Effects of NOx Control on Pollutant Emissions in Natural-Gas Fueled StationaryReciprocating Engines. Topical Report, September 1991-June 1992

摘要

Field tests were performed on five natural gas reciprocating engines. Fourengines were retrofitted with the following NOx control technologies: a nonselective catalytic reduction (NSCR) system retrofitted on a 4-cycle rich-burn engine; a selective catalytic reduction (SCR) system retrofitted on a 4-cycle lean-burn engine; and combustion modifications (PreCombustion Chamber (PCC)) retrofitted on two lean-burn engines (one 2-cycle and one 4-cycle). These controls are candidate technologies to reduce NOx emissions from natural gas prime movers. The fifth engine, a 2-cycle lean-burn engine, was tested without NOx controls. The field test program quantified the effects of these NOx controls on pollutant emissions, and found that, in some cases, NOx reduction can result in increased carbon monoxide (CO), total unburned hydrocarbons (TUHC), nonmethane hydrocarbons (NMHC), and formaldehyde emissions. Benzene, toluene, and formaldehyde were the major air-toxic compounds found in the exhausts of all engines tested, at concentrations of less than 0.3 ppm, for benzene and toluene, and 20 ppm, for formaldehyde. In general, benzene and toluene emissions decreased with the addition of either combustion modification and exhaust gas treatment controls. Formaldehyde emissions decreased across the rich-burn catalysts. Volatile organic compound (VOC, measured as NMHC) emissions increased when lean-burn combustion modifications and the SCR control system were applied, but decreased when the NSCR control system was applied.