CA2515981C - Method and device for controlling paper machine, and program and storage medium - Google Patents
Method and device for controlling paper machine, and program and storage medium Download PDFInfo
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- CA2515981C CA2515981C CA2515981A CA2515981A CA2515981C CA 2515981 C CA2515981 C CA 2515981C CA 2515981 A CA2515981 A CA 2515981A CA 2515981 A CA2515981 A CA 2515981A CA 2515981 C CA2515981 C CA 2515981C
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- control
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- retention
- consistency
- ash content
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- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
- D21H23/00—Processes or apparatus for adding material to the pulp or to the paper
- D21H23/02—Processes or apparatus for adding material to the pulp or to the paper characterised by the manner in which substances are added
- D21H23/04—Addition to the pulp; After-treatment of added substances in the pulp
- D21H23/06—Controlling the addition
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- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21G—CALENDERS; ACCESSORIES FOR PAPER-MAKING MACHINES
- D21G9/00—Other accessories for paper-making machines
- D21G9/0009—Paper-making control systems
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
- D21F1/00—Wet end of machines for making continuous webs of paper
- D21F1/66—Pulp catching, de-watering, or recovering; Re-use of pulp-water
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- Feedback Control In General (AREA)
- Control Of Non-Electrical Variables (AREA)
Abstract
The present invention provides a control device for a paper machine. With this device, even if a retention control and a paper ash content control are performed using a short control period, it is possible to avoid problems such as hunting resulting from mutual interaction between the controls using a simple and inexpensive configuration.
As a result, the retention and the ratio of paper ash content can be precisely controlled. Thus, in a paper machine (1), the present invention uses an automatic control system (3) to control retention and the ratio of paper ash content at least in a wet part (2a). The automatic control system (3) includes a feedback control loop for automatically controlling the retention, a feedback control loop for automatically controlling the ratio of paper ash content, and a decoupling control section (30) incorporated between the feedback control loops to cancel adverse effects of mutual interaction between the loops.
As a result, the retention and the ratio of paper ash content can be precisely controlled. Thus, in a paper machine (1), the present invention uses an automatic control system (3) to control retention and the ratio of paper ash content at least in a wet part (2a). The automatic control system (3) includes a feedback control loop for automatically controlling the retention, a feedback control loop for automatically controlling the ratio of paper ash content, and a decoupling control section (30) incorporated between the feedback control loops to cancel adverse effects of mutual interaction between the loops.
Description
SPECIFICATION
METHOD AND DEVICE FOR CONTROLLING PAPER MACHINE, AND
PROGRAM AND STORAGE MEDIUM
Technical Field The present invention relates to a method and device for controlling a paper machine, and more specifically, to retention in a wet part of the paper machine and improvement of control of ash content in paper.
Background Art In recent years, in connection with the operation of a paper machine in the pulp and paper industry, there is a technical trend to incorporate retention control into a wet part process that significantly affects product quality, to stabilize a wet part of the paper machine, thus improving operability and product quality.
The retention in the wet part process of the paper machine refers to the material ratio at which a pulp material (mainly composed of pulp and containing ash) injected by a head box of the paper machine onto a filter wire in the wire part remains on the wire. The retention can be approximated by the expression shown below, using the consistency (CH B) of a material supplied to the head box and the consistency of white water filtered through the wire and falling into a white water silo under the wire.
Retention -{(CH $- CW W) /CH B) x 100-% Expression 1 The retention value is an important index for determining whether or not the paper machine wire part operation is good. It has been found that a method for controlling the retention is to slightly increase or reduce the dosage of retention aid ( chemicals ) for a very small amount of polymer added to a material supplied to the head box.
In the retention control, the retention is controlled and a variation in white water consistency (CW W) is used as a monitor value for the retention. That is, the retention control takes the following form: a special consistency sensor installed in the wet part of the paper machine measures the white water consistency ( CW W) online.
The white water consistency (CW w) is then utilized to increase or reduce the added flow (dosage) of the retention aid while monitoring the state of the total consistency of wire white water, not the retention value itself (see Non-Patent Documents 2, 3, and 4). Here, not the retention value itself but the total consistency of white water is used because the retention can be maintained at a fixed value keeping the total consistency of white water at a constant value. Then, even with a fixed retention value, if the consistency (CH B) of the material supplied to the head box and the white water consistency (CW W) simultaneously change greatly at the same ratio, the use of the expression as an index results in an apparently stably fixed retention value. This prevents the stabilization of the wet part.
As described above, the retention control adjusts the retention of a pulp material fed from the head box onto the wire part. A feedback control loop is configured as follows. In the retention control, the total consistency of white water flowing down from the wire part is measured online using a low consistency sensor. The amount of retention aid (chemicals) added to the pulp material is increased or reduced so that the measured value is equal to a preset target value. The control loop is usually provided with PID controller utilized to perform PI control (proportional control plus integral feed back control).
Retention control is thus realized (see, for example, Non-Patent Documents 2 and 3).
The PID controller is often used for the control loop of process control in chemical plants and pulp and paper plants. A basic system will be described below. A sensor attached to a control terminal measures the state quantity for temperature, flow ratio, or the like to be controlled.
If there is a actuating error between the measured value and the target value, an manipulated signal (control signal) of a magnitude calculated by the PID controller is output to an operation terminal for, for example, a steam valve or a flow valve. Feedback control is used to perform control in a one loop form on a one-to-one correspondence.
In a recent large-scale plant, a large number of (several hundred to several thousand) control loops of this kind are incorporated into a DCS (Distributed Control System) in a central control system, to centrally control the actual plant online.
On the other hand, paper produced by a paper machine contains, depending on paper types, a specified amount of about 0 to 20% ash content such as calcium carbonate or talc in accordance with prescriptions in order to improve surface property and printing compatibility. This is managed as the ratio of ash (f iller) content in paper during production. In the paper machine, in order to maintain a ratio of ash (filler) content in paper, which is formed as a product, at a specified value, a Quality Control System, i.e., QCS (Basis Weight and Moisture Measurement Sensor) has hitherto been used to control the ratio of paper ash content. The paper ash content control is realized by configuring a feedback control loop such that the Quality Control System is used to measure the ratio of ash content in paper and such that the content of ash flow added to the pulp material is controlled so that the measured value is equal to the target value.
The conventional method uses the feedback control for controlling the ratio of paper ash content using the Quality Control System and the feedback control loop for controlling the retention using the low consistency sensor DOCSTOR: 1408423\1 to independently control the ratio of paper ash content and retention (white water consistency of the wire part) on the basis of these control loops.
[Patent Document 11 Japanese Patent Laid-Open No. 1998-325092 [Non-Patent Document 1]
Mika Kosonen, Calvin Fu, Seyhan Nuyan, Risto Kuusisto, Taisto Huhtelin (Metso Automation): Narrowing gap between theory and practice: Mill experiences with multi-variable predictive control, Control Systems 2002 Proceedings (2002), pp. 54-pp. 59 [Non-Patent Document 2]
Kortelainen, Nokelainen et al.: Application of Latest Retention Monitoring System in fine paper Plants, Japan PAPPI Journal, 43-7(1989), pp. 39-pp.45 [Non-Patent Document 3]
Jukka Nokelainen, Timo Rantala, Pasi Tarhonen: Practical experiences of the wet end consistency control, Pira, 1(1992) [Non-Patent Document 4]
Mori, Kaku, Sueda, Mizuno, Iio, Yamada: Retention Control system of paper machine for many grades production, Japan Technical Association of the Pulp and Paper Industry (Japan TAPPI) Journal, February (2002), pp.86-pp.95 However, if the retention control and the paper ash content control are simultaneously performed as described above, then disadvantageously, these controls interact DOCSTOR: 1408423\1 with each other to cause hunting in the control terminal in the paper ash content control, thus degrading stability.
Further, in the retention control for maintaining a fixed value, the total consistency of white water may become unstable. Thus, if the above two types of controls are simultaneously performed, the expected control effect is not achieved and in some cases the opposite effect is obtained. This may degrade product quality.
The conventional retention control system requires expensive special sensors mostly developed overseas.
Accordingly, it is very recently that earnest domestic efforts have started to be made on the retention control introduction. Further, it has not substantially been known that the retention control and the paper ash content control interact with each other.
Even in overseas paper machine processes that have taken initiative in dealing with the retention control, the mutual interaction phenomenon has probably been long observed. However, the mutual interaction seems to seldom have been regarded as a problem. Even overseas, it is probably after about 2001 that counter measures started to be taken for the recognized mutual interaction problem (see, for example, Non-Patent Document 1).
Further, even at present, when the mutual interaction problem is often discussed, inadequate approaches are probably taken to avoid the adverse effect of the mutual interaction. That is, if the degree (magnitude) of the DOCSTOR: 1408423\1 mutual interaction is small, the magnitude of interaction is neglected and the control loops are used independently.
Even if a slightly significant mutual interaction occurs, all the tuning parameters for the PID controller or the tuning parameters for only one of the loops are reduced so as to prevent inconveniences resulting from unstable processes.
On the other hand, a study has been reported in which for the mutual interaction between a plurality of control loops, an attempt is made to positively eliminate the mutual interaction using multi-variable control called "model predictive control" (see, for example, Non-Patent Document 1).
The method utilizing the model prediction control is a control system that precisely and collectively cancels the adverse effects of the mutual interaction between a large number of variables in a process including the ratio of paper ash content and retention. This control system is complicated and requires high costs for introduction.
In connection with this, the applicant has proposed a control system that requires a long time to vary the dosage of a retention aid because if the increase and reduction in the dosage of the retention aid is controlled within a short period using the PID controller, the formation of paper products (variation in basis weight) may be degraded (control system that requires about 30 minutes to vary the amount ( dosage ) of retention aid added in a ramp manner) . Since this is a moderate control system, the above mutual interaction does not occur between the retention control and the paper ash content control (see, for example, Patent Document 1 and Non-Patent Document 4).
However, today, there is a demand for realizing more precise control by performing frequent output control within a short period to increase the response speed of the retention and the ratio of paper ash content control.
In this case, such mutual interaction as described above may occur and the solution to this problem is recognized as an important goal.
Disclosure of the Invention The present invention focuses on the above problems of the conventional art. It is an object of the present invention to provide a control device for a paper machine which, even if retention control and a paper ash content control are performed within a short time using a PID
controller, a Quality Control System, or the like, can avoid problems such as hunting resulting from the mutual interaction between the controls using a simple and inexpensive configuration, thus precisely controlling the retention and the ratio of the paper ash content.
To achieve this object, the present invention has the following configuration.
A first aspect of the present invention is a method for controlling a paper machine, the method automatically DOCSTOR: 1408423\1 controlling retention and a ratio of paper ash content at least in a wet part, the method being characterized in that:
a decoupling control mechanism is incorporated between a feedback loop for automatically controlling the retention and a feedback loop for automatically controlling the ratio of paper ash content, to cancel adverse effects of mutual interaction between the loops.
A second aspect of the present invention according to the first aspect characterized in that: the automatic retention control is performed by measuring the consistency of white water in a wire part (consistency of white water resulting from dehydration in the wire part) in the wet part and increasing or reducing the amount of retention aid dosage to a thin stock flow depending on the white water consistency and the automatic control of the ratio of paper ash content is performed by measuring the content of ash in paper after the paper has been dried and increasing or reducing the amount of ash flow added to the thin stock flow depending on the ratio of paper ash content.
A third aspect of the present invention according to the second aspects characterized in that the consistency of white water in the wire part measured for the automatic retention control is the consistency of white water filtered through a wire in the wire part and flowing down into a white water silo below the wire. The consistency of white water is normally the total consistency of white water but may be the consistency of pulp in white water DOCSTOR: 1650002\1 or the consistency of ash. The total consistency of white water refers to the consistency of pulp in white water plus the consistency of ash in white water.
A fourth aspect of the present invention according to the first or third aspect characterized in that the decoupling control function uses a decoupling control element for steady state characteristic compensation which compensates for the magnitude of mutual interaction between the feedback control loops at the same time.
A fifth aspect of the present invention according to the first or third aspect characterized in that the decoupling control function uses a decoupling control element for dynamic state characteristic compensation which compensates for the magnitude of mutual interaction between the feedback control loops taking a time delay into account.
A sixth aspect of the present invention is a control device for a paper machine which controls retention and a ratio of paper ash content at least in a wet part using an automatic retention control system, the device being characterized in that: the automatic control system comprises: a feedback control loop for automatically controlling the retention; a feedback control loop for automatically controlling the ratio of paper ash content;
and a decoupling control section incorporated between the feedback control loops to cancel adverse effects of mutual interaction between the loops.
DOCSTOR: 1650002\1 A seventh aspect of the present invention according to the sixth aspect characterized in that: the feedback control loop for automatically controlling the retention comprises a low consistency sensor used to measure the consistency of white water in the wire part in the wet part and a control section that transmits a control signal to a retention operation terminal in a paper machine process so as to increase or reduce the dosage of retention aid added to a thin stock flow on the basis of an actuating error between the white water consistency detected using the low consistency sensor and a predetermined target value, the feedback control loop for automatically controlling the ratio of paper ash content comprising ash flow detecting means for measuring the amount of ash in paper after the paper has been dried and a paper ash control section that transmits a control signal to a paper ash flow operation terminal in the paper machine process so as to increase or reduce the amount of ash flow added to a thin stock flow on the basis of an actuating error between the amount of paper ash flow detected using the ash flow detecting means and a predetermined target value, the decoupling control section having a decoupling control element that compensates for the magnitude of mutual interaction.
An eighth aspect of the present invention according to the seventh aspect characterized in that the decoupling control element is a feed forward compensating element 1]
input to each operation terminal of each of the feedback control loops in order to compensate for the magnitude of mutual interaction.
A ninth aspect of the present invention according to the eighth aspect characterized in that the decoupling control element is determined on the basis of a response block for each feedback control loop and an interaction block that causes the feedback control loops to interact with each other.
A tenth aspect of the present invention is a program for allowing a computer to execute the control method set forth in any of the first to fifth aspects.
An eleventh aspect of the present invention is a computer readable storage medium in which the program set forth in the tenth aspect is stored.
Brief Description of the Drawings FIG. 1 is a diagram conceptually showing the general configuration of a paper machine used in an embodiment of the present invention;
FIG. 2 is a block diagram showing a paper ash content control loop and a retention control loop in a control system of the paper machine shown in FIG. 1;
FIG. 3 is a diagram showing variations in the total consistency of white water, the amount of ash content in DOCSTOR: 1408423\1 paper, and paper machine speed, as well as the added flow (dosage) of retention aid, the diagram also showing that the retention is not controlled but only the paper ash content control is performed;
FIG. 4 is a diagram showing variations in the total consistency of white water, the amount of ash content in paper, the added flow ( dosage ) of retention aid, and paper machine speed, the diagram also showing that decoupling control is not performed but the retention and the ratio of paper ash content are simultaneously controlled;
FIG. 5 is a diagram showing variations in the total consistency of white water, the amount of ash content in paper, the added flow ( dosage ) of retention aid, and paper machine speed, the diagram also showing that the retention and paper ash content are simultaneously controlled using a control device according to the present embodiment;
FIG. 6 is a diagram approximately showing a response gain K, dead time Ti, and time constant T2 obtained if a step input is applied to a process;
FIG. 7 is a block diagram showing a state in which the ratio of paper ash content control loop and the retention control loop are independent of each other; and FIG. 8 is a block diagram showing a state in which mutual interaction occurs between the paper ash content control loop and the retention control loop.
Best Mode for Carrying Out the Invention An embodiment of the present invention will be described below with reference to the drawings.
FIG. 1 is a diagram conceptually showing the general configuration of a paper machine used in an embodiment of the present invention.
As shown in the figure, the illustratiod paper machine 1 consists of a paper machine process 2 that executes a paper sheet making process and a control system 3 that controls the paper machine process 2.
First, the configuration of the paper machine process will be described.
In a wet part 2a of the paper machine process 2, the thin stock flow of a low consistency injected by a head box 4 is filtered using a wire part 6 comprising, for example, a wire 5 rotating endlessly. A pulp mat remaining on the wire 5 is fed to the succeeding press part 7, where the pulp mat is further filtered. Further, the pulp mat filtered by the press part 7 is heated and dried by the succeeding dryer part 8. The pulp mat is then wound around a reel part 9 to form a roll of paper.
On the other hand, the wet part 2a constitutes a white water circulating system 12. In the white water circulating system 12, the white water flows down from the wire 5 owing to the dehydration of the wire part 6 and is then stored in a white water silo 10. The white water is then supplied by the pump 11 to the head box.
In the white water circulating system 12, the thick DOCSTOR: 1408423\1 stock flow supplied by a pump 13 is supplied to a path leading from the white water silo 10 to the pump 11 via a stock box 14 and a valve (stock control valve)15. The thick stock flow is sent to the head box 4 as well as the white water supplied from white water silo 10.
In the white water circulating system 12, a path leading from the pump 11 to head box 4 connects to an ash supply path 16 along which a pump is used to supply ash flow from an ash flow source (not shown) and a retention aid chemical supply path 17 along which a pump 17a is used to supply a retention aid chemical from a retention aid source (not shown). An ash (filler) flow control valve 18 and a flow meter 19 are connected to the ash supply path 16. The opening of the valve 18 is controlled by an ash flow control section 20 so that a flow ratio detected by the flow meter 19 has a value corresponding to a control signal corresponding to a manipulated variable output by the control system 3, described later.
Further, the retention aid supply path 17 connects to a retention aid dosage control valve 21 (control may be performed using a metering pump) and a flow meter 22.
The opening of the valve 21 is controlled by a retention aid dosage added flow control section 23 so that a flow ratio detected by the flow meter 22 has a value corresponding to a control signal corresponding to a manipulated variable output by the control system 3.
In the paper machine process 2, the consistency of the white water flowing down into the white water silo 10 has been detected by a low consistency sensor (white water consistency detecting means) 24. The detected value has been input to the control system 3.
In this embodiment, an example of the low consistency sensor 24 is a sensor that loads, into a CPU connected to a sensor, a total of 14 kinds of detection signals including five kinds of signals about a polarized light quantity ratio obtained utilizing the nature that when a laser beam is transmitted throughpulp fibers, an optical axis rotates through about 90 for polarization, a variation in laser beam scattering form caused by fine grains of an ash content such ascalcium carbonate, the quantity of scattering light in back reflection, the quantity of xenon light absorbed by a lignin component in pulp fiber while the light is being transmitted through a sample in order to distinguish fine pulp fiber from the ash component, and the quantity of scattering light in back reflection. The sensor then checks the signals against measurements obtained through manual analysis, and selects about five signals that are highly correlated with one another by multiple regression analysis. The sensor then statistically determines coefficient values for a regression model equation to convert the signals into consistencies (the sensor is manufactured by Metso Automation Kayani, Finland). The range of measurements by the low consistency sensor 24 is total consistency 51.5% and ash consistency s 0.8%.
DOCSTOR: 1408423\1 The special sensor enables the online measurement of, for example, the consistency of the thin stock flow supplied to the head box 4 and the consistency of white water filtered through the wire 5 and flowing down into the white water silo 10 while separating the pulp component from the ash component; in the prior art, these consistencies can be determined only by offline measurements. These two measurements can be used to continuously determine the amount of each material remaining on the wire after dehydration in the wire part 6 ((1) total retention, (2) pulp retention, and (3) ash retention), on the basis of online calculations.
Further, a measurement frame and a sensor head 25b of a Quality control system in which a plurality of sensors are mounted are installed in a rear part of the paper machine process 2, for example, the reel part 9. The sensor head 25b is scanned across paper width so that the sensor head 25b of the Quality control system and a control section 25a can measure the paper ash content and other physical properties of paper (basis weight, moisture, thickness, colour, and the like) . An ash sensor provided in the sensor head 25b measures the ratio of paper ash content and utilizes the nature that ash component in paper absorbs X rays more than pulp. The ash sensor measures the ratio of paper ash content by using an ionization chamber to detect the intensity of X rays transmitted through paper DOCSTOR: 1408423\1 and attenuated.
In the paper machine process 2 configured as described above, the retention control in the wire part 6 is performed as follows. The low consistency sensor 24 is used to measure online the total consistency of white water flowing from the wire 5 down into the white water silo 10. The PI controller 26, provided in the control system 3, described later, then performs feedback control with short period outputs to control the opening of the control valve 21 (or the flow ratio of the metering pump) so as to match the target value and the predetermined value to increase or reduce the dosage of retention aid added to the thin stock flow.
That is, during operation, control is performed as follows using the feedback control loop, described later.
When there is an increase in the total consistency of white water being measured using the low consistency sensor 24, this means a decrease in the retention in the wire part corresponds to an increase. Accordingly, the flow rate (dosage) of retention aid being added to the thin stock flow is increased. When the total consistency of the white water decreases, the flow rate (dosage) of retention aid being added to the thin stock flow is reduced. This control operation is performed online using a short period such as one second.
The retention aid chemical is normally a highly viscous liquid polymer agent. The consistency of DOCSTOR: 1408423\1 retention aid dosage to the thin stock flow is about 200 to 500 ppm. The addition requires management of a very low flow rate (although depending on production rate, dosage of about 10 to 20 litre/min) . Accordingly, the pump 17a is a centrifugal pump or the like if the control valve 21 is provided. The pump 17a is a variable flow type metering pump if the control valve 21 is not provided. Such a small increase or reduction in the dosage ratio of the retention aid enables the retention of the thin stock flow component in the wire part 6 (total consistency of white water) to be controlled.
On the other hand, the flow rate of ash added to the thin stock pulp is adjusted so that the ratio of paper ash content meets the corresponding product specification.
That is, during operation, when the ratio of paper ash content increases above the target value, the added flow control section 20 reduces the opening of the valve 18 on the basis of a control signal from Quality control system control section 25a to reduce the flow ratio of ash fed by the pump 16a. When the paper ash content decreases, the opening of the valve 18 and the ash flow are increased to achieve the target paper ash content.
Now, description will be given of the control system 3, which controls the paper machine process 2.
The control system 3 according to this embodiment comprises an input setting section 28 that inputs various data and instructions including the required target values DOCSTOR: 1408423\1 of the ratio of paper ash content and white water total consistency, a controller 29 that controls the ash flow control section 20 and retention aid dosage flow control section 23 in accordance with the target values of the ratio of paper ash content and white water total consistency set by the input setting section 28, and Quality control system control section 25a.
The controller 29 has a function for a decoupling control section 30. The functions of the PI controller 26 and decoupling control section 30 are realized by the CPU in accordance with a program stored in the computer.
This program can be stored in currently available various storage media.
The Quality control system control section 25a transmits a control signal to the ash flow control section on the basis of the target value of the paper ash content received by the input setting section 28 and the ratio of the paper ash content detected value detected by the sensor head 25b of the Quality control system. This constitutes 20 a feedback control loop (referred to as an paper ash control loop below) Ll for controlling the ratio of the paper ash content for the paper machine process2 as shown in FIG.
2.
Further, the PI controller 26 transmits a control signal to the retention aid dosage added flow control section 23 on the basis of the target value of the total consistency of white water set by the input setting section 28 and the consistency value obtained by the low consistency sensor 24. This constitutes a feedback control loop (referred to as a retention control loop below) L2 for controlling the retention.
Of the two feedback control loops L1 and L2, the paper ash control loop L1 is actually used in conventional paper machines. However, in recent years, the requirement has been made that the retention in the wire part be controlled using a short control period of about one second so that the retention is stabilized. To deal with this, it has become necessary to allow the paper ash control loop L1 and the retention control loop L2 to coexist.
When the paper ash control loop L1 and the retention control loop L2 coexist, if they are independent of each other as shown in FIG. 7, ideal feedback control can be performed so as to maintain the ratio of paper ash content and the retention at the desired target values. In FIG.
7, G11 denotes a response block for paper ash which is obtained during the paper machine process 2 by the Quality control system control section 25a and Quality control system head 25b by controlling the ash flow control section 20. G22 denotes a response block for the total consistency of white water (retention) which is obtained during the paper machine process by the PI control section by controlling the dosage of the retention aid. Here, a block of a process refers to a transfer function for a control system for the process.
However, it has become clear that actually the following occurs if the retention control loop L2 is incorporated into the paper machine 1 into which the ash control loop L1 has already been incorporated.
Interaction blocks G21 and G12 cause mutual interaction between the control loops L1 and L2 during the paper machine process as shown in the control block diagram in FIG. 8.
Consequently, hunting occurs in the total consistency of white water and in the ratio of paper ash content to make the control state unstable. That is, if a change is made to one of the two variables to be controlled during the paper machine process 2, the ratio of paper ash content and the total consistency of white water, for example, the total consistency of white water is changed, then the ratio of paper ash content, the other variable, is affected and changed. As a result, the two variables cannot be independently controlled.
In FIGS. 7 and 8, if G1l, G12, G21, and G22 are collectively denoted as Gab, this indicates a responsive block when the magnitude of operation of an operation terminal a during the process is defined as Xa and when the magnitude of a change in an output terminal affected by the operation is defined as Yba. Then, if the output range of the controller is not taken into account, the magnitude ( gab ) of the gain of the response block is given by:
gab = Yba/Xa Expression 2 The mutual interaction between the control loops is expected to result from, for example, a process (A) or (b) described below.
Process (A) If an increase in the total consistency of white water in the wire part occurs as a disturbance, the above retention control is correspondingly performed to increase the dosage of the retention aid (polymer) (step Al) . This increases the retention in the wire part (lowers the total consistency of white water in the wire part) and increases the ratio of paper ash content (step A2) . As a result, the Quality control system performs the paper ash content control to reduce the ratio of paper ash content and thus the ash flow is reduced (step A3) . This lowers the content of ash in the thin stock flow injected by the head box 4, thus reducing the consistency of white water ash and thus the total consistency of white water (step A4) . Then, the retention control is performed to reduce dosage of the retention aid (step A5 ). Hunting occurs in the dosage of the retention aid and in the ratio of paper ash content owing to the above mutual interaction between the retention control and the paper ash content control (step A6).
Process (B) On the other hand, if the ratio of paper ash content DOCSTOR: 1408423\1 becomes insufficient as a disturbance, the paper ash content control in the Quality control system control section 25a is activated to increase the ash flow (step B1). The consistency of the thin stock ash injected by the head box 4 rises to increase the total consistency of white water (step B2) . At the same time, the consistency of the white water component increases (step B3) . As a result, the retention control is activated to increase the dosage of the retention aid chemical. The retention in the wire part 6 is increased to increase the ratio of paper ash content. This reduces the total consistency of white water and the consistency of white water ash (step B4).
Then, the retention control reduces the dosage of the retention aid chemical, while reducing the ratio of paper ash content (step B5) . The above operation causes hunting in the dosage of the retention aid chemical and in the ratio of paper ash content (step B6).
As is apparent from the above process, it is understandable that mutual interaction necessarily occurs between the two control loops Ll and L2 for the retention control and the paper ash content control, though the level of occurrence varies.
To avoid the adverse effect of the mutual interaction between the feedback control loops Ll and L2, the decoupling control section 30 was provided as shown in FIGS.
1 and 2, according to the present embodiment. The decoupling control section 30 adds a signal obtained by DOCSTOR: 1408423\1 multiplying a control output m2 from the PI controller 26 by a decoupling control block Cl, to a control output ml from the Quality control system control section 25a, and to a control output m2 output by the PI controller 26 by multiplying the control output ml from the Quality control system control section 25a by a decoupling control block C2 as shown in FIG. 2.
Here, the decoupling control block Cl and C2 can be calculated as theoretical values as follows. The PI
controller 26 is set in a manual operation mode while the paper machine process 2 is stable. An output from the PI
controller 26 is varied step by step to examine the response characteristic of the PI controller 26. Then, the calculations shown below are executed.
In the decoupling control with two inputs and two outputs shown in FIG. 2, let ul be the output value of a decoupling control element in the ash control loop, let u2 be the output value of a decoupling control element in the retention control loop, let yl be the amount of paper ash content, and let y2 be the total consistency of white water. Then, these values are given by:
ul = ml +(C1 x m2) Expression 3 u2 = (C2 x ml) + m2 Expression 4 yl =(G11 x ul) +(G12 x u2) Expression 5 y2 = (G21 x ul) + (G22 x u2) Expression 6 ul and u2 are deleted from Expressions 4 and 5.
yl = G11 X{m1 +(C1 x m2)) + G12 x{(C2 x ml) + m2}
_ (Gil + (G12 x C2)} x ml +{(G11 x Ci) + G12) x m2 Expression 7 y2 = G22 x{m2 + (C2 x ml)) + G21 x{(C1 x m2) + ml) _ {G21 + (G22 x C2)} x m1 +{(G21 x Cl) + G22) x m2 Expression 8 To make inputs and outputs associated with Expressions 7 and 8 non-interactional, the conditions expressed by Expressions 9 and 10 are required.
{(G11 x Cl) + G12} = 0 Expression 9 {G21 + (G22 x C2)) = 0 Expression 10 Decoupling control static gains Cl and C2 are determined as follows from Expressions 9 and 10 Cl = -(G12/G11) Expression 11 C2 = -(G21/G22) Expression 12 Here, the decoupling control elements Cl and C2 determined are substituted into Expressions 7 and 8 to determine the I/O relationship.
yl ={G11 -(G12 x G21)/G22) x ml Expression 7' y2 ={G22 -(G12 x G21)/G11} x m2 Expression 8' Therefore, in the above calculations, it is necessary that G11 x G22 - G12 x G21 0 0.
As is apparent from Expression 7', the amount yl of paper ash content is affected only by an ash flow operation ml. Further, as is apparent from Expression 8' the total consistency y2 of white water is affected only by a retention aid dosage operation m2. That is, the addition of the decoupling control element enables the control loops to be controlled independently though they are under mutual interaction.
The values of the decoupling control blocks Cl and C2 are determined while examining the operation response characteristic by varying the output from the operation terminal step by step while the paper machine process is stable. If only the static characteristics of the process are taken into account, only the static gains of the blocks G11, G22, G12, and G21 may be used in the above expressions.
If the values of the decoupling control blocks Cl and C2 determined by the above calculations are applied to the actual paper machine process 2, it is essential to perform a tuning operation for matching.
As described above, in the embodiment of the present invention, the decoupling control section 30 is incorporatiod between the paper ash content control loop L1 and the retention control loop L2; the decoupling control section 30 performs the non-interaction calculations and control on the basis of the decoupling control blocks Cl and C2 and the like. This positively cancels the adverse effects of the mutual interaction between these control loops L1 and L2. In other words, when a retention operation is performed using one of the control loops, for example, the retention control loop L2, the adverse effect of the mutual interaction between the control loops is considered to be a kind of disturbance.
Then, the signal obtained by multiplying the control signal from the control loop L2 by the interaction coefficient is simultaneously added or subtracted to prematurely cancel an amount of interaction which one of the control loops may offer to the other control loop, on the basis of feed forward control. Thus, even if the ratio of paper ash content and retention are controlled using a short period of about one second, then as shown in FIG. 7, the respective controls can be kept independent of each other.
Further, the retention (total consistency of white water) and the ratio of paper ash content can be brought closer to the target values set for the wet part.
FIGS. 3 to 5 show variations in the total consistency of white water, the amount of ash content in paper, and the dosage of the retention aid observed if the retention control and the of paper ash content control are performed using a conventional control device and the control device according to the present embodiment.
FIG. 3 shows that the retention is not controlled but only the paper ash content control is performed. As shown in the figure, the total consistency of white water varies substantially.
FIG. 4 shows that the retention control loop L2 and the paper ash content control loop L1 are simultaneously controlled independently. As shown in the figure, the total consistency of white water and the ratio of paper ash content, which are control terminals, interact with each other and become very unstable. As a result, divergent vibration occurs.
In contrast, in the present embodiment, in which the decoupling control is applied to between the two control loops, the target retention control and the paper ash content control can be simultaneously and stably performed as shown in FIG. 5. Clearly, the adverse effect of the mutual interaction has been sufficiently avoided. In addition, before and after a grade change time, the total consistency of white water and the ratio of paper ash content are unstable. This is because the grade (type of paper) is being changed.
In the applicant's trial, a variation in the amount of ash in paper under the paper ash content control using a Quality control system was 0 . 4 to 0. 5% according to the conventional art (see FIG. 3) . However, according to the present embodiment, which also used the decoupling control, the variation could be reduced to about 0.2% (see FIG.
5).
Further, with the retention control by the decoupling control section, the total consistency of white water, which was a final obj ect , could be controlled to maintain an almost fixed value.
In the above embodiment, steady state characteristic compensation is mainly described which compensates for mutual interaction processes using only the static gain DOCSTOR: 1408423\1 as a decoupling control element. However, the present invention is expected to have its control performance improved by using dynamic characteristic compensation that takes not only a static response gain K but also time delays such as a dead time Tl and a time constant T2 into account as decoupling control elements. Generally, response in this process can be approximated as a dead time plus first order lag model as shown FIG. 6. In this case, the transfer function G (also referred to as a block) can be expressed as a function of the static response gain K, dead time T1, and time constant T2. That is, G = G(K, Ti, T2).
Substituting this directly into Expressionslland12 makes it possible to determine the decoupling control blocks Cl and C2 for dynamic characteristic compensation. With the notation of transfer functions commonly used in the field of automatic control, if.for example, the processes are assumed to be approximated using a dead time + first order lag model, then G = G(K, T1, T2) = {K x e x p(-Tl x S)}/{1 + (T2 X S)}. Here, S in the expression denotes a Laplace operator for an S plane (complex plane) for a Laplace transformation executed on the relation between an input and output for a process response.
It has also been found that the mutual interaction between the control loops often occurs in processes with a smaller value for the retention in the wire part. The present invention is particularly effective on such processes.
(Other Embodiments) In the description of the above embodiment, the retention control is performed so as to fix the total consistency of white water. However, it is expected that in the future, not only the total consistency of white water but also the consistency of pulp in white water and the content of ash flow will be controlled. To realize this, it is possible to utilize the decoupling control shown in the above embodiment.
In this case, the pulp consistency, the ash consistency, and the ratio of paper ash content should interact with one another. Accordingly, the control terminal is composed of the pulp consistency and the ash consistency. The control operation terminal is composed of the opening of a valve for a thick stock pulp which increases or reduces the flow ratio of pulp stock, the opening of an ash addition valve, and the opening of a valve for dosage of the retention aid. Then, decoupling control elements for all the combinations of the above parameters are similarly incorporated between the loops for control.
As a result, both pulp and ash consistency can be maintained at the desired fixed values.
As described above, in a paper machine that automatically performs at least two types of control, retention control and the paper ash content control, the present invention provides a decoupling control section between a control loop for the retention control and a DOCSTOR: 1408423\1 control loop for the paper ash content control.
Consequently, even if the retention control and the ratio of the paper ash content control are performed using a short control period, both controls can be stably performed. As a result, it is possible to stably manufacture paper products with the desired basic weight, the paper ash content, and the like while maintaining the desired retention (total consistency of white water). Therefore, product quality can be greatly improved.
Industrial Applicability As described above, the present invention can be easily implemented as an inexpensive and simple structure in which a decoupling control section is provided between the retention control and the paper ash content control.
Therefore, the present invention is very useful in the pulp and paper industry.
METHOD AND DEVICE FOR CONTROLLING PAPER MACHINE, AND
PROGRAM AND STORAGE MEDIUM
Technical Field The present invention relates to a method and device for controlling a paper machine, and more specifically, to retention in a wet part of the paper machine and improvement of control of ash content in paper.
Background Art In recent years, in connection with the operation of a paper machine in the pulp and paper industry, there is a technical trend to incorporate retention control into a wet part process that significantly affects product quality, to stabilize a wet part of the paper machine, thus improving operability and product quality.
The retention in the wet part process of the paper machine refers to the material ratio at which a pulp material (mainly composed of pulp and containing ash) injected by a head box of the paper machine onto a filter wire in the wire part remains on the wire. The retention can be approximated by the expression shown below, using the consistency (CH B) of a material supplied to the head box and the consistency of white water filtered through the wire and falling into a white water silo under the wire.
Retention -{(CH $- CW W) /CH B) x 100-% Expression 1 The retention value is an important index for determining whether or not the paper machine wire part operation is good. It has been found that a method for controlling the retention is to slightly increase or reduce the dosage of retention aid ( chemicals ) for a very small amount of polymer added to a material supplied to the head box.
In the retention control, the retention is controlled and a variation in white water consistency (CW W) is used as a monitor value for the retention. That is, the retention control takes the following form: a special consistency sensor installed in the wet part of the paper machine measures the white water consistency ( CW W) online.
The white water consistency (CW w) is then utilized to increase or reduce the added flow (dosage) of the retention aid while monitoring the state of the total consistency of wire white water, not the retention value itself (see Non-Patent Documents 2, 3, and 4). Here, not the retention value itself but the total consistency of white water is used because the retention can be maintained at a fixed value keeping the total consistency of white water at a constant value. Then, even with a fixed retention value, if the consistency (CH B) of the material supplied to the head box and the white water consistency (CW W) simultaneously change greatly at the same ratio, the use of the expression as an index results in an apparently stably fixed retention value. This prevents the stabilization of the wet part.
As described above, the retention control adjusts the retention of a pulp material fed from the head box onto the wire part. A feedback control loop is configured as follows. In the retention control, the total consistency of white water flowing down from the wire part is measured online using a low consistency sensor. The amount of retention aid (chemicals) added to the pulp material is increased or reduced so that the measured value is equal to a preset target value. The control loop is usually provided with PID controller utilized to perform PI control (proportional control plus integral feed back control).
Retention control is thus realized (see, for example, Non-Patent Documents 2 and 3).
The PID controller is often used for the control loop of process control in chemical plants and pulp and paper plants. A basic system will be described below. A sensor attached to a control terminal measures the state quantity for temperature, flow ratio, or the like to be controlled.
If there is a actuating error between the measured value and the target value, an manipulated signal (control signal) of a magnitude calculated by the PID controller is output to an operation terminal for, for example, a steam valve or a flow valve. Feedback control is used to perform control in a one loop form on a one-to-one correspondence.
In a recent large-scale plant, a large number of (several hundred to several thousand) control loops of this kind are incorporated into a DCS (Distributed Control System) in a central control system, to centrally control the actual plant online.
On the other hand, paper produced by a paper machine contains, depending on paper types, a specified amount of about 0 to 20% ash content such as calcium carbonate or talc in accordance with prescriptions in order to improve surface property and printing compatibility. This is managed as the ratio of ash (f iller) content in paper during production. In the paper machine, in order to maintain a ratio of ash (filler) content in paper, which is formed as a product, at a specified value, a Quality Control System, i.e., QCS (Basis Weight and Moisture Measurement Sensor) has hitherto been used to control the ratio of paper ash content. The paper ash content control is realized by configuring a feedback control loop such that the Quality Control System is used to measure the ratio of ash content in paper and such that the content of ash flow added to the pulp material is controlled so that the measured value is equal to the target value.
The conventional method uses the feedback control for controlling the ratio of paper ash content using the Quality Control System and the feedback control loop for controlling the retention using the low consistency sensor DOCSTOR: 1408423\1 to independently control the ratio of paper ash content and retention (white water consistency of the wire part) on the basis of these control loops.
[Patent Document 11 Japanese Patent Laid-Open No. 1998-325092 [Non-Patent Document 1]
Mika Kosonen, Calvin Fu, Seyhan Nuyan, Risto Kuusisto, Taisto Huhtelin (Metso Automation): Narrowing gap between theory and practice: Mill experiences with multi-variable predictive control, Control Systems 2002 Proceedings (2002), pp. 54-pp. 59 [Non-Patent Document 2]
Kortelainen, Nokelainen et al.: Application of Latest Retention Monitoring System in fine paper Plants, Japan PAPPI Journal, 43-7(1989), pp. 39-pp.45 [Non-Patent Document 3]
Jukka Nokelainen, Timo Rantala, Pasi Tarhonen: Practical experiences of the wet end consistency control, Pira, 1(1992) [Non-Patent Document 4]
Mori, Kaku, Sueda, Mizuno, Iio, Yamada: Retention Control system of paper machine for many grades production, Japan Technical Association of the Pulp and Paper Industry (Japan TAPPI) Journal, February (2002), pp.86-pp.95 However, if the retention control and the paper ash content control are simultaneously performed as described above, then disadvantageously, these controls interact DOCSTOR: 1408423\1 with each other to cause hunting in the control terminal in the paper ash content control, thus degrading stability.
Further, in the retention control for maintaining a fixed value, the total consistency of white water may become unstable. Thus, if the above two types of controls are simultaneously performed, the expected control effect is not achieved and in some cases the opposite effect is obtained. This may degrade product quality.
The conventional retention control system requires expensive special sensors mostly developed overseas.
Accordingly, it is very recently that earnest domestic efforts have started to be made on the retention control introduction. Further, it has not substantially been known that the retention control and the paper ash content control interact with each other.
Even in overseas paper machine processes that have taken initiative in dealing with the retention control, the mutual interaction phenomenon has probably been long observed. However, the mutual interaction seems to seldom have been regarded as a problem. Even overseas, it is probably after about 2001 that counter measures started to be taken for the recognized mutual interaction problem (see, for example, Non-Patent Document 1).
Further, even at present, when the mutual interaction problem is often discussed, inadequate approaches are probably taken to avoid the adverse effect of the mutual interaction. That is, if the degree (magnitude) of the DOCSTOR: 1408423\1 mutual interaction is small, the magnitude of interaction is neglected and the control loops are used independently.
Even if a slightly significant mutual interaction occurs, all the tuning parameters for the PID controller or the tuning parameters for only one of the loops are reduced so as to prevent inconveniences resulting from unstable processes.
On the other hand, a study has been reported in which for the mutual interaction between a plurality of control loops, an attempt is made to positively eliminate the mutual interaction using multi-variable control called "model predictive control" (see, for example, Non-Patent Document 1).
The method utilizing the model prediction control is a control system that precisely and collectively cancels the adverse effects of the mutual interaction between a large number of variables in a process including the ratio of paper ash content and retention. This control system is complicated and requires high costs for introduction.
In connection with this, the applicant has proposed a control system that requires a long time to vary the dosage of a retention aid because if the increase and reduction in the dosage of the retention aid is controlled within a short period using the PID controller, the formation of paper products (variation in basis weight) may be degraded (control system that requires about 30 minutes to vary the amount ( dosage ) of retention aid added in a ramp manner) . Since this is a moderate control system, the above mutual interaction does not occur between the retention control and the paper ash content control (see, for example, Patent Document 1 and Non-Patent Document 4).
However, today, there is a demand for realizing more precise control by performing frequent output control within a short period to increase the response speed of the retention and the ratio of paper ash content control.
In this case, such mutual interaction as described above may occur and the solution to this problem is recognized as an important goal.
Disclosure of the Invention The present invention focuses on the above problems of the conventional art. It is an object of the present invention to provide a control device for a paper machine which, even if retention control and a paper ash content control are performed within a short time using a PID
controller, a Quality Control System, or the like, can avoid problems such as hunting resulting from the mutual interaction between the controls using a simple and inexpensive configuration, thus precisely controlling the retention and the ratio of the paper ash content.
To achieve this object, the present invention has the following configuration.
A first aspect of the present invention is a method for controlling a paper machine, the method automatically DOCSTOR: 1408423\1 controlling retention and a ratio of paper ash content at least in a wet part, the method being characterized in that:
a decoupling control mechanism is incorporated between a feedback loop for automatically controlling the retention and a feedback loop for automatically controlling the ratio of paper ash content, to cancel adverse effects of mutual interaction between the loops.
A second aspect of the present invention according to the first aspect characterized in that: the automatic retention control is performed by measuring the consistency of white water in a wire part (consistency of white water resulting from dehydration in the wire part) in the wet part and increasing or reducing the amount of retention aid dosage to a thin stock flow depending on the white water consistency and the automatic control of the ratio of paper ash content is performed by measuring the content of ash in paper after the paper has been dried and increasing or reducing the amount of ash flow added to the thin stock flow depending on the ratio of paper ash content.
A third aspect of the present invention according to the second aspects characterized in that the consistency of white water in the wire part measured for the automatic retention control is the consistency of white water filtered through a wire in the wire part and flowing down into a white water silo below the wire. The consistency of white water is normally the total consistency of white water but may be the consistency of pulp in white water DOCSTOR: 1650002\1 or the consistency of ash. The total consistency of white water refers to the consistency of pulp in white water plus the consistency of ash in white water.
A fourth aspect of the present invention according to the first or third aspect characterized in that the decoupling control function uses a decoupling control element for steady state characteristic compensation which compensates for the magnitude of mutual interaction between the feedback control loops at the same time.
A fifth aspect of the present invention according to the first or third aspect characterized in that the decoupling control function uses a decoupling control element for dynamic state characteristic compensation which compensates for the magnitude of mutual interaction between the feedback control loops taking a time delay into account.
A sixth aspect of the present invention is a control device for a paper machine which controls retention and a ratio of paper ash content at least in a wet part using an automatic retention control system, the device being characterized in that: the automatic control system comprises: a feedback control loop for automatically controlling the retention; a feedback control loop for automatically controlling the ratio of paper ash content;
and a decoupling control section incorporated between the feedback control loops to cancel adverse effects of mutual interaction between the loops.
DOCSTOR: 1650002\1 A seventh aspect of the present invention according to the sixth aspect characterized in that: the feedback control loop for automatically controlling the retention comprises a low consistency sensor used to measure the consistency of white water in the wire part in the wet part and a control section that transmits a control signal to a retention operation terminal in a paper machine process so as to increase or reduce the dosage of retention aid added to a thin stock flow on the basis of an actuating error between the white water consistency detected using the low consistency sensor and a predetermined target value, the feedback control loop for automatically controlling the ratio of paper ash content comprising ash flow detecting means for measuring the amount of ash in paper after the paper has been dried and a paper ash control section that transmits a control signal to a paper ash flow operation terminal in the paper machine process so as to increase or reduce the amount of ash flow added to a thin stock flow on the basis of an actuating error between the amount of paper ash flow detected using the ash flow detecting means and a predetermined target value, the decoupling control section having a decoupling control element that compensates for the magnitude of mutual interaction.
An eighth aspect of the present invention according to the seventh aspect characterized in that the decoupling control element is a feed forward compensating element 1]
input to each operation terminal of each of the feedback control loops in order to compensate for the magnitude of mutual interaction.
A ninth aspect of the present invention according to the eighth aspect characterized in that the decoupling control element is determined on the basis of a response block for each feedback control loop and an interaction block that causes the feedback control loops to interact with each other.
A tenth aspect of the present invention is a program for allowing a computer to execute the control method set forth in any of the first to fifth aspects.
An eleventh aspect of the present invention is a computer readable storage medium in which the program set forth in the tenth aspect is stored.
Brief Description of the Drawings FIG. 1 is a diagram conceptually showing the general configuration of a paper machine used in an embodiment of the present invention;
FIG. 2 is a block diagram showing a paper ash content control loop and a retention control loop in a control system of the paper machine shown in FIG. 1;
FIG. 3 is a diagram showing variations in the total consistency of white water, the amount of ash content in DOCSTOR: 1408423\1 paper, and paper machine speed, as well as the added flow (dosage) of retention aid, the diagram also showing that the retention is not controlled but only the paper ash content control is performed;
FIG. 4 is a diagram showing variations in the total consistency of white water, the amount of ash content in paper, the added flow ( dosage ) of retention aid, and paper machine speed, the diagram also showing that decoupling control is not performed but the retention and the ratio of paper ash content are simultaneously controlled;
FIG. 5 is a diagram showing variations in the total consistency of white water, the amount of ash content in paper, the added flow ( dosage ) of retention aid, and paper machine speed, the diagram also showing that the retention and paper ash content are simultaneously controlled using a control device according to the present embodiment;
FIG. 6 is a diagram approximately showing a response gain K, dead time Ti, and time constant T2 obtained if a step input is applied to a process;
FIG. 7 is a block diagram showing a state in which the ratio of paper ash content control loop and the retention control loop are independent of each other; and FIG. 8 is a block diagram showing a state in which mutual interaction occurs between the paper ash content control loop and the retention control loop.
Best Mode for Carrying Out the Invention An embodiment of the present invention will be described below with reference to the drawings.
FIG. 1 is a diagram conceptually showing the general configuration of a paper machine used in an embodiment of the present invention.
As shown in the figure, the illustratiod paper machine 1 consists of a paper machine process 2 that executes a paper sheet making process and a control system 3 that controls the paper machine process 2.
First, the configuration of the paper machine process will be described.
In a wet part 2a of the paper machine process 2, the thin stock flow of a low consistency injected by a head box 4 is filtered using a wire part 6 comprising, for example, a wire 5 rotating endlessly. A pulp mat remaining on the wire 5 is fed to the succeeding press part 7, where the pulp mat is further filtered. Further, the pulp mat filtered by the press part 7 is heated and dried by the succeeding dryer part 8. The pulp mat is then wound around a reel part 9 to form a roll of paper.
On the other hand, the wet part 2a constitutes a white water circulating system 12. In the white water circulating system 12, the white water flows down from the wire 5 owing to the dehydration of the wire part 6 and is then stored in a white water silo 10. The white water is then supplied by the pump 11 to the head box.
In the white water circulating system 12, the thick DOCSTOR: 1408423\1 stock flow supplied by a pump 13 is supplied to a path leading from the white water silo 10 to the pump 11 via a stock box 14 and a valve (stock control valve)15. The thick stock flow is sent to the head box 4 as well as the white water supplied from white water silo 10.
In the white water circulating system 12, a path leading from the pump 11 to head box 4 connects to an ash supply path 16 along which a pump is used to supply ash flow from an ash flow source (not shown) and a retention aid chemical supply path 17 along which a pump 17a is used to supply a retention aid chemical from a retention aid source (not shown). An ash (filler) flow control valve 18 and a flow meter 19 are connected to the ash supply path 16. The opening of the valve 18 is controlled by an ash flow control section 20 so that a flow ratio detected by the flow meter 19 has a value corresponding to a control signal corresponding to a manipulated variable output by the control system 3, described later.
Further, the retention aid supply path 17 connects to a retention aid dosage control valve 21 (control may be performed using a metering pump) and a flow meter 22.
The opening of the valve 21 is controlled by a retention aid dosage added flow control section 23 so that a flow ratio detected by the flow meter 22 has a value corresponding to a control signal corresponding to a manipulated variable output by the control system 3.
In the paper machine process 2, the consistency of the white water flowing down into the white water silo 10 has been detected by a low consistency sensor (white water consistency detecting means) 24. The detected value has been input to the control system 3.
In this embodiment, an example of the low consistency sensor 24 is a sensor that loads, into a CPU connected to a sensor, a total of 14 kinds of detection signals including five kinds of signals about a polarized light quantity ratio obtained utilizing the nature that when a laser beam is transmitted throughpulp fibers, an optical axis rotates through about 90 for polarization, a variation in laser beam scattering form caused by fine grains of an ash content such ascalcium carbonate, the quantity of scattering light in back reflection, the quantity of xenon light absorbed by a lignin component in pulp fiber while the light is being transmitted through a sample in order to distinguish fine pulp fiber from the ash component, and the quantity of scattering light in back reflection. The sensor then checks the signals against measurements obtained through manual analysis, and selects about five signals that are highly correlated with one another by multiple regression analysis. The sensor then statistically determines coefficient values for a regression model equation to convert the signals into consistencies (the sensor is manufactured by Metso Automation Kayani, Finland). The range of measurements by the low consistency sensor 24 is total consistency 51.5% and ash consistency s 0.8%.
DOCSTOR: 1408423\1 The special sensor enables the online measurement of, for example, the consistency of the thin stock flow supplied to the head box 4 and the consistency of white water filtered through the wire 5 and flowing down into the white water silo 10 while separating the pulp component from the ash component; in the prior art, these consistencies can be determined only by offline measurements. These two measurements can be used to continuously determine the amount of each material remaining on the wire after dehydration in the wire part 6 ((1) total retention, (2) pulp retention, and (3) ash retention), on the basis of online calculations.
Further, a measurement frame and a sensor head 25b of a Quality control system in which a plurality of sensors are mounted are installed in a rear part of the paper machine process 2, for example, the reel part 9. The sensor head 25b is scanned across paper width so that the sensor head 25b of the Quality control system and a control section 25a can measure the paper ash content and other physical properties of paper (basis weight, moisture, thickness, colour, and the like) . An ash sensor provided in the sensor head 25b measures the ratio of paper ash content and utilizes the nature that ash component in paper absorbs X rays more than pulp. The ash sensor measures the ratio of paper ash content by using an ionization chamber to detect the intensity of X rays transmitted through paper DOCSTOR: 1408423\1 and attenuated.
In the paper machine process 2 configured as described above, the retention control in the wire part 6 is performed as follows. The low consistency sensor 24 is used to measure online the total consistency of white water flowing from the wire 5 down into the white water silo 10. The PI controller 26, provided in the control system 3, described later, then performs feedback control with short period outputs to control the opening of the control valve 21 (or the flow ratio of the metering pump) so as to match the target value and the predetermined value to increase or reduce the dosage of retention aid added to the thin stock flow.
That is, during operation, control is performed as follows using the feedback control loop, described later.
When there is an increase in the total consistency of white water being measured using the low consistency sensor 24, this means a decrease in the retention in the wire part corresponds to an increase. Accordingly, the flow rate (dosage) of retention aid being added to the thin stock flow is increased. When the total consistency of the white water decreases, the flow rate (dosage) of retention aid being added to the thin stock flow is reduced. This control operation is performed online using a short period such as one second.
The retention aid chemical is normally a highly viscous liquid polymer agent. The consistency of DOCSTOR: 1408423\1 retention aid dosage to the thin stock flow is about 200 to 500 ppm. The addition requires management of a very low flow rate (although depending on production rate, dosage of about 10 to 20 litre/min) . Accordingly, the pump 17a is a centrifugal pump or the like if the control valve 21 is provided. The pump 17a is a variable flow type metering pump if the control valve 21 is not provided. Such a small increase or reduction in the dosage ratio of the retention aid enables the retention of the thin stock flow component in the wire part 6 (total consistency of white water) to be controlled.
On the other hand, the flow rate of ash added to the thin stock pulp is adjusted so that the ratio of paper ash content meets the corresponding product specification.
That is, during operation, when the ratio of paper ash content increases above the target value, the added flow control section 20 reduces the opening of the valve 18 on the basis of a control signal from Quality control system control section 25a to reduce the flow ratio of ash fed by the pump 16a. When the paper ash content decreases, the opening of the valve 18 and the ash flow are increased to achieve the target paper ash content.
Now, description will be given of the control system 3, which controls the paper machine process 2.
The control system 3 according to this embodiment comprises an input setting section 28 that inputs various data and instructions including the required target values DOCSTOR: 1408423\1 of the ratio of paper ash content and white water total consistency, a controller 29 that controls the ash flow control section 20 and retention aid dosage flow control section 23 in accordance with the target values of the ratio of paper ash content and white water total consistency set by the input setting section 28, and Quality control system control section 25a.
The controller 29 has a function for a decoupling control section 30. The functions of the PI controller 26 and decoupling control section 30 are realized by the CPU in accordance with a program stored in the computer.
This program can be stored in currently available various storage media.
The Quality control system control section 25a transmits a control signal to the ash flow control section on the basis of the target value of the paper ash content received by the input setting section 28 and the ratio of the paper ash content detected value detected by the sensor head 25b of the Quality control system. This constitutes 20 a feedback control loop (referred to as an paper ash control loop below) Ll for controlling the ratio of the paper ash content for the paper machine process2 as shown in FIG.
2.
Further, the PI controller 26 transmits a control signal to the retention aid dosage added flow control section 23 on the basis of the target value of the total consistency of white water set by the input setting section 28 and the consistency value obtained by the low consistency sensor 24. This constitutes a feedback control loop (referred to as a retention control loop below) L2 for controlling the retention.
Of the two feedback control loops L1 and L2, the paper ash control loop L1 is actually used in conventional paper machines. However, in recent years, the requirement has been made that the retention in the wire part be controlled using a short control period of about one second so that the retention is stabilized. To deal with this, it has become necessary to allow the paper ash control loop L1 and the retention control loop L2 to coexist.
When the paper ash control loop L1 and the retention control loop L2 coexist, if they are independent of each other as shown in FIG. 7, ideal feedback control can be performed so as to maintain the ratio of paper ash content and the retention at the desired target values. In FIG.
7, G11 denotes a response block for paper ash which is obtained during the paper machine process 2 by the Quality control system control section 25a and Quality control system head 25b by controlling the ash flow control section 20. G22 denotes a response block for the total consistency of white water (retention) which is obtained during the paper machine process by the PI control section by controlling the dosage of the retention aid. Here, a block of a process refers to a transfer function for a control system for the process.
However, it has become clear that actually the following occurs if the retention control loop L2 is incorporated into the paper machine 1 into which the ash control loop L1 has already been incorporated.
Interaction blocks G21 and G12 cause mutual interaction between the control loops L1 and L2 during the paper machine process as shown in the control block diagram in FIG. 8.
Consequently, hunting occurs in the total consistency of white water and in the ratio of paper ash content to make the control state unstable. That is, if a change is made to one of the two variables to be controlled during the paper machine process 2, the ratio of paper ash content and the total consistency of white water, for example, the total consistency of white water is changed, then the ratio of paper ash content, the other variable, is affected and changed. As a result, the two variables cannot be independently controlled.
In FIGS. 7 and 8, if G1l, G12, G21, and G22 are collectively denoted as Gab, this indicates a responsive block when the magnitude of operation of an operation terminal a during the process is defined as Xa and when the magnitude of a change in an output terminal affected by the operation is defined as Yba. Then, if the output range of the controller is not taken into account, the magnitude ( gab ) of the gain of the response block is given by:
gab = Yba/Xa Expression 2 The mutual interaction between the control loops is expected to result from, for example, a process (A) or (b) described below.
Process (A) If an increase in the total consistency of white water in the wire part occurs as a disturbance, the above retention control is correspondingly performed to increase the dosage of the retention aid (polymer) (step Al) . This increases the retention in the wire part (lowers the total consistency of white water in the wire part) and increases the ratio of paper ash content (step A2) . As a result, the Quality control system performs the paper ash content control to reduce the ratio of paper ash content and thus the ash flow is reduced (step A3) . This lowers the content of ash in the thin stock flow injected by the head box 4, thus reducing the consistency of white water ash and thus the total consistency of white water (step A4) . Then, the retention control is performed to reduce dosage of the retention aid (step A5 ). Hunting occurs in the dosage of the retention aid and in the ratio of paper ash content owing to the above mutual interaction between the retention control and the paper ash content control (step A6).
Process (B) On the other hand, if the ratio of paper ash content DOCSTOR: 1408423\1 becomes insufficient as a disturbance, the paper ash content control in the Quality control system control section 25a is activated to increase the ash flow (step B1). The consistency of the thin stock ash injected by the head box 4 rises to increase the total consistency of white water (step B2) . At the same time, the consistency of the white water component increases (step B3) . As a result, the retention control is activated to increase the dosage of the retention aid chemical. The retention in the wire part 6 is increased to increase the ratio of paper ash content. This reduces the total consistency of white water and the consistency of white water ash (step B4).
Then, the retention control reduces the dosage of the retention aid chemical, while reducing the ratio of paper ash content (step B5) . The above operation causes hunting in the dosage of the retention aid chemical and in the ratio of paper ash content (step B6).
As is apparent from the above process, it is understandable that mutual interaction necessarily occurs between the two control loops Ll and L2 for the retention control and the paper ash content control, though the level of occurrence varies.
To avoid the adverse effect of the mutual interaction between the feedback control loops Ll and L2, the decoupling control section 30 was provided as shown in FIGS.
1 and 2, according to the present embodiment. The decoupling control section 30 adds a signal obtained by DOCSTOR: 1408423\1 multiplying a control output m2 from the PI controller 26 by a decoupling control block Cl, to a control output ml from the Quality control system control section 25a, and to a control output m2 output by the PI controller 26 by multiplying the control output ml from the Quality control system control section 25a by a decoupling control block C2 as shown in FIG. 2.
Here, the decoupling control block Cl and C2 can be calculated as theoretical values as follows. The PI
controller 26 is set in a manual operation mode while the paper machine process 2 is stable. An output from the PI
controller 26 is varied step by step to examine the response characteristic of the PI controller 26. Then, the calculations shown below are executed.
In the decoupling control with two inputs and two outputs shown in FIG. 2, let ul be the output value of a decoupling control element in the ash control loop, let u2 be the output value of a decoupling control element in the retention control loop, let yl be the amount of paper ash content, and let y2 be the total consistency of white water. Then, these values are given by:
ul = ml +(C1 x m2) Expression 3 u2 = (C2 x ml) + m2 Expression 4 yl =(G11 x ul) +(G12 x u2) Expression 5 y2 = (G21 x ul) + (G22 x u2) Expression 6 ul and u2 are deleted from Expressions 4 and 5.
yl = G11 X{m1 +(C1 x m2)) + G12 x{(C2 x ml) + m2}
_ (Gil + (G12 x C2)} x ml +{(G11 x Ci) + G12) x m2 Expression 7 y2 = G22 x{m2 + (C2 x ml)) + G21 x{(C1 x m2) + ml) _ {G21 + (G22 x C2)} x m1 +{(G21 x Cl) + G22) x m2 Expression 8 To make inputs and outputs associated with Expressions 7 and 8 non-interactional, the conditions expressed by Expressions 9 and 10 are required.
{(G11 x Cl) + G12} = 0 Expression 9 {G21 + (G22 x C2)) = 0 Expression 10 Decoupling control static gains Cl and C2 are determined as follows from Expressions 9 and 10 Cl = -(G12/G11) Expression 11 C2 = -(G21/G22) Expression 12 Here, the decoupling control elements Cl and C2 determined are substituted into Expressions 7 and 8 to determine the I/O relationship.
yl ={G11 -(G12 x G21)/G22) x ml Expression 7' y2 ={G22 -(G12 x G21)/G11} x m2 Expression 8' Therefore, in the above calculations, it is necessary that G11 x G22 - G12 x G21 0 0.
As is apparent from Expression 7', the amount yl of paper ash content is affected only by an ash flow operation ml. Further, as is apparent from Expression 8' the total consistency y2 of white water is affected only by a retention aid dosage operation m2. That is, the addition of the decoupling control element enables the control loops to be controlled independently though they are under mutual interaction.
The values of the decoupling control blocks Cl and C2 are determined while examining the operation response characteristic by varying the output from the operation terminal step by step while the paper machine process is stable. If only the static characteristics of the process are taken into account, only the static gains of the blocks G11, G22, G12, and G21 may be used in the above expressions.
If the values of the decoupling control blocks Cl and C2 determined by the above calculations are applied to the actual paper machine process 2, it is essential to perform a tuning operation for matching.
As described above, in the embodiment of the present invention, the decoupling control section 30 is incorporatiod between the paper ash content control loop L1 and the retention control loop L2; the decoupling control section 30 performs the non-interaction calculations and control on the basis of the decoupling control blocks Cl and C2 and the like. This positively cancels the adverse effects of the mutual interaction between these control loops L1 and L2. In other words, when a retention operation is performed using one of the control loops, for example, the retention control loop L2, the adverse effect of the mutual interaction between the control loops is considered to be a kind of disturbance.
Then, the signal obtained by multiplying the control signal from the control loop L2 by the interaction coefficient is simultaneously added or subtracted to prematurely cancel an amount of interaction which one of the control loops may offer to the other control loop, on the basis of feed forward control. Thus, even if the ratio of paper ash content and retention are controlled using a short period of about one second, then as shown in FIG. 7, the respective controls can be kept independent of each other.
Further, the retention (total consistency of white water) and the ratio of paper ash content can be brought closer to the target values set for the wet part.
FIGS. 3 to 5 show variations in the total consistency of white water, the amount of ash content in paper, and the dosage of the retention aid observed if the retention control and the of paper ash content control are performed using a conventional control device and the control device according to the present embodiment.
FIG. 3 shows that the retention is not controlled but only the paper ash content control is performed. As shown in the figure, the total consistency of white water varies substantially.
FIG. 4 shows that the retention control loop L2 and the paper ash content control loop L1 are simultaneously controlled independently. As shown in the figure, the total consistency of white water and the ratio of paper ash content, which are control terminals, interact with each other and become very unstable. As a result, divergent vibration occurs.
In contrast, in the present embodiment, in which the decoupling control is applied to between the two control loops, the target retention control and the paper ash content control can be simultaneously and stably performed as shown in FIG. 5. Clearly, the adverse effect of the mutual interaction has been sufficiently avoided. In addition, before and after a grade change time, the total consistency of white water and the ratio of paper ash content are unstable. This is because the grade (type of paper) is being changed.
In the applicant's trial, a variation in the amount of ash in paper under the paper ash content control using a Quality control system was 0 . 4 to 0. 5% according to the conventional art (see FIG. 3) . However, according to the present embodiment, which also used the decoupling control, the variation could be reduced to about 0.2% (see FIG.
5).
Further, with the retention control by the decoupling control section, the total consistency of white water, which was a final obj ect , could be controlled to maintain an almost fixed value.
In the above embodiment, steady state characteristic compensation is mainly described which compensates for mutual interaction processes using only the static gain DOCSTOR: 1408423\1 as a decoupling control element. However, the present invention is expected to have its control performance improved by using dynamic characteristic compensation that takes not only a static response gain K but also time delays such as a dead time Tl and a time constant T2 into account as decoupling control elements. Generally, response in this process can be approximated as a dead time plus first order lag model as shown FIG. 6. In this case, the transfer function G (also referred to as a block) can be expressed as a function of the static response gain K, dead time T1, and time constant T2. That is, G = G(K, Ti, T2).
Substituting this directly into Expressionslland12 makes it possible to determine the decoupling control blocks Cl and C2 for dynamic characteristic compensation. With the notation of transfer functions commonly used in the field of automatic control, if.for example, the processes are assumed to be approximated using a dead time + first order lag model, then G = G(K, T1, T2) = {K x e x p(-Tl x S)}/{1 + (T2 X S)}. Here, S in the expression denotes a Laplace operator for an S plane (complex plane) for a Laplace transformation executed on the relation between an input and output for a process response.
It has also been found that the mutual interaction between the control loops often occurs in processes with a smaller value for the retention in the wire part. The present invention is particularly effective on such processes.
(Other Embodiments) In the description of the above embodiment, the retention control is performed so as to fix the total consistency of white water. However, it is expected that in the future, not only the total consistency of white water but also the consistency of pulp in white water and the content of ash flow will be controlled. To realize this, it is possible to utilize the decoupling control shown in the above embodiment.
In this case, the pulp consistency, the ash consistency, and the ratio of paper ash content should interact with one another. Accordingly, the control terminal is composed of the pulp consistency and the ash consistency. The control operation terminal is composed of the opening of a valve for a thick stock pulp which increases or reduces the flow ratio of pulp stock, the opening of an ash addition valve, and the opening of a valve for dosage of the retention aid. Then, decoupling control elements for all the combinations of the above parameters are similarly incorporated between the loops for control.
As a result, both pulp and ash consistency can be maintained at the desired fixed values.
As described above, in a paper machine that automatically performs at least two types of control, retention control and the paper ash content control, the present invention provides a decoupling control section between a control loop for the retention control and a DOCSTOR: 1408423\1 control loop for the paper ash content control.
Consequently, even if the retention control and the ratio of the paper ash content control are performed using a short control period, both controls can be stably performed. As a result, it is possible to stably manufacture paper products with the desired basic weight, the paper ash content, and the like while maintaining the desired retention (total consistency of white water). Therefore, product quality can be greatly improved.
Industrial Applicability As described above, the present invention can be easily implemented as an inexpensive and simple structure in which a decoupling control section is provided between the retention control and the paper ash content control.
Therefore, the present invention is very useful in the pulp and paper industry.
Claims (11)
1. A method for controlling a paper machine, the method automatically controlling retention and a ratio of paper ash content at least in a wet part, the method comprising the steps of:
automatically controlling the retention using a first feedback loop and automatically controlling the ratio of paper ash content using a second feedback loop, the loops having a decoupling control mechanism incorporated therebetween to cancel adverse effects of mutual interaction between the loops.
automatically controlling the retention using a first feedback loop and automatically controlling the ratio of paper ash content using a second feedback loop, the loops having a decoupling control mechanism incorporated therebetween to cancel adverse effects of mutual interaction between the loops.
2. The method for controlling a paper machine according to Claim 1, wherein:
the automatic retention control is performed by the steps of:
measuring the consistency of white water in a wire part in the wet part and increasing or reducing the amount of retention aid dosage to a thin stock flow depending on the white water consistency; and the automatic control of the ratio of paper ash content is performed by the steps of:
measuring the content of ash in paper after the paper has been dried and increasing or reducing the amount of ash flow added to the thin stock flow depending on the ratio of paper ash content.
the automatic retention control is performed by the steps of:
measuring the consistency of white water in a wire part in the wet part and increasing or reducing the amount of retention aid dosage to a thin stock flow depending on the white water consistency; and the automatic control of the ratio of paper ash content is performed by the steps of:
measuring the content of ash in paper after the paper has been dried and increasing or reducing the amount of ash flow added to the thin stock flow depending on the ratio of paper ash content.
3. The method for controlling a paper machine according to Claim 2, wherein the consistency of white water in the wire part measured for the automatic retention control is the consistency of white water filtered by passing through a wire in the wire part and flowing down into a white water silo below the wire.
4. The method for controlling a paper machine according to Claim 1, further comprising the step of:
performing the decoupling control function using a decoupling control element for steady state characteristic compensation which compensates for the magnitude of mutual interaction between the feedback control loops at the same time.
performing the decoupling control function using a decoupling control element for steady state characteristic compensation which compensates for the magnitude of mutual interaction between the feedback control loops at the same time.
5. The method for controlling a paper machine according to Claim 3, further comprising the step of:
performing the decoupling control function using a decoupling control element for steady state characteristic compensation which compensates for the magnitude of mutual interaction between the feedback control loops at the same time.
performing the decoupling control function using a decoupling control element for steady state characteristic compensation which compensates for the magnitude of mutual interaction between the feedback control loops at the same time.
6. The method for controlling a paper machine according to Claim 1, further comprising the step of:
performing the decoupling control function using a decoupling control element for dynamic state characteristic compensation which compensates for the magnitude of mutual interaction between the feedback control loops taking a time delay into account.
performing the decoupling control function using a decoupling control element for dynamic state characteristic compensation which compensates for the magnitude of mutual interaction between the feedback control loops taking a time delay into account.
7. The method for controlling a paper machine according to Claim 3, further comprising the step of:
performing the decoupling control function using a decoupling control element for dynamic state characteristic compensation which compensates for the magnitude of mutual interaction between the feedback control loops taking a time delay into account.
performing the decoupling control function using a decoupling control element for dynamic state characteristic compensation which compensates for the magnitude of mutual interaction between the feedback control loops taking a time delay into account.
8. A control device for a paper machine which controls retention and a ratio of paper ash content at least in a wet part using an automatic control system, the device comprising:
a feedback control loop for automatically controlling the retention;
a feedback control loop for automatically controlling the ratio of paper ash content; and a decoupling control section incorporated between the feedback control loops to cancel adverse effects of mutual interaction between the loops.
a feedback control loop for automatically controlling the retention;
a feedback control loop for automatically controlling the ratio of paper ash content; and a decoupling control section incorporated between the feedback control loops to cancel adverse effects of mutual interaction between the loops.
9. The control device according to Claim 8, wherein the feedback control loop for automatically controlling the retention comprises a low consistency sensor used to measure the consistency of white water in the wire part in the wet part and a control section that transmits a control signal to a retention operation terminal in a paper machine process so as to increase or reduce the dosage of retention aid added to a thin stock flow on the basis of an actuating error between the white water consistency detected using the low consistency sensor and a predetermined target value, the feedback control loop for automatically controlling the ratio of paper ash content comprising ash flow detecting means for measuring the amount of ash in paper after the paper has been dried and an ash control section that transmits a control signal to a paper ash flow operation terminal in the paper machine process so as to increase or reduce the amount of ash flow added to the thin stock f low on the basis of the actuating error between the amount of the paper ash flow detected using the ash flow detecting means and a predetermined target value, the decoupling control section having a decoupling control element that compensates for the magnitude of mutual interaction between the feedback control loop for automatically controlling the retention and the feedback control loop for automatically controlling the ratio of paper ash content.
10. The control device for a paper machine according to Claim 9, wherein the decoupling control element is a feed forward compensating element input to each operation terminal of each of the feedback control loops in order to compensate for the magnitude of mutual interaction.
11. The control device for a paper machine according to Claim 10, wherein the decoupling control element is determined on the basis of a response block for each feedback control loop and an interaction block that causes the feedback control loops to interact with each other.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2003035686A JP4063100B2 (en) | 2003-02-13 | 2003-02-13 | Paper machine control method, control device, program, and storage medium |
| JP2003-035686 | 2003-02-13 | ||
| PCT/JP2004/000753 WO2004072367A1 (en) | 2003-02-13 | 2004-01-28 | Paper machine control method, control device, program and storage medium |
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| CA2515981A1 CA2515981A1 (en) | 2004-08-26 |
| CA2515981C true CA2515981C (en) | 2010-06-22 |
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|---|---|---|---|
| CA2515981A Expired - Fee Related CA2515981C (en) | 2003-02-13 | 2004-01-28 | Method and device for controlling paper machine, and program and storage medium |
Country Status (5)
| Country | Link |
|---|---|
| JP (1) | JP4063100B2 (en) |
| CN (1) | CN100558981C (en) |
| CA (1) | CA2515981C (en) |
| FI (1) | FI20050807A (en) |
| WO (1) | WO2004072367A1 (en) |
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| DE10351771A1 (en) | 2003-11-06 | 2005-06-09 | Voith Paper Patent Gmbh | Process for producing a fibrous web |
| DE102005002638A1 (en) * | 2005-01-20 | 2006-07-27 | Voith Paper Patent Gmbh | ash determination |
| US20060162887A1 (en) * | 2005-01-26 | 2006-07-27 | Weinstein David I | System and method to control press section dewatering on paper and pulp drying machines using chemical dewatering agents |
| JP2007011866A (en) * | 2005-07-01 | 2007-01-18 | Yokogawa Electric Corp | Nonintefering control method for process control system and process control system |
| JP4779762B2 (en) * | 2006-03-30 | 2011-09-28 | 栗田工業株式会社 | Effect monitoring method and injection amount control method for papermaking chemicals |
| JP2008025087A (en) * | 2006-06-21 | 2008-02-07 | Nippon Paper Industries Co Ltd | Measuring method and measuring apparatus for sample concentration of papermaking stock |
| KR20230133886A (en) | 2021-02-12 | 2023-09-19 | 쿠리타 고교 가부시키가이샤 | Guessing device, guessing system, guessing program and guessing method |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH02160992A (en) * | 1988-12-12 | 1990-06-20 | Toshiba Corp | Control device of weighing of paper making plant |
| JP2754801B2 (en) * | 1989-11-18 | 1998-05-20 | 横河電機株式会社 | Profile non-interference control device |
| FI92729C (en) * | 1993-10-29 | 1994-12-27 | Valmet Paper Machinery Inc | Multilayer headbox pulp feed system and method in multilayer headbox operation |
| JP3728867B2 (en) * | 1997-05-23 | 2005-12-21 | 王子製紙株式会社 | Method and apparatus for automatically controlling the concentration of filtered white water in the wire part of a paper machine and a method for setting a target concentration of filtered white water |
-
2003
- 2003-02-13 JP JP2003035686A patent/JP4063100B2/en not_active Expired - Fee Related
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- 2004-01-28 CA CA2515981A patent/CA2515981C/en not_active Expired - Fee Related
- 2004-01-28 WO PCT/JP2004/000753 patent/WO2004072367A1/en active Application Filing
- 2004-01-28 CN CNB2004800042827A patent/CN100558981C/en not_active Expired - Fee Related
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| CA2515981A1 (en) | 2004-08-26 |
| CN100558981C (en) | 2009-11-11 |
| JP2004263309A (en) | 2004-09-24 |
| WO2004072367A1 (en) | 2004-08-26 |
| JP4063100B2 (en) | 2008-03-19 |
| CN1751155A (en) | 2006-03-22 |
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