Oil and water separation in marine oil spill clean-up operations |
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| Institution: | 1. Environmental Marine Technology & Associates, 2230 Central Avenue, Vienna, VA 22182, USA Tel: (+1) (703) 698 1565; Fax: (+1) (703) 698 6232;2. U.S.C.G. Research and Development Center, 1082 Shennecossett Road, Groton, CT 06340, USA (Tel: (+1) (860) 441 2733; Fax: (+1) (860) 441 2792);3. IKU Petroleum Research Trondheim, Norway (Tel: (+47) (73) 591100; Fax: (+47) (73) 591102);1. College of Chemical Engineering, Jiangsu Provincial Key Lab for the Chemistry and Utilization of Agro-forest Biomass Jiangsu Key Lab of Biomass-based Green Fuels and Chemicals, Nanjing Forestry University (NFU), Nanjing 210037, PR China;2. School of Material Science and Engineering, Xi’an Jiaotong University, Xi’an 710049, PR China;3. Center for Quantitative Synthetic Biology, Institute of Synthetic Biology, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, PR China;4. Lab General Biochemistry & Physical Pharmacy, Department of Pharmaceutics, Ghent University, 9000, Belgium;5. Laboratory of Biopolymer Based Functional Materials, Jiangsu Co-Innovation Center of Efficient Processing and Utilization of Forest Resources, Nanjing Forestry University, Nanjing 210037, PR China;1. Center for Separation and Purification Materials & Technologies, Suzhou Key Laboratory of Separation and Purification Materials & Technologies, National and Local Joint Engineering Laboratory of Municipal Sewage Resource Utilization Technology, School of Environmental Science & Engineering, Suzhou University of Science and Technology, Suzhou 215009, Peoples Republic of China;2. Department of Chemistry, Queen''s University, 90 Bader Lane, Kingston, Canada K7L 3N6;1. Natural Resources Canada, CanmetENERGY in Devon, 1 Oil Patch Drive, Devon, AB T9G 1A8, Canada;2. Department of Chemical and Materials Engineering, University of Alberta, 9211 116 St, Edmonton, AB T6G 1H9, Canada;1. College of Transport and Communications, Shanghai Maritime University, Shanghai, 201306, China;2. School of Navigation, Wuhan University of Technology, Wuhan, 430063, China;3. Hubei Key Laboratory of Inland Shipping Technology, Wuhan, Hubei, 430063, China;4. School of Environmental Science and Engineering, Southern University of Science and Technology, Shenzhen, 518055, China |
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| Abstract: | This paper discusses the changes in spilled oil properties over time and how these changes affect differential density separation. It presents methods to improve differential density, and operational effectiveness when oil-water separation is incorporated in a recovery system. Separators function because of the difference in density between oil and seawater. As an oil weathers this difference decreases, because the oil density increases as the lighter components evaporate. The density also increases as the oil incorporates water droplets to form a water-in-oil emulsion. These changes occur simultaneously during weathering and reduce the effectiveness of separators. Today, the state-of-the-art technologies have limited capabilities for separating spilled marine oil that has weathered.For separation of emulsified water in an emulsion, the viscosity of the oil will have a significant impact on drag forces, reducing the effect of gravity or centrifugal separation. Since water content in an emulsion greatly increases the clean up volume (which can contain as much as two to five times as much water as the volume of recovered oil), it is equally important to remove water from an emulsion as to remove free water recovered owing to low skimmer effectiveness. Removal of both free water and water from an emulsion, has the potential to increase effective skimming time, recovery effectiveness and capacity, and facilitate waste handling and disposal. Therefore, effective oil and water separation in marine oil spill clean-up operations may be a more critical process than credited because it can mean that fewer resources are needed to clean up an oil spill with subsequent effects on capital investment and basic stand-by and operating costs for a spill response organization.A large increase in continuous skimming time and recovery has been demonstrated for total water (free and emulsified water) separation. Assuming a 200 m3 storage tank, 100 m3 h−1 skimmer capacity, 25% skimmer effectiveness, and 80% water content in the emulsion, the time of continuous operation (before discharge of oil residue is needed), increases from 2 to 40 h and recovery of oil residue from 10 to 200 m3.Use of emulsion breakers to enhance and accelerate the separation process may, in some cases, be a rapid and cost effective method to separate crude oil emulsions. Decrease of water content in an emulsion, by heating or use of emulsion breakers and subsequent reduction in viscosity, may improve pumpability, reduce transfer and discharge time, and can reduce oily waste handling, and disposal costs by a factor of 10. However, effective use of emulsion breakers is dependant on the effectiveness of the product, oil properties, application methods and time of application after a spill. |
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