In the configuration design of glass furnace lining, shaped refractory bricks are mainly used. According to the working conditions of different parts of the glass furnace, the materials and properties of the refractory bricks used are also different. The following are the 9 most commonly used refractory bricks for glass furnace linings in China:
1. Silica brick
Silica bricks are acidic refractory materials. Silica bricks for glass kilns are siliceous refractory products mainly used for building high-temperature parts of glass kilns, mainly phosphorus quartz. The melting point of quartz and cristobalite (1670°C, 1713°C). High-quality silica bricks have the characteristics of high purity and density, high softening temperature under load, low refiring change, good creep resistance at high temperature, high compressive strength at room temperature, reasonable mineral phase composition, low true density, and accurate size. As the current photovoltaic glass furnaces become larger and larger, the glass melting temperature is also high, and the silica bricks are limited by low refractoriness (16901730°C) and poor thermal shock stability (14 times of heat exchange in water), which cannot meet the requirements of the melting section. The use of the large dome is required, but the superstructure of the cooling section has become the best choice.
2. Clay bricks
Clay brick is an acidic refractory material, and its acidity gradually weakens with the increase of Al2O3 content in the brick, and its thermal conductivity is the lowest among all refractory materials. Although its refractoriness is as high as 1700°C, the softening temperature under load is only about 1300°C. When it is corroded by a large amount of R2O, the softening temperature will further drop to about 1050°C, so it cannot bear load and pressure when used at high temperature. The thermal expansion rate of clay bricks is the smallest among common refractory materials. At the same time, because clay bricks have fine crystals, small pores and uniform distribution, and stress is easily buffered, they have strong thermal shock resistance in a wide range and can be used in kilns. Important parts such as flue material selection.
3. High alumina brick
Aluminosilicate refractories with Al2O3 content greater than 48% are collectively referred to as high-alumina refractories. According to the content of Al2O3, it is divided into 3 grades:
Class I: Al2O3>75%;
Class II: Al2O3 60%75%;
Ⅲ and so on: Al2O3 48% 60%.
In the range of Al2O3 content less than 71.8%, with the increase of Al2O3 content, the main crystal phase mullite in high-alumina products increases; in the range of Al2O3 greater than 71.8%, with the increase of Al2O3 content, the number of mullite decreases and The amount of corundum increases. The refractory properties of the product increase with the increase of Al2O3 content. Compared with clay refractories, high-alumina refractories have the outstanding advantages of high refractoriness and softening temperature under load, and high-alumina refractory products have higher thermal conductivity than clay products. The thermal shock resistance of high-alumina refractory products is between those of clay products and siliceous products, and can be used for edge-blocking bricks for glass furnace chimney insulation layer.
4. Sillimanite brick
Compared with clay bricks, sillimanite bricks and mullite bricks have a higher softening point under high temperature load, and have a dense and fine-grained structure, which is not easy to cause bubbles in the glass liquid, which is very suitable for the discharge port structure.
5. Mullite brick
The main crystal phase of mullite brick is mullite, the refractoriness of mullite is about 1850℃, the softening temperature under load is high, the creep rate at high temperature is low, the thermal shock resistance is good, and the acid slag erosion resistance can be selected as The vertical flue substructure and the inner surface of the horizontal flue.
6. Fused mullite brick
Fused mullite uses high alumina bauxite as raw material, and mixes different bauxite into mullite composition (3Al2O3-2SiO2), the mass percentage is: Al2O372%, SiO2 28%. The main crystal phases are mullite and corundum, and the glass phase is filled between the crystal phases. Its resistance to glass erosion is stronger than that of sintered refractories, but not as good as fused refractories. Adding a small amount (7% 8.5%) of zirconium dioxide can make the mullite crystal smaller and the brick structure dense, and the mullite increase to 60% 70%, which relatively reduces the content of the glass phase and reduces the product quality. crack. Fused mullite bricks have low thermal expansion coefficient, good thermal shock resistance and strong glass erosion resistance.
7. Fused zirconium corundum brick
Fused zirconium corundum brick belongs to Al2O3-ZrO2-SiO2 system (AZS brick for short). According to the ZrO2 content, it can be divided into three grades: 33%, 36%, and 41%.
Compared with fused mullite bricks, fused zirconium corundum bricks have better corrosion resistance to glass liquid. The main reasons are:
①The main crystal phase in zirconium corundum brick is corundum and baddeleyite zircon which coexist closely, both of which have good corrosion resistance.
② Between the glass phase filling in the zirconium corundum brick and the above crystal phase, this glass phase is eroded by high temperature glass liquid to form albite glass with higher viscosity, which is more viscous due to the melting of a certain amount of ZrO2. The layer of high-viscosity glass remains on the surface of the brick, which is not easy to spread and protects the brick body. The corrosion resistance of fused zirconium corundum bricks increases with the increase of ZrO2 content. Among them, the melting temperature of ZrO2 is as high as about 2700 ℃, and it has high resistance to media such as acid, alkali and glass liquid.
Fused zirconium corundum bricks are not only used for high temperature and severe erosion parts in contact with molten glass, but also widely used in the upper structure of glass melting furnaces.
8. Fused corundum brick
Fused corundum brick a-b-Al2O3 (94.5%96.5%) is made of high-purity alumina as raw material, introduces a small amount of soda ash, and melts at 20002200 ℃. The crystal structure is composed of 45%55% a-Al2O3 and 45%60 % b-Al2O3 phase composition, because a larger amount of b-Al2O3 is intertwined between a-Al2O3 crystals, the original a-Al2O3 tubular microstructure becomes a scaly structure, and the crystals are much smaller than when they exist alone. , so its corrosion resistance is second only to a-Al2O3, and the thermal deformation of the brick body is greatly improved, so it becomes the best choice for large slat refractories in the passage pool wall and the clarification area of the melting part.
Make the refractory erosive at high temperature: AZS-41#>AZS-36#>AZS-33#>a-b-Al2O3, this is because the main crystal phase in the fused zirconium corundum brick is corundum (a- Al2O3) and baddeleyite zircon (ZrO2), both of which have good corrosion resistance. The corrosion resistance of fused zirconium corundum increases with the increase of ZrO2 content. Due to the high strength requirements of the sill bricks, and considering that the volatiles of the glass liquid are easy to accumulate here, the 33# fused AZS bricks should be selected for the smelting bricks of the melting furnace. Volatiles and alkali vapors are more likely to accumulate here. Generally, fused bricks with higher ZrO2 content should be selected, and 41# fused AZS bricks are the best.
9. Zirconium-containing refractory bricks
Zirconium-containing refractory products are refractory products made of zirconium oxide (ZrO2) and zircon (ZrSiO4) as raw materials. Zirconia series products, zircon series products, zirconium mullite and zirconium corundum series products belong to this type of products. According to different production processes, zirconium-containing refractory products are divided into sintered products, fused cast products and non-fired products. Zirconium-containing refractory products have the characteristics of high melting point, low thermal conductivity and good chemical stability, especially good corrosion resistance to molten glass.
The properties of zirconium-containing refractories depend on the properties of ZrO2. Dense, stabilized zirconia has a melting point of 2677°C and a service temperature of 2500°C. The bulk density fluctuates between 4.55.5g/cm3 due to the purity of raw materials and manufacturing methods, and the bulk density of dense zirconia products can reach 5.75g/cm3. The mechanical strength of zirconia products is very high, and the strength is maintained until 13001500 ° C. The thermal conductivity of ZrO2 is much lower than that of all other oxide materials. This characteristic of ZrO2 can be used as a high temperature thermal insulation layer.
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