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WO2019009792A1 - Procédé de fonctionnement d'un réacteur vertical continu comprenant une zone de pré-hydrolyse et la conception du réacteur en tant que telle - Google Patents

Procédé de fonctionnement d'un réacteur vertical continu comprenant une zone de pré-hydrolyse et la conception du réacteur en tant que telle Download PDF

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Publication number
WO2019009792A1
WO2019009792A1 PCT/SE2018/050715 SE2018050715W WO2019009792A1 WO 2019009792 A1 WO2019009792 A1 WO 2019009792A1 SE 2018050715 W SE2018050715 W SE 2018050715W WO 2019009792 A1 WO2019009792 A1 WO 2019009792A1
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WO
WIPO (PCT)
Prior art keywords
reactor
prehydrolysis
continuous vertical
liquid
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.)
Ceased
Application number
PCT/SE2018/050715
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English (en)
Inventor
Krister SJÖBLOM
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 Technologies Oy
Valmet AB
Original Assignee
Valmet Oy
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 Oy, Valmet AB filed Critical Valmet Oy
Publication of WO2019009792A1 publication Critical patent/WO2019009792A1/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
    • 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
    • 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
    • D21C7/00—Digesters
    • 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
    • D21C9/008—Prevention of corrosion or formation of deposits on pulp-treating equipment
    • 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
    • D21C9/08—Removal of fats, resins, pitch or waxes; Chemical or physical purification, i.e. refining, of crude cellulose by removing non-cellulosic contaminants, optionally combined with bleaching
    • 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
    • D21C3/22—Other features of pulping processes
    • D21C3/226—Use of compounds avoiding scale formation

Definitions

  • the invention relates to an improved method for operating a continuous vertical reactor or digester with a prehydrolysis zone, avoiding build-up of sticky deposits on the wall of the reactor, as well as a reactor design that enables implementation of the inventive method.
  • Prehydrolysis kraft cooking has been implemented both in two-vessel systems and in single- vessel systems, where the hydrolysis takes place in almost the entire first vessel of a two- vessel systems and in the upper part of the single-vessel system, i.e. the latter requiring a swing from acidic conditions to alkaline conditions in the same vessel.
  • the swing from acidic conditions to alkaline conditions takes place between vessels or starting in the bottom part of the first vessel directly ahead of transfer to second vessel.
  • the invention relates to the problem with formation of sticky deposits in prehydrolysis, which deposits clog up surfaces, screens and liquor withdrawal compartments.
  • prehydrolysis which deposits clog up surfaces, screens and liquor withdrawal compartments.
  • a boundary layer of anti-fouling liquid is established on the reactor wall in the prehydrolysis zone to prevent sticky reaction products of the hydrolysis to be deposited on the surface of the equipment.
  • any alkali charge is avoided as that would neutralize the released wood acidity from establishing the required pH for the prehydrolysis.
  • An anti-fouling liquid is within this context a liquid that is either neutral or alkaline.
  • suitable anti-fouling liquids are neutral or alkaline solutions, liquid surfactants, solvents, water and mixtures thereof.
  • the anti-fouling liquid is alkaline, advantageously with a pH above 8, and even more preferably above 9.
  • An alkaline boundary layer is advantageous in that it will counteract formation of deposits by keeping solubilized the hydrolysis reaction products, dissolved substances from the biomass and possible precursors that are prone to form deposits.
  • the anti-fouling liquid used is any of alkali, SO2, sulfite or bisulfite solution, water, or mixtures thereof.
  • Alkali usage has the positive effect of dissolving any acidic sticky compounds and keeping them solubilized, and if applied as a layer on the reactor wall it will not impede the hydrolysis of the bulk part of the material volume.
  • the released acid compounds mainly from acetyl groups in the hemicellulose part of the lignocellulosic raw material, will keep the pH low in the bulk of the raw material to enable the prehydrolysis. Applying a sulfite solution resulting in sulfonation of certain compounds, e.g.
  • aromatic moieties from lignin is known to make them more soluble and thus less prone to precipitate under prehydrolysis conditions.
  • Water may also be used, especially if a continuous flushing flow, i.e. mechanical removal from the surface of reactor wall, is sufficient.
  • the liquid may be any mixture of alkali, SC /sulfite/bisulfite and water. If kraft white liquor is to be used as alkali source, oxidized white liquor is preferred to avoid the risk of formation of gaseous hydrogen sulfide.
  • a control member is used for regulating the flow of the anti- fouling liquid in said supply channel. Further, the anti-fouling liquid needs to be preheated close to the prehydrolysis temperature before being introduced into the prehydrolysis reactor.
  • the inventive method is used for inhibiting the formation of sticky deposits in an acidic prehydrolysis zone of continuous vertical reactors, wherein lignocellulosic material is fed continuously to the top of said reactor and said lignocellulosic material being subjected to hydrolysis in at least a part of the continuous vertical reactor and at least hydrolyzed lignocellulosic material is fed out from the bottom of said continuous vertical reactor.
  • a layer of alkaline liquid boundar' layer is established at the interior wall of the continuous vertical reactor in a position corresponding to at least 30 % of the lower final part of the total vertical length of the prehydrolysis zone, i.e.
  • the layer of alkaline liquid can be established at the wall of the continuous vertical reactor in a position corresponding to at least 50 % of the lower part of the total vertical height of the prehydrolysis zone. This creates a longer (higher) vertical layer, that may be needed when hydrolyzing cellulosic material that releases sticky deposits to a larger extent early in the prehydrolysis process.
  • the supplied alkaline liquor when it enters the reactor, is preferably preheated to a temperature close to the temperature of the cellulose material in the prehydrolysis zone of the reactor.
  • the pH of the alkaline liquor layer at the end of the prehydrolysis zone should at least be in the range of 8-10.
  • the pH of the liquor as supplied to the reactor can be higher according to the general aspects of the invention, i.e. depending on the type of lignocellulosic raw material, the hydrolysis temperature and the solids-to-liquid ratio in the bulk of the lignocellulosic raw material.
  • the inventive reactor design i.e. depending on the type of lignocellulosic raw material, the hydrolysis temperature and the solids-to-liquid ratio in the bulk of the lignocellulosic raw material.
  • the inventive reactor design according to the invention is applied in a continuous vertical reactor or digester, wherein Hgnocellulosic material is fed continuously to an inlet in the top of the reactor and at least hydrolyzed Hgnocellulosic material is fed out from an outlet in the bottom of the reactor, said reactor comprising an acidic prehydrolysis zone in at least the upper part of the reactor.
  • a layer of alkaline anti- fouling liquid is established on the inner reactor wall by injecting alkaline liquid from an alkali liquid source through distribution nozzles arranged around the circumference of the interior wall of the continuous vertical reactor in a position corresponding to at least 30 % of the lower part of the total vertical height of the prehydrolysis zone.
  • the distribution nozzles can be arranged around the circumference of the interior wall of the continuous vertical reactor in a position corresponding to at least 50 % of the lower part of the total vertical height of the prehydrolysis zone.
  • the distribution nozzles can be arranged around the circumference of the interior wall of the continuous vertical reactor behind a vertical guide plate that directs the flow of alkaline anti-fouling liquid downwards and in parallel with the interior wall of the continuous vertical reactor.
  • This design is preferably implemented in new reactors being designed to apply the layer of anti-fouling liquid.
  • the design with a guide plate will assure that a layer of alkaline liquor is readily formed in the reactor before it is being exposed to the descending plug of Hgnocellulosic material,
  • At least one additional layer of alkaline liquid can be established by injecting alkaline anti-fouling liquid through a second set of distribution nozzles arranged around the circumference of the interior wall of the continuous vertical reactor in a position located at a distance from and below the first established layer of alkaline liquid at least 10% of the total vertical height of the prehydrolysis zone.
  • no extraction screens are located in the wail of the prehydrolysis zone between the positions for alkali injection and the end of the prehydrolysis zone.
  • the extraction screens may interfere in a negative way with the established anti-fouling liquid boundaiy layer at the interior wall of the continuous vertical reactor and causing a radial flow.
  • Fig. la shows a prior art steam phase prehydrolysis zone in a reactor.
  • Fig, lb shows a prior art liquid phase prehydroly sis zone in a reactor.
  • Fig. lc shows a prior art liquid phase prehydrolysis zone in upper part of a reactor.
  • Fig. 2a shows a single reactor/digester according to prior art with an upper prehydrolysis zone and a subsequent kraft cooking zone.
  • Fig, 2b shows the screen section between the upper prehydrolysis zone and a subsequent kraft cooking zone in Fig. 2a.
  • Fig. 2c shows the displacement flow profile established in the screen section in Fig. 2b
  • Fig. 3a shows a steam phase prehydrolysis zone in a reactor according to the invention.
  • Fig, 3b shows a liquid phase prehydrolysis zone in a reactor according to the invention.
  • Fig, 3c shows a liquid phase prehydrolysis zone in upper part of a reactor according to the invention.
  • Fig. 4 shows a first alternative seen in a vertical cross section of the vertical reactor for forming the alkaline layer on the inner surface of the reactor wall.
  • Fig, 5 shows a second alternative seen in a vertical cross section of the vertical reactor for forming the alkaline layer on the inner surface of the reactor wall.
  • Fig. 6 shows the inventive nozzles, as seen in a horizontal cross section of the vertical reactor, arranged around the circumference of the interior wall of the continuous vertical reactor.
  • Fig, 7 shows a third alternative, as seen in a horizontal cross section of the vertical reactor, for forming the alkaline layer on the inner surface of the reactor wall.
  • Fig, 8 shows a fourth alternative, as seen in a horizontal cross section of the vertical reactor, for forming the alkaline layer on the inner surface of the reactor wall.
  • Fig. 9 shows a fifth alternative, as seen in a horizontal cross section of the vertical reactor, for forming the alkaline layer on the inner surface of the reactor wall.
  • Fig. 10 shows a sixth alternative, as seen in a horizontal cross section of the vertical reactor, for forming the alkaline layer on the inner surface of the reactor wall.
  • Figs, la-lc show three different conventional prior art implementations of a prehydrolysis zone in a vertical reactor.
  • lignocellulosic material flow PIN
  • steam ST is also added to establish the temperature needed to attain the necessary conditions for prehydrolysis.
  • An upper level, CLEV, of lignocellulosic material is established.
  • the vertical height of the prehydrolysis zone is indicated by Hyd.
  • the lignocellulosic material is finally fed out from the bottom of the vertical reactor in flow POUT.
  • Fig. la shows a vertical reactor where the prehydrolysis zone Hyd is established in a steam phase prehydrolysis zone Hyd.
  • This steam phase prehydrolysis zone ends near the bottom where typically the hydrolysed lignocellulosic material is diluted with a washing/diluting liquid, indicated by Wash, and some of the dissolved organic material from the hydrolysis process, mainly carbohydrates from hemicellulose, is withdrawn in a bottom screen SC, indicated by the flow Rec.
  • Fig. lb shows a vertical reactor where most of the prehydrolysis zone Hyd is established in a liquid-phase prehydrolysis zone.
  • a short steam-phase heating zone can precede the liquid- phase zone as indicated.
  • An upper level CLEV of lignocellulosic material and an upper level LLEV of liquid are established.
  • the liquid-phase prehydrolysis zone ends near the bottom where some of the dissolved organic material from the hydrolysis process, mainly carbohydrates from hemicellulose, can be withdrawn in a bottom screen SC, indicated by the flow Rec.
  • the liquid-phase prehydrolysis differs from the autohydrolysis in a steam-phase prehydrolysis zone by the fact that acid is added, typically H2SO4, and that the required temperature is about 20-40 °C lower than that in a steam-phase hydrolysis zone; the latter typically held at 160-190 °C.
  • the embodiments shown in Figs, la and lb are conventionally applied in two-vessel reactor systems, where the first vessel is used for prehydrolysis and a second vessel most often is used for alkaline kraft cooking.
  • other type of cooking processes can follow in the second vessel, such as sulfite cooking, and different variants of kraft cooking such as MCC, EMCC, Lo-Solids or Compact Cooking.
  • Fig. lc shows a vertical reactor where only the upper part of the vertical reactor is used as a prehydrolysis zone, Hyd, in this case a liquid-phase prehydrolysis zone.
  • This embodiment is applied in single-vessel reactor systems where a prehydrolysis zone is established in the upper part, typically 30-60 % of the vertical height of the reactor.
  • An upper level CLEV of lignocellulosic material and an upper level LLEV of liquid are established.
  • the liquid-phase prehydrolysis zone Hyd ends at a screen section SC located after a concurrent prehydrolysis zone, but before a countercurrent cooking zone Cook below the screen section SC, where some of the dissolved organic material from the prehydrolysis zone, mainly carbohydrates from hemicellulose, can be extracted in the screen section SC, indicated by the flow Rec.
  • Fig. 2a shows another visualization of a prior art single-reactor system which is similar to the single reactor shown in Fig. lc.
  • additional screen sections SC2 and SC3 implemented in the cooking zone, but those have no impact on the prehydrolysis zone or the current invention, and are therefore not described in more detail.
  • the screen section SC ending the prehydrolysis zone is shown in more detail in Fig. 2b.
  • the screen section SC in Fig. 2b comprises two screen rows, an upper screen row and a lower screen row. Liquor withdrawn from the lower screen row is lead to a circulation pump after which alkaline liquor is added, here in form of white liquor WL.
  • the pressurized alkaline liquor is reintroduced into the reactor in three positions: first via a central pipe CP, secondly via nozzles to the upper screen row, and thirdly via nozzles to the lower screen row.
  • the pressurized alkaline liquor supplied to the central pipe and the upper screen row will also pass through a heater He, before being added to the reactor.
  • a radial displacement pattern is developed with a flow of heated alkaline liquor from the central pipe and the upper screen row, which then will be extracted through the lower screen row. This kind of solution will add alkaline liquor to the end of the prehydrolysis zone.
  • Figs. 3a, 3b, and 3c represent a modification of the systems shown in Figs, la, lb and lc, respectively.
  • Fig. 3a has everything similar to that in Fig. la, except for the introduction of an anti-fouling liquid layer, Lay, that is established over a vertical height AL in the reactor in the prehydrolysis zone, by adding an alkaline liquor LAL.
  • Fig. 3b has everything similar to that in Fig. lb, except for the introduction of an anti-fouling liquid layer, Lay, that is established over a vertical height AL in the reactor in the prehydrolysis zone, by adding an alkaline liquor LAL.
  • Fig. 3c has everything similar to that in Fig. lc, except for the introduction of an anti-fouling liquid layer, Lay, that is established over a vertical height AL in the reactor in the prehydrolysis zone, by adding an alkaline liquor LAL.
  • Fig. 4 shows a first embodiment in which a nozzle NZ supplies alkaline liquor to the upper part of a chamber formed between a vertical guide plate GP and a step out in the reactor wall.
  • the width CT of the chamber establishes an alkaline liquor volume that flows vertically downwards passing the lower lip of the guide plate GP.
  • the descending column of lignocellulosic material can expand slightly as indicated and a liquor layer with a thickness LT is maintained on the reactor wall.
  • This embodiment is preferably implemented in new reactor vessels where the step out in the reactor wall can be included when the reactor is designed.
  • Fig. 5 shows a second embodiment visualizing how a nozzle NZ supplies alkaline liquor through the wall of a reactor, but without any step out or guide plate.
  • the thickness of the liquor layer established is indicated by LT.
  • This embodiment is preferably implemented as an upgrade in already installed reactor vessels where the alkaline layer is intended to be implemented to reduce the problem with sticky deposits, and where the costs for changing the reactor wall with a step out would be excessively high.
  • Fig. 6 shows a horizontal cross section of the reactor with the nozzles NZ evenly distributed around the circumference of the interior wall of the reactor, as implemented in a reactor with a step out according to Fig. 4.
  • the distance between two neighboring nozzles is determined by the amount of alkaline liquor supplied and the production rate in the reactor, i.e. how fast the column of lignocellulosic material moves downward.
  • the established alkaline boundary layer around the circumference of the inner reactor wall below the step out is indicated by the solid line LT in Fig. 4.
  • To start with is the total volume of alkaline liquor added by all nozzles determined by calculating the void volume occurring below the step out as the plug descends, assuming no radial expansion of the lignocellulosic raw material column.
  • This volume is preferably the minimum volume added, but it may be increased or decreased by 5-20 % depending on the type of lignocellulosic material treated in the reactor, i.e. if it is chopped annual plants or wood chips from hardwood or softwood.
  • the flow of alkaline liquor needed may be adjusted after inspection of the interior wall of the reactor during shut down when the reactor is empty. The chemicals added will result in a different coloring on the wall when a layer is established, and the color on the wall above the nozzles will be different from the color below the nozzles.
  • Fig. 7 is shown in a horizontal cross section of the reactor with the nozzles NZ evenly distributed around the circumference of the interior wall of the reactor, as implemented in a reactor without a step out or without a vertical guide plate, i.e. according to Fig. 5.
  • the nozzles NZ penetrate the reactor wall at a 90-degree angle in the horizontal plane, and directed to the very center of the reactor.
  • the nozzles can also be slightly angled in a vertical plane as shown in Fig. 4, i.e. at an angle a.
  • Fig. 8 shows a horizontal cross section of the reactor with the nozzles NZ evenly distributed around the circumference of the interior wall of the reactor, as implemented in a reactor without a step out or without a vertical guide plate, i.e. according to Fig. 5.
  • the nozzles NZ penetrate the reactor wall at a pointy angle ⁇ in the horizontal plane, and directed to establish a tangential flow along the interior wall of the reactor.
  • the nozzles can also be slightly angled in a vertical plane as shown in Fig. 5, i.e. at an angle a.
  • Fig. 9 shows a horizontal cross section of the reactor with the nozzles NZ evenly distributed around the circumference of the interior wall of the reactor, as implemented in a reactor with a step out and a vertical guide plate GP, i.e. according to Fig. 4.
  • the nozzles NZ penetrate the reactor wall at a pointy angle ⁇ in the horizontal plane, and directed to establish a tangential flow along the interior wall of the reactor and into the chamber formed between the reactor wall and the guide plate GP.
  • the nozzles can also be slightly angled in the vertical plane as shown in Fig. 5, i.e. at an angle a.
  • the number of nozzles can be reduced as indicated in Fig. 10, as the chamber may be evenly filled around the circumference by the tangentially flow established and before the descending column with lignocellulosic material meets the alkaline liquid layer below the lower lip of the guide plate.
  • the invention may be modified in several different ways in comparison with the preferred embodiments shown in Figs. 4 to 10.
  • One alternative embodiment is to supply anti-fouling liquid at more than one vertical position in the reactor.
  • a first group of nozzles for anti-fouling liquid supply can be arranged in a height position at about 70-90 %, preferably 80 %, above the end of the prehydrolysis zone, and a second set of nozzles be arranged in a height position at about 50- 70 %, preferably 60 %, above the end of the prehydrolysis zone, and even a third set of nozzles may be arranged in a height position at about 30-50 %, preferably 40 %, above the end of the prehydrolysis zone.

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  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Wood Science & Technology (AREA)
  • Paper (AREA)
  • Physical Or Chemical Processes And Apparatus (AREA)

Abstract

L'invention concerne un procédé d'inhibition de l'accumulation de dépôts de produits de réaction collants sur les surfaces internes du réacteur dans une zone de pré-hydrolyse acide de cuves ou digesteurs verticaux continus et une conception de réacteur qui permet la mise en œuvre du procédé selon l'invention. Selon le procédé et le réacteur de l'invention, une couche (Lay) de liquide alcalin est établie sur la paroi interne du réacteur dans la zone de pré-hydrolyse, laquelle couche alcaline empêche la formation et l'adhérence de dépôts collants sur la paroi interne du réacteur vertical.
PCT/SE2018/050715 2017-07-04 2018-07-02 Procédé de fonctionnement d'un réacteur vertical continu comprenant une zone de pré-hydrolyse et la conception du réacteur en tant que telle Ceased WO2019009792A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE1750871A SE541646C2 (en) 2017-07-04 2017-07-04 Method for operating a continuous vertical reactor comprising a prehydrolysis zone and the reactor design as such
SE1750871-4 2017-07-04

Publications (1)

Publication Number Publication Date
WO2019009792A1 true WO2019009792A1 (fr) 2019-01-10

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PCT/SE2018/050715 Ceased WO2019009792A1 (fr) 2017-07-04 2018-07-02 Procédé de fonctionnement d'un réacteur vertical continu comprenant une zone de pré-hydrolyse et la conception du réacteur en tant que telle

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SE (1) SE541646C2 (fr)
WO (1) WO2019009792A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP3947808A4 (fr) * 2019-03-29 2022-12-28 Valmet Ab Procédé et agencement dans un procédé de production de pâte à papier en continu

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3413189A (en) * 1964-01-29 1968-11-26 Kamyr Ab Method of performing hydrolysis and alkalic digestion of cellulosic fiber material with prevention of lignin precipitation
US5676795A (en) * 1992-12-02 1997-10-14 Voest-Alpine Industrieanlagenbau Gmbh Process for the production of viscose pulp
EP2034090A1 (fr) * 2007-08-07 2009-03-11 Andritz, Inc. Procédé et appareil de semi-chimique réduction en pate
WO2012158075A1 (fr) * 2011-05-13 2012-11-22 Metso Paper Sweden Ab Procédé compact d'obtention de pâte préalablement hydrolysée

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3413189A (en) * 1964-01-29 1968-11-26 Kamyr Ab Method of performing hydrolysis and alkalic digestion of cellulosic fiber material with prevention of lignin precipitation
US5676795A (en) * 1992-12-02 1997-10-14 Voest-Alpine Industrieanlagenbau Gmbh Process for the production of viscose pulp
EP2034090A1 (fr) * 2007-08-07 2009-03-11 Andritz, Inc. Procédé et appareil de semi-chimique réduction en pate
WO2012158075A1 (fr) * 2011-05-13 2012-11-22 Metso Paper Sweden Ab Procédé compact d'obtention de pâte préalablement hydrolysée

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP3947808A4 (fr) * 2019-03-29 2022-12-28 Valmet Ab Procédé et agencement dans un procédé de production de pâte à papier en continu

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Publication number Publication date
SE541646C2 (en) 2019-11-19
SE1750871A1 (en) 2019-01-05

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