Insulation materials for glass kilns and types of commonly used refractory materials
Refractory materials are the main components of glass melting furnaces. They have a decisive impact on glass quality, energy consumption and product costs. The future of glass melting technology depends to a certain extent on the advancement of refractory material manufacturing technology and the improvement of product quality.
For large float lines, the glass furnace usually consists of an L-shaped hanging wall (usually using silica bricks), a melting section (the area in direct contact with the glass liquid uses electric fused bricks, and the top part uses silica bricks or electric fused bricks). Fused bricks), clamping neck (silica bricks are usually used), cooling section including ear pool (corundum material is usually used in places that are in direct contact with the glass liquid, and silica bricks or corundum are used in places that are not in direct contact with the glass liquid), annealing kiln, The regenerator (composed of high alumina bricks, clay bricks, directly bonded magnesia bricks) and other parts.
Commonly used insulation materials are as follows:
Silica bricks for glass kiln:
Silica bricks are commonly used in glass melting furnaces, and their main component is silica (Si0z). The silica bricks used in glass melting furnaces require Si0, with a content of more than 94%, a maximum operating temperature of about 1600~1650°C, and a density of 1.8~1.95g/cm?. The apparent porosity is required to be less than 22%. The greater the porosity, the worse the quality of the silica bricks. The appearance of silica bricks is mostly white crystals, and the microscopic composition is tridymite crystals. Since silica bricks undergo crystallization transformation and volume expansion at high temperatures, especially at around 180~270℃ and 573℃, crystallization transformation occurs. It is more intense, so during the kiln baking and cold repair process, it is necessary to adapt to the crystallization transformation of silica bricks and take appropriate measures such as elastic ties, etc. Expansion joints should be left in silica brick masonry.
The working temperature of silica bricks is about 200°C higher than that of clay bricks, but its resistance to erosion by glass liquid and alkaline flying materials is poor, so it is used to build structures such as large towers, parapets and small furnaces. When masonry, high-silica refractory mud or silica brick powder and other substances similar in composition to silica bricks should be used as cementing materials.
List of commonly used refractory materials for glass kilns
Clay bricks for glass kiln:
The main components of clay bricks are Alz0; and Si02. AIz0: content is between 30% and 45%, Si0; is between 51% and 66%, density is 1.7~2.4g/cm; apparent porosity is 12%~21 %, the maximum operating temperature is 1350~1500℃. In the glass industry clay bricks are used to build the bottom of kiln tanks. The working part and the pool wall of the passage, the wall of the regenerator, the grille, the lower checker bricks and the flue. As the temperature rises, the volume of clay bricks will expand. When the temperature exceeds 1450°C, the volume will shrink again.
High alumina brick：
The main components of high alumina bricks are also SiO, and AlzO:, but Alz0; should be greater than 46%. Made of corundum, high alumina or sillimanite minerals (AIzO:-SiOz). The density is 2.3~3.0g/cm’, the apparent porosity is about 18%~23%, and the maximum operating temperature is 1500~1650℃. When the porosity of high alumina bricks is lower, the corrosion resistance is better. High alumina bricks can be used to build cooling section pool walls, regenerators, regenerator walls, etc.
Mullite Bricks
The main component of mullite bricks is AIz0:, its content is about 75%. Because it is mainly mullite crystals, it is called mullite bricks. Density 2.7~3.
2g/cm;, open porosity 1%~12%, maximum operating temperature is 1500~1700℃. Sintered mullite is mainly used for building regenerator walls.
Fused mullite is mainly used for building pool walls, observation holes, wall stacks, etc.
Fused zirconium corundum brick:
Fused zirconium corundum bricks are also called tin iron bricks. Generally, fused zirconium corundum bricks are divided into three grades according to the zirconium content: 33%, 36%, and 41%. Zirconium corundum bricks used in the glass industry contain 50% to 70% Alz0, 20% to 40% ZrOz, density 3.4~4.0g/cm, apparent porosity 1%~10%, and the maximum operating temperature is about 1700°C. , fused zirconium corundum bricks with a zirconium content of 33% and 36% are used to build kiln pool walls, flame space breast walls, small furnace flame vents, small furnace flats, small furnace stacks, tongues, etc., with a zirconium content of 41 % fused berkelium corundum bricks are used to build corners of pool walls, liquid holes and other parts where the refractory materials are most severely eroded by the glass liquid. This material is the most widely used fused cast refractory material in the glass industry.
Fused alumina bricks:
It mainly refers to fused α, B corundum, fused B corundum cast refractory bricks, mainly composed of 92%~94% A1z0: corundum crystal phase, density 2.9~3.05g/cm, apparent porosity 1%~10%, the highest The operating temperature is around 1700°C.
Fused alumina has excellent resistance to glass leakage and hardly pollutes the glass liquid. It is widely used in the working part tank wall, tank bottom, flow channel, working part forehearth tank wall, forehearth tank bottom and other parts that come into contact with the glass liquid and are required to be free of refractory material contamination.
Quartz brick:
The main component of quartz bricks is Si02, which contains up to 99%, has a density of 1.9~2g/cm', a refractory degree of 1650°C, an operating temperature of about 1600°C, and is acid-resistant. It is used to build pool walls of acid boron glass. , flame space thermocouple hole brick, etc.
Alkaline refractory materials:
Alkaline refractory materials mainly refer to magnesia bricks, alumina-magnesia bricks, magnesia-chrome bricks, and forsterite bricks. Its performance is corrosion resistance of alkaline materials, and its refractoriness is 1900~2000℃. It is widely used in the upper wall of the regenerator, the regenerator wall, the grid body, and the partial structure of the small furnace of the glass melting furnace. Insulation bricks for glass kilns: The glass melting furnace has a large heat dissipation area and low thermal efficiency. In order to save energy and reduce consumption, a large amount of insulation materials need to be used for comprehensive insulation. In particular, the pool walls, bottom, and walls of the regenerator, melting section, and working section must be insulated to reduce heat dissipation. Insulation bricks have a large porosity, are very light, and have a density of no more than 1.3g/cm?. Since the heat transfer performance of air is very poor, insulation bricks with large porosity have a thermal insulation effect. Its thermal conductivity coefficient is 2 to 3 times lower than that of ordinary refractory materials, so the greater the porosity, the better the thermal insulation effect. There are many different types of insulation bricks, including clay insulation bricks, silica insulation bricks, high alumina insulation bricks, etc.
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