From the beginning, in the glass manufacturing industry, users of continuous operation of glass furnaces have faced a common headache: the service life of glass furnaces is generally short. This problem not only affects production efficiency but also increases the operating cost and maintenance burden of enterprises. To effectively extend the furnace life of glass furnaces, researchers and engineers have carried out a lot of research and development work, and are committed to exploring various possible solutions.To make the glass furnace have a long furnace life, it is necessary to have a scientific and reasonable furnace design. This includes the structural layout of the furnace, the optimization of thermal parameters, and the rationality of the operation process. At the same time, regarding the matching and selection of refractory materials, it is also necessary to continuously learn from the experience and lessons in the operation of the previous furnace, and carry out continuous improvement and optimization.
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As an important part of the glass furnace, the quality and performance of refractories are directly related to the service life of the furnace. After years of research and development, the internal quality and appearance quality of refractory materials have been significantly improved. These improvements are not only reflected in the high-temperature resistance and erosion resistance of the material but also the stability and reliability of the material. With the continuous improvement of the quality of refractory materials, the selection and reasonable matching of refractory materials have more and more influence on the life of glass furnaces. Different refractories have different physical and chemical properties and are suitable for different working environments and conditions. Therefore, when selecting refractories, it is necessary to consider multiple factors such as the performance, cost, and maintainability of materials according to the specific needs and working environment of glass furnaces.
This paper will focus on the use of fused cast AZS block, a typical refractory material and casting method, to further explain the importance of refractory selection and matching. As one of the refractories commonly used in glass furnaces, the stability and reliability of the performance of fused cast AZS block have a crucial impact on the overall life of the furnace. By comparing the application effect of different varieties and casting methods of fused cast AZS blocks in the furnace, we can more deeply understand the important role of refractory selection and matching in improving the life of glass furnaces.
Fused cast AZS block according to the different zirconium content is divided into: 33#, 36#, and 41# three varieties.
Fused cast AZS 33 block
Fused cast AZS 33 block is mainly composed of alumina (Al2O3), zirconia (ZrO2), and silicon dioxide (SiO2). The proportion of its chemical composition is determined according to the Al2O3-ZrO2-SiO2 ternary phase diagram and is named according to the order of the content of each component. The "33" in fused cast AZS 33 block means that the content of alumina is about 33%. In addition to the main components mentioned above, fused cast AZS 33 block tiles may also contain small amounts of other oxides such as sodium oxide (Na2O) and potassium oxide (K2O), the content of which is strictly controlled to ensure the overall performance of the material. Fused cast AZS 33 block has a dense microstructure, which makes it resistant to glass liquid erosion performance, not easy to produce stones or other defects in glass furnaces, while it has a high density and low porosity, which helps to improve its erosion resistance and overall strength. Fused cast AZS 33 blocks have high compressive strength and can withstand high temperature and pressure environments in glass furnaces. The erosion rate of fused cast AZS block in glass liquid is slow, and it can keep its shape and performance stable for a long time.
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Fused cast AZS 36 block
The chemical composition of fused cast AZS 36 blocks mainly includes alumina (Al2O3), zirconia (ZrO2), and silicon dioxide
(SiO2). Its name is based on the chemical composition ratio of Al2O3-ZrO2-SiO2 ternary phase diagram and in order of content from high to low. The "36" in fused cast AZS 36 block means that the content of alumina is about 36% while containing a relatively high amount of zirconia (usually around 36%) and a moderate amount of silica. Fused cast AZS 36 block improves the ZrO2 content, increases the corrosion resistance of molten glass, and is used in the glass liquid contact part of a wide range of melting tanks, but cannot be used in the furnace where the erosion is particularly serious. In terms of chemical composition, the ratio of SiO2 to Na2O is small, and the restriction of impurities is slightly relaxed. So its precipitation is the worst. However, there is no need for the fused cast AZS 36 block variety to pay attention to the pollution of glass liquid like the working tank and the feeding channel. Fused cast AZS36 blocks are extremely resistant to erosion, thanks to their dense microstructure and the presence of chain-like zirconia crystals. These crystals can effectively resist the erosion of glass liquid and extend the service life of refractory materials. At the same time, it has good high-temperature stability and thermal shock resistance. Compared to AZS33, AZS36 has higher erosion resistance and better overall performance, so it is suitable for higher temperatures and harsher working environments.
Fused cast AZS 41 block
The main chemical components of fused cast AZS 41 block include alumina (Al2O3), zirconia (ZrO2), and silicon dioxide (SiO2). Its name comes from the chemical composition ratio of Al2O3-ZrO2-SiO2 ternary phase diagram and is arranged in order of content from high to low. The "41" in fused cast AZS 41 block means that it has an alumina content of about 41% while containing a relatively high amount of zirconia (usually around 41%, but generally lower than the alumina content), and a moderate amount of silica. This combination of chemicals gives fused cast AZS 41 block excellent fire resistance and corrosion resistance. Fused cast AZS 41 block #ZrO2has the highest content, and SiO2 has a large ratio to Na2. Due to the extreme control of impurities such as Fe2O3and TiO2, the matrix glass increases the viscosity of the glass. Therefore, the fused cast AZS 41 block has the highest erosion resistance and the best precipitation among the three varieties. Fused cast AZS 41 blocks are used in the key parts of the most intense erosion in the melting pool of the glass furnace and the life of the furnace, namely: the throat, the corner block, the weir block, the bubbling block, etc. Fused cast AZS 41 block ZrO2 high content, dense organization, matrix glass hard, on the other hand, due to the heating process prone to crack, so it is necessary to pay attention to the temperature change when the furnace temperature. In addition, cracks are also prone to occur in the production process, and the pass rate is poor compared with the other two varieties, and complex shapes cannot be produced.
Fused cast AZS block can be divided into regular casting (PT), tilt casting (QX), void-free casting (WS), and end casting (ZWS) according to different casting methods.
Regular casting (PT)
Fused cast AZS blocks due to the liquid solidification volume shrinking more than 20%, so the center will appear cavity (shrinkage hole), to reduce the shrinkage hole, as far as possible use a large casting head in the casting, and fill. Before removing the casting head, if the holding time is too long, the soup hole is completely cured, and the casting head removal becomes difficult, which will lead to cracks in the product and reduce the yield. According to the size of the product, the design uses different casting heads, and the time to remove them is also different. If this benchmark is followed correctly, the volume of the shrinkage hole can be reduced by about 10%. However, in the regular casting method, there are residual pores in the center below the soup mouth, which is inevitable, so the shape design of the product and the position of the casting mouth are very critical, and the design should take into account the position of the pores when the product is used in the safest place so that to some extent, it can make up for the defects of the shrinkage hole. In addition, the fused cast AZS block cooled rapidly near the skin, crystallized very fine, and the organization was dense; The internal cooling is slow, the crystallization is large, the internal organization is not dense, the crystallization around the shrinkage hole is coarse and large, forming a coarse crystalline structure with a large gap, and the dense part of the skin has the largest corrosion resistance, and the larger the internal crystalline structure, the smaller the corrosion resistance.
Tilt casting (QX)
The shrinkage hole of the sidewall blocks of the dissolving tank is concentrated in the lower part, so that the upper part becomes a
dense epidermal tissue, and the purpose of improving the erosion resistance is achieved by this casting method. After casting, the incubator is tilted until fully cured, so that the shrinkage holes are gathered on one side and the dense layer on the other side is thickened. As shown in A, this method is applied to the sidewall blocks of the glass dissolving tank whose lower part is less eroded by liquid glass erosion. However, in the tank furnace used to strengthen the thermal insulation of the sidewall blocks of the furnace bottom and sidewalls, the glass liquid temperature of the furnace bottom is high or the flow rate of the glass liquid is excessive in the multi-foaming glass furnace, as shown in B,the erosion of the lower part of the sidewall blocks should not be ignored. It is best not to choose QX products.
Void -free casting (WS)
No shrinkage cavity means cutting off the pore part and leaving only the dense part as the product. The existence of pores has a great influence on the life of the furnace, so use shrinkage cavity-free products. A casting head larger than the fault area of the product part is designed above the mold of the product part. As the solidification layer of the product part continues to shrink, it is constantly supplemented from the casting head part until the product is solidified and formed, and then the pores of the product part are removed, that is, the void-free casting method. Due to the reduction of the feed liquid in the solidification riser, it is necessary to add new melt from the electric furnace until the product is completely solidified before the casting head is cured.
End casting (ZWS)
The void-free casting method is to make the product part all dense tissue, to use a large casting head, the cost is high.ZWS is smaller and lower cost than the WS casting head, so a small number of pores and coarse crystal structures are allowed to remain on the cutting surface after removing the casting head. This is contrary to the concern about using QX as the sidewall block of the melting pool described above. ZWS has no problem in use and durability and can be produced at a cheaper price than WS. Therefore, glass furnace life designs long sidewall blocks, basically using this casting method.
As the core equipment in glass production, the selection of refractory materials and precautions in different parts of the glass furnace are important, which is directly related to the service life, production efficiency, and product quality of the furnace. When selecting refractory materials, it is necessary to consider the working environment, temperature, erosion degree, mechanical stress, and physical and chemical properties of the material.
►For the melting part, including the sidewalls and bottom of the furnace, refractory materials need to have very high erosion resistance and high-temperature stability due to direct contact with high-temperature liquid glass. The sidewall is often used fused cast AZS block, such as AZS-33, AZS-41, etc. These materials contain different proportions of alumina and zirconia, which can effectively resist the erosion of glass liquid. The bottom of the furnace is often a multi-layer composite structure, the main layer using clay bricks, above the protective layer and wear-resistant layer, wear-resistant layer mostly using fused cast AZS block or dense zircon brick to improve wear resistance and erosion resistance.
►The parts of the throat, especially the cover blocks, are subjected to high-speed erosion and wear of the glass liquid, so it is necessary to choose non-shrinkage hole fused cast AZS blocks with excellent wear resistance. Throat, weir, and bubble blocks generally choose 41#WS blocks and require the dense internal organization of the block, no loose tissue and tiny pores exist, and require high processing accuracy, brick joints should be less than 0.5 mm.
►The selection tuck stone is generally selected 33#, to prevent the tuck stone from falling off and melting damage, the lower tuck stone of the port to choose WS or ZWS products, other parts of the tuck stone can use PT casting, but pay attention to change the position of the shrinkage hole, and hook part of the tuck stone to clear the specifications of the crack.
►The part of the front wall is subjected to wear, corrosion, and flame erosion of the compound, which is one of the weak links of the furnace. AZS-33 blocks or high-quality silicon bricks are often used, and air cooling measures are used to improve the service life. Rort parts, including the port neck and nozzle bricks, need to be resistant to high temperature, erosion resistance, and a certain degree of thermal shock resistance, according to the fuel type, can choose silicon brick, kaolin brick, or 33 blocks.
►For furnace crown block, generally choose silicon brick, but to the A12O3 content and Na2O content of silicon brick specifications, and the accuracy of the combined surface of silicon brick should also be required to improve the quality of silicon brick, at the same time, when building a furnace, baking furnace should pay attention to the arch segment difference and brick seam, and strictly by the thermal expansion curve of silicon brick heating furnace.
In the selection process, it is also necessary to pay attention to the construction and maintenance of refractory materials. During construction, it should be ensured that the thickness of the brick joint and the allowable deviation of the masonry meet the regulations, and pay attention to the choice of dry laying and wet laying methods and the retention of expansion joints. During maintenance, the wear and corrosion of refractory materials should be regularly checked, the damaged refractory materials should be replaced in time, and the temperature changes during baking and cooling should be paid attention to avoid severe temperature fluctuations leading to damage to refractory materials.
The life of the glass furnace is related to many conditions, such as the rationality of the furnace design, the reasonable selection and matching of refractory materials, the masonry, and construction of the furnace, the rationality of the temperature rise of the furnace when the furnace is baked has a great relationship, after the furnace production begins, the stability of various production conditions of the furnace, and the daily maintenance of the furnace have a greater impact on the service life of the furnace. Therefore, improving the life of the furnace is a systematic project, which requires strict management control from design, selection of refractory materials, construction, furnace, and production and maintenance.
Henan SNR Refractory Co., Ltd（SNR） produces a variety of high-quality fused cast AZS blocks.If you have any needs, please contact us.
