A new approach for the effective removal of NOx from flue gas by using an integrated system of oxidation−absorption−biological reduction

Abstract

A new process of NOx removal from flue gas, using an integrated system of oxidation−absorption−biological reduction (OABR), is introduced. The experimental results show that increasing the NOx oxidation ratio in flue gas can effectively improve the NOx removal efficiency of the OABR system. The NOx removal efficiency could reach 98.8% with 0.02 M NaHCO3 as the chemical absorbent and under the condition of the optimal NOx oxidation ratio of 50%. During stable operation, the OABR system could maintain a high NOx removal efficiency (above 94%) under the following conditions: 1−8 vol% (104−8 × 104 ppmv) O2, 200−800 ppmv NOx, 0.5−1.5 L/min gas flow rate and 100−800 ppmv SO2. The nitrogen equilibrium results showed that about 59% of the nitrogen in the inlet NOx were transformed to N2 through microbial denitrification, 37% of the nitrogen were converted to biological nitrogen for microbial growth, and only 1.1% of the nitrogen remained in the liquid phase. This new approach has an excellent NOx removal performance and great potential for industrial application.