GB2033786A - Separation of liquid materials having different densities - Google Patents

Abstract

A floating platform (10) a central turbine (12) for inducing a downward draught of air to the on underside (34) of the platform, which has an inverted dish shape, so as to form underneath the platform a cushion of air at a slightly excess pressure to atmospheric to cause the platform to be lifted in the same manner as a hovercraft. Spinning centrifuges (18, 20) are mounted symmetrically around the central axis of the platform, the two centrifuges being adapted to rotate in opposite directions to produce a gyro effect causing the whole structure to be self-levelling even in rough seas. The continuous downward draught of air forces oil and water to enter the centrifuges through inlets (40, 44) and (42, 46). Water separated from the oil exits through outlets (52, 54) and oil is sucked up from the centre regions of the centrifuges through recovery pipes (30, 32) for storing in tanks located on the platform or in an adjacent floating vessel. <IMAGE>

Description

SPECIFICATION Improvements in and relating to the separation of liquid materials having different densities Field of invention This invention concerns devices for separating liquids having different densities and in particular to apparatus for retrieving a first liquid material which is floating on a second liquid material of higher density than the first liquid material. The invention is of particular application to the retrieval of crude oil spilled at sea.

Background to the invention Oil spillage at sea has become a serious problem in recent years and previous attempts to recover spilt oil from the surface of the sea has met with little success. In general the only method of dealing with oil spillage at sea which has hitherto met with any degree of success is to spray a liquid detergent on the affected area so as to cause the oil to break up into tiny particles which are then dispersed by the natural wave action of the sea so that the oil slick which would otherwise form is broken up.

Although the method has met with some success the effect of dispersing large quantities of oil into the sea in this way is still to be evaluated and it is not clear that applying detergent in this manner avoids pollution but merely creates a different form of pollution which for the time being appears more acceptable than the pollution caused by the crude oil slick coming ashore or causing a problem to wildlife at sea.

Object of the invention It is an object of the present invention to provide equipment which can be taken to the site of an oil spillage both rapidly and efficiently and which can be moved into and over an area affected by oil spillage in such a manner as not to cause severe break-up of the oil slick which usually forms after crude oil has been spilt at sea so as to recover the oil from the surface of the sea and leave the sea clear and free from the oil spillage.

The invention According to the present invention apparatus for achieving the above object comprises a platform adapted to float on the sea, drive means mounted on the platform for rotating a turbine to produce a downward air thrust below the platform, the peripheral underside regions of the platform being shaped so as to cause the cushion of air to become trapped under the platform, at least one and preferably two centrifuge separator units mounted on the platform, duct means communicating from the peripheral underside of the platform and the interior of the separating centrifuge or centrifuges so that water and oil displaced by the continued downward flow of air is forced through the duct means into the centrifuge or centrifuges, suction means communicating with the central interior of each centrifuge for removing low density liquid material from the central region of each centrifuge and drainage means communicating with the radially outer regions of each centrifuge for draining away higher density liquid material which accumulates in the radially outer regions within each centrifuge.

The apparatus effectively separates oil from sea water since the oil will tend to congregate in the central region of a centrifuge whilst the sea water will be separated therefrom being of higher density and will tend to accumulate around the interior wall of the centrifuge.

Preferably conduit or duct means is provided for conveying the oil drawn up the suction means from the centre of each centrifuge into some container which may be a suitable tanker having spare capacity located close to the apparatus or may comprise integral tanks or floating tanks forming part of the apparatus.

Typically stabilising means is provided around the external periphery of the apparatus so as to accommodate undue wave motion.

Preferably means is provided for moving the apparatus laterally across the surface of the sea and for controlling the direction in which it moves.

Typically the means for moving the apparatus laterally comprises one or more propeller units as on a hovercraft or one or more jet engines.

Depending on the mode of propulsion used so the direction in which the air stream from the propeller or jet can be altered to adjust the direction in which the unit travels so as to produce movement in one direction or the other or a rudder may be incorporated so as to deflect the water displaced as a result of movement of the unit through the water so as to produce a desired change in direction.

One of the problems which has always beset any attempt to scoop or suck oil from the surface of the sea lies in the fact that the sea is continually moving and the waves present an undulating and continually moving surface. Collisions at sea rarely occur on days when the sea is calm and usually occur because of adverse weather conditions which usually cause the sea to be rough. Under these conditions it is essential that the apparatus which is sent in to recover the oil can stand up to the considerable buffeting and rolling motion which is induced by the waves and a preferred embodiment of the invention involves the use of at least two centrifuges mounted symmetrically about the centre of the platform one spinning in one direction and the other spinning in the opposite direction of rotation about two parallel vertical axes.The result is to produce a gyro effect which is self levelling and the result is an exceptionally stable craft even in very high seas.

Obviously such a craft will only have stability about an axis which extends horizontally between the axes of the two spinning centrfuges and additional stability can be provided by providing further centrifuge pairs also spinning in opposite directions of rotation and mounted around a central point on the platform so that the craft has stability about two perpendicuar horizontal axes.

The result is an exceptionally stable craft which will ride through and over waves without any tendency to tip.

Obviously apparatus such as has been described could be moved relatively quickly from a convenient port location on a coastline to a scene of an accident or spillage at sea but in order to do so suitable quantities of fuel would be needed and when on site further considerable quantities of fuel would be needed to drive the power source to provide the power for the turbine and the centrifuges.

According to a preferred aspect of the invention the platform includes integral or separable and floating tanks which at the outset of a journey to a spillage are filled with appropriate fuel such as petroleum spirit or diesel fuel or liquefied gas as appropriate to the engine which is to be powered and when the apparatus arrives at the scene of the spillage those tanks which have been emptied in order to provide fuel for the turbine power source and the drive means for conveying the apparatus to the scene are then filled with the oil as it is recovered from the sea thus enabling the apparatus to go into action immediately even though another tanker having appropriate capacity is not on hand.As the apparatus works its way over an oil slick further quantities of its own self-contained fuel will be absorbed and this will make further room available for the oil which is recovered from the surface of the sea to be stored therein.

According to a preferred feature of the invention the storage tanks include baffles which sealingly engage the walls of the tanks and separate upper and lower regions within the tanks so that fuel for use by the drive means on the apparatus is stored below the baffles and recovered oil can be immediately pumped into the same tank above the baffle as the baffle moves down the tank as fuel is drawn therefrom.

Preferably a single turbine is arranged in the centre of the platform to improve stability and the drive means therefor is mounted coaxially therewith also in the centre of the platform.

The invention relies on the principle that (a) water is to all intents and purposes incompressible, (b) air can be compressed into a confined space above water to produce a reactive and opposite force, (c) fluids rotated at high speed will separate according to their densities by centrifugal force, and (d) that fluid can be sucked through an aperture by the flow of fluid past that aperture i.e.

the Venturi effect.

The first two principles are embodied in the hovercraft known per se, the turbine producing the downward thrust for lifting the hovercraft being capable at the same time of producing an equal and opposite suction much like a vacuum cleaner by exploiting the Venturi effect in the design of the equipment. The absence of appreciable draught minimises the break-up of slick through turbulence and resultant sludge-lump formations.

To this end the air intake for the turbine derives at least some of its air from the centrifuges from the upper regions thereof so that there is a suction effect from the duct means which communicate between the centrifuges and the peripheral underside of the platform to thereby cause oil and water to be sucked through the duct means and into the centrifuges.

The suction produced at the intake of the turbine causes the mixture of oil and water together with some air to be sucked up through the ducts into the spinning centrifuges where the constituent fluids are separated and the air passes to the air intake of the turbine. Typically filters are provided to prevent oil and sea water from entering the turbine air intake.

Since crude oil or indeed most oils are considerably less dense than water the centrifuge will produce a separation in a radial direction as between the oil and the water, the water tending to move to the radially outermost regions within the centrifuge and the oil remaining near the centre. By sucking out the contents of the centrifuge from the centre the oil content can be removed virtually free from water and by providing drainage apertures in the radially outermost regions of the centrifuge so the water will drain away out of the lower regions of the centrifuge relatively free from oil. This water can be returned to the sea. Typically it is returned to the underside of the platform so that if there has not been complete separation the water may be recirculated through the ducting means and into the centrifuge once again where further separation may occur.

In order to control the suction effect which may be too great, inlet valves are conveniently provided in the upper regions of the centrifuge chambers to admit controlled quantities of air into the centrifuge chambers and an air intake may be provided for the turbine completely separate from the centrifuge chambers to allow fresh air also to enter the turbine air inlet. By adjusting the relative areas of opening of the different air intake devices to the turbine so just the right suction effect can be obtained in the ducting communicating with the underside of the platform so as to lift up just the required quantity of air and oil mixture so that correct separation can be achieved in the centrifuges.

Advantages of the invention The invention offers various advantages over other methods of clearance such as (1) it is clean so far as personnel and equipment are concerned; (2) it does not dissipate the slick into fine particles which may still produce harmful pollution at a distant place nor does it form a slick into sludge lumps which may sink to the sea bed out of sight but are nevertheless ecologically harmful; (3) it can be carried out at high speed;; (4) it can be carried out non-stop as it is not necessary to carry large quantities of other chemicals to deal with the slick on a chemical basis and indeed in a large enough piece of apparatus, a small oil refinery plant could be mounted thereon so as to recover diesel fuel from crude oil spilt on the surface of the sea to provide a continual source of power for the drive means driving the turbine etc. so that the apparatus could in theory carry on indefinitely until the whole of the oil slick had been dealt with; (5) it does not further pollute the water with chemicals as does already known detergent methods of dispersion;; (6) although the apparatus may be very large it can nevertheless be rendered relatively manoeuvrable and can either be carried to an area of the sea at which a spillage has occurred on another craft or towed on pontoons or it can be self-powered in the form of a giant hovercraft; (7) basic parts of the equipment are readily if separately available and can be speedily and cheaply assembled since the unit could be constructed from a number of empty oil tankers with the platform carried in between the tankers either by way of outriggers or simply linked thereto by flexible links in the form of hawsers or chains or ropes.

Specific areas of engineering development It is envisaged that the operation of apparatus incorporating the invention will be controlled to a large extent by the size and shape of the mouths of the centrifuges which must be dimensioned and placed strategically to produce optimum advantage and create sufficient back pressure without seriously affecting the efficiency of the upward flow of air and water and oil into the centrifuges. Furthermore the design of the shape and position of the openings in the ducting through which the oil and water is sucked by the suction effect provided typically by the air intake of the turbine producing the downward air thrust must also be designed so as to pick up the oil and water mixture as efficiently as possible and convey this to the interior of the centrifuges with the minimum of resistance to flow etc.

Other aspects of the invention involve (1) the provision of streamlined outboard tanks and floats and stabilisers located at the end of rigid arms in the form of outriggers which may be pivoted at least at one end and preferably at both ends into which crude oil recovered from the surface of the sea is pumped, the streamlined outboard tanks being surmounted on hydrofoil tripods or the like; (2) pneumatic lifting arms or the like may be provided on a gantry to pull up the floats, the opposing weight of opposite arms balancing one another; (3) vent holes may be provided together with airtight bungs to regulate the height of the craft when the craft is not engaging a slick but is self-propelling as a hovercraft to the locus in quo;; (4) filters in the form of wire mesh or the like may be provided at the entrances to the ducting in the peripheral underside of the platform; (5) a gantry mounted over the platform may conveniently provide support for swivelling air screws which may be four in number in order to provide powered thrust in four different directions for complete manoeuvrability; (6) a lower deck below the gantry but above the centrifuges may provide control rooms and observations rooms and personnel quarters where it is envisaged that the craft will be used for extended periods of time away from port; (7) a plenum chamber cowl may be surmounted on the top of the turbine air intake to achieve optimum air flow and minimum drag; (8) streamlining of the gantry and float and tank legs and hydraulic arms will allow the craft to progress more quickly to the site of a spillage;; (9) control means may be provided to control the operation of bow and stern ducting intake, centrifuge voiding vents, hydraulic arm evacuation pumps, steerage of rotating air screw supports when provided, screw fuel pumps, rate of suction into satellite tanks from centrifuge tanks, junction control into specific slick tanks, junction control of fuel from fuel tanks and navigational aids.

Where a large number of separate tanks are fed from the outputs from the centrifuges of a single craft, control means is preferably provided to allow the operator to select which tank is to be filled or which tanks are to be filled at any particular time so as to preserve approximate balance between the tanks.

A hydrodynamic bow and stern may be added to the platform to facilitate the rapid movement of the apparatus from a port to a scene of a spillage.

In an alternative arrangement the patform may be located within a converted hull for4 example of a super-tanker one side of which is adapted to be let down in the form of an elongated flap into the sea, the lower deck of the modified super-tanker being inclinable by jacks to provide a launching slip-away for the retrieval/separation unit The apparatus can be adapted to communicate with the tanker and the latter can provide the empty ballast tanks into which the spilled oil can be pumped as it is separated and collected by the apparatus embodying the invention.

The invention will now be described by way of example with reference to the accompanying drawings.

In the drawings Figure 1 is a cross-section through one embodiment of apparatus embodying the invention, Figure 2 is a plan view of the apparatus shown in Fig. 1 and Figure 3 is a cross-section through a floating hull adapted to contain apparatus such as shown in Figs. 1 and 2.

Detailed description of the drawings Figs. 1 and 2 illustrate one form of apparatus embodying the invention. Essentially this comprises a platform generally designated 10 a central area of which contains a large turbine generally designated 12 driven from a central shaft 14 which in turn is powered by a large power unit shown diagrammatically at 16.

The latter also provides power for two centrifuge units each of which is in the form of a hollow cylindrical drum 18 and 20 which are mounted diametrically opposite to each other about the centre of the platform and include vertical drive shafts 22 and 24 which are rotated from the drive unit 16 or from separate drive units which are shown in dotted outline at 26 and 28. Where for example the main drive unit includes an oil pump (not shown) the subsidiary drive units 26 and 28 may comprise hydraulic motors fed with oil under pressure from the oil pump.

The centrifuges additionally include central vertical extraction pipes 30 and 32 which communicate with empty tanks (not shown) which may form part of the overall structure of the platform 10 or may be floating tanks or outrigger tanks attached to the platform or may comprise the tanks of a tanker or other ship or floating structure which is associated with or comes to the aid of the apparatus when in use.

Detail of the connections and ducting and pipework from the upper end of the suction tubes 30 and 32 is not shown.

The underside of the platform is in the form of a generally inverted dish shape as designated by reference numeral 34 which defines a central opening through which the air blast from the turbine 12 passes to the underside of the platform. Peripherally the underside 34 is joined to an upright wall 36 at opposite ends and to similar walls on either side.

As shown in Fig. 1, at opposite ends an external wall 38 is provided spaced from the wall 36 and the chamber formed between the two walls provides ducting having an opening at 40 at one end and 42 at the opposite end through which oil and water can be sucked (as will hereinafter be described). At the uppr end the chamber between the two walls 36 and 38 determinate in an opening 44 on the one hand and 46 on the other hand into the upper and opened mouth of the centrifuge 18 and 20 respectively.

Each of the spinning centrifuges 18 and 20 includes drainage apertures at the radially outermost regions designated by reference numerals 48 and 50 and drainage ducts are provided through which water which passes through the drainage outlets 48 and 50 can pass, the drainage ducts being denoted by reference numerals 52 and 54 respectively.

Typically these communicate with the underside of the platform but to avoid possible reverse flow one-way valves are provided or baffles or the like to produce sufficient back pressure in the wrong direction as to force air from the turbine to push oil and water up through the chambers defined between the walls 36 and 38 preferentially rather than through the passages 52 and 54. Alternatively the ducts for the water separated by the centrifuge communicate externally of the underside of the platform so that there is no possibility for the oil and water and air from the turbine to attempt to travel up the passages 52 and 54 which would then not be provided.

The air blast from the turbine 12 produces a cushion of high pressure air below the underside 34 of the platform which causes the later to be lifted in known manner (as per the hovercraft principle) but not sufficient to cause the air to escape en masse, sufficient air escaping to maintain the pressure just sufficient to lift the weight of the platform. In this condition the passage of air, oil and water through the chambers between the walls 36 and 38 causes oil and water to be scooped up and forced into the centrifuges 18 and 20 which because they are spinning immediately cause the water to move to the radially outer regions of the centrifuges 18 and 20 and the less dense oil to remain in the central region where it is sucked up through the tubes 30 and 32.

The drives to the two centrifuges 18 and 20 are arranged so that the two centrifuges spin in counter directions of rotation so that a gyro effect is produced tending to stabilise the craft even in heavy seas.

Observation windows designated by reference numerals 56 and 58 are provided to allow operating personnel to see the degree of separation within the centrifuges. Control means (not shown) is provided for varying the speed of operation of the centrifuges and the speed of operation of the turbine and valve means shown diagrammatically at 60 and 62 and at 64 and 66 is provided for controlling the admission of air into the upper regions of the centrifuges and into the air intake of the turbine from the upper regions of the centrifuges so that the actual through-flow of air through and around the apparatus can be controlled to a fine degree to produce just the required degree of lift and scoop to provide just the required degree of fluid within the centrifuges.

As shown in Fig. 2, the platform can be subdivided around the centrifuge units and around the central turbine area so as to provide separate strengthened storage tanks which are numbered 51 to 70. The tanks may be used to store fuel for powering the power unit 6 and/or 26 and 28 when these are provided separately and/or may provide storage for separated oil gathered from a slick.

Transportation of the apparatus from a port to a site of a spillage may well involve travelling over many hundreds of miles of sea and to this end a streamlined craft may be more efficient than trying to tow or motivate the apparatus in the form of a hovercraft. To this end a streamlined hull typically in the form of a super-tanker hull shown in cross-section in Fig. 3 and denoted by reference numeral 72 may be provided one side of which may be adapted to be let down typically in sections so as to rest on or slightly below the surface of the water on which the hull floats, lowered sections being denoted by reference numeral 74 and sections still remaining up along that side being denoted by reference numeral 76, and the interior of the hull may be adapted to be flooded or may simply include a flat floor on which the apparatus generally designated 10 rests or floats and means is provided in the form of ropes designated by reference numeral 78 or hawsers or the like for pulling the apparatus 10 into the hull when the side panels have been lowered as at 74. Typically the hull 72 is adapted to be flooded so that the apparatus can be floated into the hull and after the wall of the hull is moved from the position at 74 to the position at 76 the hull can be pumped out to a greater or lesser extent to allow the ship to then move the apparatus either to the scene of a spillage or from the scene back to port.

Alternatively the lower deck of the supertanker may be inclined by jacks to provide a launching slipway for the retrieval/separation unit, not shown.

Claims (20)

1. Apparatus for separating liquids having different densities for retrieving a first liquid material floating on a second liquid material of higher density than the first liquid material comprises a platform adapted to float on the second liquid material, drive means mounted on the platform for rotating a turbine to produce a downward air thrust below the platform, peripheral underside regions of the platform being shaped so as to cause a cushion of air to become trapped under the platform, at least one and preferably two centrifuge separator units mounted on the platform, duct means communicating from the peripheral underside of the platform and the interior of the separating centrifuge or centrifuges so that the two liquid materials displaced by continued downward flow of air are forced through the duct means into the centrifuge or centrifuges, suction means communicating with the central interior of each centrifuge for removing the lower density liquid material from the central region of each centrifuge and drainage means communicating with the radially outer regions of each centrifuge for draining away the higher density liquid material which accumulates therein.

2. Apparatus as claimed in claim 1 further comprising conduit or duct means for conveying the lower density liquid material drawn up the suction means from the centre of each centrifuge into a container.

3. Apparatus as claimed in claim 2 in which the container comprises a second vessel adapted to float on the second liquid material.

4. Apparatus as claimed in claim 2 in which the container comprises an integral tank forming part of the apparatus.

5. Apparatus as claimed in any one of the preceding claims further comprising stabilising means located around the external periphery of the apparatus to accommodate wave motion of the second liquid material.

6. Apparatus as claimed in any one of the preceding claims further comprising means for moving the apparatus laterally across the said second liquid material and for controlling the direction in which it moves.

7. Apparatus as claimed in claim 6 wherein the means for moving the apparatus laterally comprises one or more propeller units or one or more jet engines.

8. Apparatus as claimed in claim 7 further comprising means for altering the direction in which the air stream from the propeller or jet can be altered to adjust the direction in which the unit travels so as to produce movement in one direction or the other.

9. Apparatus as claimed in claim 7 or 8 further comprising rudder means for deflecting the water displaced as a result of movement of the unit through the water so as to produce the desired change of direction.

10. Apparatus as claimed in any one of the preceding claims in which the platform includes integral or separable and floating tanks which can be filled with an appropriate fuel for driving the apparatus to allow it to be conveyed to the scene of an accident at sea and means for replacing the fuel in the tanks with a spillage of oil collected from the surface of the sea by the apparatus.

11. Apparatus as claimed in claim 10 in which the storage tanks include baffles which sealingly engage the walls of the tanks and separate upper and lower regions within the tanks so that fuel for use by the apparatus is stored below the baffles and recovered oil can be pumped into the tanks above the baffles as the baffle means move down the tanks as fuel is drawn therefrom.

12. Apparatus as claimed in any one of the preceding claims in which a single turbine is arranged in the centre of the platform to improve stability and the drive means therefor is mounted coaxially therewith also in the centre of the platform.

13. Apparatus as claimed in any one of the preceding claims wherein the air intake for the turbine derives at least some of its air from the centrifuges from the upper regions thereof so that there is a suction effect from the duct means which communicate between the centrifuges and the peripheral underside of the platform to thereby cause the two different density liquid materials to be sucked through the duct means and into the centrifuges.

14. Apparatus as claimed in claim 13 in which the suction at the intake of the turbine causes the mixture of the two different density liquid materials together with air to be sucked up through the ducts into the spinning centrifuges where the two different density liquid materials are separated and the air passes to the air intake of the turbine.

15. Apparatus as claimed in claim 13 or 14 which includes filters to prevent the liquid materials from entering the turbine air intake.

16. Apparatus as claimed in claim 15 which further comprises inlet valve means for controlling the suction effect in the upper regions of the centrifuge chambers to admit controlled quantities of air into the centrifuge chambers.

17. Appa#ratus as claimed in claim 1 5 or 16 further comprising a separate air intake for the turbine completely separate from the centrifuge chambers to allow fresh air also to enter the turbine inlet in a controlled manner.

18. Apparatus as claimed in any one of the preceding claims wherein the platform includes a hydrodynamic bow and stern to facilitate the rapid movement of the apparatus from a port to the scene of a spillage at sea.

19. Apparatus as claimed in any one of the preceding claims when mounted within a ship hull typically a supertanker conversion, one side of which is adapted to be let down in the form of an elongated flap into the sea, below the deck of a modified hull being inclinable by jacks to provide a launching slipway for the apparatus.

20. Apparatus for the separation of liquid materials having different densities and particularly for the recovery of an oil spillage at sea constructed arranged and adapted to operate substantially as herein described with reference to and as illustrated in the accompanying drawing.