WO2017127004A1 - Étape de dioxyde de chlore à des fins de régulation de la viscosité de pâtes pour usages chimiques - Google Patents

Étape de dioxyde de chlore à des fins de régulation de la viscosité de pâtes pour usages chimiques Download PDF

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Publication number
WO2017127004A1
WO2017127004A1 PCT/SE2016/051253 SE2016051253W WO2017127004A1 WO 2017127004 A1 WO2017127004 A1 WO 2017127004A1 SE 2016051253 W SE2016051253 W SE 2016051253W WO 2017127004 A1 WO2017127004 A1 WO 2017127004A1
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WO
WIPO (PCT)
Prior art keywords
chlorine dioxide
stage
viscosity
pulp
charge
Prior art date
Application number
PCT/SE2016/051253
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English (en)
Inventor
Maria WENNERSTRÖM
Solveig NORDÉN
Original Assignee
Valmet Ab
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 Valmet Ab filed Critical Valmet Ab
Priority to EP16886677.0A priority Critical patent/EP3405611A4/fr
Publication of WO2017127004A1 publication Critical patent/WO2017127004A1/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
    • D21C1/00—Pretreatment of the finely-divided materials before digesting
    • D21C1/04—Pretreatment of the finely-divided materials before digesting with acid reacting compounds
    • 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
    • D21C9/12—Bleaching ; Apparatus therefor with halogens or halogen-containing compounds
    • D21C9/14—Bleaching ; Apparatus therefor with halogens or halogen-containing compounds with ClO2 or chlorites
    • D21C9/144—Bleaching ; Apparatus therefor with halogens or halogen-containing compounds with ClO2 or chlorites with ClO2/Cl2 and other bleaching agents in a multistage process
    • 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
    • D21C9/12—Bleaching ; Apparatus therefor with halogens or halogen-containing compounds
    • D21C9/14—Bleaching ; Apparatus therefor with halogens or halogen-containing compounds with ClO2 or chlorites
    • 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

  • Chlorine dioxide stage for controlling viscosity
  • the present disclosure relates in general to a method for producing dissolving pulp of low viscosity from lignocellulosic material.
  • the dissolving process for producing low viscosity pulp conventionally contains a first hydrolysis stage followed by a kraft cooking stage, an optional oxygen delignification stage further reducing the lignin content and viscosity and thereafter bleaching for viscosity reduction and brightness increase.
  • Dissolving pulp has emerged as a reborn alternative growing market for pulp mills and much attention has been given to modify the pulping processes to be able to produce different grades of dissolving pulp which is used to produce a multitude of products like Rayon-grade pulp or specialty pulps.
  • the interest to find alternative textile materials to cotton has increased due to short term shortage and increase in costs for cotton and an increased competition in long term for land to grow an increasing demand of cotton on.
  • Dissolving pulp can consist of cotton linters, pulp originating from wood or annual plants made by the sulfite process or the prehydrolysis kraft process.
  • dissolving pulp is generally referred to as a bleached pulp produced from wood that has a high alpha cellulose content, typically over 92%, and only small content of hemicelluloses, typically below 10%. Hence, the wood yield of dissolving pulp from the process is typically low at about 35-40%.
  • Dissolving pulp is used to manufacture various cellulose-derived products such as rayon yarn for use in e.g. textile industry and specialty chemicals and materials such as cellulose acetate and carboxy methyl cellulose. When making rayon yarns the dissolving pulp is converted to cellulose xanthate which dissolves in caustic soda and the resulting viscous liquid is extruded in acidic baths to yield fibers.
  • the dissolving pulp can be dissolved in ionic solvents to make extruding to fibers possible.
  • the viscosity of the dissolving pulp is both low and within a specific range suitable for the process, in order to run derivatisation/dissolution process smoothly.
  • the required intrinsic viscosity in the finally bleached dissolving pulp must be as low as 350 ml/g and within a narrow
  • viscosity is used as the dominant pulp property for dissolving pulp.
  • the viscosity number is expressed as intrinsic viscosity and measured in ml/g.
  • a standard test method for intrinsic viscosity of cellulose could be found in ISO-standard ISO 5351 .
  • viscosity measurements is indicative for the average molecular weight of the cellulose polymers, i.e. the length of the cellulose chains.
  • the length of the cellulose chains impact the derivatisation and solubilisation process as well as the
  • the viscosity is often about or below 900 ml/g after cook or at least below 800 ml/g after prebleaching, i.e. oxygen delignification or other pre bleaching stages (where kappa and viscosity reduction is an objective over increase in brightness) and below 600 ml/g after final bleaching.
  • the viscosity target for the final dissolving pulp is kept within a relatively narrow range, for example within 450-500 ml/g.
  • the problem with production of dissolving pulp is to reach the low viscosity of the final pulp requested and most often is extended and intensified cooking, i.e. both longer cooking time and tougher cooking conditions as of alkali charge and temperature, needed in order to obtain a low enough viscosity after the cook.
  • a problem with extended cooking occurs if it is desired to increase the production in existing pulp mills as increased production results in decreased cooking time if the equipment is the same. This results in higher viscosity when the throughput of the lignocellulosic material increases. After cooking the pulp is normally oxygen delignified in order to further reduce lignin content and viscosity.
  • the viscosity reduction does not reach a sufficient low level after cooking and oxygen delignification, it has with some standard bleaching sequences been found to be almost impossible to reach the final viscosity level by implementing tougher process conditions in final bleaching.
  • the viscosity reduction may be increased marginally in the order of 50 ml/g in final bleaching, by implementing tougher bleaching conditions in the final bleaching stages as of temperature and additional bleaching agents or increased charge of the standard bleaching agents used.
  • Ozone stages are also capable of reducing viscosity to a larger extent, but this at expense of increased costs, especially in an existing bleaching plant.
  • the main objective problem with the present invention is to enable increased production of dissolving pulp in existing pulp mills while still being able to reach the lower viscosity requested in bleached dissolving pulp, and being able to control this low viscosity within a narrow range suitable for the final dissolving pulp grade.
  • the invention is applied in ECF bleaching sequences not using any elemental chlorine nor hypochlorite as bleaching chemicals, i.e. so called C or H bleaching stages.
  • the invention is based upon the assumption that larger viscosity reductions may be implemented in the Do-stage if agents with strong chain cleavage abilities located close to or neighboring to cellulose are increased. This can be achieved by e.g. an increase in hydroxyl radical formation.
  • the invention relates to a method for producing low viscosity dissolving pulp from lignocellulosic material, said dissolving process comprising a first acidic hydrolysis process followed by a kraft cooking process reaching a kappa number in the washed cooked pulp below 30, said cooked and washed pulp subsequently further delignified in an optional oxygen delignification stage and finally bleached in 2-5 bleaching stages, and wherein the final target viscosity of the bleached dissolving pulp is primarily controlled by combining chlorine dioxide and hydrogen peroxide bleaching in a first chlorine dioxide stage, often referred to as a Do-stage.
  • the first chlorine dioxide stage is conventionally in a position where the lignin content is still measured, and typically lies above a kappa number of 4-8, typically 10-20, and often referred to a pre-bleaching stage. After the Do position the kappa number is so low that instead ISO brightness is measured. Characteristic reaction kinetics in a Do stage is that the charge of chlorine dioxide could most often not be controlled by measuring residual levels of chlorine dioxide as all charge is consumed due to surplus of organic material consuming chlorine dioxide.
  • the combination of chlorine dioxide and hydrogen peroxide in a first chlorine dioxide stage may obtain a reduction of viscosity in the range of 200-350 ml/g, where at least 90-170 ml/g is contributed to the chlorine dioxide charge per se and at least 60-130 ml/g is contributed to the hydrogen peroxide charge per se.
  • the first chlorine dioxide stage is possible to adjust whereby a large range of viscosity reduction could be obtained.
  • the total production may be increased in any existing mills, which increased production is compensated by increased viscosity reduction in the bleach plant.
  • a commercial dissolving line with Cook-O-D-E-P may then be easily be converted to a Cook-O- DP-E-P, and meet the increasing viscosity that may result from production increases, and where the first chlorine dioxide stage, Do, is gradually changed to a DP stage with increasing additional charge of hydrogen peroxide.
  • the inventive method is applied for producing low viscosity dissolving pulp from lignocellulosic material, said dissolving process comprising a first acidic hydrolysis process followed by a kraft cooking process reaching a kappa number in the washed cooked pulp below 30, said cooked and washed pulp subsequently further delignified in an optional oxygen delignification stage and finally bleached in 2-5 stages containing at least a first chlorine dioxide stage (Do), and wherein the final target viscosity of the bleached dissolving pulp is primarily controlled by adjusting the conditions in the first chlorine dioxide stage using H2O2- charge and additionally pH and temperature, obtaining a basic viscosity reduction in the first chlorine dioxide stage by the chlorine dioxide charge in the range of 90-170 ml/g by said adjustment of time and temperature in the first chlorine dioxide stage , said first chlorine dioxide stage being further reinforced by hydrogen peroxide addition in order to obtain an additional viscosity reduction in said first chlorine dioxide stage in the range 60-130 ml/g at least.
  • washed and cooked pulp may also be subjected to an oxygen delignification stage with a subsequent washing obtaining an oxygen delignified and washed pulp before being subjected to the first chlorine dioxide stage.
  • the kappa number from the cook may be sufficiently low, whereby this oxygen delignification stage may be omitted, but strongly preferred if the mill is subject to major production increases.
  • the bleaching sequence is preferably a D-(w)- E-(w)-P-(w) sequence, where the viscosity control is made in the first chlorine dioxide stage (D) using different charge of peroxide addition converting the bleaching sequence to a (DP)-(w)- E-(w)-P-(w) sequence .
  • the inventive method use the conditions in the first chlorine dioxide (D)- stage are used as a primary control for the final viscosity of dissolving pulp, enabling total viscosity modifications in the first chlorine dioxide stage in the range 200-350 ml/g by altering charge of hydrogen peroxide, chlorine dioxide, temperature and pH.
  • the cooking process according to the inventive method could equally well take place in a batch digester or a continuous digester. If the production is increased in an existing batch digester the cooking time needs to be reduced so that each batch digester may be emptied more frequently. If the production is increased in an existing continuous digester is normally the retention time in the digester reduced and thereby is the viscosity reduction decreased. The reduced retention time in batch or continuous digesters may in part be compensated by increasing the temperature, but this at high costs as this requires addition of steam capable of increasing the temperature at the normal cooking temperature at about 140-170°C.
  • the oxygen delignification can take place in one or two successive treatment vessels.
  • the (DP)-stage can take place in one treatment vessel.
  • Figure 1 Show an example of a complete fiberline for manufacturing dissolving pulp
  • Figure 2 Show an oxygen delignification stage followed by (DP)-stage
  • Figure 4 Show impact of H2O2 charge in (DP) on ISO brightness
  • Figure 5 Show the development of viscosity and brightness in a
  • the invention is related to a method for producing low viscosity dissolving pulp from lignocellulosic material, said dissolving process comprising a first acidic hydrolysis process followed by a kraft cooking process reaching a kappa number in the washed cooked pulp below 30, said cooked and washed pulp subsequently further delignified in an oxygen delignification stage and finally bleached in 2-5 bleaching stages.
  • the principle layout of such a dissolving process is shown in Figure 1 .
  • Lignocellulosic material preferably wood chips (CH) are fed to a first hydrolysis stage (Prehyd), followed by a kraft cooking stage (Cook), and thereafter oxygen delignification (O2), before final bleaching in a first chlorine dioxide/peroxide bleaching stage, (DP) an extraction stage, (EP), a second chlorine dioxide bleaching stage, (D1 ), and finally a peroxide stage, (P) or chlorine dioxide stage, D2 from which the dissolving pulp is fed out.
  • the first stage Prehyd+Cook+02 are more or less standard stages but the final bleaching stages could have other
  • the first stage following oxygen delignification is an acidic stage (A, D or Z) followed by alkaline extraction (E, (EP), (EOP)) and an acidic bleaching stage (D) before an optional alkaline bleaching stage (such as P stage).
  • E alkaline extraction
  • EOP alkaline extraction
  • D acidic bleaching stage
  • Such alternative configurations could be; Z-D-EP-D or Z-D-P or D0-EP-D1 -D2 or D0-(EP)-D-P or A- D-(EP)-D or (DP)-(EP)-(DP)-D.
  • Figure 2 is the first (DP)-stage shown in more detail before the final bleaching FB, with washing stages shown between O and (DP). Mixing positions are indicated for charge of acid (H2SO4), Steam (ST), chlorine dioxide (CIO2) and hydrogen peroxide (H2O2). The charges are not necessarily made with individual mixers for each charge, and additional points of different media can be done in another order.
  • the pulp studied was a hardwood ( Russian Birch) pulp which after hydrolysis and cook had a kappa number of 12.8, an intrinsic viscosity of 1205 ml/g and an ISO brightness of 41.7 %. After oxygen delignification the kappa number was 4.3, intrinsic viscosity 874 ml/g and ISO brightness 59.1 %.
  • the oxygen delignified pulp was bleached with the sequences Do-(EP)-Di-P and (DP)-(EP)-Di-P with conditions shown in the table below.
  • Pulp brightness after (DP)-(EP) was slightly higher than after D-(EP). The bleaching efficiency was thus the same or slightly better for pulps bleached (DP)-(EP) as for pulp bleached D-(EP).
  • the H2O2 charge was varied from 0-4 kg/odt when bleaching for 90 and 120 minutes at 90°C in (DP).
  • Figure 3 viscosity is shown versus H2O2 charge. The results show that the viscosity is reduced with increased H2O2 charge, from 700 ml/g when bleaching without H2O2 to 560 ml/g when bleaching with 4 kg H202/odt. Bleaching for 90 and 120 minutes in (DP) showed similar results.

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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)

Abstract

La présente invention concerne un procédé amélioré de production de pâte pour usages chimiques à partir d'un procédé de cuisson de kraft par hydrolyse. Le nouveau procédé permet de réguler la viscosité de la pâte de manière efficace grâce à un ajout de peroxyde d'hydrogène à une première étape de dioxyde de chlore et par un ajustement de la charge de peroxyde d'hydrogène, la réduction de viscosité totale peut être ajustée dans une large plage de viscosité permettant une production accrue dans des procédés commerciaux de dissolution en utilisant des séquences de blanchiment courtes D-(w)-E-(w)-P-(w) converties en une séquence de blanchiment DP-(w)-E-(w)-P-(w).
PCT/SE2016/051253 2016-01-18 2016-12-13 Étape de dioxyde de chlore à des fins de régulation de la viscosité de pâtes pour usages chimiques WO2017127004A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP16886677.0A EP3405611A4 (fr) 2016-01-18 2016-12-13 Étape de dioxyde de chlore à des fins de régulation de la viscosité de pâtes pour usages chimiques

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE1650050-6 2016-01-18
SE1650050A SE1650050A1 (en) 2016-01-18 2016-01-18 Chlorine dioxide stage for controlling viscosity in dissolving pulps

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WO2017127004A1 true WO2017127004A1 (fr) 2017-07-27

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2019165324A1 (fr) * 2018-02-23 2019-08-29 Gp Cellulose Gmbh Nouvelles pâtes de bois dissolvantes et procédés de fabrication et d'utilisation de telles pâtes de bois dissolvantes

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6048437A (en) * 1995-09-22 2000-04-11 Mitsubishi Gas Chemical Company, Inc. Process for bleaching chemical pulp with chlorine dioxide, peroxide and Na2 M0 O4 as reaction catalyt
WO2009139693A1 (fr) * 2008-05-13 2009-11-19 Metso Paper, Inc. Procédé de blanchiment de pâte avec de l'ozone, du dioxyde de chlore et du peroxyde
JP2013227705A (ja) * 2012-04-27 2013-11-07 Oji Holdings Corp 溶解パルプの製造方法
WO2015195030A1 (fr) * 2014-06-17 2015-12-23 Valmet Ab Procédé de production de pâte dissolvante à partir d'un matériau lignocellulosique

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Publication number Priority date Publication date Assignee Title
SE9000340L (sv) * 1990-01-31 1991-08-01 Eka Nobel Ab Foerfarande vid blekning av lignocellulosahaltigt material
US6331354B1 (en) * 1996-08-23 2001-12-18 Weyerhaeuser Company Alkaline pulp having low average degree of polymerization values and method of producing the same
CN103122594B (zh) * 2012-11-19 2014-03-12 山东轻工业学院 一种溶解浆的生产方法

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6048437A (en) * 1995-09-22 2000-04-11 Mitsubishi Gas Chemical Company, Inc. Process for bleaching chemical pulp with chlorine dioxide, peroxide and Na2 M0 O4 as reaction catalyt
WO2009139693A1 (fr) * 2008-05-13 2009-11-19 Metso Paper, Inc. Procédé de blanchiment de pâte avec de l'ozone, du dioxyde de chlore et du peroxyde
JP2013227705A (ja) * 2012-04-27 2013-11-07 Oji Holdings Corp 溶解パルプの製造方法
WO2015195030A1 (fr) * 2014-06-17 2015-12-23 Valmet Ab Procédé de production de pâte dissolvante à partir d'un matériau lignocellulosique

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See also references of EP3405611A4 *

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2019165324A1 (fr) * 2018-02-23 2019-08-29 Gp Cellulose Gmbh Nouvelles pâtes de bois dissolvantes et procédés de fabrication et d'utilisation de telles pâtes de bois dissolvantes
CN111902578A (zh) * 2018-02-23 2020-11-06 Gp纤维素有限责任公司 新型溶解木浆及其制备和使用方法
US11105042B2 (en) 2018-02-23 2021-08-31 Gp Cellulose Gmbh Dissolving wood pulps and methods of making and using the same
US11661704B2 (en) 2018-02-23 2023-05-30 Gp Cellulose Gmbh Dissolving wood pulps and methods of making and using the same

Also Published As

Publication number Publication date
SE539163C2 (en) 2017-04-25
EP3405611A1 (fr) 2018-11-28
SE1650050A1 (en) 2017-04-25
EP3405611A4 (fr) 2019-09-25

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