GB2372222A

GB2372222A - Solids/Liquids Separator

Info

Publication number: GB2372222A
Application number: GB0103613A
Authority: GB
Inventors: Nigel R C Shepherd
Original assignee: Haigh Engineering Co Ltd
Current assignee: Haigh Engineering Co Ltd
Priority date: 2001-02-14
Filing date: 2001-02-14
Publication date: 2002-08-21
Anticipated expiration: 2021-02-14
Also published as: GB0103613D0; IE20011076A1; GB2372222B

Abstract

A solids/ liquids separator comprises a fluid channel (15) having side walls (17) which form weirs. Fluid flows over the side walls (17) on to mesh (19) outside the fluid channel. The mesh (19) is arranged to catch solids whilst allowing passage of liquids. Transfer means are arranged to transfer solids from the mesh (19) back to the fluid channel (15).

Description

SOLIDS/LIOUIDS SEPARATOR The present invention relates to separators for separating solids from liquids, for example solids entrained in household sewage or other slurries, e. g. in waste water treatment plants.

In particular this invention relates to bypass or filters also known as storm screens.

Such screens are used, for example, where normal flow does not require separation at a point, but in certain abnormal conditions additional flow must be sent to waste and the additional flows require the solids to be separated from the liquids. One example of this is in the inlet to sewage treatment plants where after a storm or heavy rain fall there is a great deal of additional volume entering the plant. The normal separators could not deal with this full volume. In these conditions the liquid is mainly rain water and may safely be passed to waste or storage, but the more hazardous solid content needs immediate treatment. In these circumstances the storm screen is utilised to effect this separation.

An example of a traditional storm screen is shown in GB 1 598 103. In this apparatus normal flow flows through a discharge pipe. In storm conditions the additional flow is diverted over a screen, a mesh with opening size to prevent solid matter passing therethrough but allow liquids passage. The liquid is then separated and can be disposed of. The solids remain on the screen and a rotating brush sweeps the screen to an overflow trough. This prevents the solids from blocking the screen. The solid matter is passed back to the main flow where it can be taken to the normal separators. As will be clear this apparatus requires specially designed flow area around it and cannot be the normal channel through which the sewage flows. This storm screen may well often be located in a side channel of the main flow.

Other designs of storm screen are also known. For

example these involve the flow being diverted into a side channel where separation can be effected. In many cases brushes are used to sweep the screened solids back into the flow, but often the screened solids are again separated from overflow liquid due to the design of the design of the return.

The present invention seeks to provide a solids/liquids separator for separating solid matter from liquids in an overflow situation.

According to the present invention there is provided a solids/liquids separator comprising a fluid channel for fluid to flow therealong having a side wall forming a weir of a predetermined height, and a mesh outside the fluid channel which is arranged to catch solids flowing over the weir whilst allowing passage of liquids and further including transfer means arranged to transfer solids from the mesh to the fluid channel. The invention thus provides a separator which can be simply put into the main fluid channel and incorporates a side weir to divert the overflow for separation. This then allows a much simpler design of overflow for solids return system. The present invention thus allows a simplification compared to previously known storm screens as the separator does not require side channels or other specially designed areas to incorporate the separator.

In a preferred embodiment of the invention, there is provided in the separator an opposed side wall of the fluid channel forming another weir, a further mesh being provided outside the fluid channel which is arranged to catch solids flowing over the weir thus allowing passage of liquids, and further including further transfer means arranged to transfer solids from the further mesh to the fluid channel.

This embodiment is particularly preferred as it allows a significant increase in the capacity of the separator without complicating the design. In this preferred embodiment the fluid channel is provided between opposed

side weirs. The twin side weirs can be advantageous as the twin weirs allow a greater relative fall to the screened solids compared to a single weir. This encourages the return of the screened solids to the overflow.

The solids/liquids separator of the invention is particularly preferred for separating overflow liquids from a fluid channel rather than for separating the main flow of the channel.

In the separator of the invention, it is preferred for the or each mesh to have a curved cross section in the direction of flow down the channel. This allows simple clearing of the mesh by the transfer means.

It is preferred for the transfer means to comprise a reciprocating brush means. The reciprocating brush allows for advantageous control of the sweeping action, for example holding solids close to the maximum height of the mesh to allow draining of fluid from the solids before being swept back into the fluid channel. This is advantageous compared to rotary brush or other transfer means.

The brush means is a wear part of the system. Once in situ it is advantageous if this has good wear characteristics. It is preferred for the brush to be formed out of a polymeric material, preferably selected from the group consisting of polypropylene, polyethylene, polyurethane and polystyrene. In any case, it is preferred for the brush to be releasably mounted on the transfer means so as to allow easy replacement of worn brushes.

To allow for continuous adjustment of the transfer means in contact with the mesh, it is preferred for this to include resilient biasing against the mesh. This adjusts for the wear of the part against the mesh throughout the lifetime of the wear part.

The transfer means is driven by a drive means. If there are more than one transfer means, it is preferred for there to be a common drive means thus saving on cost and

complexity of the arrangement. The twin side weirs are a particularly preferred embodiment for this purpose as it is very simple to allow for a balanced and simple system. The side weirs enable capacity to be increased simply by increasing the length of the side weir.

The drive means will be controlled by a control means.

This can be programmed to clear the mesh in preferred cycles, for example as previously mentioned with pauses in the brush stroke, etc.

The transfer means will normally transfer the solids directly into a chute leading to the fluid channel. This is a particularly simple design which is not liable to clog.

Advantageously, the separator has the or each transfer means arranged to transfer solids into the fluid channel downstream of the or each weir. This prevents the separated solids being liable to repeated overflow separation.

According to a second aspect of the present invention, there is provided a method of separating solids from liquids comprising the steps of: (a) flowing a mixed solids/liquids fluid along a fluid channel having a side wall generally parallel to the direction of flow; (b) allowing fluid for separation to flow over said side wall onto a mesh, the mesh being sized to retain solids from the fluid whilst allowing liquids to pass therethrough; and (c) transferring said retained solids back into the fluid channel. The second aspect of the invention will normally be conducted in a separator according to the first aspect of the invention.

The preferred embodiment of the present invention will now be described with reference to the accompanying drawing, in which: Fig. 1 shows a separator according to a preferred

embodiment of the present invention ; Fig. 2 depicts a sectional view from the side of the separator of Figure 1; Fig. 3 is a sectional end view along the line B shown in Fig. 2; Fig. 4 shows a cross-sectional view along line A-A of Fig. 2; Fig. 5 shows a sectional view along line C of Fig. 2; and Fig. 6 shows a plan view from the top of the separate of Fig. 1.

Fig. 1 depicts a preferred embodiment of the solids/liquids separator 10 of the present invention. The separator 10 comprises a housing 12 with an inlet port 14 (Fig. 6) and an outlet 16.

Close to the outlet 16 opposed chutes 18 open into the fluid channel 15 extending between inlet 14 and outlet 16.

The chutes 18 open downstream of the weirs so as to prevent separated solids being caught in the flow which might direct the separated solids over the weirs. An arm of a transfer means 20 is shown attached to drive means 30. The separator 10 is designed to fit directly into a fluid channel (not shown).

As seen best from Fig. 5 and Fig. 6, the housing 12 includes an internal fluid channel 15 extending between the inlet 14 and outlet 16. In Figs. 2 through 6 the flow of the mixed solid liquid slurry which will flow through the separator in the"storm"overflow condition are shown by arrows. A solid arrow indicates the passage of solids only. A hatched arrow indicates the passage of mixed solids and liquids and an open arrow indicates the passage of liquid only.

As seen clearly from Fig. 5 the mixed solid liquid slurry flows along fluid channel 15. The channel 15 is formed between side walls 17 which are generally parallel to the direction of the main flow along the fluid channel.

The side walls each form a weir. In the"storm"overflow conditions flow will occur over the side walls 17.

In a storm screen, it is normal to separate out the overflow liquid which is then allowed to run to waste. The overflowed liquid may drain in any fashion. It is however preferred for the overflowed liquid from all weirs to be directed to a single overflow liquid outlet that, e. g. passes under the fluid channel. This can be useful when locating the separator especially in instances where there are other physical structures e. g. walls surrounding the separator. The overflow solids must be returned to the main flow for proper treatment as the solids tend to be contaminated. In the separator 10 of the present invention, the majority of the heavier solids will occur towards the lower regions of the fluid channel 15 due to gravity. However, some solids will be entrained in with the liquids which flows over the side walls 17. The fluid which flows over the side walls 17 falls onto a mesh 19.

The mesh 19 has openings therein sized to prevent the desired size of solids from falling therethrough whilst allowing passage to liquid. The liquid is then allowed to run to waste as shown in Fig. 5. The solids are retained on the mesh 19.

The separator 10 can include height adjustment means (not shown). The height adjustment means alter the effective height of the or each side weir. The height adjustments normally comprise plate means. The plate means forms the side wall of the fluid channel which is movable to set the height of the respective side weir. Of course normally both side walls will have a height adjustment means. Thus the amount of liquid allowed to flow before an "overflow"condition occurs may be adjusted in situ.

In the preferred illustrated and preferred embodiment shown of the invention, the mesh 19 are designed as curved screens as shown best in Fig. 2. The design of the mesh 19 is matched to the movement of a brush 24 which brush 24

forms the wear part of a transfer means 20.

The transfer means 20 is driven by drive means 30.

The twin brushes of the transfer means 24 is driven in a reciprocating fashion by arms 25.

As is clear from the Figures, the illustrated embodiment shows an example having two meshes 19, one alongside each side wall 17. Each screen 19 has associated therewith a brush 24. These brushes as joined together via a common rod 26 to the transfer means 20. The common transfer means 20 for the two screens allows a clear cost saving and efficiency of the preferred embodiment of the invention.

The brush 24 is resiliently mounted on the transfer means. This allows for self-adjustment as the brush wears through use. Furthermore, the brushes 24 are releasably mounted on the transfer means 20 so as to allow simple replacement of the brushes when they are fully worn.

The transfer means is driven by drive means 30. The drive means 30 is controlled by a control unit. The control unit can be programmed to allow any cycle of brushing. There is sometimes provided a pause at the point where the brush is close to the highest point of the curved mesh 19, in order to allow any liquids to drain through the solids back through the mesh 19. This minimizes the amount of fluid returned to the fluid channel. Solids swept along the screen 19 are returned to the main fluid channel 15 along chutes 18. As will be appreciated, this a very simple design not liable to clogging etc by the wet solids.

The transfer means of the present invention is particularly preferred for the self-adjusting nature of the resilient mounting of the brush means 24. The brush means 24 are contained within an elongated block in which there are several openings. In each opening a brush cartridge is located. Each brush cartridge comprises, e. g. 32 strands of bristle all within a stainless steel tube which is crimped to hold the bristle. The cartridge is held against

moving by a backstop. Several cartridges extend from the block. The block is very simple to replace in situ.

The bristles are normally made from polypropylene as this material wears slowly. The separate brush cartridges are preferred as this provides a natural grid through which the liquid can flow thus minimizing the liquid which is passed back into the main fluid channel 15.

As will be seen most clearly from Fig. 2, the brushes 24 are supported on arms 25. The arms 25 are joined together by a common rod 26 of the transfer means 20. A single motor/gearbox arrangement 30 is used to provide the partial rotating movement of the brush. The control of the brushes 24 are provided through a control unit (not shown).

The control unit may be an integral unit or could form a separate unit.

In the illustrated embodiment the drive is configured to drive the brush means to sweep the mesh 19 at 6 rpm (revolutions per minute), but of course this will be variable depending upon the particular installation. It is preferred for there to be periods when the brush means 24 remain stationary. Sensors can be provided to only operate the drive means when the flow in the fluid channel is an overflow situation, i. e. when water flows over the side walls 17.

The drive means 30 is shown as a single electric motor. Alternatively, the drive means may be a compressed air drive.

It will be appreciated that the separator 10 of the present invention is particularly suited for direct installation into a fluid channel without the need for extensive redesign of the fluid channel for the overflow separation facility.

The present invention does not have any moving sealing joints. This minimises the risk of screened solids passing through and damaging the separator.

Claims

CLAIMS :

1. A solids/liquids separator comprising a fluid channel for fluid to flow therealong having a side wall forming a weir of a predetermined height, and a mesh outside the fluid channel which is arranged to catch solids flowing over the weir whilst allowing passage of liquids, and further including transfer means arranged to transfer solids from the mesh to the fluid channel.

2. A separator according to claim 1, wherein an opposed side wall of the fluid channel forms another weir, a further mesh is provided outside the fluid channel which is arranged to catch solids flowing over the other weir whilst allowing passage of liquids, and further including further transfer means arranged to transfer solids from the further mesh to the fluid channel.

3. A separator according to claim 1 or claim 2, wherein the weir or weirs act as an overflow outlet.

4. A separator according to any one of the preceding claims, wherein the or each mesh has a curved cross-section in the direction of flow in the channel.

5. A separator according to any one of the preceding claims, wherein the or each transfer means comprise a reciprocating brush means.

6. A separator according to claim 5, wherein the brush means is formed from a polymeric material.

7. A separator according to claim 6, wherein the polymeric material is selected from the group consisting of: polypropylene; polyethylene; polyurethane; and polystyrene.

8. A separator according to any one of claims 5 to 7, wherein the brush means is releasably mounted on the transfer means.

9. A separator according to any one of the preceding claims, wherein the or each transfer means is resiliently biased against the or each mesh.

10. A separator according to any one of the preceding claims, wherein the or each transfer means is driven by a drive means.

11. A separator according to claim 10, wherein the drive means is controlled by control means.

12. A separator according to any one of the preceding claims, wherein the or each transfer means is arranged to transfer solids directly into a chute leading to the fluid channel.

13. A separator according to any one of the preceding claims, wherein the or each transfer means is arranged to transfer solids into the fluid channel downstream of the or each weir.

14. A method of separating solids from liquids comprising the steps of: (a) flowing a mixed solids/liquids fluid along a fluid channel having a side wall generally parallel to the direction of flow; (b) allowing fluid for separation to flow over said side wall onto a mesh, the mesh being sized to retain solids from the fluid whilst allowing liquids to pass therethrough; and (c) transferring said retained solids back into the fluid channel.

15. A method of claim 14, conducted in a solids/liquids separator according to any one of claims 1 to 13.

16. A solids/liquids separator as hereinbefore described with reference to and/or as illustrated by the accompanying drawings.

17. A method of separating solids from liquids as hereinbefore described with reference to and/or as illustrated by the accompanying drawings.