PRODUCTION OF PHOSPHORIC ACID BY A TWO-STAGE CRYSTALLIZATION PROCESS

摘要

A process and system for producing phosphoric acid. Phosphate rock is dissolved in phosphoric acid in a reaction vessel to form a slurry. The slurry is then reacted in a first stage of crystallization with sulfuric acid to produce calcium sulfate hemihydrate and phosphoric acid. The product acid is separated from the hemihydrates via filtration, and the filter cake is then reacted, in a second crystallization step, with additional sulfuric acid to produce dihydrate calcium sulfate (gypsum) and recovery solution. The gypsum is separated from the recovery solution via filtration and removed as a by-product. The recovery solution is recycled back to the transformation tank and to the hemihydrate filtration step. A feed acid tank combines wash solution, recovery solution and product acid. Once adjusted to a target P2O5 concentration, it is fed to the initial reactor vessel to dissolve the phosphate ore.