DE10043142A1 - Stock inlet control uses pulp density sensors and flow meters to register the pulp condition for comparison with nominal values for deviations to be corrected rapidly by a control circuit - Google Patents

Abstract

To control the operation of a stock inlet (1) according to pulp density, at a papermaking or cardboard prodn. machine, the actual pulp density is measured by a density sensor (17,17.1,17.2) in the main (3) and side (13) flows. The throughput at the side flow (13) is measured by at least one flow meter (18.1). At least one monitor (19) measures the machine speed. The mean web dry weight actual value is computed by a computing model to be compared with a nominal value. On a deviation between actual and nominal values, setting units (18.2,18.3) are activated to adjust the main flow feed (2) and/or the side flow feed (12). The measurements at the flow meter (18) for the main flow stream (3) are taken into account by the computing model to compute the actual mean web dry weight. To calibrate the computing model, at least one web weight sensor is used and pref. at the end of the papermaking or cardboard prodn. machine. A retention agent is fed as an additive (21) into the main flow feed (2). The deg. of retention is maintained at a generally constant level by a control circuit which has at least one consistency sensor at the side flow feed (12) and/or the stock inlet (1), a retention agent control valve and a control unit. Ash is fed in to the main flow feed (2) as an additional additive (21), with its length profile controlled by the control circuit. An Independent claim is included for a stock inlet assembly with pulp density sensors (17,17.1,17.2), at least one flow meter (18.1), at least one machine speed monitor (19) and a control circuit.

Description

The invention relates to a method for regulating a material density-controlled Headbox of a paper or board machine according to the preamble of the An claim 1 and a device for regulating a density-regulated substance on a paper or board machine according to the preamble of the An Proverbs 8

From the German published application DE 42 39 845 A1 (PA 05015 DE II) der Applicant is a method for controlling a transverse or longitudinal profile of a Quality feature, for example the basis weight, for paper or card clay production process known. For this, the basis weight of the current Material web, paper or cardboard web, for example by a traver sensor as a measurement variable, preferably at the end of the paper or card sound machine, especially in front of the trolley, measured and this measurement size read into the control device for profile control. The The control / regulator device then has actuators based on a control program controlled to influence the basis weight cross-section.

A disadvantage of this method is that it has a dead time of 60 seconds and more, depending on the machine speed and design, and further when changing types and starting up and starting up the paper or cardboard  machine a long settling time until a stable rule is reached results.

Furthermore, from German published patent application DE 196 34 996 A1 (PA 10362 DE) the applicant a stock density-controlled headbox with a pulp con known regulation of assistance. One travels in the cross machine direction sensor behind the headbox measured the basis weight cross-section. Actuators are made via a control computer connected to this sensor controlled, which are each assigned to a diluent supply line. Furthermore, a consistency sensor is assigned to each feed line an additional control line is connected, which is also an actuator for the controls the relevant supply line, preferably each supply line only one, both the movable basis weight sensor and the ever has associated actuator associated consistency sensor. With the help of Consistency sensors, separate regulation is the regulation of the Basis weight cross-section subordinate or subordinate and serves to compensate for longitudinal profile fluctuations that would otherwise appear as noise in can show the signals of the basis weight sensor and / or the determ would make the basis weight profile difficult or impossible. This disclosed headbox has the disadvantage of placing the The basis weight cross-section of the sensor in turn leads to longer dead times leads to a longer settling time of the control system come here.

It also belongs to the prior art that the supply line (main flow) for the pulp suspension (QH strand) of a stockbox with a density control retention agent supplied to a paper or board machine by means of a so  mentioned stand-alone control loop and the retention constant to keep.

It is therefore an object of the invention, a method and an apparatus of the to improve the type mentioned above in such a way that a better and faster regulation of the longitudinal profile of at least one compo material web to a setpoint is made possible.

This object is fiction, in a method of the type mentioned accordingly solved by the fact that the respective consistency in the QH strand and in the QL Strand is measured with a respective fabric density sensor that subsequently the throughput in the QL line is measured with at least one flow meter, that subsequently the machine speed with at least one device it is measured that the mean otro web weight (actual value) is determined using a Calculation model calculated and the calculated average otro web weight (Actual value) is compared with a target value for the mean otro web weight and that in the event of a deviation, at least one of the supply lines (Main flow) and / or the actuator assigned to the supply line (secondary flow) is operated. The mean otro web weight, more precisely the mean otro Web weight in the machine direction (longitudinal profile) is calculated from the mean of the average otro web weight in the cross machine direction (cross profile) and it can from the respective weights of fibrous materials inorganic additives, such as ash, and other substances consist.

In a further embodiment of the invention, the throughput in the QH Strand measured with a flow meter and used in the calculation of the average Path weight (actual value) taken into account by means of a calculation model.  

By measuring the properties mentioned there are the advantages that any deviations in terms of regulation and control are compensated for and that the longitudinal profile of the at least one component of the material web is already better and faster regulated in the field of sheet formation, and not only in the areas following the sheet formation.

Furthermore, the measurement of the consistency in the fresh substance (QH strand) can be a white correction of the mass flow and ultimately of the mean Allow web weight. That means boring interference in the Fresh substance density can be corrected directly, practically in feed-forward mode nen.

At least one is preferably used to calibrate the calculation model Basis weight sensor, preferably at the end of the paper or board machine attached, used. This type of basis weight sensor has been counting since ge space time to the state of the art, has as such under operating conditions proven and is therefore suitable when neglecting the dead time and The settling time is excellent for calibration purposes, especially for Calibrate the calculation model.

With regard to the achievement of certain material web qualities, it is of Advantage if the supply line (main stream) is a retention agent as an additive is fed. The degree of retention is preferably determined by means of a control loop that consists of at least one consistency sensor in the feed line (secondary flow) and / or in the headbox, an actuator (retention agent valve) and a control unit, constant or approximately constant held. This control procedure can also be combined with the previous one control procedures described above can be applied.  

In a further embodiment of the invention it is proposed that in the feed line (main stream) at least one additional additive, in particular ash, supplied, preferably by means of a regulating the longitudinal profile of the same Control loop is supplied regulated. Through this type of feeding and through a separate measurement of the total density and the filler and / or Ash content is a real filler or ash control. The Ash control is particularly important in the manufacture of highly filled SC papers decisive advantage.

This object is fiction, in a device of the type mentioned accordingly solved in that at least one material density sensor in the QH line and in the QL line for measuring the respective material density it is provided that furthermore at least one flow meter in the QL line for measuring the throughput it is provided that at least one device for measuring the Machine speed is provided and that at least one Control unit for calculating the average otro web weight, for Comparison with a target value for the average otro web weight and, at Deviation, for actuating at least one of the supply line (main flow) and / or the actuator assigned to the feed line (secondary flow) is.

With regard to the further configurations of the device according to the invention is ver on the corresponding subclaims and the description of the figures grasslands.

It is understood that the above and below still apply purifying features of the invention not only in the specified combination  nation, but can also be used in other combinations or alone are without departing from the scope of the invention.

Further features and advantages of the invention result from the Unteran say and the following description of preferred embodiments with reference to the drawing.

Show it

Fig. 1: a first control diagram of a stock density-controlled headbox of a paper or board machine according to a first embodiment according to the Invention;

FIG. 2: a second control scheme according to FIG. 1 with a second embodiment according to the invention; and

Fig. 3: a third control scheme according to FIG. 1 with a third, he advanced embodiment of the invention.

Fig. 1 shows a first control diagram of a stock box 1 of a paper or board machine.

The stock density-controlled headbox 1 has a feed line (main stream) 2 for the fiber suspension (QH strand) 3 , the stock density-controlled headbox 1 in the flow direction F, represented by an arrow, the stock suspension 3 in the feed line 2, a vertical classifier 4 and a headbox pump 5 are connected upstream. The feed line 2 receives the fiber suspension 3 in degassed form as accept 6 from a ventilation tank 7 , which in turn is preceded by three cleaner stages 8 in series. The three cleaner stages 8 are supplied with thick matter by means of a line 9 . The other, the three Cleaner Stu fen 8 upstream modules of the stock preparation are not shown because they are familiar to the expert and have no role in the invention.

The stock density-controlled headbox 1 shoots the stock density-controlled fiber stock suspension 3 'between the two screens (top screen, bottom screen) 10.1 , 10.2 of a schematically illustrated gap former 10 together with white water I-chest 10.3 for collecting the white water I 10.4 occurring in the gap former 10 , one of which initially shown press section 11 follows in the direction of movement of the generated material web.

The consistency-controlled headbox 1 also has a supply line (secondary flow) 12 for the dilution water (QL line) 13 , the consistency-controlled headbox 1 in the flow direction F ′, represented by an arrow, of the dilution water 13 in the supply line 12, a vertical classifier 4 'and a dilution water pump 14 are connected upstream. The feed line 12 receives the dilution water 13 in degassed form from a ventilation tank 7 ', which is fed with white water I 10.4 of the white water I chest 10.3 by means of a pump 15 together with line 16 . The white water I 10.4 can also be supplied by means of the line 16.1 , represented by a dash-dot line, directly to the supply line (secondary flow) 12 for the dilution water (QL line) 13 bypassing the ventilation container 7 '. Furthermore, the white water I 10.4 obtained in the stock density-regulated headbox 1 can be fed directly to the three cleaner stages 8 by means of the line 16.2 together with the pump 15.2 .

According to the invention, a material density sensor 17 , 17.1 is now provided both in the QH line 2 and in the QL line 13 for measuring the respective material density. Furthermore, a flow meter 18 , 18.1 together with an evaluation unit is provided both in the QH line 2 and in the QL line 13 for measuring the respective throughput. To measure the machine speed v _M , a device 19 , for example a tachometer or a pitot tube, is attached in the region of the gap former 10 . All measurement signals are fed to a control unit 20 for calculating the mean otro web weight, for comparison with a target value for the mean otro web weight and, in the event of a deviation, for actuating at least one of the feed line (main flow) ( 2 ) and / or the feed line ( Secondary flow) ( 12 ) associated actuator 18.2 , 18.3 provided.

A non-illustrated basis weight sensor, which is used to calibrate the calculation model, is in the area of the paper or board machine, preferably at the end thereof. Its measurement signal is fed to the control unit 20 via the line 21 .

In addition, a material density sensor 17.2 is attached for measuring the material density of the mixed flow in the region of the nozzle of the material density-controlled headbox 1 , the measurement signal of which in turn is fed to the control unit 20 .

The material density-controlled headbox 1 can be further divided across its width by dividing walls into sections with partial flows (QL strands) leading sections, as is known for example from the German patent application DE 40 19 593 A1 (PA 04598 DE) of the applicant . The content of this published specification is hereby incorporated in full in the disclosure content of this application, without further reference being made to it. The flowmeters together with evaluation units and the actuators can then be fitted in the partial flows carried in the sections in this embodiment, the control scheme explained above remaining essentially the same.

A second control scheme of a consistency-controlled headbox 1 of a paper or board machine is shown in FIG. 2, based on the control scheme of FIG. 1, to which reference is made below.

According to the invention, a retention agent 21.1 can be supplied to the supply line (main line) 2 as additive 21 . The degree of retention is by means of a conventional control circuit consisting of at least one known consistency sensor 22 in the feed line (secondary flow) 12 and / or in the headbox 1 , an actuator (retention agent valve) 23 and a control unit 24 , constant or approximately constant is durable. A flow meter 25 can also be connected to the control unit 24 , the measurement signals of which are taken into account when regulating the retention agent 21.1 .

FIG. 3 shows a third control scheme of a stock box 1 of a paper or board machine, based on the control scheme of FIG. 1, to which reference is made below.

According to the invention the supply line (main current) 2 is an additive 21 in which an actuator 23 having supply line (main current) 2 fed to the Fa serstoffsuspension (QH strand) 3 as well. The additive is preferably 21 ash 21.2 . The supply takes place in a controlled form by means of a conventional control circuit, which consists of at least one known consistency sensor 22 , an actuator 23 and a control unit 24 , can be kept constant or approximately constant. The at least one consistency sensor 22 can be fitted in the feed line (secondary flow) 12 and / or in the headbox 1 and / or in the feed line (main flow) 2 . A flow meter 25 can also be connected to the control unit 24 , the measurement signals of which are taken into account when regulating the additive 21 , in particular ash 21.2 .

The three control schemes outlined together with the associated devices are outstandingly suitable for realizing the method according to the invention for controlling a stockbox 1 of a paper or board machine that is controlled by density.

In summary, it should be noted that a method and a device of the type mentioned are created, which in the area  the sheet formation better and faster regulation of the longitudinal profile of min allow at least one component of the material web to a setpoint.  

List of reference numbers

1

Controlled headbox

2nd

Supply line (main stream)

3rd

Fiber suspension (QH strand)

3rd

'' Fiber suspension

4

,

4

'' Vertical sifter

5

Headbox pump

6

Acceptance

7

,

7

'' Vent tank

8th

Cleaner level

9

,

16

,

16.1

,

16.2

management

10th

Gapformer

10.1

Top sieve

10.2

Bottom sieve

10.3

Siebwasser-I-Bütte

10.4

Siebwasser-I

11

Press section

12th

Supply line (secondary flow)

13

Dilution water (QL strand)

14

Dilution water pump

15

,

15.2

pump

17th

,

17.1

,

17.2

Fabric density sensor

18th

,

18.1

,

25th

Flow meter

18.2

,

18.3

,

23

Actuator (medium)

19th

Facility

20th

,

24th

Control unit

21

Additive

21.1

Retention aid

21.2

ash

22

Consistency sensor
F, F 'flow direction
v _M

Machine speed

Claims (14)

1. A method for controlling a stock density-controlled headbox ( 1 ) of a paper or board machine, with a common, at least one to give possibility for at least one additive ( 21 ) and an actuator ( 18.2 ) having supply line (main stream) ( 2 ) for the fibrous suspension (QH line) ( 3 ), a plurality of sections each having an actuator ( 18.3 ) with sectional partial flows into which the common feed line ( 2 ) branches, and with means ( 18.3 ) for influencing the sectional partial flows of fiber suspension ( 3 ') in the individual sections, which branch out from a common supply line (secondary flow) ( 12 ) for the dilution water (QL line) ( 13 ), which has an actuator ( 18.3 ), characterized by the following process steps:

• 1. 1.1 measurement of the respective material density in the QH line ( 3 ) and in the QL line ( 13 ) with a respective material density sensor ( 17 , 17.1 , 17.2 );
• 2. 1.2 measurement of the throughput in the QL line ( 13 ) with at least one flow meter ( 18.1 );
• 3. 1.3 measurement of the machine speed (v _M ) with at least one device ( 19 );
• 4. 1.4 Calculation of the mean otro web weight (actual value) using a calculation model;
• 5. 1.5 comparison of the calculated mean otro web weight (actual value) with a target value for the mean otro web weight; and
• 6. 1.6 in the event of a deviation actuation of at least one of the supply line (main flow) ( 2 ) and / or the supply line (secondary flow) ( 12 ) associated actuator ( 18.2 , 18.3 ).

2. The method according to claim 1, characterized in that the throughput in the QH line ( 3 ) is additionally measured with a flow meter ( 18 ) and is taken into account in the calculation of the average otro web weight (actual value) by means of a calculation model. 3. The method according to claim 1 or 2, characterized, that to calibrate the calculation model at least one area weight sensor, preferably at the end of the paper or board machine brought, used. 4. The method according to any one of the preceding claims, characterized in that in the feed line (main stream) ( 2 ) as an additive ( 21 ) a retentive agent ( 21.1 ) is supplied. 5. The method according to claim 4, characterized in that the degree of retention by means of a control circuit, which consists of at least one consistency sensor ( 22 ) in the feed line (secondary flow) ( 12 ) and / or in the headbox ( 1 ), an actuator (retention agent valve) ( 23 ) and a control unit ( 24 ), is controlled constant or approximately constant. 6. The method according to any one of the preceding claims, characterized in that in the supply line (main stream) ( 2 ) at least one additional additive ( 21 ), in particular ash ( 21.2 ), is supplied. 7. The method according to claim 6, characterized in that the longitudinal profile of the further additive ( 21 ) is controlled by means of a control circuit constant or approximately constant. 8. Device for regulating a stock density-controlled headbox of a paper or board machine, with a common, at least one possibility to give for at least one additive ( 21 ) and an actuator ( 18.2 ) having feed line (main stream) ( 2 ) for the fibrous suspension (QH Line) ( 3 ), a plurality of sections each having an actuator ( 18.3 ) with sectional partial flows into which the common feed line ( 2 ) branches, and with means ( 18.3 ) for influencing the sectional partial flows of fiber suspension ( 3 ') in the individual sections, which branch out from a common supply line (bypass flow) ( 12 ) for the dilution water (QL line) ( 13 ) having an actuator ( 18.3 ), characterized in that

• 1. 8.1 that at least one material density sensor ( 17 , 17.1 , 17.2 ) is provided in the QH line ( 3 ) and in the QL line ( 13 ) for measuring the respective material density;
• 2. 8.2 that at least one flow meter ( 18.1 ) is provided in the QL line ( 13 ) for measuring the throughput;
• 3. 8.3 that at least one device ( 19 ) for measuring the machine speed (v _M ) is provided; and
• 4. 8.4 that at least one control unit ( 20 ) for calculating the average otro web weight, for comparison with a target value for the average otro web weight and, in the event of a deviation, for actuating at least one of the feed line (main stream) ( 2 ) and / or the Supply line (partial flow) ( 12 ) associated actuator ( 18.2 , 18.3 ) is provided.

9. The device according to claim 8, characterized in that a flow meter ( 18 ) is provided in the QL line ( 3 ) for measuring the throughput, the measurement data of which are taken into account in the calculation of the average otro web weight. 10. The device according to claim 8 or 9, characterized, that at least one basis weight sensor, which is used to calibrate the loading invoice model is used in the field of paper or cardboard machine, preferably at the end, is attached. 11. Device according to one of the preceding claims 8 to 10, characterized in that the supply line (main stream) ( 2 ) as an additive ( 21 ) a retention agent ( 21.1 ) can be supplied. 12. The apparatus according to claim 11, characterized in that the degree of retention by means of a control circuit, which consists of at least one consistency sensor ( 22 ) in the feed line (secondary flow) ( 12 ) and / or in the headbox ( 1 ), an actuator (retention agent valve) ( 23 ) and a control unit ( 24 ) is constant or approximately constant controllable. 13. Device according to one of the preceding claims 8 to 12, characterized in that in the feed line (main stream) ( 2 ) at least one additional additive ( 21 ), in particular ash ( 21.2 ), can be fed. 14. The apparatus according to claim 13, characterized in that the longitudinal profile of the further additive ( 21 ) by means of a control circuit is constant or approximately constant controllable.