Test Procedures for Measuring Exhaust Emissions From Natural Gas Transmission Engines

Abstract

The measurement of exhaust components from large natural gas transmission engines involves collection of the exhaust sample, transfer of the sample to the analytical instrumentation, measurement of individual component concentrations, and calculations of emission results in terms of mass, fuel specific, and brake specific rates. The major exhaust components measured include nitrogen oxides (NOx ), total hydrocarbons (THC), carbon dioxide (CO2 ), carbon monoxide (CO), and oxygen (O2 ). Collection of the exhaust sample requires proper probe design and placement in the exhaust system. Transfer of the sample to the analytical instruments must maintain sample integrity from the point where the sample is removed from the exhaust stream to the point at which the sample enters the instrument for analysis. Various analytical techniques are used to measure the exhaust emission concentrations. These techniques include chemiluminescence for NOx , flame ionization for THC, nondispersive infrared (NDIR) for CO2 and CO, and polarography for O2 . Calculation of the emission results in terms of mass fuel specific, and brake specific rates utilizes the measured emission concentrations, the engine operating parameters, and the “total carbon” method for data reduction and presentation.