What are the Refractory Bricks for the Lining of the Glass Kilns? The lining of the glass kiln is subject to chemical erosion, mechanical erosion, and large temperature fluctuations, and the refractory materials used for the glass kiln lining are like…Contact RS Refractory Company for a Free Quote. Glass is mainly made by using silica sand and soda ash as raw materials through high-temperature melting. A Glass melting furnace is thermal equipment for melting glass, usually made of refractory bricks.
Fused AZS Refractory Bricks for Glass Furnaces
Refractory Materials for Glass Furnaces
Glass melting furnaces can be divided into two categories: pool kilns and crucible kilns. According to the operation mode, it is divided into continuous operation furnaces and intermittent operation furnaces. According to the heating method, it can be divided into the flame kiln and electric heating kiln. So, how should refractory bricks be used in glass kilns? Perhaps manufacturers of refractory materials for glass kilns will answer such questions for us. Refractory Bricks Used for Glass Kiln. Because refractory bricks are widely used, from low temperature to medium temperature to high temperature, it is a necessity for the construction of the lining structure of industrial kilns.
When we choose refractory materials, we must consider many aspects. How to choose our applicable refractory brick products. First, we need to see which type of brick we need. Refractory bricks have different brick types and different uses. Secondly, we must see which kind of furnace is used and then the quality of refractory bricks. When determining the demand, the quality of the refractory bricks meets the standard and then compares the prices. Selection of refractory bricks for glass kiln is the most common type of kiln used in the glass industry. It is made of refractory bricks. There are flame-type pool kilns and electric-heated pool kilns.
The crucible kiln is to put the glass batch materials into the crucible, and then put them in the kiln to heat them together and then pour them into glass products after the materials are melted. The characteristic of this kiln is that the molten glass does not directly contact the kiln lining and the crucible is generally made of high-alumina refractory bricks and clay refractory bricks. The damage to the lining of the glass melting furnace is mainly chemical erosion and has the effect of thermal stress. The degree and speed of chemical attack are closely related to the location of use, the temperature of the furnace, and the type of molten glass. Of course, the quality of the lining itself is also very important. When choosing refractory bricks for glass melting furnaces (https://www.hy-refractory.com/service/product_knowledge/glass-tank-furnace-refractories.html), consideration should be given to the type of furnace, the location of its use, and its damage mechanism, the type of melting glass, and the type of fuel.
Fused AZS Bricks for Glass Kiln
Fused Zirconia Corundum Bricks for Glass Kilns
Fused Zirconia Corundum Bricks. Categories Refractory Bricks. WikiTags: Lining of the Glass Kilns, Refractory Bricks. At present, fused zirconia corundum bricks and corundum bricks are widely used at home and abroad at the wall and bottom of the glass kiln in contact with the molten glass. The lower layer of the melting pool is built with clay refractory bricks. What are the precautions when using clay refractory bricks in the glass kiln? Clay refractory bricks are commonly used refractory bricks in blast furnaces, hot blast stoves, heating furnaces, ceramics, and refractory brick firing kilns. In order to achieve the best results, we need to pay attention to the following matters when used in a glass furnace.
Large Fireclay Refractory Bricks for Glass Kiln
Large Fireclay Bricks for the Glass Kilns
Large Fireclay Bricks for the Glass Kilns. 1. Clay refractory bricks cannot bear weight or be compressed when used at high temperatures. Therefore, it can only be used on the lower part of the pool wall or at a lower temperature at the bottom of the pool. 2. The gap between refractory bricks is controlled within 1.5mm~2mm. 3. The inside of the kiln shell should be flat without unevenness, let alone tilted.4. When using refractory bricks, clean the dust and slag scraps on the inner wall of the kiln shell to avoid loosening. 5. Leave a little expansion joint between the refractory bricks. 6. Bond clay refractory bricks with special cement for refractory bricks. 7. The lining of important parts and parts with complex shapes should be pre-laid first. 8. The lock seam should be firm. When processing bricks, bricks should be finely processed with a brick cutter, and manual processing of bricks should not be used. The capped bricks in the rotary kiln and under the brick slabs should not be less than 70% of the original bricks. In flat joint bricks and curved bricks, it shall not be less than 1/2 of the original bricks. It must be locked with original bricks. The processing surface of the brick should not face the inner side of the furnace. 9. Clay refractory bricks must be stored in a dry warehouse. Having mastered the selection techniques and methods of these refractory brick materials for glass kilns, I believe you will easily find the refractory bricks for glass kilns that best suit your production needs. For more information, please stay tuned to this blog.
And also the Insulating Fire Bricks Used for Kiln Linings. Insulating Fire Bricks of different materials, when used for kiln linings, can increase the heat storage function of industrial kilns and reduce the loss of energy… Contact Rongsheng for Free Quote of Refractory Bricks Categories.
RS Cement Kiln Lining Refractory Bricks for Sale. Commonly used refractory bricks in cement kilns include low-temperature and alkali-resistant bricks, and high-temperature and high-temperature Silicon Carbide Mullite Bricks. Cement Kiln Lining Refractory Bricks … For Free Quote at inquiry@global-refractory.com.
Alkaline Refractory Bricks for Cement Kilns
Why Use Alkaline Refractory Bricks for Precalcined Cement Kilns? During the calcination process of the pre-calcining kiln clinker, a large amount of melt (liquid phase) appears in the kiln material from the back end of the upper transition zone. Some ingredients in the kiln material are calcined in the melt-through of the raw maturation material until it is out of the kiln. Within this range, alkaline refractory bricks that withstand high temperatures can meet their process performance requirements. The masonry length of alkaline refractory bricks is about (6~10)D of the kiln diameter, which is also the most severely damaged part of the lining brick. The use of the lining brick in this part directly affects the operation rate of the kiln. Therefore, the technological progress product performance, and output status of basic refractory bricks are paid attention to by people.
Alkali Resistant Bricks for Rotary Kilns
Magnesia Chrome Bricks for Cement Kiln
At present, the alkaline refractory bricks used in the pre-calcining kiln are mainly spinel magnesia bricks that directly join magnesia-chrome bricks and magnesia-aluminum bricks. This article mainly introduces the direct bonding of magnesia-chrome bricks. Directly Bonded Magnesia-Chrome Brick, Brief Introduction of Directly Bonded Magnesia-Chrome Brick for Cement Kilns. Magnesia-chrome bricks appeared in the 1930s. At that time, the performance of silicate-combined magnesia-chrome bricks (common magnesia-chrome) was still relatively poor and was used in traditional rotary kilns. Beginning in the 1960s, there have been direct-joined magnesia chrome bricks (straight magnesia bricks) with better performance.
Due to the high-temperature resistance, melt erosion resistance, redox resistance, mechanical stress resistance, and excellent kiln hanging performance of straight magnesia bricks, after being put into use, it is widely used in the transition zone and firing zone of the preheater kiln. Become the mainstream. In the 1980s, the output and diameter of the pre-calcining kiln were further expanded. In addition, due to the rapid increase in crude oil prices, coal with high ash content and petroleum coke with high sulfur content gradually replaced fuel oil. The high content of alkali sulfur makes the straight magnesia bricks in the upper and lower transition zones of the kiln vulnerable to damage and shortens the service life.
As a result, magnesia-aluminum spinel bricks with strong alkali-sulfur corrosion resistance have been used in the upper and lower transition zones of some large-scale pre-calcining kilns. At this point, the dominance of magnesia bricks began to break. In the late 1980s, some industrialized countries further emphasized the problem of chromium pollution, that is, when magnesia-chrome bricks are used in cement kilns, Cr3+ is transformed into Cr6+ which is harmful to the environment and the human body. Industrialized countries have formulated a series of regulations on environmental protection, sanitation, and cement-related ingredients. Fully monitor the residual bricks of cement kiln magnesia-chrome bricks, the drainage of cement plants, and the chromium content of cement products. In the 1990s, some cement companies in industrialized countries used relatively cheap industrial waste as raw material fuel due to environmental protection needs. Increased the alkali sulfur’s erosion of kiln lining materials, and put forward more demanding requirements for alkali refractories.
Magnesia Chrome Bricks for Cement Kilns
To promote the further optimization of magnesia-chrome bricks, super-direct bonded magnesia-chrome bricks with better performance have appeared in the pre-calcining kilns with more severe working conditions. On the other hand, the process of chromium-free alkaline bricks is accelerated to further improve and improve technology. In the 21st century, chromium-free alkaline bricks have completely replaced magnesia-chrome bricks in some industrialized countries and have better performance than magnesia-chrome bricks. It is specifically reflected in the development trend of the further increase in the operation rate of the pre-calciner kiln and the further decrease in brick consumption. In my country, in 2014, the Ministry of Environmental Protection formulated the solid waste production cement pollution control standard, which specified the limit of the pollutant content in cement products, Cr6+, to be 0.05mg/L. Its value is close to that of industrialized countries. It can be said with certainty that the limit value will definitely become stricter over time.
Although restricted by environmental protection regulations, magnesia-chrome bricks are still used by some cement plants due to their excellent kiln-hanging properties and relatively low prices. They are the most consumed variety in cement production. But the general trend is to decline year by year. At present, some people of insight in my country’s cement industry have raised the issue of chromium pollution in some conferences and articles, which has attracted the attention of relevant leaders.At the same time, some design units have reduced or stopped using magnesia-chrome bricks in their drawings. Some large domestic cement groups and foreign-funded enterprises have partially or completely stopped using magnesia-chrome bricks. The above situation greatly reduces the usage of magnesia-chrome bricks. In addition, the fuel used in some areas contains high sulfur content, which intensifies the chemical erosion of magnesia-chrome bricks, forcing companies to reduce or stop using them.
As the country further strengthens the environmental protection of water resources and controls the chromium content in cement. The regulation on the limit value of hexavalent chromium in magnesia-chrome brick residual bricks will be strict with time. In the end, forcing magnesia-chrome bricks to withdraw from the cement kiln, manufacturers that produce magnesia-chrome bricks must arouse great attention. Rongsheng Refractory Manufacturer provides high-quality refractory materials for cement kilns. Including direct bonding of magnesia chrome bricks, magnesia spinel bricks, and various wear-resistant castables. For more information about alkaline refractory bricks, please visit our website: https://rongshengrefractory.com/several-kinds-of-alkaline-refractory-bricks/.
Refractory Materials for Cement Rotary Kilns
Cement Kiln Lining Refractory Bricks Refractory Bricks for Cement Kiln
For the firing zone of the cement rotary kiln, a stable and strong kiln skin is required. Because it can protect the refractory lining and reduce the heat loss through the kiln body. A few centimeters of stable kiln skin can not only extend the life of the lining material by nearly 100% but also reduce the temperature of the kiln body by several hundred degrees. This means reducing heat loss by up to 25%.
When the local kiln appears thick skin, it is known as “ring formation.” It will hinder the operation of the kiln considerably. The most serious is that it has built an unfixed cross-section of the kiln, which hinders the steady flow of materials and fuel gas into the kiln. Once the kiln skin is looped, it cannot fall off by itself, and the kiln has to be stopped in order to deal with it. Rotary Kiln in the Cement PlantThe rate of kiln shutdown due to loop formation accounted for 80%. The change cycle ranges from once a month to more than once a week. It is for this reason that people have been studying methods to prevent or deal with kiln skin loops that hinder operation.
Therefore, it is considered whether it can be prevented by selecting suitable refractory materials, or at least the occurrence of ring formation can be reduced. Classification and Location of Kiln Skins and Ring Formation. According to the material flow, the kiln skin and ring formation in the preheater, rotary kiln, and cooler are divided into different types. According to these classifications, the raw material loop occurs in the decomposition zone where the material temperature is between 800°C and 1200°C. The sintering ring occurs at the front end of the firing zone where the material temperature is 1200~1350℃.
The clinker ring occurs at the end of the firing zone where the material temperature is 1200~1400℃. Another obstacle to the formation of kiln skins is the slurry ring on the wet long kiln. The skin on the suspension preheater and decomposition belt of the rotary short kiln, and the well-known “clinker mushroom tumor” on the cooler inlet chute. Refractory Material Affects the Possibility and Limit of Ring FormationThe chemical atmosphere in the kiln and the normal operating conditions affect the desired formation of the kiln skin and cause the trouble of material ring formation. However, refractory materials can also affect the stability of the kiln skin due to their different bonding strength. Experiments have shown that dolomite bricks have the strongest bonding force, followed by magnesia-chrome bricks and direct-bonded magnesia-chrome bricks (MgO content 60~70%), and magnesia spinel bricks (Almag 85) are the weakest.
Magnesia Aluminum Spinel Bricks for Cement Kilns
Magnesia Spinel Bricks for Cement Kilns
Magnesia Spinel Bricks Manufacturer. The “Mineral-Chemistry” study confirmed that the bonding force at the interface between the kiln skin and different bricks was measured by the mineral composition of the “kiln skin-brick” interface and the liquid “wetting” angle. Therefore, a layer of C3S enrichment zone with high refractoriness is formed on the interface between kiln skin and brick. This layer of C3S also contains tricalcium aluminate and ferrite phases. If the temperature drops below the stability limit of C3S (1250°C), C3S usually decomposes into C2S and secondary free CaO. But obviously, the incorporation of foreign ions, such as MgO, will stabilize C3S. Due to the decrease of the local CaO/SiO2 ratio in the area close to the surface of the brick, a C2S-rich boundary layer is formed, which results in a lower bonding force on the magnesia-chrome brick. In the presence of Cr2O3, C2S is partially stabilized.
However, if the interface temperature drops, that is, if the kiln skin becomes thicker, β-C2S will be converted to γ-C2S, with a volume expansion of 10%, resulting in “pulverization” and weakening of the binding force of the ring to the lining. So that the knot loops fall off. Magnesia spinel bricks have a particularly strong “chalking” effect. Although a C2S-rich layer is formed, the liquid phase obviously does not infiltrate the bricks to such an extent. On the other hand, there is no adequate amount of ions that can stabilize β-C2S. If the temperature drops in the contact zone, it is easier to form γ-C2S, so that the ring of materials will fall off. Because the magnesia spinel brick has a higher control of Fe2O3 content, it will not generate a C2S layer enriched with iron-free aluminate. The situation of magnesia chrome brick is the opposite because it contains higher Fe2O3.
Based on the previous observations, it is clear that magnesia spinel bricks can cause the ring to fall off, or prevent the formation of a C2S-rich ring layer that hinders operation. These loops mainly occur before and after the decomposition zone and the firing zone. Lining with magnesium spinel bricks can also prevent the formation of “clinker mushroom tumors” at the inlet chute of the cooler. As to whether the magnesia spinel brick can successfully eliminate the problem of skinning containing potassium sulfate, potassium carbonate, silica calcite, alkali metal sulfate, and alkali metal chloride, it is still worth discussing.
The looping of slurry in the cyclone, short dry kiln flue chamber, long wet kiln, and skin on the wall and top of the hot gas chamber of the grate preheater are all such problems. Obviously, the lining made of Almag85 grade magnesia spinel bricks shows that it can effectively prevent the formation of clinker rings, sintered rings, and raw material rings. Learn more about the magnesia alumina spinel bricks from Rongsheng Refractory Manufacturer.
The ignition and baking of the glass kiln are based on the physical and chemical properties of the refractory materials used in the kiln, that is the thermal expansion properties of the refractory materials. After heating and baking, the refractory material completes the internal crystal transformation and volume change, so that it can be used normally at high temperatures.
In the past, AZS bricks were expensive. Therefore, the kiln is not used or only used in small quantities in key parts. In the past two decades, with the development of high-efficiency and energy-saving kiln technology, AZS bricks have been widely used. AZS is increasingly used not only for the pool walls that are in contact with the glass liquid but also for the flame space. Due to the influence of traditional inertial thinking, most glass factories currently only consider the thermal expansion of silica bricks when baking kilns, but do not pay attention to the thermal expansion of AZS bricks. Therefore, fracture problems of AZS bricks often occur before and after the kiln is put into operation, which directly affects the life of the kiln.
Glass Kiln AZS Refractory Bricks
Thermal Expansion Characteristics of AZS Bricks
AZS brick contains a certain amount of ZrO2, which is a homogeneous polycrystalline. That is, the same chemical composition can form three types of crystals with different structures and properties due to different temperature conditions. There are three types: monoclinic ZrO2, tetragonal ZrO2, and cubic ZrO2.
Changes in the crystal system are often accompanied by changes in volume. Taking 33# AZS as an example, it was found through experiments that when the temperature range is 0-1100°C, the bricks gradually expand as the temperature rises. When the temperature range is 1100-1200℃, the bricks shrink violently as the temperature rises. The linear expansion rate dropped from about 0.8% to about 0.6%, which is what is usually called abnormal expansion. This is caused by the transformation of the ZrO2 monoclinic system into the ZrO2 tetragonal system. When the temperature is higher than 1200°C, the bricks begin to expand again as the temperature rises.
It can be seen from laboratory testing data that the overall expansion is not large below about 1600°C.
Precautions when Baking the Glass Kiln
The kiln has a fire-amplification stage. The fire in the hot-air kiln is generally 900-1000℃. The practice has proved that most of the fractures of AZS bricks occur after a fire. The reason is that the temperature rise rate is too fast during the 1100-1200°C period when monoclinic ZrO2 transforms into tetragonal ZrO2. Therefore, it is generally required that the speed does not exceed 15°C/hour. Many manufacturers control it at 5°C/hour, and the speed does not exceed 15°C/hour in other temperature ranges. In this way, the AZS bricks have sufficient time to undergo crystal transformation and avoid fracture.
There is a temperature difference of several hundred degrees between the flame contact surface and the non-contact flame surface during the kiln baking process. In order for the outside of the brick to be able to undergo crystalline transformation safely, it is necessary to maintain a low heating rate within a larger temperature range. Therefore, the temperature range in the kiln is usually expanded from the theoretical 1100-1200℃ to about 1100-1350℃.
The upper 300-400 mm of the pool wall bricks are not insulated during normal production and need to be cooled. To reduce the temperature difference between the inside and outside of the kiln, insulation materials such as aluminum silicate fiber should be used for temporary insulation to prevent brick breakage. When the temperature reaches above 1500°C, the insulation fiber can be taken out.
When cooling the pool wall tiles, the cooling air inlet should be opened gradually. Generally, it is opened 5 times, and 20% is opened every hour.
The quality of the kiln’s work is related to the life of the kiln. Therefore, it is extremely important to correctly grasp the expansion performance of fused zirconium corundum bricks, standardize it in the kiln heating curve, and implement it carefully. Rongsheng refractory material manufacturer can provide a comprehensive range of lining bricks for glass kilns, including silica bricks, corundum bricks, corundum mullite bricks, AZS bricks, etc. Feel free to contact us for details.
High-temperature-resistant inorganic adhesives have been widely used in the heat-resistant bonding of metals, ceramics, graphite, oxides, and other materials. Easy to use, used for direct bonding of high-temperature resistant materials. The coating can be sprayed directly on the surface of a high-temperature substrate of 400-1000°C. When the water evaporates, the coating will instantly adhere to the surface of the substrate, forming a uniform and dense high-temperature resistant protective coating with good thermal shock resistance.
High-Temperature Gunning Refractory Material for Lining Repair
It also has good strength at high temperatures, with an average compressive strength of 90Mpa and a tensile strength of 8Mpa at 1300°C. After applying high-temperature inorganic adhesive on the kiln windshield, hanging parts, and cracks, the bond will be firm and will not cause any damage to the kiln lining. Adhesives are easy to use and play a very important role in the normal operation of the furnace. It has been successfully used in rotary kilns, drying furnaces, and combustion chambers in the cement industry. Heating furnaces and smelting furnaces in the machinery industry. Electric furnaces, roasters, and blast furnaces in the metallurgical and chemical industries. Tunnel kilns in the ceramic industry, boilers in the thermal power industry, and other types of kilns.
The high-temperature-resistant expansion glue uses a high-temperature inorganic silicate modified solution as the film-forming material, and is composed of rare earth oxides, re-expanded mullite, and vaporized SiO2 powder as fillers. The cured coating film has a temperature resistance of up to 2200°C and can maintain good thermal stability, bonding performance, wear resistance, and corrosion resistance in high-temperature environments. The coating has a high linear expansion coefficient, and the coating expansion rate can reach 15% under high-temperature conditions.
The kiln lining protective coating uses the company’s special high-temperature resistant inorganic silicate modified solution as the film-forming substance and is composed of nano-scale alumina, silicon carbide, rare earth oxides, ceramic fibers, etc. The cured coating film has high-temperature resistance, which can reach 1800°C, thermal shock resistance, high adhesion, good heat insulation, strong aging resistance, and convenient construction. It can be sprayed directly on the surface of various materials lining the kiln, including insulation bricks, castables, metals, ceramics, refractory fibers, quartz sand, silicon carbide, quartz glass, etc.
High-aluminum poly-light brick is a high-performance lightweight thermal insulation material with excellent performance and wide application prospects. Rongsheng Refractory Materials Manufacturer has an in-depth understanding of the characteristics, application fields, and preparation processes of high-alumina poly-light bricks. It can provide high-performance lightweight insulation materials for high-temperature industrial furnaces, including high-aluminum poly-light bricks, mullite insulation bricks, micro-nano insulation series, etc.
High-Alumina Poly Light Insulation Brick
Characteristics of High Alumina Poly Light Bricks
High-aluminum poly light brick is a kind of lightweight brick made of high-aluminum clinker as the main raw material, adding an appropriate amount of polymer and additives, and sintering at high temperatures. It has the following characteristics:
Lightweight and high strength. High-aluminum poly-light bricks are lightweight and high-strength. Its density is only 0.6-1.0g/cm3, but its strength is as high as 5-20MPa.
High fire resistance. The fire resistance of high-alumina poly light bricks is as high as 1300°C, which can meet the protection needs of high-rise buildings and high-temperature equipment.
Heat insulation. High alumina poly-light bricks have excellent thermal insulation properties. Its thermal conductivity is only 0.2-0.4W/(m·K), which can reduce the energy consumption of buildings.
Strong corrosion resistance. High alumina poly light bricks can resist the erosion of various chemical substances, such as acids, alkalis, salts, etc. Therefore, it is widely used in the chemical industry and other fields.
Convenient construction. High alumina poly-light bricks have standard sizes and are easy to install and construct. At the same time, its lightweight also facilitates transportation and installation.
Application Fields of High Alumina Poly Light Bricks
High alumina poly light bricks are used in kiln linings in metallurgy, machinery, ceramics, chemical, and other industries. It is not corroded by solutions and is used in insulation layers. It is an ideal energy-saving product.
RS High-Alumina Poly Light Insulation Brick
Application Advantages of High Alumina Poly Light Bricks
Lightweight. Compared with traditional refractory bricks, high-alumina poly-light bricks are lighter in weight and are easier to transport and construct. It reduces the overall load of the furnace body and reduces the requirements for the furnace body support structure.
Reduce energy consumption. High-alumina poly-light bricks have good thermal insulation properties and can effectively reduce heat transmission and thermal radiation losses. By using high-aluminum polylight bricks, fuel consumption can be reduced and energy efficiency improved.
Extended service life. High-alumina polylight bricks have excellent fire resistance and corrosion resistance, which can extend the service life of the furnace body. It can reduce ablation and wear inside the furnace and ensure the stability and safety of the furnace structure.
The technology is widely used. Due to the characteristics and advantages of high-alumina poly-light bricks, it has been widely used in various industrial fields. Such as steel, metallurgy, chemical industry, building materials, and other industries, especially suitable for kilns and furnaces in high-temperature environments.
Preparation Technology of High Alumina Poly Light Bricks
The preparation process of high-alumina poly light bricks mainly includes the following steps:
Ingredients. Mix high-aluminum clinker, polymers, additives, and other raw materials evenly according to a certain proportion.
Forming. Put the mixed raw materials into the mold and press it into shape.
Dry. The molded green body is dried to remove moisture from the green body.
High-temperature sintering. The dried green body is put into a high-temperature kiln for sintering, turning it into a lightweight brick with excellent properties.
Finished product inspection. Conduct quality inspection on high-alumina poly-light bricks, and qualified products can be shipped out of the factory.
Rongsheng High Alumina Poly Light Brick Manufacturer
As a high-performance lightweight thermal insulation material, high-aluminum polylight bricks have broad application prospects and important practical value. This article introduces the characteristics, application fields, and preparation process of high-aluminum poly-light bricks, providing a reference for readers to understand high-aluminum poly-light bricks. With the continuous development of science and technology, it is believed that high-alumina poly-light bricks will be more widely used in the future. To purchase high-quality lightweight insulation products, please contact us.
The main purpose of the carbon fiber graphitization treatment furnace is to induce the graphitization crystal orientation of the fiber to increase the elastic modulus of the carbon fiber. The production of carbon fiber is carried out in a high-temperature sealed graphitization furnace. Both ends of the furnace are sealed with high-purity argon gas. The heating element is made of graphite material, and the graphite tube is both the furnace tube and the heating element of the high-temperature furnace. The heating temperature is generally between 2500°C and 2800°C.
The life of the graphitization furnace depends on the properties of the refractory material. The furnace shell of the graphitization furnace is rolled from ordinary carbon steel plates. Special refractory materials are used as insulation materials in the shell, which are generally composed of heat-resistant layer, heat insulation layer and protective layer. In order to ensure the airtightness of the furnace, the inner surface of the refractory lining must be round and smooth. Otherwise, the air tightness of the lining will be affected and it will not be resistant to airflow erosion. In addition, there are temperature measuring holes and pressure measuring holes on the furnace.
Graphitization Furnace Corundum Material
When using the graphitization furnace, great attention must be paid to temperature changes caused by rapid cooling and rapid heating. When production is stopped for maintenance, if the furnace cannot be kept warm by gas or other heat sources, the front and rear of the furnace must be tightly blocked to prevent the furnace from bursting due to rapid cooling. Prevent metal objects from entering the furnace and contacting the corundum lining, because metal and corundum materials generate a low melting point eutectic, which reduces the refractoriness and causes partial melting of the furnace body. The cooling water jacket must be designed reasonably to prevent burnout due to local overheating and to prevent water from entering the furnace and causing the furnace body to explode. In addition, carbon black fillers must not be affected by moisture. The graphitization furnace must be covered, and the flue gas must be treated to meet standards before it can be discharged.
Special insulation materials are selected as insulation materials for high-temperature graphitization furnaces, which refer to single materials such as high-purity oxides, non-oxides and carbon with melting points above 1800°C. Or they are made of various composite materials and produced using traditional production techniques or special production techniques. Its products are new refractory materials with special properties and special uses. The main function of high-temperature graphitization furnace insulation materials is to reduce heat energy loss and save energy. Ensure the needs of production process and improve equipment capabilities. Improve working conditions, achieve safe production, and extend the operation period of equipment.
Graphitization furnace insulation materials play the dual roles of heat preservation and electrical insulation in the graphitization furnace. Insulation materials have a very important influence on the temperature rise of graphitization furnace. The quality and thickness of the insulation material determine to a large extent the thermal energy utilization efficiency of the graphitization furnace and the temperature difference in various parts of the furnace, and determine the energy consumption during graphitization of carbon fiber. Insulation materials are also related to the safety and performance of refractory masonry and furnace building structures. The electrical insulation of the insulation material is key to ensuring that electric current acts effectively on the furnace tube. It requires low thermal conductivity and good thermal insulation performance. It has high resistivity and good electrical insulation properties. Does not hinder the discharge of gas in the furnace. Does not react with products in the furnace at high temperatures. Cheap and easy to purchase in large quantities.
Corundum (α-AL2O3) is produced by electrofusion or sintering of industrial alumina or bauxite ore. The mineral composition of corundum is a-AL2O3, its density is about 3. 85 ~ 4. 01g/cm3, its melting point is 2050°C, and its deformation temperature is 1750°C. It has good thermal conductivity, good electrical insulation and chemical stability, and can resist the erosion of NaOH, Na2CO3, etc. And it has the ability to resist the action of reducing agents (such as hydrocarbon chemicals, hydrogen and free metals, etc.) below 1800°C. It has the characteristics of high mechanical strength under high temperature, good thermal shock resistance, strong corrosion resistance, and small thermal expansion coefficient. It is the best lining material for various high temperature furnaces.
[Tips]Carbon fiber is a fibrous carbon material. Its biggest feature is its high elastic modulus and light weight. The deformation resistance of high elastic modulus carbon fiber is more than 2 times greater than that of steel and 5 to 6 times greater than that of aluminum alloy. The specific gravity of carbon fiber is less than 1/4 of steel and 1/2 of aluminum. Carbon fiber is a fiber with a carbon content of more than 90%, which is made from polyacrylonitrile fiber, pitch fiber, viscose fiber or phenolic fiber through oxidation, carbonization and other processes. Those with a carbon content higher than 99% are called graphite fibers.
Lightweight mullite insulation brick is a kind of insulation brick, which is an insulating refractory brick made of mullite as aggregate. Mullite insulation bricks are white, can be directly exposed to flames, and have high refractoriness. Mainly used in hot blast furnace tops, blast furnace shafts, and bottoms, glass melting furnace regenerators, ceramic sintering kilns, dead-end furnace linings in petroleum cracking systems, etc.
Lightweight mullite insulation bricks
The dimensions of conventional lightweight mullite insulation bricks are 230 x 114 x 65mm. Common models of lightweight mullite insulation bricks include JM23, JM26, JM28, and JM30. The main difference between them is the content of aluminum oxide and iron oxide. Different contents can withstand different refractory temperatures, thermal conductivity, and thermal expansion rates.
Low Iron JM23 JM26 JM28 Mullite Insulation Bricks
Characteristics of low-iron JM23 lightweight mullite insulation bricks
Low thermal conductivity and good thermal insulation effect.
Low thermal melt. Due to low thermal conductivity, mullite series lightweight insulation bricks store very little heat energy. The energy-saving effect is obvious in intermittent operation.
Low impurity content and very low oxide content such as iron metal. Therefore, the fire resistance is high. The higher aluminum content allows it to maintain good performance under a reduced atmosphere.
High hot compressive strength.
The appearance dimensions are precise, speeding up the masonry work and reducing the usage of refractory mud. The strength and stability of the masonry are ensured, thereby extending the life of the lining.
It can be processed into special shapes to reduce the number of bricks and joints.
RS refractory material manufacturer can provide lightweight mullite insulation bricks, with standard sizes and customized sizes. Low iron JM model, contact us for a free quote and sample.
Rongsheng Mullite Insulation Brick
Lightweight mullite insulation bricks for industrial kilns
Lightweight mullite insulation bricks for industrial kilns are a widely used energy-saving material. Has the following characteristics. Lightweight. The density of mullite insulation bricks is less than or equal to 1000 kg/cubic meter. It is much lighter than traditional stone or metal thermal insulation materials, which can reduce the burden and weight of the kiln. Insulating properties. Mullite insulation bricks have high porosity and large porosity, which can effectively improve thermal insulation performance and reduce heat loss and transmission. Durability. Mullite insulation bricks have very good durability due to their porous structure. Its stability and durability can be guaranteed even in high-temperature environments. Easy to process. Mullite insulation bricks can be mechanically crushed or pressed into different shapes and sizes for easy use and processing. In industrial kilns, mullite insulation bricks are often used for thermal insulation and preventing heat loss. This material can effectively reduce the energy consumption and cost of the kiln, and improve production efficiency and safety.
Low-iron JM23 lightweight mullite insulation brick manufacturer and RS refractory insulation brick manufacturer produce mullite lightweight insulation bricks with industrial Al₂O₃ powder, clay, well-sintered bauxite, and kyanite as the main raw materials. Add wood chips (1mm screen) and polystyrene balls (diameter 0.2~0.5mm) to prepare lightweight bricks. It has the characteristics of high-temperature strength, low porosity, and corrosion resistance. Widely used in high-temperature industrial kiln linings.
Mullite insulation brick is a new type of thermal insulation refractory material, low iron JM23 lightweight mullite insulation brick. According to the difference in density, it can be divided into lightweight mullite insulation bricks and corundum mullite bricks (also called heavy mullite insulation bricks). Mullite insulation bricks are divided into JM23, JM26, JM28, and JM30 according to their grades. Mullite insulation bricks are divided into 1350 mullite insulation bricks, 1450 mullite insulation bricks, 1550 mullite insulation bricks, etc. according to different use temperatures. Moreover, 1550 mullite bricks can be directly exposed to flames and have the characteristics of high-temperature resistance, small thermal conductivity, and significant energy-saving effects.
Mullite insulation brick product price
The price of mullite insulation brick JM23 is 2,600 yuan/ton, and the use temperature is 1,350°C.
The price of mullite insulation brick JM26 is 3,200 yuan/ton, and the use temperature is 1,450°C.
The price of mullite insulation brick JM28 is 4200 yuan/ton, and the use temperature is 1550℃.
The price of mullite insulation brick JM30 is 4,800 yuan/ton, and the use temperature is 1,600°C.
JM23 lightweight mullite insulation bricks, the body density of lightweight mullite insulation bricks is 0.6, 0.8, 1.0, 1.2g/cm3. Mullite lightweight thermal insulation bricks are suitable for high air temperature metallurgical hot blast furnaces, molten steel impactors, slag lines, the roof of steelmaking electric arc furnaces, the forehearth of glass melting furnaces, regenerator arches, and superstructures. The lining of ceramic sintering kilns, ceramic roller kilns, tunnel kilns, electric porcelain drawer kilns, dead-end furnaces of petroleum cracking systems, glass crucible kilns and various electric furnaces. The walls of the clarifier can be in direct contact with flames.
To learn more about RS low-iron JM23 lightweight mullite insulation bricks, please contact us.
The selection of refractory materials for hot blast stoves is mainly determined by the temperature of the hot blast. When the wind temperature is lower than 900°C, clay bricks are generally used, and their service life can reach about 20 years. When the air temperature is between 900 and 1100°C, high-alumina bricks, mullite bricks, or sillimanite bricks are used for the furnace lining and checker bricks in the high-temperature part. When the air temperature is higher than 1100°C, high alumina bricks, mullite bricks, and silica bricks are generally used as furnace lining or checker bricks.
In recent years, newly built or renovated blast furnace hot blast stoves in various countries mainly adopted external combustion type. The supply air temperature is 1200~1350℃, and the vault temperature is generally 1500~1550℃, even close to 1600℃. Therefore, the high-temperature parts of the furnace lining and the upper layer of checker bricks are generally constructed with silica bricks, which has better results.
Low Creep High-Alumina Bricks for Hot Blast Stoves
What is the Alumina Content of High-Alumina Refractory Bricks Used in Hot Blast Stoves?
Regarding the high alumina refractory bricks with alumina content used in a new hot blast stove, it is generally recommended to choose high alumina refractory bricks with higher alumina content. High-alumina refractory bricks usually have an alumina content between 48% and 80%, which can provide better fire resistance and corrosion resistance.
The use of high alumina bricks in the medium temperature zone and high and low temperature alternating zones of hot blast furnaces.
The medium temperature area of the hot blast stove (600~1150℃) refers to the middle part of the flame in the combustion chamber, and in the regenerative type it refers to the middle part of the checker bricks, the transition section from high temperature to low temperature. In this area, low creep high alumina bricks or high-grade andalusite bricks are generally selected. For internal combustion and external combustion hot blast stoves, the area from the top of the burner to the vicinity of the hot blast outlet. As well as the top-fired hot blast stove, the space enclosed by the inner wall of the burner – the pre-combustion chamber, is a high and low temperature alternating area (35~1100℃). The temperature changes in this area are mainly caused by the mutual conversion of the “combustion-air supply” cycle of the hot blast stove. It is advisable to choose andalusite or cordierite bricks with good thermal shock resistance.
The hot air ducts of hot air stoves are also traditionally made of andalusite bricks. In recent years, with the increase in wind temperature, refractory bricks using andalusite-mullite composite have also appeared.
Kinds of Low-Creep High-Alumina Bricks for Hot Blast Furnace
There are many types of high alumina bricks, and their properties vary greatly depending on the Al2O3 content and crystal form.
Low creep high alumina bricks
The main characteristic of low creep high alumina bricks is their good creep resistance. Domestic production of low creep high alumina bricks generally uses bauxite as the main raw material. The “three stone” minerals (andalusite, sillimanite, and kyanite) are additives. Among the “three stone” minerals, the addition of andalusite is more common.
Adding tristone to solve the creep resistance problem of high-alumina products lies in the final mulliteization of tristone. During the firing process of high alumina bricks, the three stones will undergo mullite formation, and the reaction will directly generate mullite. The accompanying SiO2 will react with high-alumina materials again, causing secondary mulliteization. After the final firing is completed, the three stones in the crystal phase will be completely converted into mullite, and n(Al2O3)/n(SiO2) is close to 3:2, forming a stable columnar mullite crystal phase structure. This structure determines that high alumina bricks have good creep resistance.
Andalusite bricks
Andalusite bricks have good high-temperature properties, and their high-temperature creep resistance is better than high-alumina bricks and most mullite bricks. Moreover, the volume expansion associated with high-temperature mullite formation is small, and it has good thermal shock resistance. It is an ideal low-creep refractory material.
The main raw material used in the production of andalusite bricks is andalusite, and the proportion is generally higher than 40%. If it is made into andalusite-mullite composite brick, a part of mullite or corundum should also be added. If the mullite raw material is synthetic mullite. The crystals should be thicker to reduce the number of grain boundaries, weaken the slip of the crystals at high temperatures, and enhance the creep resistance of the bricks.
Cordierite bricks
The linear expansion coefficient of cordierite bricks is small. The linear expansion coefficient at 20~900℃ is (1.25~1.92)×10-6℃-1, and it has good thermal shock resistance. However, the refractoriness of cordierite is low, only 1370℃. When the firing temperature is too high, a glass phase is easily produced. Pure cordierite bricks cannot be well used in high and low-temperature alternating areas due to their low operating temperature range. In actual production applications, cordierite is often added as an auxiliary raw material, which has a significant effect on improving the thermal shock resistance of bricks.
In the glass manufacturing industry, the same glass products and the same glass kiln have different maintenance times, repair parts, and kiln service life. What are the causes of corrosion of fused AZS refractory brick pool walls in glass furnaces? Normal material erosion is within the designed use time range of the material, while abnormal material erosion is a malignant condition that occurs in a location that is not necessarily fixed and within the designed service life of the material. The hidden negative effects of these situations are huge, affecting not only the economic interests of glass companies. To a certain extent, it also affects and restricts the healthy development of the entire glass industry.
Fused Cast AZS Brick #36
Harmful Components and Corrosion Mechanisms in Fused AZS Refractory Bricks
Glass phase
The phase composition of fused cast azs refractory products is baddeleyite, corundum, a small amount of mullite, glass phase, and pores. In the manufacturing process of fused cast azs refractory bricks, in order to reduce and eliminate residual thermal stress, a certain amount of glass phase is required in the product as an absorbent to buffer thermal stress. However, the existence of the glass phase also brings some disadvantages. In terms of the resistance of refractory materials to the erosion of glass liquid, the glass phase is the weak link. During the erosion process, the glass phase first precipitates and is replaced with the high-temperature glass melt, thereby accelerating the erosion of the crystal. Under high-temperature use conditions, the glass phase will also ooze out and release bubbles, thereby contaminating the glass melt.
Carburizing
Generally, zirconium corundum fused cast refractories brick products produced by the reduction method have serious carburization. According to literature reports, the corresponding carbon content can be judged according to the color of the cross-section of the refractory material: light gray 0.03%~0.06%, off-white <0.03%, gray 0.08%~0.18%, dark gray 0.15%~0.19%. Even products produced by advanced oxidation methods (long arc and oxygen blowing) contain some carbon (<0.01%). Carburizing exists in the form of carbides, mixed nitrogen compounds, sulfides, solid carbon, and residual reducing gases. When used under oxidizing conditions, gas is released, causing the glass phase to seep out and the temperature to decrease. When the AZS refractory brick contains a large amount of glass phase (#33 is generally about 20%), it will soften and ooze out at temperatures above 1100°C. And as the temperature increases, the loss intensifies. The exudation of the glass phase is related to the carbon, carbide, low-priced iron and titanium, and other impurities present in the brick. When there is an oxidizing atmosphere in the kiln, oxygen diffuses to the bricks and reacts with these impurities to release CO2, SO2, and other gases. These gases squeeze out the molten glass phase and form nucleation bubbles on the surface. The crystalline phase is lost due to the loss of the combination of the glass phase. This is the cause of the erosion of AZS refractory bricks.
fused AZS refractory bricks for glass furnaces
The entry of harmful components in the production process of fused AZS refractory bricks
Sand inclusion and other foreign matter enter the product
For the casting model produced by adding quartz sand and water glass, the sand inclusion phenomenon refers to the high-temperature molten liquid gradually rising in the model during pouring, similar to that of pool wall bricks. The part not covered by the melt undergoes high temperature, and the sand on the surface breaks away in lumps and falls into the melt, forming a sand inclusion phenomenon. Due to the high temperature of 1750℃, the added sand skin exists in the glass state inside the product. In addition, there is a flat material program during the melting process. The flat material tool is a cast steel drill. If the steel drill is exposed to high-temperature molten liquid for a long time, its texture will soften. When prying the unmelted material block, the steel drill may break. The broken steel drill may be completely melted in the melt, increasing the iron content in the product. It is also possible that it is not completely melted and enters the product during pouring.
Oxidation uniformity of fused AZS refractory bricks
The degree of oxidation or uniformity of oxidation of fused AZS refractory bricks is one of the key indicators of whether the quality of the product is excellent. Each manufacturer has complete system requirements in formulating the oxygen-blowing process, but most of them have defects in setting the position of the oxygen lance. It is an inevitable phenomenon that the oxygen lance hole is blocked during oxygen blowing. Oxygen guns generally have seven oxygen outlets distributed around or at the bottom of the ball head. When one or several oxygen outlets are blocked, uneven oxidation of the product will occur. It can be seen if it is serious, but it is difficult to judge intuitively if it is not serious. Even on a single brick, there will be color inconsistency. Dark color indicates a large amount of carburization, and light color indicates a small amount of carburization. The clogging of the oxygen lance hole directly leads to poor oxidation effect of the product and increased carburization of the product. When the glass furnace is operating, the glass phase is precipitated along with bubbles, mostly carbon dioxide gas.
The formation of gaps in glass furnaces
1 Grinding or masonry kiln
When the product is processed and ground, the flatness of the machine tool surface cannot meet the requirements after aging, causing the product to be convex or recessed in the middle. During pre-assembly, the gap is evened up and down, making it seem that the gap is not large. During the kiln masonry construction, due to foundation flatness errors or defects in the bottom of the product, the builder’s negligence caused the bottom of the product to be elevated. When the final kiln is baked, the expansion of the product may not be shaped according to the uniform gap, which may cause the gap at the bottom or upper part of the pool wall brick to be significantly enlarged.
2 Kiln sill specification design
In a glass kiln, improper arrangement of kiln sill bricks will also cause the kiln sill to be deformed due to the impact of glass liquid. Since the kiln ridge bricks must withstand the impact of the molten glass turning over, the kiln ridge must have sufficient thickness and support. The height of the supporting bricks needs to exceed 1/2 of the height of the kiln sill bricks for more effective support. When the kiln sill bricks are deformed by the impact of glass liquid, the gap between the bricks will become wider.
3 kiln deformation
In the temperature range of the kiln, the zirconium component in the fused AZS refractory brick transforms from the monoclinic phase to the tetragonal phase at 1100°C. Some volume changes will occur at this time. The temperature decrease when the temperature is unstable will cause some volume changes in the opposite direction. This temperature fluctuation causes the reverse volume change of the zirconium component, which is the fundamental reason for the explosion of the product. When baking the kiln, a heat preservation stage is usually set at 1100°C to fully convert the volume of the fused AZS refractory bricks.
To sum up,
the reasons for the erosion of the fused AZS refractory brick pool wall in glass furnaces are as follows. Listed here for reference by refractory material manufacturers and glass production companies to choose a suitable solution for their own glass furnace refractory lining. Reduce maintenance costs, increase production capacity, and create more economic benefits.
(1) The glass liquid is seamless. The gaps between the products will cause mechanical erosion of the glass liquid backflow. When glass precipitates in the gaps, it is accompanied by the precipitation of bubbles, which intensifies the erosion of the gaps in the product. When accepting the entire kiln, the stricter the requirements for gaps, the better.
(2) When constructing the kiln, ensure that the foundation is stable and there must be no overhead products. The expansion joints should be reserved reasonably or the masonry personnel should strictly control their work.
(3) The height and width specifications of the inner protective bricks of the kiln sill bricks should be appropriately increased. The protective bricks must effectively play a supporting role.
(4) The production process of fused AZS refractory bricks requires effective system management to determine whether the oxygen lance outlet holes are blocked. The position of the oxygen lance should be set to facilitate observation of the status of the oxygen lance outlet hole.
(5) For sand molds made of quartz sand and water glass, the proportion of water glass should not be less than 8%. A small amount of water glass will cause the surface sand to fall off during pouring, which will bring inherent hidden dangers to the product. It is best to choose fused AZS refractory bricks made from resin sand models.
The hazards of magnesia-chrome waste bricks. Cr in magnesia chrome bricks has many beneficial effects. However, under high temperatures, and alkaline and oxidizing atmospheres, some chromium will be converted into water-soluble hexavalent chromium, causing serious harm. Cr+ is highly harmful to human skin and mucous membranes. It can cause papules, ulcers, nasal septum perforation, and respiratory inflammation. It can also cause skin cancer and lung cancer. For example, the risk of lung cancer among workers working with chromic acid and chromium-containing pigments is 10 to 30 times higher than that of the general population.
Magnesia Chrome Bricks
In cement rotary kilns, the areas where refractory materials corrode the fastest are mainly the fire point at 9.5~16m and the location without kiln skin at 27~33m. However, the waste bricks dismantled from 3~9.5m and 16~25m are the ones that emit the most Cr+. The Cr+ carried by these two parts of waste bricks accounts for 92% of the total discharged hexavalent chromium, while the Cr+ discharged from other parts only accounts for 8%.
A 4000t/d cement kiln dismantles 181t of magnesia-chrome bricks at one time, and the waste bricks carry an average of Cr+183kg. The average Cr6+ content is about 1kg/t or 1000mg/kg, which is 20,000 times higher than the Cr6+ content of 0.05 mg/L allowed by national environmental standards for Level IV. Therefore, a single discharge of magnesia-chromium bricks can harm 3.6 million tons of pure water. In other words, 2.5 tons of water will be harmed for every 1 ton of clinker produced! It can be seen that the harm of magnesia-chrome waste bricks to the environment and the threat to human health are very alarming.
It is very unreasonable to use magnesia chrome bricks in the 3~9m and 27~33m sections in the cement rotary kiln. At a position 3 to 9 meters inside the kiln, close to the kiln entrance, the oxygen partial pressure is high. The chromium in the magnesia-chromium bricks is easily oxidized, causing the fire bricks to contain high hexavalent chromium, which seriously harms the environment. At 27~33m in the kiln, the hot end temperature and alkali content in the transition zone are very high. Cr in magnesia-chrome bricks is easily converted into K2CrO4 and volatilizes, causing the magnesia-chrome bricks to corrode quickly. Therefore, magnesia-chrome bricks are only used in the most severely corroded parts 9.5 to 16 meters inside the kiln, and chromium-free alkaline bricks can be used in other parts. In this way, it does not affect the life of the kiln lining and reduces the harm of waste bricks.
Suppression of the Hazards of Magnesia-Chrome Waste Bricks
After suppression treatment, the hexavalent chromium in the magnesia-chrome waste bricks can be destroyed, so that the waste bricks can meet the requirements for safe discharge. The most economical known inhibition method is thermal reduction inhibition – the waste bricks are buried in carbon and heat treated at 900~1000℃, and CO gas is used to reduce hexavalent chromium into non-toxic substances.
When treated at around 900°C, hexavalent chromium in waste bricks can be removed. Make the Cr6+ content of the immersion liquid <0.05mg/L, meeting the requirements of Class IV water stipulated in the national environmental standards. In the same way, firing in a weak reducing atmosphere before stopping the kiln will also help reduce the Cr6+ content in magnesia-chrome waste bricks.
