The proposed technology generally relates to refiner segments for a refiner of lignocellulosic material. More specifically it relates to a refiner segment that is provided with refining bars arranged in different bar zones on the refiner segment surface. Embodiments herein also relates to a refiner rotor or a refiner stator comprising refining segments with refining bars arranged in different bar zones. Another embodiment of the proposed technology provides a refiner comprising at least one of a refiner rotor or a refiner stator provided with refiner segments having refining bars arranged in different bar zones on the refiner segment surface.
To mechanically produce pulp or fibers from lignocellulosic material, e.g, wood, wood chips are fed into a refiner which refines the prepared, e.g., the steamed wood chips into fiber or pulp. This sounds simple enough but to do it an efficient and continuous manner poses substantial challenges. To make the process as efficient as possible one needs to be able to refine with a stable disc gap and this will in turn require at least two things:
Designing a refiner is therefore subject to a lot of challenges that need to be fulfilled in order to ensure an efficient feeding and subsequent grinding of e.g., wood chips. When it comes to feeding efficiency it is beneficial if the material can be fed into the grinding area or grinding zone with as small restrictions or disturbances as possible. A common refiner of lignocellulosic material usually comprises a rotor unit and a stator unit that are aligned along a pulp feeding axis facing each other. The refining of the material is performed in a bounded area between the rotor unit and the stator unit. During use of the refiner, material, e.g., pulp, is fed into an area arranged in between, and bounded by, the stator unit and a rotor unit. The rotor unit facing the stator unit may in particular versions be arranged on a rotatable shaft that can be rotated by means of an electrical motor. The purpose of the rotor unit, which in the following will be simply referred to as a rotor, is to grind the pulp between a surface of the stator unit and a surface of the rotor. The rotor and/or stator are often provided with refining segments on their surfaces. The purpose of these refining segments is to improve the grinding action on the material. The refining segments are in turn often provided with additional structures to improve the refining action even further. These structures often comprises refining bars arranged on the surface of the rotor and/or the stator. The refining bars protrudes from the surface of the rotor disc/stator disc and faces the material flow. To ensure an efficient material flow in the area between the stator and rotor these refining bars must be provided in a fashion where they disturb the material flow as little as possible while they at the same time produces an efficient grinding of the material. It is a highly non-trivial challenge to fulfill both these criteria's.
The proposed technology aims to overcome at least some of the challenges associated with the design of refining segments for a refiner of e.g., lignocellulosic material.
It is an object to provide a refining segment that enables an efficient material flow while at the same time allowing for an efficient grinding action.
It is a further object to provide a refining segment that allows steam produced during the refining process to stream backwards, toward the material feeding flow, with a reduced influence on the flow.
It is yet another object to provide a rotor or rotor disc comprising such a refining segment. An additional object is to provide a refiner comprising such a rotor.
These and other objects are met by embodiments of the proposed technology.
According to a first aspect, there is provided a refiner segment for a refiner of lignocellulosic material, the refiner segment being part of a refiner disc comprising a center area, wherein the refiner segment comprises a number N, N≥2, of bar zones arranged at different radial positions with regard to a radial direction R extending from the center area of the refiner disc towards the periphery of the refiner segment, each of the bar zones being defined by a corresponding set of refining bars distributed angularly and encircling the center area, where refining bars belonging to different but neighboring bar zones are angularly offset and where refining bars belonging to different but neighboring bar zones are arranged in such a way that a tangential direction of a particular refining bar belonging to a bar zone points in a direction towards the mid-point between two refining bars belonging to a neighboring bar zone and wherein the length of refining bars belonging to different bar zones decreases from a largest length for refining bars belonging to the innermost bar zone, with regard to the center of said refining disc, to the smallest length for refining bars belonging to the outermost bar zone adjacent the periphery of said refiner segment.
According to a second aspect of the proposed technology there is provided a refiner segment according to the first aspect, wherein the refiner disc is a rotor refiner disc.
According to a third aspect there is provided a refiner comprising a rotor refiner disc according to the second aspect.
Embodiments of the proposed technology provides refiner segments together with corresponding rotor discs, stator discs and refiners that yield both an efficient material flow within an into the refiners refining area and an efficient refining action on lignocellulosic material such as e.g., wood.
Other advantages will be appreciated when reading the detailed description.
The embodiments, together with further objects and advantages thereof, may best be understood by making reference to the following description taken together with the accompanying drawings, in which:
Throughout the drawings, the same reference designations are used for similar or corresponding elements.
For a better understanding of the proposed technology, it may be useful to begin with a brief overview of an example of a traditional refiner where the proposed technology may be used. This will then be followed by an analysis of the technical problems and challenges associated with the design of refiner segments.
In order to describe a refiner reference is made to
During use, lignocellulosic material such as wood chips or prepared wood, e.g., pulp, will be fed by means of a feeding mechanism, not shown, through the feeding channel 14. The material will pass through the hole 32 in the stator 20* and enter an area 19. The area 19 is essentially defined by the open area between the rotor 100* and the stator 20* and this area can be quite small during operation. The lignocellulosic material flowing into the area 19 will be incident on the center plate 17 on the rotor 100*. The center plate 17 acts to steer the lignocellulosic material out towards the refining segments on the rotor and/stator.
In order to provide a more detailed description of a rotor-stator arrangement in which the proposed technology may be used reference is made to
Having described a potential working mode for a refiner it should be clear that the demands put on a refiner segment are quite high and often contradictory. The refining bars provided on the refiner segment aims to provide an efficient grinding action on the incoming material, a purpose that suggest that they should be given a prominent structure, i.e., they should protrude from the surface of the refiner segments. An efficient and even grinding or refining of the material requires however also that the incoming material is evenly distributed in the refining area. A general configuration of refining bars on a refining segment may however cause areas of varying material concentration. The refining bars should therefore be arranged on the refining segment in such a way that the incoming flow of lignocellulosic material gets evenly distributed and can be steered in a controlled manner towards the outer refining areas, e.g., towards the refining segments of p-segment type. The dual purposes of the refining bars make the design of a refining segment very tricky. One additional and substantial problem that negatively affects the material flow is the impact caused by water steam produced during the refining of the material. Since the material to be refined naturally comprises water, the substantial pressure in the housed rotor and stator arrangement will produce significant amounts of water steam. It should also be noted that there, during use of the refiner, is present a pressure peak in the vicinity of the p-segments, this pressure peak posits a hindrance to the possible motion of the water steam and a lot of the produced water steam will as a consequence move backwards toward the center of the arrangement, i.e., towards the material inlet 32. This backward directed movement of steam will interact with the incoming material flow and make it harder to achieve an even material flow without substantial material concentrations.
The proposed technology provides a refiner segment whose design has shown to provide a satisfactory refining action while at the same time ensuring an efficient and controlled flow of lignocellulosic material. The proposed technology provides in particular mechanisms that will reduce the negative impact the back-travelling steam have on the material flow. This is accomplished at least in part due to a particular configuration of refining bars that will enable the main material flow to occur on one refining disc side, e.g., on the rotor side of a rotor-stator arrangement while the other refining disc side, e.g., the stator side, can be occupied by back-travelling water steam. This will reduce the interaction between incoming wood chips and back-travelling water steam.
In order to obtain these positive effects the proposed technology provides a refiner segment 10 for a refiner 1 of lignocellulosic material. The refiner segment 10 being part of a refiner disc 100 comprising a center area 11, wherein the refiner segment 10 comprises a number N, N≥2, of bar zones Zi, i=1, 2, . . . N arranged at different radial positions with regard to a radial direction R extending from the center area 11 of the refiner disc 100 towards the periphery of the refiner segment 10, each of the bar zones Zi being defined by a corresponding set of refining bars ZiRBi, i=1, 2, . . . M, distributed angularly and encircling the centrally located through-hole 11, where refining bars ZiRBi belonging to different but neighboring bar zones Zi, Zi+1 are angularly offset.
In other words, there is provided a refiner segment 10 that is integrated with a refining disc 100, or is adapted to be attached to a refining disc 100. The refining segment have a surface that comprises a number of refining bars ZiRBi that are arranged in an angular fashion around a common center area 11 in such a way that they form distinct bar zones Zi that encircles a common center on the refining disc 100. A particular bar zone Zi is defined as the area on the refining segment that comprises a corresponding set of refining bars ZiRBi. Hence a number of refining bars Z1RB1 are provided in an innermost area, corresponding to bar zone Z1, with regard to the center area of the refiner disc 100, a number of refining bars Z2RB2 are provided in an area, corresponding to bar zone Z2, that lies outside the innermost area. The directions are in relation to a radial direction having its origin in the center 11 of the refiner disc 100. This pattern is repeated so that a number of concentric bar zones are defined along the surface of the refining segment 100. Each bar zone comprises its own refining bars and refining bars belonging to neighboring bar zones may be spatially offset, i.e., arranged in such a way that there is a radial distance between refining bars belonging to neighboring bar zones. This is for example illustrated in
There are a number of advantages that can be obtained with refining segments according to the proposed technology. They provide in particular an energy economical feeding with minimum restrictions. The refining segment of the proposed technology provides a lot of open volume. This open volume can carry the material flow without forcing it towards the opposite side of the rotor-stator arrangement. The proposed refining segment also provide the highly desirable feature that it enables an even feed not only over the spatial disc geometry but also over time, and in particular a uniform flow over time despite the fact that the incoming material feed itself might be non-uniform. The proposed technology enables this feature by having a refining bar pattern that allows a material buffering effect. When sub-flows over the refining segments emerges from one bar zone and reaches a new bar zone, the sub-flows will mix with already existing flows. This mixing of sub-flows paired with potential turbulence and friction caused by the mixing will yield a slight material buffering effect. This buffering effect will in turn ensure a more uniform material flow over time.
Having described the cooperating features of a refining segment 10 that enables both an efficient grinding of the material and an efficient material flow, in what follows a number of embodiments of the proposed technology will be described with reference to the accompanying drawings. Other embodiments, however, are contained within the scope of the subject matter disclosed herein, the disclosed subject matter should not be construed as limited to only the embodiments set forth herein; rather, these embodiments are provided by way of example to convey the scope of the subject matter to those skilled in the art.
A particular embodiment of the proposed technology provides a refiner segment 10 wherein the angular offset between all neighboring bar zones Zi are in the same angular direction, the angular direction being the direction opposite to the intended rotational direction of the refiner segment 10. This embodiment provides an improved material flow since at least some of the refining bars belonging to different but neighboring bar zones can cooperate to obtain a uniform flow both spatially and over time. This embodiment is illustrated schematically in
Another embodiment of the proposed technology provides a refiner segment 10, wherein the refining bars of a particular bar zone are distributed angularly in a band of essentially equidistantly spaced refining bars ZiRBi that encircles the center 11 of the refiner disc 100. This embodiment is schematically illustrated in, for example,
Yet another particular embodiment of the proposed technology provides a refiner segment 10, wherein the different bar zones comprises bands with different number of equidistantly spaced refining bars ZiRBi. Such an embodiment is illustrated in
By way of example, the proposed technology provides a refiner segment 10, wherein refining bars ZiRBi belonging to different but neighboring bar zones are arranged in such a way that a tangential direction of a particular refining bar ZkRBk belonging to a bar zone Zi, points in a direction towards the mid-point between two refining bars Zk+1RBk+1 belonging to a neighboring bar zone Zi, Zi+1.
A specific embodiment of the proposed technology provides a refiner segment 10, wherein the refining bars are provided with geometrical shapes such as straight edged bars, rounded bars, conical bars, arrow-shaped bars with or without chamfers, etc. By way of example, the proposed technology provides a refiner segment 10, wherein at least a subset of the refining bars ZiRBi belonging to a particular bar zone Zi have a geometrical shape that is distinct from the geometrical shape of refining bars ZkRBk belonging to other bar zones Zk.
Another embodiment of the proposed technology provides a refiner segment 10, wherein the length of refining bars belonging to different bar zones decreases from a largest length for refining bars Z1RB1 belonging to the innermost bar zone Z1, with regard to the center 11 of the refining disc 100, to the smallest length for refining bars ZNRBN belonging to the outermost bar zone ZN adjacent the periphery of the refiner segment 10. By providing refining bars belonging to different bar zones with different length dimensions ensures that the open volume on the bar zone remain sufficiently large. With open volume is here intended the area on the refining segment where the material is allowed to flow freely, without interacting with any refining bars. Since the number of provided refining bars become higher towards the periphery of the refining segment, with a purpose of obtaining an efficient flow, the open volume may decrease. This may be compensated by a stepwise shortening of refining bars, i.e., the farther out from the center of the refining segment or refining disc the refining bars are provided, the shorter they are, this is schematically illustrated in e.g.,
According to a particular embodiment of the proposed technology there is provided a refiner segment 10, wherein at least a subset of the refining bars ZiRBi is provided on the surface of the refiner segment 10 in such a way that an angle α is formed between the radial direction of the refiner segment 10 and the length direction of a refining bar ZiRBi. The lower part of
A particular version of the above mentioned embodiment provides a refiner segment 10, wherein the angle α formed between the radial direction of the refiner segment 10 and the length direction of a refining bar ZiRBi defines the bar feeding angle and wherein the angle α takes value in the interval 0°<α≤60°.
Another particular embodiment of the proposed technology provides a refiner segment 10, wherein refining bars ZiRBi belonging to different bar zones Zi have different widths, and wherein the widths decreases from a largest width for refining bars Z1RB1 belonging to the innermost bar zone Z1, with regard to the center 11 of the refiner disc 100, to the smallest width for refining bars ZNRBN belonging to the outermost bar zone ZN adjacent the periphery of the refiner segment 10. The purpose of this embodiment is the same as in the embodiment described above regarding refining bars having different lengths. That is, it ensures that a satisfactory degree of open volume that can carry the material flow is present on the refining segment even when the number of refining bars increases toward the periphery.
In still another embodiment of the proposed technology the refining segment may be provided on a refining disc 100 that also comprises refining segments 34,34* of p-segment type.
It should be noted that the proposed technology may be utilized on both the rotor side of a refiner and on the stator side. The proposed technology may be provided in the form of a refining segment that can be attached a refining disc 100 that in turn can be attached to the rotor 100* or stator 20*. The refining disc 100 may in this particular case be referred to as a segment holder, see
A particular embodiment of the proposed technology provides a refiner segment 10, wherein the refiner segment 10 comprises the refiner disc 100. That is, the refining segment 10 can be provided in the shape of a refiner disc that can be either a rotor refiner disc or a stator refiner disc.
According to a particular version of the latter embodiment there is provided a refiner segment 10, wherein the refiner disc 100 is a rotor refiner disc. As was mentioned earlier, the refining segment 10 according to the proposed technology may form part of a refiner disc 100 or be attached to a refiner disc 100. A refining segment may be provided in the shape of a circle, optionally with a removed central area 11, as is shown in e.g.
An alternative embodiment of the proposed technology provides a refiner segment 10 wherein the refiner disc 100 is a stator refiner disc 20*. A schematic cross-sectional view from the side of a stator refiner disc 20* is illustrated on the right side of
The proposed technology may however also be used in a rotor-stator arrangement or a refiner 1 where the stator disc 20* is adapted to cooperate with a rotor refiner disc 100 that comprises a refining segment as has been described earlier. The stator disc may also be provided with refining segments according to what has been described earlier. The stator disc 20* is adapted to face, and cooperate with, the rotor refiner. The stator refiner disc 20 is provided in the form of an essentially circular shape having a center area provided with a hole that defines a material inlet 32. The stator disc may also be provided with two different but adjacent surface regions, a first surface region that is arranged adjacent to, and encircling, the inlet 32, and a second surface region that is arranged adjacent to, and encircling, the first surface region. The second surface region is essentially planar while the first surface region is inclined relative the second region where the inclination is in a direction opposite the intended material flow direction during use. The fact that the first surface region is inclined relative the second region provides more open volume closer to the center of the stator disc 20*. This open volume can be occupied by water steam and thus provides ample space for any back-travelling steam.
Another particular embodiment of the proposed technology provides a refiner 1 comprising a rotor refiner disc 10 provided with refining segments as described herein.
The proposed technology also provides a refiner 1 comprising a rotor refiner disc 10 provided with refining segments as described herein and a stator refiner disc 20 as described above.
Generally, all terms used herein are to be interpreted according to their ordinary meaning in the relevant technical field, unless a different meaning is clearly given and/or is implied from the context in which it is used. All references to a/an/the element, apparatus, component, means, step, etc. are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, step, etc., unless explicitly stated otherwise. Any feature of any of the embodiments disclosed herein may be applied to any other embodiment, wherever appropriate. Likewise, any advantage of any of the embodiments may apply to any other embodiments, and vice versa. Other objectives, features and advantages of the enclosed embodiments will be apparent from the following description.
Number | Date | Country | Kind |
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1850192-4 | Feb 2018 | SE | national |
Filing Document | Filing Date | Country | Kind |
---|---|---|---|
PCT/SE2019/050038 | 1/22/2019 | WO |
Publishing Document | Publishing Date | Country | Kind |
---|---|---|---|
WO2019/164433 | 8/29/2019 | WO | A |
Number | Name | Date | Kind |
---|---|---|---|
11665 | Dickson | Sep 1854 | A |
191740 | Williams | Jun 1877 | A |
257623 | Speer | May 1882 | A |
316478 | McKee | Apr 1885 | A |
858267 | Dellinger | Jun 1907 | A |
1595282 | Bauer | Aug 1926 | A |
3149792 | Textor | Sep 1964 | A |
3815834 | Gilbert | Jun 1974 | A |
4039154 | Peterson | Aug 1977 | A |
5112443 | Virving et al. | May 1992 | A |
5383617 | Deuchars | Jan 1995 | A |
5683048 | Virving | Nov 1997 | A |
5704559 | Froberg | Jan 1998 | A |
6443353 | Kleinschnittger et al. | Sep 2002 | B1 |
20040149844 | Antensteiner | Aug 2004 | A1 |
20070164143 | Sabourin | Jul 2007 | A1 |
20110155828 | Gingras | Jun 2011 | A1 |
20130270377 | Gingras | Oct 2013 | A1 |
20170073893 | Bilodeau | Mar 2017 | A1 |
20180345291 | Knight | Dec 2018 | A1 |
Number | Date | Country |
---|---|---|
0611599 | Aug 1994 | EP |
WO 2012115526 | Aug 2012 | WO |
Entry |
---|
Extended European Search Report, Application No. 19758005.3, dated Oct. 27, 2021, 7 pages. |
Number | Date | Country | |
---|---|---|---|
20210017706 A1 | Jan 2021 | US |