Method for producing insoluble calcium sulfate anhydrite
AssigneeUnited States Gypsum Company
InventorRobert E. McCleary
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Abstract
Naturally occurring or man-produced calcium sulfate dihydrate is subjected to a process which involves concomitant flash calcination, utilizing co-current contact of the gypsum with a gaseous heat source, and self-comminutation to produce the insoluble calcium sulfate anhydrite in relatively pure and finely comminuted form without the use of specially-sized feed rock and extensive mechanically motivated grinding of the product required by prior means known in this art.
Claims9
A method for producing insoluble calcium sulfate anhydrite characterized in undergoing about greater than four-fold self-comminution during calcining comprising the steps of:
- (1) introducing finely divided calcium sulfate dihydrate particles at ambient temperatures and hot gas into a calcining zone, said gas entering at a temperature of from about 1500.degree. to about 2400.degree. F;
- (2) maintaining co-current linear flow of the particles and gas in the calcining zone;
- and
- (3) maintaining the particles in the calcining zone for a time sufficient to remove the water of crystallization of the particles while the particles undergo an about four-fold to seven-fold self-comminution, producing insoluble calcium sulfate anhydrite.
The method of producing insoluble calcium sulfate anhydrite characterized in flash calcination with an about four-fold to about seven-fold self-comminution of the calcining particles comprising the steps of:
- (1) feeding calcium sulfate dihydrate particles having an average surface area on the order of about 1000 square centimeters per gram at a temperature of about 70.degree. F into a vertically disposed calcining zone;
- (2) feeding hot gas at a temperature of about 2000.degree. F into the calcining zone;
- (3) rapidly passing the dispersed particles in an upwardly flowing and then horizontally flowing hot gas stream in co-current linear fashion in about 2 seconds whereby the water of crystallization of the hydrate particles is flashed off without chemical decomposition of the calcium sulfate and the particles undergo comminution;
- (4) cooling the calcined particles;
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- (5) recovering insoluble calcium sulfate anhydrite particles having an average surface area on the order of about 5,000 square centimeters per gram.
Dependencies are inferred from the claim text.