A Surface-Active Chemical System for Controlling and Recovering Spilled Oil from the Ocean
Authors: Milz E.A. , Fraser J.P. 
Published: December 2007

A system involving the use of a surface-tension modifier is feasible for controlling and recovering oil spilled on the ocean in a wide range of weather conditions. Tests have led to the conclusion that the chemicals are less harmful to the ecology than are the oils they help to recover.

Introduction

In the past, oil-spill containment and recovery under severe weather conditions has been achieved with only marginal success. It is generally accepted now that the effectiveness of existing mechanical booms is limited to wave heights under 4 ft and current velocities under 1 knot. Severe wave and wind action has generally caused mechanical failure of the booms. In those instances when booms have been effective in containing oil, wave action was not significant.

The objective of the research reported here has been to evolve a system for oil-slick control and oil recovery that would be largely independent of the limitations that weather imposes on mechanical containment devices and on most existing oil recovery devices. The constraints placed upon the system were that it be effective under severe weather conditions and that it be highly mobile, preferably air transportable. The system that has evolved and that is reviewed here consists of the following:

Oil-slick control by means of surface-activechemical agents that possess spreading forcesgreater than those of most oils. The surfacechemical agent prevents the spreading of oil onwater and in most cases causes an oil slick tocontract so as to occupy a much smaller areaof water surface. Generation and spreading of an open-cell, flexible polyurethane foam at the site of the spill. Pick-up of the oil-soaked polyurethane foam byeasily transportable net booms or by ship trawlsor purse seins. All pick-up activity is to behandled by marine equipment that generally isavailable in the coastal regions of the U. S.

Extensive research has been conducted on surface-active chemicals and their effects on various types of oil under a variety of weather conditions. The toxicity of one of the most effective of these chemicals to the marine and littoral ecology has also been investigated. Development work has been done on ways of generating and spreading foam, using boats or helicopters. Work has also been performed on net booms for recovering foam, on a squeezing technique for regenerating the foam, and on a system for ultimately disposing of it.

Oil-Slick Control Spreading of Oil on Water

Cochran and Scott and others discussed at length the spreading of oil on water. After the initial spreading period in which gravitational forces play a large part, the only important force tending to cause the oil to spread is surface tension. Thin oil slicks tend to spread on water in response to the force imbalance shown schematically in Fig. 1. Three forces operate on an oil slick: the surface tension of water, w, which tends to spread the oil on the surface of the water; the surface tension of the oil, o, and the interfacial tension between the oil and the water ow. Both o and ow tend to cause the oil droplets or slick to contract upon itself.

JPT

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