This research project was conducted in two separate phases.
Phase I: Was funded by Alaska Department of Environmental Conservation, Alaska Clean Seas BP Exploration (Alaska) Inc. and consisted of a modest laboratory scale program to evaluate the burning characteristics of four Alaska risk oils: Drift River crude from Cook Inlet, Endicott crude oil, Pt. McIntyre crude oil from the North Slope and IF-30 fuel oil, a common bunker fuel for vessels. In Phase I, a sample of each oil was weathered for one week in a wind tunnel. Emulsion formation tendency and stability was tested for each oil using the standard rotating flask technique. Both weathered and fresh samples of each oil were tested. The effectiveness of three emulsion breaking chemicals was tested. Baseline burn tests were conducted to determine the natural burning characteristics of water-free and emulsified slicks of fresh and weathered oils. Burn efficiency and burn rate were calculated from the data gathered in the burn tests.
Phase II: Involved design and construction of an outdoor wave tank and a series of mid-scale burn tests, which were conducted in the tank in August and September 1997. Phase II was a Joint Industry Project (JIP)with the Alaska Department of Environmental Conservation, Alaska Clean Seas and its member companies Alyeska Pipeline Services Company, ARCO, BP, and Exxon, ARCO Marine, Canadian Coast Guard, Clean Sound, Cook Inlet Regional Citizens Advisory Group, Cook Inlet Spill Prevention and Response Inc., Minerals Management Service, U.S. Coast Guard, and the Western Canada Marine Response Corporation.
Complete. Phase I the ignition and burning of all oil selected for this phase was limited by the formation of water-in-oil emulsions. The burning of emulsions was found to be oil specific, with some oils (e.g. Drift River) being much easier to ignite and burn than others (e.g. Pt. McIntyre). The application of chemical breakers to emulsions of the four oils extended the limits of ignition and burnability. The chemical emulsion breaker EXO-O894 appears to be the best of the three tested.
Phase II of this project (Mid-scale burns in waves) was conducted in August/September 1997 at the ARCO Fire Training Grounds in Prudhoe Bay, AK. A custom tank was designed and built for this project. It is of all-steel construction and is road-transportable. The inside dimensions are 12 m (40 ft) long x 2.4 m (8 ft) wide x 2.25 m (7.4 ft) high. The tank is fitted with a simple hydraulically driven wave paddle at one end and a passive wave absorber at the other end. Complete drawings are found in the appendix of the final report.
In Phase II, two crude oils were tested: Alaska North Slope (ANS) crude oil and Milne Pt. Crude oil. A total of 58 experimental burns were conducted, 31 with ANS crude oil and 27 with Milne Pt. Crude oil. Several repeat burns with ANS crude were conducted. Water temperature in the tank ranged from 3 to 9o C over the course of the tests. Air temperatures ranged from 0 to 4o C. Most tests were conducted in winds of 2 to 8 m/s.
The mid-scale tests demonstrated that larger oil and emulsion slicks of ANS and Milne Pt. Crudes could be successfully burned in waves. Emulsified slicks of ANS with water contents greater than 25% requires treatment with emulsion breakers and a period of settling for successful ignition and efficient burning. Milne Pt. Emulsions ignited and burned easily without treatment.
A mid-scale test slick of 60% water emulsion of weathered ANS crude was successfully burned in the highest waves tested, with an oil removal efficiency of 79%, after treatment with emulsion breakers. A similar test slick of 60% water emulsion of weathered Milne Pt. Crude was successfully burned in the highest wave tested, without the need for treatment with emulsion breakers, with an oil removal efficiency of 83%. At this larger scale, increasing wave steepness (or wave energy) appeared to reduce both burn rates and burn efficiencies of the unemulsified oil slicks. For emulsified slicks, increasing wave steepness did not appear to appreciably affect the oil burning rates, but did reduce the oil removal efficiencies.
Comparing the results of the laboratory burns with the mid-scale tests, it appears that the laboratory tests were a good predictor of the likely success of ignition and the oil removal efficiency for the mid-scale tests; however, they did not adequately predict trends in oil burn rate as a function of wave steepness at the larger scale. In order to predict the likely success of an in situ burning operation with a specific oil it is still necessary to carry out small-scale test burns with fresh and weathered oil and emulsions. This is also true for determining the efficacy of emulsion breakers use in extending the in situ burning window of opportunity with a given oil. A catalog of in situ burning characteristics of oils tested to date should be compiled.
A final report on both phases of this research project was completed.