Abstract: Process thermodynamics analysis was made of the mechanism of P-NH₃ polluted droplets formation in the exhaust gas discharged from a 600 kt•a^-1 diammonium phosphate (DAP) production line.The key factor was the overly high humidity of tail gas, which caused condensation taking place locally in the stack.A recirculation technique was proposed to combine the tail gas dehumidification into the process of monoammonium phosphate (MAP) production in which the heat energy, released from reducing water content in the tail gas below 0.065 kg H₂O•(kg air)^-1, could be used to substitute as much as 45% of the heat energy consumption for a 240 kt•a^-1 MAP production line.To obtain the high efficiency of secondary energy utilization for this process,an unique technique was developed to integrate the processes of partial condensation of tail gas with falling film evaporation of raw phosphoric acid.The feasibility was demonstrated by the pilot experiments in which the total heat transfer coefficient reached 500—600 W•m^-2•K^-1.Some other advantages were also found significant for phosphoric acid concentration compared with the traditional technique, such as lower evaporation temperature，lower recycling rate and especially expansion of evaporation surface areas. The experimental results displayed a very promising future application for the cleaner process of MAP production combined with recirculation of DAP exhaust gases.