Magnesium bricks play an indispensable role as an important refractory material in modern industrial production, especially in the field of glass manufacturing. They not only need to withstand extremely high temperatures, but also resist the erosive effects of molten glass. With the advancement of technology and the growth of market demand, the quality and performance of magnesium bricks have become one of the key factors in ensuring production efficiency and product quality. This article examines ten frequently asked questions about the use of magnesium bricks, with the aim of providing relevant practitioners with practical information and advice to help them better understand and address the various challenges of magnesium bricks in glass furnaces. From the selection of magnesium bricks to installation and maintenance to performance evaluation, we will answer these key questions one by one in order to promote a more efficient use of magnesium bricks in glass manufacturing.
1. What are the main components and content standards of magnesium bricks?
2. How are magnesium bricks produced?
3. What are the main applications of magnesium bricks in glass furnaces?
4. What are the refractory properties and erosion resistance of magnesium bricks?
5. How to improve the service life of magnesium bricks?
6. What are the principles of magnesium brick selection?
7. How is the environmental performance of magnesium bricks?
8. What problems can be encountered in the use of magnesium bricks?
9. What are the maintenance requirements for magnesium bricks?
10. What are the advantages of magnesia bricks compared with other refractory materials?
1.What are the main components and content standards of magnesium bricks?
The main component of magnesium bricks is magnesium oxide (MgO), and its content standards are as follows:
Main ingredient: The content of magnesium oxide (MgO) is usually above 90%. Magnesium bricks are made from high-purity magnesium oxide as the main raw material.
Secondary Ingredients: In addition to magnesium oxide, magnesium bricks may also contain a small amount of other oxides, such as silicon dioxide (SiO2), ferric oxide (Fe2O3), alumina (Al2O3), etc. The presence of these ingredients is intended to improve the magnesium bricks' certain properties, such as their structural stability or resistance to erosion.
Content standard: For the content of magnesium oxide, the standard usually stipulates that it should be above 90% to ensure that the magnesium bricks have enough refractoriness and chemical stability. For other impurity components, there is usually a certain limit to avoid affecting the overall performance of magnesium bricks.
2. How are magnesium bricks produced?
(1) Raw material preparation
First choose high quality magnesium sand as the main raw material, the magnesium oxide content in magnesium sand is usually very high. A small amount of flux (such as calcium, aluminum and other oxides) may be added as needed to improve the sintering properties and erosion resistance of magnesium bricks.
(2) Crushing and mixing
The magnesium sand and other raw materials will be crushed to achieve a certain particle size requirements. The crushed raw materials are mixed thoroughly to ensure the uniform distribution of the ingredients.
(3) Molding
Use special equipment to press the mixed raw materials into shape. Common molding methods include dry pressing and wet pressing. According to the shape and size of the required magnesium bricks, choose the corresponding mold for pressing.
(4) Drying
The molded magnesium bricks are placed in the drying room for preliminary drying to remove excess water.
(5) Sintering
After preliminary drying, the magnesium bricks are fed into a pre-firing furnace to further remove moisture and start the sintering process. Subsequently, the bricks are fed into the main sintering furnace for a long period of time at high temperatures (usually above 1500°C) to ensure the densification and stability of the bricks.
(6) Cooling and inspection
After sintering, the bricks are cooled naturally in the furnace to room temperature. After cooling, the magnesium bricks are inspected for size, appearance and physical properties to ensure compliance with the standards.
(7) Packaging and storage
Magnesium bricks passing the quality inspection will be properly packed to prevent damage during transportation. Finished products should be stored in a dry and ventilated place to avoid moisture.
(8) Preparation before application
Depending on the actual need, it may also be necessary to cut or resize magnesium bricks on site. Before installation, a layer of protective material is sometimes applied to the surface of magnesium bricks to enhance their corrosion resistance.
3. What are the main applications of magnesium bricks in glass furnaces?
Magnesium bricks are mainly used in the following key areas in glass furnaces, which require very high performance of refractories to withstand extreme conditions such as high temperatures, chemical attack and mechanical abrasion:
Regenerator
►Regenerator lattice body: Magnesium bricks are particularly widely used in the heat storage chamber lattice body, especially in the top layer of the lattice body, where high-grade magnesium bricks are usually used. This is because the regenerator is one of the more fluctuating and erosive areas of the glass furnaces, requiring high purity magnesium bricks to provide excellent refractory properties and erosion resistance.
►Lower middle layer: Although the lower middle layer may have slightly lower purity requirements for magnesium bricks, it is still necessary to use mid-range magnesium bricks to ensure the stability and durability of the overall structure.
Transition layer
In some designs, magnesium bricks are also used as a transition layer between magnesium bricks and other refractory materials such as zircon bricks, in order to alleviate the differences in thermal stress and chemical erosion between different materials, and to improve the stability and service life of the overall structure.
►Bottom of the melting end: The bottom of the melting end is the core area of glass melting, which needs to withstand the highest temperature and the strongest chemical erosion. Magnesium bricks are very suitable for the bottom of the melting end due to their excellent erosion resistance and high temperature stability.
►Breast wall (side wall): The breast wall is the side wall of the melting tank, which also needs to withstand high temperatures and the erosion of molten glass. The use of magnesium bricks here helps to protect the furnace structure from erosion and maintains an even distribution of heat.
►Port (small melting unit above the melting end): The port is used for preheating and partially melting the raw material, and magnesium bricks are used here to improve melting efficiency and protect the furnace from erosion.
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►Corners of the melting end: The corner areas are places in the melting end where localized overheating and increased erosion are likely to occur. The application of magnesium bricks effectively protects these critical areas.
►Coolers and runners: The coolers are used to control the temperature of the molten glass, while the runners are the channels that transport the molten glass to the molding machine. The application of magnesium bricks here ensures the long-term stable operation of these components.
►Throat: The throat is the exit of the molten glass out of the melting end into the molding machine, where the temperature and erosion are very serious, and the use of magnesium bricks can effectively extend the service life of the throat.
►Hot surface of the furnace: the hot surface is the surface in direct contact with the molten glass in the melting end, and this part is also one of the key areas for magnesium brick application.
The application of magnesium bricks in the glass furnace is mainly concentrated in the key parts such as the lattice body of the regenerator, and its high purity of magnesium oxide content and excellent refractory and anti-erosion properties provide a strong guarantee for the stable operation of the glass furnace. At the same time, with the continuous progress of glass production technology and environmental protection requirements are increasingly improved, the performance requirements of refractory materials such as magnesium bricks are also increasing. Therefore, in the selection of magnesium bricks, need to take into account its composition, purity, physical properties and compatibility with other materials and other factors, in order to ensure the smooth progress of glass production and product quality and stability.
4. What are the refractory properties and erosion resistance of magnesium bricks?
Refractoriness
►High refractoriness: The refractoriness of magnesium bricks is above 2000°C, which means that it can maintain a stable structure and properties at very high temperatures and is not easy to melt or soften. This characteristic makes magnesium bricks ideal for use in high temperature environments such as glass furnaces.
►High load softening temperature: The load softening temperature of magnesium bricks is also high, generally between 1500~1550℃, while the load softening temperature of high purity magnesium bricks can reach 1800℃. This means that under a certain load, magnesium bricks can maintain their shape and strength at higher temperatures and are not easy to deform or collapse.
Erosion resistance
►Strong erosion resistance to alkaline slag: magnesium bricks belong to alkaline refractory materials and have strong resistance to alkaline slag (such as silicate slag). This characteristic makes magnesium bricks perform well in high-temperature industrial furnaces that use alkaline slag, such as steelmaking electric furnaces and glass furnaces.
►Poor resistance to acidic slag: However, magnesium bricks are relatively weak against acidic slag and cannot come into direct contact with acidic products. If it is in the furnace lining with acidic materials, it needs to be separated by other refractory materials (e.g. high alumina bricks) before it can be used.
►Chemical stability: magnesium bricks have good chemical stability, and are not easy to have chemical reactions with glass liquids and other media at high temperatures, thus ensuring the purity and quality of glass products.
Other Characteristics
►High thermal conductivity: The thermal conductivity of magnesium bricks is second only to carbon bricks and silicon carbide bricks in refractory products, which means that it has good thermal conductivity, which helps the heat distribution and temperature control in the furnace. However, it should be noted that the thermal conductivity of magnesium bricks will decrease with the increase of temperature.
►Poor thermal shock resistance: Magnesium bricks have relatively poor thermal shock resistance. They are susceptible to rupture or damage when undergoing rapid temperature changes. Therefore, care needs to be taken to control the rate of temperature change during use to avoid excessive thermal stress on magnesium bricks.
5. How to improve the service life of magnesium bricks?
Selection of high-quality magnesium bricks: Choose high-purity magnesium bricks, especially the MgO content in magnesium sand should be as high as possible, while controlling the content of impurities, especially those components that are prone to melt formation under high temperature conditions, such as B2O3 and SiO2. Attention is given to physical properties such as porosity and magnesite grain size. In general, low porosity and large grain size contribute to the durability of magnesite bricks.
Proper design and construction: Ensure that magnesium brick masonry is structurally sound to avoid unnecessary accumulation of thermal and mechanical stresses. Ensure that brick joints are minimized and filled with suitable sealing materials to reduce the possibility of penetration of molten material.
Optimize furnace operating conditions: Maintain stable temperatures to avoid thermal shock damage caused by rapid temperature changes. Control the composition of the molten glass to minimize erosion of the magnesium bricks. Minimize frequent start-up and shutdown operations, as these processes can cause additional thermal stress on the magnesium bricks.
Regular inspection and maintenance: Inspect magnesium bricks regularly to identify and address potential damage or wear. Regular cleaning of substances deposited on the surface of magnesium bricks prevents the formation of hot spots or causes uneven erosion. Replace or repair magnesium bricks that have shown signs of wear.
Use of protective coatings: Coating the surface of magnesium bricks with an erosion-resistant protective layer, such as a zirconia-based composite material, can be effective in improving their resistance to erosion.
Improve the formula of molten glass: Reduce the erosion of magnesium bricks by adjusting the composition of molten glass.
Adopting advanced construction techniques: Adopt advanced construction techniques and tools to ensure the precision and tightness of magnesium brick masonry. Use high-performance refractory materials such as high-purity magnesium bricks or magnesium bricks with special additives when necessary.
Utilize online monitoring system: Install an online monitoring system to monitor the operating status of the furnace in real time, including temperature distribution, pressure and other parameters, in order to detect and respond to abnormalities in a timely manner.
6. What are the principles of magnesium brick selection?
6.1 Use of the environment and working conditions
Temperature conditions: Choose the suitable magnesium bricks according to the maximum working temperature of the furnace or high temperature equipment. Generally speaking, the refractoriness of magnesium brick is above 2000℃, which is suitable for high temperature environment. However, the specific selection should also consider the temperature fluctuation during the operation of the equipment.
Atmospheric conditions: Magnesium bricks belong to alkaline refractory materials, suitable for alkaline or neutral atmosphere. In acidic atmosphere, magnesium bricks have poor erosion resistance, need to be used with caution or take appropriate measures.
Aggressive media: Consider the aggressive media that may be present in the equipment, such as slag, flue gas, etc. Magnesium bricks are more resistant to alkaline slag, but sensitive to acidic media.
6.2 Material and performance requirements
Purity: Choosing high purity magnesium bricks can improve its refractory performance and erosion resistance. High purity magnesium bricks have less impurity content and more stable crystal structure.
Density and strength: magnesium bricks with high density and strength can better resist deformation and damage at high temperatures. These properties are usually related to the manufacturing process and the quality of the raw material.
Thermal conductivity and thermal shock stability: Choose the right magnesium brick with the right thermal conductivity and thermal shock stability for your specific needs. In some cases, magnesium bricks with low thermal conductivity are required to minimize heat loss, while in environments with large temperature variations, magnesium bricks with good thermal shock stability are required to prevent cracking.
6.3 Economy and sustainability
Cost-effectiveness: Comprehensively consider the price, service life and maintenance cost of magnesium bricks, and choose cost-effective products. Under the premise of guaranteeing performance, reasonable control of costs.
Environmental protection and sustainability: pay attention to the environmental performance and sustainability of magnesium bricks. Choose magnesium brick products that meet environmental standards to reduce the impact on the environment. At the same time, consider the reuse and recycling value of magnesium bricks to promote the recycling of resources.
6.4 Supplier reputation and technical support
Supplier reputation: Choose suppliers with good reputation and word-of-mouth to ensure the quality and supply stability of magnesium bricks. The credibility of the supplier can be assessed by checking relevant information, consulting industry insiders or conducting field visits.
Technical support and service: The supplier should provide comprehensive technical support and service, including magnesium brick selection advice, use guidance, after-sales service. During the selection process, we should fully communicate with the supplier to understand the performance characteristics and application scope of the product in order to make the right choice.
7.How is the environmental performance of magnesium bricks?
7.1 Environmental considerations in the production process
The main raw material of magnesium bricks is magnesium sand, and the mining and processing process needs to pay attention to the impact on the environment, such as taking measures to reduce dust pollution and soil erosion. In the production process of magnesium bricks, through the use of efficient production equipment and technology, it can reduce energy consumption and reduce the emission of carbon dioxide and other greenhouse gases.
7.2 Environmental advantages during use
Magnesium bricks have excellent high-temperature resistance and can work stably for a long time in a high-temperature environment, which reduces the need for frequent replacement and lowers the generation of waste. Due to the low thermal conductivity and good heat preservation performance of magnesium bricks, the heat loss of the furnace can be effectively reduced, thus reducing energy consumption and related pollutant emissions.
7.3 Erosion resistance
Magnesium bricks have good resistance to chemical erosion and can maintain structural integrity in harsh working environments, reducing the risk of environmental pollution caused by erosion.
7.4 Recycling possibilities
Although magnesium bricks are usually not directly recycled, discarded magnesium bricks can be used in the production of other building materials through specific processing methods (e.g. crushing and screening) to realize the recycling of resources.
7.5 Reducing harmful emissions
The use of magnesium bricks helps to reduce gas emissions in the furnace, especially harmful emissions such as sulfur dioxide (SO2) and nitrogen oxides (NOx). The long service life of magnesium bricks means less maintenance, which in turn reduces the amount of waste and pollutants that may be generated during maintenance.
7.6 Environmentally friendly design
As technology develops, some new magnesium bricks are made with environmentally friendly materials, for example by reducing the use of additives that are harmful to the environment. Continuous improvement of the production process, such as the use of low temperature sintering technology, reduces the impact on the environment.
As a high-performance refractory material, magnesium brick has good environmental performance in the production and use process. Through continuous technological progress and management optimization, magnesium bricks will continue to play its positive role in environmental protection in future applications.
8. What problems can be encountered in the use of magnesium bricks?
♦ Erosion: Magnesium bricks may be eroded by acidic or basic components of the molten material. For example, in glass furnaces, acidic components such as SiO2 in the molten glass may erode magnesium bricks. The scouring action of the molten material as it flows may also lead to physical erosion of magnesium bricks.
♦ Thermal shock damage: Magnesium bricks undergoing rapid temperature changes may experience thermal stresses that can lead to cracking or spalling of the bricks. This is due to the poor thermal shock resistance of magnesium bricks. Frequent start-up and shut-down operations can lead to temperature fluctuations, increasing the risk of thermal shock damage.
♦ Spalling: Due to the inhomogeneity of the internal structure of magnesium bricks, such as uneven distribution of pores, internal stresses may arise during use, leading to spalling of the bricks. External mechanical forces may also cause spalling on the surface or inside of magnesium bricks.
♦ Cracks: Thermal stresses are one of the main causes of cracks in magnesium bricks, especially when experiencing temperature changes. Mechanical stresses can also lead to cracks, especially if the brick is subjected to external forces.
♦ Molten material penetration: If the brick joints are not treated properly, molten material may penetrate into the brick joints, leading to accelerated erosion. The brick itself may also lead to melt penetration if it has defects, such as excessive porosity.
♦ Melt reaction: Magnesium bricks may react chemically with certain components in the melt, resulting in a deterioration of their properties. Unfavorable chemical reactions may occur when magnesium bricks are in contact with other refractory materials, such as silica bricks and clay bricks.
♦ Thermal expansion problems: If the coefficients of thermal expansion of magnesium bricks and other materials do not match, this may lead to deformation of the bricks or the entire structure. Uneven temperature distribution within the kiln may also result in inconsistent thermal expansion, which can cause stresses.
♦ Sediment problem: Solid particles in the melt can accumulate on the surface of magnesium bricks to form deposits, which affect heat transfer efficiency and the service life of the bricks. Deposits are difficult to remove and long-term accumulation can reduce the performance of magnesium bricks.
9. What are the maintenance requirements for magnesium bricks?
♦ Avoid moisture: Ensure that magnesium bricks are stored in a dry environment to avoid moisture. Magnesium bricks that have been subjected to moisture may develop internal stresses during use due to evaporation of moisture, resulting in cracking or rupture of the bricks. Check the condition of the magnesium bricks before use to ensure that there is no moisture absorption.
♦ Prevent mechanical damage: In the process of handling and installation, hold the magnesium bricks gently, avoid collision and falling, so as not to cause rupture or damage to the magnesium bricks. Ensure that the magnesium bricks are firmly installed and will not move or fall off during use.
♦ Monitor temperature: Maintain stable temperature conditions and avoid drastic temperature fluctuations. Sudden changes in temperature may cause thermal stresses in the magnesium bricks, which can lead to cracks or fractures. Although magnesium bricks have a high degree of refractoriness, their properties may change when subjected to ultra-high temperatures and over long periods of time. It is important to know the temperature of the environment in which it will be used in advance to ensure that the magnesium brick can withstand it.
♦ Chemical compatibility: Consider the effect of chemicals that may be present in the use environment on magnesium bricks, and avoid contact with chemicals that are incompatible with magnesium bricks. Avoid direct contact between magnesium bricks and silicon bricks, which usually need to be separated by neutral bricks to prevent chemical reactions.
♦ Regular inspection: Periodically check the appearance of magnesium bricks, noting any cracks, spalling or erosion. Verify that the magnesium bricks are still performing their functions effectively, such as insulation and erosion resistance.
♦ Cleaning of deposits: Regularly clean deposits from the surface of magnesium bricks to avoid the formation of hot spots or causing uneven erosion.
♦ Preventive maintenance: Replace magnesium bricks as soon as you notice any signs of damage or deterioration in performance to avoid affecting the normal operation of the entire system.
♦ Use of protective coatings: Where necessary, a protective layer against erosion can be applied to the surface of the magnesium bricks to increase their durability
♦ Online monitoring system: For important applications, an online monitoring system can be installed to monitor the status of the magnesium bricks in real time, including temperature, pressure and other key parameters, in order to detect abnormalities in time.
10.How do magnesium bricks compare to other refractory materials?
High refractoriness
The refractoriness of magnesium bricks is extremely high, usually up to 2000℃ or more, and some high-purity magnesium bricks can even reach 1800℃ or more. This is due to its main crystalline phase of high melting point of magnesite, and the content of up to 87% or more. Compared with siliceous refractories (such as silica bricks, refractoriness is generally around 1600℃) and some other common refractories, magnesium bricks show stronger stability and durability in high-temperature environments.
Excellent resistance to alkaline slag erosion
Magnesium bricks belong to alkaline refractory materials, which have strong resistance to the erosion of alkaline slag (such as calcium ferrate slag system, calcium silicate slag system, etc.). Compared with acidic refractory materials (such as silica refractory materials), magnesium bricks are more stable in alkaline environments and are less likely to be eroded. This is especially important for industrial fields involving alkaline slag, such as iron and steel smelting and non-ferrous metal smelting.
Good high-temperature strength and thermal stability
Magnesium bricks can still maintain high strength at high temperatures and are not easily deformed or ruptured. At the same time, its thermal stability is also good, can maintain relatively stable performance in the environment of rapid temperature changes. Although some refractory materials also have a certain degree of strength at high temperatures, but magnesium bricks in the comprehensive performance is more outstanding. Especially in the high temperature and the existence of chemical erosion environment, magnesium brick advantage is more obvious.
Processability and adaptability
Magnesium bricks can be made into many types and specifications of products through different processes, such as fired magnesium bricks, re-bonded magnesium bricks, chemically bonded magnesium bricks and so on, in order to meet the needs of different industrial fields. Compared with other refractory materials, magnesium bricks are more flexible and diverse in terms of processability and adaptability. This allows magnesium bricks to be used in a wider range of application scenarios and to perform better.
Economy
Although the raw material price of magnesium bricks may be higher, their excellent performance and long service life give them an advantage in terms of overall economics. In the long run, the use of magnesium bricks reduces the frequency of refractory replacements and maintenance costs, thereby reducing overall production costs. As a result, magnesium bricks tend to be the material of choice in a number of industrial sectors that require high refractory performance.
This article provides an in-depth understanding of magnesium bricks. From the performance characteristics of magnesium bricks to the use and maintenance, to the solutions of common problems, every detail is related to the quality of the final product and production efficiency. As a company specializing in providing quality magnesium brick solutions, we understand the challenges faced by our customers in practical applications and are committed to solving them through technological innovation and strict quality control. Our magnesium brick products not only have excellent refractory performance and erosion resistance, but are also designed and manufactured with our customers' actual needs in mind.
If you are looking for a reliable magnesium brick supplier or want to know more about magnesium bricks, please do not hesitate to contact us. We look forward to working with you to promote the development of high temperature industry and create a better future.
