NO_xRemoval from Simulated Flue Gas by Chemical Absorption−Biological Reduction Integrated Approach in a Biofilter

Abstract

A chemical absorption-biological reduction integrated approach, which combines the advantages of both the chemical and biological technologies, is employed to achieve the removal of nitrogen monoxide (NO) from the simulated flue gas. The biological reduction of NO to nitrogen gas (N2) and regeneration of the absorbent Fe(II)EDTA (EDTA:ethylenediaminetetraacetate) take place under thermophilic conditions (50 +/- 0.5 degrees C). The performance of a laboratory-scale biofilter was investigated for treating NO(x) gas in this study. Shock loading studies were performed to ascertain the response of the biofilter to fluctuations of inlet loading rates (0.48 approximately 28.68 g NO m(-3) h(-1)). A maximum elimination capacity (18.78 g NO m(-3) h(-1)) was achieved at a loading rate of 28.68 g NO m(-3) h(-1) and maintained 5 h operation at the steady state. Additionally, the effect of certain gaseous compounds (e.g., O2 and SO2) on the NO removal was also investigated. A mathematical model was developed to describe the system performance. The model has been able to predict experimental results for different inlet NO concentrations. In summary, both theoretical prediction and experimental investigation confirm that biofilter can achieve high removal rate for NO in high inlet concentrations under both steady and transient states.

Re-acclimation performance and microbial characteristics of a thermophilic biofilter for NOx removal from flue gas

“…However, our previous work showed a low NO elimination capacity in the biofilter which could result in a large size of the bioreactor and hence increase the cost of NO removal from flue gas. Experimental results showed that, compared with our previous work (Zhang et al 2008), this biofilter packed with a packing material possessing larger specific surface area (1200 m 2 m −3 ) exhibited a higher NO removal efficiency and capacity. For example, at a NO loading rate of 25.9 g NO m −3 h −1 , an increase of the surface area of the packing material from 325 to 1200 m 2 m −3 resulted in an increase of NO removal capacity by 30 % compared to our NO concentration, mg m -3 NO removal efficiency, % previous work (Zhang et al 2008).…”

“…The feasibility of NO x removal from the flue gas by chemical absorption-biological reduction integrated process in a biofilter was demonstrated in our previous work (Zhang et al 2008). However, our previous work showed a low NO elimination capacity in the biofilter which could result in a large size of the bioreactor and hence increase the cost of NO removal from flue gas.…”

“…After the inoculation of dedicate denitrifying and iron-reducing bacteria, the biofilter showed a good performance on the NO removal at typical conditions of the chemical absorption-biological reduction process. Over 70 % of NO was removed at conditions of 50°C, 300 ppm NO, 0.9 % O 2 (v/v), and 20 mM of total FeEDTA (Zhang et al 2008). The maximum NO x removal capacity of the biofilter was 18.78 g m −3 h −1 at a loading rate of 28.68 g m −3 h −1 .…”

“…The feasibility of NO x removal in a biofilter using CABR concept was demonstrated under thermophilic conditions (50±0.5°C) in our previous work (Zhang et al 2008). A biofilter packed with 7.6 l of polyhedral sphere with a specific surface area of 325 m 2 m −3 was used to investigate its performance of NO removal.…”

“…Furthermore, the packing with high surface area also provides more surface area for the attachment of the microorganism which can also enhance the regeneration of Fe(II)EDTA. In our previous work, only the effect of gaseous components e.g., SO 2 , NO, and O 2 on the performance of NO x removal was investigated in the biofilter (Zhang et al 2008). To optimize the operation conditions, the effects of the total FeEDTA concentration, the gas residence time (GRT), and the liquid flow rate on the performance of NO x removal are essential.…”