What refractory materials are needed for the main components of a glass furnace?

What refractory materials are needed for the main components of a glass furnace?

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), 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, direct bonded magnesia chromium bricks) and other parts.

Refractory materials for glass kilns are mainly divided into the following categories:

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%, a high-temperature operating temperature of about 1600-1650°C, and a density of 1.8-1.95g/cm3. The apparent porosity is required to be less than 22%.Since silica bricks undergo crystallization transformation and volume expansion at high temperatures, especially at around 180-270°C and 573°C, the crystallization transformation occurs. So 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 crown, breastwall and port. 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 Al2O3 content is between 30%-45%, SiO3 is between 51%-66%, the density is 1.7-2.4g/cm3, and the apparent porosity is 12%- 21%, high temperature use 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 vent, 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 brick

The main components of high alumina bricks are also SiO2 and Al2O3, 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 high-temperature 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 crystals, it is called mullite bricks. The density is 2.7-3 2g/cm3, the open porosity is 1%-12%, and the high temperature 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 alumina brick

Fused zirconium alumina bricks are also called tin iron bricks. Generally, fused zirconium alumina bricks are divided into three grades according to the zirconium content: 33%, 36%, and 41%. The zirconium alumina 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 use temperature is about 1700 ℃.Fused zirconium alumina bricks with a zirconium content of 33% and 36% are used to build side wall of tank, flame space breast walls, jack arch of port, , small furnace stacks, tongue vents, etc. Fused zirconia alumina bricks containing 41% zirconium are used to build corners of pool walls, liquid holes and other areas where refractory materials are severely eroded by glass liquid.

6.Fused alumina brick

It mainly refers to fused α, β corundum and fused β corundum cast refractory bricks, which are mainly composed of 92%-94% Al2O3 corundum crystal phase, density 2.9-3.05g/cm3, and apparent porosity 1%-10 %, the high temperature use temperature is about 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.

7.Quartz brick

The main component of quartz bricks is SiO2, which contains 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.

8.Alkaline refractory materials

Alkaline refractory materials mainly refer to magnesia bricks, alumina-magnesia bricks, magnesia-chrome bricks, and forsterite bricks. Its performance is resistance to erosion by 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. 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 2-3 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.