An on-line infrared spectroscopic system with a modified multipath White cell for direct measurements of N2O from NH3-SCR reaction

Abstract

An on-line, continuous IR-based N 2 O measurement system has been developed by combining with a variable multipath "White cell" to avoid a huge amount of the well-known artifact errors in actual N 2 O concentrations determination when analyzing grab samples taken from stationary sources, such as fossil fuel-fired power plants. For solving the problems confronted in earlier stages of this study, the gas cell had to have modifications of the feed through of gas sample flows, the multilayer coatings of stainless steel mirrors, and the thermal efficiency to provide high cell inner temperatures in flowing gas samples. These modifications allow good tolerance of the gas cell to gases and chemicals, such as NO x and NH 3 , and NH 4 NO 3 driven from them, and its usage for a long lifetime even under harsh conditions. They also offer excellent performance not only in directly determining the extent of N 2 O formation during the course of NH 3 -SCR reaction over a sample of a commercial V 2 O 5 -WO 3 /TiO 2 catalyst, but also in simultaneously monitoring changes in concentrations of NO, NO 2 and NH 3 during the reaction. Each reference peak was chosen in gasphase spectra for N 2 O, NO x , NH 3 and H 2 O, and CO 2 as a possible interference, and the modified gas cell was finely tuned to obtain their spectra with a high resolution under optimal operating conditions. The catalyst gave significant amounts of N 2 O formation at reaction temperatures greater than 350 o C, and attention should be paid to the possibility of N 2 O production from commercial NH 3 -SCR deNO x processes with V 2 O 5 /TiO 2 -based catalysts.

The Role of Fe2O3 Species in Depressing the Formation of N2O in the Selective Reduction of NO by NH3 over V2O5/TiO2-Based Catalysts

“…Details of the modified Model MARS 0.75 L/8.0 V White gas cell (Zemini Scientific Instr., Buena Park, CA, USA) combined with a Thermo Electron Nicolet 7600 FT-IR spectrophotometer (Thermo Fisher Scientific, Waltham, MA, USA) used in the present study to measure conversions of NO and NH 3 and the extent of N 2 O production in NH 3 -SCR reaction have been described earlier [6,68]. A continuous purge of this system was allowed by flowing a compressed air at a rate of 15 L/min that had passed through a train of large volume silica traps to remove H 2 O in the air.…”

“…A continuous purge of this system was allowed by flowing a compressed air at a rate of 15 L/min that had passed through a train of large volume silica traps to remove H 2 O in the air. The NH 3 -SCR reaction with catalyst samples was conducted in a continuous flow type I-shaped 3/8 OD quartz reactor placed in a three-independent temperature adjustable electric furnace (Lindberg/Blue M Model HTF55347C, Thermo Electron Corp., Asheville, NC, USA) coupled with a Lindberg/Blue M Model CC584343PC PID controller [6,16,27,68]. All gas feed lines were maintained at a temperature near 180 • C to prevent the homogeneous reaction between NO and O 2 , and the condensation of H 2 O produced in the reaction.…”

“…All gas flows were accurately controlled by using a Model 5850E mass flow controller (Brooks Instr., Hatfield, PA, USA) and a Model F-200CV one (Bronkhorst High-Tech, Ruurlo, The Netherland). Details of the standard procedures to collect the gas-phase spectra have been provided elsewhere [6,68].…”

High Temperature and High Concentration SCR of NO with NH3 for the Oxyfuel Combustion Process: Fitting of Kinetics to Data from a Laboratory Reactor Experiment

“…Kim et al [28] showed the 54 ppm N 2 O was formed on 1.68% V 2 O 5 -WO 3 /TiO 2 catalyst at 745 K. In another study [29] on a commercial catalyst with 1.43% V 2 O 5 and 7.56% WO 3 the formation of 20 ppm N 2 O at a NO conversion of 85% at 750 K was presented. Similar results were obtained by [30].…”

Formation of N2O in NH3-SCR DeNOxing Reaction with V2O5/TiO2-Based Catalysts for Fossil Fuels-Fired Power Stations

“…2(b)). [1,3,17,20,25]. [4,27], and the concentrations of N 2 O formed have been calculated using the N 2 selectivity data in Refs.…”