CN116324083A

CN116324083A - Control of fibrous material handling

Info

Publication number: CN116324083A
Application number: CN202180066903.8A
Authority: CN
Inventors: M·肯珀
Original assignee: Voith Patent GmbH
Current assignee: Voith Patent GmbH
Priority date: 2020-09-30
Filing date: 2021-09-28
Publication date: 2023-06-23
Also published as: EP4222308A1; US20230243097A1; DE102021125006A1; WO2022069433A1

Abstract

The invention relates to a method for controlling a device for processing a fibrous material (1), wherein the device has a housing (2) in which at least one first and one second processing tool (3, 4) are arranged, each of which processing tools (3, 4) is fastened to a base plate (7, 8), has a rotationally symmetrical shape, is arranged coaxially to one another, rotates relative to one another about a common axis (5), defines a processing gap (6) through which the fibrous material (1) flows, and each has a processing contour (9) which is directed towards the processing gap (6), wherein at least one base plate (7, 8) of the processing tools (3, 4) is mounted so as to be axially movable in order to compensate for wear of the processing contour (9). The control of the device is improved in that the distance(s) between the base plates (7, 8) of the processing tools (3, 4) of the processing gap (6) is determined, and in that the value of the total Power (PG) is adjusted in dependence on the change in the distance(s) between the base plates (7, 8) of the processing gap (6) in order to control the total Power (PG).

Description

Control of fibrous material handling

The invention relates to a method for controlling an apparatus for processing fibrous material, wherein the apparatus has a housing in which at least one first and one second processing tool are arranged. The treatment tools are each fixed on the base plate and have a rotationally symmetrical shape and are arranged coaxially to one another and rotate relative to one another about a common axis. The treatment tools define a treatment gap through which the fibrous material flows and each have a treatment contour directed toward the treatment gap, wherein at least one base plate of the treatment tools is mounted so as to be axially movable in order to compensate for wear of the treatment contour. To adjust the total power, the width of the process gap is adjusted until a predetermined total power is reached.

Because of the relatively high consistency of the fibers during processing, high-intensity mechanical processing is possible in such devices (refiners, dispersers, pulpers) even though the relatively movable processing tools do not come into contact, but pass by each other at a small distance. Here, very considerable forces occur. Apparatuses of the above-mentioned type are used, for example, for improving the quality of pulp, TMP (i.e. thermomechanical pulp) or fibrous material obtained from waste paper.

It has long been known to mill pulp fibers, i.e. fresh pulp and/or waste paper pulp, in order to be able to obtain the desired properties in the fibrous web thus produced, in particular in terms of strength, porosity, shaping and surface.

For refiners used in this process, the grinding surfaces are formed by exchangeable grinding elements which are screwed to the respective base plate, as a result of relatively rapid wear.

In order to obtain the desired fibre properties, in particular the degree of grinding, the grinding attachment must be adapted as much as possible to the fibre material to be treated, also in order to prevent excessive wear of the attachment.

In addition, in order to increase the efficiency of the fiber treatment, an optimal use of the available abrasive surface is sought.

It is known from US 2004/0112,997 A1 and DE 2 939 587 A1 and DE 3 602,833 A1 to measure or calculate the idle power once before being put into operation and use it as a basis for machine control.

If the height of the treatment profile of the treatment tool is reduced due to wear, this results in a reduction of the idle or pumping power. This also results in an increase in the specific power of the device, which is important for the targeted treatment intensity, if the total power remains unchanged, resulting in an excessive treatment, in particular excessive grinding, of the fibers. In the process, a constant total power is established by an axial displacement adjustment of the axially displaceable base plate.

If the gap is too small, there is again a risk that the current consumption is too high and the process tool is in contact.

It is known from DE 10 2016 207 726 A1 to determine the idle power during operation. However, for this purpose, it is necessary to idle or to flow water through the refiner and to open and close the treatment gap and at the same time to measure the idle power. The detected idle power in this case is then used as a basis for continued operation.

The object of the invention is to achieve reliable and efficient operation of these devices in as simple a manner as possible.

According to the invention, this object is achieved in that the distance between the base plates of the processing tool of the processing gap is changed during operation of the apparatus in order to control the total power, and in that the value of the total power is selected in dependence on the measured distance between the base plates of the processing gap. Measuring the distance is also understood to mean in particular a change in distance from an initial value. The distance can on the one hand be measured directly by measuring, for example, the distance of the process tool or of the base plate on which the process tool is fixed. But the distance may also be measured indirectly. For example, in one embodiment, the distance change can be deduced from the drive position of an axially movable base plate for tracking the processing tool.

Since the idle power of the apparatus decreases relatively strongly during the run time of the processing tool as the profile wear of the processing tool increases, the total power, which consists of idle or pumping power and specific power important for the target processing intensity, should be adjusted accordingly. This makes it possible to cope with an unnecessary increase in specific power and thus fiber processing strength effectively and simply.

This is particularly possible because the usual width of the process gap is many times smaller than the profile height of the process tool and therefore the width of the process gap can be ignored in the control. When the fibre suspension is fed, the formation of the treatment gap is effected in operation and the treatment gap width is adjusted until a predetermined total power is reached. Since the width of the process gap is negligible compared to the profile height, the change in gap width of the process gap is also negligible compared to the change in position due to wear of the fitting, wherein the process gap width can also be flow dependent. The profile height can thus be determined from the measured distance/distance change or from an initial value. For a device with one treatment gap, the profile height corresponds to half the distance between the base plates, and for a device with two treatment gaps, the profile height is one quarter of the determined distance value after deduction of the width of the distance established by the non-profile components. It is also possible to determine the reduction of the distance starting from the initial distance value and to determine the reduction of the profile height directly therefrom. The corresponding total power is adjusted as a function of the determined profile height and the desired process strength.

In one embodiment, it is provided that the wear of each fitting is given in a form rounded to 0.1mm, preferably 0.5mm. A displacement sensor or an incremental encoder is used as a sensor for determining the position or the change in position.

To simplify the control, the value of the total power should be chosen solely on the basis of the measured distance between the base plates of the process gap or in combination with the desired grinding energy. The measurement distance corresponds to the determination of the contour height. Preferably, the relation between the profile height and the associated idle power is stored in a characteristic map. The characteristic map may be read in by the operator before being put into operation or may already be provided by the manufacturer of the device. It is therefore not necessary to determine the idling power during operation.

In a preferred embodiment, it is provided that in a device with double play, the rotor is supported in a floating manner. Thus, the distance between the processing tools can be readjusted by the axially movable processing tools to correspond to the height of the contours for the two gaps.

The total power can be controlled more precisely when the total power is selected taking into account further values, such as the flow and the consistency and/or the mass of the fibre suspension.

Advantageously, the value of the total power is adjusted at least in case the distance between the base plates detecting the treatment gap is changed to at least 1 mm. This corresponds to a reduction of 0.5mm per treatment profile in the treatment gap.

It is generally sufficient, however, to reselect the value of the total power at predetermined time intervals, at most once a day, preferably at least once a week, depending on the measured distance change between the base plates of the treatment gap. Between these time intervals, the distance between the base plates is reduced in correspondence with the wear of the treatment profile, so as to keep the total power constantly at the respective current value.

In the control or regulation of the apparatus, as much as possible, the idling power should also be considered, which is related to the fibre material flow per unit time and is usually between 40 and 250, in particular between 40 and 150kWh per ton dry weight, for example in the case of refiners.

After intervention of the device, for example by updating only a part of the fitting, the distance value measured when opening and/or closing the process gap can be used once as a new initial value for the idle power in order to establish a relationship with the stored characteristic map. In the subsequent control of the total power, in addition to the distance values, further links to other parameter values can also be used for controlling the total power and thus also for controlling the specific power of the device.

It may furthermore be provided that the idle power is measured before each shut down of the refiner. In addition or alternatively, it may be provided that the idling power is determined only after a predetermined minimum operating time. This prevents the idling power from being determined every time in the case of frequent stoppage of the apparatus several times per day. Due to the stored characteristic map and the corresponding tracking of the total power, it is entirely sufficient to make an idle power determination every 1 to 2 weeks. This can reliably prevent an undesirably high grinding power.

It has been common practice to determine the idling power of the device when it is put into operation and to store the idling power for control or to use a predetermined value for this purpose.

As the operating time of the respective processing tool advances and thus the wear of the processing tool, in particular the profile of the processing tool, increases, the current idle power of the apparatus decreases. The total power consumption must be correspondingly reduced.

However, since the idling power is regarded as constant at the time of control/regulation so far, it may be caused that the total power consumed is excessively set at a value of 20% and above for the target processing intensity.

In order to be able to store the initial value for the control in the memory after the replacement of the at least one processing tool, it may be advantageous for the idling power to be measured by the service person and to be supplied or for the idling power to be measured by the control device itself, in particular when the processing gap is closed.

Independently of this, the value of the total power for controlling the device should be selected such that the specific power of the device, which is important for the target processing strength and is generated by the difference between the total power and the idling power, is constant over the operating time. Thereby, stable processing strength can be ensured. A specific power is considered constant if the deviation of the specific power from its arithmetic average is less than 5%.

If the re-determination of the total power value is not carried out continuously but at defined time intervals, the length of these time intervals should be selected such that possible changes due to wear of the treatment profile are tolerable for the specific power that is increasing at the time. A change of less than 5% of the last idling power employed and/or a change of position of less than 1mm per gap is considered to be tolerable.

In determining the value of the total power as a function of the distance between the base plates of the treatment gap, the values stored in the memory of the control device, in particular the characteristic map, should advantageously be used. The stored values or characteristic curve families have been specified by the manufacturer of the device or have been determined in advance in the test by the operator of the device.

These values stored in the memory are based on knowledge or experience about the idle power in the case of the corresponding distance between the two base plates of the process gap and the degree of wear of the process profile associated therewith. Taking into account the desired fibre treatment strength and thus the specific power, a predetermined value of the total power of the control is derived as a sum.

For a simple construction of the apparatus, one process tool should be rotated and the other process tool should not be rotated, wherein at least one process tool is axially movably supported.

In a particular embodiment, the processing tool and the base plate can also be designed as one piece.

It is also possible for the housing to have a plurality of, in particular two, parallel treatment gaps arranged next to one another, which preferably each have a treatment tool that rotates on an axis and a non-rotating treatment tool.

In this case, two processing tools adjacent to the respective other processing gap are fastened to a common base plate, wherein the common base plate and at least one processing tool not fastened to the base plate are mounted so as to be axially displaceable.

The method according to the invention is particularly advantageously used in refiners, in particular LC (low consistency) refiners, wherein the consistency of the fibre material is between 2 and 6%, in particular between 3.5 and 4.5% of the dry weight.

The fibrous material may also be, inter alia, TMP, high-yield fibrous suspensions, MDF (i.e. medium density fiberboard) fibrous material, wood chips or the like.

The present invention will be described in detail with reference to examples.

In the drawings:

figure 1 shows a schematic cross-sectional view of a refiner cut through, and

fig. 2 shows the power P of spinning _L Is changed and the total power P _G Adjustment over time t and over the distance s between the base plates 7, 8.

According to fig. 1, the paper fibre material 1 is pressed directly into the central, i.e. radially inner, region of the refiner fitting formed by the two

treatment tools

3, 4.

One of the treatment tools 3 is stationary and thus designed as a stator, while the other treatment tool 4 is rotatably supported in the refiner housing 2.

The

processing tools

3, 4 each have a rotationally symmetrical shape, wherein two annular grinding surfaces are arranged parallel to one another. The treatment gap 6 between the grinding surfaces is adjusted by axial displacement in order to achieve a predetermined total power. The treatment strength of the paper fibre material 1, also called fibre suspension, flowing into the gap is determined by the gap width of the treatment gap 6. This gap width of the process gap 6 is negligible in its axial extension compared to the height of the process contour 9 of the

process tools

3, 4.

The rotating grinding surface 9 is displaced in the direction of rotation by a shaft rotatably mounted in the housing 2. The shaft is driven by a drive means also present in the housing 2. In the example shown, the fibre suspension 1 to be ground enters the treatment gap 6 between the grinding surfaces of the two

treatment tools

3, 4 via a feed opening through the center.

The fibre suspension 1 passes radially outwards through the cooperating grinding surfaces and leaves the connected annular space through the discharge opening.

The two grinding surfaces are each formed by a plurality of grinding plates, which each extend over a circumferential section of the respective grinding surface. A plurality of grinding plates are arranged side by side in the circumferential direction to produce a continuous grinding surface.

The grinding plate and thus the grinding surface have a treatment profile 9 directed towards the treatment gap 6, which treatment profile is usually formed by a plurality of substantially radially extending grinding strips and grooves between the grinding strips.

Means for axially displacing the non-rotating processing tool 3, known per se, are not shown. The amount of axial movement is measured by the displacement sensor 10. The rotating processing tool 4 does not change its axial position. The axial movement can also be measured by an incremental encoder, not shown, on the drive means in order to adjust the axial position of the non-rotating but axially movable processing tool 3.

Furthermore, the

processing tools

3, 4 are fixed to the respective base plates 7, 8.

Unlike the example shown here, the treatment gap 6 can extend not only perpendicularly to the rotation axis 5, but also obliquely thereto as in a cone refiner. Furthermore, the housing 2 may also comprise a plurality of, in particular two, treatment gaps 6.

Fig. 2 illustrates the actual idle power P of the refiner _L The change in the distance S decreases with increasing operating time t and thus also with increasing wear of the treatment profile 9 of the

treatment tool

3, 4.

The total power P supplied to the processing device _G From idling power P _L And the specific power P responsible for the treatment strength, i.e. the grinding power, of the fiber suspension 1 _S Composition is prepared.

In case the idle power is known, the total power is adjusted to a predetermined value corresponding to the desired processing intensity. To avoid specific power P _S The idle power P used is adapted accordingly, using stored values or stored characteristic curves, as a function of the measured distance s between the base plates 7, 8 or the distance between the

processing tools

3, 4, to be significantly higher than the target processing strength of the fiber suspension 1 at the operating time of the

processing tools

3, 4 _L 。

By varying the distance s between the base plates 7, 8 of the

processing tools

3, 4 of the processing gap 6 during operation, the total power P taken by the apparatus can be controlled simply and efficiently _G . It is essential to the invention that the total power P is selected in dependence on the distance s between the base plates 7, 8 of the treatment gap 6 _G Is a value of (2).

Here, the total power P _G The value of (2) is preferably chosen such that the specific power P of the device, which is important for the target processing strength, is _S As constant as possible over the run time.

The total power P is selected in dependence on the distance s between the base plates 7, 8 of the treatment gap 6 _G The values stored in the memory of the control device are used, and are specified by the manufacturer of the device or are determined in experiments by the operator of the device.

Total power P _G The value predetermined for the control device can be based on the process gap 6 as indicated by the dashed line in fig. 2The distance s between the plates 7, 8 is continuously adjusted.

But alternatively according to fig. 2 for the total power P _G It is also possible to readjust the total power P at defined time intervals as a function of the distance s between the base plates 7, 8 of the treatment gap 6 _G Is a value of (2). Alternatively, it can also be provided that the total power is adjusted as a function of the change s. The idle power corresponding to the distance s is used as a basis for the adjustment.

Between corresponding adjustments, the total power P _G Is kept constant. Specific power P _S A slight rise in (c) occurring during this period can be tolerated.

Idle power P important for controlling processing equipment _L The value of (2) is updated by the measured distance.

Under usual operating parameters such as pressure, flow and consistency, during opening and/or closing of the treatment gap 6, the idle power P is carried out in the presence of the fibre material 1 _L Is verified. The verification may be scheduled every 1-2 weeks, up to once a day.

For this purpose, the idle power P of the treatment device is measured when the treatment gap is opened and/or closed _L And checking the idling power P _L Whether the adopted value of (c) matches the measured value. In this way, a fault in the distance measurement can also be reliably detected if the measured value of the free-wheeling power deviates significantly from the value stored for the respective distance.

The idle power P is measured when the treatment device is put into operation or when the

treatment tool

3, 4 or its fittings are replaced, also when the treatment gap 6 is closed _L And stores it in a memory as an initial value for control.

For at least approximately real idle power P _L Not only has an influence on the comparison power and the corresponding total power to be regulated, but also can be achieved below a predetermined minimum idle power P _L It is inferred that there is correspondingly high wear in the

processing tools

3, 4, which makes it necessary to replace the processing tools. It can also be provided that the user is prompted if the distance value falls below a predetermined value, so that the user can plan and prepare for something other thanThe grinding fittings are replaced as long as needed.

Claims

1. Method for controlling an apparatus for processing a fibrous material (1), wherein the apparatus has a housing (2) in which at least one first processing tool (3) and one second processing tool (4) are arranged, which processing tools (3, 4) are each fixed to a base plate (7, 8), have a rotationally symmetrical shape, are arranged coaxially to one another, are rotated relative to one another about a common axis (5), define at least one processing gap (6) through which the fibrous material (1) flows and each have a processing profile (9) which is directed towards the processing gap (6), wherein at least one base plate (7, 8) of a processing tool (3, 4) is mounted so as to be axially movable in order to compensate for wear of the processing profile (9), characterized in that the distance between the base plates (7, 8) of the processing tools (3, 4) of a processing gap (6) is measured during operation of the apparatus, and in that the total power (P) is selected as a function of the distance(s) between the base plates (7, 8) of the processing gap (6) _G ) Is a value of (2).

2. Method according to claim 1, characterized in that the total power (P) is selected only as a function of the distance(s) between the base plates (7, 8) of the treatment gap (6) _G ) Is a value of (2).

3. Method according to claim 1, characterized in that the total power (P) is selected in combination with a further value as a function of the distance(s) between the base plates (7, 8) of the treatment gap (6) _G ) Is a value of (2).

4. Method according to any of the preceding claims, characterized in that the total power (P) is adjusted at least in case a change of the distance between the base plates (7, 8) of the treatment gap (6) of at least 1mm is detected _G ) Is a value of (2).

5. A method according to any one of claims 1 to 3, characterized in that at least every time at predetermined time intervalsAdjusting the total power (P) according to the distance(s) between the base plates (7, 8) of the treatment gap (6) for 1 to 2 weeks _G ) Is a value of (2).

6. Method according to any of the preceding claims, characterized in that after replacement of at least one process tool (3, 4), the idle power (P) is measured, preferably while closing the process gap (6) _L ) And stores it in a memory as an initial value for control.

7. Method according to any of the preceding claims, characterized in that the specific power (P _S ) Is kept constant over the operating time, the specific power is determined by the total power (P _G ) And the idle power (P _L ) The difference results and the changed idle power is taken into account here.

8. Method according to any of the preceding claims, characterized in that the total power (P) is determined in accordance with the distance(s) between the base plates (7, 8) of the treatment gap (6) _G ) For the values stored in the memory of the control device, in particular the characteristic map is used.

9. Use of a method according to any of the preceding claims in a refiner, in particular an LC refiner.

10. An apparatus for processing fibrous material, wherein the apparatus has a housing (2) in which at least one first processing tool (3) and a second processing tool (4) are arranged, wherein the processing tools (3, 4) are each fixed to a base plate (7, 8), have rotationally symmetrical shapes, are arranged coaxially to one another, are rotated relative to one another about a common axis (5), define at least one processing gap (6) through which the fibrous material (1) flows, and each have a processing contour (9) which points to the processing gap (6), wherein at least one base plate (7, 8) of a processing tool (3, 4) is mounted so as to be axially movable in order to compensate for wear of the processing contour (9), characterized in that a sensor is provided for determining the position of the axially movable processing tool and a characteristic map is stored in memory, wherein the characteristic map contains a dependence of the change in the distance of the idle power from the processing tools (3, 4).

11. The apparatus according to claim 10, characterized in that the apparatus comprises an indication of wear of the processing tool (3, 4), wherein the signal is triggered below a predetermined distance value or a predetermined distance change.