Article pubs.acs.org/est
A Biophysicochemical Model for NO Removal by the Chemical Absorption−Biological Reduction Integrated Process Jingkai Zhao,† Yinfeng Xia,† Meifang Li,† Sujing Li,† Wei Li,*,† and Shihan Zhang*,‡ †
Key Laboratory of Biomass Chemical Engineering of Ministry of Education, Institute of Industrial Ecology and Environment, College of Chemical and Biological Engineering, Zhejiang University, Yuquan Campus, Hangzhou 310027, China ‡ College of Environment, Zhejiang University of Technology, Hangzhou 310032, China S Supporting Information *
ABSTRACT: The chemical absorption-biological reduction (CABR) integrated process is regarded as a promising technology for NOx removal from flue gas. To advance the scale-up of the CABR process, a mathematic model based on mass transfer with reaction in the gas, liquid, and biofilm was developed to simulate and predict the NOx removal by the CABR system in a biotrickling filter. The developed model was validated by the experimental results and subsequently was used to predict the system performance under different operating conditions, such as NO and O2 concentration and gas and liquid flow rate. NO distribution in the gas phase along the biotrickling filter was also modeled and predicted. On the basis of the modeling results, the liquid flow rate and total iron concentration were optimized to achieve >90% NO removal efficiency. Furthermore, sensitivity analysis of the model revealed that the performance of the CABR process was controlled by the bioreduction activity of Fe(III)EDTA. This work will provide the guideline for the design and operation of the CABR process in the industrial application.
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NO removal efficiency.15−17 It has been confirmed that the main end product of the NO reduction in the CABR system was nitrogen gas while N2O was an intermediate.18 Batch experimental results showed that the Fe(III)EDTA reduction rate was the limitation to achieving high NO removal capacity.19 All the above investigations confirmed the feasibility of NO removal using the CABR process in a lab-scale reactor and also provided some information to effectively operate the integrated process. However, there was limited information on the process analysis of the CABR system which can provide insight on the design of the bioreactor for practical application. In general, the NO removal in the CABR integrated process includes four steps: (1) diffusion of NO and O2 from bulk gas phase to gas− liquid interface, (2) reaction of NO and O2 with Fe(II)EDTA in the gas−liquid interface to form Fe(II)EDTA-NO and Fe(III)EDTA, (3) diffusion of bound NO and Fe(III)EDTA from the bulk solution to the biofilm, and (4) reduction of the bound NO and Fe(III)EDTA in the biofilm of the biofilter. Gambardella et al. studied the mass transfer property in the system;20,21 Winkelman et al. developed a rate-based model only for the absorber unit based on setting parameters;22 Chen
INTRODUCTION Emission of nitrogen oxides (NOx) and their induced secondary contaminations, such as PM2.5,1−3 acid deposition,4 urban ozone smoke,5,6 and ozone depletion, are harmful to human health. Currently, selective catalytic reduction (SCR) is the main technology applied for NOx removal, but it is not suitable for middle and small industry boilers because of its high cost and the imperfection of low temperature SCR application (
