GB2385285A

GB2385285A - Oil/water separation utilising vortex and plate separators

Info

Publication number: GB2385285A
Application number: GB0203757A
Authority: GB
Inventors: Alun Kynric Lewis; Thomas Merlin Maddock
Original assignee: MANTIS OIL SEPARATION Ltd
Current assignee: MANTIS OIL SEPARATION Ltd
Priority date: 2002-02-18
Filing date: 2002-02-18
Publication date: 2003-08-20
Anticipated expiration: 2022-02-18
Also published as: GB0203757D0; GB2385285B

Abstract

Oil is separated from water by means of a vortex separator 12 followed by a plate separator 27, and the oil recovered from the plate separator is transferred back to a floating oil vortex in the vortex separator 12 for removal. The vortex separator 12 has a spiral wall 14 which develops the floating oil vortex 13 when the oil and water mixture enters through inlet pipe 10. Water and residual oil then pass via pipe 23 to the plate separator 27, and downwardly though its closely spaced corrugated plates inclined at an angle of 45{. Oil rises up to the top of the plates, collects in a well 30, and is transferred via escape pipe 31 and pump 33 to an outlet 32 in the floating oil vortex 13, and thence to main oil removal pipe 18. Water depleted of oil is removed from the plate separator 27 through exit 29 and weir valve chamber 49, which controls levels in the system. The vortex separator may expand in size below the vortex zone to encourage the deposition of sludge (Figs 3, 4) and the spiral wall may be modified (14b, Fig 4). More than one vortex separator may be provided.

Description

IMPROVEMENTS IN OIL-WATER SEPARATORS Technical Field This application relates to improvements in the efficiency of plate oil/water separators. By applying the principles of the invention to such a plate separator, (referred to below as'the plate separator",) efficiency of the separation of the oil from the water is considerably increased. This increase is accompanied by a comparable fall in the cost of equipping, cleaning and maintenance of the plate separator. The invention enables a replacement plate separator of much smaller size to do what was achieved by the original separator that it has replaced. The consequent economy is substantial.

An ancillary benefit of the preferred form of the invention is the removal of sludge. The sludge in question is the sludge which is"heavier", (i. e. , 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 denote objects of larger size, in many cases buoyant which are removed if necessary by passing the mixture through a trash rack.

The invention as carried out according to the preferred embodiment ensures that a significant proportion of the sludge may be removed before the entry of the mixture into the plate separator.

The plate separator concept has been used worldwide since its development in the 1950s.

The present invention is applicable to all plate separators in which: i. The flow of oily water (which may or may not be accompanied by sludge) enters the separator through an admission port; ii. The oil is released from the water in the separator by a coalescing medium which coalesces oil globules in an aqueous environment; iii. The buoyant oil rises to the top of the water and is fed out of the plate separator for collection, and iv. The oil depleted water is discharged from an exit outlet.

The expression "plate separator" is defined accordingly for the purposes of this specification.

The plate separator when working contains at least the amount of liquid to cover the operative parts. This may be achieved, inter alia, by controlling the flow through the outlet.

In the United Kingdom, the plate separators designated as the"TPS"Separators (Tilted

Plate Separators) have been widely used and have acquired a dominant position.

The TPS Separator is based upon the principle of using as a coalescing medium a plate pack consisting of a multiple of corrugated, parallel and closely spaced plates inclined at an angle of 45 degrees (or more or less depending upon the application) to the horizontal. The oily water, which may be accompanied by sludge is fed into the separator. Within the plate separator, it is passed through a baffle or, in another design, is directed towards a single corrugated plate so as in each case to spread the flow over the entire cross sectional area of the coalescing separator plate pack On entering the plate pack from the upper end, laminar flow conditions are created.

An oil globule in a groove has only to rise a very short distance to the plate above when it encounters another oil globule. The two oil globule coalesce. Further oil globules join in until a stream is formed which flows up to the top of the corrugated plate. At the top, they form droplets. These break offand, accompanied by the other droplets from the rest of the coalescing plate pack rise in the direction of the surface of the water. Any sludge which consists of heavy particles will slide down within the plate pack and will be deposited below the pack for later collection.

The flow of the oily water may proceed downwards and parallel to the corrugations of the corrugated plates in the coalescing plate pack. The oil liberated from the oily water proceeds upwardly as the water proceeds downwardly giving rise to a"counter current"flow.

Alternatively, the flow of the oily water will proceed horizontally, e. g. at 90 degrees to the direction of the corrugations. The liberated oil follows an upward path, and then the flow is referred to as"the cross flow." The TPS plate separators have been used in refineries, oil fired power stations, coastal and road tankers, oil production platforms and oil terminals, petrol-chemical works, oil storage tanks and surface drainage installations. A standard TPS pack as used in the oil industry will contain from 45 to 50 corrugated plates in an unit 1750mm long by 1000mm wide by 1000mm from base to the tops of the plates. The plates are supported at each end of the pack and are held at a spacing in the order of 20mnL The detailed description of the invention in this specification will be limited to the invention as applied to the TPS separators. It will be understood, however that the invention is not consigned to the TPS plate separators only. The invention in its broader scope will be useful when applied to the range of plate separators which answer to the definition of a plate separator mentioned above.

Disclosure of the Invention.

According to the present invention, there is provided a method of separating oil from water in a flow in which: (i. ) A flow of oily water (hereinafter called'the primary mixture") enters a vortex zone (referred to below as'the principal vortex zone") in which it is subjected to rotational forces to form a whirling fluid mass within which part of the oil separates out to form a discreet, floating oil vortex; (ii. ) The mixture of water and the residue of the remaining oil (hereinafter called'the secondary mixture") is withdrawn from the principal vortex zone and enters admission port of a plate separator as herein defined above; (iii. ) Oil is separated from the water by a coalescing medium within the plate separator and rises in an aqueous environment to the upper regions of the plate separator; (iv. ) Means are provided for the oil separated by the coalescing medium (referred to below as''the recovered oil") to be transferred from the plate separator and to mix with the discreet, floating oil vortex in the principal vortex zone; (v) Outlet means are provided whereby the oil from the discrete, floating oil vortex and the recovered oil that has been mixed with it is withdrawn for collection; (vi. ) Outlet exit means are provided for the discharge of the oil depleted secondary mixture from the plate separator.

The present invention therefore ensures that all the recoverable oil in the flow of oily water eventually finds its way to the principal vortex zone and be recovered through the outlet means.

Reference is made below to how the preferred outlet means is operated.

If desired, the operation of the present invention may be enhanced by the use of reliable and accurate valve control means to control the flow of the oil depleted water at the final exit.

The control means may comprise a conventional flow control valve such as a gate valve governed manually or by sensors that respond to fluid surface levels within the vortex zone.

Alternatively and advantageously, control may be by weir flow control over the rim of a downstream sluice gate. In the preferred embodiment of the invention, the control is effected by the use of 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 upper end which regulates the flow of the fluid flowing through the final exit by acting as a discharge means.

The vertical disposition of the expanded open end may be regulated so that it acts as the

rim of a weir of variable height that governs a. the rate of flow of liquid out of, or, alternately, into the pipe member and/or, b. respectively the surface level of a body of liquid which for the time being is connected to liquid inside, or alternatively outside the pipe member.

The said rim is preferably maintained in an horizontally disposed plane. The pipe may be mounted telescopically on to or within a fixed lower pipe or socket, e. g. by way of a screw mounting, and precise regulation of the weir rim height is attainable.

When the primary mixture is subjected to rotational forces as mentioned in (i. ) above, the greater part of the recoverable oil is left behind in the floating oil vortex which is supported by the secondary mixture. The secondary mixture only carries away a fraction of the recoverable oil. The secondary mixture goes on to the plate separator. The recoverable oil in that fraction is separated out by the coalescing medium, and it eventually finds its way back to the principal oil vortex. From there, an oil removal pipe transfers the whole of the recoverable oil for collection. By applying the process of the present invention to the separation of oil from water, the amount of oil to be extracted by the coalescing medium in the plate separator is much reduced. Other advantages from the carrying out of the process of the invention are referred to below.

The Vortex Zone The rotational forces in the vortex zone may be due to the action of forces acting from outside, e. g. a stirrer or a paddle or else electronically driven'fleas".

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 either of two configurations: a. the wall configuration will be that of a spiral when seen in plan view and which defines a spiral path between the adjacent coils of progressively diminishing radius from the inlet in the direction of the centre. This path is adapted to receive and guide the flow or of a layer of the flow of the primary mixture so as to cause a whirling fluid mass in which the major part of the oil separates to form a discreet floating oil vortex. This wall member will be called for the purposes of this specification'the spiral wall". b. the wall configuration will also be a spiral when seen in plan view. This path is also adapted to receive and guide the flow or of a layer of the flow of the primary mixture so as to cause a whirling fluid mass in which the major part of the oil separates to form a discreet

floating oil vortex. But the sides of each of the coils will lean outwardly away from the centre of the spiral so that at in plan view, the bases of each coil extends further out from the centre than the summits. Such construction will be called for the purposes of this specification"a modified spiral wall".

The vortex zone may be situated in a vortex chamber having a bottom and the chamber comprises outlet means in or near the bottom whereby the secondary mixture escapes for further separation.

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 flow of liquid introduced into the vortex zone is induced to rotate according to any of the expedients mentioned above, but below the vortex zone, there is no"bottom". A discrete floating oil vortex is formed in the vortex zone and is supported by the rotating secondary mixture. On leaving the vortex zone, the secondary mixture flows freely downwardly without interruption. Where the vortex chamber comprises an"incomplete bottom", that is, a bottom that is only partly below the area on plan view affected by the rotational forces above, the vortex zone will be called'the partly bottomless vortex zone".

The bottomless vortex zone may be brought about by attaching the outer coiled curve of the spiral wall or the modified spiral wall to the inner edge of the vessel in which the vortex zone is situated.

The regulation and further regulation of the concentration of oil entering the plate separator.

The original primary mixture may be passed through a preliminary vortex zone (called in this specification'the advance vortex zone") upstream of the principal vortex zone that is connected with and feeds the plate separator. There will appear floating on the secondary mixture the first discrete, floating oil vortex. Outlet means are provided whereby this oil together with any recovered oil transferred from the plate separator is withdrawn for collection.

The secondary mixture from the advance vortex zone is then treated as a primary mixture. It is fed into the principal vortex zone that is connected to the plate separator. A discrete but smaller floating oil vortex supported by a diluted mixture of water and oil is formed. Outlet means are provided as indicated for the advance vortex zone. The mixture of water and the residue of the remaining oil enters the plate separator. The plate separator is called upon to extract oil from a mixture the oil content of which has already been diluted twice by passage through the successive vortex zones.

Similarly, an additional two or more advance vortex zones may be added in line. The water together with the oil that escaped capture in the floating oil vortex in an earlier vortex zone or zones is treated as the "primary mixture" of the next vortex chamber in line. Where there is one advance vortex zone, the plate separator is called upon to extract oil from a mixture that has been through two vortex zones. For the purpose of this specification, the mixture is called a"tertiary mixture"of oil and water. Where there are two advance vortex chambers in line, the mixture will be called a"depleted tertiary mixture".

A substantial proportion of oil can be removed from the mixture which the plate separator has to deal with. Under stable conditions, an advance floating oil vortex will capture in the order of 90 per cent. or more of the oil in the primary mixture. , leaving the secondary mixture with the order of 10 per cent. or less. Where there are two or more advance vortex chambers in line, the proportion of oil left over for the plate separator to work on is reduced substantially. Although there could theoretically be three or more advance vortex chambers in line, (for which the expression ( & c.) may be used), addition of not more than two advance vortex zones in line before the principal vortex zone will be found to be sufficient for most purposes.

The present invention comprises three distinct operations in the separation of oil and water. i. ) The First Operation removes the majority of the oil from the flowing mixture of oil and water. This may be a primary, secondary, tertiary or depleted tertiary mixture ( & c.) as the context permits. This is done by forming a discrete, floating oil vortex which captures most of the oil in the vortex zone or, if an one or more advance vortex zones are used, in the several vortex zones. Each one of the vortex zones mentioned has an outlet for the floating oil. It is preferred as a matter of convenience that the outlets lead to a common discharge pipe or conduit. The water together with the oil which has missed being taken up in the discrete, floating oil vortex or vortices is passed on to the plate separator. ii.) The Second Operation is carried by the coalescing medium in the plate separator and consists of separating the recoverable oil from the flowing secondary, tertiary or depleted tertiary mixture ( & c) as the case may be. The said oil is referred to herein as the recovered oil. iii. ) The Third Operation is to deliver the recovered oil to the discrete, floating oil vortex in the principal vortex zone, or, where any advance vortex zone has been used, to any of

the discrete, floating oil vortices, and preferably, the first in line. The recovered oil mixes with the floating oil in whatever vortex zone it is delivered. Together, they flow through the outlet.

The escape pipe.

The recovered oil floats upwardly from the coalescing medium to the closed roof of the plate separator from which it is taken by an upwardly directed escape pipe which carries it to the discrete, floating oil vortex in the vortex zone. If there are one or more advance vortex zone or zones, the recovered oil is carried upwardly to any one of the vortex zones, and preferably the first in line. It is delivered through at outlet maintained at or near the surface of the floating oil vortex. It mixes with the floating oil of the vortex zone. As referred to already, outlet means are provided for the mixture. Below the surface level of the fluid within the vortex zone, the apparatus which includes the coalescing medium will be full of liquid. The buoyancy of the recovered oil as it proceeds to and through the upwardly directed escape pipe will ensure that the apparatus can readily operate automatically. Any water entrapped by the recovered oil and that travels up the escape pipe will be discharged by the escape pipe outlet into the vortex zone. There, it will find its way to the secondary (or tertiary or depleted tertiary ( & c.)) mixture which supports the floating oil vortex. If desired, a suitable pump may also cause or assist the contents of the escape pipe to arrive at the outlet.

Level of the inlet to the oil removal pipe.

The level of the floating oil vortex generated by the whirling fluid 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 removal pipe or pipes in the vortex or in any advance vortex. In such a vortex, the inlet to the pipe is located at or near to the middle of the vortex zone and at a position a short distance above the level of the water when water alone flows through the vortex zone. With the introduction of oil in the water, whether by way of a primary, secondary, tertiary, or depleted tertiary mixture & c., a discrete, floating oil vortex is formed around the inlet. As more and more oil bearing water 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.

Automatic operation is enhanced by the use of a reliable and accurate downstream means for controlling the fluid surface level within the vortex zone.

The problem of sludge.

An ancillary advantage flows from the practice of this invention in cases where sludge has to be removed from the oily water from which oil is to be separated. The First Operation outlined above under i. ) above may also be used as a preliminary step to precipitate out sludge carried in the flow of the mixture thus reducing the proportion of sludge that enters the plate separator during the Second Operation outlined under ii.) above. The space between the vortex zone and the entry port into the plate separator may be designed to comprise a sludge trap which traps the sludge that falls from the vortex zone. The sludge, which is constituted of materials that are heavier than water, on entering the vortex zone reacts to the centrifugal forces of the whirling fluid mass and is encouraged to congregate and, to some extent, may coagulate 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 vessel in which the zone is situated. This promotes the concentration of the sludge away from the centre of the flow which, in plan view, is positioned below the centre of the vortex zone.

The concentration of the falling sludge at the centre of the flow is lowered by i. the use of a bottomless vortex zone; i. the use of an continuously expanding area through which the flow flows after leaving the vortex zone, and ii. the use of a modified spiral wall as defined above that will direct the sludge to move away from the centre of the flow as it goes through the vortex zone.

A downwardly directed opening which in plan view is positioned below the centre of the vortex zone is employed to take the secondary, tertiary or depleted tertiary ( & c.) mixture to the plate separator. The opening is positioned as far away as circumstances allow from the higher concentrations of sludge which fall from the outer parts of the vortex. Baffles or defection plates may be mounted above the opening to discourage the sludge from getting into the opening.

The sludge removal exercise mentioned above can be repeated in conjunction with a like sludge trap or traps, each one operating below an advance vortex zone. With two or more such advance vortex zones accompanied by a sludge trap in line, the proportion of the sludge entering the plate separator is much reduced.

The present invention extends the scope and application of the plate separator as follows : i. The concentration of the oil in the oily mixture, (the primary mixture) fed into the plate separator is considerably reduced. As a consequence, the purity of the exit water from the plate separator is enhanced. ii. The oil recovered from the plate separator is fed back to the vortex zone and joins the floating oil vortex which contains the major part of the oil originally present in the primary mixture. This facilitates the collection of the entire recoverable oil from the apparatus. iii. The volume of oil per unit of the primary mixture that the plate separator is called upon to deal with is much reduced. Consequently, there is savings in maintenance and cleaning costs and in the replacement of the operative parts, in particular the corrugated plates of the coalescing plate pack. iv. Where an advance vortex zone is used, the mixture which the plate separator is called upon to deal with becomes a highly diluted tertiary mixture of oil in water, and the foregoing advantages are enhanced. Where two or more advance vortex zones in line are used, the enhancement is even greater. v. The apparatus may be adapted to remove heavier than water sludge before a diluted mixture enters the plate separator. Where advance vortex zones are used, the proportion of sludge can be diminished to a very small fraction of its original concentration. vi. The plate separator adapted in accordance with the present invention will enhance the volume of the primary mixture of oil and water dealt with, in some cases several fold.

As a result, the present invention finds application in adverse conditions. A sudden and or unexpected change in the water or oil or sludge in the primary mixture may be accommodated. The plate separator can be called upon to separate no more than a small fraction of the oil from the water, and especially so when one or more advance vortex zones are used. With the use of one or more advance vortex zone, the plate separator is reduced to picking out and separating the fine particles of oil that have not being taken up by one or other of the several floating oil vortices present. vii. The process of the invention promotes the narrowing of the distance between the corrugated plates in the coalescing pack thus bringing the fine particles closer together to coalesce with each other.

viii. The present invention enables the size, weight and bulk of the plate separator to be considerably reduced to perform the same oil/water separation operations as were performed under the prior art. ix. The invention may be set to work automatically when oil contaminates the content of flowing water. The apparatus of the invention can be in a state of inactivity when flowing water flows through it. But as soon as the flowing water has oil added to it, the device can become active. The discrete, floating oil vortex is automatically formed in the principal vortex chamber and joined automatically by the recovered oil from the plate separator coming through the escape pipe. The position of the inlet to the oil removal pipe ensures that the whole of the removable oil is automatically removed by one outlet. If one or more advance vortex zones are used, the method of the invention may be adapted to work automatically as described above.

The invention in its broad aspect covers the device whereby the invention may be put into effect. Accordingly, it covers apparatus which has the combination of the following features, that is to say: A. A component adapted to act as a vortex zone to accommodate rotational forces upon a flow of oily water (the primary mixture) so as to form a whirling fluid mass within which part of the oil separates to form a discrete, floating oil vortex; B. Outlet means adapted to withdraw for collection the oil from the discrete, floating oil vortex; C. Means for withdrawing the water and the residue of the remaining oil (the secondary mixture) from the vortex zone ; D. Means adapted to cause the secondary mixture to enter the admission port of a plate separator as defined herein; E. Means adapted to separate the oil isolated from the secondary mixture by a coalescing medium within the separator; F. Means adapted to transfer the oil so separated to or near to the discrete, floating oil vortex in the vortex zone; G. Means for the discharge of oil depleted secondary mixture from the plate separator.

The outlet means under B. above may advantageously be a oil removal pipe the inlet of which is positioned above the level of the surface of water when water alone flows through the vortex zone and below the level of the surface of the oil when a discrete, floating oil vortex is formed

in the vortex zone.

In addition, the invention covers a modification of the above apparatus in which one or more advance vortex zones are used. Accordingly, it covers apparatus which has the combination of the following features, that is to say: H. The principal vortex zone identified under A. above is connected to one or more components which is or are adapted to act as vortex zones in line, ('the advance vortex zones"), each vortex zone being adapted to accommodate rotational forces upon a flow of oily water so as to form a whirling fluid mass within which part of the oil separates to form a discrete, floating oil vortex; 1. Outlet means are adapted to withdraw for collection the oil from the discrete, floating oil vortex from each vortex zone including the principal vortex zone and the recovered oil mixed with it ; J. The second or later vortex zones, including the principal vortex zone are adapted to receive the water and the residue of the remaining oil that supported the discrete, floating oil vortex of its predecessor ; K. Means adapted to cause the mixture of water and residue of the remaining oil from the principal vortex zone to enter the admission port of a plate separator; L. Means adapted to separate oil from such mixture by a coalescing medium within the plate separator; M. Means to transfer the oil so separated (the recovered oil) to or near to the discrete, floating oil vortex of any of the vortex zones, and preferably the first in line ; N. Means for the discharge of oil depleted water from the plate separator The outlet means under I. above may, advantageously in each vortex zone including the principal vortex zone, be a oil removal pipe the inlet of which is positioned above the level of the surface of water when water alone flows through the vortex zone and below the level of the surface of the oil when a discrete, floating oil vortex is formed in the vortex zone.

A downstream control means referred to in this specification may be added to the apparatus and the modification of such apparatus of the present invention mentioned above.

The invention will now be described by reference to the schematic drawings (not to scale) appended hereto in which the plate separator is a TPS separator comprising a coalescing plate pack consisting of closely spaced corrugated plates inclined at an angle of 45 degrees.

Figure 1 represents, in plan view, a spiral wall of a device in a vortex zone according to the preferred form of the present invention and having at the centre a pipe 5 which constitutes an oil outlet means from the discreet oil floating vortex when formed within the vortex zone.

Figure 2 represents an embodiment of the invention and includes the vortex zone above a sludge trap connected to the admission port of a plate separator of the TPS (Tilted Plate Separator) type, the upper reaches of which in turn is connected to the vortex zone by an escape pipe and, optionally, a downstream weir valve for controlling the flow Figure 3 and Figure 4 represent alternatives to the vortex zone and sludge trap of Figure 2 in which the sludge flows through a continuously expanding area after leaving the vortex zone and a modified spiral wall is used in the vortex zone of Figure 4.

Figure 3 and/or Figure 4 may also represent advance vortex zones as described herein.

In Figure 1,1 represents a plan view of a spiral wall member extending from the outer end 2 to the inner point 3 and defining between the locations 2 and 3 a spiral path 4.5 represents the inlet of an oil removal pipe that extends upwardly to the location of the vortex of floating oil when formed within the vortex zone. Preferably, the height of level of the upper rim of the wall member of the spiral is progressively lowered along the direction towards the centre 3 as indicated in Figure 2 to 4 inclusive.

In Figure 2, primary mixture 10 as defined above enters the principal vessel 12 through the entry 11 at the upper part of vessel 12. On entry, it encounters a wall member 14 of a bottomless vortex zone. The wall member 14 has the spiral configuration of a helix when seen in plan view and defines a spiral path of progressively diminishing radius towards the centre.

The wall member transforms the flowing primary mixture into a whirling fluid mass within which a non-turbulent, discrete floating vortex of oil 13 with its surface layer 15 floats on the mixture of water and the residue of the remaining oil 16, (the secondary mixture). The upper rim 17 which surrounds the inlet of the opening to an oil removal pipe 18 is positioned to take away the oil in the floating vortex. The position of the upper rim 17 may be conveniently adjusted to take away the oil as follows. Water is initially passed through the vortex zone, and the upper rim 17 is positioned just above the water surface. When the floating vortex of oil is formed, the surface level of water is replaced by oil. The surface of the liquid rises. It eventually surmounts the upper rim 17. Oil flows over into the interior of pipe 18 and away for disposal. Where there are one or more advance vortex zones, the oil from any corresponding outlet thereto may join the oil in pipe18.

The rise of the surface level is a significant feature of the working of the present invention.

Where water is passed through the apparatus, the position of the upper rim protects the interior of the oil removal pipe 18. But the presence of oil in the whirling flow will find the oil migrating towards the centre of the whirling liquid. On receiving more oil, it begins to form a floating oil vortex which, with more oil, has its surface layer elevated until it reaches and surmounts the upper rim 17 of the oil removal pipe. Together with the advantages afforded by the escape pipe 31 which leads the oil recovered from the corrugated plates in the coalescing pack, (see below), the apparatus of the invention may be left to work automatically to capture all the recoverable oil from an unregulated flow of water which, on unforseen or unexpected occasions may be contaminated with oil.

The reference to the path of the secondary mixture below will be taken to imply, for the sake of convenience a reference to the path of the tertiary and depleted tertiary mixture ( & c.) where the context admits, mutatis mutandis.

The secondary mixture flows downwardly from the spiral wall member 14 to a relatively enlarged space surrounding 19. The current of the flow will, temporarily, be restricted. When the primary mixture is contaminated by sludge which is heavier than water, a significant proportion of the sludge in the rotating fluid mass will migrate to the outer part of the vortex zone. On leaving the zone, particularly when the vortex zone is a bottomless vortex zone, a diminishing centrifugal force will continue to act upon the sludge as it falls to the lower part of the vessel 12, further promoting the concentration of the sludge away from the centre of the flow which, in plan view, is positioned below the centre of the vortex zone. The lower part of the vessel 12 is designed to act as a sludge trap. Recoverable sludge will fall to the bottom at 20 from which it is removed as occasion demands, by e. g. a pipe extending to the sludge through the bottom of the principal vessel 12 or through the surface above.

The secondary mixture passes upwardly through a downwardly directed opening 21 positioned below the centre of the vortex zone and above the bottom layer of sludge at 20. It is therefore positioned as far away as circumstances allow from the higher concentrations of sludge which fall from the outer parts of the vortex zone. Baffles or deflection plates 22 may be mounted above and below the opening 21 to discourage the sludge from getting into the opening.

The secondary mixture having entered at the opening 21 is led by pipe 23 through

the entry port of the plate separator and enters at 24 the inlet compartment 25 of the plate separator.

The secondary mixture then passes through a flow baffle 26 to dissipate the flow across the width of the pack of coalescing plates which are housed in the housing 27. It enters the housing 27 under laminar flow conditions, and the flow is directed downwardly at 45 degrees to the horizontal towards the bottom of the coalescing plate pack. As a result of the laminar flow, oil globules are released. They rise against the flow of the secondary mixture and coalesce on the undersides of the plates with other globules. Eventually, a stream of globules work their way to the top of the plates. The oil takes on the appearance of droplets which finally break free. Additional oil droplets are freed from the other corrugated plates.

The oil depleted secondary mixture passes through the bottom of the housing of the coalescing plate separator 27 into the outlet compartment 28 and out through the exit 29.

The oil recovered from the secondary mixture by the coalescing plates in the housing 27 flows up to the downwardly facing well 30 that is connected to an escape pipe 31 which enters the vessel 12 containing the vortex zone. This escape pipe has an outlet 32 at or near the surface 15 of the floating oil vortex 13. The outlet 32 is kept at the level 15 of the surface of the vortex 13 or else near to such surface. A float (not shown) or other device provides buoyant support to the outlet 32 so that it may rise and fall with the surface of the liquid in the vortex zone.

When the surface 15 of the oil in the vortex chamber is higher than the inverted well 30, the natural buoyancy of the oil will find its way to the outlet 32. It is important in this case that the apparatus below the level 15 is full of liquid and that control is exercised where necessary upon the volume of oil depleted water that passes through the exit 29. Where the level 15 approaches the level of the downwardly facing well 30, a pump 33 may be used to cause or encourage the oil in the pipe 31 to reach the outlet 32.

The recovered oil from the pipe or tube 31 on reaching the outlet 32 will mingle with the oil in the floating vortex and be carried away by the oil outlet means constituted by the pipe 18.

From time to time, a quantity of water will inevitably pass through the tube or pipe 31 to the outlet 32. The presence of water at outlet 32 should be disregarded. The water will sink through the floating oil vortex to unite with the secondary mixture which supports the oil If circumstances make it necessary or desirable that a downstream control of the level in

the vortex zone be used, the exit 29 may be connected to a feed pipe 48 which is connected to a weir valve chamber 49. Inside the chamber 49, a discharge pipe 40 supports a telescopically mounted pipe member 41 having an expanded open end 42 provided with an horizontal rim 43. Sealing means (e. g. "0" rings) are provided between pipe 40 and the pipe member 41.

Means (not shown) are provided to regulate the height of the telescopically mounted pipe member 41 and, with it, the level of its expanded end 42 and rim 43. Precise regulation of the upward and downward movement of the rim may be secured by providing an appropriate screw threaded telescopic mounting of the pipe 41 on the discharge pipe 40.

Figure 3 represents a vessel 12a and its contents which has the same elements numbered as the vessel represented as 12 in Figure 2 save that the letter"a"is added to the digits in Figure 3 by which the elements are identified. The vessel 12a comprises an expanding area as one goes down below the vortex zone. This helps the falling sludge to avoid in part the downwardly directed opening 21 a that takes in the secondary mixture for delivery into the plate separator.

Figure 4 has the same elements numbered as Figure 3 save that the letter"b"is added to the digits in Figure 4 by which the elements are identified. 14B designates a'"modified spiral wall" as defined above. Figure 4 also comprises an expanding area for vessel 12b for the same purpose as the expanding area for vessel 12a in Figure 3.

An advance vortex zone may be represented by Figure 3 and/or Figure 4. Thus taking Figure 3 first, the oily water which constitutes the primary mixture is subjected in the vessel 12a to rotational forces by the spiral wall 14a in the advance vortex zone. A discrete, floating oil advance vortex 13a is formed. When the surface 15a of the floating oil vortex surmounts the inlet 17a of the oil removal pipe 18a, oil flows into the pipe. The mixture of water and the residue of the remaining oil enter the downwardly directed opening 21a and is led by pipe 23a ; i. ) to the principal vessel 12 through the entry 11 at the upper part of vessel 12; and the separation of recoverable oil from the water proceeds as mentioned above, provided that in the preferred embodiment, the escape pipe 31 leads to the outlet 32a, or ii. ) to a vessel having the same elements as Figure 3. The pipe 23a discharges the mixture into a vessel such as 12a, and the process in Figure 12a is repeated once or more than once, depending upon the dilution sought after, or iii.) into the vessel 12b through the entry lib where the mixture is subjected to rotational forces by the modified spiral wall 14A in the vortex zone and a discrete, floating oil advance vortex 13b is formed. When the surface of the floating oil vortex surmounts

the inlet 17b of the oil removal pipel8b, oil flows into the pipe.

The resultant mixture of water and the oil that has not been taken up by the discrete, floating oil vortices under ii.) and iii.) above is led to the principal vessel 12 and the separation of recoverable oil from the water proceeds as mentioned above. The escape pipe 31 may lead to an outlet in the principal vortex zone or any advance vortex zone such as 32a and/or 32b, and preferably the first in line. Under ii.) and iii) above, the outlet 32a preferably receives the recovered oil from the escape pipe 31 at 32a. In such a case, the outlet for recovered oil in the intermediate advance vortex zones which follow should be discounted.

The oil collected from the discrete, floating oil vortices set up in the principal vortex zone and in the advance vortex zone or zones may conveniently be lumped together in a pipe or conduit to facilitate access.

Claims

CLAIMS 1. A method of separating oil from water in a flow in which: (i. ) The flow of oil and water (hereinafter called "the primary mixture") enters a vortex zone (referred to below as"the principal vortex zone") in which it is subjected to rotational forces to form a whirling fluid mass within which part of the oil separates out to form a discreet, floating oil vortex; (ii.) The mixture of water and the residue of the remaining oil (hereinafter called'the secondary mixture") is withdrawn from the principal vortex zone and enters the admission port of a plate separator as herein defined above ; (iii.) Oil is separated from the water by a coalescing medium within the plate separator and rises in an aqueous environment to the upper regions of the plate separator; (iv. ) Means are provided for the oil separated by the coalescing medium (referred to below as'the recovered oil") to be transferred from the plate separator and to or near to the discreet, floating oil vortex in the principal vortex zone ; (v) Outlet means are provided whereby the oil from the discrete, floating oil vortex and the recovered oil that has been mixed with it is withdrawn for collection ; (vi. ) Outlet exit means are provided for the discharge of the oil depleted secondary mixture from the plate separator.
2. A method as claimed in claim 1 in which the primary mixture on entering the vortex zone encounters a wall member having the configuration of a spiral when seen in plan view which defines a spiral path of progressively diminishing radius adapted to receive the flow or a layer of the flow of the primary mixture and guide the same along the said path so as to form a whirling fluid mass.
3. A method as claimed in claim 1 or in claim 2 in which the outlet means for the oil from the discrete, floating oil vortex is fed by an inlet of a oil removal pipe, the inlet being placed at a level which is a. higher than the level of the surface of water when water alone flows through the vortex zone and b. lower than the level of the surface of the discrete, floating oil vortex.
4. A method as claimed in any preceding claim where the means provided to transfer the recovered oil from the plate separator to or near to the discrete, floating oil vortex in the principal vortex zone comprise a pipe (herein called"an escape pipe") between the upper

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reaches of the plate separator, such pipe having an outlet which is located in or near to the said floating oil.
5. A variation of the method as claimed in any preceding claim in which: a. The original primary mixture enters a first advance vortex zone and is subjected to rotational forces to form a whirling fluid mass within which part of the oil separates out from the primary mixture to form a first discrete, floating oil vortex; b. The secondary mixture that supports the first discrete, floating oil vortex is subjected to a method as claimed in any of the preceding claims as if it were a primary mixture and part of the oil present in the secondary mixture separates out in the principal vortex zone to form a second discrete, floating oil vortex; c. The mixture of water and the residue of the remaining oil that supports the second discrete, floating oil vortex in the principal vortex zone (herein called'the tertiary mixture) is withdrawn from such zone and enters the admission port of the plate separator; d. Oil is separated from the water by the coalescing medium within the plate separator and rises in an aqueous environment to the upper regions of the plate separator; e. Recovered oil from the plate separator is transferred to or near to either of the discrete, floating oil vortices, and preferably the first; f The recovered oil in either case mixes with the discrete, floating oil of the chosen vortex for which outlet means are provided.
6. A variation of the method as claimed in claim 5 in which: g. There are two or more advance vortex zones in line, each one having a vortex zone where a whirling fluid mass of water and oil results in part of the oil introduced into the several vortex zones separating to form discrete, floating oil vortices; h. The procedure under claim 5 is extended with each second and later vortex zone including the principal vortex zone being fed by the mixture of water and oil that has supported the discrete, floating oil vortex of its predecessor; i. Oil is separated from the water by the coalescing medium and recovered oil from the plate separator is transferred to or near to any of the discrete, floating oil vortices and preferably the first in line; j. The recovered oil mixes with the discrete, floating oil of the chosen vortex zone for which outlet means are provided.

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7. A method as claimed in any of the preceding claims in which any vortex zone may be a bottomless vortex zone as defined herein.
8. A method as claimed in any of the preceding claims in which any vortex zone may comprise a modified spiral wall as defined herein.
9. A method as claimed in claim 7 or claim 8 wherein any vortex zone is positioned in a vessel the bottom of which is adapted to form a sludge trap and the mixture of water and the residue of the remaining oil that has not been captured by the discrete, floating oil vortex of the vortex zone flows to the next vortex zone or, as the case may be, flows on to the admission port of a plate separator through an opening which is above the bottom of the vessel and below the centre of the vortex zone when seen in plan view.
10. A method as claimed in claim 9 in which the opening faces downwards.
11. A method as claimed in any of the preceding claims wherein a valve control means is used to control the flow of oil depleted water at the final exit.
12. A method as claimed in claim 11 in which the valve is a weir valve contained in a weir valve chamber connected to the final exit and containing a telescopic pipe member having an expanded, open upper end which regulates the flow of the fluid present through the final exit by acting as a discharge means at a predetermined height for the oil depleted water passing through the chamber.
13. Apparatus for the separation of oil and water in a flow comprising: A. A component adapted to act as a vortex zone to accommodate rotational forces upon a flow of oily water (the primary mixture) so as to form a whirling fluid mass within which part of the oil separates to form a discrete, floating oil vortex; B. Outlet means adapted to withdraw for collection the oil from the discrete, floating oil vortex and any recovered oil mixed with it; C. Means for withdrawing the water and the residue of the remaining oil (the secondary mixture) from the vortex zone; D. Means adapted to cause the secondary mixture to enter the admission port of a plate separator as defined herein; E. Means adapted to separate the oil isolated from the secondary mixture by a coalescing medium within the separator ; F. Means adapted to transfer the oil so separated (the recovered oil) to or near to the discrete, floating oil vortex in the vortex zone;

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G. Means for the discharge of oil depleted secondary mixture from the plate separator.
14. Apparatus as claimed in claim 13 wherein the outlet means mentioned under B. is an oil removal pipe the inlet of which is positioned above the level of the surface of water when water alone flows through the vortex zone and below the level of the surface of the oil when a discrete, floating oil vortex is formed in the vortex zone.
15. Apparatus for separating oil and water in a flow comprising the combination of the following features, that is to say: H. A component adapted to act as a vortex zone having the same features as the component under claim 13 A. above (herein described as'the principal vortex zone); I. Connections between the principal vortex zone and components adapted to act as vortex zones in line, ("the advance vortex zones"), each advance vortex zone being adapted to accommodate rotational forces upon a flow of oily water so as to form a whirling fluid mass within which part of the oil separates to form a discrete, floating oil vortex; J. Outlet means adapted to withdraw for collection the oil from the discrete, floating oil vortex from each vortex zone including the principal vortex zone and any recovered oil mixed with it; K. The second or later vortex zones, including the principal vortex zone are adapted to receive the mixture of water and the residue of the remaining oil that supported the discrete, floating oil vortex of its predecessor; L. Means adapted to cause the mixture of water and residue of the remaining oil from the principal vortex zone to enter the admission port of a plate separator as defined herein; M. Means adapted to separate oil from such mixture by a coalescing medium within the separator; N. Means to transfer the oil so separated (the recovered oil) to or near to the discrete, floating oil vortex of any of the vortex zones, and preferably the first in line; O. Means for the discharge of oil depleted water from the plate separator.
16. Apparatus as claimed in claim 15 wherein the outlet means mentioned under J. is an oil removal pipe the inlet of which is positioned above the level of the surface of water when water alone flows through the vortex zone and below the level of the surface of the oil when a discrete, floating oil vortex is formed in the vortex zone.

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17. Method of the invention substantially as described by reference to the accompanying drawings.

18 Apparatus of the invention substantially as described by reference to the accompanying drawings.

17. Method of the invention substantially as described by reference to the accompanying drawings.

18 Apparatus of the invention substantially as described by reference to the accompanying drawings.

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Amendments to the claims have been filed as follows

1. A method of separating oil from water in a flow in which: (i. ) The flow of oil and water (hereinafter called'the primary mixture") enters a vortex zone (referred to below as'the principal vortex zone") in which it is subjected to rotational forces to form a whirling fluid mass within which part of the oil separates out to form a discreet, floating oil vortex; (ii. ) The mixture of water and the residue of the remaining oil (hereinafter called''the secondary mixture") is withdrawn from the principal vortex zone and enters the admission port of a plate separator comprising a plate pack consisting of a multiple of corrugated, parallel and closely spaced plates inclined to the horizontal ; (iii. ) The secondary mixture enters the plate pack from the upper end and laminar flow conditions are created and oil is separated from the water and rises in an aqueous environment to the upper regions of the plate separator ; (iv. ) Pipe means (herein referred to as"an escape pipe") are provided to transfer the said separated oil (referred to below as'the recovered oil") from the upper regions of the plate separator to mix with the discreet, floating oil vortex in the principal vortex zone; (v) Outlet means are provided whereby the oil from the discrete, floating oil vortex and the recovered oil that has been mixed with it is withdrawn for collection ; (vi. ) Outlet exit means are provided for the discharge of the oil depleted secondary mixture from the plate separator.

2. A method as claimed in claim 1 in which the primary mixture on entering the vortex zone encounters a wall member having the configuration of a spiral when seen in plan view which defines a spiral path of progressively diminishing radius adapted to receive the flow or a layer of the flow of the primary mixture and guide the same along the said path so as to form a whirling fluid mass.

3. A method as claimed in claim 1 or in claim 2 in which the outlet means for the oil from the discrete, floating oil vortex is fed by an inlet of a oil removal pipe, the inlet being placed at a level which is a. higher than the level of the surface of water when water alone flows through the vortex zone and b. lower than the level of the surface of the discrete, floating oil vortex.

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4. A method as claimed in any preceding claim where the escape pipe has an outlet which is located in or near to the said discrete, floating oil vortex in the principal vortex zone.

5. A variation of the method as claimed in any preceding claim in which: a. The original primary mixture enters a first advance vortex zone and is subjected to rotational forces to form a whirling fluid mass within which part of the oil separates out from the primary mixture to form a first discrete, floating oil vortex ; b. The secondary mixture that supports the first discrete, floating oil vortex is subjected to a method as claimed in any of the preceding claims as if it were a primary mixture and part of the oil present in the secondary mixture separates out in the principal vortex zone to form a second discrete, floating oil vortex; c. The mixture of water and the residue of the remaining oil that supports the second discrete, floating oil vortex in the principal vortex zone (herein called"the tertiary mixture) is withdrawn from such zone and enters the admission port of the plate separator, and the procedure of claim 1, (ii) and (iii) repeated, mutatis mutandis; d. Escape pipe means are provided to transfer the recovered oil from the plate separator to or near to either of the discrete, floating oil vortices, and preferably the first; e. The recovered oil in either case mixes with the discrete, floating oil of the chosen vortex and outlet means are provided for the mixture.

6. A variation of the method as claimed in claim 5 in which: g. There are two or more advance vortex zones in line, each one having a vortex zone where a whirling fluid mass of water and oil results in part of the oil introduced into the several vortex zones separating to form discrete, floating oil vortices; h. The procedure under claim 5 is extended with each second and later vortex zone including the principal vortex zone being fed by the mixture of water and oil that has supported the discrete, floating oil vortex of its predecessor; i. Recovered oil is separated from the water that enters the plate separator after the last vortex zone and is transferred via escape pipe means to or near to any of the discrete, floating oil vortices, and preferably the first in line; j. The recovered oil mixes with the discrete, floating oil of the chosen vortex zone for which outlet means are provided for the mixture.

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7. A method as claimed in any of the preceding claims in which any vortex zone may be a bottomless vortex zone as defined herein.

8. A method as claimed in any of the preceding claims in which any vortex zone may comprise a modified spiral wall as defined herein.

9. A method as claimed in claim 7 or claim 8 wherein any vortex zone is positioned in a vessel the bottom of which is adapted to form a sludge trap and the mixture of water and the residue of the remaining oil that has not been captured by the discrete, floating oil vortex of the vortex zone flows to the next vortex zone or, as the case may be, flows on to the admission port of a plate separator through an opening which is above the bottom of the vessel and below the centre of the vortex zone when seen in plan view.

10. A method as claimed in claim 9 in which the opening faces downwards.

11. A method as claimed in any of the preceding claims wherein a valve control means is used to control the flow of oil depleted water at the final exit.

12. A method as claimed in claim 11 in which the valve is a weir valve contained in a weir valve chamber connected to the final exit and containing a telescopic pipe member having an expanded, open upper end which regulates the flow of the fluid present through the final exit by acting as a discharge means at a predetermined height for the oil depleted water passing through the chamber.

13. Apparatus for the separation of oil and water in a flow comprising: A. A component adapted to act as a vortex zone to accommodate rotational forces upon a flow of oily water (the primary mixture) so as to form a whirling fluid mass within which part of the oil separates to form a discrete, floating oil vortex ; B. Outlet means adapted to withdraw for collection the oil from the discrete, floating oil vortex; C. Means for withdrawing the water and the residue of the remaining oil (the secondary mixture) from the vortex zone ; D. Means adapted to cause the secondary mixture to enter the admission port of a plate separator comprising a plate pack as defined herein; E. Means adapted to separate the oil isolated from the secondary mixture by the plate pack within the separator; F. Escape pipe means adapted to transfer the oil so separated (the recovered oil) to or near to the discrete, floating oil vortex in the vortex zone;

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G. Means for the discharge of oil depleted mixture from the plate separator.

14. Apparatus as claimed in claim 13 wherein the outlet means mentioned under B. is an oil removal pipe the inlet of which is positioned above the level of the surface of water when water alone flows through the vortex zone and below the level of the surface of the oil when a discrete, floating oil vortex is formed in the vortex zone.

15. Apparatus for separating oil and water in a flow comprising the combination of the following features, that is to say: H. A component adapted to act as a vortex zone having the same features as the component under claim 13 A. above (herein described as"the principal vortex zone); I. Connections between the principal vortex zone and components adapted to act as vortex zones in line, ("the advance vortex zones"), each advance vortex zone being adapted to accommodate rotational forces upon a flow of oily water so as to form a whirling fluid mass within which part of the oil separates to form a discrete, floating oil vortex; J. Outlet means adapted to withdraw for collection the oil from the discrete, floating oil vortices from each vortex zone including the principal vortex zone and any recovered oil mixed with it; K. The second or later vortex zones, including the principal vortex zone are adapted to receive the mixture of water and the residue of the remaining oil that supported the discrete, floating oil vortex of its predecessor; L. Means adapted to cause the mixture of water and residue of the remaining oil from the principal vortex zone to enter the admission port of a plate separator as defined herein; M. Means adapted to separate oil from such mixture by a plate pack as defined herein within the plate separator; N. Escape pipe means to transfer the oil so separated (the recovered oil) to or near to the discrete, floating oil vortex of any of the vortex zones, and preferably the first in line ; O. Means for the discharge of oil depleted water from the plate separator.

16. Apparatus as claimed in claim 15 wherein the outlet means mentioned under J. is an oil removal pipe the inlet of which is positioned above the level of the surface of water when

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water alone flows through the vortex zone and below the level of the surface of the oil when a discrete, floating oil vortex is formed in the vortex zone.