Diammonium phosphate fertilizer manufacturing

Diammonium phosphate with grade 18:46:0, industrial manufacturing process requires five starting materials .

  • Anhydrous liquid & vapour ammonia (99.5% pure NH3)
  • Phosphoric acid (52-54% P2O5)
  • Sulfuric acid (93-98% H2SO4)
  • Urea prills(99% NH2CONH2)
  • Filler

Diammonium phosphate fertilizer manufacturing process flowsheet brief description:

Liquid ammonia is fed to the pre-neutraliser through dispersion distributor located at the bottom. Phosphoric acid 54% P2O5 is injected into the pre-neutraliser from the top. Agitator with variable driven motor is provided in the reactor for thorough mixing to yield slurry.

Chemical reaction take place in the diammonium phosphate fertilizer manufacturing pre-neutraliser

Preneutraliser used in Diammonium phosphate Fertilizer Manufacturing

Diagram of DAP making preneurtraliser reactor

  • NH3+H3PO4 → NH4H2PO4 (Mono ammonium phosphate)
  • NH4H2PO4 + NH3 → (NH4)2HPO4 (Diammonium phosphate)

The resulting boiling slurry from pre-neutraliser is fed on the rotating bed of recycle material in a rotary drum granulator and therefore it is ammoniated to 1.8 to 1.85 moleration by sparging liquid ammonia through the formation of recent granules bed in the granulator. The moist granulated material discharged from granulator is dried in a rotary dryer using hot-quenched gas to reduce the moisture content of the material from about 3% to 1%. Cascade screen separated the dried material based on the size of granule particles. The screened out particles are cooled by the rotary drum cooler the inclined rotation enhance huge quantity of hot granules to contact with cool air blown counter currently from the outlet. The oversize materials from the screens are pulverized and recycled to the granulator.

The grade of the DAP is adjusted by addition of urea and filler. Conveyor system transports the Diammonium phosphate fertilizer to the bagging system.Scrubbing system traps the fumes obtained from the granulator and pre-neutraliser and the dry scrubber cleans vent out air that carries the fertilizer particles generated from pulverizers, screens and product cooler. Finally tail gas scrubber further scrubbers the air before discharging it into the atmosphere.

Process flow sheet diagram of diammonium phosphate fertilizer manufacturing
Process flow sheet diagram of diammonium phosphate fertiliser manufacturing in large scale

DAP manufacturing flowsheet diagram