Enhanced biological removal of NOx from flue gas in a biofilter by Fe(II)Cit/Fe(II)EDTA absorption

A mixed absorbent had been proposed to enhance the chemical absorption–biological reduction process for NOx removal from flue gas. The mole ratio of the absorbent of Fe(II)Cit to Fe(II)EDTA was selected to be 3. After the biofilm was formed adequately, some influential factors, such as the concentration of NO, O2, SO2 and EBRT were investigated. During the long-term running, the system could keep on a steady NO removal efficiency (up to 90%) and had a flexibility in the sudden changes of operating conditions when the simulated flue gas contained 100–500 ppm NO, 100–800 ppm SO2, 1–5% (v/v) O2, and 15% (v/v) CO2. However, high NO concentration (>800 ppm) and relative short EBRT (<100 s) had significant negative effect on NO removal. The results indicate that the new system by using mixed-absorbent can reduce operating costs in comparison with the single Fe(II)EDTA system and possesses great potential for scale-up to industrial applications.