EP1116825A2 - Method for regulating fiber orientation - Google Patents

Abstract

The invention relates to a method for controlling a fiber orientation cross profile of a fiber web produced in a paper or board machine with a means (2, 19a, 19b, 19c) for influencing a speed cross profile of a fiber suspension jet (5) at the exit of the headbox nozzle, with deviations of the fiber orientation cross profile due to measured deviations are corrected in at least one component of the cross-speed profile. <IMAGE>

Description

The invention relates to a method for regulating a fiber orientation cross profile a fiber web produced in a paper or board machine with a means for Influencing a cross-speed profile of a fiber suspension beam at the exit of a headbox nozzle.

The problem of fiber orientation in paper or paper is from a variety of prior art Cardboard webs known. The closest state of the art is German patent application DE 197 33 454 A1. The basic idea of this Disclosure is from the cross section of the basis weight or a correlating variable to recognize when a Change of the fiber orientation cross profile takes place without measuring it directly. With this registration, a headbox with a density control - optionally also with a flow control that can be set in sections across the width of the machine - And also a sensor traversing between the headbox and the former disclosed. This sensor does not measure the basis weight itself, but that from the Headbox emerging mass of stock suspension or Solids content in the stock suspension. Via at least one other sensor Additional data, between dryer section and winding device especially about fiber orientation profiles of the dry fibrous web, be won. The control signals then take place via computing and control units to the flow control valves and / or orifice actuators and / or removal / supply devices for fiber suspension or dilution water.

It is an object of the invention to further better methods for measuring and influencing fiber orientation and control loops to control fiber orientation to find.

The object is solved by the features of claim 1.

The inventors have recognized that the movement of the fiber suspension jet when exiting the headbox nozzle, provides information that is appropriate Analysis provide information about fiber orientation.

The inventors noticed that the alignment of the headbox emerging fiber suspension jet have a decisive influence on the Has fiber orientation. In the event of a smaller gap opening at one point Cross flows already occur within the headbox nozzle, that is, the Stock suspension partially evades the narrower gap and creates one transverse flow component. This movement continues outside the headbox nozzle, causing a fan-like expansion of the Fibrous suspension jet results.

Because of the non-homogeneous alignment of the fiber suspension jet there are also different arrangement statistics for the width of the machine Fibers on the wire of the former and ultimately an uneven one Cross fiber orientation profile. The fiber orientation cross profile of the generated The fibrous web thus experiences through the different beam alignment significant deviations across the machine width.

In addition to the influence of the gap width cross profile on the alignment of the fiber suspension beam is also the influence of sectional volume flows in the headbox, for example due to inconsistent metering of fluids, known. This also has an impact on the fiber orientation cross profile.

So there is an at least largely clear correlation between the Cross profile Alignment of the fiber suspension beam, that is, the cross profile of the velocity vectors of the fiber suspension jet at the exit from the Headbox nozzle with the later fiber orientation cross profile of the finished web in front. Since deviations in the local speed vectors also a Deviation of the local speed components in the machine direction can, in a first approximation, also by simply measuring the Speed profile of the fiber suspension jet - in machine direction - after the headbox nozzle, especially about changes that occur Changes in the fiber orientation cross profile are closed. An example such measurements is the so-called cross-correlation measurement, in which the Duration of the appearance of the same optical pattern - created by laser beams - is determined at a certain distance from each other in the machine direction, from which the flow velocity in the machine direction can be calculated.

In addition to the simple measurement of the speed profile, you can also use a Cross-correlation measurement, in which the offset of an optical pattern in Transverse direction is taken into account, the speed vector transverse profile is measured and then the angular deviations of the velocity vectors from one Main direction or a transverse component of the speed in correlation to the Fiber orientation cross profile can be set. In addition to optical measurement methods can also, for example, Doppler measurements with ultrasound or the like be used.

Overall, there will be small speed deviations and / or angular deviations viewed in cross section and a control procedure to reduce this Deviations and thus to reduce deviations in the fiber orientation cross profile generated. As actuators to influence the deviations in the Speed profile can be used all means that the speed profile influence in the headbox, such as the aperture of the Headbox or a sectional flow control.

The invention therefore basically sees two different types of reference measurements the movement of the fiber suspension jet. On the one hand the evaluation of the measured values such that only the exit speed of the Beam is measured in the machine direction, because a different beam alignment correlates with a deviation of the exit speed from the Headbox nozzle. On the other hand, there is also the possibility of a direct one Angular measurement of the velocity vector of the fiber suspension beam to make. It goes without saying that both evaluations are used can.

According to the idea of the invention, the inventors therefore propose the method for controlling a fiber orientation cross profile of a fiber web produced in a paper or board machine with a means to influence a Cross-sectional velocity profile of a fiber suspension jet at the exit of a Headbox nozzle to be designed so that deviations in the fiber orientation cross profile due to measured deviations in at least of a component of the cross-speed profile.

The at least one measured and control-relevant component can be advantageous of the cross-speed profile the amount of the speed component in the machine direction, the amount of the speed component in Cross machine direction or the angular deviation of the fiber suspension beam be, preferably for measuring the movement of the fiber suspension beam the movement on the surface of the pulp suspension jet can be measured.

For this purpose, a measuring device, preferably exactly in the CD direction (= Cross direction to machine direction), over the fiber suspension jet traverse. It can also be advantageous only over the area of a current fault be traversed.

Specifically, there can be a correlation between the cross profile of the at least one measured and control-relevant component of the cross-speed profile and one measured directly on the resulting paper or cardboard web Cross-fiber orientation profile are created by assigning profile pairs, wherein a pair of profiles each have at least one typical value of the cross-speed profile and at least a typical value of the fiber orientation cross profile at a specific point on the train or a corresponding one Deviation from a reference value contains.

The determined fiber orientation cross profile can be either "online" or "offfline" can be measured, of course an "online" measurement a faster and allows more direct control. The time offset can also be taken into account here be that from a measurement of certain speed components on Headbox and the later, after passing the web through the Paper machine, fiber orientation measurement at this point of the paper or Cardboard web results.

This method can also be advantageous by setting non-parallel ones Velocity vectors fiber orientation errors coming from the former the press or dryer section originate, are corrected.

A suitable manipulated variable for influencing the cross-speed profile advantageous the sectional setting and control of the gap opening of the aperture of the Headbox using a separate control unit. In a further embodiment, the Sectional gap opening of a subordinate control unit, its Setpoint from the separate control unit ("master-slave principle") or from one offline measurement of fiber orientation is maintained, regulated. This subordinated Control loop performs due to the faster adjustment of local changes in the gap opening to a more constant gap opening of the aperture and thus also to more stable fiber orientation cross profiles.

It is also suitable as a manipulated variable for influencing the cross-speed profile the sectionally regulated throughput of stock suspension in the headbox. This Change of the throughput for the sectional influencing of the speed cross profile can according to the invention by throttling a sectional Volume flow, by supplying additional fluid into the sectional volume flow, by withdrawing fluid from the sectional volume flow or Combination of the above measures can be achieved.

In addition, it is also possible to avoid changing the basis weight cross profile the paper or cardboard web also the consistency, if necessary through a coupling of fiber orientation control and basis weight control, to regulate sectionally, a combination of consistency and material density being particularly advantageous Volume flow control can be used.

An advantageous embodiment of the method according to the invention also lies therein, control parameters determined in the course of the control process, that is, empirical values the past by comparing changes in the Cross-speed profile and resulting changes in cross-fiber orientation profile, in the form of a database, preferably in at least one Control unit, save and make it available "online" to the control.

Additional features and advantages of the invention will appear from the following Description of preferred embodiments with reference to FIG the painting.

The invention will be explained in more detail below with reference to the drawings. It represent:

Figur 1:

eine Draufsicht auf die erfindungsgemäße Messeinrichtung;

Figur 2:

eine schematische Draufsicht auf eine Papiermaschine; und

Figur 3:

eine Prinzipzeichnung zur sektionalen Regelung der Spaltöffnung.

Show it

Figure 1:

a plan view of the measuring device according to the invention;

Figure 2:

a schematic plan view of a paper machine; and

Figure 3:

a principle drawing for the sectional regulation of the gap opening.

FIG. 1 illustrates the method according to the invention using a schematic Representation of a part of the headbox 1, arranged across the width Actuators 8a, 8b, 8c for the diagonally arranged panel 2.

Positions 9a, 9b, 9c show the current travel of the diaphragm 2. It is in this top view because of the inclination of the panel 2 visible that this in Area of travel 9b is deformed. This results in a narrower nozzle gap below the headbox lip. The speed vectors 10a ... 10k show a fan shape on the surface of the Fibrous suspension beam 5 with the beam directions and the associated Velocity vectors.

One can clearly see that the speed vectors 10e ... 10g are different Have length than the speed vectors at the edge 7 of the fiber suspension beam 5. Over this fiber suspension jet is the Traversierrahmen 6 arranged. The measuring device 4 moves along its Traverse path 3.

The edges 7 of the fiber suspension beam 5 are shown by the dotted line illustrated. A first measuring point 11 is located in the measuring device 4, for example punctiform - arranged. Due to the fixed spatial allocation to second measuring point 12 - which is designed in a matrix-like manner like a line camera - A reference system results, which determines the determination of an X partial vector 13 in Machine direction (MD) and a Y-part vector 14 in the transverse direction (CD) enables (route determination).

By knowing the flow velocity from the undisturbed area of the fiber suspension jet, the speed components of the Determine the X and Y part vectors. The two measurements can also be used to determine the determine the respective beam angle (angle of the speed vector). Measuring and Control lines were not shown in this figure for reasons of clarity drawn.

FIG. 2 shows the control and signal lines that are essential to the invention drawn. The control unit 15 is connected to the signal lines 26a, 26b, 26c and this in turn is connected to the sensors 17a, 17b, 17c of the gap width. The associated control lines 28a, 28b, 28c are on the actuators of the diaphragm 8a, 8b, 8c connected.

The control unit 16 receives the signal from the measuring device 27 and the fiber orientation signal of the measuring frame 24, or alternatively manually entered Fiber orientation values 25 from offline measurements. This control unit 16 controls the flow-through valves 19a, 19b, 19c via the lines 29a, 29b, 29c, or via the lines 30a, 30b, 30c the substance mixing valves 18a, 18b, 18c on the headbox. Optionally, the control unit 15 can be via a controller coupling 23 can be connected to the control unit 16.

FIG. 3 shows a basic drawing for the sectional control of the gap opening. The setpoint for the position, preferably sectional position of the aperture 2 of the Headbox 1 is from the separate control unit 15 of the subordinate control unit 15.1 in accordance with the master-slave principle of control technology using a cable given. The control loop of the control unit 15.1 comprises an actuator 8d for the Sectional diaphragm 2, which is connected to the control unit 15.1 via the control line 28d is connected, and a sensor 17d for determining the sectional position of the sectional aperture 2, which via the signal line 26d with the control unit 15.1 is connected.

The method according to the invention thus provides a further, better method Measurement and influencing of fiber orientation and control loops for control the fiber orientation, in particular the fiber orientation cross profile, the Response speed of the control process is very short since the control is already for changes in the orientation of the pulp suspension beam at the beginning of the Manufacturing process reacts and not the passage of a paper web through the Paper machine with subsequent measurement of the fiber orientation cross profile must be waited for.

It is understood that the aforementioned features of the invention are not only in the specified combination, but also in other combinations or can be used alone without leaving the scope of the invention.

Reference list

1

Headbox

2nd

cover

3rd

Traversierweg

4th

Measuring device

5

Pulp suspension jet

6

Traversing frame

7

Edge of the fiber sheet

8a, 8b, 8c, 8d

Actuators of the aperture

9a, 9b, 9c

Travel of the aperture

10a, 10b, ..

Velocity vectors

11

first measuring point

12th

second measuring point

13

X part vector

14

Y part vector

15, 15.1, 16

Control unit

17a, 17b, 17c, 17d

Gap width sensors

18a, 18b, 18c

Mixing valves

19a, 19b, 19c

Flow valves

20th

Shaper, press section, dryer section

21

Measuring frame

22

Winding machine

23

Controller coupling

24th

Signal of the fiber orientation from the measuring frame

25th

Fiber orientation measurements ("offline")

26a, 26b, 26c, 26 d

Signal lines gap width

27

Signal from the measuring device

28a, 28b, 28c, 28d

Control lines for actuators of the panel

29a, 29b, 29c

Control lines for flow valves

30a, 30b, 30c

Control lines for substance mixing valves

Claims (19)

Method for controlling a fiber orientation cross profile of a fiber web produced in a paper or board machine with a means (2, 19a, 19b, 19c) for influencing a speed cross profile of a fiber suspension jet (5) at the exit of a headbox nozzle,
characterized,
that deviations in the fiber orientation cross profile are corrected on the basis of measured deviations in at least one component of the speed cross profile. Method according to claim 1,
characterized,
that the at least one measured and control-relevant component of the cross-speed profile is the amount of the speed component in the machine direction. Method according to one of claims 1 to 2,
characterized,
that the at least one measured and control-relevant component of the cross-speed profile is the amount of the speed component in the cross-machine direction. Method according to one of the preceding claims 1 to 3,
characterized,
that the at least one measured and control-relevant component of the cross-speed profile is the angular deviation of the fiber suspension jet (5). Method according to one of the preceding claims 1 to 4,
characterized,
that when measuring the movement of the fiber suspension jet (5) the movement on the surface of the fiber suspension jet (5) is measured. Method according to one of the preceding claims 1 to 5,
characterized,
that a measuring device (4) traverses, preferably exactly in the CD direction, over the fiber suspension jet (5). Method according to claim 6,
characterized,
that the measuring device (4) traverses only over the area of a current fault in the transverse profile. Method according to one of the preceding claims 1 to 7,
characterized,
that a correlation between the transverse profile of the at least one measured and control-relevant component of the speed transverse profile and a fiber orientation transverse profile directly measured on the paper or cardboard web being produced is established by assigning profile pairs, wherein a profile pair each has at least one typical value of the speed transverse profile and at least one typical value of the fiber orientation cross profile at a particular point on the web or a corresponding deviation from a reference value. Method according to one of the preceding claims 1 to 8,
characterized,
that the determined fiber orientation cross profile is measured "online" or "offline". Method according to one of the preceding claims 1 to 9,
characterized,
that by setting non-parallel speed vectors (10a..10k) fiber orientation errors, which originate from the former of the press or dryer section (20), are corrected. Method according to one of the preceding claims 1 to 10,
characterized by
that the gap opening of the diaphragm (2) is controlled sectionally by a separate control unit (15) to influence the cross-speed profile. A method according to claim 11,
characterized,
that the gap opening of the diaphragm (2) is controlled sectionally by a subordinate control unit (15.1), which receives its setpoint from the separate control unit (15) ("master-slave principle") or from an offline measurement of the fiber orientation. Method according to one of the preceding claims 1 to 12,
characterized,
that the throughput is controlled sectionally to influence the cross-speed profile. Method according to the preceding claim 13,
characterized,
that a change in the throughput for the sectional influencing of the speed cross profile is achieved by throttling a sectional volume flow. Method according to the preceding claim 13,
characterized,
that a change in the throughput for the sectional influencing of the cross-speed profile is achieved by supplying additional fluid into the sectional volume flow. Method according to the preceding claim 13,
characterized,
that a change in the throughput for the sectional influencing of the cross-speed profile is achieved by withdrawing fluid from the sectional volume flow. Method according to the preceding claim 13,
characterized,
that a change in the throughput for the sectional influencing of the cross-speed profile is achieved by a combination of the characteristic features from at least two of claims 14 to 16. Method according to one of the preceding claims 1 to 17,
characterized,
that in order to avoid changing the basis weight cross-section of the paper or cardboard web, the consistency is also controlled sectionally, if necessary by coupling fiber orientation control and basis weight control. Method according to one of the preceding claims 1 to 18,
characterized,
that control parameters determined in the control process are stored in at least one control unit (15, 16) in the form of a database and are available "online".

Images