Mechanisms of NOx removal from flue gas by zero valent iron
- National Taipei University of Technology, Taipei (Taiwan). Institute of Environment Planning and Management
Chemical reaction between nitric oxide (NO) and zero valent iron (ZVI) was studied in a packed-bed column process with high temperatures based on ZVI strong reducing abilities. For six controlled temperatures of 523- 773 K and 400 ppm of NO (typical flue gas temperature and concentration), under short empty bed contact time, NO was completely removed for temperature of 573-773 K but not for 523 K. Breakthrough curves were conducted for the five working temperatures, and the results indicated that NO reductions by ZVI were varied from 2 to 26.7 mg NO/g ZVI. Higher temperature and longer EBCT achieved better NO removal efficiency. X-ray diffraction (XRD) and electron spectroscopy for chemical analysis (ESCA) were conducted to analyze the crystal structure and oxidation state of the reacted ZVI. Three layers of iron species were detected by XRD: ZVI, Fe{sub 3}O{sub 4}, and Fe{sub 2}O{sub 3}. ZVI was the most prevalent species, and Fe{sub 3}O{sub 4} and Fe{sub 2}O{sub 3} were less from the XRD analysis. By ESCA, the oxidation state on the reacted ZVI surface was determined, and the species was identified as Fe{sub 2}O{sub 3}, which is the most oxidizing species for iron. Therefore, three layers from the ZVI core to the ZVI surface can be identified: ZVI, Fe{sub 3}O{sub 4}, and Fe{sub 2}O{sub 3}. Combining the results from XRD and ESCA, the mechanisms for ZVI and NO can be proposed as two consecutive reactions from lower oxidation state (ZVI) in the core to higher oxidation state on the iron surface (Fe{sub 2}O{sub 3}). Because there was only {lt}5% ZVI used to remove NO comparing to theoretical ZVI used based on the proposed stoichiometry, it can be concluded that the heterogeneous reaction only occurred on the ZVI surface instead of on bulk of the ZVI. 11 refs., 8 figs., 3 tabs.
- OSTI ID:
- 20772651
- Journal Information:
- Journal of the Air and Waste Management Association, Vol. 56, Issue 6; Other Information: f10919@ntut.edu.tw; ISSN 1047-3289
- Country of Publication:
- United States
- Language:
- English
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