Dramatically Lower Detection for Measurement of Non-methane Organic Compounds (NMOC) with Modified SCAQMD Method 25.3
Oral Presentation
Prepared by R. Bramston-Cook, E. Bramston-Cook
Lotus Consulting, 5781 Campo Walk, Long Beach, CA, 90803, United States
Contact Information: [email protected]; 310-569-0128
ABSTRACT
This paper reports on the construction of a measurement system to allow a very large volume of sample to be injected, and to dramatically enhance the ability to measure low levels of non-methane organics for emitting from relatively clean combustion sources, such as gas turbines . Samples are loaded into a fixed volume sample loop, up to 400 ml, to make the allocation independent of the sample matrix. The loop is maintained at a constant temperature, to minimize effects from Charles’ Gas Law. Any excess pressure from canisters and on-line sampling is released to atmosphere prior to injection to achieve steady loop pressure and thus an effective constant volume, per Boyle-Mariotte‘s Gas Law. Then the sample is transferred into a multi-layer, hydrophobic absorbent trap maintained near ambient temperature, without cryogen, to capture all organics from ethane and heavier. Methane, carbon monoxide, carbon dioxide, oxygen, nitrogen and water pass through the trap to vent. The trap is then pneumatically isolated, heated rapidly to 250 oC, injected into an oxidation catalyst, and on to a reduction catalyst to effectively convert all non-methane organics to methane for measurement by flame ionization detection. Typical run times are under 8 minutes. Oxygen, nitrogen, methane, carbon dioxide and carbon monoxide can be measured separately and concurrently by a thermal conductivity detector.
Results from tests for linearity, detection limits and catalyst efficiencies are presented. Examples for a variety of sample types, including ambient air, vehicle exhaust, aerobic digester and other combustion sources illustrate the performance capabilities of the system. Direct comparisons are made with equivalent tests from the other method approaches.
Oral Presentation
Prepared by R. Bramston-Cook, E. Bramston-Cook
Lotus Consulting, 5781 Campo Walk, Long Beach, CA, 90803, United States
Contact Information: [email protected]; 310-569-0128
ABSTRACT
This paper reports on the construction of a measurement system to allow a very large volume of sample to be injected, and to dramatically enhance the ability to measure low levels of non-methane organics for emitting from relatively clean combustion sources, such as gas turbines . Samples are loaded into a fixed volume sample loop, up to 400 ml, to make the allocation independent of the sample matrix. The loop is maintained at a constant temperature, to minimize effects from Charles’ Gas Law. Any excess pressure from canisters and on-line sampling is released to atmosphere prior to injection to achieve steady loop pressure and thus an effective constant volume, per Boyle-Mariotte‘s Gas Law. Then the sample is transferred into a multi-layer, hydrophobic absorbent trap maintained near ambient temperature, without cryogen, to capture all organics from ethane and heavier. Methane, carbon monoxide, carbon dioxide, oxygen, nitrogen and water pass through the trap to vent. The trap is then pneumatically isolated, heated rapidly to 250 oC, injected into an oxidation catalyst, and on to a reduction catalyst to effectively convert all non-methane organics to methane for measurement by flame ionization detection. Typical run times are under 8 minutes. Oxygen, nitrogen, methane, carbon dioxide and carbon monoxide can be measured separately and concurrently by a thermal conductivity detector.
Results from tests for linearity, detection limits and catalyst efficiencies are presented. Examples for a variety of sample types, including ambient air, vehicle exhaust, aerobic digester and other combustion sources illustrate the performance capabilities of the system. Direct comparisons are made with equivalent tests from the other method approaches.
