Hemihydrate process for phosphoric acid manufacture

Claim 1

A METHOD FOR THE PRODUCTION OF STRONG PHOSPHORIC ACID OF AT LEAST 40% P205 CONCENTRATION WHICH COMPRISES REACTING PHOPSPHATE ROCK WITH STRONG AQUEOUS PHOSPHORIC ACID OF AT LEAST 40% P205 CONTENT IN A DIGESTING STEP AT TEMPERATURES OF AT LEAST 80* C. AND INTRODUCING THE RESULTING MONOCALCIUM PHOSPHATE SOLUTION INTO A FIRST PREAND ADDITIONAL PHOSPHORIC ACID, SAID SULFURIC ACID BEING ADDED IN SAID PRECIPITITAING GAND CRYSTALLING STEP IN AMOUNTS FROM 1.5% TO 3% LESS THAN THE STOICHIOMETRIC EQUIVALENT OF THE MONOCALCIUM PHOSPHATE PRECIPITAING ABOUT 85% TO 90% OF THE CALCIUM SULFATE AS HEMIHYDRATE MAINTAINING THEREIN A TEMPERATURE OF AT LEAST 40% P205 A PHOSPHORIC ACID CONCENTRATION OF AT LEAST 40% P205 THEREBY FORMING A SUSPENSION OF SMOOTH AND EASILY FILTERABLE CALCIUM SULFATE HEMIHYDRATE CRYSTAL AGGLOMERATES IN PHOSPHORIC ACID WHICH ALSO CONTAINS THE REMAINING MONOCALCIUM PHOSPHATE, RECOVERING A PORTION OF SAID PHOSPHORIC ACID CONTAINING CALCIUM SULFATE HEMIHYDRATE CRYSTAL AGGLOMERATES IN SUSPENSION AND RECYCLING SAID PORTION TO SAID INITIAL DIGESTION STEP, PASSING THE REMAINING PORTION OF THE PHOSPHORIC ACID WITH SUSPENDED CALCIUM SULFATE HEMIHYDRATE CRYSTALS AGGLOMERATES TO A SECOND PRECIPITATION AND CRYSTALLIZATION STEP AND REACTING SAID REMAINING SOLUBLE TION OF THE MONOCALCIUM PHOSPHATE WITH ADDITIONAL SULFURIC ACID SUFFICIENT TO PRECIPITATE THE REMAINING SOLUBLE CALCIUM AS CALCIUM SULFATE, AND SEPARATING THE THUS PRODUCED STRONG PHOSPHORIC ACID OF AT LEAST 40% P205 CONTENT FROM THE PRECIPITATE CALCIUM SULFATE BY FILTRATION.

Claim 2

A METHOD FOR THE PRODUCTION OF STRONG PHOSPHORIC ACID OF AT LEAST 40% P205 CONCENTRATION WHICH COMPRISES REACTING PHOPSPHATE ROCK WITH STRONG AQUEOUS PHOSPHORIC ACID OF AT LEAST 40% P205 CONTENT IN A DIGESTING STEP AT TEMPERATURES OF AT LEAST 80* C. AND INTRODUCING THE RESULTING MONOCALCIUM PHOSPHATE SOLUTION INTO A FIRST PREAND ADDITIONAL PHOSPHORIC ACID, SAID SULFURIC ACID BEING ADDED IN SAID PRECIPITITAING GAND CRYSTALLING STEP IN AMOUNTS FROM 1.5% TO 3% LESS THAN THE STOICHIOMETRIC EQUIVALENT OF THE MONOCALCIUM PHOSPHATE PRECIPITAING ABOUT 85% TO 90% OF THE CALCIUM SULFATE AS HEMIHYDRATE MAINTAINING THEREIN A TEMPERATURE OF AT LEAST 40% P205 A PHOSPHORIC ACID CONCENTRATION OF AT LEAST 40% P205 THEREBY FORMING A SUSPENSION OF SMOOTH AND EASILY FILTERABLE CALCIUM SULFATE HEMIHYDRATE CRYSTAL AGGLOMERATES IN PHOSPHORIC ACID WHICH ALSO CONTAINS THE REMAINING MONOCALCIUM PHOSPHATE, RECOVERING A PORTION OF SAID PHOSPHORIC ACID CONTAINING CALCIUM SULFATE HEMIHYDRATE CRYSTAL AGGLOMERATES IN SUSPENSION AND RECYCLING SAID PORTION TO SAID INITIAL DIGESTION STEP, PASSING THE REMAINING PORTION OF THE PHOSPHORIC ACID WITH SUSPENDED CALCIUM SULFATE HEMIHYDRATE CRYSTALS AGGLOMERATES TO A SECOND PRECIPITATION AND CRYSTALLIZATION STEP AND REACTING SAID REMAINING SOLUBLE TION OF THE MONOCALCIUM PHOSPHATE WITH ADDITIONAL SULFURIC ACID SUFFICIENT TO PRECIPITATE THE REMAINING SOLUBLE CALCIUM AS CALCIUM SULFATE, AND SEPARATING THE THUS PRODUCED STRONG PHOSPHORIC ACID OF AT LEAST 40% P205 CONTENT FROM THE PRECIPITATE CALCIUM SULFATE BY FILTRATION.