OIL RECOVERY WITH NOVEL SKIMMER SURFACES UNDER COLD CLIMATE CONDITIONS

Abstract

ABSTRACT Increasing oil exploration, production and transport in Arctic waters will increase the risk of an oil spill occurring in cold and ice-infested waters. The mechanical oil spill recovery equipment currently used in warmer waters was not designed to collect much more viscous oils, or oil-ice mixtures. The presence of ice crystals in oil emulsions affects the adhesion processes between an oil slick and the surface of an oleophilic skimmer and prevents oil from being efficiently recovered. Novel drum skimmer surface geometry and materials, tailored to the conditions present under cold climates, are expected to significantly increase the rate of oil recovery, reducing cost and risk. The objective of this project was to perform a comprehensive analysis of the adhesion between oil or ice-in-oil mixtures and various surface patterns and materials, under cold climate conditions. This knowledge was then applied to improve existing mechanical response equipment so that it can be applied efficiently under these conditions. The novel recovery surfaces that proved to increase the recovery efficiency of a drum skimmer up to two times in warm waters were also successful in cold climate conditions. In the first phase of the project, laboratory bench-scale tests of different surface materials were conducted, to determine contact angle and amount of oil adhered at sub-freezing conditions, with and without ice. It became clear that the physicochemical property that would be most significantly influence by cold climate conditions would be viscosity, and that the presence of ice would also have an important effect on viscosity, although to a varying degree depending on the initial oil viscosity. Neoprene was the best material surface, of those tested here, for adhering oil even under oil/ice conditions. Based on the results of the laboratory tests at subfreezing conditions, we selected materials and surface patterns with the highest oil recovery potential under cold climate conditions, and performed field scale oil spill recovery tests with three different oils at the U.S. Army Corps of Engineers Cold Regions Research and Engineering Laboratory (CRREL), located in Hanover, NH. This provided valuable information about the correlation between the laboratory tests and full scale experiments. It also demonstrated the potential of the skimmer modifications under conditions similar to response operations. The field tests were very successful, with high rates of oil recovery under cold climates, with and without ice present. However, the presence of ice does decrease the overall rate of oil recovery to some extent. The outcome of this project advanced our understanding of the adhesion of oil and oil emulsions (water containing and ice-containing) to recovery surface material under cold climate conditions. This research will facilitate selection of materials and surface configurations that result in significantly higher recovery rates of oil spills in cold and ice-infested waters. This will ultimately lead to a faster oil spill cleanup and greater protection of natural resources.