METHOD FOR PRODUCTION OF EXTRACTION PHOSPHORIC ACID Russian patent published in 1997 - IPC

FIELD: technology of extractive phosphorous acid, production of fertilizer. SUBSTANCE: reusable phosphoric acid is preliminary treated by portion of sulfuric acid, the process is carried out in the presence of crystals of strontium sulfate. Said strontium sulfate is used as inoculation, its quantity being 0.05-0.5 % of mass of phosphate raw materials. Phosphate raw materials are then decomposed by thus obtained acid mixture and by residue of sulfuric acid. Then reaction mass is separated to prepare production acid and precipitate, the latter being washed to prepare reusable phosphoric acid. Mentioned above crystal inoculation also may contain calcium sulfate, its quantity being 0.1-10 parts per 1 part of strontium sulfate. Said inoculation is used as $$$ itself or it is produced by adding of strontium-containing acid soluble minerals, salts or their supersaturated solutions. EFFECT: improves efficiency of the method. 1 tbl