METHOD FOR REFINING CELLULOSE FIBERS IN AQUEOUS SUSPENSION AS WELL AS REFINER FILLING TO IMPLEMENT SAID METHOD

Abstract

The invention relates to a method for refining cellulose fibers in aqueous suspension, using a plurality of refiner fillings having refining edges, of which one is operated on at least one stator and another is operated on at least one rotor, and the suspension to be refined is processed between the two refiner fillings. A partial flow of the suspension delivered to the outlet side flows back on the back side of the refiner filling on the stator side, and then flows through openings located between the refining edges of the refiner filling on the stator side, and again into the refining zone. This leads to particularly uniform and economical refining.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This is a continuation of PCT application No. PCT/EP2009/004739, entitled “METHOD FOR REFINING CELLULOSE FIBERS IN AQUEOUS SUSPENSION AND REFINER FILLING FOR PERFORMING THE SAME”, filed Jul. 1, 2009, which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method for refining aqueous suspended cellulose fibers whereby these fibers are carried in an aqueous suspension between refiner fillings each of which are equipped on their face side with refining edges and which are located either on a rotor or a stator providing rotational movement relative to each other and which are pressed against each other, whereby mechanical refining is transferred onto the cellulose fibers and whereby suspension is delivered to the inlet side of refiner fillings and is then discharged again from outlet side of refiner fillings.

2. Description of the Related Art

It has been known for a long time that cellulose fibers, that is virgin cellulose fibers or waste paper fibers, are refined so that the subsequently produced paper has the desired characteristics, especially strength, formation and surface. Refining processes of the type considered here have utilized refining tools which are often equipped with bars referred to as blades and which can generally be screwed to the rotor or stator of the refiner. The refiner tools are generally referred to as fillings. The relevant machinery is known as refiners. The method may typically be accomplished by disk refiners or cone refiners.

Refiner fillings for refining of cellulose fibers, utilizing refiner bars and grooves located between them are known for example from DE 20 2005 007 551 U1.

DE 37 00 613 A1 describes disk refiners for processing of a fibrous suspension in paper production, whereby rotor and stator fittings are equipped with axially oriented openings. This divides the suspension which is to be refined into many axial partial flows, refines it and discharges it from the refiner. A similar principle is also employed in the method addressed in DE 10 2004 039 986 A1.

What is needed in the art is a method of cellulose refining which would provide uniform and particularly economical refining, in other words one in which the desired technological refining changes are as uniform as possible on all fibers.

SUMMARY OF THE INVENTION

The present invention provides a method for refining aqueous suspended cellulose fibers whereby these fibers are carried in an aqueous suspension between refiner fillings each of which are equipped on their face side with refining edges and which are located either on a rotor or a stator providing rotational movement relative to each other and which are pressed against each other, whereby mechanical refining is transferred onto the cellulose fibers and whereby suspension is delivered to the inlet side of refiner fillings and is then discharged again from outlet side of refiner fillings, characterized in that a partial flow of suspension which was delivered to outlet side flows through at least one hollow chamber located on backside of stator-side refiner filling and then through openings which are located between refining edges of stator-side filling to refining edges of this refiner filling.

The present invention further provides a refiner filling to implement the method described in the preceding paragraph, with an inlet side and an outlet side for suspension between which refiner edges suitable for refining suspension are located, characterized in that it has at least one, preferably several hydraulic connections between outlet side and refiner edges through which the suspension can get from outlet side to refiner edges. This refiner filling is especially suitable for the method of the present invention.

A considerable number of various refiner fillings has already been developed, which differ from each other in regard to blade width, number of blades and angle of blade edges relative to the radius. However, the inventive method contributes to a substantial improvement since it offers the possibility to direct the suspension flow so that an additional possibility of influence upon the refining effect provided by the refiner is created. In particular, the return flows inside the stator-side fillings are intensified. Already known fillings can here be used on the rotor side. The effect can be explained as follows:

In a conventional blade type filling the grooves are to be considered as flow channels for the suspension. Here it can be assumed that due to the rotational movement of the rotor and the fibrous stock suspension which is carried along by it, a strong pressure build-up occurs from the inside radial areas to the outside radial areas. Similar action occurs also in rotary pumps, obviously in much stronger form. Because of this pressure differential a backflow of the suspension occurs from radially outside to radially inside in the non-rotating cavities of the stator which are provided according to the invention. This backflow may be influenced by selecting or changing the cross section of the flow-carrying surfaces. On the path which is being taken by the back-flowing suspension inside the cavities, a transfer can occur through the openings which are located between the refining edges of the stator-side refiner filling to the refiner edges of the opposite refiner filling. Since these return flows lead to a repeat of the refining processes, refining becomes more uniform which is of particular advantage, both technologically and economically. The inventive measures can strengthen this transfer.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein:

The invention is further explained with the assistance of and reference to schematic drawings:

FIG. 1 shows the principle of the inventive method;

FIG. 2 shows implementation of the method—in this example with a disk refiner;

FIG. 3 shows an example of inventive refiner filling (section) viewed in direction of the back side;

FIGS. 4-9 show details regarding the various embodiments of stator fillings;

FIG. 10 shows a top view of one sector of usable rotor-side refiner filling;

FIG. 11 shows additional forms for the openings in the stator refiner filling; and

FIG. 12 shows implementation of the method with a cone refiner

Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate embodiments of the invention, and such exemplifications are not to be construed as limiting the scope of the invention in any manner.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings, and more particularly to FIG. 1, there is shown a schematic sketch of the suspension flows which occur when implementing the inventive method in a double disk refiner with one rotor 9 and two stators 8 and 8′. Suspension S which is to be refined is added in a central region of the double disk refiner, gets between rotor 9 and stators 8 and 8′ and is carried toward the outside where it is refined. As a result of the rotational movement a strong pressure buildup occurs on the path from infeed side 5 to outlet side 6, in other words from radially inside to radially outside. The result is that a partial suspension flow S′ returns from radially outside to radially inside. Since stators 8 and 8′ are equipped with openings in radial direction, the suspension which flows back comes again into the refining zone. The refined portion S″ flows out of annulus 17 through a connection pipe.

The arrows for the suspension flows are drawn with hollow tips in all drawings.

FIG. 2 illustrates a schematically depicted section of a disk refiner suitable for the method. A refiner filling 1 is mounted on a stator 8 and a refiner filling 2 on a rotor 9 which are detachable by means of screws 12. The rotor-side refiner fillings 2 are blade fillings which are equipped with refiner bars 7. In the illustrated example suspension S which is to be refined is delivered to inlet side 5 of refiner fillings 1 and 2 through the center of stator 8. This depiction shows an exaggeration of the distance between refiner fillings 1 and 2. In operation it only amounts to a fraction of millimeters. Suspension S passes the conspiring refiner fillings 1 and 2, emerges again on the outlet side, collects in annulus 17, and a refined portion S″ leaves annulus 17 via an appropriate connection pipe. A partial flow S′ of the suspension flows through a hollow chamber 14 located on backside 11 of the stator-side refiner filling 1 and then through openings 15 which are located between refining edges 3 of stator-side refining fillings 1 to refining edges 3 of this refiner filling 1. Such surfaces are considered to be refining edges which—in conspiring together with refining edge of an opposing filling (generally rotor with stator fillings)—transfer the refining effort to the fibers. Refining fillings 2 on the rotor side are equipped with refiner bars 7 which represent their refining edges. No return flow of suspension is generated on the backside of the rotor fillings. Rotor 9 is driven by a shaft 13. Generally known means with which power is generated to press the two refiner fillings against each other are not illustrated.

FIG. 3 illustrates a refiner filling 1 suitable for the method, shown in direction of backside 11 (see FIG. 2). In order to support refining plate 12 which is equipped with openings 15 a support 10 is provided which can be welded, soldered or detachably connected with refining plate 12. It may also form a single component with refining plate 12, for example as shown in FIG. 5. Support 10 is open on its radial outer side, whereby the support elements are spoke-like, and are equipped with an enclosed ring on their radial inside. In between are hollow spaces 14. The design is further clarified by the cross section of the side view in FIG. 4, whereby here refining plate 12 and support 10 consist of different components. Refining edges 3 are formed by the edges of openings 15.

FIG. 6 illustrates an example where refining edges 3′ are formed by refiner bars 7 which protrude from a refining plate 12′ which is equipped with openings 15. This may offer advantages if a great number of refining edges 3′ are required. In addition, protruding refiner bars 7 may possibly be better protected against wear and tear. It is advantageous to then close off the grooves located between the refiner bars in radial direction toward the outside.

Grinding plate 12″ in FIG. 7 is not equipped with the hollow spaces 14 which are open toward outlet side 6. These hollow spaces 14 are instead integral in stator 8. Refining plate 12″ therefore represents refiner filling 1 which can be screw connected with stator 8.

Advantageous measures can be taken in order to take care of the flow of partial flow S′, especially in order to avoid troubling swirls and stagnation points. In particular, additional hydraulic guide elements and guide surfaces are to be provided for this purpose which, based on their shape, allow an as constant and an as loss free transportation of the suspension as possible from outlet side 6 to refining edges 3 or 3′. Several options which can be used individually, or in combination with each other, for this purpose are shown in FIG. 8 and FIG. 9. Here, the radial outside of refining plate 12′″ is equipped with a rounded protruding turning element 18 which can also have an asymmetrical shape as shown in the detail in FIG. 9. In addition, hollow spaces 14 may be equipped with guide elements 19, 20, and 21 which are aligned in a way so that the liquid flowing in hollow spaces 14 is rerouted to openings 15. The transitions of hollow spaces 14 to openings 15 can be rounded with the assistance of guide surfaces 22, 23 and 24 in a way so that the flow can be diverted without a break. The depiction in FIG. 8 shows a few examples, whereby the pitch (deviation opposite the radius) of openings 15 and their edges cannot be recognized.

It must also be considered that a wear and tear zone 25 exists on the upper areas of refining edges 3 where possibly the flow caretaking measures would not be advantageous.

FIG. 10 shows the section of a generally known refiner filling 2 which can be utilized on the rotor side when implementing the method. It contains a plurality of refiner bars 7 between which grooves 26 are located for the transport of suspension S from infeed side 5 to outlet side 6. Refiner bars 7 are often combined into groups where they are positioned parallel to each other. In a favorable fabrication this would allow for a large number of refiner bars, located at a selectable angle of intersection with the radius.

As shown in FIG. 3 the shape of openings 15 which are located between the refining edges can be slotted, at an angle to the radius or precisely in radial direction. FIG. 11 shows examples of additional forms such as round holes or polygons/squares. Variations in placement and size of openings 15 provide possibilities to influence the distribution of the return flow of the suspension. For example, openings which are located closer to the inside in radial direction can be larger in order to equalize lower pressure of the return flow in that location.

The current invention not only improves refining with disk or double disk refiners, but also with cone refiners whereby the effect with a steep cone angle is greater than with a flat one. FIG. 12 shows the method schematically utilizing a cone refiner where rotor 9 is truncated and carries the refiner filling on its circumference. The conspiring refiner filling is located at the periphery of the rotor and is connected with truncated stator 8. Suspension S is carried in axial direction between the fillings from infeed side 5 to outlet side 6. The steeper the cone, the greater the pressure build up which is being produced. It can be clearly seen that the refining fillings of stator 8 are provided with hollow spaces 14 and openings 15 in order to return a partial flow S′ from outlet side 6. The illustration in FIG. 12 is greatly simplified, is however sufficient to explain the principle of the invention with this example.

The method can also be arranged so that in addition to the measures, in particular in combination with the measures described in the claims the flow cross section in grooves 26 of refiner filling 2 on the rotor side is changed by different groove width and/or depth. The groove width and/or groove depth therefore increases or decreases from the inside toward the outside. In particular this allows for the pressure build up through rotor 9 and thereby also the return flow in stator 8 to be influenced and to facilitate the transfer of return flow of suspension into the refining zone.

While this invention has been described with respect to at least one embodiment, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.

Claims

1. A method for refining a plurality of aqueous suspended cellulose fibers, said method comprising the steps of:

carrying the plurality of cellulose fibers in an aqueous suspension between a stator-side refiner filling and a rotor-side refiner filling, said stator-side refiner filling being located on a stator and including a first face side and a first plurality of refining edges on said first face side, said rotor-side refiner filling being located on a rotor and including a second face side and a second plurality of refining edges on said second face side, said stator and said rotor providing a rotational movement relative to each other;

pressing said stator-side refiner filling and said rotor-side refiner filling against each other;

transferring a mechanical refining onto said plurality of cellulose fibers;

delivering said aqueous suspension to an inlet side of said stator-side and said rotor-side refiner fillings and then discharging again said aqueous suspension from an outlet side of said stator-side and said rotor-side refiner fillings;

flowing a partial flow of said aqueous suspension which was delivered to said outlet side through at least one hollow chamber located on a backside of said stator-side refiner filling and then through a plurality of openings which are located between certain ones of said first plurality of refining edges of said stator-side refiner filling and other ones of said first plurality of refining edges of said stator-side refiner filling.

2. The method according to claim 1, wherein at least partially said stator-side refiner filling is used, a plurality of edges of said plurality of openings at least partially forming said first plurality of refining edges.

3. The method according to claim 1, wherein at least partially said stator-side refiner filling is used, at least partially said first plurality of refining edges are formed by a plurality of refiner bars which protrude from a refining plate which is equipped with said plurality of openings.

4. The method according to claim 1, wherein said at least one hollow chamber is at least one hollow space, said stator-side refiner filling being used and being equipped with a plurality of said hollow space and said plurality of openings, said aqueous suspension being carried through said plurality of hollow spaces from said outlet side to said plurality of openings.

5. The method according to claim 1, wherein said at least one hollow chamber is at least one hollow space, said stator-side refiner filling being used, being equipped with said plurality of openings, and being connected detachably with a support in such a way that at least one said hollow space is formed through which said partial flow of said aqueous suspension is carried from said outlet side to said plurality of openings.

6. The method according to claim 1, wherein said at least one hollow chamber is at least one hollow space, said stator-side refiner filling being used, being equipped with said plurality of openings, and being connected detachably with a support in such a way that a plurality of said hollow space are formed through which said partial flow of said aqueous suspension is carried from said outlet side to said plurality of openings.

7. The method according to claim 1, wherein a greater part of said aqueous suspension is carried through said rotor-side refiner filling from said inlet side to said outlet side.

8. The method according to claim 1, wherein said rotor-side refiner filling is used, no return flow of said aqueous suspension being generated on a backside of said rotor-side refiner filling, said rotor-side refiner filling being equipped with a plurality of refiner bars and a plurality of grooves located between said plurality of refiner bars.

9. The method according to claim 1, wherein said at least one hollow chamber is at least one hollow space, said aqueous suspension flowing in a plurality of said hollow space being directed by a plurality of hydraulic guide elements in a direction toward said plurality of openings thereby one of reducing and totally avoiding a plurality of swirls.

10. The method according to claim 1, wherein said aqueous suspension flowing through said plurality of openings is directed in a direction of said first plurality of refining edges by way of a plurality of guide surfaces which limit said plurality of openings whereby a plurality of swirls are one of reduced and totally avoided.

11. A refiner filling, comprising:

an inlet side for an aqueous suspension;

an outlet side for said aqueous suspension;

a first plurality of refiner edges located between said inlet side and said outlet side, said first plurality of refiner edges being suitable for refining said aqueous suspension;

at least one hydraulic connection between said outlet side and said first plurality of refiner edges through which said aqueous suspension can get from said outlet side to said first plurality of refiner edges, the refiner filling being a stator-side refiner filling and being configured for being used in a method for refining a plurality of aqueous suspended cellulose fibers, said method including the steps of: carrying said plurality of cellulose fibers in said aqueous suspension between said stator-side refiner filling and a rotor-side refiner filling, said stator-side refiner filling being located on a stator and including a first face side and said first plurality of refiner edges on said first face side, said rotor-side refiner filling being located on a rotor and including a second face side and a second plurality of refiner edges on said second face side, said stator and said rotor providing a rotational movement relative to each other; pressing said stator-side refiner filling and said rotor-side refiner filling against each other; transferring a mechanical refining onto said plurality of cellulose fibers; delivering said aqueous suspension to said inlet side of said stator-side and said rotor-side refiner fillings and then discharging again said aqueous suspension from said outlet side of said stator-side and said rotor-side refiner fillings; flowing a partial flow of said aqueous suspension which was delivered to said outlet side through at least one hollow chamber forming said at least one hydraulic connection located on a backside of said stator-side refiner filling and then through a plurality of openings which are located between certain ones of said first plurality of refiner edges of said stator-side refiner filling and other ones of said first plurality of refiner edges of said stator-side refiner filling.

12. The refiner filling according to claim 11, wherein a plurality of said hydraulic connection are between said outlet side and said first plurality of refiner edges and are configured for getting said aqueous suspension from said outlet side to said first plurality of refiner edges.

13. The refiner filling according to claim 11, wherein said at least one hollow chamber is at least one hollow space and the refiner filling includes an area of said backside, said at least one hollow space being located in said area of said backside of the refiner filling, being closed on said inlet side, being open on said outlet side, and being connected hydraulically with said plurality of openings which are located between said first plurality of refiner edges.

14. The refiner filling according to claim 13, wherein the refiner filling includes a plurality of said hollow space which are located in said area of said backside of the refiner filling, are closed on said inlet side, are open on said outlet side, and are connected hydraulically with said plurality of openings which are located between said first plurality of refiner edges.

15. The refiner filling according to claim 13, wherein said plurality of hollow spaces are open on said backside.

16. The refiner filling according to claim 13, wherein said plurality of hollow spaces are closed on said backside.

17. The refiner filling according to claim 11, wherein said plurality of openings include a plurality of edges that at least partially form said first plurality of refiner edges.

18. The refiner filling according to claim 11, wherein the refiner filling includes a refining plate that is equipped with said plurality of openings, the refiner filling being equipped on said first face side with a plurality of refiner bars which protrude over said refining plate.

19. The refiner filling according to claim 11, wherein said at least one hollow chamber is at least one hollow space, the refiner filling including a plurality of said hollow space and being equipped with a plurality of guide elements in said plurality of hollow spaces, said plurality of guide elements being positioned so that a liquid flowing in said plurality of hollow spaces is directed to said plurality of openings.

20. The refiner filling according to claim 11, wherein the refiner filling includes a plurality of edges which limit said plurality of openings, said plurality of edges being a plurality of guide surfaces which are positioned so that a liquid flowing in said plurality of openings is continuously directed to said first plurality of refiner edges.