggregate, meeting the demands of different industrial environments. Further classification by porosity divides refractory aggregates into dense aggregates and lightweight aggregates. Dense aggregates, with a porosity of no more than 30%, are known for their high density and high strength. These aggregates can be further subdivided into ultra-dense aggregates, high-density aggregates, and regular dense aggregates, each excelling in refractoriness, thermal stability, and mechanical strength.   In contrast, lightweight aggregates have a porosity exceeding 45%, characterized by low density and excellent insulation properties. Lightweight aggregates can also be subdivided into regular lightweight aggregates, ultra-lightweight aggregates, and special lightweight aggregates, such as alumina and zirconia hollow spheres. These lightweight aggregates not only exhibit excellent refractory properties in high-temperature environments but also effectively reduce thermal conductivity and improve energy efficiency. PART 03 Particle Size of Refractory Aggregates The particle size of refractory aggregates is a crucial aspect of refractory material preparation, directly affecting the material's structural performance and high-temperature stability. In the formulation of monolithic refractories, aggregates are precisely classified into coarse, medium, and fine particles based on their particle size.   This classification is not arbitrary but determined by the critical particle size, or maximum particle size. For instance, for aggregates with a maximum particle size of 8mm, coarse aggregates range from 8-3mm, medium aggregates from 3-1mm, and fine aggregates from 1-0.088mm. Notably, particles smaller than 0.088mm are no longer considered aggregates but are defined as fines or matrix materials, playing a filling and bonding role in refractory materials.   An ideal particle size distribution is key to achieving the densest packing. In this ideal state, the voids left by the contact of coarse aggregates are precisely filled by medium aggregates, and the voids left by medium aggregates are further filled by fine aggregates. This sequential filling method forms a solid aggregate skeleton, with the remaining voids filled by fines. However, due to the complex and irregular shapes of refractory aggregate particles, achieving this ideal particle size distribution is challenging in actual production. Therefore, strict testing is usually required to determine the optimal aggregate size distribution. In practice, the distribution ratio of coarse, medium, and fine aggregates generally maintains a range of (35-45):(30-40):(15-25). This ratio ensures the stability of the aggregate skeleton while maximizing the density and high-temperature performance of the refractory materials.   PART 04 Shape of Refractory Aggregates The shape of refractory aggregates is a complex and diverse research area. Most refractory aggregate particles are composed of multiphase polycrystalline materials, with their shape influenced by multiple factors. Firstly, the crystal structure, crystallization habits, and impurity content of each phase in the material affect the particle shape. These intrinsic factors, like the aggregate's "genes," determine its basic shape characteristics.   Furthermore, different processing methods significantly impact the shape of refractory aggregates. For instance, mullite produced by the electrofusion method typically forms columnar polycrystalline aggregates due to its crystallization habits. During crushing, these columnar polycrystalline aggregates tend to fracture along the weaker grain boundaries, producing many columnar polycrystalline particles.   In contrast, mullite produced by the sintering method may form needle-like, columnar, plate-like, or granular shapes due to environmental constraints during crystal growth. These diverse crystal shapes intertwine during growth, resulting in highly irregular particle shapes upon crushing, such as flake, needle-columnar, or spindle shapes.   Additionally, the final shape of refractory aggregate particles is closely related to the material's density and crushing method. For example, high alumina bauxite clinker with ultra-dense and high-density properties tends to produce flake or spindle-shaped particles when subjected to impact or extrusion crushing methods. In contrast, grinding crushing methods may result in irregular granular or near-spherical particles.   Therefore, selecting the appropriate crushing method is crucial to obtaining suitable aggregate particle shapes for monolithic refractory materials. This process requires comprehensive consideration of factors such as crystal structure, crystallization habits, impurity content, and processing methods to ensure the final product's performance and quality.   PART 05 Applications of Refractory Aggregates The application of refractory aggregates is a complex field involving multiple factors, with particle shape having a particularly significant impact on construction performance. Different shapes of aggregate particles exhibit various characteristics when formulating monolithic refractory materials.   Specifically, particles with irregular shapes, such as flake, columnar, needle-columnar, and angular, exhibit relatively poor rheological properties when mixed into slurries. This is because these shapes do not allow for smooth sliding within the slurry, affecting the overall rheological properties. However, these irregular shapes offer unique advantages in certain applications. For instance, when formulating spray coatings and ramming materials, these irregular particles can interlock and form a pinning effect, enhancing bonding strength.   Conversely, near-spherical and spherical particles exhibit better rheological properties when mixed into slurries. These shapes allow for smoother sliding within the slurry, improving rheology and thixotropy, thus enhancing bulk density. Therefore, these rounded particles are ideal for formulating castables, coatings, and press-formed materials.   PART 06 As an important material in the high-temperature industrial field, refractory aggregates continually expand their performance and application range. With advancements in technology and industrial development, refractory aggregates will play an increasingly important role in future high-temperature industries. This article aims to help readers better understand the classification and applications of refractory aggregates, providing a reference for research and practice in related field.

Differences Between Refractory Castables and Refractory Plastics in Industrial Kilns Introduction: In the construction and maintenance of industrial kilns, refractory materials play a crucial role. Among these, refractory castables and refractory plastics are widely used. Although both belong to the category of refractory materials, they have unique characteristics and uses. Today, let's delve into the differences between these two materials. 1. Thermal Expansion Design Refractory castables and refractory plastics exhibit significant differences in their thermal expansion design, which directly affects the structural integrity and high-temperature stability of the kiln lining. Refractory Castables: Expansion Joints: During installation, expansion joints must be reserved, typically using PVC expansion boards. While this method accommodates the material's expansion due to temperature changes, it may impact the overall structural continuity of the kiln lining or base. Refractory Plastics: Zero Expansion Design: The design principle here is more advanced, adhering to a "zero" expansion design. This means the material formula and structural design are finely tuned to ensure that, under high temperatures, internal tensile and compressive stresses are maintained at very low levels. This design ensures the kiln lining remains highly stable in high-temperature environments, significantly enhancing the overall integrity and service life of the kiln lining. In summary, the "zero" expansion design of refractory plastics exhibits superior performance in maintaining the structural integrity of the kiln lining. 2. Thermal Shock Resistance The thermal shock resistance of refractory castables and refractory plastics also differs significantly. Refractory Plastics: Exceptional Thermal Shock Resistance: They can handle drastic temperature fluctuations within the kiln and even withstand direct flame impacts without performance degradation or structural damage. This material can endure frequent shutdowns and rapid heating processes without the risk of spalling or cracking. Its thermal shock resistance is 3 to 6 times that of ordinary refractory castables, thanks to its advanced material formulation and precise manufacturing processes. Refractory Castables: Moderate Thermal Shock Resistance: They often struggle under conditions of rapid temperature changes, with the kiln lining prone to spalling, cracking, and other issues, severely affecting the normal operation and lifespan of the equipment. Hence, from a professional perspective, refractory plastics are the ideal choice for kiln linings in high-temperature equipment due to their significant advantage in thermal shock resistance. 3. Kiln Drying Methods There are marked differences in the kiln drying processes of refractory castables and refractory plastics. Refractory Castables: Extended Curing and Drying: After construction, they require a relatively lengthy curing, aging, and drying process to achieve the desired physical and chemical properties. Control of environmental temperature and humidity is crucial, especially in winter, where strict anti-freeze measures must be taken to prevent material damage, increasing construction complexity and time costs. Refractory Plastics: Flexible and Efficient Drying: They can be constructed year-round without seasonal restrictions, significantly enhancing project scheduling flexibility. Notably, refractory plastics do not require additional curing time post-construction and can be heated and dried immediately, with a heating rate of up to 50°C per hour. Generally, the kiln temperature can reach operational requirements within 24 hours, greatly shortening the drying cycle and reducing associated costs. This efficient drying method optimizes production processes and significantly improves equipment utilization and economic efficiency. 4. Construction Techniques The construction techniques of refractory castables and refractory plastics have significant differences, affecting construction efficiency, quality control, and material lifespan. Refractory Plastics: Simplified Process: The construction process includes unpacking, molding, ramming, demolding, finishing, and direct drying. The process is designed to be simple and efficient, particularly advantageous in roof construction due to pre-loading and molding techniques, ensuring synchronous deformation of roof steel structures and linings, thus evenly distributing stress on anchor bricks and preventing breakage or roof collapse. Refractory Castables: Complex Process: The process involves precise water proportioning, mold setting, mixing, pouring, vibrating, curing, demolding, and drying. Each step requires high precision and meticulous control, as any negligence can adversely affect the final performance. Even with stringent construction methods, refractory castables are prone to secondary deformation issues after demolding, leading to uneven stress on anchor bricks and affecting the overall stability and lifespan of the kiln. 5. Quality Control in Construction Quality control during the construction of refractory castables and refractory plastics varies distinctly. Refractory Plastics: Superior Quality Stability: The material undergoes precise ratio control during production, ensuring its composition's stability and consistency. When used on-site, its uniformity and quality are effectively guaranteed, minimizing the impact of human factors on the final kiln lining quality, thereby enhancing construction quality controllability and reliability. Refractory Castables: High Complexity in Quality Control: The construction process requires precise control of additives, dry mixing, wet mixing, vibrating, and other key steps, each directly affecting the final quality. This demands extensive professional knowledge and experience to ensure accurate operations and strict quality control at every stage, making the quality control process more challenging and requiring meticulous management and precise operations to ensure the kiln lining's performance and quality. Conclusion In the construction and maintenance of industrial kilns, refractory castables and refractory plastics each have their strengths. Refractory castables, with their high flowability and robust structural support, are crucial for key areas like the kiln base and walls. On the other hand, refractory plastics, with their excellent plasticity and ease of construction, are ideal for roof repairs and emergency repairs. Understanding and leveraging the unique properties of these two materials provides strong support for the safe and efficient operation of industrial kilns.

The standard dimensions of refractory bricks are 230×114×65 mm. According to relevant regulations in China, common refractory bricks are categorized into five types: Straight bricks Side arch bricks Vertical arch bricks Vertical thick bricks Arch foot bricks The frequently mentioned standard refractory brick is a specific size within the straight bricks category. These bricks are made from refractory clay or other refractory materials and are typically light yellow with a brown hue. They can withstand high temperatures ranging from 1580°C to 1770°C and endure various chemical and physical changes and mechanical actions under such high temperatures. Different types of refractory bricks can be used together. What Are Refractory Bricks Made Of? Refractory bricks are made from refractory clay and other refractory materials. They are categorized into two types: unshaped refractory materials and shaped refractory materials. Unshaped refractory materials, also known as castables, are composed of various aggregates and binders and need to be mixed with liquids. Shaped refractory materials refer to refractory bricks, which have standard shapes and must be cut according to construction requirements. Tips for Choosing Refractory Bricks Determine Requirements: First, consider what type of bricks you need and the specific kind of refractory clay bricks you want. Choose the Right Manufacturer: When selecting refractory bricks, it is essential to choose a reliable manufacturer. Compare products from different manufacturers, not only in terms of price but also considering their reputation and after-sales service. Types and Uses of Refractory Bricks Refractory bricks can be classified based on their production process into fired bricks, unfired bricks, and fused bricks, among others. Based on shape and size, they can be divided into standard bricks, common bricks, and special-shaped bricks. These materials are widely used, for instance, in constructing blast furnaces for ironmaking or converters. The type of furnace determines the kind of bricks used. Summary of Refractory Brick Standards The standard dimensions of refractory bricks are 230×114×65 mm, representing the length, width, and height respectively. While this is the standard size, there are also non-standard refractory bricks available.

Product Specifications Size: 230mm × 114mm × 65mm Product Introduction Mullite insulating bricks, also known as lightweight mullite bricks or mullite thermal insulation bricks, are high-quality insulating refractory bricks made from high-grade bauxite clinker as the main raw material, mixed with a suitable amount of clay, additives, and water to form a plastic or slurry material, which is then extruded and fired at high temperatures. Mullite insulating bricks primarily consist of mullite (3Al₂O₃·2SiO₂) as the main crystalline phase. The alumina content typically ranges between 40% and 75%. Besides mullite, bricks with lower alumina content contain small amounts of glass phase and quartz, while those with higher alumina content contain small amounts of corundum.   Lightweight mullite insulating bricks are widely used in emerging industrial kilns and high-temperature equipment. As global energy conservation demands increase, the development of lightweight insulating materials is accelerating. Lightweight mullite bricks are ideal insulating refractory materials domestically and internationally due to their excellent chemical stability, high temperature resistance, precise dimensions, uniform structure, aesthetic appearance, and low thermal conductivity. They are extensively used in hot blast stoves, glass crucibles, metal smelting furnaces, ceramic tunnel kilns, roller kilns, electric porcelain shuttle kilns, among others, offering broad market prospects. Product Price For the prices of JM23, JM26, JM28, and JM30 mullite insulating bricks, please contact us immediately. We will provide you with the most favorable prices and high-quality products.   Product Classification Mullite insulating bricks are classified by grade into JM23, JM26, JM28, and JM30. They are also classified by density into lightweight mullite insulating bricks and corundum mullite bricks (also known as dense mullite insulating bricks). By usage temperature, they are classified into 1350°C mullite insulating bricks, 1450°C mullite insulating bricks, and 1550°C mullite insulating bricks, with the 1550°C mullite bricks capable of direct flame contact, featuring high temperature resistance, low thermal conductivity, and significant energy-saving effects.   Product Features The low thermal conductivity of mullite insulating bricks results in excellent thermal insulation. They have low heat storage and thermal conductivity, making them highly energy-efficient for intermittent operations. Low impurity content ensures high refractoriness, and high alumina content allows good performance in reducing atmospheres. High compressive strength at high temperatures ensures the stability and strength of the brickwork. Accurate dimensions speed up construction, reduce the use of refractory mortar, and enhance the strength and stability of the lining, thus extending its lifespan. Easily processed into special shapes as per customer requirements, reducing the number of bricks and joints needed. product Applications Mullite insulating bricks can be used as hot surface refractory linings or as back insulating layers for other refractory materials. They are mainly used in the tops of hot blast stoves, furnace bodies, and furnace bottoms of blast furnaces, regenerator chambers of glass melting furnaces, ceramic sintering kilns, dead corners of petrochemical cracking systems, ethylene cracking furnaces, tubular heating furnaces, ammonia converters, gas generators, high-temperature shuttle kilns, tunnel kilns, ceramic roller kilns, and pusher plate kilns, among other industrial furnaces.

The basic method for lead smelting is the sintering blast furnace method (i.e., the roasting-reduction smelting method). The furnace types include blast furnaces, lead-zinc closed blast furnaces, QSL (oxygen bottom-blown) furnaces, and KIVCET direct smelting furnaces.   Refractory Materials for Lead-Zinc Closed Blast Furnaces The lead-zinc closed blast furnace is a new type of furnace that combines lead smelting and zinc smelting to process lead-zinc oxide ores or lead-zinc mixed sulfide ores. It is a thermal device capable of directly producing lead and zinc. The lead-zinc closed blast furnace mainly consists of a closed blast furnace, a condenser (i.e., a lead mist chamber), a flue, and is connected to lead and zinc refining equipment. A standard furnace has 36 tuyeres with a tuyere area of about 10m². The working layer of the furnace hearth lining and the water-cooled panel lining of the furnace waist are generally built with magnesia-chrome bricks. The non-working layer of the furnace hearth and other parts of the furnace body are built with clay bricks and dense clay bricks. High-alumina cement refractory castables are commonly used for on-site casting of the furnace top and the inclined channels connecting the lead mist chamber, although these can also be made as precast blocks for hoisting and masonry. The bottom and top of the lead mist chamber are built with dense clay bricks or high-strength refractory castables. The side walls, which are subject to erosion by lead mist and chemical attack, deteriorate quickly and need to be built with clay-bonded silicon carbide bricks. The rotors and shafts inside the lead mist chamber are made of graphite or silicon carbide materials. Ordinary clay bricks are used for the flue and other areas.   The furnace generally has a lifespan of 3 to 4 years. The linings of the feed port, furnace waist, tuyere area, and slag line area are prone to damage and require several minor repairs during each furnace campaign. The lead mist chamber and flue have a lifespan equivalent to several furnace campaigns, but the rotor and shaft need multiple replacements. The bottom and top of the lead-zinc separation chamber are usually built with clay bricks or dense clay bricks, with the non-working layer of the side walls built with clay bricks and the working layer with magnesia-chrome bricks. The bottom of the lead trough and lead discharge trough is built with high-alumina bricks with an Al₂O₃ content of 65%, and the walls with magnesia-chrome bricks or chrome bricks. The trough can also be cast with refractory castables of the same material to form a strong integral lining. The cover plates of the trough are made of precast blocks of high-alumina cement refractory castables. The linings of the lead-zinc separation chamber and trough are in relatively good condition, suffer little damage, and can last for several furnace campaigns. The combustion chambers, heat exchanger rooms, and chimneys of the lead tower and zinc tower are generally built with clay bricks and can also last for several furnace campaigns.      

Unburned refractory bricks are refractory materials that can be directly used without firing. They have advantages such as energy saving, good thermal shock stability, and simple processing, which allow them to replace fired refractory products in a wide range of applications. Unburned refractory bricks have many characteristics different from fired refractory products in terms of processing. These are mainly reflected in the following aspects: Good Raw Material Calcination: Unburned refractory bricks do not undergo firing processes and are used directly after drying. Well-calcined raw materials can minimize volume changes during use, preventing cracking of the furnace body. Reasonable Particle Size Distribution and High Molding Pressure: It is best to use granules with a flaky or angular shape, with a ratio of granules to fine powder of 7:3 or 75:25. A molding pressure of over 630 tons with more than 6 strikes is recommended. Selection of Suitable Binders: Based on current usage, a single binder usually cannot meet the requirements, and composite binders are commonly used. Selection of Additives: Unburned bricks undergo significant shrinkage during use, and delayed sintering on the surface may cause structural flaking, reducing the performance of the bricks. This can be partially addressed by selecting appropriate additives. Control of Drying System: Proper control of the drying system is essential. The binding methods of unburned refractory materials are ceramic bonding or direct chemical bonding, where the hardening of the binder provides sufficient strength for the refractory material's use without the need for complex firing processes. The use of unshaped refractory materials eliminates the firing and molding processes, resulting in energy savings, increased production, improved product qualification rates, and reduced raw material consumption. The simplification of production processes and elimination of complex processing restrictions inherent in ceramic or direct bonding have led to improvements in certain properties. The critical particle size of ingredients for unburned bricks or unshaped materials can be appropriately increased, significantly improving the products' thermal stability. Using binders such as phosphate salts, high-purity alumina cement, tar, resin, etc., not only reduces or eliminates the introduction of foreign impurities but also enhances the performance due to the advantageous final reaction products such as Al2O3, CA2, and C formed by chemical bonding. Additionally, the use of various additives and reinforcing materials such as steel fibers can produce unburned refractory materials with excellent properties such as slag resistance, resistance to CO and H2 gases, volume stability, high thermal strength, anti-spalling, and anti-creep. The Utilization Value of Unburned Magnesia-Calcium Carbon Bricks: 1.Due to their lack of firing requirements and superior performance, as well as their flexibility in structural design, unburned magnesia-calcium carbon bricks will become the main direction of development for this series of refractory materials. 2.The development of unburned magnesia-calcium bricks is not only due to their superior technical performance but also because of their high economic benefits. 3.The use and development of unburned refractory materials are of significant importance in the current situation of energy shortage.

Magnesia-carbon bricks have been widely used in converters, electric furnaces, and ladles due to their excellent high-temperature resistance, slag corrosion resistance, and good thermal shock stability, making them highly suitable for steelmaking requirements. The utilization of carbon materials, which are difficult to wet by slag and molten steel, along with the high refractoriness, high slag resistance, solubility resistance, and low temperature creep properties of magnesia, allows magnesia-carbon bricks to be applied in severely worn areas such as slag lines and ladle mouths. So far, due to the extensive use of magnesia-carbon bricks in steelmaking processes and the improvement of iron and steel smelting technology, significant economic benefits have been achieved. However, magnesia-carbon bricks have shown disadvantages such as high graphite consumption, increased heat consumption, continuous carbon increase in the molten steel, and pollution of the molten steel, resulting in high costs. To reduce raw material costs and obtain clean molten steel, the low-carbonization of magnesia-carbon bricks can effectively address these issues.   The characteristics of magnesia-carbon bricks mainly include the following aspects: 1.Microstructure: Denseness of Structure: The denseness of magnesia-carbon bricks depends on the types and amounts of binders and antioxidants, the type of magnesia, the particle size, and the addition of graphite. In addition, the molding equipment, brick pressing technology, and heat treatment conditions also have certain influences. To achieve a visible porosity rate of less than 3.0% and ensure a molding pressure of 2t/cm2, it is necessary to use magnesia-carbon bricks with a particle size of less than 1mm for tuyere bricks and ladle mouth bricks. Different binders have certain effects on the denseness of magnesia-carbon bricks, and binders with higher residual carbon rates result in higher bulk densities. The addition of different antioxidants has significantly different effects on the denseness of magnesia-carbon bricks. Below 800 degrees Celsius, the visible porosity rate increases with the oxidation of antioxidants. Above 800 degrees Celsius, the visible porosity rate of non-metallic magnesia-carbon bricks remains unchanged, while that of metallic magnesia-carbon bricks decreases significantly, reaching only half of the rate at 1450 degrees Celsius. Among them, magnesia-carbon bricks containing metallic aluminum have the lowest visible porosity rate. Heating Rate: The heating rate during the use of magnesia-carbon bricks also affects the change in visible porosity rate. Therefore, when using magnesia-carbon bricks for the first time, it is recommended to increase the temperature slowly to ensure complete decomposition of the binder at a lower temperature. During the use of magnesia-carbon bricks, the impact of temperature difference on the porosity rate is also significant. The greater the temperature difference, the faster the increase in porosity rate.   2.High-Temperature Performance: High-Temperature Mechanical Properties: The effectiveness of different additives in improving the high-temperature strength of magnesia-carbon bricks varies. Studies have shown that for flexural strength above 1200°C, the sequence is: no additives < calcium boride < aluminum < aluminum-magnesium < aluminum + calcium boride < aluminum-magnesium + calcium boride, with aluminum-magnesium + boron carbide falling between aluminum-magnesium and aluminum-magnesium + calcium boride.   Thermal Expansion Performance: The participation expansion value of magnesia-carbon bricks without added metals is much lower than that with added metals, and the participation expansion value increases with the increase in metal addition. Anisotropy: The thermal expansion and high-temperature flexural strength of magnesia-carbon bricks vary in different directions due to the orientation of flake graphite. The bricks have higher high-temperature strength and lower thermal expansion in the vertical direction.