Evaluation of NOx Removal from Flue Gas by a Chemical Absorption-Biological Reduction Integrated System: Glucose Consumption and Utilization Pathways

Biological reduction of nitric oxide (NO) with ferrous chelate is the main step for the chemical absorption-biological reduction (CABR) integrated method to remove nitrogen oxide (NOx) from flue gas. Heterotrophic bacteria play a dominant role in the CABR process, and their reactivity is seriously affected by carbon source and electron donor. Therefore, the consumption and utilization pathways of glucose were investigated. The study on glucose metabolites shows that the accumulation of acetate should be alleviated, which make it possible to keep running the bioreactor normally, although the volatile fatty acids (VFAs) may be beneficial as an electron donor for the reactions in CABR. The reduction of complex NO mainly depends upon the concentration of Fe(II) and acetate. The main utilization pathway of glucose can be expressed as glucose -> pentanoic acid -> butyric acid -> propionic acid -> acetic acid -> CO2. Under experimental conditions of 670 mg m(-3) NO inlet concentration, 0-10% O-2 concentration, and 8 h of hydraulic retention time (HRT), more than half of inlet elemental carbon (glucose) was released in the form of gas after 240 h of operation. VFAs, especially acetic acid, mainly existed in the liquid phase, and CO2 was mainly observed in the gas phase.