Wet Method Phosphoric Acid Production

   Phosphoric acid is an important industrial acid used for fertilizer manufacturing and it is also used in food production.  Click on the link below for a simply process flow diagram, with a description found below.

Process Flow Diagram

    Phosphate rock in the form of fluoroapatite is fed to a series of reactors along with recycled phosphoric acid from the process.  The phosphoric acid-fluoroapatite slurry is mixed with sulfuric acid which is added to the reactor series as a leaching agent.  After completing the reaction series, the process stream is washed with evaporator condensate while being forced through a filter.   The filtercake is composed primarily of gypsum (CaSO₄ 2H₂O). The product acid is concentrated to 75-100% by a series of evaporators and then cooled before entering storage.

Primary Reactions:

Ca₃(PO₄)₂ + 4H₃PO₄ ---> 3Ca(H₂PO₄)₂
3Ca(H₂PO₄)₂ + 3H₂SO₄ + 6H₂O ---> 3CaSO₄ 6H₂O + 6H₃PO₄
Reaction temperatures range from 105 ⁰F to 175 ⁰F, decreasing through the process.