Increasing the DAP Production Capacity of DAP2 Plant of Razi Petrochemical Complex by Controlling the Concentrations of Aluminum and Iron Oxides

Di-ammonium Phosphate (DAP) is one of the best chemical fertilizers used individually or in combination with other fertilizers or soil nutrients. It is usually produced through reaction of wet phosphoric acid with ammonia in a pipe or tank reactor followed by the granulation process. Produced slurry in the reactor is sprayed onto the seed granules, and granule growth occurs. Granules leaving the granulator are first dried and then screened to separate out the product size. In this work, the influence of phosphoric acid impurities on the granulometery and production rate of produced DAP in Razi Petrochemical Complex is experimentally investigated. It is found that the generation of a large number of fine particles due to deficiency of Al2O3 and Fe2O3 in the reactor may speed up the adhesion and coalescence of the DAP granules in the granulator, and thus large amounts of weak big lumps of the product are obtained. When these lumps pass through the crushers, a large amount of dust and fine particles in the recycle stream is produced, which leads to serious operational problems and reduces the production rate. According to the experimental measurements in DAP2 plant (based on pipe reactor) of Razi Petrochemical Complex, a correlation is found between the total concentrations of Al2O3 + Fe2O3 in the phosphoric acid entering the pipe reactor and DAP granulometery. In order to enhance the granulation quality without operational difficulty, the total concentration of aluminum and ferric oxides in the phosphoric acid entering the reactor should be controlled at 2.2 ± 0.1 wt%. This is an interesting result which can be used for improvement of the operational condition of DAP production plants. Applying this to the DAP2 plant of Razi Petrochemical Complex in Iran resulted in an 80% decrease in C.V. of the produced DAP granules and 65% increase in production rate.

کلیدواژه ها:

DAP ، Granulometery ، Aluminum Oxide ، Iron Oxide ، phosphoric acid