EP0016065A1

EP0016065A1 - Vessel for scavenging oil

Info

Publication number: EP0016065A1
Application number: EP79900710A
Authority: EP
Inventors: Edward Victor Byers
Original assignee: Individual
Current assignee: Individual
Priority date: 1978-07-05
Filing date: 1980-02-12
Publication date: 1980-10-01
Also published as: NO792211L; IT7924126A0; WO1980000161A1; IT1166895B

Abstract

Un navire (10) pour evacuer le petrole des nappes de petrole possede une construction a double coque dans laquelle les deux coques servent a la fois de flotteur et de moyen de ramassage du petrole flottant a la surface. Les coques consistent en deux coquilles cylindriques (12, 14) qui sont montees sur leurs axes respectifs (16). Les coquilles (12, 14) sont fermees pour assurer la flottabilite et leurs surfaces externes sont oleophiles pour que le petrole s'y accumule. Lorsque le navire (10) se deplace vers l'avant les coquilles cylindres (12, 14) tournent, transversalement par rapport a la direction de deplacement, dans des sens opposes. Une cuvette longitudinale (34, 70) est montee entre les coquilles (12, 14) pour recuperer le petrole et chaque coquille (12, 14) possede un dispositif a lames (36, 38, 74) pour guider dans la cuvette (34, 70 le petrole enleve des coquilles (12, 14)). Des dispositifs sont decrits pour des coquilles a rotation interne et externe. La cuvette (34, 70) peut porter une quille stabilisatrice (72) et une structure de cuvette est decrite pour separer le petrole de l'eau. L'extremite avant (18) du navire peut etre pourvue de structures (28) de guidage du petrole entre les coquilles ou le long de leurs cotes exterieurs. La possibilite d'utiliser des surfaces hydrophiles est etudiee.A vessel (10) for discharging oil from the oil slicks has a double hull construction in which the two hulls serve both as a float and as a means of collecting oil floating on the surface. The shells consist of two cylindrical shells (12, 14) which are mounted on their respective axes (16). The shells (12, 14) are closed to ensure buoyancy and their external surfaces are oleophilic so that the oil accumulates there. When the ship (10) is moving forward the cylinder shells (12, 14) rotate, transverse to the direction of movement, in opposite directions. A longitudinal bowl (34, 70) is mounted between the shells (12, 14) to recover the oil and each shell (12, 14) has a blade device (36, 38, 74) to guide in the bowl (34, 70 oil removes shells (12, 14)). Devices are described for internally and externally rotated shells. The bowl (34, 70) can carry a stabilizing keel (72) and a bowl structure is described to separate the oil from the water. The front end (18) of the vessel may be provided with structures (28) for guiding the oil between the shells or along their outer dimensions. The possibility of using hydrophilic surfaces is being studied.

Description

Title: Vessel for Scavenging Oil Technical Field

This invention relates to a vessel for removing patches of oil or other oleaginous substances from the surface of water or aqueous solutions, and has particular, though not exclusive application to the scavenging of large oil patches, which are commonly known as oil slicks, from the surface of the sea Background Art Much attention has been given in recent times to the reduction of pollution from oil spillage at sea. Various methods have been proposed to deal with the serious pollution problems that arise when large quanti¬ ties of oil are lost from tankers or other vessels. The oil tends to float in large slicks at or adjacent the surface of the.sea.

One method of removing these oil slicks is by chemical dispersion, using chemicals to break up the oil. Such techniques are well known. They are expensive to perform and are often unsatis actory with heavy, viscid oil which tends to become even more viscid under the weathering action at sea.

Other methods are primarily mechanical, for example, collecting the oil with the aid of booms which is not practical for very large slicks or passing an end¬ less rope of oleophilic material through the slick, the oil gathered thereby being removed for disposal. Where the oil slick is at a distance out to sea, the means for dispersing or removing the oil have to be carried by and specially mounted on a vessel. Disclosure of the Invention

The present invention provides a vessel for removing oil (which herein includes other oleaginous substances) from a patch of oil at or adjacent the surface of a watery medium (which herein includes aqueous solutions and specific examples of which are se or estuary waters) including: a plurality of generally hollow cylindrical structures, each being mounted for rotation about its axis and each bearing at least one continuous oleophili or hydrophilic surface extending cireumferentially abou its axis, each of said structures being disposed for partial immersion in the watery medium so that upon rotation each portion of each oleophilic or hydrophilic surface passes periodically through a surface zone of t watery medium to accrete oil thereto, and the hollows o the cylindrical structures being sealed to provide buoy for the vessel; means for removing accreted oil from the oleophilic or hydrophilic surfaces; and means for collecting the oil thus removed. The vessel preferably comprises two such cylindrical structures that have their axes extending longitudinally of the vessel and defining respective sides of the vessel, and further including means couple to said two cylindrical structures to rotate same in ' opposite directions.

The two hollow cylindrical structures are arranged to provide the required buoyancy for the vesse which in this respect may be likened to a twin-hulled catamaran. This last-mentioned vessel may be provided with a bow-shaped, apron acting as a bow for the vessel and shaped to direct oil to the outer sides of the cylindrical structures for collection thereby. In an alternative construction the front of the vessel is provided with diverging vanes or the like aiding in directing the flow of the watery medium to the area between the two cylindrical structures as the vessel moves forward. The oil collecting means of the vessel preferably comprises a trough extending between the two cylindrical structures, the oil removal means being arranged to discharge the removed oil into the trough. The trough may have a sloping bottom with a chamber at ^'•: the deeper end of the trough having an inlet from the lower part of the trough to collect water in the chamber, and with a .well at the shallower end of the trough arranged to receive liquid, i.e. primarily oil, spilled over from the shallower end. . The trough may additionally carry a keel depending therefrom to stabilize the vessel.

With regard to sloping-bottomed trough with the chamber and well, it will be shown in the subsequent more detailed description how this feature can be used to separate water from the oil in cases where a substantial amount of water enters the trough. The lighter oil forms an upper layer spilling into the well rom which it may be pumped. The heavier water enters the chamber through the lower aperture and can be discharged therefrom, for example discharged into the water medium by a gravity feed through a depending pipe.

Brief Description of the Drawings Pig. 1 shows a plan view of a catamaran kind of vessel embodying the invention having inwardly, rotating cylindrical hulls; Fig. 2 shows a transverse section through the vessel of Fig. 1;

Fig. 3 shows an axial section through the vesse demonstrating a preferred form of collecting trough; Fig. 4 shows a transverse section through a similar vessel but adapted for outwardly rotating hulls; and

Fig. 5 shows a simplified plan view of a catamaran vessel similar to Fig. 1 but having a modified bow section.

Description of the preferred Embodiments The figures illustrating the catamaran vessel and modifications thereto of Figs. 1 to 5 are diagrammat in order to show clearly the essential elements of the apparatus and various modifications to it.

Referring to Figs. 1 and 2, the vessel 10 comprises two longitudinally-extending parallel hulls each comprised of a sealed, hollow cylindrical shell 12 and 14 closed at its ends and having projecting axial shafts 16 about which each shell is rotated. The shafts are mounted for rotation in transverse rigidly connected frames 18 and 20 which togethe with the shells form the essential buoyant structure of the vessel. As seen in Fig. 2 the shells float partly immersed in the sea 1. The rear frame 20 of the vessel carries a prope

22 driven by an engine (not shown) and also carries a pa of rudders 24. The vessel is thus driven in the directi indicated by arrow 26. The front frame 18 may carry a pair of forwardly and divergingly projecting vanes or booms 28 having their inward ends secured in line with t respective cylindrical shells, to aid in directing the floating oil into the area between the hulls 12 and 14 a indicated by arrows 30 as the vessel moves forward. Suc an arrangement is applicable in cases where the oil is t be scavenged from the area between the hulls. The vanes 28 lie in the surface zone of the sea.

.____ .. 'Ji

- The inward oil deflection provided by the vanes 28 is appropriate to the case where the cylindrical shells are rotated inwardly as seen in plan view, i.e. they rise out of the sea at their outer surfaces as seen in Fig. 2." The shells are rotated in opposite directions by means 32 coupled to the shafts 16 and driven by the main or an auxiliary engine. The shells have an oleo¬ philic surface. To this end the shells may be of metal and carry an oleophilic plastics coating such as poly- ethylene or polypropylene. However, tests have indicated that a plain slightly rusty steel surface is sufficiently oleophilic. The shells illustrated have plain cylin¬ drical surfaces and a sufficient rate of accretion onto these surfaces has been achieved with light oils about which more is said below. At the cost of extra compli¬ cation the surface could be provided with projections such as rib^'s or teeth. The oil from the patch 2 between the shells accretes on the cylindrical surfaces as they enter the surface zone and is carried under the shells, being maintained there by hydrostatic pressure, then carried upwardly and inwardly for removal from the surfaces. In the illustrated case of inwardly rotating shells with plain surfaces, the accreted oil is removed and discharged into a centrally-mounted trough 34. The trough is carried by longitudinal supports (not shown) mounted to the transverse .frames 18 and 20. As seen in Fig. 2, the trough 34 is generally V-shaped and its edges are formed as or are fitted with doctor blades 36 and 38 extending along the upper and inner surfaces of the shells 18 and 20 respectively to scrape the accreted oil off the shells and direct it into the trough.

Figs. 1 and 2 illustrate a trough of uniform cross-section in the rear end of which a pump 40 is mounted to pump the collected oil to some larger vessel through a pipe-line 42.

V; ._' " The trough 34 may also serve to support a keel to stabilize the vessel as is shown in Fig. 4..

A modification of the trough is seen in Fig. 3 which is a longitudinal, axial cross-section through th vessel fitted with the modified trough. In this case the trough 50, provided with doctor blades, as before, is shaped to have a sloping bottom 52 that is deeper at the forward end of the vessel than aft. At the rear, t shallow end of the trough leads to a well 54 in which i located the pump 40 for discharging the oil. .At the deeper end, the trough has a chamber 56 having an aperture 56 communi-cating with the lower part of the tr The chamber 56 also has an upper vent 59 together with depending outlet pipe 60. the upper end of which project into the chamber and which leads downwardly into the se for a sufficient distance to be below the level of the oil patch being scavenged.

The modified trough serves to. separate the lig oil 3 from water 4. Quantities of water may enter the trough by being shipped over the sides, i.e. over the h or enter as spray in rough weather. It is desirable to separate and discharge such substantial amounts of wate before pumping from the trough. The water sinks to the deeper part of the trough, enters chamber 56. and overfl into pipe 60 for return to the sea. The upper end of t pipe should thus be sufficiently high to provide an adequate working head of the oil floating on the water the trough. The lighter oil spills over the shallow en of the trough into well 54 and is pumped out. The trou is provided with perforate lateral walls or baffles 62 impede large-scale motions of the liquid in the trough the event of heavy pitches of the vessel.

Referring to Fig. 4, there is shown a transver cross-section in which the cylindrical shells 12 and 14 are rotated outwardly as seen in plan view, i.e. they enter the water at their outer surfaces. The oil could

o collected in a respective trough located at the outer side of each shell 12 and 14 leading to a well at the rear of the vessel but preferably it is collected as shown in an axially-extending trough 70 between the hulls which is shown as carrying a keel 72 to stabilize the vessel. The oil here is mainly collected from the surface zones outside the hulls and to remove it from rotating surfaces the framework supports two reflexed doctor blades 74 acting on the upper, inner surfaces of respective ones of the hulls. The concavities of the blades face generally inwardly toward the trough 74 and mounted within the concavities and coacting with the blades 74 are respective longitudinally-extending rollers 76 which rotate, in the directions indicated by the arrows 78, adjacent cylindrical surfaces and at a peri¬ pheral speed somewhat in excess of that of the surfaces. The reflexed doctor blades and rollers remove oil from the cylindrical surfaces and guide it for discharge into the t ough. The trough is provided with a pair of doctor blades 80 engaging rollers 76 to discharge oil clinging thereto into the trough. It will be noted that a roof section 82 extends between the reflexed doctor blades 74 to form therewith a complete roofing structure for the trough. This is of benefit in reducing the amount of water that is able to enter the trough. Consequently the oil/water separation measures proposed wLth reference to Fig. 3 may not be necessary.

With the outwardly rotating shells of Fig. 4, the vanes 28 of Fig. 1 can be replaced by, for example, a detachable, shaped bow piece such as shown in Fig. 5.

The vessel 90 in .Fig. 5 is similar to the vessel 10 of Fig. 1 and has the same support structure or frame¬ work (not shown for simplicity in Fig. 5) in which is rotatably supported two cylindrical shells 92 and 94 whose construction is similar to that of shells 12 and 14 of vessel 10 and thus will not be further described. Fig. 5 shows one major difference which lies in a bow structure 96 cooperating with the shells to guide oil to the outer sides of the vessel as it moves forward in the direction of arrow 98. The forward and rear end portions of the cylindrical structures are streamlined to assist motion through the water.

The bow structure 96 for the vessel is in the 0 form of a bow-shaped apron.100 which is secured to the forward framework that supports the shells, i.e. the transverse structure 18 in Fig. 1 of the apron 98 > terminates in respective rearward portions 102 that longitudinally overlap the forward end portions of the 5 cylindrical structures 92 and 94 and are recurved so as to aid in directing oil onto the cylindrical side ^■ - ^" sur aces as. the vessel moves forward as indicated by arrows 104. The cylindrical structures are coupled to means such as illustrated in Fig. 1 for driving the 0 structure in opposite directions with each portion of t continuous oleophilic surfaces periodically entering th surface zone of water on the outer sides of the vessel. If the shells are rotated outwardly as shown in Fig. 4 will be readily apparent that oil is accreted on the 5 surface of the shells in a manner analogous to that described above. To remove and dispose of the oil the vessel may be equipped and operated as described with reference to Fig. 4.

If the vessel 90 is operated to have the 0 cylindrical shells rotated inwardly as shown in Fig. 2, then the collecting trough arrangement can correspondin be changed to a form such as shown in Fig. 2.

A twin-hull vessel of the kind described above may have the cylindrical shells of say 20 metres in 5 length and 3.5 metres in diameter. In the foregoing description, the accretion of oil to the cylindrical shell surface is achieved by use of oleophilic surfaces. It is found that when using oleophilic surfaces the accretion of the oil thereto takes place at the point where the moving surface enters the surface zone. It is, however possible to reverse this situation by using a hydrophilic surface, the accretion occurring as the surface leaves the surface zone. Hydrophilic surfaces which are wetted by water or aqueous solutions in preference to oil or other oleaginous substances are not readily realised but such a surface may be provided by means of covering the cylindrical surfaces of the hulls with natural fibres such as cotton in the form of a woven cloth; such a surface needs to be first wetted with water before being employed to scavenge oil. The technique may be of value with highly aqueous emulsions.

Industrial Applicability

The catamaran kind of vessel described is a purpose-designed craft for scavenging oil slicks. It combines into one structure, the oil accretion means and the hull of the vessel. The vessel has particular ability, in large bodies of water, such as the open sea, for disposing of large oil slicks through which the vessel can be driven in successive sweeps. The smooth shelled structuresdescribed aid propulsion and simplify the doctor blade arrangement required to remove the accreted oil. These structures are felt to be particularly suitable for lighter oils and while no absolute upper bound can be given, oils up to a viscosity of 2 0 SAE are particularly mentioned.

Claims

CLAIMS :

1. A vessel for removing oil from a patch of oil at or adjacent the surface of a watery medium includin a plurality of generally hollow cylindrical structures, each being mounted for rotation about its axis and each bearing at least one continuous oleophil or hydrophilic surface extending circumferentially abo its axis, each of said structures being disposed for partial immersion in the watery medium so that upon rotation each portion of each oleophilic or hydrophili surface passes periodically through a surface zone of watery medium to accrete oil thereto, and the hollows the cylindrical structures being sealed to provide buo ancy for the vessel; means for removing accreted oil from the oleop or hydrophilic surfaces; and means for collecting the oil thus removed.

2. A vessel as set forth in Claim 1 in which the axes of said cylindrical structures are parallel. 3. A vessel as set forth in Claim 1 or 2 in which the axes of said cylindrical structures extend longitudinally of the vessel. . A vessel as set forth in Claim 3 further comprising a bow structure having rearward recurved portions longitudinally overlapping the forward end portions of the cylindrical structures.

5. A vessel as set forth in any one of Claims 1 to in which said cylindrical structures comprise plain cylindrical oleophilic or hydrophilic. surfaces. 6. A vessel as set forth in Claim 1 comprising two such cylindrical structures that have their axes exten longitudinally of the vessel and defining respective si of the vessel, and further including means coupled to s two cylinder structures to rotate same in opposite directions.

^> O /., WI 7. A vessel as set forth in Claim 6 further comprising a bow structure having rearward recurved portions longitudinally overlapping the forward end portions of said two cylindrical structures. 5 8. A vessel as set forth in Claim 6 further / comprising forwardly directed and diverging means carried at the front of the vessel to aid in directing the flow of the watery medium to the area between the two cylindrical structures.

10 9. A vessel as set forth in Claim 6, 7 or 8 in which the oil collecting means comprises a trough extending between the cylindrical structures, the oil removal means being arranged to discharge the removed oil into the trough.

15 10. A vessel as set forth in Claim 9 in which the trough has a sloping bottom with a chamber at the deeper end of the trough having an aperture communicating with the trough at the lower part thereof to allow water to flow into the chamber, and with a well at the shallower

20 end of the trough arranged to receive oil spilled over from the shallower end.

11. A vessel as set forth in Claim 10 in which said chamber has a pipe depending therefrom for discharging water accumulated therein back into the watery medium.

25 12. A vessel as set forth in Claim 11 in which said pipe extends upwardly into the chamber to have its upper end above the level of the shallow end of said trough.

13. A vessel as set forth in any one of Claims 9 to

30 12 further comprising a keel depending from the trough to stabilize the vessel.

OMPI ,, V/IFO 14. A vessel as claimed in any one of Claims 9 to 1 in which for each cylindrical structure the oil removal means comprises a reflexed doctor blade acting at the upper inner surface of the cylindrical structure with t concavity of the blade facing inwardly, and a rotatably mounted roller extending lengthwise of the blade and disposed in the concavity thereof; and further compris a roof structure extending between the doctor blades to overlie the trough. 15. A vessel as set forth in any one of Claims 6 to 14 in which said two cylindrical structures comprise plain cylindrical oleophilic or hydrophilic surfaces.