CA2736723A1 - Press washer for washing cellulose pulp - Google Patents
Press washer for washing cellulose pulp Download PDFInfo
- Publication number
- CA2736723A1 CA2736723A1 CA2736723A CA2736723A CA2736723A1 CA 2736723 A1 CA2736723 A1 CA 2736723A1 CA 2736723 A CA2736723 A CA 2736723A CA 2736723 A CA2736723 A CA 2736723A CA 2736723 A1 CA2736723 A1 CA 2736723A1
- Authority
- CA
- Canada
- Prior art keywords
- pulp
- vat
- passage
- washing
- arrangement
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- 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
Landscapes
- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Wood Science & Technology (AREA)
- Paper (AREA)
Abstract
The invention relates to a press washer (100) for cellulose pulp comprising two co-operating perforated press rolls (110, 110'). An inner vat (120) is provided at a distance from the perforated rolls, an inner pulp passage (122, 122') being formed for each press roll between the roll surface and the inner vat. An outer vat (140) is provided at a distance from the inner vat so as to form an outer pulp passage (142, 142') for each press roll. A pulp inlet is arranged beneath the pinch (114), whereby, in operation, pulp introduced via the inlet is transported through the outer pulp passage (zone for pulp distribution) opposite the direction of rotation (R, R') and thereafter through the inner pulp passage in the direction of rotation before reaching the pinch. This press washer offers a simple and cost-efficient construction as well as excellent pulp formation.
Description
Press washer for washing cellulose pulp TECHNICAL FIELD
The present invention relates to washing of cellulose pulp and in particular to press washing with two co-operating cylindrical press rolls.
BACKGROUND
Pulp washing is a key operation in the chemical pulping line. There are many different types of washers available, some of which are based on press washing and comprise means for pressing the pulp such that fluid is removed. After pressing, the pulp is normally diluted to a desired thickness.
A well-known type of press washer has two co-operating cylindrical press rolls, arranged with their rotation center in the same horizontal plane. The outer surface of each press roll is perforated and, during operation, cellulose pulp is input to a restricted space between the perforated roll surface and a restriction member, such as a trough, whereby a pulp web is formed on the perforated roll surface. The press rolls are arranged to rotate in opposite directions so as to transport the respective pulp webs in the direction of rotation to be pressed in a so-called pinch or nip where the distance between the press rolls is smallest.
The fluid removed from the pulp (i.e. the filtrate) passes through the perforated roll surface in a radially inward direction and can for example be transported to the ends of the respective press roll by means of axial filtrate channels. There is often a supply of washing liquid to the press washer and since the washing liquid displaces fluid in the pulp, the washing principle will in such a case be a combination of dewatering, displacement and pressing.
A press washer of the described general type is disclosed in US Patent 3,980,518, for example. In this kind of washing arrangement, pulp is input separately to each drum and there is one pulp distribution unit (inlet box) for each drum. The pulp is in US
Patent 3,980,518 distributed onto the press rolls through an adjustable narrow gap.
Another example of a pulp distribution unit is disclosed in WO 94/10380, where pulp is deflected in a curved passage in order to supply the press rolls with a uniformly distributed and parallel flow. WO 03/016618 describes an arrangement with several distribution units that are separately controlled.
Known press washers of the described general type have pulp input mechanisms associated with a comparatively complicated design (inlet box features, overall washing arrangement, pipe layout, instruments, etc.) and alternatives/improvements would be desirable.
SUMMARY
A general object of the invention is to provide an improved arrangement for washing cellulose pulp. A specific object is to achieve an improved pulp input mechanism.
Another object is to achieve appropriate pulp distribution and formation.
These objects are achieved in accordance with the attached claims.
Briefly, the present invention proposes a washing arrangement comprising a pulp inlet arranged beneath the pinch, which together with an inner and outer vat structure form a most advantageous pulp input and distribution mechanism. The incoming pulp is transported through a zone for pulp distribution defined by the outer vat and thereafter formed on the roll surface and transported through a zone for dewatering and pressing (and washing) defined by the inner vat. This provides for a comparatively simple and cost-efficient washing arrangement, still associated with excellent pulp distribution and formation.
More specifically, in accordance with the invention is provided an arrangement for washing cellulose pulp comprising two press rolls with perforated outer surfaces, arranged to rotate in opposite directions during operation such that the pulp is pressed into a pinch between the press rolls, an inner vat, arranged at a distance from the perforated outer surfaces so as to partially enclose the press rolls in the circumferential direction, an inner pulp passage being formed for each press roll substantially between the perforated outer surface and the inner vat, and a pulp inlet for introducing pulp to the washing arrangement. The washing arrangement further comprises an outer vat, arranged at a distance from the inner vat so as to at least partially enclose the inner vat and form an outer pulp passage for each press roll, the outer pulp passage being connected to the inner pulp passage. The pulp inlet is connected to a central portion of the outer vat, whereby, in operation, pulp introduced via the pulp inlet is transported through the outer pulp passage substantially opposite the direction of rotation and thereafter through the inner pulp passage substantially in the direction of rotation before reaching the pinch.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention, together with further objects and advantages thereof, may best be understood by reference to the following description and appended drawings, in which:
Fig. 1 is a schematic transverse cross-section of a washing arrangement according to an exemplifying embodiment of the present invention;
Fig. 2 is a schematic transverse cross-section of a washing arrangement according to another exemplifying embodiment of the present invention;
Fig. 3A is a schematic transverse cross-section of a washing arrangement with a pulp input unit according to still another exemplifying embodiment of the present invention; and Fig. 3B is a schematic and partial side view of the pulp input unit of the washing arrangement in Fig. 3A.
DETAILED DESCRIPTION
In the drawings, similar or corresponding elements will be denoted by the same reference numbers.
It should be noted that, although the following description primarily refers to "upright" washing arrangements, i.e. washing arrangements where the pulp at the perforated outer surface of the press roll reaches the pinch from below, the teachings are applicable also on "upside-down"
arrangements, i.e. where the pulp reaches the pinch from above. Upside-down arrangements with pulp inlets at the top and outlets at the bottom hence lie within the scope of the present invention.
Fig. 1 is a schematic transverse cross-section of a washing arrangement according to an exemplifying embodiment of the present invention. The illustrated washing arrangement 100 comprises two co-operating cylindrical press rolls/drums 110, 110', arranged to rotate in opposite directions R, R' during operation and each having a perforated outer surface 112, 112', such as a surface of perforated metal sheet. The rotation centers are normally arranged in the same horizontal plane and it may often be preferred that one rotation center is fixed, whereas the other rotation center is allowed to slide somewhat.
The washing arrangement 100 further presents an inner vat 120, arranged at a distance from the perforated outer surfaces 112, 112' of the press rolls 110, 110' so as to partially enclose the press rolls in the circumferential direction, whereby an inner pulp passage 122, 122' is defined for each press roll between the perforated outer surface 112, 112' and the inner vat 120. Outside the inner vat 120, there is an outer vat 140 arranged to form an outer pulp passage 142, 142' for each press roll. As seen in Fig. 1, the outer vat 140 defines an outer wall of the respective outer pulp passage 142, 142'. There is a pulp inlet 130 at the bottom of the press washer 100 in Fig. 1, centrally arranged in the area beneath the co-operating press rolls 110, 110'.
The pulp inlet 130 is connected to a central portion of the outer vat 140, "central" with respect to the extension of the outer vat in the circumferential direction (as seen in Fig. 1). The outer pulp passage 142, 142' is connected to the pulp inlet 130 at one end and to its corresponding inner pulp passage 122, 122' at the other end.
In general, the inner vat 120 and the outer vat 140, respectively, comprises non-interrupted surfaces substantially enclosing the entire inner pulp passages 122, 122' and outer pulp passages 142, 142', respectively, in the circumferential direction and covering the entire press rolls 110, 110' in a longitudinal (i.e. axial) direction. However, there may also be embodiments with one or more interruptions in the inner and/or outer vat surface, such as interruptions in the inner vat in the vicinity of washing zones.
During operation, the press rolls 110, 110' rotate in opposite directions R, R' and pulp fed from the pulp inlet 130 is transported through the respective outer pulp passages 142, 142' in a direction substantially opposite these rotations. As the pulp enters the inner pulp passages 122, 122', a pulp web (not shown) is formed on the respective perforated outer surfaces 112, 112' of the press rolls 110, 110'. The pulp first comes in contact with the perforated outer surface 112, 112' at the upper portion of the respective press roll 110, 110' and the pulp web is formed 5 "spontaneously" due to a pressure difference between the inner vat 120 and the inside of the press roll 110, 110'. In the inner pulp passage 122, 122', the pulp is, guided by the inner vat 120, transported in the direction of rotation R, R' of the press rolls 110, 110' and eventually pressed in a pinch/nip 114 where the distance between the press rolls 110, 110' is smallest.
The inner pulp passage 122, 122' for each press roll 110, 110' is thus a space where pulp, during operation, is transported in direction of rotation substantially between the perforated outer roll surface 112, 112' and the inner vat 120 and further to the pinch 114. Basically, the inner pulp passage 122, 122' extends from where the pulp, at the end of the outer pulp passage 142, 142', meets a substantially clean press roll surface to the pinch 114.
Preferably, the inner pulp passage 122, 122' extends, in the circumferential direction, so as to, in operation, provide a pulp web on the perforated outer surface 112, 112' of about 220-270 from the beginning of the inner pulp passage to the pinch 114. In other words, the angle defined by the lines intersecting the rotation center and the pinch 114 and the beginning of the inner pulp passage 122, 122', respectively, preferably lies within the interval of 220-270 . The inner pulp passage 122, 122' may be converging, diverging, or parallel to the perforated outer surface 112, 112', or, alternatively, a combination of said features.
The illustrated press rolls 110, 110' comprise a plurality of axial filtrate channels 116, 116', arranged to receive filtrate that passes through the perforated outer surfaces 112, 112'. Filtrate is, during operation, transported through the perforated outer surfaces 112, 112' and radially inwards into the axial filtrate channels 116, 116', and thereafter typically collected and output from the washing arrangement 100, e.g. at one or both ends.
As will be further described below, washing liquid is in the example of Fig. 1 supplied to the pulp web (with devices 156). Furthermore, pulp is in this example output by means of a screw arrangement 118, which transfers the pulp to a subsequent process stage (not shown), such as a standpipe or another unit where the pulp may be diluted and processed.
The present invention relates to washing of cellulose pulp and in particular to press washing with two co-operating cylindrical press rolls.
BACKGROUND
Pulp washing is a key operation in the chemical pulping line. There are many different types of washers available, some of which are based on press washing and comprise means for pressing the pulp such that fluid is removed. After pressing, the pulp is normally diluted to a desired thickness.
A well-known type of press washer has two co-operating cylindrical press rolls, arranged with their rotation center in the same horizontal plane. The outer surface of each press roll is perforated and, during operation, cellulose pulp is input to a restricted space between the perforated roll surface and a restriction member, such as a trough, whereby a pulp web is formed on the perforated roll surface. The press rolls are arranged to rotate in opposite directions so as to transport the respective pulp webs in the direction of rotation to be pressed in a so-called pinch or nip where the distance between the press rolls is smallest.
The fluid removed from the pulp (i.e. the filtrate) passes through the perforated roll surface in a radially inward direction and can for example be transported to the ends of the respective press roll by means of axial filtrate channels. There is often a supply of washing liquid to the press washer and since the washing liquid displaces fluid in the pulp, the washing principle will in such a case be a combination of dewatering, displacement and pressing.
A press washer of the described general type is disclosed in US Patent 3,980,518, for example. In this kind of washing arrangement, pulp is input separately to each drum and there is one pulp distribution unit (inlet box) for each drum. The pulp is in US
Patent 3,980,518 distributed onto the press rolls through an adjustable narrow gap.
Another example of a pulp distribution unit is disclosed in WO 94/10380, where pulp is deflected in a curved passage in order to supply the press rolls with a uniformly distributed and parallel flow. WO 03/016618 describes an arrangement with several distribution units that are separately controlled.
Known press washers of the described general type have pulp input mechanisms associated with a comparatively complicated design (inlet box features, overall washing arrangement, pipe layout, instruments, etc.) and alternatives/improvements would be desirable.
SUMMARY
A general object of the invention is to provide an improved arrangement for washing cellulose pulp. A specific object is to achieve an improved pulp input mechanism.
Another object is to achieve appropriate pulp distribution and formation.
These objects are achieved in accordance with the attached claims.
Briefly, the present invention proposes a washing arrangement comprising a pulp inlet arranged beneath the pinch, which together with an inner and outer vat structure form a most advantageous pulp input and distribution mechanism. The incoming pulp is transported through a zone for pulp distribution defined by the outer vat and thereafter formed on the roll surface and transported through a zone for dewatering and pressing (and washing) defined by the inner vat. This provides for a comparatively simple and cost-efficient washing arrangement, still associated with excellent pulp distribution and formation.
More specifically, in accordance with the invention is provided an arrangement for washing cellulose pulp comprising two press rolls with perforated outer surfaces, arranged to rotate in opposite directions during operation such that the pulp is pressed into a pinch between the press rolls, an inner vat, arranged at a distance from the perforated outer surfaces so as to partially enclose the press rolls in the circumferential direction, an inner pulp passage being formed for each press roll substantially between the perforated outer surface and the inner vat, and a pulp inlet for introducing pulp to the washing arrangement. The washing arrangement further comprises an outer vat, arranged at a distance from the inner vat so as to at least partially enclose the inner vat and form an outer pulp passage for each press roll, the outer pulp passage being connected to the inner pulp passage. The pulp inlet is connected to a central portion of the outer vat, whereby, in operation, pulp introduced via the pulp inlet is transported through the outer pulp passage substantially opposite the direction of rotation and thereafter through the inner pulp passage substantially in the direction of rotation before reaching the pinch.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention, together with further objects and advantages thereof, may best be understood by reference to the following description and appended drawings, in which:
Fig. 1 is a schematic transverse cross-section of a washing arrangement according to an exemplifying embodiment of the present invention;
Fig. 2 is a schematic transverse cross-section of a washing arrangement according to another exemplifying embodiment of the present invention;
Fig. 3A is a schematic transverse cross-section of a washing arrangement with a pulp input unit according to still another exemplifying embodiment of the present invention; and Fig. 3B is a schematic and partial side view of the pulp input unit of the washing arrangement in Fig. 3A.
DETAILED DESCRIPTION
In the drawings, similar or corresponding elements will be denoted by the same reference numbers.
It should be noted that, although the following description primarily refers to "upright" washing arrangements, i.e. washing arrangements where the pulp at the perforated outer surface of the press roll reaches the pinch from below, the teachings are applicable also on "upside-down"
arrangements, i.e. where the pulp reaches the pinch from above. Upside-down arrangements with pulp inlets at the top and outlets at the bottom hence lie within the scope of the present invention.
Fig. 1 is a schematic transverse cross-section of a washing arrangement according to an exemplifying embodiment of the present invention. The illustrated washing arrangement 100 comprises two co-operating cylindrical press rolls/drums 110, 110', arranged to rotate in opposite directions R, R' during operation and each having a perforated outer surface 112, 112', such as a surface of perforated metal sheet. The rotation centers are normally arranged in the same horizontal plane and it may often be preferred that one rotation center is fixed, whereas the other rotation center is allowed to slide somewhat.
The washing arrangement 100 further presents an inner vat 120, arranged at a distance from the perforated outer surfaces 112, 112' of the press rolls 110, 110' so as to partially enclose the press rolls in the circumferential direction, whereby an inner pulp passage 122, 122' is defined for each press roll between the perforated outer surface 112, 112' and the inner vat 120. Outside the inner vat 120, there is an outer vat 140 arranged to form an outer pulp passage 142, 142' for each press roll. As seen in Fig. 1, the outer vat 140 defines an outer wall of the respective outer pulp passage 142, 142'. There is a pulp inlet 130 at the bottom of the press washer 100 in Fig. 1, centrally arranged in the area beneath the co-operating press rolls 110, 110'.
The pulp inlet 130 is connected to a central portion of the outer vat 140, "central" with respect to the extension of the outer vat in the circumferential direction (as seen in Fig. 1). The outer pulp passage 142, 142' is connected to the pulp inlet 130 at one end and to its corresponding inner pulp passage 122, 122' at the other end.
In general, the inner vat 120 and the outer vat 140, respectively, comprises non-interrupted surfaces substantially enclosing the entire inner pulp passages 122, 122' and outer pulp passages 142, 142', respectively, in the circumferential direction and covering the entire press rolls 110, 110' in a longitudinal (i.e. axial) direction. However, there may also be embodiments with one or more interruptions in the inner and/or outer vat surface, such as interruptions in the inner vat in the vicinity of washing zones.
During operation, the press rolls 110, 110' rotate in opposite directions R, R' and pulp fed from the pulp inlet 130 is transported through the respective outer pulp passages 142, 142' in a direction substantially opposite these rotations. As the pulp enters the inner pulp passages 122, 122', a pulp web (not shown) is formed on the respective perforated outer surfaces 112, 112' of the press rolls 110, 110'. The pulp first comes in contact with the perforated outer surface 112, 112' at the upper portion of the respective press roll 110, 110' and the pulp web is formed 5 "spontaneously" due to a pressure difference between the inner vat 120 and the inside of the press roll 110, 110'. In the inner pulp passage 122, 122', the pulp is, guided by the inner vat 120, transported in the direction of rotation R, R' of the press rolls 110, 110' and eventually pressed in a pinch/nip 114 where the distance between the press rolls 110, 110' is smallest.
The inner pulp passage 122, 122' for each press roll 110, 110' is thus a space where pulp, during operation, is transported in direction of rotation substantially between the perforated outer roll surface 112, 112' and the inner vat 120 and further to the pinch 114. Basically, the inner pulp passage 122, 122' extends from where the pulp, at the end of the outer pulp passage 142, 142', meets a substantially clean press roll surface to the pinch 114.
Preferably, the inner pulp passage 122, 122' extends, in the circumferential direction, so as to, in operation, provide a pulp web on the perforated outer surface 112, 112' of about 220-270 from the beginning of the inner pulp passage to the pinch 114. In other words, the angle defined by the lines intersecting the rotation center and the pinch 114 and the beginning of the inner pulp passage 122, 122', respectively, preferably lies within the interval of 220-270 . The inner pulp passage 122, 122' may be converging, diverging, or parallel to the perforated outer surface 112, 112', or, alternatively, a combination of said features.
The illustrated press rolls 110, 110' comprise a plurality of axial filtrate channels 116, 116', arranged to receive filtrate that passes through the perforated outer surfaces 112, 112'. Filtrate is, during operation, transported through the perforated outer surfaces 112, 112' and radially inwards into the axial filtrate channels 116, 116', and thereafter typically collected and output from the washing arrangement 100, e.g. at one or both ends.
As will be further described below, washing liquid is in the example of Fig. 1 supplied to the pulp web (with devices 156). Furthermore, pulp is in this example output by means of a screw arrangement 118, which transfers the pulp to a subsequent process stage (not shown), such as a standpipe or another unit where the pulp may be diluted and processed.
In the proposed arrangement, the outer pulp passage constitutes a zone for distribution of the pulp by means of pump pressure and, as will be described below, possible also stirring at the pulp inlet. The actual washing activities take place as the pulp is transported on the perforated roll surface in the inner pulp passage, which accordingly constitutes a zone for dewatering, displacement and pressing. (In embodiments without addition of washing liquid, the inner pulp passage is just a zone for dewatering and pressing.) Moreover, the beginning of the inner pulp passage may be viewed as a zone for pulp formation in the sense that this is where the pulp web is formed on the press roll.
The illustrated washing arrangements of Fig. 1, 2, and 3A all disclose means for washing liquid addition arranged in connection with the inner vat 120 such that, in operation, washing liquid is added to the pulp in the inner vat 120. Using washing liquid addition devices 156, such as nozzles, or simple apertures/holes, the washing liquid is typically distributed over the pulp web by means of a pressure difference. In the illustrated exemplifying embodiments, the means for washing liquid addition includes a partitioning wall 152 arranged substantially between the inner vat 120 and the outer vat 140 such that a space for washing liquid 154 is defined by the partitioning wall 152 and the inner vat 120. The space for washing liquid 154 may contain lines/pipes for the washing liquid to be added to the inner vat 120 or, alternatively, washing liquid could be flowing freely therein.
The space for washing liquid 154 extends, in the circumferential direction, so as to enclose at least a portion of the respective inner pulp passages 122, 122'. In the embodiment of Fig. 1, the partition wall 152 extends between the two lowermost points of the inner vat 120, thus forming a space for washing liquid 154 enclosing only the last portion of the respective inner pulp passages 122, 122'. Washing liquid is in this embodiment supplied to the pulp web at a single position per press roll 110, 110' in the circumferential direction. (In the longitudinal direction there may be a plurality of washing liquid addition points distributed axially.) In the embodiment of Fig. 2, the space for washing liquid 154 extends, in the circumferential direction, so as to enclose substantially the entire inner pulp passage 122, 122' and comprises two washing liquid addition devices 156 per press roll, distributed circumferentially. The number and position of the washing liquid addition devices 156 may of course vary and there may very well be more than two washing liquid addition devices distributed circumferentially.
In the embodiment of Fig. 3A, the space for washing liquid 154 extends between the two outermost (left and right) points of the inner vat 120, thus forming a space for washing liquid 154 enclosing a substantial portion of the inner pulp passage 122, 122'. As seen in Fig. 3A, the partitioning wall 152 may be integrally formed e.g. with a pulp input unit 132.
According to particular advantageous embodiments illustrated in Figs. 1, 2 and 3A, the partitioning wall 152 serves as an inner wall of at least a portion of the respective outer pulp passages 142, 142', the partitioning wall being a guide surface for the pulp in that portion of the outer pulp passages 142, 142'. Preferably, the partitioning wall 152 is then arranged such that the pulp flow does not encounter sharp edges or throttles, i.e. such that a smooth outer pulp passage 142, 142' is accomplished. The pulp distribution is thereby further improved.
Washing liquid addition is optional in the washing arrangement of the present invention. The described feature of a partitioning wall 152 serving as a guide surface is not restricted to applications with washing liquid addition but may be useful also in pure dewatering presses.
Also in such cases, the partitioning wall 152 is arranged substantially between the inner vat 120 and the outer vat 140 and forms an inner wall of at least a portion of the outer pulp passage 142, 142'. The partitioning wall is a guide surface for the pulp in that portion of the outer pulp passage.
There may, on the other hand, also be embodiments with washing liquid addition but without the partitioning wall 152 (and the space for washing liquid 154), in which cases washing liquid is added directly to the inner vat 120.
A washing arrangement 100 with a pulp input unit 132 according to an exemplifying embodiment of the invention will now be described with reference to Figs. 3A
and 3B. In this embodiment there is a single pulp inlet arranged to feed pulp to both press rolls, typically from a position at about half the roll length. The feed consistency of the pulp is normally in the range of 3-14% . The pulp input unit 132 is arranged at the pulp inlet 130, preferably right beneath the pinch, or slightly displaced. It comprises a length distribution unit 134 extending along substantially the entire length of the press rolls 110, 110', and agitator means 138 rotatably mounted within the length distribution unit 134. The length distribution unit 134, e.g. a pipe parallel to the press rolls, is in the example of Fig. 3B provided with a plurality of apertures 136 distributed lengthwise.
The illustrated washing arrangements of Fig. 1, 2, and 3A all disclose means for washing liquid addition arranged in connection with the inner vat 120 such that, in operation, washing liquid is added to the pulp in the inner vat 120. Using washing liquid addition devices 156, such as nozzles, or simple apertures/holes, the washing liquid is typically distributed over the pulp web by means of a pressure difference. In the illustrated exemplifying embodiments, the means for washing liquid addition includes a partitioning wall 152 arranged substantially between the inner vat 120 and the outer vat 140 such that a space for washing liquid 154 is defined by the partitioning wall 152 and the inner vat 120. The space for washing liquid 154 may contain lines/pipes for the washing liquid to be added to the inner vat 120 or, alternatively, washing liquid could be flowing freely therein.
The space for washing liquid 154 extends, in the circumferential direction, so as to enclose at least a portion of the respective inner pulp passages 122, 122'. In the embodiment of Fig. 1, the partition wall 152 extends between the two lowermost points of the inner vat 120, thus forming a space for washing liquid 154 enclosing only the last portion of the respective inner pulp passages 122, 122'. Washing liquid is in this embodiment supplied to the pulp web at a single position per press roll 110, 110' in the circumferential direction. (In the longitudinal direction there may be a plurality of washing liquid addition points distributed axially.) In the embodiment of Fig. 2, the space for washing liquid 154 extends, in the circumferential direction, so as to enclose substantially the entire inner pulp passage 122, 122' and comprises two washing liquid addition devices 156 per press roll, distributed circumferentially. The number and position of the washing liquid addition devices 156 may of course vary and there may very well be more than two washing liquid addition devices distributed circumferentially.
In the embodiment of Fig. 3A, the space for washing liquid 154 extends between the two outermost (left and right) points of the inner vat 120, thus forming a space for washing liquid 154 enclosing a substantial portion of the inner pulp passage 122, 122'. As seen in Fig. 3A, the partitioning wall 152 may be integrally formed e.g. with a pulp input unit 132.
According to particular advantageous embodiments illustrated in Figs. 1, 2 and 3A, the partitioning wall 152 serves as an inner wall of at least a portion of the respective outer pulp passages 142, 142', the partitioning wall being a guide surface for the pulp in that portion of the outer pulp passages 142, 142'. Preferably, the partitioning wall 152 is then arranged such that the pulp flow does not encounter sharp edges or throttles, i.e. such that a smooth outer pulp passage 142, 142' is accomplished. The pulp distribution is thereby further improved.
Washing liquid addition is optional in the washing arrangement of the present invention. The described feature of a partitioning wall 152 serving as a guide surface is not restricted to applications with washing liquid addition but may be useful also in pure dewatering presses.
Also in such cases, the partitioning wall 152 is arranged substantially between the inner vat 120 and the outer vat 140 and forms an inner wall of at least a portion of the outer pulp passage 142, 142'. The partitioning wall is a guide surface for the pulp in that portion of the outer pulp passage.
There may, on the other hand, also be embodiments with washing liquid addition but without the partitioning wall 152 (and the space for washing liquid 154), in which cases washing liquid is added directly to the inner vat 120.
A washing arrangement 100 with a pulp input unit 132 according to an exemplifying embodiment of the invention will now be described with reference to Figs. 3A
and 3B. In this embodiment there is a single pulp inlet arranged to feed pulp to both press rolls, typically from a position at about half the roll length. The feed consistency of the pulp is normally in the range of 3-14% . The pulp input unit 132 is arranged at the pulp inlet 130, preferably right beneath the pinch, or slightly displaced. It comprises a length distribution unit 134 extending along substantially the entire length of the press rolls 110, 110', and agitator means 138 rotatably mounted within the length distribution unit 134. The length distribution unit 134, e.g. a pipe parallel to the press rolls, is in the example of Fig. 3B provided with a plurality of apertures 136 distributed lengthwise.
The apertures 136 are preferably arranged such that, in operation, the pulp enters the respective outer pulp passage 142, 142' in a direction substantially corresponding to the general pulp flow direction in the outer pulp passage 142, 142'. Accordingly, in Fig. 3A
arrows indicate that the pulp leaves the length distribution unit 134 through the apertures 136 in directions perpendicular to the length axes of the press rolls 110, 110' and the length distribution unit 134. In this way, there will be less disturbances in the pulp flow in the beginning of the outer pulp passage 142, 142' and therefore a more efficient pulp flow and a better pulp distribution can be achieved.
The skilled person realizes that the number and shape of apertures may vary within the scope of the invention. For example, the circular holes 136 in Fig. 3B may be replaced by slots or the like. Alternatively, instead of the plurality of apertures, the length distribution unit may be provided with a gap (i.e. one elongated aperture/opening) extending in the longitudinal direction. In accordance with the preceding paragraph, it would then be preferred to have two gaps, arranged at opposite sides of the length distribution unit 134, whereby, in operation, the pulp enters the outer pulp passage 142, 142' in a direction substantially corresponding to the general pulp flow direction in the outer pulp passage.
The agitator means 138 is axially arranged within the length distribution unit. It can for example comprise a screw, a bladed shaft, a fluted shaft, a slotted shaft, a shaft with pins, or a combination of two or more of these. The agitator means 138 keeps the pulp in motion so as to achieve an appropriate lengthwise pulp distribution in the washing arrangement. An advantage of this solution is that the pressure drop in the pulp input unit will be low as compared to the pressure drop in prior art arrangements. Efficient pulp distribution can therefore be achieved while keeping the pump pressure at the inlet low. The low pressure drop associated with the proposed pulp distribution with agitator means may also make it possible to do without orifices, or the like, which are often used in conventional pulp input arrangements. The proposed pulp input unit offers a comparatively simple and cost-efficient solution.
Another embodiment of the present invention (not shown) comprises an "open"
pulp input unit, in the sense that there is an open space between the agitator means and the outer pulp passage instead of a wall (or similar restriction) with aperture(s). The agitator means would still be axially arranged in the area beneath the pinch.
Although the invention has be described with reference to specific illustrated embodiments, it is emphasized that it also covers equivalents to the disclosed features, as well as changes and variants obvious to a man skilled in the art. Thus, the scope of the invention is only limited by the appended claims.
arrows indicate that the pulp leaves the length distribution unit 134 through the apertures 136 in directions perpendicular to the length axes of the press rolls 110, 110' and the length distribution unit 134. In this way, there will be less disturbances in the pulp flow in the beginning of the outer pulp passage 142, 142' and therefore a more efficient pulp flow and a better pulp distribution can be achieved.
The skilled person realizes that the number and shape of apertures may vary within the scope of the invention. For example, the circular holes 136 in Fig. 3B may be replaced by slots or the like. Alternatively, instead of the plurality of apertures, the length distribution unit may be provided with a gap (i.e. one elongated aperture/opening) extending in the longitudinal direction. In accordance with the preceding paragraph, it would then be preferred to have two gaps, arranged at opposite sides of the length distribution unit 134, whereby, in operation, the pulp enters the outer pulp passage 142, 142' in a direction substantially corresponding to the general pulp flow direction in the outer pulp passage.
The agitator means 138 is axially arranged within the length distribution unit. It can for example comprise a screw, a bladed shaft, a fluted shaft, a slotted shaft, a shaft with pins, or a combination of two or more of these. The agitator means 138 keeps the pulp in motion so as to achieve an appropriate lengthwise pulp distribution in the washing arrangement. An advantage of this solution is that the pressure drop in the pulp input unit will be low as compared to the pressure drop in prior art arrangements. Efficient pulp distribution can therefore be achieved while keeping the pump pressure at the inlet low. The low pressure drop associated with the proposed pulp distribution with agitator means may also make it possible to do without orifices, or the like, which are often used in conventional pulp input arrangements. The proposed pulp input unit offers a comparatively simple and cost-efficient solution.
Another embodiment of the present invention (not shown) comprises an "open"
pulp input unit, in the sense that there is an open space between the agitator means and the outer pulp passage instead of a wall (or similar restriction) with aperture(s). The agitator means would still be axially arranged in the area beneath the pinch.
Although the invention has be described with reference to specific illustrated embodiments, it is emphasized that it also covers equivalents to the disclosed features, as well as changes and variants obvious to a man skilled in the art. Thus, the scope of the invention is only limited by the appended claims.
Claims (10)
1. An arrangement (100) for washing cellulose pulp comprising two press rolls (110, 110') with perforated outer surfaces (112, 112'), arranged to rotate in opposite directions (R, R') during operation such that the pulp is pressed into a pinch (114) between the press rolls;
an inner vat (120), arranged at a distance from the perforated outer surfaces (112, 112') so as to partially enclose the press rolls (110, 110') in the circumferential direction, an inner pulp passage (122, 122') being formed for each press roll substantially between the perforated outer surface and the inner vat; and a pulp inlet (130) for introducing pulp to the washing arrangement;
characterized by an outer vat (140), arranged at a distance from the inner vat (120) so as to at least partially enclose the inner vat and form an outer pulp passage (142, 142') for each press roll (110, 110'), the outer pulp passage being connected to the inner pulp passage;
and in that the pulp inlet (130) is connected to a central portion of the outer vat (140), whereby, in operation, pulp introduced via the pulp inlet is transported through the outer pulp passage substantially opposite the direction of rotation (R, R') and thereafter through the inner pulp passage (122, 122') substantially in the direction of rotation (R, R') before reaching the pinch.
an inner vat (120), arranged at a distance from the perforated outer surfaces (112, 112') so as to partially enclose the press rolls (110, 110') in the circumferential direction, an inner pulp passage (122, 122') being formed for each press roll substantially between the perforated outer surface and the inner vat; and a pulp inlet (130) for introducing pulp to the washing arrangement;
characterized by an outer vat (140), arranged at a distance from the inner vat (120) so as to at least partially enclose the inner vat and form an outer pulp passage (142, 142') for each press roll (110, 110'), the outer pulp passage being connected to the inner pulp passage;
and in that the pulp inlet (130) is connected to a central portion of the outer vat (140), whereby, in operation, pulp introduced via the pulp inlet is transported through the outer pulp passage substantially opposite the direction of rotation (R, R') and thereafter through the inner pulp passage (122, 122') substantially in the direction of rotation (R, R') before reaching the pinch.
2. The washing arrangement of claim 1, characterized in that the inner pulp passage (122, 122') extends, in the circumferential direction, so as to, in operation, provide a pulp web on the perforated outer surface (112, 112') of 220-270° from the beginning of the inner pulp passage to the pinch (114).
3. The washing arrangement of claim 1 or 2, characterized by a pulp input unit (132) arranged at the pulp inlet (130) and comprising a length distribution unit (134) extending along substantially the entire length of the press rolls (110, 110') and provided with at least one aperture (136) for output of pulp to the outer pulp passages (142, 142'); and agitator means (138) rotatably mounted within the length distribution unit.
4. The washing arrangement of claim 3, characterized in that the at least one aperture (136) is arranged such that, in operation, the pulp enters the outer pulp passage (142, 142') in a direction substantially corresponding to the general pulp flow direction in the outer pulp passage.
5. The washing arrangement of claim 3 or 4, characterized in that the agitator means (138) comprises means selected from the group of: a screw; a bladed shaft; a fluted shaft; a slotted shaft; and a shaft with pins.
6. The washing arrangement of any of previous claims, characterized by means for washing liquid addition arranged in connection with the inner vat (120) such that, in operation, washing liquid is added to the pulp in the inner vat.
7. The washing arrangement of claim 6, characterized by a partitioning wall (152) arranged substantially between the inner vat (120) and the outer vat (140), a space for washing liquid (154) being defined by the partitioning wall and the inner vat.
8. The washing arrangement of claim 7, characterized in that the space for washing liquid (154) extends, in the circumferential direction, so as to enclose substantially the entire inner pulp passage (122, 122') and comprises two or more washing liquid addition devices (156) distributed circumferentially.
9. The washing arrangement of claim 7 or 8, characterized in that the partitioning wall (152) is an inner wall of at least a portion of the outer pulp passage (142, 142'), the partitioning wall being a guide surface for the pulp in said at least a portion of the outer pulp passage.
10. The washing arrangement of any of claims 1-5, characterized by a partitioning wall (152) arranged substantially between the inner vat (120) and the outer vat (140), the partitioning wall (152) forming an inner wall of at least a portion of the outer pulp passage (142, 142'), the partitioning wall being a guide surface for the pulp in said at least a portion of the outer pulp passage.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| SE0802072A SE0802072A2 (en) | 2008-10-01 | 2008-10-01 | Washing press for washing cellulose pulp |
| SE0802072-9 | 2008-10-01 | ||
| PCT/SE2009/051072 WO2010039092A1 (en) | 2008-10-01 | 2009-09-28 | Press washer for washing cellulose pulp |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2736723A1 true CA2736723A1 (en) | 2010-04-08 |
Family
ID=42073711
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA2736723A Abandoned CA2736723A1 (en) | 2008-10-01 | 2009-09-28 | Press washer for washing cellulose pulp |
Country Status (5)
| Country | Link |
|---|---|
| EP (1) | EP2344694A4 (en) |
| CN (1) | CN102171393B (en) |
| CA (1) | CA2736723A1 (en) |
| SE (1) | SE0802072A2 (en) |
| WO (1) | WO2010039092A1 (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| SE537341C2 (en) * | 2012-09-25 | 2015-04-07 | Valmet Oy | Liquid distributor for a washing machine and a washing machine |
| CN103410037A (en) * | 2013-07-12 | 2013-11-27 | 海南金海浆纸业有限公司 | High-pressure spraying cleaning device of double-roller squeezing pulp washer |
| SE546043C2 (en) * | 2021-09-24 | 2024-04-23 | Valmet Oy | Apparatus for washing cellulose pulp comprising a liquid distributor |
Family Cites Families (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| SE318182B (en) * | 1968-04-23 | 1969-12-01 | Karlstad Mekaniska Ab | |
| SE349075B (en) * | 1969-10-21 | 1972-09-18 | Karlstad Mekaniska Ab | |
| SE380300C (en) * | 1974-03-04 | 1984-10-18 | Sunds Ab | DEVICE FOR LIQUID TREATMENT OF A FIBER SUSPENSION |
| SE507579C2 (en) * | 1993-09-08 | 1998-06-22 | Sunds Defibrator Ind Ab | Liquid treatment device with sliding part of trough |
| SE504011C2 (en) * | 1994-12-12 | 1996-10-21 | Sunds Defibrator Ind Ab | dewatering |
| CN2255448Y (en) * | 1995-11-30 | 1997-06-04 | 王锡元 | Looped-network replaceable squeezing wash engine |
| AT405420B (en) * | 1997-05-26 | 1999-08-25 | Andritz Patentverwaltung | DEVICE FOR DRAINING AND WASHING FIBER FIBER SUSPENSIONS |
| CN2441845Y (en) * | 2000-09-21 | 2001-08-08 | 潍坊市轻工机械研究所 | Double roller replacable wash engine |
| SE0602268L (en) * | 2006-10-27 | 2008-04-15 | Metso Paper Inc | Washing press comprising separation of filtrate |
-
2008
- 2008-10-01 SE SE0802072A patent/SE0802072A2/en not_active IP Right Cessation
-
2009
- 2009-09-28 CN CN200980139748.7A patent/CN102171393B/en not_active Expired - Fee Related
- 2009-09-28 CA CA2736723A patent/CA2736723A1/en not_active Abandoned
- 2009-09-28 WO PCT/SE2009/051072 patent/WO2010039092A1/en active Application Filing
- 2009-09-28 EP EP09818061.5A patent/EP2344694A4/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| SE532973C2 (en) | 2010-06-01 |
| SE0802072A1 (en) | 2010-04-02 |
| WO2010039092A1 (en) | 2010-04-08 |
| EP2344694A1 (en) | 2011-07-20 |
| CN102171393A (en) | 2011-08-31 |
| SE0802072A2 (en) | 2010-07-20 |
| CN102171393B (en) | 2013-03-27 |
| EP2344694A4 (en) | 2013-07-24 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| WO2007004968A1 (en) | A roll body for a press roll | |
| DE2832840A1 (en) | DRYERS FOR PAPER TRAILS | |
| RU2471030C2 (en) | Device for washing and dehydration of pulp stock | |
| CA2736723A1 (en) | Press washer for washing cellulose pulp | |
| US1347724A (en) | Apparatus for extracting water from wood-pulp and the like | |
| JP5255696B2 (en) | Dispensing device for feeding cellulose pulp | |
| CN101529016B (en) | Press washer comprising separation of filtrates | |
| EP2620544B1 (en) | Pulp suspension washer press, and method for washing and dewatering a liquid pulp suspension | |
| EP2764156B1 (en) | Pulp distribution device | |
| CA2872229C (en) | Liquid distributor for a washing apparatus, and washing apparatus | |
| CN118019890A (en) | Apparatus for washing cellulose pulp | |
| US6395132B1 (en) | Washing system and washer for a fiber suspension | |
| SE2151176A1 (en) | Liquid distributor | |
| DE102009016425A1 (en) | Drying cylinder for e.g. paper machine, has limiting constructions for limiting condensate flow from inner surface of hollow cylinder into discharging areas, and collecting unit arranged in discharging areas | |
| CA2737310A1 (en) | Apparatus and method for dewatering cellulose pulp with improved dewatering efficiency | |
| WO2002059418A1 (en) | Device for dewatering and washing of a fibrous suspension | |
| DE19726209A1 (en) | Steam-heated hollow roller used for e.g. drying in the paper-making industry |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Discontinued |
Effective date: 20150929 |