1. Field of the Invention
This invention relates generally to a method for controlling liquid hydrocarbon spills.
More particularly, this invention relates to a method for bodying spilled hydrocarbon liquids to render those liquids non-flowing and amenable to recovery.
In one specific embodiment of the invention, oil spilled on water is contained and immobilized by dissolving in the oil particles of a relatively high molecular weight cryogenically comminuted, rubbery polymer applied to the oil as a slurry in a liquid cryogenic refrigerant.
2. Description of the Prior Art
A wide variety of solid materials have been used to absorb spilled liquid hydrocarbons. Materials commonly used include straw, newspaper, expanded perlite, and a number of polymeric materials of various compositions and configurations. Examples of polymers used to absorb and recover spilled hydrocarbons include particulate expanded polystyrene and polystyrenebutadione as shown by U.S. Pat. No. 3,929,631; a foam of an ethylene-alkyl acrylate copolymer recited in U.S. Pat. No. 3,819,514; granular polyurethane particles described in U.S. Pat. No. 3,657,125 and polyolefin fibers applied as a water slurry as shown by Japanese Patent No. 49-96980.
It is also known to apply refrigerants including solid or liquid carbon dioxide and liquid nitrogen to oil spills on water for the purpose either of solidifying the oil or of manipulating its movement. Cole et al in U.S. Pat. No. 3,614,873, for example, disclose the use of solid carbon dioxide particles of freeze oil floating on water thus allowing mechanical removal to the oil from the water. Ross et al in U.S. Pat. Nos. 4,031,707 and 4,129,431 disclose techniques for manipulating, or herding, a petroleum mass on water using blocks of solid carbon dioxide or other low temperature material to change the surface tension of the petroleum or to solidify it. Techniques utilizing refrigeration produce effects which necessarily are transitory in nature as both a water body and the atmosphere act as essentially infinite heat sinks which rapidly bring the chilled oil back to temperature equilibrium with the ambient environment.
It has also been recognized that a number of hydrocarbon polymers affect the viscosity characteristics of the hydrocarbon liquid in which they are dissolved. At low concentrations of polymer in hydrocarbon, in the general range of about 5 to 1000 ppm (0.0005% to 0.1%), the fluid flow friction loss is substantially reduced and this effect is utilized on a commercial basis to increasc flow of crude oil and petroleum products through pipelines. At somewhat higher polymer concentrations, on the order of 2000 to 5000 ppm (0.2% to 0.5%), a significant increase in viscosity of the hydrocarbon is observed. At and above about 5000 ppm the liquid begins to gel and at still higher polymer concentrations above about 2% depending upon the particular liquid hydrocarbon or hydrocarbon fraction, the liquid becomes a rubbery semi-solid or solid.
It is common knowledge in the art that non-crosslinked solid polymers are soluble to varying degrees in compatible liquids. The linear hydrocarbon polymers in general and the rubbery hydrocarbon polymers specifically are known to display a relatively high degree of solubility in hydrocarbon liquids. Examples of rubbery hydrocarbon polymers which display a significant degree of solubility in hydrocarbon liquids such as crude oil or kerosene include polyisoprene, polybutadiene, styrene-butadiene copolymers, polyisobutylene and the like.
However, it is also recognized in the art that relatively high molecular weight polymers dissolve very slowly even in the best of solvents. Hours, days or even weeks of contact are required to dissolve such polymers in hydrocarbons at modestly high concentration levels. For example, Meier et al in U.S. Pat. No. 3,801,508 show that 22 hours of stirring contact was required to completely dissolve 1.5 grams of hydrogenated polyisoprene in 200 cc of cyclohexane. Dissolving the same polymer under identical conditions in West Texas crude oil required 70 hours. Attempts to dissolve ethylene-propylene copolymers in the same solvents were incomplete at the end of 168 hours.
Prior art approaches to dissolving a polymer in a liquid hydrocarbon generally include contacting the polymer with the hydrocarbon at ambient to relatively elevated temperatures. It is generally accepted that an increase in temperature will speed dissolution of the polymer as will an increase in surface area as by comminution of the polymer into relatively small particles. Because many of the rubbery polymeric materials are relatively soft and resilient, they are extremely difficult and often impossible to comminute by conventional grinding techniques. Even after comminution, the soformed particles tend to stick and clump together thus negating the practical effect of comminution.
One example of prior art techniques for dissolving rubbery polymers; i.e., polyisobutylene, in hydrocarbons such as kerosene is shown by U.S. Pat. No. 3,215,154. Patentees disclose that a commercial polyisobutylene resin preground to a particle size of about 10 to 20 U.S. standard screen scale requires some 2 hours of stirring contact with kerosene until the solution attains sufficient viscosity to keep the undissolved resin particles dispersed. Another 3 to 5 hours is required for complete dissolution of the polymer particles. Patentees also teach that heating up to about 200.degree. F. increases the rate of solution.
It can thus be appreciated that, were prior art techniques used in the application of polymer particles to spilled hydrocarbons, little if any practical change in the physical characteristics of the spilled hydrocarbon could be expected.