NO x Removal Characteristics in Plasma plus Catalyst Hybrid Process Y. H. Lee, 1,4 J. W. Chung, 2 Y. R. Choi, 3 J. S. Chung, 1 M. H. Cho, 1 and W. Namkung 1 Received January 14, 2003; revised July 31, 2003 NO x removal characteristics and NO conversion trends were investigated for plas- ma process, catalytic process, and plasma catalytic hybrid process. In the experi- ments, we studied effects of the flow rate and the carrier gas on the NO conversion in the plasma process, and effects of ammonia concentration and temperature on the NO x removal in the catalytic process. We also investigated the synergetic effect of a plasma-catalytic hybrid process. Dielectric barrier discharge was combined with V 2 O 5 –WO 3 =TiO 2 catalyst for removing nitrogen oxides. The maximum con- versions of nitrogen oxides were approximately 52, 80, and 98% at the temperature of 100, 200, and 300xC, respectively. The optimal energy density, ammonia con- centration, and ratio of nitrogen oxides exist for the highest removal of nitrogen oxides in the plasma catalytic hybrid process. KEY WORDS: Plasma catalytic hybrid process; carrier gas; dielectric barrier discharge; V 2 O 5 –WO 3 =TiO 2 catalyst; nitrogen oxides. 1. INTRODUCTION Globally, quantities of nitrogen oxides (NO x ) are produced by man- made emissions. Nitrogen oxides are formed when fuel is burned at a high temperature, as in combustion processes. The primary sources of NO x are motor vehicles, electric utilities, and other industrial, commercial, and residential sources that burn fuels. It is highly toxic, causing serious lung damages with delayed effects. It also plays a major role in the atmospheric reactions that produce ground-level ozone or smog. Many countries have 1 School of Environmental Science and Engineering, Pohang Univerity of Science and Tech- nology, Pohang, Kyungbuk 790-784, Republic of Korea. 2 Department of Environmental Engineering, Jinju National University, 150 Chilamdong, Jinju, Kyungnam 660-758, Republic of Korea. 3 Pohang Accelerator Laboratory, San-31 Hyoja-dong, Pohang, Kyungbuk 709-784, Republic of Korea. 4 To whom correspondence should be addressed. Telephone: + 82-54-279-2758; fax: + 82-54- 279-3099; e-mail: yhlee69@postech.ac.kr Plasma Chemistry and Plasma Processing, Vol. 24, No. 2, June 2004 ( g 2004) 137 0272-4324=04=0600-0137=0 g 2004 Plenum Publishing Corporation