9 types of refractory bricks for Glass furnace

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 a 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 gradually cooled down to leave the tin bath at 600℃.

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:

1. Silica bricks for glass kiln

Silica bricks are commonly used in glass melting furnaces, and their main component is silicon dioxide (SiO2). The silica bricks used in glass melting furnaces require a SiO2 content of more than 94%, an upper limit of use 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 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°C and 573°C, the crystallization transformation becomes more intense. It is very 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. Silica brick masonry should have expansion joints.

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. Therefore, 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.

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%, and the content of SiO3 is between 51% and 66%. The density is 1.7~2.4g/cm3, and the apparent porosity is 12%~21%. The upper limit is The 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.

3. High alumina bricks for glass kiln

The main components of high alumina bricks are also SiO2 and Al203, but Al2O3 should be greater than 46%. Made of corundum, high alumina or sillimanite minerals (Al2O3-SiO2). The density is 2.3~3.0g/cm3, the apparent porosity is about 18%~23%, and the upper limit of use 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, regenerator roofs, regenerator walls, etc.

4. Mullite bricks

The main component of mullite bricks is Al2O3, and its content is about 75%. Because it is mainly mullite crystallization, it is called mullite bricks. The density is 2.7-3 2g/cm3, the open porosity is 1%-12%, and the upper limit of use 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.

 

5. 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 their zirconium content: 33%, 36%, and 41%. The zirconium corundum brick used in the glass industry contains 50%~70% Al2O3 and 20%~40% ZrO2. The density is 3.4~4.0g/cm3, the apparent porosity is 1%~10%, and the upper limit of use temperature is about 1700℃, including 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 praseodymium corundum bricks are used to build corners of pool walls, liquid holes and other areas where refractory materials are severely eroded by glass liquid. This material is a very widely used cast refractory material in the glass industry.

6. Fused alumina bricks

It mainly refers to electric fused α, β corundum and electric 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%, upper limit use The temperature is around 1700℃.

Fused alumina has good 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 material channel tank wall, material channel bottom and other parts that come into contact with the glass liquid and require no refractory material contamination at the same time.

7. Quartz bricks

The main component of quartz bricks is SiO2, its content can be as high as more than 99%, the density is 1.9~2g/cm3, the refractory degree is 1650℃, the working temperature is about 1600℃, it is acid corrosion resistant, and is used to build the pool walls of acid boron glass. Flame space thermocouple hole brick, etc.

8. 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.

9. Insulation 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. The porosity of insulation bricks is very large, the quality is very light, and the density does not exceed 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.