WO2007073310A1 - Washing apparatus for washing cellulose pulp - Google Patents

Washing apparatus for washing cellulose pulp Download PDF

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Publication number
WO2007073310A1
WO2007073310A1 PCT/SE2006/001477 SE2006001477W WO2007073310A1 WO 2007073310 A1 WO2007073310 A1 WO 2007073310A1 SE 2006001477 W SE2006001477 W SE 2006001477W WO 2007073310 A1 WO2007073310 A1 WO 2007073310A1
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WO
WIPO (PCT)
Prior art keywords
drum
formation zone
pulp
inlet pipe
washing apparatus
Prior art date
Application number
PCT/SE2006/001477
Other languages
French (fr)
Other versions
WO2007073310A9 (en
Inventor
Johan Bylander
Jörgen T. LUNDBERG
Tomas WIKSTRÖM
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.
Publication of WO2007073310A1 publication Critical patent/WO2007073310A1/en
Publication of WO2007073310A9 publication Critical patent/WO2007073310A9/en

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Classifications

    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21D—TREATMENT OF THE MATERIALS BEFORE PASSING TO THE PAPER-MAKING MACHINE
    • D21D1/00—Methods of beating or refining; Beaters of the Hollander type
    • D21D1/20—Methods of refining
    • D21D1/40—Washing the fibres
    • 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

Definitions

  • the present invention relates to a washing apparatus for washing of cellulose pulp.
  • washing equipment for separating the liquor of the digestion from the pulp is included. Washing equipment is included later on in the process for separation of bleach liquors after bleaching stages. There are a number of different kinds of washing equipments operating according to various principles.
  • One well-known kind of washing apparatus is the drum washer where the pulp is dewatered on a rotatable filter drum after addition of washing liquid that displaces the liquor remaining in the pulp web after preceding process stages, e.g. a digestion stage or bleaching stage.
  • the static pressure causes the displaced liquid to pass through a perforated metal sheet arranged on the rotatable drum.
  • a further development of the original drum washer is the pressurized displacement washer, where the filtrate at pressure is caused to pass through the perforated metal sheet. The increase in the pressure difference results in a more effective/faster displacement of the filtrate.
  • the drum is provided with compartments in which the pulp locates itself in long and narrow rectangles towards the metal sheet in the axial direction of the drum.
  • the subdivision in compartments of the drum ensures that the pulp cake does not break up and moves, but instead maintains the form produced at application on the pulp.
  • the compartments are made up of compartment walls arranged axially along the whole axle of the drum.
  • washing liquid intended for a specific washing stage In order to maintain maximal washing efficiency, it is desirable to assure that washing liquid intended for a specific washing stage not is transferred to a subsequent washing stage. A pressure difference between the stages results in that added washing liquid strives for moving itself towards the lower pressure.
  • the respective zones are sealed with axial seals.
  • the axial seals are located between the rotating drum and the surrounding casing. The filtrates from the zones, respectively, are separated by seals in a peripheral end valve arranged at one or both of the gables of the drum.
  • Pulp for washing is introduced in the formation zone via an inlet opening.
  • supply pipes for feeding of a suspension of the pulp into the formation zone at the discharge side of the drum are directly connected to a main pipe for feeding of the pulp suspension to the washing apparatus.
  • Each supply pipe is arranged to feed a flow of pulp suspension directly towards the pulp compartments on the drum, i.e. in direction radially towards the drum. In the area where the fed pulp suspension in this way reaches the pulp compartments, the fibre concentration in the pulp compartments becomes high.
  • a part of the pulp suspension does not end up directly in the pulp compartments, but are gathered in a lower compartment of the formation zone, before the pulp suspension finally is put into the pulp compartments when they passes the lower compartment where the pulp is aggregated.
  • the aggregation of pulp in the lower compartment of the formation zone results in that a part of the pulp becomes inoperative and does not circulate in certain inactive areas in the formation zone.
  • the present invention aim to achieve an effective and improved washing apparatus where favourable circulation and even fibre concentration of the pulp suspension in the formation zone at the inlet part of the drum washer can be provided for, and where at least partly the drawbacks associated with what is previously known, according to the state of the art, can be eliminated.
  • the washing apparatus comprises a rotatable drum, provided with a number of outer compartments for the paper pulp to be washed, which compartments are defined by axial compartment walls and distributed along the circumference of the drum; a stationary casing that surrounds the drum, whereby an annular space is defined between the casing and the drum; a number of seals that are arranged to seal between the casing and the compartment walls of the compartments, such that the annular space is divided in a formation zone at the ascending side of the drum for formation of the pulp in the compartments of the drum during rotation of the drum, at least one washing zone for washing of the formed pulp at overpressure, and a discharge zone for discharge of the washed pulp from the annular space; and at least one inlet pipe for feeding of a suspension of the pulp to be washed into the formation zone.
  • the washing apparatus is characterised in that the formation zone is dimensioned such that the pulp suspension that occurs in the formation zone is brought by the drum when this rotates and forms a rotating flow in the formation zone, and that the inlet pipe is arranged to feed the pulp suspension in the formation zone in direction essentially tangentially towards the periphery of the drum such that said rotating flow of pulp suspension is maintained in the formation zone during operation.
  • the feeding of the pulp suspension into the formation zone is carried out in direction essentially tangentially towards the periphery of the drum and essentially in accordance with the rotating flow, the advantage is obtained that the risk that the pulp would become stationary anywhere in the formation zone is essentially reduced or eliminated, since the rotating flow of the pulp suspension is maintained in the formation zone during operation. Besides, an uneven fibre concentration of the pulp suspension in the pulp compartments can be avoided.
  • a first part of the inlet pipe at the connection to the formation zone can be arranged to extend in a direction substantially radially towards the drum and, in a second part in its extension into the formation zone, curved.
  • the curving of the second part of the inlet pipe is extending in the circumference direction of the drum. The curving is preferably within the range of 60-120 degrees towards the radial direction of the drum.
  • a rotational flow of pulp suspension in the formation zone is formed when the drum is rotating and this rotating flow is maintained during operation.
  • Said rotational flow may typically be larger than the flow of incoming pulp suspension in the formation zone and the rotational direction of the rotational flow is controlled by the rotation of the drum.
  • the rotational flow of pulp suspension in the formation zone should not be interrupted and the feeding of the pulp suspension should thus be done in a direction that follows the rotational direction of the rotational flow.
  • the inlet pipe for feeding of the pulp suspension opposite the rotational direction of the drum is then suitably arranged to feed the pulp suspension into the formation zone in a position that is relatively closer to the casing than the drum.
  • feeding in is instead carried out in the rotational direction of the drum.
  • the inlet pipe for feeding in of the pulp suspension in the rotational direction of the drum is in this case suitably arranged to feed the pulp suspension into the formation zone in a position that is relatively closer to the drum than the casing.
  • the washing apparatus can comprise at least two inlet pipes, distributed along the axial direction of the drum.
  • the inlet pipes might be connected to an inlet chamber for distribution of the pressure and flow of the pulp suspension before the pulp is fed in through the inlet pipes into the formation zone.
  • at least a deflection plate can be provided substantially centrally in the inlet chamber for deflection of a flow of pulp that is fed into the inlet chamber.
  • Fig. IA schematically shows, in a cross-sectional view, a formation zone and an inlet pipe for pulp suspension, forming a part of a washing apparatus according to an embodiment of the present invention
  • Fig. IB schematically shows, in a cross-sectional view, a formation zone and an inlet pipe for pulp suspension, forming a part of a washing apparatus according to an alternative embodiment of the present invention
  • Fig. 2 schematically shows, in a perspective view obliquely from above, a drum according to an embodiment of the present invention, intended for the washing apparatus according to Figs. IA or IB,
  • Fig. 3 shows schematically in an explanatory sketch, a cross-section of a washing apparatus with a formation zone similar that in fig. IA according to an embodiment of the present invention where the drum in fig. 2 is arranged in the washing apparatus, and
  • Fig. 4 schematically shows, in perspective, an explanatory sketch of an inlet chamber and a plurality of inlet pipes of the washing apparatus according to fig. IA.
  • Figs. IA-B and Fig. 2 shows separate main components of a washing apparatus for washing of cellulose pulp, according to the pressurized displacement washer kind.
  • the washing apparatus comprises a rotatable drum 2, provided with a number of outer compartments 4, having a bottom 6 of perforated metal sheet, in which compartments the paper pulp to be washed is placed during feeding on the drum.
  • Each compartment 4 has a bottom 6 and two compartment walls 8.
  • the compartment walls are arranged axially with respect to the axle 10 of the drum and distributed along the circumference 12 of the drum.
  • the washing apparatus may comprise a stationary support (not shown) having two opposite transverse beams (not shown) .
  • the drum 2 extends between the transverse beams and is rotatably journalled on the both transverse beams 16 of the support.
  • a stationary cylindrical casing 18, having two opposite gables, encloses the drum 2, whereby an annular space 20 (see Fig. 3) is defined between the casing 18 and the drum 2.
  • Washing liquid is supplied to the annular space 20 and, at pressure, the filtrate is caused to pass the perforated metal sheet that forms the bottom 6 in the pulp compartments 4 on the drum 2.
  • the increase in pressure difference results in an improved dewatering of the pulp.
  • the pulp locates itself in the compartments 4 on the drum in long and narrow rectangles towards the metal sheet in the axial direction of the drum.
  • the subdivision in compartments of the drum ensures that the pulp cake does not break up and moves, but instead maintains the formation produced at application on the pulp.
  • the perforated metal sheet, on which the pulp deposits, is located on a distance from the main surface of the drum such that filtrate channels 21 are formed in the space between the drum 2 and the perforated metal sheet.
  • washing liquid intended for a specific washing stage In order to maintain maximum washing efficiency, it is desirable to assure that washing liquid intended for a specific washing stage not is transferred to a subsequent washing stage. A pressure difference between the stages results in that added washing liquid aims for moving towards the lower pressure.
  • the respective stages are sealed with axial seals 22.
  • the axial seals are positioned between the rotating drum 2 and the surrounding casing 18. The filtrates from the respective stages are lead out through one or both gables of the drum. As evident from Fig.
  • the washing apparatus comprises several seals 22 arranged on the casing 18 and that seals between the casing and the compartment walls 8 of the compartments, such that the annular space 20 is divided in a formation zone F for forming of the pulp in the compartments 4 of the drum, during rotation of the drum in clockwise direction R, a first washing zone Tl and a second washing zone T2 for washing of the formed pulp at overpressure, and a discharge zone U for discharge of the washed pulp via a discharge opening 26 from the annular space. Pulp to be washed is fed in the formation zone via the inlet opening 30.
  • the washing apparatus comprises at least an inlet pipe 30 for feeding of a suspension of the pulp to be washed into the formation zone. Feeding of the pulp suspension is carried out essentially tangentially towards the periphery P of the drum.
  • a first part 32 of the inlet pipe 30 at the connection to the formation zone can be arranged to extend in a direction substantially radially towards the drum and in a second part 34 in its extension into the formation zone it can be curved.
  • the curving of the second part 34 of the inlet pipe 30 is extending in the circumference direction of the drum. The curving can be within the range of 60-120 degrees towards the radial direction of the drum.
  • the washing apparatus can also comprise two or more inlet pipes 30, as evident from fig. 4.
  • the inlet pipes are distributed axially with respect to the axle of the drum.
  • the inlet pipes 30 are preferably connected to an inlet chamber 36 for distribution of the pressure and flow of the pulp suspension before the pulp is fed in through the inlet pipes 30 into the formation zone F.
  • Preferably the pressure in all inlet pipes is about the same.
  • At least a deflection plate 38 can be provided straight in front of a discharge opening 39 for a connection pipe 40, which is arranged for feeding the pulp suspension into the inlet chamber.
  • the discharge opening 39 of the connection pipe 40 is arranged substantially centrally to a long side of the inlet chamber and the deflection plate is then preferably substantially centrally arranged within the inlet chamber 36 straight in front of the discharge opening 39 of the connection pipe.
  • a flow of pulp that is fed into the inlet chamber, via the connection pipe 40 can be laterally redirected by the deflection plate 38 in the inlet chamber such that a flow of pulp suspension, fed through to the inlet chamber and directed straight towards the inlet pipes 30 in the inlet chamber, at the opposite side opposite the discharge opening 39 of the connection pipe, is prevented.
  • the formation zone F is formed of a part of the annular space 20 and has a certain extension in the circumference direction. In radial direction, this part/zone extends further out from the drum 2 and its compartments walls 8, than surrounding parts of the annular space 20.
  • the formation zone may in that connection be regarded as an area generally defined by the drum 2 and an extension in radial direction of the casing 18, see fig. 3.
  • the radial extension of the casing 18 results in that the volume of the formation zone F becomes sufficiently large in order for the pulp suspension, that is located in the formation zone F, to be able to form a rotating flow within the formation zone F.
  • the rotating flow in the formation zone is indicated by arrows in figure IA and IB.
  • the formation zone F is dimensioned such that the pulp suspension that occurs in the formation zone is brought by the drum 2 when this rotates and forms said rotating flow in the formation zone.
  • the rotating direction of the rotational flow is controlled by the rotation of the drum 2.
  • the rotating direction of the rotational flow in the formation zone will be inverted relatively the rotating direction of the drum.
  • the rotating direction of the drum is clockwise and the rotational flow in the formation zone then circulates counter-clockwise .
  • the rotational flow of the pulp suspension in the formation zone should not be interrupted and the feeding of the pulp suspension should thus be carried out such that the rotational flow is followed and maintained during operation.
  • the inlet pipe 30, according to an embodiment of the present invention as shown in fig. IA, is arranged to feed the pulp suspension in a direction R2 into the formation zone F that is substantially opposite the rotational direction Rl of the drum, this means that the inlet pipe 30 can be arranged in a later, first part 41 of the formation zone F in order not to disturb the rotational flow.
  • later part 41 is meant a part of the formation zone F where adjacent compartments, opposite the inlet pipe, on the drum are on their way to leave the formation zone during rotation of the drum.
  • the inlet pipe 30 is suitably arranged to feed the pulp suspension into the formation zone F in a position that is relatively closer to the casing 18 than the drum 2, as evident from fig. IA.
  • the inlet pipe 30, according to an embodiment of the present invention as shown in fig. IB is arranged to feed the pulp suspension in a direction R2 into the formation zone F that is essentially similar to the rotational direction of the drum Rl, the inlet pipe 30 can preferably be arranged in an earlier, second part 42 of the formation zone F such that the rotational flow in the formation zone is not influenced.
  • “earlier” part 42 is meant a part of the formation zone F where adjacent compartments, opposite the inlet pipe, on the drum just previously has entered into the formation zone during rotation of the drum.
  • the inlet pipe 30 is suitably arranged to feed the pulp suspension into the formation zone F in a position that is relatively closer to the drum 2 than the casing 18.
  • a washing apparatus shows a formation zone with a self-circulating pulp suspension (during operation) , and by performing injection of pulp suspension such that the rotational flow is not disturb or counteracted, but instead is maintained or strengthened, improved pulp formation is obtained and a system that is less sensitive for disturbances and variations than previous known feeding mechanisms.

Abstract

The present invention relates to a washing apparatus for washing of cellulose pulp, comprising a rotatable drum (2) , provided with a number of outer compartments (4) for the paper pulp to be washed, and a stationary casing (18) that surrounds the drum. An annular space (20) is defined between the casing and the drum. The annular space is divided in a formation zone (F) , at least one washing zone (Tl, T2) and a discharge zone (U) . The washing apparatus comprises at least one inlet pipe (30) for feeding of a suspension of the pulp to be washed into the formation zone. Feeding of the pulp suspension is carried out in direction essentially tangentially towards the periphery (P) of the drum.

Description

Washing apparatus for washing cellulose pulp
The present invention relates to a washing apparatus for washing of cellulose pulp.
In all fibre lines, some kind of washing equipment for separating the liquor of the digestion from the pulp is included. Washing equipment is included later on in the process for separation of bleach liquors after bleaching stages. There are a number of different kinds of washing equipments operating according to various principles.
One well-known kind of washing apparatus is the drum washer where the pulp is dewatered on a rotatable filter drum after addition of washing liquid that displaces the liquor remaining in the pulp web after preceding process stages, e.g. a digestion stage or bleaching stage. The static pressure causes the displaced liquid to pass through a perforated metal sheet arranged on the rotatable drum. A further development of the original drum washer is the pressurized displacement washer, where the filtrate at pressure is caused to pass through the perforated metal sheet. The increase in the pressure difference results in a more effective/faster displacement of the filtrate.
According to a known design of a pressurized displacement washer, the drum is provided with compartments in which the pulp locates itself in long and narrow rectangles towards the metal sheet in the axial direction of the drum. The subdivision in compartments of the drum ensures that the pulp cake does not break up and moves, but instead maintains the form produced at application on the pulp. The compartments are made up of compartment walls arranged axially along the whole axle of the drum. In a drum washer, a number of various washing stages can be carried out, with separate addition of washing liquid to the various stages and also return of filtrate from a stage as washing liquid to another.
In order to maintain maximal washing efficiency, it is desirable to assure that washing liquid intended for a specific washing stage not is transferred to a subsequent washing stage. A pressure difference between the stages results in that added washing liquid strives for moving itself towards the lower pressure. For the purpose of being able to separate different washing stages, that are carried out in one washing zone on the drum, and also formation stage, that is carried out in a formation zone on the drum, and discharge stage (increased pulp concentration zone forms a first part of the discharge zone) , that is carried out in a discharge zone on the drum, the respective zones are sealed with axial seals. The axial seals are located between the rotating drum and the surrounding casing. The filtrates from the zones, respectively, are separated by seals in a peripheral end valve arranged at one or both of the gables of the drum.
Pulp for washing is introduced in the formation zone via an inlet opening. According to a known construction of a washing apparatus, supply pipes for feeding of a suspension of the pulp into the formation zone at the discharge side of the drum, are directly connected to a main pipe for feeding of the pulp suspension to the washing apparatus. Each supply pipe is arranged to feed a flow of pulp suspension directly towards the pulp compartments on the drum, i.e. in direction radially towards the drum. In the area where the fed pulp suspension in this way reaches the pulp compartments, the fibre concentration in the pulp compartments becomes high. A part of the pulp suspension does not end up directly in the pulp compartments, but are gathered in a lower compartment of the formation zone, before the pulp suspension finally is put into the pulp compartments when they passes the lower compartment where the pulp is aggregated. The aggregation of pulp in the lower compartment of the formation zone results in that a part of the pulp becomes inoperative and does not circulate in certain inactive areas in the formation zone. Thus, uneven distribution and concentration of fibres in the pulp, that is introduced in the pulp compartments on the drum, arises .
The present invention aim to achieve an effective and improved washing apparatus where favourable circulation and even fibre concentration of the pulp suspension in the formation zone at the inlet part of the drum washer can be provided for, and where at least partly the drawbacks associated with what is previously known, according to the state of the art, can be eliminated.
These objects are achieved with a washing apparatus for washing of cellulose pulp according to the present invention. The washing apparatus comprises a rotatable drum, provided with a number of outer compartments for the paper pulp to be washed, which compartments are defined by axial compartment walls and distributed along the circumference of the drum; a stationary casing that surrounds the drum, whereby an annular space is defined between the casing and the drum; a number of seals that are arranged to seal between the casing and the compartment walls of the compartments, such that the annular space is divided in a formation zone at the ascending side of the drum for formation of the pulp in the compartments of the drum during rotation of the drum, at least one washing zone for washing of the formed pulp at overpressure, and a discharge zone for discharge of the washed pulp from the annular space; and at least one inlet pipe for feeding of a suspension of the pulp to be washed into the formation zone. The washing apparatus is characterised in that the formation zone is dimensioned such that the pulp suspension that occurs in the formation zone is brought by the drum when this rotates and forms a rotating flow in the formation zone, and that the inlet pipe is arranged to feed the pulp suspension in the formation zone in direction essentially tangentially towards the periphery of the drum such that said rotating flow of pulp suspension is maintained in the formation zone during operation.
Thanks to that the feeding of the pulp suspension into the formation zone is carried out in direction essentially tangentially towards the periphery of the drum and essentially in accordance with the rotating flow, the advantage is obtained that the risk that the pulp would become stationary anywhere in the formation zone is essentially reduced or eliminated, since the rotating flow of the pulp suspension is maintained in the formation zone during operation. Besides, an uneven fibre concentration of the pulp suspension in the pulp compartments can be avoided.
A first part of the inlet pipe at the connection to the formation zone can be arranged to extend in a direction substantially radially towards the drum and, in a second part in its extension into the formation zone, curved. The curving of the second part of the inlet pipe is extending in the circumference direction of the drum. The curving is preferably within the range of 60-120 degrees towards the radial direction of the drum.
As mentioned above, according to the present invention, a rotational flow of pulp suspension in the formation zone is formed when the drum is rotating and this rotating flow is maintained during operation. Said rotational flow may typically be larger than the flow of incoming pulp suspension in the formation zone and the rotational direction of the rotational flow is controlled by the rotation of the drum. The rotational flow of pulp suspension in the formation zone should not be interrupted and the feeding of the pulp suspension should thus be done in a direction that follows the rotational direction of the rotational flow. According to an embodiment of the present invention, this means that feeding takes place in direction opposite the rotational direction of the drum in washing apparatuses that has feeding of the pulp suspension in the later part of the formation zone, that forms a part of the formation zone where adjacent pulp compartments, opposite the inlet pipe, on the drum is about to leave the formation zone during rotation of the drum. The inlet pipe for feeding of the pulp suspension opposite the rotational direction of the drum is then suitably arranged to feed the pulp suspension into the formation zone in a position that is relatively closer to the casing than the drum. According to an alternative embodiment, for washing apparatuses that has feeding in the earlier part of the formation zone, feeding in is instead carried out in the rotational direction of the drum. By earlier part of the formation zone is meant a portion of the formation zone where adjacent pulp compartments, opposite the inlet pipe, just previously has entered into the formation zone during rotation of the drum. The inlet pipe for feeding in of the pulp suspension in the rotational direction of the drum is in this case suitably arranged to feed the pulp suspension into the formation zone in a position that is relatively closer to the drum than the casing.
According to yet another preferred embodiment, the washing apparatus can comprise at least two inlet pipes, distributed along the axial direction of the drum. In that respect the inlet pipes might be connected to an inlet chamber for distribution of the pressure and flow of the pulp suspension before the pulp is fed in through the inlet pipes into the formation zone. Further, at least a deflection plate can be provided substantially centrally in the inlet chamber for deflection of a flow of pulp that is fed into the inlet chamber.
The present invention will now be described more in detail in embodiments, with reference to the attached drawings, without limiting the interpretation of the invention thereto, in which
Fig. IA schematically shows, in a cross-sectional view, a formation zone and an inlet pipe for pulp suspension, forming a part of a washing apparatus according to an embodiment of the present invention,
Fig. IB schematically shows, in a cross-sectional view, a formation zone and an inlet pipe for pulp suspension, forming a part of a washing apparatus according to an alternative embodiment of the present invention, Fig. 2 schematically shows, in a perspective view obliquely from above, a drum according to an embodiment of the present invention, intended for the washing apparatus according to Figs. IA or IB,
Fig. 3 shows schematically in an explanatory sketch, a cross-section of a washing apparatus with a formation zone similar that in fig. IA according to an embodiment of the present invention where the drum in fig. 2 is arranged in the washing apparatus, and
Fig. 4 schematically shows, in perspective, an explanatory sketch of an inlet chamber and a plurality of inlet pipes of the washing apparatus according to fig. IA.
The same reference numerals have been used for corresponding features in the different embodiments shown in Figs. 1-3.
Figs. IA-B and Fig. 2 shows separate main components of a washing apparatus for washing of cellulose pulp, according to the pressurized displacement washer kind. The washing apparatus comprises a rotatable drum 2, provided with a number of outer compartments 4, having a bottom 6 of perforated metal sheet, in which compartments the paper pulp to be washed is placed during feeding on the drum. Each compartment 4 has a bottom 6 and two compartment walls 8. The compartment walls are arranged axially with respect to the axle 10 of the drum and distributed along the circumference 12 of the drum. The washing apparatus may comprise a stationary support (not shown) having two opposite transverse beams (not shown) . The drum 2 extends between the transverse beams and is rotatably journalled on the both transverse beams 16 of the support. A stationary cylindrical casing 18, having two opposite gables, encloses the drum 2, whereby an annular space 20 (see Fig. 3) is defined between the casing 18 and the drum 2.
Washing liquid is supplied to the annular space 20 and, at pressure, the filtrate is caused to pass the perforated metal sheet that forms the bottom 6 in the pulp compartments 4 on the drum 2. The increase in pressure difference results in an improved dewatering of the pulp. The pulp locates itself in the compartments 4 on the drum in long and narrow rectangles towards the metal sheet in the axial direction of the drum. The subdivision in compartments of the drum ensures that the pulp cake does not break up and moves, but instead maintains the formation produced at application on the pulp. The perforated metal sheet, on which the pulp deposits, is located on a distance from the main surface of the drum such that filtrate channels 21 are formed in the space between the drum 2 and the perforated metal sheet. Thus, along the circumference 12 of the drum, there are at least as many filtrate compartments as pulp compartments 4. In a drum washer, several washing stages can be carried out, with separate addition of washing liquid to the various stages and also return of filtrate from one stage as washing liquid to another stage.
In order to maintain maximum washing efficiency, it is desirable to assure that washing liquid intended for a specific washing stage not is transferred to a subsequent washing stage. A pressure difference between the stages results in that added washing liquid aims for moving towards the lower pressure. For the purpose of being able to separate different washing stages Tl, T2, and also formation stage F and discharge stage U, the respective stages are sealed with axial seals 22. The axial seals are positioned between the rotating drum 2 and the surrounding casing 18. The filtrates from the respective stages are lead out through one or both gables of the drum. As evident from Fig. 3, the washing apparatus comprises several seals 22 arranged on the casing 18 and that seals between the casing and the compartment walls 8 of the compartments, such that the annular space 20 is divided in a formation zone F for forming of the pulp in the compartments 4 of the drum, during rotation of the drum in clockwise direction R, a first washing zone Tl and a second washing zone T2 for washing of the formed pulp at overpressure, and a discharge zone U for discharge of the washed pulp via a discharge opening 26 from the annular space. Pulp to be washed is fed in the formation zone via the inlet opening 30.
According to the present invention the washing apparatus comprises at least an inlet pipe 30 for feeding of a suspension of the pulp to be washed into the formation zone. Feeding of the pulp suspension is carried out essentially tangentially towards the periphery P of the drum. According to an embodiment as evident from fig. IA, a first part 32 of the inlet pipe 30 at the connection to the formation zone can be arranged to extend in a direction substantially radially towards the drum and in a second part 34 in its extension into the formation zone it can be curved. The curving of the second part 34 of the inlet pipe 30 is extending in the circumference direction of the drum. The curving can be within the range of 60-120 degrees towards the radial direction of the drum. The washing apparatus can also comprise two or more inlet pipes 30, as evident from fig. 4. The inlet pipes are distributed axially with respect to the axle of the drum. The inlet pipes 30 are preferably connected to an inlet chamber 36 for distribution of the pressure and flow of the pulp suspension before the pulp is fed in through the inlet pipes 30 into the formation zone F. Preferably the pressure in all inlet pipes is about the same. At least a deflection plate 38 can be provided straight in front of a discharge opening 39 for a connection pipe 40, which is arranged for feeding the pulp suspension into the inlet chamber. Preferably the discharge opening 39 of the connection pipe 40 is arranged substantially centrally to a long side of the inlet chamber and the deflection plate is then preferably substantially centrally arranged within the inlet chamber 36 straight in front of the discharge opening 39 of the connection pipe. Owing to the deflection plate 38, a flow of pulp that is fed into the inlet chamber, via the connection pipe 40, can be laterally redirected by the deflection plate 38 in the inlet chamber such that a flow of pulp suspension, fed through to the inlet chamber and directed straight towards the inlet pipes 30 in the inlet chamber, at the opposite side opposite the discharge opening 39 of the connection pipe, is prevented.
As evident from fig. 3, in particular, but also in fig. IA and fig. IB, the formation zone F is formed of a part of the annular space 20 and has a certain extension in the circumference direction. In radial direction, this part/zone extends further out from the drum 2 and its compartments walls 8, than surrounding parts of the annular space 20. The formation zone may in that connection be regarded as an area generally defined by the drum 2 and an extension in radial direction of the casing 18, see fig. 3. The radial extension of the casing 18 results in that the volume of the formation zone F becomes sufficiently large in order for the pulp suspension, that is located in the formation zone F, to be able to form a rotating flow within the formation zone F. The rotating flow in the formation zone is indicated by arrows in figure IA and IB.
Consequently, the formation zone F is dimensioned such that the pulp suspension that occurs in the formation zone is brought by the drum 2 when this rotates and forms said rotating flow in the formation zone. In this connection, the rotating direction of the rotational flow is controlled by the rotation of the drum 2. To be precise, this means that the pulp suspension in the vicinity of the of the drum 2 essentially follows the motion of the adjacent part of the drum 2 while the pulp suspension radially further away from the drum is moving substantially in direction opposite the direction of motion of the periphery of the drum in the formation zone F. In other words, the rotating direction of the rotational flow in the formation zone will be inverted relatively the rotating direction of the drum. In the views that are shown in figs. IA and IB, for example, the rotating direction of the drum is clockwise and the rotational flow in the formation zone then circulates counter-clockwise .
As mentioned above, the rotational flow of the pulp suspension in the formation zone should not be interrupted and the feeding of the pulp suspension should thus be carried out such that the rotational flow is followed and maintained during operation. If the inlet pipe 30, according to an embodiment of the present invention as shown in fig. IA, is arranged to feed the pulp suspension in a direction R2 into the formation zone F that is substantially opposite the rotational direction Rl of the drum, this means that the inlet pipe 30 can be arranged in a later, first part 41 of the formation zone F in order not to disturb the rotational flow. By the term "later" part 41 is meant a part of the formation zone F where adjacent compartments, opposite the inlet pipe, on the drum are on their way to leave the formation zone during rotation of the drum. In that respect, the inlet pipe 30 is suitably arranged to feed the pulp suspension into the formation zone F in a position that is relatively closer to the casing 18 than the drum 2, as evident from fig. IA. On the other hand, if the inlet pipe 30, according to an embodiment of the present invention as shown in fig. IB, is arranged to feed the pulp suspension in a direction R2 into the formation zone F that is essentially similar to the rotational direction of the drum Rl, the inlet pipe 30 can preferably be arranged in an earlier, second part 42 of the formation zone F such that the rotational flow in the formation zone is not influenced. By the term
"earlier" part 42 is meant a part of the formation zone F where adjacent compartments, opposite the inlet pipe, on the drum just previously has entered into the formation zone during rotation of the drum. In that respect, the inlet pipe 30 is suitably arranged to feed the pulp suspension into the formation zone F in a position that is relatively closer to the drum 2 than the casing 18.
Thus, a washing apparatus according to the present invention shows a formation zone with a self-circulating pulp suspension (during operation) , and by performing injection of pulp suspension such that the rotational flow is not disturb or counteracted, but instead is maintained or strengthened, improved pulp formation is obtained and a system that is less sensitive for disturbances and variations than previous known feeding mechanisms.

Claims

Claims
1. A washing apparatus for washing of cellulose pulp, comprising: a rotatable drum (2), provided with a number of outer compartments (4) for the paper pulp to be washed, which compartments are defined by axial compartment walls (8) and are distributed along the circumference (18) of the drum, a stationary casing (18) that surrounds the drum, whereby an annular space (20) is defined between the casing and the drum, a number of seals that are arranged to seal between the casing and the compartment walls of the compartments, such that the annular space is divided in a formation zone (F) at the ascending side of the drum for formation of the pulp in the compartments of the drum during rotation (Rl) of the drum, at least one washing zone (Tl, T2) for washing of the formed pulp at overpressure, and a discharge zone (U) for discharge of the washed pulp from the annular space, and at least one inlet pipe (30) for feeding of a suspension of the pulp to be washed into the formation zone, characterised in that the formation zone (F) is dimensioned such that the pulp suspension that occurs in the formation zone is brought by the drum (2) when this rotates and forms a rotating flow in the formation zone, and that the inlet pipe (30) is arranged to feed the pulp suspension into the formation zone (F) in direction essentially tangentially towards the periphery (P) of the drum such that said rotating flow of the pulp suspension is maintained in the formation zone during operation.
2. Washing apparatus according to claim 1, characterised in that the inlet pipe (30) is arranged to feed the pulp suspension in a direction (R2) into the formation zone (F) that is substantially opposite the rotational direction (Rl) of the drum.
3. Washing apparatus according to claim 2, characterised in that the inlet pipe (30) for feeding the pulp suspension opposite the rotational direction of the drum is arranged in a first, later part (41) of the formation zone (F), that forms a part of the formation zone (F) where adjacent compartments, opposite the inlet pipe, on the drum are on their way to leave the formation zone during rotation of the drum.
4. Washing apparatus according to claim 2 or 3, characterised in that the inlet pipe (30) for feeding the pulp suspension opposite the rotational direction of the drum is arranged to feed the pulp suspension into the formation zone (F) in a position that is relatively closer to the casing (18) than the drum (2).
5. Washing apparatus according to claim 1, characterised in that the inlet pipe (30) is arranged to feed the pulp suspension in a direction (R2) into the formation zone (F) that is substantially similar to the rotational direction (Rl) of the drum.
6. Washing apparatus according to claim 1, characterised in that the inlet pipe (30) for feeding the pulp suspension in the rotational direction of the drum is arranged in an second, earlier part (42) of the formation zone (F) , that forms a part of the formation zone (F) where adjacent compartments, opposite the inlet pipe, just previously has entered into the formation zone during rotation of the drum.
7. Washing apparatus according to claim 5 or 6, characterised in that the inlet pipe (30) for feeding the pulp suspension in the rotational direction of the drum is arranged to feed the pulp suspension into the formation zone (F) in a position that is relatively closer to the drum (2) than the casing (18) .
8. Washing apparatus according to any of the preceding claims, characterised in that a first part (32) of the inlet pipe (30) at the connection to the formation zone is arranged to extend in a direction substantially radially towards the drum and in a second part (34) in its extension into the formation zone is curved.
9. Washing apparatus according to claim 8, characterised in that the curving of the second part (34) of the inlet pipe (30) is extending in the circumference direction of the drum and that the curving is within the range of 60- 120 degrees towards the radial direction of the drum.
10. Washing apparatus according to any of the preceding claims, characterised in that it comprises at least two inlet pipes (30), distributed with respect to the axial direction of the drum.
11. Washing apparatus according to claim 10, characterised in that the inlet pipes (30) are connected to an inlet chamber (36) for distribution of the pressure and flow of the pulp suspension before the pulp is fed in through the inlet pipes (30) into the formation zone (F) .
12. Washing apparatus according to claim 11, characterised in that at least a deflection plate (38) is provided substantially centrally in the inlet chamber (36) for redirection of a flow of pulp that is fed into the inlet chamber.
PCT/SE2006/001477 2005-12-22 2006-12-21 Washing apparatus for washing cellulose pulp WO2007073310A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE0502865-9 2005-12-22
SE0502865A SE531152C2 (en) 2005-12-22 2005-12-22 Washing machine for washing pulp with rotating flow in the propagation zone

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WO2007073310A1 true WO2007073310A1 (en) 2007-06-28
WO2007073310A9 WO2007073310A9 (en) 2007-08-30

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2900865A4 (en) * 2012-09-25 2016-06-15 Valmet Oy Liquid distributor for a washing apparatus, and washing apparatus

Citations (5)

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Publication number Priority date Publication date Assignee Title
US4266413A (en) * 1979-01-26 1981-05-12 Enso-Gutzeit Osakeyhto Means for washing cellulose pulp
US4292123A (en) * 1978-06-01 1981-09-29 Enso-Gutzeit Osakeytio Procedure and apparatus for cellulose washing
US4995988A (en) * 1988-11-11 1991-02-26 Sunds Defibrator Rauma Oy Method and apparatus for thickening a slurry using a compression plate
EP0315737B1 (en) * 1987-11-11 1991-10-23 A. Ahlstrom Corporation Method and apparatus for treating pulp
SE501774C2 (en) * 1993-09-30 1995-05-15 Kvaerner Pulp Equipment As Perforated drum for thin film dewatering of recycled paper pulp - contains device for creating different pressures inside the drum

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4292123A (en) * 1978-06-01 1981-09-29 Enso-Gutzeit Osakeytio Procedure and apparatus for cellulose washing
US4266413A (en) * 1979-01-26 1981-05-12 Enso-Gutzeit Osakeyhto Means for washing cellulose pulp
EP0315737B1 (en) * 1987-11-11 1991-10-23 A. Ahlstrom Corporation Method and apparatus for treating pulp
US4995988A (en) * 1988-11-11 1991-02-26 Sunds Defibrator Rauma Oy Method and apparatus for thickening a slurry using a compression plate
SE501774C2 (en) * 1993-09-30 1995-05-15 Kvaerner Pulp Equipment As Perforated drum for thin film dewatering of recycled paper pulp - contains device for creating different pressures inside the drum

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2900865A4 (en) * 2012-09-25 2016-06-15 Valmet Oy Liquid distributor for a washing apparatus, and washing apparatus

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SE0502865L (en) 2007-06-23
WO2007073310A9 (en) 2007-08-30
SE531152C2 (en) 2009-01-07

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