GB2282763A

GB2282763A - Improvements relating to screening apparatus

Info

Publication number: GB2282763A
Application number: GB9420759A
Authority: GB
Inventors: Clifford Michael Spiller
Original assignee: CLEAR SpA Ltd
Current assignee: CLEAR SpA Ltd
Priority date: 1993-10-16
Filing date: 1994-10-14
Publication date: 1995-04-19
Anticipated expiration: 2014-10-14
Also published as: GB9321390D0; GB9420759D0; GB2282763B

Abstract

The invention relates to the provision of a drum (10) for use in apparatus for separating liquids from solids in a liquid/solid mixture. The wall of the drum is formed from either of a perforated plate material or a series of wires (12, 14) having a wedge shaped cross section and in one embodiment the drum wall is formed from a series of shaped segments fixed together. The drum is provided having a frustoconical shape and mounted for rotation such that the separated solids are induced to be despatched via the wider of the two ends by the shape of the drum wall. The drum may be used in one embodiment with a compactor device for subsequent treatment of the separated solids. The shape of the drum provides improved separation of the solid and liquid matter. <IMAGE>

Description

Improvements Relating to Screening Apparatus This invention relates to the provision of screening apparatus for the separation of solids from a liquid such as is required for example in the provision of screening apparatus in the treatment of effluent from a factory or sewage but may equally be used in any application where a medium containing liquids and solids is required to be screened to separate the liquid and solids.

There are many differing forms of screening apparatus available for the separation of solids from a liquid and furthermore there are several alternative types of media for the screening of the effluent or sewage. The typical form of apparatus which is available is provided in a drum mounted in a horizontal or inclined axis with the walls of the drum running substantially parallel to the said axis and with at least one open end for the introduction and/or extraction of the liquids or solids from the interior of the drum. The drum can either be partially submerged in the effluent which is to be screened or may be provided adjacent effluent introducing means which introduce the effluent onto the walls of the drum for the screening thereof. Typically the screening drums are mounted to provide for the rotation of the drum, the rotational movement causing the screening media to pass through the effluent hence causing improved separation of the effluent to occur and also improving the flow of the liquid through the screening media and leaving the solids deposited on the other side of the media.

The screening media used to form the walls of the drum is typically any of a plurality of wedge wires, perforated plate material or mesh material. Each of the media has advantages in particular areas of use but one common problem is the blockage of the gaps in the media through which the separated liquids pass by the solids material which has been screened.

In an attempt to overcome this problem devices such as scraper blades adapted to pass along the surface of the drums to remove any solids material therefrom and/or conventional lifting staves have been used to move and, in relationship with spray means, deposit solids in collection troughs as appropriate. While these devices do improve the problem of solids blockage and hence the screening process, any improvement is only limited.

The aim of the present invention is to provide a screening drum which is of a form to provide improved screening and separation of the solids held in an effluent from the liquid.

The drum is of a shape such that the liquid is encouraged to pass through the screening media of the walls of the drum and the solids trapped thereby are encouraged to move to one end of the drum.

The present invention provides apparatus for the screening of an effluent to separate the solid material therefrom, the said apparatus comprising a drum mounted to be rotatably movable about its longitudinal axis and at least a substantial part of the wall of said drum is formed of a screening media and wherein the walls of the drum converge toward one end of the drum to form a substantially frustoconically shaped drum.

The angle of convergence of the wall of the drum is adjustable to suit the material to be screened but in all cases the form of the drum will be frustoconical.

Typically the drum wall is formed from perforated plate cut and shaped to form the frustoconical drum wall. Alternatively the perforated plate is cut and shaped to form a segment of the drum wall and the drum wall is formed from a plurality of said segments joined together to form the frustoconical shape.

In an alternative embodiment the walls of the drum are formed from a plurality of wires of wedge shaped cross section arranged to run longitudinally of the drum. Typically the wall of the drum is formed from a plurality of segments and each of said segments is substantially formed from wedge shaped wires.

Preferably each segment is formed from a series of wedge wires joined together by a plurality of perpendicularly mounted support bars.

The gap between adjacent wires is maintained constant as the walls of the drum converge toward one end of the drum.

The wedge wire segments are fitted such that the base portions of the wedge wires face either inwardly or outwardly of the interior of the drum to face the direction of flow of the effluent to be screened.

In one embodiment the drum of the invention is provided at least partially submerged in the effluent to be screened and the separated solids material is collected in solid collection means, such as a compactor screw.

In an alternative embodiment the effluent to be screened is introduced to the wall of the drum from a supply pipe or chute and the separated solids material collected at the widest end of the drum. Typically the effluent is introduced into or against the walls adjacent the narrow end of the drum.

Typically the drum is provided to be attached to and mounted on conventional drive mechanisms and, in one embodiment is provided on the internal face of the wall with lifting means to induce movement of the solids material toward the widest end of the drum. In one embodiment the lifting means are staves mounted at an angle to the vertical plane.

In one aspect of the invention there is provided a method of forming a frustoconically shaped drum comprising placing a series of wedge shaped wires in fixed spaced relationship to form a plate, cutting the same into at least one trapezoidal segment, forming the segment in a rolling mill to form a curved segment, and joining a number of segments together to form the side wall of the frustoconically shaped drum.

Specific embodiments of the invention will now be described with reference to the accompanying drawings wherein; Figure 1 illustrates an elevational view of the drum of the invention in a first embodiment; Figure 2 illustrates an end elevation of Figure 1; and Figure 3 illustrates an end elevation of the drum in a second embodiment.

Referring firstly to Figure 1 there is shown a drum 2 of the invention of frustoconical shape. The said drum comprises end flanges 4 and 6 and, intermediate these flanges, drum wall 8.

In this embodiment the wall 8 is formed from a plurality of trapezoidal segments 10 attached together along flanges 12 provided along the longitudinal edges of the segments. In this embodiment each segment is formed from a plurality of wedge wires 14 indicated at various parts on Figure 1 for illustration but it should be appreciated that substantially all of each segment is formed from the wedge wires. The gap between each pair of adjacent wedge wires is maintained substantially constant along the length of the wall of the drum. Figure 2 illustrates an end view of the drum 2 and shows the end flange 6 provided with a plurality of bolt holes 18 to allow the drum to be attached to drive means and/or solids collection means which collect solid matter induced by the angle of the drum walls and the rotation of the drum to travel to the widest end of the drum. Again the wedge wires 14 are illustrated to clearly show that the gaps therebetween are maintained constant.

Figure 3 illustrates an end elevation of a second embodiment of the drum of the invention wherein the wall 8 of the drum is formed from either one piece or a plurality of segments, each formed from perforated plate 20. In this case the preforations are illustrated 22 but it should be appreciated that a considerably greater number of preforations 22 will be provided along the length of the wall of the drum. Also shown is the flange 4 of the narrower end of the drum and this flange is again provided with a plurality of bolt holes 18 to allow the drum end to be attached to drive means and/or effluent supply means if for example the effluent is to be introduced to the drum through the narrow end.

The spacing of the wedge shaped wires and the size and quantity of perforations provided is dependent on the size of drum to be provided, the volume of effluent to be screened and the solids content of the effluent.

To form the screen from perforated material the drum walls can either be formed from one cut and formed piece of sheet perforate material or alternatively may be formed , as with wedge shaped wire walls, from segments. In the segmential construction each segment is provided with longitudinal flanges and, in the flat form is of trapezoidal shape.

Typically this is cut from flat sheet and then the same is partially curved in a roll former such that the subsequent bolting together of the segments forms the frustoconical drum of the invention.

In one embodiment the effluent is introduced from a trough into the interior of the drum where the effluent contacts the rotating drum wall. The impact and subsequent induced movement of the effluent by rotation and the effect of the wedge wires, or perforated plate, and lifting means, causes the liquid to separate from the solids and pass through the drum wall to be collected. The solids remaining in the drum are gradually moved to the wider end of the drum by the slope of the wall due to the frustoconical shape and the solids are removed from this end.

The drum of this invention allows substantial improvements in the discharge of solid material which has been separated from the effluent through the wider end of the drum toward which the solids are induced by rotation of the drum and the angle of the walls. This improvement is achieved without the need to utilise internal lifting staves and such like and therefore an internal screening surface is provided which is free of any obtrusions and hence reduces the opportunity for solids to snag and reduces the occurence of blockages of the screening walls.

The improvement in the discharge of solids allows effluents which it would previously not be possible to screen to be screened. The inducement of solids which are separated from the effluent to move off the screening area toward the wider end of the drum also results in a reduction in the time of retention of solids in the screen and hence effluent in the drum. Thus the throughput rate of effluent can be increased without detrimentally affecting the screening process and thus the screen of the invention represents considerable improvements over existing screens in terms of reduction in downtime due to blockage and the volumes of effluent which can be screened.

Claims

1. Apparatus for the screening of an effluent to separate the solid material therefrom, said apparatus including a drum mounted to be rotatably movable about its longitudinal axis and at least a substantial part of the wall of said drum is formed from a screening media and wherein the wall of the drum converges toward one end of the drum to form a substantially frustoconically shaped drum.

2. Apparatus according to claim 1 wherein the wall of the drum is formed from shaped perforated plate material.

3. Apparatus according to claim 2 wherein the perforated sheet material is provided in a series of curved segments, said segments joined together to form the wall of the drum.

4. Apparatus according to claim 1 wherein the wall of the drum is formed from a plurality of wires of wedge shaped cross section held in a spaced relationship.

5. Apparatus according to claim 4 wherein the drum wall is formed from a series of segments joined together and each of the segments is substantially formed from a plurality of wedge shaped wires held in spaced relationship.

6. Apparatus according to claim 5 wherein the wedge shaped wires are held in a spaced relationship by support bars attached thereto and mounted perpendicularly to the wedge shaped wires.

7. Apparatus according to any of claims 4-6 wherein the wedge shaped wires are arranged with the base of the wires facing toward the effluent material.

8. Apparatus according to claim 1 wherein the drum is mounted on conventional drive means provided at at least one end thereof to rotatably drive the drum during use.

9. Apparatus according to claim 1 wherein the drum is mounted to be at least partially submerged in the effluent to be screened.

10. Apparatus according to claim 1 wherein the effluent is introduced into the drum from a trough or supply pipe to impact on the inner face of the drum wall.

11. Apparatus according to claim 9 or 10 wherein the separated solids material is collected in solid collection means.

12. Apparatus according to claim 11 wherein the solid collection means is a compactor screw.

13. Apparatus according to any of the preceding claims wherein there is provided a series of lifting means attached to the inner face of the drum and spaced therealong.

14. A method for forming the wall of a drum for use in screening apparatus for separating solid material from an effluent, comprising the steps of placing and holding a series of wedge shaped wires in fixed spaced relationship to form a plate, cutting the plate into at least one trapezoidal segment, forming the segment in a rolling mill to a curved shape, and joining a series of said segments together to form the side wall of a frustocinically shaped drum.

15. Apparatus as hereinbefore described with reference to the accompanying drawings.