Glass kilns are a type of melting device that must be possessed by the glass manufacturing industry. Glass melting furnaces have multiple forms according to the type of glass products and the scale of production. The more common one is the glass tank kiln, which is used to produce glass bottles, flat glass, etc. The daily output of a large tank kiln can reach several hundred tons. However, there are also very small crucible kilns, which are specially used to produce optical glass, process glass, etc.
Glass tank kilns can be divided into horizontal flame kilns and horseshoe flame kilns according to their combustion methods. The horizontal flame kiln is a furnace with several pairs of ports on the furnace walls on both sides along the flow direction of the glass liquid. The flame is ejected from the nozzle of the small furnace on one side, horizontally passes through the molten pool, and then discharged into the heat storage chamber through the nozzle of the ports on the opposite side, and repeatedly changes direction for heating. At present, large glass kilns in my country are of this type. The horseshoe flame kiln (end-fire kiln) has a bunch of blast holes at the end of the molten pool (front wall). The flame ejected from one blast hole passes through the molten pool vertically, returns from the end of the molten pool, and is discharged from another blast hole into the regenerator. It changes direction every certain period of time. Because its flame runs in a horseshoe shape, it is called a horseshoe flame kiln, which is usually used in small and medium-sized glass kilns.
The molten pool temperature of the glass melting furnace is as high as 1500℃, and the bottom and wall of the pool are eroded by the glass liquid for a long time. In the regenerator, due to the high temperature of the flue gas and the high dust content, the production conditions of the brick grid are also very bad. Therefore, the refractory materials used in the glass melting furnace must be able to resist the severe erosion under high temperature and not pollute the glass liquid. In recent years, AZS (AL2O3-ZrO2-SiO2) series of electric fused bricks have been used in important parts such as the molten pool, and high-alumina bricks and alkaline bricks have been used as lattice bricks in the regenerator, which have achieved obvious results. In order to save, glass kilns with insulation structures are also increasing.
01 Full oxygen combustion technology for glass melting furnace
Full oxygen combustion technology is a technology with obvious energy-saving and environmental protection effects. At present, only a few large float glass melting furnaces have been built and put into production in the world and use full oxygen combustion technology, but it is still blank in the application of domestic float glass production lines. Furnaces using full oxygen combustion technology no longer need to change fires, and there is no regenerator structure in air-assisted combustion furnaces. Full oxygen combustion technology can greatly reduce energy consumption and exhaust gas emissions in the production process and improve the quality of glass. Now, the attractiveness of this technology is increasing day by day with the continuous reduction of oxygen costs and the continuous increase of energy costs. It is believed that in the near future, this technology will be promoted and applied in domestic float glass production lines.
02 Using full oxygen combustion glass melting furnace
The exhaust gas volume of the full oxygen combustion furnace is less than that of the air-assisted combustion furnace, and the flue gas temperature is relatively high. It can be used to generate steam, preheat batch materials or broken glass, thermal power generation, prepare oxygen required for full oxygen combustion, or preheat oxygen and combustion gas. According to the results of a large number of laboratory studies that have been conducted so far, the energy-saving effect of directly preheating the batch material with the high-temperature exhaust gas of the oxyfuel combustion kiln is more obvious. The high-temperature exhaust gas of the oxyfuel combustion kiln can preheat the batch material to 510℃. The oxyfuel combustion plus the batch material preheating can reduce energy consumption by 37% compared with the traditional air-assisted combustion process. The increasing energy costs make investment in this technology more and more valuable.
03 New melting and clarification technology
In theory, the temperature of glass liquid formation can be 1450℃. Usually, the maximum melting temperature of the float glass melting furnace reaches 1580~1600℃, mainly for high-temperature clarification to eliminate bubbles in the glass liquid. By adopting the decompression clarification technology, the melting and clarification functions of the melting part of the traditional glass melting furnace are completely separated through the change of the kiln structure, that is, the melting and clarification functions of the glass are completely separated, which can reduce the melting temperature, save energy, and effectively eliminate bubbles and improve the melting quality of the glass liquid. After decompression degassing, the number of microbubbles can be reduced to 0.2/kg glass liquid; the melting and clarification temperature can also be reduced by 150℃, so it can save 30% of the fuel required for melting and clarification, and reduce the emission of nitrogen oxides, which is beneficial to environmental protection and prolongs the life of the melting furnace. Foreign research has made certain progress and achieved success in industrial trials. This is a forward-looking and very promising technology that will surely bring a major breakthrough to glass melting technology.
04 Bubbling combustion technology
The purpose of the research is to strengthen the circulation of glass liquid, while promoting the clarification and homogenization of glass liquid, without wasting energy. The solution to the problem is: spraying combustible gas from the bottom of the melting furnace, the gas can stir the glass liquid when it rises in the glass liquid, and when the gas reaches the surface of the glass liquid, it reacts and burns with the residual oxygen in the kiln under the high temperature atmosphere, and the combustion heats the surface of the glass liquid. That is, it plays a stirring and heating role at the same time, which not only reduces energy consumption, but also shortens the heating time.
05 Convection melting technology
The glass is heated in the melting furnace, mainly by radiation, and partly by convection. In convection melting, one or more lances are mounted on the crown, with the flame directed vertically downward to the melt surface. This convection method promotes heat transfer and saves energy. The technology has been installed in several experimental furnaces and can also be used as an innovation in melting furnaces. Convection melting can also be used when modifying melting furnaces.
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