| NOx REDUCTION BY SNCR AND ITS REACTION MECHANISM UNDER OXIDIZING DIESEL FLUE
GAS CONDITIONS
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| Chang Mo Nam† |
| Division of Environmental Engineering, Yeungnam College of Science and Technology, Daegu 705-037, Korea |
Corresponding Author:
Chang Mo Nam ,Tel: +82-53-650-9284, Fax: +82-53-625-5722, Email: cmnam@ync.ac.kr
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Received: September 15, 2002; Accepted: December 14, 2002. |
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| ABSTRACT |
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Direct injections of NHj/urea into a simulated cylinder were performed for oxidizing diesel NOx reduction where a diesel fuelled combustion-driven flow reactor was designed with the aim of simulating diesel engine geometry, aerodynamics and combustion products. NOx reduction tests were carried out over a wide range of air/fuel ratios (A/F = 20-40) using an initial NOx level of 530 ppm and for molar ratios (/? = Nlfi/NOx) or normalized stoichiometric ratios (NSR = NH/NOx for urea) of 0.5-2.0. The results show that effective NOx reduction with NHj/urea occurred over an injection temperature range of 1,100-1,400 K in which the temperature window of urea was wider and shifted upward. NOx reduction increased with increasing molar ratios, and about a 15-40% reduction of NOx was achieved at optimum conditions. The effects of engine and exhaust parts on NOx reduction potential are discussed following temperature profiles, and together with comparisons of urea with NH3 DeNOx characteristics. Through sensitivity and rate-of-production analyses, a reduced reaction mechanism for N/H/O species is suggested as a basic model of the SNCR process. Thus, key and detailed reaction paths are analyzed, understood for NOx reduction and NIlj oxidation. Validity and reliability of this model are further discussed. |
| Keywords:
diesel NOx | NOx reduction | reaction mechanism | SNCR |
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