Production of feed grade dicalcium phosphate

Claim 1

A PROCESS FOR THE PRODUCTION OF FEED GRADE DICALCIUM PHOSPHATE WHICH COMPRISES DIGESTING GROUND TRICALCIUM PHOSPHATE ROCK CONTAINING FLUORINE AND METALLIC IMPURITIES AT ABOUT 140*-190* F. WITH SUFFICIENT AQUEOUS SULFURIC ACID TO CONVERT SUBSTANTIALLY ALL OF ITE TRICALIUM PHOSPHATE TO CALCIUM SULFATE AND AQUEOUS PHOSPHORIC ACID WHILE SIMULTANEOUSLY DISSOLVING MOST OF THE FLUORINE AND METALLIC IMPURITIES FROM THE ROCK, THE DIGESTION BEING CARRIED OUT IN THE PRESENCE OF A QUANTITY OF AN ADDED OXIDIZING AGENT SUFFICIENT TO MAINTAIN THE DISSOLVED METALLIC IMPURITIES OF THE ROCK IN OXIDIZED CONDITION, SEPARATING THE CALCIUM SULFATE FROM THEE IMPURE PHOSPHORICACID SO PRODUCED, COOLING AND DILUTING THE RESULTING PHOSPHORIC ACID SOLUTION WITH WATER TO A TEMPERATURE NOT HIGHER THAN ABOUT 100* F. AND A P2O5 CONTENT OF ABOUT 8-12%, ADDING A QUANTITY OF AQUEOUS LIME SLURRY SUFFICIENT TO RAISE THE PH OF THE DILUTE PHOSPHORIC ACID SOLUTION TO2.6-3.2 AND AGITATING THE MIXTUE AT A TEMPERATURE NOT HIGHER THAN 110* F. TO CONVERTA MINOR PROPORTION OF THE PHOSPHORIC ACID INTO A DICALCIUM PHOSPHATE PRECIPITATE CONTAINING SUBSTANTIALLY ALL OF THE FLUORINE AND METALLIC IMPURITIES THAT WERE DOSSOLVED THEREIN, FILTERING OFF AND RECOVERING THIS PRECIPITATE, AGITATING RESULTING FILTRATE AT A TEMPERATURE NOT HIGHER THAN 110* F. WITH AN ADDITIONAL QUANTITY OF LIME SLURRY SUFFICIENTTO RAISE THE PH TO ABOUT 6.0-6.3 AND THEREBY CONVERTING THE REMAINDER OF THE PHOSPHORIC ACID THEREIN INTO FEED GRADE DICALCIUM PHOSPHATE, AND FILTERING OFF AND DRYING THE DICALCIUM PHOSPHATE SO OBTAINED.