WO2011075041A1 - Drum and apparatus for processing cellulose-containing pulp, where rewetting is prevented, and method for manufacturing the drum - Google Patents

Drum and apparatus for processing cellulose-containing pulp, where rewetting is prevented, and method for manufacturing the drum Download PDF

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Publication number
WO2011075041A1
WO2011075041A1 PCT/SE2010/051308 SE2010051308W WO2011075041A1 WO 2011075041 A1 WO2011075041 A1 WO 2011075041A1 SE 2010051308 W SE2010051308 W SE 2010051308W WO 2011075041 A1 WO2011075041 A1 WO 2011075041A1
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WO
WIPO (PCT)
Prior art keywords
filtrate
drum
channel
barrier
pulp
Prior art date
Application number
PCT/SE2010/051308
Other languages
French (fr)
Inventor
Stefan Gullback
Original Assignee
Metso Paper, Inc.
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
Application filed by Metso Paper, Inc. filed Critical Metso Paper, Inc.
Priority to CN201080056345.9A priority Critical patent/CN102652196B/en
Publication of WO2011075041A1 publication Critical patent/WO2011075041A1/en

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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
    • B01D33/06—Filters with filtering elements which move during the filtering operation with rotary cylindrical filtering surfaces, e.g. hollow drums
    • B01D33/073—Filters with filtering elements which move during the filtering operation with rotary cylindrical filtering surfaces, e.g. hollow drums arranged for inward flow filtration
    • B01D33/09—Filters with filtering elements which move during the filtering operation with rotary cylindrical filtering surfaces, e.g. hollow drums arranged for inward flow filtration with surface cells independently connected to pressure distributors
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
    • D21C9/02—Washing ; Displacing cooking or pulp-treating liquors contained in the pulp by fluids, e.g. wash water or other pulp-treating agents
    • D21C9/06—Washing ; Displacing cooking or pulp-treating liquors contained in the pulp by fluids, e.g. wash water or other pulp-treating agents in filters ; Washing of concentrated pulp, e.g. pulp mats, on filtering surfaces
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
    • D21C9/18—De-watering; Elimination of cooking or pulp-treating liquors from the pulp

Definitions

  • the present invention relates to a drum for an apparatus for processing cellulose-containing pulp, the drum being rotatable about an axis of rotation and provided with an outer surface permeable to liquid, the outer surface being formed by at least one plate which also forms at least one inner surface facing the axis of rotation, and a plurality of filtrate channels which extend along the axial extension of the drum and are provided inwardly of the inner surface, the drum being arranged to receive the pulp on the outer surface.
  • Each filtrate channel is arranged to guide and discharge filtrate, located in the filtrate channel, which has been transported to the filtrate channel from the pulp via the outer surface, and each filtrate channel is defined by at least a first and a second axial channel wall having a substantially radial extension.
  • Each filtrate channel of a plurality of filtrate channels is provided with an axially extending filtrate barrier which defines a gap be- tween itself and the inner surface and is arranged to prevent the flow of filtrate from the filtrate channel to the outer surface of the drum, and at the same time, the filtrate barrier defines at least one filtrate opening for allowing filtrate to pass from the gap to the filtrate channel.
  • the present invention relates to an apparatus for processing cellulose-containing pulp, which is provided with such sort of drum, and to a method for manufacturing such a drum.
  • Fibre lines producing cellulose-based products comprise some type of washing equipment for separating the liquor of the cooking from the cellulose- containing pulp. Later on in the process, washing equipment is also provided to separate bleaching liquors after the bleaching steps. There are a number of different types of washing equipment operating according to different principles.
  • a roll press When producing cellulose-based products, a roll press is frequently used for washing and/or dewatering the cellulose-containing pulp.
  • the roll press comprises two co-operating and counter-rotating press rolls, each having a permeable outer surface, a so called mantle surface, whereby the outer surface is permeable to liquid pressed out of the pulp.
  • the pulp is deposited on the permeable outer surface and pressed in the roll nip, or the press nip, between the press rolls, whereby liquid is pressed out of the pulp.
  • the roll press also includes one or more washing zones prior to the press nip.
  • One example of such a roll press is disclosed in US 3,980,518.
  • drum washer which comprises a rotating filter drum, where the cellulose-containing pulp is deposited and dewa- tered on the filter drum, which has a permeable outer surface, after the addition of washing liquid which displaces the liquor remaining on the pulp web after the preceding process step, for example a cooking step or bleaching step.
  • the static pressure causes the contaminated liquid, called filtrate, to pass through the outer surface permeable to liquid.
  • the pressurized displacement washer where the filtrate, under overpressure, is forced to pass through the permeable outer surface.
  • WO2008/140396 One example of a drum washer is disclosed in WO2008/140396.
  • the roll/drum of both the drum washer and the roll press is often provided with a plurality of filtrate channels which extend along the axial extension of the roll, or drum, and are provided inwardly of the permeable outer surface.
  • the filtrate channels receive filtrate, which has been transported through the outer surface, from the pulp situated on the outer surface, and subsequently, the filtrate is axially transported and discharged from the filtrate channel to a filtrate container connected thereto.
  • US 5,470,471 discloses a press roll where baffle plates are anchored inside the filtrate channels of the press roll in order to prevent the rewetting of the pulp.
  • US 4,581 ,139 describes a baffle insert member which is inserted in a fil- trate channel of a rotary vacuum drum washer in order to prevent the rewetting of pulp.
  • the baffle insert members are described as exchangeable.
  • the object of the present invention is to provide an improved drum for apparatuses for processing cellulose-containing pulp, where the rewetting of the pulp is prevented.
  • the above-mentioned object of the present invention is attained by providing a drum of the kind mentioned in the introductory part of the description, comprising the features that the filtrate barrier is mounted to the drum by being sandwiched by and between the first axial channel wall of the filtrate channel and the inner surface.
  • the filtrate barrier abuts, where it is sandwiched, the first axial channel wall of the filtrate channel and the inner surface of the at least one plate.
  • substantially all of the filtrate channels are provided with an axially extending filtrate barrier.
  • Examples of such features that may be excluded in drums for drum washers are the intermediate rewetting barriers which previously have been provided between the outer surface and the filtrate channels and extend over a plurality of filtrate channels in the direction of rotation and, for some filtrate channels, form a wall completely separating the filtrate channel and the outer surface.
  • the intermediate rewetting barriers which previously have been provided between the outer surface and the filtrate channels and extend over a plurality of filtrate channels in the direction of rotation and, for some filtrate channels, form a wall completely separating the filtrate channel and the outer surface.
  • openings are required in the axial channel walls of the filtrate channels, which axial channel walls have a substantially radial extension, and this is expensive.
  • the present invention provides a radical decrease in the amount of welding work when manufacturing the drum in relation to manufacturing prior-art drums.
  • the drum according to the present invention is especially advantageous for drum washers.
  • the filtrate barrier is made of the same material as the reminder of the drum and/or the at least one plate.
  • the material is resistant to the conditions in question and resistant to the effect of the filtrate. Examples of materials are, e.g., stainless steel, bur also other materials may be used.
  • the filtrate barrier may made of a material different from the mate- rial of the at least one plate and/or the remainder of the drum.
  • the filtrate barrier may be in the form of a section or a plate, such as a sheet.
  • the thickness of the filtrate barrier may be approximately 1-2 mm, whereas the thickness of the at least one plate may be approximately 3-6 mm, but other dimensions are possible.
  • the at least one plate may be one plate or a plurality of plates, e.g.
  • the filtrate barrier may be sandwiched by one plate or a plurality of plates.
  • the at least one plate, which forms the outer surface, may comprise one or a plurality of plates provided with apertures, e.g. perforated.
  • a plurality of filtrate channels may comprise two or more filtrate channels.
  • the processing of the pulp by means of the innovative drum may comprise washing, pressing, washing and pressing, or filtering.
  • the drum may, e.g., be a filter drum of a drum washer, a roll, or a press roll of a roll press for washing and/pr dewatering pulp.
  • the filtrate barrier rests against the second axial channel wall of the filtrate channel, and the filtrate barrier is provided with the at least one filtrate opening.
  • the position of the filtrate barrier may be maintained in an efficient and uncomplicated manner, and a dislocation of the filtrate barrier or a deflection of the filtrate barrier toward the axis of rotation over time is avoided.
  • an improved drum is provided, where the rewetting of pulp is prevented.
  • the filtrate barrier is biased against the second axial channel wall of the filtrate channel.
  • the positioning of the filtrate barrier is further improved and the position of the filtrate barrier can be maintained in an even more efficient and uncomplicated manner, whereby the dislocation of the filtrate barrier or the deflection of the filtrate barrier toward the axis of rotation over time is avoided.
  • an improved drum is provided, where the rewetting of pulp is prevented.
  • the at least one filtrate opening is provided adjacent to one of the first and second axial channels walls of the filtrate channel. This location of the filtrate opening is effective to prevent the transport of filtrate from the filtrate channel to the outer surface of the drum, and thereby, the rewetting of the pulp is prevented, whereby an improved drum is obtained, where the rewetting of pulp is prevented.
  • the at least one filtrate opening is provided adjacent to the second axial channel wall of the filtrate channel.
  • the filtrate barrier comprises a first portion which is located fur- thest away from the outer surface of the drum in relation to the remainder portion of the filtrate barrier, and the at least one filtrate opening is provided at or adjacent to said first portion.
  • the filtrate barrier is axially bent so that an axially extending bend, which protrudes toward the axis of rotation, is provided at or adjacent to the first portion.
  • the filtrate barrier has an axially extending first edge at which the filtrate barrier is sandwiched between the first axial channel wall of the filtrate channel and the inner surface, and along substantially the entire axial extension of the first edge the filtrate barrier is sandwiched by and between the first axial channel wall and the inner surface.
  • an efficient mounting of the filtrate barrier is attained.
  • each filtrate barrier extends past the first axial channel wall of the filtrate channel and into an adjacent filtrate channel.
  • the mounting of the filtrate barrier is further reinforced and the drum becomes more resistant to wear and its durability is improved.
  • each filtrate barrier extends past the first axial channel wall of the filtrate channel and into an adjacent filtrate channel
  • each filtrate barrier rests or is biased against the second axial channel wall of the filtrate channel and against the filtrate barrier of an adjacent filtrate channel.
  • the filtrate barrier extends along substantially the entire axial extension of the filtrate channel.
  • the rewetting is efficiently prevented, especially with regard to axially long drums, and the embodiment provides an improved drum where rewetting of pulp is prevented.
  • an apparatus for processing cellulose-containing pulp comprising at least one rotatable first drum provided with an outer surface permeable to liquid, the outer surface being formed by at least one plate which also forms at least one inner surface, and a plurality of filtrate channels provided inwardly of the inner surface, the apparatus being arranged to receive the pulp on the outer surface of the drum and process the pulp located on the outer surface while rotating the drum, and the apparatus is arranged to process the pulp at least by removing filtrate from the pulp and transporting the filtrate from the pulp to the filtrate channels through the outer surface, characterized in that said drum comprises the features mentioned in any of the claims 1 to 11 , or mentioned in any of the above-mentioned embodiments of the drum.
  • the apparatus is arranged to rest on a floor and comprises an application zone for applying pulp to the outer surface of the drum and a removal zone for removing pulp from the outer surface, the drum being arranged to rotate in a direction of rotation from the application zone to the removal zone so that each filtrate channel is moved into the removal zone in a direction toward said floor.
  • the apparatus comprises at least one washing zone for washing the pulp located on the outer surface.
  • each filtrate channel is moved into the removal zone in a direction toward said floor
  • the apparatus is arranged such that the axial channel wall of the first and second axial channel walls of the filtrate channel, adjacent to which the at least one filtrate opening is provided, arrive at the removal zone after the opposite axial channel wall of the filtrate channel during the rotation of the drum.
  • the apparatus comprises a rotatable second drum, the first and second drums being arranged to rotate in opposite directions of rotation and define a press nip between them, in which press nip the pulp is pressed, and the apparatus is arranged to feed the pulp in the direction of rotation of the drums through the press nip.
  • the apparatus comprises two drums
  • the apparatus is arranged to rest on a floor, and the axes of rotation of the drums are lying in a plane which is substantially parallel to said floor
  • the apparatus is arranged such that, in the press nip, the one of the first and second axial channel walls of the filtrate channel adjacent to which the at least one filtrate opening is provided is positioned further away from said floor in relation to the opposite axial channel wall of the filtrate channel.
  • the above-mentioned object of the present invention is also attained by providing a method for manufacturing a drum according to any of the claims 1 to 11 , or according to any of the above-mentioned embodiments of the drum, the method comprising the following steps: placing each filtrate barrier against the first axial channel wall of each filtrate channel; applying the at least one plate to each filtrate barrier at the first axial channel wall of each filtrate channel; and mounting each filtrate barrier to the drum by sandwiching each filtrate barrier between the first axial channel wall of each filtrate channel and the inner surface of the at least one plate.
  • the method is characterized by fixing each filtrate barrier to the first axial channel wall of each filtrate channel after the step of placing the filtrate barrier against the first axial channel wall of each filtrate channel and before the step of applying the at least one plate to each filtrate barrier. Said fixing facilitates said sandwiching of the filtrate barrier and further facilitates the mounting of the filtrate barriers.
  • Fig. 1 is a schematic partial side view of a prior-art roll press during op- eration
  • Fig. 2 is a schematic partial perspective view of an embodiment of the drum according to the present invention.
  • Fig. 3 is a schematic partial side view of the drum of Fig. 2;
  • Fig. 4 is a schematic side view of a first embodiment of the apparatus according to the present invention, provided with drums according to the present invention
  • Fig. 5 is a schematic side view of a second embodiment of the apparatus according to the present invention, provided with a drum according to the present invention.
  • Fig. 6 is a flow chart illustrating aspects of the method according to the present invention.
  • Fig. 1 illustrates the rewetting of cellulose-containing pulp with regard to a prior-art roll press having two co-operating and counter-rotating press rolls 102, 104 rotating in different directions of rotation Ri and R ⁇ .
  • the pulp is fed in the di- rection of rotation of the press rolls 102, 104 and through a press nip 106 formed between the press rolls.
  • the pressure of the pulp 108 decreases and the filtrate 110, which has not been discharged from the filtrate channels 112, 114, returns through the outer surface 116, 118 of each press roll 102, 104 and dilutes the pulp 108.
  • Fig. 1 illustrates the rewetting of cellulose-containing pulp with regard to a prior-art roll press having two co-operating and counter-rotating press rolls 102, 104 rotating in different directions of rotation Ri and R ⁇ .
  • the pulp is fed in the di- rection of rotation of the press rolls 102, 104 and through a press nip
  • the rewetting is illustrated by arrows from the interior of the press rolls 102, 104 to zone A (rewetting zone) above the press nip 106.
  • the pulp has a maximum dryness B prior to the rewetting zone A, whereas the pulp 108 leaving the roll press has the reduced dryness C because of the rewetting.
  • Fig. 2 schematically shows a partial perspective view of an embodiment of the drum 130 for an apparatus for processing cellulose-containing pulp according to the present invention, where the drum 130 is provided with an outer surface 132 permeable to liquid, which is only illustrated at the end of the drum 130 and is otherwise removed in order to illustrate the filtrate barriers 134 of the drum 130, the filtrate barriers extending along the axial extension of the drum 130.
  • the outer surface 132 is formed by or defined by at least one plate 135 which also forms or defines at least one inner surface 137.
  • the at least one plate 135 may comprise a plate provided with holes, e.g. perforated, or a plurality of plates provided with holes, which may be mounted and joined in ways known to the skilled person, e.g. by welding and subsequent turning of the welding seams.
  • the filtrate barriers 134 are not exposed along the axial extension of the drum 130 as they are covered by the outer surface 132.
  • Fig. 3 shows a schematic side view of the drum of Fig. 2.
  • the outer surface 132 and the inner surface 137 extend around the circumference of the drum 130.
  • the at least one plate 135 may extend around the entire circumference of the drum 130.
  • One plate 135 may extend around the entire circumference of the drum 130, or a plurality of plates may be positioned after one another around the entire circumference of the drum 130.
  • the drum 130 is rotatable in a direction of rotation R 3 about an axis of rotation 302 (the axis of rotation 302 is shown in Fig. 5) and is provided with one or a plurality of filtrate channels 136 which extend along the axial extension of the drum 130 and are provided inwardly of the inner surface 137.
  • Each filtrate channel 136 is provided with a filtrate barrier 134.
  • each filtrate barrier 134 extends along substantially the entire axial extension of the filtrate channel 136.
  • the drum is adapted to receive pulp on the outer surface 132, and each filtrate channel 136 is adapted to guide, e.g. axi- ally guide, and discharge filtrate, located in the filtrate channel 136, which has been transported to the filtrate channel 136 from the pulp through the outer surface 132.
  • Each filtrate channel 136 may be defined, or limited, by a first axial channel wall 138, 140 having a substantially radial extension, by a second axial channel wall 140, 142 having a substantially radial extension, by an inner channel wall 144, or bottom wall, which is radially closest to the axis of rotation 302 of the drum and extends in the direction of rotation R3, and by the inner surface 137 of the at least one plate 135.
  • Two adjacent filtrate channels 136 may have a radially extending channel wall 140 in common.
  • the common radially extending channel wall 140 forms the first axial channel wall 140 of one of the filtrate channels 136 and at also forms the second axial channel wall 140 of the second filtrate channel 136.
  • the filtrate barrier 34 defines a gap 146 between itself and the inner sur- face 137 and is adapted to prevent the flow of filtrate from the filtrate channel 136 to the outer surface 132 of the drum 130, and at the same time, the filtrate barrier 134 defines a plurality of filtrate openings 148 for allowing filtrate to pass from the gap 146 to the filtrate channel 136.
  • the filtrate barrier 134 defines a gap 146 between the inner surface 137 and a main part of the filtrate channel 136, the filtrate barrier 134 separating the filtrate channel 136 into a gap 146 and a main part.
  • the filtrate barrier 134 may define only one filtrate opening 148 which may extend along substantially the entire extension of the filtrate channel 136.
  • the filtrate barrier 134 may be in the form of a plate in which the filtrate openings 148 are formed.
  • the filtrate barrier 134 is mounted to the drum 130 by being sandwiched by and between the first axial channel wall 138, 140 of the filtrate channel 136 and the inner surface 137 of the at least one plate 135. More specifically, the filtrate barrier 134 may be sandwiched between the radially outer axially extending edge of the first axial channel wall 138, 140 and the inner surface 137.
  • the filtrate barrier 134 has an axially extending first edge 150 at which the filtrate barrier 134 may be sandwiched between the first axial channel wall 140 of the filtrate channel 136 and the inner surface 137.
  • the filtrate barrier 134 is sandwiched by and be- tween the first axial channel wall 140 of the filtrate channel 136 and the inner surface 137.
  • Each filtrate barrier 134 may extend past the first axial channel wall 138, 140 of the filtrate channel 136 and into an adjacent filtrate channel 134.
  • the filtrate barrier 134 may rest, or may be moderately biased, against the second axial channel wall 140, 142 of the filtrate channel 136 and against the filtrate barrier 134 of an adjacent filtrate channel 136.
  • the filtrate barrier 134 may have a plurality of tongues 152 defining the filtrate openings 148.
  • the tongues 152 may rest, or be moderately biased, against the second axial channel wall 140, 142 of the filtrate channel 136 and against the filtrate barrier 134 of an adjacent filtrate channel 136.
  • the filtrate openings 148 may be provided adjacent to the second axial channel wall 140, 142 of the filtrate channel 136.
  • the filtrate barrier 134 may have a first portion 54 which is located furthest away from the outer surface 132 of the drum 130 in relation to the remainder portion of the filtrate barrier 134, and the filtrate openings 148 may be provided at or adjacent to said first portion 154.
  • the filtrate barrier 134 may be axially bent so that an axially extending bend 156, or edge, which protrudes toward the axis of rotation 302, is provided at or adjacent to the first portion 154. This provides for an efficient drainage of filtrate from the gap 146 to the filtrate channel 136.
  • the filtrate barrier 134 forms an angle with the outer surface 132 such that the total area of all filtrate openings 148 is larger than the area that is defined by the filtrate barrier 134 and the inner surface 137 and that lies in a radially extending plane intersecting the border between the filtrate openings 148 and the main part of the filtrate barrier 134.
  • the filtrate barriers 134, the channel walls 138, 140, 142, 144 of the filtrate channel 136 and the at least one plate 135 may be made of the same material which is resistant to the conditions in question and to the effect of the filtrate, e.g. stainless steel.
  • the drum 130 may be provided with, or be connected to, known equipment for effecting the application of pulp on the outer surface, the washing of pulp and the dewatering of pulp, which equipment is well known to the person skilled in the art.
  • Fig. 4 schematically shows a first embodiment of the apparatus according to the present invention for processing cellulose-containing pulp by washing and pressing the pulp.
  • the apparatus is in the form of a so called roll press and comprises a rotatable first drum 202, in the form of a press roll, and a rotatable second drum 204, in the form of a press roll, each drum 202, 204 being rotatable in a direction of rotation R 1t R 2 , about an axis of rotation 203, 205 and has an outer surface 206, 208 permeable to filtrate pressed out of the pulp.
  • Each outer surface 206, 208 may be formed by at least one plate 21 1 , 213 which also forms at least one inner surface 215, 217 facing the axis of rotation 203, 205.
  • Each drum 202, 204 has a plurality of filtrate channels 210, 212 which extend along the axial extension of each drum 202, 204 and are provided inwardly of the inner surface 215, 217 to guide and discharge evacuated filtrate.
  • Each filtrate channel 210, 212 may be defined, or limited, by the inner surface 215, 217, a radially inner wall 218, 220 provided on an axial central drum 222, 224 and a first and a second axial channel wall 226, 228, 230, 232 having a substantially radial extension.
  • Each channel wall may extend along the entire axial extension of each press roll 202, 204 and be provided with at least one outlet for discharging filtrate therefrom in a conventional manner known to the skilled person.
  • the drums 202, 240 are arranged to rotate in opposite directions Ri, R 2 .
  • the apparatus of this embodiment is arranged to receive the pulp on the outer surface 206, 208 of each drum 202, 204 from two pulp distribution devices 234, 236 arranged to deposit pulp on the outer surface 206, 208, and the pulp is fed in a gap 209 in the direction of rotation of the drums 202, 204 while processing the pulp located on the outer surface during rotation of the drum.
  • the pulp is fed through a press/roll nip 238 defined by the drums 202, 204, in which press nip 238 the pulp is pressed to remove filtrate from the pulp.
  • filtrate is removed from the pulp and transported from the pulp to the filtrate channels 210, 212 through the outer surface 206, 208.
  • the apparatus is arranged to rest on a floor and the axes 203, 205 of rotation of the drums 202, 204 are lying in a plane which is substantially parallel to said floor.
  • the apparatus may be arranged to feed the pulp through the press nip 238 in a substantially vertical direction from below upwards.
  • one or a plurality of washing zones may be provided in conventional ways known to the skilled person.
  • each filtrate channel 210, 212 an axially extending filtrate barrier 134 is mounted by being sandwiched by and between the first axial channel wall 226, 230 of the filtrate channel 210, 212 and the inner surface 215, 217 of the at least one plate 211 , 213, as disclosed in connection with Figs. 2 and 3.
  • This embodiment of the apparatus is arranged such that, in the press nip 238, the second axial channel wall 228, 232 of the filtrate channel 210, 212, adjacent to which the at least one filtrate opening is provided, is positioned further away from said floor in relation to the first axial channel wall 226, 230 of the filtrate channel 210, 212.
  • the roll press may comprise further units and equipment well known to the skilled person.
  • Fig. 5 schematically shows an axial cross-section of a second embodiment of the apparatus according to the present invention, in the form of a drum washer, arranged to dewater cellulose-containing pulp, provided with the rotatable drum 130 as shown in Figs. 2 and 3, which rotates in the direction of rotation f? 3 about the axis of rotation 302.
  • the apparatus may comprise a vat 304 which houses the drum 130 and is provided with an inlet 306 via which the cellulose-containing pulp is fed to the vat 304.
  • the apparatus may comprise a vacuum zone V in which the pulp is sucked toward the outer surface of the drum 130 by means of vacuum.
  • the apparatus may comprise an application zone P in which pulp is applied to the outer surface 32 and forms a mat or cake, the application zone P extending into the vacuum zone V.
  • the apparatus may comprise a non-vacuum removal zone AZ where the pulp is removed from the outer surface 132 and is transported to the next process step in ways known to the skilled per- son, Between the vacuum zone V and the non-vacuum removal zone AZ, there are cut off zones Bi and B 2 . These cut off zones Bi and B 2 and the other zones AZ and V are provided in manners known to the skilled person.
  • the drum washer may be provided with one or a plurality of washing zones.
  • the drum washer is arranged to rest on a floor, and the drum 130 is arranged to rotate in the direction of rotation R 3 from the application zone P, via washing zones, to the removal zone AZ so that each filtrate channel 136 is moved into the removal zone AZ in a direction toward said floor.
  • the drum washer according to this embodiment is arranged such that the second axial channel wall 140, 142 of the filtrate channel 136 (see Figs. 2 and 3), adjacent to which the at least one filtrate opening 148 is provided, arrive at the removal zone AZ after the first axial channel wall 138, 140 of the filtrate channel 136 during the rotation of the drum 130. It is also possible to provide a drum washer without vacuum zones, and the outer surface of the drum may be provided with external axial compartments in which the pulp may be formed in the application zone.
  • the major part of the rewetting of the pulp occurs at or adjacent to the non-vacuum removal zone AZ.
  • This rewetting is inhibited or prevented by the filtrate barriers 134 of the filtrate channels 136.
  • the drum washer may comprise further units and equipment well known to the skilled person, and may, e.g., be provided with a stationary gas-proof outer casing which encloses the drum 130.
  • Fig. 6 shows a flow chart illustrating aspects of the method according to the present invention for manufacturing a drum as disclosed above.
  • the method comprises the following steps: Each filtrate barrier is placed against the first axial channel wall of each filtrate channel, more precisely, against the radially outer axial edge of the first axial channel wall, at step 601. Each filtrate barrier is rested against the second axial channel wall of the filtrate channel, at step 602. Each filtrate barrier is fixed to the first axial channel wall of each filtrate channel, e.g. by spot welding, at step 603.
  • the at least one plate e.g. in the form of a plurality of plates provided with holes, is applied to each filtrate barrier at the first axial channel wall of each filtrate channel, at step 604.
  • Each filtrate barrier is mounted, at step 605, to the drum by sandwiching each filtrate barrier between the first axial channel wall of each filtrate channel and the inner surface of the at least one plate.
  • the filtrate barrier may be sandwiched by welding the plates and shrinking the outer surface around the drum.

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Abstract

A drum (130; 202, 204) for an apparatus for processing cellulose-containing pulp, the drum (130; 202, 204) being rotatable about an axis of rotation (302; 203, 205) and having an outer surface (132; 206, 208) permeable to liquid, the outer surface being formed by at least one plate (135; 211, 213) which also forms at least one inner surface (137; 215, 217) facing the axis of rotation, and a plurality of filtrate channels (136; 210, 212) provided inwardly of the inner surface, the drum (130; 202, 204) being arranged to receive the pulp on the outer surface, and each filtrate channel (136; 210, 212) guides and discharges filtrate, located in the filtrate channel, which has been transported to the filtrate channel from the pulp via the outer surface, and each filtrate channel is defined by at least a first and a second axial channel wall (138, 140, 142; 226, 228, 230, 232) having a substantially radial extension, each filtrate channel of a plurality of filtrate channels (136; 210, 212) being provided with an axial filtrate barrier (134) which defines a gap (146) between itself and the inner surface and is arranged to prevent the flow of filtrate from the filtrate channel to the outer surface of the drum and defines at least one filtrate opening (148) for allowing filtrate to pass from the gap to the filtrate channel, the filtrate barrier (134) being mounted to the drum by being sandwiched by and between the first axial channel wall of the filtrate channel and the inner surface. An apparatus for processing cellulose-containing pulp comprising such a drum, and a method for manufacturing such a drum.

Description

Drum and apparatus for processing cellulose-containing pulp, where rewetting is prevented, and method for manufacturing the drum
Technical Field
The present invention relates to a drum for an apparatus for processing cellulose-containing pulp, the drum being rotatable about an axis of rotation and provided with an outer surface permeable to liquid, the outer surface being formed by at least one plate which also forms at least one inner surface facing the axis of rotation, and a plurality of filtrate channels which extend along the axial extension of the drum and are provided inwardly of the inner surface, the drum being arranged to receive the pulp on the outer surface. Each filtrate channel is arranged to guide and discharge filtrate, located in the filtrate channel, which has been transported to the filtrate channel from the pulp via the outer surface, and each filtrate channel is defined by at least a first and a second axial channel wall having a substantially radial extension. Each filtrate channel of a plurality of filtrate channels is provided with an axially extending filtrate barrier which defines a gap be- tween itself and the inner surface and is arranged to prevent the flow of filtrate from the filtrate channel to the outer surface of the drum, and at the same time, the filtrate barrier defines at least one filtrate opening for allowing filtrate to pass from the gap to the filtrate channel. Further, the present invention relates to an apparatus for processing cellulose-containing pulp, which is provided with such sort of drum, and to a method for manufacturing such a drum.
Background of the Invention
Fibre lines producing cellulose-based products comprise some type of washing equipment for separating the liquor of the cooking from the cellulose- containing pulp. Later on in the process, washing equipment is also provided to separate bleaching liquors after the bleaching steps. There are a number of different types of washing equipment operating according to different principles.
When producing cellulose-based products, a roll press is frequently used for washing and/or dewatering the cellulose-containing pulp. The roll press comprises two co-operating and counter-rotating press rolls, each having a permeable outer surface, a so called mantle surface, whereby the outer surface is permeable to liquid pressed out of the pulp. The pulp is deposited on the permeable outer surface and pressed in the roll nip, or the press nip, between the press rolls, whereby liquid is pressed out of the pulp. Normally, the roll press also includes one or more washing zones prior to the press nip. One example of such a roll press is disclosed in US 3,980,518.
Another known washing equipment is the drum washer which comprises a rotating filter drum, where the cellulose-containing pulp is deposited and dewa- tered on the filter drum, which has a permeable outer surface, after the addition of washing liquid which displaces the liquor remaining on the pulp web after the preceding process step, for example a cooking step or bleaching step. The static pressure causes the contaminated liquid, called filtrate, to pass through the outer surface permeable to liquid. A further development of the original drum washer is the pressurized displacement washer, where the filtrate, under overpressure, is forced to pass through the permeable outer surface. One example of a drum washer is disclosed in WO2008/140396.
The roll/drum of both the drum washer and the roll press is often provided with a plurality of filtrate channels which extend along the axial extension of the roll, or drum, and are provided inwardly of the permeable outer surface. The filtrate channels receive filtrate, which has been transported through the outer surface, from the pulp situated on the outer surface, and subsequently, the filtrate is axially transported and discharged from the filtrate channel to a filtrate container connected thereto.
When large amounts of filtrate are involved, which is common, especially with regard to rolls, or drums, having a long axial extension, rewetting is a problem that arises, i.e. that the filtrate which have been transported to the filtrate channels flows back through the outer surface and dilutes the washed and/or pressed pulp. In fig. 1 , this rewetting is illustrated with regard to a prior-art roll press having two co-operating and counter-rotating press rolls.
US 5,470,471 discloses a press roll where baffle plates are anchored inside the filtrate channels of the press roll in order to prevent the rewetting of the pulp.
US 4,581 ,139 describes a baffle insert member which is inserted in a fil- trate channel of a rotary vacuum drum washer in order to prevent the rewetting of pulp. The baffle insert members are described as exchangeable.
In US 6,311 ,849 and WO2007/004968, respectively, roll presses are disclosed, having two co-operating and counter-rotating press rolls, where the filtrate channels have been configured to prevent the rewetting of pulp. The Object of the Invention
The object of the present invention is to provide an improved drum for apparatuses for processing cellulose-containing pulp, where the rewetting of the pulp is prevented. Summary of the Invention
The above-mentioned object of the present invention is attained by providing a drum of the kind mentioned in the introductory part of the description, comprising the features that the filtrate barrier is mounted to the drum by being sandwiched by and between the first axial channel wall of the filtrate channel and the inner surface.
By means of the present invention, rewetting of the pulp is prevented in an efficient way. By means of the present invention, the mounting of the filtrate barrier to the drum and to the filtrate channel of the drum is facilitated, and the production of drums/press rolls for apparatuses for processing cellulose-containing pulp is thus facilitated. The structure of the drum is simplified and is less complicated, which in turn provides a less expensive drum. By means of the present invention, an efficient processing of cellulose-containing pulp is attained, where the process comprises washing and/or dewatering the pulp. According to an advantageous embodiment of the drum according to the present invention, the filtrate barrier abuts, where it is sandwiched, the first axial channel wall of the filtrate channel and the inner surface of the at least one plate. According to an advantageous embodiment of the drum according to the present invention, substantially all of the filtrate channels are provided with an axially extending filtrate barrier.
By sandwiching the filtrate barrier between the first axial channel wall of the filtrate channel and the inner surface of the at least one plate, a plurality of features of prior-art drums, which have contributed to the complexity of the drum, may be excluded.
Examples of such features that may be excluded in drums for drum washers are the intermediate rewetting barriers which previously have been provided between the outer surface and the filtrate channels and extend over a plurality of filtrate channels in the direction of rotation and, for some filtrate channels, form a wall completely separating the filtrate channel and the outer surface. For this known solution, openings are required in the axial channel walls of the filtrate channels, which axial channel walls have a substantially radial extension, and this is expensive.
By means of the present invention, complicated attachments of the filtrate barrier are avoided, as disclosed in prior art, e.g., in US 5,470,471 , where it is suggested, inter alia, that axial grooves are provided in the channel walls of the filtrate channel, e.g. adjacent to a roll shell located inside of and spaced from the perforated outer surface on which the pulp is applied. In the grooves the filtrate barriers are axially inserted. By the present invention, no axial grooves are required in the channel walls of the filtrate channel, which is a time consuming and thus expensive process.
Further, the present invention provides a radical decrease in the amount of welding work when manufacturing the drum in relation to manufacturing prior-art drums. The drum according to the present invention is especially advantageous for drum washers.
Advantageously, the filtrate barrier is made of the same material as the reminder of the drum and/or the at least one plate. Advantageously, the material is resistant to the conditions in question and resistant to the effect of the filtrate. Examples of materials are, e.g., stainless steel, bur also other materials may be used. However, the filtrate barrier may made of a material different from the mate- rial of the at least one plate and/or the remainder of the drum. The filtrate barrier may be in the form of a section or a plate, such as a sheet. The thickness of the filtrate barrier may be approximately 1-2 mm, whereas the thickness of the at least one plate may be approximately 3-6 mm, but other dimensions are possible. The at least one plate may be one plate or a plurality of plates, e.g. two or more plates. One plate or a plurality of plates after one another may extend around the circumference of the drum. One plate or a plurality of plates after one another may extend along the longitudinal extension of the drum. The filtrate barrier may be sandwiched by one plate or a plurality of plates. The at least one plate, which forms the outer surface, may comprise one or a plurality of plates provided with apertures, e.g. perforated. A plurality of filtrate channels may comprise two or more filtrate channels.
The processing of the pulp by means of the innovative drum may comprise washing, pressing, washing and pressing, or filtering. The drum may, e.g., be a filter drum of a drum washer, a roll, or a press roll of a roll press for washing and/pr dewatering pulp.
According to an advantageous embodiment of the drum according to the present invention, the filtrate barrier rests against the second axial channel wall of the filtrate channel, and the filtrate barrier is provided with the at least one filtrate opening. By means of this embodiment, the position of the filtrate barrier may be maintained in an efficient and uncomplicated manner, and a dislocation of the filtrate barrier or a deflection of the filtrate barrier toward the axis of rotation over time is avoided. Hereby, an improved drum is provided, where the rewetting of pulp is prevented.
According to a further advantageous embodiment of the drum according to the present invention, the filtrate barrier is biased against the second axial channel wall of the filtrate channel. By means of this embodiment, the positioning of the filtrate barrier is further improved and the position of the filtrate barrier can be maintained in an even more efficient and uncomplicated manner, whereby the dislocation of the filtrate barrier or the deflection of the filtrate barrier toward the axis of rotation over time is avoided. Hereby, an improved drum is provided, where the rewetting of pulp is prevented.
According to another advantageous embodiment of the drum according to the present invention, the at least one filtrate opening is provided adjacent to one of the first and second axial channels walls of the filtrate channel. This location of the filtrate opening is effective to prevent the transport of filtrate from the filtrate channel to the outer surface of the drum, and thereby, the rewetting of the pulp is prevented, whereby an improved drum is obtained, where the rewetting of pulp is prevented.
According to yet another advantageous embodiment of the drum according to the present invention, the at least one filtrate opening is provided adjacent to the second axial channel wall of the filtrate channel. By positioning the filtrate opening at the axial edge that is not sandwiched between the inner surface of the at least one plate and the first axial channel wall, the mounting of the filtrate barrier and the production of the filtrate barrier per se are facilitated, and an improved drum is attained, where rewetting of the pulp is prevented.
According to an advantageous embodiment of the drum according to the present invention, the filtrate barrier comprises a first portion which is located fur- thest away from the outer surface of the drum in relation to the remainder portion of the filtrate barrier, and the at least one filtrate opening is provided at or adjacent to said first portion. By means of this embodiment, an inclination of the filtrate barrier in relation to the outer surface is attained, which is efficient for the dewatering of pulp, especially when the filtrate channel is located at the vertically higher positions during the rotation of the drum. Filtrate which has arrived at the gap flows quicker and more efficiently downward into the filtrate channel because of said inclination. Thus, an improved drum is obtained, where the rewetting of pulp is prevented, by means of this embodiment.
According to a further advantageous embodiment of the drum according to the present invention, the filtrate barrier is axially bent so that an axially extending bend, which protrudes toward the axis of rotation, is provided at or adjacent to the first portion. By means of said bend of the filtrate barrier, an efficient biasing and/or abutment of the filtrate barrier against the second axial channel wall is attained, and the above-mentioned inclination of the filtrate barrier may be set in an efficient manner.
According to another advantageous embodiment of the drum according to the present invention, the filtrate barrier has an axially extending first edge at which the filtrate barrier is sandwiched between the first axial channel wall of the filtrate channel and the inner surface, and along substantially the entire axial extension of the first edge the filtrate barrier is sandwiched by and between the first axial channel wall and the inner surface. Hereby, an efficient mounting of the filtrate barrier is attained.
According to yet another advantageous embodiment of the drum accord- ing to the present invention, each filtrate barrier extends past the first axial channel wall of the filtrate channel and into an adjacent filtrate channel. By means of this embodiment, the mounting of the filtrate barrier is further reinforced and the drum becomes more resistant to wear and its durability is improved.
According to an advantageous embodiment of the drum according to the present invention, where each filtrate barrier extends past the first axial channel wall of the filtrate channel and into an adjacent filtrate channel, each filtrate barrier rests or is biased against the second axial channel wall of the filtrate channel and against the filtrate barrier of an adjacent filtrate channel. By means of this embodiment, the stability of the position of the filtrate barrier is further improved, and the position of the filtrate barrier may be maintained in a yet more efficient and uncomplicated manner.
According to a further advantageous embodiment of the drum according to the present invention, the filtrate barrier extends along substantially the entire axial extension of the filtrate channel. Hereby, the rewetting is efficiently prevented, especially with regard to axially long drums, and the embodiment provides an improved drum where rewetting of pulp is prevented.
The features of one or a plurality of the above-mentioned embodiments may be combined in various possible ways providing further possible embodi- ments of the drum according to the present invention.
Further, the above-mentioned object of the present invention is attained by providing an apparatus for processing cellulose-containing pulp, comprising at least one rotatable first drum provided with an outer surface permeable to liquid, the outer surface being formed by at least one plate which also forms at least one inner surface, and a plurality of filtrate channels provided inwardly of the inner surface, the apparatus being arranged to receive the pulp on the outer surface of the drum and process the pulp located on the outer surface while rotating the drum, and the apparatus is arranged to process the pulp at least by removing filtrate from the pulp and transporting the filtrate from the pulp to the filtrate channels through the outer surface, characterized in that said drum comprises the features mentioned in any of the claims 1 to 11 , or mentioned in any of the above-mentioned embodiments of the drum. By means of the apparatus of the present invention, the rewetting of pulp is efficiently prevented, and by way of the improvements of the drum, the apparatus is improved in corresponding ways as disclosed above.
According to an advantageous embodiment of the apparatus according to the present invention, the apparatus is arranged to rest on a floor and comprises an application zone for applying pulp to the outer surface of the drum and a removal zone for removing pulp from the outer surface, the drum being arranged to rotate in a direction of rotation from the application zone to the removal zone so that each filtrate channel is moved into the removal zone in a direction toward said floor. By this embodiment, an efficient and improved drum washer is attained, where rewetting is prevented in an efficient manner.
According to a further advantageous embodiment of the apparatus according to the present invention, where each filtrate channel is moved into the removal zone in a direction toward said floor, the apparatus comprises at least one washing zone for washing the pulp located on the outer surface. By means of this embodiment, an efficient and improved drum washer is attained, where rewetting is prevented in an efficient manner.
According to a further advantageous embodiment of the apparatus according to the present invention, where each filtrate channel is moved into the removal zone in a direction toward said floor, the apparatus is arranged such that the axial channel wall of the first and second axial channel walls of the filtrate channel, adjacent to which the at least one filtrate opening is provided, arrive at the removal zone after the opposite axial channel wall of the filtrate channel during the rotation of the drum. By means of this embodiment, an efficient and improved drum washer is attained, where rewetting is prevented in an efficient manner.
According to another advantageous embodiment of the apparatus according to the present invention, the apparatus comprises a rotatable second drum, the first and second drums being arranged to rotate in opposite directions of rotation and define a press nip between them, in which press nip the pulp is pressed, and the apparatus is arranged to feed the pulp in the direction of rotation of the drums through the press nip. By means of this embodiment an efficient and improved roll press is attained, where rewetting is prevented in an efficient manner.
According to further advantageous embodiment of the apparatus according to the present invention, where the apparatus comprises two drums, the apparatus is arranged to rest on a floor, and the axes of rotation of the drums are lying in a plane which is substantially parallel to said floor, and the apparatus is arranged such that, in the press nip, the one of the first and second axial channel walls of the filtrate channel adjacent to which the at least one filtrate opening is provided is positioned further away from said floor in relation to the opposite axial channel wall of the filtrate channel. By means of this embodiment an efficient and improved roll press is attained, where rewetting is prevented in an efficient manner.
The above-mentioned object of the present invention is also attained by providing a method for manufacturing a drum according to any of the claims 1 to 11 , or according to any of the above-mentioned embodiments of the drum, the method comprising the following steps: placing each filtrate barrier against the first axial channel wall of each filtrate channel; applying the at least one plate to each filtrate barrier at the first axial channel wall of each filtrate channel; and mounting each filtrate barrier to the drum by sandwiching each filtrate barrier between the first axial channel wall of each filtrate channel and the inner surface of the at least one plate. By means of the innovative method of the present invention, a facilitated production of the drum is attained, and a resulting simplified and effective drum is attained, where rewetting of pulp is prevented in an efficient manner.
According to an advantageous embodiment of the method according to the present invention, the method is characterized by fixing each filtrate barrier to the first axial channel wall of each filtrate channel after the step of placing the filtrate barrier against the first axial channel wall of each filtrate channel and before the step of applying the at least one plate to each filtrate barrier. Said fixing facilitates said sandwiching of the filtrate barrier and further facilitates the mounting of the filtrate barriers.
The above-mentioned features and embodiments of the drum, apparatus and method, respectively, according to the present invention may be combined in various possible ways providing further advantageous embodiments.
Further advantageous embodiments of the drum, apparatus and method according to the present invention and further advantages with the present invention emerge from the dependent claims and the detailed description of embodi- ments.
Brief Description of the Drawings
The present invention will now be described, for exemplary purposes, in more detail by way of embodiments and with reference to the enclosed drawings, in which:
Fig. 1 is a schematic partial side view of a prior-art roll press during op- eration;
Fig. 2 is a schematic partial perspective view of an embodiment of the drum according to the present invention;
Fig. 3 is a schematic partial side view of the drum of Fig. 2;
Fig. 4 is a schematic side view of a first embodiment of the apparatus according to the present invention, provided with drums according to the present invention; Fig. 5 is a schematic side view of a second embodiment of the apparatus according to the present invention, provided with a drum according to the present invention; and
Fig. 6 is a flow chart illustrating aspects of the method according to the present invention.
Detailed Description of Preferred Embodiments
Fig. 1 illustrates the rewetting of cellulose-containing pulp with regard to a prior-art roll press having two co-operating and counter-rotating press rolls 102, 104 rotating in different directions of rotation Ri and R∑. The pulp is fed in the di- rection of rotation of the press rolls 102, 104 and through a press nip 106 formed between the press rolls. Subsequent to the press nip 106, the pressure of the pulp 108 decreases and the filtrate 110, which has not been discharged from the filtrate channels 112, 114, returns through the outer surface 116, 118 of each press roll 102, 104 and dilutes the pulp 108. In Fig. 1 , the rewetting is illustrated by arrows from the interior of the press rolls 102, 104 to zone A (rewetting zone) above the press nip 106. The pulp has a maximum dryness B prior to the rewetting zone A, whereas the pulp 108 leaving the roll press has the reduced dryness C because of the rewetting.
In a drum washer of the sort shown in connection with Fig. 5, the risk of rewetting of the pulp is highest adjacent to and at the removal zone, where the pulp is removed from the outer surface of the drum.
Fig. 2 schematically shows a partial perspective view of an embodiment of the drum 130 for an apparatus for processing cellulose-containing pulp according to the present invention, where the drum 130 is provided with an outer surface 132 permeable to liquid, which is only illustrated at the end of the drum 130 and is otherwise removed in order to illustrate the filtrate barriers 134 of the drum 130, the filtrate barriers extending along the axial extension of the drum 130. The outer surface 132 is formed by or defined by at least one plate 135 which also forms or defines at least one inner surface 137. The at least one plate 135 may comprise a plate provided with holes, e.g. perforated, or a plurality of plates provided with holes, which may be mounted and joined in ways known to the skilled person, e.g. by welding and subsequent turning of the welding seams. Generally, the filtrate barriers 134 are not exposed along the axial extension of the drum 130 as they are covered by the outer surface 132. Fig. 3 shows a schematic side view of the drum of Fig. 2.
With reference to Figs. 2 and 3, the outer surface 132 and the inner surface 137 extend around the circumference of the drum 130. The at least one plate 135 may extend around the entire circumference of the drum 130. One plate 135 may extend around the entire circumference of the drum 130, or a plurality of plates may be positioned after one another around the entire circumference of the drum 130. The drum 130 is rotatable in a direction of rotation R3 about an axis of rotation 302 (the axis of rotation 302 is shown in Fig. 5) and is provided with one or a plurality of filtrate channels 136 which extend along the axial extension of the drum 130 and are provided inwardly of the inner surface 137. Each filtrate channel 136 is provided with a filtrate barrier 134. The inner surface 137 of the at least one plate 135 faces the axis of rotation 302 (the axis of rotation 302 is shown in Fig. 5). Advantageously, each filtrate barrier 134 extends along substantially the entire axial extension of the filtrate channel 136. The drum is adapted to receive pulp on the outer surface 132, and each filtrate channel 136 is adapted to guide, e.g. axi- ally guide, and discharge filtrate, located in the filtrate channel 136, which has been transported to the filtrate channel 136 from the pulp through the outer surface 132. Each filtrate channel 136 may be defined, or limited, by a first axial channel wall 138, 140 having a substantially radial extension, by a second axial channel wall 140, 142 having a substantially radial extension, by an inner channel wall 144, or bottom wall, which is radially closest to the axis of rotation 302 of the drum and extends in the direction of rotation R3, and by the inner surface 137 of the at least one plate 135. Two adjacent filtrate channels 136 may have a radially extending channel wall 140 in common. The common radially extending channel wall 140 forms the first axial channel wall 140 of one of the filtrate channels 136 and at also forms the second axial channel wall 140 of the second filtrate channel 136.
The filtrate barrier 34 defines a gap 146 between itself and the inner sur- face 137 and is adapted to prevent the flow of filtrate from the filtrate channel 136 to the outer surface 132 of the drum 130, and at the same time, the filtrate barrier 134 defines a plurality of filtrate openings 148 for allowing filtrate to pass from the gap 146 to the filtrate channel 136. In other words, the filtrate barrier 134 defines a gap 146 between the inner surface 137 and a main part of the filtrate channel 136, the filtrate barrier 134 separating the filtrate channel 136 into a gap 146 and a main part. Alternatively, the filtrate barrier 134 may define only one filtrate opening 148 which may extend along substantially the entire extension of the filtrate channel 136. The filtrate barrier 134 may be in the form of a plate in which the filtrate openings 148 are formed.
The filtrate barrier 134 is mounted to the drum 130 by being sandwiched by and between the first axial channel wall 138, 140 of the filtrate channel 136 and the inner surface 137 of the at least one plate 135. More specifically, the filtrate barrier 134 may be sandwiched between the radially outer axially extending edge of the first axial channel wall 138, 140 and the inner surface 137. The filtrate barrier 134 has an axially extending first edge 150 at which the filtrate barrier 134 may be sandwiched between the first axial channel wall 140 of the filtrate channel 136 and the inner surface 137. Advantageously, along substantially the entire axial extension of the first edge 150, the filtrate barrier 134 is sandwiched by and be- tween the first axial channel wall 140 of the filtrate channel 136 and the inner surface 137. Each filtrate barrier 134 may extend past the first axial channel wall 138, 140 of the filtrate channel 136 and into an adjacent filtrate channel 134. The filtrate barrier 134 may rest, or may be moderately biased, against the second axial channel wall 140, 142 of the filtrate channel 136 and against the filtrate barrier 134 of an adjacent filtrate channel 136. The filtrate barrier 134 may have a plurality of tongues 152 defining the filtrate openings 148. The tongues 152 may rest, or be moderately biased, against the second axial channel wall 140, 142 of the filtrate channel 136 and against the filtrate barrier 134 of an adjacent filtrate channel 136. Thus, the filtrate openings 148 may be provided adjacent to the second axial channel wall 140, 142 of the filtrate channel 136.
The filtrate barrier 134 may have a first portion 54 which is located furthest away from the outer surface 132 of the drum 130 in relation to the remainder portion of the filtrate barrier 134, and the filtrate openings 148 may be provided at or adjacent to said first portion 154. The filtrate barrier 134 may be axially bent so that an axially extending bend 156, or edge, which protrudes toward the axis of rotation 302, is provided at or adjacent to the first portion 154. This provides for an efficient drainage of filtrate from the gap 146 to the filtrate channel 136. According to an advantageous embodiment of the drum according to the present invention, the filtrate barrier 134 forms an angle with the outer surface 132 such that the total area of all filtrate openings 148 is larger than the area that is defined by the filtrate barrier 134 and the inner surface 137 and that lies in a radially extending plane intersecting the border between the filtrate openings 148 and the main part of the filtrate barrier 134.
The filtrate barriers 134, the channel walls 138, 140, 142, 144 of the filtrate channel 136 and the at least one plate 135 may be made of the same material which is resistant to the conditions in question and to the effect of the filtrate, e.g. stainless steel.
Otherwise, the drum 130 may be provided with, or be connected to, known equipment for effecting the application of pulp on the outer surface, the washing of pulp and the dewatering of pulp, which equipment is well known to the person skilled in the art.
Fig. 4 schematically shows a first embodiment of the apparatus according to the present invention for processing cellulose-containing pulp by washing and pressing the pulp. The apparatus is in the form of a so called roll press and comprises a rotatable first drum 202, in the form of a press roll, and a rotatable second drum 204, in the form of a press roll, each drum 202, 204 being rotatable in a direction of rotation R1t R2, about an axis of rotation 203, 205 and has an outer surface 206, 208 permeable to filtrate pressed out of the pulp. Each outer surface 206, 208 may be formed by at least one plate 21 1 , 213 which also forms at least one inner surface 215, 217 facing the axis of rotation 203, 205. Each drum 202, 204 has a plurality of filtrate channels 210, 212 which extend along the axial extension of each drum 202, 204 and are provided inwardly of the inner surface 215, 217 to guide and discharge evacuated filtrate.
Each filtrate channel 210, 212 may be defined, or limited, by the inner surface 215, 217, a radially inner wall 218, 220 provided on an axial central drum 222, 224 and a first and a second axial channel wall 226, 228, 230, 232 having a substantially radial extension. Each channel wall may extend along the entire axial extension of each press roll 202, 204 and be provided with at least one outlet for discharging filtrate therefrom in a conventional manner known to the skilled person.
The drums 202, 240 are arranged to rotate in opposite directions Ri, R2. The apparatus of this embodiment is arranged to receive the pulp on the outer surface 206, 208 of each drum 202, 204 from two pulp distribution devices 234, 236 arranged to deposit pulp on the outer surface 206, 208, and the pulp is fed in a gap 209 in the direction of rotation of the drums 202, 204 while processing the pulp located on the outer surface during rotation of the drum. The pulp is fed through a press/roll nip 238 defined by the drums 202, 204, in which press nip 238 the pulp is pressed to remove filtrate from the pulp. At least in the region of the press nip 238, filtrate is removed from the pulp and transported from the pulp to the filtrate channels 210, 212 through the outer surface 206, 208. The apparatus is arranged to rest on a floor and the axes 203, 205 of rotation of the drums 202, 204 are lying in a plane which is substantially parallel to said floor. The apparatus may be arranged to feed the pulp through the press nip 238 in a substantially vertical direction from below upwards. Along the transport of the pulp between each pulp distribution device 234, 236 and the press nip, one or a plurality of washing zones may be provided in conventional ways known to the skilled person.
In each filtrate channel 210, 212, an axially extending filtrate barrier 134 is mounted by being sandwiched by and between the first axial channel wall 226, 230 of the filtrate channel 210, 212 and the inner surface 215, 217 of the at least one plate 211 , 213, as disclosed in connection with Figs. 2 and 3. This embodiment of the apparatus is arranged such that, in the press nip 238, the second axial channel wall 228, 232 of the filtrate channel 210, 212, adjacent to which the at least one filtrate opening is provided, is positioned further away from said floor in relation to the first axial channel wall 226, 230 of the filtrate channel 210, 212. The roll press may comprise further units and equipment well known to the skilled person.
Fig. 5 schematically shows an axial cross-section of a second embodiment of the apparatus according to the present invention, in the form of a drum washer, arranged to dewater cellulose-containing pulp, provided with the rotatable drum 130 as shown in Figs. 2 and 3, which rotates in the direction of rotation f?3 about the axis of rotation 302. The apparatus may comprise a vat 304 which houses the drum 130 and is provided with an inlet 306 via which the cellulose-containing pulp is fed to the vat 304. The apparatus may comprise a vacuum zone V in which the pulp is sucked toward the outer surface of the drum 130 by means of vacuum. In the vacuum zone V, filtrate is transported from the pulp via the outer surface 132, permeable to liquid, and the gap 146, defined by the filtrate barrier 134, to the respective filtrate channel 136. The apparatus may comprise an application zone P in which pulp is applied to the outer surface 32 and forms a mat or cake, the application zone P extending into the vacuum zone V. The apparatus may comprise a non-vacuum removal zone AZ where the pulp is removed from the outer surface 132 and is transported to the next process step in ways known to the skilled per- son, Between the vacuum zone V and the non-vacuum removal zone AZ, there are cut off zones Bi and B2. These cut off zones Bi and B2 and the other zones AZ and V are provided in manners known to the skilled person. The drum washer may be provided with one or a plurality of washing zones. The drum washer is arranged to rest on a floor, and the drum 130 is arranged to rotate in the direction of rotation R3 from the application zone P, via washing zones, to the removal zone AZ so that each filtrate channel 136 is moved into the removal zone AZ in a direction toward said floor. The drum washer according to this embodiment is arranged such that the second axial channel wall 140, 142 of the filtrate channel 136 (see Figs. 2 and 3), adjacent to which the at least one filtrate opening 148 is provided, arrive at the removal zone AZ after the first axial channel wall 138, 140 of the filtrate channel 136 during the rotation of the drum 130. It is also possible to provide a drum washer without vacuum zones, and the outer surface of the drum may be provided with external axial compartments in which the pulp may be formed in the application zone.
In prior-art drum washers without filtrate barriers, the major part of the rewetting of the pulp occurs at or adjacent to the non-vacuum removal zone AZ. By the innovative drum of the present invention, this rewetting is inhibited or prevented by the filtrate barriers 134 of the filtrate channels 136. The drum washer may comprise further units and equipment well known to the skilled person, and may, e.g., be provided with a stationary gas-proof outer casing which encloses the drum 130.
Fig. 6 shows a flow chart illustrating aspects of the method according to the present invention for manufacturing a drum as disclosed above. The method comprises the following steps: Each filtrate barrier is placed against the first axial channel wall of each filtrate channel, more precisely, against the radially outer axial edge of the first axial channel wall, at step 601. Each filtrate barrier is rested against the second axial channel wall of the filtrate channel, at step 602. Each filtrate barrier is fixed to the first axial channel wall of each filtrate channel, e.g. by spot welding, at step 603. The at least one plate, e.g. in the form of a plurality of plates provided with holes, is applied to each filtrate barrier at the first axial channel wall of each filtrate channel, at step 604. Each filtrate barrier is mounted, at step 605, to the drum by sandwiching each filtrate barrier between the first axial channel wall of each filtrate channel and the inner surface of the at least one plate. The filtrate barrier may be sandwiched by welding the plates and shrinking the outer surface around the drum. It is to be understood that one of the above-mentioned step or a plurality of the above-mentioned steps of the disclosed method may be excluded. It is to be understood that the method may be supplemented by one further step or a plurality of further steps, which steps may be known to the skilled person.
The invention shall not be considered limited to the embodiments illustrated, but can be modified and altered in many ways within the scope of the appended claims. For example, the filtrate barrier and the filtrate openings may be configured in many ways within the scope of the appended claims.

Claims

1. A drum (130; 202, 204) for an apparatus for processing cellulose-containing pulp, the drum (130; 202, 204) being rotatable about an axis of rotation (302; 203, 205) and provided with an outer surface ( 32; 206, 208) permeable to liquid, the outer surface being formed by at least one plate (135; 211 , 213) which also forms at least one inner surface (137; 215, 217) facing the axis of rotation, and a plurality of filtrate channels (136; 210, 212) which extend along the axial extension of the drum and are provided inwardly of the inner surface, the drum (130; 202, 204) being arranged to receive the pulp on the outer surface, and each filtrate channel (136; 210, 212) is arranged to guide and discharge filtrate, located in the filtrate channel, which has been transported to the filtrate channel from the pulp via the outer surface, and each filtrate channel (136; 210, 212) is defined by at least a first and a second axial channel wall (138, 140, 142; 226, 228, 230, 232) having a substantially radial extension, each filtrate channel of a plurality of filtrate channels (136; 210, 212) being provided with an axially extending filtrate barrier (134) which defines a gap (146) between itself and the inner surface and is arranged to prevent the flow of filtrate from the filtrate channel to the outer surface of the drum, and at the same time, the filtrate barrier (134) defines at least one filtrate opening (148) for allowing filtrate to pass from the gap (146) to the filtrate channel (136; 210, 212), characterized in that the filtrate barrier (134) is mounted to the drum (130; 202, 204) by being sandwiched by and between the first axial channel wall (138, 140; 226, 230) of the filtrate channel (136; 210, 212) and the inner surface (137; 215, 217).
2. A drum according to claim 1 , characterized in that the filtrate barrier (134) rests against the second axial channel wall (140, 142; 228, 232) of the filtrate channel (136; 210, 212), and in that the filtrate barrier (134) is provided with the at least one filtrate opening (148).
3. A drum according to claim 2, characterized in that the filtrate barrier (134) is biased against the second axial channel wall (140, 142; 228, 232) of the filtrate channel (136; 21 , 212).
4. A drum according to claim 2 or 3, characterized in that the at least one filtrate opening (148) is provided adjacent to one of the first and second axial channels walls (138, 140, 142; 226, 228, 230, 232) of the filtrate channel (136; 210, 212).
5. A drum according to claim 4, characterized in that the at least one filtrate opening (148) is provided adjacent to the second axial channel wall (140, 142; 228, 232) of the filtrate channel.
6. A drum according to any of the claims 1 to 5, characterized in that the filtrate barrier (134) comprises a first portion (154) which is located furthest away from the outer surface of the drum (130; 202, 204) in relation to the remainder portion of the filtrate barrier (134), and in that the at least one filtrate opening (148) is provided at or adjacent to said first portion (154).
7. A drum according to claim 6, characterized in that the filtrate barrier (134) is axially bent so that an axially extending bend, which protrudes toward the axis of rotation, is provided at or adjacent to the first portion (154).
8. A drum according to any of the claims 1 to 7, characterized in that the filtrate barrier (134) has an axially extending first edge (150) at which the filtrate barrier (134) is sandwiched between the first axial channel wall (138, 140; 226, 230) of the filtrate channel and the inner surface (137; 215, 217), and in that along substantially the entire axial extension of the first edge (150) the filtrate barrier (134) is sandwiched by and between the first axial channel wall (138, 140; 226, 230) and the inner surface.
9. A drum according to claim 8, characterized in that each filtrate barrier (134) extends past the first axial channel wall (138, 140; 226, 230) of the filtrate channel and into an adjacent filtrate channel (136; 210, 212).
A drum according to claim 9, characterized in that each filtrate barrier rests or is biased against the second axial channel wall (140, 142; 228, 232) of the filtrate channel and against the filtrate barrier (134) of an adjacent filtrate channel (136; 210, 212).
1 1 . A drum according to any of the claims 1 to 10, characterized in that the filtrate barrier (134) extends along substantially the entire axial extension of the filtrate channel (136; 212, 212).
12. An apparatus for processing cellulose-containing pulp, comprising at least one rotatable first drum (130; 202, 204) provided with an outer surface (132; 206, 208) permeable to liquid, the outer surface being formed by at least one plate
(135; 21 1 , 213) which also forms at least one inner surface (137; 215, 217), and a plurality of filtrate channels (136; 210, 212) provided inwardly of the inner surface, the apparatus being arranged to receive the pulp on the outer surface (132, 206, 208) of the drum and process the pulp located on the outer surface (132; 206, 208) while rotating the drum, and the apparatus is arranged to process the pulp at least by removing filtrate from the pulp and transporting the filtrate from the pulp to the filtrate channels (136; 210, 212) via the outer surface (132; 206, 208), characterized in that said drum (132; 202, 204) comprises the features mentioned in any of the claims 1 to 1 1 .
13. An apparatus according to claim 12, characterized in that the apparatus is arranged to rest on a floor and comprises an application zone (P) for applying pulp to the outer surface (132) of the drum (130) and a removal zone (AZ) for removing pulp from the outer surface, the drum (130) being arranged to rotate in a direction of rotation (R3) from the application zone (P) to the removal zone (AZ) so that each filtrate channel (136) is moved into the removal zone (AZ) in a direction toward said floor.
14. An apparatus according to claim 12 or 13, characterized in that the apparatus is arranged such that the axial channel wall of the first and second axial channel walls (138, 140, 142) of the filtrate channel (136), adjacent to which the at least one filtrate opening (148) is provided, arrive at the removal zone (AZ) after the opposite axial channel wall (138, 140) of the filtrate channel (136) during the rotation of the drum.
15. An apparatus according to claim 12, characterized in that the apparatus comprises a rotatable second drum (204), in that the first and second drums (202, 204) are arranged to rotate in opposite directions of rotation (Ri, R2) and de- fine a press nip (238) between them, in which press nip (238) the pulp is pressed, and in that the apparatus is arranged to feed the pulp in the direction of rotation (Ri, R2) of the drums (202, 204) through the press nip (238).
16. An apparatus according to claim 15, characterized in that the appara- tus is arranged to rest on a floor and the axes of rotation (203, 205) of the drums
(202, 204) are lying in a plane which is substantially parallel to said floor, and in that the apparatus is arranged such that, in the press nip (138), the one of the first and second axial channel walls (226, 228, 230, 232) of the filtrate channel (210, 212), adjacent to which the at least one filtrate opening (148) is provided, is posi- tioned further away from said floor in relation to the opposite axial channel wall (226, 230) of the filtrate channel (210, 212).
17. A method for manufacturing a drum according to any of the claims 1 to 11 , the method comprising the following steps:
■ placing (601 ) each filtrate barrier against the first axial channel wall of each filtrate channel,
■ applying (604) the at least one plate to each filtrate barrier at the first axial channel wall of each filtrate channel, and
■ mounting (605) each filtrate barrier to the drum by sandwiching each filtrate barrier between the first axial channel wall of each filtrate channel and the inner surface of the at least one plate.
18. A method according to claim 17, characterized by fixing (603) each filtrate barrier to the first axial channel wall of each filtrate channel after the step of placing the filtrate barrier against the first axial channel wall of each filtrate channel and before the step of applying the at least one plate to each filtrate barrier.
PCT/SE2010/051308 2009-12-15 2010-11-26 Drum and apparatus for processing cellulose-containing pulp, where rewetting is prevented, and method for manufacturing the drum WO2011075041A1 (en)

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CN201080056345.9A CN102652196B (en) 2009-12-15 2010-11-26 Drum and apparatus for processing cellulose-containing pulp, where rewetting is prevented, and method for manufacturing the drum

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SE0950964-7 2009-12-15
SE0950964A SE534655C2 (en) 2009-12-15 2009-12-15 Drum for processing cellulose pulp, apparatus comprising the drum and method of making the drum

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WO2013055284A1 (en) * 2011-10-12 2013-04-18 Metso Paper Sweden Ab Device for preventing rewetting of cellulose pulp
WO2014182224A1 (en) * 2013-05-07 2014-11-13 Valmet Ab An apparatus for washing and/or dewatering pulp and an insert for preventing rewetting of pulp
EP3322500A4 (en) * 2015-07-15 2019-03-13 Luxembourg S.à.r.l. GL&V A rotary drum filtering apparatus
SE1751312A1 (en) * 2017-10-24 2019-04-25 Valmet Oy Pressure relief drum washer and a method for manufacturing the drum washer

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US3680708A (en) * 1970-09-10 1972-08-01 Improved Machinery Inc Rotary drum filter
US5470471A (en) * 1993-05-14 1995-11-28 Ingersoll-Rand Company Anti-rewet deck for press rolls

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US2073384A (en) * 1932-05-13 1937-03-09 Oliver United Filters Inc Filter
GB1045580A (en) * 1964-01-20 1966-10-12 Improved Machinery Inc Wire wound filter with underlying peripherally spaced cover elements
US3680708A (en) * 1970-09-10 1972-08-01 Improved Machinery Inc Rotary drum filter
US5470471A (en) * 1993-05-14 1995-11-28 Ingersoll-Rand Company Anti-rewet deck for press rolls

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2013055284A1 (en) * 2011-10-12 2013-04-18 Metso Paper Sweden Ab Device for preventing rewetting of cellulose pulp
CN103987892A (en) * 2011-10-12 2014-08-13 维美德公司 Device for preventing rewetting of cellulose pulp
WO2014182224A1 (en) * 2013-05-07 2014-11-13 Valmet Ab An apparatus for washing and/or dewatering pulp and an insert for preventing rewetting of pulp
EP2994567A4 (en) * 2013-05-07 2016-12-14 Valmet Oy An apparatus for washing and/or dewatering pulp and an insert for preventing rewetting of pulp
EP3322500A4 (en) * 2015-07-15 2019-03-13 Luxembourg S.à.r.l. GL&V A rotary drum filtering apparatus
SE1751312A1 (en) * 2017-10-24 2019-04-25 Valmet Oy Pressure relief drum washer and a method for manufacturing the drum washer
SE541307C2 (en) * 2017-10-24 2019-06-25 Valmet Oy Pressure relief drum washer and a method for manufacturing the drum washer

Also Published As

Publication number Publication date
SE0950964A1 (en) 2011-06-16
CN102652196A (en) 2012-08-29
SE534655C2 (en) 2011-11-08
CN102652196B (en) 2014-07-09

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