Process for reducing radioactive contamination in phosphogypsum
AssigneeUnited States Gypsum Company
InventorsJay W. Palmer, John C. Gaynor
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Abstract
A process of two crystallization stages for reducing radioactive contamination of phosphogypsum is disclosed. In the process anhydrite crystals are obtained through dehydration of the radiation containing phosphogypsum in strong sulfuric acid; a portion of the anhydrite crystals containing the radioactive contamination is converted to substantially radiation free gypsum by crystallizing out on a large solids concentration of radiation free gypsum seed crystals; and coarse radiation free gypsum crystals are separated from small anhydrite crystal relics containing substantially all of the radioactive contamination.
Claims17
A process for reducing radioactivity in waste product phosphogypsum containing radioactive contamination comprising the steps of
- dehydrating the phosphogypsum to calcium sulfate anhydrite containing radioactive contamination;
- in the presence of radiation free gypsum seed crystals rehydrating a substantial proportion, but less than all, of the anhydrite, to a substantially free of radio-activity gypsum of larger particle size than the anhydrite;
- and separating the larger particle size gypsum from the anhydrite containing radioactive contamination.
A process for reducing radioactive contamination in waste product phosphogypsum which comprises:
- (a) feeding phosphogypsum containing radioactive contamination, water and sulfuric acid to a dehydrating zone and mixing them to form a slurry,
- the quantities being charged to the dehydrating zone being such as to provide a slurry comprising by weight about 50-70% sulfuric acid and about 10-60% total solids at a temperature of about 70.degree.-140.degree. C.;
- withdrawing an anhydrite slurry from said dehydrating zone and passing it to a first separation zone to separate sulfuric acid and anhydrite;
- withdrawing product sulfuric acid from the first separation zone
- withdrawing anhydrite containing radioactive contamination from the first separation zone;
- (b) feeding said anhydrite, conventional hydration accelerator, and gypsum seed crystals to a rehydrating zone and mixing them to form a second slurry,
- the quantities being charged to the rehydrating zone being such as to provide a second slurry comprising by weight about 1-20% accelerator and about 10:90 to 90:10 proportions of gypsum to anhydrite,
- converting a substantial proportion but not all of the anhydrite to gypsum;
- (c) passing the second slurry to a second separation zone to separate unconverted anhydrite and gypsum;
- withdrawing anhydrite containing radioactive contamination;
- and
- withdrawing substantially radioactive contamination free gypsum product.
Dependencies are inferred from the claim text.