Liquid purification or separation – Processes – Separating
Reexamination Certificate
2001-04-27
2003-04-01
Popovics, Robert J. (Department: 1724)
Liquid purification or separation
Processes
Separating
C210S800000, C210S237000, C210S242300, C210S251000, C210S923000, C037S307000, C037S340000, C037S341000, C037S398000, C037S461000
Reexamination Certificate
active
06540925
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to an oil recovery method and an oil recovery apparatus and, more particularly, to a method and apparatus for efficiently recovering oil spilled over the water surface of, for example, sea water by accidents or the like, by separating the oil from the water without using expensive and special recovery ships or recovery apparatuses of conventional types.
2. Background Information
Oil spilled over the ocean by oil field accidents, tanker accidents or the like has been recovered by special or multi-purpose recovery apparatuses for a suction-type oil recovery ship or a dredger-type oil recovery ship. However, since all of these apparatuses are expensive, the number of ships disposed at various areas, including harbors, is limited. Furthermore, large-sized facilities are required for mooring or storing these apparatuses. Additionally, if oil spill accidents or the like occur at areas far from the harbors in which these apparatuses are disposed, it becomes difficult to take immediate actions to conduct a recovery plan.
There is also known an excavating bucket system by which oil is recovered by skimming it using excavating buckets of floating cranes or gravel gathering and carrying ships (i.e., gut ships).
At the time of the heavy oil spill accident involving the oil tanker Nakhodka in the Japanese Sea in January 1997, various oil recovery machines were used. At that time, since the spilled oil was heavy oil having a high viscosity, suction-type oil recovery apparatuses were poor in efficiency, and the most efficient method of removing the oil was by skimming it with buckets of the gut ships. However, when using the excavating bucket system, a large amount of sea water and the like is recovered together with the spilled oil in a mixed state. Accordingly, since the recovery efficiency of the oil is low and a large amount of water is recovered together with the oil in a mixed state, the transport volume of the recovered oil is substantial, and the facilities (pits) on the land for receiving the recovered oil for post-treatment are required to be large in capacity.
Under such circumstances, as a method for more efficiently recovering oil as compared with the conventional methods, the present inventors have invented a bucket of a grab type having a slanting bottom plate and a shell provided with apertures or slits. The present inventors have filed Japanese Patent Application No. 130156 in 1999 covering the grab-type bucket together with a measurement technique for measuring oil viscosity and a method for oil recovery. However, from tests and observations made after such filing, it was found that before the oil and water are completely separated, a part of the oil tends to drop through the apertures or slits provided on the upper portion of the bucket. There is therefore a demand for a technique by which the water and oil are further securely separated.
Further, in a recovery operation using the foregoing grab-type bucket, in the step of closing the bucket, the water surface in the bucket is raised and the floating oil on the surface and the water may sometimes flow out of the bucket. Thus, there is also demand to further increase the recovery efficiency of the oil.
Moreover, with respect to heavy oil having a high viscosity, the foregoing grab-type bucket system can separate the oil and water efficiently depending upon the bucket. However, since tankers navigating the waters near the Sakhalin sea and the Okhotsk sea mostly carry crude oil, and the viscosity of crude oil is lower than that of heavy oil, a phenomenon has been seen that it is impossible to efficiently separate the oil and water. It was found that this phenomenon is attributable to the fact that in the case of crude oil, the time-lag between the drainage of water from the bucket and the start of dropping of the oil is short, while in the case of an oil having a low viscosity, the oil drops immediately after the dropping of water, whereby separation of the oil and water becomes difficult.
Further, when the spilled oil surging to the seashore is treated with heavy machines, the treated oil mostly forms a mixture with sand or gravel, and then forms a large amount of secondary contaminants, whereby secondary separation operations by manpower are required. Furthermore, in the secondary separation operations, since the separation of oil components adhered to the sand or the like is extremely difficult, it has been reported that the secondary contaminants are left as they are for a long period of time. Further, there have been reported serious examples of secondary pollution, for example, effusion of oil incorporated in sediments, and therefore there are few techniques for efficiently recovering a large amount of oil at the waterside.
SUMMARY OF THE INVENTION
The present invention has been made in view of the foregoing drawbacks in the conventional art.
It is an object of the present invention to provide an oil recovery method and an oil recovery apparatus by which spilled oil and water are efficiently separated at the initial step of the recovery operation to increase the recovery efficiency of the spilled oil.
It is another object of the present invention to provide a recovery apparatus of a bucket system type by which the separation of water and the spilled oil to be recovered can easily be confirmed and the recovery efficiency of oil only is high.
Still another object of the present invention is to provide an oil recovery apparatus which can be manufactured at low cost and can be easily transported to areas affected by oil spillage.
Another object of the present invention is to provide an oil recovery apparatus which can be housed in facilities that are simple and small-sized, since the apparatus is adapted for use only in emergencies such as oil spill accidents.
Still another object of the present invention is to provide an oil recovery method by which oil recovery is conducted efficiently while preventing water and sand from penetrating even if the recovery is made on the seashore or the like.
The foregoing and other objects of the present invention are carried out by an oil recovery method comprising the steps of skimming water and oil having a preselected viscosity and floating on the water surface using a bucket, separating the water and oil to a lower portion and an upper portion of the bucket, respectively, utilizing a difference in specific gravities thereof, draining the water located at the lower portion of the bucket through apertures disposed on a bottom plate of the bucket and having a preselected aperture diameter and length so that the oil located at the upper portion of the bucket gradually flows into the apertures at a rate in accordance with the oil viscosity after the water is drained, and discharging the oil from the bucket before the oil drains out of the apertures.
According to the present invention, the bottom plate of the bucket is mounted for undergoing movement between a closed position and an open position, and the discharging step comprises discharging the oil from the bucket by opening the bottom plate. In an alternative embodiment, the discharging step comprises discharging the oil from the bucket by inclining the bucket.
Thus the present invention relates to an improvement of a bucket for skimming the spilled oil, by which the oil and water can efficiently be separated and the recovery rate can be increased. This is accomplished by providing the apertures on the bottom plate of the bucket for the purpose of removing or taking out water from the skimmed mixture of oil and water to recover the oil only.
The present inventors have conducted various experiments with the apertures of on the bottom plate of the bucket for separating water from the mixture of oil and water. As a result, it was found that Hagen-Poiseuille's law is applicable as an approximate formula. In Hagen-Poiseuille's law, the flow rate per unit time can be determined by the viscosity of a liquid, the diameter of a tube, the leng
Maida Katsuyuki
Saeki Hiroshi
Takahashi Shinjiro
Adams & Wilks
Nishimuragumi Co., Ltd.
Popovics Robert J.
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