Abrading element and abrading device for a refiner

Abstract

The utility model relates to a kind of grinding elements (2) for precision grinder, the grinding element has multiple grinding strips (21) and multiple grooves (22) extending between these grinding strips (21), and wherein, some of these grinding strips (21) split radially outward in split section (26), and these grinding strips (21) have the thickness less than the thickness outside the split section (26) at least in one section within split area (26) after splitting (27). The utility model relates to grinding device.

Description

Technical Field

[0001] This utility model relates to a grinding plate with grinding surfaces for grinding aqueous suspensions, preferably for grinding suspended pulp fibers between two grinding surfaces that rotate relative to each other and form a grinding gap. The grinding surfaces consist of a plurality of grinding strips and a plurality of grooves extending between these grinding strips. Background Technology

[0002] It has long been known to impart desired properties, particularly in terms of strength, formability and surface properties, to fiber webs made from pulp fibers, i.e. virgin pulp and / or waste pulp fibers, by milling them.

[0003] In the precision grinding mills used, due to relatively rapid wear, the grinding surface consists of replaceable grinding plates, also known as grinding accessories, that are bolted to the corresponding support surfaces.

[0004] To achieve the desired fiber properties, especially the degree of abrasion, the abrasion accessories must be optimally matched with the fiber material to be treated, while avoiding excessive wear of the accessories.

[0005] Document EP 2 722 433 illustrates an abrasive plate or abrasive plate segment having grooves and connecting strips. The grooves of the abrasive plate segment of the abrasive plate are either substantially completely closed by the full-height retaining strips or partially closed by the full-height retaining strips. In some embodiments, the retaining strips are arranged only in the radially outer region between the abrasive strips.

[0006] Document EP 1 670 592 B1 discloses a segmented grinding plate with grinding strips. The grinding strips are radially oriented. Therefore, the grinding plate segment can be used independently of the direction of rotation, and the direction of rotation can be changed during operation.

[0007] Documents EP 4 063 561 and EP 3 450 624 show an abrasive plate with baffles. The baffles are arranged at an angle relative to the abrasive strips so that the generated steam can return radially inward. For steam to pass through, recesses are provided so that the steam can flow radially inward within the abrasive surface without entering the gaps formed between the abrasive surfaces. Utility Model Content

[0008] The technical problem to be solved by this invention is to improve fiber processing efficiency.

[0009] The technical problem described herein is solved by a grinding element for a fine grinding mill, the grinding element having a plurality of grinding strips and a plurality of grooves extending between these grinding strips, wherein some of these grinding strips are radially outwardly split in a split section, wherein, after splitting, these grinding strips have a circumferential thickness in at least one segment within the split region that is less than the thickness outside the split section.

[0010] The technical problem described herein is also solved by a grinding device for grinding aqueous suspended pulp fibers between two grinding surfaces that form a grinding gap and rotate relative to each other, wherein at least one of these grinding surfaces has a grinding element of the aforementioned type, wherein a baffle and a grinding strip have obtuse angles on the radially inner side for forming a processing edge on the baffle so that the suspension flows in by the relative movement of the grinding surfaces.

[0011] The technical problem described herein is also solved by a grinding device for grinding water-based suspended pulp fibers between two grinding surfaces that form a grinding gap and rotate relative to each other, wherein at least one, preferably two, of these grinding surfaces has a grinding element of the type described above.

[0012] By taking measures, the abrasive strip of the abrasive element has a smaller circumferential thickness in at least one segment within the splitting section than outside the splitting section, allowing the fibers to be processed by the abrasive element with a smaller thickness. This improves the efficiency of the abrasive element.

[0013] In a preferred embodiment, the thickness of these abrasive strips is reduced by at least 15% after splitting. Particularly preferably, the abrasive strips are reduced in thickness by at least 20% and up to a maximum of 30% after splitting. Particularly preferably, the thickness is reduced directly by 25% after splitting. Thus, the abrasive strips have sufficient stability under load and provide additional treatment of the fiber suspension using abrasive strips with a smaller thickness.

[0014] In a preferred embodiment, the abrasive element has multiple perforations for fixing in the abrasive apparatus. The abrasive element is subject to wear and must be replaced periodically. Typically, multiple perforations for fixing are provided in the abrasive element. However, it has been shown that the abrasive strip adjacent to the perforations may withstand higher loads. To provide a particularly robust abrasive element, it has proven particularly advantageous to design the abrasive strip, constructed circumferentially adjacent to these perforations, to be thickened. The thickened abrasive strip design has a greater circumferential thickness. Thus, the abrasive strip can withstand higher loads in this area.

[0015] In the preferred embodiment, the thickened or reinforced abrasive strip is the portion of the split section before splitting. This allows for optimal utilization of the geometry of the abrasive element's abrasive surface. The reinforced section of the abrasive strip can then be split. This arrangement facilitates a dense arrangement of abrasive strips, making this abrasive element particularly efficient.

[0016] In one embodiment, multiple baffles are constructed between circumferentially adjacent grinding strips. These baffles convey the suspension flowing in the grooves into the grinding gaps. Thus, the baffles help improve the treatment of the suspension. It is particularly preferred that the baffles be positioned in the radially outer region to better mix the suspension from the grooves and the suspension flowing in the gaps, which promotes more uniform treatment of the suspension.

[0017] The grinding element is particularly suitable for LC grinding: LC grinding refers to the processing of suspensions with a concentration in the range of 3% to 6% by weight.

[0018] It has proven particularly advantageous to incorporate grinding elements with baffles in the stator of the grinding apparatus. These baffles allow for the control and / or reduction of backflow. This is especially beneficial for power loss / no-load power.

[0019] In a preferred embodiment, the grinding strips are arranged extending purely radially outside the split section. This allows the grinding elements to be used regardless of the direction of rotation. If the grinding elements are manufactured by casting, the number of casting molds required is reduced, which is advantageous for manufacturing costs. Warehousing management is also simplified due to the reduced number of variations.

[0020] In a preferred embodiment, the abrasive strips within the splitting section have a smaller circumferential thickness over at least 1 / 3, preferably 2 / 3, of the length of the split portion within the splitting section. This allows the grooves between the thinned abrasive strips to reach the groove width outside the splitting region, which has a favorable effect on flow characteristics.

[0021] In the preferred embodiment, the grooves outside the split section have a uniform circumferential width. The groove design has a minimum groove width. If the groove width is smaller, the risk of clogging increases. If the groove is wider than needed, the edge length is reduced, thereby decreasing the processing efficiency. The goal is to maximize the edge length under stable operating conditions.

[0022] In the preferred embodiment, the grinding strips outside the split section are designed to have the same thickness.

[0023] In a preferred embodiment, multiple baffles are provided within multiple grooves, preferably in the radially outer region at 2 / 3 of the radial extension dimension of the grinding element. This improves the fiber processing effect. The baffles optimize the hydraulic capacity. It has been shown that when the height of the processing element decreases, the flow direction in the stator may change from countercurrent to cocurrent. This cocurrent flow can be prevented by providing baffles in the grooves.

[0024] On the other hand, it may be necessary to appropriately increase the hydraulic capacity in the radially inner region in order to deliver as much suspension as possible to the grinding device.

[0025] The hydraulic capacity of the grinding surface typically deteriorates with increased wear, and the grinding element may need to be removed prematurely due to insufficient capacity. By significantly increasing the height of the grinding strip in the radially inner region, the open area of ​​the inner region is expanded. This increases the hydraulic capacity and extends service life.

[0026] The grinding strips and stop bars are called processing elements. The reduction in height is due to wear.

[0027] Particularly preferred is that adjacent extending abrasive strips are connected by the stop strip. The stop strip thus helps to enhance the stability of the abrasive surface.

[0028] In a preferred embodiment, an obtuse angle is provided radially inward at the connection point between the baffle and the abrasive strip on the radially inner side. Thus, the baffle can function as an abrasive strip and also treat the fibers in the fiber suspension. This further contributes to the efficiency of the abrasive element.

[0029] A grinding apparatus for grinding aqueous suspended pulp fibers between two grinding surfaces forming a grinding gap and rotating relative to each other. At least one of these grinding surfaces has at least one of the aforementioned grinding elements.

[0030] In the grinding apparatus, preferably at least one grinding surface is provided with a baffle. The baffle is connected to the grinding strip at an obtuse angle on its radially inner side to form a processing edge. The suspension flows from the obtuse angle side of the baffle and is processed through the boundary edge of the baffle. This inclined orientation of the baffle improves the efficiency of the grinding apparatus because, in addition to the grinding strip, the baffle also functions as a processing element.

[0031] In a preferred embodiment, the grinding strip is configured with an axial extension dimension that is 15%, preferably 25%, larger on the radially inner side than on the radially outer side. Preferably, the variation in the axial extension dimension of the grinding strip does not exceed 25% of the axial extension dimension of the grinding strip in the radially outer region. The height of the grinding strip increases gradually. The height of the grinding strip starting from the radially inner side is considered to be after reaching the maximum height, i.e., after the end of the slope starting from the radially inner side. The radially outer side refers to the range from the radially outer end of the grinding strip to the radially inner side -5%. By changing the height of the grinding strip, the capacity of the grinding surface in the inner region can be increased. Even under wear conditions, this will have a positive impact on the usability of the grinding accessories.

[0032] The flow direction of the suspension is determined by the relative motion of the grinding surfaces, and it always has a flow component towards the radially outward side when being conveyed towards the radially inward side. Attached Figure Description

[0033] The present invention will now be described in conjunction with the accompanying drawings. In the drawings:

[0034] Figure 1 A cross-sectional schematic diagram of the grinding device is shown.

[0035] Figure 2 The image shows a segment of an abrasive plate with baffles in the radially outer region.

[0036] Figure 3 A partial view of the segments of the grinding plate is shown.

[0037] Figure 4 A detailed diagram of the split region is shown.

[0038] Figure 5 The diagram shows segments of a grinding plate with notches for fixing.

[0039] Figure 6 Showing the grinding strip, and

[0040] Figure 7 The image shows an overlay of the grinding surfaces. Detailed Implementation

[0041] Figure 1 A grinding apparatus 1 is shown. In this grinding apparatus 1, the grinding gap 3 is composed of a stationary grinding surface 4 coupled to the housing and a grinding surface 4 rotating about a rotation axis 10. This grinding apparatus for processing fiber-containing suspensions is also known as a fine grinding mill, especially for the preparation of pulp fibers.

[0042] Here, two annular grinding surfaces 4 extend parallel to each other, and the distance between the grinding surfaces 4 is usually adjustable. In addition to the flat grinding surfaces 4 shown here, conical grinding surfaces, called processing surfaces, can also be used. The rotating grinding surfaces 4 are moved in the direction of rotation by a shaft 10 rotatably supported within the housing, and this shaft 10 is driven by a drive device not shown.

[0043] In the illustrated embodiment, the fiber suspension 1 to be ground enters the grinding gap 3 between the two grinding surfaces 4 through the center via the feed port. Alternatively, it can be fed in through openings in the grinding surfaces. The fiber suspension S passes radially outward through the cooperating grinding surfaces 4 and is discharged from the annular chamber through the discharge port 6.

[0044] Not shown are known devices for generating pressure to press the two grinding surfaces 4 together. The two grinding surfaces 4 are each composed of multiple... Figure 2 The fan-shaped or annular grinding portion 8 shown is formed as a grinding element. However, a grinding surface 4 can also be formed using a single grinding element 2. The grinding element 2 has a substrate 18. Processing elements 20 are provided on the substrate, here consisting of a grinding strip 21 and a baffle 23. (See attached...) Figure 2 As shown, the baffle 23 constructed between the grinding strips 21 is disposed in the radially outer region.

[0045] The grinding portions 8 extend circumferentially and are arranged side by side axially. Each grinding portion 8 is formed from a substrate 18, which has a plurality of processing elements 20 and grooves 22 located therebetween. Grinding strips 21 and baffles 23 are provided as processing elements 20.

[0046] The grinding strip 21, which is parallel to the substrate 18, has a longitudinal cross-sectional shape, wherein the top surface of the grinding strip 21 facing the processing gap 3 generally extends parallel to the outer surface of the substrate 18.

[0047] according to Figure 3 The splitting section 26 is described in more detail below. Radially inward of the split point 27, the splitting section 26 has a thickened abrasive strip in region 28. After splitting into two abrasive strips 21, the abrasive strips 21 gradually taper in a local region 29 of the section after splitting 27. Outside the splitting section 26, the abrasive strips 21 are designed to have the same thickness. The groove 22 has a constant diameter outside the splitting section. In the radially outer region, approximately two-thirds of the outer abrasive surface, a plurality of baffles 23 are provided in the groove 22. The baffles 23 are connected to adjacent abrasive strips 21. The baffles are angularly oriented relative to the abrasive strips and have an obtuse angle 24 radially inward. The orientation of the baffles 23 depends on the flow direction of the suspension within the abrasive gap 3. The suspension flows towards the radially inward-pointing boundary edge of the baffle 23. This boundary edge of the baffle thus serves as a processing edge 25 and contributes to processing efficiency. Because the baffle 23 is inclined to provide a surface for the edge 25, the grinding element is preferably used in accordance with the rotation direction by means of the baffle orientation. In a double-disc grinding mill, when the grinding surfaces of the rotor 16 are axially arranged between the grinding surfaces of the stator 17, grinding elements with baffles 23 having different orientations are required. If the baffle 23 is not provided and the grinding strip 21 extends radially ±5°, the grinding element 2 can be used regardless of the rotation direction while maintaining constant efficiency.

[0048] Figure 4 The split section is shown magnified. The groove 22 extends radially inward in region 31 after split 27, specifically increasing the edge length of the provided abrasive strip 21. The thickness 30 of the abrasive strip 21 decreases during the same process, but because the connection of the abrasive strip 21 before split 27 enhances the mechanical strength of the abrasive strip in this region, the smaller thickness of the abrasive strip 21 in region 29 does not result in a loss of load-bearing capacity.

[0049] Figure 5 A grinding section with perforations 35 for fixing in the grinding apparatus 1 is shown. Adjacent to the perforations 35 in the circumferential direction, the grinding strip 21 is provided with a thickened region 28, which is part of the split section 26.

[0050] Optimization of edge length:

[0051] The arrangement of the retaining bars 23 actually has the disadvantage of reducing the cutting edge length of the grinding strips 21. To compensate for this loss, and even increase the cutting edge length, these retaining bars 23 are oriented such that the retaining bars 23 of the stator 17 and the grinding strips 21 of the rotor 16 form a desired intersection angle. The relative movement between the rotor 16 and the stator 17 causes the intersection angle between the grinding strips 21 of the rotor 16 and the retaining bars 23 of the stator to close in the inner diameter direction. Therefore, the retaining bars 23 perform the same function as the grinding strips of the stator.

[0052] Optimization of hydraulic capacity:

[0053] This indicates that when the height of the abrasive strip 21 decreases due to wear, the flow direction within the stator 17 may change from countercurrent to cocurrent. This cocurrent flow can be prevented by providing a baffle 23 to the abrasive element 2 of the stator 17, thus potentially limiting the hydraulic capacity at the end of its service life. For this reason, the internal area of ​​the stator 17 is not equipped with baffles 23 in the processing element for over-the-counter (OCC). Therefore, the suspension can flow in the conveying direction, which is particularly beneficial to capacity when the abrasive strip 21 is severely worn.

[0054] To increase hydraulic capacity, the angle of the grinding strips 21 is varied from rotor 16 to stator 17 for the grinding surface composed of grinding elements with a small intersection angle, such as 30-40°. For stator 17, the grinding strips 21 are arranged radially at 0° with a deviation of ±5°. The grinding strips 23 of rotor 16 are arranged at a predetermined radial angle, for example, 30° relative to the radial direction. Therefore, the pumping effect of the grinding surfaces of rotor 16 and stator 17 is improved.

[0055] By using a 0° orientation for the grinding strip 21 in the stator 17, casting molds can be saved. This solution for different grinding strip angles between the rotor and stator is applicable to different fittings of the rotor 16 and stator 17.

[0056] In the perforation 35, the laterally extending abrasive strip 21 is designed with a large thickness. This reduces damage caused by foreign matter / impurities in the suspension.

[0057] Figure 6 Abrasive strip 21 is shown. Abrasive strip 21 has an axially extending extension 31, also referred to as the height of the abrasive strip. This increases the volume of the groove 22 defined between the abrasive strips in that region. The abrasive element 2 has a uniform axial extension dimension. The gap width remains constant. The substrate 18 supporting the abrasive strip 21 is designed with a reduced thickness 19 in the radially inner region. The reduced thickness of the substrate 18 compensates for the larger extension dimension of the abrasive strip 21 in the inner region. This allows for better flow of the suspension in the radially inner region.

[0058] As wear intensifies, the hydraulic capacity of the grinding section typically deteriorates, potentially necessitating premature removal of the grinding element 2 due to insufficient hydraulic capacity. To increase hydraulic capacity, for example, when the remaining height of the grinding strip 21 in the radially outer third of the grinding element 2 is 2 mm, the open area in the inner region of the grinding element 2 can be increased by significantly increasing the height of the grinding strip 21 radially inward, for example, by increasing it by 1 mm to 3 mm, and particularly by 1.5 mm. The initial height of the grinding strip 21 in the radially outer region is typically 10 mm, 8 mm, or 6 mm. Therefore, with a continuous radial inward increase of 1.5 mm, when the height of the grinding strip 21 is 8 mm inside the outer radius, the initial result will be a height of 9.5 mm for the grinding strip 21.

[0059] Figure 7 The extension direction of the processing element 20 of the rotor and stator fittings is shown. The extension direction of the grinding strip of rotor 16 is shown in the foreground. The background shows the extension direction of the grinding strip 21 and the baffle 23 of stator 17. The processing elements facing each other in the gap and their interaction are caused by the relative positions of the processing elements relative to each other. The processing edges can be clearly seen here.

[0060] Explanation of reference numerals in the attached figures

[0061] 1 Grinding device

[0062] 2 Grinding elements

[0063] 3 Grinding gap

[0064] 4 Grinding surface

[0065] 5. Feed Inlet

[0066] 6. Discharge port

[0067] 8 Grinding section

[0068] 9. Axial extension dimension of grinding element

[0069] 10 Rotation axis

[0070] 16 rotors

[0071] 17 Stator

[0072] 18 substrate

[0073] 19. Axial reduction in thickness of the substrate

[0074] 20. Processing components (connecting strips, stop bars)

[0075] 21 Grinding strips

[0076] 22 Grooves

[0077] 23 stop bars

[0078] 24 Angle between the grinding strip and the stop strip

[0079] 25. Processing edges

[0080] 26 Split Sections

[0081] 27. Split

[0082] 28 Thickened area of ​​the grinding strip

[0083] 29. Area with tapered abrasive strips

[0084] Thickness of 30 grinding strips

[0085] 31. Axial extension dimension of the grinding strip

[0086] 32 obtuse angle

[0087] 35 perforations

[0088] S fiber suspension

Claims

1. A grinding element (2) for a fine grinding mill, said grinding element having a plurality of grinding strips (21) and a plurality of grooves (22) extending between these grinding strips (21), wherein, A portion of these abrasive strips (21) are radially outwardly split in a split section (26), characterized in that, after splitting (27), these abrasive strips (21) have a circumferential thickness in at least one segment within the split section (26) that is less than the thickness outside the split section (26).

2. The grinding element (2) according to claim 1, characterized in that, These abrasive strips (21) have a thickness reduced by at least 15% after splitting (27).

3. The grinding element (2) according to claim 1, characterized in that, The abrasive element has multiple perforations for fixing, wherein the abrasive strip (21) constructed circumferentially adjacent to these perforations (35) is thickened.

4. The grinding element (2) according to claim 3, characterized in that, The thickened grinding strip (21) is the part of the split section (26) before the split (27).

5. The grinding element (2) according to claim 1, characterized in that, Multiple connecting baffles (23) are constructed between adjacent grinding strips (21) in the circumferential direction.

6. The grinding element (2) according to claim 5, characterized in that, The baffle (23) is constructed only in the radially outer region.

7. The grinding element (2) according to claim 1, characterized in that, The grinding strips (21) outside the split section (26) are arranged in a purely radial direction.

8. The grinding element (2) according to claim 1, characterized in that, The grinding strip (21) within the split section (26) has a smaller circumferential thickness over at least 1 / 3 of the length of the segment after splitting (27) within the split section (26).

9. The grinding element (2) according to claim 8, characterized in that, The grooves (22) outside the split section (26) have the same circumferential width and the same circumferential thickness.

10. The grinding element (2) according to claim 1, characterized in that, The groove (22) and / or abrasive strip (21) have a circumferentially decreasing extension dimension within the split section after splitting (27).

11. The grinding element (2) according to claim 1, characterized in that, Multiple baffles (23) are provided in multiple grooves (22).

12. The grinding element (2) according to claim 11, characterized in that, Multiple baffles (23) are provided in the radially outer region of 2 / 3 of the radially extended dimension of the grinding element (2).

13. The grinding element (2) according to claim 11, characterized in that, An obtuse angle (32) is provided radially inward at the connection position between the stop bar (23) and the grinding bar (21) on the radially inner side.

14. The grinding element (2) according to claim 1, characterized in that, The grinding strip (21) has an axial extension dimension (31) that is 15% larger on the radially inner side than on the radially outer side.

15. A grinding apparatus (1) for grinding aqueous suspended pulp fibers between two grinding surfaces (4) forming a grinding gap (3) and rotating relative to each other, wherein, At least one of these grinding surfaces (4) has a grinding element (2) according to claim 11, characterized in that the baffle and the grinding strip have an obtuse angle on the radially inner side for forming a processing edge (25) on the baffle (23) so that the suspension can flow in by the relative movement of the grinding surfaces.

16. A grinding apparatus (1) for grinding aqueous suspended pulp fibers between two grinding surfaces (4) forming a grinding gap (3) and rotating relative to each other, characterized in that, At least one of these grinding surfaces (4) has a grinding element (2) according to any one of claims 1 to 14.

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