Rotor for pressurized screen drum, pressurized screen system and method for removing solid contaminants

Abstract

The invention relates to a rotor for a pressurized screen drum, a pressurized screen system and a method for removing solid contaminants. A rotor for a pressurized screen drum for screening contaminants from a solid slurry or solid suspension, the rotor comprising a cylindrical hub, a plurality of foils spaced radially outward from the cylindrical hub, and a plurality of struts, wherein each of the plurality of foils is coupled to the cylindrical hub by two or more of the plurality of struts, and each of the plurality of struts is a sweep forward strut having a forward edge.

Description

This invention patent application is a divisional application of the invention patent application with international application number PCT / US2023 / 065983, international application date April 20, 2023, application number 202380010250.0 entering the Chinese national phase, and name “Rotor with forward-swept struts for a pressure screen cylinder”. CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority to U.S. Provisional Patent Application No. 63 / 333,283, filed on April 21, 2022, and entitled “ROTOR WITH FORWARD-SWEATED STRUT FOR PRESSURE SCREW CYLINDER,” the entire contents of which are incorporated herein by reference. background Technical Field

[0002] The present application relates generally to screening (sieving) devices for removing oversized solid contaminants from a solid suspension, and in particular to a pressure screen with a cylindrical filter having a rotor with forward-swept struts. Background Art

[0003] In the papermaking industry, the process of making paper requires the production of pulp, which is a solid suspension of fibers, such as cellulose fibers or other fibers. Depending on the source of the fibers, the pulp may include solid contaminants of various concentrations and sizes, such as wood chips, fiber bundles, metal flakes, hardened adhesives or other contaminants. For example, the increasing use of recycled paper as a source of fiber may increase the presence of hardened adhesives, metal chips and wood chips in the pulp. These excessive solid contaminants may reduce the quality of the paper and / or cause flow interruptions of the pulp in the head box of a Fourdrinier machine or other papermaking processes.

[0004] Before the pulp is introduced into the papermaking process, the pulp is usually screened (screened) to remove these oversized solid contaminants from the pulp. Screening the pulp can also be used to classify the pulp according to fiber length or fiber hardness. Pulp screening (screening) can be accomplished by introducing the pulp into a pressure screen, where the acceptable portion of the pulp passes through holes or slots in the screen. The solid contaminants or unacceptable portion of the pulp (e.g., long fibers or rigid fibers if screening is performed based on the characteristics of the fibers) do not pass through the slots or holes in the screen, but are discharged from a rejection outlet of the pressure screen device. The pressure screen device can also be used to remove oversized solid contaminants from pulp and solid suspensions in other industries outside the pulp and papermaking industry.

[0005] A pressure screen device for screening paper pulp generally includes a pressure screen cylinder and a rotor disposed in the pressure screen cylinder. The rotor has a plurality of foils (foils, thin sheets), and the rotation of the rotor causes the plurality of foils to traverse (sweep) circumferentially around the inner surface of the pressure screen cylinder. The movement of the foils along the inner surface of the pressure screen cylinder causes a pressure pulse, which removes contaminants and fibers entangled (mat-like attached) to the inner surface of the pressure screen cylinder to prevent the screen from being blocked by solid contaminants and fibers. Summary of the invention

[0006] For conventional rotors for pressure screens, the rotor includes a hub and a plurality of foils, which are generally oriented parallel to the axis of rotation of the rotor. Each foil is connected to the hub by a plurality of pillars. The pillars of conventional rotors extend radially outward to the foils. The rotor assembly rotates to allow pulp fibers and contaminants naturally supplied to the screening area to pass through. In addition, as the rotor rotates and the foils move, contaminants and fibers fall off from the inner surface of the pressure screen, and the fallen contaminants and fibers can be collected on the forward edge of the pillar at the outward end of the pillar, and the pillar is connected to each foil in each foil at the outward end. The fibers and contaminants captured on the forward edge of the pillar can accumulate more fibers and solids, and the deposits on the forward edge of the pillar can continue to accumulate. The deposits of solid contaminants and fibers can even extend to the leading edge of the foil. This phenomenon is called tandem and may increase rotor resistance, which may increase the motor power required to rotate the rotor. Contaminants and fibers accumulated on the forward edges of the struts near the foil and on the leading edge of the foil may also disturb the flow under the foil, thereby negatively affecting the pressure pulses generated by the foil under the foil as it traverses around the inner surface of the pressure screen cylinder. This may reduce the effectiveness of the foil in dislodging contaminants and entangled fibers from the inner surface of the pressure screen cylinder, which may reduce the productivity of the pressure screen cylinder.

[0007] Therefore, there is a continuing need for a rotor for a pressure screen cylinder that can reduce stringing to maintain the effect of the foil in removing contaminants and entangled fibers from the inner surface of the pressure screen cylinder, as well as reducing drag on the rotor. The pressure screen rotor of the present disclosure meets this need and solves these problems by including (combining) forward-swept struts extending between the hub of the rotor and the foil. The forward-swept struts reduce the severity of the corners where the struts are connected to the foil, and the fluid dynamics generated by the forward-swept struts create a flow stream or flow field that moves fibers and contaminants that fall off from the pressure screen cylinder or from the general local flow field inward toward the hub of the rotor, rather than allowing contaminants and fibers to collect on the forward edge of the struts near the foil and / or on the leading edge of the foil. Compared with other alternative methods for reducing stringing, the forward-swept struts can be made thinner, and the thinner struts of the forward-swept struts disclosed herein can reduce drag due to their reduced cross-sectional area. Since the flow stream generated by the forward-swept struts transports contaminants and fibers inward, the forward-swept struts reduce the collection of contaminants and fibers at the more outward portion of the forward edge of the struts and / or on the leading edge of the foil.

[0008] In addition, the pressure drum rotor disclosed herein may have a release area disposed at or near the site of the support connected to the hub portion of the rotor. The release area is an area of ​​the support near the inward end that has a thickness greater than the thickness of the support. The release area of ​​greater thickness allows the forward edge of the support at the inward end of the support to have a larger radius of curvature so that contaminants and fibers are not captured on the forward edge of the support at the site where the support is connected to the hub. Instead, contaminants and fibers slide over the forward edge of the support and return to the fiber slurry. In addition, due to the swept shape of the forward edge, any fiber moving inward along the forward edge of the support encounters a local thickening at the release area of ​​the support and slides off the forward edge of the support.

[0009] According to one or more aspects of the present disclosure, a rotor of a cylindrical pressure screen for screening contaminants from a solid slurry may include a cylindrical hub, a plurality of foils radially spaced outward from the hub, and a plurality of struts coupling the plurality of foils to the hub. Each of the plurality of struts is a forward-swept strut having a forward edge.

[0010] According to one or more other aspects of the present disclosure, a pressure screening system for removing contaminants from a solid slurry or suspension may include a pressure screen cylinder having a plurality of openings, a rotor of any aspect disclosed herein, and a drive motor operatively coupled to the rotor. The rotor may be disposed within the pressure screen cylinder, and the drive motor may be configured to rotate the rotor relative to the pressure screen cylinder.

[0011] According to another aspect of the present disclosure, a method for removing solid contaminants from a solid suspension or a solid slurry may include contacting the solid suspension or the solid slurry with a pressure screen cylinder, the pressure screen cylinder including a cylinder wall having an inner surface, an outer surface, and a plurality of openings extending through the cylinder wall from the inner surface to the outer surface. The contact of the solid suspension with the screen cylinder may cause at least a portion of the solid suspension or the solid slurry to pass through the plurality of openings. The method also includes rotating a rotor disposed in the pressure screen cylinder. The rotor may include a cylindrical hub, a plurality of foils (sheets / sheets / plates) radially spaced outward from the hub, and a plurality of struts connecting the plurality of foils to the hub. Each of the plurality of foils is radially spaced from the inner surface of the cylinder wall, and each of the plurality of struts may be a forward-swept strut (forward-swept strut) having a forward edge, the shape of the forward edge being designed so that the outward end of the forward edge is disposed in front of at least 50% of the other portion of the forward edge with respect to the direction of rotation of the rotor. The rotation of the rotor can cause each of the plurality of foils to generate a pressure pulse, which causes solid contaminants and fibers entangled to the inner surface of the pressure screen cylinder to fall off. The forward-swept pillars can generate a flow stream and / or flow field that moves the solid contaminants and fibers inwardly and prevents the solid contaminants and fibers from being collected on the forward edges of the pillars and / or on the leading edges of the foils. The method also includes collecting acceptable solid suspensions through the plurality of openings of the screen cylinder.

[0012] It is to be understood that both the foregoing summary and the following detailed description describe various embodiments and are intended to provide an overview or framework for understanding the nature and character of the claimed subject matter. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The accompanying drawings are included to provide a further understanding of the various embodiments and are incorporated in and constitute a part of this specification. The accompanying drawings illustrate various embodiments described herein and together with the description serve to explain the principles and operations of the claimed subject matter.

[0014] Figure 1 schematically depicts a front perspective view of a pressure screen cylinder and a rotor disposed within the pressure screen cylinder, wherein the pressure screen cylinder is depicted in partial cross-section, according to one or more embodiments shown and described herein;

[0015] Figure 2 Schematically depicts a schematic diagram of a device according to one or more embodiments shown and described herein. Figure 1 A front perspective view of a pressure screen drum;

[0016] Figure 3 Schematically depicts a schematic diagram of a device according to one or more embodiments shown and described herein. Figure 1 A front perspective view of a rotor;

[0017] Figure 4 schematically depicts a top view of one embodiment of a rotor for a pressure screen cylinder according to one or more embodiments shown and described herein;

[0018] FIG5 schematically depicts a top view of a conventional rotor of the prior art;

[0019] FIG6 schematically depicts the accumulation of contaminants and fibers on the forward edge of the struts of the conventional rotor of FIG5;

[0020] Figure 7 Schematically depicts a schematic diagram of a device according to one or more embodiments shown and described herein. Figure 3 and 4 A top view of a support of a rotor;

[0021] Figure 8 schematically depicts a top view of another embodiment of a strut for a rotor according to one or more embodiments shown and described herein;

[0022] Fig. 9A Schematically depicts a schematic diagram of a device according to one or more embodiments shown and described herein. Figure 7 The pillars along Figure 7 a cross-sectional view taken along reference line 9-9;

[0023] Fig. 9B schematically depicts a cross-sectional view of a strut having an asymmetric front surface with a leading edge according to one or more embodiments shown and described herein;

[0024] Fig.10 schematically depicts a top view of another embodiment of a rotor and a pressure screen cylinder according to one or more embodiments shown and described herein;

[0025] Fig.11 Schematically depicts a schematic diagram of a device according to one or more embodiments shown and described herein. Fig.10 a top view of a portion of a rotor;

[0026] Fig.12 Schematically depicts a schematic diagram of a device according to one or more embodiments shown and described herein. Fig.11 a front view of a portion of a rotor;

[0027] Fig.13 Schematically depicts a schematic diagram of a device according to one or more embodiments shown and described herein. Fig.11 a side view of a portion of a rotor;

[0028] Fig.14 schematically depicts a front perspective view of a rotor modeled in an example according to one or more embodiments shown and described herein;

[0029] Fig.15 Schematically depicts a schematic diagram of a device according to one or more embodiments shown and described herein. Fig.14 A top view of the rotor;

[0030] Fig.16 Graphically depicted is modeling of streamlines near a rotor surface for a rotor having forward-swept struts according to one or more embodiments shown and described herein. DETAILED DESCRIPTION

[0031] Reference will now be made in detail to embodiments of a rotor for a pressure screen cylinder, examples of which are illustrated in the accompanying drawings. Whenever possible, the same reference numerals will be used throughout the drawings to refer to the same or like parts.

[0032] Reference now Figure 1 , illustrates an embodiment of a pressure screening device for removing solid contaminants from a solid suspension or slurry according to the present disclosure. The pressure screening device includes a pressure screen cylinder 10 and a rotor 100 disposed within the pressure screen cylinder 10. The rotor 100 includes a cylindrical hub 110, a plurality of foils (foils, sheets / sheets / plates) 120 radially spaced outward from the hub 110, and a plurality of struts 140 coupling the plurality of foils 120 to the hub 110. Each of the struts 140 is a forward-swept strut having a forward edge 146. The forward edge 146 may be curved so that an outward end 144 of the forward edge 146 of the strut is disposed forward of a larger portion (e.g., greater than 50%) of the remaining forward edge 146 of the strut 140 with respect to the rotation direction 102 of the rotor 100. As previously described, the forward-swept struts 140 disclosed herein can reduce stringing (e.g., the accumulation of contaminants and fibers at the outward ends 144 of the struts 140). Reducing stringing can reduce drag and the power required to rotate the rotor 100, as well as avoiding stringing caused by reduced effectiveness of the foil 120 in generating pressure pulses against the inner surface 14 of the pressure screen drum 10 to dislodge contaminants and fibers.

[0033] Unless otherwise stated, any method described herein is not intended to be construed as requiring that its steps be performed in a particular order, nor is it intended to require a particular orientation of any apparatus. Thus, where a method claim does not specifically recite the order to be followed by the steps of the method, or where any apparatus claim does not specifically recite the order or orientation of individual components, or where the steps are not otherwise specifically stated in the claims or specification to be limited to a particular order, or where no particular order or orientation of components of the apparatus is recited, no order or orientation is intended to be inferred in any respect. This applies to any possible non-explicit basis for interpretation, including: logical matters regarding arrangement of steps, flow of operations, order of components, or orientation of components; obvious meaning derived from grammatical organization or numbering, and the number or type of embodiments described in the specification.

[0034] Directional terms used herein—eg, up, down, right, left, front, back, top, bottom—are made with reference only to the drawings drawn and the coordinate axes provided and are not meant to imply an absolute orientation.

[0035] As used herein, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to "a" component includes aspects having two or more such components unless the context clearly dictates otherwise.

[0036] As used herein, the terms “longitudinal” and “axial” refer to orientations or directions that are generally parallel to the central axis A of the pressure drum and / or the rotational axis B of the rotor 100 .

[0037] As used herein, the term "radial direction" refers to the direction from the pressure screen cylinder ( Figure 1 )’s center axis A and / or the direction of any radial line extending outward from the rotational axis B of the rotor 100.

[0038] As used herein, the terms "upstream" and "downstream" refer to the relative position of a feature with respect to the direction of flow of a solid suspension or slurry. For the screen cylinder of the present disclosure, the flow of the solid suspension is generally from the interior of the pressure screen cylinder, through the openings in the pressure screen cylinder, radially outward, to the outer surface of the pressure screen cylinder.

[0039] As used herein, the term "solid contaminants" or "oversized solid contaminants" may refer to solid objects, such as wood chips, metal pieces, dried adhesive, strings, or other contaminants, which are not intended and are not desired to be in a solid suspension or slurry, and can be distinguished from solid components, such as fibers, etc., that are intended to be in a solid suspension.

[0040] As used herein, the terms "front" and "rear" refer to a position on an object relative to the direction of motion of the object, wherein "front" refers to the direction of motion and "rear" refers to the direction away from the direction of motion. The "forward edge" of the strut disclosed herein refers to the edge of the strut facing the direction of rotation of the rotor, and the "rearward edge" of the strut refers to the edge of the strut facing the direction opposite to the direction of rotation of the strut.

[0041] As used herein, the term "inwardly" refers to a radial direction toward a hub of a rotor, and the term "outwardly" refers to a radially outward direction away from the hub.

[0042] As used herein, the term "leading edge" refers to the edge of the foil of the rotor facing the direction of rotation of the rotor. The term "trailing edge" refers to the edge of the foil of the rotor facing the direction opposite to the direction of rotation of the rotor.

[0043] As used herein, the term “forward sweep” refers to the shape of the forward edge of the strut wherein at least a portion of the outboard end of the forward edge of the strut is positioned forward of other portions of the forward edge of the strut that are closer to the inboard end of the strut with respect to the direction of rotation of the rotor.

[0044] As used herein, the term "congruent" means completely coincident when superimposed.

[0045] In the pulp and paper industry, pulp screening can be accomplished by a pressure screening (screening) process using a screen cylinder. The pressure screening process can include introducing a solid suspension, such as a solid suspension of fibers, into a pressure screen cylinder. The fibers can be any type of fiber, such as, but not limited to, cellulose fibers, cotton fibers, glass fibers, or other fibers. The screen cylinder can be an outward flow screen cylinder, wherein an acceptable portion of the solid suspension flows radially outward through the screen cylinder.

[0046] See now Figure 1 , one embodiment of a pressure screen drum 10 including a rotor 100 of the present disclosure is schematically depicted. The pressure screen drum 10 includes a drum wall 12 having an inner surface 14 and an outer surface 16. The drum wall 12 includes a plurality of openings extending radially through the drum wall 12 from the inner surface 14 to the outer surface 16. In various embodiments, the drum wall 12 may include a unitary drum wall including a metal drum having holes or slots drilled or milled into the metal drum to provide substantially radial openings through the drum wall 12.

[0047] refer to Figure 2In various embodiments, the cylinder wall 12 of the pressure screen cylinder may include a plurality of longitudinally arranged profiled bars 18, which define a plurality of grooves extending the length of the cylinder. In these embodiments, the profiled bars 18 may be coupled to at least one support ring 20 at the attachment end of the profiled bars 18. In various embodiments, the pressure screen cylinder 10 may include a plurality of support rings 20. The pressure screen cylinder 10 may also include an annular end flange 22 at either axial end of the pressure screen cylinder 10. Each of the profiled bars 18 is longitudinally aligned with the central axis A of the pressure screen cylinder 10 (e.g., parallel to the central axis A of the pressure screen cylinder 10) and longitudinally aligned with each of the other profiled bars 18. The profiled bars 18 may be arranged side by side along the circular inner circumference or outer circumference of the support ring 20 to form the cylinder wall 12. The cylinder wall 12 formed by the plurality of profiled bars 18 may include a groove defined between each pair of adjacent profiled bars 18. The groove may extend the length of the pressure screen cylinder 10 between the two annular end flanges 22. Further features and aspects of the support structure and operation of the pressure screen cylinder 10 of the present disclosure may be found in U.S. Patent No. 8,469,198, the entire contents of which are incorporated herein by reference. Figure 1 and Figure 2 1 and 2, depicted as an outward-flowing pressure screen drum, wherein acceptable solid suspension flows radially outward through slots defined between forming bars 18. Pressure screen drum 10 may be operable to separate solid contaminants from the solid suspension. Other configurations for pressure screen drum 10 are contemplated, provided that pressure screen drum 10 has a drum wall 12 having an inner surface on which solid contaminants and oversized fibers collect into a mat during operation of pressure screen drum 10.

[0048] Reference again Figure 1 , a rotor 100 is disposed within a pressure screen cylinder 10. The rotor 100 includes a hub 110, a plurality of foils 120 radially spaced outward from the hub 110, and a plurality of struts 140 coupling each of the plurality of foils 120 to the hub 110. The rotor 100 is operably coupled to a rotor drive motor (not shown) that operates to rotate the rotor 100 within the pressure screen cylinder 10. The rotor 100 rotates in a rotational direction 102 relative to the pressure screen cylinder 10. The rotor 100 has an axis of rotation B. The axis of rotation B of the rotor 100 is substantially congruent (coincident) with a central axis A of the pressure screen cylinder.

[0049] Reference again Figure 1, the hub 110 may be a cylindrical hub centered on the rotation axis B of the rotor 100. The hub 110 may be a solid shaft, or a hollow cylindrical shaft. The hub 110 has a proximal end 114 operably coupled to the rotor drive motor and a distal end 116 extending into the pressure screen cylinder 10. The hub 110 may be operably coupled to the rotor drive motor (not shown) to rotate the rotor 100 relative to the pressure screen cylinder 10. The hub 110 has an outer surface 112 that faces radially outwardly toward the inner surface 14 of the pressure screen cylinder 10.

[0050] Reference now Figure 3 , the rotor 100 includes a plurality of foils 120 spaced apart from the hub 110 in a radial direction, such that the foils 120 travel along the inner surface 14 of the pressure screen cylinder 10 when the rotor 100 rotates. In various embodiments, each of the foils 120 may have an airfoil cross-sectional shape. Each of the foils 120 has a leading edge 122 facing the direction of rotation 102 and a trailing edge 124 facing in the opposite direction of the leading edge 122 of the foil 120. In various embodiments, each of the foils 120 may have a blunt or hemispherical leading edge 122 and a tapered (conical) trailing edge 124. However, it is understood that the leading edge 122 and the trailing edge 124 of the foil 120 may have any shape effective for generating pressure pulses at the inner surface 14 of the pressure screen cylinder 10, and the scope of the present disclosure is not intended to be limited to the cross-sectional shape of the foil 120. Each of the foils 120 has an inner surface 126 facing radially inwardly toward the hub 110 and an outer surface 128 facing radially outwardly toward the inner surface 14 of the pressure screen drum 10. Figure 4 , the foil 120 can be radially positioned so that the gap G between the outer surface 128 of the foil 120 and the inner surface 14 of the drum wall 12 of the pressure screen drum 10 has a minimum distance from about 1 mm to about 15 mm, for example, from about 2 mm to about 10 mm. Without reducing the effectiveness of the rotor design discussed herein, the gap G can be greater or less than the aforementioned range. The gap G defined between the outer surface 128 of the foil 120 and the inner surface 14 of the drum wall 12 can be called the screen working area.

[0051] Reference again Figure 3, each of the foils 120 may be oriented generally vertically such that an acute angle C between a leading edge 122 of the foil 120 and a line S that is parallel to the rotation axis B and intersects the leading edge 122 of the foil 120 is less than or equal to about 40 degrees, less than or equal to about 30 degrees, or even less than or equal to about 20 degrees. In various embodiments, the foils 120 may be angled such that the acute angle C is greater than 0 (zero) and less than or equal to 40 degrees. When the foils 120 are angled, each of the foils 120 may be slightly spiral shaped such that a gap G between an outer surface 128 of the foil 120 and an inner surface 14 of the pressure screen drum 10 is the same along the entire length of the foil 120. In various embodiments, the foils 120 may be vertical such that a leading edge 122 of the foil 120 is parallel to the rotation axis B of the rotor 100 (e.g., such that the angle theta is equal to 0 (zero)).

[0052] The rotor 100 may have a number of foils 120 sufficient to release entangled solid contaminants and fibers from the inner surface 14 of the pressure screen cylinder 10 to prevent the pressure screen cylinder 10 from being partially or completely blocked by the solid contaminants and fibers. The rotor 100 may have greater than or equal to 4 foils 120, such as 4, 5, 6, 7, 8, 9 or greater than 9 foils 120.

[0053] Reference again Figure 3 and Figure 4 , each of the plurality of foils 120 is coupled to the hub 110 by a plurality of struts 140. As used herein, the term "strut" refers to a structure that couples the foil 120 to the hub 110 of the rotor 100 or to the hub portion of a strut ring that is directly connected to the hub 110. A strut may include an arm, fin, rod, blade, bar, or other structure that extends radially outward from the hub 110 or the hub portion 162 of the strut ring 160 to the foil 120. Each strut 140 is directly connected to the inner surface 126 of the foil 120 at an outward end 144 of the strut 140 and is coupled to the hub 110 at an inward end 142 of the strut 140. In various embodiments, the strut 140 may be directly connected to the outer surface 112 of the hub 110. In other embodiments, rotor 100 may include a plurality of support rings 160 directly connected to outer surface 112 of hub 110, and support 140 may extend radially outward from support rings 160 to foil 120. Support 140 couples foil 120 to hub 110 so that foil 120 rotates with hub 110 during operation of pressure screen cylinder 10 while also allowing slurry or solid suspension to flow axially through the center of pressure screen cylinder 10 during operation. In various embodiments, each foil 120 may be coupled to hub 110 by at least 2 or at least 3 support 140.

[0054] Reference again Figure 1 During operation of the pressure screen drum 10, slurry is axially introduced into the interior volume of the pressure screen drum 10. The slurry may be a slurry including pulp fibers for papermaking dispersed in a liquid medium such as water, but the pressure screen drum 10 and rotor 100 of the present disclosure are not intended to be limited thereto. The solid slurry or suspension flows into the pressure screen drum 10, causing the liquid medium and fibers having a size less than a threshold size to pass through the openings in the drum wall 12 of the pressure screen drum 10. Contaminants and fibers that are too large for the papermaking process do not pass through the openings in the drum wall 12 and are collected on the inner surface 14 of the drum wall 12 of the pressure screen drum 10. The collected solid contaminants and fibers may form a mat on the inner surface 14 of the drum wall 12 that reduces or prevents acceptable slurry flow through the openings in the drum wall 12 of the pressure screen drum 10.

[0055] During operation, the rotor 100 rotates within the pressure screen drum 10. The rotation of the rotor 100 causes the plurality of foils 120 to traverse (sweep) circumferentially around the inner surface 14 of the drum wall 12 of the pressure screen drum 10. The movement of the foils 120 along the inner surface 14 of the pressure screen drum 10 generates pressure pulses in the screen working area, which act to remove solid contaminants and fibers entangled to the inner surface 14 of the pressure screen drum 10. Removal of entangled solid contaminants and fibers can reduce or prevent the clogging of the openings in the pressure screen drum 10 by contaminants, and reintroduce solid contaminants and fibers back into the incoming slurry or solid suspension. The solid contaminants and the rejected oversized fibers that fall off the pressure screen drum 10 through the rotor foils 120 flow to the rejection outlet of the pressure screen drum 10 and are removed from the system. The acceptable fibers released from the inner surface 14 return to the incoming slurry or solid suspension and can be reintroduced into the pressure screen drum 10 so as to have a chance to pass through the openings to an acceptable outlet again.

[0056] Referring now to FIG5 , one example of a conventional rotor 200 for a pressure screen drum 10 is schematically depicted in a top view. In the conventional rotor 200 of FIG5 , the struts 240 coupling the foil 220 to the hub 210 are rods extending radially outward along a straight line from the hub 210 to the foil 220. These struts 240 have forward edges that are positioned along the straight line and form a substantially right angle with the foil 220 at the outward ends 244 of the struts 240.

[0057] During the operation of the pressure screen drum and the rotor, the rotor rotates and the movement of the foil causes the contaminants and fibers to be detached from the inner surface 14 of the pressure screen drum 10. Now referring to FIG. 6, the conventional rotor 200 of FIG. 5 is schematically depicted in a top view. As shown in FIG. 6, the contaminants and fibers that fall off can be collected on the forward edge 246 of the pillar 240, especially at the position where the pillar 240 is connected to each foil in each foil 220 (e.g., at the outward end 244 of the pillar 240). The fibers and contaminants initially captured on the forward edge 246 of the pillar 240 can accumulate more contaminants and fibers, and the deposits 400 on the forward edge 246 of the pillar can continue to accumulate on the pillar 240 and on the leading edge of the foil 220. This phenomenon is called stringing (connecting together). The deposits 400 of solid contaminants and fibers caused by stringing will increase the rotor resistance, and the rotor resistance increases the motor power required to rotate the rotor 200. Deposits 400 of contaminants and fibers accumulated on the forward edge 246 of the struts 240 proximate the foil 220 and on the leading edge of the foil 220 may also interfere with the pressure pulses generated by the leading edge of the foil 220 and reduce the effectiveness of the foil 220 in dislodging contaminants and fibers from the inner surface 14 of the pressure screen cylinder 10.

[0058] The thickness of the struts 240 at the outward ends 244 may be increased to reduce the accumulation of solid contaminants and fibers on the forward edges 246 of the struts 240. For example, increasing the thickness of the struts 240 to greater than or equal to 1.5 inches (about 38 mm) such that the radius of curvature of the forward edges of the struts 240 is greater than or equal to about 0.75 inches (about 19 mm) may reduce the likelihood of solid contaminants and fibers being caught on the forward edges 246 at the outward ends 244 of the struts 240. However, increasing the thickness of the struts 240 at the outward ends 244 may increase the drag created by the movement of the struts 240 through the slurry during operation. The increased drag on the struts 240 may significantly increase the power load required to rotate the rotor 200.

[0059] Reference again Figure 3 and Figure 4, the rotor 100 of the present disclosure addresses these issues by including the struts 140 as forward-swept struts. The forward-swept design of the struts 140 disclosed herein creates a flow field around the forward edges 146 of the struts 140 that transports solid contaminants and fibers that are dislodged from the pressure screen drum 10 or from the overall flow field around the struts 140 in an inward direction (e.g., radially inward toward the hub 110). The forward-swept design of the struts 140 that moves the solid contaminants and fibers inward can reduce or prevent the accumulation of contaminants and fibers on the forward edges 146 of the struts 140 and / or on the leading edges 122 of the foils 120. This in turn can reduce or prevent the deposition of solid contaminants and fibers that would interfere with the pressure pulses generated by the passage of the foil 120 over the inner surface 1 of the pressure screen drum 10, and can reduce the drag acting on the struts 140 caused by the accumulation of contaminants and fibers on the outward ends 244 of the struts 140. The forward swept design of the struts 140 disclosed herein may also enable the struts 140 to be made thinner, which may further reduce the drag created by movement of the struts 140 through a solid slurry or suspension.

[0060] Reference again Figure 3 and Figure 4 As previously described, the rotor 100 includes a hub 110, a plurality of foils 120, and a plurality of struts 140 coupling the plurality of foils 120 to the hub 110. In various embodiments, the rotor 100 may include a plurality of strut rings 160 coupled to the hub 110, wherein each strut ring 160 may include a hub portion 162 and each support 140 may extend radially outward from the hub portion 162 of the strut ring 160 to the foils 120. The hub portion 162 may be an annular disk coupled to the hub 110 at a radially inner edge 164 and coupled to the plurality of struts 140 at a radially outer edge 166 of the annular disk. In certain embodiments, the struts 140 may be directly coupled to the hub 110 at the inward end 142 of the struts 140.

[0061] Reference now Figure 7, the strut 140 disclosed herein has a forward edge 146 having a forward-swept shape. The forward edge 146 having a forward-swept shape generally refers to that the shape of the forward edge 146 of the strut 140 is designed so that the forward edge 146 at the outward end 144 of the strut 140 is disposed in front of the rest of the forward edge 146 of the strut 140 with respect to the rotational direction 102 of the rotor 100. In various embodiments, the shape of the forward edge 146 of the strut 140 is designed so that the forward edge 146 at the outward end 144 of the strut 140 is disposed in front of most of the rest of the forward edge 146 of the strut 140 with respect to the rotational direction 102 of the rotor 100. The forward-swept shape of the forward edge 146 of the strut 140 does not refer to any forward protrusion of material at or close to (e.g., within less than 1 cm) the outward end 144 of the strut 140, the forward protrusion of material being solely for the purpose of connecting the strut 140 to the foil 120 or the hub 110.

[0062] The forward edge 146 of the support post 140 may be shaped such that a point P on the forward edge 146 at the outward end 144 of the support post 140 OUT The forward edge 146 of the support 140 is disposed in front of the majority of the other portions of the forward edge 146 of the support 140 with respect to the rotation direction 102 of the rotor 100. The forward edge 146 of the support 140 may be shaped so that a point P on the forward edge 146 at the outward end 144 of the support 140 OUT The forward edge 146 of the strut 140 may be curved such that a point on the forward edge 146 at the outward end 144 of the strut 140 (e.g., point P OUT ) is arranged at least 50%, at least 75%, or even at least 90% ahead of the rest of the forward edge 146 of the strut 140 with respect to the rotation direction 102 of the rotor 100. In various embodiments, the forward edge 146 of the strut 140 has a concave curve (concave curvature). In various embodiments, at least 25%, at least 35%, at least 50%, or even at least 90% of the forward edge 146 of the strut 140 has a concave curve (concave curvature). In various embodiments, the forward edge 146 of the strut 140 is continuously curved from the outward end 144 to the inward end 142. The curvature of the forward edge 146 here refers to the curvature in a horizontal plane, meaning that the curvature of the forward edge is in a plane perpendicular to the rotation axis of the rotor and radially passes through the strut 140. In various embodiments, the radius of curvature of the forward edge 146 may increase as the radial distance between a point on the forward edge 146 of the strut 140 and the rotation axis 102 of the rotor 100 decreases. Reference Figure 7 In various embodiments, at least a portion of the forward edge 146 of the strut 140 can be straight (i.e., extending in a straight line rather than being curved) and angled such that the outward end 144 is forward of the inward end 142 of the forward edge 146. In various embodiments, at least 50%, at least 75%, at least 85%, at least 90%, at least 95%, or even at least 98% of the forward edge 146 of the strut 140 is straight (i.e., extending in a straight line rather than being curved).

[0063] Reference again Figure 7 , point P on support 140 IN The (inboard point) is the point at which the forward edge 146 of the strut 140 is attached to the hub 110 or to the hub portion 162 of the strut ring 160 at the inboard end 142 of the strut 140. Point P OUT The (outer point) is the point on the strut 140 where the forward edge 146 of the strut 140 is attached to the foil 120 at the outward end 144 of the strut 140. The radius R IN is a point P on the inward end 142 of the forward edge 146 of the support 140 and is centered on the rotation axis B of the rotor 100 and passes through. IN The radius of the circle. Radius R OUT is a point P on the outward end 144 of the forward edge 146 of the support 140, centered on the rotation axis B of the rotor 100 and passing through. OUT The radius of the circle. Point P (for example, point P1 or point P2) is set at point P IN and point P OUT The radius R is the radius of a circle having the rotation axis B of the rotor 100 as its center and passing through the point P on the forward edge 146 of the pillar 140 .

[0064] refer to Figure 7 The first point P1 is on the forward edge 146 of the support 140 at point P IN With P OUT The second point P2 is an arbitrary point between the forward edge 146 of the support 140 and the radius R1 is the radius of a circle centered on the rotation axis B of the rotor 100 and passing through the point P1. IN With P OUT The radius R2 is the radius of a circle centered on the rotation axis B of the rotor 100 and passing through the point P2. OUT The radial line D passing through P1 and the radial line E passing through P1 define an angle α1, and the radial line E passing through P OUTThe radial line D passing through P2 and the radial line F passing through P2 define an angle α2. In various embodiments, when the radius R2 is greater than the radius R1 and the angle α2 is less than the angle α1, the forward edge 146 of the strut 140 can be considered to have a forward swept shape (a forward swept shape). The angles α1 and α2 are measured as respectively Figure 7 The angle of counterclockwise movement from line D to line E or line F. In various embodiments, when radius R2 is greater than radius R1, angle α2 is less than angle α1, and the distance between points P2 and P1 is P IN Point and P OUT The forward edge 146 of the strut 140 may be considered to have a forward swept shape when the distance between points along the forward edge 146 is at least 5%, at least 10%, or at least 15%.

[0065] In various embodiments, point P on the forward edge 146 of the support 140 OUT The support 140 is disposed forward of a point P with respect to the direction of rotation 102 of the rotor 100, wherein the point P is disposed on the forward edge 146 of the support 140 at a radius R greater than or equal to (R IN +((R OUT -R IN ) / 2)). In various embodiments, at point P on the forward edge 146 at the outward end 144 of the support 140 OUT The point P is located at the inward end 142 of the forward edge 146. IN In various embodiments, point P on the forward edge 146 at the outward end 144 of the support 140 OUT Set it in front of point P. OUT Point P on the forward edge 146 of the support 140 IN With point P OUT All positions between them are in front of point P.

[0066] Reference again Figure 7 In various embodiments, when point P is at the forward edge 146 and the radius R is equal to (R IN +((R OUT -R IN ) / 2) of the circle, point P OUT The point P may be arranged to be greater than or equal to 5 degrees, greater than or equal to 10 degrees, greater than or equal to 15 degrees, or even greater than or equal to 20 degrees, such as from 5 degrees to 50 degrees, in front of the point P with respect to the rotation direction of the rotor 100. In other words, the point P extends from the rotation axis B and passes through the point P. OUT The radial line D of the rotation axis forms an angle α1 (alpha) with the radial line E extending from the rotation axis B and passing through the point P1. In various embodiments, when the point P is at the forward edge 146 and the radius R is equal to (R IN +((R OUT-R IN ) / 2) of the circle, point P OUT The angle α1 may be greater than or equal to 3 degrees, greater than or equal to 5 degrees, greater than or equal to 10 degrees, greater than or equal to 15 degrees, or even greater than or equal to 20 degrees, such as from 3 degrees to 50 degrees. The forward edge 146 of the support 140 may be curved so that the angle α follows the point P. OUT The radius R to at least a point P on the forward edge 146 of the support 140 decreases and increases, wherein the radius R is equal to (R IN +((R OUT -R IN ) / 2). In various embodiments, the forward edge 146 of the support 140 may be bent such that the angle α increases with the radius R from point P OUT To point P IN In various embodiments, the forward edge 146 of the support 140 is from point P on the forward edge 146. OUT The rotor 100 is continuously curved to a point P, wherein the radius R of a circle centered on the rotation axis B of the rotor 100 and passing through the point P is less than or equal to (R IN +((R OUT -R IN ) / 2).

[0067] Reference now Figure 8 In various embodiments, the forward edge 146 of the strut 140 may be considered to have a forward swept shape, even if the forward edge 146 of the strut 140 curves forward near the inboard end 142 of the strut 140. Figure 8 In the schematically depicted embodiment, point P3 is shown as being disposed on the forward edge 146 of the support 140 proximate the inboard end 142. Point P3 and point P IN In front of the points P1 and P2, a smaller radial distance from the point P3 to the axis of rotation B and a significantly larger angle α3 are shown. IN Also in P OUT However, since P2 is in front of P1 and P OUT In front of P1 and P2, the forward edge 146 of the strut 140 is still considered to be swept forward (swept forward). Therefore, the forward edge 146 of the strut 140 has a swept forward shape, even though only the portion of the forward edge 146 closest to the outboard end 144 of the strut 140 is angled or bent in the forward direction as the radial distance from the rotation axis B increases.

[0068] As previously described, the forward swept shape of the struts 140 can reduce the likelihood of contaminants and fibers being caught on the forward edges 146 of the struts 140, which can enable the thickness of the struts to be reduced. Fig. 9A , the figure schematically depicts the Figure 7 A cross section of one embodiment of the support 140 is taken along reference line 9-9 in FIG. In various embodiments, the support 140 may have a thickness T S , the thickness can be less than 1.5 inches (38 mm), such as from 0.25 inches (6.4 mm) to less than 1.5 inches (38 mm), or from 0.5 inches (12.7 mm) to 1.25 inches (about 32 mm). The forward swept design of the strut 140 disclosed herein can provide greater flexibility in determining the thickness of the strut 140 to balance resistance and stringing.

[0069] In various embodiments, forward edge 146 of strut 140 includes front surface 150 extending from top surface 152 of strut 140 to bottom surface 154 of strut 140. Front surface 150 may have any cross-sectional shape and the present disclosure is not limited thereto. Fig. 9A and 9B The following embodiments described in the present invention are intended to illustrate the relationship between thickness, the radius of curvature of the front surface 150, and the series connection. In each embodiment, as Fig. 9A As shown, the front surface 150 can have a hemispherical shape having a radius of curvature ξ that is less than about 0.75 inches (19 mm), less than or equal to 0.5 inches (12.7 mm), less than or equal to 0.4 inches (10.2 mm), less than or equal to 0.3 inches (7.6 mm), or even less than or equal to 0.25 inches (6.35 mm), such as from 0.1 inches to 0.75 inches. The radius of curvature ξ of the front surface 150 refers to the radius of curvature ξ of the front surface 150 in a vertical plane (e.g., Fig. 9A The radius of a circle H on a plane parallel to the Z axis and vertically bisecting the support 140 in the middle of the plane is a circle having an arc that is congruent (coincident) with the hemispherical profile of the front surface 150. The rearward edge 148 is Fig. 9A 148 is shown as having a tapered shape. However, it is understood that the rearward edge 148 can have any suitable shape, including a hemispherical shape or other shapes. The profile of the rearward edge 148 has no effect on the stringing.

[0070] Reference now Fig. 9BIn various embodiments, the front surface 150 of the forward edge 146 of the pillar 140 can have a non-hemispherical shape. In various embodiments, the front surface 150 of the forward edge 146 can have an asymmetric shape, such as but not limited to having two or more sections with different radii of curvature. The asymmetric shape of the front surface 150 of the pillar 140 can further help reduce the accumulation of solid contaminants and fibers from the forward edge 146 of the pillar 140. For a symmetrical shape of the front surface 150, such as a hemispherical shape, the forces on the solid contaminants and fibers captured on the front edge 146 are balanced, which can tend to keep the solid contaminants and fibers captured on the front edge 146. In contrast, the asymmetric shape of the front surface 150 can result in an unbalanced force acting on the solid contaminants and fibers captured on the front edge 146. In particular, the asymmetric shape of the front surface 150 can alter the flow path around the forward edge 146 of the strut 140 such that the velocity of the fluid directed above the top surface 152 of the strut 140 is different than the velocity of the fluid directed below the bottom surface 154 of the strut 140. The difference in fluid velocity above and below the strut 140 can cause the force exerted on the solid contaminants and fibers due to the fluid flow to be greater on one side of the strut 140, which can operate to pull the solid contaminants and fibers away from the forward edge 146 of the strut 140.

[0071] refer to Fig. 9B , the front surface 150 can have a first segment 156 and a second segment 158. The first segment 156 can have a first radius of curvature corresponding to a radius of a circle H1 that is congruent (coincident) with the first segment 156. The second segment 158 ​​can have a second radius of curvature corresponding to a radius of a circle H2 that is congruent (coincident) with the second segment 158, wherein the second radius of curvature is different from the first radius of curvature. Other contour shapes of the front surface 150 of the forward edge 146 of the strut 140 are also contemplated.

[0072] The forward-swept struts 140 create flow lines that convey material inwardly toward the hub 110. Thus, during operation, the forward-swept struts 140 cause solid contaminants and fibers that are dislodged from the inner surface 14 of the pressure screen cylinder 10 or in the general flow field around the struts 140 to move inwardly toward the inward ends 142 of the struts 140 and the hub 110, rather than being collected on the forward edges 146 of the struts 140 at the outward ends 144 or on the leading edges 122 of the foils 120. In various embodiments, some solid contaminants and fibers may still be captured in the wedge-shaped pockets at the points P1 where the inward ends 142 of the struts 140 are coupled to the hub 110 or the hub portion 162 of the strut ring 160. The accumulation of contaminants and fibers near the inward ends 142 of the struts 140 is less of a problem because the accumulation at the inward ends 142 of the struts 140 does not interfere with the operation of the foils 120 to generate pressure pulses against the inner surface 14 of the pressure screen cylinder 10. Additionally, due to the accumulation closer to the rotational axis B of the rotor 100, the linear velocity of the inboard ends 142 of the struts 140 is less than the linear velocity of the outboard ends 144 of the struts 140. The reduced linear velocity at the inboard ends 142 reduces the effect of deposits of contaminants and fibers on the drag of the rotor 100. However, such deposits at the inboard ends 142 of the struts 140 still have some effect on the drag and the power required to rotate the rotor 100, although this effect is more limited.

[0073] Reference now Figure 10-13 In various embodiments, the rotor 100 disclosed herein may include a relief area 170 located at the inboard end 142 of each strut 140 where the inboard end 142 is coupled to the hub 110 or the hub portion 162 of the strut ring 160. The relief area 170 may be disposed at the forward edge 146 of the strut 140 such that the relief area 170 forms at least a portion of the forward edge 146 of the strut 140 at the area where the inboard end 142 of the strut 140 is coupled to the hub 110 or the hub portion 162 of the strut ring 160. The relief area 170 may form less than 50%, less than or equal to 30%, less than or equal to 20%, less than or equal to 15%, less than or equal to 10%, or even less than or equal to 5%, such as from 1% to 50% of the forward edge 146 of the strut 140.

[0074] The thickness T of the release area 170 R It can be greater than the thickness T of the support 140 S The thickness T of the release area 170 is R It may be sufficient to increase the radius of curvature ξ of the front surface 150 of the forward edge 146 of the strut 140, the hub portion 162 of the strut ring 160, or both at the point where the inward end 142 of the strut 140 is coupled to the hub 110 or the strut ring 160. In various embodiments, the relief region 170 may have a thickness TR , so that the radius of curvature ξ of the front surface 150 of the forward edge 146 of the support 140 at the inward end 142 is greater than or equal to 0.75 inches (19.1 mm), greater than or equal to 1.0 inches (25.4 mm), greater than or equal to 1.25 inches (31.8 mm), or even greater than or equal to 1.5 inches (38.1 mm), such as approximately 0.75 inches to 6 inches.

[0075] The thickness T of the release area 170 R Greater than the thickness T of the support 140 S In various embodiments, the thickness T of the release region 170 is R The thickness T of the support 140 may be S 1.25 times, at least 1.5 times, at least 1.75 times, at least 2 times, at least 2.25 times, or even at least 3 times the thickness T of the support 140, such as S In various embodiments, the thickness T of the release region 170 is about 1.25 to 10 times greater than that of the release region 170. R The thickness TS of the strut 140 may be greater than or equal to about 35 mm, greater than or equal to about 37 mm, or even greater than or equal to about 40 mm. In various embodiments, the thickness TS of the strut 140 may increase with decreasing radial distance from the axis of rotation B of the rotor 100, from a minimum thickness near the outward end 144 of the strut 142 to a thickness T of the relief region 170 at the inward end 142 of the strut 140. R The thickness T of the release area 170 is R It may be at least 1.25 times, at least 1.5 times, at least 1.75 times, at least 2 times, at least 2.25 times, or even at least 3 times the minimum thickness near the outward end 144 of the strut 140 .

[0076] The greater thickness of release region 170 provides a greater radius of curvature ξ of inward end 142 of strut 140. The greater radius of curvature ξ of release region 170 may cause contaminants and fibers that pass along forward edge 146 of strut 140 in a radially inward direction from outward end 144 to inward end 142 to disengage from inward end 142 of strut 140. Solid contaminants released from strut 140 by release region 170 may move toward a reject outlet of pressure screen drum 10 where they may be removed from the pressure screening device. Any acceptable fibers released by release region 170 may be returned to the slurry or suspension for reintroduction into pressure screen drum 10.

[0077] Reference again Figure 8In various embodiments, the forward edge 146 of the strut 140 may be swept forward (swept forward) near the outward end 144 of the strut 140, but may bend back in the forward direction near the inward end 142 of the strut 140. In these embodiments, the release region 170 may be positioned at the inflection point of the forward edge 146. The inflection point is a point on the forward edge 146 where movement along the forward edge 146 in the inward or outward direction results in movement forward from the inflection point with respect to the direction of rotation of the rotor 100. The inflection point creates a pocket where solid contaminants and fibers may be trapped on the forward edge 146 of the strut 140. Providing the release region 170 at the inflection point of the forward edge 146 may help release any fibers or contaminants that flow inward from the forward edge 146 of the strut 140.

[0078] As previously mentioned, the pressure screen drum 10 including the rotor 100 with the forward swept struts 140 can be used to process solid suspensions of cellulose or other fibers in the pulp and paper industry, as described herein. However, the pressure screen drum 10 and the rotor 100 of the present disclosure with the forward swept struts 140 may be used to screen solid suspensions and / or slurries to remove oversized solid contaminants in mining and drilling applications, food preparation and processing operations, water treatment processes, coating operations, and other industries.

[0079] Reference again Figure 1In various embodiments, a method of removing oversized solid contaminants from a slurry or solid suspension may include contacting the slurry or solid suspension with a pressure screen drum 10 including a rotor 100. The pressure screen drum 10 may have any of the features of the pressure screen drum 10 previously described herein. In particular, the pressure screen drum 10 may include a drum wall 12 having an inner surface 14, an outer surface 16, and a plurality of openings extending through the drum wall 12 from the inner surface 14 to the outer surface 16. Contact of the solid suspension or solid slurry with the pressure screen drum 10 causes at least a portion of the solid suspension or solid slurry to pass through the openings in the drum wall 12. The method may also include rotating the rotor 100 disposed within the pressure screen drum 10. The rotor 100 may have any of the features of the rotor 100 previously described herein. In various embodiments, the rotor 100 includes a cylindrical hub 110, a plurality of foils 120 spaced radially outward from the hub 110, and a plurality of struts 140 coupling the plurality of foils 120 to the hub 110. Each of the plurality of foils 120 is radially spaced from the inner surface 14 of the drum wall 12. The struts 140 are forward-swept struts having curved forward edges 146 such that the outward ends 144 of the forward edges 146 are disposed forward of the inward ends 142 of the forward edges 146 with respect to the rotational direction 102 of the rotor 100. The rotation of the rotor 100 causes each of the plurality of foils 120 to generate a pressure pulse that dislodges solid contaminants and fibers entangled to the inner surface 14 of the pressure screen drum 10. The forward-swept struts 140 generate fluid streamlines that move the solid contaminants and fibers inward toward the hub 110 and prevent the solid contaminants and fibers from being collected on the forward edges 146 of the struts 140, the leading edges 122 of the foils 120, or both. The method may further include collecting acceptable solid suspensions from the plurality of openings of the pressure screen drum 10. The method may further include collecting solid contaminants rejected from a rejection outlet of the pressure screen drum. Example

[0080] Embodiments of the present disclosure will be further illustrated by the following examples, which should not be construed as limitations on the presently described disclosed and / or claimed embodiments.

[0081] Example 1

[0082] In Example 1, the rotation of a rotor with forward-swept struts within a fluid is modeled using Ansys R19.2 engineering simulation software. Fig.14 and Fig.15 , the modeled rotor 100 is shown in a side view ( Fig.14 ) and top view ( Fig.15) is schematically depicted. The modeled rotor 100 includes nine foils 120, oriented at an angle to the vertical and slightly curved at both ends. Each foil 120 is attached to the hub 110 by three support rings 160, which have support rings 140 extending radially outward from the support rings 160 to the foils 120. The support 140 is forward-swept (forward-swept) so that the outward end 144 of the forward edge 146 is forward-swept relative to the rest of the forward edge 146 of the support 140. Fig.16 The modeling of the rotation of the rotor 100 with the modeling of the forward swept struts 140 is graphically presented. Fig.16 As shown, the rotation of rotor 100 and the movement of forward-swept struts 140 through the fluid create streamlines 190 along forward edges 146 of struts 140 that direct fluid and material in an inboard direction, radially inward, toward hub 110 .

[0083] Comparative example 2: Pressure screen drum operation with standard rotor

[0084] In Comparative Example 2, a pressure screen drum with a standard rotor is operated to screen pulp. The pressure screen drum has slots with a slot width of about 0.21 mm. The standard rotor of Comparative Example 2 has 6 foils, and each of the 6 foils is connected to the hub by 3 struts extending radially between the hub and the inner surface of the foil. The struts are cylindrical rods extending radially between the hub and the inner surface of the foil, similar to the prior art depicted in Figure 5. The outer diameter of the struts including the cylindrical rods is about 30 mm. The nominal feed concentration of the pulp slurry introduced into the pressure screen drum of Comparative Example 2 is 2.8%.

[0085] The pressure screen drum and the standard rotor were run for an extended period of time to screen the pulp slurry. During the run, the rejection rate, thickening factor, drive speed and power consumption were recorded. The thickening factor was determined by measuring the consistency of the reject slurry leaving the reject outlet and the consistency of the feed slurry entering the screen. The thickening factor is the ratio of the consistency of the reject slurry to the consistency of the feed slurry. The average power consumption during the run is provided in Table 1 below.

[0086] After the pressure screen drum runs, the pressure screen drum is stopped and the drum is emptied to check the standard rotor. Upon inspection, the standard rotor does not have stringing (i.e., paper fibers accumulate on the leading edge of the support near the foil). Therefore, the leading edge of the standard rotor including a cylindrical rod with an outer diameter of 30 mm has sufficient curvature to prevent stringing.

[0087] Example 3: Pressure screen drum operation with a rotor having forward-swept struts

[0088] In Example 3, the standard rotor in the pressure screen drum of Comparative Example 2 was replaced by a rotor with forward-swept struts of the present disclosure. The pressure screen drum with the rotor of Example 3 with forward-swept struts was then run to screen pulp. The rotor of Example 3 is similar to Figure 3 The rotor 100 depicted in FIG. The rotor of Example 3 has 7 foils tilted at an angle. Each of the foils is coupled to the hub by three forward-swept struts having a thickness of 12 mm. The nominal feed consistency of the pulp slurry introduced into the pressure screen drum of Comparative Example 2 is 2.8%.

[0089] The pressure screen drum and the rotor of Example 3 with forward-swept struts were run for a long time to screen the pulp slurry. During the run, the production rate (rate), rejection rate, thickening factor, drive speed and power consumption were recorded. The production rate was maintained the same as that of Comparative Example 2. The rejection rate and thickening factor of Example 3 were comparable to the values ​​of Comparative Example 2. The average power consumption of Example 3 is provided in Table 1 below. After the pressure screen drum was run, the pressure screen drum was stopped and the screen drum was emptied to check the series connection of the rotor of Example 3. Upon inspection, the rotor of Example 3 with forward-swept struts did not show series connection. Table 1 Comparative Example 2 Example 3 Improvement percentage Rotor Type standard Forward Sweep -- Number of blades 6 7 -- power 77 59 23.4％ Observed concatenation none none --

[0090] Both the standard rotor of Comparative Example 2 and the rotor of Example 3 with forward swept struts reduce stringing (e.g., fiber accumulation on the leading edge of the struts adjacent to the foil). The rotor of Example 3 has one additional foil. One of ordinary skill in the art would have thought that the additional foil and the additional three struts of the rotor of Example 3 would require more power. However, it was unexpectedly discovered that even with the additional foil, the average power required for the rotor of Example 3 was more than 23% less than the power required to operate the standard rotor. Thus, the rotor of Example 3, including the forward swept struts, eliminates the stringing problem while still being able to operate at a lower power than the standard rotor of Comparative Example 2.

[0091] Although various embodiments of the rotor 100 for the pressure screen drum 10 and methods for using the rotor 100 and the pressure screen drum 10 have been described herein, it should be understood that it is contemplated that each of these embodiments and techniques can be used alone or in combination with one or more embodiments and techniques. It will be apparent to those skilled in the art that various modifications and variations can be made to the embodiments described herein without departing from the spirit and scope of the claimed subject matter. Thus, this specification is intended to cover modifications and variations of the various embodiments described herein if such modifications and variations fall within the scope of the appended claims and their equivalents.

Claims

1. A rotor for a pressure screen drum for screening contaminants from a solid slurry or solid suspension, the rotor comprising a cylindrical hub, a plurality of foils radially spaced outward from the cylindrical hub, and a plurality of struts, wherein each of the plurality of foils is coupled to the cylindrical hub by two or more of the plurality of struts, and each of the plurality of struts is a forward-swept strut having a forward edge.

2. The rotor according to claim 1, characterized in that For each strut of the plurality of struts, an outward end of the forward edge of the strut is disposed at least 50% forward of the forward edge with respect to an axis of rotation of the rotor.

3. The rotor according to claim 1, characterized in that For each strut of the plurality of struts, an outward end of the forward edge of the strut is disposed forward of an inward end of the forward edge of the strut with respect to the axis of rotation of the rotor.

4. The rotor according to claim 1, characterized in that: P IN is a point on said forward edge of each of said plurality of struts at an inboard end; P OUT is a point on said forward edge of each of said plurality of struts at an outward end; R IN is the rotation axis of the rotor and the P IN The radial distance between R OUT is the rotation axis of the rotor and the P OUT The radial distance between P is on the forward edge at P IN and the P OUT points between; R is the radius of a circle centered on the axis of rotation of the rotor and passing through P; When P is set on the forward edge and R is greater than or equal to (R IN +((R OUT -R IN ) / 2)) at the position, the P OUT Arranged in front of the P with respect to the direction of rotation of the rotor.

5. The rotor according to any one of claims 1 to 4, characterized in that: The shape of the forward edge of each of the plurality of struts is straight in a plane perpendicular to the rotation axis of the rotor.

6. The rotor according to any one of claims 1 to 4, characterized in that: At least 50% of the forward edge of each of the struts is shaped to be straight in a plane perpendicular to the axis of rotation of the rotor.

7. The rotor according to any one of claims 1 to 4, characterized in that: The shape of the forward edge of each of the plurality of struts is curved in a plane perpendicular to the rotation axis of the rotor.

8. The rotor according to claim 7, characterized in that The radius of curvature of the forward edge of each of the plurality of struts increases with increasing radial distance from the axis of rotation of the rotor.

9. The rotor according to any one of claims 1 to 4, characterized in that: The shape of the forward edge of each of the plurality of struts has a concave curvature on a plane perpendicular to the rotation axis of the rotor.

10. The rotor according to claim 9, characterized in that At least 25% of the forward edge of each strut in the plurality of struts has a concave curvature.

11. The rotor according to any one of claims 1 to 4, characterized in that: The front surface of each of the plurality of struts has an asymmetric shape in a vertical plane.

12. The rotor according to claim 1, characterized in that The rotor also includes a relief region positioned at an inboard end of the plurality of struts, wherein each of the relief regions is disposed at a forward edge of each of the plurality of struts such that the relief region constitutes at least a portion of the forward edge of each strut.

13. The rotor according to claim 12, characterized in that The thickness of the relief region measured in the axial direction is greater than or equal to 1.25 times the thickness of each of the plurality of struts measured in the axial direction.

14. A rotor according to any one of claims 12 or 13, characterized in that The front surface of the forward edge of each of the struts has a radius of curvature at the relief region that is greater than or equal to 0.75 inches.

15. The rotor according to any one of claims 1-4 or 12-13, characterized in that: The thickness of the outward end of each of the plurality of struts is less than or equal to 1.5 inches.

16. A rotor according to any one of claims 1-4 or 12-13, characterized in that: Each foil of the plurality of foils is spiral, and an acute angle between a leading edge of each foil and a straight line parallel to the rotation axis of the rotor and intersecting the leading edge of the foil is greater than 0 degrees and less than or equal to 40 degrees.

17. A pressure screening system for removing contaminants from a solid slurry or suspension, the pressure screening system comprising a pressure screen cylinder having a plurality of openings, a rotor according to claim 1 disposed within the pressure screen cylinder, and a drive motor operatively connected to the rotor, wherein the drive motor is configured to rotate the rotor relative to the pressure screen cylinder.

18. The pressure screening system according to claim 17, characterized in that: The pressure screen drum is operable to separate solid contaminants from a solid suspension or solid slurry.

19. A method for removing solid contaminants from a solid suspension or solid slurry, the method comprising introducing the solid suspension or the solid slurry into a pressure screening system according to any one of claims 17 or 18, rotating the rotor relative to the pressure screen cylinder, and collecting acceptable solid suspension from a plurality of openings of the pressure screen cylinder, wherein: Contact of the solid suspension or the solid slurry with the pressure screen cylinder causes at least a portion of the solid suspension or the solid slurry to pass through the plurality of openings; The rotation of the rotor causes the plurality of foils to generate pressure pulses, and the pressure pulses cause solid contaminants and fibers entangled to the inner surface of the pressure screen cylinder to fall off; as well as The forward-swept struts create a flow field that moves solid contaminants and fibers inwardly and prevents solid contaminants and fibers from collecting on the forward edges of the plurality of struts and the leading edges of the plurality of foils.

20. A method for removing solid contaminants from a solid suspension or solid slurry, the method comprising: contacting the solid suspension or the solid slurry with a pressure screen cylinder, the pressure screen cylinder comprising a cylinder wall, the cylinder wall having an inner surface, an outer surface, and a plurality of openings extending through the cylinder wall from the inner surface to the outer surface, wherein contacting the solid suspension or the solid slurry with the pressure screen cylinder causes at least a portion of the solid suspension or the solid slurry to pass through the plurality of openings; The rotor in the pressure screen drum is rotated, wherein: The rotor includes a cylindrical hub, a plurality of foils spaced radially outward from the hub, and a plurality of struts coupling the plurality of foils to the hub; Each foil of the plurality of foils is radially spaced from the inner surface of the barrel wall; Each strut of the plurality of struts is a forward swept strut having a forward edge; The rotation of the rotor causes the plurality of foils to generate pressure pulses, which dislodge solid contaminants and fibers entangled to the inner surface of the pressure screen cylinder; and the forward-swept struts create a flow field that moves solid contaminants and fibers inwardly and prevents solid contaminants and fibers from collecting on the forward edges of the plurality of struts and the leading edges of the plurality of foils; and Acceptable solid suspension is collected from the plurality of openings of the screen cylinder.

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