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16

WWW.PRAYON.COM

TWO-CRYSTAL PROCESS OR DA-HF (DI ATTACK AND HEMI FILTRATION)

The Prayon DA-HF process

©

for producing

phosphoric acid by sulphuric acid attack

of natural phosphate rocks is a modern

process leading to high P

2

O

5

yield and

giving, as a by-product, hemihydrate calcium

sulphate. Dihydrate calcium sulphate is

produced in the attack section where the

phosphate is attacked by sulphuric acid.

Then, the gypsum slurry recrystallizes

into hemihydrate calcium sulphate in the

conversion section before being filtered to

produce the phosphoric acid.

This process has been developed to

produce phosphoric acid with a high P

2

O

5

content (about 32 -35%) while only one

filtration step is required.

THE MAIN CHARACTERISTICS OF

THE PROCESS ARE

+

high strength phosacid

+

high P

2

O

5

recovery (97.5-98%)

+

reduced CAPEX for high efficiency process

+

self-drying gypsum

RECOMMENDED FOR LOCATIONS

+

to adapt current Dihydrate process plant

and improve profitability

+

with medium high-cost rock

+

with potential market for gypsum

Phosphate

Flash Cooler

Filter

Steam

Water

Phosphoric Acid 32-35% P

2

O

5

Calcium

Sulphate

Hemihydrate

H

2

SO

4

Reaction

RPA

Conversion

DIHYDRATE

HEMIHYDRATE

Vacuum