Patent Publication Number: US-2022213659-A1

Title: Floating-oil recovery device

Description:
This is a continuation application of International Patent Application No. PCT/JP2020/028683 filed on Jul. 27, 2020 claiming priority upon Japanese Patent Application No. 2020-074276 filed on Apr. 17, 2020, of which full contents are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a floating-oil recovery technique to facilitate recovering the floating oil spilled out over the ocean or the like, and relates to a floating-oil recovery device suitable for recovering the floating oil deteriorating to high viscosity, in particular. 
     Description of the Background Art 
     As countermeasures against oil spill accidents, the spilt oil has forcibly been recovered or an oil treatment agent has been distributed over the water surface to decompose the oil while measures being taken to prevent the oil floating on the water surface from spreading out. 
     As measures of preventing the oil from spreading out, a float-type water pollution prevention boom has widely been known, and the spread of oil has been regulated by said boom extended on the water (Patent Document 1). 
     Further, a method of jetting high-velocity water from a ship toward the water surface in a curtain shape to prevent the spread of oil has also been proposed. 
     As a method of recovering the oil floating on the water surface, navigating an oil recovery vessel equipped with an oil recovery facility to recover the oil has been known. 
     For such an oil recovery vessel, applying a method of directly skimming the oil floating on the water surface (Patent Documents 2, 3) and applying a method of recovering the oil through the oil recovery facility mounted on said vessel have been known (Patent Documents 4, 5). 
     The oil recovery facility equipped with a water absorption pump or an evacuation device, an oil-water separation device, and the like has supplied a mixed fluid recovered in a state having water and oil mixed with each other to the oil-water separation device, and the oil-water separation device has separated to recover only the oil. 
     PRIOR ART DOCUMENTS 
     Patent Documents 
     Patent Document 1: Japanese Patent Application Laid-Open Publication No. H04-64614 
     Patent Document 2: Japanese Patent Application Laid-Open Publication No. S59-230887 
     Patent Document 3: Japanese Patent Application Laid-Open Publication No. H11-152080 
     Patent Document 4: Japanese Patent Application Laid-Open Publication No. H04-266588 
     Patent Document 5: Japanese Patent Application Laid-Open Publication No. 2005-13880 
     PROBLEMS TO BE SOLVED 
     The conventional oil spread prevention techniques had the following problems: 
     [1] It has taken a lot of time and labor to mount the float-type water pollution prevention boom extended on the water, and the oil has easily been adhered to the water pollution prevention boom, which has provided difficulty in maintenance. 
     [2] When the oil is adhered to the water pollution prevention boom, it has taken a lot of time and labor to dismount such a heavier water pollution prevention boom adhered with the oil and remove the adhered oil. 
     [3] In the method of preventing the spread of oil by jetting high-velocity water from the ship toward the water surface in a curtain shape, the oil has easily been caused to sneak into the water to dissipate to the surrounding water area by a force of the high-velocity water flow. 
     The conventional oil recovery techniques had the following problems: 
     [1] The oil recovery facility has been upsized and as a result, the oil recovery cost has increased. 
     [2] When sucking and recovering an oil-water mixed fluid having floating oil and water mixed with each other for oil recovery, due to a thin film of floating oil spread on the water surface, a recovery ratio of the floating oil in the oil-water mixed fluid has been relatively low, and therefore a recovery efficiency of the floating oil has been relatively low. 
     [3] Due to non-synchronization in vertical movement between the oil recovery vessel and the oil floating over the water surface by waves, a suction ratio of the floating oil from a suction port positioned deeper under the water surface has been lowered. Further, upon exposure of the suction port coming out of the sea, the negative pressure state has been interrupted by sudden release from a load, and it has been difficult for the suction port to stably suck the oil. 
     [4] The water separated in the oil-water separation tank has been discharged to the local sea area as it is. 
     It has been technically difficult to completely separate water from oil in the oil-water separation tank, and for this reason, even the oil mixed in the drainage has caused water pollution in the local sea area. 
     [5] Upon use of an oil recovery vessel, the oil recovery facility itself in such an oil recovery vessel has been of high resistance to the water flow, which has lowered the level of movement performance of said oil recovery vessel. 
     [6] There has been some case that garbage is mixed in the floating oil. The accidentally sucked-in solid garbage has been likely to cause failure of the suction pump and blockage of the pipe. 
     [7] After recovery of the oil, it has been necessary to disassemble the suction pump and the like to clean them, and it has taken a lot of time and labor for such cleaning of the oil recovery facility, which has provided difficulty in maintenance. 
     [8] It has been known that some sorts of oil such as heavy oil of class C deteriorate to high viscosity when being mixed with seawater. 
     Conventionally, it has been technically difficult to recover highly viscous oil such as heavy oil of class C, and it has been desired to propose a new technique enabling highly viscous oil to be recovered. 
     The conventional method of treating oil through the use of an oil treatment agent had the following problems: 
     [1] The oil treatment agent has not worked merely by being distributed over. In order to cause the oil treatment agent to perform any functions, it has been necessary for the oil treatment agent to be forcibly stirred to be mixed with the oil. 
     [2] Stirring the oil treatment agent and the oil such that they are mixed with each other could not be performed by human power, and it has been necessary to use a device dedicated to stirring/mixing, which has resulted in increase of the oil treatment cost. 
     SUMMARY OF THE INVENTION 
     The present invention is made in view of the above-described problems, and the objective thereof is to provide at least one of the following aspects of a floating-oil recovery device: 
     [1] A device is capable of efficiently recovering floating oil while regulating the spread of floating oil without making any direct contact with the floating oil. 
     [2] A device is capable of recovering floating oil deteriorating to high viscosity. 
     [3] A device is capable of suppressing deterioration of water quality in the local water area. 
     [4] A device is capable of performing stirring/mixing of an oil treatment agent through the use of the same device used for recovering the floating oil. 
     [5] A device is capable of having ease of maintenance. 
     [6] A device is capable of being downsized and lightweight, which enhances the level of movement performance of a ship equipped with the same device. 
     MEANS FOR SOLVING PROBLEMS 
     One aspect of the present invention provides a floating-oil recovery device comprising: a bubble-curtain generation mechanism configured to discharge air into water to generate a bubble curtain in the water so as to increase a thickness of a film of floating oil while regulating spread of the floating oil; and an ejector configured to recover an oil-water mixed fluid having the floating oil and the water mixed with each other by jetting high-velocity water toward the film of floating oil enclosed with the bubble curtain to destroy the film of floating oil. 
     Another aspect of the present invention may provide a floating-oil recovery device comprising: a bubble-curtain generation mechanism configured to discharge air into water to generate a bubble curtain in the water so as to increase a thickness of a film of floating oil while regulating spread of the floating oil; an ejector configured to recover an oil-water mixed fluid having the floating oil and the water mixed with each other by jetting high-velocity water toward the film of floating oil enclosed with the bubble curtain to destroy the film of floating oil; and an oil-water separation tank that oil is therein separated to be recovered from the oil-water mixed fluid recovered by the ejector. 
     Still another aspect of the present invention may provide a floating-oil recovery device comprising: a support frame to be attached to a portion of a ship; a bubble-curtain generation mechanism configured to discharge air from a bottom portion of the support frame into water to generate a bubble curtain in the water so as to regulate spread of floating oil; an ejector including a nozzle for jetting high-velocity water toward the film of floating oil enclosed with the bubble curtain to destroy the film of floating oil, and an intake pipe for taking in the high-velocity water jetted through the nozzle so as to generate negative-pressure suction force, thereby to recover an oil-water mixed fluid having the floating oil and the water mixed with each other into the intake pipe; and an oil-water separation tank, to be mounted on the ship, that oil is therein separated to be recovered from the oil-water mixed fluid recovered by the ejector, wherein an oil-water recovery pipe is connected between the ejector and the oil-water separation tank, and wherein a water supply pipe provided with a high-velocity water supply unit is connected between the oil-water separation tank and the nozzle so that the water separated in the oil-water separation tank is circulated to be supplied to the nozzle as the high-velocity water through the water supply pipe and the high-velocity water supply unit. 
     As other aspects of the present invention, the floating-oil recovery device of said still another aspect of the present invention may be provided, wherein a portion of the ejector having a float attached thereto is supported pivotably on a portion of the support frame so as to be swingable in a vertical direction in such a manner that a height of oil and water taken in by the ejector follows a change in water level. 
     As other aspects of the present invention, the floating-oil recovery device of said one aspect, said another aspect, or said still another aspect of the present invention may be provided, wherein the bubble-curtain generation mechanism includes: an aeration pipe arranged on a support frame to be attached to a portion of a ship; an air supply unit having an air pump and a motor mounted on the ship; and an air supply pipe connected between the aeration pipe and the air supply unit, and wherein the bubble curtain is generated by an ascending flow of a group of bubbles discharged from the aeration pipe. 
     As other aspects of the present invention, the floating-oil recovery device of said still another aspect of the present invention may be provided, wherein the oil-water separation tank includes: a main tank that the oil-water mixed fluid recovered by the ejector is stored therein; and a plurality of partition plates arranged in the main tank, wherein oil and water are separated with the aid of difference in specific gravity in the main tank. 
     As other aspects of the present invention, the floating-oil recovery device of said still another aspect of the present invention may be provided as further comprising: an auxiliary tank, mounted on the ship, that an oil treatment agent is stored therein; an oil treatment agent supply unit configured to supply the oil treatment agent stored in the auxiliary tank to the water supply pipe; and an auxiliary pipe connected between the oil treatment agent supply unit and the water supply pipe, wherein the film of floating oil and the oil treatment agent floating on a water surface are stirred to be mixed through the use of the ejector having the intake pipe arranged such that an outlet side of the intake pipe faces into the water. 
     ADVANTAGEOUS EFFECTS OF THE INVENTION 
     The present invention can achieve at least one of the following advantageous effects: 
     [1] As a result of combining: the bubble-curtain generation mechanism having the function of preventing the spread of floating oil and increasing the thickness of the film of floating oil by the bubble curtain; and the ejector having an ejector function (Venturi effect) to recover the floating oil in the form of an oil-water mixed fluid, a recovery ratio of the floating oil in the oil-water mixed fluid can be enhanced, and therefore a recovery efficiency of the floating oil can be significantly improved. 
     [2] Needless to say that it can be applied to the recovery of low-viscosity floating oil, the floating oil deteriorating to high viscosity having been considered to be difficult for recovery can be recovered efficiently by jetting high-velocity water to destroy the film of floating oil. 
     [3] The floating oil can be recovered in a non-contact manner through the use of the ejector instead of a known suction pump while the spread of floating oil can be effectively regulated through the use of the bubble curtain instead of a known float-type water pollution prevention boom. 
     It is possible, therefore, to avoid failure caused by blockage, air-biting, and the like of the pipe due to garbage or the like during recovery of floating oil. After recovery of floating oil, any troublesome and time-consuming cleaning operation of the float-type water pollution prevention boom and the suction pump is not needed. As a result, such a floating-oil recovery device becomes significantly easier in maintenance than the conventional device. 
     [4] In a case where the water separated in the oil-water separation tank is circulated to be used as high-velocity water, an amount of the discharged oil component can be reduced and the deterioration of water quality in the local water area can be suppressed. 
     [5] In a case where a portion of the ejector having a float attached thereto is supported pivotably on a portion of the support frame so as to be swingable in a vertical direction, even if the water surface having the oil floating thereon changes up and down, a height of the oil and water taken in by the ejector can be automatically adjusted so as to follow a change in water level. 
     As a result, the floating oil can be efficiently recovered without being greatly affected by waves. 
     [6] For stirring and mixing the oil treatment agent with the floating oil, the same floating-oil recovery device can be applied, only by a simple operation such as replacing some pipe of said device. 
     [7] Since the structure of the floating-oil recovery device is simple and lightweight, it is possible to enhance the level of movement performance of the ship equipped with the same device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an overall explanatory view of a floating-oil recovery device in an embodiment according to the present invention applied to a ship. 
         FIG. 2  is a schematic view showing a model of floating-oil recovery device according to the present invention. 
         FIG. 3  is another schematic view showing the model of floating-oil recovery device according to the present invention. 
         FIG. 4  is a plan view of an ejector as seen from above the sea surface. 
         FIG. 5  is a cross-sectional view along V-V in  FIG. 4 . 
         FIG. 6  is a side view of the ejector. 
         FIG. 7  is a schematic view showing another model of floating-oil recovery device using an oil treatment agent. 
     
    
    
     DESCRIPTIONS OF EMBODIMENTS OF THE INVENTION 
     Hereinafter, a floating-oil recovery device in an embodiment according to the present invention will be described in detail with reference to the drawings. 
     [1] Outline of Floating-Oil Recovery Device 
     Embodiments will be described with reference to  FIGS. 1, 2 . In this example, an embodiment applied to the floating oil spilled out over the sea surface will be described, and such an embodiment may also be applied to the floating oil spilled out over the water surface such as those of rivers and lakes. 
     A floating-oil recovery device  10  in an embodiment according to the present invention is a device capable of improving the efficiency of recovering floating oil while suppressing the spread of floating oil in a non-contact manner. 
     The recovery device  10  includes: a support frame  20  attached integrally to a portion of a ship  60 ; a bubble-curtain generation mechanism configured to discharge air from a bottom portion of the support frame  20  into water to generate a bubble curtain in the water so as to regulate the spread of floating oil; and an oil-water recovery mechanism configured to recover the floating oil whose spread is regulated by the bubble curtain. 
     In this example, an embodiment using the recovery device  10  mounted on the ship  60  such as a catamaran will be described. The ship  60  is not, however, limited to the catamaran, and may include a single-hulled vessel and towing vessel. Further, a position at which the ship  60  is attached with the recovery device  10  may be the front, side, or rear position of the ship  60 . 
     Hereinafter, the main elements will be described in detail. 
     [2] Support Frame 
     In the descriptions of the support frame  20 , an “A” side of an intake direction of floating oil is defined as a “front side,” and an opposite side to the “A” side of the intake direction of floating oil is defined as a “rear side.” 
     With reference to  FIGS. 2, 3 , the support frame  20  is a rigid frame body to be arranged thereon with: an aeration pipe  30  for discharging air into water; and an ejector  40  for destroying to recover a film of floating oil through the use of a high-velocity water jet flow. The support frame  20  in a substantially rectangular parallelepiped shape is obtained as a result of assembling rigid members such as single pipes arranged vertically and horizontally. 
     The support frame  20  has at least: a bottom frame portion  21  to be arranged thereon with the aeration pipe  30  in a flat C-shape or in a flat U-shape; and a front-side horizontal support shaft  22  for supporting the ejector  40  pivotably on a front-side upper portion of the support frame  20 . 
     The attachment height of the support frame  20  with respect to the ship  60  is adjustable. 
     [3] Bubble-Curtain Generation Mechanism 
     In an embodiment according to the present invention, a known oil boom is no longer used as floating-oil containment means. 
     In an embodiment according to the present invention, the spread of floating oil is regulated through the use of a bubble-curtain generation mechanism. 
     With reference to  FIGS. 2, 3 , the bubble-curtain generation mechanism includes: the aeration pipe  30  arranged on the bottom frame portion  21  of the support frame  20 ; an air supply unit  31  having an air pump and a motor mounted on the ship  60 ; and an air supply pipe  32  connected between the aeration pipe  30  and the air supply unit  31 . 
     The aeration pipe  30  is a pipe or tube having both ends closed and a peripheral surface perforated with a plurality of aeration holes  30   a  along a longitudinal direction of the pipe or tube between both the ends. 
     As a result of continuously or intermittently supplying air through the air supply unit  31  and the air supply pipe  32 , a flat C-shaped or flat U-shaped bubble curtain can be generated in the water immediately above the aeration pipe  30 . 
     In this example, an embodiment having the aeration pipe  30  arranged on three sides, other than the front side, of the bottom frame portion  21  of the support frame  20  will be described. The number of aeration pipes  30  arranged on each side is appropriately selected. 
     The reason why the aeration pipe  30  is not arranged on the front side of the support frame  20 , i.e., the “A” side of the intake direction for the floating oil, is to take in the floating oil through the front side into a region surrounded by the bubble curtain generated above along the three sides of the bottom frame portion  21  of the support frame  20 . The reason why the aeration pipe  30  is arranged on the three sides of the bottom frame portion  21  of the support frame  20  is to confine the taken-in floating oil inside the region surrounded by the bubble curtain so as to prevent the floating oil from flowing outside the surrounded region. 
     In other words, the bubble curtain not only performs the function of preventing the spread of floating oil “O,” but also performs the function of confining the floating oil inside the bubble curtain so as to increase the thickness of the film of floating oil “O” (a floating oil film thickening function). 
     [4] Oil-Water Recovery Mechanism 
     The oil-water recovery mechanism is a mechanism configured to enable the floating oil to be pipe-transported in the form of oil-water mixed fluid obtained as a result of destroying the film of floating oil through the use of a high-velocity water jet flow. 
     With reference to  FIGS. 2, 3 , the oil-water recovery mechanism includes: an ejector  40  supported by the support frame  20  in a pivotable and rotatable manner around the front-side horizontal support shaft  22  of the support frame  20 ; an oil-water separation tank  50  mounted on the ship  60 ; a high-velocity water supply unit  51  having a water supply pump and a motor; a water supply pipe  52  connected between the ejector  40  and the high-velocity water supply unit  51 ; and an oil-water recovery pipe  53  connected between the ejector  40  and the oil-water separation tank  50 . 
     [4.1] Ejector 
     The ejector  40  shown in  FIG. 6  will be described. The ejector  40  includes: a nozzle  41  for jetting high-velocity water; an intake pipe  44  positioned at a jetting side of the nozzle  41 ; and a float  45  for adjusting automatically a height of oil and water taken in by the ejector  40  such that the height follows a change in local water level. 
     The ejector  40  is not limited to an embodiment shown in  FIG. 6 , and any devices capable of sucking a mixed fluid of floating oil and water by an ejector function (Venturi effect) may be applied. 
     In this example, an embodiment having one ejector  40  deployed for one support frame  20  will be described; and alternatively, a plurality of ejectors  40  may be deployed for one support frame  20 . 
     [4.1.1] Nozzle 
     A water supply pipe  42  bent in a J-shape has an inlet side connected to an outlet tip of the water supply pipe  52 , and the nozzle  41  is provided at an outlet tip of the water supply pipe  42 . High-velocity water can be continuously jetted through the nozzle  41  toward an inlet port of the intake pipe  44 . 
     [4.1.2] Intake Pipe 
     The intake pipe  44  is provided at an inlet tip of the oil-water recovery pipe  53 . 
     High-velocity water jetted from the nozzle  41  can be taken in, by the intake pipe  44 , through the opening (inlet port) at the end of the intake pipe  44 . 
     As a result of the occurrence of the ejector function (Venturi effect) induced by jetting high-velocity water into the intake pipe  44 , the mixed fluid of floating oil and water located around a region of the opening (inlet port) at the end of the intake pipe  44  can be sucked into the intake pipe  44 . 
     [4.1.3] Coupling Plate 
     A coupling plate  47  is a member for coupling integrally the water supply pipe  42 , the intake pipe  44 , and a coupling lever  46  of the float  45  arranged in parallel with each other. 
     By such a member, the nozzle  41  and the opening of the intake pipe  44  are mutually arranged at a predetermined position. 
     [4.1.4] Gap Between Nozzle and Intake Pipe 
     In this example, an open-type ejector, having the intake pipe  44  arranged so as to have a predetermined gap G from a jetting side of the nozzle  41  such that the oil and water around the jet flow are taken into the intake pipe  44  through the predetermined gap G, will be described. The ejector may be a closed-type ejector capable of jetting high-velocity water through the nozzle  41  inserted structurally into an end of the intake pipe  44  such that the oil and water around the jet flow in the vicinity of the end are taken into the intake pipe  44 . 
     In the open-type ejector, oil can be taken in optimally by adjusting the gap G in accordance with the viscosity or the like of the floating oil. 
     [4.1.5] Pivotal Support Structure of Ejector 
     As shown in  FIGS. 2, 5 , the ejector  40  is supported by the support frame  20  so as to be pivotable as well as movable up and down with respect to the front-side horizontal support shaft  22  of the support frame  20 . 
     In this example, an embodiment, having a pivot plate  43   a  interposed between the front-side horizontal support shaft  22  and the intake pipe  44 , and a plurality of U-bolts  43   c  and U-bolts  43   b  fixed to the pivot plate  43   a  for retaining the front-side horizontal support shaft  22  and the intake pipe  44 , respectively, so as to support the ejector  40  pivotably, is shown. A known pivotal support structure may be applied. 
     [4.1.6] Float 
     The ejector  40  is provided with the float  45 , and as a result, the height of oil and water taken in by the ejector  40  can be automatically adjusted so as to follow a change in water level. 
     In this example, an embodiment attached with the float  45  through the coupling lever  46  is shown. Alternatively, the float  45  may be attached to a portion of the water supply pipe  42  or the intake pipe  44 , which is associated with the omission of the coupling lever  46 . 
     [4.2] Oil-Water Separation Tank 
     With reference to  FIG. 3 , the oil-water separation tank  50  has a mechanism configured to separate the mixed fluid of floating oil and water recovered by the ejector  40  into the floating oil and the water. 
     In this example, a method of separating floating oil and water with the aid of difference in specific gravity will be described; and alternatively, a known separation method such as a cyclone method can be applied to the oil-water separation tank  50 . 
     An embodiment in this example will be described. The oil-water separation tank  50  has a main tank  55  and a plurality of partition plates  56  arranged vertically at intervals in the main tank  55 . 
     The terminal end of the oil-water recovery pipe  53  is connected to the vicinity of the bottom portion of the main tank  55  so that the sucked oil-water mixed fluid is discharged into the main tank  55 . 
     The suction pipe  54  is connected between the vicinity of the bottom portion of the main tank  55  and a suction side of the high-velocity water supply unit  51  so that the water separated in the main tank  55  can be circulated to be used through the suction pipe  54 , the water supply pipe  52 , the water supply pipe  42 , and the nozzle  41 . 
     An oil recovery tank  57  is provided next to the main tank  55  so as to allow the main tank  55  to overflow with the separated oil and recover the separated oil in the oil recovery tank  57 . 
     In  FIG. 3 , V 1  denotes a switching valve interposed between the suction pipe  54  and the water supply pipe  52 , V 2  denotes an on-off valve provided in the oil-water recovery pipe  53 , and V 3  denotes a drain valve provided in a portion of the oil-water separation tank  50 . 
     Floating-Oil Recovery Method 
     A method of recovering floating oil through the use of the floating-oil recovery device  10  will be described. 
     In an embodiment according to the present invention, a taken-in floating-oil spread prevention step by the bubble-curtain generation mechanism, an oil-water recovery step by the ejector  40 , and an oil-water separation step by the oil-water separation tank  50  are proceeded with in parallel. 
     [1] Floating-Oil Spread Prevention Step 
     In an embodiment according to the present invention, the bubble-curtain generation mechanism is used as means for preventing the spread of floating oil without using a known oil boom. 
     A method for containment of the floating oil “O” will be described with reference to  FIGS. 2 to 5 . 
     The air supply unit  31  shown in  FIGS. 2, 3  is operated to supply gas such as air through the air supply pipe  32  toward the aeration pipe  30  arranged in a flat C-shape or in a flat U-shape. 
     When air or the like is supplied to the aeration pipe  30 , as shown in  FIGS. 4, 5 , a group of bubbles  33  is discharged into the water through the aeration holes  30   a  of the aeration pipe  30 , and the surrounding water entrained with the floating group of bubbles  33  forms an ascending water flow  34  in a curtain shape. 
     A bubble curtain is generated by the ascending water flow  34  isolated from the surrounding sea area and the group of bubbles  33  floating on the water surface. 
     The floating oil “O” is taken in inside an area surrounded by the bubble curtain through an open space of the bubble curtain. 
     The bubble curtain is generated in a curtain shape continuous over a below-water section from a depth not less than a film-thickness of floating oil “O” to the water surface as well as an above-water section as an upper part of the bubble curtain having the group of bubbles  33  rising from the water surface. 
     Therefore, as the bubble curtain regulates the spread of the taken-in floating oil “O,” a film-thickness of the floating oil “O” confined inside the area surrounded by the bubble curtain increases. 
     [2] Oil-Water Recovery Step 
     A method of recovering the floating oil “O” inside an area surrounded by the bubble curtain will be described with reference to  FIGS. 3, 4, 6 . 
     [2.1] Recovery of Oil and Water 
     The high-velocity water supply unit  51  shown in  FIG. 3  is operated to supply continuously water through the water supply pipe  52  toward the nozzle  41  at the outlet tip of the water supply pipe  42 . 
       FIG. 6  shows a state where high-velocity water “J” is jetted continuously from the nozzle  41  toward the inlet port of the intake pipe  44 . When the high-velocity water “J” is jetted continuously from the nozzle  41  toward the inlet port of the intake pipe  44 , the mixed fluid of the local water and the floating oil “O” located around the nozzle  41  is sucked by an ejector function (Venturi effect). 
     The sucked mixed fluid of the floating oil “O” and the local water is transported to the oil-water separation tank  50  through the oil-water recovery pipe  53  shown in  FIG. 3 . 
     In particular, the high-velocity water “J” destroys the lump of the floating oil “O” inside the intake pipe  44 , and as a result, the mixed fluid becomes a kneaded mixture having destroyed product “O” of the floating oil “O” kneaded with water. 
     The “water” here includes not only the high-velocity water “J” jetted from the nozzle  41  but also the local water such as the surrounding seawater taken in by the high-velocity water “J.” 
     Assuming that there is no bubble curtain, the floating oil “O” spread widely on the sea surface would be sucked, and for this reason, an amount of the local water taken in would increase significantly so that a recovery ratio of the floating oil “O” would decrease. 
     On the other hand, by the bubble-curtain generation mechanism combined with the ejector  40 , the film of floating oil enhanced in thickness by the bubble curtain gathers at the inlet portion of the ejector  40  so that the oil recovery ratio increases and the recovery efficiency of the floating oil “O” is significantly improved. 
     Further, the floating oil is recovered along with water which reduces the recovery ratio thereof for the local water, and as a result, a blockage accident in the intake pipe  44  and the oil-water recovery pipe  53  is unlikely to occur. 
     Still further, the suction pump is not used as means for recovering the floating oil “O,” and therefore, even if foreign matter such as garbage is mixed in the floating oil “O,” there is no concern of suck-in foreign matter&#39;s causing failure of the suction pump. 
     [2.2] Case of Highly Viscous Floating Oil 
     If the floating oil “O” is heavy oil of class C, it deteriorates to high viscosity when being mixed with seawater. 
     It has been difficult to recover the floating oil “O” deteriorating to high viscosity by the conventional vacuum suction. 
     On the other hand, the ejector  40  can recover the floating oil “O” while jetting high-velocity water “J” to destroy the film of floating oil “O,” and as a result, the floating oil “O” can be efficiently recovered by the ejector  40  even if the film of floating oil “O” deteriorates to high viscosity. 
     [2.3] Automatic Adjustment of Oil and Water Taking-In Height 
     As shown in  FIG. 6 , the ejector  40  is provided with a float  45 , and the base end of the ejector  40  is supported pivotably by the support frame  40  so that the ejector  40  can swing in a vertical direction around the front-side horizontal support shaft  22  of the support frame  40 . 
     As a result, even if the water surface of the floating oil “O” changes up and down, the height of the oil and water taken in by the ejector  40  is automatically adjusted so as to follow a change in water level. As a consequence, the floating oil “O” can be recovered efficiently without being affected by waves. 
     Even if an ejector portion of the ejector  40  floating from the sea surface is exposed to the atmosphere due to the influence of waves, it is possible for the ejector  40  to avoid failure of an unrecoverable state caused by air-biting because the ejector  40  is not a device of negative-pressure suction type. 
     [3] Oil-Water Separation Step 
     With reference to  FIG. 3 , the mixed fluid transported to the oil-water separation tank  50  through the oil-water recovery pipe  53  is separated into oil and water with the aid of difference in specific gravity. 
     The main tank  55  overflows with the oil separated therein, and the separated oil overflowing the main tank  55  is recovered in the oil recovery tank  57 . 
     In general, complete separation of water and oil in the storage tank body  55  is technically difficult contrary to expectations. 
     For this reason, if the water separated in the main tank  55  is discharged to the local sea area as it is, for example, the oil component mixed in the separated water is discharged, which may cause water pollution in the local sea area. 
     By circulating to use the water separated in the main tank  55  as high-velocity water to be jetted from the nozzle  41  instead of discharging it to the local sea area as it is, an amount of the discharged oil component can be reduced and the deterioration of water quality in the local sea area can be suppressed. 
     Further, by circulating to use the water separated in the main tank  55  for recovery of the floating oil “O,” the recovered oil can be concentrated in the main tank  55 . 
     [4] Cleaning Step 
     The bubble-curtain generation mechanism formed in the water does not make any direct contact with the floating oil “O,” and as a result, it is not necessary to clean the aeration pipe  30  and the like. 
     The ejector  40  having finished recovering the floating oil “O” can be cleaned sufficiently by cleaning simply a pipeline thereof having the intake pipe  44  and oil-water recovery pipe  53  so that the maintenance thereof is easy. 
     The following two methods can be applied for cleaning the intake pipe  44  and oil-water recovery pipe  53 : 
     One is a method (backwashing method) by which a terminal end of the oil-water recovery pipe  53  is detached, and cleaning water is flushed through the oil-water recovery pipe  53  back from the terminal end. 
     The other is a method by which the floating-oil recovery device  10  is operated, in the sea area where the floating oil “O” is not present, with the terminal end of the oil-water recovery pipe  53  being connected to the oil-water separation tank  50  so as to clean the intake pipe  44  and the oil-water recovery pipe  53 . 
     Other Embodiments 
     Hereinafter, other embodiments will be described. In the following descriptions, the same portions as those of the above-described embodiments are added with the same reference numerals, and the detailed descriptions thereof will be omitted. 
     1. Configuration 
     [1] Treatment of Floating Oil Using Oil Treatment Agent 
     As described above, the floating-oil recovery device  10  can not only recover the floating oil without making any direct contact with the floating oil but also mix an oil treatment agent  65  into the floating oil on the sea surface by replacing some pipe of the device  10  to decompose the floating oil. 
     [2] Ejector 
       FIG. 7  shows the nozzle  41  and the intake pipe  44  provided at the outlet tip of the water supply pipe  42 ; however, the ejector  40  may include the nozzle  41 , the intake pipe  44 , and the float  45  as in the above-described embodiments. 
     [2.1] Removal of Oil-Water Recovery Pipe 
     In this example, without the oil-water recovery pipe  53  as a result of detachment thereof from an outlet side of the intake pipe  44 , the mixed fluid containing the oil treatment agent  65  generated in such a detached intake pipe  44  is discharged to the floating oil. 
     [2.2] Direction of Discharge Side of Intake Pipe 
     The detached intake pipe  44  is positioned so that its discharge side (outlet side) faces into the sea. 
     The discharge side of the intake pipe  44  may be bent in a U-shape, or may be straight without being any bent. 
     In short, it is sufficient that the mixed fluid containing the oil treatment agent  65  can be discharged toward the sea surface through the intake pipe  44 . 
     [3] Additional Facility 
     This will be described with reference to  FIG. 7 . In addition to the configuration described above, the floating-oil recovery device  10  includes an auxiliary tank  60  storing the oil treatment agent  65 , an oil treatment agent supply unit  61  having a supply pump and a motor, and an auxiliary pipe  62  connected between the auxiliary tank  60  and the water supply pipe  52  on an outlet side of the high-velocity water supply unit  51 . 
     In an embodiment according to the present invention, the oil treatment agent  65  is supplied to the nozzle  41  by utilizing the water supply pipe  52  and the auxiliary pipe  62 . 
     [3.1] Oil Treatment Agent 
     The oil treatment agent  65  is a treatment agent in a liquid or powder form capable of decomposing oil by an oxidizing action or a microbial digestive action, and known surfactants and solvents having low toxicity to secondary contamination and marine organisms can be used. 
     [3.2] Oil Treatment Agent Supply System 
     The tip of the auxiliary pipe  62  connected to the discharge side of the oil treatment agent supply unit  61  joins a portion of the water supply pipe  52  so that the oil treatment agent  65  can be supplied to the water supply pipe  52  through the oil treatment agent supply unit  61  and the auxiliary pipe  62 . 
     [3.3] Water Intake Source for Water Supply Pipe 
     The water intake source of the water supply pipe  52  may be the oil-water separation tank  50  shown in  FIG. 3 , and water may be taken in from other than the oil-water separation tank  50 . 
     The water intake source of the water supply pipe  52  shown in  FIG. 7  will be described. A water intake pipe  63  may be connected to a portion of the three-way switching valve V 1  provided on the suction side of the high-velocity water supply unit  51 , and water may be transported to the water supply pipe  52  through the water intake pipe  63  pulled into the sea. 
     2. Floating-Oil Treatment Method 
     A treatment method using the oil treatment agent in this example will be described. 
     [1] Supply of Oil Treatment Agent 
     The high-velocity water supply unit  51  and the oil treatment agent supply unit  61  are operated to supply continuously water mixed with the oil treatment agent  65  to the water supply pipe  42 . 
     [2] Stirring and Mixing of Oil Treatment Agent and Oil 
     When high-velocity water mixed with the oil treatment agent  65  is jetted from the nozzle  41  toward the inlet port of the intake pipe  44 , the floating oil located around the nozzle  41 , the high-velocity water mixed with the oil treatment agent  65 , and the sucked local water are mixed in the intake pipe  44  and are discharged into the sea by the Venturi effect. 
     The mixed fluid containing the oil treatment agent  65  discharged into the sea is discharged in a spiral form through the intake pipe  44  so that stirring and mixing of the oil treatment agent  65  and the lump layer of the floating oil on the sea surface proceeds. 
     3. Effects of this Example 
     In this example, the oil treatment agent  65  can be mixed with the floating oil on the sea surface to perform the decomposition treatment by a simple operation of replacing some pipe of the floating-oil recovery device  10 . 
     In general, when an oil treatment agent is used, the treatment effect is low if the oil treatment agent is sprayed only, and it is important to stir and mix the oil treatment agent with the oil. 
     Since the floating oil has an appropriate viscosity, the oil treatment agent needs to be mixed with the floating oil using a mechanical stirring force. 
     In an embodiment according to the present invention, the oil treatment agent and the floating oil can be efficiently stirred and mixed by utilizing the existing ejector so that it is not necessary to arrange any additional stirring and mixing unit dedicated for mechanically mixing the oil treatment agent and the floating oil. 
     REFERENCE NUMERALS 
     O Floating oil 
     A Floating-oil intake direction 
     V 1  Switching valve 
     V 2  On-off valve 
     V 3  Drain valve 
       10  Floating-oil recovery device 
       20  Support frame 
       21  Bottom frame portion of support frame 
       22  Front-side horizontal support shaft of support frame 
       30  Aeration pipe 
       30   a  Aeration hole 
       31  Air supply unit 
       32  Air supply pipe 
       33  Group of bubbles 
       34  Ascending water flow 
       40  Ejector 
       41  Nozzle 
       42  Water supply pipe 
       44  Intake pipe 
       45  Float 
       46  Coupling lever 
       47  Coupling plate 
       50  Oil-water separation tank 
       51  High-velocity water supply unit 
       52  Water supply pipe 
       53  Oil-water recovery pipe 
       54  Suction pipe 
       55  Main tank 
       56  Partition plate 
       57  Oil recovery tank 
       60  Ship