Two-stroke lean burn natural gas engine oxidation catalyst degradation and regeneration via washing

Hackleman, Bryan, author
Olsen, Daniel, advisor
Bandhauer, Todd, committee member
Carter, Ellison, committee member
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Lean burn two stroke engines are used extensively for stationary applications including power generation, cogeneration and compression. Natural gas is abundant, relatively inexpensive, and combustion produces less CO2, particulate matter, and SOx than gasoline and diesel. However, the Natural gas industry continues to be impacted by increasingly stricter emissions limits. One approach to comply with these emission limits is outfitting engines with an oxidation catalyst. Oxidation catalysts are proven to reduce hydrocarbon and carbon monoxide emissions, but surface poisoning due to lube oil carry over diminishes performance. Zinc, phosphorus, and sulfur found in oil additives poison the catalysts surface, and readily leach into an acidic environment. Two commercial catalyst modules were aged at a field site on a slipstream of a GMVH-12 engine until they no longer met the National Emissions Standards for Hazardous Air Pollutants (NESHAP) formaldehyde limit. The oxidation catalyst modules underwent a washing process of immersion into caustic soda, neutral water, and acetic acid baths. The surface chemistry of samples was analyzed on a scanning electron microscope (SEM-EDS) and X-ray photoelectron spectroscopy (XPS). Catalytic performance testing was carried out by a slipstream of a laboratory Cummins QSK-19G engine, five gas analyzer and Fourier transform infrared spectroscopy (FTIR). The washing process removed the majority of surface poisons and improved the catalytic performance. The modules were then aged again until non-compliance with emissions limits occurred. The modules were periodically tested for poison accumulation and catalytic performance to determine the rate of degradation post-washing. These results were used to compare with that of a new catalyst to estimate the increase in lifespan from washing. The results of the experiments reported here should encourage the use of washing as a low cost partial regeneration procedure for oxidation catalysts.
2018 Summer.
Includes bibliographical references.
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