Refractory materials and insulation materials for electric heating forehearth in glass factories
The refractory materials used in the forehearth were commonly used sillimanite bricks in the past. In order to improve the quality of the glass, fused zirconium corundum bricks are now commonly used. α-alumina and β-alumina fused cast bricks are also used. However, this kind of bricks It is difficult to make thin-walled or complex-shaped products. AZS fused zirconium corundum bricks produced by the oxidation method are not easy to cause stones, streaks or bubbles in the glass liquid, and can produce quite complex shapes, so they have been widely used in the manufacture of forehearth bricks recently. Some glass factories use standard-shaped sintered corundum bricks to build the material duct. When building, the brick seams must be tightly joined, otherwise the glass liquid will penetrate through the brick seams and cause severe upward perforation and erosion of the corundum bricks, causing stones and streaks in the glass. and other defects.
In electrically heated forehearths, the electrical conductivity of refractory materials is of great significance. Usually, the heating temperature range of refractory materials is 1000~1500℃, and its electrical conductivity is 9-15 times smaller than that of molten glass. In a general sense, the electrical conductivity of refractory bricks should be as small as possible, so as to avoid unnecessary induced current heating and prevent harmful ion exchange between refractory materials and molten glass. This harmful ion exchange will contaminate the glass liquid and cause quality degradation.
The electric heating forehearth must have a good insulation layer to reduce heat loss and improve thermal efficiency. The outer wall temperature of the forehearth refractory material is usually below 500°C, and ordinary insulation materials can be used. Considering the convenience of masonry and the material having certain mechanical strength, lightweight clay bricks can be used for insulation in the inner layer and aluminum silicate fiber is used in the outer layer.
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