Refining Segment for Refiner

Abstract

A refining segment (4, 8) for a refiner (1) for refining fibrous material has a body (20) with a front side (21) and a backside (22). The front side has a refining surface (5, 9) and the backside has a background surface (23). The refining segment has a first end edge (15) and a second end edge (16) opposite to the first end edge, and a first side edge (17) and a second side edge (18) opposite to the first side edge. The first side edge and the second side edge extend between the first end edge and the second end edge. The refining segment has backside support projections (29, 30) which project from the background surface and extend substantially along the first side edge and the second side edge without support projections extending substantially along the first end edge and the second end edge on the background surface.

Description

STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT

Not applicable.

BACKGROUND OF THE INVENTION

The invention relates to refiners for refining fibrous material and especially to a refining segment for a refiner for refining fibrous material.

Refiners used for refining fibrous material, such as refiners used for manufacturing mechanical pulp or in any low consistency refining, comprise typically two refining elements opposite to each other and turning relative to each other, i.e., one or both of them is/are rotating. The refining elements comprise refining surfaces provided with blade bars and blade grooves therebetween, the blade bars being intended to defiber and refine the material to be refined and the blade grooves being intended to convey the material to be refined forward along the refining surfaces. The refining surface of the refining element is typically formed of several refining segments fastened to a body of the respective refining element. The complete refining surface of the refining element is thus formed of the refining surfaces of several refining segments fastened next to each other in the refining element.

Effective manufacturing of paper and paperboard gives rise to the tendency to increase volumes of the production lines. In view of the refining this often means an increase in the size and the number of the refiners that are many times additionally connected in series with each other. The connection of several large refiners in series may, however, make the control of a complete refining shop challenging, for example in view of control of pressures prevailing over single refiners or over the complete refining shop, and in view of maintaining at the same time the quality level of the refined fibrous material fulfilling demands set in view of quality of a final product. Numerous requirements concerning on the refining may, in turn, often result in complex control applications in the refining section.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a novel refining segment for a refiner for refining fibrous material, as well as a novel refiner for refining fibrous material.

The invention is based on the idea of recirculating a portion of the fibrous material to be refined through a space arranged on a backside of the refining segment.

An advantage of the invention is an additional way to affect the pressure prevailing over the refiner in operation, which in turn, may make control of several series-connected refiners easier. Additionally, the recirculation of the fibrous material over the backside of the refining also prevents the fibrous material having unintentionally entered on the backside of the refining segment to accumulate or be trapped therein.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following the invention will be described in greater detail by means of preferred embodiments with reference to the accompanying drawings.

FIG. 1 is a schematic general side view of a disc refiner in cross-section.

FIG. 2 is a schematic front view of a refining segment for a disc refiner.

FIG. 3 is a schematic background view of the refining segment of FIG. 2.

FIG. 4 is a schematic cross-sectional view of the refining segment of FIGS. 2 and 3.

For the sake of clarity, the figures show some embodiments of the invention in a simplified manner. Like reference numerals identify like elements in the figures.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a schematic side view of a general construction of a refiner 1 in cross-section, which refiner 1 may be used for refining a fibrous material, such as a wood material containing lignocellulose or another fiber material suitable to be used for manufacturing paper or paperboard, for example. The refiner 1 shown in FIG. 1 is a disc refiner but conical refiners, conical-disc-refiners and cylindrical refiners could be used as well as an example here. Generally, a refiner comprises at least two substantially oppositely positioned refining elements at least one of which is rotating, and a refining gap formed between each two substantially oppositely positioned refining elements. In the following a refiner with only one rotatable refining element is described.

The refiner 1 of FIG. 1 comprises a frame 2 and a stationary, fixed refining element 3, i.e., a stator 3, supported on the frame 2. The stator 3 comprises two or more stator refining segments 4, each of them comprising blade bars and blade grooves therebetween. The blade bars and the blade grooves in each stator refining segment 4 form a refining surface 5 of the respective refining segment 4, the refining surface 5 of each stator refining segment 4 thereby providing a part of a refining surface of the stator 3. A complete refining surface of the stator 3 is formed of the refining surfaces 5 of a necessary number of the stator refining segments 4 fastened next to each other in the stator 3 so that the complete refining surface 5 extending over the whole circumference of the stator 3 is provided. For the sake of clarity, both the refining surface of each single stator refining segment 4 as well as the complete refining surface of the stator 3 are herein denoted with the same reference sign 5.

The refiner 1 further comprises a rotatable refining element 6, i.e., a rotor 6 of the refiner 1. The rotor 6 comprises a rotor frame 7. The rotor 6 further comprises two or more rotor refining segments 8 supported to the rotor frame 7, each rotor refining segment 8 comprising blade bars and blade grooves therebetween. The blade bars and the blade grooves in each rotor refining segment 8 form a refining surface 9 of the respective refining segment 8, the refining surface 9 of each rotor refining segment 8 thereby providing a part of a refining surface of the rotor 6. A complete refining surface of the rotor 6 is formed of the refining surfaces 9 of a necessary number of the rotor refining segments 8 fastened next to each other in the rotor 6 so that the complete refining surface 9 extending over the whole circumference of the rotor 6 is provided. For the sake of clarity, both the refining surface of each single rotor refining segment 8 as well as the complete refining surface of the rotor 6 are herein denoted with the same reference sign 9.

The rotor frame 7 is connected to a driving motor 10 by a shaft 11 so that the rotor 6 can be rotated relative to the stator 3 in a direction of arrow RD, for instance, the arrow RD thus indicating an intended rotation direction RD of the rotor 6.

The refiner 1 may also comprise a loading device which, for the sake of clarity, is not shown in FIG. 1. The loading device can be used for moving back and forth the rotor 6 attached to the shaft 11, as schematically shown by arrow S, to adjust a size of a refining gap 12 between the stator 3 and the rotor 6, wherein the fibrous material is refined. In some other types of refiners, the loading device can be used for moving the stator as well.

The fibrous material to be refined is fed into the refiner 1, into the refining gap 12 therein, via a feed channel 13 in a manner shown by arrow F. The material refined is removed via a discharge channel 14 from the refiner 1, as schematically shown by arrow D. The fibrous material to be refined is fed into the refiner 1 in a form of pulp suspension being a mixture comprising at least water and virgin fibrous material and/or recycled fibrous material. The consistency of the fibrous material to be refined is typically between 3-40%.

FIG. 2 is a schematic front view of a refining segment 4, 8 applicable to be used for forming a part of the refining surface 5, 9 of the stator 3 or the rotor 6 of a disc refiner 1, whereby the complete refining surfaces 5, 9 in the stator 3 and the rotor 6 are provided by arranging necessary number of the refining segments 4, 8 of FIG. 2 next to each other around a circumference of the stator 3 or the rotor 6. FIG. 3 is a schematic background view of the refining segment of FIG. 2 and FIG. 4 is a schematic cross-sectional view of the refining segment of FIGS. 2 and 3 along a line B-B in FIG. 3. The refining surface 5, 9 of the refining segment 4, 8 is omitted in FIG. 4.

The refining segment 4, 8 comprises an inner end edge 15 or a first end edge 15 being intended to be directed towards an inner periphery of the stator 3 or the rotor 6. The refining segment 4, 8 further comprises an outer end edge 16 or a second end edge 16 opposite to the inner end edge 15 in a longitudinal direction of the refining segment 4, 8, the outer end edge 16 being intended to be directed towards an outer periphery of the stator 3 or the rotor 6. The refining segment 4, 8 further comprises a first side edge 17 extending from the inner end edge 15 of the refining segment 4, 8 up to the outer end edge 16 of the refining segment 4, 8. The refining segment 4, 8 further comprises a second side edge 18 opposite to the first side edge 17 in a circumferential direction of the refining segment 4, 8. The second side edge 18 extends from the inner end edge 15 of the refining segment 4, 8 up to the outer end edge 18 of the refining segment 4, 8. The inner 15 and the outer 16 end edges together with the first 17 and second 18 side edges contribute to define a periphery 19 of the refining segment 4, 8. In conical refiners, typically, the radially . . . smaller end of the stator/rotor is considered to refer to the inner periphery of the stator/rotor and the radially larger end of the stator/rotor is considered to refer to the outer periphery of the stator/rotor.

The refining segment 4, 8 has a longitudinal direction or a longitudinal axis extending between the inner end edge 16 and the outer end edge 17. The longitudinal direction or the longitudinal axis of the refining segment 4, 8 is denoted schematically in FIGS. 2 and 3 with the arrow X shown, for the sake of clarity, on the left side of the refining segment 4, 8. The longitudinal axis X of the refining segment 4, 8 also implies a radial direction of the refining segment for a refining segment intended to a disc refiner and an axial direction of the refining segment for a refining segment intended to a conical refiner or a cylindrical refiner. The direction of the refining segment 4, 8 perpendicular to the longitudinal axis X of the refining segment 4, 8 is a circumferential direction or a transverse axis of the refining segment 4, 8. The circumferential direction or the transverse axis of the refining segment 4, 8 is denoted schematically in FIG. 2 with the arrow C shown, for the sake of clarity, below the refining segment 4, 8.

The refining segment 4, 8 comprises a body 20 or a substrate 20 having a front 21, i.e., a front side 21, to be directed towards the refining gap 12 of the refiner 1 and a backside 22 comprising a background surface 23 to be directed towards the frame 2 of the refiner 1 in case of the stator refining segment 4 or towards the frame 7 of the rotor 6 in case of the rotor refining segment 8. The front side 21 of the refining segment body 20 is provided with blade bars 24 and blade grooves 25 between the blade bars 24, the blade bars 24 and the blade grooves 25 together providing the refining surface 5, 9 of the refining segment 4, 8. The blade bars 24 are intended to defiber and refine the material to be refined and the blade grooves 25 are intended to convey the material to be refined between the blade bars 24 forward along the refining surface 5, 9. The refining surface 5, 9 of the refining segment 4, 8 further comprises feed grooves 26 extending from the inner end edge 15 of the refining segment 4, 8 towards the outer end edge 16 of the refining segment 4, 8 for feeding or distributing the material to be refined on the refining surface 5, 9. The refining segment 4, 8 may further comprise one or more fastening holes 27 extending through the refining segment body 20 and intended to receive proper fastening members 28, such as bolts, for fastening the respective refining segment 4, 8 to the frame 2 of the refiner 1 or to the frame 7 of the rotor 6. The one or more fastening holes 27 are typically located at a center part of the refining segment 4, 8, a distance apart from the end 15, 16 and side 17, 18 edges of the refining segment 4, 8.

The refining surface 5, 9 of the refining segment 4, 8 is shown in FIG. 2 for a purpose of exemplary illustration only. The actual implementation of the refining surface 5, 9 may vary in many ways.

If the refining segments 4, 8 are fastened to the stator 3 and/or the rotor 6 in some other manner, for example with fasteners adapted to fix to the refining segment 4, 8 at the side edges 17, 18 thereof, the fastening holes 27 in the refining segment 4, 8 may be omitted. In that case the refining segment 4, 8 of FIGS. 2 to 4 would not comprise the fastening holes 27 now being shown therein.

The refining segment 4, 8 further comprises on the background surface 23 of the refining segment 4, 8 support projections 29, 30 projecting from the background surface 23 of the refining segment 4, 8. The support projections 29, 30 extend at the first 17 and second 18 side edge of the refining segment 4, 8 substantially along the first side edge 17 and the second side edge 18. Thus, the refining segment 4, 8 comprises on the periphery 19 of the refining segment 4, 8 a first support projection 29 extending at the first side edge 17 on the background surface 23 substantially along the first side edge 17 of the refining segment 4, 8 and a second support projection 30 extending at the second side edge 18 on the background surface 23 substantially along the second side edge 18 of the refining segment 4, 8 but does not comprise support projections substantially extending along the first 15 and the second 16 end edges on the background surface 23 of the refining segment 4, 8. The support projections 29, 30 do not substantially extend at the first end edge 15 or at the second end edge 16 along the respective end edges 15, 16 of the refining segment 4, 8, i.e., they extend at the first end edge 15 or at the second end edge 16 along the respective end edges 15, 16 of the refining segment 4, 8 substantially only a measure of their dimension in the circumferential direction C of the refining segment 4, 8.

The first support projection 29 and the second support projection 30 shown in the embodiment of FIGS. 3 and 4 are thus elongated support projections 29, 30 extending substantially along the side edges 17, 18 of the refining segment 4, 8 on the background surface 23 of the body 20 of the refining segment 4, 8. Because there are no support projections substantially extending along the end edges 15, 16 of the refining segment 4, 8, the background surface 23 of the body 20 of the refining segment 4, 8 is substantially free from the support projections on the periphery 19 of the refining segment 4, 8 at the first end edge 15 and the second end edge 16.

The support projections 29, 30 are intended to support the refining segment 4, 8 to the frame 2 of the refiner 1 in case of the stator refining segment 4 or to the frame 7 of the rotor 6 in case of the rotor refining segment 8 such that there is some free volume between the background surface 23 of the refining segment 4 and the frame 2 of the refiner 1 or between the background surface 23 of the refining segment 8 and the frame 7 of the rotor 6 at the center part of the refining segment 4, 8 between the support projections 29, 30. A surface of the frame 2 of the refiner 1 or a surface of the frame 7 of the rotor 6 is schematically illustrated in FIG. 4 with the broken line denoted with the reference signs 2′, 7′. The first 29 and the second 30 support projections at the side edges 17, 18 of the refining segment 4, 8 thus form, together with the first 15 and the second 16 end edges of the refining segment 4, 8 being substantially free from the support projections, an open flow space 32 extending in the longitudinal direction X of the refining segment 4, 8 between the inner end edge 15 and the outer end edge 16 of the refining segment 4, 8 on the backside 22 of the refining segment 4, 8. The open flow space 32 on the side of the background surface 23 of the refining segment 4, 8 provides a volume or a flow channel, wherein a portion of the fibrous material to be refined and intended to enter or having entered on the backside 22 of the refining segment 4, 8 may freely flow back towards the inner periphery of the stator 3/rotor 6, as shown schematically in FIG. 3 with the arrows denoted with the reference sign BF.

The flow space 32 on the side of the background surface 23 of the refining segment 4, 8 allows an intentional backside recirculation for a portion of the fibrous material to be refined from the outer periphery of the stator 3/rotor 6 towards the inner periphery of the stator 3/rotor 6. Because there is typically pressure increase over the refiner, i.e., pressure increase from the feed of refiner to the outlet of the refiner, this recirculation of the fibrous material may be applied especially in the stator 3 of the refiner 1 to reduce the pressure build-up in the refiner 1, that further allowing several large refiners 1 to be operated in series without a risk of creating too high pressure. This backside recirculation means also that there is no need for an external recirculation line. This backside recirculation is also self-regulating, i.e., no separate control applications are needed to implement that.

The open flow space 32 on the side of the background surface 23 of the body 20 of the refining segment 4, 8, and especially the recirculation of the fibrous material on the backside of the refining segments 4, 8 provides an exchange of the fibrous material on the backside 22 of the refining segments 4, 8 which also prevents the fibrous material having unintentionally entered on the backside 22 of the refining segment 4, 8 to accumulate or be trapped therein. This accumulating or trapping of the fibrous material could possibly cause instability in the rotation of the rotor 6, and therefore applying the disclosed recirculation in the rotor 6 too is also advantageous.

Over time, the accumulated or trapped fibrous material would possibly start to decay or become rotten. By the continuous exchange of the fibrous material on the backside 22 of the refining segments 4, 8 also events are prevented wherein the possibly rotten fibrous material becoming loose from the backside 22 of the refining segment 4, 8 would enter among the fibrous material to be refined and deteriorate the cleanliness of the final product or cause color defects therein. By this way, the hygiene or other quality of the final product may be improved, this being especially important for paper grades with high bacteriological cleanliness requirements.

In addition to the refining segment 4, 8 being substantially free from the support projections on the periphery of the refining segment 4, 8 at the first end edge 15 and the second end edge 16 of the refining segment 4, 8, the background surface 23 of the refining segment 4, 8 disclosed is also free from any support projections that would extend in the circumferential direction C of the refining segment 4, 8 between the first 29 and second 30 support projections and would reach up to the first 29 and second 30 support projections that extend along the first side edge 17 and the second side edge 18 of the refining segment 4, 8. This provides a large uninterrupted flow space 32 on the backside 22 of the refining segment 4, 8.

According to an embodiment of the refining segment 4, 8, following the embodiment shown in FIG. 3, the support projections 29, 30 at the first side edge 17 and the second side edge 18 of the refining segment 4, 8 are arranged to extend from the first end edge 15 of the refining segment 4, 8 towards the second end edge 16 of the refining segment 4, 8 substantially unbrokenly. The substantially unbroken elongated structure of the support projections 29, 30 has the effect that the refining segment 4, 8 can be supported very rigidly to the stator 3 and/or to the rotor 6. Another effect of the substantially unbroken elongated structure of the support projections 29, 30 is the prevention of the flow of the recirculating fibrous material along the circumferential direction C from one refining segment 4, 8 to a neighboring refining segment 4, 8, what could disturb the recirculation of the fibrous material.

Furthermore, in the embodiment of the refining segment 4, 8 of FIG. 3, the support projections 29, 30 are not arranged to extend from the first end edge 15 of the refining segment 4, 8 up to the second end edge 16 of the refining segment 4, 8. With this kind of support projection 29, 30 dimensioning a weight of the refining segment 4, 8 may be reduced without substantially affecting negatively the rigidity of the side edge area of the refining segment 4, 8. Less weight of the refining segment 4, 8 means lower manufacturing and freight costs as well as it is easier to assemble.

According to an embodiment of the refining segment 4, 8, the support projections 29, 30 at the first side edge 17 of the refining segment 4, 8 and the second side edge 18 of the refining segment 4, 8 are arranged to extend from the first end edge 15 of the refining segment 4, 8 up to the second end edge 16 of the refining segment 4, 8 substantially unbrokenly. With this kind of support projection 29, 30 dimensioning the rigidity of the side edge areas of the refining segment 4, 8 may still be increased. This kind of the support projection 29, 30 dimensioning may be especially useful in the stator 3 of the refiner 1, because it effectively guides the recirculating portion of the fibrous material to the backside 22 of the refining segments 4, 8, without allowing the recirculating portion of the fibrous material to flow in the circumferential direction C in an excessive manner. The refining segment 4, 8 of FIG. 3 may be modified to present this kind of embodiment by lengthening the support projections 29, 30 to reach up to the second end edge 16 of the refining segment 4, 8.

According to an embodiment of the refining segment 4, 8, the refining segment 4, 8 comprises at least one fastening hole 27 extending through the refining segment body 20 and intended to receive a fastening member 28 intended to fasten the refining segment 4, 8 in the refiner 1, and furthermore the refining segment 4, 8 comprises on the background surface 23 of the refining segment 4, 8 at least one auxiliary support projection 31 projecting from the background surface 23 around each fastening hole 27. The embodiment like this is shown schematically in FIGS. 3 and 4, wherein each fastening hole 27 is surrounded by the auxiliary support projection 31 projecting from the background surface 23 of the refining segment 4, 8. This auxiliary support projection 31 provides an additional support for the refining segment 4, 8 at the center part thereof when the refining segment 4, 8 is fastened to the stator 3 or to the rotor 6, thereby increasing the rigidity of the refining segment 4, 8 fastened to the stator 3 or to the rotor 6. The number of the fastening holes 27 in the refining segment 4, 8 may vary but typically the number of the fastening holes 27 is so limited that the auxiliary support projections 31 do not substantially decrease the volume of the flow space 32.

Preferably the auxiliary support projection 31 is an unbroken circumferential projection around the fastening hole 27, as shown in the embodiment of FIG. 3, whereby the auxiliary support projection 31 also forms a kind of an additional sealing at the fastening hole 27 for preventing the fibrous material to flow from the backside 22 of the refining segment 4, 8 to the front side 21 of the refining segment 4, 8 through the fastening hole 27, or vice versa.

The unbroken circumferential form of the auxiliary support projection 31 around the fastening hole 27 may have a variety of cross-sectional shapes but the annular shape of the auxiliary support projection 31 is preferable in view of minimizing disturbances in the flow of the fibrous material portion recirculating through the flow space 32.

According to an embodiment of the refining segment 4, 8, the support projections 29, 30 and/or the auxiliary support projections 31 are uniform parts of the body 20 of the refining segment 4, 8 on the background surface 23 of the refining segment 4, 8. The support projection 29, 30 and/or the auxiliary support projection 31 being a uniform part of the body 20 of the refining segment 4, 8 is easy to manufacture at the same time when the refining segment 4, 8 is manufactured by casting or 3D-printing manufacturing methods. The support projections 29, 30 and/or the auxiliary support projections 31 could, however, be also originally separate parts that may be fastened to the body 20 of the refining segment 4, 8 by welding or soldering, for example.

It is emphasized that in addition to the disc refiner disclosed above the refining segment of the solution described may be applied in other kinds of disc refiners too. In addition to the disc refiners the refining segment of the solution described herein is applicable to conical refiners and cylindrical refiners and to refiners comprising both a conical portion and a disc portion, as well.

It will be obvious to a person skilled in the art that, as the technology advances, the inventive concept can be implemented in various ways. The invention and its embodiments are not limited to the examples described above but may vary within the scope of the claims.

Claims

1-10. (canceled)

11. A refining segment for a refiner for refining fibrous material, the refining segment comprising: a body comprising a front side and a backside, the front side comprising a refining surface and the backside comprising a background surface, wherein the body has a first end edge and a second end edge opposite to the first end edge, and a first side edge and a second side edge opposite to the first side edge, the first side edge and the second side edge extending between the first end edge and the second end edge; andsupport projections projecting from the background surface and extending on the background surface substantially along the first side edge and the second side edge without comprising support projections extending substantially along the first end edge and the second end edge on the background surface, wherein an open flow space is defined between the support projections extending along the first side edge and the second side edge.

12. The refining segment of claim 1 wherein the background surface of the refining segment is substantially free from support projections at the first end edge and the second end edge on the background surface.

13. The refining segment of claim 1 wherein the background surface of the refining segment is free from any support projections extending between and up to the support projections extending along the first side edge and the second side edge.

14. The refining segment of claim 1 wherein the support projections are elongated projections extending along the side edges of the refining segment.

15. The refining segment of claim 1 wherein the support projections at the first side edge and the second side edge are arranged to extend from the first end edge towards the second end edge substantially unbrokenly.

16. The refining segment of claim 15 wherein the support projections at the first side edge and the second side edge terminate at a position spaced from the second end edge.

17. The refining segment of claim 15 wherein the support projections at the first side edge and the second side edge are arranged to extend from the first end edge up to the second end edge.

18. The refining segment of claim 1 further comprising: portions of the body defining at least one fastening hole extending through the body of the refining segment and positioned to receive a fastening member extending therethrough for fastening the refining segment in the refiner; andat least one auxiliary support projection projecting from the background surface away from the refining surface, and wherein each fastening hole extends through and is surrounded by one of the at least one auxiliary support projections.

19. The refining segment of claim 18, wherein each auxiliary support projection is an unbroken circumferential projection around the fastening hole which it surrounds.

20. The refining segment of claim 18 wherein the support projections (29, 30) and the at least one auxiliary support projection are uniform parts of the body of the refining segment.

21. A refining segment of claim 1 further comprising a refiner within which the refining segment is fixed.

22. A refining segment for a refiner for refining fibrous material, the refining segment comprising: a body comprising a front side and a backside, the front side comprising a refining surface and the backside comprising a background surface, wherein the body has a first end edge and a second end edge opposite to the first end edge, and a first side edge and a second side edge opposite to the first side edge, the first side edge and the second side edge extending between the first end edge and the second end edge;a first support projection projecting from the background surface and extending on the background surface substantially along the first side edge;a second support projection projecting from the background surface and extending on the background surface substantially along the second side edge, wherein an open flow space extending in a longitudinal direction is defining permitting flow of fluid containing fibrous material from the first end edge of the background surface to the second end edge of the background surface; andan auxiliary support projection projecting from the background surface away from the refining surface and positioned between the first support projection and the second support projection, wherein a fastening hole extends through the body of the refining segment and the auxiliary support projection and is positioned to receive a fastening member extending therethrough for fastening the refining segment in the refiner.

23. The refining segment of claim 22 wherein the background surface of the refining segment is substantially free from support projections at the first end edge and the second end edge on the background surface.

24. The refining segment of claim 22 wherein the support projections at the first side edge and the second side edge are arranged to extend from the first end edge towards the second end edge substantially unbrokenly.

25. The refining segment of claim 24 wherein the support projections at the first side edge and the second side edge terminate at a position spaced from the second end edge.

26. The refining segment of claim 24 wherein the support projections at the first side edge and the second side edge are arranged to extend from the first end edge up to the second end edge.

27. The refining segment of claim 22, wherein the auxiliary support projection is an unbroken circumferential projection around the fastening hole which it surrounds.

28. The refining segment of claim 22 wherein the support projections and the at least one auxiliary support projection are uniform parts of the body of the refining segment.

29. A refining assembly having a plurality of refining segments mounted to a refining element for a refiner for refining fibrous material, wherein each refining segment comprises: a body comprising a front side and a backside, the front side comprising a refining surface and the backside comprising a background surface, wherein the body has a first end edge and a second end edge opposite to the first end edge, and a first side edge and a second side edge opposite to the first side edge, the first side edge and the second side edge extending between the first end edge and the second end edge;support projections projecting from the background surface and extending on the background surface substantially along the first side edge and the second side edge without comprising support projections extending substantially along the first end edge and the second end edge on the background surface, the support projections engaging the refining element; andwherein the plurality of refining segments are fixed to the refining element by a plurality of fasteners, and wherein a plurality of open flow spaces are defined between the refining segments and the refining element for the flow of fluid containing fibrous material therethrough in a longitudinal direction.