Investigation of the drying process in fine-grain alumina articles

Conclusions

Unfired alumina after acid processing contains up to 3% hydrates and oxychlorides of aluminum. In the materials fired at high temperatures the hydrates and oxychlorides of aluminum are practically absent (0.1%), and therefore cannot have any marked effect on the drying of the products. In the range 30–50° some 93.5% of the total moisture is separated. Consequently, decisive significance in the development of mechanical stresses leading to cracking in the products is shown by the rate of temperature rise in this range.

A rational drying cycle is proposed for the products. In the range 30–50° we specify a rate for temperaturerise of 1.5 deg/h. The yield of acceptable products after drying and final firing is 95%. It is desirable to dry, and subsequently carry out high-temperature firing, in a continuous process.