Process for production of particulate fertilizer having a shell of an ammonium salt of phosphoric acid

Claim 1

A PROCESS FOR MANUFACTURING NITROGEN AND PHOSPHORUS CONTAINING MIXED FERTILIZER COMPRISING THE STEPS CARRIED OUT IN THE FOLLOWING SEQUENCE: (A) WETTING WITH PHOSPHORIC ACID CONTAINING FROM ABOUT 10 TO 30 PERCENT WATER A MOVING BED OF DISCRETE SOLID PARTICLES OF CONTROLLED SIZE WITHIN THE RANGE OF ABOUT 6 TO 24 MESH (U.S.STANDARD) OF AT LEAST ONE WATER-SOLUBLE FERTILIZER COMPOSITION WITH THE PROVISION THAT ONE-FOURTH TO THREE-FOURTHS OF THE PARTICLES IN THE MOVING BED ARE RECYCLED FROM STEPS (C) AND (D) AND THAT PARTICLES OF DIFFERING CHEMICAL COMPOSITION POSSESS SUBSTANTIALLY IDENTICAL PARTICLE SIZE DISTRIBUTION; (B) MIXING THE DISCRETE SOLID PARTICLES AFTER WETTING WITH ACID IN STEP (A) TO YIELD A FREE-FLOWING BED OF ACID-WET PARTICLES; (C) REACTING AMMONIA WITH THE FREE-FLOWING BED OF ACID WET PARTICLES OF STEP (B) AT A TEMPERATURE BELOW ABOUT 200*F. (93*C.) WHILE SUBJECTING SAID PARTICLES TO A ROLLING MOTION TO YIELD A FREE-FLOWING BED OF PARTICLES OF SUBSTANTIALLY SPHERICAL SHAPE; (D) DRYING THE PARTICLES OF SUBSTANTIALLY SPHERICAL SHAPE PRODUCED IN STEP (C) TO YIELD A UNIFORM, FREE-FLOWING, STORAGE STABLE FERTILIZER COMPOSITION CONSISTING PREDOMINANTLY OF PARTICLES POSSESSING A CORE OF WATERSOLUBLE FERTILIZER COMPOSITION AND AN INTIMATELY BONDED SHELL OF AN AMMONIUM SALT OF PHOSPHORIC ACID; AND (E) RECYCLING TO STEP (A) A PORTION OF THE PARTICLES PRODUCED BY STEPS (C) AND (D).