The three major thermal equipment for glass production takes float glass as an example, including float glass melting furnace, float glass tin bath and glass annealing furnace.
In the glass production process, the glass melting furnace is responsible for melting batch materials into molten glass and clarifying, homogenizing and cooling to the required temperature for forming.
The tin bath is the key equipment for glass forming. The molten glass with a temperature of 1050~1100℃ flows into the tin liquid surface in the tin bath from the flow channel. The molten glass is flattened and polished on the surface of the tin bath, and controlled by mechanical drawing, sidewall and drawing machine to form a glass ribbon with the required width and thickness. And it will leave the tin bath when it gradually cools to 600°C during the forward process.
The function of the annealing furnace is to eliminate the residual stress and optical inhomogeneity of float glass, and to stabilize the internal structure of the glass. The continuous glass ribbon with a temperature of about 600℃ caused by the tin bath enters the annealing furnace through the transition roller table.
Refractory materials are all required in these three thermal equipment. The following 9 types of refractory products are commonly used in glass melting furnaces:
1 Silica brick for glass kiln
Silica bricks are widely used in glass melting furnaces, and the main component is silicon dioxide (SiO2). The silica bricks used in the glass melting furnace require a SiO2 content of 94% or more, 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°C and 573°C, 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.
2 Clay bricks for glass kiln
The main components of clay bricks are Al2O3 and SiO2. The content of Al2O3 is between 30% and 45%, SiO3 is between 51% and 66%, the density is between 1.7 and 2.4g/cm3, and the apparent porosity is between 12% and 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.
3 High alumina brick for glass kiln
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.
4 Mullite Brick
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 2.2-3 2g/cm3, the open porosity is 1%-12%, and the maximum operating temperature is 1500~1700℃. Sintered mullite is mainly used to build the wall of the regenerator.
Fused mullite is mainly used to build pool walls, observation holes, wall stacks, etc.
5 Fused Zirconia Corundum Brick
Fused zirconium corundum bricks are also called white iron bricks. Generally, fused zirconium corundum bricks are divided into 3 grades of 33%, 36%, and 41% according to the content of zirconium. The zirconium corundum bricks used in the glass industry contain 50%~70% Al2O3 and 20%~40% ZrO2. The density is 3.4~4.0g/cm3, the apparent porosity is 1%~10%, and the maximum use temperature is 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 of the refractory that are eroded most severely by glass liquid. This material is the most widely used fused cast refractory material in the glass industry.
It mainly refers to fused α, β corundum and fused β corundum 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 and the bottom of the forehearth.
7 Quartz Brick
Quartz bricks are mainly composed of SiO2, with a maximum content of more than 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.
8 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.
9 Thermal insulation brick for glass kiln
The heat dissipation area of the glass melting furnace is large and the thermal efficiency is low. In order to save energy and reduce consumption, a large amount of insulation materials are required 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. The thermal insulation brick has 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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