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UBC Theses and Dissertations

Characterization of the effects of fuel and entrained salt on soot morphology Trivanovic, Una


Soot is an important contributor to climate change and has negative effects on human health. These impacts depend on the morphological properties which influence the optical properties, mobility and surface area available to adsorb other contaminants. Different combustion sources may produce soot with different morphologies and thus, different environmental and health impacts. Three soot sources were studied: a dual-fuel natural gas marine engine and two laboratory gas flares. The ship studied operated on its normal route during the measurement campaign and was run both in dual-fuel mode, and diesel-only mode to serve as a comparison. Dual-fuel mode produced substantially less soot, ~96% less, than diesel-only mode at all loads except idle. Soot morphology appeared to be independent of operating load but did vary slightly based on fuelling mode. Dual-fuel mode produced on average smaller aggregates than diesel-only mode however, the small dual-fuel mode aggregates tended to have slightly larger primary particles when compared to diesel-only generated aggregates. Overall the differences in morphology are small compared to the reduction in the amount of soot produced. Gas flaring is used in the oil and gas industry to dispose of gas. The laboratory flares studied were designed to simulate conditions which would be found in the upstream oil and gas industry. Raman spectroscopy showed that the heavier fuels had more graphitic nanostructures and transmission electron microscopy (TEM) and mobility size distributions showed that the aggregates tended to be larger. The relationship between the primary particle size and the aggregate size, did not depend on the fuel. During hydraulic fracturing operations, it is likely that the flowback fluids become entrained in the flare fuels resulting in liquids with inorganic salts becoming part of the combustion process. The morphology of the soot did not change due to the salt however, most of the soot particles became internally mixed with the salt. Unlike soot, salt tends to be an effective cloud condensation nucleus (CCN) and the large number of salt particles will likely influence local cloud formation. Furthermore, the salt particles which attach to the soot may turn the soot itself into an effective CCN.

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