ABSTRACT
Removing oil from the environment by mechanical recovery is the most accepted response option for oil spilled to water. We are evaluating a semipermeable boom skirt that will significantly advance mechanical recovery collection rates. The maximum tow speed of standard curtain booms is limited to less than a knot (0.5 m/s) to avoid entrainment failure. Further, towing large ocean booms requires two large vessels because the potentially >1 m deep boom skirt faces major resistance from water as it moves. Our semipermeable boom skirt consists of a mesh screen coated with a material that makes it highly permeable to water flow (hydrophilic) and essentially impermeable to oil flow (oleophobic). We’ve completed experiments that found that coated mesh screens allow water to pass with a pressure drop over 20 times lower than when we attempted to pass oil through the screen. In a 3 m long laboratory flume, the semipermeable boom was as effective in capturing oil as an impermeable boom while letting water pass through it easily.
Experiments performed thus far have used low-viscosity, fresh, unemulsified oils. Real-world oils will be weathered and emulsified to some extent resulting in viscosities 10 – 100 or more times greater than the fresh oils we’ve tested so far. Testing of oils more representative of real-world oils (weathered and emulsified) will increase chances of success for this concept immensely as the flow of viscous fluids through porous media (e.g., mesh screens) is directly proportional to the fluid's viscosity. That is, increasing the viscosity of the oil by 10 or 100 times will increase the ability of any screen to retain oil by the same amount. This paper will describe the research completed on this novel concept.