Reuse of an aerobically treated wastewater effluent for the removal of SO 2 in the flue gas

Abstract

Aerobically treated wastewater effluent (ATWE), intrinsically having high alkalinity, was used to remove sulfur dioxide (SO 2) in the flue gas of a coal power plant. Experimental results conducted in a four sieve-tray tower showed that ATWE absorbed SO 2 in flue gas effectively. At a gas: liquid (G:L) ratio of 110:1, the respective SO 2 removal efficiencies were 99% and 95% for flue gases containing 1,600 and 5,000 Mg/kL of SO 2. 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 SO 2. ATWE had higher buffer capacity and SO 2 removal efficiencies as compared to seawater, a common SO 2 scrubbing medium serving as control. In addition, the equilibrium equation between SO 2 partial pressure and concentration of bisulfite (HSO 3 -) in ATWE and the kinetic equation describing the rate of SO 2 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/(m 2·s·bar) 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 SO 2 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 SO 2 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.