Long-Term Emissions Performance of Stationary Natural Gas Engines Equipped with NSCR System
This paper describes work to characterize pollutant emissions performance of non-selective catalytic reduction (NSCR) technology, including a catalyst and air-to-fuel ratio controller (AFRC), applied to four-stroke cycle rich-burn engines. Emissions and engine data were collected semi-continuously with a portable emissions analyzer on three engines in the Four Corners area. In addition, periodic emissions measurements that included ammonia were conducted several times. Data collected from October 2007 through December 2008 shows significant variation in emissions levels over hours, days, and longer periods of time, as well as seasonal variation. As a result of these variations, simultaneous control of NOx to below a few hundred parts per million (PPM) and CO to below 1,000 ppm volumetric concentration was not consistently achieved. Instead, the NSCR/AFRC systems were able to simultaneously control both species to these levels for only a fraction of the time the engines were monitored. Both semi-continuous emissions data and periodically collected emissions data support a NOx-CO trade-off and a NOx-ammonia trade-off in NSCR-equipped engines.