The three major thermal equipments produced by glass use float glass as an example, including float glass furnaces, float glass tin baths and glass annealing kiln.
In the production of glass, glass melting furnaces are responsible for melting the batch into glass and clarifying, homogenizing and cooling to the temperature required for molding.
The tin bath is the key equipment for glass forming. The glass liquid with a temperature of 1050~1100 °C flows from the flow channel into the tin liquid surface in the tin bath. The glass liquid is leveled and polished on the surface of the tin bath, and controlled by mechanical drawing, ribbing and edger to form a glass ribbon of the required width and thickness. It leaves the tin bath when it is gradually cooled to 600 °C during the forward process.
The role of the annealing kiln is to eliminate residual stress and optical non-uniformity of the float glass, as well as to stabilize the internal structure of the glass. A continuous glass ribbon having a temperature of about 600 ° C from the tin bath enters the annealing kiln through the transition roll table.
All of the three major thermal equipments require refractory materials. Glass melting furnaces are commonly used in the following nine types of refractory products:
1. Silica brick for glass kiln
Silica bricks are used more in glass melting furnaces, and the main component is silica (SiO2). The silica brick used in the glass melting furnace requires a SiO2 content of 94% or more, a maximum use temperature of about 1600 to 1650 ° C, and a density of 1.8 to 1.95 g/cm 3 . The apparent porosity requirement is less than 22%, the larger the porosity, the worse the quality of the silica brick. The appearance of silica brick is mostly white crystal, and the microscopic composition is the crystal of tridymite. Because of the transformation of crystals at high temperature, the volume expansion, especially at 180-270 ° C and 573 ° C, the crystal transformation is more In order to be fierce, in the process of roasting kiln and cold repair, it is necessary to take appropriate measures such as elastic brace to adapt to the crystallization transformation of silica brick. Silicon brick masonry should have expansion joints.
Silica bricks have a working temperature of about 200 °C higher than that of clay bricks, but they have poor erosion resistance to glass liquid and alkaline flying materials, so they are used to build large structures such as large concrete, chest walls and small furnaces. In the masonry, high-silicon refractory mud or silicon brick powder and other materials close to the silica brick composition should be used as the cementing material.
2. Clay brick for glass kiln
The main components of clay bricks are Al2O3 and SiO2. The content of Al2O3 is between 30% and 45%, the SiO3 is between 51% and 66%, the density is 1.7~2.4g/cm3, and the apparent porosity is 12%~21%. The use temperature is 1350~1500 °C. In the glass industry, clay bricks are used to build the bottom of the kiln. The wall of the working part and the passage, the wall of the regenerator, the raft, the lower lattice brick and the flue. As the temperature rises, the clay bricks expand in volume. When the temperature exceeds 1450 ° C, the volume shrinks.
3. High alumina brick for glass kilnThe main component of high alumina bricks is also SiO2 and Al2O3, but Al2O3 should be greater than 46%. It is made of corundum, high alumina bauxite orsillimanite mineral (Al2O3-SiO2). The density is 2.3~3.0g/cm3, the apparent porosity is about 18%~23%, and the maximum use temperature is 1500~1650°C. When the porosity of the high alumina brick is low, the corrosion resistance is good. High-aluminum bricks can be used to build cooling pool walls, regenerators, regenerator walls, etc.
4. Mullite brick
The main component of mullite bricks is Al2O3, which 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 °C. Sintered mullite is mainly used to build regenerator walls.The fused mullite is mainly used for laying pool walls, observation holes, wall sills, and the like.
5. Fused zirconium corundum brick
The fused zirconium corundum brick is also called white iron brick. Generally, the fused zirconium corundum brick is classified into 33%, 36%, and 41% according to the content of zirconium. Zirconium corundum brick used in the glass industry contains 50%~70% Al2O3, 20%~40% ZrO2, density 3.4~4.0g/cm3, apparent porosity 1%~10%, maximum temperature is about 1700°C, including The fused zirconium corundum brick with 33% and 36% zirconium is used for masonry kiln pool wall, flame space chest wall, small furnace squirting port, small furnace flat shovel, small furnace shovel, tongue sputum, etc. The % fused corundum brick is used to build the corners of the pool wall, fluid holes and other glass to violently eroded the most severe parts of the eclipse. This material is the most widely used fused cast refractory in the glass industry.
6. 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%, highest The use temperature is around 1700 °C.
The fused alumina has excellent anti-glass dialysis ability and hardly pollutes the glass. It is widely used in the glass wall of the working chamber of the glass melting furnace, the bottom of the tank, the flow channel, the channel wall of the working section, the bottom of the material channel, etc., and the parts which are not required to be contaminated by refractory materials.
7. Quartz brick
The main component of quartz brick is SiO2, which contains up to 99%, density of 1.9~2g/cm3, refractoriness of 1650°C, working temperature of about 1600°C, acid corrosion resistance, used to build the wall of acid boron glass. Flame space thermocouple hole bricks, etc.
8. Alkaline refractory materials
Alkaline refractory materials mainly refer to magnesia bricks, aluminum-magnesia bricks, magnesia-chrome bricks, and forsterite bricks. Its performance is corrosion resistance to alkaline materials, and the refractoriness is 1900-2000 °C. It is widely used in the upper wall of the regenerator of the glass melting furnace, the regenerator chamber, the structure of the body, and the structure of the small furnace. 9. Insulation brick 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, it is necessary to use a large amount of thermal insulation material for comprehensive thermal insulation. In particular, the pool wall, the bottom of the pool, the concrete, and the wall of the regenerator, the melting section, and the working part are insulated to reduce heat dissipation. The insulating brick has a large porosity and a very low mass, and the density does not exceed 1.3 g/cm3. Since the heat transfer performance of the air is poor, the heat insulating brick having a large porosity has an adiabatic effect. Its heat transfer coefficient is 2~3 times lower than that of general refractory materials, so the larger the porosity, the better the heat preservation effect. There are many different types of insulation bricks, such as clay insulation bricks, silicon insulation bricks, and high aluminum insulation bricks.