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WO1992013626A1 - Appareil de filtration - Google Patents

Appareil de filtration Download PDF

Info

Publication number
WO1992013626A1
WO1992013626A1 PCT/GB1992/000159 GB9200159W WO9213626A1 WO 1992013626 A1 WO1992013626 A1 WO 1992013626A1 GB 9200159 W GB9200159 W GB 9200159W WO 9213626 A1 WO9213626 A1 WO 9213626A1
Authority
WO
WIPO (PCT)
Prior art keywords
filtering
vessel
drum
residues
bearing surfaces
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/GB1992/000159
Other languages
English (en)
Inventor
Edward Victor Byers
Michael Richard Byers
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Severn Trent Water Ltd
Original Assignee
Severn Trent Water Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from GB919102018A external-priority patent/GB9102018D0/en
Priority claimed from GB919103890A external-priority patent/GB9103890D0/en
Application filed by Severn Trent Water Ltd filed Critical Severn Trent Water Ltd
Priority to GB9315297A priority Critical patent/GB2267658B/en
Publication of WO1992013626A1 publication Critical patent/WO1992013626A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D33/00—Filters with filtering elements which move during the filtering operation
    • B01D33/15—Filters with filtering elements which move during the filtering operation with rotary plane filtering surfaces
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D33/00—Filters with filtering elements which move during the filtering operation
    • B01D33/35—Filters with filtering elements which move during the filtering operation with multiple filtering elements characterised by their mutual disposition
    • B01D33/37—Filters with filtering elements which move during the filtering operation with multiple filtering elements characterised by their mutual disposition in parallel connection
    • B01D33/39—Filters with filtering elements which move during the filtering operation with multiple filtering elements characterised by their mutual disposition in parallel connection concentrically or coaxially
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D33/00—Filters with filtering elements which move during the filtering operation
    • B01D33/44—Regenerating the filter material in the filter
    • B01D33/48—Regenerating the filter material in the filter by flushing, e.g. counter-current air-bumps
    • B01D33/50—Regenerating the filter material in the filter by flushing, e.g. counter-current air-bumps with backwash arms, shoes or nozzles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D33/00—Filters with filtering elements which move during the filtering operation
    • B01D33/70—Filters with filtering elements which move during the filtering operation having feed or discharge devices
    • B01D33/76—Filters with filtering elements which move during the filtering operation having feed or discharge devices for discharging the filter cake, e.g. chutes

Definitions

  • the present invention relates to filtering apparatus for separating residues of solids from liquid filtrates, such as in sewage treatment or in filtration of raw water as part of a potable water treatment process.
  • a filtering element e.g. in the form of a mesh of fine strands of wire supported by a peripheral frame, to be cleaned by backwashing; that is, by forcing liquid back through the element, in the opposite direction to the normal flow,to dislodge matter which has accumulated on the upstream (as in normal use) face of the mesh.
  • a rotary arrangement may be used.
  • a disc filter comprising a mesh secured around its periphery to a stiff annulus is mounted in a liquid-carrying duct.
  • a seal between the periphery of the disc filter and the duct causes all liquid flowing in the duct to pass through the filter disc.
  • only a lower portion of the disc is submerged in the liquid to be filtered.
  • the filter disc is rotated to raise previously-immersed portions out of the liquid for backwashing, any matter so dislodged from the mesh being carried away to waste.
  • the known disc filter system has disadvantages. Particularly, it is difficult to maintain an effective seal between the periphery of the disc and the duct.
  • the present invention provides, in a first of its aspects, filtering apparatus for separating residues of solids from liquid filtrates comprising a rotatably mounted filtration vessel, filtering means disposed about the axis of rotation in one or more walls of the vessel to provide filtering outlets from the vessel, feeding means enabling materials to be filtered to be introduced into the vessel, means for collecting filtrate emanating from the filtering outlets at a lower level, cleaning means for dislodging residues from the filtering means at a higher level, and means within the vessel for collecting residues dislodged from the filtering means by the cleaning means, portions of the filtering means being conveyed successively between the lower and higher levels by rotation of the drum.
  • the vessel may be rotated continuously or periodically. Intermittent rotation might be used, for example, where the filtration process was part of a water treatment or similar process.
  • the cleaning means may operate by backwashing the filtering means.
  • the cleaning means comprises one or more liquid-spraying nozzles arranged externally of the vessel and operative to cause a spray of liquid to impinge on the filtering means.
  • the or each filtering means may be in the form of a mesh screen stretched across a frame. It is preferable to provide a plurality of discrete filtering elements which are individually mounted in the walls of the filtration vessel. In this way, damage to a small section of the filtering means is restricted in its effect to the element in which the damage has occurred.
  • the filtration vessel may be a generally cylindrical drum, filtering elements being mounted in at least one end wall of the drum.
  • the feeding means and the residue-collecting means comprise ducting which extends through the vessel, generally along the rotational axis, for the delivery into the vessel of materials to be filtered and the removal of residues from the vessel.
  • the vessel may be rotatably mounted on a single duct which has one or more discharge ports for delivery of materials to be filtered into the vessel, and one or more reception ports for receipt of residues cleaned from the filtering means, the discharge ports being separated from the reception ports by a sealing partition within the duct.
  • the residue-collecting means may comprise funneling means to feed residues backwashed from the filtering means into a stationary collecting trough which discharges into the one or more reception ports.
  • filtering elements constructed from a mesh clamped at its periphery to a stiff annular frame can be subject to early failure. This is primarily due to the repeated forward flow and backwashing causing cyclic stresses in the strands of the mesh close to the frame which lead to fatigue in the strands.
  • the invention provides, in a second aspect, a filtering element comprising a mesh screen, and peripheral means supporting the screen, the screen being retained between opposed convex bearing surfaces of the supporting means which form a convergent entry for the screen.
  • the strands of the screen are prevented by the bearing surfaces from being bent sharply as the screen is deflected due to pressure exerted by fluid flowing through it.
  • the magnitude of the cyclic stresses in the strands, and consequently the tendency of the strands to fatigue is reduced.
  • the convex bearing surfaces may extend to each side of a line of closest proximity between the opposed surfaces.
  • the supporting means comprises a frame to which the mesh screen is secured, retained within a box-section housing.
  • the bearing surfaces are formed along the walls of an opening in the box housing forming the convergent entry.
  • the box housing is formed of two parts (which may be adjustable relative to one another so as to maintain the bearing surfaces in contact with the strands of the mesh) .
  • the bearing surfaces are presented by components of an elastomeric material which will yield as the strands bear against it to an extent dependent upon the amount of applied cyclical pressure.
  • variable curvilinear bearing surface portions are provided by the elastic properties of the elastomeric material which adapt to variations in the pressure on the mesh.
  • a filtering element in accordance with the second aspect of the invention can, most advantageously, be used in a filtering apparatus according to the first aspect of the invention.
  • Figure 1 is a diagrammatic view of one end wall of a rotary filtration vessel within a collection tank, viewed on a section through the vessel;
  • Figure 2 is a longitudinal vertical section through the apparatus of Figure 1;
  • Figure 3 shows, in part section, a first filtering element
  • Figure 4 is a sectional view along the line A-A of Figure 3; and Figure 5 is a cross-sectional view corresponding to Figure 4 but showing a modified construction of filtering element.
  • a filtration chamber of a filtering apparatus embodying the invention is provided by a filtration vessel in the form of a drum 1.
  • the drum comprises two rigid circular end plates 2 at opposite ends of a cylindrical wall 3 secured and sealed to the end plates 2.
  • the end plates 2 are relatively located and attached to each other by annularly-arranged tie rods 4 to provide a rigid structure.
  • the end plates 2 are provided with a plurality of apertures over which filtering elements 5 are secured by, for example, bolts which are not shown, the elements being arranged in uniform circular distributions around the plates.
  • Each of the discrete filtering elements 5 (described in more detail hereinafter) consists of a peripheral supporting ring 6 to which the periphery of a filtering wire mesh screen M is secured, the mesh completely covering the aperture which is surrounded by the ring 6.
  • the apertures in the end plates, covered by filtering elements, provide filtering outlets from the drum.
  • the filtering elements 5 are shown as having a circular form, this being preferred for ease of manufacture, but other shapes may be used.
  • the end plates 2 are mounted on bearings 7 to enable the drum 1 to rotate about a horizontal axially-extending cylindrical duct 8 which, in part, forms a stationary feed duct through the drum.
  • Materials to be filtered can be admitted into one end of the duct 8 (as indicated by an arrow 9) the materials falling into the interior of the drum 1 through discharge ports in the form of slots 10. Axial progression of the materials in the duct 8 beyond the slots 10 is prevented by an internal sealing partition 11 in the duct.
  • a tubular axial extension 12 on the drum 1 permits the drum 1 to be rotated through a pulley or gear wheel 13 of the extension by suitable driving means (not shown) .
  • the duct 8 is supported outside the drum 1, adjacent to the opposite ends of the drum, by walls of a collection tank 14 in which liquid filtrate issuing from the drum 1 through the filtering elements 5 can collect.
  • the liquid can be withdrawn from the tank via an outlet tube 15 which is telescopically extendable upwardly (not shown) to permit alteration of the filtrate outlet level.
  • a proportion of the filtered liquid (up to about 10%, depending on working conditions and degree of effluent contamination) can be pumped through spraying devices 16 held above the tank 14 in fixed positions adjacent to both end plates 2 of the drum 1.
  • the devices 16 are provided with nozzles to cause the filtered effluent to be sprayed in jets 17 which impinge on opposed screens of the filtering elements 5, so flushing residues of solids which may have accumulated on the screens back towards the interior of the drum 1.
  • Catchment plates 18 forming V-shaped funneling devices, one for each filtering element 5, are attached to the inside surface of each end plate 2 adjacent to the elements 5.
  • the apex of the V is directed towards the axis of rotation of the drum 1 while the arms of the V pass to either side of a corresponding filtering element 5 to collect backwashed residues.
  • Each funneling device forms a spout 19 at the apex of the V-shape.
  • the spouts 19 feed residues backwashed from the filtering elements into a stationary collection trough 20 attached to the uppermost portion of the central duct 8 along its length within the interior of the drum 1.
  • the trough 20 conducts collected material to a reception port 21 in the trough whence it falls through an aligned aperture in the duct 8 on the far side of the partition 11 from the slots 10. The material can then drain from the duct 8 (as indicated by an arrow 22) .
  • material to be filtered flows into the drum 1 through feeding means comprising the duct 8 and slots 10.
  • Filtrate passes out of the drum 1 through those of the filtering elements 5 at a lower level into the collection tank 14.
  • the level of liquid in the collection tank 14 is maintained, by adjustment of the outlet tube 15, at a level such, that a filter element 5 in its lowermost position is fully submerged. Hydrostatic pressure of liquid in the drum 1 is sufficient to cause the filtrate to flow through the filter elements 5.
  • each filtering element 5 is successively cycled between a lower level, in which it filters liquid, and a higher level at which it passes closely in front of the spray jets 17 and is backwashed.
  • a first construction of filtering element 5 will now be described in more detail with reference to Figures 3 and 4.
  • each filtering element 5 comprises a circular annular rigid frame 30, across which the mesh screen M is stretched.
  • the frame 30 is mounted within an annular box-section housing 32 formed of two parts 34, 36, secured together by bolts in bolt holes 38 through the parts.
  • the two parts 34 and 36 of the housing 32 are provided with annular bearing surfaces 40 which are convex in cross-section as shown in Figure 4 to form a convergent entry for the screen.
  • the surfaces extend to each side of an annular line of closest proximity between them.
  • the bearing surfaces 40 lie on the circumference of a circle, the radius of which is chosen such that as the wires of the mesh screen M flex they conform to the shape of the surfaces 40 thereby limiting bending stresses to militate against the onset of metal fatigue.
  • bearing surfaces are formed by elastomeric rings 42 of circular cross-section positioned in accommodating recesses 44 in the parts 34,36 of the housing 32.
  • this superimposed stress is comprised of the tensile stress at the convex edge of the bent wires (indicated by M' in Figures 4 and 5) and the compressive stress of equal magnitude at the concave edges measured with respect to the point of contact with the opposed bearing surfaces.
  • the magnitude of the additional stress may be calculated using a knowledge of the theory of elasticity and the wire properties.
  • the stress increment may be very high and sufficient to cause the total wire stress to rise beyond the limit which will safely resist fatigue cracking over an unlimited number of stress fluctuations.
  • This safe stress limit will be known and predetermined for wires of a particular material. As an example, for a stainless steel wire of 0.1 mm diameter it will usually be adequate to use a bearing surface radius of 6 mm.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Filtration Of Liquid (AREA)

Abstract

Un appareil de filtration permettant la séparation continue de résidus de solides à partir de produits de filtrage liquides comprend un tambour de forme cylindrique monté sur pivot (1) comportant plusieurs éléments de filtrage (5) sur chacune de ses parois d'extrémité (2). Les matériaux à filtrer sont introduits dans le tambour (1) à travers un tube (8), les produits de filtrage sortant à travers un ou plusieurs des éléments de filtrage (5) au niveau de la partie inférieure du tambour (1). Des buses pulvérisantes (16) sont disposées de façon adjacente aux parois d'extrémité (2) de façon à diriger les jets de liquide sur les éléments de filtrage (5) au niveau de la partie supérieure du tambour (1), provoquant ainsi le lavage à contre-courant des éléments (5). Le matériau ainsi lavé est récupéré à l'intérieur du tambour (1) et évacué à travers le tube (8). La rotation continue du tambour permet alternativement d'assurer la filtration de liquide par chaque élément et ensuite le lavage de ceux-ci à contre-courant. Un élément de filtrage (5) utilisable avec l'appareil possède un tamis (M) sup porté à sa périphérie entre des surfaces de support courbes (40; 42) de façon à minimiser les efforts cycliques sur le tamis provoqués par des cycles continus de filtrage et de lavage à contre-courant.
PCT/GB1992/000159 1991-01-30 1992-01-28 Appareil de filtration Ceased WO1992013626A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB9315297A GB2267658B (en) 1991-01-30 1992-01-28 Filtering apparatus

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
GB9102018.0 1991-01-30
GB919102018A GB9102018D0 (en) 1991-01-30 1991-01-30 Filtration device
GB9103890.1 1991-02-25
GB919103890A GB9103890D0 (en) 1991-02-25 1991-02-25 Rotary fluid filtration apparatus

Publications (1)

Publication Number Publication Date
WO1992013626A1 true WO1992013626A1 (fr) 1992-08-20

Family

ID=26298352

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB1992/000159 Ceased WO1992013626A1 (fr) 1991-01-30 1992-01-28 Appareil de filtration

Country Status (4)

Country Link
GB (1) GB2267658B (fr)
IE (1) IE920296A1 (fr)
PT (1) PT100066A (fr)
WO (1) WO1992013626A1 (fr)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2001021281A1 (fr) * 1999-09-22 2001-03-29 Hennig, Inc. Procede et appareil d'epuration d'un fluide de refroidissement
US8070963B2 (en) 2007-07-09 2011-12-06 Odis Irrigation Equipment Ltd. Method and system for backwashing a filter
CN117379868A (zh) * 2023-12-12 2024-01-12 山西裕英永旭新材料有限责任公司 一种压滤罐

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
RU2203722C2 (ru) * 2001-07-18 2003-05-10 Плешанов Евгений Васильевич Агрегат для очистки сточных вод

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2454604A1 (de) * 1974-11-18 1976-05-20 Kito Machine Industry Co Drehfilter
DE2737600A1 (de) * 1977-08-20 1979-03-01 Kloeckner Humboldt Deutz Ag Vorrichtung zur reinigung des vom filterkuchen befreiten filterbelags von feststoff-fluessigkeitsfiltern
EP0331825A1 (fr) * 1988-03-07 1989-09-13 Mei Tai Co., Ltd. Dispositif de nettoyage pour bandes filtrantes

Family Cites Families (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3392839A (en) * 1965-09-27 1968-07-16 Andale Co Multiple element strainer sandwich
SE315490B (fr) * 1968-04-03 1969-09-29 H Nilsson
US3972817A (en) * 1972-12-08 1976-08-03 Myrens Verksted A/S Filter, especially for back water
US3941702A (en) * 1974-11-14 1976-03-02 Kito Machine Industries Company Limited Rotary strainer
US4200530A (en) * 1977-05-20 1980-04-29 Emmanuel Mechalas Rotary filter
LU79466A1 (fr) * 1978-04-18 1979-05-25 Sidmar Nv Procede et installation de traitement et de manutention de laitier metallurgique
US4724077A (en) * 1986-06-09 1988-02-09 Tadao Uchiyama Rotary drum filter with sliding perforated buckets

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2454604A1 (de) * 1974-11-18 1976-05-20 Kito Machine Industry Co Drehfilter
DE2737600A1 (de) * 1977-08-20 1979-03-01 Kloeckner Humboldt Deutz Ag Vorrichtung zur reinigung des vom filterkuchen befreiten filterbelags von feststoff-fluessigkeitsfiltern
EP0331825A1 (fr) * 1988-03-07 1989-09-13 Mei Tai Co., Ltd. Dispositif de nettoyage pour bandes filtrantes

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2001021281A1 (fr) * 1999-09-22 2001-03-29 Hennig, Inc. Procede et appareil d'epuration d'un fluide de refroidissement
US6571959B1 (en) 1999-09-22 2003-06-03 Robin C. Moore Coolant fluid cleaning method and apparatus
US8070963B2 (en) 2007-07-09 2011-12-06 Odis Irrigation Equipment Ltd. Method and system for backwashing a filter
CN117379868A (zh) * 2023-12-12 2024-01-12 山西裕英永旭新材料有限责任公司 一种压滤罐

Also Published As

Publication number Publication date
GB9315297D0 (en) 1993-10-20
IE920296A1 (en) 1992-07-29
GB2267658A (en) 1993-12-15
GB2267658B (en) 1995-06-07
PT100066A (pt) 1994-03-31

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