METHOD FOR PRODUCTION OF PHOSPHORIC ACID Russian patent published in 1995 - IPC

FIELD: production of mineral fertilizers. SUBSTANCE: method involves two-stage decomposition of phosphate raw materials and circulating phosphoric acid. The first decomposition stage uses 75-85 wt.-% of the total amount of phosphate raw materials and phosphoric acid with the temperature of reaction mass ranging from 85 to 92 C. The second decomposition stage utilizes the remaining amount of said reagents. The mass fraction of the solid phase at the second stage is maintained at 15 20% and the content of SO23

^- in the liquid phase, at the level of 15-25% g/l. The resulting suspensions are separated as follows. The suspension of the second stage is separated in the first zone of the vacuum filter, receiving a production acid. Then the suspension of the first stage is filtered through the formed layer of sediment in the second zone of the vacuum filter, receiving both the cake and the circulating phosphoric acid directed to the second decomposition stage. The cake is washed with water to receive the circulating phosphoric acid delivered to the first phosphate decomposition stage. EFFECT: higher efficiency. 3 cl, 2 tbl