Introduction to the Physical and Chemical Properties of Silicon Carbide Abrasives
Starting from the basic production process and production equipment of sintering 2-5mm tabular alumina, several ways of energy saving and consumption reduction are discussed.
At present, most of the raw materials for producing 2-5mm tabular alumina in China are industrial alumina powder, and calcined alumina powder is obtained by high-temperature treatment of industrial alumina powder. Therefore, compared with industrial alumina powder, calcined alumina powder has higher activity and sintering performance, and can appropriately reduce the sintering temperature. However, due to the high cost of calcined alumina powder, this is also the reason why some 2-5mm tabular alumina manufacturers in China do not choose it. Therefore, considering comprehensively, the use of industrial alumina and calcined alumina powder in raw materials can control the cost of raw materials, improve the sintering performance of raw materials, reduce the sintering temperature, reduce the use of natural gas, reduce energy consumption, and thus reduce production costs. At present, some manufacturers have adopted this method for trial production and achieved good results.
The raw materials used for 2-5mm tabular alumina need to be ball-milled into fine powder before balling. At present, most manufacturers only control the particle size of the ball mill to 325 mesh pass rate, and have not studied the particle size of fine powder. However, the particle size of the raw material is an important factor affecting the sintering effect. The reduction of particle size increases the specific surface area of the raw material, increases the sintering activity, promotes the sintering effect, and reduces the temperature required for sintering, thereby reducing the amount of natural gas used.
The sintering process of 2-5mm tabular alumina is a solid phase sintering process, which makes the powder body strong through material migration and leads to densification and recrystallization. Therefore, the density of the semi-finished ball of 2-5mm tabular alumina is an important factor affecting the sintering effect of the product. The improvement of the density of the semi-finished product is to change the contact state between the powder particles, shorten the distance between the particles, increase the contact area, and increase the speed and efficiency of energy transfer between the solid phases, thereby improving the sintering effect.
Since a large amount of water is added to the semi-finished balls during the molding process, its moisture content is as high as 18-23%. Therefore, it must be dried before entering the vertical kiln. The moisture content of the semi-finished balls before entering the kiln is required to be less than 5%, otherwise a large number of ball explosions and fragments will appear in the kiln, which will affect the atmosphere distribution of the entire kiln, reduce the combustion efficiency of natural gas, and increase natural gas consumption. At the same time, a large amount of countercurrent hot air is discharged from the kiln mouth of the vertical kiln into the atmosphere, causing heat energy loss and waste. For this reason, most manufacturers will also use waste heat for drying, but due to the design of the drying chamber, in addition to the countercurrent hot air supply of the vertical kiln, the drying chamber also needs to provide additional energy to heat the burner to generate hot air and promote the rapid drying of the raw material balls. Although a good drying effect can be achieved in the end.
The firing process of 2-5mm tabular alumina is a process of rapid firing and rapid cooling. Therefore, the finished product is still at a high temperature and has high heat energy when it comes out of the kiln furnace machine. If it relies on natural cooling, it will not only affect its production efficiency, but also cause a large waste of heat energy. Therefore, it is possible to consider installing a cooling bin under the furnace machine for cold air cooling, and at the same time, the hot air after cooling is recycled and sent to the front drying bin to improve the drying effect of the drying bin. After passing through the cooling bin, the temperature of the 2-5mm tabular alumina finished ball can be lower than 35℃, and it can be processed later to improve production efficiency. In addition, a large amount of heat is recycled and utilized, which reduces energy consumption.
