EP4590895B1 - Zweistufige imprägnierung in der ht-ctmp-produktion - Google Patents

Zweistufige imprägnierung in der ht-ctmp-produktion

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Publication number
EP4590895B1
EP4590895B1 EP23837246.0A EP23837246A EP4590895B1 EP 4590895 B1 EP4590895 B1 EP 4590895B1 EP 23837246 A EP23837246 A EP 23837246A EP 4590895 B1 EP4590895 B1 EP 4590895B1
Authority
EP
European Patent Office
Prior art keywords
wood chips
impregnation
chips
impregnated
zone
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.)
Active
Application number
EP23837246.0A
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English (en)
French (fr)
Other versions
EP4590895A1 (de
Inventor
Thomas Lindstedt
Thomas Granfeldt
Per Engstrand
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.)
Billerud AB
Original Assignee
Billerud AB
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Publication of EP4590895A1 publication Critical patent/EP4590895A1/de
Application granted granted Critical
Publication of EP4590895B1 publication Critical patent/EP4590895B1/de
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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
    • D21C1/00—Pretreatment of the finely-divided materials before digesting
    • D21C1/06—Pretreatment of the finely-divided materials before digesting with alkaline reacting compounds
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21B—FIBROUS RAW MATERIALS OR THEIR MECHANICAL TREATMENT
    • D21B1/00—Fibrous raw materials or their mechanical treatment
    • D21B1/02—Pretreatment of the raw materials by chemical or physical means
    • D21B1/021—Pretreatment of the raw materials by chemical or physical means by chemical means
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21B—FIBROUS RAW MATERIALS OR THEIR MECHANICAL TREATMENT
    • D21B1/00—Fibrous raw materials or their mechanical treatment
    • D21B1/04—Fibrous raw materials or their mechanical treatment by dividing raw materials into small particles, e.g. fibres
    • D21B1/12—Fibrous raw materials or their mechanical treatment by dividing raw materials into small particles, e.g. fibres by wet methods, by the use of steam
    • D21B1/14—Disintegrating in mills
    • D21B1/16—Disintegrating in mills in the presence of chemical agents
    • 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
    • D21C1/00—Pretreatment of the finely-divided materials before digesting
    • D21C1/02—Pretreatment of the finely-divided materials before digesting with water or steam

Definitions

  • the present invention relates to the field of production of high temperature chemithermomechanical pulp (HT-CTMP) to be used in the manufacture of paperboard.
  • HT-CTMP high temperature chemithermomechanical pulp
  • US4486267 discloses a high yield chemithermomechanical (CTMP) process for obtaining high strength hardwood pulps, wherein hardwood chips are subjected to a two-stage chemical treatment prior to defibration, the first consisting of chip impregnation and reaction with an alkaline liquor followed by a second stage treatment with sulfite and/or bisulfite.
  • CMP chemithermomechanical
  • US4900399 discloses production of chemimechanical pulp from lignocellulosic material in a process in which the material is impregnated in two stages.
  • the material is treated in the first stage with alkaline and, subsequent to passing an intermediate draining and reaction step, in the second stage with a solution that contains peroxide.
  • the quantities of alkali and peroxide charged are fully optional and are independent of one another.
  • the material is then optionally subjected to a further drainage and reaction step, and thereafter pre-heated at a temperature of between 50° C. and 100° C., whereafter the material is refined in one or two stages.
  • An objective of the present disclosure is to realize more of the potential of the high temperature (HT) step in production of HT-CTMP, in particular when such production is based on hardwood.
  • CTMP chemithermomechanical pulp
  • Figures 1-3 illustrate a system for producing HT-CTMP according to embodiments of the present disclosure.
  • the present disclosure provides a method of preparing chemithermomechanical pulp (CTMP).
  • the method comprises the step of pre-impregnating wood chips with a pre-impregnation liquid to obtain pre-impregnated wood chips.
  • the pre-impregnation liquid typically comprises alkali such as NaOH.
  • the temperature of the pre-impregnation liquid is preferably at least 70°C, such as 70°C-99°C, such as 80°C-99°C. At such a relatively high temperature, the viscosity of the pre-impregnation liquid is lower, which facilitates the absorption thereof.
  • the pre-impregnation liquid is preferably aqueous.
  • the wood chips comprise hardwood chips, such as birch wood chips or maple wood chips.
  • hardwood chips such as birch wood chips or maple wood chips.
  • at least 55% by dry weight of the wood chips may be hardwood chip, such as birch wood chips or maple wood chips.
  • the average length of the hardwood chips may be below 20 mm to aid impregnation.
  • the pre-impregnation step may comprise feeding wood chips to a pre-impregnation zone comprising the pre-impregnation liquid.
  • a plug screw or another compressing device
  • the wood chips expand in the pre-impregnation zone and absorb the pre-impregnation liquid.
  • the wood chips supplied to the pre-impregnation step has undergone pre-steaming.
  • the method may further comprise a step of pre-steaming the wood chips prior to the pre-impregnation step.
  • the residence time of the wood chips in the pre-streaming step may be at least 10 min, such as at least 15 min, such as at least 20 min, such as at least 22 min.
  • the upper limit may be 60 min, such as 30 min.
  • the steam supplied to the pre-steaming step is typically of atmospheric pressure.
  • the pre-steaming step may be carried out in a steam bin.
  • the chips are fed to an upper part of the steaming bin and withdrawn from a lower part of the steaming bin. Further, the steam is typically supplied in the lower part of the steaming bin.
  • the temperature in the upper part of the steaming bin is typically 90°C - 99°C.
  • the pre-impregnation liquid comprises alkali (typically in the form of NaOH).
  • NaOH may be fed to the pre-impregnation step in an amount of 1-8 kg per tonne of dry wood chips, such as 2-8 kg per tonne of dry wood chips, such as 3-5 kg per tonne of dry wood chips. Reducing the amount of NaOH in the pre-impregnation liquid (and impregnation liquid), may result in a CTMP having increased bulk and brightness.
  • the step of pre-steaming the maple wood chips may be preceded by a step of washing the maple wood chips with water.
  • the method further comprises the step of feeding the pre-impregnated wood chips to an impregnation zone using a plug screw (or another compressing device).
  • a plug screw is however preferred.
  • the impregnation zone comprises an impregnation liquid.
  • the impregnation liquid comprises alkali (typically NaOH) and/or sulfite (preferably added as Na 2 SO 4 ).
  • the pre-impregnated wood chips expand in the impregnation zone and absorb the impregnation liquid, thereby providing impregnated wood chips.
  • the temperature of the impregnation liquid is preferably at least 70°C, such as 70°C-99°C, such as 80°C-99°C. At such a relatively high temperature, the viscosity of the impregnation liquid is lower, which facilitates the absorption thereof.
  • the impregnation liquid is preferably aqueous.
  • alkali in the form of NaOH is fed to the impregnation zone in an amount of 5-25 kg per tonne of dry wood chips, 9-25 kg per tonne of dry wood chips, such as 9-20 kg per tonne of dry wood chips. In one embodiment, the alkali in the form of NaOH is fed to the impregnation zone in an amount of 5-20 kg per tonne of dry wood chips, such as 5-15 kg per tonne dry wood chips. This is associated with obtaining a satisfactory bulk and brightness of the final CTMP.
  • Na 2 SO 3 is fed to the impregnation zone in an amount of 5-30 kg per tonne of dry wood chips, such as 15-25 kg per tonne of dry wood chips. In another embodiment, Na 2 SO 3 is fed to the impregnation zone in an amount of 5-25 kg per tonne dry wood chips, such as 5-20 kg per tonne dry wood chips, such as 5-18 kg per tonne dry wood chips. It has been found that a CTMP having satisfactory properties can be obtained while having a low sulfite consumption. Furthermore, the addition of sulfite in the impregnation liquid may increase the brightness of the CTMP prior to bleaching and thus a pulp with a higher bulk may be obtained at a given brightness after bleaching.
  • the impregnation liquid may comprise a higher concentration of alkali (e.g. NaOH) than the pre-impregnation liquid.
  • alkali may be fed at a higher rate to the impregnation zone than to the step of pre-impregnating wood chips.
  • the impregnation liquid comprises sulfite and has a pH below 10.9. Such a pH reflects are relatively low (or no) supply of NaOH.
  • the method further comprises the step of transferring the impregnated wood chips to a heating zone without compressing the impregnated wood chips.
  • the transfer of the impregnated chips may comprise lifting the impregnated wood chips out of the impregnation zone using a transport screw and then allowing the impregnated wood chips to fall into a heating zone in which the heat-treatment takes place.
  • the method further comprises the step of heating the impregnated wood chips in the heating zone with steam to obtain pre-treated wood chips.
  • the temperature of the steam used for said heating is above 140°C, preferably at least 150°C, such as at least 160 ° C
  • the CTMP produced by the method can be referred to as HT-CTMP.
  • An upper limit for the steam temperature may be 190°C.
  • the residence time in the heating zone is no more than two minutes. This results in sufficient softening of the chips while maintaining a low energy consumption.
  • the method also comprises the step of defibration of the pre-treated wood chips.
  • This step is typically carried out at high consistency, e.g. 35 wt.% - 50 wt.%.
  • the high-consistency defibration may be succeeded by low-consistency refining and/or bleaching. Embodiments of such low-consistency refining and/or bleaching is described below in the Examples section.
  • the defibration of the pre-treated wood chips is typically carried out under pressure.
  • Figures 1-3 illustrate exemplary embodiments of a system for producing CTMP.
  • a chipper 101 is used to prepare chips from wood.
  • chips In case of hardwood, in particular maple wood, it is preferable to prepare chips that are relatively short, such as ⁇ 20 mm, to aid impregnation.
  • Softwood chips are generally easier to impregnate and can hence be longer, such as 22-24 mm.
  • the settings of a conventional wood chipper can be adjusted to achieve such lengths. Shorter chips from such a chipper are also thinner.
  • the chips from the chipper 101 are typically stored in at least one silo 102.
  • silo 102 When different types of wood are mixed in the system, there is typically one silo for each type of wood, such as one hardwood chips silo 102a and one softwood chips silo 102b.
  • a chips mixing system 103 is typically arranged downstream the silos 102a, 102b.
  • the chips from the chips mixing system 103 are optionally stored in an aerobic environment in a maturation silo 104 for a period of at least 24 h (typically about 72 h).
  • a typical temperature in the maturation silo 104 is 60°C, which can be achieved by feeding low-pressure steam into the maturation silo 104.
  • the treatment of the chips in the maturation silo 104 degrades triglycerides. The degradation products can then be extracted in downstream process steps.
  • the chips are washed in a chips washing arrangement 106.
  • a conditioning device 105 Upstream the chips washing arrangement 106, a conditioning device 105 may be arranged.
  • the conditioning device 105 is typically a chip steaming bin.
  • the purpose of the conditioning device 105 is to provide chips of fairly constant temperature.
  • the conditioning device 105 may also, to some extent, reduce variations in moisture content. During cold winter months, ice on the chips is melted in the conditioning device 105, which facilitates the downstream washing and processing.
  • the conditioning device 105 may be particularly advantageous when there is no upstream maturation silo. In case there is an upstream maturation silo, the conditioning device 105 may be omitted.
  • the chips are typically soaked and agitated in water and then dewatered.
  • the washed and dewatered chips are then steamed in a pre-steaming bin 107.
  • the residence time of the chips in the pre-steaming bin 107 is typically at least 10 min.
  • the pre-steaming step softens the chips and make them more elastic, which is advantageous in the downstream impregnation steps.
  • a plug screw 115 feeds the steamed chips from the pre-steaming bin into a pre-impregnation chamber 116.
  • the steamed chips which were compressed in the plug screw 115, expands in a bath of pre-impregnation liquid 117 in the pre-impregnation chamber 116. During the expansion, the chips absorb pre-impregnation liquid.
  • the temperature of the pre-impregnation liquid is preferably 80°C-99°C.
  • the pre-impregnation liquid may comprise alkali. In such case, alkali can be fed to the pre-impregnation chamber in an amount of 3-5 kg per tonne of dry wood chips.
  • the impregnation liquid may however be preferred to use warm water without any NaOH or other alkali as the impregnation liquid.
  • the (expanded and impregnated) chips are lifted from the bath of pre-impregnation liquid 117 by means of a transport screw 118.
  • the pre-impregnation step further softens the chips and make them more elastic, which facilitates the downstream steps of impregnation and heat-treatment.
  • the pre-impregnation step assists in realizing the full potential of the "HT" technology in HT-CTMP production.
  • a plug screw 119 feeds the pre-impregnated chips from the impregnation chamber into a reactor 120.
  • the pre-impregnated chips which were compressed in the plug screw 119, expands in a bath of impregnation liquid 121 in the reactor 120.
  • the chips absorb impregnation liquid, which preferably has a temperature of 80°C-99°C.
  • the impregnation liquid preferably comprises sulfite and optionally alkali.
  • Na 2 SO 3 is preferably fed to the reactor in an amount of 10-20 kg per tonne of dry wood chips.
  • the (expanded and impregnated) chips are lifted from the bath of impregnation liquid 121 by means of a transport screw 122 and are then allowed to fall over an edge 123 and into steaming area 124 of the reactor 120, in which they are heated by steam having a temperature above 140°C, preferably at least 150°C, such as at least 160°C.
  • the residence time in the steaming area 124 is less than two minutes.
  • the chips treated in the reactor 120 are transferred to the chips defibrator 114 without flashing off any steam on the way.
  • the dry matter content is about 45%-50% (in case there is no plug screw between the steaming area 124 and the chips defibrator 114, the dry matter content may however be as low as 30%).
  • the pulp from the chips defibrator 114 is subjected to flashing in a steam separator 125 and then pulped in a first pulper 126.
  • the pulp from the first pulper 126 is then treated in a first dewatering press 127.
  • the pressate from the dewatering press 127 contains extractives (and dissolved wood substances and residual chemicals) that are unwanted in the final CTMP product.
  • Separation of extractives by pressing in this position is advantageous since the pulp still has very high freeness (typically >650 ml or even >700 ml) and is thus easily dewatered.
  • Limiting the residence time in the first pulper 126 to below 10 min (typically about 3 min) is advantageous since it limits the time available to the extractives to be adsorbed onto the fibers before the first dewatering press 127.
  • the pulp from the dewatering press 127 is subjected to middle consistency (MC) bleaching in a MC bleach tower 128 using unreacted peroxide from the downstream high consistency (HC) bleaching and, if needed, make-up quantities of NaOH and peroxide.
  • MC means 10 wt.% - 12 wt.%.
  • the MC-bleached pulp is treated in a second dewatering press 129 also producing a pressate.
  • the pulp from the second dewatering press has a consistency of about 30%-35% and is subjected to high consistency (HC) bleaching in a HC bleach tower 130 using fresh peroxide and alkali (and optionally a peroxide stabilizer, such as a silicate or a non-silicate stabilizer and/or a chelating agent, such as DTPA or EDTA).
  • HC-bleached fibers from the HC bleach tower 130 are pulped in a second pulper 131 (residence time: ⁇ 10 min, such as about 3 min) to produce a pulp having a consistency of about 4 wt.% - 6 wt.%.
  • This pulp is then subjected to low consistency (LC) refining in LC refiners 132.
  • LC low consistency
  • a third dewatering press 133 then separates a third pressate from the LC-refined pulp.
  • the fibers from the third dewatering press 133 are pulped in a third pulper 134 (residence time: ⁇ 10 min, such as about 3 min) to produce a pulp having a consistency of 2 wt.% - 4 wt.%.
  • Screens 135 are then used to separate a reject from the pulp from the third pulper 134.
  • the separated reject is collected in a reject tank 136.
  • the design of the remaining parts of the system depends on if only market pulp is produced (i.e. all CTMP is subjected to flash drying and baling) or if there is an adjacent board-making machine to which at least part of the CTMP is supplied without drying.
  • the pulp from the screens 135 are cleaned in cleaners 137 to provide cleaned pulp and second reject that is collected in a second reject tank 138.
  • the cleaners 137 are preferably cyclones that separate unwanted heavy particles.
  • the cleaned pulp is then filtered in a disc filter 139 and collected in a MC tower 140.
  • a fourth dewatering press 141 produces dewatered fibers and a fourth pressate.
  • the dewatered fibers are led to an arrangement for fiber treatment and shredding 142 and then to a flash drying arrangement 143. Finally, bales of the dried fibers from the flash drying arrangement 143 are formed in a baling arrangement 144.
  • the pulp from the screens is filtered in a disc filter 145 and treated in a fourth dewatering press 146 such that a fourth pressate and an MC pulp are obtained.
  • the MC pulp is collected in a MC tower 147.
  • a fifth dewatering press 148 produces dewatered fibers and a fifth pressate from MC pulp from the MC tower 147.
  • the dewatered fibers are led to an arrangement for fiber treatment and shredding 149 and then to a flash drying arrangement 150.
  • bales of the dried fibers from the flash drying arrangement 150 are formed in a baling arrangement 151.
  • MC pulp from the MC tower 147 is led to a board-making machine.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Mechanical Engineering (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Wood Science & Technology (AREA)
  • Paper (AREA)

Claims (11)

  1. Verfahren zur Herstellung von chemithermomechanischem Zellstoff (CTMP), umfassend die Schritte:
    - Vorimprägnieren von Holzschnitzeln mit einer Vorimprägnierflüssigkeit, um vorimprägnierte Holzschnitzel zu erhalten;
    - Zuführen der vorimprägnierten Holzschnitzel zu einer Imprägnierzone mittels einer Stopfschnecke, wobei die Imprägnierzone eine Imprägnierflüssigkeit aufweist, die Sulfit und/oder Alkali umfasst, so dass sich die vorimprägnierten Holzschnitzel in der Imprägnierzone ausdehnen und die Imprägnierflüssigkeit aufnehmen, wodurch imprägnierte Holzschnitzel bereitgestellt werden;
    - Überführen der imprägnierten Holzschnitzel in eine Heizzone, ohne die imprägnierten Holzschnitzel zu verdichten;
    - Erhitzen der imprägnierten Holzschnitzel in der Heizzone mit Dampf, der eine Temperatur von mehr als 140 °C, beispielsweise mindestens 150 °C, insbesondere mindestens 160 °C aufweist, um vorbehandelte Holzschnitzel zu erhalten; und
    - Defibrillieren der vorbehandelten Holzschnitzel,
    wobei die Verweilzeit in der Heizzone nicht mehr als zwei Minuten beträgt.
  2. Verfahren nach Anspruch 1, wobei die Imprägnierflüssigkeit Sulfit umfasst und einen pH-Wert von weniger als 10,9 aufweist.
  3. Verfahren nach einem der Ansprüche 1 oder 2, wobei die in die Imprägnierzone zugeführte Menge an Sulfit (berechnet als Na2SO3) 10 kg bis 30 kg, beispielsweise 15 kg bis 25 kg, pro Tonne Trockensubstanz der dem Schritt b) zugeführten Holzschnitzel beträgt.
  4. Verfahren nach einem der vorangehenden Ansprüche, wobei der Schritt des Vorimprägnierens von Holzschnitzeln das Zuführen der Holzschnitzel zu einer Vorimprägnierzone umfasst, die die Vorimprägnierflüssigkeit aufweist, wobei die Zuführung mittels einer Stopfschnecke erfolgt, so dass sich die Holzschnitzel in der Vorimprägnierzone ausdehnen und die Vorimprägnierflüssigkeit aufnehmen.
  5. Verfahren nach einem der vorangehenden Ansprüche, wobei die Holzschnitzel Laubholz, beispielsweise Birke oder Ahorn, umfassen.
  6. Verfahren nach einem der vorangehenden Ansprüche, wobei der Schritt des Überführens der imprägnierten Holzschnitzel das Herausfördern der imprägnierten Holzschnitzel aus der Imprägnierzone mittels einer Förderschnecke und anschließend das Herabfallenlassen der imprägnierten Holzschnitzel in die Heizzone umfasst.
  7. Verfahren nach einem der vorangehenden Ansprüche, wobei die dem Vorimprägnierungsschritt zugeführten Holzschnitzel einem Vordämpfungsschritt unterzogen wurden, vorzugsweise über eine Zeitdauer von mindestens 10 Minuten.
  8. Verfahren nach einem der vorangehenden Ansprüche, wobei in dem Schritt des Vorimprägnierens der Holzschnitzel Alkali in einer Menge von 1 kg bis 8 kg pro Tonne Trockensubstanz der Holzschnitzel, beispielsweise 2 kg bis 8 kg pro Tonne Trockensubstanz der Holzschnitzel, insbesondere 3 kg bis 5 kg pro Tonne Trockensubstanz der Holzschnitzel zugeführt wird.
  9. Verfahren nach einem der vorangehenden Ansprüche, wobei Alkali mit einer höheren Dosiermenge der Imprägnierzone zugeführt wird als in dem Schritt des Vorimprägnierens der Holzschnitzel.
  10. Verfahren nach einem der vorangehenden Ansprüche, wobei Alkali in einer Menge von 9 kg bis 25 kg Trockensubstanz der Holzschnitzel, beispielsweise 9 kg bis 20 kg pro Tonne Trockensubstanz der Holzschnitzel der Imprägnierzone zugeführt wird.
  11. Verfahren nach einem der Ansprüche 1 bis 7, wobei die Vorimprägnierflüssigkeit kein Alkali umfasst.
EP23837246.0A 2022-12-21 2023-12-20 Zweistufige imprägnierung in der ht-ctmp-produktion Active EP4590895B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE2251536 2022-12-21
PCT/EP2023/086986 WO2024133480A1 (en) 2022-12-21 2023-12-20 Two-step impregnation in ht-ctmp production

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EP4590895A1 EP4590895A1 (de) 2025-07-30
EP4590895B1 true EP4590895B1 (de) 2025-12-03

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Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SE416481B (sv) * 1977-05-02 1981-01-05 Mo Och Domsjoe Ab Fofarande och anordning for behandling av vedflis for avlegsnande av tungmetaller och harts
US4486267A (en) * 1983-11-14 1984-12-04 Mead Corporation Chemithermomechanical pulping process employing separate alkali and sulfite treatments
SE454186C (sv) * 1985-03-13 1989-09-25 Eka Nobel Ab Saett foer framstaellning av kemimekanisk massa

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WO2024133480A1 (en) 2024-06-27

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