For large float lines, the structure of glass furnace is usually composed of L-shaped hanging wall (usually using silica bricks), melting part (the area in direct contact with glass liquid should use electric melting bricks, and silica bricks or electric melting bricks are used near the top), neck (usually using silica bricks), cooling part including ear pool (the place in direct contact with glass liquid usually uses corundum material, and the place not in direct contact with glass liquid uses silica bricks or corundum), annealing furnace, heat storage chamber (made of high alumina bricks, clay bricks, and directly bonded magnesia chrome bricks) and other parts.
1. Arch top
The arch top (including arch angle) of the melting part and cooling part of the glass melting furnace is at a working temperature of 1600 degrees Celsius. The refractory materials used in these parts must be able to withstand high temperature, load, and the scouring effect of alkali vapor and batch materials. Therefore, the refractory materials used as the top must have high refractoriness, high load softening temperature and good creep resistance, and low thermal conductivity. The refractory materials at high temperature cannot pollute the glass liquid. The bulk density of the material must also be small and the high temperature strength is good. High-performance high-purity silica bricks have the above characteristics: 1. The high load temperature is close to its refractoriness; 2. Good stability at high temperature and high compressive strength; 3. Since the main component SiO2, the content is greater than 96%, which is the same as the main element composition of glass, the corrosive substances under high temperature conditions will basically not pollute the glass liquid; 4. The price is cheap. Therefore, in various glass arch tops, high-purity and excellent silica bricks have become the preferred choice in the production process of various glasses. The chemical erosion caused by the high-temperature chemical reaction of flying materials 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 arch bricks. The research results show that the corrosion process of the excellent glass kiln silica bricks used in the arch 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.
Structure of glass kiln
2. Pool wall
A) 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 main condition for refractory materials in this part is that they have good resistance to glass liquid erosion and cannot pollute the glass liquid. Domestic glass kilns are generally built with fused zirconium corundum bricks, α-β corundum bricks, and β corundum bricks. Fused zirconium corundum bricks have excellent high temperature and glass liquid resistance. This is because they have obtained the eutectic of baddeleyite and α-Al2O3 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 α-β corundum bricks and β 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, because they do not contain ZrO2 crystals, their reaction layer viscosity is small and they are not very stable at high temperatures. Therefore, the diffusion rate ratio between the brick surface and the glass liquid is very large, and the kiln lining is damaged quickly. However, when the operating temperature of the kiln is lower than 1350℃, the corrosion resistance of α-β corundum bricks and β corundum bricks is better than that of fused zirconium corundum bricks. Therefore, α-β corundum bricks and β corundum bricks are ideal refractory materials for cooling parts and other parts when the temperature is lower than 1350 degrees Celsius.
B) Parts not in direct contact with glass liquid The parts of the melting and cooling pool walls that are not in direct contact with the glass liquid (also called breast walls) are 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-turn and straight bricks are often used in this part. 3. Regenerator (1) Regenerator arch and side walls The inner surface of the regenerator arch and side walls are eroded by high temperature, dust, and alkali vapor. From top to bottom, the degree of erosion gradually decreases. The selection of refractory materials is determined according to the temperature and erosion degree of the top, middle and lower sections of the glass furnace regenerator. It is generally recommended to use silica bricks and excellent silica bricks for the top and side walls, and low-porosity clay bricks and high-alumina bricks for the middle side walls; 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, the upper part of the side wall generally uses ordinary magnesia-chrome bricks and directly bonded magnesia-chrome bricks. Magnesia-alumina bricks and other alkaline bricks have also achieved good results.
(2) Lattice body
Because the entire brick body is under high temperature load, dust and alkali vapor, the erosion degree of the lattice body will be more serious than that of 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 refractory material of the lattice body 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 body: the temperature is relatively high, reaching 1400-1540℃, and the erosion by alkali vapor and dust is also more serious. Generally, electric melting and combined magnesia bricks are used. Since there are relatively few silicates in the fused rebonded magnesium brick, the periclase crystals have grown and the periclase has formed direct bonds, which slows down and stops the rate at which the periclase crystals gradually increase under the action of alkali vapor, and it is not easy for the brick to crack or pulverize.
Upper part of the lattice: The temperature here can reach 1100-1430℃, and 95# rebonded magnesium bricks are generally used.
Middle part of the lattice: The temperature is 800-1100℃. In the range of 800-1100 degrees Celsius, alkali metal sulfates condense, and magnesium and calcium lattices are severely eroded by SO3 and Na2O and react chemically, which will cause very large brick expansion and serious damage. Therefore, this part is not suitable for the use of magnesium bricks, but magnesium-aluminum spinel bricks or directly bonded magnesium-chrome bricks or magnesium-zirconium bricks and forsterite bricks should be used.
Lower part of the grid: This section has low operating temperature, heavy load, and little alkali erosion, but it is close to the flue and directly affected by cold air. The required material should be able to withstand rapid cooling and heating, and the price should be low. Therefore, low-porosity clay bricks with relatively low prices are generally used.
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