METHOD FOR PRODUCING EXTRACTIVE PHOSPHORIC ACID Russian patent published in 1997 - IPC

FIELD: phosphoric acid production from various types of phosphate raw materials, such as apatite and phosphorite ores. SUBSTANCE: proposed method comprises following steps of: decomposing phosphate raw materials with sulfuric and recirculated acids, crystallizing precipitated calcium sulfate in presence of seeding particles, separating product-laden slurry and washing calcium sulfate precipitate. Seeding particles are produced by grinding portion of calcium sulfate precipitate, and they are introduced into process in amount 0.5-120 seeding particles having size 1-1000 mcm per each 100 particles of precipitated product-laden slurry having same particle size range, average size of seeding particles being at least 1.2 times less than average size of particles of product-laden slurry precipitate. Precipitate particles are comminuted either directly in slurry, or after its decomposition. Optionally, before comminution, precipitate can be divided into coarse and fine fractions in weight ratio 1:(O.1-10), respectively. One of these fractions is recycled back to reaction volume, while other is directed to comminution. EFFECT: method is applicable for processing wide variety of phosphate raw materials. 3 cl, 2 tbl