PHOSPHORIC ACID PURIFICATION: COMPARING THE PROCESS CHOICES.

In the fertilizer industry, the major reason for purifying wet-process phosphoric acid is to produce clear solution fertilizers that can be stored for extended periods without precipitation of solids. Today's solution fertilizers are prepared either from unpurified wet-process acid, or from wet-process acid purified in respect to magnesium only. Solvent extraction techniques are already commercial for purifying wet-process phosphoric acid. Other types of processes, however, are under laboratory or pilot-plant development at TVA; indirect purification by a urea-phosphate pyrolysis method is especially promising.