Three major thermal equipment for glass production
The three major thermal equipment for glass production, taking float glass as an example, include float glass melting furnaces, float glass tin baths and glass annealing furnaces.
In the glass production process, the glass melting furnace is responsible for melting the batch materials into molten glass, clarifying, homogenizing and cooling it to the temperature required for molding.
The tin bath is the key equipment for glass molding. The glass liquid with a temperature of 1050~1100℃ flows from the flow channel to the tin liquid surface in the tin bath. The molten glass is flattened and polished on the surface of the tin bath, and is controlled by mechanical pulling, edge retaining and edge drawing machines to form a glass ribbon with the required width and thickness. And when it gradually cools to 600℃ during the forward process, it leaves the tin bath.
The function of the annealing kiln is to eliminate the residual stress and optical unevenness of float glass, and to stabilize the internal structure of the glass. The continuous glass strip with a temperature of about 600°C from the tin bath enters the annealing kiln through the transfer roller table.
These three major thermal equipment all require the use of refractory materials. The following 9 types of refractory materials are commonly used in glass melting furnaces:
01Silica bricks for glass kiln
Silica brick for glass melting furnace refers to the silicon refractory products used to build the high-temperature parts of the glass tank kiln (not in contact with the glass liquid). The pool kiln is a complex and huge masonry made of various refractory materials. Its vaults mostly use silica bricks, and the parapets and small furnaces were all made of silica bricks. Some glass kilns also use silica bricks for their regenerator vaults and checker bricks. Silica bricks have no pollution to glass liquid. The main component of silica bricks is SiO2. If there are any pieces falling off or surface droplets during use, it will not affect the quality of the glass liquid. The shape of the product should be regular, and the dimensional deviation should not be greater than ±1% of the design value. The taper of the wedge-shaped bricks should be accurate. Cracks with a width greater than 0.5mm and cooling cracks caused by improper cooling, cracks on the working surface and non-working surfaces are not allowed. Length should be limited individually. The distortion of the brick surface shall not be greater than 0.5% of the brick length.
02Clay bricks for glass kiln
Clay refractory bricks are weakly acidic refractory materials. During the high-temperature calcination process, the internal microstructure of the clay brick changes and forms dense crystals, which results in high refractoriness, high strength and good corrosion resistance. . The characteristics of clay bricks are mainly reflected in their high refractoriness, good thermal stability and low thermal conductivity. This allows the clay bricks to withstand long-term operations in high-temperature environments and maintain structural stability and integrity. At the same time, the thermal conductivity of clay bricks is low, which helps reduce heat loss inside the kiln and improve thermal efficiency.
03High alumina bricks for glass kiln
When high alumina bricks are used in glass kilns, they are mainly used in regenerators, as well as refractory accessories for working pools, forehearths and feeders, such as stirring paddles, homogenizing barrels, punches, etc. High alumina bricks for glass kilns are the general name for aluminum silicate refractory materials with an Al2O3 content greater than 48%. According to the Al2O3 content, it is divided into three grades: first-grade high alumina bricks, Al2O3>75%; second-grade high alumina bricks, Al2O3 60% to 75%; third-grade high alumina bricks, Al2O3 48% to 60%.
Compared with clay bricks, most of the properties of high-alumina bricks for glass kilns are better than clay bricks. The only one thing that is worse than clay bricks is the thermal stability performance. With the difference in Al2O3 content, general high alumina bricks can be divided into three brands: (LZ)-75, (LZ)-65, (LZ)-55, (LZ)-48.
Since the main component of high alumina bricks is Al2O3, they can resist the corrosion of acidic and alkaline slags, and also have certain resistance to the corrosion of iron oxide scales. Therefore, they are often used to build the ceiling, bottom and lower furnace wall of soaking furnaces. On continuous heating furnaces, the furnace bottom, furnace walls, burner bricks, ceilings, etc. can all be built with high alumina bricks. High alumina bricks are also often used as checker bricks to build regenerators.
04mullite bricks
The main component of mullite bricks is Al2O3, and its content is about 75%. Because it is mainly mullite crystals, it is called mullite bricks. 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 building regenerator walls. Fused mullite is mainly used for building pool walls, observation holes, wall stacks, etc.
05Fused 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 their zirconium content: 33%, 36%, and 41%. 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 operating temperature is about 1700°C. Fused zirconium corundum bricks with a zirconium content of 33% or 36% are used to build kiln pool walls, flame space breast walls, small furnace flame vents, small furnace flat vents, small furnace stacks, tongue vents, 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.
06Fused alumina brick
It mainly refers to fused α, β corundum and fused β corundum cast refractory bricks. It is 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 around 1700℃.
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.
07 quartz brick
The main component of quartz bricks is SiO2, which contains up to more than 99%, has a density of 1.9~2g/cm3, 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.
08Alkaline 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.
09Insulation bricks for glass kiln
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. Especially in the regenerator, melting section, working section and other parts of the pool wall, bottom, wall, etc., all 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/cm3. 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.
10Insulation boards for glass kilns
Glass furnaces are key thermal equipment that consumes energy in the glass industry. Choosing Helu ceramic fiber boards as backing insulation boards for glass furnaces will help maintain the sealing and insulation effects of the furnaces. Use various durable refractory materials, such as capacitor refractory materials, or zirconium, chromium, corundum, spinel and alkaline refractory materials, high-density, high-strength refractory materials, backing insulation ceramic fiber boards, etc. and provide reasonable With supporting equipment, the overall service life of the kiln can be increased simultaneously. The quality of furnace building materials has a crucial impact on kiln output, glass quality, fuel consumption and furnace age. The use of refractory materials should also be expanded. In the long run, spending extra money on refractory materials is worth it.
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