GB2271298A - Settling tank with vortex valve outlet - Google Patents

Abstract

A settling tank includes a vortex valve, in the form of a horizontal cylindrical chamber with a tangential inlet 51 and axial outlet 52, to remove floating matter from a region thereof. In Figs. 1 - 3 the chamber extends radially between an annular dip plate 8 and the outer wall of the tank, at the downstream end of a baffle 14 which contains matter to flow beneath radial overflow 7 (See GB 2223957A). Inlet 51 extends the whole length of the valve chamber to collect and discharge matter flowing along the underside of baffle 14. This happens only when the overall flow in the tank, and hence the surface level therein, is high. In Figs. 4, 5 the chamber extends across the top of a rectangular tank, with a baffle directing surface matter downwards into the inlet. <IMAGE>

Description

VORTEX VALVE FLOW CONTROL This invention relates to a vessel adapted for the through-flow of a liquid and including a vortex valve flow control disposed to intercept surface flow in the vessel. More particularly, but no exclusively, this invention relates to an arrangement in which the vortex valve flow control is disposed so as to intercept floatable and neutrally-buoyant material at or just below the liquid surface of a separating device of circular cross-section and in which there is a generally circulating flow of liquid. GB-A-2249642 (and equivalent document WO-A-92/08059) relate to a vortex valve flow control having a vortex chamber which is an elongate circular cylinder and which has a relatively high coefficient of discharge, but advantageously only requires a relatively low head to initiate vortex flow in the vortex chamber.

According to a first aspect of the present invention, there is provided a vessel having a primary liquid inlet means and a primary liquid outlet means, and including a vortex valve flow control device disposed to intercept surface flow in the vessel and discharge away from the primary liquid outlet.

Preferably, the arrangement includes an inclined deflector plate adapted to deflect surface flow in the vessel downward and direct said surface flow to the inlet of the said vortex valve flow control.

The vortex valve discharges away from the primary liquid outlet so as to enable matter floating on or near the liquid surface to be separated from the primary flow. The vortex valve will therefore typically be situated in an upper region of the vessel.

A vortex valve flow control is a device for controlling fluid flow by an hydraulic effect without requiring moving parts, and comprises a housing defining a vortex chamber, the housing having an inlet through which liquid may enter the vortex chamber in a manner to prompt swirl within the vortex chamber and an outlet at one axial end of the vortex chamber.

Preferably, the vortex valve flow control employed in the present invention is one in which the vortex chamber is an elongate circular cylinder, preferably having a length at least one and a half times the diameter of the outlet, and the outlet represents at least 50% of the area of the end of the vortex chamber in which it is situated.

The outlet of the vortex valve of the present invention may connect to a pipe or to a channel. The outlet is circular in cross-section and has an area which represents at least 50% of the area of the end of the vortex chamber in which it is situated. More preferably, the opening represents at least 80% of the area of the end of the-vortex chamber. Most preferably, the outlet end of the vortex chamber is fully open.

The length of the vortex chamber is at least one and a half times the diameter of the outlet opening.

Preferably, the length should be about twice the diameter of the outlet opening.

The constraints on the area of the outlet and the length of the vortex chamber mean that the overall length of the chamber will be greater than the diameter of the chamber.

The inlet or mouth to the vortex chamber is preferably tangential and will normally represent at least 30%, more preferably at least 50% of the length of the vortex chamber. Most preferably, the inlet to the vortex chamber extends substantially the full length of the vortex chamber. The height (or width) of the mouth may be from as low as 10%, up to 89% of the radius of the vortex chamber. More preferably, the height of the mouth is at least 20% of the radius of the vortex chamber.

The vortex valves of the present invention can be constructed to have coefficients of discharge of 0.4 and above. This enables high rates of flow to be achieved with low pressure heads. Moreover, vortex flow in the vortex valves described herein is initiated at relatively low pressure heads and this makes them especially suitable for use in the present invention where their function is to intercept surface flow of a moving body of liquid. For instance, it has been found that heads as little as one times the diameter of the vortex chamber can give rise to initiation. The cylindrical flow controls of this invention may be controlled accurately and avoid the problem encountered with conventional flow controls of high velocity shooting flow. Moreover, because the inlet and outlet of the vortex valve are relatively large, there is a reduction in the risk of blockage.

The present invention is particularly suited for use in a vessel having a cylindrical outer wall and a concentric inner wall disposed in an upper region of the vessel defining between them an annular channel in which liquid may flow in a circulating manner. In this arrangement, the vortex valve flow control is positioned in the annular channel between the outer wall and the inner wall to intercept surface flow in the vessel outside the inner wall and to discharge that flow substantially horizontally in a controlled manner.

The inlet to the vortex valve may preferably extend the full width of the annular gap.

Preferably, a deflector is provided which deflects surface flow in the annular channel downwardly, and directs it to the inlet to the vortex valve. This deflector may be in the form of a part-annulus, when viewed from above, extending part of the way around the annular channel defined between the outer wall of the vessel and the said inner wall. In cross section, the deflector may have the shape of a venturi in order to accelerate liquid flow to the inlet of the vortex valve.

In this embodiment, the outlet means is preferably a weir defining an upper liquid surface in the vessel.

The deflector is suitably positioned so that its downstream end is above the level of the weir and the lower end is below the level of the weir. This will ensure that the flow delivered to the inlet of the vortex flow is below the level of liquid in the vessel defined by the weir and ensures that a positive pressure head is applied to the vortex valve, so that vortex flow in the vortex chamber of the vortex valve is initiated. Thus, in this embodiment, the vortex valve is situated with its axis slightly below the level of the weir. Preferably, the vortex valve is arranged so that there is a pressure head of about one times the diameter of the vortex chamber; this would require that the top of the vortex valve is at or below the same level as the weir.

The apparatus of the present invention is particularly suited for use in association with a separating device of the general type first described in our British Patent Publication No. 2082941, which is a device for separating components of a fluid mixture.

This earlier device is essentially a gravitational separator and it relies on the matter which is to be separated to be settleable under gravity. Floatable material floats to the surface of liquid in the vessel and collects in the annular space outward of the dip plate. The present invention is particularly suited to collecting floatable material accumulating in the annular space at the top of gravitational separators of this general type.

A typical gravitational separator to which the apparatus of the present invention may be connected is a low energy gravitational separator for separating solid matter from a liquid mixture carrying the solid matter comprising: (a) a vessel having a cylindrical outer wall and a base at one end, (b) a body which is provided within the vessel and which defines with the base an annular opening spaced from the outer wall, (c) an annular dip plate in an upper region of the vessel and spaced from the outer wall of the vessel for stabilising flow patterns in the vessel, (d) a vessel inlet for introducing the liquid mixture into the vessel, (e) an outlet in communication with an upper region of the vessel for removing from the vessel a treated liquid, and (f) a solids collection region centrally disposed of the base for collecting solid matter separated from the liquid mixture, the arrangement of the components of the separator being such that, in use with a circulating flow of liquid and solid matter within the vessel which is such that any separation of the solid component of the liquid in the vessel is brought about primarily by gravity, there is created a stabilised shear zone in the circulating liquid between an outer, relatively fast circulating region and an inner, relatively slowly circulating region and there is caused an inward sweeping effect of solids accumulated at the base of the vessel towards the said annular opening.

The vortex valve flow control is dispose to intercept surface flow in the vessel in the annular space between the outer wall and the concentric annular dip plate.

The outlet of the separator will normally be on the central axis of the vessel and communicate with a spillway which extends radially across the upper region of the vessel. In this arrangement, a deflector may be provided to smooth circulating flow between the outer wall and the dip plate below the spillway; this deflector may also be used to direct surface flow to the vortex valve flow control.

When the gravitational separator is required to separate solid material from the liquid mixture in an efficient manner, i.e. to remove as much as possible of the settleable material therefrom (for instance when the separator functions as a storm water overflow), there should preferably be provided, in an upper region of the vessel, a horizontally oriented baffle plate the periphery of which defines, with the inner surface of the dip plate, an annular gap through which liquid must flow to reach the outlet; this ensures that liquid cannot flow upwardly to the top of vessel toward the outlet in a substantially axial direction and encourages the generally toroidal flow in the vessel referred to above.

Gravitational separators of the type described above may be employed in a method of separating from a liquid mixture a solid component of that mixture which method comprises: (i) introducing the liquid mixture into a gravitational separator comprising: (a) a vessel having a cylindrical outer wall and a base at one end, (b) a body which is provided within the vessel and which defines with the base an annular opening spaced from the outer wall, (c) an annular dip plate in an upper region of the vessel and spaced from the outer wall of the vessel for stabilising flow patterns in the vessel, (d) an inlet formed for introducing the liquid mixture into the vessel, (e) an outlet in communication with an upper region of the vessel for removing from the vessel a treated liquid, and (f) a solids collection region centrally disposed of the base for collecting solid matter separated from the liquid mixture, the arrangement of the components of the separator being such that, in use with a circulating flow of the liquid mixture within the vessel which is such that any separation of the solids components of the liquid in the vessel is brought about primarily by gravity, there is created a stabilised shear zone in the circulating liquid between an outer, relatively fast circulating region and an inner, relatively slowly circulating region and there is caused an inward sweeping effect of solids accumulated at the base of the vessel towards the said annular opening;; (ii) causing a circulating flow of the liquid mixture within the vessel, said circulating flow being of such that any separation of the solids components of the liquid in the vessel is brought about primarily by gravity and there is created a stabilised shear zone in the circulating liquid between an outer, relatively fast circulating region and an inner, relatively slowly circulating region and there is caused an inward sweeping effect of any solids accumulated at the base of the vessel towards the said annular opening low energy rotational motion in the vessel; and (iii) permitting solids to settle under gravity and be concentrated at the solids collection region.

The arrangement of the present invention may be also used in an arrangement in which liquid flow through the vessel is in a direct line between inlet and outlet, for example a stilling pond. Instead of a conventional scum board to collect floatables, a vortex valve is provided, in accordance with the invention to intercept surface flow carrying floatable and neutrally buoyant matter. A suitable deflector may be provided to direct flow to the vortex valve inlet situated slightly below the liquid surface. A weir (separate from the main outlet) may be provided to define the liquid surface.

By the term "surface flow" herein, we mean the flow of liquid at or near the surface of the body of water in which floatable matter and neutrally buoyant material collects.

For a better understanding of the present invention, and to show how the same may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings in which: Figure 1 is a section through an arrangement in accordance with the present invention; Figure 2 is a plan view of the arrangement shown in Figure 1; Figure 3 is a simplified perspective view of part of the arrangement shown in Figures 1 and 2; Figure 4 is a section through another arrangement in accordance with the present invention; and Figure 5 is a plan view of the arrangement shown in Figure 4.

The separating unit shown in Figures 1, 2 and 3 is of the type described in our EP-A-0363050 and comprises a vessel 1 having a cylindrical outer wall 2 and a sloping, conical base 3. Within the vessel 1 there is provided a flow modifying member 4 in the shape of a cone which defines with the base 3 an annular opening 5 which is spaced from the outer wall 2 of the vessel.

The lower peripheral edge 4a of the cone should be approximately half-way between the outer wall 2 and the central axis of the vessel 1. A tangential inlet 6 (indicated by dotted lines) to the vessel 1 through the outer wall 2 is provided by which a liquid containing solid components may be introduced into the vessel 1.

There is also provided a tangential outlet duct 7 and an annular dip plate 8 which is concentric with the outer wall 2 and spaced from the outer wall 2 defining an annular slot 9. The dip plate 8 is supported by horizontal beams 100. The outlet duct 7 is formed as a spout in the dip plate 8. The outlet duct 7 has side walls 10a and lOb and a base 11 and extends through the outer wall 2 of the vessel 1 at an upper region thereof. The upper edges 10a', lOb' of the sides 10a and 10b of the outlet duct 7 are at the same level as the top of the dip plate 8 whilst the base 11 of the outlet duct is at a height approximately one third of the way down the dip plate 8. The dip plate 8 has an upper edge 12' which is broken by the outlet duct 7 side walls 10a, 10b, and a lower annular edge 13 which is continuous.

In the annular slot 9 between the outer wall 2 and the dip plate 8 there is provided a curved flow modifying plate or deflector 14 which extends radially across the annular slot 9 and leads from a level at approximately the upper edge 12' of the dip plate 12 to a level approximately at the base 11 of the outlet duct 7. The curved portion 14 reaches the level of the bottom 11 of the outlet duct 7 slightly upstream of the outlet duct 7. In the short length between the outlet duct 7 and the position at which the curved plate 14 terminates there is provided a flat plate 15 which is in approximately the same plane as the base 11 of the outlet duct 7.

The deflector 14 also directs surface flow in the vessel 1 to the inlet 51 of a vortex valve flow control 50. The vortex valve 50 is in the form of an elongate circular cylinder disposed radially between the outer wall 2 and the inner dip plate 8. The deflector 14 meets the housing of the vortex valve 50 immediately above the inlet and therefore directs flow into the inlet. Vortex motion is established in the vortex chamber and a controlled flow is passed out of the outlet 53 of the vortex valve. Since the surface flow in the vessel 1 will contain the majority of the floatable material, this invention is able to remove that floatable matter rapidly and avoid the danger that the matter will become entrained back in the normal flow and contaminate the cleansed output. More details of this device may be found in our GB-A-2249642.

Under normal operating conditions of the separator, collected water, typically domestic foul water entrained with for instance rain water from road run-off enters the vessel 1 through the inlet 6.

Normally, the rate at which liquid enters the vessel will be relatively slow and the separator will act almost as a clarifying vessel in which material heavier than the water entering sinks to the base 3 of the vessel 1, whilst clean water will slowly spill into the outlet duct 7 and will be carried away. The liquid in the vessel 1 will be circulating only very slowly, if at all.

Under storm conditions, however, in which large amounts of sediment, detritus and other solid matter is carried in the water run-off, the liquid entering the vessel 1 through the tangential inlet 6 will be travelling at a much higher velocity because of the high pressure head from liquid backed-up in the drainage system. Under these conditions, the vessel 1 will quickly fill and the liquid mixture being tangentially introduced into the vessel 1 via the inlet 6 will circulate in the direction shown by the arrows in the vessel (Figure 1). As described in our British Patent Specification No. 2082941, this circulating flow within the vessel is sufficient to cause an inward sweeping effect toward the annular opening 5 in the base of solids accumulated at the base of the vessel.

However, the energy of the circulating fluid is not so large that centrifugal forces have any substantial effect on the particles of solid matter rotating in the vessel 1. The accumulated matter at the base may be removed via a central outlet (not shown). The flow modifying member 4 assists in creating a secondary, toroidal flow in the vessel whilst the annular dip plate 8 stabilises a shear zone between an outer, relatively fast flow and an inner, relatively slow flow of liquid in the vessel 1.

Under storm conditions, the upper level of liquid in the vessel 1 will be close to the top of the annular dip plate 8, probably around the level shown in Figure 3 by the line 20.

As described in our EP-A-0363050, the deflector 14 directs liquid flowing in the vessel 1 smoothly around the outlet duct 7. The radius of curvature of the plate 14 increases steadily to a maximum about half-way along its length and then decreases to zero where the plate 14 meets the flat plate 15. The flow modifying plate 14 has the shape of one half of a venturi, which shape is mathematically determined to cause a minimum of turbulence in flowing liquid..

It is to be appreciated that any shape of flow modifying plate is suitable which causes liquid rotating in the vessel to be directed to a level at or below the level of the base 11 of the outlet 7 without causing excessive turbulence. To this end, sharp edges are to be discouraged and rounded edges are provided on the outlet duct 7 and the flow modifying means 14, 15 so as to smooth flow in the vessel 1.

The arrangement of the present invention ensures that floatable and neutrally buoyant matter at the liquid surface is intercepted and disposed during the storm conditions. This is of particular advantage during storms in which the level of liquid in the vessel may fluctuate permitting floatable matter to escape into the clean water outlet.

The flow from the duct 7 may be directed to a separating barrier of the type described in our British Patent Application No. 9211516.1 The separator of the present invention may be a separator in accordance with our British Patent No.

2158741 in which there is provided a further inlet by which a "energising fluid" may be introduced into the vessel in a manner to cause or enhance rotational movement of the liquid in the vessel.

The vessel shown in Figure 1 has a base region which is in accordance with our British Patent No.

2189413. However, the base region of the separator may be as shown in the drawings of our British Patent No.

2082941.

Figures 4 and 5 illustrates another arrangement in accordance with the present invention. Vessel 200 is a stilling pond in which the liquid level is defined by a weir 201. The vessel has an inlet 202 and an outlet 203. In place of a scum board, a vortex valve flow control 204 is provided to intercept surface flow in the vessel and discharge that surface flow containing floatable matter away from the main flow. Vortex valve 204 is of the type described in our GB-A-2249642 having a vortex chamber which is an elongate circular cylinder. Surface flow is directed to the vortex valve inlet 206 by deflector plate 207 which has, in crosssection, a venturi shape to accelerate flow to the vortex valve 204.

Claims (8)

CLAIMS:

1. A vessel having a primary liquid inlet means and a primary liquid outlet means, and including a vortex valve flow control device disposed to intercept surface flow in the vessel and discharge away from the primary liquid outlet.

2. An arrangement according to claim 1, further comprising an inclined deflector plate adapted to deflect surface flow in the vessel downward and direct said surface flow to the inlet of the said vortex valve flow control.

3. An arrangement according to claim 1 or 2, wherein the vortex valve flow control has a vortex chamber which is an elongate circular cylinder.

4. An arrangement according to claim 3, wherein the vortex chamber has a length at least one and a half times the diameter of the outlet, and the outlet represents at least 50% of the area of the end of the vortex chamber in which it is situated.

5. An arrangement according to any preceding claim, wherein the vessel has a cylindrical outer wall and a concentric inner wall disposed in an upper region of the vessel defining between them an annular channel in which liquid may flow in a circulating manner, the said vortex valve flow control being located in the annular channel between the outer wall and the inner wall to intercept surface flow in the vessel outside the inner wall and to discharge that flow in a controlled manner.

6. An arrangement according to claim 5, wherein a deflector is provided to deflect surface flow in the annular channel downwardly, and direct it to the inlet to the vortex valve.

7. An arrangement according to any one of claims 1 to 4, wherein the vessel is substantially rectangular having its inlet and outlet in opposite end walls, liquid flow through the vessel being in a substantially direct line between inlet and outlet.

8. A combined vessel and vortex valve flow control substantially as hereinbefore described, with reference to the accompanying drawings.