Phosphoric Acid Plant Sustainability

Author(s) Bouffard, Leif., Belle, Doug
Fertilizers, Industrial & Feed Phosphates, Phosphates 2014, 23-25 March, Paris Marriott Rive Gauche, France
In order to address concerns associated with the financial liability for the final closure of a Phosphate Fertilizer Facility and the ultimate disposition of the cooling pond, Hatch has evaluated the use of Series Filtration (Double Filtration) of phosphogypsum and a Closed Loop Cooling Water System as an economical approach to addressing this issue.  These commercially proven technologies were selected as a means of reducing cooling pond acidity and eliminating the loss of water soluble P2O5 to the Gypsum Stack.  The process provides improved recovery of phosphoric acid (water soluble P2O5) which directly results in improved Plant P2O5 efficiencies and lower P2O5 concentration in the cooling pond water.  Phosphoric Acid is normally the highest concentration of the acidic components of the cooling pond water which must be neutralized prior to closure. Improved recovery of P2O5 also leads to improved recovery of sulfuric acid.  Employing the Closed Loop Cooling Water System provides a P2O5 free transport fluid for stacking of phosphogypsum which drastically reduces the loss of water soluble P2O5 to the gypsum stack. The combination of Series Filtration and Closed Loop Cooling along with an Acid Recovery System ultimately leads to a significant reduction in cooling pond water acidity and recovers the valuable constituents which would make the cooling ponds a financial liability at closure.  Improved overall recovery of P2O5 can translate into an income of between $76 and $120 million over a 15 year period.  Assuming a cost of $20/1000 gallons to lime neutralize cooling pond water for the plant in this example, would avoid over $30 million in treatment costs.  This brings the total financial benefit to $106 to $150 million over a 15 year period. There are significant paybacks for the implementation of these processes while a phosphoric acid plant is in operation.