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Show I CONTINUOUS NH3 MONITORING PROBE SYSTEM PROTOTYPE : PRELIMINARY BENCH-SCALE TESTING AND FIELD TRIALS--TROUBLESHOOTING AN SCR SYSTEM ~< "'~~ ~ by : Paper No . 25 G. Sag~n Shareef, K.L. Johnson, P.A . May, D.H . Doerle, and M. W. Hartman Radian Corporation INTRODUCTION Research Triangle Park, North Carolina ABSTRACT This paper presents the results of Phase I of a threephase internal research program to develop a continuous NH3 monitoring tool for use in field troubleshooting commercial SCR and SNCR systems . The design of a first generation prototype NH3 monitoring probe is described . Preliminary results from a bench-scale study of NH3 oxidation on a stainless steel reactor are presented . Initial field demonstration trials troubleshooting a commercial SCR system are also described . Finally, plans for future R&D are discussed . Control of nitrogen oxide (NOx ) emissions from stationary combustion sources has become an increasingly important issue at local, state, and national levels in the U.S . , and throughout the world . Not only does NOx create a direct health hazard as an air pollutant, but it also plays a key role in the formation of ozone and photochemical smog, is a major constituent of acid rain, and is a chemically reactive gas in the upper atmosphere. As a result, increasingly stringent regulations mandating the reduction of NOx emissions are being implemented. For many combustion systems, advanced postcombustion NOx control technologies such as selective catalytic reduction (SCR) and selective noncatalytic reduction (SNCR) are considered and applied when NOx emissions reductions greater than those attainable via conventional combustion modifications are required. Both SCR and SNCR technologies employ NH3 as the primary reducing agent in converting NOx to Nz. (Urea can also be used in these processes.) The quantity of NH3 introduced into the combustion system is based on stoichiometric considerations . Aqueous or anhydrous NH3 is vaporized and usually diluted with air (or steam) and then injected into the |