For large float lines, the structure of glass furnaces is usually composed of L-shaped hanging walls (usually using silica bricks), melting parts (the area in direct contact with the glass liquid should use electric fused bricks, and the area near the top should use silica bricks or electric fused bricks), necks (usually using silica bricks), cooling parts including ear pools (the area in direct contact with the glass liquid usually uses corundum materials, and the area not in direct contact with the glass liquid uses silica bricks or corundum), annealing furnaces, and heat storage chambers (made of high-alumina bricks, clay bricks, and directly bonded magnesia-chrome bricks).
1. Arch top.
The arch top (including arch angle) of the melting and cooling parts of the glass melting furnace is at an operating temperature of 1600°C. The refractory materials used in these parts must be able to withstand high temperatures, loads, and the scouring of alkali vapor and batch materials. Therefore, the refractory materials used as the top must have extremely high refractoriness, high load softening temperature, good creep resistance, and low thermal conductivity. The refractory materials at high temperatures cannot contaminate the glass liquid, and the material density must be small and have good high-temperature strength.
And high-performance, high-quality, high-purity silica bricks have the above characteristics:
a. The load temperature is high and close to its refractoriness;
b. Good stability at high temperature and high compressive strength;
c. Because the main component SiO2, the content is >96%, which is the same as the main element composition of glass, the corrosive substances under high temperature conditions basically will not pollute the glass liquid;
d. The price is cheap.
Therefore, in various glass bridge tops, high-purity and high-quality silica bricks have become the first choice in the production process of various glasses.
The chemical erosion caused by the high-temperature chemical reaction of waste and alkali vapor with refractory materials, as well as the crystal transformation and structural density changes caused by phase migration and temperature are the main reasons for the damage of the top bricks.
The research results show that the corrosion process of high-quality glass kiln silica bricks used in the top of the kiln under the high temperature of the kiln is basically caused by impurity migration and impurity phase change, and the chemical erosion and melting effect can be basically ignored. The effect of phase change and self-purification makes the kiln operation zone gradually change its performance, and its high-temperature performance is improved.
2. Pool wall
1) Parts in contact with glass liquid
The parts of the pool wall of the melting part and the cooling part that are in direct contact with the glass liquid are subject to high temperature, chemical erosion caused by the glass liquid and mechanical and physical scouring caused by the flow. The most important condition for refractory materials in this part is to have good resistance to glass liquid erosion and not to pollute the glass liquid.
Fused zirconium corundum bricks, d-B corundum bricks and B corundum bricks are commonly used for masonry outside domestic glass kilns. Fused zirconium corundum bricks have excellent high temperature and glass liquid resistance. This is because it has obtained the eutectic of baddeleyite zircon and a-A1203 with very good corrosion resistance that sintered refractory materials cannot obtain, so it is very suitable as a pool wall brick for the melting part of the glass kiln.
The main crystal phase of Alpha-beta corundum bricks and beta corundum bricks is corundum, and the glass phase content is only 1%-2%. They have good corrosion resistance. Compared with the performance of fused zirconium corundum bricks, since they do not contain Zr02 crystals, the viscosity of their reaction layer is small and they are not very stable at high temperatures. Therefore, the diffusion rate between the surface of the brick and the glass liquid is relatively large, and the kiln lining is damaged faster. However, when the operating temperature of the kiln is lower than 1350°C, the corrosion resistance of Alpha-beta corundum bricks and Beta corundum bricks is better than that of fused zirconium corundum bricks. Therefore, Alpha-beta corundum bricks and Beta corundum bricks are ideal refractory materials for cooling parts and other parts when the temperature is lower than 1350°C.
2) Parts not in direct contact with glass liquid
The part of the melting part and cooling part pool wall that is not in direct contact with the glass liquid (also called breast wall) is mainly affected by the scouring of alkali vapor and batch materials. Depending on the design, some use corundum materials and some use silica bricks. Both materials can meet the requirements. Therefore, hook bricks and straight bricks are often used in this area.
3. Regenerator
1) Regenerator arch and side wall
The inner surface of the regenerator arch and side wall is corroded by high temperature, dust and alkaline vapor. The degree of corrosion gradually decreases from top to bottom. The selection of refractory materials is determined according to the temperature and degree of corrosion of the top, middle and lower sections of the glass furnace regenerator. Silica bricks are generally used for the top and sides, and low-porosity clay bricks and high-alumina bricks are generally recommended for the middle side wall; general clay bricks and low-porosity clay bricks are generally used for the lower part of the kiln. According to different designs, in recent years, ordinary magnesia-chrome bricks and direct-bonded magnesia-chrome bricks are generally used in the upper part of the side wall, and alkaline bricks such as magnesia-alumina bricks have also achieved good results.
2) Lattice body
Because the entire brick body is under high temperature load, dust and alkaline vapor, the lattice body will be corroded more severely than the arch and side wall, so the use conditions are more stringent. The blockage and collapse of the lattice body are often one of the important reasons for the shutdown and cold repair of the glass kiln. Therefore, the lattice refractory material is required to have high physical strength, low creep rate, strong defense against alkali erosion caused by changes in kiln temperature and atmosphere, no dust adhesion, and slow damage.
At the top of the lattice: the temperature is the highest, reaching 1400-1540°C, and the erosion by alkali vapor and dust is the most serious. Generally, fused rebonded magnesia bricks are used. Since there are relatively few silicates in fused rebonded magnesia bricks, the periclase crystals have grown, and direct bonds have been formed between the periclases, which delays and curbs the rate at which the periclase crystals gradually increase under the action of alkali vapor, and it is not easy to cause the bricks to crack or pulverize.
A. Upper part of the lattice: The temperature here can reach 1100-1430°C, and generally 95# rebonded magnesia bricks are used.
B. Middle part of the lattice: The temperature is 800-1100°C. In the range of 800-1100 degrees Celsius, alkali metal sulfate condenses, and magnesium and calcium lattices are severely corroded by SO3 and Na20 and chemically react, which will cause the larger bricks to expand and be severely damaged. Therefore, this part is not suitable for the use of magnesium bricks, but magnesium-aluminum spinel bricks or directly combined with magnesium-chrome bricks or magnesium-zirconium bricks and forsterite bricks should be used.
C. Lower part of the lattice: This section has a low operating temperature, heavy load, and little alkali corrosion, but it is close to the flue and is directly affected by cold air. The required material should be able to withstand rapid cooling and heating, and it is OK to choose a low-priced one. Therefore, low-porosity clay bricks with relatively low prices are generally used.
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