10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
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Physico-chemical Characterization of Small-scale Gas Flaring
Alberto Baldelli, Ramin Dastanpour, Una Trivanovic, Melina Jefferson, Jason S. Olfert, Alireza Moallemi, Kevin Thomson, Matthew Johnson, Olga Popovicheva, STEVEN ROGAK, University of British Columbia
Abstract Number: 863 Working Group: Carbonaceous Aerosol
Abstract The properties of particulate emissions affect their impact on the environment and the human health. Flaring operations in the oil and gas industries can be major sources of soot, but are presently not well characterized. Carleton University has a laboratory flame that approaches the scale of a small industrial flare. This facility was used to study emissions relevant to flaring in Canadian oil and gas production. Three fuel compositions (mixtures of methane, ethane, propane, butane, N2, and CO2), a range of exit velocities (0.5 to 1.5 m/s), and burner diameters of 38, 51, and 76 mm were studied.
A broad suite of optical, physical, and chemical characterization techniques was used to allow a comprehensive characterization of the gas flare particulate emissions. Individual particles were analyzed using High Resolution Transmission Electron Microscopy (HRTEM), Raman Spectroscopy, and Scanning Electron Microscopy coupled by Energy Dispersive X-ray (SEM-EDX) spectroscopy. Furthermore, a Fourier transform infrared (FTIR) was used on bulk samples of soot for a deeper analysis of its chemical structure. The major type is soot distinguished by agglomerates of ultrafine primary particles of 30 ± 10 nm diameter containing from a few up to hundreds of spheres. HRTEM images are characterized by the length, tortuosity and separation of individual graphene fringes in soot. Analysis of Raman spectroscopy is sensitive to the degree of graphitization and crystal sizes in disordered carbon. We found here that Raman spectra were very similar for soot from all fuels considered. From EDX we found that as expected, every particle was composed mainly of C and O. Cluster analyses of composition data proposes the separation of into characteristic groups representative of various gaseous fuel mixtures and operation conditions. Group “Elemental Carbon” accounts for 86 to 97% of particles while Group “Oxidized Soot”, which are for the 70% made of oxygen, appeared with abundance of a few percent.
Characterization of bulk composition by thermo-optical transmission (TOT) method using a semi-continuous OC/EC analyzer with organic vapour trap, showed the particulate to have a very high elemental to total carbon (EC/TC) ratio across all flare test points. For the organic fraction, FTIR spectra shows the major classes of organic compounds determined by aliphatic C-C-H, aromatic C=C, and carbonyl C=O functionalities.