PROCESS FOR THE PREPARATION OF CALCIUM SULPHATE ANHYDRITE AND CALCIUM SULPHATE ANHYDRITE OBTAINED BY THIS PROCESS

摘要

The invention relates to a process for the preparation of calcium sulphate anhydrite in which calcium sulphate dihydrate is recrystallized at elevated temperature using concentrated sulphuric acid.
The recrystallization is performed using sulphuric acid at an H2SO2-concentration of 40-65 wt. %, calculated relative to the quantity of liquid phase in the recrystallization mixture. A temperature of between 40 and 90 DEG C and a residence time of 5-30 minutes is applied for the preparation of calcium sulphate anhydrite with an average particle size of 0.5-3 mu , and a temperature of between 20 and 45 DEG C and a residence time of 30 minutes to 3 hours is applied for the preparation of calcium sulphate anhydrite with an average particle size of 10-20 mu .
According to the invention a very pure calcium sulphate anhydrite is obtained, which is suitable for industrial application, for example in the building or paper industry.