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Characterization of Emissions and Residue from Measures to Improve Efficiency of In Situ Oil Burns
Citation:
Aurell, J., B. Gullett, A. Holder, R. Conmy, D. Sundaravadivelu, N. Lamie, AND K. Stone. Characterization of Emissions and Residue from Measures to Improve Efficiency of In Situ Oil Burns. 2021 International Oil Spill Conference, Virtual, May 10 - 14, 2021.
Impact/Purpose:
This work covers quantification of the emissions and oil residue from the purposeful burning of oil slicks at sea. In this work, at-sea oil slick burns were simulated in an outdoor laboratory and emissions and residues were sampled. The findings from this work will assist in assessing the environmental impact and efficacy of purposeful oil burns as spill cleanup remediation. This work would be of interest to federal agencies required to respond to spills, to state and regional governments interested in assessing potential environmental risk of oil burns.
Description:
The efficiency of in situ burns of crude oil on water was determined in two field campaigns while testing varied boom configurations, air-assist nozzles, and insulation layers to improve combustion. Comprehensive measurements of air emissions and residual, unburned oil were made to quantify and characterize the effect of technical modifications to demonstrate improvements in situ burn techniques and technologies. The combustion plume was sampled with a crane-suspended instrument system. Emission measurements quantified carbon monoxide, carbon dioxide, particulate matter less than 2.5 µm (PM2.5), black carbon and light-absorbing (ultraviolet) PM, elemental/organic/total carbon, polyaromatic hydrocarbons, polychlorinated dibenzo- dioxin and -furans, and volatile organic compounds including carbonyls. Post-burn residue samples were collected with oil absorbent pads and analyzed for monoaromatic hydrocarbons, polycyclic aromatic hydrocarbons, alkanes, and total petroleum hydrocarbons. The insulation tests consisted of both carbon fiber sheets and crumb rubber layers meant to limit heat loss from the combusting oil to the water below. Tests were conducted with 40 L and 80 L of Alaska North Slope oil within a catenary-shaped boom in a 5 m x 10 m outdoor, salt water tank. Combustion efficiencies based on the degree of carbon oxidation in the plume ranged from 83% to 89%. Post-burn, residual oil samples were collected and analyzed. The oil mass loss ranged from 54% to 91%. Total petroleum hydrocarbon residues ranged from 3.2% to 28.6% of the initial oil mass. The second set of tests were conducted in a 14 m x 2.4 m x 2.4 m tank to characterize variations in boom length/width ratios, the use of injection air, nozzle angle, and presence or absence of waves. Combustion tests were done with 30 L of Alaska North Slope oil within an outdoor, fresh water, 63 m3 tank. Plume measurements of carbon combustion efficiencies ranged from 85% to 93%. Measurement of residual oil showed that the oil mass loss ranged from 89% to 99%. A three-fold variation in PM2.5 emission factors was observed from the test conditions. Results suggest that the most effective burns in terms of combustion efficiency and oil consumption were those that have high length to width boom ratios and injection air.
