Refractory materials used in foreign glass kilns mainly include the following six categories:
1. AZS and high zirconia bricks
The production process of fused AZS bricks is mainly to improve their corrosion resistance and wear resistance. In addition to adopting oxidation melting to reduce the carbon content of the product to 0.005 and increase the glass phase precipitation temperature to 1450℃, the casting and annealing processes have also been improved. Now, fused AZS with very small or even no shrinkage cavities and high zirconia bricks with ZrO2 content of more than 90% have been produced, and their thermal shock resistance is very good. For example, high zirconia bricks with ZrO295, Si021.4, stabilizer 3.7, volume density 4.7g/cm3, porosity 18.4, thermal shock resistance from room temperature to 1400℃ (15 minutes interval) can reach 15~20 times. Japan has produced a fused-cast zirconia brick with a zirconium oxide content of 90%, called ZFC brick. Its corrosion resistance is better than that of AZS brick with a ZrO2 content of 40. At 1500~1600℃, no glass phase precipitates after 16 hours, and the pollution to glass is minimal. After 40 times of thermal shock resistance test at 800~1250C, there is no crack.
2. Chrome bricks and chrome-containing bricks
Dense chromium oxide bricks formed by isostatic pressing are used for the side walls, necks or other severely corroded parts of E glass and C glass tank kilns, and their service life can reach 6~7 years. In recent years, new progress has been made in chromium-containing products, such as adding Cr203 to AZS bricks to form A1203-Zr02-Si02-Cr203 refractory materials. At high temperatures, Cr203 forms a solid solution with A1203 on the one hand, and on the other hand, because Cr203 is a high melting point substance, it enters the glass phase of the brick to increase the viscosity of the glass phase, thereby increasing the seepage temperature of the glass phase, which greatly improves the glass corrosion resistance of glass products. A US company has produced a rebonded fused AZS/Cr203 refractory material with excellent chemical composition and physical properties. Compared with the original AI203/Cr203 material, it reduces power consumption by 4% per furnace period, increases output by 15%, reduces costs by 3.75%, and does not affect glass quality. This type of brick can be formed by machine pressing, manual ramming or isostatic pressing, and then sintered at high temperature.
3. Alkaline bricks
High-purity direct-bonded alkaline bricks fired at 1800℃ are widely used in regenerator walls and Germany has launched a new material, the trade name is RUBINAIEZ, its chemical composition is MgO75, ZrO213.5, Si029.5, it is a periclase brick bonded with zircon. In the early stage of sintering, the zirconium silicate in the brick structure reacts with magnesium oxide, forming a protective layer of forsterite and zirconium oxide around the periclase particles. This structure greatly improves the brick's resistance to alkali and sulfate erosion, and has a good effect as a checkerboard brick in the middle of the regenerator.
4. Olivine magnesia brick
Olivine binder phase has particularly strong corrosion resistance. By increasing the forsterite content in the binder phase of magnesia brick, the corrosion resistance of magnesia brick can be improved. For this reason, 20% forsterite fine powder is added to the ingredients of magnesia brick to form a forsterite binder matrix that can protect magnesia particles and reduce corrosion. This brick is relatively cheap and has been widely used in the middle of the lattice body of the glass kiln regenerator abroad.
5. Barium feldspar olivine brick
In view of the good corrosion resistance of olivine and its insufficient thermal shock resistance, the introduction of barium feldspar in its binder phase can significantly improve the thermal shock resistance of the brick. Barium feldspar is formed during the firing process and only exists in the binder matrix phase. When the content of barium feldspar is 15, the performance of silicon is the best, and the operating temperature is about 1250"C. Studies have shown that barium feldspar can resist the corrosion of alkali and sulfate.
6. Amorphous refractory materials
The application of amorphous refractory materials in glass kilns is also a development trend. The UK uses refractory concrete prefabricated blocks to build heat storage chambers, checker brick bottom arches, flues, small furnace support plates, burners, etc., which greatly reduces the joints of the kiln structure, improves the furnace construction speed and shortens the cold repair time. ERSOL of France Xiyin is an amorphous refractory series made of ER1681 fused particles as the main component. It is used in conjunction with fused bricks on the bottom of the pool. It has excellent resistance to glass erosion and has a weak tendency to precipitate bubbles and form stones. Some Japanese glass kiln pool bottoms have all used ER2SOL series amorphous materials. The theoretical research on refractory materials for glass kilns abroad revolves around how to further improve the resistance to glass erosion and improve mechanical properties, in order to further extend the life of the furnace.
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