WO2021232132A1 - Procédé de débouchage ou de nettoyage d'un tamis dans un lessiveur de cuisson kraft à cuisson continue - Google Patents

Procédé de débouchage ou de nettoyage d'un tamis dans un lessiveur de cuisson kraft à cuisson continue Download PDF

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Publication number
WO2021232132A1
WO2021232132A1 PCT/BR2021/050221 BR2021050221W WO2021232132A1 WO 2021232132 A1 WO2021232132 A1 WO 2021232132A1 BR 2021050221 W BR2021050221 W BR 2021050221W WO 2021232132 A1 WO2021232132 A1 WO 2021232132A1
Authority
WO
WIPO (PCT)
Prior art keywords
screen
washing liquor
ring
liquor
digester
Prior art date
Application number
PCT/BR2021/050221
Other languages
English (en)
Inventor
Carlos Verciano Costa SANTOS
Carlos Alberto MOROMIZATO
Gláucio Francisco DE MOURA
Jeferson Borges DA SILVA
Jonatas Carlos Pereira DE ARAÚJO
Lucas Ramos LIMA
Maria Emília Drummond BLONSKI
Paulo Jose DE CASTRO
Ricardo Gardiman SAVACINI
Thais Simões De Almeida RIBEIRO
Valdemir Rodrigues ALVES
Original Assignee
Suzano S.A.
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 Suzano S.A. filed Critical Suzano S.A.
Priority to FI20226149A priority Critical patent/FI20226149A1/fi
Priority to CN202180036782.2A priority patent/CN115667621A/zh
Priority to SE2251530A priority patent/SE2251530A1/en
Priority to BR112022023799A priority patent/BR112022023799A2/pt
Publication of WO2021232132A1 publication Critical patent/WO2021232132A1/fr

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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
    • D21C7/00—Digesters
    • D21C7/12—Devices for regulating or controlling
    • 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
    • D21C7/00—Digesters
    • D21C7/14—Means for circulating the lye

Definitions

  • the present invention is related to a method for unplugging or cleaning a screen in a continuous process kraft cooking digester process.
  • Plugging of the screens may be caused by operational instabilities (overheating) or by the presence of calcium carbonate incrustations.
  • the main symptom of this clogging is an increase in the pressure differentials of the screens (SPD), followed by a reduction in the extraction flow.
  • SPD value becomes critical, alkalinization procedures are used, with hot liquor or cold liquor. These alkalinizations tend to become more frequent with the increase of the lifetime of the digestor.
  • Plugging occurs when the cellulose material is retained at the screen slots
  • Calcium carbonate incrustations may also occur at the screen and may lead to clogging of the screen slots, also decreasing cooking liquid to transpose the screen. Both situations produce an increase in the pressure differentials of the screens (SPD), followed by a reduction in the extraction flow.
  • SPD pressure differentials of the screens
  • the present invention is related to a continuous Kraft cooking digester comprising a plurality of screens, each screen having a digestion zone facing side and a digestor wall facing side, the plurality of screens disposed in a screen ring, the screen ring having at least one screen flow outlet leaving the digestor and at least one screen flow inlet entering the screen ring; the at least one screen flow inlet entering the screen ring providing a washing liquor to the screen for: unplugging, alkalinization treatment or both, without stopping the system.
  • Fig. 2 is a depiction of screens rings located in a digester.
  • Fig. 3 is a side view of the interior of a screen ring while spent liquor leaves the cooking digester via an outlet.
  • FIG. 4 is a side view of the interior of a screen ring while washing liquor enters the screen ring via an inlet.
  • FIG. 5 is a side view of the interior of a screen ring while washing liquor enters the screen ring via the spend liquor outlet.
  • the term “cooking liquor” is meant to be a treatment liquid that is intended to be added to the cellulose material flowing in the digestion vessel, i.e. the digestor.
  • the cooking liquor may be kraft cooking liquor comprising sodium hydroxide and sodium sulfide, but could also comprise steam, hot spent cooking liquor, i.e. black liquor from a previous digestion, as well as a mixture of two or more of following liquids: black liquor, white liquor, dilution liquids from subsequent washing stages (i.e. wash filtrate from such wash stages), steam (added directly in order to heat the treatment liquor) or its condensates.
  • Black liquor for instance, is an aqueous solution made up of organic materials, such as lignin, resinous compounds, polysaccharides, alcohols. Black liquor also contains inorganic materials from the pulping or cooking system. White liquor is understood as an aqueous mixture of sodium hydroxide and sodium sulfide.
  • washing liquor is meant to be a hot washing liquor comprising a weak black liquor, a strong black liquor, a white liquor or mixtures thereof.
  • cellulose material is meant to be fragments of wood, such as wood chips, sawdust, and preferably wood chips, but also any other material originated from wood in a comminuted form, such as sawdust or pin chips, all obtained from either hardwood or softwood or annual plants.
  • the chips undergo gradual dissolving, and a large fraction, typically approximately 50 percent in a Kraft process, of the original wood is dissolved in the cooking fluid in the form of metals and organic material such as, for example, turpentine, tall oil and hemicellulose, and disappears with the black liquor to the evaporation process.
  • a large fraction typically approximately 50 percent in a Kraft process
  • organic material such as, for example, turpentine, tall oil and hemicellulose
  • the screen structures 6 are positioned at the digester wall in the form of square screen surfaces, either as a continuous line of screens, or alternating a screen and a blunt square, around the complete circumference of the digester wall, composed of several square screen surfaces, forming a screen ring.
  • a screen and blunt surface alternate, resembling a chessboard pattern in the screen section of the digester (FIG. 2).
  • a first and a second screen section may be arranged in the upper (“hot”) and lower (“cold”) part of the digester, respectively.
  • the first screen section is arranged in the upper part of the digester and second screen section 7 is arranged in the lower part.
  • the vertical distance between the lowermost part of the first screen section (6) and the uppermost part of the second screen section (7) may be, e.g. 5- 12 m.
  • a screen structure is for draining treatment liquor from a suspension of comminuted cellulose material and treatment liquor in an substantially cylindrical digester vessel, with the screens in close proximity to the inside of the digestor wall 8 of the digester 1 forming a screen chamber 9 between the wall 8 of the digester 1 and the screen 10.
  • a typical screen configuration is a slotted plate equipped with screen slots SS which are made by either machine milling or water cutting jet technique, and the perforated or slotted plate facing the suspension of cellulose material in the digestion zone.
  • Another configuration has bars facing the suspension of cellulose material, and the bars are preferably vertically arranged in parallel to each other and forming a screen slot SS between neighboring bars, and the screen is positioned at a distance from the digester wall 8 enabling a free unobstructed flow of withdrawn cooking liquor between the digester wall and the screen.
  • the combination of screen structure 6 and screen chamber 9 form the screen ring 13.
  • the withdrawn cooking liquor is removed by outlets 11 .
  • the screen slot SS typically has a dimension between 2-10 mm, where the slot is adapted to the quality of chips that are used in the cooking process. Chips that are better defined and well-chopped with a low content of finely divided material are cooked in digesters having larger screen slots, while chips with a higher content of finely divided material require a smaller screen slot.
  • the digester wall 8 is the wall of the pressure vessel and the screens 10 are positioned inside the digester wall facing the suspension of comminuted cellulose material as it descends through the digester as a pulp column in the downwards.
  • the screens may be arranged to have a digestion retention time of between 15-20 minutes.
  • Kraft cooking digester comprising a plurality of screens 10, each screen having a digestion zone I facing side and a digestor wall 8 facing side, the plurality of screens 10 disposed in a screen ring 13, the screen ring 13 having at least one screen flow outlet 11 leaving the digestor and at least one screen flow inlet 12 entering the screen ring 13, the screen flow inlet 12 entering the screen ring 13 providing a washing liquor into the screen for: unplugging, alkalinization treatment, or both, without stopping the system.
  • Unplugging is to be understood as the releasing of pluggings at the screen and alkalinization treatment is to be understood as washing away incrustations at the screen 10, i.e. at the screen 13 bars.
  • the alkalinization is a hot alkalinization.
  • the present invention provides an alkalinization method for a screen 10 in a continuous process Kraft cooking digester comprising applying an incoming flow 100 of washing liquor by means of a inlet 12 towards the screen 10 in a screen ring 13, the washing liquor trespassing the screen 10 into a digestion zone I, providing at least one of: unplugging, alkalinization treatment, or both, without stopping the system.
  • the cooking liquor is withdrawn from the screen chamber 9. If this screen ring screen is positioned at the lower extraction zone, the extracted cooking liquor may be sent to a heat exchanger for heating. During extraction, the outlet 11 allows the spent liquid to leave the screen chamber 9. Meanwhile the inlet 12 is closed.
  • the extracted cooking liquor i.e. white liquor
  • the extracted cooking liquor may be sent to a conduit carrying a black liquor and conveyed to the inlet 12 of any of the screen rings 13. While the washing liquor is fed into the inlet 12, the outlet 11 is closed.
  • the washing liquor is conveyed from the heat exchanger 200 to the outlet 11 of a screen in a screen ring 13, reversing the flow of the cooking liquor and achieving the screen chamber 9, the screen 10 and the screen slots SS.
  • washing liquor when washing liquor reaches the screen 10 it produces a counter-flow that flushes out the debris placed at the screen slots SS, produces an erosion of incrustations in the screen 10 surface, or both.
  • the washing liquor may be flushed to the screen chamber 9 through a single dedicated inlet 12.
  • several dedicated inlets 12 may serve each screen chamber 9 at a screen ring if the screen chambers in the same screen ring are not in fluid communication with each other.
  • several dedicated inlets 12 may serve a single screen ring 13 if the screen chambers 9 in the same screen ring are in fluid communication with each other.
  • the inwards-flowing washing liquor displaces the cooking liquor towards the screens 10 and into the digester interior I.
  • the washing liquor when passing through the screen slots SS formed between neighboring bars, the washing liquor produces removal of the debris trapped between the bars. The passage of washing liquor displaces the debris back into the digester interior I.
  • the alkaline washing liquor produces the removal or erosion of incrustations, such as calcium carbonate.
  • the incoming flow of washing liquor to the screen is provided by an incoming dedicated conduit in connection to the outlet 11.
  • the outlet becomes an inlet 12 when the flow is reversed by means of the incoming washing liquor displacing the outcoming spend liquor towards the interior of screen chamber 9 and the interior of the digester.
  • each inlet 12 is provided with a dedicated conduit that supplies washing liquor.
  • one inlet 12 may be connected to a conduit leaving a heat exchanger that heats the washing liquor, may it be a black liquor, for instance.
  • a pump at the conduit may be provided to increase pressure, if necessary.
  • the washing liquors may originate from heating purged weak black liquor or pumped heated white liquor.
  • both are used, depending on the level of alkalinization needed, for instance, when it is necessary to adjust the desired residual and eliminating the impact of increasing residual alkali for evaporation resulting from alkalinization.
  • the conduits in connection with the inlets 12 are connected to reservoirs of white liquor and/or black liquor or, alternatively, to a heat exchanger also connected to one of such reservoirs.
  • substantially all the white liquor and the black liquor used are locally produced.
  • a screen cleaning method in a continuous Kraft cooking digester during operation comprising applying an incoming flow 100 of washing liquor to a screen 10, the incoming flow trespassing the screen towards the interior I of the digester providing at least one of: unplugging, alkalinization treatment, or both, without stopping the system.
  • the incoming flow 100 is provided by a conduit in connection with the screen ring 13 by an inlet 12.
  • the incoming conduit is a dedicated conduit, which means the conduit serves one only screen ring 13.
  • any configuration of inlets in the screen rings 13 may be accomplished. For instance, at FIG. 6, only the screen rings of the upper screen section may receive the incoming dedicated conduits conducting the incoming washing liquor.
  • all screen rings at the upper part of the digestor may receive the conduits and only two screen rings at the lower part of the digestor may receive the dedicated conduits conducting the incoming washing liquor.
  • every screen ring 13 of a screen section may receive at least one dedicated conduit.
  • a first washing liquor 100 may be fed into one screen, a second washing liquor may be fed into another screen and third washing liquor may be fed into a third screen, concordantly.
  • all screens are capable of receiving washing liquor, i.e. all screens may receive washing liquor at the same time or in tandem, following an established order, conducted by a program or a feeding logic.
  • the order of flushing the screens is usually dependent of the level of incrustation and/or severity of plugging or the cleaning needed at the particular screen or screen assembly or screen ring. However, preferably, the order is dictated by preventive procedure dependent of the operation needs.
  • the washing liquor enters the screen ring 13 once its pressure overcomes the pressure inside the screen chamber 9, the difference of pressure between the screen chamber 9 and the incoming dedicated conduit should be at a noticeable differential.
  • the incoming washing liquid should be pumped at least at a differential of 10%.
  • the washing liquid may be at a pressure of about 4.95 bars.
  • the pressure could reach values up to 10 bars.
  • the washing liquid flow 100 may vary from 150-450m 3 /h. Ideally, the washing liquid flow may be from 0.5-3.5 m 3 /ADt (Air Dry Ton), preferably from 1.5-3 m 3 /ADt.
  • a desired pressure for an unplugging procedure may be of 7 bars. If removing incrustations on a screen in a continuous process Kraft cooking digester is intended, intermediary flows may be used as 2 m 3 /ADt. Nonetheless, higher pressures may be used as preventive measures and lower pressures may be used for unplugging procedures.
  • the washing liquor may vary the amounts of weak black liquor, strong black liquor or white liquor, or their mixtures. For instance, a washing liquor may be 90% weak black liquor and 10% white liquor for a preventive operation, or, in another aspect, it may comprise 60% of white liquor for cooking a severe plugging at the screen.
  • the screen ring closer to the digestor top may receive a washing liquor for 10 minutes at 150 m 3 /h, followed by the ring immediately below, preferably after the interruption of the washing liquor flow into the first ring, flow of washing liquor into the second screen ring may commence and last for, e.g. another 10 minutes.
  • a third screen ring will receive the washing liquor after completion of the second ring washing, successively, until the fifth screen ring is alkalinized and the alkalinization of the upper screen section is completed.
  • the alkalinization of another screen section may begin, with each of its screen ring receiving the hot alkalinization, successively, in tandem, for example, and for 10 minutes at, for instance, 450m 3 /h.
  • This procedure may accommodate a longer time for a given screen ring.
  • one of the screen rings of a six screen ring section may be subjected to longer periods or volumes.
  • a screen ring may be subjected to a hot alkalinization for 4 hours, instead of 10 minutes.
  • Completion of the screen section may be met with a discontinuation of the hot alkalinization for some time, e.g. 4 hours, before the cycle again starts again at. i.e. a screen ring of the upper screen section, or may start immediately after finishing the all screen rings at another screen section.
  • the process may be automatic and instructions for opening and closing the valves at the dedicated conduits in connection to the inlets may be performed manually or by a programmed system, without stopping the system. Alternatively, this procedure may be random, for instance, the operator may decide a more adequate order due the needs of the immediate process.
  • the pressure at the washing liquor 100 at the inlet 12 of each screen section 13 is 10% higher than the pressure of the withdrawn liquors at the screen chamber 9. In this way, an efficient displacement of debris is achieved once the washing liquor moves from the inlet 12 towards the screen chamber 9 and to the digestor interior I, and it is possible to maintain a stable chip column movement.
  • the present methods may be also accomplished by the steps of: a) supplying a washing liquor to a first screen ring 13 via a first inlet 12, the first inlet in connection with a first dedicated conduit having a first washing liquor controlling valve, opening the first washing liquor controlling valve and supplying the washing liquor to the first screen ring 13; supplying a washing liquor to the first screen ring for 5-300 minutes; closing the first washing liquor controlling valve; repeating the steps for a subsequent screen ring, i.e.
  • the first ring should be understood as the first ring to receive the washing liquid, not necessarily a first ring in a screen section.
  • the first screen ring may be any ring in a digestor, and the subsequent ring may be any other screen ring in the digestor.
  • the method may be completely automated, i.e., following a previously established order pattern, without stopping the system.
  • the present invention enables, a reduction of losses caused by operation stops to perform hot alkalinizations in the digestor; thus providing greater operational flexibility due to the feasibility of hot alkalinizations whenever necessary, even preventively, without the clogging of the screens reaching critical levels that impair the stability of the digestor.

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  • Paper (AREA)

Abstract

La présente invention concerne un procédé de débouchage ou de nettoyage d'un tamis dans un procédé de lessiveur de cuisson kraft à cuisson continue, le lessiveur de cuisson kraft continue comprenant une pluralité de tamis, chaque tamis ayant un côté faisant face à la zone de lessivage et un côté faisant face à la paroi de lessiveur, la pluralité de tamis étant disposés dans une mâchoire annulaire de tamis, la mâchoire annulaire de tamis ayant au moins une sortie d'écoulement de tamis sortant du lessiveur et au moins une entrée d'écoulement de tamis entrant dans la mâchoire annulaire de tamis ; l'au moins une entrée d'écoulement de tamis entrant dans la mâchoire annulaire de tamis fournissant une lessive au tamis pour : le débranchement, le traitement d'alcalinisation ou les deux, sans arrêter le système.
PCT/BR2021/050221 2020-05-22 2021-05-24 Procédé de débouchage ou de nettoyage d'un tamis dans un lessiveur de cuisson kraft à cuisson continue WO2021232132A1 (fr)

Priority Applications (4)

Application Number Priority Date Filing Date Title
FI20226149A FI20226149A1 (fi) 2020-05-22 2021-05-24 Menettely jatkuvatoimisessa sulfaattikeittimessä olevan koksin siivilän tukkeutumisen poistamiseksi tai puhdistamiseksi
CN202180036782.2A CN115667621A (zh) 2020-05-22 2021-05-24 连续法牛皮纸蒸煮塔中筛网的解堵或清洁方法
SE2251530A SE2251530A1 (en) 2020-05-22 2021-05-24 Method for unplugging or cleaning a screen in a continuous process kraft cooking digester
BR112022023799A BR112022023799A2 (pt) 2020-05-22 2021-05-24 Digestor de cozimento kraft contínuo, método de alcalinização, método de desentupimento, método de prevenção, método de limpeza, licor de lavagem e método de fornecimento de um licor de lavagem

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US202063029134P 2020-05-22 2020-05-22
US63/029,134 2020-05-22

Publications (1)

Publication Number Publication Date
WO2021232132A1 true WO2021232132A1 (fr) 2021-11-25

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Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/BR2021/050221 WO2021232132A1 (fr) 2020-05-22 2021-05-24 Procédé de débouchage ou de nettoyage d'un tamis dans un lessiveur de cuisson kraft à cuisson continue

Country Status (7)

Country Link
CN (1) CN115667621A (fr)
BR (1) BR112022023799A2 (fr)
CL (1) CL2022003257A1 (fr)
FI (1) FI20226149A1 (fr)
SE (1) SE2251530A1 (fr)
UY (1) UY39227A (fr)
WO (1) WO2021232132A1 (fr)

Citations (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3711367A (en) * 1970-02-11 1973-01-16 Kamyr Ab Screening device in cellulose digesters
US4040901A (en) * 1976-08-16 1977-08-09 Esco Corporation Mounting for sectional screen
US4568419A (en) * 1984-02-27 1986-02-04 Laakso Oliver A Method of treating comminuted cellulosic fibrous material in a vertical vessel
WO1994025668A1 (fr) * 1993-05-04 1994-11-10 Kamyr, Inc. Reduction des matieres solides dissoutes pendant la production de pate a papier
JPH0995884A (ja) * 1995-10-02 1997-04-08 Kubuana Parupingu Kk 蒸解釜内部スクリーンの閉塞防止装置
US5681453A (en) * 1993-04-05 1997-10-28 Kvaerner Pulping Technologies Aktiebolag Reciprocal movable screens in a vertically elongated vessel
US5770072A (en) * 1994-02-18 1998-06-23 Kvaerner Pulping Ab Multiple inlet valve with means to isolate each inlet individually and direct a reverse flow therethrough
US5824188A (en) * 1993-05-04 1998-10-20 Ahlstrom Machinery Inc. Method of controlling the pressure of a continuous digester using an extraction-dilution
US20090038767A1 (en) * 2007-08-07 2009-02-12 Andritz Inc. Method and System for Semi-Chemical Pulping
US20100071864A1 (en) * 2008-09-23 2010-03-25 Andritz Inc. Hinged screen plate for drum pulp washer and method for cleaning the plate
US7799173B2 (en) * 2007-01-18 2010-09-21 Andritz Inc. Screen plates having diagonal slots with curved inlets for a digester
BR112013000565A2 (pt) * 2010-07-09 2017-09-19 Metso Paper Sweden Ab método e sistema para impregnação de cavacos

Patent Citations (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3711367A (en) * 1970-02-11 1973-01-16 Kamyr Ab Screening device in cellulose digesters
US4040901A (en) * 1976-08-16 1977-08-09 Esco Corporation Mounting for sectional screen
US4568419A (en) * 1984-02-27 1986-02-04 Laakso Oliver A Method of treating comminuted cellulosic fibrous material in a vertical vessel
US5681453A (en) * 1993-04-05 1997-10-28 Kvaerner Pulping Technologies Aktiebolag Reciprocal movable screens in a vertically elongated vessel
WO1994025668A1 (fr) * 1993-05-04 1994-11-10 Kamyr, Inc. Reduction des matieres solides dissoutes pendant la production de pate a papier
US5824188A (en) * 1993-05-04 1998-10-20 Ahlstrom Machinery Inc. Method of controlling the pressure of a continuous digester using an extraction-dilution
US5770072A (en) * 1994-02-18 1998-06-23 Kvaerner Pulping Ab Multiple inlet valve with means to isolate each inlet individually and direct a reverse flow therethrough
JPH0995884A (ja) * 1995-10-02 1997-04-08 Kubuana Parupingu Kk 蒸解釜内部スクリーンの閉塞防止装置
JP2835825B2 (ja) * 1995-10-02 1998-12-14 クヴァナパルピング株式会社 蒸解釜内部スクリーンの閉塞防止装置
US7799173B2 (en) * 2007-01-18 2010-09-21 Andritz Inc. Screen plates having diagonal slots with curved inlets for a digester
US20090038767A1 (en) * 2007-08-07 2009-02-12 Andritz Inc. Method and System for Semi-Chemical Pulping
US20100071864A1 (en) * 2008-09-23 2010-03-25 Andritz Inc. Hinged screen plate for drum pulp washer and method for cleaning the plate
BR112013000565A2 (pt) * 2010-07-09 2017-09-19 Metso Paper Sweden Ab método e sistema para impregnação de cavacos

Also Published As

Publication number Publication date
UY39227A (es) 2021-12-31
FI20226149A1 (fi) 2022-12-21
CN115667621A (zh) 2023-01-31
SE2251530A1 (en) 2022-12-21
BR112022023799A2 (pt) 2022-12-27
CL2022003257A1 (es) 2023-06-30

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