Reuse of an aerobically treated wastewater effluent for the removal of SO2 in the flue gas

Abstract

Aerobically treated wastewater effluent (ATWE), intrinsically having high alkalinity, was used to remove sulfur dioxide (SO2) in the flue gas of a coal power plant. Experimental results conducted in a four sieve-tray tower showed that ATWE absorbed SO2 in flue gas effectively. At a gas:liquid (G:L) ratio of 110:1, the respective SO2 removal efficiencies were 99% and 95% for flue gases containing 1,600 and 5,000 Mg/kL of SO2. When the G:L ratio increased to 220:1, the removal efficiency was slightly lowered to 93% for the flue gas containing 1,600 Mg/kL of SO2. ATWE had higher buffer capacity and SO2 removal efficiencies as compared to seawater, a common SO2 scrubbing medium serving as control. In addition, the equilibrium equation between SO2 partial pressure and concentration of bisulfite (HSO3-) in ATWE and the kinetic equation describing the rate of SO2 absorption in the sieve-tray tower by ATWE were established. The absorbing coefficients in the kinetic equation were determined to be 1.96 ± 0.37 mol/(m2ásábar) for gas phase and 0.00184 ± 0.00049 m/s for liquid film. The enhancement factor of the absorbing coefficient in liquid film was 14.28 ± 1.79, resulting in 93% of the decrease of liquid film resistance. The SO2 absorption rate in the sieve-tray tower was mainly affected by the gas film resistance, representing 96% of the total resistance. Experimental results of this study confirmed that the removal of SO2 from the flue gas of coal power plants by ATWE was cost-effective. This process does not require the addition of any chemicals and produces no secondary pollution.