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Show Experimental Study on NOx and N20 Emissions from a CFB Combustor X. S. Wang, N. A. Akhtar and B.M. Gibbs Department of Fuel and Energy, University of Leeds, LS2 9JT, U.K. ABSTRACT The possibilities of controlling NOx and N20 emissions from a circulating fluidized-bed (CFB) combustor were investigated. It was found that the NOx emission increased whilst the N 20 emission decreased with increasing temperature. Both NOx and N20 emissions were found to increase with increasing excess air factor. Compared to unstaged combustion, the staged combustion appeared to be more effective in controlling the NOx emission. The effect of air staging on the N 20 emission was, however, found to be small. In order to minimise NOx and N20 emissions from a CFB combustor, the emission ofNOx and N20 needs to be controlled in stages. INTRODUCTION In the recent years, continuing efforts have been made to optimise the control of NOx and N20 emissions from coal combustion in fluidized-bed combustors. The work of Roby and Bowman (1987) showed that the reduction of N20 became more effective at higher temperatures. Boyd (1990) and Leckner et al (1992) observed an increase in NOx but a decrease in N20 emission with increasing temperature. Moritomi et al (1990) suggested that an effective reduction in N20 emission was possible at higher temperatures. Gavin and Dorrington (1993) also observed a higher NOx and a lower N20 emission with increasing temperature. Lundqvist et al (1991) found that the NOx emission generally increased with increasing temperature. Gierse (1990) and Basak et al (1991) observed the sensitivity of NOx emission with both temperature and excess air factor. Kullendorff and Andersson (1985) reported an increase in N Ox emission with increasing excess air factor. Leckner and Gustavsson (1991) reported a reduction in the NOx emission of upto 800/0 at 2% 02 in the flue. Mjomeil et al (1991) reported N20 emission in range 40 to 250 ppmv (at 6% 02), whilst Hiltunen et al (1991) reported the N20 emission from 30 to 130 ppmv (30/0 02). The staged combustion has been demonstrated to be effective in controlling the emission of NOx by Suzuki et a1 (1990), Steinruck (1990) and Asai et al (1990). In this paper we report on results of an experimental study of the effect of operating conditions on NOx and N20 emissions from a CFB |