Method for extracting pure alpha-alumina from clays
Abstract
Abstract A METHOD FOR CONVERTING THE ALUMINUM CONTAINED IN CLAYS TO A-ALUMINA WHICH IS OF SUFFICIENT PURITY TO PERMIT ITS DIRECT REDUCTION TO ALUMINUM METAL IN A HALL ELECTROLYTIC CELL. THE METHOD INCLUDES CALCINING THE ALUMINUMCONTAINING CLAY LEACHING THE CALCINED CLAY WITH AQUEOUS NITRIC ACID, FLOCCULATING THE INSOLUBLE IMPURITIES TO AID IN THEIR SEPARATION BY SETTLING AND FILTRATION, CONTACTING THE FILTRATE WITH AN ION-EXCHANGE LIQUID TO REMOVE THE SOLUBLE FERRIC IRON ALONG WITH OTHER METALLIC IMPURITIES, INTRODUCING THE SUBSTANTIALLY PURE ALUMINUM NITRATE SOLUTION INTO A FLUIDIZED BED OF THE PRODUCT ALUMINA MAINTAINED AT A TEMPERATURE PREFERABLY BETWEEN ABOUT 200 AND 210*C., AND HAVING A FLUIDIZING GAS CONTAINING A CONTROLLED AMOUNT OF WATER VAPOR TO HYDROLYZE THE ALUMINUM NITRATE, THUS MAKING IT POSSIBLE TO REMOVE ABOUT 90 TO 95% OF THE NITRATE AS NITRIC ACID VAPOR, AND FINALLY HEATING THE HYDROLYZED DRY PRODUCT FROM THE FLUIDIZED BED TO DRIVE OFF THE REMAINING NITRATE AS OXIDES OF NITOGEN, AND CONVERTING THESE SOLIDS TO A-ALUMINA.
Inventors
- 👤 Richard W Hyde
- 👤 Stanley V Margolin
Bibliographic Details
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