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.
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.
