As an important refractory material, fused cast blocks are particularly widely used in glass furnaces. Because of the harsh working environment of the glass furnace, refractory materials are required to have high refractoriness, strong erosion resistance, good wear resistance, and erosion resistance, so choosing the right type of fused cast block is important to ensure the stable operation and prolong the service life of glass furnace. The following is a detailed analysis of the kinds of fused cast blocks suitable for use in glass furnaces, divided into four points:
1. Overview of fused cast blocks
2.Types of fused cast blocks suitable for use in glass furnaces
3. Precautions for the use of fused cast blocks
Fused cast blocks refer to the refractory product cast after melting the compound at a high temperature using the electric melting method. According to the different raw materials and compositions, fused cast blocks can be divided into many types, such as fused zirconium corundum block (AZS blocks）, fused corundum block, fused quartz block, and so on. These fused cast blocks have their characteristics in chemical composition, physical properties, and application fields.
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A fused zirconium corundum block（AZS block) is one of the most widely used cast blocks in glass furnaces, its main components are Al2O3, ZrO2, and SiO2, made by electric melting method after combining with a certain proportion. According to the different content of ZrO2, fused zirconium corundum block can be divided into AZS-33, AZS-36, and AZS-41 three grades.
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Advantages:
►High corrosion resistance: Fused zirconium corundum block (AZS block） has a very high resistance to glass corrosion and can resist the erosion of glass liquid at high temperature, to ensure the integrity of the furnace structure.
►Low pollution: The block produces less pollution from the glass liquid during use, which is conducive to maintaining the quality and purity of the glass.
►Good wear resistance and erosion resistance: Fused zirconium corundum block（AZS block) can withstand the erosion and wear of glass liquid, to ensure the long-term stable operation of key furnace parts.
►The structure is stable and dense: The rock phase structure is composed of the eutectoid and glass phases of corundum and zirconium plagioclase, and the structure is thick, which can resist volume change and stress damage at high temperatures.
Application field:
Fused zirconium corundum block is mainly used in glass furnaces in direct contact with the glass liquid, such as side wall, melting end paving, doghouse, throat, bubbling, etc. Among them, AZS-33 blocks are suitable for relatively low temperature and less corrosive parts; AZS-36 blocks are ideal for side walls, and other parts with high corrosion resistance and temperature requirements; AZS-41 blocks are especially suitable for severely corroded parts of glass furnaces, such as bottoms, dam blocks, corners, etc.
Caution:
►Irregular changes in thermal expansion: The thermal expansion curve of fused zirconium corundum blocks has an anomaly near 1000°C because the ZrO2 crystals in this temperature range will undergo a reversible crystal transition (from monocline to tetragonal), resulting in a large volume change. Therefore, ZRO2-containing fused zirconium corundum blocks are not suitable for use in places where the temperature often fluctuates sharply around 1000°C. When baking the furnace, especially in the temperature range of 900°C to 1150°C, the temperature change should not be too fast. Generally, it should not exceed 15°C/h, to prevent the explosion caused by temperature mutations.
►Shrinkage hole problem: When pouring molding, shrinkage holes often appear at the casting mouth, and there are more pores in this part of the block body, resulting in poor density. When laying the wall of the glass melting pool, the shrinkage hole is usually oriented towards the furnace to prevent the leakage of glass liquid when the block erosion is very thin. When used in the upper flame space of the tank furnace, the shrinkage hole can be used outward to extend the service life, because the problem of liquid glass leakage is not easy to occur here.
►The eutectic problem between materials: When fused zirconium corundum blocks are in contact with other types of refractory materials such as clay blocks, eutectic phenomena may occur at high temperatures, resulting in difficult separation of materials. To avoid this situation, the combustion temperature should be controlled and direct contact between the two materials should be avoided.
►Temperature control: In the process of use and oven, temperature changes must be strictly controlled to avoid sharp temperature rises and falls, especially in the sensitive temperature range, to prevent damage to the block structure.
A fused cast high alumina brick is made from high-purity alumina by an electric melting process. The thermal expansion coefficient is minimal, the thermal shock resistance is good, and the corrosion resistance of boron glass liquid is strong.
Advantages:
►High melting point and high hardness: The fused cast high alumina brick has a high melting point and high hardness so that it can withstand erosion and erosion in high-temperature environments.
►Excellent erosion resistance and wear resistance: Corundum is the main crystal phase, so the fused cast high alumina brick has good erosion and wear resistance and is suitable for erosion and serious wear parts.
►Strong corrosion resistance: Although its corrosion resistance is slightly worse than that of fused cast high alumina brick, it can still meet the requirements for use in many glass furnace parts.
Application field:
A fused cast high alumina brick is suitable for the upper structure of the working end of the glass furnace, the combustion port at the back of the melting zone, and the nearby parapet wall and port. In addition, the fusion-cast α-Al2O3 block is mainly used for melting borosilicate glass, opal glass, and sulfate-containing melt, because its high-temperature erosion resistance may be better than that of fused quartz block in some cases.
Caution:
►Thermal expansion and thermal shock stability: The coefficient of thermal expansion of fused cast high alumina brick is relatively low, but it is still necessary to pay attention to the uniform change of temperature in use to avoid sudden temperature fluctuations resulting in thermal shock damage. The slow change in temperature helps to reduce thermal stress and extend the life of the block.
►Chemical erosion: Although fused cast alumina high bricks have strong chemical stability, they can still be attacked by certain chemicals, especially when reducing atmospheres, and their corrosion resistance may decrease. When used, contact with strong alkaline or certain metal oxides should be avoided to avoid accelerating the loss of the block.
►Mechanical strength: During use and handling, heavy objects or mechanical impact should be avoided, which may cause cracks or damage to the block body.
►Upper-temperature limit: The use temperature of fused cast high alumina brick should be lower than its maximum operating temperature, and generally should not exceed 1800°C, long-term working temperature is recommended not to exceed 1650°C, to maintain its structural integrity and performance.
►Installation and maintenance: When installing fused cast high alumina bricks, ensure the block joints are tight to avoid forming weak links. Check the condition of the block body regularly and repair or replace damaged blocks promptly to prevent further structural damage.
►Material compatibility: When used with other types of refractory materials, We should pay attention to matching the coefficient of thermal expansion between materials to avoid structural problems caused by differences in thermal expansion.
►Environmental factors: Fused cast high alumina bricks may absorb water in a humid environment. Before use, ensure the block body is dry to avoid cracking caused by water vapor expansion at high temperatures.
Fused silics brick are made of high-purity quartz sand using the electrofusion method. Its thermal expansion coefficient is minimal, its thermal shock resistance is good, and its boron-resistant glass liquid has strong overall properties.
Advantages:
►Low coefficient of thermal expansion: The coefficient of thermal expansion of fused silics brick is minimal, which can resist thermal stress damage at high temperatures.
►Good thermal shock resistance: It is not easy to crack during rapid cooling at high temperatures, and is suitable for parts with large temperature changes.
►Strong corrosion resistance of boron-containing glass liquid: It has strong corrosion resistance to boron-containing glass liquid.
Application field:
Fused silics brick is mainly used in parts with strong corrosion resistance to borosilicate glass liquid, such as some key parts of borosilicate glass furnace. However, it is not resistant to the erosion of sodium-calcium-silicon glass solution, so it is necessary to choose according to the glass composition when using.
Caution:
►Thermal expansion management: Pay attention to the thermal expansion characteristics of fused silics bricks, and leave an appropriate expansion gap when designing and installing. Under the conditions of high temperature use, the stress that may be caused by thermal expansion should be considered to avoid structural damage.
►Chemical erosion protection: Although fused silics bricks have good chemical stability, they may be eroded in specific environments, especially alkaline environments. Avoid direct contact with strongly alkaline substances or take appropriate protective measures.
►Maintenance and cleaning: Regular inspection of block wear, timely replacement of damaged blocks. Use proper cleaning methods to avoid strong chemicals that can damage the surface of the block.
When selecting the fused cast blocks suitable for use in glass furnace, the following matters should be noted:
A.Temperature adaptability
The fused block must be able to withstand the maximum operating temperature of the glass furnace, usually between 1400°C and 1650°C, or even higher. Thermal expansion characteristics must be taken into account to ensure that the block does not crack or cause structural damage when the temperature changes.
B. Chemical stability
Fused blocks should have good chemical stability and be able to resist the erosion of glass solutions, especially for specific types of glass (such as sodium-calcium glass, etc.).Chemical reactions between block and glass raw materials, melts, volatile substances and furnace gases need to be considered.
C. Thermal shock stability
The operating conditions of the glass furnace may have rapid changes in temperature, and the fuse block must be able to withstand these thermal shocks without cracking or peeling.
D.Mechanical strength
Blocks shall have sufficient mechanical strength to resist physical shock and wear during furnace operation.
E. Thermal conductivity
Thermal conductivity has a significant impact on energy efficiency, and low thermal conductivity fused blocks help reduce heat loss.
F. Assembly and maintenance
The assembly gap of the electric fused block should be as small as possible to reduce the scouring of the glass solution on the block. The ease of installation and maintenance cycle of the block should be considered to ensure easy replacement and repair.
G. Appearance and internal quality
The color of the block, the number of pores, the presence of shrinkage holes and cracks will affect the performance and life of the fused block.Surface defects and internal defects can lead to early block failure.
H. Cost-effectiveness
Consider the purchase cost, service life and maintenance cost of electric fused blocks to achieve the best economic benefits.
I. Supplier reputation
Select suppliers with good reputation and successful cases to ensure the quality and performance of electric fused blocks.
Forglass furnace, fused zirconium corundum blocks (AZS blocks) and fused corundum blocks are more suitable for use in key parts because of their excellent erosion resistance, wear resistance and erosion resistance. Among them, AZS block is especially suitable for the parts directly in contact with glass liquid, such as side wall, working end, etc. The fused corundum block is suitable for the upper structure of the working pool and the combustion port at the back of the melting zone. Of course, in the specific selection also need to be based on the glass composition, furnace structure and use conditions and other factors for comprehensive consideration.
In summary, as a high-performance refractory material, fused cast blocks show many advantages in high temperature industrial applications. From excellent erosion resistance to excellent thermal stability to high heat resistance and low thermal conductivity, it is undoubtedly the material of choice in many high-temperature applications.
Henan SNR Refractory Co., Ltd is specialized in the production of fused cast blocks, each block embodies our pursuit of quality. Using advanced manufacturing processes and selected raw materials, our fused cast blocks not only meet your needs for high temperature operations, but also effectively reduce maintenance costs and improve production efficiency.
We believe that by choosing our fused cast blocks, you will get a longer product life, a more stable production process and higher economic benefits!
If you need anything, please contact us.
E-mail:moon@snrefractory.com
Web:www.snrefractory.com
