Phospho-gypsum recovery process

摘要

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 DEG -600 DEG C. to vaporize the fluorine values, the P2O5 values and water and reacting the hot vapors with lime or limestone to remove the fluorine values as fluorspar. The P2O5 values are subsequently condensed and used in a phosphoric acid plant. The dry phospho-gypsum is heated to 1200 DEG -1250 DEG C. under reducing conditions to produce SO2 gas and siliceous lime. The SO2 is then passed through a lime or limestone scrubber to eliminate any remaining fluorine values, dried and utilized in a contact sulfuric acid plant.