Refractory materials are the main components of glass melting furnaces, which have a decisive influence on glass quality, energy consumption and product costs. The future of glass melting technology depends to a certain extent on the progress of refractory manufacturing technology and the improvement of product quality.
For large float lines, the glass furnace is usually composed of an L-shaped suspended wall (usually using silica bricks), a melting part (the area directly in contact with the molten glass should use electric fused bricks, and the top part using silica bricks or electric Melting bricks), necks (usually silica bricks), cooling parts including ear pools (corundum materials are usually used where they are in direct contact with molten glass, and silica bricks or corundum are used where they are not in direct contact with molten glass), annealing kilns, Regenerator (consisting of high-alumina bricks, clay bricks, directly combined with magnesia-chrome bricks) and other parts.
Commonly used insulation refractory materials are as follows:
Silica brick for glass kiln:
Silica bricks are widely used in glass melting furnaces, and the main component is silicon dioxide (SiO₂). The silica brick used in the glass melting furnace requires a SiO₂ content of more than 94%, a maximum operating temperature of about 1600~1650℃, and a density of 1.8~1.95g/cm³. The apparent porosity is required to be less than 22%. The larger the porosity, the worse the quality of the silica brick. The appearance of silicon bricks is mostly white crystals, and the microscopic composition is tridymite crystals. Because silicon bricks undergo crystal conversion and volume expansion at high temperatures, especially at 180~270℃ and 573℃, the crystal conversion is more Because it is fierce, it is necessary to adapt to the crystal transformation of silica bricks and take appropriate measures such as elastic strips during the baking and cold repair process. The silicon brick masonry should be left with expansion joints.
The working temperature of silica bricks is about 200℃ higher than that of clay bricks, but its resistance to corrosion to molten glass and alkaline flying materials is poor, so it is used for masonry structures such as large slabs, parapets and small furnaces. When masonry, use high-silicon refractory mud or silica brick powder and other materials close to the composition of silica bricks as the cementing material.
List of commonly used refractories for glass furnaces
Clay bricks for glass kiln:
The main components of clay bricks are Al₂O₃ and SiO₂, the content of Al₂O₃ is between 30%~45%, the content of SiO₃ is between 51%~66%, the density is 1.7~2.4g/cm³, the apparent porosity is 12%~21%, the highest The operating temperature is 1350~1500℃. In the glass industry, clay bricks are used to build the bottom of the kiln. The pool wall of the working department and the passage, the wall of the regenerator, the chute, the lower checker brick and the flue. As the temperature rises, the volume of clay bricks will expand. When the temperature exceeds 1450℃, the volume will shrink again.
High alumina brick:
The main components of high alumina bricks are also SiO₂ and Al₂O₃, but Al₂O₃ should be greater than 46%. It is made of corundum, high alumina bauxite or sillimanite minerals (Al₂O₃-SiO₂) as raw materials. The density is 2.3~3.0g/cm³, the apparent porosity is about 18%~23%, and the maximum operating temperature is 1500~1650℃. When the porosity of high alumina bricks is low, the corrosion resistance is better. High-alumina bricks can be used to build cooling pool walls, regenerator walls, and regenerator walls.
Mullite bricks:
The main component of mullite brick is Al₂O₃, and its content is about 75%. Because it is mainly mullite crystal, it is called mullite brick. The density is 2.7~3.2g/cm³, the open porosity is 1%~12%, and the maximum operating temperature is 1500~1700℃. Sintered mullite is mainly used for masonry walls of regenerators.
Fused mullite is mainly used to build pool walls, observation holes, wall stacks, etc.
Fused Zirconium Corundum (AZS)Brick:
Fused zirconium corundum bricks are also called white iron bricks. Generally, fused zirconium corundum bricks are divided into 3 grades according to the zirconium content of 33%, 36%, and 41%. The zirconium corundum bricks used in the glass industry contain 50%~70% Al₂O₃, 20%~40% ZrO₂, density 3.4~4.0g/cm³, apparent porosity 1%~10%, and maximum use temperature of about 1700℃. The fused zirconium corundum bricks with 33% and 36% zirconium content are used for masonry of kiln pool walls, flame space breast walls, small furnace vents, small furnace flat turrets, small furnace stacks, tongue turrets, etc., with a zirconium content of 41 % Of the fused corundum bricks are used to build the corners of pool walls, liquid holes and other parts where the refractory material is eroded most severely by glass liquid. This material is the most widely used fused cast refractory material in the glass industry.
Fused alumina brick:
It mainly refers to fused α, β corundum, fused β corundum fused cast refractory bricks, mainly composed of 92%~94% Al₂O₃ corundum crystal phase, density 2.9~3.05g/cm³, apparent porosity 1%~10%, the highest The operating temperature is about 1700°C.
Fused alumina has excellent resistance to glass dialysis and hardly pollutes molten glass. It is widely used in the working part of the glass melting furnace, such as the wall, the bottom, the runner, the wall of the working part, the bottom of the forehearth, etc., which are in contact with the molten glass and require no refractory pollution.
Quartz brick:
Quartz bricks are mainly composed of SiO₂, with a maximum content of over 99%, a density of 1.9~2g/cm³, a refractoriness of 1650°C, a working temperature of about 1600°C, and resistance to acid corrosion. They are used to build the wall of acid boron glass. Flame space thermocouple hole brick, etc.
Alkaline refractories:
Alkaline refractories mainly refer to magnesia bricks, aluminum magnesia bricks, magnesia chrome bricks and forsterite bricks. Its performance is corrosion resistance to alkaline materials, and its refractoriness is 1900~2000℃. It is widely used in the upper wall of the regenerator of the glass melting furnace, the regenerator trellis, the grid body, and the partial structure of the small furnace. Insulation bricks for glass kilns: The heat dissipation area of glass kilns is large and the thermal efficiency is low. In order to save energy and reduce consumption, it is necessary to use a large amount of insulation materials for comprehensive insulation. Especially in the regenerator, melting part, working part and other parts of the pool wall, pool bottom, chute, wall should be insulated to reduce heat dissipation. Insulation bricks have a large porosity, a very light weight, and a density not exceeding 1.3g/cm³. Because the heat transfer performance of air is very poor, the thermal insulation brick with a large porosity has a thermal insulation effect. Its thermal conductivity is 2 to 3 times lower than that of general refractory materials, so the greater the porosity, the better the insulation effect. There are many different types of thermal insulation bricks, including clay thermal insulation bricks, silicon thermal insulation bricks, high alumina thermal insulation bricks, etc.
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