WO2024003457A1 - Procédé de réduction de viscosité d'une pâte à dissoudre - Google Patents

Procédé de réduction de viscosité d'une pâte à dissoudre Download PDF

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Publication number
WO2024003457A1
WO2024003457A1 PCT/FI2023/050404 FI2023050404W WO2024003457A1 WO 2024003457 A1 WO2024003457 A1 WO 2024003457A1 FI 2023050404 W FI2023050404 W FI 2023050404W WO 2024003457 A1 WO2024003457 A1 WO 2024003457A1
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WO
WIPO (PCT)
Prior art keywords
stage
bleaching
pulp
viscosity
acidic
Prior art date
Application number
PCT/FI2023/050404
Other languages
English (en)
Inventor
Tiina HAATAINEN
Janne Vehmaa
Original Assignee
Andritz 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 Andritz Oy filed Critical Andritz Oy
Publication of WO2024003457A1 publication Critical patent/WO2024003457A1/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
    • 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
    • D21C9/10—Bleaching ; Apparatus therefor
    • 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
    • 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
    • D21C3/00—Pulping cellulose-containing materials
    • D21C3/02—Pulping cellulose-containing materials with inorganic bases or alkaline reacting compounds, e.g. sulfate processes
    • 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
    • D21C9/10—Bleaching ; Apparatus therefor
    • D21C9/1057—Multistage, with compounds cited in more than one sub-group D21C9/10, D21C9/12, D21C9/16
    • 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
    • D21C9/10—Bleaching ; Apparatus therefor
    • D21C9/16—Bleaching ; Apparatus therefor with per compounds
    • D21C9/163—Bleaching ; Apparatus therefor with per compounds with peroxides

Definitions

  • the present disclosure relates to a method for reducing the viscosity of dissolving pulp .
  • Dissolving wood pulp is bleached pulp that has a high cellulose content .
  • Viscosity is one of the most important properties of dissolving pulp .
  • a typical commercial dissolving pulp has an intrinsic viscosity of less than 700 ml /g and most of the cases the viscosity is in the range of 400 - 600 ml /g .
  • the final viscosity of the dissolving pulp is controlled by bleaching with ozone .
  • the ozone stage requires high investment costs , especially in an existing bleaching plant .
  • the inventors have recogni zed the need for an effective and low-cost method for reducing the viscosity of dissolving pulp .
  • a method for reducing the viscosity of dissolving pulp comprises : a) producing cellulose pulp by a kraft cooking with a prehydrolysis step or a soda cooking with a prehydrolysis step, wherein the obtained cellulose pulp has a cellulose content of at least 88 % , b) bleaching the obtained cellulose pulp, wherein the bleaching comprises at least one acidic peroxide stage , wherein the cellulose pulp is treated with a mineral acid and a hydrogen peroxide , and at least one other bleaching stage .
  • the present disclosure relates to a method for reducing the viscosity of dissolving pulp, wherein the method comprises : a) producing cellulose pulp by a kraft cooking with a prehydrolysis step or a soda cooking with a prehydrolysis step, wherein the obtained cellulose pulp has a cellulose content of at least 88 % , b) bleaching the obtained cellulose pulp, wherein the bleaching comprises at least one acidic peroxide stage , wherein the cellulose pulp is treated with a mineral acid and a hydrogen peroxide , and at least one other bleaching stage .
  • the prehydrolysis step may be used to minimi ze hemicellulose content in the cellulose pulp by heating wood chips in between 120 ° C - 170 ° C with steam or water, to de-esterify the acetyl groups present in the hemicellulose .
  • the cellulose pulp may be cooked with kraft or soda cooking process using white liquor or other alkali source . Viscosity after the cooking is in the range of 800 - 1500 ml /g . All wood species which are used for paper pulp production can be used in this method .
  • the cellulose pulp may be subj ected to oxygen delignification .
  • the goal of oxygen delignification is to reduce the lignin content of unbleached pulp before using more expensive bleaching chemicals .
  • the commercial dissolving pulp has an intrinsic viscosity of less than 700 ml /g and most of the cases the viscosity is in the range of 400 - 600 ml /g .
  • the cellulose pulp is produced by a kraft cooking with a prehydrolysis step . In one embodiment , the cellulose pulp is produced by a soda cooking with a prehydrolysis step .
  • the viscosity of the cellulose pulp after cooking is in the range of 800 - 1500 ml/g. In one embodiment, the viscosity of the cellulose pulp after bleaching is less than 700 ml/g, or in the range of 400-600 ml/g.
  • the cellulose pulp has a cellulose content of at least 90%, or at least 92%, or at least 95%.
  • the cellulose pulp is subjected to oxygen delignification.
  • the mineral acid is hydrochloric acid or sulphuric acid.
  • the mineral acid is used in amount of 1 - 5 kg/adt, or 2 - 4 kg/adt.
  • the unit "kg/adt" should be understood in this specification, unless otherwise stated, as kg/air dried ton of pulp.
  • the hydrogen peroxide is used in amount of 1 - 20 kg/adt, or 2-10 kg/adt, or 2 - 6 kg/adt, or 3 - 5 kg/adt.
  • the mineral acid and the hydrogen peroxide are fed into the reactor simultaneously.
  • the mineral acid is first fed into the reactor and then hydrogen peroxide is fed into the reactor.
  • the hydrogen peroxide is first fed into the reactor and then the mineral acid is fed into the reactor.
  • the bleaching consists of acidic peroxide stage and one other bleaching stage. In one embodiment, the bleaching consists of acidic peroxide stage and two other bleaching stages. In one embodiment, the bleaching stages can be carried out in any order .
  • the other bleaching stage is P, Eop, Ep, Eo, D, H, C, or A stage. In one embodiment, the bleaching stage is a combination stage D/C or A/D.
  • the bleaching stage “P” should be understood in this specification, unless otherwise stated, as an alkaline stage with hydrogen peroxide (H2O2 ) .
  • the bleaching stage “Eop” should be understood in this specification, unless otherwise stated, as an alkaline extraction bleaching stage using sodium hydroxide with subsequent addition of oxygen and hydrogen peroxide solution as a reinforcing agent .
  • the bleaching stage “Ep” should be understood in this specification, unless otherwise stated, as an extraction stage using NaOH with subsequent addition of H2O2 solution as a reinforcing agent .
  • the bleaching stage “Eo” should be understood in this specification, unless otherwise stated, as an extraction stage using NaOH with subsequent addition of gaseous oxygen as a reinforcing agent .
  • the bleaching stage “D” should be understood in this specification, unless otherwise stated, as a chlorine dioxide stage (CIO2 ) .
  • the bleaching stage “Z” should be understood in this specification, unless otherwise stated, as an ozone stage (O3 ) .
  • the bleaching stage “Px” should be understood in this specification, unless otherwise stated, as an acidic peroxide stage , wherein cellulose pulp is treated with a mineral acid and a hydrogen peroxide .
  • the bleaching stage “A/Z” should be understood in this specification, unless otherwise stated, as an acidic wash stage followed by ozone stage .
  • the bleaching stage “Da” should be understood in this specification, unless otherwise stated, as a chlorine dioxide stage with an acidic stage .
  • the bleaching stage "Do” should be understood in this specification, unless otherwise stated, as a first chlorine dioxide stage .
  • the bleaching stage “A” should be understood in this specification, unless otherwise stated, as an acidic wash stage .
  • the bleaching stage “C” should be understood in this specification, unless otherwise stated, as a chlorine stage (CI2 ) .
  • the bleaching stage “H” should be understood in this specification, unless otherwise stated, as a hypochlorate , NaOCl , Ca (OCl ) 2 stage .
  • the bleaching stage “D/C” should be understood in this specification, unless otherwise stated, as a chlorine and chlorine dioxide stage .
  • the bleaching stage “A/D” should be understood in this specification, unless otherwise stated, as an acidic wash stage followed by chlorine dioxide stage .
  • the bleaching is performed in the following sequence : Px-Eop, or Px-D, or Px-Ep, or any combination of Px-stage and D-stage and alkaline peroxide stage .
  • the bleaching sequence "Px-Eop" should be understood in this specification, unless otherwise stated, as the bleaching sequence of acidic peroxide stage ( Px) and alkaline extraction bleaching stage using sodium hydroxide with subsequent addition of oxygen and hydrogen peroxide solution as a reinforcing agent (Eop) .
  • the bleaching sequence "Px-D” should be understood in this specification, unless otherwise stated, as the bleaching sequence of acidic peroxide stage ( Px) and chlorine dioxide stage ( D) .
  • bleaching sequence "Px- Ep” should be understood in this specification, unless otherwise stated, as the bleaching sequence of acidic peroxide stage ( Px) and extraction stage using NaOH with subsequent addition of hydrogen peroxide solution as a reinforcing agent (Ep) .
  • the expression "bleaching sequence” should be understood in this specification, unless otherwi se stated, as a combination of individual bleaching stages .
  • the pH during the acidic peroxide stage is in the range of 1 . 5 - 5 . 5 , or 2 - 4 . 5 .
  • the temperature during the acidic peroxide stage is in the range of 50 - 100 °C, or 60 - 95 ° C .
  • the process time in the acidic peroxide stage is 20 - 240 min, or 60 - 120 min .
  • the pulp consistency during the acidic peroxide stage is in the range of 5 - 15% , or 7 - 12 % , calculated as dry content .
  • the viscosity decrease of the pulp in the acidic peroxide stage is in the range of 100 ml /g - 150 ml /g . In one embodiment , the viscosity decrease of the pulp in the acidic peroxide stage is in the range of 100 ml /g - 200 ml /g . Viscosity can be measured according to standard I SO 5351 : 2010 but not limited to this method and all same type of viscosity measurement methods can be used as a reference .
  • the acidic peroxide stage as described in this application has the added utility of reducing the viscosity of dissolving pulp . Further, the inventors surprisingly found out that the bleaching sequence of acidic peroxide stage and alkaline extraction bleaching stage using sodium hydroxide with subsequent addition of oxygen and hydrogen peroxide solution as a reinforcing agent efficiently reduced the viscosity of dissolving pulp . Further, the acidic peroxide stage as described in this application has the added utility of reducing the content of metals in the dissolving pulp .
  • cellulose pulp was bleached in a Px stage.
  • comparative examples were made by bleaching the cellulose pulp in an A/Z stage and in a Da stage.
  • the cellulose pulp used in these examples was prehydrolysed oxygen-delignified kraft pulp.
  • Viscosity was measured according to standard ISO 5351:2010.
  • ISO Brightness was measured according to standard ISO 2470-1:2016.
  • the cellulose pulp was treated with sulfuric acid and hydrogen peroxide.
  • the cellulose pulp was treated with chlorine dioxide and sulfuric acid.
  • the cellulose pulp was treated with sulfuric acid and ozone.
  • the bleaching conditions are presented in the below table.
  • cellulose pulp was first bleached in the chlorine dioxide stage (DO) and then further bleached in the acidic peroxide stage.
  • DO chlorine dioxide stage
  • a comparative example was made by bleaching the cellulose pulp first in the DO stage and then in the Eop stage.
  • the cellulose pulp used in these examples was prehydrolysed oxygen-delignified kraft pulp.
  • Viscosity was measured according to standard ISO 5351:2010.
  • ISO Brightness was measured according to standard ISO 2470-1:2016.
  • the cellulose pulp was treated with sulfuric acid and hydrogen peroxide .
  • the cellulose pulp was treated with sodium hydroxide with subsequent addition of oxygen and hydrogen peroxide solution as a reinforcing agent .
  • the bleaching conditions are presented in the below table .

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  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Wood Science & Technology (AREA)
  • Chemical & Material Sciences (AREA)
  • Inorganic Chemistry (AREA)
  • Paper (AREA)
  • Polysaccharides And Polysaccharide Derivatives (AREA)

Abstract

L'invention concerne un procédé de réduction de la viscosité de la pâte à dissoudre. Le procédé de réduction de viscosité de pâte à dissoudre comprend : a) la production de pâte de cellulose par une cuisson kraft avec une étape de préhydrolyse ou une cuisson à la soude avec une étape de préhydrolyse, la pâte de cellulose obtenue ayant une teneur en cellulose d'au moins 88 %, b) le blanchiment de la pâte de cellulose obtenue, le blanchiment comprenant au moins une étape de peroxyde acide, la pâte de cellulose étant traitée avec un acide minéral et un peroxyde d'hydrogène, ainsi qu'au moins une autre étape de blanchiment.
PCT/FI2023/050404 2022-06-29 2023-06-29 Procédé de réduction de viscosité d'une pâte à dissoudre WO2024003457A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FI20225592A FI20225592A1 (fi) 2022-06-29 2022-06-29 Menetelmä liukosellun viskositeetin alentamiseksi
FI20225592 2022-06-29

Publications (1)

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WO2024003457A1 true WO2024003457A1 (fr) 2024-01-04

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FI (1) FI20225592A1 (fr)
WO (1) WO2024003457A1 (fr)

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2013227705A (ja) * 2012-04-27 2013-11-07 Oji Holdings Corp 溶解パルプの製造方法
WO2017105322A1 (fr) * 2015-12-14 2017-06-22 Valmet Ab Procédé de régulation de la viscosité dans des pâtes pour dissolution

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2013227705A (ja) * 2012-04-27 2013-11-07 Oji Holdings Corp 溶解パルプの製造方法
WO2017105322A1 (fr) * 2015-12-14 2017-06-22 Valmet Ab Procédé de régulation de la viscosité dans des pâtes pour dissolution

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FI20225592A1 (fi) 2023-12-30

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