During the production and operation, the melting furnace is constantly eroded and washed by flames, exhaust gas and glass liquid. After about five years, some parts will be seriously damaged, threatening the normal production and the service life of the kiln body. This requires that when the kiln age reaches more than eight years without adding glass water, stopping production and keeping the melting furnace running, a certain part should be repaired. This is the "hot repair" of the melting furnace. Generally, the parts that are often hot-repaired include pool wall bricks, heat storage chamber lattice bricks, small furnace arches and slope arches, nozzle bricks, large arches or heat storage chamber arches with dissolution holes, bubbler replacement and other parts.
The significance of hot repair
The hot repair of the melting furnace is a necessary means to ensure the normal operation of the kiln and extend the kiln life. The kiln is the main thermal equipment for glass production. Daily maintenance alone cannot solve all problems. Hot repair is to maintain the kiln so that it can better serve production. After thermal repair, the severely burned parts are basically restored to their original structural state, meeting the process requirements, maintaining normal production, and extending the kiln life; after thermal repair, the heat dissipation of severely burned parts can be reduced, saving energy and reducing consumption; for some parts that have been proven to be inconsistent with production conditions in practice, they can be improved, supplemented or transformed through thermal repair, so as to achieve the purpose of increasing production; thermal repair is an indispensable and powerful measure to ensure the safe operation of the melting furnace, avoid personal and equipment accidents, and improve economic benefits.
Selection of thermal repair process and refractory materials
At present, there is a new thermal repair welding process called ceramic welding technology. This process is a material composed of a mixture of dry refractory powder and ultra-fine metal powder, which is sprayed onto the high-temperature surface of the melting furnace refractory material with an oxygen flow. The metal powder in contact with the hot surface quickly ignites and burns, releasing a large amount of heat energy, so that the surface temperature of the melting furnace refractory material is as high as 2000℃ or more, causing the mixed powder of the refractory material to melt quickly and tightly combine with the refractory matrix to be repaired. The molten material fills the small holes, connecting surfaces, gaps, etc. on the refractory bricks and repairs them to the original good state.
The equipment for hot gunning consists of a powder mixer, a material delivery system, and control equipment that can adjust different spray parameters. If the inside of the melting furnace needs to be repaired, a water-cooled spray gun that can penetrate deep into the left and right should be configured.
The key to using ceramic welding technology for hot repair is to be able to form a material that is compatible and matched with the base material. The earliest welding material used was siliceous gunning material, and the chemical composition of siliceous gunning material is generally (mass fraction): SiO2 95%, Al2O3 2.5%, CaO 2%, Fe2O3 0.5%. It is especially suitable for the siliceous crown of the melting furnace, such as the opening joint between the crown and the front wall, and the eroded parts of the flame. The repair process is not affected by the atmosphere in the kiln, and the thermal vibration resistance and corrosion resistance of the welding layer can reach the original level.
For hot spraying of fused zirconium corundum bricks, the surface should be "cleaned" first, because at high temperature, the glass phase inside the zirconium corundum brick will migrate to the surface of the brick in a short time, and the pollution of the brick surface by volatile substances in the kiln will form a glass layer. Therefore, before hot spraying, this part of the glass layer must be removed from the surface to form a good combination between the brick and the welding material.
For the fused zirconium corundum bricks of the small furnace mouth side wall, small furnace top arch, and breast wall, the chemical composition (mass fraction) of the spraying material is: SiO2 15.5%, Al2O3 50.5%, ZrO2 32%, Fe2O3 0.13%, TiO2 0.03%, CaO 1.5%, MgO 0.05%, Na2O 0.07%, K2O 0.01%.
For high-aluminum materials, mullite welding materials can be used, and the Al2O3 content in the welding materials can be as high as 98%. This material has excellent corrosion resistance and thermal vibration resistance.
The refractory materials used for hot repair should be the same material as the original design, or materials that will not produce chemical reactions with the contacting masonry, and materials that will not cause low-temperature eutectic. Fill the corroded parts according to the degree of damage, and then immediately apply hot repair mud. At present, there are many varieties of refractory materials in my country, including various sintered materials, electric melting materials, ramming materials, etc., which create conditions for hot repair.
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