Merchant Grade Acid

Vichem’s patented wet process for the production of green phosphoric acid

Wet phosphoric acid: Wet process phosphoric acid is prepared by adding sulphuric acid to calcium phosphate rock.

Vichem has continuously strived to improve existing processes and adapt them to the diminishing availability of high-quality phosphate rock, and to its increasing price. In this context, Vichem has developed and patented a process which provides a significant improvement on the attack process on phosphate rock by sulphuric acid, in accordance with the dihydrate process.

The process consists in two successive sets of reactors-separators:

• in the first reactor, approximately two thirds of the tricalcic phosphate rock capacity is attacked with sulphuric acid.
• in the second reactor, the remaining one third of the tricalcic phosphate rock is attacked with the correspondingamount of sulphuric acid, mixed with the amount of phosphoric acid produced in the first reactor. The final phosphoric acid is therefore produced in the second reactor. The final gypsum (CaSO4, 2 H2O) is recovered in the first separator.

Advantages of the process

Increase of the capacity of up to 50% by adding to the existing unit the following equipment:

• one additional reactor with cooling system, with a volume of 50% of the existing reactor
• one additional belt filter under vacuum, which surface area is 25% of the existing one.
• these two above equipments will be easy to integrate in the existing unit, and will require less space than a brand new line.

The construction and installation of the new equipment do not require the shutdown of the existing unit.

Increase of the yield and of the P₂O₅ content in the produced phosphoric acid:

• Both the rate of recovery of P₂O₅ and the P₂O₅ content in the produced phosphoric acid will be increased with this process of approximately 1.5% more than with other dihydrate processes for the same phosphate rock characteristics.
• The phosphate rock used can have a P₂O₅ content as low as 28%.

Increase of the stability:

• The stability of the process is ensured thanks to the two reactor-filter sets, even if the concentration in the phosphate rock changes.

Revamping and debottlenecking:

• It is easy to add in an existing process a reactor-separator couple in order to increase simultaneously the capacity and the profitability of the production unit.

Vichem can design and build full phosphoric acid and fertilizer plant.