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Low-Level TNMNEOC (Total Non-Methane, Non-Ethane Organic Carbon) Measurements

Presented at the National Environmental Monitoring Conference, August 6-10 2012

M. Hueppe, E. Grosjean, D. Henricksen, and S. Parmar

Atmospheric Analysis and Consulting, Inc.1534 Eastman Ave., Suite A Ventura, CA 93003, 805-650-1642


Current emissions standards for Combustion Turbines subject to the 2.0 ppmC (TNMNEOC) BACT limit has created the need of a new sampling and analysis protocol able to accurately measure TNMNEOC at this level.

The measurement of non-methane and/or non-ethane organic compounds is a rapid screening method to determine the total organic content in gaseous samples except methane and/or ethane. This approach equalizes the response for all hydrocarbons with the use of catalytic oxidation and reduction systems. These systems are commonly referred to as TCA (Total Carbon Analyzers). The most commonly used method for low level TNMNEOC measurement is SCAQMD 25.3. The sampling train for the method utilizes both an impinger and a canister to capture the condensable and non-condensables. Each sample fraction is then analyzed separately; the canister portion on the TCA and the aqueous portion on a TOC.

The official performance requirement of South Coast AQMD Method 25.3/EPA 035 is the ability to detect at 1.0 ppmC for both fractions however the PQL for the canister fraction is 1.0 ppmV as propane and approximately 0.1 ugC/ml for the impinger. Under standard sampling protocol, this equates to approximately a total PQL for both fractions around 5.0 ppmC and carries with it a 20% error margin. This of course is 2.5x high than the standard to be achieved, thus this method cannot be used to accurately test these engines as written, and there are no other approved methods currently available.

In this paper, we have discus methods to lower the MDL and PQL of the NMNEOC measurements by modifying the sampling train and analytical set-up, so that reliable measurements can support low NMNEOC emission rules.

Please contact AAC for a pdf copy of the full paper.