WO2011107339A1

WO2011107339A1 - Method for refining cellulose fibres in aqueous suspension, and refiner fillings for its implementation

Info

Publication number: WO2011107339A1
Application number: PCT/EP2011/052089
Authority: WO
Inventors: Fabian Waltner
Original assignee: Voith Patent Gmbh
Priority date: 2010-03-01
Filing date: 2011-02-14
Publication date: 2011-09-09
Also published as: DE102010002459A1

Abstract

The method serves for the refining of cellulose fibres which are passed in aqueous suspension between refiner strips (3) located on the contact faces of refiner fillings. They are affixed either to a rotor or to a stator. In preferred embodiments, the refiner strips (3) have curved refining edges, and the grooves (7) between them do not have either a cross-connection to adjacent grooves (7) or an abrupt change in groove direction or abrupt change in groove width (N1, N2, N3). The invention achieves advantages in terms of refining technology and economics.

Description

The invention relates to a method according to the preamble of claim 1.

It has long been known that pulp fibers, i. H. Frischzellstoff- or waste paper fibers, are ground so that the paper produced later from the desired properties, in particular strength, formation and surface, has. Grinding methods of the type considered here use grinding tools which are provided with strips designated as knives. The corresponding machines are usually called Mahlrefiner. When grinding tools one speaks of trimmings.

Refiner sets for grinding pulp fibers with grinding bars and grooves in between are e.g. known from DE 10 2005 004 344 A1.

The invention is based on the object to provide a method for pulp grinding, with which it is possible to carry out the grinding economically, in particular with lower energy consumption and low wear on the grinding tools.

This object is achieved by the features mentioned in claims 1 and 2.

The claims 6 to 20 each describe particularly suitable for the process Mahlgarnituren. With the aid of the invention it is possible to guide the suspension through the grinding area of the grinding device (refiner) with less hydraulic losses. In particular, the grinding surfaces of the grinding sets used are both in terms of grinding technology and in terms of their hydraulic properties optimized. The grinding surface is the area of a Mahlgarnitur on which the Mahlleisten and grooves are, often a part of the clothing surface for the attachment of fasteners, usually screws, is kept free. In these parts that are not calculated for the grinding surface, the features according to the invention need not necessarily be fulfilled. During grinding, the grooves located between the milling strips serve as flow channels for the transport of the fiber suspension. The groove width is the shortest distance between two adjacent Mahlleisten, so it is approximately perpendicular to the longitudinal extent of the groove. If the grooves on the grinding surfaces from the suspension inlet to the suspension outlet run continuously, without sudden change in the groove direction and without sudden change in the groove width, the flow of the fiber suspension to be ground can be performed with low hydraulic losses.

By means of the invention, the available grinding surface can be optimally utilized, that is to say a maximum number of grinding bars can be accommodated on the grinding surface. It is known that the length and number of grinding bars ("knives") as well as the speed at which these are moved past each other have a great influence on the milling effect, since these parameters determine the secondary edge length, eg in Ws / km With the same grinding performance transferred with a refiner, a higher secondary edge length results in a lower specific edge load and vice versa The specific edge load affects the grinding technology to the extent that the grinding becomes gentler with lower specific edge load, which in many cases, especially A high secondary edge length is obtained when grinding sets are used which have as many and as long as possible grinding strips Such a measure can be carried out particularly advantageously in an advantageous embodiment of the invention s. As is known, there is also a connection between the cutting angle and the achieved grinding effect. The cutting angle is the angle in which the mutually moving grinding edges (ie of rotor and stator) meet. In general, a larger cutting angle leads to a gentler grinding than a smaller one. If fittings are used in which the cutting angle increases from radially inward to radially outward, then this can be adapted to the grinding state of the fibrous material located at this point. The method can therefore be designed advantageously so that already more fully ground pulp is ground with a larger cutting angle, as less ground. In addition, this course of the cutting angle ensures that with increasing radially outward encounter speed of Mahlleisten and the cutting angle is greater. By further embodiments of the Mahlgarnituren used can thus achieve grinding technological advantages, in particular as regards the use of the strength potential of the fibers by gentle grinding.

The invention will be explained with reference to schematic drawings. Showing:

Fig. 1: the implementation of the method using the example of a Scheibenrefiners;

Fig. 2: a typical grinding set from the prior art;

Fig. 3-8: each a special embodiment of the invention

Grinding sets;

FIG. 9 shows a fitting ring composed of four grinding segments; FIG.

Fig. 10: Parts of adjacent grinding segments in a perspective view.

The method according to the invention can be carried out in a grinding device, as shown schematically in section in FIG. On a stator 8 is a Mahlgarnitur 1 and on a rotor 9, a grinding set 2 releasably secured by means of screws 12. For the screws 12, the sets have 1 and 2 screw holes 10. The Mahlgarnituren 1 and 2 are Knife sets, which are provided with Mahlleisten 3, which can be seen for example in Figs. 3, 7 and 8 in plan view. In the example shown here, the suspension S to be milled passes through the center of the stator 8 in and between the grinding sets 1 and 2. In this illustration, the axial distance between the grinding sets 1 and 2 is greatly exaggerated. In operation, it is only fractions of a millimeter. The suspension S passes through the cooperating Mahlgarnituren 1 and 2, exits at the outlet side again, collects in the annular space 15 and leaves this as a ground suspension S ^' via a corresponding nozzle. The rotor 9 is driven by a shaft 1 1, on the axis of rotation of the centers M of Mahlgarnituren 1 and 2 are. Not shown are the means known per se, with which a force is generated to press the two Mahlgarnituren against each other.

A typical prior art refiner is shown in FIG. The grinding bars 4, 4 ^' and 4 ^" and grooves 7 ^' are straight and have a constant width The angle of attack α lies between the grinding edge and the radius R defined by the center M. It is important for the cutting angle. Adjacent grinding bars 4 are sector-wise In order to compensate for this at least partially, the grinding bars 4 ^' in the adjacent sector (drawn on the left) are not parallel to the grinding bars 4 of the sector drawn on the right but are inclined to them The skewing of the sectors relative to one another approximately corresponds to the offset angle γ around which adjacent sectors are arranged rotated about the center M. In order to avoid too large grinding-gap-free spaces between adjacent sections, shortened grinding bars 4 ^"are inserted there.

FIG. 3 shows a grinding set suitable for the method according to the invention without a scale drawing being present. Here, the Mahlleisten 3 are executed in a curved shape, and adjacent Mahlleisten 3 rotated by the offset angle γ to the center M against each other. Between the same long Mahlleisten 3 are grooves 7, which serve as flow channels for the suspension S. They run here on the grinding surface with particular advantage without interruption and without cross-connection to adjacent grooves from the inlet 5 to the outlet 6, as well as without sudden change in the direction of the groove or sudden change in the groove width.

Grooves 7 and grinding strips 3 can be designed in the following way:

1 . The groove width N1, N2 and N3 is constant over the entire length, so that a flow channel with a constant flow cross-section is formed. The Mahlleisten 3 are of different lengths over their length.

2. The groove widths vary over the groove length, in particular so that the groove width N1 at the inlet 5 is equal to the groove width N3 at the outlet 6, while the groove widths N2 are larger at the points lying therebetween. As a result, the flow can be slowed down there. It is from

Advantage, when the grooves 7 on the grinding surface have a groove width N1 or N2 or N3 between 2 and 8 mm, preferably between 2 and 5 mm. In the example of Fig. 3, the groove width N1 at the inlet 5 and the groove width N3 at the outlet 6 are each about 2.5 mm, while at one point in between the groove width N2 with about 3.5 mm has the largest value. The

Bar width B1 is the same size as bar width B2, as well as the values in between.

3. Mixed forms from 1. and 2nd, so variation of groove width and Mahlleistenbreite over the length.

The groove depth T is advantageously between 2 and 20 mm (see Fig. 1). The cross section of the grinding bars 3 and grooves 7 is generally rectangular, although there are other shapes. For better clarity, some Mahlleisten 3 are cut, so drawn with a hatch. If the grinding set drawn in FIG. 3 is used on a rotor, as a rule the direction of rotation 14 is indicated as shown here. The grinding edges (cut edges) are then in this illustration on the left side of the grinding bars 3. As already mentioned, the cutting angle in milling process of this kind is an essential parameter. Fig. 4 shows an example of a circular arc grinding bar 3, the grinding edge of the inlet 5 tangent to the set by the center point M radius R, which leads at this point at the same shaped Gegengarnitur to a zero-degree cutting angle. At the outlet 6, on the other hand, the angle of attack a3 is 65 degrees, so here the angle of intersection (equal to twice a3 with the countershaft of the same shape) is 130 degrees. It increases steadily between inlet 5 and outlet 6 of the pitch a2. Adjacent Mahlleisten 3 (another Mahlleiste 3 is only partially drawn) are not parallel to each other but are rotationally arranged around the center M at an angle which is ideally equal to the offset angle γ adjacent Mahlleisten 3 in the circumferential direction. As a result, the angle of attack and thus the cutting angle on a circumferential line is constant, which is a great advantage over the prior art shown in FIG. In certain cases, a small deviation can be allowed, that is to say that then the angle of the rotary arrangement deviates up to a maximum of 3 degrees, preferably a maximum of 1 degree, from the respective offset angle γ,

If also at the inlet 5 a cutting angle greater than 0 degrees is cheaper, can be constructed as shown in FIG. Therein, the inlet-side angle of attack a1 = 15 degrees and the outlet-side angle of attack a3 are again 65 degrees. This too is just an example and does not exclude other angle combinations.

The shape of the grinding bar 3 is in Fig. 3 to 5 is selected as a circular arc. There are also other bow shapes appropriate, whereby the variation of the cutting angle receives another degree of freedom. So z. B. offer an elliptical shape of Mahlleisten 3 ^'of FIG. 6 advantages, especially because a longer grinding edge is possible, also in each case at the same angles of attack a1 and a3 (see Fig. 5) in the inlet 5 or outlet 6. Longer grinding edges may be desirable to increase the secondary edge length. The ellipse used (center line ME) lies with its smaller radius of curvature in the vicinity of the inlet 5.

Usually Mahlgarnituren are produced as segments and only in the refiner to circular rings composed. Are known 45-degree segments, 60-degree segments and 90-degree segments in which the segment boundaries (ie joints in the assembled state) are radial. This results in Schrägmessergarnituren that at least some Mahlleisten be cut through the segment boundaries. In order to avoid the resulting hydraulic losses during operation by vortex, the segment boundaries 13 and 13 ^', as shown in FIGS. 3, 7, 8 and 9, are advantageously adapted to the respectively closest grinding bars 3 or grooves 7, so that they run in the same direction as this one. Fig. 9 illustrates a garnish ring composed of four 90-degree segments with their segment boundaries 13 and 13 ^'designed in the manner described. In this figure, the Mahlleisten and grooves are only hinted. In most cases, the Mahlgarnituren as shown in Figs. 7, 8 and 9, provided with screw holes 10, which reduce the usable grinding surface something. The usable Mahlfläche lies between the outer circle with diameter D2 and the inner circle with diameter D1 minus the surface of the screw holes 10. Fig. 8 shows that the benefits of adapted to the grooves or Mahlleisten sector boundaries 13 and 13 ^' even with Mahlgarnituren with straight milling strips 3 ^" and grooves 7 ^' can be realized if their angle of attack α is greater than zero, in this case, for example, 45 degrees. Neighboring grinding strips 3 ^" are each rotated by the offset angle γ relative to one another. The example shown has through grooves 7 ^' , here with a constant groove width. 10 is a perspective view of parts of two adjacent refining segments in the region of the inlet 5 of a clothing ring. Grinding bars 3, grooves 7 and segment boundaries 13 and 13 ^' are designed in a circular arc. The left-hand segment terminates at the segment boundary 13 ^' visible here with a projection which serves to form a groove 7, wherein its width 15 can also be smaller than the desired groove width N1. This may have its meaning in that z. B. also the adjacent refining segment with a groove-forming projection terminates (not realized here), or that the refining segments are to be mounted with a distance 16. This distance 16, which is here greatly exaggerated for clarity, has the advantage that the surfaces at the segment boundaries 13 and 13 ^'are less complicated to work with, since they do not have to be precisely fitting.

In the grinding segments shown in FIGS. 7, 9 and 10, the grinding bars 3 and grooves 7 extend as far as the inner edge of the clothing in order to utilize the grinding surface as far as possible. However, the peripheral speed is the lowest here.

The suitable for the process sets or grinding segments are z. B. made of alloyed chrome steel. They can be poured. The grooves can also be milled, especially with small groove widths. The surface is usually smooth, but also roughened surfaces are conceivable.

Claims

claims

1 . Process for grinding aqueous suspended pulp fibers,

- In which these fibers in an aqueous suspension (S) between Mahlleisten (3, 3 ^' , 3 ^" ) are guided, which are on the grinding surfaces of Mahlgarnituren (1, 2), which either on a rotor (9) or a Stator (8) are fixed and rotated relative to each other and pressed against each other, whereby mechanical grinding work is transmitted to the pulp fibers,

- In which the grinding edges of the Mahlleisten (3, 3 ^' , 3 ^" ) relative to the radius (R) an angle of attack (a, al, a2, a3), at least on the majority of the Mahlleisten (3, 3 ^' , 3 ^" ) is greater than 4 degrees, and

in which at least part of the suspension (S) is conveyed by grooves (7, 7 ^' ) lying between the grinding strips (3, 3 ^' , 3 ^" ), in each case by a radially inner inlet to a radially outer outlet, characterized

at least partially such grinding sets (1, 2) are used, in which the grooves (7, 7 ^' ) on the grinding surfaces in each case continuously from the inlet (5) to the outlet (6) without cross-connection to adjacent grooves (7, 7 ^' ) , as well as without sudden change in the groove direction or sudden change in the groove width (N1, N2, N3) run.

2. Process for the milling of water-suspended pulp fibers,

- In which these fibers in an aqueous suspension (S) between Mahlleisten (3, 3 ^' , 3 ^" ) are guided, which are on the grinding surfaces of Mahlgarnituren (1, 2), which either on a rotor (9) or a Stator (8) are fixed and rotated relative to each other and pressed against each other, whereby mechanical grinding work is transmitted to the pulp fibers, - In which the grinding edges of the Mahlleisten (3, 3 ^' , 3 ^" ) relative to the radius (R) an angle of attack (a, al, a2, a3), at least on the majority of the Mahlleisten (3, 3 ^' , 3 ^" ) is greater than 4 degrees, and

that at least partially such Mahlgarnituren (1, 2) are used, in which at least 80% of the Mahlleisten (3, 3 ^' ), preferably all Mahlleisten (3, 3 ^' ) have curved grinding edges.

3. The method according to claim 1 or 2,

characterized,

that the grinding is carried out in a disc refiner.

4. The method according to claim 1 or 2,

characterized,

that the grinding is carried out in a cone refiner.

5. The method according to claim 1, 2, 3 or 4,

characterized,

that segmented Mahlgarnituren (1, 2) are used, and that the segment boundaries (13, 13 ^' ) are adapted to the nearest Mahlleisten (3) or grooves (7), so that they run in the same direction as this.

6. grinding set (1, 2) for carrying out the method according to claim 1, 2, 3, 4 or 5, which is provided with Mahlleisten (3, 3 ^' , 3 ^" ) whose grinding edges relative to the radius (R) an angle ( α1, α2, α3) which is greater than 4 degrees at least on the predominant part of the grinding strips (3, 3 ^' , 3 ^" ) and between which grooves (7, 7 ^' ) are located,

characterized, that the grooves (7, 7 ^' ) on the grinding surfaces in each case continuously from the inlet (5) to the outlet (6) without cross-connection to adjacent grooves (7, 7 ^' ), as well as without sudden change of the groove direction or sudden change in the groove width (N1 , N2, N3).

7. Mahlgarnitur (1, 2) for performing the method according to claim 1, 2, 3, 4 or 5, which is provided with Mahlleisten (3, 3 ^' , 3 ^" ), the grinding edges with respect to the radius (R) an angle ( α1, α2, α3) which is greater than 4 degrees at least on the predominant part of the grinding strips (3, 3 ^' , 3 ^" ) and between which grooves (7) are located,

characterized,

that at least 80% of the grinding strips (3, 3 ^' ), preferably all the grinding strips (3, 3 ^' ) have bent grinding edges.

8. grinding set (1, 2) according to claim 6 or 7,

characterized,

in that the grinding edges have an angle of attack (α1, α2, a3,) increasing from the inlet (5) to the outlet (6).

9. grinding set (1, 2) according to claim 6 and 7,

characterized,

10. grinding set (1, 2) according to claim 6, 7, 8 or 9,

characterized,

the grinding edges have an angle of attack (a1) between 0 and 15 degrees relative to the radius (R) at the inlet (5) and an angle of attack (a3) between 15 and 80 degrees, preferably between 30 and 70 degrees, at the outlet (6).

1 1. Grinding assembly (1, 2) according to one of claims 6 to 10,

characterized,

that the grinding edges from the inlet (5) to the outlet (6) form the shape of a circular arc.

12. grinding set (1, 2) according to one of claims 6 to 10,

characterized,

that the grinding edges from the inlet (5) to the outlet (6) form the shape of an elliptical arc.

13. The method according to any one of the preceding claims,

characterized,

at least 90% of the grinding strips (3, 3 ^' , 3 ^" ), preferably all the grinding strips (3, 3 ^' , 3 ^" ) have the same length.

14. grinding set (1, 2) according to one of claims 6 to 13,

characterized,

in that adjacent grinding bars (3, 3 ^' , 3 ^" ) are rotated at an angle around the center (M), the offset angle γ, in the neighboring grinding bars (3, 3 ^' , 3 ^" ) about the center point (M) is rotationally relative to each other offset are equal to a maximum deviation of 3 degrees.

15. grinding set (1, 2) according to one of claims 6 to 14,

characterized,

the groove width (N1, N2, N3) on the grinding surface is constant.

16. The method according to claim 15,

characterized,

that the width (B) of the Mahlleisten (3, 3 ^' , 3 ^" ) is not constant on the grinding surfaces.

17. grinding set (1, 2) according to one of claims 6 to 14, characterized,

the groove width (N1, N2, N3) on the grinding surface is not constant.

Method according to claim 17,

characterized,

the width of the milling strips (3, 3 ^' , 3 ^" ) on the grinding surface is constant.

Grinding assembly (1, 2) according to one of claims 6 to 18,

characterized,

the grooves (7, 7 ^' ) on the grinding surfaces have a groove width (N1, N2 between 2 and 8 mm, preferably between 2 and 5 mm.