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Abstract

This disclosure involves a process for treating wet phospho-gypsum, a by-product from wet phosphoric acid manufacture, to remove fluorine values so as to make the sulfur values in the phospho-gypsum usable in making sulfuric acid in a contact sulfuric acid plant. The process involves drying the phospho-gypsum at 400.degree.-600.degree. C. to vaporize the fluorine values, the P.sub.2 O.sub.5 values and water and reacting the hot vapors with lime or limestone to remove the fluorine values as fluorspar. The P.sub.2 O.sub.5 values are subsequently condensed and used in a phosphoric acid plant. The dry phospho-gypsum is heated to 1200.degree.-1250.degree. C. under reducing conditions to produce SO.sub.2 gas and siliceous lime. The SO.sub.2 is then passed through a lime or limestone scrubber to eliminate any remaining fluorine values, dried and utilized in a contact sulfuric acid plant.

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First Claim