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The Central-Prayon Process (CPP) is used to one of Prayon’s production site and has been in operation for more than 40 years. This is a model of the circular economy in the phosphoric acid world as more than 90% of its co-product phosphogypsum is reused in the cement or plaster industry.
It consists in the attack of the phosphate rock under dihydrate conditions. Dihydrate slurry is filtered on a Prayon tilting pan filter to recover the phosphoric acid. Then, the gypsum slurry is converted to hemihydrate by the addition of sulfuric acid and steam in a specific circular reactor designed by Prayon. Hemihydrate slurry is filtered on a Prayon tilting pan filter to recover a high-quality calcium sulfate.
Depending on the rock processed, the ex-filter acid strength is typically 32-34% P2O5 and the typical P2O5 recovery efficiency is 98-99%.