DE102008039001A1 - Aqueously suspended cellulose fiber e.g. old paper fiber, refining method for double disk refiner, involves guiding suspension between refining devices, where part of blocks of devices has cutting width extended from inner to outer sides - Google Patents

Abstract

The method involves guiding a cellulose fiber in aqueous suspension between refining devices (1, 2) provided with refining blocks (3). The refining devices are rotationally moved relative to each other and pressed against each other. Mechanical refining energy is transferred to the cellulose fiber. The suspension is guided between the refining devices and is discharged from the refining devices. The refining devices are partially used, where a part of the refining blocks has a cutting width (5), which is extended from inner side to outer side in a radial direction. An independent claim is also included for a refining device for performing a method for refining aqueously suspended cellulose fiber.

Description

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

since It has long been known that pulp fibers, i. H. Frischzellstoff- or recycled paper fibers, ground so that later paper made from this the desired properties, especially strength, formation and surface, has. Milling methods of the type considered here use grinding tools, which are provided with strips designated as knives. The corresponding Machines are usually called Mahlrefiner. At the grinding tools one speaks mostly of trimmings.

Refinergarnituren for grinding pulp fibers with Mahlleisten and intervening grooves are z. B. from the DE 20 2005 007 551 U1 known.

Of the Invention is based on the object, a method for pulp grinding to create, with which it is possible, the grinding economically and to carry out particularly uniformly, d. H. that the desired Mahltechnologischen changes in all fibers are as equal as possible.

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

The Claims 14 and 15 each describe for the Method particularly suitable Mahlgarnituren.

With Help with these described measures it is possible the pressures and the flows of the fiber suspension in the grinding area of a grinding machine used for the process to be controlled and favorably influenced.

It is known that the number of knives as well as the speeds, with which the knives are moved past each other, a big one Have influence on the grinding effect, as these are the secondary edge length determine, depending on the transferring Grinding performance which gives specific edge load. The specific one Edge load is z. In Ws / km. Considering this relationship is a bigger one Number of different grinding sets have been developed essentially by knife width, number of knives and the angle differentiate the knife edge to the radius. In many cases For example, a refiner for such processes is constructed that the largest possible number of knives on it, to the effect of grind too optimize. The inventive method proposes as a significant improvement that the blade width and / or the groove width can be changed so that the following additional Influences on the operation of the refiner used can be:

1. Specific edge load

generally known there is a relationship between the degree of grinding and the load capacity of the Paper or cellulose fiber during grinding. By the invention can be taken into account that more ground Fiber often more sensitive to high secondary edge load is. Wider blades result in otherwise identical geometrical Ratios to a smaller number of edges and thus to a higher secondary edge load. Will the width the knife gets bigger at the inner edge, so it becomes that is, the grinding state of the pulp at this point customized.

2. Milling pressure

In the known Mahlrefinern the trimmings are against each other pressed that transferred the desired power can be. This results in relatively high grinding pressures, whose height depends on the area, the the grinding bar has at the appropriate place of the clothing. With Help of the invention can be the grinding pressures occurring to adapt to the requirements of the milling process by the blade width changes over the axial extent of the clothing. In particular, the blade width at the radially outward lying larger areas, causing there the grinding pressure is lower than in the more inner. But they are too Cases conceivable, especially when grinding robust Fibers where a smaller knife thickness in the outer Range is desired, for. B. around there a stronger to perform fiber-shortening grinding. That's the way it is possible, a long pulp in a single grinding pass first to shorten and then to fibrillate.

3. Backflows within the trimmings

For geometric reasons, the width of the grooves lying 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 tune the width of the knife and the groove, taking into account both the special requirements for edge loading and grinding pressure and also the flow guidance within the clothing. 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 assume that it is the solution the task of the invention is sufficient, the grooves with the uneven flow cross section only to be provided at the grinding sets used on the stator become. But it is equally well conceivable, the flow cross-section of the To vary grooves also in the rotor sets, so there too become larger in the flow direction let to the rotor-side flow channels to adapt to the increased recirculation amount. To what extent, that depends on whether a large internal circulation to improve the grinding result.

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

1 : the implementation of the process using the example of a disc refiner;

1a : Modification of in 1 shown stator assembly;

2 - 4 in each case a part (sector) of a mill set according to the invention which can be used in plan view;

5 : the implementation of the method using the example of a double disc refiner.

The process according to the invention can be carried out in a grinding device as described in US Pat 1 is shown schematically in section. On a stator 8th is a grinding set 1 and on a rotor 9 a grinding set 2 detachable with the help of screws 12 attached. In the Mahlgarnituren 1 and 2 it concerns knife sets, which with Mahlleisten 3 are provided, the z. Tie 2 - 4 can be seen in plan view. The slurry S to be ground passes through the center of the stator in the example shown here 8th into the grinding sets 1 and 2 , In this illustration, the axial distance that the Mahlgarnituren 1 and 2 have from each other, greatly exaggerated. In operation, it is only fractions of a millimeter. The suspension S passes through the cooperating Mahlgarnituren 1 and 2 , comes out on the drain side again, accumulates in the annulus 7 and partially leaves the annulus 7 via a corresponding nozzle. Another part of the suspension flows through the between the Mahlleisten 3 lying grooves 4 in the stator 8th at least part of their length back. In special cases, it may be beneficial if the grooves 4 in the stator 8th closed on the inside (s. 1a ), because this also favors the return flows. The rotor 9 gets through a wave 11 driven. 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 going through 2 to 4 represented by sectors without a true-to-scale drawing. Many sets of disc and double disc refiners are constructed on a base plate 13 (annular or sectioned) strip-shaped elevations, so the Mahlleisten 3 , also called "knives", are present. The cross-section of the grinding bars 3 is generally rectangular, although there are other shapes. The top of these grinding bars 3 , So the surfaces carrying the grinding edges, which complete the set towards Gegengarnitur, lie in a radial plane. Between the grinding bars 3 are the grooves 4 that z. B. also have a rectangular cross-section and serve as flow channels for the suspension. Their groove depth T is advantageously between 2 and 20 mm (s. 1 ). For better clarity, the Mahlleisten 3 the grinding sets 1 respectively. 2 drawn drawn, so provided with a hatch. One recognizes in 2 a 90 ° sector of the grinding set, in which the Mahlleisten 3 with regard to their blade width 5 zoom in from the inside to the outside in the radial direction. The set shown is designed so that between the Mahlleisten 3 lying grooves 4 a constant groove width 6 to have.

The 3 shows another also suitable for the process set 1 respectively. 2 in which the Mahlleisten 3 a constant blade width 5 while the intervening grooves 4 radially inward are considerably narrower than radially outward. (groove width 6 smaller inside than outside). In the 3 shown set is used with particular advantage as a stator, z. B. in cooperation with a rotor assembly according to 2 or 4 ,

Another possibility is according to 4 in a grinding set with grinding bars 3 , whose blade width 5 is constant while the intervening grooves 4 reduced in size from inside to outside as seen in the radial direction. (groove width 6 larger inside 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 due to a number of shorter grinding bars 3 ' performed 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 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 radially inside 50% of the radially outer cross-sectional area, this is also true if the groove depth T by removal of Mahlleisten 3 halved.

The method can also be configured such 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 according to 5 be proceeded. You can see there between two the trimmings 1 respectively. 1' carrying stators 8th respectively. 8th' lying rotor 9 , on both sides of each Mahlgarnituren 2 respectively. 2 ' having. 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.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 202005007551 U1 [0003]

Claims (15)

Process for the milling of water-suspended pulp fibers, in which these fibers are mixed in an aqueous suspension (S) with grinding strips ( 3 . 3 ' ) provided grinding sets ( 1 . 1' . 2 . 2 ' ), 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 supplied and discharged from these again, characterized in that at least partially Mahlgarnituren ( 1 . 1' . 2 . 2 ' ) are used, in which at least a part of the Mahlleisten ( 3 ) a blade width ( 5 ), which increases seen from the inside outwards in the radial direction. Process for the milling of water-suspended pulp fibers, in which these fibers are mixed in an aqueous suspension (S) with grinding strips ( 3 . 3 ' ) provided grinding sets ( 1 . 1' . 2 . 2 ' ), 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 supplied and discharged from these again, characterized in that at least partially Mahlgarnituren ( 1 . 1' . 2 . 2 ' ) are used, in which at least a part of the Mahlleisten ( 3 ) 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 in that the blade width ( 5 ) has changed by at least 20% from inside to outside over at least 80% of its length. A method according to claim 1, 2 or 3, characterized in that the between the Mahlleisten ( 3 . 3 ' ) 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 mixed in an aqueous suspension (S) with grinding strips ( 3 . 3 ' ) provided grinding sets ( 1 . 1' . 2 . 2 ' ), 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 supplied and discharged from these again, characterized in that at least partially Mahlgarnituren ( 1 . 1' . 2 . 2 ' ) are used, in which at least part of the between the Mahlleisten ( 3 . 3 ' ) lying grooves ( 4 ) a groove width ( 6 ), which increases seen from the inside outwards in the radial direction. Process for the milling of water-suspended pulp fibers, in which these fibers are mixed in an aqueous suspension (S) with grinding strips ( 3 . 3 ' ) provided grinding sets ( 1 . 1' . 2 . 2 ' ), 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 supplied and discharged from these again, characterized in that at least partially Mahlgarnituren ( 1 . 1' . 2 . 2 ' ) are used, in which at least part of the between the Mahlleisten ( 3 . 3 ' ) lying grooves ( 4 ) a groove width ( 6 ), which decreases seen from the inside to the outside in the radial direction. Method according to claim 5 or 6, characterized in that the groove width ( 6 ) has changed by at least 20% from inside to outside over at least 80% of its length. Method according to claim 5, 6 or 7, characterized in that the milling strips ( 3 . 3 ' ) with a tolerance of -10% to + 10% a constant blade width ( 5 ) to have. Method according to one of the preceding claims, characterized in that the groove depth (T) of the between the Mahlleisten ( 3 . 3 ' ) lying grooves ( 4 ) is between 3 and 20 mm, preferably between 3 and 10 mm. Method according to one of the preceding claims, characterized in that the milling strips ( 3 . 3 ' ) a blade width ( 5 ) of at least 1 mm and not more than 30 mm. Method according to one of the preceding claims, characterized in that on the stator ( 8th . 8th' ) used grinding set ( 1 . 1' ) Grooves ( 4 ) whose groove width ( 6 ) is increased seen from the inside to the outside in the radial direction. A method according to claim 11, characterized in that only the grinding set used on the stator ( 1 . 1' ) Grooves ( 4 ) whose groove width ( 6 ) is increased seen from the inside to the outside in the radial direction. Method according to one of claims 1 to 11, characterized in that on the rotor ( 9 ) used grinding set ( 2 . 2 ' ) Grooves ( 4 ) whose groove width ( 6 ) is increased seen from the inside to the outside in the radial direction. Grinding set ( 1 . 1' . 2 . 2 ' ) for the application of the method according to any one of the preceding claims, which with Mahlleisten ( 3 . 3 ' ) between which grooves ( 4 ), characterized in that in the grinding set ( 1 . 1' . 2 . 2 ' ) at least part of the milling strips ( 3 . 3 ' ) lying grooves ( 4 ) a blade width ( 5 ), which changes in the radial direction from the inside to the outside. Grinding set ( 1 . 1' . 2 . 2 ' ) for the application of the method according to one of the preceding method claims, which with Mahlleisten ( 3 . 3 ' ) between which grooves ( 4 ), characterized in that in the grinding set ( 1 . 1' . 2 . 2 ' ) at least part of the between the Mahlleisten ( 3 ) lying grooves ( 4 ) a groove width ( 6 ), which changes in the radial direction from the inside to the outside.