Method for preparing potassium phosphates

Claim 1

THE PROCESS OF PREPARING CRYSTALLINE POTASSIUM PHOSPHATE HAVING A POTASSIUM TO PHOSPHOROUS MOLAR RATIO BETWEEN ABOUT 1.5:1 AND ABOUT 2.1:1 FROM A SOLID MIXTURE OF ION AND ALUMINUM PHOSPHATES PHOSPHATES OBTAINED IN THE PRODUCTION OF PHOSPHORIC ACID WHICH COMPRISES ADMIXING SAID SOLID MIXTURE WITH WATER, SILICA IN AN AMOUNT SUFFICIENT TO PROVIDE A SIO2/AL2O3 MOLAR RATIO IN EXCESS OF ABOUT 2:1 AND AN AMOUNT OF A STRONGLY BASIC POTASSIUM COMPOUND SELECTED FROM THE GROUP CONSISTING OF POTASSIUM COMPOUND POTASSIUM CARBONATE, AND MIXTURE THEREOF, IN AN AMOUNAT IN EXCESS OF 115% OF THE STOICHIOMETRIC PROPORTION REQUIRED TO FORM TRIPOTASSIUM ORTHOPHOSPHATE WITH THE PHOSPHATE VALUES IN SAID MIXTURE, TO ADJUST THE PH OF THE RESULTING SLURRY TO ABOVE ABOUT 10, HEATING THE RESULTING SLURRY TO A TEMPERATURE ABOVE 300*F. WHEREBY PHOSPHATE VALUES ARE CONVERTED INTO WATER SOLUBLE POTASSIUM ORTHOPHOSPHATES, SLURRYING THE HEAT-TREATED MATERIAL WITH WATER TO YIELD AN AQUEOUS SOLUTION OF POTASSIUM ORTHOPHOSPHATES PREDOMINATING IN TRIPOTASSIUM ORTHOPHOSPHATE AND CONTAINING WATER INSOLUBLE COMPOUNDS OF IRON AND ALUMINUM, SEPARATING SAID ORTHOPHOSPHATE SOLUTION FROM SAID WATER INSOLUBLE COMPOUNDS, ADMIXING SAID SEPARATED ORTHOPHOSPHATE SOLUTION WITH AND AQUEOUS MONOPOTASSIUM ORTHOPHOSPHATE SOLUTION ANS A STRONGLY BASIC COMPOUND SELECTED FROM THE POTASSIUM TO PHOSPHATE MOLE HYDROXIDE, POTASSIUM CARBONATE AND MIXTURES THEREOF IN PROPORTIONS TO ADJUST THE POTASSIUM TO PHOSPHATE MOE RATIO OF THE MIXTURE TO BETWEEN ABOUT 1.5:1 AND ABOUT 2,1:1, AND HEATING THE RESULTING MIXTURE TO DRYNESS AT A TEMPERATURE BELOW THE FUSION TEMPERATURE OF THE SOLIDS.