GB2354461A - Corrugated plate separator with non uniform plate - Google Patents

Abstract

In a corrugated plate separator for separating oil (or a flowable mass of denser particles) from water, the or each plate has adjacent longitudinal grooves disposed between corresponding ridges, and the depth of each groove increases progressively along the length of the groove, simultaneously with a progressive decrease in the angle between the groove sides, as shown in Fig 1. Thus one end of the plate has deep grooves enclosing a small angle and the other end has shallow grooves enclosing a large angle. In the separator of Fig 4, the plates 23, 29 are tilted, with the deep groove end uppermost, and arranged between barrier plates 26. Water containing dispersed globules of oil is supplied through pipe 21 and passes up the grooves in the plate towards the top, where a layer of oil is formed and taken off through overflow pipes (75-77, Fig 6). Each single plate shown may be replaced by a stack of corrugated plates (Fig 5, not shown). The separator may be used with an upstream flow stabiliser (58, Fig 6) and a downstream level control weir (69). An oil filter (66) may also be provided to remove any residual oil. To separate particles from water, the flow is downwardly over the tilted plates.

Description

2354461

CORRUGATED PLATE SEPARATORS Technical Field

Tilted Plate separator oil interceptors are well known. They have been extensively marketed in the United Kingdom and elsewhere. Such interceptors (referred to below as "Tilted Plate Separatore') are provided with banks of tilted plates having corrugations which, in use, extend longitudinally along the direction of fluid flow or, as in the case of the CROSSPAK (T.M.) Compact Separators, transversely and across such direction. When oil contaminated water flows through a Tilted Plate Separator, dispersed globules of oil coalesce to form oil droplets. On achieving a critical size, such droplets rise to the water surface. In an analogous manner, when using such separators to separate from water flowable particles having a higher density than water, the separated particles flow downwardly in a slurry like mass until they are tipped off the lower edges of the corrugated plates. The corrugations described and used according to the prior art are in general of a substantially uniform cross sectional shape along their lengths.

Disclosure of the Invention

According to the present invention, there is provided a corrugated plate for use in separating two masses of flowable matter having different specific gravities which comprises adjacent longitudinal grooves disposed between corresponding ridges, the depth of each groove being arranged to increase progressively simultaneously with a progressive decrease in the mean angle between the groove sides when proceeding along the one or other longitudinal direction.

For the purposes 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 located 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.

Also according to the present invention, there is provided apparatus for separating two masses of flowable matter having different specific gravities which comprises at least one, and preferably a plurality of tilted corrugated plates of the invention.

Furthermore, there is provided a method of separating two such masses by the use of such apparatus.

Although in its broadest scope the present invention provides means and a method for the separation of a liquid and a flowable mass of denser particles, its principal application lies in the provision of means and a method for the separation of two liquids having different respective specific gravities, in particular, oil and water.

A particularly important aspect of the present invention lies in the provision of apparatus as mentioned above for separating two liquids of different specific gravities which comprises downstream valve means for controlling during operation:

i. Fluid flow through the apparatus and/or ii. The fluid surface level or levels within the apparatus.

By "fluid surface level" is meant the uppermost liquid surface level at any point. Thus when water only is present, the fluid surface level will be the surface level of the water. But when a layer of oil floats on the water, the fluid surface level will be the surface level of the oil.

The use of the downstream valve means referred to enhances the efficiency and reliability of the apparatus and facilitates a way of carrying out the invention in which separated liquid of lower specific gravity, e.g. oil may be arranged to flow out of the apparatus of its own accord.

In practice, the preferred form of downstream valve means is a weir valve. In a particularly advantageous embodiment of the present invention, the weir valve is a valve as described in the Specification of our co-pending United Kingdom Patent Application No. GB 9922369.5. For the purposes of this specification, such a weir valve is referred to herein as a "Tulip Valve".

A corrugated plate of the invention when made from sheet material will have on its reverse side complementary ridges and grooves which correspond with the grooves and ridges respectively on its face side. The cross-sectional shape of the individual grooves progressively changes as one progresses in the one or other longitudinal direction along the groove. As the depth of a groove increases, the mean angle between the sides decreases, and vice versa. Thus where a groove has substantially planar side walls, its cross sectional shape at one end will be that of a shallow "V" or, in the limiting case, a straight line. Each arm of the "V" becomes longer as the depth of the groove increases in the direction towards the other end, whilst the angle between the arms becomes smaller; and vice versa in the opposite direction.

When put to use in a tilted plate separator to separate two masses of flowable matter having dfferent specific gravities, each corrugated plate of the invention is arranged to be disposed so that the progressive increase in the depth of the grooves accompanied by a simultaneous decrease in the mean angle between the sides of the grooves occurs in the direction of flow of the flowable matter which:

i. In the case of two liquids, is in most cases along an upwardly inclined path in contact with one or more downwardly facing tilted corrugated plates of the invention, and ii. In the case of a liquid and a flowable mass of denser particles, is along a downwardly inclined path in contact with one or more upwardly facing tilted corrugated plates of the invention. In exceptional cases, the flow in the case of two liquids may be along a downwardly inclined path in contact with one or more downwardly facing tilted corrugated plates of the invention with their grooves increasing in depth or height and the mean angle between the groove walls decreasing the direction of flow Arrangement of the tilted plates.. Tilted plate apparatus of the invention for separating two liquids of different specific gravities is assembled using one or a plurality of separator plates of the invention. Where a plurality of plates is used, the plates may be arranged as:

i. "Stacked Plate'units, or ii. A "Serial Plate" arrangement which consists of a. a series of single plates of the present invention acting in sequence, or b. a series of discrete Stacked Plate units acting in sequence, or C. any combination of a. and b. Stacked Plate unit. By this expression is meant a plurality of corrugated plates of the invention arranged in a stack of substantially parallel tilted plates. Within each stack, each intermediate plate is located in close proximity to its neighbouring plates above and below. As in the case of the single corrugated plate of the invention, during operation, the submerged tilted Stacked Plate unit is arranged for upward flow of oil and water along the downwardly facing grooves with the mean angle between the respective groove walls decreasing along the direction of flow. The oil particles tend to rise towards the apices of the inverted grooves. There, they are constrained to move along a path that becomes progressively more restricted. This promotes coagulation leading to the formation of droplets which eventually break free from the upper edges of the plates and float to the surface.

In the alternative and exceptional situation where the flow is in the downward direction, the flow is directed along downward facing grooves with the mean angle between the respective groove walls decreasing along the direction of flow. This will also result in coagulation and the formation of droplets which are driven by the flow to the lower end of the tilted plate or plates from where they may be swept along to a zone where they rise to the surface.

In the case of the separation of a liquid from a flowable mass of denser particles, a plate or a stack of corrugated plates according to the present invention is disposed so that upwardly facing plates accept a downwardly flowing stream of liquid carrying with it a slurry of the particles. The mean angles between the sides of the upwardly facing grooves decrease along the direction of downward flow. The particles of the slurry are forced closer together. They eventually fall off the lower edge or edges of the plates.

In the case of known tilted plate oil separators, the plates within the plate packs are often inclined at an angle of 45 degrees to the horizontal. This inclination is said to represent the optimum for maximising the effective separation surface area and for promoting the movement of oil along the underside of each plate. The expression "effective separation surface area7' in this context represents the horizontal component of the surface area of the inclined plates.

By adopting the groove design of the present invention, the "effective separation surface area" of the corrugated plates remains unchanged. On the other hand, the sides of the corrugations become progressively steeper and larger in area along the direction of flow.

Plate Divergence Angle" and "Mean Plate Line".

As seen from a side view (i.e. in elevation), the lines of the respective ridges on the upper and under side of each plate will diverge along the direction of flow. For the purposes of this specification, the angle of divergence will be referred to as "the Plate Divergence Angle". The expression "Mean Plate Line" will be used to designate the line that bisects the Plate Divergence Angle.

When using corrugated plates made in accordance with the present invention in tilted plate separators, the Mean Plate Line may be inclined at an angle of 45 degrees to the horizontal. However, it will be a matter of trial and experiment in any particular case to ascertain the most favourable Plate Divergence Angle and Mean Plate Line inclination having regard, inter alia, to the relative proportions of oil and water in the oil/water feed, the rate of flow of the feed, the degree of final separation aimed for and the viscosity of the oil to be separated.

The corrugations of the present invention when seen in plan view may run parallel to each other. However, if desired, such corrugations when seen in plan view may be formed so as to diverge in the direction of flow, or, alternatively, to converge in such direction. The optimum disposition of the corrugations for any particular purpose is arrived at by calculation and/or by trial and error having regard to the particular type of separation called for.

The downwardly facing grooves of the separator plates of the present invention may be provided with additional means to promote the coagulation and/or aggregation of small droplets held in suspension in the feed liquid, e.g. ribs or projections which may, for example, be of a "herringbone" pattern adapted to direct droplets towards the apex of a groove.

The Mean Plate Lines (as defined above) of like facing grooves in adjacent plates within a stack of plates are, in general, aligned parallel to each other. Given a constant overall rate of flow, the geometry of the arrangement will determine at any part along the length of a plate the ratio of the surface contact area to the rate of flow. This ratio will be varied where the distance and/or the angle between the Mean Plate Lines of adjacent plates is varied. This is a consideration which may be borne in mind when seeking the optimum operating design in a particular case. Serial Plate arrangement This arrangement is directed to the separation of two liquids exemplified below by oil and water. In the Serial Plate arrangement, the tilted corrugated plates of the invention are arranged so as to act in sequence within a separation chamber to separate oil from water. The sequence may be of single tilted corrugated plates of the invention or of discrete tilted Stacked Plate units of two or more corrugated plates of the invention, or of single tilted plates and discrete units disposed in any order so as to act in sequence along the line of the fluid flow. The use of Stacked Plate units can enhance the working capacity of a separation chamber that is enclosed within a limited space.

The corrugated plates of the Serial Plate arrangement are aligned in sequence below the water surface within a separation chamber and are tilted so that the mixture comprising oil and water flows in an upward direction in contact with the downwardly facing grooves whose depth increases in the direction of flow. The upper edge of each plate terminates below the liquid surface. Oil and/or droplets of coagulated oil break off the upper edge and rise to the surface. The area where the oil separated out by the first tilted plate or tilted Stacked Plate unit accumulates is referred to for the purposes of this specification as "the first surface accumulation zone". A barrier extending downwardly from above the fluid surface isolates the first surface accumulation zone from a second corresponding surface accumulation zone which receives oil from the upper rim or rims of a second tilted plate or tilted Stacked Plate unit. Likewise, each successive like surface accumulation zone in sequence is isolated by a barrier from its preceding surface accumulation zone. The barrier in each case directs the flow of water down to the vicinity of the base of the separation chamber. The water takes with it the oil that has not been left behind in the previous surface accumulation zone. The fluids flow under the barrier and then upwardly in contact with the downwardly facing grooves of the next grooved plate or Stacked Plate unit as the case may be. Oil that is separated out by such grooved plate or Stacked Plate unit rises to the surface of the next surface accumulation zone. The sequence is repeated as many times as may be deemed necessary or desirable to achieve the required degree of separation. Oil in progressively diminishing amounts accumulates in the successive surface accumulation zones. Oil depleted water is removed from below the liquid surface of the last surface accumulation zone. If desired, such water may be passed through a filter matrix to entrap finely divided oil particles that have survived passage through the separation chamber.

Removal of separated oil: "Density Differential" principle.

The separated oil may be removed from the respective surface accumulation zones by conventional means such as the use of suction pipes, siphons, scoops or buckets.

Preferably, however, the oil is removed according to an important aspect of the present invention according to which separated oil flows out of the apparatus of the invention for collection and storage of its own accord. This aspect brings into play what is referred to herein for the purposes of this Specification as the "Density Differentiar' principle.

When a layer of oil floats on water, the fluid surface level is elevated. This phenomenon is a necessary consequence of the difference between the respective specific gravities of oil and water. Since the specific gravity of floating oil is less than that of the underlying water, it follows that the volume of floating oil required to displace a given volume of water will be greater than the volume of the water displaced. The thicker the layer of the floating oil, the more will its surface level be elevated. Here lies the Density Differential principle.

In order to apply this principle to the separation of oil and water according to the present invention, there are provided within the several surface accumulation zones or within selected zones oil removal pipe inlets leading onto oil removal pipes. The rims of the respective inlets are positioned at a level set by reference to the "normal" working level of water in the separation chamber when the apparatus is put to work. In general, such level is imposed by the level of the separation chamber's fluid outlet. The rims of the several inlets are set at a level that is a short distance above the said normal working level of the water. In an advantageous working embodiment, each inlet member faces upwardly and is adjustably mounted on its associated oil removal pipe so that the inlet, and with it the level of its rim may be raised or lowered.

The rim levels are set so that: i. When water alone flows through the separation chamber, the inlet rims stand proud of the water surface, but ii. When a surrounding or proximate layer of floating oil attains a particular thickness, oil flows over the rim and into the inlet.

During the operation of the Serial Plate separator arrangement, oil will accumulate at the fastest rate within the first surface accumulation zone. The oil will likewise accumulate in the successive surface accumulation zones, but at successively slower rates. Depending on the circumstances and the number of successive surface accumulation zones, the rate of accumulation in any one or more such zones downstream may become negligible. Up to that point, separated oil that attains a fluid surface level above the level of the rim of any removal pipe inlet flows out through the inlet of its own accord.

Following passage through the last surface accumulation zone and the removal of almost all of the oil, the water will still carry with it traces of residual oil in the form of very finely divided particles which are resistant to coagulation into droplets. At that stage, further oil separation may be carried out by passing the water through an oil absorbent matrix filter of a known kind, e.g. a porous polyurethane foam or matted fibre matrix of the kind widely used in oil/water separators. Preferably, this is done by way of a downward flow.

In many current oil/water separators, such matrices or a sequence of such matrices with varying degrees of porosity constitute the principal expedient whereby the oil is separated from water. In such arrangements, they absorb a substantial proportion if not all of the oil that is separated. When the filters become saturated, they must be re-constituted or replaced. This limits their utility where there is a high percentage of oil in the oil/water feed flow. It also entails additional steps and expense in the recovery of the oil from the filter matrices.

The method of the present invention on the other hand ensures that the filter matrix is called upon to deal with no more than residual traces of oil present in the water flowing out of the separation chamber. The cost and effort involved in re-constituting and/or replacing the filter matrix is substantially reduced. Almost all of the oil that was in the original feed mixture flows out of the separation chamber of its own accord for immediate collection and storage. No further steps are necessary for its recovery.

Surface level and flow control.

The operation of the apparatus of the present invention is much enhanced by the use of reliable and accurate downstream means for controlling the fluid surface levels within the apparatus and the related feature of the control of rate of flow through the apparatus. With reliable control of fluid surface levels and/or fluid flow, the apparatus may be adapted for trouble free operation under different conditions and in conjunction with fluids of varying densities and viscosities to give a satisfactory measure of separation.

The control means may comprise a conventional flow control valve such as a gate valve that is operated manually or governed by sensors that respond to fluid surface levels within the separation chamber. 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, control is effected by the use of a Tulip Valve.

A Tulip Valve as referred to herein consists of a weir valve which comprises a pipe member having an expanded upper end bounded at least in part by a rim, the length of the rim or of its horizontal projection being significantly greater than the inner circumference of the pipe member, together with means whereby the vertical disposition of the rim may be regulated so that it acts as the rim of a weir of variable height that governs:

i. the rate of flow of liquid out of, or alternatively into the pipe member and/or ii. respectively the surface level of a body of liquid which for the time being is:

a. connected to liquid within the pipe member, or b. connected to liquid outside the pipe member.

The length of the rim or of its horizontal projection as the case may be will exceed the inner circumference of the pipe member by a factor of at least between one and one third to one and one and a half to one, preferably of at least two to one, advantageously of at least three to one, and usefully of at least four to one. The rim may be contained and maintained within an horizontally disposed plane. Alternatively, the rim may comprise upwardly extending projections. For the purposes of the present invention, it is preferred to use a Tulip Valve having the horizontal planar rim.

The description that follows of the use of the Differential Density principle in the method of the present invention is directed, where relevant, to the use of such a Tulip Valve.

Other valve means may be employed in the same manner as a Tulip Valve, but they afford neither comparable ease of operation nor comparable precision and reliability.

Downstream surface fluid level control.

In the context of the present invention, the Tulip Valve regulates the flow of decontaminated water that has passed through the separation chamber. The setting of its weir rim also determines the fluid surface level upstream in the separation chamber. It can thus be used to set the working surface level of the water that flows through the separation chamber by suitable adjustment of the level of its weir rim. This having been done, the level of the oil removal inlet rims are adjusted so that the inlet rims become positioned at the appropriate short distance above the working surface level of the water. This short distance will represent the desireable extent of the rise of the fluid surface level of a thickening layer of floating oil above the working water level as the layer accumulates additional oil. As soon as the fluid surface level of the oil moves upwardly more than the short distance, oil pours into the inlet. Alternatively, of course, given a satisfactory initial level on the part of the inlet rims, the level of the Tulip Valve weir rim may be adjusted by reference to the level of the weir rims to achieve a like result.

A filter matrix chamber may be included in the main flow stream, either between the separation chamber and the Tulip Valve or downstream of the Tulip Valve.

In addition to facilitating the application of the Density Differential principle, the Tulip Valve may be usefully employed in regulating precisely and reliably the rate of flow through the apparatus. Advantage may be taken of the ease and potential high precision of its operation. In this connection, reference is made to the text of the aforesaid Specification of United Kingdom Patent Application No. GB 9922369.5.

Upstream Stabilisation.

There are circumstances where the manner of the transference and delivery of the oil and water feed mixture to the separation chamber can give rise to random irregularities in the rate of flow and to the transmission of disruptive elements within the flow. For example, direct pumping of an oil/water mixture can result in the transmission of turbulence, pulsations and/or vibrations which can be prejudicial to the stability and smooth running of the separation process. The situation is aggravated when air is admixed with the oil/water mixture. Such admixture is inevitable when the oil/water feed mixture is drawn from a surface oil skimmer such as the skimmer described in the Specification of our copending International Patent Application No. PCT/GB 99/01327. In this and in other cases, it is desirable to stabilise the flow before it enters the separation chamber.

Upstream stabilisation of the feed flow before it enters the separation chamber is brought about by passing the flow through a stabilisation. chamber whereby such turbulence, pulsations and vibrations are dampened or eliminated. Such a stabilisation chamber is described in the Specification of our co-pending United Kingdom Patent Application No.GB 9922368.7. It houses, or else it may consist of a device that is referred to in that Specification and herein as the "Clock Spring Guide". The Clock Spring Guide operates to convert a liquid flow into a vortex. It comprises a wall member in the form of an helix when seen in plan view that stands on a base member so as to define an helical path of progressively diminishing radius adapted to receive the flow and guide the same along the said path to the zone around the centre of the helix, such zone comprising liquid outlet means passing through the base member. Seen from above, the helical wall member resembles an unwound spiral clock spring, the inner end of which stops short of the geometrical centre of the helix and preferably stops short of the outlet means. Hence the designation "Clock Spring Guide".

By passing the feed mixture delivered by the pump along the spiralling helical path that fies between the helical walls of the Clock Spring Guide, the said disruptive elements are dampened down. Where substantially all the flow passes between the walls, then for all practical purposes, the disruptive elements are eliminated. This enables a smooth, turbulence free flow to enter the separation chamber.

Where the apparatus of the invention receives its feed mixture by way of gravity flow from a tank or reservoir, the problems referred to above seldom arise.

The invention will now be described by reference to the schematic drawings appended hereto in which:

Figure I represents a corrugated plate with grooves formed in accordance with the present invention.

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 a separation chamber which houses a Serial Plate arrangement of discreet unitary grooved plates of the invention and barrier plates disposed in series.

Figure 5 represents a detail of a Stacked Plate unit in a modification of the arrangement of Figure 4 whereby a Stacked Plate unit is substituted for one or more of the unitary grooved plates of Figure 4.

Figures 6 and 7 represent in side view and partial plan view respectively apparatus according to the present invention which includes, disposed in series:

i. An upstream stabilisation chamber; H. A separation chamber of the kind represented in Figure 4 which includes means for the removal of oil pursuant to the application of the Density Differential principle,, iii. A filter chamber containing an oil filter matrix, e.g. matted fibrous polyurethane or porous polyurethane foam adapted to separate out residual oil from water, and iii. A Tulip Valve adapted to control the upstream rate of flow and/or the fluid surface levels within the separation chamber.

In Figure 1, 1 represents a corrugated plate with downwardly facing grooves 2, 3 and 4 and complementary upwardly facing grooves 5 and 6. The outer plate edges, ridges and groove base lines when seen in plan view are arranged to be parallel to each other. 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 "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 I I which represents the location of the base line I I of groove 2.

Adjacent the other end, points 9' and 10' are also located on thedownwardly 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 locations 9' and 10', and the space between the groove walls is progressively constricted.

Figure 2 represents a cross-sectional view of the "shallow groove/large angle" end of a Stacked Plate unit comprising separator plates according to the present invention.

Figure 3 represents a cross-sectional view of the "deep groove/small angle" end of the Stacked Plate unit of Figure 2.

In Figure 4, a mixture of the oil and water to be separated flows through a pipe 21 into a separation chamber 20 which houses a Serial Tilted Plate arrangement of grooved plates of the invention. The pipe outlet 22 directs the mixture against the lower part of the downwardly facing side of the first tilted plate 23 as seen in side view. Tilted plate 23 and its grooves extend from the separation chamber base 27 upwardly to a level below the water surface. The depth of the grooves increases in the upward direction. The oil/water mixture is redirected so that it proceeds upwardly in contact with the downwardly facing grooves of plate 23. Oil from the mixture separates out and rises from the upper edge of the plate to the surface of the water where it floats as a layer 24 within the first surface accumulation zone 25.

Zone 25 is bounded by a barrier plate 26 which extends downwardly from above the fluid surface. At its lower end, it stops short of the base 27 of the separator chamber so as to provide a gap 28. In a useful embodiment of the present invention, base 27 overlies a layer of resilient impermeable material on which the respective bottom edges of the several tilted grooved plates of the invention rest. The weight of the plates bearing on the resilient material, supplemented if necessary by additional weights provides an effective sea]. Alternatively, the bottom edges of the plates may be fitted into sealing slots.

Water and the remainder of the oil that has not been left behind in layer 24 continues its flow downwardly to the vicinity of base 27 of the separator chamber and through the gap 28 beneath the bottom of the barrier 26. The direction of the flow is reversed, and the fluids move upwardly in contact with the grooves on the underside of the next tilted grooved plate of the invention 29. Additional oil breaks off from the upper edge or edges of plate 29 and rises to the surface of the second surface accumulation zone 30 to form a floating layer of oil 3 1.

The process is repeated each time the fluid flow encounters a like combination of barrier and tilted grooved plate of the invention. At each successive surface accumulation zone, the amount of oil left behind diminishes. The number of successive combinations of barrier and grooved plate, and hence of surface accumulation zones, will depend upon the degree of separation sought and the cost advantages or disadvantages of adding finther barrier/grooved plate combinations. The limit is reached when any of the oil that is still carried by the flow of water is in such a finely divided state as to call for other measures for finther extraction. The thickness of the layer of oil in the final oil separation zones, even after prolonged operation may be no more than minimal. Such oil as may be present may in practice be swabbed off the water surface using oleophilic rags, swabs or sponges. Oil depleted water flows out of the separator chamber through outlet 32.

Figure 5 represents schematically in part a Stacked Plate unit that has replaced one of the corrugated plates of the invention in the arrangement shown in Figure 4.

In Figure 5, the shallow grooved ends of a plurality of tilted grooved plates of the invention 41 to 45 inclusive making up a Stacked Plate unit are disposed in longitudinally staggered relationship to each other with the shallow grooved end of the outermost plate 41 extending beyond the corresponding end of its next adjacent grooved plate 42 which in turn extends beyond that of the third, 43, and so on. The bottom edge of plate 41 abuts against the resilient base layer 47 of the separation chamber to provide a seal at 46 in the manner already described, mutatis mutandis, in relation to the unitary grooved plates. Alternatively, the bottom edge may be fitted into a slot that provides an effective seal. Each of the several grooved plates within the Stacked Plate unit extends upwardly and terminates below the surface of a surface accumulation zone. A barrier plate 50 guides the flow of oil contaminated water down to the gap 51 between the bottom of the barrier plate and the base 47 of the separation chamber. The sealed support at 46 ensures that the flow is deflected upwardly so that it progresses in contact with the grooved undersides of the several plates 41 to 45 inclusive. After losing a portion of the oil at the surface accumulation zone located above the plates (not shown), the flow is guided downwardly by barrier plate 55 to the gap 5 6 between the bottom of barrier plate 5 5 and the base 47. It then encounters the lower end of another like tilted Stacked Plate arrangement or, alternatively, the lower end of a single tilted grooved plate of the kind described by reference to Figure 4.

In Figures 6 and 7, 60 represents a separation chamber which comprises a Serial Plate arrangement of tilted corrugated plates of the invention together with their associated barrier plates arranged as described, mutatis mutandis, in Figure 4. Stabilised oil contaminated water from the stabilisation chamber 58 enters the separation chamber through inlet pipe 61. Oil separates out and floats to the surface within the respective surface accumulation zones. Oil depleted water comprising a small percentage only of the oil in the original oil contaminated water flows out of the separation charnber through outlet pipe 65 and into the upper end of an oil separation matrix filter chamber 66. The flow proceeds downwardly through the matrix or matrices 67, 67' and onwardly through pipe 68 to the Tulip Valve chamber 69. The Tulip Valve exit pipe 70 supports a telescopically mounted pipe member 71 having an expanded open end 72 provided with an horizontal rim 73. Sealing means (e.g. "0" rings) are provided between the pipe 70 and the pipe member 71. Means (not shown) are provided to regulate the height of the telescopically mounted pipe member 71 and, with it, the level of its expanded end 72 and the rim 73. 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 71 on the exit pipe 70. Alternatively, such regulation may be effected by rack and pinion means, or screw mounted means or other means well known per se for adjusting the length of intermediate support members.

During operation, oil depleted water from the filter matrix chamber 66 passes through the outlet pipe 68 into the Tulip Valve chamber 69. Its surface level within chamber 66 is governed by the level of the Tulip Valve weir rim 73. This can be varied and set with precision. The fluid connection through pipe 65 to the separation chamber 60 enables the fluid surface level within the separation chamber 60 also to be governed by the level of the Tulip Valve rim 73.

Within the separation chamber 60, layers of floating oil 81, 82 and 83 are represented as having accumulated on the surface of the water in the first 3 surface accumulation zones. Located in such zones are the inlets 75, 76 and 77 of oil removal pipes (not shown). The inlets are represented schematically and for the purpose of explanation in Figures 6 and 7 as being set in the side wall facing sideways. In general and in actual practice, it is preferred that the inlets be located within the respective surface accumulation zones facing upwardly and screw mounted for precise adjustment of the respective vertical levels of the inlet rims.. Such levels are determined by reference to the working level of water within separation chamber 60. Water unaccompanied by oil is passed through the separation chamber. Its level is adjusted so as to arrive at the desired working level by adjustment of the level of the weir rim 73 of the downstream Tulip Valve. When the desired working level of the water has been secured, the inlet rims are set at a level that is at the appropriate short distance above the working level of the water that results in the admission of oil into any inlets when floating oil in its proximity has attained a sufficient thickness.

The setting sequence may be reversed. The level of the inlet rims may be set firstly and the working level of the water secondly by adjustment of the height of the weir rim 73. By reason of the maintained difference in level between the water surface and the inlet rims, water cannot flow out of the separation chamber 60 through any of the inlets in the course of operation.

(In the case where there is no downstream surface regulating means such as a Tulip Valve and the working level of the water is dictated by, for example, the level of the separation chamber's fluid outlet, the necessary adjustments are made to the levels of the inlet rims alone.) As surface oil accumulates in any surface accumulation zone in a continuously thickening layer, the fluid surface level (i.e. that of the floating oil) will rise. Each inlet within a zone (exemplified herein by inlets 75, 76 and 77) is set with its rim at a level so that when the thickness of the oil layer in its particular zone exceeds a certain value, oil will flow over the rim into the inlet and then away through that inlet's associated oil removal pipe.

In Figure 6, the floating oil layer 81 in the first surface accumulation zone within the separation chamber 60 is represented as being thick enough to raise the oil surface level above the rim of inlet 75. Oil spills over into the inlet 75 and is carried away by its associated oil removal pipe (not shown).

Within the second surface accumulation zone, the floating oil layer 82 is represented as being thick enough to raise the oil surface up to the rim of the inlet 76. With the accumulation of additional oil, layer 82 will increase in thickness. As its surface level rises, oil will spill over into inlet 76.

Within the third surface accumulation zone, the surface level of the floating oil layer 83 is represented as not having risen to the level of the rim of inlet 77. In due course, such surface level can be expected to rise until oil eventually spills over into the inlet.

Successively smaller amounts of oil accumulate in the successive downstream surface accumulation zones. Eventually, a stage is reached where it becomes more convenient to remove such surface oil as accumulates in downstream surface accumulation zones using other means, e. g. oleophilic rags, swabs, sponges or the like.

The rate of fluid flow through the separation system and the fluid surface levels within the system may be adjusted rapidly and with precision by raising or lowering the Tulip Valve weir rim 73. If desired, a second Tulip Valve arrangement may be located downstream of the subsisting Tulip Valve so as to accommodate any unexpected and undesired surges in the liquid flow rate through the system. The weir rim of the second Tulip Valve is set at a level that is marginally higher than that of the first. In this way, the effect of a sudden increase or surge in fluid flow is limited to no more than a marginal raising of the fluid surface level within the system.

The stabilisation chamber 58 as represented in Figures 6 and 7 is interposed as may be necessary or desirable between the oil/water feed delivery system and the separation chamber 60. When called upon to operate, a turbulent, pulsating stream prone to internal vibrations is admitted through the inlet 59 to face an encounter with a Clock Spring Guide housed within the chamber. The Guide guides the stream into the helical path that leads towards its central zone between the coils of its wall member 78. The height of the wall member's rim may be evenly maintained along its length, or else, advantageously, it may increase. As the troubled feed stream travels along the helical path, its disruptive elements are palliated. It emerges, much pacified, through the base outlet aperture 79 that leads to a lower chamber 80. There, it is further placated by an encounter with one or more horizontal baffle plates 8 1 disposed across its path before it continues, now flowing serenely through pipe 61 into the separation chamber 60.

Claims (17)

1. A corrugated plate for use in separating two masses of flowable matter having different specific gravities which comprises adjacent longitudinal grooves disposed between corresponding ridges, the depth of each groove being arranged to increase progressively simultaneously with a progressive decrease in the mean angle between the groove sides (as herein defined) when proceeding along the one or other longitudinal direction.

2. Apparatus for separating two masses of flowable matter having different specific gravities which comprises at least one, and preferably a plurality of tilted corrugated plates as claimed in claim 1.

3. Apparatus as claimed in claim 2 adapted to separate a liquid and a flowable mass of particles of higher density in which the corrugated plates are tilted so as to allow downward flow of the liquid and particles to be separated over the upwardly facing surfaces of the plates along the direction of the grooves that increase progressively in the depth in the direction of flow.

4. Apparatus as claimed in claim 2 adapted to separate two liquids of different specific gravities (exemplified below by oil and water) which comprises a separation chamber together with means whereby a flow of the oil and water to be separated (referred to below as "the feed flow) is caused to impinge against the lower end of one or more tilted plates located within the chamber and proceed upwardly in contact with the downwardly facing surface of the plate or plates along the direction in which the depth of the grooves increases progressively as the flow proceeds.

5. Apparatus as claimed in claim 4 which comprises downstream valve means for controlling the fluid surface level or levels within the separation chwnber.

6. Apparatus as claimed in claim 5 in which the downstream valve means is constituted by a Tulip Valve as referred to herein.

7. Apparatus as claimed in either of claims 5 or 6 which comprises oil removal pipe inlets leading out of the separation chamber and in which the downstream valve means is adapted to be set to provide a fluid surface level within the separation chamber i. that is below but close to the level of any or each of the inlet rims when water alone passes through the chamber ii. that will allow oil to flow over such inlet rim into its associated oil removal pipe when the oil surface level rises to the level of the rim upon the accumulation of floating oil around and/or proximate to such inlet rim.

8. Apparatus as claimed in any of claims 4 to 7 which comprises i. a plurality of corrugated plates as claimed in claim I arranged in sequence with each respective lower rim in sealed contact with the base of the separation chamber and each upper rim adapted to be submerged below water level during operation, and ii. barrier means located between successive plates in the sequence, the lower rim of each barrier being located above the base of the separation chamber so as to provide a gap adapted to allow the feed flow to pass below the barrier during operation and the upper rim of each barrier being adapted to extend above the fluid surface level during operation.

9. A modification of the apparatus as claimed in claim 8 in which Stacked Plate units as refer-red to herein are substituted for any or all of the corrugated plates and, in relation to each Stacked Plate unit, the reference to the lower rim in sealed contact with the base of the separation chamber is to be taken to be a reference to the lower rim that is lowest of the lower rims in any particular Stacked Plate unit.

10. Apparatus as claimed in either of claims 8 or 9 in which each or any of the fluid zones between successive barrier means is provided with an oil removal pipe inlet leading out of the separation chamber and in which the downstream valve means is adapted to set a fluid surface level within any such zone i. that is below but close to the level of the inlet rim of the oil removal pipe when water alone passes through the chamber, and I that will allow oil to flow over such inlet rim into its associated oil removal pipe when the oil surface level rises to the level of the rim upon accumulation of floating oil around and/or proximate to the inlet rim.

11. Apparatus as claimed in any of claims 7 to 10 in which the level of the rim of the inlet of any of the oil removal pipes is adjustable vertically.

12. Apparatus as claimed in any of claims 4 to 10 which includes filter matrix means that is located downstream of the separation chamber and adapted to separate fine residual particles of oil from the feed flow.

13. Apparatus as claimed in any of claims 4 to I I which includes fluid flow stabilising means located upstream of the separation chamber.

14. Apparatus as claimed in claim 13 in which the fluid flow stabilising means comprises a chamber that houses the device described herein and referred to as a "Clock Spring Guide".

15. A method of separating oil from water in which an oil and water feed flow is passed through apparatus as claimed in any of claims 4 to 14 above.

16. Apparatus as claimed in any of claims 4 to 14 above substantially as described herein by reference to the drawings.

17. A method as claimed in claim 15 substantially as herein described.