DA-HF Process

03 Da Hf Process 05

The Prayon DA-HF Process

The Prayon DA-HF Process is a modern process developed and industrially implemented by Prayon. It is an economic and efficient solution to produce phosphoric acid and valuable gypsum as a co-product.

It consists in the attack of the phosphate rock under dihydrate conditions. 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 good-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 97%.


  • low investment cost, especially in the case of revamping an existing Dihydrate plant
  • high P2O5 recovery
  • low P2O5 content in the phosphogypsum, suitable for cement and building applications.
  • self-drying phosphogypsum with a final moisture around 10%
  • limited grinding of the rock
  • low cadmium in the product acid


  • where 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 building applications)
  • to increase production capacity by 20% with limited changes in an existing Dihydrate plant