BACKGROUND
Unless otherwise indicated herein, the materials described in this section are not prior art to the claims in this application and are not admitted to being prior art by inclusion in this section.
In the refining of lignocellulosic materials, there is often a need to apply low intensity refining energy to furnishes (e.g., stock). Refining is generally achieved by using refiner plate designs featuring arrays of substantially parallel bars and grooves, and the intensity of the refining energy is defined by the inverse of the number of bars. Low intensity refining is achieved with a large number of bars on the refiner plates. In all applications, and especially in low consistency refining where usually 3.0-5.5% of the stock is fiber, and the rest is water, there is a point at which the probability of plugging the grooves with unseparated particles such as wood chips, wood particles, paper flakes, etc., fiber bundles or contaminants such as pieces of plastic, metal, stones, etc. (especially in recycled grades) becomes substantial.
The plugging point is primarily related to the groove width in comparison to the size of larger particles. Generally, if the particles are similar sized or slightly wider than the grooves, there is a probability that they will be forced into the inlets of the grooves via centrifugal forces and/or flow pattern of the incoming stock through the plates. If the size differential and compressibility of the particles is a match, those particles will stop in the grooves, wedge themselves solidly, and plug the grooves. This will gradually restrict the flow capacity of the refiner as more grooves become plugged over time. The plugging effect causes a significant loss of lifetime for the refiner plates, and often forces a mill to make unplanned maintenance stops to replace the refiner plates.
Refiner plate designs typically use bars of constant width, or sometimes bars having a tapered width-either with bars narrower at the inlet of a zone, or alternatively wider at the inlet of a zone. Some designs feature bars that change width between zones, for example, getting wider in zones with a lower bar density, but the bar widths are substantially constant, such as shown in FIG. 10, or change very gradually within a given refining zone. FIG. 10 illustrates bars 1010a-1010c and grooves 1020a-1020b having substantially constant width. Feedstock particles flowing in the flow direction 1030 can be compressed as they enter the grooves 1020a-1020b become lodged in the constant width grooves 1020a-1020b thereby plugging the grooves.
One way to prevent plugging is to use refiner plate having wider grooves, but this causes the refining intensity to increase and results in poor fiber development. Flaring groove widths (width narrowest at inlet of bar refining section and gradually increasing towards the periphery) offer some improvement in plugging reduction since particles that can squeeze through the inlet should be able to move forward in a groove that gets wider along its length. Unfortunately, this benefit is limited by two aspects: first, the rate of groove width increase is generally very slow which does not provide the required plugging prevention—those grooves are often observed to be plugged; and second, flaring grooves generally result in a loss of number of bar crossings for the stock compared to parallel bar designs—this goes against the desired target of increasing bar crossings.
There is a need for a refiner plate design that provides grooves that are narrower than a size normally allowed by the raw material without increased plugging tendencies, thereby reliably maintaining the flow capacity of a refiner throughout the lifetime of the refiner plates and permitting application of low intensity refining to the furnish in order to maximize the development of its properties.
BRIEF DESCRIPTION OF THE DRAWINGS
Aspects and features of the various embodiments will be more apparent by describing examples with reference to the accompanying drawings, in which:
FIG. 1 is a perspective view illustrating narrowed grooves between refining bars of a refiner plate at a refining zone inlet according to some aspects of the present disclosure;
FIG. 2 is a diagram illustrating an example of a refining bar pattern at an inlet to a refining zone of a refiner plate according to some aspects of the present disclosure;
FIGS. 3A-3F are diagrams illustrating examples of shapes for the transition portion of a refining bar for providing narrowed grooves at the inlet of the refining zone and corresponding side views of the refining bar according to some aspects of the present disclosure;
FIGS. 3G and 3H are diagrams illustrating examples of shapes for the transition portion of a refining bar on an inlet chamfer according to some aspects of the present disclosure;
FIG. 3J is a diagram illustrating an example of refining bars providing narrowed grooves at the inlet of the refining zone and widening along the length on the refining bars according to some aspects of the present disclosure;
FIGS. 4A-4D are diagrams illustrating examples of chamfers or ramps of refining bars according to some aspects of the present disclosure;
FIGS. 5A-5C illustrate examples of arrangements of refining bars for providing narrowed grooves at a refining zone inlet of a refiner plate according to some aspects of the present disclosure;
FIG. 6 illustrating an example of refining bars having alternate lengths for providing narrowed grooves at a refining zone inlet according to some aspects of the present disclosure;
FIG. 7 is a diagram illustrating an example of refining bars for providing narrowed grooves at the inlet of an outer refining zone where the refining bars are not joined to an inner refining zone according to some aspects of the present disclosure;
FIG. 8 is a diagram illustrating an example of refining bars for providing narrowed grooves at the inlet of an outer refining zone where the refining bars are partially joined to an inner refining zone according to some aspects of the present disclosure;
FIG. 9 is a diagram illustrating an example of alternating refining bars for providing narrowed grooves at a refining zone inlet according to some aspects of the present disclosure; and
FIG. 10 is diagram illustrating bars and grooves of a conventional refiner plate showing a feedstock flow direction.
DETAILED DESCRIPTION
While certain embodiments are described, these embodiments are presented by way of example only, and are not intended to limit the scope of protection. The apparatuses, methods, and systems described herein may be embodied in a variety of other forms. Furthermore, various omissions, substitutions, and changes in the form of the example methods and systems described herein may be made without departing from the scope of protection.
Aspects of the present disclosure can provide particle size filtering at the inlets of refiner plate grooves. Providing filtering at the groove inlets may prevent particles likely to plug from entering the grooves. Any particles that pass the groove inlet are unlikely to get stuck in the groove past the entry point. The particle size filtering inlet may be applied at the inlet of any zone that may have a tendency to plug based on the groove width and the incoming stock conditions. For example, the particle size filtering can be applied at the inlet (e.g., the inner end) of all the refining zones of a refiner plate, at the inlet of less than all the refining zones of a refiner plate, or at the inlet of only one zone of the refiner plate.
According to aspects of the present disclosure, inlet filtering may be accomplished by forming narrowed grooves using refining bars that are wider at the inlet of a refining zone than along the remaining length of the groove. The widened refining bars may be formed by widening the bar as a step, a chamfer, a curved profile, or a combination of those configurations. Widened portions of a bar may be formed on one side of the bar only or may be distributed evenly or unevenly between the two sides of the bar. The widened portion may be short, thereby preventing the widened portion from becoming the location where particles can be trapped. If a particle can squeeze through the narrowed groove inlet created by the widened bars, then the particle should be free to continue flowing along the remainder of the groove.
FIG. 1 is a perspective view illustrating narrowed grooves 140 between refining bars 100a, 100b of a refiner plate according to some aspects of the present disclosure. In some implementations, the refiner plate may be a one-piece ring or a one-piece cone. In some implementations, a plurality of refiner plate segments may form a refiner plate in the shape of a ring or a cone. As shown in FIG. 1, a widened refining bar 100a, 100b may include a widened portion 110a, 110b and a narrow portion 120a, 120b in a circumferential direction of a refiner plate or refiner plate segment. A chamfered transition 130a, 130b may provide the transition between the widened portion 110a, 110b and the narrow portion 120a, 120b. In various implementations, the transition may be a step, a chamfer, a curved profile, or a combination of those configurations.
The widened portions 110a, 110b may narrow the groove 140 between the widened portions 110a, 110b of the refining bars 100a, 100b at the inlet of a refining zone thereby restricting the size of a particle entering the groove 140. Since the groove 140 becomes wider between the narrow portions 120a, 120b of the widened refining bars 100a, 100b, any particle having a size that can pass between the widened portions 110a, 110b of the refining bars 100a, 100b at the inlet of a refining zone is unlikely to become trapped as it moves along the groove 140. The widened portions 110a, 110b of the refining bars 100a, 100b may include ramps 150a, 150b or other structures configured to deflect larger particles unable to pass through the inlet towards and into the refining gap between the refiner plates.
FIG. 2 is a diagram illustrating an example of a refining bar pattern 200 at an inlet 210 to a refining zone 220 of a refiner plate according to some aspects of the present disclosure. As illustrated in FIG. 2, refining bars 250a, 250b may include narrow portions 255a, 255b and wide portions 260a, 260b connected by transition portions 265a, 265b. The wide portions 260a, 260b may be disposed at the inlet 210 of the refining zone 220 and may be wider than the narrow portions 255a, 255b in a circumferential direction of a refiner plate or refiner plate segment. The wide portions 260a, 260b of the refining bars 250a, 250b may be configured to restrict the particle size entering the groove 270 at the inlet 210 of the refining zone 220 by narrowing the groove 270. The narrow portion 255 of the refining bar 250 may extend from the transition portion 265 substantially the remaining length of the refining bar 250.
The wide portions 260a, 260b of the refining bars 250a, 250b may have an increased width of approximately 0.2-1.5 mm over the width of the narrow portions 255a, 255b of the refiner bars 250a, 250b. The wide portions 260a, 260b of the refining bars 250a, 250b may narrow the groove 270 at the inlet 210 of the refining zone 220 by 5-30% of the groove width between the narrow portions 255a, 255b of the refining bars 250a, 250b.
The refining bar configuration of the present disclosure can result in a narrow groove 270 between wide portions 260 of adjacent refining bars 250 at the inlet 210 of the refining zone 220 and a wide groove 275 that is wider than the narrow groove 270 extending from the transition portions 265 substantially the remaining length of the adjacent refining bars 250. In some implementations, all the refining bars may have wide portions that narrow the grooves between the wide portions of adjacent refining bars at the inlet of a refining zone. In some implementations, less than all the refining bars may have wide portions that narrow the grooves between the wide portions and adjacent refiner bars without widened portions at the inlet of a refining zone. In some implementations, all the refining zones may include refining bars having wide portions at the inlet. In some implementations, less than all the refining zones may include refining bar having wide portions at the inlet.
Particles larger than the narrow groove 270 between the wide portion 260 of the refining bar 250 may be deflected by ramps 280 or chamfers on the wide portions 260 towards and into the refining gap between opposing refiner plates where they will be separated into smaller particles.
The transition portion of the refining bar may be formed in a variety of different shapes. FIGS. 3A-3F are diagrams illustrating examples of shapes for the transition portion of a refining bar for providing narrowed grooves at the inlet of the refining zone and corresponding side views of the refining bar according to some aspects of the present disclosure. Referring to FIG. 3A, the refining bar 310 may have a wide portion 312 that is reduced to a narrow portion 314 by the transition portion 316 having a chamfer on both sides of the refining bar 310. FIG. 3B illustrates an example of a refining bar 320 with a transition portion 326 between the wide portion 322 and the narrow 324 portion having radius on both sides of the refining bar 320.
The refining bar 330 illustrated in FIG. 3C may include a transition portion 336 having step on both sides of the refining bar 330 between the wide portion 332 and the narrow portion 334. FIG. 3D illustrates a transition portion 346 between the wide portion 342 and the narrow portion 344 of the refining bar 340 having a chamfer 348 on only one side of the refining bar.
The refining bar 350 illustrated in FIG. 3E may include a transition portion 356 having an extended wide portion 352 in a radial direction and a chamfer on both sides of the refining bar 340 to reduce the wide portion 352 to the narrow portion 354. FIG. 3F shows a refining bar 360 with a transition portion 366 having a chamfer on one side of the refining bar and a radius 368 on the opposite side to reduce the wide portion 362 of the refining bar 360 to the narrow portion 364. It should be appreciated that other configurations of the transition portion providing a wider inlet portion of the refining bar may be used without departing from the scope of the present disclosure.
In some implementations, the transition portion of the refining bars may be provided on a chamfer or ramp that faces the inlet of the refiner plate. FIGS. 3G and 3H are diagrams illustrating examples of shapes for the transition portion of a refining bar on an inlet chamfer according to some aspects of the present disclosure. Referring to FIG. 3G, the chamfer may be a ramp 372 rising at an angle from the substrate 374 to the top of the refining bar 376. The base of the ramp 372 may extend a length ‘b’ linearly along the substrate 374 of the refining plate segment 370. A transition portion 378 may begin at a linear distance ‘a’ along the substrate 374 of the refining plate segment 370 on the chamfer 372 and may terminate at, before, or beyond the top of the refining bar 376. A ratio of the linear distance ‘a’ to the length of the chamfer ‘b’ may be greater than 0.5 (e.g., a/b>0.5).
In FIG. 3H, the groove width ‘a’ at the inlet of a refining zone may be equal to or less than a linear distance ‘b’ along the substrate 384 of the refining plate segment 380 from the beginning of a transition portion 388 on the chamfer 382 to a termination of the chamfer 382 at the top of the refining bar 386 (e.g., b≤a). Other configurations of chamfers and/or transition portions may be provided without departing from the scope of the present disclosure.
FIG. 3J is a diagram illustrating an example of refining bars providing narrowed grooves at the inlet of the refining zone and widening along the length on the refining bars according to some aspects of the present disclosure. As illustrated in FIG. 3J, adjacent refining bars 392a, 392b may provide a narrow groove having a width ‘a’ at the inlet of a refining zone and a wider groove having a width ‘b’ at the termination of the transition zone 394a, 394b (e.g., b>a). Continuing along the length of the groove, the groove may narrow to a width ‘c’ which is greater than the width ‘a’ but less than the width ‘b’ (e.g., b>c>a).
In some implementations, the refining bars that face the inlet of the refiner plate may have a chamfer or ramp. The chamfer or ramp may deflect any material that is fed towards the restrictive inlet of the refining zone towards the refining gap in between the opposing refining discs. FIGS. 4A-4D are diagrams illustrating examples of chamfers or ramps of refining bars according to some aspects of the present disclosure. Referring to FIG. 4A, the refining bar 415 may have an angle of approximately 90° (e.g., no chamfer or ramp) with respect to the substrate 417. Particles that are too large to enter the inlet may move into the refining gap between the refiner plates where they will be separated into smaller particles.
FIG. 4B illustrates a ramp 420 rising at an acute angle from the substrate 427 to the top of the refining bar 425. Particles that are too large to enter the inlet may flow up the ramp 420 into the refining gap between the refiner plates. FIG. 4C illustrates at arcuate chamfer 430 between the substrate 427 in the top of the refining bar 435. FIG. 4D illustrates a chamfer 440 that extends from the top of the refining bar 445 an angle but is truncated before reaching the substrate 447.
The chamfers or ramps can reduce the potential to trap particles at the inlet of the given refining zone that may cause restriction of flow into the grooves between the refining bars and through the refiner. Other configurations of chamfers or ramps may be provided without departing from the scope of the present disclosure.
Widening the refining bars at a fixed radial position can cause a flow restriction due to a drop in available volume at a given radial location. According to aspects of the present disclosure, the radial location of the refining zone inlet may be distributed relative to the center of the refining disk and arranged at an angle relative to a radial arc running across the refiner plate segment. The refining zone inlet may be arranged in a sawtooth pattern, a chevron pattern, a scattered transition, etc. The positioning of the refining bar ends may follow a curved line, a straight line, or a combination.
FIGS. 5A-5C illustrate examples of arrangements of refining bars for providing narrowed grooves at a refining zone inlet of a refiner plate according to some aspects of the present disclosure. In some implementations, the refiner plate may be a one-piece ring or a one-piece cone. In some implementations, a plurality of refiner plate segments may form a refiner plate in the shape of a ring or a cone. FIG. 5A illustrates a non-distributed refining zone inlet. The non-distributed refining zone inlet may cause a pinch point for the flow capacity. The pinch point may be resolved by using a distributed refining zone inlet transition. The distributed refining zone inlet transition may be configured in a shape other than a smooth arcuate shape. Nonlimiting examples of a distributed refining zone inlet transition may be a Z-transition refining zone inlet 515 for a refiner plate segment 510 as illustrated in FIG. 5B or a chevron-transition refining zone inlet 525 for a refiner plate segment 520 as illustrated in FIG. 5C. As illustrated in FIGS. 5B and 5C, adjacent refiner bars may have different radial distances from an inner circumference 512, 522 of the refiner segments 510, 520 to inner ends 517, 527 of the adjacent refiner bars. Other shapes for a distributed refining zone inlet transition may be used without departing from the scope of the present disclosure.
Alternatively, the length of individual refining bars at the refining zone inlet may be alternated to prevent radial flow restriction. FIG. 6 illustrates an example of refining bars having alternate lengths for providing narrowed grooves and a refining zone according to some aspects of the present disclosure. Referring to FIG. 6, refining bars 610 and 620 may have a first length while refining bars 630 and 640 have a length shorter than refining bars 610 and 620. Refining bar 650 may have a third length shorter than bars 610 and 620 but longer than refining bars 630 and 640. As illustrated for example in FIGS. 5B and 5C, adjacent refiner bars may have different radial distances from an inner circumference of a refiner segments to inner ends of adjacent refiner bars.
As illustrated in FIG. 6, a refining bar 610 having a first length may be adjacent to a refining bar 630 having a second length, the refining bar 630 may be adjacent to a refining bar 650 having a third length, the refining bar 650 may be adjacent to a refining bar 640 having a second length, and the refining bar 640 having a second length may be adjacent to a refining bar 620 having a first length. By alternating the positions of the first, second, and third length refining bars as illustrated in FIG. 6, pinch points (e.g., flow restrictions) at the refining zone inlet may be avoided. Arrangements of refining bars having a distribution of two or more lengths can alleviate a flow restriction at the inlet of a refining zone.
Widening of the refining bars in a circumferential direction of a refiner plate or refiner plate segment at the inlet of a refining zone can apply where the start of one refining zone is not connected to a previous refining zone, but it can also apply where two or more refining zones are connected via a number of bars, dams, links, or any other means. FIG. 7 is a diagram illustrating an example of refining bars 725 for providing narrowed grooves at the inlet of an outer refining zone where the refining bars are not joined to an inner refining zone according to some aspects of the present disclosure.
Referring to FIG. 7, refining bars 710 of an inner refining zone 705 are not joined to an outer refining zone 720. Refining bars 725 at the inlet to the refining zone 720 may include a widened portion 727 to restrict the particles entering the outer refining zone 720. The size of the particles admitted into the outer refining zone 720 may be determined by the spacing between the widened portions 727 of the widened refining bars 725. Particles larger than the spacing between the widened portions 727 may be deflected by ramps or chamfers (see, for example, FIGS. 4A-4D) on the widened portions 727 towards and into the refining gap between opposing refiner plates.
FIG. 8 is a diagram illustrating an example of refining bars 825 for providing narrowed grooves at the inlet of an outer refining zone where the refining bars are partially joined to an inner refining zone according to some aspects of the present disclosure. As shown in FIG. 8, refining bars 810a and 810b may join the inner refining zone 805 to the outer refining zone 820. Refining bar 825 is disposed in the outer refining zone 820. The refining bar 825 may include a widened portion 827 at the inlet to the outer refining zone 820. The size of the particles admitted into the outer refining zone 820 may be determined by the spacing between the widened portion 827 of the widened refining bar 825 and the sides 812a, 812b of the refining bars 810a and 810b. Particles larger than the spacing between the widened portion 827 may be deflected by ramps or chamfers (see, for example, FIGS. 4A-4D) on the widened portions 827 towards and into the refining gap between opposing refiner plates.
It should be appreciated that the examples of FIGS. 7 and 8 are nonlimiting illustrative examples and that other implementations may be provided without departing from the scope of the present disclosure.
In some implementations, a restrictive refining zone inlet may be provided by alternating a standard refining bar and a widened refining bar. FIG. 9 is a diagram illustrating an example of alternating refining bars for providing narrowed grooves at a refining zone inlet according to some aspects of the present disclosure. Referring to FIG. 9, standard refining bars 910a-c may be alternated with widened refining bars 920a, 920b at the inlet of a refining zone. The alternating refining bar configuration may provide narrow grooves 930a-d at the refining zone inlet to limit the size of particles entering the grooves 930a-d. Limiting the size of the particles entering the grooves 930a-d at the inlet makes it unlikely that the particles will become trapped and plug the grooves 930a-d. Larger particles may be deflected by ramps or chamfers (see, for example, FIGS. 4A-4D) on the standard refining bars 910a-c as well as the widened refining bars 920a, 920b towards and into the refining gap between opposing refiner plates.
The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the protection. For example, the example apparatuses, methods, and systems disclosed herein can be applied to single disc, double disc, counter-rotating, flat, conical, cylindrical or any other type of refining equipment, running at low, medium, or high consistency. Also, the features and attributes of the specific example implementations disclosed above may be combined in different ways to form additional implementations, all of which fall within the scope of the present disclosure.
Although the present disclosure provides certain example embodiments and applications, other embodiments that are apparent to those of ordinary skill in the art, including embodiments which do not provide all of the features and advantages set forth herein, are also within the scope of this disclosure. Accordingly, the scope of the present disclosure is intended to be defined only by reference to the appended claims.
Patent Application
20240295075
