Method for controlling a device for treating high-consistency fiber material

Description

[0001] The invention relates to a method for controlling a device for treating high-consistency fiber material, comprising a housing in which a first treatment tool and a second treatment tool are arranged, wherein the treatment tools are each fastened to a base plate, have a rotationally symmetrical shape, are arranged coaxially to one another, rotate relative to one another about a common axis and delimit a treatment gap through which the fiber material flows radially, the gap width of which can be changed via an axial displacement of at least one base plate of a treatment tool.

[0002] Due to the high consistency of the fiber during treatment, intensive mechanical processing is possible with such devices (dispersers, refiners), even though the treatment tools, which are movable relative to one another, do not touch each other but rather move past each other at a very close distance. This generates considerable forces.

[0003] Devices of the above-mentioned type are used, for example, to improve the quality of pulp, TMP or fiber obtained from waste paper.

[0004] It is known that paper pulp can be homogenized and significantly improved by dispersion. In many cases, pulp is used that has a dry matter content between 15 and 35% and has been heated to a temperature well above ambient. It is advisable to perform the heating when the pulp already has the consistency required for dispersion. EP 1147806 A1 discloses a device for treating high-consistency pulp in which the distance between treatment tools can be adjusted.

[0005] It has also been known for a long time to refining cellulose fibres, i.e. fresh pulp and / or waste paper fibres, in order to achieve the desired properties in the fibre web produced therefrom, in particular with regard to strength, porosity, formation and surface.

[0006] In the refiners used, the grinding surfaces are formed by replaceable grinding sets screwed to the corresponding base plate due to the relatively rapid wear.

[0007] In order to achieve the desired fiber properties, especially the degree of freeness, the refining sets must be adapted as best as possible to the fiber to be treated, also to prevent excessive wear of the sets.

[0008] In addition, optimal use of the available grinding surface is sought to increase the efficiency of fiber treatment.

[0009] In all cases, a gap that is too large reduces the effectiveness of the treatment. A gap that is too small, on the other hand, risks excessive electrical current consumption and contact between the treatment tools.

[0010] Therefore, sensors have been developed to measure the current gap width, but these are very expensive.

[0011] The object of the invention is to enable safe and efficient operation of these devices using the simplest possible means.

[0012] According to the invention, the object was achieved in that, in order to determine the minimum distance between the base plates, the vibrations of the device, in particular at least one element thereof, are recorded and the distance between the base plates rotating relative to one another is reduced until the frequency and / or the amplitude and / or the change in the frequency and / or the change in the amplitude of the vibrations exceeds a limit value and the distance is defined as the minimum distance when the limit value is exceeded.

[0013] Typically, with new processing tools or new grinding sets, the zero point at which the processing tools come into contact with each other is set while the device is at a standstill. Starting from this zero point, a minimum distance is then defined between the opposing base plates of the processing tools, with a certain safety margin.

[0014] However, as the treatment surface of the treatment tools facing the gap increases, the gap between the treatment tools increases. This results in a reduction in the applied drive power and a reduced efficiency of the fiber treatment.

[0015] As a result, it is necessary to redetermine the zero point when the machine is at a standstill, which involves considerable effort and requires a certain amount of know-how.

[0016] In contrast, the inventive solution allows a safe and simple determination of the minimum distance between the base plates during relative rotation of the treatment tools to each other.

[0017] The speed during the determination of the minimum distance between the base plates can often even be in the range of the operating speed.

[0018] However, to avoid damage, it may sometimes be advantageous if the speed during the determination of the minimum distance between the base plates is below the operating speed, preferably below 1,000 revolutions per minute.

[0019] As the distance decreases, the opposing treatment tools approach each other, which influences the vibration behavior of the treatment device.

[0020] At the latest when the treatment tools come into contact without pressing force, the vibrations change so much that this can be used to determine the minimum distance.

[0021] It has proven particularly safe if the distance between the base plates rotating relative to each other is reduced until the change in the frequency of the vibrations exceeds a limit value and the distance is set as the minimum distance when the limit value is exceeded.

[0022] The distance between the base plates can generally be reduced continuously or in steps, preferably in decreasing increments. This can be done manually, but should preferably be controlled.

[0023] However, to prevent damage to the treatment tools, the distance between the base plates during operation should be set to a specified value, which is preferably between 0.1 and 0.4 mm, above the minimum distance as a safety distance.

[0024] The minimum distance between the base plates should always be determined during commissioning of the device and / or after changing a treatment tool.

[0025] Since the distance between the treatment tools increases due to wear during operation, the determination of the minimum distance between the base plates should also be carried out during operation, preferably at certain time intervals, in particular periodically.

[0026] In order to make the determination of the minimum distance between the base plates as reliable as possible, the treatment gap should be flowed through by the fiber material during the determination of the minimum distance, whereby when determining the minimum distance between the base plates, one or more parameters of the fiber material, preferably all essential ones, are advantageously within a given operating range.

[0027] The essential parameters of the fiber material are, in particular, the amount of fiber material flowing through the treatment gap, the electrical power consumption of the treatment device, the temperature and the density of the fiber material.

[0028] Alternatively, for the sake of simplicity, the minimum distance can be determined even when no fiber material is flowing through the treatment gap, particularly during commissioning or after changing a treatment tool.

[0029] Regardless of the specific design, the invention also enables a method for measuring the treatment gap width during operation of a device for treating high-consistency fiber. For this purpose, after determining the minimum distance, the axial distance change between the base plates is measured starting from the minimum distance and used as a reference for the current treatment gap width.

[0030] The display of the treatment gap width is particularly important for dispersers and has so far been inadequate due to the small gap widths.

[0031] The axial distance change between the base plates can be measured using displacement sensors, especially inductive displacement sensors.

[0032] To simplify the design of the device, one treatment tool should rotate and the other should not, with only one treatment tool being mounted for axial movement. In special designs, the treatment tool and base plate can also be constructed as a single piece.

[0033] The application of the method according to the invention is particularly advantageous in a disperser, a deflaker or a refiner.

[0034] The fiber material can also be TMP, high-yield pulp, MDF fiber, wood chips or similar materials.

[0035] The invention will be explained in more detail below using two exemplary embodiments.

[0036] The attached drawing shows: Figure 1 : a schematic cross-section through a disperser; Figure 2 : by a refiner and Figure 3: the change in the distances s between the base plates of the treatment tools over the vibration frequency f.

[0037] The high consistency paper pulp 1 is produced according to Figure 1 directly into the central area of the disperser set, which is formed by the two treatment tools 3,4.

[0038] While one treatment tool 3 is stationary, i.e. does not rotate and is thus designed as a stator, the other treatment tool 4 is rotatably mounted in the housing 2 of the disperser.

[0039] The disperser assembly with the stator and rotor is fed radially from the inside.

[0040] As is known, dispersion is achieved by teeth 9 being moved relatively close to each other at a relatively high speed and the fiber material 1 located therebetween being subjected to strong shear forces.

[0041] For this purpose, the fiber 1 can be preheated using superheated steam. After dispersion, the dispersed fiber 1 falls downward through outlet 11.

[0042] If the axial position of the stator base plate 7 and the rotor base plate 8 is changed relative to each other, the gap 6 between the treatment tools 3, 4 also changes, whereby the performance of the disperser can be controlled in a manner known per se.

[0043] The treatment tools 3, 4 each have a rotationally symmetrical shape. The coaxially arranged treatment tools 3, 4 each have several annular teeth 9 arranged concentrically to their center, between which there are tooth gaps through which the fiber material 1 flows radially outward.

[0044] Between the rows of teeth there are annular spaces which are arranged in such a way that at least one row of teeth of a treatment tool 3,4 extends into an annular space of the other, complementary treatment tool 4,3.

[0045] In contrast, Figure 2 a grinding arrangement with a grinding gap 6, which is formed by a stationary, ie non-rotating, treatment tool 3 coupled to the housing 2 and a treatment tool 4 rotating about a rotation axis 5.

[0046] The two circular grinding surfaces run parallel to each other, whereby the gap distance between them can be adjusted via an axial displacement, usually of the non-rotating treatment tool 3.

[0047] The rotating grinding surface is moved in the direction of rotation by a shaft mounted rotatably in the housing 2. This shaft is driven by a drive also located in the housing 2.

[0048] In the example shown, the fiber suspension 1 to be ground passes through an inlet through the center into the grinding gap 6 between the grinding surfaces of the two treatment tools 3, 4.

[0049] The fiber suspension 1 passes the interacting grinding surfaces radially outwards and leaves the adjoining annular space through an outlet.

[0050] Both grinding surfaces are each formed by several grinding plates, each of which extends over a circumferential segment of the corresponding grinding surface.

[0051] When arranged side by side in the circumferential direction, the grinding plates form a continuous grinding surface.

[0052] The grinding plates and thus also the grinding surfaces are generally formed by a plurality of essentially radially extending grinding bars 10 and grooves in between.

[0053] Not shown are the conventional means by which the non-rotating treatment tool 3 is axially displaced and the extent of this axial displacement is measured. The rotating treatment tool 4 does not change its axial position.

[0054] What both designs have in common is that the treatment tools 3, 4 are mounted on corresponding base plates 7, 8. Unlike the examples shown here, the treatment gap 6 can run not only perpendicularly but also inclined to the rotation axis 5, as is the case with conical refiners, for example.

[0055] When the treatment device is put into operation and / or after changing a treatment tool 3, 4 and / or during operation of the treatment device, the minimum distance sm between the base plates 7, 8 is determined when the corresponding treatment tool 4 rotates.

[0056] During the determination of the minimum distance s M, the speed is in the range of the operating speed or advantageously below the operating speed, preferably below 1,000 revolutions per minute.

[0057] By determining the minimum distance s M , damage or excessive wear of the treatment tools 3,4 during operation can be prevented.

[0058] Furthermore, by determining the minimum distance s M during operation, a treatment gap 6 between the treatment tools 3, 4 that becomes excessively large due to wear can be counteracted. For this purpose, the minimum distance s M between the base plates 7, 8 should be determined at specific time intervals, preferably periodically, taking into account that average wear can easily amount to 0.1 mm per day.

[0059] Since this process takes place during rotation, downtime of the treatment device is minimized.

[0060] In order to prevent excessive wear of the treatment tools 3,4, it may be advantageous to set the distance s between the base plates 7,8 during operation by a predetermined value above the minimum distance s M as a safety distance ss.

[0061] In both embodiments, in order to determine the minimum distance s M between the base plates 7,8, the vibrations are recorded via one or more sensors arranged on the housing 2.

[0062] At the same time, the distance s between the base plates 7,8 rotating relative to each other is continuously reduced, starting with a relatively large distance, until the change in frequency Δf exceeds a limit value.

[0063] The distance s at this limit value exceedance is then defined as the minimum distance s M .

[0064] For both use cases, Figure 3 the course of the oscillation frequency f during the reduction of the distance s between the base plates 7,8.

[0065] It is advantageous to carry out the measurement in the absence of fiber 1.

Claims

1. Method for controlling a device for treating high-consistency fibrous material (1), comprising a housing (2) in which a first treatment tool (3) and a second treatment tool (4) are arranged, wherein the treatment tools (3, 4) are each fixed to a base plate (7, 8), have a rotationally symmetrical form, are arranged coaxially with respect to each other, rotate relative to one another about a common axis (5) and delimit a treatment gap (6) through which the fibrous material (1) flows radially and of which the gap width can be varied via an axial displacement of at least one base plate (7, 8) of a treatment tool (3, 4), characterized in that to determine the minimum distance (sM) between the base plates (7, 8), the oscillations on the device are detected and the distance (s) between the base plates (7, 8) rotating relative to one another is reduced until the frequency (f) of the oscillations exceeds a limiting value, and the distance (s) when the limiting value is exceeded is defined as the minimum distance (sM).

2. Method for controlling a device for treating high-consistency fibrous material (1), comprising a housing (2) in which a first treatment tool (3) and a second treatment tool (4) are arranged, wherein the treatment tools (3, 4) are each fixed to a base plate (7, 8), have a rotationally symmetrical form, are arranged coaxially with respect to each other, rotate relative to one another about a common axis (5) and delimit a treatment gap (6) through which the fibrous material (1) flows radially and of which the gap width can be varied via an axial displacement of at least one base plate (7, 8) of a treatment tool (3, 4), in particular according to Claim 1, characterized in that to determine the minimum distance (sM) between the base plates (7, 8), the oscillations on the device are detected and the distance (s) between the base plates (7, 8) rotating relative to one another is reduced until the amplitude of the oscillations exceeds a limiting value, and the distance (s) when the limiting value is exceeded is defined as the minimum distance (sM).

3. Method for controlling a device for treating high-consistency fibrous material (1), comprising a housing (2) in which a first treatment tool (3) and a second treatment tool (4) are arranged, wherein the treatment tools (3, 4) are each fixed to a base plate (7, 8), have a rotationally symmetrical form, are arranged coaxially with respect to each other, rotate relative to one another about a common axis (5) and delimit a treatment gap (6) through which the fibrous material (1) flows radially and of which the gap width can be varied via an axial displacement of at least one base plate (7, 8) of a treatment tool (3, 4), in particular according to Claim 1 or 2, characterized in that to determine the minimum distance (sM) between the base plates (7, 8), the oscillations on the device are detected and the distance (s) between the base plates (7, 8) rotating relative to one another is reduced until the change in the frequency (Δf) of the oscillations exceeds a limiting value, and the distance (s) when the limiting value is exceeded is defined as the minimum distance (sM).

4. Method for controlling a device for treating high-consistency fibrous material (1), comprising a housing (2) in which a first treatment tool (3) and a second treatment tool (4) are arranged, wherein the treatment tools (3, 4) are each fixed to a base plate (7, 8), have a rotationally symmetrical form, are arranged coaxially with respect to each other, rotate relative to one another about a common axis (5) and delimit a treatment gap (6) through which the fibrous material (1) flows radially and of which the gap width can be varied via an axial displacement of at least one base plate (7, 8) of a treatment tool (3, 4), in particular according to one of the preceding claims, characterized in that to determine the minimum distance (sM) between the base plates (7, 8), the oscillations on the device are detected and the distance (s) between the base plates (7, 8) rotating relative to one another is reduced until the change in the amplitude of the oscillations exceeds a limiting value, and the distance (s) when the limiting value is exceeded is defined as the minimum distance (sM).

5. Method according to one of the preceding claims, characterized in that the distance (s) between the base plates (7, 8) is adjusted during operation by a predefined value above the minimum distance (sM) as a safety margin (ss).

6. method according to one of the preceding claims, characterized in that the distance (s) between the base plates (7, 8) is reduced in steps, preferably in decreasing steps.

7. method according to one of Claims 1 to 5, characterized in that the distance (s) between the base plates (7, 8) is reduced continuously.

8. Method according to one of the preceding claims, characterized in that the determination of the minimum distance (sM) between the base plates (7, 8) is carried out during the start-up of the device and / or following a change of a treatment tool (3, 4).

9. Method according to one of Claims 1 to 7, characterized in that the determination of the minimum distance (sM) between the base plates (7, 8) is carried out during the operation of the device.

10. Method according to Claim 9, characterized in that the determination of the minimum distance (sM) between the base plates (7, 8) is carried out at specific time intervals, preferably periodically.

11. Method according to one of the preceding claims, characterized in that the rotational speed during the determination of the minimum distance (sM) between the base plates (7, 8) lies in the region of the operating rotational speed.

12. Method according to one of Claims 1 to 10, characterized in that the rotational speed during the determination of the minimum distance (sM) between the base plates (7, 8) lies below the operating rotational speed, preferably below 1000 revolutions per minute.

13. Method according to one of the preceding claims, characterized in that the fibrous material (1) flows through the treatment gap (6) during the determination of the minimum distance (sM).

14. Method according to Claim 13, characterized in that during the determination of the minimum distance (sM) between the base plates (7, 8), at least the quantity of fibrous material (1) flowing through the treatment gap (6) or the temperature of the fibrous material (1) or the consistency of the fibrous material (1) or the electrical power consumption of the treatment device lie in a predefined operating range.

15. Method according to one of Claims 1 to 12, characterized in that the fibrous material (1) does not flow through the treatment gap (6) during the determination of the minimum distance (sM).

16. Use of the method according to one of the preceding claims in a disperger or a refiner or a deflaker.