Crystal modification in wet process phosphoric acid production
AssigneeNalco Chemical Company
InventorsE. Michael Kerr, Lawrence J. Connelly, William J. Roe, Robert M. Vallowe
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Abstract
A wet process production of phosphoric acid in which phosphate rock is digested, whereby phosphoric acid is released and calcium sulfate crystals are formed, employs a polymeric crystal modifier in the digestion stage of the process to improve the separation of the raw phosphoric acid product from the calcium sulfate crystals and to increase the concentration of phosphoric acid in the raw phosphoric acid product.
Claims19
A wet process phosphoric acid production process comprising the steps of digesting phosphate rock in a slurry containing sulfuric acid, whereby phosphoric acid is released and calcium sulfate crystals are formed, and then separating the phosphoric acid from the calcium sulfate crystals, the improvement comprising:
- adding to said slurry, in an amount effective for calcium sulfate crystal formation improvement, a polymer containing monomer units of Formula I, ##STR3## wherein R is hydrogen or methyl and R.sub.1 and R.sub.2 are independently hydrogen, alkyl or sulfoalkyl substituents;
- wherein said polymer is comprised of monomer units of said Formula I wherein both of R.sub.1 and R.sub.2 are hydrogen and monomer units of said Formula I wherein one of said R.sub.1 and R.sub.2 is a sulfoalkyl substituents;
- wherein said polymer is present at the calcium sulfate crystal nucleation phase of said digestion step;
- and
- wherein said polymer is added in a water-soluble salt form.
A wet process phosphoric acid production process comprising the steps of digesting phosphate rock in a slurry containing sulfuric acid, whereby phosphoric acid is released and calcium sulfate crystals are formed, and then separating the phosphoric acid from the calcium sulfate crystals, the improvement comprising;
- adding to said slurry, in an amount effective for calcium sulfate crystal formation improvement, a polymer containing monomer units of Formula I, ##STR5## wherein R is hydrogen or methyl and R.sub.1 and R.sub.2 are independently hydrogen, alkyl or sulfoalkyl substitutents;
- wherein said polymer is comprised of monomer units of said Formula I wherein both of R.sub.1 and R.sub.2 are hydrogen and monomer units of said Formula I wherein one of said R.sub.1 and R.sub.2 is a sulfoalkyl substituent;
- wherein said polymer is present at the calcium sulfate crystal nucleation phase of said digestion step;
- wherein said polymer is added in a water-soluble salt form;
- and
- wherein said calcium sulfate crystals formed are substantially at least 40 microns long and at least 10 microns wide.
Dependencies are inferred from the claim text.