Process waters in phosphate manufacturing
OwnerGordon F. Palm, R. George Hartiginventors
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Abstract
Modification of phosphoric acid manufacturing provides improved process waters: decontaminated water pH-adjusted to be only slightly acidic, scrubber process water, gypsum stack water, and a composite of the latter two waters. The composite water undergoes two-stage neutralization with clarification, eliminating precipitatable contaminants, in forming the pH-adjusted water, which in turn is useful in forming scrubber process water or gypsum stack water, as needed, Resulting gypsum stacks and rainfall surge ponds, having been made relatively fluoride-free through such processing modification, and preferably also having been lined, supersede previous gypsum stacks and acid gypsum ponds—whether lined or not.
Claims1
In wet-process manufacturing of phosphoric acid, also productive of waste gases, waste gypsum solids as gypsum filter cake and slurry, and liquid drainage therefrom, containing as contaminants soluble fluorides, metal salts, and radioactive compounds, at a pH of about 2,
- the improvement comprising washing waste gypsum filter cake with nearly neutral non-scaling process water produced by the following steps:
- scrubbing some of said waste gases and combining the resulting liquid with liquid drainage from the waste gypsum;
- and
- partially neutralizing and clarifying the combined liquids to a pH of about 4.5, removing insoluble contaminants in the underflow, then alkalizing and clarifying the clarified liquid to a pH of about 11, removing more insoluble contaminants in the underflow;
- and then re-acidifying the resulting clarified decontaminated liquid to a pH of about 6 to 7.
Dependencies are inferred from the claim text.