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KMID : 1024520030120010047
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Journal of the Environmental Sciences
2003 Volume.12 No. 1 p.47 ~ p.54
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Application of SNCR/SCR Combined process for effective operation of SCR Process
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Choi Sung-Woo
Choi Sang-Ki
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Abstract
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This paper have examined the optimum combination of SNCR and SCR by varying SNCR injection temperature and NSR ratio along with SCR space velocity. NOx reduction experiments using a SNCR/SCR combined process have been conducted in simple NO/NH/O gas mixtures. Total gas flow rate was kept constant 4 liter/min throughout the SNCR and SCR reactors, where initial NOx concentration was 500 ppm in the presence of 5% O. Commercial catalyst, sulfated VO5/-WO/TiO, was used for SCR NOx reduction. The residence time and space velocity were around 1.67 sec, 2,400 h-1/ and 6,000 h-1/ in the SNCR and SCR reactors, respectively. SNCR NOx reduction effectively occurred in a temperature window of 900-950. About 88% NOx reduction was achieved with an optimum temperature of 950 and NSR=1.5. SCR NOx reduction using commercial VO5/-WO-SO/TiO catalyst occurred in a temperature window of 200-450 80-98% NOxreduction was possible with SV=2400 h-1/ and a molar ratio of 1.0-2.0. A SNCR/SCR(SV=6000 h-1/) combined process has shown same NOx reduction compared with a stand-alone SCR(SV=2400 h-1/) unit process of 98% NOx reduction. The NH-based chemical could routinely achieve SNCR/SCR combined process total NOx reductions of 98% with less than 5 ppm NH slip at NSR ranging from about 1.5 to 2.0, SNCR temperature of 900-950, and SCR space velocity of 6000 h-1/. Particularly, more than 98% NOx reduction was possible using the combined process under the conditions of TSNCR/=950, TSCR/=350, 5% O, SV=6000 h-1/ and NH/NOx=1.5. A catalyst volume was about three times reduced by SNCR/SCR combined process compared with SCR process under the same controlled conditions.
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KEYWORD
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SNCR/SCR combined process, SNCR, SCR, NOx
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