Machanism And Process Analysis Of NO_x Removal From Simulated Flue Gas By Chemical Absorption-biological Reduction Integrated System

A chemical absorption-biological reduction integrated approach is employed to achieve the removal of nitrogen monoxide (NO) from the simulated flue gas with the advantages of low cost, completely reduction of NO and high removal efficiency. In this dissertation, the stoichiometry and mechanism of Fe(II)EDTA-NO reduction was investigated; the effect of environmental factors, such as oxygen, on the complex sorbent regeneration was discussed; the feasibility of biological packed column with the integrated process was studied; through the analysis of biological reduction of NO process, involving the gas, liquid, solid three-phase mass transfer, the kinetic model was established. The main original conclusions of this dissertation are:(1) According to stoichiometry and intermediate product analysis, reduction of NO to N2 was found to be biologically catalyzed with nitrous oxide (N2O) as an intermediate. The main product of complexed NO reduction was N2. Fe(II)EDTA and Glucose can be Simultaneously served as electron donor for complexed NO reduction. In addition, glucose is the preferred and primary electron donor.(2) NO2-, NO3- and oxygen had a certain inhibition of biological Fe(III)EDTA reduction. NO2- and NO3-, mainly as a competitive electron acceptor, prevented the electron transfer to Fe(III)EDTA. Formation of Fe(II)EDTA-NO also resulted in the inhibition of Fe(III)EDTA reduction. Oxygen affected Fe(III)EDTA reduction rate mainly due to both reasons:1) chemical oxidation process increasing the Fe(III)EDTA loading; 2) the toxic effects of oxygen on microorganisms decreasing the microbial activity.(3) Biological packed tower could effectively remove nitrogen oxides from flue gas, steady state removal efficiency under continuous operation could be maintained for a long term operation. Effect of several key parameters such as Total iron concentration, inlet NO, SO2, oxygen concentration, gas flow rate, liquid flow rate, packed column height, and reactor shutdown idle on the NO removal have been investigated in the biological packed tower. Additionally, the microbial community structure in the biological packed tower was analyses with the PCR-DGGE technology.(4) Based on the analysis of biological reduction of NO process and two-film theory, involving the gas, liquid, solid three-phase mass transfer, the kinetic model was established. According to the developed model, Fe(II)EDTA is a key parameter affecting the operation of the integrated prcoss. The biological packed tower can achieve 90% of NOx removal when the Fe(II)EDTA concentration in the liquid phase was up to 3.4 mM.