GB2319484A

GB2319484A - Drum screening apparatus

Info

Publication number: GB2319484A
Application number: GB9724520A
Authority: GB
Inventors: Arthur Hanson
Original assignee: Robbins & Myers Ltd; Robbins and Myers Ltd
Current assignee: Robbins & Myers Ltd; Pfaulder Process Solutions Group Stonehouse Ltd
Priority date: 1996-11-20
Filing date: 1997-11-20
Publication date: 1998-05-27
Also published as: GB9624090D0; GB9724520D0

Abstract

The invention which is the subject of this application relates to screening apparatus for removing solids material from effluent such as sewage, food waste and the like. The screening apparatus includes a drum screen with a screening wall onto which the effluent is impacted and which has slots 18 which allow the passage of the liquid but retain the solids material. The screening wall comprises a series of segments 2 which are held on support means (14,figs 4 and 5) in respective positions. The use of a series of supported segments held in the required configuration allows adaptive construction of the same and allows greater flexibility in forming screening walls of different dimension but ensuring performance characteristics are maintained. Preferably, there are 4 segments forming the drum periphery and the ends of each segment preferably have apertures 8 for the supports (14), alternative segments having a recessed end 6 to define the width of the separating slots 18. Preferably the screen has lifting fingers (22, Fig 5) to move the separated material onto a helix conveyor where it is passed to a compactor.

Description

Screening apparatus The invention which is the subject of this application relates to screening apparatus for the processing of fluid material to separate solids and fibrous material from the liquid in the material.

There are many forms and uses for screening apparatus and typically in current screening apparatus there is provided a drum mounted for rotation about a horizontal axis and the longitudinal screening walls of the drum are formed from a series of metal hoops or wound wire with adjacent wires held in a spaced relationship such that during rotation the liquid which is separated from the material passes through the spaces to be collected while the solids and fibrous material remain trapped inside the drum as the same cannot pass through the narrow elongate spaces. In order to encourage separation of materials such as sludge it is normally the case that an arm is provided to rotate inside a screening drum and said arm is typically provided with a series of teeth there along which, during rotation of the arm about the horizontal axis, fit into and pass round the spaces defined between the metal hoops thus squeezing the solid material against the hoops and squeezing the liquids from the same and through the spaces.

This known apparatus is found to be relatively complex and expensive to manufacture and, due to the types of material being processed, the number of moving parts in the screen are susceptible to blockages and/or damage.

The aim of the present invention is to provide screening apparatus for use in the processing and separation of effluent such as sludge and also to provide an alternative screen construction to those which are currently available and which can be used for any screening process.

The present invention relates to a screen for use in the separation of solid and fibrous material from a liquid, wherein the screening wall is formed from a plurality of elongate segments, each of said segments held in respective location so as to form a screening wall having a plurality of elongate slots defined between said segments.

Typically the screen is a drum screen and a series of said segments are arranged in an end-to-end relationship to form a band around the screening wall, and said screening wall is formed of a series of said bands held in spaced relationship along said wall. In one embodiment said bands are from a series of segments held in an end to end relationship and each segment linearly offset with respect to the segments at respective ends thereof.

Typically at least one end of each of the segments is formed with a protrusion or recess formed to allow the end of a further segment to be placed in register therewith. Each end of each segment can be provided with an aperture to allow the same to be slid onto a supporting rod. In this embodiment, when said segments are slid onto respective, spaced supporting rods, the screening wall is formed.

Typically each segment is of a length and shape to form approximately a quarter of the overall circumference of a substantially circular or multisided screening wall and there is provided four supporting rods, each spaced 90" apan around the screening wall. The supporting rods are typically arranged to lie perpendicularly to the linear axis of the segments when mounted thereon.

In one embodiment there is provided a drum screen wherein a screening wall is formed from a series of segments held at respective spaced positions to form the screening wall and wherein respective linearly adjacent segments are offset with respect to segments at respective ends thereof and have a slot formed to at least one elongate side thereof. Typically the ends of respective linearly adjacent segments overlap and the protrusion of overlap defines the width of the slot formed at that protrusion.

The segments can be formed from modified Teflon based polyethylene or stainless steel or any other suitable material.

In a further aspect of the invention there is provided screening apparatus for separating solid material from liquid upon the introduction of effluent into or onto a drum screen, said drum screen having a screen wall formed from a plurality of segments supported held in position by support means spaced around the periphery of said screening wall and along the length thereof.

Typically each segment is provided, at at least one end thereof, with a shoulder for location with the end of an adjacent segment. The shoulder is typically of a thickness so as to protrude from the linearly adjacent segment and the extent of said protrusion defines the spacing between axially adjacent segments on the screening wall.

The support means are preferably support rods onto which the segments can be slid and are held in relative position in engagement with the end plates of the drum screen.

The supporting rods can in one embodiment include a locating key formed along the length thereof and said segments are provided with apertures with matching key formations therein to allow engagement and positioning of the segments on said supporting rods.

If required lifting fingers can be provided on the interior of the screening wall by sliding same onto the supporting rods at spaced intervals.

The apparatus can be provided with effluent inlet means to introduce the effluent onto the external face of the screening wall or to introduce the effluent onto the internal face of the screening wall.

Typically means can be provided to collect solid material from the screening wall and remove same from slots in the screening wall.

Thus the screening wall can in one embodiment of the invention be formed by sliding a plurality of bands, each comprising a plurality of segments as so described onto the supporting rods to form a screening wall formed of a plurality of said bands.

When the screening wall is incorporated in a drum screen used to separate sludge material the sludge is introduced into the drum from an inlet tank which forms an integral part of the machines construction. The flow of the sludge into the tank is controlled by means of an actuated valve. The valve is opened and closed in response to a level sensing device which is fitted within the inlet tank. A collection trough is provided inside the drum to collect screened material which is lifted by the fingers and then dropped into the collection trough. Typically the material in the trough then passes to a compactor where the screenings are compacted into a plug and any remaining liquid removed.

Specific embodiments of screening apparatus including a drum screen and a drum in use for treating sludge are now shown with reference to the accompanying drawings wherein: Figure 1 illustrates a segment of the invention; Figure 2 illustrates a band formed from segments of the invention; Figure 3 illustrates in detail the arrangement between the ends of adjacent segments when forming the screening wall; Figure 4 illustrates a partially formed screening wall of the invention; Figure 5 shows a drum screen according to one embodiment of the invention and a section of the screening wall; and Figures 6, 7 and 8 show a drum screen of the invention provided for use for treating sludge.

Referring firstly to Figure 1 there is shown a segment 2 of a type for forming a band of a screening wall. The segment 2 is provided at each end 4, 6 with an aperture 8 and at one end with a recess portion 10.

Figure 2 illustrates a band 12 of the invention formed from four segments 2. The segments are not joined together but the ends are arranged such that the end 4 without a recess registers with the recess portion 10 in the end 6 of the adjacent segment such that a degree of registration and location between the segments is provided. When the segments are in their correct position the apertures 8 in adjacent segment ends 4, 6 register to allow a rod to pass there through. The relationship between adjacent ends 4 and 6 of the segments 2 in the band 12 is shown more clearly in Figure 3 wherein the end 4 locates in the recess 10 in the end 6 such that the apertures 8 are in line.

Figure 4 illustrates a partially constructed screening wall of the invention wherein a series of bands 12 are held in position on a series of rods 14 which in turn are held in position on an end plate 16. To form the screening wall the bands are slid into position on the rods 14 with each rod passing through two in-line apertures 8 of adjacent segment ends 4, 6. The segments are slid along the rods as shown by 12' to come into contact with previously applied segments. The arrangements of the ends of the segments causes slots 18 to be created between adjacent segments 2 along the rods and this is more clearly shown in Figure 3 where a first series of segments is shown in full lines and a second series of segments is shown in broken lines with the slots 18 shown between adjacent segments of the respective bands.

Figure 5 illustrates a drum screen formed according to the invention and illustrates partially the positioning of the segments which form the screening wall. The drum has a first end plate 16 towards which the segments are packed during formation of the screening wall and a second end plate 20 to which the rods 14 are bolted once all the segments 12 have been placed in position. In the embodiment shown, in addition to segments being mounted on the rods 14 a plurality of fingers 22 are provided at spaced intervals.

The fingers are provided in an angled position to provide a lifting and separating action on the screening solids which gather at the base of the drum. The fingers are slid into position as the bands are slid onto the rods and in one embodiment a number of segments have especially formed ends to allow the fingers to be fitted without causing alteration to the size of the slots 18 between the bands.

Figures 6, 7 and 8 show a drum screen 24 with a screening wall which can be formed as described above and in this instance the drum screen is arranged for the treatment of sludge. In this embodiment the sludge is introduced into the drum interior from the inlet tank 26 and discharged against the screening wall of the drum. The drum is mounted for rotation as shown by arrow 28 and as the drum rotates the sludge impacts against the screening wall and the liquid therein escapes through the slots 18 in the wall to a collection trough. The screenings which remain in the drum are picked up and broken by the fingers 22 which pass through the material and as the screenings are lifted they fall into a collection trough 30 from which they are moved by helical screw to a compactor 32.

Thus the present invention provides screening apparatus which can include a screening wall formed from a series of segments which provides a throughput of treatment of material which is substantially greater than that which can be achieved using the conventional screening walls.

Claims

1. A screen for use in the separation of solid and fibrous material from a liquid, wherein a screening wall is formed from a plurality of elongate segments, each of said segments held in respective location so as to form a screening wall having a plurality of elongate slots defined between said segments.

2. A screen according to Claim 1 wherein the screening wall is provided in a drum screen and a series of said segments are arranged in an end-to-end relationship to form a band around the screening wall, and said screening wall is formed of a series of said bands held in spaced relationship along said wall.

3. A screen according to claim 2 wherein each of said bands is formed from a series of segments held in an end to end relationship and each segment linearly offset with respect to the segments at respective ends thereof.

4. A screen according to Claim 2 wherein at least one end of each of the segments is formed with a protrusion or recess formed to allow the end of a further segment to be placed in register therewith.

5. A screen according to Claim 1 wherein each end of each segment is provided with an aperture to allow the same to be slid onto a supporting rod.

6. A screen according to Claim 5 wherein when said segments are slid onto respective, spaced supporting rods, the screening wall is formed.

7. A screen according to Claim 5 wherein the screening wall is circular or multisided and each segment is of a length and shape to form approximately a quarter of the overall circumference of a substantially circular or multisided screening wall.

8. A screen according to Claim 7 wherein there is provided four supporting rods, each spaced 90" apart around the screening wall.

9. A screen according to claim 8 wherein said supporting rods are arranged to lie perpendicularly to the linear axis of the segments when mounted thereon.

10. A screen according to claim 1 wherein a screening wall is formed from a series of segments held at respective spaced positions to form the screening wall and wherein respective linearly adjacent segments are offset with respect to segments at respective ends thereof and have a slot formed to at least one elongate side thereof.

11 A screen according to claim 10 wherein the ends of respective linearly adjacent segments overlap and the protrusion of overlap defines the width of the slot formed at that protrusion.

12. A screen according to any preceding claims wherein the segments are formed from modified Teflon based polyethylene or stainless steel or any other suitable material.

13 Screening apparatus for separating solid material from liquid upon the introduction of effluent into or onto a drum screen, said drum screen having a screen wall formed from a plurality of segments supported held in position by support means spaced around the periphery of said screening wall and along the length thereof.

14. Screening apparatus according to Claim 13, wherein each segment is provided, at at least one end thereof, with a shoulder for location with the end of an adjacent segment.

15. Screening apparatus according to Claim 14 wherein the shoulder is of a thickness so as to protrude from the linearly adjacent segment and the extent of said protrusion defines the spacing between axially adjacent segments on the screening wall.

16. Screening apparatus according to claim 13 wherein the support means are support rods onto which the segments can be slid.

17. Screening apparatus according to Claim 16 wherein the supporting rods are held in relative position in engagement with the end plates of the drum screen.

18. Screening apparatus according to Claim 16 wherein the supporting rods include a locating key formed along the length thereof and said segments provided with apertures with matching key formations therein to allow engagement and positioning of the segments on said supporting rods.

19. Screening apparatus according to claim 13 wherein said apparatus includes a drum screen, a trough for introducing the effluent to be separated into the drum screen to impact onto the screening wall of the drum screen, a helix conveyor to remove solids material from the screen wall and a compactor into which the helix conveyor leads.

20. Screening apparatus according to claim 19 wherein the screening wall includes separating and lifting fingers which pass through the solids material and move same into the helix conveyor.

21. Screening apparatus according to any of the preceding claims wherein lifting fingers are provided on the interior of the screening wall by sliding same onto the supporting rods at spaced intervals.

22. Screening apparatus according to any of the preceding claims wherein the drum screen is driven to be rotatable.

23. Screening apparatus according to any of the preceding claims wherein the drum screen is provided with effluent inlet means to introduce the effluent onto the external face of the screening wall.

24. Screening apparatus according to any of claims 1-23 wherein the drum screen is provided with effluent inlet means to introduce the effluent onto the internal face of the screening wall.

25. Screening apparatus according to any of the preceding claims wherein there is provided means to collect solid material from the screening wall and remove same from slots in the screening wall.

26. A drum screen and screening apparatus as hereinbefore described with reference to the accompanying drawings.