GB2100614A

GB2100614A - Backwashing filters using removable nozzle

Info

Publication number: GB2100614A
Application number: GB08211803A
Authority: GB
Inventors: Bernhard Gruber
Original assignee: Schenk Filterbau GmbH
Current assignee: Schenk Filterbau GmbH
Priority date: 1981-05-06
Filing date: 1982-04-23
Publication date: 1983-01-06
Also published as: JPS57190614A; IT1153512B; DE3117777A1; FR2505203A1; BE893081A; NL8201616A; IT8221083A0

Abstract

A movable backflow flushing nozzle (22, 26) cleans the filter surfaces (8) arranged around a central distribution conduit (5) in a filter housing. The filter chambers (7) are annular and filtration is provided by filter cartridges (8) with an inward flow via duct (2). The two end faces of the filter cartridges (8) are open towards the chamber (13) and duct (3) for the filtered liquid. <IMAGE>

Description

SPECIFICATION Filter arrangement for the separation of solid particles from liquids The invention relates to a filter arrangement for the separation of solid particles from liquids.

A filter arrangement has been proposed comprising a housing with an inlet communicating with a centrally located distributing conduit, the latter having a plurality of radial bores distributed along its length and opening into respective ones of a row of filter chambers in each of which is arranged a filter, a discharge outlet communicating with a chamber arranged downstream of the filters for containing the filtered liquid, and a movable flow reversing device capable of selectively connecting one or more of the filter chambers to a dirt removal facility, the pressure in the latter being arranged to be lower than the pressure in the chamber containing the filtered liquid. One known filtration process proceeds in an outward direction.When filtering highly viscous liquids, as happens, for instance, in the textile industry during the processing of cellulose mixtures, the filter elements require regular cleaning. For this purpose, there is provided a flow reversing device, by means of which the filter elements can be flushed regularly and the contaminants are discharged. This is achieved by the provision of two pistons fitted to a tubular connecting rod, which are movably arranged inside the distributing pipe or conduit and join the filter elements to be cleaned to a device the pressure in which is lower than the pressure prevailing in the chamber containing the filtered liquid. In this way, contaminants are flushed off the filter surface.

This filter arrangement, however, has the disadvantage of filter elements of unsuitable form and design. Each filter element consists of a star-shaped, folded filtering unit. When dirt accumulates during operation in the filter corners, the filter buckles outwards. This results in extreme loading of the folds, in particular as a result of the frequent load alternation incurred during pressure build-up and reduction (filtration and flushing), and eventually in the failure of the elements. Through the cracks in the filter element, contaminated liquid enters the chamber containing the filtered liquid, thus affecting its quality. The contaminants are further retained in the folds during the flushing process, resulting in rapid dislocation of the filter cloth.

The present invention therefore aims at providing a filter arrangement which is highly efficient and the filter elements of which are capable of high loading.

According to the present invention there is provided a filter arrangement for the separation of solid particles from liquids, the filter arrangement comprising a housing with an inlet communicating with a centrally located distributing conduit, the latter having a plurality of radial bores distributed along its length and opening into respective ones of a row of filter chambers in each of which is arranged a filter, a discharge outlet communicating with a chamber arranged downstream of the filters for containing the filtered liquid, and a movable flow reversing device capable of selectively connecting one or more of the filter chambers to a dirt removal facility, the pressure in the latter being arranged to be lower than the pressure in the chamber containing the filtered liquid, the filter chambers each being of a substantially annular design and the filters each comprising a cartridge the end faces of which are open towards the chamber for containing the filtered liquid.

Through the liquid to be filtered flows outward, the filtration proper in the filter chambers proceeds in an inward direction. This results in a large filter surface. At the same time, the chambers containing the contaminated liquid, i.e. the filter chambers, can be kept small. Since both end faces of the filter cartridges are open towards the chamber containing the filtered liquid, uniform discharge and even loading of the filter cartridges are ensured.

Depending on the diameter of the distributing pipe and on its length, a large number of filter cartridges can be incorporated. Several filter cartridges may, for instance, be arranged concentrically over the circumference of the distributing pipe, thus forming a complete filter element. Where the length of the distributing pipe is a multiple of that of the complete filter elements, which will usually be the case, several filter elements can be arranged in sequence.

The filter cartridges with their inward flow can be of a very robust design, thus eliminating the problems involved in the high loading incurred during filtration and the flushing of the cleaning process.

For reversing the flow, various devices may be used.

The arrangement can utilise the flow reversing device hereinbefore described but, of course, is by no means excluded from using other flow reversing devices, for instance one by means of which the flow through each individual filter element could be reversed.

A simple and easily fitted solution is, for instance, to be found in the mounting and seating of the filter cartridges in a disc with a cover or a disc with a second disc in a laterally reversed arrangement, which discs are provided with a plurality of location holes for the filter cartridges arranged around their circumference.

A considerable advantage is offered by the fact thatwhen a filter cartridge is damaged, only this particular cartridge has to be replaced, in contrast to known systems, which require the replacement of complete filter elements.

The location holes in the discs, may, at the same time, form the annular spaces into which the inlet bores open out. If two series of filter elements with filter cartridges are arranged in tandem along the distributing pipe, the provision of discharge gaps between adjacent discs is an improvement.

This arrangement and design of the filter elements and filter cartridges ensures a very even discharge and loading both during filtration and during the flushing of the filter surfaces.

To increase the filtering capacity, two or more rows of filter elements can be arranged radially above the distributing pipe, the outer filter cartridges being supplied with contaminated liquid either by way of suitable inlet bores fed with liquid from the inner filter chambers or else directly by way of inlet bores leading off the distributing pipe.

To save space, two or more distributing pipes having filter elements arranged around their circumferences may be arranged to lie parallel in one common housing, the filtered liquid collecting in a common chamber. In this way, several filter units can be arranged in one housing.

The invention also provides a filter arrangement for the separation of solid particles from liquids, the filter arrangement comprising a housing with an inlet communicating with a centrally located distributing conduit, the latter having a plurality of radial bores distributed along its length and opening into respective ones of a row of filter chambers in each of which is arranged a filter, a discharge outlet communicating with a chamber arranged downstream of the filters for containing the filtered liquid, and a movable flow reversing device capable of selectively connecting one or more of the filter chambers to a dirt removal facility, the pressure in the latter being arranged to be lower than the pressure in the chamber containing the filtered liquid.

The piston may be star-shaped to ensure optimum supply of contaminated liquid to those filter cartridges which are not being flushed at the time.

This solution, being independent of the type and form of the filter elements and filter cartridges used, ensures a considerably more intensive cleaning of the filter surfaces during reversed flow. Instead of flushing all filter surfaces distributed around the circumference of any particular section, only part of the filter surfaces of this particular section is flushed at any one time, resulting in a more efficient cleaning action. This is achieved by simply rotating the piston in a cycle to ensure that all the inlet bores of a filter element are consecutively made to coincide with the bores in the piston.

In order to save inlet bores and reduce the clearance volume on the contaminated water and flushing side, one inlet bore may suitable feed two adjacent filter chambers. In this way, the number of inlet bores for the filter chambers can be halved.

A simple solution for supplying the remaining filter elements with contaminated water by way of inlet bores lies in the provision of a piston having four bores in a crosswise arrangement. The invention does, of course, not exclude other arrangements or solutions, such as a flow reversing piston having one, two, three or a plurality of arms and bores. This permits continued filtration by some filter cartridges within any one filter element, while the remaining cartridges are being flushed.

An embodiment of the present invention will now be described by way of example only, with reference to the accompanying drawings, in which :- Figure 7 is a longitudinal section through a filter arrangement according to the invention; Figure 2 is an enlarged view of part of the longitudinal section, showing the filter cartridges according to the invention incorporated in annular filter elements; Figure 3 is a section along Ill - Ill of Figure 1; Figure 4 is a section along Ill - Ill of Figure 1 taken from another further development of the invention; and Figure 5 is a cutaway portion of a section along Ill Ill, showing several filter cartridges above one another within an annular filter element.

Referring to the drawings, a filter arrangement has a housing 1 with an inlet line 2, a discharge line 3 and a flushing outlet 4. Within the housing 1, a distributing conduit or pipe 5 is centrally arranged, its walls being provided with a plurality of inlet bores 6 opening into filter chambers 7. Filtration is effected by filter cartridges 8 seated in the location holes 9 of discs 10. The discs 10 are fitted round the circumference of the distributing pipe 5, their location holes facing each other in an essentially laterally reversed paired arrangement, which enables them to retain a row of filter cartridges 8 arranged round the circumference of a section of the distributing pipe 5, thus forming a complete annular filter element.

Instead of pairs of discs 10 facing each other, just one disc may be used as an alterative, the other end of the filter cartridges of any one row being seated in the bores of a cover.

The filter cartridges 8 are open at their end faces.

In the same way, the discs 10 have ports 11 in the region of the end faces of the filter cartridges 8. The discs 10 are, furthermore, so designed and so fitted to the distributing pipe 5 that between each pair of contiguous discs 10, and thus between individual rows of filter cartridges 8, there are discharge gaps 12 in the circumferential region, which communicate with the ports 11 and thus with the interior of the filter cartridges 8. In this way, a connection with the annular chamber 13 containing the filtered liquid is created, from where the filtered liquid is discharged by way of the discharge line 3. In place of the discharge gaps 12, it is of course feasible to provide suitable passages, such as bores in the discs 10, to establish communication between the chamber 13 containing the filtered liquid and the interior of the cartridges 8 or the ports 11 respectively.

To ensure complete separation of the parts containing the contaminated liquid from these containing the filtered liquid, seals 14 are provided between discs 10 forming a pair, seals 15 between the filter cartridges 8 and the discs 10 and seals 16 between the discs 10 and the distributing pipe 5.

The filter chambers 7 are designed as annular spaces, each defined by two discs 10 and the circumference of a filter cartridge 8. The inlet bores 6 open out into the central region of the filter chambers 7. In the same region, the discs 10 are provided with recesses 17 or shoulders, thus ensuring a better distribution of the liquid flowing into the filter chamber.

A section of the inlet bores 6 for each row is designed as a control element 19 with radial bores 18, which is clamped between two discs 10 holding a row of filter cartridges 8. The purpose of this element 19, which may be omitted if preferred, is to ensure the precise control of the flow to the filter element.

To provide accurate and simple seating for the cartridges 8 in the discs 10, the latter are equipped with end rings 20, in which the seals 15 are seated.

By means of the end rings 20, the filter cartridges 8 are fitted into the location holes of the discs 10. The diameters of the end rings 20 are a little larger than the diameters of the corresponding filter cartridges 8, thus determining the size of the annular filter chambers 7. To simplify the manufacturing process, the location holes 9 and the ports 11 are combined into stepped bores.

The discs 10, together with the control elements 19, are axially clamped to the distributing pipe 5 by means of a clamping device 21.

The flow reversing device comprises two movable pistons 22 arranged on a traversing tube 23 within the distributing pipe 5. Each piston 22 has one or several perforations 24 extending in the longitudinal direction, permitting liquid to flow into the bores 6 behind the piston 22 while the filter elements are cleaned. In place of two pistons 22, one only or several may be provided - depending on the number of filter baskets arranged in tandem.

The traversing tube 23 is equipped with a traversing device 25 driven by gearing 26 not illustrated in detail. In this way, the piston 22 is able to move in the longitudinal direction.

Depending on the number of bores 6 distributed round the circumference of any one section of the distributing pipe 5, each piston 22 may be provided with the same number of radial bores 27, which can be made to coincide with the inlet bores 6. If preferred, the piston 22 may alternatively be provided with two or more rows of bores 27, allowing several filter cartridges 8 to be cleaned consecutively, if required.

Instead of equipping the piston 22 with the same number of bores 22 as there are inlet bores 6, each piston can, if necessary, be provided with a substantially smaller number of bores 27.

In Figure 3, for instance, only four bores 27 are shown, arranged in a crosswise configuration. These bores 27 are starting in the traversing tubes 23 and opening out into four inlet bores 6. In this way, the filter chambers 7 communicating with the inlet bores 6 can be intensively flushed. Following this, the distributing tube 5 is, together with the piston or pistons 22, indexed by means of equipment not illustrated in detail, enabling anothersetoffourfilter chambers 7 to be flushed and cleared of accumulations of solids.

Instead of four bores 27, it is of course possible to provide other numbers, such as two, three, six, eight, twelve etc.; the number selected will usually be a fraction of the total number of inlet bores 6.

Figure 4, which is a section similar to that shown in Figure 3, illustrates another embodiment of the invention, which essentially corresponds to the one described above. The only difference lies in the fact that any one inlet bore 6 supplies two adjacent filter chambers 7 with contaminated liquid, thus providing for their joint connection to the flow reversing device. In this way, the number of inlet bores 6 is halved. This arrangement offers the further advantage that the liquid flows substantially tangentially into the filter chambers 7, thus creating a whirling effect beneficial to filtration and flushing.

The reduction in the number of inlet bores to be provided round the circumference results in a less costly manufacturing process and, with certain products, in an improved filtering effect.

At the flushing outlet 4, a lower pressure, usually atmospheric pressure, is prevailing, thus ensuring a differential pressure relative to the chamber containing the filtered liquid, which may, for instance, be subjected to an operating pressure of 50 bar. This results in the sudden cleaning of the filter cartridges and removal of the contaminants accumulated thereon.

The piston 22 can move along the inside of the distributing pipe 5 in a continiibus or intermittent motion. When the inlet bores 6 communicate with the bores 27 in the piston 22, communication with the flushing outlet 4 is established via the traversing tube 23, the passage 28 in the traversing tube and the annular space 29. The differential pressure caused by this in the filter chambers 7 results in reverse flow through these and in the removal of contaminants accumulated on the filter surface by way of the passages 6,27,28 and the flushing outlet 4.

In order to increase the capacity of the filter arrangement, several rows of filter cartridges can as indicated in cutout form in Figure 5 - be arranged above each other in any one section. If this is done, the outer filter cartridges can either be supplied with liquid from the inner filter cartridges, or else via separate inlet bores leading off the distributing pipe 5. To save space, these rows of filter cartridges would usually be staggered, and the inlet bores for the outer filter cartridges could then pass through between the inner filter cartridges.

Another way of accommodating a maximum number of filter elements in a small space would be the incorporation of two or more distributing pipes with filter cartridges arranged round their circumferences in one housing in a parallel arrangement. The filtered liquid from these could then be discharged into one common chamber. A consecutive arrangement of the filter elements would be another alternative.

The filter cartridges can simply be designed as cylindrical units. Other possibilities are, of course by no means excluded. The only essential condition is that, in the interests of a large filter surface and favourable flow conditions, the liquid should flow through the filter in the inward direction during filtration, the contaminated liquid being fed to the filter chambers in the manner described above to ensure optimum control and minimum flow-back of contaminated liquid from the inside of the filter element.

Claims

1. Afilterarrangementfortheseparation of solid particles from liquids, the filter arrangement comprising a housing with an inlet communicating with a centrally located distributing conduit, the latter having a plurality of radial bores distributed along its length and opening into respective ones of a row of filter chambers in each of which is arranged a filter, a discharge outlet communicating with a chamber arranged downstream of the filters for containing the filtered liquid, and a movable flow reversing device capable of selectively connecting one or more of the filter chambers to a dirt removal facility, the pressure in the latter being arranged to be lower than the pressure in the chamber containing the filtered liquid, the filter chambers each being of a substantially annular design and the filters each comprising a cartridge the end faces of which are open towards the chamber for containing the filtered liquid.

2. A filter arrangement according to Claim 1, wherein a plurality of rows of filter cartridges are distributed round the circumference of the distributing conduit and are arranged lengthwise of the distributing conduit.

3. A filter arrangement according to Claim 1 or 2, wherein the filter cartridges of the or each row are seated in location holes of a disc mounted on the distributing conduit, the disc having ports in the region of the end faces of the filter cartridges.

4. A filter arrangement according to Claim 3, wherein the filter cartridges of the or each row are located between two discs in a substantially laterally reversed arrangement.

5. A filter arrangement according to Claim 4, wherein the filter cartridges are provided with end rings, by means of which they are retained in the discs.

6. A filter arrangement according to Claim 5, wherein the diameters of the end rings are larger than the diameters of the filter cartridges, and the location holes together with the filter cartridges define annular filter chambers, into which the radial bores open.

7. A filter arrangement according to Claim 6, wherein the location holes have recesses enlarging the filter chambers in the region of ports of the radial bores.

8. A filter arrangement according to Claim 6 or 7, wherein, for the or each row of filter cartridges, a control element associated with each of the radial bores is clamped between the adjacent discs and defines a through bore communicating between the radial bore and the respective filter chamber.

9. A filter arrangement according to any of Claims 3 to 8, wherein when a plurality of the discs are mounted lengthwise of the distributing conduit, the discs are clamped by a common clamping device.

10. A filter arrangement according to any of Claims 3 to 9, when dependent on Claim 2, wherein between adjacent rows of filter cartridges arranged lengthwise of the distributing pipe, a discharge gap is provided in the circumferential region between adjacent discs of adjacent rows.

11. A filter arrangement according to any of the preceding Claims, wherein each of the filter cartridges is of cylindrical shape and the respective radial bore opens into the annular filter chamber substantially midway along the cylindrical cartridge.

12. A filter arrangement according to any of Claims 1 to 11, wherein each radial bore opens into two filter chambers arranged side by side circumferentially.

13. A filter arrangement according to any of Claims 1 to 12, wherein two or more rows of filter cartridges are spaced radially outwardly of the distributing conduit.

14. A filter arrangement according to Claim 13, wherein the radial bores opening into the filter chambers of the radially outer filter cartridges lead off the radially inner filter chambers.

15. A filter arrangement according to Claim 13, wherein the radially spaced rows of filter cartridges are circumferentially staggered and the radial bores for the radially outer filter cartridges pass from the distributing conduit between the radially inner filter cartridges.

16. A filter arrangement according to any of the preceding Claims, wherein a plurality of parallel distributing conduits having filter cartridges arranged round their circumferences are accommodated in one housing with a common chamber for the filtered liquid.

17. A filter arrangement for the separation of solid particles from liquids, the filter arrangement comprising a housing with an inlet communicating with a centrally located distributing conduit, the latter having a plurality of radial bores distributed along its length and opening into respective ones of a row of filter chambers in each of which is arranged a filter, a discharge outlet communicating with a chamber arranged downstream of the filters for containing the filtered liquid, and a movable flow reversing device capable of selectively connecting one or more of the filter chambers to a dirt removal facility, the pressure in the latter being arranged to be lower than the pressure in the chamber containing the filtered liquid, said movable flow reversing device comprising at least one piston capable of axial movement within the distributing conduit, the piston having radial bores capable of communicating with the radial bores of the distributing conduit, and having fewer bores than the number of radial bores opening into said row of filter chambers, the piston being rotatable about its longitudinal axis.

18. A filter arrangement according to Claim 17, wherein the piston can be so indexed that the radial bores thereof can conincide with all the radial bores of the distributing conduit in turn.

19. Afilter arrangement according to Claim 17, wherein the piston is provided with four radial bores arranged in a crosswise configuration.

20. A filter arrangement according to any of Claims 17 to 19, wherein each radial bore of the distributing conduit opens into two filter chambers arranged side by side circumferentially.

21. A filter arrangement for the separation of solid particles from liquids, substantially as hereinbefore described with reference to the accompanying drawings.