Manufacture of complex fertilizers

Claim 1

IN A METHOD FOR THE PREPARATION OF A COMPLEX FERTILIZER MATERIAL OF THE CHARACTER DESCRIBE BY THE SOLUBILIZING OF INSOLUBLE NATURAL CALCIUM PHOSPHATES IN AN ACID DIGESTION STEP AND THEN NEUTRALIZING ACIDIC PRODUCTS OF SAID DIGESTION STEP WHILE AVOIDING HIGH TEMPERATURE AND CONCENTRATION CONDITIONS TENDING TO CONVERT SAID SOLUBILIZED PHOSPHATES TO INSOLUBLE FORM DURING SAID NEUTRALIZING, THE STEPS WHICH COMPRISES DIGESTING SAID INSOLUBLE CALCIUM PHOSPHATES WITH A MINERAL ACID REACTANT SELECTED FROM THE GROUP CONSISTING OF NITRIC ACID, MIXTURES OF NITRIC AND SULPHURIC ACIDS, AND MIXTURES OF NITRIC AND PHOSPHORIC ACIDS FOR SOLUBILIZING SAID PHOSPHATES TO FORM AN ACID FERTILIZER PASTE CONTAINING WATER-SOLUBLE P2O5 AND CALCIUM NITRATE, PARTIALLY NEUTRALIZING SAID ACID FERTILIZER PASTE BY ADDING THERETO AMMONIA IN AN AMOUNT NO MORE THAN ABOUT 50% OF THAT WHICH WOULD COMPLETELY NEUTRALIZE SAID ACID FERTILIZER PASTE, CONTINOUSLY ADMIXING SAID AMMONIA THROUGH SAID ACID FERTILIZER PASTE DURING SAID PARTIAL NEUTRALIZING STEP AND MAINTAINING THE TEMPERATURE THEREOF AT LESS THAN ABOUT 75*C, FOR AVOIDING TEMPERATURE AND AMMONIA CONCENTRATION CONDITIONS TENDING TO CAUSE COMPLETE NEUTRALIZATION OF SAID FERTILIZER PASTE AND CONVERSION OF SAID SOLUBILIZED PHOSPHATES THEREIN TO INSOLUBLE FORM CEASING TO ADD SAID AMMONIA TO SAID ACID FERTILIZER PASTE AFTER SAID PARTIAL NEUTRALIZING STEP AND PRIOR TO COMPLETE NEUTRALIZATION OF SAID PASTE, ADMIXING IN A SEPARATE STEP ADDITIONAL AMMONIA WITH A PORTION OF SAID COMPLEX FERTILIZER MATERIAL PREVIOUSLY PRODUCED IN A PREVIOUS CYCLE OF THIS METHOD FOR AFFIXING SAID ADDITIONAL AMMONIA THERETO, THEREAFTER COMPLETING THE NEUTRALIZATION OF SAID ACID FERTILIZER PASTE IN A SECOND NEUTRALIZING STEP BY ADMIXING THEREWITH SAID PORTION OF SAID PREVIOUSLY PRODUCED COMPLEX FERTILIZER MATERIAL WITH SAID ADDITIONAL AMMONIA AFFIXED THEREON, AND THEREAFTER SEPARATING SAID THUS COMPLETELY NEUTRALIZED FERTILIZER PASTE INTO ONE PORTION FOR USE AS SAID FINISHED COMPLEX FERTILIZER PRODUCT OF THIS METHOD AND ANOTHER PORTION FOR ADMIXTURE INTO SAID SECOND NEUTRALIZING STEP OF A SUBSEQUENT CYCLE OF THIS METHOD WITH SAID ADDITIONAL AMMONIA AFFIXED THEREON.