WO2011098147A1

WO2011098147A1 - Method for refining aqueously suspended cellulose fibers and refiner filling for carrying out said method

Info

Publication number: WO2011098147A1
Application number: PCT/EP2010/051852
Authority: WO
Inventors: Markus FÜRSATTEL; Paul-Wilhelm Sepke; Herrmann Post; Michael Kramer
Original assignee: Voith Patent Gmbh
Priority date: 2010-02-15
Filing date: 2010-02-15
Publication date: 2011-08-18

Abstract

The invention relates to a method for refining aqueously suspended cellulose fibers and that uses at least two refiner fillings (1, 2), of which one is operated on a stator (8) and the other is operated on a rotor (9), and the suspension (S) to be refined is processed between the two refiner fillings. The refiner fillings (1, 2) used are used at least partially with refining strips (3) of uneven blade width (5) and/or grooves (4) having a differing groove width (6). Thus, in particular the specific edge loading can be optimally adjusted to the state of the fibers to be refined.

Description

Method for grinding aqueous suspended pulp fibers and grinding set for its implementation

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. The grinding tools are usually referred to as trimmings.

Refiner sets for grinding pulp fibers with grinding bars and grooves in between are e.g. known from DE 20 2005 007 551 U1.

The invention is based on the object to provide a process for pulp grinding, with which it is possible to carry out the grinding economically and particularly evenly, i. that the desired Mahltechnologischen changes in all fibers are as equal as possible.

This object is solved by the features mentioned in claims 1, 2, 5 and 6.

Claims 14 and 15 each describe particularly suitable grinding sets for the method. With the aid of these measures described, it is possible to control and favorably influence the pressures and the flows of the fiber suspension in the grinding area of a grinding machine used for the method.

It is known that the number of knives and the speeds at which the knives are moved past one another have a great influence on the grinding action, since these determine the secondary edge length, which results in the specific edge load depending on the transferring grinding performance , The specific edge load is e.g. given in Ws / km. Taking into account these relationships, a larger number of different Mahlgarnituren has been developed, which differ mainly by knife width, number of knives and the angle of the knife edges to the radius. In many cases, a grinding set for such methods is constructed so that as many knives as possible can be placed on it to optimize the effect of grinding. The method according to the invention proposes, as a substantial improvement, that the blade width and / or the groove width be changed in such a way that the following additional possibilities of influencing the operation of the refiner can be used:

1 . Specific edge load

As is known, there is a relationship between grinding degree and load capacity of the paper or cellulose fiber during grinding. By the

The invention can be taken into account that more highly ground pulp is often more sensitive to high secondary edge load. Wider blades result in otherwise identical geometrical

Conditions to a lower number of edges and thus to a higher secondary edge load. If the width of the knives at the inner edge becomes larger, then it is adapted to the grinding state of the fibrous material located at this point. 2. Milling pressure

In the known Mahlrefinern the trimmings are pressed against each other so that the desired performance can be transmitted. In this case, relatively high grinding pressures occur, the amount of which depends on the area that the grinding bar has at the corresponding point of the clothing. With the aid of the invention, the grinding pressures which occur can be adapted to the requirements of the grinding process by changing the blade width over the axial extension of the clothing. In particular, the blade width can be greater at the radially outer regions, whereby there the grinding pressure is lower than in the more inner.

However, cases are also conceivable, in particular when grinding robust fibers where a smaller knife thickness in the outer region is desired, e.g. There to perform a more fibrous shortening grind. Thus, it is possible to first shorten a long pulp in a single grinding pass and then to fibrillate it.

3. Backflows within the trimmings

For geometric reasons, the width of the nuches between the knives depends on how the measures already mentioned (uneven blade width) are carried out. It can also be said that the invention makes it possible to coordinate knife width and groove width, in which both the special requirements for edge loading and grinding pressure as well as the flow guidance within the unit are taken into account. The grooves are to be regarded as flow channels for the suspension. It can be assumed that as a result of the rotational movement of the rotor and the pulp suspension entrained by it, a strong pressure build-up takes place from the radially inner to the radially outer regions. Similar events occur in Centrifugal pumps on, of course, in much stronger form. Due to this pressure difference takes place in the non-rotating grooves, ie between the blades of the stator, at least partially, a back flow of the suspension from radially outside to radially inside instead. This backflow can be influenced by changing the groove width in the flow direction. On the way, the back-flowing suspension travels within a groove, a transition from the open side of the groove, so in the axial direction to Gegengarnitur take place. This effect is enhanced by a decreasing groove width in the flow direction. Thus, the exit of the suspension from the grooves lying between the milling strips is conveyed into the milling zone, that is to the knife edges. This repetition of the grinding operations, the grinding is uniform, which is technically and energetically of particular advantage. With the measures according to the invention, this transition can be strengthened.

In many cases, it can be assumed that it is sufficient to achieve the object according to the invention to provide the grooves with the uneven flow cross-section only in the Mahlgarnituren that are used on the stator. However, it is equally well possible to vary the flow cross-section of the grooves also in the rotor fittings, so also there to be larger in the flow direction to adjust the rotor-side flow channels to the increased recirculation. To what extent, this depends on whether a large internal circulation should improve the grinding result.

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

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

disc refiner;

FIG. 1 a shows a modification of the stator assembly shown in FIG. 1; FIG. Figure 2-4: each a part (sector) of a usable according to the invention

Grinding set in plan view;

Fig. 5: the implementation of the method using the example of a

Double disk.

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. The meal sets 1 and 2 are sets of knives provided with grinding bars 3, e.g. can be seen in plan view in Figs. 2-4. In the example shown here, the suspension S to be grounded passes through the center of the stator 8 into 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 7 and partially leaves the annular space 7 via a corresponding nozzle. Another portion of the suspension flows through the lying between the grinding bars 3 grooves 4 in the stator 8 at least through part of their length back. In special cases, it may be advantageous if the grooves 4 in the stator 8 are closed on the inside (see Fig. 1 a), because this also favors the return flows. The rotor 9 is driven by a shaft 1 1. Not shown are the means known per se, with which a force is generated to press the two Mahlgarnituren against each other.

A standard grinding set has a large number of grinding bars. This is represented by figures 2 to 4 on the basis of sectors, without here a Maßstäbl iche drawing vorlie. Many sets for disc and Doppelscheibenrefiner are constructed so that on a base plate 13 (annular or sectioned) strip-shaped elevations, ie the Mahlleisten 3, The cross-section of the grinding strips 3 is generally rectangular, although there are other shapes as well.The upper side of these grinding strips 3, ie the surfaces carrying the grinding edges, which terminate the clothing in the direction of the counter-assembly, lie in one The grooves 4, which for example also have a rectangular cross-section and which serve as flow channels for the suspension, are located between the grinding strips 3. Their groove depth T is advantageously between 2 and 20 mm (see FIG the grinding bars 3 of the grinding sets 1 and 2 are drawn, that is to say hatched, and a 90 ° sector of the grinding set is shown in Fig. 2, the grinding bars 3 being radially outwardly from inside to outside with respect to their blade width 5 The set shown is designed such that the grooves 4 lying between the grinding strips 3 have a constant groove width 6. The F FIG. 3 shows another set 1 or 2 which is likewise suitable for the method, in which the grinding bars 3 have a constant blade width 5, while the intermediate grooves 4 are considerably narrower radially inwards than radially outwardly. (Groove width 6 in less than outside). The set shown in FIG. 3 is used with particular advantage as a stator assembly, for example in cooperation with a rotor assembly according to FIG. 2 or FIG. 4.

Another possibility is shown in FIG. 4 in a Mahlgarnitur with Mahlleisten 3, the blade width 5 is constant, while the lying between them lying grooves 4 in Rad ialer direction decreases from the inside to the outside. (Groove width 6 inside larger than outside). Not all grinding bars are shown here. This illustration also shows measures that may be required when constructing annular grinding sets geometrically so that as many grinding bars as possible can be accommodated. This is done here by a number of shorter Mahlleisten 3 ^' in the radially outer region. Such measures are familiar to the detail designer of such Mahlgarnituren and therefore only hinted at here. Sets of the type according to FIG. 4 are particularly suitable as rotor sets. A particular advantage of these solutions is that with increasing wear of Mahlgarnituren the flow cross sections in the individual grooves, although smaller, but their size ratios remain about the same. Example: If the flow cross-sectional area of the groove 4 in the new condition of the clothing is radially inside 50% of the radially outer cross-sectional area, this also applies if the groove depth T has been halved by removal of Mahlleisten 3.

The method can also be designed so that in addition to, in particular in combination with the measures described in the claims, the flow cross section in the grooves 4 is changed by different groove depth T. Thus, the groove depth increases or decreases from the inside to the outside, the increase of the groove depth T in the stator and the decrease in the rotor being particularly advantageous. This also makes it possible to influence the return flow in the grooves, in particular to promote the transfer of the suspension flowing back into the grooves into the grinding zone.

Should the process be carried out with a double-disc refiner; then proceed as shown in FIG. 5. One recognizes there a between two the sets 1 and 1 ^' supporting stators 8 and 8 ^' lying rotor 9, which on both sides each Mahlgarnituren 2 and 2 ^' has. The position of rotor and stator is shown here in the operating state, ie the grinding bars are pressed against each other. Double disc refiners are particularly compact and efficient.

Claims

claims

1 . Process for the milling of water-suspended pulp fibers, in which these fibers are guided in an aqueous suspension (S) between grinding sets (1, 1 ^' , 2, 2 ^' ) provided with grinding bars (3, 3 ^' ), which are either on a rotor or a stator and are rotated relative to each other and pressed against each other, whereby mechanical grinding work is transferred to the pulp fibers and wherein the suspension (S) between the Mahlgarnituren (1, 1 ^' , 2, 2 ^' ) is fed and discharged again .

characterized,

that at least partially Mahlgarnituren (1, 1 ^' , 2, 2 ^' ) are used, in which at least a part of the Mahlleisten (3) have a blade width (5), which increases seen from the inside to the outside in the radial direction.

2. A process for grinding aqueous pulp fibers, in which these fibers in an aqueous suspension (S) between Mahlleisten with (3, 3 ^' ) provided Mahlgarnituren (1, 1 ^' , 2, 2 ^' ) are guided, which is either a rotor or a stator and are rotated relative to each other and pressed against each other, whereby mechanical grinding work is transmitted to the pulp fibers and wherein the suspension (S) between the Mahlgarnituren (1, 1 ^' , 2, 2 ^' ) and fed from these again is discharged,

characterized,

that at least partially Mahlgarnituren (1, 1 ^' , 2, 2 ^' ) are used, in which at least a portion of the Mahlleisten (3) have a blade width (5), which decreases seen from the inside to the outside in the radial direction.

Method according to claim 1 or 2,

characterized,

that the blade width (5) changes by at least 20% from inside to outside over at least 80% of its length.

Method according to claim 1, 2 or 3,

characterized,

that between the Mahlleisten (3, 3 ^' ) lying grooves with a tolerance of -10% to + 10% have a constant groove width.

Process for the milling of water-suspended pulp fibers, in which these fibers are guided in an aqueous suspension (S) between grinding sets (1, 1 ^' , 2, 2 ^' ) provided with grinding bars (3, 3 ^' ), which are either on a rotor or a stator and are rotated relative to each other and pressed against each other, whereby mechanical grinding work is transferred to the pulp fibers and wherein the suspension (S) between the Mahlgarnituren (1, 1 ^' , 2, 2 ^' ) is fed and discharged again .

characterized,

that at least partially Mahlgarnituren (1, 1 ^' , 2, 2 ^' ) are used, in which at least a portion of lying between the Mahlleisten (3, 3 ^' ) grooves (4) have a groove width (6) extending from the inside to outside seen in the radial direction increases.

Process for the milling of water-suspended pulp fibers, in which these fibers are guided in an aqueous suspension (S) between grinding sets (1, 1 ^' , 2, 2 ^' ) provided with grinding bars (3, 3 ^' ), which are either on a rotor or a stator and are rotated relative to each other and pressed against each other, whereby mechanical grinding work is transferred to the pulp fibers and wherein the suspension (S) between the Mahlgarnituren (1, 1 ^' , 2, 2 ^' ) is fed and discharged again . characterized,

that at least partially Mahlgarnituren (1, 1 ^' , 2, 2 ^' ) are used, in which at least a portion of lying between the Mahlleisten (3, 3 ^' ) grooves (4) have a groove width (6) extending from the inside to externally reduced seen in the radial direction.

7. The method according to claim 5 or 6,

characterized,

the groove width (6) changes by at least 20% from inside to outside over at least 80% of its length.

8. The method according to claim 5, 6 or 7,

characterized,

the milling strips (3, 3 ^' ) have a constant blade width (5) with a tolerance of -10% to + 10%.

9. Method according to one of the preceding claims,

characterized,

in that the groove depth (T) of the grooves (4) located between the milling strips (3, 3 ^' ) is between 3 and 20 mm, preferably between 3 and 10 mm.

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

characterized,

the milling strips (3, 3 ^' ) have a blade width (5) of at least 1 mm and at most 30 mm.

1 1. Method according to one of the preceding claims,

characterized,

that on the stator ^'Beating equipment used (1, 1 (8, ^8)' having) the grooves (4), the groove width (6) increases from inside to outside seen in the radial direction.

12. The method according to claim 1 1,

characterized,

that only the grinding set (1, 1 ^' ) used on the stator has grooves (4) whose groove width (6) increases seen from the inside to the outside in the radial direction.

13. The method according to any one of claims 1 to 1 1,

characterized,

the grinding set (2, 2 ^' ) used on the rotor (9) has grooves (4) whose groove width (6) increases seen from the inside to the outside in the radial direction.

14. grinding set (1, 1 ^' , 2, 2 ^' ) for applying the method according to one of the preceding claims, which is provided with Mahlleisten (3, 3 ^' ), between which there are grooves (4),

characterized,

in that at the grinding set (1, 1 ^' , 2, 2 ^' ) at least part of the grinding bars (3, 3 ^' ) lying grooves (4) has a blade width (5) which changes in the radial direction from the inside to the outside.

15. Mahlgarnitur (1, 1 ^' , 2, 2 ^' ) for applying the method according to one of the preceding method claims, which is provided with Mahlleisten (3, 3 ^' ), between which there are grooves (4),

characterized,

in that at the grinding set (1, 1 ^' , 2, 2 ^' ) at least a part of the grooves (4) lying between the grinding bars (3) has a groove width (6) which changes in the radial direction from the inside to the outside.