Enhanced NO_x removal from flue gas by an integrated process of chemical absorption coupled with two-stage biological reduction using immobilized microorganisms

摘要

An integrated process of metal chelate absorption coupled with two stage bio-reduction using immobilized cultures has been proposed to continuously removal of NOx, and the effects of SO2, NO and O2 concentration, gas/liquid flow rate on NO_x removal efficiency were investigated. Although nitrogen-containing components, such as Fe(II)EDTA-NO, NO2~- and NO3~- in the scrubbing solution, inhibited the bio-reduction of Fe(III)EDTA obviously, it was feasible to abate the inhibition effect by using the two stage bio-reduction'system, and thus to improve NO_x removal efficiency. The removal efficiency decreased slowly with the increase of SO2,02, NO concentration and gas flow rate, and increased with the increase of liquid flow rate. Continuously operating for 18 days, a high removal efficiency around 95% was reached by using the two-stage bio-reduction system with immobilized microorganisms, while the value decreased to 85% after 5 days of operation by using the suspended microorganisms, at a constant gas flow rate of 60 L/h containing 424-450 mg/m~3 NO, 2428-2532 mg/m~3 SO2 and 3% O2.