Production of granular diammonium phosphates

Claim 1

A PROCESS FOR THE PRODUCTION OF HIGH-ANALYSIS GRANULAR DIAMMONIUM PHOSPHATE FERTILIZER MATERIAL WHICH COMPRISES CONTINUOUSLY AMMONIATING WET PROCESS PHOSPHORIC ACID CONTAINING ABOUT 30 TO ABOUT 76 WEIGHT PERCENT P2O5 IN A PRENEUTRALIZER VESSEL TO FORM A FLURRY OF AMMONIUM PHOSPHATES THEREIN; MAINTAINING AN NH3:H3PO4 MOLE RATIO IN THE RANGE OF ABOUT 1.3 TO ABOUT 1.5 IN SAID PRENEUTRALIZER VESSEL; INTRODUCING A STREAM OF SAID SLURRY, A STREAM OF AMMONIATING FLUID, AND PARTICLES OF UNDERSIZE PRODUCT FROM A LATER-MENTIONED SIZING STEP INTO THE UPPER END OF AN INCLINED ROTATING DRUM; THEREIN MAINTAINING A BED OF ROLLING DISCRETE PARTICLES OF DIAMMONIUM PHOSPHATE; CONTINUOUSLY INTRODUCING ADDITIONAL AMMONIATING FLUID BENEATH THE SURFACE OF SAID BED IN A BROAD STREAM COUNTERCURRENT TO THE UPWARD MOVEMENT OF SAID PARTICLES IN SUCH PATH, THE BREADTH OF SAID STREAM EXTENDING SUBSTANTIALLY THE ENTIRE LENGTH OF SAID BED; MAINTAINING AN NH3:H3PO4 MOLE RATIO OF ABOUT 2 IN SAID DRUM; RECOVERING THE AMMONIA EVOLVED IN SAID DRUM BY PASSING THE OFFGAS THROUGH SCRUBBING MEANS; RETURNING THE RECOVERED AMMONIA FROM SAID SCRUBBING MEANS TO SAID PRENEUTRALIZER VESSEL; WITHDRAWING DIAMMONIUM PHOSPHATE MATERIAL FROM THE LOWER END OF SAID DRUM; INTRODUCING SAID WITHDRAWN MATERIAL INTO SIZING MEANS; RETURNING PARTICLES OF PREDETERMINED SIZE FROM SAID SIZING MEANS INTO THE UPPER END OF SAID DRUM; AND WITHDRAWING FROM SAID SIZING MEANS GRANULAR PARTICLES OF DIAMMONIUM PHOSPHATE AS PRODUCT, SAID PROCESS BEING CHARACTERIZED BY THE FACT THAT SUBSTANTIALLY ALL OF THE HEAT NECESSARY TO EVAPORATE THE NECESSARY AMOUNT OF WATER FROM THE SYSTEM FOR PRODUCING SAID GRANULAR PRODUCT IS SUPPLIED BY THE CHEMICAL HEAT OF REACTION OF THE REACTANTS, THEREBY SUBSTANTIALLY ELIMINATING THE NEESSITY FOR SUPPLYING EXTERNAL HEAT TO THE SYSTEM COMPRISING SAID PROCESS.