Concentrations of particulate matter (PM, PM10, PM2.5) from gas-fired gas turbines typically are near or below the overall method detection and quantitation limits of traditional hot filter/cooled impinger methods used for PM/PM10/PM2.5 emissions measurements (e.g., USEPA reference methods 5, 201A, 202). The test results can be highly variable, and may significantly overstate emissions even with application of best practices optimized to minimize bias and variability.
An emerging test protocol for modifying USEPA Conditional Test Method 39 (CTM 39), a dilution sampling method for determining PM10/PM2.5 emissions from stationary sources, was used to accurately measure much lower PM concentrations. The lower concentrations are believed to be more representative of actual PM emissions from gas turbines. The modifications include adding ambient air sample collection and analysis methods for improved method sensitivity. Data from several testing programs are presented to illustrate the limitations of traditional methods for determining PM emissions, including measurement challenges associated with post-combustion emission controls such as SCR. Results from the modified method are presented to demonstrate the potential improvement compared with traditional hot filter/cooled impinger methods.