Numerical simulation of bypass evaporation system treating FGD wastewater using high temperature flue gas.

A novel zero-liquid discharge (ZLD) technology for desulfurization wastewater treatment is put forward in this paper. A ZLD reconstruction project performed on 2 × 320 MW desulfurization system was taken as the research object, to study the evaporator structure and the key factors affecting spray evaporation through CFD numerical simulation. The result shows that when the evaporator diameter is 2.4 m, the central density difference and the temperature difference of evaporator outlets are 0 kg/L and 0°C, under this condition, the wall sticking can be avoided effectively, and the uniformity of evaporator's outlet flow field is improved. As for the same amount of wastewater, small atomized particle size, high flue gas flow rate and high flue gas temperature are conducive to complete evaporation, and the optimum atomized particle size is 100-150 µm, flue gas velocity is 3-4 m/s and flue gas temperature is 250-260°C. In order to reduce adverse impact on the main flue duct, the optimized design scheme that extracting flue gas before and after the air preheater is put forward in the purpose of energy saving.