an ammonia phosphoric acid of between about 1 450 and 1 500 in order to achieve a maximum solubility of the ammonium phosphates and reducing water content furthermore the reaction between ammonia j and phosphoric acid p is highly exothermic thus generating sufficient energy for raising the temperature at 116 u00b0 c and evaporating a great amount of the water contained in the phosphoric acid p a blower suctions gas produced by the granulator containing ammonia air and dust which is conduced into a washing and recuperating system comprising a humid cyclone followed by a ventury scrubber washer both of which are feed with fresh phosphoric acid in order to capture the dust as ammonium phosphates sludge dry solids and recover the ammonia gas as mono ammonic phosphate the phosphoric acid exiting the washing and recuperating system is received into a pump equipped tank which recycles most of the phosphoric acid to the washing and recuperating system but a small amount is feed to the pre neutralizer into which it reacts with ammonia j the granulated product obtained in step e is feed to a dryer 10 in order to reduce the water content until 3 0 k feeding the dry granulated product to a rotary screen 11 which classifies the dry product by size as u201c normal size u201c above normal size u201d and u201c below normal size u201d which are predetermined by client the product having an above normal size is grinded and mixed with product having a size below normal and is recycled to the ribbon mixer of step h l the product having a u201c normal size u201d is transferred to.