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pp.997-1004
The objective of this research was to test whether, under controlled laboratory conditions, hybrid SNCR/SCR process improves NOx removal efficiency in comparison with the SNCR only. The hybrid process is a combination of a redesigned existing SNCR with a new downstream SCR. NOx reduction experiments using a hybrid SNCR/SCR process have been conducted in simple NO/NH3/O2 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% or 15% O2. Commercial catalysts, V2O5-WO3-SO4/TiO2, were used for SCR NOx reduction. The residence time and space velocity were around 1.67 seconds and 2,400 h-1 or 6000 h-1 in SNCR and SCR reactors, respectively.
NOx reduction of the hybrid system was always higher than could be achieved by SNCR alone at a given value of NH3SLIP. Optimization of the hybrid system performance requires maximizing NOx removal in the SNCR process.
An analysis based on the hybrid system performance in this lab-scale work indicates that a equipment with NOxi=500 ppm will achieve a total NOx removal of about 90 percent with NH3SLIP ≤ 5 ppm only if the SNCR NOx reduction is at least 60 percent. A hybrid SNCR/SCR process has shown about 26～37% more NOx reduction than a SNCR unit process in which a lower temperature of 850℃ turned out to be more effective.
