Wet Process Phosphoric Acid - Production Problems And Solutions

Wet process phosphoric acid (WPA) is produced by the attack of sulphuric acid on phosphate rock. The composition and purity of WPA depends mainly upon the composition of the rock used. In spite of the great variety of rocks, different phosphoric acid processes and plant procedures, the problems associated with WPA production are basically similar. Since rather low grade and low quality rocks are increasingly processed worldwide there is an upward trend to add mineral modifiers such as clays and silicas, including a tailor-made perlite, to these rocks. They increase gypsum filterability and washing, reduce corrosion and fluorine emission and improve the quality of the concentrated acid product and derived fertilisers.