✅ Phosphoric Acid Production Methods

Phosphoric acid (H₃PO₄) is primarily produced through two main industrial processes: the Wet Process and the Thermal Process.

⭐ 1. Wet Process Phosphoric Acid (WPA)

The Wet Process is the most widely used method globally, mainly for producing phosphoric acid for fertilizers.

✔️ Process Flow:

1. Raw Materials:

• Phosphate rock (mainly containing calcium phosphate)

• Sulfuric acid (H₂SO₄)

• Water

2. Reaction:
   The phosphate rock reacts with sulfuric acid and water to form phosphoric acid and gypsum (calcium sulfate dihydrate) as a by-product.

   Chemical Reaction:

   Ca5(PO4)3F+5H2SO4+10H2O→3H3PO4+5CaSO4⋅2H2O+HFCa₅(PO₄)₃F + 5H₂SO₄ + 10H₂O → 3H₃PO₄ + 5CaSO₄·2H₂O + HF

   Ca5(PO4)3F+5H2SO4+10H2O→3H3PO4+5CaSO4⋅2H2O+HF

3. Filtration:
   Gypsum is separated from the liquid phosphoric acid.

4. Concentration:
   The phosphoric acid solution is concentrated by evaporation to the desired strength.

✔️ Features:

• Mainly used in the fertilizer industry.

• Lower purity, containing impurities such as fluorides and heavy metals.

• Cost-effective for large-scale production.

⭐ 2. Thermal Process Phosphoric Acid (TPA)

The Thermal Process produces very high-purity phosphoric acid, suitable for food, pharmaceutical, and electronic industries.

✔️ Process Flow:

1. Raw Materials:

• Elemental phosphorus (P₄)

• Air (oxygen)

• Water

2. Combustion:
   Elemental phosphorus is burned in air to form phosphorus pentoxide (P₂O₅).

   Chemical Reaction:

   P4+5O2→2P2O5P₄ + 5O₂ → 2P₂O₅

       P4+5O2→2P2O5

1. Hydration:
   The phosphorus pentoxide reacts with water to form phosphoric acid.

   Chemical Reaction:

   P2O5+3H2O→2H3PO4P₂O₅ + 3H₂O → 2H₃PO₄

       P2O5+3H2O→2H3PO4

1. Purification:
   The acid is purified to remove residual impurities.

✔️ Features:

• Produces high-purity phosphoric acid (food-grade, electronic-grade, pharmaceutical-grade).

• Higher production costs due to the use of elemental phosphorus and energy.

• Preferred when stringent quality is required.

✅ Comparison of Wet Process and Thermal Process