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WO2003000984A1 - Procede de reglage d'un processus de lavage de pate et determination de son efficacite - Google Patents

Procede de reglage d'un processus de lavage de pate et determination de son efficacite Download PDF

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Publication number
WO2003000984A1
WO2003000984A1 PCT/FI2002/000486 FI0200486W WO03000984A1 WO 2003000984 A1 WO2003000984 A1 WO 2003000984A1 FI 0200486 W FI0200486 W FI 0200486W WO 03000984 A1 WO03000984 A1 WO 03000984A1
Authority
WO
WIPO (PCT)
Prior art keywords
washing
washing process
pulp
efficiency
diffusion
Prior art date
Legal status (The legal status 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 status listed.)
Ceased
Application number
PCT/FI2002/000486
Other languages
English (en)
Inventor
Juri Lahtinen
Mikko Ulvinen
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Valmet Automation Oy
Metso Paper Automation Oy
Original Assignee
Metso Automation Oy
Metso Paper Automation Oy
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 Automation Oy, Metso Paper Automation Oy filed Critical Metso Automation Oy
Priority to EP02727635A priority Critical patent/EP1425466A1/fr
Priority to US10/479,951 priority patent/US20040134630A1/en
Priority to CA002450884A priority patent/CA2450884A1/fr
Publication of WO2003000984A1 publication Critical patent/WO2003000984A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
    • D21C9/02—Washing ; Displacing cooking or pulp-treating liquors contained in the pulp by fluids, e.g. wash water or other pulp-treating agents

Definitions

  • the invention relates to a method of adjusting a pulp washing process. [0002] The invention further relates to a method of determining the efficiency of a pulp washing process.
  • brown pulp refers to unbleached pulp.
  • the special characteristics of brown pulp washing include e.g. several factors decreasing the washing potential, such as undecomposable pulp fractions, soap, inorganic material and foam.
  • the operation of the washers used for washing brown pulp is based either on displacement washing or on dilution-extraction washing.
  • the displacement washing cleaner washing water is conveyed through dirty, stan- dard-consistency stock such that the cleaner liquid pushes the dirtier liquid out of the pulp pad.
  • the displacement washing is implemented as filter washing wherein filtering is always carried out while subjected to some kind of pressure, and the pressure or suction caused by a fluid column formed during the filtering, or the pressure or suction obtained using a pump, pushes the liquid in the stock through the holes in the drum serving as a filter, which means that the pulp precipitates onto the drum.
  • the brown pulp to be washed in pressure diffusers and atmospheric washing diffusers and the washing liquid are conveyed to opposite ends of a diffuser.
  • the pulp moves between screen rings.
  • the washing liquid is fed into the pulp flow, and the dis- placed liquid is removed through the screen rings, into a filtrate tank.
  • the washed pulp is removed from the diffuser by means of a specific doctor. Dur- ing the washing, the entire screen ring system moves cyclically up and down.
  • the screen surface is cleaned by the counter-motion against the direction of travel of the pulp.
  • a modern brown pulp washing line comprises the above- disclosed washers, wherein a plurality of such washers have been arranged in series.
  • the washers are coupled in order to enable a perfect counter-current washing to be achieved.
  • the cleanest washing liquid which can be warm water or adequately clean, recycled water fraction from a paper mill, usually secondary condensate of an evaporating plant, is conveyed to the last washing step.
  • the filtrate is discharged to become the washing liquid in the previous washing step, and the most concentrated liquor is removed through a digester house to the evaporating plant.
  • the operation of the washing line devices is usually controlled by a device-specific adjusting system, which is practically always an automatic system.
  • the aim of the adjusting system is to adjust the operation of a washing line and possibly of other washing-dependent functions to be optimal economically.
  • Other washing-dependent functions mainly include a screening department and an evaporating plant.
  • the washing efficiency is to be determined on the basis of on-line measurements.
  • Washing loss describes the amount of dirt that is transferred together with the pulp to the next washing step. It is presented as a Na 2 SO 4 content in post-washing pulp to indicate inorganic washing loss remaining in the stock. A COD (chemical oxygen demand) value, which describes the amount of organic material remaining in the pulp better than the Na 2 SO 4 content, is also used.
  • the only known possible way to measure washing loss on- line is to measure conductivity. This, however, gives very unreliable results since measuring devices get dirty with time, which causes drifting errors. In practice, washing loss can only be determined by laboratory analyses, i.e. in practice it cannot be applied to optimization or on-line adjustment of washing.
  • a dilution factor represents the amount of washing liquid used per a certain number of washings.
  • a displacement ratio describes the amount of dissolved material removed from pulp during washing. However, the displacement ratio cannot be reliably measured on-line; therefore, no reliable results will be obtained from adjustments based thereon.
  • a Norden efficiency factor indicates the correspondence between the number of perfect dilution-extraction processes and the real process under examination. The Norden efficiency factor can be used for adjusting, but the result is a complex multivariable model which, in order to operate, requires a highly complex adjusting system and detailed information on the washing process. These, however, are not generally available, so extensive and expensive investments in adjustment and measuring devices are required in order to apply the model.
  • the method disclosed in US Patent No. 5,282,131 aims to avoid the problems caused by long delay times in the adjustment of washing.
  • the publication discloses a method for predicting the amount of dry solids to be conveyed to the evaporating plant. The method can only be applied to drum filter washers. The disclosed method does not work with the existing washers since the technical properties of the equipment restrict the range of the amount of clean washing water to be fed into a washing line to be so narrow that it cannot be adjusted in the extent required by the method. Furthermore, the model does not work if something unexpected occurs during the washing process.
  • An object of the present invention is to provide a novel and improved method of adjusting and measuring a brown pulp washing process.
  • the method of the invention for adjusting a pulp washing process is characterized by
  • the method of the invention for determining the efficiency of a pulp washing process is characterized by [0023] modelling the maximum washing capacity of the washing process
  • the idea underlying the invention is that the quality of a washing process is determined by determining its maximum washing capacity. Furthermore, the idea underlying a preferred embodiment of the invention is that the efficiency of a washing process is determined on-line. Further, the idea underlying a second preferred embodiment of the invention is that the maximum washing capacity of a washing process is described as its washing potential in diffusion. Furthermore, the idea underlying a third preferred embodiment of the invention is that the washing potential in diffusion is determined in the following manner:
  • a fourth preferred embodiment of the invention comprises measuring the washing process of an entire washing line.
  • An advantage of the invention is that it enables the efficiency of substantially all known washers to be monitored, including atmospheric diffusers, pressure diffusers, digester washings, press-type washers, drum washers, wire washers and centrifuge-type washers. A slow diffusion taking place in the pulp tanks of a washing line can also be taken into account.
  • the method of the invention is applicable both to displacement and dilution wash- ings.
  • the implementation of the method in already existing washers and washing lines does not require expensive changes in the measuring equipment thereof, but only the variables that can be measured or determined from the process can be selected to be used.
  • the method can be applied to any commonly used washing process, i.e. a washer or a washing line.
  • a further advan- tage of the method of the invention is that it comprises no mathematically exact formulas but only some basic rules, according to which e.g. the delay time and concentration differences should be as extensive as possible. Consequently, it is easy to optimize the washing result.
  • Figure 1 is a schematic and highly simplified view showing a washer to which a method of the invention has been applied, and
  • Figure 2 is a schematic and highly simplified view showing an adjustment event of the invention.
  • the washing potential in diffusion describes the washing efficiency under the prevailing conditions and which washing factors affect the washing efficiency.
  • the washing efficiency is described by indicating the maximum possible theoretical washing efficiency that can be obtained. The higher the washing potential in diffusion, the more efficient the washing.
  • the washing potential describes the maximum washing capacity of a washing liquor. It depends e.g. on the electric conductivity of the washing liquor. Diffusion refers to the movement of substances due to the random movement of mole- cules.
  • the washing potential in diffusion describes the movement of liquid molecules between the pulp to be washed under examination and the washing liquid, wherein the liquid molecules in the pulp fibres are replaced by other liquid molecules.
  • the washing potential in diffusion is based on a completely new approach to a washing process wherein washing is carried out by levelling the concentrations of the components to be removed from the pulp to be washed in the washing medium and in the pulp to be washed.
  • the driving force of the washing is the concentration difference between the components.
  • the basics of the approach can be further led to the second law of thermodynamics.
  • the method of the invention for determining and adjusting the efficiency of a washing process differs from the known methods in that the method of the invention allows only directly-measurable variables, such as flows, temperatures, consistencies and filtrate conductivity, to be used. It is also irrelevant which variables are to be or can be used or what the measuring devices of the washing equipment are since the washing potential in diffusion is capable of utilizing all washing variables.
  • the washing potential in diffusion is capable of describing all washing processes in an unbiased manner, which is impossible in the prior art solutions. Norden efficiency factors, for example, do not describe washing in an unbiased manner but, according to these fac- tors, displacement washing is always more efficient than dilution washing, which is not true.
  • An entire brown pulp washing line is adjusted and optimized. As is well known to one skilled in the art, washing is carried out as dictated by other partial processes in a pulp manufacturing process.
  • the arrangement of a brown pulp washing line is determined on the basis of the pulp to be washed and the manner in which it is cooked.
  • Drum washers and press washers can be used for washing brown pulp obtained from batch cooking.
  • the washing line further comprises pulp and filtrate tanks that serve as intermediate stor- ages and buffers between cooking and washing. The volume of the tanks preferably enables substantially continuous washing.
  • At least one diffuser is first applied to continuous cooking and, subsequently, other washer types.
  • the measurable and adjustable variables of the exemplary washing line are: 1. conductivity of the washing liquid to be conveyed to the washing line
  • the washing potential in diffusion can be utilized for optimiz- ing the washing process e.g. by calculating an estimate of the washing potential in diffusion of the entire washing process after half the washing time t has elapsed. This enables adjustment procedures to be carried out in order to optimize the process.
  • the efficiency of the washing of a washing line can also be determined by calculating washer- or washing-step-specific washing potential in diffusion separately for each washer or washing step in the line.
  • the washing line is divided into successive steps. Integration of a step is stopped at a point in time when the particular step ends, and the calculation is continued by integrating the next step. Finally, all steps are summed up, which gives the washing potential in diffusion of the entire washing line. Naturally, the calculation has to take into account the pulp tanks on the line as well as other process steps that usually even out concentration differences.
  • the washing taking place in a single washer or washing step can also be divided into two or more steps.
  • the washing potential in diffusion of each step is determined separately, and the washing potential in diffusion of the entire washer or washing step is obtained by summing up the washing potentials in diffusion of the steps.
  • the washing taking place in a TwinRoll press washer for example, can be divided into three parts: the first step before the nip of a press, the second step the nip, and the third step the pulp conveyor screw after the nip.
  • the washing potential in diffusion is an exponential model; therefore, it takes into account the dynamics of a process. It also takes into account the way in which a change in different variables affects the washing efficiency.
  • the washing potential in diffusion also takes into account so-called slow diffusion, i.e. the washing efficiency of the various pulp tanks in a washing line, which is a most essential feature as far as the modern washing line thinking is concerned.
  • slow diffusion i.e. the washing efficiency of the various pulp tanks in a washing line
  • pulp has a very long delay time.
  • the washing efficiency of a filtrate tank can be determined by measuring the consistency of the pulp conveyed to the tank and the pulp conveyed therefrom. This gives a concentration change.
  • the washing potential in diffusion can be calculated for the particular tank.
  • the washing potential in diffusion can be applied for describing the efficiency of different washers and comparing changes in efficiency with each other. It can be applied as a so-called Soft Sensor for describing the operation of washers.
  • a Soft Sensor is a model of a non-measurable variable, which is based on other, measurable variables. It can also consist of modification of measured information into a more usable form. Since there are several characteristics of brown pulp that cannot be measured directly, Soft Sensors are very useful in this connection.
  • FIG. 2 is a schematic and highly simplified view showing an adjustment event of the invention.
  • a washing line 2 to be adjusted comprises one or more washers.
  • the washers and/or washing liquid of the wash- ing line 2 is/are measured for the above-mentioned variables, for example.
  • Measurement results 3 are fed into an adjusting device 4 adjusting the operation of the washing line.
  • the adjusting device 4 comprises a model describing the maximum washing capacity of the washing line 2.
  • the adjusting device 4 processes the measurement results 3 and determines an adjustment message 5 on the basis of these results.
  • the adjustment message 5 is transmitted to the washing line wherein actuators carry out the procedures according to the adjustment message 5.

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  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Wood Science & Technology (AREA)
  • Paper (AREA)

Abstract

L'invention concerne un procédé de réglage d'un processus de lavage pâte, et la mesure de son efficacité. Ces procédés consistent à modeler la capacité de lavage maximale du processus de lavage, sélectionner les variables du processus de lavage à mesurer, mesurer les variables du procédé de lavage, régler le procédé de lavage ou déterminer l'efficacité du procédé de lavage au moyen du modèle et des mesures.
PCT/FI2002/000486 2001-06-21 2002-06-06 Procede de reglage d'un processus de lavage de pate et determination de son efficacite Ceased WO2003000984A1 (fr)

Priority Applications (3)

Application Number Priority Date Filing Date Title
EP02727635A EP1425466A1 (fr) 2001-06-21 2002-06-06 Procede de reglage d'un processus de lavage de pate et determination de son efficacite
US10/479,951 US20040134630A1 (en) 2001-06-21 2002-06-06 Method of adjusting pulp washing process and determining efficiency
CA002450884A CA2450884A1 (fr) 2001-06-21 2002-06-06 Procede de reglage d'un processus de lavage de pate et determination de son efficacite

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FI20011336A FI20011336A0 (fi) 2001-06-21 2001-06-21 Menetelmä sellumassan pesuprosessin säätämiseksi ja tehokkuuden määrittämiseksi
FI20011336 2001-06-21

Publications (1)

Publication Number Publication Date
WO2003000984A1 true WO2003000984A1 (fr) 2003-01-03

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Application Number Title Priority Date Filing Date
PCT/FI2002/000486 Ceased WO2003000984A1 (fr) 2001-06-21 2002-06-06 Procede de reglage d'un processus de lavage de pate et determination de son efficacite

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US (1) US20040134630A1 (fr)
EP (1) EP1425466A1 (fr)
CA (1) CA2450884A1 (fr)
FI (1) FI20011336A0 (fr)
WO (1) WO2003000984A1 (fr)

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9852649B2 (en) * 2001-12-13 2017-12-26 Mind Research Institute Method and system for teaching vocabulary
AU2011332305A1 (en) * 2010-11-23 2013-06-13 Rhodia Operations Guar process monitoring methods
US20150376834A1 (en) * 2013-02-07 2015-12-31 University Of Maine System Board Of Trustees Extraction of lignocellulosics for production of fibers and a precipitate-free hemicellulose extract
JP2023502066A (ja) 2019-11-14 2023-01-20 バックマン ラボラトリーズ インターナショナル，インコーポレイティド パルプ工場における褐色洗浄処理の予測制御システム及び方法
AR122640A1 (es) * 2020-06-17 2022-09-28 Suzano Sa Método para tratar un condensado en un proceso de fabricación de pulpa

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6074522A (en) * 1997-08-01 2000-06-13 Seymour; George W. Process to optimize pulp washing variables

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Publication number Priority date Publication date Assignee Title
US4732651A (en) * 1984-08-31 1988-03-22 International Paper Company Method for monitoring and controlling a pulp washing system
US5282131A (en) * 1992-01-21 1994-01-25 Brown And Root Industrial Services, Inc. Control system for controlling a pulp washing system using a neural network controller

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6074522A (en) * 1997-08-01 2000-06-13 Seymour; George W. Process to optimize pulp washing variables

Non-Patent Citations (7)

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Title
CULLINAN HARRY T.: "The efficiency of pulp washing with regard to lignin removal", APPITA JOURNAL, vol. 44, no. 2, 1991, pages 91 - 94, XP002956512 *
DATABASE PAPERCHEM [online] SAVITSKII S.N. ET AL.: "Modeling of pulp washing for process control", XP002956508, retrieved from 00312622 accession no. Dialog Database accession no. (AB6308411) *
DATABASE PAPERCHEM [online] SUKHANOVA N.N. ET AL.: "Static model of pulp washing in continuous-process vertical digesters", XP002956510, retrieved from 00312625 accession no. Dialog Database accession no. (AB6308414) *
MANCHIRAJU S. ET AL.: "Brown stock washer performance and control", DOREST PRODUCTS SYMPOSIUM (JAMES D. LISIUS), 1989 - 1990, SAN FRANCISCO, CHICAGO, pages 61 - 66, XP002956509 *
PERKINS J.K. ET AL.: "Brown stock washing efficiency displacement ratio method of determination", TAPPI, vol. 37, no. 3, March 1954 (1954-03-01), pages 83 - 89, XP002956511 *
SB. NAUCHN. TR. VNIIB, AVTOMAT. ALGORIT. PROTSESSOV UPRAVLENIYA TSELLYUL.-BUMAZH. PROIZVOD. (SKOPIN, I.I., ED.), 1988, pages 35 - 43 *
SB. NOUCHN. TR. VNIIB, AVTOMAT. ALGORIT. PROTSESSOV UPRAVLENIYA TSELLYUL.-BUMAZH. PROIZVOD. (SKOPIN, I.I., ED.), 1988, pages 43 - 54 *

Also Published As

Publication number Publication date
CA2450884A1 (fr) 2003-01-03
US20040134630A1 (en) 2004-07-15
EP1425466A1 (fr) 2004-06-09
FI20011336A0 (fi) 2001-06-21

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