Refining segment

Abstract

To provide a refining segment (4) for a refiner (1) for refining a fiber material containing lignocellulose.SOLUTION: A refining segment includes an inner end (20), an outer end (21) on the opposite side of the inner end, and a refining surface (5) including refining bars (25) and refining grooves (26) between these refining bars. The refining surface includes at least one recess (27, 27', 27'') at least partially extending from the outer end of the refining segment toward the inner end, and at least partially forms at least one backflow guide groove (28) extending at least partially from the outer end of the refining segment toward the inner end. A volume of at least one recess is constituted so as to decrease toward the inner end and a volume of at least one backflow guide groove is constituted so as to decrease toward the inner end.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to the refining of fibrous materials, and more particularly to a refining segment for a refiner for refining lignocellulose-containing fibrous materials.

Background Art

[0002] Refiners used for refining fibrous materials, such as refiners used in the production of mechanical pulp or refiners used for any low-consistency refining, typically include two refining elements that face each other and rotate relative to each other, i.e., one or both rotate. The refining elements include a refining surface provided with refining bars and refining grooves between those refining bars. The refining bars are intended to defiber and refine the material to be refined, i.e., pulp, and the refining grooves are intended to convey the material to be refined forward along the refining surface. The refining surfaces of the refining elements are typically formed from several refining segments fixed to the body of each refining element, whereby the refining segments include a refining surface provided with refining bars and refining grooves between those refining bars. In this case, the complete refining surface of the refining element is thus formed from the refining surfaces of several refining segments fixed adjacent to each other within the refining element. An example of such a refining segment is shown in Finnish Patent No. 126263, where the refining segment includes a refining surface provided with refining bars and refining grooves between those refining bars. The refining surface is provided with specific supply grooves that extend from the inner end edge of the refining bars towards the outer end edge of the refining segment and convey the material to be refined and the already refined material towards the outer edge of the refining segment, thereby increasing the refining capacity. Alternatively, the refining segment may be a single uniform piece extending over the entire circumference of each refining element, whereby the refining bars and refining grooves within the refining surface of this single uniform piece form the complete refining surface of the refining element. This type of refining segment is also called a refiner filling.

[0003] All processes for manufacturing pulp from lignocellulosic materials produce shives as an undesirable quality issue. Shives are particles, fiber bundles, or pieces of wood produced by incomplete splitting of the wood material into fibers during cooking or mechanical processing. Shives not only contaminate the quality of the pulp produced but also deteriorate the operation of some processing devices such as refiners. Shives tend to clog the refining surface, thereby reducing the quality of the pulp produced and reducing the capacity of the refiner. Therefore, it is necessary to reduce the amount or proportion of shives in the pulp. SUMMARY OF THE INVENTION

[0004] An object of the present invention is to provide a novel refining segment for refining fiber materials.

[0005] The present invention is characterized by the features of the independent claims.

[0006] Based on the idea of improving the refining effect applied to the fiber material to be refined, the present invention collects the fiber material, reverses the shives in it on the refining surface of the refining segment, and guides the reversed fiber material and the shives in it in a controlled manner back to the refining gap in the refiner to achieve the expected refining effect.

[0007] An advantage of the present invention is to reduce the amount of shives, which are known as by-products of fiber production and should be removed during fiber processing, without impairing pulp properties, actually other pulp quality parameters such as strength. When the amount of shives in the pulp decreases, the formation and smoothness are improved.

[0008] Some embodiments of the present invention are disclosed in the dependent claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The present invention will be described in more detail below with reference to the accompanying drawings by preferred embodiments.

Figure 1

Figure 2

Figure 3

Figure 4A

Figure 4B

Figure 5A

Figure 5B

Figure 6

Figure 7

DETAILED DESCRIPTION OF THE INVENTION

[0010] Figure 1 is a schematic side view of a cross-section of the refiner 1. The refiner 1 can be used, for example, to refine a fibrous material derived from wood or plants containing lignocellulose. The fibrous material refined by the refiner 1 is in the form of a pulp suspension, that is, a mixture of water, the fibrous material, and optionally some additives. In refining, the consistency of the pulp suspension supplied to the refiner 1 can vary according to actual needs. The consistency of the pulp suspension supplied to the refiner 1 can vary, for example, based on the raw materials and the intended final product. For low-consistency refining applications, the consistency of the pulp suspension supplied to the refiner 1 is typically less than 6%, typically between 2.5% and 5.5%. For high-consistency refining applications, the consistency of the pulp suspension supplied to the refiner 1 is typically greater than 25%, typically between 35% and 50%. The refining segments disclosed herein can be used in both low-consistency refiners and high-consistency refiners. Further, although the refiner 1 shown in Figure 1 is a conical refiner, disc-type refiners, conical disc-type refiners, and cylindrical refiners can also be used in the same way.

[0011] The refiner 1 in Figure 1 includes a frame 2 and a fixed stator 3 supported by the frame 2, and the stator 3 forms the fixed refining element of the refiner 1. The stator 3 includes two or more stator refining segments 4, and each stator refining segment 4 extends only partially around the stator 3. An example of such a stator refining segment 4 is schematically shown in Figure 2. The stator refining segment 4 includes refining bars and refining grooves between those refining bars. The refining bars and refining grooves of the stator refining segment 4 form the refining surface 5 of each refining segment 4, whereby the refining surface 5 of each stator refining segment 4 provides a part of the refining surface of the stator 3. On the complete refining surface 5 of the stator 3, a required number of stator refining segments 4 are fixed to the stator 3 adjacent to each other to form the refining surface 5 that extends over the entire circumference of the stator 3, whereby a complete refining surface 5 that extends over the entire circumference of the stator 3 is provided. For clarity, in this specification, both the refining surface of each single stator refining segment 4 and the complete refining surface of the stator 3 are denoted by the same reference numeral 5.

[0012] The refiner 1 further includes a rotor 6 of the refiner 1, and the rotor 6 forms a rotatable refining element of the refiner 1. The rotor 6 includes a rotor frame 7. The rotor frame 7 is connected to a rotatable shaft 10 used to rotate the rotor 6 around its central axis. The rotor 6 further includes two or more rotor refining segments 8, and each rotor refining segment 8 only partially extends across the circumference of the rotor 3. Thus, the rotor refining segment 8 can be similar to, for example, the stator refining segment 4 schematically shown in FIG. 2. The rotor refining segment 8 is supported by the rotor frame 7, and each rotor refining segment 8 includes refining bars and refining grooves between those refining bars. The refining bars and refining grooves of the rotor refining segment 8 form a refining surface 9 of the respective refining segment 8, whereby the refining surface 9 of each rotor refining segment 8 provides a part of the refining surface of the rotor 6. On the complete refining surface of the rotor 6, a required number of rotor refining segments 8 are fixed to the rotor 6 adjacent to each other to form a refining surface 9, thereby providing a complete refining surface 9 extending across the entire circumference of the rotor 6. For the sake of clarity, in this specification, both the refining surface of each single rotor refining segment 8 and the complete refining surface of the rotor 6 are denoted by the same reference numeral 9.

[0013] Alternatively, the refining segment may also be a single uniform piece extending across the entire circumference of the stator 3 or the rotor 6, whereby the refining bars and refining grooves within the refining surface of this single uniform piece form the complete refining surface of the stator 3 or the rotor 6.

[0014] The fiber material to be refined is supplied into the refiner 1 and is supplied, as indicated by the arrow F, through the supply channel 12 into the refining gap 11 left between the stator 2 and the rotor 6 facing each other. The refined material is removed from the refiner 1 through the discharge channel 13, as schematically indicated by the arrow D.

[0015] FIG. 2 schematically shows the stator refining segment 4 as seen obliquely from above. The stator refining segment 4 includes a main body 4a, a front surface 4b facing the refining gap 11 of the refiner 1, i.e., facing the rotor 6, and a back surface 4c facing the frame 2 of the refiner 1.

[0016] The stator refining segment 4 of FIG. 2 is applicable for use in forming a part of the refining surface 5 of the stator 3 of the conical refiner 1, whereby the complete refining surface 5 in the stator 3 is provided by arranging the required number of stator refining segments 4 of FIG. 2 adjacent to each other along the circumference of the stator 3. The solutions described in this specification below exemplify in particular the conical and disc-shaped stator refining segments 4 applicable for use in a conical refiner 1, a disc-type refiner, or a conical disc-type refiner, but this solution can be applied respectively to rotor refining segments applicable for use in a conical refiner 1, a disc-type refiner, or a conical disc-type refiner, and to stator and rotor refining segments applicable for use in a cylindrical refiner. Further, this solution may be applied respectively to refining segments extending across the entire circumference of the stator 3 or the rotor 6 as a single uniform piece.

[0017] The refining segment 4 includes an inner edge 20 or a first end edge 20 intended to face the inner circumference of the stator 3. The refining segment 4 further includes an outer edge 21 or a second end edge 21 that is on the side opposite to the inner edge 20 in the longitudinal direction of the refining segment 4, and the outer edge 21 is intended to face the outer circumference of the stator 3. Generally, the refining segment has a longitudinal direction extending from the inner edge 20 to the outer edge 21, that is, a longitudinal axis LA, and the width direction is the direction crossing the longitudinal axis. When attached to the refiner, the longitudinal axis LA of the refining segment is oriented substantially axially with respect to the conical and cylindrical refiners, and is oriented radially with respect to the refiner in the case of a disk-type refiner. Further, in a conical refiner, typically, the end with a smaller radius in the radial direction of the stator / rotor is considered to point to the inner circumference of the stator / rotor, and the end with a larger radius in the radial direction of the stator / rotor is considered to point to the outer circumference of the stator / rotor. In a disk-type refiner, the portion of the refining segment closest to the center of the refiner in the radial direction is considered to point to the inner circumference of the stator / rotor, and the portion of the refining segment furthest from the center of the refiner in the radial direction is considered to point to the outer circumference of the stator / rotor.

[0018] The refining segment 4 further includes a first side edge 22 extending from the inner edge 20 of the refining segment 4 to the outer edge 21 of the refining segment 4. The refining segment 4 further includes a second side edge 23 that is on the side opposite to the first side edge 22 in the circumferential direction of the refining segment 4. The second side edge 23 extends from the inner edge 20 of the refining segment 4 to the outer edge 21 of the refining segment 4. The inner edge 20 and the outer edge 21, together with the first side edge 22 and the second side edge 23, contribute to defining the periphery 24 of the refining segment 4. In the case of a refining segment extending over the entire circumference of the stator 3 or the rotor 6 as a single uniform piece, there are no side edges of the refining segment, and only the corresponding end edges 20, 21 are present.

[0019] On the front surface of the refining segment 4, a refining bar 25 and a refining groove 26 between the refining bars 25 are provided, and the refining bar 25 and the refining groove 26 together provide the refining surface 5 of the refining segment 4. The purpose of the refining bar 25 is to defibrate and refine the material to be refined, and the purpose of the refining groove 26 is to convey the material refined between the refining bars 26 forward along the refining surface 5. The material to be refined is supplied onto the refining surface 5 beyond the inner edge 20 of the refining segment 4, and the already refined material is discharged from the refining surface 5 in a direction away from beyond the outer edge 21 of the refining segment 4. Generally, the refining segment can have different patterns consisting of various configurations of refining bars and refining grooves to provide specific performance according to actual manufacturing needs. For illustrative purposes only, the refining surface 5 of the refining segment 4 is shown in FIG. 2 considering the refining bar 25 and the refining groove 26. Thus, the actual embodiments of the refining surface 5 can vary in many ways. In the refining segment 4, the upper surface 4a' of the refining segment 4 forms the bottom levels of the refining bar 25 and the refining groove 26. In other words, the upper surface 4a' of the refining segment 4 forms the bottom, i.e., the bottom surface of the refining groove 26.

[0020] The dimensions of the refining bar 25 and the refining groove 26 on the refining surface 5 of the stator refining segment 4 can vary in many ways, for example, based on the raw material to be refined and the intended degree of refining or the final product. Typically, the width W25 of the refining bar 25 is about 1.3 - 7 mm, and the width W26 of the refining groove 26 is about 1.3 - 7 mm. The height of the refining bar 25, i.e., the depth of the refining groove 26 from the top of the refining bar 25 to the bottom of the refining groove 26, is typically about 5 - 10 mm. However, other ranges are also possible for the widths of the refining bar 25 and the refining groove 26 and the depth of the refining groove 26. The width W25 of the refining bar 25 and the width W26 of the refining groove 26 are schematically disclosed in FIG. 4A below. The dimensions of the refining bar and the refining groove are typically the same in each rotor refining segment.

[0021] The refining segment 4 of FIG. 1 further includes a recess 27 that extends at least partially from the outer edge 21 of the refining segment 4 (without extending to the inner edge 20 of the refining segment 4) toward the inner edge 20 of the stator refining segment 4. The recess 27 forms a backflow guide groove 28 that extends at least partially from the outer edge 21 of the refining segment 4 (without extending to the inner edge 20 of the refining segment 4) toward the inner edge 20 of the refining segment 4. The recess 27 is formed in the body 4a of the refining segment 4 below the bottom levels of the refining bars 25 and the refining grooves 26. Thus, the upper level of the recess 27 is at the same level as the upper surface 4a' of the body 4a of the refining segment 4, and the bottom, i.e., the bottom surface, of the recess 27 extends into the body 4a of the refining segment 4. This means that the recess 27 and each backflow guide groove 28 extend at least partially in the body 4a of the refining segment from the outer edge 21 of the refining segment 4 toward the inner edge 20 of the refining segment 4 and extend below the bottom levels of the refining bars 25 and the refining grooves 26. Backflow means that the flow of the fiber material to be refined flows in the reverse direction on the refining surface of the refining segment, i.e., in the direction from the outer edge of the refining segment toward the inner edge of the refining segment. The purpose of the backflow guide groove 28 is to guide the fiber material and the sheaves therein to flow back and be refined in the refining gap 11. Further, in the longitudinal direction of the recess 27 from the outer edge 21 of the refining segment 4 toward the inner edge 20 of the refining segment 4, the volume of the recess 27 decreases toward the inner edge of the refining segment 4, and the volume of the backflow guide groove 28 is configured to decrease toward the inner edge 20 of the refining segment 4. In the example of FIG. 2, and in the examples of FIGS. 4A, 4B, 5A, and 5B shown later, the refining segment 4 includes a single backflow guide groove 28, but in actual embodiments, the number of backflow guide grooves 28 in the stator refining segment may be more than one. The recess 27 can be formed in the body 4a of the refining segment 4 by removing material from the refining segment 4 or excluding material from the refining segment 4.

[0022] The purpose of using the countercurrent guide groove 28 in the refining segment 4 is to collect the fiber material flowing countercurrent on the refining surface 5 of the refining segment 4, that is, flowing in the direction from the outer edge 21 of the refining segment 4 toward the inner edge 20 of the refining segment 4, and the sheaves therein, and to further guide and refine the countercurrent fiber material and the sheaves therein into the refining gap 11. The guiding of the fiber material and the sheaves therein into the refining gap 11 is carried out in response to the volume of the countercurrent guide groove 28 decreasing in its longitudinal direction toward the inner edge 20 of the refining segment 4. Thus, due to the decrease in the volume of the countercurrent guide groove 28, the countercurrent fiber material and the sheaves therein are pushed into the refining gap 11 and refined. This countercurrent of the fiber material on the refining surface 5 of the refining segment 4 can occur, for example, in response to the pressure spreading to the outer edge 21 of the refining segment 4 being Low less than the pressure spreading to the inner edge 20 of the refining segment 4, and the possible countercurrent typically becomes stronger on the stator side than on the rotor side. The countercurrent guide groove 28 may extend to the inner edge 20 of the refining segment 4, but if the countercurrent guide groove 28 does not extend to the inner edge 20 of the refining segment 4, it is possible for the fiber material to flow countercurrent in the countercurrent guide groove and reach the inner edge 20 of the refining segment 4, thereby avoiding the possibility of disturbances when supplying the fiber material to be refined into the refining gap 11.

[0023] Thus, the effect of the countercurrent guide groove 28 is to guide the countercurrent fiber material and the sheaves therein, or to push the countercurrent fiber material and the sheaves therein into the refining gap 11 for refining. Also, the countercurrent control groove 28 provides more open volume within the refining segment, thereby mixing more of the fiber material on the refining surface of the refining segment. Due to these effects of the countercurrent guide groove 28, without impairing other pulp quality parameters such as the properties and strength of the pulp, when the amount of sheaves decreases and the amount of sheaves in the pulp decreases, the formation and smoothness, etc. are also improved.

[0024] Figure 4A schematically shows the second stator refining segment 4 from above, and Figure 4B schematically shows a side view of a cross-section of the refining segment 4 of Figure 4A. Figures 4A and 4B are shown to explain in more detail some features of the countercurrent guide groove 28. For clarity, the dimensions of the refining bar 25, the refining groove 26, and the countercurrent guide groove 28 therein are highly exaggerated relative to the dimensions of the refining segment 4. Further, the dimensions of the refining bar 25, the refining groove 26, and the countercurrent guide groove 28 do not necessarily have a fixed scale relative to each other.

[0025] Referring to FIGS. 2, 4A, and 4B, the countercurrent guide groove 28 has a first end 28a at the outer edge 21 of the refining segment 4 and a second end 28b facing the inner edge 20 of the refining segment 4. Thus, the longitudinal direction of the countercurrent guide groove 28 is the direction of the groove from the first end 28a of the countercurrent guide groove 28 to the second end 28b of the countercurrent guide groove 28.

[0026] In the embodiments of FIGS. 2, 4A, and 4B, the countercurrent guide groove 28 is linear and is configured to extend in a substantially straight line direction from the outer edge 21 of the refining segment 4 to the inner edge 20 of the refining segment 4 in its longitudinal direction. In other words, in the embodiments of FIGS. 2, 4A, and 4B, the tangent of the virtual center line of the countercurrent guide groove 28 extends in a substantially straight line direction from the outer edge 21 of the refining segment 4 to the inner edge 20 of the refining segment 4, that is, in a position substantially parallel to the longitudinal direction or the longitudinal axis LA of the refining segment 4. In such an embodiment, the countercurrent guide groove 28 is considered to extend substantially completely from the outer edge 21 of the refining segment 4 to the inner edge 20 of the refining segment 4.

[0027] According to another embodiment (not shown), the linear countercurrent guiding groove 28 can be arranged at an inclined position with respect to the longitudinal direction or the longitudinal axis LA of the refining segment 4, whereby the countercurrent guiding groove 28 can be configured to extend only partially in its longitudinal direction towards the inner edge 20 of the refining segment 4. In this case, different from the embodiments of FIGS. 2, 4A, and 4B, the tangent of the virtual center line of the countercurrent guiding groove extends partially towards the inner edge 20 of the refining segment 4 and also extends partially towards one of the side edges 22, 23 of the refining segment 4. Thereby, the countercurrent guiding groove 28 is considered to extend only partially from the outer edge 21 of the refining segment 4 towards the inner edge 20 of the refining segment 4. The angle between the center line of the countercurrent guiding groove 28 and the longitudinal axis LA of the refining segment 4, that is, the angle between the tangent of the center line of the countercurrent guiding groove 28 and the longitudinal axis LA of the refining segment 4, may be, for example, between 10 and 50 degrees along the longitudinal direction of the countercurrent guiding groove 28.

[0028] According to an alternative embodiment schematically shown in FIG. 7 below, the countercurrent guiding groove 28 is curved, whereby the countercurrent guiding groove 28 is configured to curve and extend at least partially from the outer edge 21 of the refining segment 4 towards the outer edge 22 of the refining segment 4 in its longitudinal direction. In that case, different from the embodiments of FIGS. 2, 4A, 4B, 5A, 5B, and 6, the tangent of the virtual center line of the countercurrent guiding groove 28 extends only partially towards the inner edge 20 of the refining segment 4 and also extends partially towards one of the side edges 22, 23 of the refining segment 4 at at least some points in the longitudinal direction of the countercurrent guiding groove 28. Thereby, the countercurrent guiding groove 28 extends only partially from the outer edge 21 of the refining segment 4 towards the inner edge 20 of the refining segment 4.

[0029] According to this solution, the volume of the recess 27 decreases towards the inner edge 20 of the refining segment 4, and the volume of the reverse flow guiding groove 28 is configured to decrease towards the inner edge 20 of the refining segment 4. Decreasing the volume of the reverse flow guiding groove 28 towards the inner edge 20 of the refining segment 4, that is, towards the second end 28b of the reverse flow guiding groove 28, can be implemented by, for example, at least one of decreasing the width of the recess 27 towards the inner edge 20 of the refining segment 4 or decreasing the depth of the recess 27 towards the inner edge 20 of the refining segment 4. Thus, decreasing the volume of the reverse flow guiding groove 28 towards the inner edge 20 of the refining segment 4 can be achieved, for example, by decreasing the width and / or depth of the recess 27 towards the inner edge 20 of the refining segment 4.

[0030] According to one embodiment, the width of the reverse flow guiding groove 28 decreases in its longitudinal direction such that the width W28b at the second end 28b of the reverse flow guiding groove 28 is about 0% to 95% of the width W28a at the first end 28a of the reverse flow guiding groove 28. The width W28a at the first end 28a of the reverse flow guiding groove 28 can be, for example, about 5 mm to 20 mm.

[0031] According to one embodiment, the depth of the backflow guide groove 28 is configured to decrease in the longitudinal direction thereof such that the depth at the second end 28b of the backflow guide groove 28 is smaller than the depth at the first end 28a of the backflow guide groove 28. The depth D28 of the backflow guide groove 28 is schematically shown at the first end 28a of the backflow guide groove 28 in FIG. 4B. According to one embodiment, the depth D28 of the backflow guide groove 28 is configured to decrease toward its second end 28b, whereby the bottom 28c of the backflow guide groove 28, i.e., the bottom of the recess 27, rises at an angle α of about 0.1 to 5 degrees from the first end 28a of the backflow guide groove 28 toward the second end 28b of the backflow guide groove 28, and is configured to reduce the volume of the backflow guide groove 28 toward the second end 28 of the backflow guide groove 28. The depth at the first end 28a of the backflow guide groove 28 can be, for example, about 3 to 10 mm below the bottom of the refining groove 26. Thus, as described above, the recess 27, and thus each backflow guide groove 28, extends at least partially from the outer edge 21 of the refining segment 4 toward the inner edge 20 of the refining segment 4 below the bottom levels of the refining bar 25 and the refining groove 26 in the body 4a of the refining segment 4.

[0032] According to one embodiment, the recess 27, and thus the backflow guide groove 28, is configured to extend between the outer edge 21 of the refining segment 4 and the inner edge 20 of the refining segment 4, from the outer edge 21 of the refining segment 4 to a distance of about 25% to 75% of the length of the refining segment. In other words, the backflow guide groove 28 is configured to be located in a portion of the refining segment that extends from the outer edge of the refining segment 4 to about 25% to 75% of the longitudinal dimension of the refining segment 4 from the outer edge 21 of the refining segment 4. Thus, the backflow guide groove 28 starts at the outer edge 21 of the refining segment 4 and ends at a portion of the refining segment 4 between the outer edge 21 and the inner edge 20 of the refining segment 4. Referring to the example of FIG. 4A including the linear backflow guide groove 28, this means that the length L28 of the linear backflow guide groove 28 is selected such that it is about 25% to 75% of the dimension of the refining segment 4 in the longitudinal direction of the refining segment 4. The larger the volume in which the fiber material can flow back on the refining surface 5 of the stator refining segment 4, the wider the backflow guide groove 28 can be selected to efficiently guide the backflow of the fiber material into the refining gap 11.

[0033] FIG. 5A schematically shows the third stator refining segment 4 from above, and FIG. 5B schematically shows a side view of a cross-section of the refining segment 4 of FIG. 5A. The embodiments of FIGS. 5A and 5B are substantially the same as the embodiments of FIGS. 4A and 4B, but in addition, the embodiments of FIGS. 5A and 5B include holes 29a, 29b, 29c that extend through the refining segment body 4a. The holes 29a, 29b, 29c are arranged in line with the backflow guide groove 28, whereby the holes 29a, 29b, 29c extend from the bottom 28c of the backflow guide groove 28 to the back 4c of the refining segment. For clarity, the dimensions of the holes 29a, 29b, 29c are not necessarily to scale and are exaggerated compared to other features of the refining segment.

[0034] The holes 29a, 29b, 29c provide the possibility that at least a part of the fiber material flowing backward in the backflow guide groove 28 enters the holes 29a, 29b, 29c and flows through the holes 29a, 29b, 29c into the back surface 4c of the refining segment 4. That part of the fiber material can flow to the inner edge 20 of the refining segment 4 and flow backward into the refining gap 1 between the stator 3 and the rotor 6 at the inner edge 20 of the refining segment 4. As schematically shown by the arrow indicated by the reference symbol R in FIG. 5B, this circulation of the fiber material has the effect of recirculating the fiber material in the refiner, thereby subjecting the fiber material to the refining effect multiple times.

[0035] According to an embodiment not shown, at least some of the holes 29a, 29b, 29c can be located in the central portion of the refining segment 4, that is, the portion of the refining segment 4 including the refining bar 25 and the refining groove 26, but are not arranged in a straight line with the backflow guide groove 28, whereby the above-described recirculation of the fiber material may be increased.

[0036] In the embodiments of FIGS. 5A and 5B, the holes 29a, 29b, 29c are circular. The shape and size of the holes can vary according to the actual embodiment of the refining segment 4, but typically, the shape and size of the holes are constant in a single refining segment 4. Generally, the larger the number of holes and the larger the size of the holes, the more efficient the recirculation effect can be provided. However, the number and size of the holes must of course be limited in consideration of, for example, the structural durability of the refining segment 4 and the intended ability of the refining. This is because the more holes there are, the shorter the cutting edge length of the refining segment 4 and the less refining effect the fiber material to be refined receives.

[0037] An example of the sheave reduction in refining is schematically shown in the figure of FIG. 3 showing the test results of an actual experiment. The fibrous material is refined in a refiner including a stator refining segment provided with a countercurrent guiding groove 28 and openings 29a, 29b, 29c provided in this groove 28 (solid line with triangular identifier), refined in a refiner including a stator refining segment provided with a countercurrent guiding groove 28 and not provided with openings 29a, 29b, 29c in this groove 28 (solid line with square identifier), and refined in a refiner including a stator refining segment including a similar refining surface except that the countercurrent guiding groove 28 is not provided (dashed line with an identifier like x). The horizontal axis of the figure represents the CSF (Canadian Standard Freeness) value of the fiber suspension in milliliters (ml) measured according to the ISO standard ISO5267, and the vertical axis of the figure represents the reduction rate (%) of the sheaves. The drawing of FIG. 3 shows that the amount of sheaves in the refined fibrous material clearly decreased when the stator refining segment provided with the countercurrent guiding groove 28 was applied. When holes 29a, 29b, 29c aligned in a straight line with the countercurrent guiding groove 28 were provided in the stator refining segment, the reduction in the amount of sheaves was even more remarkable.

[0038] FIG. 6 is a schematic view of a set of fourth stator refining segments 4 arranged adjacent to each other as seen obliquely from above. The basic structure of the refining segment 4 in FIG. 6 is the same as that shown and described in the above figure, but instead of having a single recess 27 in the substantially middle section of the refining segment 4, the refining segment 4 in FIG. 6 includes a first recess 27' at the first side edge 22 of the refining segment 4 and a second recess 27'' at the second side edge 23 of the refining segment 4. The first recess 27' and the second recess 27'' extend along the respective side edges 22, 23 of the refining segment 4 from the outer edge 21 of the refining segment 4 toward the inner edge 20 of the refining segment 4. Further, the volumes of the first recess 27' and the second recess 27'' are configured to decrease toward the inner edge 20 of the refining segment 4.

[0039] When assembling the refined surface 5 of the stator 3, the refined segments 4 are arranged adjacent to each other, so that the first side edge 22 of the refined segment 4 is arranged with respect to the second side edge 23 of the adjacent refined segment, as shown in Fig. 6 with two adjacent refined segments 4 as an example. When the first side edge 22 of the right refined segment 4 is arranged with respect to the second side edge 23 of the right refined segment 4, the first recess 27' of the right refined segment 4 and the second recess 27'' of the left refined segment 4 together form a countercurrent guide groove 28 that extends from the outer edge 21 to the inner edge 20 of the refined segment 4 at the connection part of the refined segment 4, and the volume of the countercurrent guide groove 28 is configured to decrease towards the inner edge 20 of the refined segment 4.

[0040] The advantage of the embodiment of the refined segment 4 shown in Fig. 6 is the uniform refined surface in the middle section of the refined segment 4, whereby the loss of the cutting edge length of the refined segment 4 is typically less than that of the refined segment 4 where the countercurrent guide groove 28 is on the middle section of the refined segment 4. Another advantage is that the manufacture of the refined segment 4 is easy, especially when holes are also used at this position of the countercurrent guide groove 28.

[0041] Fig. 7 schematically shows the fifth stator refined segment 4 seen obliquely from above. The refined segment 4 in Fig. 7 is a flat or disk-shaped refined segment 4 applicable for use in a disk-type refiner or a conical disk-type refiner. The basic structure of the refined segment 4 in Fig. 7 is the same as that disclosed above. The refined segment 4 in Fig. 7 also includes recesses 27 that form the countercurrent guide groove 28. Further, there are holes 29a, 29b that are aligned with the countercurrent guide groove 28. Fig. 7 also discloses a fastening opening 30 that extends through the refined segment body 4a and is intended to receive appropriate fixing members such as bolts for fixing the refined segment 4 to the frame 2 of the refiner 1.

[0042] In the embodiment of the refining segment 4 of FIG. 7, the countercurrent guide groove 28 is curved, whereby the countercurrent guide groove 28 is configured to curve and extend at least partially from the outer edge 21 of the refining segment 4 toward the inner edge 20 of the refining segment 4 in its longitudinal direction, whereby the tangent of the virtual center line CL of the countercurrent guide groove 28 extends only partially toward the inner edge 20 of the refining segment 4 at at least some points in the longitudinal direction of the countercurrent guide groove 28 and extends partially toward the first side edge 22 of the refining segment 4, whereby the countercurrent guide groove 28 extends only partially from the outer edge 21 of the refining segment 4 toward the inner edge 20 of the refining segment 4. The angle β between the center line CL of the countercurrent guide groove 28 and the longitudinal axis LA of the refining segment 4, that is, the angle β between the tangent of the center line CL of the countercurrent guide groove 28 and the longitudinal axis LA of the refining segment 4, may vary, for example, in the range of 10 to 50 degrees along the longitudinal direction of the countercurrent guide groove 28.

[0043] As technology advances, it will be apparent to those skilled in the art that the concepts of the present invention can be realized in various ways. The present invention and its embodiments are not limited to the above examples and can be modified within the scope of the claims.

Claims

1. A refining segment (4) for a refining vessel (1) for refining a lignocellulose-containing fibrous material, the refining segment comprising: An inner edge (20), and an outer edge (21) opposite to the inner edge (20); a refining surface (5) including refining bars (25) and refining grooves (26) between the refining bars; The refining surface (5) of the refining segment (4) includes at least one backflow guide groove (28) extending at least partially from the outer edge (21) of the refining segment (4) toward the inner edge (20) of the refining segment (4), the backflow guide groove (28) extending in a direction transverse to the extension direction of the refining bar (25) and the refining groove (26); A cross-sectional area of ​​the at least one backflow guide groove (28) perpendicular to the upper surface (4a') of the refining segment (4) is configured to decrease toward the inner end edge (20) of the refining segment (4); The depth of the backflow guide groove (28) is configured to decrease from the outer end edge (21) of the refining segment (4) toward the inner end edge (20) of the refining segment. Refining segment.

2. The refining segment of claim 1, wherein the at least one backflow guide groove (28) is configured to extend at least partially from the outer edge (21) of the refining segment (4) toward the inner edge (20) of the refining segment (4) without extending to the inner edge (20) of the refining segment (4).

3. The refining segment of claim 1, wherein the width of the backflow guide groove (28) is configured to decrease toward the inner edge (20) of the refining segment (4).

4. The refining segment of claim 3, wherein the reverse flow guide groove (28) has a first end (28a) located at the outer edge (21) of the refining segment (4) and a second end (28b) at least partially facing toward the inner edge (20) of the refining segment (4), and the width (W28b) of the second end (28b) of the reverse flow guide groove (28) is 0 to 95% of the width (W28a) of the first end (28a) of the reverse flow guide groove (28).

5. The refining segment according to claim 3 or 4, wherein the width (W28a) of the first end (28a) of the backflow guide groove (28) is 5 to 20 mm.

6. The refining segment according to claim 1, wherein the reverse flow guide groove (28) has a first end (28a) located at the outer edge (21) of the refining segment (4) and a second end (28b) at least partially facing toward the inner edge (20) of the refining segment (4), and the bottom (28c) of the reverse flow guide groove (28) is configured to rise at an angle (α) of 0.1 to 5 degrees from the first end (28a) of the reverse flow guide groove (28) toward the second end (28b) of the reverse flow guide groove (28b), and the cross-sectional area of ​​the reverse flow guide groove (28) decreases toward the inner edge (20) of the refining segment (4).

7. The refining segment according to claim 1 or 6, wherein the depth (D28) at the first end (28a) of the backflow guide groove (28) is 3 to 10 mm below the bottom of the refining groove (26).

8. The refining segment of claim 1, wherein the backflow guide groove (28) is configured to extend from the outer end edge (21) of the refining segment (4) to a distance of 25% to 75% of the length of the refining segment (4) between the outer end edge (21) of the refining segment (4) and the inner end edge (20) of the refining segment (4).

9. The refining segment of claim 1, wherein the backflow guide groove (28) is substantially straight and configured to extend in a substantially straight direction from the outer end edge (21) of the refining segment (4) to the inner end edge (20) of the refining segment (4).

10. The refining segment of claim 1, wherein the backflow guide groove (28) is curved and configured to extend in a curved manner from the outer end edge (21) of the refining segment (4) toward the inner end edge (20) of the refining segment (4).

11. 2. The refining segment of claim 1, wherein the refining surface (5) of the refining segment (4) includes holes (29a, 29b, 29c) extending through the blade segment body (4c).

12. The refining segment of claim 11, wherein the holes (29a, 29b, 29c) are aligned with the at least one backflow guide groove (28).

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