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.

Experimental study on removal of NO using adsorption of activated carbon/reduction decomposition of microwave heating.

Experimental studies were carried out on flue gas denitrification using activated carbon irradiated by microwave. The effects of microwave irradiation power (reaction temperature), the flow rate of flue gas, the concentration of NO and the flue gas coexisting compositions on the adsorption property of activated carbon and denitrification efficiency were investigated. The results show that: the higher of microwave power, the higher of denitrification efficiency; denitrification efficiency would be greater than 99% and adsorption capacity of NO is relatively stable after seven times regeneration if the microwave power is more than 420 W; adsorption capacity of NO in activated carbon bed is 33.24 mg/g when the space velocity reaches 980 per hour; adsorption capacity declines with increasing of the flow rate of flue gas; the change in denitrification efficiency is not obvious with increasing oxygen content in the flue gas; and the maximum adsorption capacity of NO was observed when moisture in flue gas was about 5.88%. However, the removal efficiency of NO reduces with increasing moisture, and adsorption capacity and removal efficiency of NO reduce with increasing of SO2 concentration in the flue gas.

Experimental study on the simultaneous desulfurization and denitrification by duct injection.

The highly active absorbent with oxidization based on fly ash, lime and additive was prepared. Experiments of simultaneous desulfurization and denitrification were carried out using fixture bed and duct injection. The influencial factors for the absorptive capacity of the absorbent were studied. The absorptive capacities of 120.7 mg for SO2 and 43.7 mg for NOx were achieved at a Ca/(S + N) molar ratio 1.2, respectively, corresponding removal efficiencies of 87% and 76%, while spent absorbent appeared in the form of dry powder. The optimal temperature and humidity of flue gas treated with this process were shown to be approximately 50 degrees C, and 5% respectively. The mechanism of removal for SO2 and NOx was investigated. In comparison with traditional dry FGD, this process appears to have lower cost, less complicated configuration and simpler disposal of used absorbent. The valuable references can be provided for industrial application by this process. The foreground of application will be vast in China and in the world.