Refractory materials are the main component of glass melting furnaces and have a decisive influence on glass quality, energy consumption and product costs. The future of glass melting technology depends to some extent on the progress of refractory manufacturing technology and the improvement of product quality.
For large float lines, the glass melting furnace usually consists of an L-shaped overhanging wall (usually using silica bricks), a melting section (the area in direct contact with the molten glass should be made of electrofused bricks and the top of silica) composed of bricks or electrofused bricks), a neck section (usually using silica bricks), a cooling section including an ear cell (the area in direct contact with the molten glass is usually made of corundum material and the area not in direct contact is made of silica bricks or corundum) with molten glass), annealing furnace, heat storage chamber (composed of high alumina bricks, clay bricks, directly combined with magnesium-chromium bricks) and other parts, the commonly used insulation materials are as follows.
Silicon bricks are widely used in glass melting furnaces, the main component is silicon dioxide (SiO2). Silicon bricks used in glass furnaces require SiO2 content of more than 94%, the highest use temperature of about 1600 ~ 1650 ℃, the density of 1.8 ~ 1.95g/cm3. requires an apparent porosity of less than 22%. The larger the porosity, the worse the quality of silicon bricks. The appearance of silica bricks is mostly white crystals, and the microscopic composition is scaled quartz crystals. Because silicon bricks undergo crystallization transformation and volume expansion at high temperature, especially at 180-270℃ and 573℃, the crystallization transformation will be more violent. Because of the ferocity, in the baking and cold repair process to adapt to the crystallization transformation of silica brick, and take appropriate elastic strip and other measures. Silica brick masonry should be left with expansion joints. The working temperature of silica brick is about 200℃ higher than that of clay brick, but the corrosion ability of molten glass and alkaline flyings is poor. Therefore, it is used for masonry structures such as masonry, railings and small furnaces. For construction, high-silica refractory clay or silica brick powder and other materials close to the composition of silica brick are used as cementing materials. However, its corrosion ability to molten glass and alkaline flight materials is poor. Therefore, it is used for masonry structures such as masonry, railings and small furnaces. For construction, materials close to the composition of silica bricks, such as high-silica refractory clay or silica brick powder, are used as the cementing material. However, its corrosion ability to molten glass and alkaline flight materials is poor. Therefore, it is used for masonry structures such as masonry, railings and small furnaces. During construction, high-silica refractory clay or silica brick powder and other materials close to the composition of silica brick are used as the cementing material.
The main components of clay bricks are Al2O3 and SiO2. the Al2O3 content is between 30% and 45%, the SiO3 content is between 51% and 66%, the density is between 1.7 and 2.4g/cm3, the apparent porosity is between 12% and 21%, and the maximum working temperature is 1350~1500℃. In the glass industry, clay bricks are used to build the bottom of the furnace. The working section and the walls of the channels of the pool, the walls of the heat storage chamber, the lattice, the lower lattice bricks and the flue. As the temperature increases, the volume of the clay bricks expands. When the temperature exceeds 1450°C, the volume shrinks again.
The main component of quartz bricks is SiO2, the highest content of 99% or more, density 1.9~2g/cm3, refractoriness 1650℃, working temperature about 1600℃, acid corrosion resistance. Used to build acidic boron glass pool wall. Flame space thermocouple hole brick, etc.
The main component of mullite brick is Al2O3, the content is about 75%. Because it is mainly mullite crystal, so called mullite brick. Density 2.2-3 2g/cm3, open porosity 1%-12%, maximum use temperature 1500~1700℃. Sintered mullite is mainly used for the masonry wall of heat storage chamber. Electrofused mullite is mainly used for building pool walls, observation holes, wall stacks, etc.
Electrofused zirconium corundum brick is also called white iron brick. Generally, fused zirconium corundum bricks are classified into 33%, 36% and 41% according to zirconium content. The zirconium corundum brick used in glass industry contains 50%~70% Al2O3 and 20%~40% ZrO2. density 3.4~4.0g/cm3, apparent porosity 1%~10%, maximum use temperature about 1700℃. Zirconium content of 33% and 36% of the electrofused zirconium corundum brick used for masonry furnace pool wall, flame space chest wall, small furnace mouth, small hearth, small furnace stack, tongue hanging, etc., zirconium content of 41% of the electrofused corundum brick used for masonry pool wall corners, liquid holes and other refractory by the most serious parts of the glass liquid erosion.
The main components of high alumina brick is also SiO2 and Al2O3, but Al2O3 should be greater than 46%. Made of corundum, high alumina bauxite or silica line mineral (Al2O3-SiO2) as raw material. The density is 2.3~3.0g/cm3, the apparent porosity is about 18%~23%, and the maximum use temperature is 1500~1650℃. When the porosity of high alumina brick is low, the corrosion resistance is better. High alumina brick can be used to build cooling pool wall, heat accumulator wall and heat accumulator wall.
The glass 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 are needed for comprehensive insulation. In particular, the pool wall, pool bottom, chute, wall, melting part, working part, etc. in the heat storage room must be insulated to reduce heat dissipation. Insulation brick porosity is large, very light weight, the density does not exceed 1.3g/cm3. because of the air heat transfer performance is very poor, porosity of the insulation brick has a thermal insulation effect. Its thermal conductivity is 2 to 3 times lower than the general refractory materials, so the greater the porosity, the better the insulation effect. There are many types of insulation bricks.
Mainly refers to the electrofusion α, β corundum and electrofusion β corundum electrofusion casting refractory bricks, mainly composed of 92% to 94% of Al2O3 corundum crystalline phase, density 2.9 ~ 3.05g/cm3, apparent porosity 1% ~ 10%, the highest working temperature of about 1700 ° C. Electrofusion alumina has excellent resistance to glass permeability, almost no pollution of molten glass fused glass. It is widely used in glass furnace working part of the pool wall, pool bottom, runner, working part of the channel wall, channel bottom and other places that are in contact with glass liquid and require no refractory contamination.
Alkaline refractory materials mainly refers to magnesium bricks, aluminum-magnesium bricks, magnesium-chromium bricks, magnesium-olivine bricks. Its performance to alkaline substances with corrosion resistance, refractoriness of 1900 ~ 2000 ℃. It is widely used in the upper wall of the heat storage chamber of glass melting furnace, heat storage chamber lattice, lattice frame, local structure of small melting furnace, etc.
