As a large and important raw material in refractory materials, tabular alumina is produced through rapid sintering in a large shaft kiln, which consumes a lot of energy. Therefore, from the perspective of production technology, reducing its energy consumption is the key to improving tabular alumina. Necessary way to be competitive.
Starting from the basic production process and production equipment of sintered tabular alumina, several ways to save energy and reduce consumption are discussed here.
1. Raw material selection. Comprehensive consideration, in terms of raw materials, industrial alumina and calcined alumina powder are used in combination. After compounding and using in a certain proportion, it can not only control the cost of raw materials, but also improve the sintering performance of raw materials, reduce the sintering temperature, and reduce the amount of natural gas. Reduce energy consumption, thereby reducing production costs.
2. Improvements in ball milling technology. The raw materials used for tabular alumina need to be ball-milled into fine powder before being balled. At present, most manufacturers only control the passing rate of the powder particle size of the ball mill to 325 mesh, and have not studied the fine powder particle size. However, the particle size of the raw material is an important factor affecting the sintering effect. The reduction of the particle size will increase the specific surface area of the raw material, increase the sintering activity, promote the sintering effect, reduce the temperature required for sintering, and thus reduce the consumption of natural gas.
The particle size of the raw material powder is mainly realized through the control of the ball mill. The production efficiency of the steel ball in the ball mill is 20%~30% higher than that of the ceramic ball, and the power consumption is saved by 10%~15%. In addition, under the same conditions, the particle size of fine powder produced by steel grinding balls is about 5% smaller than that produced by ceramic balls. In this way, the sintering activity of raw materials can be greatly improved and the energy required for sintering can be reduced. consumption.
3. Use residual heat to dry completely. A large amount of water is added to the semi-finished ball during the molding process, and its moisture content reaches 18%~23%. Therefore, it must be dried before entering the shaft kiln. It is required that the moisture content of the semi-finished ball before entering the kiln is lower than 5%. There will be a large amount of fried ball debris in the kiln, which will affect the atmosphere distribution of the entire kiln, reduce the combustion efficiency of natural gas, and increase the consumption of natural gas. At the same time, a large amount of countercurrent hot gas is discharged into the atmosphere from the mouth of the shaft kiln, causing heat energy to be lost and wasted. For this reason, most manufacturers will also use waste heat for drying treatment. However, due to the design problem of the drying chamber, in addition to the countercurrent hot air power supply of the vertical kiln, the drying chamber also needs to provide additional energy for heating the burners to generate heat. air, which promotes rapid drying of raw balls. Although this method can finally achieve a good drying effect, it increases the consumption of natural gas.
In order to achieve the effect of complete drying of semi-finished balls only by the countercurrent hot air energy of the shaft kiln, a Chinese company has invented a drying chamber for corundum raw material balls with improved heat exchange. The drying chamber includes a heating chamber, and the upper part of the heating chamber is equipped with a The drying work area of the air inlet and the air outlet, the lower part of the heating chamber is the discharge area, and the hot air conveying pipe is arranged in the drying work area. After the hot air enters the main pipe of the hot air delivery pipe from the air inlet, it flows along each branch pipe to heat the wall of the hot air delivery pipe. The semi-finished corundum ball enters the drying work area of the heating chamber through the feed pipe, and on the one hand, it exchanges heat with the hot air in the drying work area to achieve the drying effect; on the other hand, it contacts the wall of the hot air delivery pipe for heat Exchange to realize the drying of corundum semi-finished balls. The water content of the balls dried by this method is basically less than 5%, which has a good drying effect. At the same time, the countercurrent hot air energy at the kiln mouth is also recycled to reduce the consumption of natural gas in the drying bin.
4. Improve combustion system efficiency. The shaft kiln combustion system is the most important and energy-consuming place for the production of tabular alumina. Tabular alumina is rapidly sintered at a high temperature of 1900 ° C to 1950 ° C, and such a high sintering temperature is achieved through the combustion of natural gas. Therefore, improving the combustion efficiency of natural gas in the burner is an important way to save energy.
The combustion of natural gas is a chemical exothermic process, and the adequacy of its combustion is determined by the ratio between natural gas and combustion-supporting air and the uniformity of mixing between them. If the combustion-supporting air is not enough, it may lead to insufficient combustion of natural gas, and if the proportion of combustion-supporting air is too high, it will take away part of the heat and cause energy waste.
In order to improve the efficiency of the combustion system and reduce the consumption of natural gas, it is first necessary to improve the combustion system, including burners, gas mixing devices, etc., to ensure that the combustion of natural gas can be fully and concentrated.
5. Make full use of the waste heat of the furnace. The firing of tabular alumina is a process of rapid firing and rapid cooling. Therefore, when the finished product comes out of the kiln, it still has a relatively high temperature and high heat energy. If it relies on natural cooling, it will not only affect its production efficiency, but also cause a large amount of waste of heat energy. Therefore, it can be considered to install a cooling chamber under the furnace for cooling by cold air, and at the same time, the cooled hot air is recycled and sent to the front drying chamber to improve the drying effect of the drying chamber. After passing through the cooling chamber, the temperature of the finished plate-shaped corundum ball can be lower than 35°C, which can be processed later to improve production efficiency. In addition, a large amount of heat recovery reduces energy consumption.
6. Process crushing system improvements. The processing and crushing system of tabular alumina is basically processed by the Barmac method. However, the Barmac lining and wear-resistant body are now made of wear-resistant iron, and the problem caused by this material is that it is brought into the finished tabular alumina. More Fe impurities affect product quality. In addition, its consumption is high and expensive. Now some manufacturers have begun to use 99 porcelain wear-resistant lining bricks instead of wear-resistant iron for Barmac, and they have also achieved good results. This method can reduce the cost of the original wear-resistant material by 50% to 70%, and at the same time, it can also reduce the content of iron impurities in the product.
