GB2314032A

GB2314032A - Solids screening apparatus

Info

Publication number: GB2314032A
Application number: GB9612187A
Authority: GB
Inventors: Anthony William Collins
Original assignee: CPL ENVIRONMENTAL Ltd; ECOLOGICAL PRODUCTS Ltd
Current assignee: CPL ENVIRONMENTAL Ltd; ECOLOGICAL PRODUCTS Ltd
Priority date: 1996-06-11
Filing date: 1996-06-11
Publication date: 1997-12-17
Also published as: GB9612187D0

Abstract

Solids screening apparatus (10) comprises a rotatable drum (14) for receiving the material to be screened. The material comprises a liquid component and a solid component. The drum (14) defines an outlet for the solid component, and comprises a screen (16) for screening at least some of the solid component from the liquid component. The apparatus (10) further includes at least one conduit (30) provided in the drum (14) and being rotatable therewith. The, or each, conduit (30) is so arranged to collect at least some of the screened solid component on rotation of the drum (14) and deliver the collected solid component towards the solid component outlet where the collected solid component can exit from the drum (14).

Description

Improvements in or relating to screening apparatus This invention relates to screening apparatus. More particularly, but not exclusively, this invention relates to solids screening apparatus for use in the treatment of sewage, or paper pulp or other industrial materials comprising a solid material in a liquid material.

Known screening apparatus comprises a rotating drum having a shell in the form of a screen. Sludge enters the drum at one end, passing through the drum to enable water to pass through the screen and pass away as screened effluent. The remaining solid pass out of the drum via the outlet.

It is a disadvantage of such a system that solids are not removed efficiently from the drum.

According to this invention there is provided solids screening apparatus comprising a rotatable drum for receiving the material to be screened, the material comprising a liquid component and a solid component, the drum defining an outlet for the solid component, and comprising a screen for screening at least some of the solid component from the liquid component and the apparatus further including at least one conduit provided in the drum and being rotatable therewith, the, or each, conduit being so arranged to collect at least some of the screening solid component on rotation of the drum and deliver the collected solid component towards the solid component outlet where the collected solid component can exit from the drum.

Preferably, the screen constitutes at least part of a shell of the drum.

The, or each, conduit may be in the form of a channel and is desirably arranged at an angle of greater than OO relative to the axis of rotation of the - drum. Preferably, the conduits are arranged at an angle of between 0 and 100 relative to the axis of the drum, more preferably at substantially 50.

Preferably, the arrangement of the, or each, conduit is such that the, or each, conduit slopes downwardly towards the outlet after collection of the solid component. In the preferred embodiment, the solid component outlet is provided at the inlet end of the drum.

Preferably, the drum has a first end region and a second end region, wherein the solid component outlet is provided at the first end region, and the, or each, conduit extends substantially from the first end region to the second end region.

The apparatus may include a plurality of such conduits mounted on the inside of the shell. Conveniently, the conduits are substantially equispaced. Preferably, the apparatus includes eight or any other suitable number of substantially equispaced conduits.

The or each conduit may include a retaining end plate at the first end thereof to prevent solid material passing from the conduit at said first end.

Preferably, the apparatus includes an inlet for incoming sludge at one end region. In the preferred embodiment, the inlet is provided at the first end region of the drum.

The drum may be rotatable by a gearing arrangement attached to drive means. Preferably, the gearing arrangement includes a driven sprocket fixedly mounted on the drum, and a drive sprocket attached to drive means, the driven sprocket and the drive sprocket being in meshing engagement, preferably either by direct meshing or via a belt or chain. The drive means is preferably in the form of a motor.

Guide means may be provided to guide the rotation of the drum and hold the drum in place. The guide means preferably comprise trunnion wheels adapted to engage the drum. Preferably, the drum is rotatably mounted in a frame, and the trunnion wheels hold the drum in the frame.

Preferably, the apparatus includes first and second sets of trunnion wheels, the first set being conveniently provided at the first end region, and the second set being conveniently provided at the second end region. Each set may comprise a plurality of pairs of trunnion wheels substantially equispaced about the drum. Preferably, each set comprises three pairs of trunnion wheels.

The apparatus may further include chopping means to chop the solid material exiting from the drum. The chopping means may comprise macerator pumps. In one embodiment the solid material exiting the drum is conveyed by a screw conveyor.

The apparatus may further include a by-pass through which excess sludge can be passed. Preferably, the by-pass is capable of handling an overflow in the drum.

Preferably, the screen comprises a plurality of apertures, and may be in the form of wedgewire, a mesh, or a perforated plate. The screen may be formed of stainless steel or a plastics material.

An embodiment of the invention will now be described by way of example only with reference to the accompanying drawings, in which: Fig. 1 is a side view of screening apparatus; Fig. 2 is a view along the lines II-II in Fig. 1; Fig. 3 is a view along the lines III-III in Fig. 1; Fig. 4 is a side view of the area marked IV in Fig. 3.

Figs. 5A and 5B are representations of the first end regions of alternative conduits; and Fig. 6 is a close up of part of the apparatus for processing screened solids.

Referring to the drawings, there is shown screening apparatus 10 for screening sewage sludge to remove solid material of a desired particle size from the liquid material of the sludge. The apparatus 10 comprises a frame 10 in which is mounted a drum 14. The drum 14 comprises a shell which is in the form of a screen 16 formed of wedgewire, a mesh, or other suitable apertured sheet. The drum 14 is rotatable about its longitudinal central axis X-X. Drive means in the form of a motor 18, and a gearing arrangement 20 is provided to rotate the drum 14. The gearing arrangement 20 comprises a drive sprocket 22 fixedly attached to the motor, and a driven sprocket 24 fixedly attached to the drum 14. Thus, the motor 18 drives the drive sprocket 22 which, in turn, drives the driven sprocket 24 to rotate the drum 14. Alternatively, the drum 14 could be driven by a belt connected between the drum 14 and the motor 18, or by directly driven by the motor 18.

The drum 14 is provided with an inlet for incoming sludge as indicated by the arrow A. The screen 16 prevents solid material greater than a predetermined particle size passing through the drum 14 and liquid effluent passes out of the drum 14 at the bottom of the apparatus 10 in the direction of the arrow B, via a trough 28 formed in the ground upon which the apparatus 10 is arranged. The drum 14 is provided with elongate conduits on the inner surface of the screen 16. The conduits are in the form of channels 30 equispaced about the inside of the drum 14.

Referring to Fig. 2, it can be seen that the drum 14 rotates in the direction as shown by the arrow C. It will be appreciated that the solids in the sludge will tend to collect at the bottom of the drum 14. Thus, as each of the elongate channels 30 passes through the sludge at the bottom drum 14, each channel 30 will scoop up some of the sludge.

The channels 30 are angled relative to the longitudinal axis X-X of the drum. The angle of the channels 30 is such that the channels 30 on the right hand side of the drum (as shown in Fig. 2) slope downwardly towards the first end region. This has the effect that gravity causes the solid material collected in each of the channels 30 tends to fall towards the first end region of the drum 14. The end of each channel is provided with a retaining plate 32 to prevent solids passing out of each channel 30. As the rotation of the drum 14 causes each channel 30 to pass beyond a certain position, the solids can pass out of the channels 30 into a collecting hopper 33 and thereafter to a solids collecting tank 35 where a macerating pump 30 chops up the solids into smaller particles and then passes them via a line 36 in the direction of the arrow D for further processing.

The apparatus 10 also includes an overflow channel 36 which the sludge can pass in the direction of the arrow E in the event that an excess of sludge should be passed to the drum 14.

Referring to Fig. 3, there is shown the second end region of the apparatus, showing the drive means 18, and the gearing arrangement 20.

Fig. 3 also shows guide means in the form of trunnion wheels 38 which engage the overflow channel 36 to hold the drum 14 in its position and allow it to rotate. The guide means also includes further trunnion wheels 40 which engage around the outer surface of the drum 14 and also hold the drum 14 in place, and allow it to rotate. Fig. 4 shows an enlarged version of one of the trunnion wheels 40, namely that shown in the area designated IV, but from a side view thereof, from which it is seen that the trunnion wheels 40 comprise a wheel 42 which is journalled on an axis 44, fixedly mounted via a connecting member 46 to the frame 12. Trunnion wheels 44 are provided at the first end region of the drum 14 in order to ensure that the drum 14 is held firmly in place. The trunnion wheels 44 engage the inner surface of the drum 14 as shown in Fig. 2.

Referring to Figs. SA and SB, there is shown alternative examples of the channels 30. Fig. 5A shows a channel 30 having a U-shaped crosssection, and having attached at its first end a solids retaining end plate 32.

Fig. SB shows a channel 30 formed from a substantially planar member 30A, the channel 30 being defined between the planar member 30A and the wall of the drum 14. The channel 30 shown in Fig. SB is also provided with a solids retaining end plate 32.

Referring to Fig. 6, there is shown a close-up of the solids collecting hopper 33, the solids collecting tank 35 and the macerator pumps 34. two of the macerator pumps are provided. One is on standby while the other is operating. Solids enter the hopper 33 as shown by the arrows F.

The above described embodiment has the advantage that the use of angled channels 30 allows the solids to move to the first end of each channel 30 whereupon the solids fall into the collecting hopper 33. This overcomes the problem associated with some prior art apparatus in which the collecting hopper becomes blocked.

Various modifications can be made without departing from the scope of the invention.

Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.

Claims

1. Solids screening apparatus comprising a rotatable drum for receiving the material to be screened, the material comprising a liquid component and a solid component, the drum defining an outlet for the solid component, and comprising a screen for screening at least some of the solid component from the liquid component and the apparatus further including at least one conduit provided in the drum and being rotatable therewith, the, or each, conduit being so arranged to collect at least some of the screened solid component on rotation of the drum and deliver the collected solid component towards the solid component outlet where the collected solid component can exit from the drum.

2. Solids screening apparatus according to claim 1 wherein the screen constitutes at least part of a shell of the drum.

3. Solids screening apparatus according to claim 1 or 2 wherein the, or each, conduit is in the form of a channel and is arranged at an angle of greater than 0 relative to the axis of rotation of the drum.

4. Solids screening apparatus according to chain 3 wherein the conduits are arranged at an angle of between 0 and 10 relative to the axis of the drum.

5. Solids screening apparatus according to claim 3 or 4 wherein the conduits are arranged at an angle substantially 5 to the axis of the drum.

6. Solids screening apparatus according to any of claims 3 to 5 wherein the arrangement of the, or each, conduit is such that the, or each, conduit slopes downwardly towards the outlet after collection of the solid component.

7. Solids screening apparatus according to any preceding claim wherein the solid component outlet is provided at the inlet end of the drum.

8. Solids screening apparatus according to any preceding claim wherein the drum has a first end region and a second end region, wherein the solid component outlet is provided at the first end region, and the, or each, conduit extends substantially from the first end region to the second end region.

9. Solids screening apparatus according to any preceding claim including a plurality of such conduits mounted on the inside of the shell.

10. Solids screening apparatus according to claim 9 wherein the conduits are substantially equispaced.

11. Solids screening apparatus according to claim 8 wherein the, or each, conduit includes a retaining end plate at the first end thereof to prevent solid material passing from the conduit at said first end.

12. Solids screening apparatus according to claim 8 or 11 includes an inlet for incoming sludge at one end region.

13. Solids screening apparatus according to claim 12 wherein the inlet is provided at the first end region of the drum.

14. Solids screening apparatus according to any preceding claim wherein the drum is rotatable by a gearing arrangement attached to drive means, the gearing arrangement including a driven sprocket fixedly mounted on the drum, and a drive sprocket attached to drive means, the driven sprocket and the drive sprocket being in meshing engagement, preferably either by direct meshing or via a belt or chain.

15. Solids screening apparatus according to any preceding claim including guide means to guide the rotation of the drum and hold the drum in place.

16. Solids screening apparatus according to claim 15 wherein the guide means comprise trunnion wheels adapted to engage the drum, the drum being rotatably mounted in a frame, and the trunnion wheels holding the drum in the frame.

17. Solids screening apparatus according to claim 16 wherein the apparatus includes first and second sets of trunnion wheels, the first set being provided at the first end region, and the second set being provided at the second end region.

18. Solids screening apparatus according to claim 17 wherein a set of trunnion wheels comprises a plurality of pairs of trunnion wheels substantially equispaced about the drum.

19. Solids screening apparatus according to any preceding claim wherein the apparatus further includes chopping means to chop the solid material from the drum.

20. Solids screening apparatus according to claim 19 wherein the chopping means comprises macerator pumps.

21. Solids screening apparatus according to claim 19 to 20, in one embodiment the solid material exiting the drum is conveyed by a screw conveyor.

22. Solids screening apparatus according to any preceding claim further including a by-pass through which excess sludge can be passed.

23. Solids screening apparatus according to any preceding claim wherein the screen comprises a plurality of apertures, and may be in the form of wedgewire, a mesh, or a perforated plate. The screen may be formed of stainless steel or a plastics material.

24. Solids screening apparatus substantially as herein described with reference to the accompanying drawings.

25. Any novel subject matter or combination including novel subject matter disclosed, whether or not within the scope of or relating to the same invention as any of the preceding claims.