LUNDBERG, Jörgen (Idrottsgatan 21, Sundsvall, 856 43, SE)
| CLAIMS
1. A roll body for a press roll (1 , 2) for washing pulp, comprising a central drum (4, 2.4) and mantle section to which at least one perforated roll plate (5, 2.5) is intended to be attached, the roll body (3, 2.3) comprising several pairs of chambers (9, 2.9, 10, 2.10; 19, 2.19, 20, 2.20) arranged along the longitudinal axis of the central drum (4, 2.4) between the central drum (4, 2.4) and the roll plate (5, 2.5), the chambers (9, 2.9, 10, 2.10; 19, 2.19, 20, 2.20) of a pair being separated from each other, and the first chamber (9, 2.9, 19, 2.19) of said pair comprises at least one inlet for liquid, which defines a flow path (11) in a substantially radial direction, whereas the second chamber (10, 2.10; 20, 2.20) of said pair comprises at least one inflow opening for the inflow of liquid, which defines a flow path (12) in a substantially tangential direction, characterized in that, at the first end of the roll body (3, 2.3), the first chamber (9, 2.9, 19, 2.19) is provided with an outlet (16, 2.16) for the discharge of liquid, whereas the second chamber (10, 2.10; 20, 2.20) is closed there, whereby discharge of liquid therefrom is prevented, and in that, at the second end of the roll body (3, 2.3), the second chamber (10, 2.10; 20, 2.20) is provided with an outlet (17, 2.17) for the discharge of liquid, whereas the first chamber (9, 2.9, 19, 2.19) is closed there, whereby discharge of liquid therefrom is prevented.
2. A roll body according to claim 1 , characterized in that one of the longitudinal walls of the first chamber (9, 2.9, 19, 2.19) comprises the roll plate (5, 2.5) itself.
3. A roll body according to claim 2, characterized in that it is only the first chamber (9, 2.9, 19, 2.19) of the chambers (9, 2.9, 10, 2.10; 19, 2.19, 20, 2.20) of said pair, which has a longitudinal wall comprising the roll plate (5, 2.5) itself, and thus is in direct communication with this.
4. A roll body according to any of the claims 1 to 3, characterized in that the inflow opening of the second chamber (10, 2.10; 20, 2.20) is arranged at a distance from the roll plate (5, 2.5).
5. A roll body according to any of the claims 1 to 4, characterized in that the inflow opening of second chamber (10, 2.10; 20, 2.20) is arranged at a distance from the envelope surface of the central drum (4, 2.4).
6. A roll body according to any of the claims 1 to 5, characterized in that the second chamber (10, 2.10; 20, 2.20) of a pair is in direct communication, via its inflow opening, with the first chamber (9, 2.9, 19, 2.19) of an adjacent pair of chambers (9, 2.9, 10, 2.10; 19, 2.19, 20, 2.20), for the inflow of liquid from said first chamber (9, 2.9, 19, 2.19).
7. A roll body according to any of the claims 1 to 6, characterized in that the roll body (3, 2.3) comprises several along the longitudinal axis of the central drum (4, 2, .4) longitudinally extending supporting ribs (6, 7, 2.6, 2.7) which extend in a substantially radial direction and are distributed over the circumference of the central drum (4, 2.4), to which said mantle section is attached, in that a partition (8, 2.8), extending longitudinally along the longitudinal axis of the central drum (4, 2, .4), is arranged in the space between two supporting ribs (6, 7, 2.6, 2.7), whereby said pair of chambers (9, 2.9, 10, 2.10; 19, 2.19, 20, 2.20) is provided between the two supporting ribs (6, 7, 2.6, 2.7) with the partition (8, 2.8) as a common wall, and in that one of the supporting ribs (6, 7, 2.6, 2.7) is provided with the inflow opening of the second chamber (10, 2.10; 20, 2.20).
8. A roll body according to claim 7, characterized in that said partition (8, 2.8) is arranged in all the spaces between two supporting ribs (6, 7, 2.6, 2.7).
9. A roll press for washing pulp, comprising two press rolls (1 , 2) between which the pulp is passed in a vertical direction from below upwards, and in the press nip (13, 32) of which the pulp is pressed, the roll body (3, 2.3) of each press roll (1 , 2) comprising a central drum (4, 2.4) and a mantle section to which at least one perforated roll plate (5, 2.5) is attached, characterized in that the roll body (3, 2.3) of at least one of the press rolls (1 , 2) comprises the features mentioned in any of the claims 1 to 8.
10. A roll press according to claim 9, characterized in that the chambers (9, 2.9, 10, 2.10; 19, 2.19, 20, 2.20) of a pair are arranged in relation to each other in such a way that the inflow opening of the second chamber (10, 2.10; 20, 2.20) of the pair is passing the press nip (13, 32) before the first chamber (9, 2.9, 19, 2.19) of said pair.
11. A roll press according to claim 9 or 10, characterized in that the inflow opening of the second chamber (10, 2.10; 20, 2.20) is arranged at such a position in relation to envelope surface of the central drum (4, 2.4) and the roll plate (5, 2.5) that a first and a second dewatering zone (Zonei, Zone2) are provided in the roll press, in which first dewatering zone (Zonei) liquid from the pulp is let in to the first chamber (9, 2.9, 19, 2.19) via the perforated roll plate (5, 2.5) and is thereafter conveyed through the first chamber (9, 2.9, 19, 2.19), and in which second dewatering zone (Zone2) liquid from the pulp is flowing in to the second chamber (10, 2.10; 20, 2.20) via the perforated roll plate (5, 2.5), the first chamber (9, 2.9, 19, 2.19) and the inflow opening, and is thereafter conveyed through the second chamber (10, 2.10; 20, 2.20).
12. A roll press according to claim 11 , characterized in that the inlets (21 , 22) of the roll press for new washing liquid open into the first dewatering zone
{Zonei). |
A ROLL BODY FORA PRESS ROLL
Technical Field
The present invention relates to a roll body for a press roll for washing pulp, comprising a central drum and mantle section to which at least one perfo- rated roll plate is intended to be attached, the roll body comprising several pairs of chambers arranged along the longitudinal axis of the central drum between the central drum and the roll plate, the chambers of a pair being separated from each other, and the first chamber of said pair comprises at least one inlet for liquid, which defines a flow path in a substantially radial direction, whereas the second chamber of said pair comprises at least one inflow opening for the inflow of liquid, which defines a flow path in a substantially tangential direction. Further, the present invention relates to a roll press for washing pulp, comprising two press rolls between which the pulp is passed in a vertical direction from below upwards, where at least one press roll comprises such a roll body.
Background of the Invention
When producing cellulose-based products, a roll press is frequently present for dewatering the cellulose-based pulp. The pulp is passed between two cooperating press rolls in a roll press, the press rolls having a perforated envelope surface, whereby the envelope surface is permeable to liquid pressed out of the pulp, and is pressed in the roll nip, or the press nip, between the press rolls, whereby liquid is pressed out of the pulp. One example of such a roll press for de- watering pulp is disclosed in SE 505 539, e.g., where the central axes of the press rolls are lying in substantially the same horizontal plane, and the pulp is passing the press nip between the press rolls in a vertical direction, from below upwards. SE 519 753 describes a sealing of a press roll in a roll press having two co-operating press rolls for dewatering material suspensions.
The above mentioned roll presses have in common that their roll bodies have a conventional structure, where the roll body comprises a longitudinal central drum, which can comprise a drum or an inner drum covered with a covering plate, or the like. The central drum is provided with several supporting ribs arranged longitudinally along the longitudinal axis of the central drum and evenly distributed along the circumference of the central drum. The purpose of these supporting ribs is to strengthen the structure, and also to provide channels which axially guide liq-
uid pressed out of the pulp to the ends of the press roll. On these supporting ribs, a mantle sections is attached, comprising several circumferential frame rings which are surrounding the roll body along its whole length, the purpose of which is to be a supporting structure for the perforated roll plates which are positioned ut- most on the press roll, since the roll plates are abutting the frame rings around their whole circumference, and to allow expressed liquid, which has passed through the roll plate, to fall downwards after the passage through the apertures of the roll plate. This is important in order to reduce the rewetting, i.e. the liquid which after the press nip flows back through the roll plate and dilutes the pressed pulp, especially for roll presses where the pulp is passed through the press nip between two press rolls in a vertical direction from below upwards, such as in SE 505 539. The result of this rewetting is that the resulting dryness of the pressed pulp from the roll press is lower, and that the pulp is contaminated by lye or liquid previously pressed out. US 6 311 849, upon which the preamble of claim 1 is based, discloses an apparatus for dewatering and washing pulp, comprising two press rolls, between which the pulp is passed in a vertical direction from below upwards, the rotation axes of the press rolls lying on a horizontal plane. The press rolls comprise several pairs of chambers arranged longitudinally along the longitudinal axis of the central drum and between the central drum and the roll plate, the chambers of a pair being separated from each other, and the first chamber of said pair comprises inlets for liquid, which defines a flow path in a substantially radial direction, whereas the second chamber of said pair comprises at least one inflow opening for the inflow of liquid, which define a flow path in a substantially tangential direction. The second chamber of a pair is in direct communication, via its inflow opening, with the first chamber of an adjacent pair of chambers for the inflow of liquid from said first chamber. From these chambers, the liquid from the pulp is then axially removed. By this, the rewetting of the pulp is reduced.
The Object of the Invention The object of the present invention is thus to attain a roll body for a press roll which provides a press roll which, in use in a roll press, is more effective in washing the pulp and provides the required purity of the washed pulp. Further, the
object is to attain a roll press for washing pulp comprising press rolls provided with such a roll body.
Summary of the Invention
The above mentioned objects are achieved by providing a roll body of the kind defined in the introductory part, where the roll body comprises the special features which are mentioned in the characterizing portion of claim 1. Above-mentioned objects are also attained by providing a roll press of the kind defined in the preamble of claim 9, where the roll body of at least one of the press rolls comprises the special features mentioned in claim 1. The inflow opening of the second chamber of the pair for the inflow of liquid, which defines a flow path in a substantially tangential direction, can, for example, be attained by providing the second chamber with a longitudinal wall extending in a substantially radial direction and provided with said at least one inflow opening.
By means of said ends of the roll body according to the present invention, a press roll is provided which, in use in a roll press, is more effective in washing the pulp and provides the required purity of the washed pulp. By means of the roll body, a system for fractionating filtrate in a press roll is attained. The filtrate can be separated in two different sections, each of which working in a certain zone in the roll press. In a first zone in the region of the press roll, a first amount of filtrate can be taken up by the first chamber via the roll plate and then discharged at the first end of the roll body, and in a second zone in the region of the press roll, a second amount of filtrate be taken up by the second chamber via the roll plate and then discharged at the second end of the roll body, whereby these two amounts of filtrate are kept completely separated. These amounts of filtrate can then be used for different purposes and at different positions in the process. For example, it is possible to use the amounts of filtrate from the different zones to obtain a counter current washing stage in a roll press having two press rolls, especially for roll presses where the pulp is passing the press nip between the press rolls in a vertical direction from below upwards. According to an advantageous embodiment of the roll body according to the present invention, one of the longitudinal walls of the first chamber comprises the roll plate itself, and advantageously, it is only the first chamber of the cham-
bers of said pair, which has a longitudinal wall comprising the roll plate itself, and thus is in direct communication with this.
According to a further advantageous embodiment of the roll body according to the present invention, the second chamber of a pair is in direct communica- tion, via its inflow opening, with the first chamber of an adjacent pair of chambers, for the inflow of liquid from said first chamber. Through this, the washing and de- watering of the pulp is made even more effective.
According to another advantageous embodiment of the roll body according to the present invention, it comprises several along the longitudinal axis of the central drum longitudinally extending supporting ribs which extend in a substantially radial direction and are distributed over the circumference of the central drum, to which said mantle section is attached, where a partition, extending longitudinally along the longitudinal axis of the central drum, is arranged in the space between two supporting ribs, whereby said pair of chambers is provided between the two supporting ribs with the partition as a common wall, and one of the supporting ribs is provided with the inflow opening of the second chamber. Advantageously, such a partition is arranged in all the spaces between two supporting ribs. Through the use of existing supporting ribs, the required amount of material is minimized when manufacturing the chambers. According to an advantageous embodiment of the roll press according to the present invention, the chambers of a pair are arranged in relation to each other in such a way that the inflow opening of the second chamber of the pair is passing the press nip before the first chamber of said pair.
According to a further advantageous embodiment of the roll press accord- ing to the present invention, the inflow opening of the second chamber is arranged at such a position in relation to envelope surface of the central drum and the roll plate that a first and a second dewatering zone are provided in the roll press, in which first dewatering zone liquid from the pulp is let in to the first chamber via the perforated roll plate and is thereafter conveyed through the first chamber, and in which second dewatering zone liquid from the pulp is flowing in to the second chamber via the perforated roll plate, the first chamber, and the inflow opening, and is thereafter conveyed through the second chamber.
According to another advantageous embodiment of the roll press according to the present invention, the inlets of the roll press for new washing liquid open
into/have their outflow in the first dewatering zone. However, other positions of the said inlets are possible.
Brief Description of the Drawings
The present invention will now be described, for exemplary purposes, in more detail by way of embodiments and with reference to the enclosed drawings, in which:
Fig. 1 is a schematic cross-section view of two press rolls, each comprising one embodiment of the roll body according to the present invention provided with perforated roll plates, Fig. 2 is a schematic perspective view of the press rolls of Fig. 1 , where the first end of each roll body is shown, Fig. 3 is a schematic perspective view of the press rolls of Fig. 1 , where the second end of each roll body is shown, and Fig. 4 is a schematic sectional view of an embodiment of the roll press according to the present invention.
Detailed Description of Embodiments
Fig. 1 shows a schematic cross-section view of a first and a second press roll 1 , 2 for washing pulp, each comprising an embodiment of the roll body 3, 2.3 according to the present invention. The roll body 3, 2.3 comprises a central drum 4, 2.4 and mantle section to which at least one perforated roll plate 5, 2.5 is intended to be attached. Further, the roll body 3, 2.3 comprises several along the longitudinal axis of the central drum 4, 2, .4 longitudinally extending supporting ribs 6, 7, 2.6, 2.7 which extend in a substantially radial direction and are distributed over the circumference of the central drum 4, 2.4, to which said mantle section is attached. The mantle section can in a conventional way comprise several frame rings which are arranged along the longitudinal axis of the central drum 4, 2.4 and attached to the supporting ribs 6, 7, 2.6, 2.7 via several flat bars. In each space between two supporting ribs 6, 7, 2.6, 2.7, a partition 8, 2.8, extending longitudinally along the longitudinal axis of the central drum 4, 2, .4, is arranged, whereby in each space between two supporting ribs 6, 7, 2.6, 2.7 a pair of chambers 9, 2.9, 10, 2.10 is provided, which chambers 9, 2.9, 10, 2.10 extend longitudinally along the longitudinal axis of the central drum 4, 2.4 between the central drum 4, 2.4 and the roll plate 5, 2.5. The chambers 9, 10, 2.9, 2.10 of said pair are completely
separated from each other by said partition 8, 2.8. The first chamber 9, 2.9 of said pair comprises an inlet for liquid, which defines a flow path 11 , 2.11 in a substantially radial direction, in the form of the apertures provided in the roll plate 5, 2.5. One of the longitudinal walls of the first chamber 9, 2.9 comprises the roll plate 5, 2.5 itself, and it is only the first chamber 9, 2.9 of the chambers 9, 2.9, 10, 2.10 of said pair, which has a longitudinal wall comprising the roll plate 5, 2.5 itself, and thus is in direct communication with this. The second chamber 10, 2.10 of said pair comprises at least one inflow opening for the inflow of liquid, which defines a flow path 12, 2.12 in a substantially tangential direction. In the roll press of Fig. 4, said flow path 12, 2.12 is extending against the direction of rotation of the press roll 1, 2. The inflow opening of said second chamber 10, 2.10 is provided in one of the supporting ribs 7, 2.7. The inflow opening of said second chamber 10, 2.10 is arranged at a distance from the roll plate 5, 2.5 and from the envelope surface of the central drum 4, 2.4. The second chamber 10, 2.10 of a pair is in direct communi- cation, via its inflow opening, with the first chamber 19, 2.19 of an adjacent pair of chambers 19, 2.19, 20, 2.20, for the inflow of liquid from said first chamber 19, 2.19. Above-mentioned construction results in that the wall of the second chamber 10, 2.10 of a pair, which consists of the supporting rib 7, 2.7 provided with said inflow opening, also forms one of the walls of the first chamber 19, 2.19 of the adja- cent pair. The first chambers 9, 2.9, 19, 2.19 are in communication with the entire inner surface of the roll plate 5, 2.5, whereby all the liquid let in through the roll plate 5, 2.5 first reaches the first chambers 9, 2.9; 19, 2.19. The chambers 9, 2.9, 10, 2.10; 19, 2.19, 20, 2.20 of a pair are arranged in relation to each other in such a way that the inflow opening of the second chamber 10, 2.10; 20, 2.20 of a pair is passing the press nip 13 before the first chamber 9, 2.9, 19, 2.19 of said pair. In the figure, the longitudinal flow of the liquid in each chamber 9, 2.9, 10, 2.10; 19, 2.19, 20, 2.20 is illustrated by means of a cross symbol 14 indicating that the flow in each chamber 10, 2.10; 20, 2.20 flows in a direction into the plane of the drawing, and a point symbol 15 indicating that the flow in each chamber 9, 2.9; 19, 2.19 flows in a direction out of the plane of the drawing.
Fig. 2 shows in a perspective view the press rolls 1 , 2 of Fig. 1 , where the first end of each roll body 3, 2.3 is shown. At this first end of the roll body 3, 2.3, the first chambers are provided with outlets 16, 2.16, indicated by black fields in the figure, for the discharge of liquid, whereas the second chambers are closed
there, whereby discharge of liquid from the second chambers at the first end of the press roll is prevented.
Fig. 3 shows in a perspective view the press rolls 1 , 2 of Fig. 1 where the second end of each roll body 3, 2.3 is shown. At this second end of the roll body 3, 2.3, the second chambers are provided with outlets 17, 2.17, indicated by black fields in the figure, for the discharge of liquid, whereas the first chambers are closed there, whereby discharge of liquid from the first chambers at the second end of the press roll is prevented.
Returning to Fig. 1 , the inflow opening of each second chamber 10, 2.10; 20, 2.20 is arranged at such a position in relation to envelope surface of the central drum 4, 2.4 and the roll plate 5, 2.5 that a first dewatering zone Zonei and a second dewatering zone Zone2 are provided in the roll press in which the press rolls are provided (see Fig. 1 ). In the first dewatering zone Zonei, liquid from the pulp is let in to the first chambers 9, 2.9, 19, 2.19 via the perforated roll plate 5, 2.5 and is thereafter conveyed through the first chambers 9, 2.9, 19, 2.19 to be discharged thereafter via the outlets of said chambers 9, 2.9, 19, 2.19 at the first end of the roll body 3, 2.3. In the second dewatering zone Zone2, liquid from the pulp is flowing in to the second chambers 10, 2.10; 20, 2.20 via the perforated roll plate 5, 2.5, the first chambers 9, 2.9, 19, 2.19 and each inflow opening, and is thereaf- ter conveyed through the second chambers 10, 2.10; 20, 2.20 to be discharged thereafter via the outlets of said chambers 10, 2.10; 20, 2.20 at the second end of the roll body 3, 2.3. The inlets 21 , 22 of the roll press for new washing liquid open into/have their outflow in the first dewatering zone Zonei.
Fig. 4 shows an embodiment of the roll press for washing pulp according to the present invention, comprising a first press roll 1 and a second press roll 2, as shown in Fig. 1-3, and each press roll 1 , 2 thus comprises a roll body 3, 2.3, as shown in Fig. 1-3. The longitudinal central axes of the press rolls 1 ,2 are lying in substantially the same horizontal plane. The pulp is fed in through an inlet 31 and pressed up towards the press nip 32 between the first and second press rolls 1 , 2, the rotation of which is indicated by vertically pointing arrows in the figure, whereby the pulp is passing the press nip 32 vertically upwards, where the pulp is dewatered and is pressed further up in a vertical direction.