Blade for refiner for refining lignocellulosic material, and refiner comprising at least one blade

Abstract

To provide a more energy efficient refiner blade while ensuring the desired fiber quality.SOLUTION: There is provided a blade for a refiner for refining lignocellulosic material. The blade (10) is delimited by an inner periphery (11) and an outer periphery (12) and includes: a blade surface (13) with a refiner portion (14) on which a plurality of refiner bars (20) is arranged, wherein each refiner bar (20) extends from an outer bar end (21) to an inner bar end (22); and at least one dam (30) that extends from an outer dam end (31) to an inner dam end (32) and connects at least three refiner bars (20), wherein the dam (30) is arranged so that a movement along a dam extension from an outer dam end (31) to an inner dam end (32) is also a movement in the first circumferential direction (D).SELECTED DRAWING: Figure 1a

Description

[Technical field]

[0001] The present invention relates to a refiner for refining lignocellulosic material during the production of pulp, and to a blade for such a refiner. [Background technology]

[0002] Disc refiners are commonly used within the pulp industry to refine lignocellulosic materials used in the production of fibrous materials such as paper and paperboard.

[0003] A disc refiner comprises two or more opposing refining elements, at least one of which is rotatable. The rotating refining elements may be referred to as rotors or rotor-side blades, and the non-rotating or stationary refining elements may be referred to as stators or stator-side blades. A refining gap is present between the refining elements, where the material to be refined is ground against the refining surface. The refining surfaces of the refining elements comprise refiner bars that serve to refine the lignocellulosic material during use, and also comprise dams that intersect the refiner bars and lift the lignocellulosic material towards the refining gap to ensure complete refining.

[0004] The refining of lignocellulosic materials is costly as the energy consumption is usually very high to reach the desired fiber quality. Although some improvements have been proposed within this area, further development is needed to provide more energy efficient refiner blades while ensuring the desired fiber quality. Summary of the Invention [Problem to be solved by the invention]

[0005] The object of the present invention is to eliminate or at least minimize the above-mentioned problems. This is achieved by a blade for a refiner and by a refiner comprising such a blade according to the attached independent claims. [Means for solving the problem]

[0006] The blade according to the present invention comprises a blade surface defined by an inner circumference and an outer circumference and having a refiner portion with a plurality of refiner bars disposed thereon, each of the refiner bars extending from an inner bar end to an outer bar end, the plurality of refiner bars being angled such that movement along the bar extension of the refiner bar from the outer bar end to the inner bar end is also a first circumferential movement, and the blade further comprises at least one dam extending from the inner dam end to the outer dam end and connecting at least three refiner bars, the dam being angled such that movement along the dam extension from the outer dam end to the inner dam end is also a first circumferential movement.

[0007] The dam is thereby configured to efficiently lift the lignocellulosic material into the refiner gap while at the same time minimizing flow restriction so as to reduce energy consumption during operation, whereby the dam is able to feed the lignocellulosic material towards the periphery along the blade to ensure that the desired refining quality is achieved, while at the same time reducing wear and energy consumption as the dam impedes the material flow less than known prior art solutions.

[0008] According to an embodiment, at least one dam has a dam height substantially equal to the bar height of at least one of the bars it crosses, ensuring that the dam can lift the lignocellulosic material up to the refining gap to improve refining quality.

[0009] According to another embodiment, the at least one dam has a dam height that is 20-99%, preferably 20-85%, of the bar height of at least one of the refiner bars to which said dam is connected, thereby achieving a subsurface dam that allows for steam flow and also improves material flow across the dam.

[0010] In one embodiment, the blade also includes at least one dam having a dam height substantially equal to the bar height, and a dam height between 20-99%, preferably between 20-85%, of the bar height of at least one of the refiner bars to which it is connected, such that the dams and subsurface dams can be combined as desired to improve the flow of lignocellulosic material and steam while at the same time providing high quality refining.

[0011] Suitably, the blade also comprises a groove extending adjacent to the dam on the side of the dam facing the periphery, which allows pumping transport of the lignocellulosic material, the material after passing the dam being allowed to flow along the groove before entering the bar grooves between the refiner bars for further transport towards the periphery, which improves energy efficiency and reduces wear on the refiner blades.

[0012] The grooves may have an increasing width toward the inner dam end such that the lignocellulosic material is urged into the bar grooves as it passes along the grooves.

[0013] The grooves also preferably have a width at the top at least equal to the width of the dam so that the grooves are wide enough to improve the flow of lignocellulosic material. The width at the top is the radial distance from the outside of the dam to the refiner bar at the point where the refiner bar begins to taper towards the blade surface.

[0014] Suitably, the groove has a depth at least equal to half the dam height of the dam adjacent to the groove, such that the groove is deep enough to improve the flow of lignocellulosic material.

[0015] Suitably, the blade also comprises a reinforcement portion where the outer dam end is connected to the refiner bar, said reinforcement portion being located on the side of the dam facing the inner circumference, thereby reducing wear and increasing the life of the blade.

[0016] Alternatively, the outer dam end of the first dam and the inner dam end of the second dam may each be connected to the same bar, with the inner dam end of the second dam being closer to the inner circumference than the outer dam end of the first dam. This avoids refiner grooves that do not intersect with the dams, and where the lignocellulosic material cannot flow across the blades without being lifted up to the refining gap. The dams may also be angled or curved to improve transport of the lignocellulosic material.

[0017] Preferably, the outer dam end of the first dam and the outer dam end of the radially adjacent dam are each connected to a different refiner bar in the first circumferential direction, whereby the dams have a radial overlap, which increases the strength of the blade and distributes areas that experience high wear across the blade, making the blade more robust overall.

[0018] In some embodiments, the blade is a blade segment having a central angle between 10° and 360°. If the blade is not circular, the blade segment may be combined with multiple, similar or identical blade segments to form a circular blade.

[0019] Also, there may be at least one section that lacks refiner bars, such that the lignocellulosic material may be transported across the blades without being refined except in the refiner section.

[0020] The present invention also relates to a refiner for refining lignocellulosic material comprising at least one blade according to any embodiment of the present invention.

[0021] Numerous additional benefits and advantages of the present invention will become readily apparent to those of ordinary skill in the art in view of the following detailed description.

[0022] The invention will now be described in more detail with reference to the accompanying drawings. [Brief description of the drawings]

[0023] [Figure 1a] FIG. 2 is a plan view from above of a blade according to a first embodiment of the present invention. [Figure 1b] FIG. 4 is a plan view from above of a blade according to a second embodiment of the present invention. [Figure 2a] FIG. 11 is a plan view from above of a blade according to a third embodiment of the present invention. [Figure 2b] FIG. 10 is a plan view from above of a blade according to a fourth embodiment of the present invention. [Figure 3a] FIG. 10 is a plan view from above of a blade according to a fifth embodiment of the present invention. [Figure 3b] 3b discloses an enlarged view of one of the dams of FIG. 3a. [Figure 3c] FIG. 13 is a plan view from above of a blade according to a sixth embodiment of the present invention. [Figure 4] FIG. 13 is a top plan view of an embodiment in which the density of refiner bars is different in each set of refiner bars. [Diagram 5] FIG. 13 is a plan view from above of an embodiment having an outer portion. [Figure 6] FIG. 13 is a plan view from above of an embodiment without grooves. [Figure 7a] FIG. 2 is a schematic side view of a groove. [Figure 7b] FIG. 13 is another schematic view from the side of the groove. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] All figures are schematic, not necessarily to scale, and generally show only those parts necessary to clarify the respective embodiment, while other parts may be omitted or merely suggested. Any reference number appearing in multiple figures refers to the same object or feature throughout the figures, unless otherwise indicated.

[0025] Figure 1a discloses a blade 10 according to a first embodiment of the present invention. The blade 10 shown in the figures according to any embodiment of the present invention may be a portion of a circular blade, only a portion of which is shown, or alternatively may be a blade segment configured to be attached together with multiple similar blade segments to form a circular blade.

[0026] In use, the blade 10 is typically mounted in a disc refiner (not shown) and serves to refine lignocellulosic material by acting as a blade in an opposing blade pair, where at least one of the pair is arranged to rotate. Typically, the blades arranged to rotate in the disc refiner are referred to as rotor blades, and the blades arranged to be stationary are referred to as stator blades. In use, a refiner gap is formed between the blades, and lignocellulosic material passing through the refiner gap is refined by the refiner bars disposed in each of the blades.

[0027] The term lignocellulosic material is used herein to mean a material that contains cellulose, and preferably also contains lignin and hemicellulose. One example of such a material is wood, others include other agricultural or forestry wastes. When refining lignocellulosic material with a disc refiner, the material is generally fed into the disc refiner through a central opening in one of the blades and refined as it moves radially outward between the pair of blades. Lignocellulosic material may also refer to a material that contains primarily cellulose, such as cotton.

[0028] The present invention has been described with reference to various embodiments, and in particular it should be noted that features from one embodiment may be freely introduced into another embodiment unless such a combination is expressly stated to be inappropriate or undesirable. Thus, the embodiments disclosed herein may be combined with each other as desired.

[0029] It should be noted that each of the embodiments shown in the figures is only a portion of a blade 10, and that the blade 10 itself can include additional portions on both the inner periphery 11, the outer periphery 12, and on either side of what is shown in each figure. Thus, the figures should be understood as embodiments having a pattern of refiner bars and dams that can be repeated throughout the blade 10 or that can be provided on only a portion of said blade 10.

[0030] The blade 10 shown in Figure 1a is defined by an inner circumference 11 and an outer circumference 12 and includes a blade surface 13. The blade surface 13 has at least one refiner section 14 including a number of refiner bars 20 extending upwardly from the blade surface 13. The refiner section 14 can extend across the entire blade surface 13, although in most embodiments the blade surface 13 also includes other portions that do not include refiner bars 20. In Figure 1a, the blade 10 is shown lacking refiner bars 20 in a portion near the inner circumference 11, which may also be provided near the outer circumference 12 or on other portions of the blade surface 13.

[0031] The refiner bars 20 each include an outer bar end 21 and an inner bar end 22, the outer bar end 21 being closer to the outer periphery 12 than the inner bar end 22. The refiner bars 20 are arranged such that movement along the bar extension from the outer bar end 21 to the inner bar end 22, i.e., movement along an individual refiner bar 20, is also a movement in a first circumferential direction D. The first circumferential direction D is the direction of rotation of the blade 10 when it is placed in the refiner, and the first rotational direction D is further perpendicular to a radial direction R, which is defined as the direction from a point on the inner periphery 11 to a point on the outer periphery 12 that is closest to the point on the inner periphery 11. A movement along a bar extension being a movement in the first circumferential direction D should be understood herein as a movement having a component directed in the first circumferential direction D. There may also be a radial component perpendicular to the first circumferential direction D.

[0032] The arrangement of the refiner bars 20 means that they are inclined with respect to the radial direction R to form a clockwise bar angle α of less than 90°. In some embodiments, the refiner bars 20 are parallel to one another, while in other embodiments, at least one of them may be non-parallel to the others. Also, in some embodiments, the refiner bars form straight lines, while in some embodiments, they may be curved. Also, in some embodiments, the refiner bars 20 may vary across the blade 10, such that some of them form straight lines, others are curved, some of them are parallel, while others are not. At the inner bar ends 22, the bars 20 are preferably tapered relative to the blade surface 13. The bar angle α may vary from one refiner bar 20 to another, but is advantageously in the range of 5° to 60°.

[0033] The refiner section 14 is also provided with at least one dam 30 connecting at least three refiner bars 20. Each dam 30 extends from an outer dam end 31 to an inner dam end 32, the outer dam end 31 being closer to the outer periphery 12 than the inner dam end 32. The dams 30 are further arranged such that movement along the dam extension from the outer dam end 31 to the inner dam end 32, i.e. along each individual dam 30, is also movement in a first circumferential direction D. This means that the dams 30 are inclined with respect to the radial direction R to form a clockwise dam angle β of less than 90°. The dam angle β may be different for each of the dams 30, but is advantageously in the range of 30° to 85°. In embodiments in which the dams 30 are curved, the dam angle β appropriately decreases when moving from the outer dam end 31 towards the inner dam end 32.

[0034] When the dam 30 is connected to the refiner bar 20, a connection angle γ is formed at the corner facing the first circumferential direction D and facing the inner circumference 11. The connection angle γ is advantageously in the range of 30° to 85°, which ensures efficient refining of the lignocellulosic material as well as low energy consumption.

[0035] Preferably, the bar angle α may vary across the segment, advantageously providing a larger bar angle α towards the center of the blade 10, i.e., towards the inner circumference 11, but a smaller bar angle α when the bar is closer to the outer circumference 12. Also, the dam angle β may vary across the segment, advantageously providing a smaller dam angle β near the inner circumference 11, but a larger dam angle β near the outer circumference 12. Thus, preferably, the bar angle α decreases and the dam angle β increases as one moves across the blade 10 in the radial direction R from the inner circumference 11 to the outer circumference 12.

[0036] In the first embodiment, refiner section 14 includes multiple dams 30 arranged in this manner, although in other embodiments, a single dam 30 may instead be provided. Also, the dams 30 shown in FIG. 1 a are provided such that a group of refiner bars 20 are connected by two or more dams 30, where the dams 30 are arranged along the same refiner bars 20 but at different distances to the inner periphery 11. In other embodiments, the dams 30 may instead be arranged such that only a portion of the refiner bars 20 connected by one dam 30 are connected by another dam 30 closer to the inner periphery 11, or such that each refiner bar 20 is connected to just one dam 30.

[0037] 1a, all refiner bars 20 are connected by at least one dam 30, and a refiner bar 20 at the inner dam end 32 of one dam 30 is also at the outer dam end 31 of another dam 30. In other embodiments, a refiner bar 20 may not be connected to any dam 30, or the placement of dams 30 may be varied as desired on the refining section 14.

[0038] The dams 30 may further define straight or curved lines and may be parallel or non-parallel to one another as desired.

[0039] The fact that the bars 20 and dams 30, with their inner bar ends 22 and inner dam ends 32, are positioned further along the first circumferential direction D than the outer bar ends 21 and outer dam ends 31 means that the dams 30 are able to lift the lignocellulosic material from the bar grooves 40 into the refining gap for improved refining, while at the same time allowing efficient transport of the lignocellulosic material from the inner circumference 11 to the outer circumference 12 across the blades 10. This reduces energy consumption, as the dams 30 present less of an obstacle to the flow of lignocellulosic material than dams 30 positioned at an angle of more than 90° to the radial direction R, i.e., the dams have their outer dam ends inclined further along the first circumferential direction D.

[0040] In the embodiment of FIG. 1a, at least one dam 30 has a dam height substantially equal to the bar height of at least one of the bars 20 that it crosses. This means that the dam 30 lifts the cellulosic material all the way to the refining gap and prevents the flow of lignocellulosic material across the dam 30 that is not refined by the refiner bars 20. A dam height substantially equal to a bar height should be understood as being equal within manufacturing tolerances or at least not differing from each other by more than 10% of their height from the blade surface 13. In the first embodiment, all dams 30 have this dam height, but in other embodiments at least one of them may be lower. A dam height substantially equal to a bar height is also advantageous for increasing the pressure between the blades during refining.

[0041] FIG. 1b discloses a second embodiment different from the first embodiment, in which at least one of the dams 30 is a subsurface dam, i.e. a dam with a dam height lower than the bar height of at least one of the refiner bars 20 connected by the dam 30. In the second embodiment, the dam height is 20-99%, preferably 20-85%, of the bar height of at least one of the refiner bars to which said dam 30 connects. This has the advantage that when using the blade 10 according to the invention, the dam 30 facilitates the flow of steam in a direction opposite to the direction of flow of the lignocellulosic material, since the dam 30 provides less flow obstruction in the bar grooves 40. At the same time, the refining efficiency is still very close to that of the first embodiment described above, since most of the lignocellulosic material is lifted up to the refiner gap, while the high-pressure steam, which normally moves along the bar grooves 40, can move freely and enter the bar grooves 40 on the outer side 34 of the dam 30. In the second embodiment of Figure 1b, all of the dams 30 are subsurface dams, while in other embodiments some of them may have full bar height as shown in Figure 1a. In some embodiments, subsurface dams are particularly advantageous towards the periphery 12 where steam backflow occurs.

[0042] FIG. 2a discloses a third embodiment of the blade 10 that differs from the first and second embodiments by including a groove 50 that extends adjacent to the dam 30 on the outer side 34 of the dam 30, i.e., the side of the dam 30 facing the outer periphery 12. The groove 50 extends along the dam 30 and is long enough to pass through at least three refiner bars 20. In one embodiment, the groove 50 extends along the entire dam 30, i.e., from the inner dam end 32 to the outer dam end 31. The grooves 50 are defined by the outer side 34 of the dam 30 and the refiner bars 20, where they begin to taper toward the blade surface 13 (shown by dashed lines in FIGS. 2a-b).

[0043] The grooves 50 can be viewed as interruptions in the refiner bars 20 that extend from the outer bar ends 21, taper toward the blade surface 13 at the grooves 50, and continue from the dams 30 toward the inner bar ends 22. Alternatively, the grooves 50 can be viewed as providing ends for the refiner bars 20 that taper toward the blade surface 13, thereby forming their inner bar ends 22. While in the third embodiment, all of the dams 30 are provided with grooves 50, in other embodiments, multiple dams 30 may lack grooves 50.

[0044] The grooves 50 have the advantage that they allow pumped transport of lignocellulosic material across the blade 10 during use. This means that as the blade 10 rotates in the first circumferential direction D, the lignocellulosic material travels down one of the bar grooves 40 to the dam 30, then is lifted up to the refiner gap and travels along the groove 50 before entering another bar groove 40. This is indicated by the dashed arrows in Figure 2a. Such transport increases the energy efficiency of the refiner and reduces wear on the blade 10 ensuring a longer life.

[0045] The groove 50 may have a width that increases from the outer dam end 31 toward the inner dam end 32, thereby facilitating the entry of lignocellulosic material into the bar groove 40 as it travels along the groove 50. The groove 50 further has a groove width at its upper end, i.e., the end furthest from the blade surface 13, that is at least equal to the top width of the dam 40. The groove width should further be understood as the width in the radial direction R from the dam 30 to the refiner bar 20 at the outer side 34 of the dam 30. At the upper end of the groove 50, the refiner bar 20 is at its full height, but preferably the refiner bar 20 tapers toward the outer side 34 of the dam 30 to reduce wear.

[0046] Figure 2b discloses a fourth embodiment of the blade 10, similar to the third embodiment in that the blade 10 comprises grooves 50 on the outside 34 of the dams 30, but also similar to the second embodiment by virtue of at least some of the dams 30 being subsurface dams. Pumping transport of the lignocellulosic material is further improved by the subsurface dams 30, which facilitate passage over the dams 30 to allow steam flow and reduce energy consumption and wear on the dams 30. The transport of the lignocellulosic material is indicated by dashed arrows similar to Figure 2a.

[0047] 3a discloses a fifth embodiment of the blade 10 in which the refiner bars 20 on one side of the groove 50 are not extensions of the refiner bars 20 on the other side of the groove 50, but are arranged at a different direction or angle to each other. The density of the refiner bars 20, i.e., the number of refiner bars 20 on a given size surface area, may also vary.

[0048] The fifth embodiment also comprises a reinforcing portion 33 on at least one dam 30, the reinforcing portion 33 being located where the outer dam end 31 is connected to the refiner bar 20. The reinforcing portion 33 is located on the side of the dam 30 facing the inner periphery 11, i.e., opposite the outer side 34. More specifically, the reinforcing portion 33 is located at the corner where the dam 30 meets the last refiner bar 20 at the outer dam end 31. The reinforcing portion 33 is thus located at a location where wear of the dam 30 from the lignocellulosic material is particularly high, thus helping to protect the dam 30 and extend the life of the blade 10. Suitably, the reinforcing portion 33 is integral with the dam 30 and refiner bar 20, but in some embodiments may instead be a separate portion that is added during manufacture to the corner between the dam 30 and the refiner bar 20 at the outer dam end 31.

[0049] In a fifth embodiment, at least one of the dams 30 also includes reinforcing portions 33 at two or more intersections of the dam 30 and the refiner bar 20, which is particularly advantageous for reducing wear on the dam 30 as a whole. Other embodiments may include reinforcing portions 33 only at the outer dam ends 31.

[0050] FIG. 3b discloses an enlarged view of the dam 30 of the blade 10 according to FIG. 3a, in which reinforcing portions 33 are provided at each intersection between the dam 30 and one of the refiner bars 20, more specifically at the corners of such intersections facing the first circumferential direction D, since these corners are the ones that experience the highest wear due to the rotation of the blade 10 during use.

[0051] 3c discloses a sixth embodiment similar to the fifth embodiment, except that at least a portion of the dam 30 is a subsurface dam 30. The reinforcing portion 33 of the fifth embodiment may be included at at least one intersection of the dam 30 with one of the refiner bars 20, preferably at least one of the refiner bars 20, at the outer dam end 31. However, the reinforcing portion 33 is not shown in FIG.

[0052] 3a and 3c, the outer dam end 31 of the first dam 30 and the inner dam end 32' of the second dam 30' are connected to the same refiner bar 20. The inner dam end 32' of the second dam 30' is closer to the inner circumference 11 than the outer dam end 31 of the first dam 30. This ensures that the transport of the lignocellulosic material across the blade 10 is efficient and low energy consuming.

[0053] In the embodiment of Figures 3a-3c, the outer dam end 31 of the first dam 30 in a radial direction perpendicular to the first circumferential direction D and the outer dam end 31'' of the adjacent dam 30'' are each connected to a different refiner bar 20. This means that the dams 30, 30'' overlap the outer dam ends 31, 31'' in the first circumferential direction D. In other words, the outer dam end 31 of the first dam 30 is offset in the first circumferential direction D from the outer dam end 31'' of the adjacent dam 30''. The advantage of this configuration is that the flow of lignocellulosic material and steam causes wear on the dams 30, 30'', especially at the outer dam ends 31, 31'', and by distributing the outer dam ends 31, 31'' in this way, the wear on the blade is also more evenly distributed than in the embodiment where the outer dam ends 31 of multiple dams 30 are connected to the same refiner bar 20 or to refiner bars arranged as extensions of each other (see, for example, Figure 2a).

[0054] 4 discloses an embodiment in which the density of refiner bars 20 varies in each set of refiner bars from inner periphery 11 to outer periphery 12. Additionally, the dams 30 are shown as subsurface dams 30 with grooves 50 provided on the outer side 34 of each dam 30.

[0055] 5 discloses an embodiment having an outer section 15 disposed on the blade surface 13 between the refiner surface 14 and the periphery 12. The outer section 15 is provided with refiner bars and dams for further refining of the lignocellulosic material after it passes through the refiner surface 14, where the refiner bars 20 and dams 30 are arranged in accordance with the present invention.

[0056] As mentioned above, the blade 10 may be a circular blade, or alternatively, may be a blade segment having a central angle between 10° and 360°. Multiple blade segments can then be attached to a refiner to form a circular blade.

[0057] The refiner section 14 may extend across the entire blade surface 13 from the inner circumference 11 to the outer circumference 12. Alternatively, there may be other sections of the blade surface 13, such as the outer section 15 disclosed above and in FIG. 5. There may also be such sections with refiner bars disposed between the refiner section 14 and the inner circumference 11. There may also be at least a portion on the blade surface 13 that is devoid of refiner bars, and such a portion may be located proximate the inner circumference 11, proximate the outer circumference 12, or on any other portion of the blade surface 13. Also, in some embodiments, there may be more than one refiner section 14 according to the present invention on the blade surface 13, with other portions having refiner bars therebetween or devoid of refiner bars.

[0058] FIG. 6 discloses an embodiment of the invention in which there are no grooves 50 and the angle of the refiner bars 20 varies across the blade 10 .

[0059] FIG. 7a discloses a groove 50 adjacent a dam 30. The groove 50 has a groove width w that is at least the width of the adjacent dam 30, but may be significantly greater. Additionally, the groove 50 has a depth d that is at least half the dam height of the adjacent dam 30. In FIG. 7a, the groove 50 has a groove width equal to the width of the adjacent dam 30 and a depth d equal to half the dam height of the dam 30. The depth d of the groove 50 is described in relation to the adjacent refiner bar 20, i.e., the refiner bar 20 that begins to taper at the groove 50. Thus, the depth d is the depth from the top end of the adjacent refiner bar 20, and the dam height is the height from the bar groove 40 adjacent the dam 30. FIG. 7b discloses a groove 50 having a groove width w that is greater than the width of the dam 30 and a depth equal to the dam height of the dam 30. In other embodiments, the dimensions of groove 50 may vary such that the groove width is equal to the depth, or alternatively, may differ from one another in any suitable manner, so long as the groove width and depth are greater than the minimum dimensions shown in FIG. 7a.

[0060] The present invention also relates to a refiner comprising at least one blade 10 according to any embodiment of the invention disclosed herein. The refiner may, in one embodiment, comprise two blades 10 according to the invention, one arranged as a rotor blade and the other arranged as a stator blade. In other embodiments, one blade 10 according to the invention may be arranged as either a rotor blade or a stator blade together with a refiner blade according to the prior art.

[0061] It should be noted that features from the various embodiments described herein may be freely combined unless expressly stated that such a combination is inappropriate. [Explanation of symbols]

[0062] 10 Blades 11 Inner circumference 12 Outer circumference 13 Blade Surface 14 Refiner surface, refiner part 15 Outer part 20 Refiner Bar 21 Outer bar end 22 Inner bar end 30 Subsurface Dam 30', 30'' Dam 31, 31'' outer dam end 32, 32' Inner dam end 33 Reinforcement part 34 Outside Dam 30 40 Bar groove 50 grooves

Claims

1. A refiner blade for refining lignocellulosic material, the blade (10) comprising a blade surface (13) defined by an inner periphery (11) and an outer periphery (12) and having a refiner portion (14) on which a plurality of refiner bars (20) are disposed, each refiner bar (20) extending from an outer bar end (21) to an inner bar end (22), the plurality of refiner bars (20) extending from the outer bar end (21) to the inner bar end (22) of the refiner bar (20) being spaced apart from each other. 2) is also movement in a first circumferential direction (D), the blade (10) further comprising at least one dam (30), the dam (39) extending from an outer dam end (31) to an inner dam end (32) and connecting the at least three refiner bars (20), and further wherein the dam (30) is positioned such that movement along the dam extension from the outer dam end (31) to the inner dam end (32) is also movement in the first circumferential direction (D).

2. The blade of claim 1 , wherein the at least one dam (30) has a dam height substantially equal to a bar height of at least one of the refiner bars (20) that the dam (30) intersects.

3. 2. The blade of claim 1, wherein at least one dam (30) has a dam height that is 20-99%, preferably 20-85%, of the bar height of at least one of the refiner bars (20) to which said dam (30) connects.

4. The blade of claim 2, further comprising at least one dam (30) having a dam height that is 20-99%, preferably 20-85%, of the bar height of at least one of the refiner bars (20) to which the dam connects.

5. A blade as claimed in any one of claims 1 to 4, wherein the blade further comprises a groove (50) extending along the dam (30) and adjacent the dam (30) on an outer side (34) of the dam (30), said outer side (34) being the side facing the outer periphery (12).

6. The blade of claim 5, wherein the groove (50) has an increasing width towards the inner dam end (32).

7. A blade according to claim 5 or 6, wherein the groove (50) has a width at its upper end at least equal to the width of the dam (30).

8. 8. The blade of claim 5, wherein the groove (50) has a depth (d) at least equal to half the dam height of the dam (30) adjacent the groove (50), said depth (d) being a depth from a top end of an adjacent refiner bar (20).

9. 9. The blade according to claim 1, further comprising a reinforcing portion (33) at which an outer dam end (31) is connected to the refiner bar (20), said reinforcing portion (33) being arranged on a side of the dam (30) facing the inner circumference.

10. 10. The blade of claim 1, wherein the outer dam end (31) of the first dam (30) and the inner dam end (32') of the second dam (30') are each connected to the same refiner bar (20), and the inner dam end (32') of the second dam (30') is closer to the inner circumference (22) than the outer dam end (31) of the first dam (30).

11. 11. The blade of claim 1, wherein a radially adjacent outer dam end (31) of a first dam (30) and an outer dam end (31'') of a radially adjacent dam (30'') are each connected to different refiner bars (20) in a first circumferential direction (D).

12. The blade (10) according to any one of the preceding claims, wherein the blade (10) is a blade portion having a central angle of between 10° and 360°.

13. The blade of any one of claims 1 to 12, further comprising at least one portion lacking a refiner bar.

14. A refiner for refining lignocellulosic material, comprising at least one blade according to any one of claims 1 to 13.

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