Experimental Modelling of Black Carbon Emissions from Gas Flares in the Oil and Gas Sector

Experiments examined the effects of flow conditions and fuel chemistry on the soot emissions from turbulent buoyant diffusion flames burning methane-dominated alkane fuels mixtures representative of upstream oil and gas sector flares. Soot (elemental carbon) in the captured plumes was measured via thermal-optical analysis. Yields were calculated within precisely-quantified uncertainties following a mass-balance procedure using CO2, CO, and CH4 gas analyzers. Experiments considered six flare diameters (12.7−76.2 mm), exit velocities up to 9.5 m/s, and thirteen multi-component fuel mixtures. Reynolds number times Froude number squared was shown to be a useful criterion to separate differing soot emissions trends which were aligned with the transition buoyant and transition shear sub-regimes of turbulent buoyant flames as defined by Delichatsios (1993). Soot emission rates in each regime were well-predicted by new empirical models based on flame volumetric flow and global mixing rate and were lower than emission factors used in current pollutant inventories.