WO2000024964A1 - Procede et dispositif pour attenuer les pulsations de la toile dans la circulation courte d'une machine a papier/carton - Google Patents

Procede et dispositif pour attenuer les pulsations de la toile dans la circulation courte d'une machine a papier/carton Download PDF

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Publication number
WO2000024964A1
WO2000024964A1 PCT/FI1999/000880 FI9900880W WO0024964A1 WO 2000024964 A1 WO2000024964 A1 WO 2000024964A1 FI 9900880 W FI9900880 W FI 9900880W WO 0024964 A1 WO0024964 A1 WO 0024964A1
Authority
WO
WIPO (PCT)
Prior art keywords
machine
rotation
screens
phase
paper
Prior art date
Application number
PCT/FI1999/000880
Other languages
English (en)
Inventor
Harri Mustonen
Original Assignee
Metso Paper, Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Metso Paper, Inc. filed Critical Metso Paper, Inc.
Priority to AU10482/00A priority Critical patent/AU1048200A/en
Publication of WO2000024964A1 publication Critical patent/WO2000024964A1/fr

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Classifications

    • 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

Definitions

  • the invention concerns a method and a device for elimination of pressure pulsations occurring in the short circulation in a paper/board machine, which paper/board machine is provided with two or more machine screens.
  • the functions of the short circulation in a paper machine include recycling of the raw-materials and the water that have passed through the wire back into the headbox, diluting of the stock to be fed into the headbox, cleaning of the stock to be fed into the headbox, and mixing of additives, media and chemicals into the stock.
  • air is removed from the liquid to be circulated, and attempts are made to accomplish the circulation so that any disturbance in the flow rate, consistency and pressure is equalized.
  • Constantly increasing running speeds of paper machines also impose ever increasing requirements on the process of the short circulation in a paper machine both in respect of the stability of the process of manufacture, the freedom from disturbance of said process, and in respect of control of the quality of the paper. Also, printing machines with constantly higher running speeds impose ever stricter requirements on the quality of the paper.
  • FI Patent No. 88,415 in which a process arrangement is described for production of headbox stock for a paper machine in the short circulation.
  • a first compartment in a combination wire pit has been arranged as a feed tank for deaeration
  • a second compartment has been arranged as a dilution tank for headbox stock, into which tank the fresh stock has been arranged to be fed.
  • the process of the short circulation in a paper machine has, as a rule, been arranged so that all new solid materials, i.e. fibres and fillers, are diluted with white water in the area of the wire pit. It is also possible to feed fillers in later process stages. As a rule, all fibrous material that has been fed into the headbox of a paper machine has been treated in deaeration and in preceding or following vortex cleaning. Thus, the consistency dynamism of the short circulation has been quite slow, which comes from the large quantities of material that move in the short circulation, which quantities are of an order of 200 cubic metres.
  • the machine screens are tuned to revolve at speeds of rotation slightly different from one another. This has the consequence that the phase difference between the pressure pulsations caused by different machine screens changes all the time.
  • the pressure pulsations are at the same phase, they amplify each other, and when they are at opposite phases, they attenuate each other efficiently.
  • the variation in the pressure pulsations of the machine screens is seen as a regularly attenuated and amplified disturbance.
  • the object of the present invention is further development of the prior-art process arrangements of the short circulation in a paper machine and providing of novel, more advantageous solutions for said arrangements.
  • the method in accordance with the invention is mainly characterized in that the machine screens are provided with phase metering detectors, the phase of the rotation of each machine screen is determined, and, based on the determination of phase, the relative speeds of rotation and/or phase differences of the machine screens are regulated so that the pressure variations arising from the machine screens neutralize each other and the pressure pulse produced in the sum flow is at the minimum.
  • the device in accordance with the invention is characterized in that the device comprises metering detectors installed correspondingly on the machine screens for determination of the speeds of rotation and/or of the phases of rotation and corresponding signal lines which pass the information on metering of the speed and/or phase of rotation to a measurement unit.
  • the machine screens of the short circulation are provided with detectors which meter the speed and/or phase of rotation of the machine screens.
  • the speeds of the machine screens are adjusted equally high, and the phases of rotation are synchronized at phases opposite to one another.
  • the pressure pulsations produced by the machine screens neutralize each other, and the disturb- ance pulse produced in the overall stock flow is attenuated as efficiently as possible.
  • the pressure pulsations are attenuated most efficiently when the relative phase difference between the machine screens is 120°.
  • the pressure pulsations are attenuated most efficiently when the relative phase difference between the machine screens is 360°/N.
  • Figure 1 illustrates the connections of the machine screens in the short circulation of a paper machine.
  • Figure 2 illustrates the mode of carrying out the method and the device in accord- ance with the invention in metering of the pressure pulsations of the machine screens.
  • Figure 3 shows an example of a result of metering of the pressure pulsations caused by machine screens.
  • Fig. 1 shows a prior-art process of the short circulation in a paper machine, to which process the method in accordance with the present invention can be applied.
  • the headbox 10 feeds a stock suspension jet J through its slice opening 11 onto the forming wire 13 running over the breast roll 14.
  • the water collecting devices 15 placed inside the loop of the wire 13 pass the water drained through the wire 13 as a flow F 1 into the wire pit 16.
  • the white water of the flow F is used in the wire pit 16 for dilution of the fresh stock to the headbox consistency.
  • a return flow F coming from vortex cleaners 18 is also passed into the wire pit 16.
  • a flow pump 17a feeds the stock flow F 5 , which has been diluted to the headbox consistency, through vortex cleaners 18 as the flow F 6 into the deaeration tank 20.
  • the deaeration tank 20 there is an air space 20a subjected to a vacuum above the free level S 0 of the stock.
  • the stock level is determined by an overflow 21 of the tank, over which a stock flow Fg flows, from which the air has been removed. This flow F 8 is passed into the wire pit 16.
  • a stock flow F 7 is passed to the suction side of the flow pump 17b.
  • the pressure side of the flow pump 17b communicates with the parallel machine screens S j ,S 2 ,S 3 .
  • the accept from the machine screens Si ,S 2 ,S 3 is passed as the intake stock flow F in into the inlet header 12 of the headbox 10.
  • the bypass flow F out of the inlet header 12 of the headbox 10 is returned to the bottom part of the deaeration tank 20.
  • Fig. 2 illustrates an exemplifying embodiment of the method and the device in accordance with the present invention.
  • three machine screens S ⁇ ,S 2 ,S 3 have been connected in parallel.
  • a stock flow F 7 is fed, and from their accept side a stock flow F in is obtained, which is passed to the headbox 10.
  • the machine screens 8 ⁇ 82,83 are correspondingly provided with metering detectors 22,23,24, from which phase and speed signals are passed correspondingly through conductors 25,26,27 to the measurement unit 28.
  • the metering detectors 22,23,24 are, for example, optical detectors or pulse detectors.
  • the measurement unit 28 determines the phases and speeds of rotation of the machine screens Si ,S 2 and S 3 and transmits the data to the control unit 29 through the conductor 30.
  • the control unit 29 regulates the relative speeds and/or phases of rotation of the machine screens S ⁇ ,S 2 and S 3 so that the pressure pulsation that is formed is eliminated as efficiently as possible.
  • the regulation of the speed and phase of rotation can be accomplished, for example, by braking down the speed of a machine screen S, , S 2 and S 3 or by connecting the machine screens 8 2 ,8 2 ,8 3 with a rpm-controlled drive.
  • the machine screens Si , S 2 and S 3 can also be connected after one drive, or their speeds can be regulated by means of a frequency converter.
  • a wiring was examined which comprises three machine screens.
  • the method in accordance with the invention can also be applied to wiring arrangements which comprise, for example, two parallel machine screens or a higher number of screens.
  • the relative setting of the phases of the machine screens is carried out so that the phase measurement of one machine screen operates as a reference, and the phases of the other machine screens are regulated in relation to the reference.
  • Application of the method in accordance with the invention does not require that the parallel machine screens are identical. For example, the numbers of blades in the machine screens can be different. If the screens differ from one another, their speeds of rotation are regulated so that the interference frequency caused by the screens is equal in respect of all machine screens. In such a case it is possible to accomplish regulation of the phase difference.
  • Fig. 3 illustrates results of metering of the pressure variations of machine screens, which results have been metered while three parallel machine screens have been in operation.
  • Each curve represents a relative pressure variation metered from the intake side of the inlet header within a time period of 200 ms.
  • a piezoelectric pressure detector has been used for metering of the pressure variations.
  • the speeds of rotation of the machine screens have been determined by means of an optical photocell.
  • the metering has been carried out from a period of time slightly longer than one revolution.
  • Each measured curve has been produced as an average from 300 samples.
  • the metering cycles have been timed so that they start precisely at the same phase of the rotation of the device, in which case random variations present in the signal have been produced as an average equal to zero, and the variation produced by the device has remained.
  • the frequencies of rotation of different machine screens always differ from one another, so that the results, computed by means of a timed time level analysis, represent the pulsation caused by each device.
  • the pressure variation curves shown in Fig. 3 can be synchronized so that the variation of their sum pressure is minimized.
  • the frequencies of rotation are adjusted equal, and the phase difference is adjusted to be 360°/3, i.e. 120° .
  • An active regulation of the phase difference can be accomplished, for example, so that, when necessary, one or several screens is/are braked down on the basis of the information obtained from the phase metering.

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  • Paper (AREA)

Abstract

Cette invention se rapporte à un procédé servant à éliminer les pulsations de pression se produisant dans la circulation courte d'une machine à papier/carton. Cette invention s'applique à une machine à papier/carton qui est pourvue d'au moins deux toiles machine (S1, S2, S3). Les toiles machine (S1, S2, S3) sont pourvues de détecteurs de mesure de phase (22, 23, 24) et les informations sur la phase mesurée par ces détecteurs sont transmises à une unité de mesure (28). Sur la base des résultats de ces mesures, les vitesses relatives de rotation et/ou les différences de phase des toiles machine (S1, S2, S3) sont régulées, pour que les variations de pression dues aux toiles machine (S1, S2, S3) se neutralisent entre elles. Ainsi, on peut réduire au minimum l'impulsion de pression produite dans le flux total (Fin). Cette invention concerne également un dispositif servant à éliminer les pulsations de pression apparaissant dans la circulation courte d'une machine à papier/carton.
PCT/FI1999/000880 1998-10-27 1999-10-22 Procede et dispositif pour attenuer les pulsations de la toile dans la circulation courte d'une machine a papier/carton WO2000024964A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU10482/00A AU1048200A (en) 1998-10-27 1999-10-22 Method and device for attenuation of screen pulsations in the short circulation in a paper/board machine

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FI982330A FI103997B (fi) 1998-10-27 1998-10-27 Menetelmä ja laite sihtipulsaatioiden vaimentamiseksi paperikoneen/kartonkikoneen lyhyessä kierrossa
FI982330 1998-10-27

Publications (1)

Publication Number Publication Date
WO2000024964A1 true WO2000024964A1 (fr) 2000-05-04

Family

ID=8552792

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/FI1999/000880 WO2000024964A1 (fr) 1998-10-27 1999-10-22 Procede et dispositif pour attenuer les pulsations de la toile dans la circulation courte d'une machine a papier/carton

Country Status (3)

Country Link
AU (1) AU1048200A (fr)
FI (1) FI103997B (fr)
WO (1) WO2000024964A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7076127B2 (en) 2003-01-14 2006-07-11 Fuji Photo Film Co., Ltd. Optical switch and safety apparatus using the same

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FI88415B (fi) * 1991-11-11 1993-01-29 Valmet Paper Machinery Inc Processarrangemang foer den korta cirkulationen i en pappersmaskin
WO1999064668A1 (fr) * 1998-06-10 1999-12-16 Valmet Corporation Processus de la circulation courte d'une machine a papier ou a carton

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FI88415B (fi) * 1991-11-11 1993-01-29 Valmet Paper Machinery Inc Processarrangemang foer den korta cirkulationen i en pappersmaskin
WO1999064668A1 (fr) * 1998-06-10 1999-12-16 Valmet Corporation Processus de la circulation courte d'une machine a papier ou a carton

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7076127B2 (en) 2003-01-14 2006-07-11 Fuji Photo Film Co., Ltd. Optical switch and safety apparatus using the same

Also Published As

Publication number Publication date
FI103997B1 (fi) 1999-10-29
FI982330A0 (fi) 1998-10-27
FI103997B (fi) 1999-10-29
FI982330A (fi) 1999-10-29
AU1048200A (en) 2000-05-15

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