Central-Prayon Process

02 Centralprayon Process 05

The Central Prayon Process or CPP

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%.


  • highest P2O5 recovery on the market
  • lowest P2O5 content in the phosphogypsum among all available technologies
  • self-drying phosphogypsum with a final moisture around 10% (lowest on the market without needing drying)
  • limited grinding of the rock


  • when medium- to high-cost rock is accessible
  • where energy cost is rather high (steam and electricity)
  • where gypsum disposal is limited and/or where a potential market for gypsum has been identified (cement or plaster applications)
  • where the supply of sulfur or sulfuric acid is expensive