GB2331027A

GB2331027A - Intermittently moving belt filter with pleats

Info

Publication number: GB2331027A
Application number: GB9723505A
Authority: GB
Inventors: Peter Anthony Miller
Original assignee: Individual
Current assignee: Individual
Priority date: 1997-11-07
Filing date: 1997-11-07
Publication date: 1999-05-12
Anticipated expiration: 2017-11-07
Also published as: GB9723505D0; GB2331027B

Abstract

In an intermittently moving belt filter of the type where a section of filter belt 21 is supported on a perforated plate 19 and sealed between a cover 27 and a receptacle 22 for filtration and then moved out for regeneration, the filter belt is pleated. The belt is made up of an upper layer of filter medium (43, Fig 6) bonded to a thicker substrate layer (47). This composite is pleated to increase the filtering surface area, and then bonded at the lower extremities to a third layer (44) of coarse mesh to give strength to the belt. Around the periphery of the belt, which is sealed between the cover and the receptacle, the composite is unpleated and the third layer is impervious. The pleats may be supported by inserts 49. In operation, liquid to be filtered and pressurised gas are supplied above the filter belt, and filtrate is removed from below the filter belt. After filtration, means 26 lift the cover away from the receptacle and the section of belt is moved out of the filter chamber by means of motor driven roller 28. On reaching deflection roller 29, the pleats are expanded and cleaned by an ultrasonic generator 38, and the belt then passes through high pressure nozzles 31, cleaning bath 33, rinsing bath (48) and a drying stage (50).

Description

DESCRIPTION A Fluid Filtering Apparatus Background: The requirements of the fluid processing and using industries concerning the purity of the fluids processed and employed are becoming increasingly demanding. The technical destinctions and boundaries conventionally made between solid/fluid separation operations, ranging from applications where visible solids in suspension are separated to operations where adsorption and separation of molecular and/or atomic species from fluids are carried out are rapidly disappearing.

The demands of the these industries point to the need for the rationalization of these operations leading to automation, universal application of the apparatus employed and less envirionmental impact as well as a much improved cost-effectiveness of the operations.

State of the art methods for submicronic separation ranging from 10'to I micron almost invariably involve the application of some form of pressurized separating apparatus depicted schematically in Fig. I at Pos.3. No essential distinction is made between the design of apparatus employed for gases and liquids. The majority of these devices consist of cartridges manually fitted with disposable wound, packed or pleated filter media. On,fouling" the filter elements are normally manually removed and replaced with fresh ones. This procedure is becoming increasingly onerous for the fluid processing and using industries. Only rarely is it possible to regenerate and reuse these invariably costly elements. Their disposal, due to hazardous contamination, often presents insurmountable problems. The recent trend with liquid purification to the so-called ,,cross-flow" technique to continuously regenerate the sub-micronic media ,,in-situ" has fallen far short of the initial expectations. The reason for this is the inherent inability of this method of removing many materials which firmly lodge in the pores of the media combined with the increased exposure of these pores to fouling. The problem is compounded by the high fluxes required through the media due to the limited area of medium available with flat or tubular element configurations. Chemical regeneration is rarely possible due to the near impossibility of completely removing the regenerating liquid from the multiplicity of ,,dead" pockets in the internals of the apparatus after use.

On the other hand, state of the art apparatus for"macro-separation"carried out with liquids in the range above I micron illustrated in Fig. 1 utilize media which are regenerated ,,in-situ" and reused. Not identical but similar apparatus are employed for separation carried out with gases. However, sub-micronic separation is seldom carried out with this array of apparatus.

This is mainly due to the inpracticability of,,in-situ" media regeneration with sub-micronic separation. The necessity for the manual removal of the media after use for disposal or regeneration is uneconomical and seldom practiced. The recent burgeoning consumption of cartridge filter elements over a wide range of industries used for both liquid and gas purification attests the attraction of a design that provides a high ratio of surface of separation to container volume combined with ease of manual removal and replacement of the element..

The goal of the present invention is to technically bridge the gap existing between the present differing practices with regard to sub-micronic and ,,macro" separation by providing innovative apparatus utilizing a high ratio of media surface to apparatus volume combined with the innovative provision of method and apparatus for media regeneration which operate fully automatically throughout the whole range of separation operations concerning fluids from reverse osmosis to macro-s/l separation in most liquid and gas processing and using industries.

The Invention According to the invention a high ratio of media area to container volume is obtained by employing an innovative range of flat, pleated sections of media capable of automatic removal from a pressure or containing vessel, whereby after removal of any solid residues with the aid of for example ultrasonic technology, the pleated section of filter media is regenerated for reuse by subjecting it to high pressure sprays followed, optionally, by further ultrasonic cleaning and rincing baths as well as dewatering devices.

Description and operation of the apparatus of the invention: Fig.2 provides a schematic illustration of the device of the invention. The apparatus comprises a movable endless filter band or belt 21 that is transported intermittently by means of a motor driven deflection roller 28 over a plane, pervious support member 19 that forms a closed exit/drainage chamber 23 for the filtered fluid. Adjacent to the support member and with respect to this member an element 27 is provided with the means 26 for moving it perpendicularly, whereby in the lowered position its adjacent edges engage and seal an overlying peripheral section of the stationary filter band 21. In a preferred embodiment of the invention the entire periphery of the sealed section of filter band 36 consists of a strip of unpleated material and the movable element 27 takes the form of a pressure resistent lid the rim of which in the sealed position engages the peripheral strip of unpleated material thereby sealing the enclosed section of filter band thus forming an upper and a lower filter chamber. In a preferred embodiment of the invention the enclosed section of the filter band 21 consists essentially of a composite of three layers of different materials illustrated in Figs.5,6,7 and 8, whereby the upper layer 43, the actual filter medium, is supported on and bonded to a second much thicker layer of porous material 47 acting as a substrate and exit/drainage member. Some preferred methods of bonding are thermal treatment, pressure and adhesives.This composite is pleated to provide a high ratio of filter surface to encompassing volume and bonded at the lower extremity to third layer 44 preferably consisting of a coarse mesh providing the main strength of the filter belt proper 21. A further preferred embodiment of the invention is to render impervious the periphery 48 of the lower layer 44 coinciding with the non-pleated section of the of the upper double layer 43, 47 that includes the strip engaged by the chamber sealing surfaces.

The composition of the upper layer ranges from membraneous materials with thicknesses in the region of a 1-20 microns and separation cut-off points from 10A to 10 microns out of what is at present a vast array of synthetic polymers and co-polymers as well as fine woven and non-woven materials providing separation from ca +1 micron. In this last mentioned category a single layer of medium can often be substituted for the double layer of the pleated material.

The methods of attaching the pleated material 43, 47 to the lower single layer of non-pleated material 44 include thermal bonding, adhesive bonding, stapling, etc.

In operation, first of all, actuators 26 locate the movable element 27 in the sealed position with respect to the stationary element 22 and a section of stationary filter band 21. The fluid to be purified is preferably introduced to the interior of element 27 by means of conduit 25 and the purified fluid after passing through the section of sealed filter band 21 exits the lower element through the outlet 24. The source of the driving force or pressure differential required for the passage of the fluid through the purifying apparatus is not shown and can consist of any of the conventional pumping means suitable for transporting and pressurizing gases and/or liquids connected to the inlet and/or the outlet sides of the separating device of the invention as well as liquids delivered at atmospheric pressure to the vessel formed by the movable element 27 and the sealed section of stationary filter band 21 and pressurized by the force of gravity.

Figs. 7 and 8 illustrates the magnified design of closely packed pleated media according to the invention suitable for the purification of fluids in the micro- and ultra-filtration as well as the reverse osmosis mode of separation. As an indication, separation areas of up to lOOm2 are made available on an area of filter band of lm2 with the apparatus of the invention. With this apparatus, operating pressures in excess of 100 bar are available as driving force.

Figs. 5 and 6 illustrate schematically pleated media according to the invention capable of sub-micronic and ,,macro" filtration, whereby spaces 45 for the accumulation of solids are provided on the filtering side of the pleats. According to the invention, the spaces 46 within the lower side of the pleated medium have sealed ends, whereby the medium is supported by appropriate inserts 49 to accomodate high pressure differentials and high fluxes of liquid filtrate of the order of up to 150 m3/m2.h. Similarly, high pressure differentials and fluxes of filtered gas are also achieved. With purification area densities of ca 10-20 m2/m2 for high flux performance filter bands, the apparatus of the invention can provide fully automatic, compact apparatus for sterile filtration of liquid and gases in such diverse industries as beer brewing, wine making, sugar processing and pharmaceutical production with the overriding additional advantage that large amounts of finely divided solids such as yeast, finely ground spent grain, muds, activated carbon, dust, etc. can be simultaneously separated and discharged. The apparatus of the present invention offers the compactness of state of the art centrifuges but exceeds these devices in product quality performance and operating costs.

Further application advantages accrue in the fields of water and effluent treatment. Similarly, considerable advantages compared with state of the art gas purification apparatus accrue with this apparatus of the invention: e.g. employing composite membraneous media out of polytetrafluorethylene, high fluxes of hot gases emitted from furnaces, stacks, chemical processes, etc can be purified in compact plant that replaces costly, space consuming pressure candle filters, scrubbers, etc which are incapable of operating in the sub-micron range of separation.

These advantages result in large part from the following further apparatus and methods of the invention: In the case of liquids, at the end of the purification operation, gas at an appropriate pressure is introduced to the movable element 27 sealing the filter element to displace the residual liquid above the pleated section of medium. The element 27 is disengaged and the pleated filter element of the filter band 21 is transported from the filter chamber by the motor driven deflection roller 28. On reaching the deflection roller 29 the pleats of the media are expanded, whereby the solids in the spaces 45 are dislodged aided by a built-in ultrasonic generator 38.

The solids are discharged through the chute 30 and are collected in a container not shown.

According to the present invention, the combination of the forced expansion of the pleats on passing around a suitable deflection roller, the effects of gravity and centrifugal force, the employment of membraneous media with non-sticking properties such as polytetrafluorethylene and the optional further aid of ultrasonic devices built into the deflection roller enable the complete discharge of residues and cakes and especially those displaying wet, sticky characteristics which have been previously regarded by those versed in the art of filtration as intractable or at least prone to cause insuperable discharge problems.

After passing the solids discharging deflection roller 29 the pleated filter element of the filter band 21 is deflected downwards by a roller illustrated in Figs.3 and 4 that, according to the invention, consists of a centrally cut-out portion 34 allowing access to the now reversed upstanding pleats of the filter element while being guided by the surfaces of the upstanding lateral sections 35 of the roller.

On being once again reversed by a further normal deflection roller, whereby the pleats of the filter element are again expanded and pass high h pressure jets of fluid from nozzles 31 which scour the pleats both internally and externally. The fluids employed are a wide variety of liquids, gases and vapours such as live steam. The object is not only to remove any remaining adhering solid material from the element but also to dislodge any material blocking the pores of the filter medium.

In the next and final stages, the element is submerged in a bath or baths 33 of cleaning liquid, where associated with a more prolonged residence time, detergents, solvents, chemicals, etc with the aid of means of agitation 37, including for example ultrasonic generators, the more persistent blocking materials in the pores of the medium are washed out, dissolved out or removed chemically (i.e. by means of an appropriate chemical reaction). Fig.9 further illustrates schematically the apparatus according to the invention indicating that further stages can be added for element regeneration: e.g. following the liquid cleaning bath 33 it can be desirable to ,,rinse" the media element in a further bath 48 to remove residual cleaning liquid. This can then be followed by a drying stage SO where by means of appropriate gas jets produced by nozzles 50 residual rinsing liquid from 48 can be removed from the element by means of entrainment and/or evaporation.

Claims

CLAIMS 1. A filter apparatus for fluids comprising a movable filter band that is arranged to be intermittently transported over a plane, pervious support member that forms a closed exit chamber for the filtered fluid, and an adjacent element movable with respect to the pervious support member that it engages peripherally to seal an overlying section of the stationary filter band, to which the turbid fluid is delivered and through which the filtered fluid passes by means of a pressure differential, thereby characterized, that the sealed section of the filter band 21 takes the form of pleated media 20.
2. A filter apparatus according to Claim 1, thereby characterized, that the periphery of the sealed section of pleated medium 36 consists of unpleated material.
3. A filter apparatus according to Claim 2, thereby characterized, that the periphery of the sealed section of pleated medium 36 consists of impervious material.
4. A filter apparatus according to Claiml, thereby characterized, that the pleated medium 20 consists of composite material composed of materials 43 and 47.
5. A filter apparatus according to Claim 1, thereby characterized, that the filter band consists of a composite material composed of the materials 43, 47 and 44.
6. A filter apparatus according to Claim 5, thereby characterized, that the material 44 of the composite medium is unpleated and makes up the material of the band proper to which the materials of the pleated medium 43 and 47 are bonded.
7. A filter apparatus according to Claim 4, thereby characterized, that the materials of the pleated medium 43 and 47 are bonded to one another.
8. A filter apparatus according to Claim 1, thereby characterized, that the filter band is transported by means of a motorized deflection roller 28.
9. A filter apparatus according to Claim 1, thereby characterized, that the pleated medium 20 is pleated in the direction at right angles to the direction of travel of the filter band.
10. A filter apparatus according to Claim 1, thereby characterized, that on leaving the filter chamber the pleated medium 20 passes under and in contact with a deflection roller 29.
11. A filter apparatus according to Claim 10, thereby characterized, that the deflection roller 29 is directly attached to a device 38 capable of causing vibration in the pleated medium 20 of the filter band in contact with the surface of the deflection roller.
12. A filter apparatus according to Claim 1, thereby characterized, that for deflection of the filter band in the opposite direction of rotation to the rollers of Claim 10 and 11, rollers 32 are cut out centrally 34 to accomodate the upstanding pleats of the pleated medium 20 while being guided by the unpleated peripheral surfaces of the pleated medium resting on the surfaces of the upstanding lateral sections 35 of the rollers.
13. A filter apparatus according to Claim 1, thereby characterized, that the pleated medium 20 of the filter band passes into a cleaning bath 33 after leaving the filter chamber.
14. A filter apparatus according to Claim 13, thereby characterized, that the pleated medium 20 of the filter band after leaving the cleaning bath 33 passes into a rinsing bath 48.
15. A filter apparatus according to Claims 13 and 14, thereby characterized, that the pleated medium 20 after leaving baths 33 and 48 is dewatered by means ofjets of gas or vapour by means of nozzles 50.
16. A filter apparatus according to Claim 1, thereby characterized, that the filter band 21 takes the form of a belt.
17. A filter apparatus according to Claim 1, thereby characterized, that the internal spaces of the individual pleats are fitted with pressure resistent inserts 49 which are suitable for the passage of high fluid fluxes.