WO1994015691A1

WO1994015691A1 - A hydraulic separation device

Info

Publication number: WO1994015691A1
Application number: PCT/GB1994/000019
Authority: WO
Inventors: David James Grantham
Original assignee: David James Grantham
Priority date: 1993-01-07
Filing date: 1994-01-06
Publication date: 1994-07-21
Also published as: AU5820794A; GB9300218D0

Abstract

An hydraulic separation device comprises two concentrically arranged radially spaced broad crested weirs (41 and 42). An intermediate baffle (43) is disposed between the weirs. Inlet flow enters the device via a central vertical pipe (40), flows divergently over weir (41), then mainly under the baffle (43) and then over the weir (42). This causes a rapid change of direction and a hydraulic compression which in turn causes certain materials such as oils to aggregate into a more readily separable form for subsequent recovery. The flow through the device may be convergent rather than divergent or a combination of the two. The number of weirs and baffles may be altered as desired.

Description

A HYDRAULIC SEPARATION DEVICE

This invention relates to a hydraulic separation device. The device is particularly, but not exclusively, intended for the treatment of water.

Water discharges can become contaminated with organic chemicals e.g. oils and glycols, by a wide range of industrial and commercial activities. Such contamination can cause serious water pollution problems. The abatement of such pollution could be achieved by removing contaminants from the water, prior to discharge.

The use of broad crested weirs to enhance the separation of separable materials from fluids is referred to in European Patent No. 0 412 658 A3.

There are a number of disadvantages with the device of this patent. The device has an intermediate section which increases its complexity. There are detrimental boundary effects. There is no provision for automatically varying the difference in weir levels or the width of the broad crested weir in accordance with flow rate which both maximises the range of flows that can be treated in a given unit and enables the unit to be "tuned" to a particular flow rate optimising a given unit's treatment efficiency. In addition this enables the second weir to be a non-broad crested variety.

According to the present invention there is provided a hydraulic separation device comprising at least two concentrically arranged circumferential weirs radially spaced from one another, an intermediate baffle disposed between the weirs, means for supplying fluid carrying materials to be separated therefrom to the weirs so that the fluid flows radially over the weirs and through the device to a fluid discharge under conditions of steady laminar flow and means for discharging separated materials.

In a preferred embodiment, one or more of the weirs are broad crested weirs. The means for supplying fluid may be such that the flow through the device is divergent or convergent. When divergent the fluid is supplied via an inlet centrally located within the innermost weir. When convergent, fluid is supplied so as to be evenly distributed concentrically around the outermost weir. The height of one or more of the weirs may be adjustable. The width of one or more of the broad crested weirs may be adjustable. The or each baffle may be partially or completely submerged in operation. The device may be operated at or above atmospheric pressure. The means for supplying fluid may be pressurised to at least 0.25 bar for a given period of time. In order that the invention may be more clearly understood, one embodiment thereof will now be described, by way of example, with reference to the accompanying drawings, in which:-

Figure 1 is a diagrammatic sectional view of an arrangement including a device according to the invention,

Figure 2 is a diagrammatic sectional view of another arrangement including a device according to the invention,

Figure 3 is a diagrammatic sectional view of a further arrangement including a device according to the invention,

Figure 4 is a diagrammatic sectional view of a still further arrangement including a device according to the invention,

Figure 5 is a diagrammatic plan view of a device forming part of the arrangement of Figure 1,2,3 or 4.

Figure 6 is a diagrammatic cross-sectional view of the device of Figure 5 taken along the line X-X of Figure 1 ,

Figure 7 is a diagrammatic plan view of an alternative device to that of Figure 5 forming part of the arrangement of Figures 1,2,3 or 4,

Figure 8 is a diagrammatic cross-sectional view of the device of Figure 7 taken along the line Y-Y of Figure 7,

Figure 9 is a diagrammatic view of part of the device of Figure 5 or Figure 7,

Figure 10 is a diagrammatic view similar to Figure 9 but with a skimmer, and

Figure 11 is a diagrammatic plan view of the part shown in Figure 10.

The ancillary infrastructure delivering the fluid to the device is so configured that the fluid will enter the device under conditions of steady non-turbulent flow. Some possible arrangements of such infrastructure are shown schematically in Figures 1 to 4.

In the arrangement of Figure 1, the fluid 1 is held back by a dam, weir or tank wall 2 and is supplied to a device 3 located on the other side thereof through a communicating passage 4.

In the arrangement of Figure 2, the fluid 11 is contained in a reservoir which is joined by a communicating passage 12 to a chamber 13 which in turn communicates with a device 14.

In the arrangement of Figure 3, the fluid 21 is disposed on both sides of a barrier 22 and devices 23, 24 disposed on opposite sides respectively of the barrier 22 are joined by a communicating passage 25.

In the arrangement of Figure 4, fluid 31 is contained in a reservoir and a passage 32 leads from the reservoir to a device 33. A pump 34 is disposed in the passage 32. A positive displacement pump is preferred.

The device itself may comprise two concentric circular weirs with intermediate baffle (s) . Fluid entering the device is directed radially over a circular broad crested weir, so that it forms a partially drowned hydraulic jump as it flows radially over the weir. The hydraulic compression created by the hydraulic jump will cause certain materials (e.g. oils) to separate from the fluid flow, by causing the materials to aggregate into a more readily separable form, without creating shearing and/or turbulent flow conditions which are detrimental to the subsequent recovery of the separable material.

The fluid stream having flowed radially away from the first broad crested weir, flows towards at least one circular baffle. The baffle (s) are either partially submerged in order to retain surface floating material, or are totally submerged in order to retain settleable material. The main body of the fluid flow will pass either under or over the baffle (s) respectively. The region in between the first weir and the baffle(s) is where the separable material can be removed by conventional separation and/or skimming devices.

Having negotiated the baffle (s) the fluid gravitates towards the lower (second) weir. The level of the top of the second circular weir will be set lower than the level of the first weir sufficient to create the hydraulic conditions needed to form a partially drowned hydraulic jump at the first weir. This will typically (but not exclusively) select for the second weir being of the broad crested type, and having smooth laminar flow freely discharging over it. A given device can be calibrated to perform efficiently over a range of flows by incorporating into the device means for varying the difference in level between the weirs or the width of one or more of the broad crested weirs. This can be achieved by various conventional mechanical engineering means. One of the simplest and perhaps most appropriate for the hydraulic separation device is to so construct the inner weir's support structure so that the weir level can be adjusted by a spindle mechanism for example as per a conventional bellmouth valve arrangement. It is preferable to adjust the inner weir because, being of a smaller diameter it should theoretically be less prone to distortion with regard to horizontal level.

The operational range of flows that can be treated in a given device can be increased by connecting a mechanism that varies the difference between the weir levels or the width of a broad crested weir to another mechanism that gauges the flow rate through the device either directly, or indirectly by monitoring the level of a water surface within the device. This would enable the difference in weir levels, or the width of a broad crested weir to be automatically adjusted to the flow rate through the device, thus providing optimum hydraulic (i.e. separation) conditions over a variable range of flow rates.

The device can be deployed with or without an aeration system, for example, fine bubble diffused air,air entraining vent pipe(s) . The device may be constructed from many types of material, for example, reinforced concrete, plastic, glass fibre reinforced plastic, metal, and wood or a combination of any or all of these. It is considered that the preferred construction for smaller installations will be epoxy coated steelwork, with stainless steel weir plates. Such steelwork devices may be precision engineered under factory conditions. Such factory built devices may be fitted to an appropriately constructed inlet feed arrangement.

A hydraulic separation device incorporating two concentric weirs with intermediate baffle (s) can be configured in one of two ways; either in a divergent flow arrangement, or in a convergent flow arrangement. Devices that incorporate more than two concentric weirs can use either: convergent, divergent, or both types of flow in the one device.

A device employing a divergent flow arrangement with two concentric circular broad crested weirs with partially submerged intermediate baffle is shown diagrammatically in Figures 5 and 6. The inlet flow enters the device via a central vertical pipe 40. The inlet arrangement prior to the device is so arranged that the flow enters the central vertical pipe in a smooth laminar flow condition. This inlet flow condition can be achieved in many ways, some of which are shown diagrammatically in Figures 1 to 4. The fluid having entered vertically through the inlet pipe 40 fixed by any suitable fixing 39 then changes direction, and flows in a direction perpendicular to the direction of the inlet flow, over a circular broad crested weir 41. The diameter of the inlet pipe 40, the velocity of the inlet flow, the width of the broad crested weir, and the downstream flow conditions are such that the fluid flowing over the weir does so under smooth laminar flow conditions, sufficient to create a partially drowned hydraulic jump. The rapid change of direction, and the hydraulic compression created by the hydraulic jump cause certain materials (e.g. oils) to separate from the fluid flow, by causing the materials to aggregate into a more readily separable form, without creating shearing and/or turbulent flow conditions which are detrimental to the subsequent recovery of the separable material.

The fluid stream having flowed radially out over the first broad crested weir 41, flows towards a circular baffle 43. A partially submerged baffle (shown in Figure 6) will retain floating material (an alternative totally submerged baffle would retain settleable material) . The main body of the fluid flow passes under the baffle 43. The region in between the first weir 41 and the baffle 43 is where the floating material can be removed by conventional separation and/or skimming devices. Alternatively, a surface skimming device can be built into the baffle arrangement (see Figures 9, 10 and 11) .

Figures 9 and 10 diagammatically respectively illustrate partial views of the device of Figures 5 and 6 without and with an integral skimming arrangement. Figure 11 is a diagrammatic plan view of the arrangement of Figure 10. Floating material 46 is collected by the baffle 43 from the flow of fluid over the weir 41 as illustrated in Figure 9. As shown in Figures 9 and 10 a buoyant weir 47 is disposed concentrically between the weir 41 and the baffle 43. The floating material is trapped between the baffle 43 and the floating weir 47 and is pumped from a central hopper 48 for discharge.

Once under the baffle 43 the water then flows towards the second circular broad crested weir 42. . The second weir 42 will normally be engineered so that the flow over it is smooth laminar flow freely discharging into a launder channel 49 for collection prior to discharge from the device.

A device employing a convergent flow arrangement with two concentric circular weirs with partially submerged intermediate baffle is shown diagrammatically in Figures 7 and 8. The inlet flow enters the device radially via an inlet feed arrangement involving a central vertical pipe 50 distributing flow to an outer distribution channel 51. The inlet arrangement prior to the device is so arranged that the flow enters the central vertical pipe 50 in a smooth laminar flow condition. This inlet flow condition can be achieved in many ways, some of which are shown diagrammatically in Figures 1 to 4. The fluid having entered the device vertically via the outer distribution channel 51 changes direction, and flows in a direction perpendicular to the direction of the inlet flow, over a circular broad crested weir 52. The diameter of the inlet pipe 50, the velocity of the inlet flow, the width of the broad crested weir 52, and the downstream flow conditions are such that the fluid flowing over the weir 52 does so under smooth laminar flow conditions, sufficient to create a partially drowned hydraulic jump. The rapid change of direction, and the hydraulic compression created by the hydraulic jump cause certain materials (i.e. oils) to separate from the fluid flow, by causing materials to aggregate into a more readily separable form, without creating shearing and/or turbulent flow conditions, which are detrimental to the subsequent recovery of the separable material.

The fluid stream having flowed radially over an outer broad crested weir 52, continues to flow inwards toward a circular baffle 53. A partially submerged baffle (shown in Figure 8) will retain floating material (an alternative totally submerged baffle would retain settleable material) . The main body of the fluid flow passes under the baffle 53. The region in between the outer weir 42 and the baffle 53 is where the floating material can be removed by conventional separation and/or skimming devices. Alternatively a surface skimming device can be built into the baffle arrangement (see Figure 10) .

Once under the baffle 53 the water then flows over a second circular broad crested weir 54. The second weir will normally be engineered so that the flow over it is smooth laminar flow freely discharging into a central sump/hopper 55 for collection prior to discharge via an outlet 56. The sump/hopper 55 can include an air entraining vent pipe 57 (shown in dashed line) to actively aerate the discharge from the device.

The devices' efficiency at a given temperature will typically (but not exclusively) be related to the covalent nature of the separable materials, the ionic nature of the fluid matrix, the difference in levels between the weirs or the width of a broad crested weir, the presence of chemical dispersing agents, and the manner in which the fluid is handled prior to entering the device, particularly with regard to pressurisation. The fluid is preferably pressurised to at least 0.25 bar for a given period of time. The separation device may be operated either at or above atmospheric pressure.

In the above described devices there are no intermediate sections thus reducing complexity. The weirs are circumferential, enabling detrimental boundary effects to be avoided. Provision for automatically varying the difference in weir levels and or the width of broad crested weir in accordance with the flow rate through the devices, enables the second (flow control) weir to be of a non-broad crested variety. The devices can operate with either a divergent radial flow, a convergent radial flow, or a combination of the two, enabling greater design flexibility, including the sequential use of devices e.g. convergent device discharging to divergent device etc. The devices can be used as an oil skimmer in conjunction with conventional oil/water separation technology.

It is expected that oil globules in water, smaller than five microns in diameter will be capable of being separated using the above described devices, in conjunction with conventional water treatment infrastructure. The devices can be used in conjunction with a hydraulic separation process to amongst other things, create a high efficiency oil water separation installation and a glycol (ethylene, and monopropylene) water separation installation.

The devices can be deployed in; streams, rivers, reservoirs, at weirs, lock gates, barrages and dams in order to improve the quality of the water passing through conventional control structures employed at these locations, with or without a means of aerating the water so treated.

It will be appreciated that the above embodiment has been described by way of example only and that many variations are possible without departing from the scope of the invention.

Claims

1. A hydraulic separation device comprising at least two concentrically arranged circumferential weirs radially spaced from one another, an intermediate baffle disposed between the weirs, means for supplying fluid carrying materials to be separated therefrom to the weirs so that the fluid flows radially over the weirs and through the device to a fluid discharge under conditions of steady laminar flow and means for discharging separated materials.

2. A hydraulic separation device as claimed in claim 1, in which one or more of the weirs are broad crested weirs.

3. A hydraulic separation device as claimed in claim 1 or 2, in which the means for supplying fluid is operative to produce a divergent flow through the device.

4. A hydraulic separation device as claimed in claim 1 or 2, in which the means for supplying fluid is operative to produce a convergent flow through the device.

5. A hydraulic separation device as claimed in claim 3, in which the means for supplying comprises an inlet centrally located within the innermost weir.

6. A hydraulic separation device as claimed in claim 4, in which the means for supplying comprises a means for distributing fluid evenly around the outermost weir.

7. A hydraulic separation device as claimed in any preceding claim, in which the height of one or more of the weirs is adjustable.

8. A hydraulic separation device as claimed in claim 2 or any of claims 3 to 7 when appendant directly or indirectly to claim 2, in which the width of one or more of the broad crested weirs is adjustable.

9. A hydraulic separation device as claimed in any preceding claim, in which the baffle may be partially or completely submerged in operation.

10. A hydraulic separation device as claimed in any preceding claim, in which means are provided for pressurising the fluid supplied by the means for supplying.

11. A hydraulic separation device as claimed in claim 10, in which the means for pressurising are operative to pressurise the fluid to at least 0.25 bar for a given period of time.

12. A hydraulic separation device as claimed in any preceding claim, arranged to be operated at or above atmospheric pressure.