WO1995025199A1

WO1995025199A1 - Breaker bar section for a high consistency refiner

Info

Publication number: WO1995025199A1
Application number: PCT/US1995/002985
Authority: WO
Inventors: Gregory Alexander Garasimowicz
Original assignee: Beloit Technologies, Inc.
Priority date: 1994-03-15
Filing date: 1995-03-10
Publication date: 1995-09-21
Also published as: AU2117695A

Abstract

An annular base (50) has radial breaker bars (38, 40) for transporting the high consistency stock from the flinger nut (24) section of the refiner (20) to the refining plates (28, 30). The radial breaker bars (38, 40) are curved so that the radial outward ends curve away from the direction of rotation. The curved bars (38, 40) aid in the transportation of pulp from the inside diameter (52) to the outside diameter (54) of the breaker bar section (26) thereby improving feeding. Improved feeding allows higher loading and at the same time, improves fiber quality.

Description

TITLE

BREAKER BAR SECTION FOR A HIGH CONSISTENCY REFINER

FIELD OF THE INVENTION This invention relates to refiners which prepare paper pulp fibers to the desired condition prior to their being delivered to a papermaking machine, and to disc refiners in particular.

BACKGROUND OF THE INVENTION During the production of fibers for papermaking, wood or other fiber source is ground into chips and/or mechanically treated such that the chips may be broken down further and refined into individual fibers.

Disc refiners are used with high density stock containing eighteen to sixty percent fiber by weight to break down clumps of fibers into individual fibers. Disc refiners are also used with low density, low consistency pulp of two to five percent fiber dry weight to increase the freeness or bonding capability of the individual fibers.

A refiner disc is a disc-shaped steel or steel-alloy casting which has a multiplicity of more-or-less radially extending bars cast on the surface thereof. The disc refiner typically utilizes pairs of opposed refiner discs. One disc is mounted on a rotor for rotation. Another disc is held opposed to the first refiner disc, either by rigid mounting or by mounting on an opposite rotating rotor. Wood pulp is refined as it passes between the rotating opposed discs. A refiner for high density stock employs an auger which is axially mounted with respect to the rotor on which the refining disk is mounted. A flinger nut may be positioned adjacent to the end of the auger which feeds the stock into a breaker bar section. The breaker bar section feeds the stock to the refiner disks where wood chips and clumps of fiber are broken down into individual fibers. Conventional breaker bar sections employ essentially radially extending rectilinear bars on the rotor opposed by stationary essentially radially extending bars mounted to the refiner housing.

In paper manufacture, the cost of the stock or wood fibers is the single largest component of the paper product's total cost. The paper fiber or stock is manufactured from wood chips which are in many aspects an industrial commodity whose price is governed by the market and not easily controlled. Thus, to improve the cost and efficiency of the papermaking process, it is important to focus on reducing the cost of processing the wood chips used to produce the stock or furnish from which the paper is made. High consistency refiners used principally with mechanical or semi-chemical pulps are relatively large consumers of power. Therefore, any improvement of through-put or power utilization in the refiner can lead to significant cost and efficiency savings.

What is needed is a breaker bar section which contributes to the efficiency and through-put of a high consistency refiner.

SUMMARY OF THE INVENTION The improved high consistency refiner of this invention employs a breaker bar section wherein the radial bars used to transport the high consistency stock from the flinger nut section of the refiner to the refining plates are curved, so that the radial outward ends of the breaker bars or blades curve away from the direction of rotation. The curved bars aid in the transportation of pulp from the inside diameter to the outside diameter of the breaker bar section, thereby improving feeding. The improved feeding in turn provides better load stability of the stock flowing to the refiner disks. Improved stability allows higher loading and at the same time, improves fiber quality. The shape of the breaker bar section bars or blades is similar to that of a high efficiency pump or impeller. The shape of the breaker bar means that the breaker bars or vanes on the moving breaker bar disc pass over the vanes of a stationary or counter-rotating breaker bar section. The point of overlap between the rotating and the non-moving or counter-rotating breaker bars moves radially outward. The amount of overlap remains essentially constant as the rotating and stationary breaker bars move with respect to each other. This produces a smoother operating machine, which leads to improved load stability, which in turn improves fiber quality.

It is an object of the present invention to provide a refiner employing a breaker bar section having improving feeding.

It is also an object of the present invention to provide a refiner employing a breaker bar section having improved loading stability.

It is a further object of the present invention to provide a refiner employing a breaker bar section which produces improved fiber quality.

Further objects, features, and advantages of the invention will be apparent from the following detailed description when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a fragmentary cross-sectional view of an exemplary high consistency stock disk refiner which may be used with the breaker bar section of this invention; FIG. 2 is an isometric view of a sector of a breaker bar section of this invention;

FIG. 3 is a top plan view of the breaker bar sector of Fig. 2;

FIG. 4 is a side elevational view of the breaker bar section sector of Fig. 3;

FIG. 5 is a top plan view of a breaker bar section of this invention shown in conjunction with primary and secondary refining disk sections;

FIG. 6 is a schematic view of overlapping sections of a prior art breaker bar section shown in solid lines with a counter-rotating or non-rotating breaker bar section shown in broken lines;

FIG. 7 is a schematic view of the breaker bar section of this invention with the rotating portion shown in solid lines and the non-rotating or counter-rotating section shown in broken lines;

FIG. 8 is a fragmentary cross-sectional view of a counter-rotating high consistency stock disk refiner which may be used with the breaker bar section of this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring more particularly to FIGS. 1-8, wherein like numbers refer to similar parts, a high-consistency pulp refiner 20 employing the improved breaker bar section 26 of this invention is shown in FIG. 1. The refiner 20 has a housing 21 and an auger 22 mounted therein which supplies a high consistency pulp or stock from a stock inlet 23. The auger 22 supplies stock to an arrangement of treating structure mounted to the housing 21 and a rotating rotor 32. Aligned with the auger 22 is a flinger nut 24 which directs the stock radially outwardly to a plurality of breaker bar segments 26. The breaker bar segments 26 are in the form of sectors of an annulus which together form an encircling section of breaker bars. One set of breaker bar segments 26 is fixed to the rotor 32, and another set is fixed to the housing. The breaker bar segments 26 discharge stock to radially outwardly positioned first refiner discs 28 and second refiner discs 30. One set of the first and second refiner discs 28, 30 is mounted to a rotor 32 parallel to a radially extending plane 34. The rotor 32 and refiner discs 28, 30 rotate about an axis 36. Another set of refiner discs is mounted to the housing.

High consistency stock is eighteen to sixty percent fiber by weight and is in the form of wood chips or semi-chemically treated wood chips which contain fiber clumps. The stock is processed by the refiner 20 to free the individual fibers in the stock in preparation for forming paper. The radial bars of the flinger nut 24 transport the stock radially outwardly under the centrifugal forces developed by the motion of the rotor 32 and the attached flinger nut 24. The breaker bar sections 26, sometimes referred to as the internal ring of the refiner discs, receives stock discharged radially outwardly from the flinger nut 24.

As best shown in Fig. 5, the breaker bar section 26 has breaker bars 38 and 40 which guide and propel this stock into the grooves 42 between the bars 44 of the refining section 28. The grooves 42 are shown with dams 43.

The breaker bar segments may be fabricated as independent units 26, as shown in FIG. 2, or as shown in Fig. 5, the breaker bar segments may be fabricated in sectors 46 which include the refiner sections 28, 30. As shown in FIG. 2, the breaker bar segments 26 are affixed to the rotor 32 by bolts (not shown) which pass through bolt holes 48 in the individual sectors 26. The breaker bar section 26 has an annular base 50 which has an inside circumference 52 that abuts the flinger nut 24 and an outside circumference 54 which abuts the refining section 28. The breaker bar segment bottom 56 is flat for mounting to the rotor 32. The upper surface 58 is preferably concave so as to provide greater flow area for the stock. It should be noted, however, that the upper surface may also be flat or conical and maintain the benefits of the breaker bar shape of this invention. A plurality of breaker bars 38, 40 extend axially from the upper surface 58of the base 50, and are preferably of two types: long bars 38 and shorter bars 40. It should be noted however, that equal length bars may be employed. Because the circumferential flow area increases from the inner circumference 52 to the outer circumference, the inner ends 60 of the shorter bars 40 are spaced from the inner circumference 52 to provide greater flow area for the stock. For the same reason the thickness of the annular base 50 decreases from the outside circumference 54 to the inside circumference 52.

As shown in FIG. 2, upstanding dams 62 extend between adjacent short breaker bars 40 and long breaker bars 38. The dams bridge the gap or flow channel 64 between the short and long bars 38, 40. In a preferred embodiment, the tops 66 of the dams 62 are of a height less than the tops 68, 70 of the bars 38, 40 so that the flow of stock is not completely occluded but rather the stock is forced to flow over the dams and so brought to a position where it can be processed by the breaker bars 38, 40. It should be noted, however, that dams may be provided whicji are at least as high as the bars. Adjacent dams are staggered radially outwardly from one another.

As shown in FIG. 1 , the breaker bar segments 26 which are mounted to the rotor 32 are parallel to and opposite non-rotating opposed breaker bar segments 72 which are rigidly mounted to the housing 21 and opposed to the breaker bar segments 26. Similarly, the refiner sections 28, 30 are opposed by stationary refiner sections 74, 76.

Operation of the breaker bar segments 26 of the present invention may be compared to the performance of a conventional breaker bar assembly as shown schematically in Fig. 6. The illustrated conventional breaker bars extend essentially radially outwardly in a strictly rectilinear pattern. A conventional breaker bar segment 78 overlies and rotates with respect to a conventional opposed breaker bar segment 80. As the conventional breaker bar segment 78 rotates with respect to the opposed conventional breaker bar segment 80, the conventional breaker bars 82 pass over each other in a discontinuous manner. In the position shown in FIG. 6, the opposed breaker bars 82 are spaced from one another, a short time later the breaker bars will overlie one another, and then will be spaced again.

The breaker bars of the segments of the present invention, as shown in Fig. 7, are continuously overlying one another as the breaker bar segments 26, 72 rotate with respect to one another. The breaker bar segment 26 has breaker bars 38, 40 which overlap with the breaker bars84, 86 of the opposed breaker bar segment 72. These overlaps 88, which are the intersections of the bars 38, 40, 84, 86, sweep radially outwardly. This relative motion improves the conveyance of stock to the refiner discs 28, 30, 74,76. The direction of rotation of the rotating breaker bar segments is shown by the arrow 90. The refiner bars 38, 40, 84, 86, have a gentle sweep in a direction away from the direction of rotation 90 as the bars extend toward the outer circumference 54. Thus, the bars 38, 40, 84, 86 have a shape similar in appearance to a high efficiency pump rotor which functions to improve the efficiency of the breaker bar segments 26 of the refiner 20. Moreover, the breaker bar segments 26 and opposed breaker bar segment 72 produce an improved feeding which in turn provides better stability in the loading or flow of stock through the refiner 20. The improved stability of the stock flow increases the amount of stock which can be passed through a given refiner and at the same time improves the quality of the fiber produced by the refiner. The improved loadability or capability of the refiner is a result of the higher efficiency. The concave shape of the top 58 of the annular base 50 also contributes to this improved performance. The breaker bar segments 26 because of their continuous smooth interaction with the opposed breaker bar segments 72 are less prone to undesirable vibrations which could result from the employment of a conventional breaker bar segment 78.

Alternatively, the breaker bar section 26 of this invention may be employed in a counter-rotating high-consistency pulp refiner 120, as shown in FIG. 8. The refiner 120 has a housing 121 and an auger 122 mounted therein which supplies a high consistency pulp or stock from a stock inlet 123. The auger 122 supplies stock to an arrangement of treating structure mounted to a first rotating rotor 132 and a counter-rotating rotor 134. The first rotor 132 and the counter-rotating rotor 134 are mounted to rotate in opposite directions.

It should be understood that the breaker bar segment base 50 shown in Figs. 2 and 4 tapers from the inside circumference 52 to the outside circumference 54 which reduces the cross section of the flow channels 64 and thus increases the velocity of the stock as it travels radially outwardly. The rate of acceleration of the stock is a complicated higher order function and a conventional linear taper between the inner circumference 52 and the outer circumference 54 is less optimal than the concave surface 58 illustrated in Figs. 2 and 4.

It should also be understood that the breaker bar segments 26 of this invention may be employed with refiners of various configurations employing various types and consistencies of stock. It should also be understood that although the breaker bar segments are shown to be constructed of annular pie-shaped sectors, they could be formed as continuous annular discs. Furthermore, the breaker bar segments 26 may be formed as a continuous part of the refining stages 28, 30 as shown in Fig. 5 or may be formed individually as illustrated in Fig. 1. The breaker bar segments and refiner discs are typically cast of materials such as white cast iron and stainless steel or other alloys combining the features of strength, wear resistance and cost effectiveness.

It should also be understood that the breaker bar segment 26 described and illustrated may be used with any suitable refining plates having varying refiner bar configurations.

It should also be understood that the breaker bar segment 26 described and illustrated may be used with any suitable disc refiner and such disc refiner may have one or more rotors and one or more counter-rotating or stationary breaker bar segments and refiner discs.

It should be understood that the invention is not limited to the particular construction and arrangement of parts herein illustrated and described, but embraces such modified forms thereof as come within the scope of the following claims.

I CLAIM:

1. A refiner (20) for wood chips and wood fibers comprising: a housing (21) having a stock inlet (23); a rotor (32) mounted for rotation about a central axis (36) within the housing (21); at least one refiner disc (28) mounted on the rotor (32) for refining papermaking stock; and a breaker bar segment (26) connected to the rotor (32) radially inwardly of the refiner disc (28) and having a multiplicity of spaced breaker bars (38,40) which protrude axially from an annular base section (50) and extend radially along the base section (50), wherein the breaker bars (38,40) curve away from the direction of rotor rotation as they extend radially.

2. The refiner (20) of Claim 1 wherein the base section (50) has a surface (58) from which the breaker bars (38,40) extend which is concave, such that the axial height of each breaker bar (38,40) is greater at locations closer to the central axis (36), thus providing increased area for stock flow.

3. The refiner (20) of Claim 1 further comprising a plurality of dams (62) which protrude from the base section (50), wherein each dam (62) extends between two neighboring breaker bars (38,40), and wherein each dam (62) has less axial extent than the neighboring breaker bars (38,40).

4. The refiner (20) of Claim 1 further comprising a second breaker bar segment (72) which is opposed to the breaker bar segment (26), wherein the second segment (72) has a plurality of axially protruding, radially extending second breaker bars (84,86) which curve in a direction opposite the direction of the breaker bar segment (26) breaker bars (38,40), such that a point of overlap

Claims

(88) of opposed breaker bars (38,40,84,86) sweeps radially outwardly when the base segment (50) is rotated with respect to the second base section (50).

5. In a refiner (20) for wood chips and wood fibers having a housing (21) with a stock inlet (23), a rotor (32) mounted for rotation about a central axis (36) in a first direction within the housing (21), and at least one refiner disc (28) mounted on the rotor (32) for refining papermaking stock, the improvement comprising: a first annular base section (50) connected to the rotor (32) radially inwardly of the refiner disc (28); and a plurality of breaker bars (38,40) which extend axially outwardly from the base section (50), wherein each bar (38,40) extends generally radially along the base section (50) and curves away from the first direction of rotation as it extends radially, thus providing an improved flow capability for papermaking stock.

6. The refiner (20) of Claim 5 wherein the base section (50) has a surface (58) from which the breaker bars (38,40) extend which is concave, such that the axial height of each breaker bar (38,40) is greater at locations closer to the central axis (36), thus providing increased area for stock flow.

7. The refiner (20) of Claim 5 further comprising dams (62) which extend between adjacent bars (38,40), wherein the dams (62) protrude axially from the base (50) a height which is less than that of the breaker bars (38,40).

8. The refiner (20) of Claim 5 further comprising a second breaker bar segment (72) which is opposed to a first breaker section (26), wherein the second segment (72) has a plurality of axially protruding, radially extending second breaker bars (84,86) which curve in a direction opposite the direction of the first base section (50) breaker bars (38,40), such that a point of overlap (88) of opposed breaker bars (38,40,84,86) sweeps radially outwardly when the first base section (50) is rotated with respect to the second section (50).

9. A breaker bar (26) and refiner bar section (28) for a wood chip and wood fiber refiner having a rotor (32) mounted for rotation about a central axis (36) in a first direction, the section (46) comprising: an annular base section (50) connected to the rotor (32) for rotation about the axis (36); a plurality of breaker bars (38,40) which extend axially outwardly from the base section (50), wherein each bar (38,40) extends generally radially along the base section (50) and curves away from the direction of rotation as it extends radially, thus providing an improved flow capability for papermaking stock; and a plurality of refiner bars (44) which protrude axially from the base section (50) and which extend generally radially along the base section (50), wherein the refiner bars (44) are located radially outwardly from the breaker bars (38,40).