WO2003000377A1

WO2003000377A1 - Separation of oil and water

Info

Publication number: WO2003000377A1
Application number: PCT/GB2002/001152
Authority: WO
Inventors: Alun Kynric Lewis; Thomas Merlin Maddock
Original assignee: Mantis Oil Separation Limited
Priority date: 2001-03-21
Filing date: 2002-03-14
Publication date: 2003-01-03
Also published as: GB0130840D0; GB2374028A; GB0202116D0

Abstract

A method for separating oil and water in a flow which comprises feeding the flow of oil and water (primary) mixture through an entry (182) into a vortex zone within (181) which, e.g., contains a helical coil shaped wall member (188) adapted to impart a rotational movement to the primary mixture so as to form a rotating fluid mass within which a non-turbulent vortex of oil (183) floats on secondary the mixture of water and the residue of the remaining oil. The secondary mixture is led downwards through an conduit (208) formed between the outer wall (195) of a chamber and an envelope (201) to the bottom of the lower housing where it encounters the bottom end of the first stacked group of tilted corrugated plates of the method. The plates withdraw oil from the secondary mixture. The recovered oil floats upwardly. It is guided by the barrier plates (193), (194) and the outer wall (195) respectively to the escape tube (198). This extends into the vortex zone and has an outlet 200 in or near to the floating oil vortex (183). The recovered oil passes through the outlet and mingles with the floating oil (183) and is carried away by pipe (186).

Description

SEPARATION OF OIL AND WATER

Technical Field

This invention relates to the separation of oil and water. Its use includes a large variety of applications. Wherever oil is used, it is inevitable that problems arise from water polluted by the spillage and leakage of oil. The proportions of the oil to water in the mixture to be separated will vary from time to time between wide limits, even for a given location. So will the volumes of oil/water mixture to be treated. The problems includes the treatment of water polluted with oil in a host of different circumstances connected with the running of a contemporary economy and also includes the separation of the surface oil that pollute the rivers and canals, the sea and all kinds of still waters. The present invention is directed to a method and device for the separation of the water free from oil and will essay to cope successfully with the problems that these different circumstances give rise to.

An ancillary advantage flows from the practice of the invention in one of the preferred forms in that the presence of heavier than water sludge (which includes silt and sediment) in the mixture of oil and water may in large part be removed in the course of the separation of the oil from water. Disclosure of the Invention

According to the present invention, there is provided a method for separating oil and water in a flow in which: i. The flow of oil and water mixture (hereinafter called the "primary mixture") enters a vortex zone in which the primary mixture is subjected to rotational forces to form a whirling fluid mass within which part of the oil separates to form a discrete, floating oil vortex, such vortex zone comprising outlet means whereby the mixture of water and the residue of the remaining oil (hereinafter called the "secondary mixture") that support the discrete floating oil vortex escapes from the vortex zone; ii. The secondary mixture is led downwards in a conduit to the bottom or near to the bottom of a chamber (hereinafter called "the lower housing") where it comes into contact with the bottom end of one or more of the downward facing, submerged and tilted corrugated plates of the invention located within the lower housing; iii. The secondary mixture is then fed upwardly to the top of such plate or plates in contact with one or more of the adjacent, downward facing, longitudinal grooves disposed between corresponding ridges, the depth of each groove being arranged to increase progressively and simultaneously with a progressively decrease in the mean angle (as defined below) between the groove sides when proceeding along the upward direction, ( the plate or plates being designated herein "the Lemer plate'Or "the Lemer plates"). iv. Oil (hereinafter called "the recovered oil") from the secondary mixture collects in the downwardly facing grooves of the submerged corrugated plates and moves to the tops of the grooves where, in the form of droplets, it breaks free to float upwardly within the lower housing; v. Means are provided for transferring the recovered oil to or near to the surface of the discrete floating oil vortex in the vortex zone; vi. Outlet means from the lower housing are provided for the oil depleted secondary mixture; vii. Separate outlet means are provided for the oil in the discrete, floating oil vortex. According to the preferred manner of carrying out the invention, the flow of the primary mixture on entering the vortex zone encounters a wall member having the configuration of an helix when seen in plan view and defines a helical path of progressively diminishing radius and which receives the flow or a layer of the flow and guides the same along the path to the zone around the centre of the helix so forming a whirling fluid mass within which part of the oil separates to form a discrete, floating oil vortex.

This specification makes use of the natural and ordinary meaning of the word 'helix' and 'helical' as defined by the current and earlier editions of the Concise Oxford Dictionaries and, furthermore, the Dictionary of the English Language by the redoubtable Dr. Samuel Johnston first published on the 15^th April 1755. The Oxford dictionaries in defining "helix" speak of "A spiral curve (like a corkscrew or a coiled curve (like a watch spring") and, in earlier editions, "Spiral (like a corkscrew, or in one plane like a watch-spring"). Dr. Johnson says; "A spiral line; a circumvolution". The definition of the word "helical" according to the Oxford dictionaries is; "Having the form of a helix" and, in earlier editions, "Spiral". Dr. Johnson says, "Spiral; with many circumvolutions".

The configuration of the wall member given above, the representation of Figure 8 and the text below relating to Figures 8 and 9 are consistent with these meanings. In the context in which "helix" and "helical" are used, they must be taken to include "spiral" in the form of an adjective and, where loosely used as a matter of common parlance, as a noun. "Lemer Plates"

The invention includes as an essential feature the separation of oil from water in the secondary mixture. This is carried out using downwardly facing, submerged and tilted corrugated plates as indicated in sub paragraph hi under the section "Disclosure of the Invention" above. The description of plates include the words "the mean angle between the groove sides". For the purpose of this specification, the expression "the mean angle between the groove sides" shall mean the angle between two lines, each extending upwardly from the same point on the base line of a groove, the one to the ridge line running along the ridge on the one side of the groove and the other to the ridge line running along the ridge located on the other side of the groove, both of the upwardly extending lines as seen in plan view being disposed at right angles to the said base line. The expression 'Lemer plate" or "Lemer plates" will be used to designate such plate or plates.

A reference to the Lemer plate or plates in use according to invention described herein is to be taken to be a reference to corrugated, submerged, tilted plate or plates a) with the mean angles of the grooves decreasing and, simultaneously, the depth of each groove increasing in the upwardly direction, and b) which is adapted to let a mixture of oil and water travels upwardly along downwardly facing grooves of the underside of which until it reaches the top.

Thus, when put to use to separate oil from water, each corrugated plate of the present invention is arranged to be disposed so that the progressive increase in depth of the grooves accompanied by a simultaneous decrease in mean angle between of the grooves sides, (which can be 180 degrees at the bottom) occur in the direction of flow. This subjects the oil carried by the water to the friction of an increasingly large area. The narrowing mean angle between the grooves serve to bring the particles of oil carried by the water in the flow closer together. The result is that the promotion by coagulation of the particles into globules and/or droplets of oil which form on the underside of the corrugated plates. Being less dense than water, they float upwardly along the downwardly facing grooves in the watery environment and eventually break off the top in the form of droplets. They continue to float upwardly towards the surface. In the context of this invention, means are provided to transfer this recovered oil to join with the floating discrete oil vortex in the whirling mass in the vortex chamber.

The water, decontaminated by the extent that the oil droplets have been got rid of, is subjected to a repeat procedure or led to the exit. One or a series of or unitary Lemer plates, or else, preferably, of "stacked plates" may be used in sequence to decontaminate the water further. Such water may be deflected to the bottom of the next Lemer plate or corrugated stacked Lemer plates. The process of the getting rid of the ever diminishing droplets of oil is repeated. By "stacked plates" is meant a series of Lemer plates of the invention arranged in a stack of substantially parallel, tilted plates between which the fluid in question flows. Within each stack, each intermediate plate is located in close proximity to its neighbouring plate; and the last plate is arranged to force the flow upwardly between the plates. See Figure 6.

The angle of tilt of the Lemer plates may vary between wide limits. The bases of the downward facing grooves may be tilted at an angle to the horizontal of under 5 degrees to a steep angle of 70 degrees or more. It will be a matter of trial and experiment in any particular case to ascertain the most favourable angle having regard, inter aha to the relative proportions of oil and water in the mixture to be dealt with, the capacity and shape of the lower housing, the rate of flow of the feed, the degree of final separation aimed for and the specific gravity and viscosity of the oil to be separated. In both ensuring the separation of the oil and maximising the surface area in contact with the mixture, an angle of 45 degrees for such downwardly facing bases is theoretically ideal; but very satisfactory results are obtained where angle is from 35 to 60 degrees, and preferably from 40 to 50 degrees to the horizontal. The lower housing.

The lower housing may be contained within a housing of any shape provided that the corrugated plates and the barrier plates (referred to below) conform with the description of the invention as made herein. The preferred embodiment of the invention is that in which the individual corrugated Lemer plates together with the barrier plates are disposed, i. each with an unbroken line from its centre part to its periphery and, ii. preferably, forming an annulus on plan view, and having the grooves of the Lemer plates and the barrier plates arranged radially around a. the centrally placed "inner conduit" which transmits the mixture of water and recoverable oil (i.e., the secondary mixture, tertiary mixture, depleted tertiary mixture and so on) from the vortex zone to the bottom or near to the bottom of the lower housing, or, alternatively, b. in plan view, the centrally placed oil escape tube for the oil recovered by the Lemer plates from the said mixture where an "outer conduit" is used to transmit such mixture from the vortex zone to the bottom or near to the bottom of the lower housing. In either case, the corrugated plates and the barrier plates, both individually and collectively preferably takes on the shape of a frustum of a cone to encircle the inner conduit or the oil escape tube respectively. Accumulation Zones.

The repeat procedure outlined above whereby an unitary corrugated plate or else one of a series of stacked plates may be used to extract oil from the secondary mixture may by assisted by dividing the lower housing into two or more "accumulation" zones in line. Each accumulation zone is furnished with a unitary or stacked Lemer plates arrangement. Each accumulation zone is followed by a barrier plate extending to the top of the accumulation zone. The barrier plate guides the recovered oil from the accumulation zone to a restricted aperture at the top leading to an escape tube. At or near the bottom of the barrier plate is an opening leading to the next accumulation zone in line or, in the last barrier plate, leading to the exit. The secondary mixture on emerging from the conduit that has guided it from the vortex zone, (be it an inner conduit or an outer conduit) is fed upwardly in contact with the downwardly facing grooves of the Lemer plate or plates of the first accumulation zone in line. The last Lemer plate in any of the accumulation zones extends from the bottom to the tops of the grooves. This forces the flow which encounters the Lemer plates at or near the bottom to move upwardly. On reaching the tops of the grooves, the direction of its travel is reversed. The flow is diverted downwardly by the upper reaches of the first barrier plate. It arrives at the opening at or near the bottom of the barrier plate which provides an entry from the first accumulation zone to the second accumulation zone. The mixture enters the second accumulation zone at or near to the to the bottom of the Lemer plate or plates and is fed upwardly in contact with the downwardly facing grooves of the second accumulation zone to the tops of the grooves. When there are three or more accumulation zones, the mixture is diverted downwardly by the second barrier plate to the opening at or near to its bottom which leads to the third accumulation zone. The process is repeated for every accumulation zone in line.

On every upward movement of the secondary mixture, recoverable oil in decreasing quantities is deposited on the downwardly facing grooves of the Lemer plate or plates. After the passage through the last accumulation zone, the oil depleted secondary mixture passes on to the exit.

At the top of each barrier plate, the downwardly facing side communicates with a restricted oil escape aperture connected to an oil escape tube that leads upwardly from the lower housing to the interior of the vortex zone. During operation, oil is separated from the secondary mixture by the Lemer plates. In the aqueous environment, the oil works its way to the tops of the Lemer plates where it accumulates as globules and/or droplets. These break off and float upwardly. They are guided by the barrier plate to the oil escape aperture leading to the oil escape tube. The oil escape tube extends to an outlet on or near the surface of the liquid in the vortex chamber which comprises a floating oil vortex that is supported by the secondary mixture. The outlet is maintained within the floating oil vortex or else sufficiently close to it that the recovered oil emerging from the outlet joins up with the oil in the vortex which eventually mingles with the floating oil.

A simple way of having the outlet held in the desired level is by having a flexible tube suitably supported by a buoyant float that rises and falls with the level of the surface of the liquid within the vortex chamber, the outlet being at the open end of the tube or adjacent to the end of the tube. The passage of the recovered oil to the outlet may be assisted by having a suitable pump. e.g. a low voltage pump acting on the contents of the aperture to urge such contents towards the outlet.

The barrier plate may be supported at the top and bottom ends. When that happens, it is convenient to make the barrier plates relatively inflexible so as to provide physical support to the Lemer plates in the respective accumulation zones either upstream or downstream, or both. Thus the barrier plate may be of metal, e.g. of stainless steel or of reinforced synthetic resin having a strength sufficient to support the Lemer plates in question. It is convenient (but not essential) to have the design of the barrier plates such that they will fit in with the design of the Lemer plates before and after in sequence.

Some water from the secondary mixture may escape with the oil through the restricted aperture to the vortex chamber. This water will eventually join up with the water already present in the vortex chamber. It will not affect the operation of the separation of the oil and water by the process described herein. It will descend through the floating oil vortex to re unite with the secondary mixture that supports the vortex and eventually be swept away down the inner or alternatively, the outer conduit as the case may be.

In the lower housing, care has to be taken that the secondary mixture is kept upstream of that part of each barrier that diverts it downwardly to the opening at or near its bottom. The opening allows the secondary mixture access to the next accumulation zone in line, but no secondary mixture should be allowed to escape to the succeeding accumulation zone or zones otherwise than through such opening.

The mixture will have a diminishing oil content on emerging from each accumulation zone in turn. The apparatus may be modified by adding or by taking away one or more accumulation zones according to the nature and constitution of the primary mixture to be treated and /or the desired result that is to be aimed at. Similar considerations apply to the number of Lemer plates contained in any individual accumulation zone.

The successive accumulation zones may be arranged so that they are level with the first accumulation zone. Any additional accumulation zones will expand the area covered by the device, especially if it were tried to emulate the first accumulation zone This could lead to difficulties when there is a shortage of space, for example on a ship, a pier or like structure.

A very useful way of arranging of the accumulation zones is to have the bases of each of the second and later accumulation zones located above the base of the previous accumulation zone in line. In one example of this arrangement, the physical embodiment of the later accumulation zone will be supported, at least in part, by a platform or staging held up by a part of the physical embodiment of its predecessor in line. This arrangement confers a substantial reduction to the area covered by the device and offers the way to have identical accumulation zones to the first in line. The device will remain effective by the addition of any number of accumulation zones (within reason) on top of the first accumulation zone.

The principle locating the base or bases of the accumulation zones above their predecessors' base or bases can be extended. Two or more accumulation zones may be arranged so that they are level with each other and may have their bases located above the base (or the bases) of the previous accumulation zone (or zones). "Inner Conduit" and "Outer Conduit".

Where in the course of the practice of the present invention, the secondary mixture leaves the vortex zone, one or other of two conduits takes it to the area which lies at or near the bottom of the lower housing.

The inner conduit is located within the lower housing. It discharges the secondary mixture on reaching a short distance from the floor of the lower housing and the mixture is fed upwardly against the grooves of a downwardly facing Lemer plate (where only one is present) or a stack of Lemer plates which belong to the first accumulation zone.

The outer conduit is located outside the lower housing. The secondary mixture is led by the conduit to the bottom of the lower housing and is discharged into the lower housing from below. It is also fed upwardly against the grooves of a downwardly facing Lemer plate or stack of Lemer plates of the first accumulation zone in like manner to the secondary mixture discharged by the inner conduit mentioned above.

By the substitution of an outer conduit for the inner conduit, the space taken by the inner conduit becomes available. The lower housing is enabled to accommodate more Lemer plate surfaces and therefore increase the effectiveness of the oil separation. The passage of the secondary mixture after it has left the vortex zone to the area below the bottom of the lower housing may also be enlarged at will. This will secure a slower and more regulated flow of the mixture. The enlarged space will accommodate sludge traps and baffle plates to reduce any sludge present before the mixture of oil and water enters the lower housing. The envelope.

A particularly useful of the application of the outer conduit is where it takes the form of an envelope to contain the whole of the lower housing. In such circumstances, the secondary mixture may flow through the space between the exterior wall of the lower housing and the inner side of the envelope which, taken together constitutes the outer conduit which leads to below the base of the lower housing. The secondary mixture enters the lower housing from below and is also fed upwardly against the grooves of a downwardly facing Lemer plate or stack of Lemer plates of the first accumulation zone as indicated above. Level of the oil removal pipe.

The level of the floating oil vortex generated by the whirling mass within the vortex zone rises above the level of the water when water alone flows through the vortex zone. This is consistent with the surface layers of water being replaced by oil which has a lower specific gravity. This provides two advantages when locating a separate oil extraction pipe. The inlet to the pipe is located at or near to the middle of the vortex zone. The inlet may be arranged to be positioned a short distance above the level of the water where water alone flows through the vortex zone. With the introduction of primary mixture, a floating oil vortex is formed around the inlet. As more and more of the primary mixture flows in, the floating oil vortex increases in size and height until eventually, the inlet sinks below the rising level of the oil vortex. As a result, oil spills over the inlet for collection. Also as a result, the automatic operation of the method of the invention becomes possible. Only in the presence of oil in the flow of water can the floating oil vortex be formed and the method become operative. The Nortex Zone

The vortex zone may be situated in a vortex chamber. It is adapted to accommodate rotational forces which form a whirling fluid mass within which a part of the oil separates to form a discrete, floating vortex, such vortex chamber comprising outlet means whereby the secondary mixture escapes through the outlet means in its bottom for further separation.

The rotational forces may be caused by any of the conventional means used to produce the desired result such as stirring or use of paddle wheels or of magnetic "fleas" driven around by amoving magnetic field. Such devices call for the assistance of outside agencies. The "helical wall" device mentioned above can achieve an excellent desired result without the intervention of an outside agency, and it is to be preferred.

The vortex zone may be also of a kind that for the purpose of this Specification is called "the bottomless vortex zone". In this case, the helical walls are maintained to cause the flow of liquid introduced into the vortex zone to rotate, but below the helical walls, the vortex zone does not have a "bottom". The secondary mixture on leaving the helix walls flows freely downwardly without interruption. The helical wall may be supported by struts or suspension means attached to elements of the housing or by attaching the outer coiled curve of the helix to the inner edge of the vessel in which the vortex zone is situated.

The final exit of the oil depleted water from the lower housing of the device may be monitored to keep the lower housing and the vortex zone full of a flow of Mquid. A controlled and/or a non return exit valve may govern the flow, e.g. in cases where the exit debouches at an unpredictable level or at levels which would otherwise affect the balance of the flow within the apparatus. See by way of example the reference below to the valve as represented in Figure 13 of the Drawings annexed hereto. The advance vortex zone or zones.

The original primary mixture may be passed through an additional one or more vortex zones in line (called in this specification "the advance vortex zones"), and a discrete, floating oil vortex is produced in one or more than one of them. The second in line of the vortex zones receives a diluted mixture of oil and water, being the secondary mixture produced by the first vortex zone. The procedure may be repeated. The "secondary mixture" of an advance vortex zone or zones which supports the floating oil becomes the "primary mixture" of the next vortex chamber in line. When one advance vortex zone is employed, the Lemer plates in the lower housing are called upon to extract oil from what may be called a "tertiary mixture" of oil and water. When there are two advance vortex zones in line, the Lemer plates deal with a "depleted tertiary mixture", and for more than two, there is yet further dilution. The tertiary, depleted tertiary and the further dilution of the mixture will be called "tertiary etc. mixture" unless the context requires a precise definition. The addition of not more than two advance vortex zones in line before the last vortex zone will be sufficient for most purposes.

This expedient has a significant advantage where the apparatus of the invention is called upon to handle a mixture of oil and water which has a high proportion of oil, or when the expected proportion of oil may rise temporarily and/or unexpectedly above the capacity of a single vortex zone or its lower housing to handle. Such conditions could well arise, for example when the apparatus of the invention is applied to separate oil from an area comprising an oil slick of indeterminate thickness on the surface of the sea, lake or river. The oil separated out by the Lemer plates in the lower housing which accepts the tertiary etc. mixture will be fed back into the advance vortex zone upstream, or if there are two such zones, preferably the first in line. Each advance vortex zone has a separate outlet means for its own floating oil vortex. The passage of the recovered oil through the oil escape aperture to the outlet in the advance vortex chamber upstream may be assisted or wholly caused by having a suitable pump, e.g. a low voltage pump acting on the contents of the escape tube to transfer such contents to the outlet.

When the flow of the primary mixture is sufficiently strong, the difference in the level of the surface in the last downstream vortex zone as compared wάth the level of one or more advance vortex zone or zones may be so small that it may be disregarded. The oil in the oil escape aperture may have a buoyancy sufficient to reach the floating oil vortex in the advance vortex zone at the appropriate level and to prevent liquid from the advance vortex zone from coming down the oil escape aperture into the lower housing. This can be the case if the apparatus of the invention together with its advance zone or zones face a strong tide or current, or if the system is mounted on a vessel having an independent means of propulsion and/or incorporates a promoter of flow e.g. an outboard engine behind the final exit.

The disposition of one or more additional advance vortex zone or zones between the original primary mixture and the inclined Lemer plates in the lower housing ensures that in practice, by far the major part of the oil is removed before it can come into contact with the Lemer plates. The problem of sludge.

An ancillary benefit of the preferred form of the invention when using an advance vortex zone is the effective removal of a significant proportion of "heavy" sludge, i.e., sludge that exhibits a higher specific gravity than water. The expression "sludge" includes all kinds of foreign matter including silt, sand and/or other heavy solids carried in the mixture of oil and water to be separated. It does not amount to "trash" which expression is used to donate objects of larger size, in many cases buoyant which are removed if necessary by passing the mixture through a trash rack.

An advance vortex chamber may be adapted to include a useful sludge trap where a bottomless vortex zone is used. The sludge on entering the vortex zone will react to the centrifugal forces of the whirling fluid mass and be encouraged to congregate and at the periphery of the vortex zone. On leaving the zone, a diminishing centrifugal force will continue to act upon the sludge as it falls to the lower part of the chamber. This is put to use in designing the exit pipe to carry the mixture to the next or last vortex zone. The mixture exits through downwardly facing opening in the centre of the vortex zone when seen in plan view. This location is as far as possible from the major concentration of the sludge that falls all around from above. Such opening may be protected by baffle plates, e.g. a cone or disc or the like. The bulk of the sludge by pass the opening and falls into a sludge trap for which space is provided in the bottom of the chamber.

The helical wall member in the vortex zone may be modified. The bases of the coils of the bottomless wall member may be arranged to be inclined outwardly so that the sludge will be projected outwardly. The area through which the mixture flows down accompanied by sludge may be expanded from the base of the vortex zone towards the bottom of the chamber, thus giving the opening to the exit pipe additional protection from the falling sludge.

Where the outer conduit involves an envelope to carry the secondary or tertiary &c. mixture between the vortex zone and the base of the lower housing, a slow, non turbulent passage of the movement between the envelope and the lower housing is enhanced by the use of the bottomless vortex zone. Droplets of oil which have escaped the floating oil vortex are encouraged to link together and travel up against the flow of the mixture to join the water/oil interface of the floating oil vortex. Below the bottom of the lower housing, the non turbulent movement of water encourages sludge to be deposited in front of baffle plates in the relatively large space which the use of the envelope makes possible. Before or at the exit of any of the devices according to the present invention, a removable and renewable conventional filter matrix, e.g. a matrix of polypropylene fibres adapted to coalesce oil droplets may be positioned in the path of the oil depleted water to trap the very fine particles of oil that have survived the previous separations.

The embodiments of the invention will now be described by reference to the schematic drawings (not to scale) appended hereto.

Figure 1 is brought in to explain what is meant by a corrugated plate the characteristics of which are set out above and which, for the purposes of this Specification is designated "the Lemer plate"; and where there are more than one such plates, "the Lemer plates". Figure 2 represents one end view of a stacked plate unit comprising such plates. Figure 3 represents the other end view of the stacked plate unit of Figure 2. Figure 4 represents in elevation a modified form of Figure 1 in which the corrugated plate is dimensioned so as to form a trapezoidal side of a box like structure which will, in the case where an inner conduit is used, contain that conduit through which the secondary mixture is led to the bottom of the lower housing. Figure 4 may also represent such side of a box like structure which will contain the escape tube when an outer conduit is used to lead the secondary mixture to an area below the lower housing.

Figure 5a represents the circular "the sharp end" of a frustum of a conical Lemer plate that has been formed so that the mean angle as defined above is an acute angle, and rather deep grooves are formed between the ridges 18.

Figure 5b represents what happens to the mean angle of Figure 5a when going down from the top or "sharp end" of the Lemer plate towards the bottom when the mean angle becomes progressively more obtuse, the grooves between the ridges 19 become progressively shallower and the Lemer plate assumes an annular form on plan view.

Figure 6 represents a detail of a stacked plate unit comprising a plurality of corrugated plates arranged in a stack of substantially parallel tilted plates with the last plate positioned so that liquid will pass upwardly between the plates and in the direction of their corrugations. Figure 7a and Figure 7b each represents the end of the upper groove of a Lemer plate at which droplets of oil collect before they float off in an upward direction. Figure 8 represents in plan view the helical wall of a device in a vortex zone. Figure 9 represents an assembly containing features of the invention. Figure 10 represents an assembly containing features the invention where the lower housing is divided up onto accumulation zones and an inner conduit leads the secondary mixture from the vortex means to an area shortly above the floor of the lower housing. Figure 11 represents a variant of Figure 10 in which an advanced vortex chamber is employed to provide secondary mixture which is fed into the vortex chamber of Figure 11 as a primary mixture, and an oil escape tube from the lower housing carries the recovered oil to the advance vortex chamber..

Figure 12 represents a variant of Figure 10 and Figure 11 in which an advance vortex chamber is employed in a strong current to provide a secondary mixture which is fed into the vortex chamber as a primary mixture.

Figure 13 represents an embodiment of a separator of the invention where the bases of the second and succeeding accumulation zones are mounted in line, one over the top of its predecessor's base. The secondary mixture (or tertiary etc. mixture) is led downwardly from the vortex zone through a conduit located outside the lower housing. Such conduit is represented as an envelope which covers the lower housing, and the secondary mixture is admitted to the first accumulation zone of the lower housing from below. Figure 13 also represents a valve to control the flow of oil depleted water from the lower housing's exit. Figure 14 represents a variant of Figure 13 in which an advance vortex zone is employed to provide secondary mixture which is fed into the main vortex zone as a primary mixture. Figure 15 represents the lower housing of the invention with the accumulation zones mounted in order, the second above the first and the third above the second. Figure 16 represents a plan view of a full Lemer plate for which Figure 15 displays a side view. The Lemer plate may be formed by vacuum formation in ABS or other suitable synthetic resin or formed in metal, e.g. aluminium or stainless steel.

In Figure 1, 1 represents the corrugated plate with downwardly facing grooves 2, 3 and 4 and complementary upwardly facing grooves 5 and 6. For the purposes of this explanatory drawing, outer plate edges, ridges and groove base lines when seen in plan view are arranged to be parallel to each other. In most of the embodiments of this invention, they converge in the direction shown as "A". The angle between the groove walls decreases in the direction shown as "A". At the same time, the height of the groove walls, (base line to ridge) increases in the direction shown by "A". So does their area per unit of distance in the direction of "A". At one end of the corrugated plate, the grooves are shallow with a large angle between the side walls. At the other end, the grooves are deep and the angle between the side walls has been reduced.

At the "shallow groove" end of the corrugated plate, points 9 and 10 on the downwardly facing walls of groove 2 are each located at a distance "d" from line 11 which represents the location of the base line 11 of groove 2.

Adjacent the other end, points 9' and 10' are also located on the downwardly facing walls of groove 2 at a distance "d" from line 11. It will be seen that the transverse distance between points 9 and 10 progressively decreases in the direction "A" towards location 9' and 10' and the space between the groove walls is progressively restricted.

Figure 2 represents a cross-sectional view of the "shallow angle/large angle end of a stacked Lemer plate unit comprising separator plates according to that described for the present invention.

Figure 3 represents a cross sectional view of the "deep groove/small angle" end of the stacked Lemer plate unit of Figure 2.

In Figure 4, the reduction of the mean angle between the groove sides on the upward path of the secondary mixture is accentuated by the convergent, non parallel disposition of the groove ridges 15 and the base lines 16.

In Figure 5a, 18 represents the plan view of the top of the grooves where its narrowest and deepest formation appear.

In Figure 5b, 19 represents the plan view towards the bottom of the grooves where the grooves are shallower and the sides of the grooves shorter.

Figure 6 represents a stacked pack of Lemer plates in operation. The mixture of oil and water comes down the space 20 and enters the zone containing the stacked plates through the entrance 21 where its direction of flow is reversed. The furthest plate 22 away from the flow of secondary mixture bars the entry to the right as seen in Figure 6 and forces the liquid to traverse the multi channel pathways between the adjacent plates 23 to 27 to the top where the droplets that come together as a result of coagulation of lesser particles congregate and eventually break free to float upwardly until they congregate at the summit of the zone. There, means of escape lead through apertures leading to the vortex chamber in which they are taken up by the whirling liquids and they eventually become part of the floating oily vortex. The oil depleted water may again be driven downwardly between the side 28 of the corrugated plate 23 to enter a zone through conduit 30 where the process is repeated using a stacked plate or an unitary plate arrangement, or else the conduit 30 acts as a final exit for the water. Figure 7a and Figure 7b represents two ends of different downward facing grooves 34 and 35 that are formed in the shape of a quill and from which the droplets of oil gather and eventually drift off in the direction of the surface of the water. A small hole 32 or 33 is inserted through the base 34 or 35 of the inverted groove. This will delay the drift off of oil until an enlarged droplet has been formed. Such droplet in turn will attract to itself particles of finely divided oil. In Figure 8, 41 represents in plan view an helical wall member extending from its outer end 42 adjacent to it entry point 40 to its inner end 43 and defining between locations 42 and 43 an helical path 44 of progressively diminishing radius A circular outlet aperture in the base member is on which the helical wall stands is represented at 45, and 46 represents the inlet of an oil removal pipe that extends upwardly through the aperture 45 to the location of the vortex of floating oil when formed within the vortex chamber. Preferably, the height of the level of the upper rim of the wall member 41 of the helix is progressively lowered along the direction towards the centre 47 as indicated in Figure 9.

In Figure 9, the representation of the assembly containing embodiment of features of the invention is designated as 60. Primary mixture as defined above enters the vortex chamber 50 through the entry point 40 and is guided by the helical wall 41 along the helical path 44. The drag effect on the liquid constrained to follow the helical path results in the formation of a vortex in which a layer of oil accumulates on the surface which in due course becomes itself a floating oil vortex 51 that hangs suspended in the configuration of an inverted bell curve above the helical wall. As more primary mixture enters the vortex chamber, more oil accretes to the oil vortex 51. The surface of the oil reaches and eventually supersedes the upper rim of the oil removal pipe 46. Oil spills over the rim and flows down the pipe 46 for collection. The secondary mixture as defined above passes through the central aperture 45 in the base of the vortex chamber into an inner conduit 20 which extends downwardly to 52 shortly above the bottom of the lower housing 60. 52 forms an entry to the zone which contains one or more Lemer plates as described above, both unitary or in the form of stacked plates as herein defined or any combination of unitary and stacked plates in series. The secondary mixture travels upwardly in contact with the downwardly facing, submerged and tilted grooves 54 disposed between corresponding ridges, the depth of each groove being arranged to increase progressively simultaneously with a progressively decrease in the mean angle (as defined above) between the groove sides. On reaching the top of 54 by 53 at the left of baffle 58, the oil depleted secondary mixture is sent down the channel 55 between the baffle 58 and the upward facing grooves backing the corresponding downwardly facing grooves 54 and enter at the bottom the next downwardly facing grooves 56; and the process is repeated. The doubly oil depleted secondary mixture passes through channel 57 and makes its exit through pipe 59.

The droplets separated from the secondary mixture break off from the tops of the grooves 54 and 56 and float away upwardly until they are temporarily caught in a trap in the space 61 between the wall 62 of the housing, the lower housing and the outer wall of the vortex chamber 50. The oil is released into the vortex chamber at the surface of the liquid present by one or more apertures 63 pointed upwardly in the direction of flow of the whirling hquid when present in the vortex chamber and in most part will eventually join the floating oil vortex. In a useful embodiment of the invention, the oil can be carried by flexible tubes 70 which constitute the extension of the several apertures 63. Each tube has a float 71 at its end further away from the wall of the vortex chamber to provide buoyant support to the outlet of the flexible tube 70 attached to it. The float 71 and with it the outlet of the flexible tube (not shown) rise and fall with the surface of the hquid in the vortex chamber. In this way, the level of the outlet becomes self adjusting. In another embodiment of the invention, a one way flap valve is used to traverse the access via the one or more apertures 63 to the vortex chamber of the droplets and/or accumulated droplets emanating from the secondary mixture. The construction of the flap valve is responsive to the upward pressure of the accumulated droplets of oil, and they are let through upwardly to the vortex chamber. Liquids in the vortex chamber are barred entry in the reverse direction.

In Figure 10, an embodiment of the invention is represented where the lower housing is divided up into three accumulation zones identified as 90,104 and 105. These are positioned between the outer wall 92 of the lower housing and the inner conduit 88 through which the secondary mixture discharged by the vortex chamber flows downwardly. Barrier plates 96, 99 and 101 are placed downstream behind the accumulation zones so as to direct the recovered, buoyant oil separated by the respective accumulation zones upwardly to apertures at the tops of the respective barrier plates. These feed the oil escape tube 98 that leads to the outlet 100 in or near the discrete, floating oil vortex 83 within the vortex chamber 81. Each accumulation zone in this embodiment is shown to comprise three Lemer plates. The bases of the downward facing grooves are tilted at 45 degrees to the horizontal.

Primary mixture as defined above enters the vortex zone 81 through the entry 82. It encounters a wall member 108 which has the configuration of a helix when seen in plan view. The flowing primary mixture is transformed into a rotating fluid mass within which a non turbulent vortex of oil 83 with its surface level 84 floats on the mixture of water and the residue of the remaining oil (the secondary mixture) around the upper part of the oil removal pipe 86. It is convenient to have the inlet 85 of the pipe 86 is positioned shortly above the hquid level when the vortex chamber contains only water. When the vortex of oil 83 is formed and the vortex chamber continues to receive additional primary mixture, the level of the surface 84 of the floating oil vortex is lifted as the volume of the oil beneath it increases.. The level 84 of the surface of the oil 83 rises and eventually supercedes the level of the inlet rim at 85. Oil spills over the rim and flows down the pipe 86 for collection. The secondary mixture passes through the central aperture 87 in the base of the vortex chamber into an inner conduit 88 which extends downwardly to a position 89 shortly above the floor 110 of the lower housing zone. Below 89, the floor 110 of the lower housing, adapted as the occasion demands, may constitute or comprise a sludge trap for any sludge carried by the secondary mixture.

The secondary mixture then enters the lower chamber. It encounters the stacked, tilted Lemer plates of the first accumulation zone 90, i.e., the downwardly facing plates 90a, 90b and 90c In the embodiment described by reference to Figure 10, the three accumulation zones comprising the Lemer plates together with the barrier plates are disposed in plan view in a series of concentric annuli of different external radii around the centre of the inner conduit 88. On the side view, they are seen as a series of frusto-conical structures around the line that runs along the centre of the inner conduit 88.

Although the preferred form of working the invention is by having a stacked Lemer plate formation in every accumulation zone, any of the accumulation zones may comprise a single or unitary Lemer plate of the present invention, in which case the description set out below should be read as if such unitary plate were the last in line of a stacked plate formation.

The flow of the secondary mixture enters the first accumulation zone at or near its bottom. Its direction of flow is reversed on contact with the Lemer plates, and the secondary mixture flows in the upward direction along the grooves on the underside of the plates. Figure 10 represents the side view of the first plate 90a in the accumulation zone 90 and part of the side view of the plates 90b and 90c. The location of the side view of the base of the grooves of every other downwardly facing plate (and including the barrier plates 96, 99 and 101) in each of accumulation zones 104 and 105 is indicated, but in the interests of simplicity, the sides of the grooves are not shown. (Similar arrangements are made for the representation of the grooves in Figures 11 to 14, mutatis mutandis.) The space taken by the barrier plates 96,99 and 101 may, for the purposes of convenience, be shaped according to the Lemer plates design so as to fit in the order of a succession of Lemer plates. Depending upon the design in question, the barrier plates may have grooves which in part accommodate a Lemer plate or plates in front as well as behind. Figure 10 indicates the bases of the downward facing grooved barrier plates 96, 99 and 101 that conform with this description. Although they have the Lemer plate design or configuration, they are not intended to act like Lemer plates. Their function is to act in the first place as barriers which directs the droplets of floating oil Hberated by the tops of the Lemer plates in the respective accumulation zones to the oil escape aperture or apertures, and, in the second place to lead the secondary mixture downward to the bottom opening by which the secondary mixture enters the next accumulation zone or, in the case of the last accumulation zone in line, the exit. A secondary function occurs when they are supported at the top at or near the oil escape apertures and at the bottom by the floor 110 of the lower chamber. Then the barrier plates may usefully act as supports for the Lemer plates.

The last plate 90c in line of the stacked Lemer plate formation of the accumulation zone 90 extends to the floor of the lower housing 110 at 93. The other plates 90a and 90b in the accumulation zone have their bottoms above the floor to accommodate entry of the secondary mixture to the undersides of the downwardly facing grooved plates. The plate 90c ensures that as the secondary mixture enters at the bottom of the lower housing, the direction of its flow is reversed and the secondary mixture goes up the undersides of the downwardly facing Lemer plates to the location indicated in the region of 94 above the top of the plates.

In a useful embodiment of the present invention, the floor 110 of the lower housing may be made of a layer of resihent, impermeable material on which the bottom edge of the tilted plate 90c rests at 93 to effect a complete seal whereby the direction of flow of the secondary mixture is reversed. (C.p. Figure 6.) The bottom edges of the Lemer plates 104c and 105c, which are respectively the last in line of the stacked plate formation in the second and third accumulation zones 104 and 105 may likewise rest upon the resihent, impermeable material. (So also may the last of the plates in any subsequent accumulation zone and any of the barrier plates). The weight of the plates bearing on the resihent material, supplemented if necessary by additional weights can provide an effective seal. Alternatively, the bottom edges of the said plates may be fitted into sealing slots.

On reaching the region 94 above the top of the Lemer plates in the first accumulation zone, the secondary mixture encounters the barrier plate 96. Its direction is reversed. The barrier plate 96 guides the secondary mixture downwardly until the mixture encounters the opening 97 at or near the bottom of the barrier plate. The mixture then passes through the opening and enters the second accumulation zone 104. There, the process of the first accumulation zone is repeated, mutatis mutandis; and so also for the third accumulation zone 105 and any subsequent accumulation zone in line.

The top of the barrier plate 96 extends to an oil escape aperture leading to oil escape tube 98 that leads upwardly into the vortex chamber 81 where it passes through a flexible part to its outlet 100. The outlet is supported by a buoyant float so that it is located at or near to the surface of the level of the hquid in the vortex chamber. Droplets of recovered oil released by the Lemer plates congregate at the top of the grooves of plates of the first accumulation zone 90. They break off to float upwardly and are guided by the barrier plate 96 to the oil escape aperture, then to oil escape tube 98 and then to the outlet 100.

Accommodation is likewise made for the recovered droplets of oil produced by each of the two other accumulation zones. The recovered oil from the three accumulation zones 90, 104 and 105 proceeds to the outlet 100 and mingles with the oil in the floating oil vortex. This is discharged through the oil removal pipe 86.

A pump 171 acting on the contents of the tube 98 may, optionally be used to urge such contents towards the outlet.

After the secondary mixture has passed through the final accumulation zone, it is passed on as oil depleted water to the exit 102 and discharged along pipe 103. A valve subject to control and or a non return exit value may be provided to control the flow at the exit.

In this embodiment of the invention illustrated by reference to Figure 10, it is seen that the length of the plates varies between the minimum 90a and the maximum 105c. The various Lemer plates will have matching configuration at their tops where the groove sides are deepest and the mean angle between the groove sides is smallest. The difference in the length from 105c to 90a is due to the (notional) cutting off of the annular periphery of the bottom of the conical structure to arrive at the smaller structure. Full length Lemer plates with mean angle extending to 180 degrees may be used in each accumulation zone in the embodiment of the invention illustrated by reference to Figures 13 to 16. In Figure 11, primary mixture enters the advance vortex zone in the chamber 120 and a rotational movement is imparted to it by any of the expedients mentioned above (preferably the "helical wall" system) so as to form within the chamber with a rotating fluid mass within which a floating vortex of oil 121 floats on the secondary mixture around the upper part of the first oil removal pipe 122. The oil is removed through the pipe 122 when the level of the surface of the floating oil rises higher than the level of the rim of the opening into the interior of the pipe. The secondary mixture is passed to an assembly at a lower level comprising a second vortex chamber 123 which has a close fitting lid 130 which insulates the contents of the vortex chamber from the atmosphere. Rotational movement is imparted to the secondary mixture and a smaller floating vortex of oil 124 is formed around the upper part of the second oil removal pipe 125. Oil is removed from the floating oil vortex 124 when the level of the surface of the floating oil has risen to above the level of the rim of the inlet of pipe 125. The mixture of water and the remaining oil (hereinafter called the "tertiary mixture") descends through an inner conduit 126 to the lower part of a lower housing bounded on the right hand side in Figure 11 by an outer wall member 136 and incorporating one or more accumulation zones between the outer wall member and the inner conduit 126.

The description of the separation operation of recovered oil from the tertiary mixture in the embodiment of Figure 11 and Figure 12 will be the same as the operation described by reference to the secondary mixture in the embodiment of Figure 10, mutatis mutandis. A downstream barrier plate for each accumulation zone is shown in Figure 11 as 129, 128 and 127 inFigure 12 as 152, 151 and 150.

In Figure 11 , the tertiary mixture continues through the accumulation zones in turn. Recovered oil is separated out. Barrier plates 129, 128 and 150 guide the oil to a downward facing sealed pool 131 whose exit is a partly flexible escape tube 132 leading upwardly to its outlet 133 at or near the surface of the floating oil vortex in the advance chamber 120. There, the recovered oil joins the oil in the vortex before being carried off by oil removal pipel22.

The passage of the recovered oil through tube 132 to its outlet 133 may be assisted or caused by a pump 172.

The use of an advance vortex zone enhances the efficiency of the separation effected by the apparatus. With the larger part of the oil having been removed beforehand, the device will gain from the fall in the oil content in the mixture. The expedient of using an additional advance vortex may be extended with an additional vortex zone or zones. The outflow of the earlier vortex zone becomes the inflow ofthe later. The lower housing underneath the last vortex zone may be adapted to send the recovered oil to any ofthe earlier vortex chambers, preferably the first. After the tertiary mixture has been through the last accumulation zone, the oil depleted water flows through exit 134. A renewable, conventional filter matrix 135 may be positioned in its path to trap the very fine particles of oil that have survived the previous separations.

In Figure 12, an advance vortex zone in chamber 140 is held in water contaminated by a floating oil slick or the like and is connected through pipes 144 and 145 to a vortex zone within the chamber 146 and a lower housing arrangement. The mouth 139 ofthe chamber 140 opens to receive a primary mixture which enters the chamber 140 at the water line. The vortex zone is adapted to impart a rotational movement to the liquids, preferably by means ofthe aforesaid "hehcal wall" structure 160. There is formed within the vortex chamber 140 a vortex of floating oil 141 with its surface level at 142 which floats on the secondary mixture around the upper part ofthe oil removal pipe 143. The oil is removed when the level o the surface 142 rises higher than the level ofthe opening into the interior ofthe pipe.

The secondary mixture is passed to second vortex zone contained in the chamber 146, and rotational movement is likewise imparted to it, and a smaller, floating oil vortex with its surface level at 147 is formed. The oil is removed by a second oil removal pipe 148 when the surface ofthe oi 147 rises higher than the level ofthe opening into the interior ofthe pipe.

The chamber 146 overlies a lower housing arrangements bounded in Figure 12 by a wall member 159. The mixture of water and remaining oil, ("the tertiary mixture") descends through an inner conduit 149, and it continues through the accumulation zones in turn. The recovered oil separated out in each accumulation zone is guided by the barrier plates 152,151 and 150 to a downward facing pool whose exit is a partly flexible escape tube leading upwardly to its outlet 155 at or near the level ofthe surface 142 ofthe floating oil vortex in the advance vortex chamber 140. There, the recovered oil mingles with the oil in the floating vortex 141 before being carried offby oil removal pipe 143. The passage ofthe oil through the tube towards outlet 155 may be wholly caused or assisted by pump 173.

As can be seen from Figure 12, both the vortex zones operate at and below the water line, and the whole ofthe lower housing is submerged. So long as the vortex zone 146 receives a fresh supply of tertiary mixture, the volume of recovered oil separated in the lower housing will gradually increase until the ever increasing volume ofthe buoyant oil becomes sufficient to get the upper layers ofthe oil up the tube 154 to emerge at its outlet 155.

The arrangement of Figure 12 may be used in the face of a strong tide or current. It may also be used in other circumstances e.g. if a strong flow of primary mixture entering the mouth 139 ofthe advance vortex chamber 140 is artificially caused or encouraged by, for example, a pump acting on the oil depleted water in the pipe 156 leading to the final exit 157 or else an outboard engine driving a propellor 158 which draws out the oil depleted water from the final exit 157. The same arrangement may be used as part of a conventional oil clearance vessel, e.g. with a conventional divergent pair of booms situated in front ofthe mouth 139 ofthe advance zone to concentrate the floating oil prior to its entering the vortex chamber. Figure 13 represents an embodiment of a separator ofthe invention for separating oil and water, and a valve to govern the flow of oil depleted water from the exit. In the separator, the secondary mixture (or tertiary etc. mixture) passes down from the vortex zone along a path that is constituted between the lower housing and an envelope which covers the lower housing. The mixture is admitted from below to the first accumulation zone and proceeds to the second accumulation zone whose base is on a higher level than that o the first.

In Figure 13, primary mixture 180 as defined above enters the vortex zone 181 through the entry 182. The vortex zone inFigure 13 is constituted by a bottomless vortex zone. The primary mixture encounters a hehcal wall member 188 which transforms it into a whirling fluid mass within which a non turbulent floating vortex of oil 183 with its surface 184 floats on the secondary mixture and the upper rim 185 ofthe opening to the oil removal pipe 186 is positioned to take away the oil in the manner outlined above in relation to relation to the embodiments described by reference to Figures 9 to 12, mutatis mutandis. The secondary mixture flows downwardly from the hehcal wall member 188 through the outer conduit 208 formed between the outer wall ofthe lower housing 195 and the envelope 201. It enters the lower housing below the Lemer plates ofthe first of three accumulation zones 190,191 and 192. (In the hope of making Figure 13 easier to understand, the three accumulations zones are shown to contain a limited number of Lemer plates each; but it will be understood that the number of Lemer plates in such stacked group may vary from time to time on a wider range.)

In Figures 13 and 14, each ofthe bases ofthe second and later accumulation zone is disposed above the base ofthe previous accumulation zone in line. This can confer a substantial benefit. The capacity ofthe apparatus may be expanded by adding any number within reason of accumulation zones on top o the accumulation zone or zones already present. Some or all of them may be of different capacities, and some or all of them may be identical. Moreover, any number of accumulation zones within reason may occupy in line the "ground floor" and any ofthe "upper stories" above. This is a significant advance over the having the accumulations zones disposed in line so that their respective bases are on the same level as the first accumulation's base. Once the idea of having the bases ofthe accumulation zones built upwardly in sequence, the manner ofthe support ofthe accumulation zones becomes an engineering problem. On ships and piers or and a whole range of industrial applications, the addition of an extra accumulation zone would normally only add less than a quarter of an unit at the most to the height ofthe lower housing which contains the first accumulation zone (or several accumulation zones mounted vertically) where the diameter or breadth ofthe lower housing is one unit.

In Figures 13 and 14, the second and later accumulation zones are comprised within a space defined at its lower end by a platform which extends from the last Lemer plate ofthe accumulation zone below and reaches out to support the last Lemer plate ofthe second or later accumulation zones as depicted in Figures 13 and 14.

In Figure 13 the secondary mixture is guided to the first accumulation zone 190. The subsequent passage is through the second accumulation zone 191 above, and then the third accumulation zone 192 above 191. After the last accumulation zone, the oil depleted secondary mixture passes out ofthe lower housing at 204 and into the final exit pipe 205 which may be monitored to keep the lower housing full of a flow of hquid. The pipe 205 may carry a renewable, conventional filter matrix (not shown) in its path to trap the very fine particles of oil which have survived the previous separations.

In each ofthe second and subsequent accumulation zones, the last Lemer plate downstream extends to the floor ofthe platform upon which the accumulation zone is based.

Figure 13 represents the side view ofthe first Lemer plate 199 in the first accumulation zone 190. The location ofthe base line of each ofthe grooves of every other downwardly facing plate (and including the barrier plates 193,194 and the side wall ofthe lower housing 195) in each ofthe accumulation zones 190, 191 and 192 is indicated; but in the interest of simplicity, the sides ofthe grooves are not shown.

The largest droplets of oil carried into the lower housing or separated by the Lemer plates ofthe first accumulation zone 190 will float upwardly to a vertical escape tube 198 under the guidance ofthe barrier plate 193 and is discharged to the floating oil vortex 183 at the outlet 200. The Lemer plates within the accumulation zones 191 and 192 act to separate further oil which floats upwardly under the respective guidance ofthe barrier plate 194 and the side wall 195 to the apertures 206 and 207 respectively leading to the main oil escape tube 198. There, the further oil joins with the recovered oil from the Lemer plates ofthe accumulation zone 190. All the recovered oil from the secondary mixture ends up at the outlet 200 where it mingles with the floating oil 183 and eventually is carried away by the pipe 186. A pump 203 acting on the contents of tube 198 may, optionally, be used to urge such contents towards the outlet 200. The final exit ofthe oil depleted water from the apparatus will be monitored to keep the lower housing, the vortex zone and the outer conduit full of a flow of hquid. The buoyant oil travelling up the tube 198 will generally find its way to the outlet 200 without the assistance of a pump 203. Downstream ofthe exit, a valve 299 mentioned below may govern the flow.

In an alternative embodiment, the bottomless vortex zone as depicted in Figures 13 and 14 . may be substituted by a vortex zone contained within a vortex chamber as referred to in Figures 10 to 12. Also, the secondary mixture from the vortex zone may travel to the bottom ofthe lower housing by an inner conduit (C.p Figures 10 to 12) and be released into the first accumulation zone, and the secondary mixture and recovered oil follow the same pathways as the secondary mixture and recovered oil, mutatis mutandis.

The distance apart ofthe Lemer plates within a group in any accumulation zone should be adjusted so that the peculiar disposition and geometry ofthe Lemer plates work together to extract a satisfactory amount of recoverable oil from the oil contaminated water passing through. The constitution and viscosity ofthe oil in the water and the temperature of operation are matters to be taken into account. The stacked Lemer plates in a group that occupies an accumulation zone should be close enough together to enable the one Lemer plate to influence and be influenced by its neighbour. The first Lemer plate 199 in the accumulation zone 190 can act in response to the proximity of a Lemer plate stuck on top ofthe conical projection ofthe boss construction 202. In the accumulation zones 191 and 192, the first Lemer plates act in response to the proximity ofthe barrier plates 193 and 194 respectively.

Depending on the thickness ofthe Lemer plates, a distance centre to centre ofthe order of less than three, and preferably two centimetres or less at the tops ofthe Lemer plates is useful. Where the oil and water mixture is free of solids or sludge, the distance between the sides of the Lemer plates may be five to fifteen millimetres with eight millimetres a satisfactory working average. The distance apart further down is not so crucial since it is at the tops ofthe plates that the mixture rubs against the grooves of greatest area and comes into contact with the sides which brings the particles in the mixture closer together. Where stacked plates are used, particularly in the radially disposed grooves ofthe Lemer plates as described in Figures 10 to 16 herein, the grooves ofthe one Lemer plate will match the ridges ofthe nearest neighbour, and vice versa. The distance apart ofthe bases ofthe Lemer plates should not less than the distance apart at the tops. In general, the bases should be no more than three times the distance apart at the tops, and, preferably, half that amount or less. The space taken by the barrier plates 193,194 and 195 (which doubles as the outer skin ofthe lower housing) may, for the purposes of convenience, be shaped according to the Lemer plate design so as to fit in the order of a succession ofthe Lemer plates. Upstream, the barrier plates 194 and 195 will have downward facing grooves to assist the recovered oil droplets from the accumulation zones immediately behind the barrier plates to find their way to the respective restricted oil escape apertures 206 and 207 above. Downstream, the corresponding ridges enable the barrier plates to fit into the order ofthe succession the Lemer plates which follow. As mentioned earlier in this Specification, the barrier plates may usefully act as reinforced supports for the Lemer plates.

In Figure 13, the path ofthe secondary mixture from the vortex zone towards the position below the lower housing is defined by the generous space provided by the outer conduit 208 between the side 195 ofthe lower housing and the envelope 201 which allows the secondary mixture to flow relatively slowly and practically unimpeded by any barrier. This will encourage a certain amount ofthe droplets of oil that have escaped the floating oil vortex 183 to join together and travel up against the secondary mixture flow and join the water/oil interface of the floating oil vortex.

In the lower housing itself, an enlarged space is provided for the downward flow ofthe secondary mixture in advance ofthe barrier plates 193 and 194 and the side 195. This is to encourage droplets of oil to follow the barrier plates upwardly to where they can enter the escape tube 198 which guides them to the outlet 200. The recovered oil from the Lemer plates as well as any oil that is recovered from the conduit 208 join the oil in the floating vortex 183 before being carried offby the oil removal pipe 186.

One or more sludge baffle plates fitted 259 transverse to the flow direction ofthe secondary mixture may be affixed to the envelope 201 below the lower housing. The mixture of water and oil is allowed to pass on over the baffle plates and on to the first accumulation zone. In a non turbulent passage ofthe flow promoted by the space allowed between the inner housing and the envelope, the sludge is collected in front ofthe baffle plate or plates and may be removed as occasion demands. The space may be enlarged by the adjustment ofthe height ofthe lower housing relative to the envelope 201 as the circumstances require. The exit valve.

Where circumstances make it necessary or desirable that a downstream control ofthe flow of oil depleted water from the lower housing be used, a valve control means may be used in which a conventional gate valve is governed manually or by sensors that respond to fluid surface levels in the vortex zone 181. Alternatively and advantageously, control may be by a weir valve as represented in Figure 13. Such weir valve is contained in a weir valve chamber 299 connected by a feed pipe 298 to the exit pipe 205 ofthe lower housing. Inside the chamber 299, a discharge pipe 290 supports a telescopicaUy mounted pipe member 291 having an expanded open end 292 with an horizontal rim 293. Sealing means (e.g. "O" rings) are provided between the discharge pipe 290 and the mounted pipe member 291. Means (not shown) are provided to regulate the level ofthe height ofthe telescopicaUy mounted pipe member 291 and, with it the level of its expanded end 292 and rim 293. The oU depleted water flows inwardly over the rim 293 and, having passed through the pipe member 291, flows to waste through discharge pipe 290. Precise regulation ofthe upward and downward movement ofthe rim may be secured by providing an appropriate screw threaded telescopic mounting ofthe pipe member 291 on the discharge pipe 290. (It is evident that the role ofthe respective discharge pipe and the mounted pipe member may be interchanged so that the former discharge pipe becomes the feed pipe 298 and the former rim 293 above the mounted pipe member 291 becomes the rim over which hquid flows outwardly to waste.) Figure 14 represents a variant of Figure 13 in which an advance vortex chamber is employed to provide secondary mixture which is fed into the vortex zone as a primary mixture.

In Figure 14, primary mixture 215 enters the vessel 220 and the hehcal waU 210 within forms a rotating fluid mass within which a floating vortex of oU 221 floats on the secondary mixture 211 around the upper part ofthe first oil removal pipe 222. The oU is removed through the pipe 222 when the level ofthe surface ofthe floating oU 221 rises higher than the level ofthe rim 223 ofthe opening into the interior ofthe pipe. The vortex zone produced by the hehcal waU 210 is depicted as a "bottomless zone". Below the bottomless zone, the flow ofthe secondary mixture passes through the relatively enlarged space surrounding 253. The current ofthe flow wiU, temporarily, be restricted. When the mixture of water and oU is contaminated by sludge, a proportion ofthe sludge in the rotating fluid mass wiU migrate to the outer part ofthe vortex zone. On leaving the zone, a diminishing centrifugal force will continue to act upon the sludge as it faUs to the lower part ofthe vessel 220, further promoting the concentration away from the centre ofthe flow which, in plan view, is positioned below the centre ofthe vortex zone. The lower part 212 of vessel 220 is designed to act as a sludge trap. Recoverable sludge w l fall to the bottom from which it is removed as occasion demands by, e.g. a pipe connected to the sludge going through the bottom ofthe vessel 220, or through the surface above.

The secondary mixture exits the vessel 220 through a downwardly directed opening 224 which, in plan view, is positioned below the centre ofthe bottomless vortex zone and as far away as circumstances aUow from the higher concentrations of sludge which faU from the outer parts ofthe vortex zone. Baffles or deflection plates (not shown on Figure 13) may be mounted above the opening 224 to discourage the sludge from getting into the opening. The opening 224 leads to pipe 225 which leads the secondary mixture through the side ofthe vessel 220 and upwardly to the mouth 226 ofthe second vortex zone comprised within the vessel 227. Rotational movement is imparted to the secondary mixture by means ofthe hehcal waU structure 228 and a smaUer, floating oil vortex 229 is formed around the upper part ofthe second oU removal pipe 230 which has an upward facing opening below a rim 231. The oh is removed through pipe 230 when the surface ofthe floating oU eventuaUy rises above the rim 231.

Figure 14 indicates the vortex zones comprised within the vessels 220 and 227 as "bottomless" vortex zones. At the price of forfeiting the advantages that come with such vortex zones, either or both the zones may be "non bottomless" or "partiaUy bottomless" and the vortex zone comprised either entirely or partly within a vortex chamber.

The oU depleted mixture ("the tertiary mixture") resulting from the extraction of oU 229 from the secondary mixture is passed through an outer conduit between an envelope 233 and the side ofthe lower housing 232 to the bottom o the lower housing. There it encounters baffle plate or baffle plates 260 which diminish the proportion of such sludge as the mixture has brought with it from the vessel 220. The mixture then enters the lower housing below the downward facing undersides ofthe Lemer plates ofthe first accumulation zone and the extraction of oil proceeds.

In Figure 14, there are four accumulation zones in the lower chamber 233. The first Lemer plate 263 is next to the cone shaped structure 262 positioned on the base ofthe apparatus. The second accumulation zone is based upon the platform 265 which rests upon the last Lemer plate 268 ofthe first accumulation zone. The third accumulation zone rests on the platform 266 which rests upon the last Lemer plate 269 ofthe second accumulation zone, and the fourth accumulation zone rests upon platform 267 which is rests upon the last Lemer plate 234 ofthe third accumulation zone. (For reasons of clarity, the various accumulation zones represented in Figures 13 and 14 are shown to contain no more than two Lemer plates each. In practice, the accumulation zones may accommodate three or more Lemer plates provided that the last Lemer plate in a vortex zone is sufficiently far from the barrier plate so as to aUow the downward flow ofthe mixture to the opening at or near the bottom ofthe barrier plate to aUow the mixture to go to the next accumulation zone in hne.)

The tertiary mixture continues to make contact with the undersides ofthe Lemer plates of the four accumulation zones in turn, leaving droplets of oU which progressively diminish in size and number before it exits. The recovered oU from the mixture is separated out in each accumulation zone and is guided upwardly by the barrier plates to the escape tube 237 which leads upwardly to its outlet 238 at or near the surface ofthe floating oU vortex 221 in the advance vortex chamber 220. There, the recovered oil mingles with the oil in the floating vortex 221 before being carried offby the oU removal pipe 222. If desired, the passage ofthe oil through the tube may be whoUy caused or assisted by pump 254.

The use and advantages ofthe arrangement of Figure 14 may be compared with the use and advantages ofthe arrangement of Figure 12 herein. The embodiment ofthe invention as Ulustrated by Figure 14 and by Figure 12 may be adapted to separate oύ^' and water from a continuous flow ofthe mixture at large. They are not confined to a flow of oU carried as a slick on a body of water.

InFigure 15, a mixture of oU and water, being the secondary, tertiary etc. mixture 270 enters the first accumulation zone of a "multi storey" lower housing which has three accumulation zones with four stacked Lemer plates in each with the inverted bases ofthe grooves tUted at 45 degrees. The first and last Lemer plates in the first accumulation zone are represented, (partly in broken lines,) in Figure 15. The last has its highest point at 271 at the "acute mean angle" end. It is a full Lemer plate with the mean angle enlarging to 180 degrees at the other end 272. The first Lemer plate in the zone has its highest point at 273. Its inverted base is also tilted at 45 degrees, and the groove ridge line is also ofthe same angle as the last Lemer plate. The first Lemer plate is positioned below the last. Consequently, it loses a portion at the "obtuse" end 275 to compensate. The Lemer plates in between the first and last lose a proportional portions ofthe "obtuse" ends. The result is that the Lemer plates aU have the same minimum mean angle at the tops, but the mean angle at the bottoms will vary depending upon the order they take in the accumulation zone as a whole.

Depending upon the design, the lower Lemer plates wiU have the forward groove sides cut back at the "acute" end if they encroach towards the centre; see the side 276.

The mixture of oU and water proceeds through the stages ofthe lower housing in the manner already referred to, mutatis mutandis. 277 and 278 represent barrier plates, and the upper "stories" ofthe second and third accumulation zones are supported (at least in part) by the last Lemer plates 279 and 280 in the first and second accumulation zones respectively. Figure 16 represents the upward facing surface of Lemer plate 279 of Figure 15 in plan view. The grooves are radiaUy disposed around a focus which is the centre line ofthe escape tube 281. (See Figure 15.) The twelve ridges on the top side represented by the radial lines such as the line between 271 and 272 correspond with twelve downward facing grooves below. The bases project upwardly at an angle of 45 degrees as Figure 15, which is ofthe same scale, demonstrates. The circle in the middle ofthe plan of Figure 16 is due to the gap between the bases ofthe grooves on the opposing sides. The bases ofthe grooves on the periphery such as at 272 have a mean angle of 180 degrees. Between them, they form a complete circle.

Claims

1 ; A method for separating oU and water in a flow in which: i. The flow of oU and water mixture (hereinafter caUed the "primary mixture") enters a vortex zone in which the primary mixture is subjected to rotational forces to form a whirling fluid mass within which part ofthe oil separates to form a discrete, floating oU vortex, such vortex zone comprising outlet means whereby the mixture of water and the residue ofthe remaining oU (hereinafter caUed the "secondary mixture") that support the discrete floating oU vortex escapes from the vortex zone; ii. The secondary mixture is led downwards in a conduit to the bottom or near to the bottom of a chamber (hereinafter called "the lower housing") where it comes into contact with the bottom end of one or more downward facing, submerged and tUted corrugated plates ofthe invention located within the lower housing; iii. The secondary mixture is then fed upwardly to the top of such plate or plates in contact with one or more ofthe adjacent, downward facing, longitudinal grooves disposed between corresponding ridges, the depth of each groove being arranged to increase progressively and simultaneously with a progressively decrease in the mean angle (as defined above) between the groove sides when proceeding along the upward direction, ( the plate or plates being designated herein "the Lemer plate'Or "the Lemer plates"). iv. OU (hereinafter caUed "the recovered oU") from the secondary mixture coUects in the downwardly facing grooves ofthe submerged corrugated plates and moves to the tops'of the grooves where, in the form of droplets, it breaks free to float upwardly within the lower housing; v. Means are provided for transferring the recovered oU to or near to the surface of the discrete floating oU vortex in the vortex zone; vi. Outlet means from the lower housing are provided for the oU depleted secondary mixture; vii. Separate outlet means are provided for the oU in the discrete, floating oU vortex.

2. A method as claimed in claim 1 in which the plates include a pack or packs of stacked Lemer plates and the last plate in a pack of stacked plates is positioned so that the flow wUl pass upwardly between the plates and in the direction of their corrugations.

3. A method as claimed in claim 1 or claim 2 in which the secondary mixture having reached the top ofthe Lemer plate or plates and having been decontaminated to the extent that the oU it contains is got rid of under the step hi. in claim 1 is deflected downwardly to the bottom ofthe next unitary plate or stacked corrugated plates ofthe invention and the step under iii. in claim 1 is repeated.

4. A method as claimed in any ofthe preceding claims in which the primary mixture on entering the vortex zone encounters a waU member device having the configuration in plan view of a helix as herein defined which defines an hehcal path of progressively diminishing radius adapted to receive the flow or a layer ofthe flow ofthe primary mixture and guide the same along the said path so as to form a whirling fluid mass.

5. A method as claimed in any preceding claim in which the inlet within the vortex zone for feeding the separate outlet means for the oU in the discrete, floating oU vortex is placed at a level which is a. higher than the level ofthe surface of water when water alone flows through the vortex zone and, (because ofthe replacement ofthe surface layers of water by oU,) b. lower than the level ofthe surface ofthe discrete, floating oU vortex, and the method of separating oU and water in a flow is engendered automatically by the presence of oU in the primary mixture.

6. A method as claimed in any ofthe preceding claims in which the vortex zone is contained within a vortex chamber and the conduit (hereinafter caUed "the inner conduit") that leads the secondary mixture downwards from the vortex zone is contained within the lower housing.

7. A method as claimed in claims 1 to 5 wherein the vortex zone is a bottomless vortex zone as herein defined.

8. A method as claimed in any preceding claim in which each Lemer plate has an annular disposition with an unbroken line from its centre part to its periphery around the central area ofthe lower housing which accommodates a. either the inner conduit, or b. where the outer conduit is used, the escape tube for the recovered oU on plan view.

9. A method according to claim 8 in which each Lemer plate has the downwardly facing grooves arranged radiaUy around its centre part.

1 . A method as claimed in any ofthe preceding claims wherein the corrugated plates are separated into two or more accumulation zones in line, each accumulation zone having one or more and, preferably, stacked Lemer plates foUowed by a barrier plate a. extending to the top ofthe accumulation zone and having an oU escape aperture at the top through which the recovered oU escapes from the accumulation zone and, b. which has an opening in or below its bottom through which a mixture of water and oU pass into the next accumulation zone in hne.

11. A method as claimed in claim 10 wherein the accumulation zone contains two or more Lemer plates in which the last Lemer plate extends from the bottom to a level that is at least level with the top ofthe preceding Lemer plates in the zone.

12. A method as claimed in claim 10 or claim 11 in which the successive accumulation zones in line are arranged so that their respective bases are on the same level as the first accumulation zone's base.

13. A method as claimed in claim 10 or claim 11 in which the base of a succeeding accumulation zone is located above the base ofthe previous accumulation zone in line.

14. A method as claimed in claim 13 in which part ofthe housing that accommodates the succeeding accumulation zone is supported at least in part by part ofthe housing that accommodates the previous accumulation zone.

15. A method as claimed in claims 1 to 5 and claims 7 to 14 in which the secondary mixture is led downwards to the bottom or near to the bottom ofthe lower housing in an outer conduit located outside the lower housing.

16. A method as claimed in claim 15 in which the outer conduit takes the form of a passage between the exterior waU ofthe lower housing and the inner side of an envelope to contain the lower housing.

17. A method as claimed in any preceding claim where one or more ofthe Lemmer plates have a mean angle at the bottom of 180 degrees.

18. A variation ofthe method as claimed in aU the preceding claims in which:

(a) The original primary mixture enters a first advance vortex chamber and is subjected to rotational forces in the first vortex zone to form a whirling fluid mass within which part ofthe oU separates out from the primary mixture in the first vortex zone to form the first discrete, floating oU vortex;

(b) The secondary mixture that supports the first discrete, floating oU vortex is subjected to a method as claimed in any ofthe preceding claims as if it were a primary mixture, and part ofthe oU present in the secondary mixture separates out to form a second discrete, floating oU vortex and another part is recovered from the lower housing;

(c) Recovered oU from the lower housing is transferred to or near to the second discrete, floating oU vortex or, preferably, to or near to the first discrete, floating oU vortex;

(d) The recovered oU in either case mingles with the discrete, floating oU ofthe chosen vortex for which the separate outlet means is provided.

19. A variation ofthe method as claimed in claim 18 in which:

(e) There are two or more advance vortex chambers in line, each one having a vortex zone where a whirling fluid mass of water and oU results in part of he oU introduced into the several vortex zone separating to form discrete, floating oU vortices;

(f) The procedure under claim 18 is extended with each second and later vortex zone being fed by the mixture of water and oil that has supported the discrete, floating oil vortex of its predecessor;

(g) Recovered oil from the lower housing associated with the last vortex zone in line is transferred to or near to any ofthe discrete, floating oU vortices and preferably to the first in hne;

(h) The recovered oU mingles with the discrete, floating oU ofthe chosen vortex zone for which the separate outlet means is provided.

20. A method as claimed in claim 18 or 19 in which a bottomless vortex zone is contained within an advance chamber and the oil/water mixture passing through the chamber carries with it particles of sludge which exhibit a higher specific gravity than water and which respond to the centrifugal forces within the vortex zone and in large measure avoid the downward facing centraUy positioned exit for the flowing mixture of oU and water as the particles faU into a sludge trap.

21. A method as claimed in any ofthe preceding claims where in a valve control means is used to control the flow of oU depleted water at the final exit.

22. A method as claimed in claim 21 in which the valve is a weir valve contained in a weir valve chamber connected to the final exit and containing a telescopic upright pipe member having an expanded open end which regulates the flow ofthe fluid present in the final exit by acting as a discharge means at a predetermined height for the oU depleted water passed to the chamber.

23. A method as claimed in any ofthe foregoing claims where a renewable matrix adapted to coalesce oh droplets to trap the fine particles of oU that have survived the previous separations is provided before or at the exit.

24. Methods ofthe invention substantiaUy as described by reference to the accompanying drawings.