Contraction and confinement of oil slicks on water, including water where ice is present, using non-ionic surfactants

#The present invention relates generally to confining oil slicks and, more particularly, to the use of at least one water-soluble non-ionic surfactant or mixtures of at least one oil-soluble surfactant and at least one water-soluble non-ionic surfactant, for reducing the size of an oil slick for more effective oil removal or in-situ burning on seawater, including seawater where ice is present.

#Oil spills due to releases of crude oil from tankers, offshore platforms, drilling rigs, and wells, as well as spills of refined petroleum (such as gasoline or diesel) and their by-products, and heavier fuels used by large ships such as bunker fuel, if uncontrolled may have devastating and lasting environmental impact. Such spills may be controlled by chemical dispersion, combustion, mechanical containment, and/or adsorption. Controlled burning can reduce the amount of oil in water, but can only be done in low wind conditions. Dispersants create smaller oil droplets which may be scattered by currents, and may degrade more easily. Dry hydrophobic, water insoluble polymers that both adsorb and absorb hydrocarbons can clean up oil spills by changing the physical state of oil from liquid to a semi-solid or a rubber-like material that floats on water, rendering it readily collectable. However, collected solidifiers must be disposed of in landfills, recycled as an additive in asphalt or rubber products, or burned as a low ash fuel. Oil-absorbing materials such as hair and fabrics may also be used. Oil may be “vacuumed” from the surface, along with some water, and the mixture centrifuged to separate the oil from the water, thereby permitting nearly pure oil to be collected, the water often being returned to the sea. Oil skimming devices may also be used.

#Typically, large floating barriers, known as booms, are used to surround and confine an oil slick, thereby enabling chemical and biological agents to be added to the oil to encourage its breakdown, and mechanical techniques to be used more efficiently.

#The accompanying drawings, which are incorporated in and form a part of the specification, illustrate the embodiments of the present invention and, together with the description, serve to explain the principles of the invention. In the drawings:

#FIG. 1 is a graph of the surface tension of seawater as a function of the concentration of BIO-SOFT®, a water-soluble non-ionic surfactant added to the seawater.

#FIG. 2 is a graph of the interfacial tension of several crude oils as a function of the concentration of BIO-SOFT®, a water-soluble non-ionic surfactant added to the seawater.

#Crude oil spreads rapidly when spilled on the surface of an open body of water forming a thin layer, making mechanical recovery of the dispersed oil inefficient. However, if oil spill control booms are utilized to confine the spilled crude oil, the oil may form masses having increased thickness over that for the unconfined oil, and often can be efficiently mechanically removed. In accordance with the teachings of embodiments of the present invention, if a small amount of water-soluble surfactant, such as BIO-SOFT® or Tween®, or a small amount of a water-soluble and oil-soluble surfactant mixture, such as Tween® and Span®, is continuously discharged adjacent to the wall of a deployed boom facing the oil slick (the inner wall of the boom), the oil slick will contract toward the center of the area enclosed by the boom. Such contraction further decreases the area of the oil slick and increases its thickness, thereby facilitating mechanical recovery thereof.

#Further, mixtures of oil-soluble surfactants, such as Span®, fluorine-based or silicon-based surfactants, and organic co-solvents, such as 2-ethyl butanol, may be utilized to confine the spilled crude oil to a limited area without a need for an oil control boom, whereby the oil is compressed into lenses having increased thickness, which can be more efficiently mechanically removed or burned in-situ. In the absence of the organic co-solvent however, the surfactant molecules cannot diffuse into or onto the body of water, or do so very slowly, rendering the surfactant inefficient as water surface tension reduction agent. Moreover, some of the useful co-solvents tend to be flammable, which makes handling, storage and application hazardous.

#In accordance with the teachings of embodiments of the present invention, oil-soluble surfactants can be utilized without an organic co-solvent for reducing the water surface tension for oil retraction away from the surfactant-dispensing location, if a water-soluble surfactant, such as BIO-SOFT® or Tween®, is mixed with the oil-soluble surfactant such that the mixture has greater water solubility than oil solubility. The oil-soluble surfactants can then diffuse into or on the body of water without the need for an organic co-solvent and, when the water-soluble surfactant or the mixture of a water-soluble surfactant and an oil-soluble surfactant is continuously discharged surrounding oil slick, the oil slick is expected to contract towards the center of the area enclosed by the surfactant mixture deployment locations. Such contraction decreases the area of the oil slick and increases its thickness, thereby facilitating mechanical recovery or in-situ burning thereof. Additionally, the replacement of the organic co-solvent with water as a co-solvent has the advantage that water is readily available anywhere there is an oil slick on water.