Advances in the Use of a Bio-Physicochemical Model to Characterize, Optimize the Chemical Absorption-Biological Reduction Integrated System for NO Removal

One promising technology for NO_x removal from flue gas is the chemical absorption-biological reduction (CABR) integrated process, in which NO is absorbed by aqueous solution of Fe(II)EDTA and the absorption product, Fe(II)EDTA-NO, is reduced biologically. At the same time, Fe(II)EDTA, oxidized by O₂ in flue gas, could be regenerated in a function of iron-reducing bacteria.

A kinetic model based on mass transfer coupled with chemical reaction and bioreduction was developed to simulate and predict the NO_x removal by the CABR system in a bio-trickling filter. The developed model was validated by the experimental results (the average relative deviation kept within 5.72%) under different operating conditions, e.g. NO/O₂ concentration, gas/liquid flow rate, and subsequently was used to predict the system performance. NO distribution at different inlet concentrations in the gas phase along the bio-trickling filter was also modeled and predicted.

Furthermore, the liquid flow rate and total iron concentration were optimized for >90% NO removal efficiency, which were 38.8 L h^-1 and 10 mM under the typical operating condition (2 L min^-1 gas stream containing 3% (v/v) oxygen and 500 ppm NO) respectively. Sensitivity analysis found that the performance of the CABR process was controlled by the bioreduction activity of Fe(III)EDTA, and the least activity has been achieved. This work could help us with the scale-up design and operation of the CABR process in the industrial application.

Graphic abstract