Hydraulic and earth engineering – Fluid control – treatment – or containment – Floatable matter containment
Reexamination Certificate
1999-12-09
2001-07-24
Neuder, William (Department: 3673)
Hydraulic and earth engineering
Fluid control, treatment, or containment
Floatable matter containment
C405S060000, C210S925000
Reexamination Certificate
active
06264398
ABSTRACT:
TECHNICAL FIELD
This invention relates to a process for the recovery of oil, for example, recovery of heavy oil or crude oil spills on the sea caused by accidents of tankers, recovery of oil deposits on rocks and seashores, recovery of oils leaked from oil tanks, and recovery and removal of oil deposits in tanks at the time of cleaning thereof.
BACKGROUND ART
Heavy oils or crude oils are occasionally discharged in sea water upon tanker accidents. Heavy oils or crude oils are mixtures of aromatic oils (aroma oils), nephthene oils, paraffin oils, etc. and contain a large amount of the aromatic oils. Because heavy oil or crude oil spills, which have a smaller specific gravity than sea water, initially afloat on a surface of the sea water in the form of lumps. Paraffin oils and naphthene oils having a low viscosity are gradually separated by diffusion from the lumps due to forces of waves or currents. The remaining aromatic oils having a high density sink in the sea. Thus, part of the oil spills deposits on the seashores and oil deposits are adhered to rocks. It is, therefore, difficult to remove the oil deposits.
In addition to a manual method in which oils are collected with an oil fence and manually recovered, processes are known for treating oil spills in which the oils are decomposed with crude oil decomposing bacteria or the oils are mixed with sea water using an emulsifier. The emulsifier and the crude oil decomposing bacteria used as a treatment agent for this purpose serve to convert the oil into fine particles which are easily mixed with the sea water by emulsion and dispersion and to accelerate the spontaneous purification (destroy of oils such as through decomposition by bacteria, and oxidation and vaporization by sunlight). However, such spontaneous purification proceeds so slowly that the known methods are not practical. Additionally, with this method, it is more and more difficult to recover the oil because, in an accident of discharge of a large amount of oil, the oil treating agent diffuses into and is diluted with a non-polluted region with time due to waves and currents. Thus, in practice, it is the general method to collect the discharged oil manually.
Tanker accident is not the sole cause of discharge of heavy oils or crude oils. Discard of waste oils from ships and discharge from oil tanks in harbors also cause such a problem. Similar to the removal of oil deposits on rocks, cleaning of oil deposits on tanks brings about a difficulty.
It is, therefore, an object of the present invention to provide a process which can easily recover oil spills. Another object of the present invention is to provide a process which can recover such oils while minimizing environmental pollution. It is a further object of the present invention to provide a process which can easily remove and recover oil deposits on solid surfaces.
DISCLOSURE OF INVENTION
The present invention is characterized in that a latex and a coagulant thereof are separately scattered on water containing an oil to diffuse the latex around the oil or in that the latex is coagulated by the coagulant to form a coagulated latex membrane around the oil in the water.
As the latex, there may be used a synthetic rubber latex and a hydrophilic polymer emulsion, such as polyvinyl acetate or polyvinyl alcohol, in addition to a natural rubber latex. The latex is a hydrophilic colloid solution in which a highly polymerized compound is dispersed in water as a dispersing medium. It is preferred that the polymer emulsion be prepared by emulsion polymerization for reasons that the product is in the form of an emulsion as such, though the present invention is not limited thereto.
The use of a natural rubber latex is most preferred. Such a latex is a colloid containing cis-1,4-isoprene polymer (about 54% by weight; concentration hereinafter is expressed in terms of % by weight), water (about 44%) and a protein (about 2%).
Any coagulant may be used as long as it can coagulate the latex. For example, polyvalent metal ions, polyvalent non-metal ions, organic acids or alkali such as ammonia may be used.
The most preferable coagulant is a salt of Mg or Ca. Magnesium chloride or calcium chloride is particularly preferable because these substances are contained in the environment such as sea water and do not bring about secondary pollution and because they are inexpensive.
The present invention is also characterized in that a lipophilic polymer emulsion gets in contact with oil deposits on solid surfaces such as rocks and tanks to solubilize the oils into the emulsion and in that the emulsion is thereafter coagulated to recover the oils.
The lipophilic polymer emulsion is an emulsion in which water of a discontinuous phase is dispersed into an oil matrix phase. For example, there may be used an emulsion prepared by adding nonylphenol ether and polyoxyethylene alkyl ether each in an amount of 0.2% to a natural rubber latex to impart strong lipophilicity.
The latex, which is a hydrophilic colloid diffuses into the water, when it is scattered around oil spills in sea water through a hose. The scattered latex coagulates by reaction with the coagulant. Because the specific gravity of the solids after the coagulation is smaller than water, a membrane is formed around the oil spills. The latex incorporated into lumps of oil spills does not coagulate as such. However, since water is generally present in the oil lumps, the latex is brought into contact with an interface between the oil and water by the action of waves and is thus coagulated.
The coagulated latex membrane is insoluble in oil but is compatible therewith. Therefore, the latex is collected in the interface between the oil spills and water and deposits on the interface of the oil spills. Since the coagulated latex membrane (hereinafter referred to simply as latex membrane) is low in stickiness, oil spills can be easily recovered. Further, since the latex membrane is lighter than water, the aroma oils are prevented from sedimenting. The oil spills are surrounded by the latex membrane to prevent the dispersion of the oil lumps.
The oil lumps surrounded by the latex membrane have no stickiness and, thus, do not deposit on rocks and sand even when they arrive at seashores. Further, since the water temperature dependency of the coagulation rate of the latex is small, oil spills can be recovered even in winter season or in cold places.
When a natural rubber latex is used, unrecovered latex gradually decomposes spontaneously and does not pollute the environment.
The present invention is mainly utilized for the recovery of oil spills in sea water. Whilst magnesium chloride and calcium chloride to be a coagulant are originally present in sea water, the concentration thereof is so small that the coagulation rate of the latex is very slow. Thus, the scattered latex is unnecessarily diffused to reduce the efficiency. Therefore, it is necessary to scatter the coagulant.
The coagulant is scattered separately from the latex, for example, by using separate hoses. However, the latex may be mixed with the coagulant in a scattering nozzle. The mixture is scattered at a scattering pressure. In this case, for the purpose of preventing the coagulation of the latex by the coagulant within the nozzle, the concentration of the coagulant is controlled to retard the coagulating power of the coagulant. Alternately, this can be achieved by sufficiently reducing the residence time of the mixture in the nozzle as compared with the time required for the coagulation.
When a salt of Mg or Ca such as magnesium chloride or calcium chloride, which is originally contained in sea water, is used as the coagulant, no environmental pollution is caused.
The latex may be a mixture of a plurality of latices. When a synthetic latex is used, it is advisable to add a decomposition enzyme, in particular a decomposition enzyme for the emulsifier in the latex, since the unrecovered latex is decomposed so that a secondary pollution can be prevented.
A lipophilic polymer emulsion is used for oil deposits on rocks, etc. In such an em
Miyagishi Kiyoe
Yamada Hiroshi
Yano Shoichiro
Yoshida Hitoshi
Foley & Lardner
Lagman Frederick L.
Neuder William
Yugenkaisha Fams
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