EP2707539B1 - Kompaktes verfahren zur herstellung von vorhydrolysiertem zellstoff - Google Patents

Kompaktes verfahren zur herstellung von vorhydrolysiertem zellstoff Download PDF

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EP2707539B1
EP2707539B1 EP11865841.8A EP11865841A EP2707539B1 EP 2707539 B1 EP2707539 B1 EP 2707539B1 EP 11865841 A EP11865841 A EP 11865841A EP 2707539 B1 EP2707539 B1 EP 2707539B1
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Prior art keywords
prehydrolysis
stage
temperature
alkaline
alkali
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French (fr)
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EP2707539A4 (de
EP2707539A1 (de
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Daniel Trolin
Stefan ANTONSSON
Jonas SAETHERÅSEN
Mikael Lindström
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Valmet AB
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Valmet Oy
Valmet AB
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    • 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
    • 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
    • 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
    • D21C3/00—Pulping cellulose-containing materials
    • D21C3/22—Other features of pulping processes
    • D21C3/26—Multistage processes

Definitions

  • the present invention relates to a process for the production of pulp in which hemicellulose is hydrolyzed into hydrolysate, and lignin is dissolved by a kraft cooking method for liberating cellulose fibers. Still more particularly, the present invention relates to a process for the production of a pulp which has a high content of alpha cellulose and can be sold as dissolving pulp.
  • a separate prehydrolysis step permits the desired adjustment of the hydrolysis of hemicelluloses by varying the hydrolysis conditions.
  • the bulk delignification is not carried out until a separate alkaline cooking step, even though some handbooks indicate that as much as 30 kg of lignin per ton of wood may be dissolved in the prehydrolysis (i.e. a small part of the total lignin content as 30 kg per ton of wood corresponds to some 3% of the wood material).
  • the conditions for prehydrolysis is most often established by heating in a hot steam phase or hot water liquid environment, where the natural wood acidity released will usually lower the pH down to about 3.5, most often referred to as auto hydrolysis. Sometimes could also additional acid and a catalyst be added.
  • the subsequent delignification step has been a conventional kraft cooking method, where white liquor has been added to the digester.
  • Fig. 8.1 is disclosed a two vessel continuous cooking system with a first up flow prehydrolysis tower followed by a down flow conventional kraft cooking digester, in which the up flow tower experienced severe pitch deposits on the extraction strainers which clogged after only 3-6 days of operation.
  • Another system is disclosed on page 107, Fig.8.2 with a one vessel hydraulic continuous digester system with a first upper prehydrolysis zone and a lower alkaline kraft cooking zone, both zones being separated by a strainer section.
  • US5589033 is disclosed a batch process for prehydrolyzed kraft pulp sold by Metso often in connection with SuperbatchTM cooking.
  • a hot 170oC prehydrolysis step in a gaseous steam phase terminated by a hot neutralization step at 155oC using heated alkali and for a duration of only 15 minutes (as shown in example 3).
  • This neutralization is followed by a hot black liquor treatment step at 148oC for a duration of 20 minutes and finally the pulp is cooked in a kraft cooking stage at 160oC for 54 minutes.
  • the degree of hydrolyzation could be controlled in a good manner by controlling the duration of each stage.
  • dissolving pulp for such end uses as spinning fibers (rayon/lyocell) is considered to be an optional method for producing textiles having less environmental impact compared with production of cotton textiles.
  • Dissolving pulp is also a base product for different additives and consistency agents and fillers in tyre cord and casings, ether and spongs, nitrocellulose and acetate.
  • dissolving pulps may be an alternative product instead of pulp for regular paper pulp making.
  • a common implementation in most prehydrolysis-kraft cooking processes is that the prehydrolysis stage has been terminated by withdrawal of the prehydrolysate, either in form of a pure acidic prehydrolysate, or in form of a neutralized prehydrolysate. As indicated before would any strainers in such process position be subjected to pitch deposits, both when the prehydrolysate is kept at its lowest pH level or if the prehydrolysate is withdrawn in a transition position where the chip suspension switch from acidic to alkaline.
  • One object of the present invention is to provide an improved prehydrolysis-kraft process for the preparation of pulp from lignin-containing cellulosic material.
  • these and other objectives have now been accomplished by a process comprising prehydrolyzing said cellulosic material in a prehydrolysis stage at a temperature in the range of about 120o and 180o C and during at least 20 minutes so as to produce a prehydrolyzed cellulosic material and an acidic hydrolysate.
  • the dissolved carbohydrates as well as any lignin dissolved in the prehydrolysis stage are maintained dissolved during this alkaline pre-extraction stage and further carbohydrates and lignin are dissolved from the cellulosic material in the alkaline pre-extraction stage.
  • the cellulosic material is transferred from the alkaline pre-extraction stage to a kraft cooking stage.
  • the characterizing part of the invention is that the strong alkali chock charge is made using liquor volumes that decrease the temperature of the resulting alkaline treatment liquor for the prehydrolysed material by at least 10% in comparison to the temperature in the prehydrolysis stage, preferably at least 12o C if the prehydrolyse temperature is about 120 oC and at least 18o C if the prehydrolyse temperature is about 180o C, in order to reduce the alkali consumption during the cooking chemical diffusion process where the alkali treatment liquor penetrates to the core of the lignin-containing cellulosic material.
  • the acidification of said prehydrolysis established only by heating and optionally adding water, and without adding any external acidifiers, only using the wood acidity released during heating reaching a pH level below 5 during the prehydrolysis.
  • the acidification of said prehydrolysis be established in a liquid filled phase and preferably is the temperature at end of the prehydrolysis in the range of 150-180oC.
  • no external acidifier is used is the temperature of the resulting mixture of alkaline treatment liquor and the prehydrolysed material below 130oC.
  • the resulting mixture of alkaline treatment liquor and the prehydrolysed material below 120oC which is well below an optimal kraft cooking temperature of about 142oC.
  • the acidification of said prehydrolysis established by heating and addition of external acidifiers, reaching a pH level below 3 during the prehydrolysis.
  • the acidification of said prehydrolysis be established in a liquid filled phase and preferably is the temperature at end of the prehydrolysis in the range 120-165 degrees C.
  • external acidifier is used is the temperature of the resulting alkaline treatment liquor for the prehydrolysed material below 125 oC.
  • Lignin condensation is a well known effect that occur in depleted alkaline environment, especially in acidic conditions, and results in "black cook", i.e. pulp with condensated lignin that is very difficult to delignify further thereafter. Lignin condensation will lead to an increased cooking temperature in order to reach the target kappa number, which in turn has a negative impact on alpha cellulose yield. If condensation of lignin is avoided during the prehydrolysis would the pulp be much easier to cook to the desired kappa number at end of the subsequent kraft cook, and with higher yield and polymerization degree of cellulose, both favorable for special grades of dissolving pulp.
  • a further embodiment of the invention is the step of maintaining the prehydrolyzed cellulosic material in said alkaline treatment liquor implemented for a time period of from about 10 to 90 minutes. Besides establishing a thorough and even alkalization of the wood material after the prehydrolyse stage according to the main objective it is also important to optimize the conditions for the alkaline pre-extraction as well as alkali impregnation ahead of cook.
  • DOC dissolved organic content
  • extracting hemicelluloses rich liquid before the kraft cook stage reduces the carry-over into the kraft cooking stage, which in turn reduces the risk for reprecipitation of hemicelluloses to occur later during the kraft cook stage, which reprecipitation is dependent on hemicelluloses concentration and high temperature.
  • the process could be implemented in a continuous digester system using at least one vessel for the prehydrolysis and one vessel for the alkaline pre-extraction stage and the kraft cooking stage.
  • the alkaline pre-extraction stage be implemented in a separate vessel and the kraft cooking stage in another separate vessel.
  • the following alkaline pre-extraction stage is also given optimum conditions for a thorough impregnation of the acidic wood material by diffusion of said alkaline treatment liquor, which results both in higher degree of alkaline dissolution of DOC as well as even pH level to the core of the wood material ahead of the alkaline cooking stage.
  • Diffusion is a time dependent process more than a displacement process obtained from by-flushing alkaline liquids, and thus the conditions for a continuous process is improved as it may not be necessary to implement internal liquid circulations throughout the stage.
  • the present invention offers the following advantages: A distinct ending of the prehydrolysis stage by both a sharp pH transition to a sufficient minimum alkali concentration and lowering of temperature, i.e. the two most dominant process conditions for prehydrolysis.
  • the neutralization of the free liquid occurs rather instantly, but more favorable conditions for neutralization of the bound liquid inside the wood material are obtained.
  • the diffusion is favored by high temperature but as the alkali consumption rate is far higher at high temperature is lower temperature essential for alkali to diffuse into the core of the wood material.
  • a relatively cold alkali charge used for interrupting the prehydrolysis is referred to as a cold alkali charge not being heated before addition.
  • Suitable alkali charge for use herein contains caustic soda, and the preferred agent is alkaline kraft cooking liquor, i.e., white liquor.
  • the effective alkali concentration, i.e. EA is most often given in % and corresponds to; 1/2 Na 2 S + NaOH.
  • white liquor typically holds a temperature of some 80-90oC when delivered from the recovery island, and a white liquor of this temperature is included by definition in the used cold alkali charge.
  • this white liquor be cooled down even further in a heat exchanger in order to reach the desired final temperature after addition at end of the prehydrolysis.
  • other alkaline filtrates could be added, preferably those having a high alkali content and a low temperature.
  • the lignin-containing cellulosic materials to be used in the present process are suitably softwood, hardwood, or annual plants.
  • prehydrolysis-kraft pulp can be obtained with a high yield of alpha cellulose with a high polymerization degree.
  • FIG. 1 shown the cooking steps of US5589033 .
  • the chips are first treated in the prehydrolysis step Pr where chips are heated by steam to 170oC for 25 minutes. Thereafter is heated white liquor added in order to establish a neutralization step Ne and the acidic prehydrolysate REC AC is withdrawn from the process.
  • the neutralization step is established at 155oC for 15 minutes. Even though the white liquor is heated is the temperature decreased some 8%.
  • the neutralization step is the neutralization liquid displaced by adding hot black liquor BL HOT , and this establish an alkaline black liquor impregnation step BL held at 148oC for 20 minutes.
  • FIG. 2 shown the cooking steps according the inventive process.
  • a first steaming step ST for the chips for the chips but this step may be avoided of the subsequent prehydrolysis is implemented in a steam phase.
  • the chips are thereafter treated in the prehydrolysis step Pr where chips are heated by steam at a temperature of between about 120o and 180o C and during at least 20 minutes so as to produce a prehydrolyzed cellulosic material and an acidic hydrolysate.
  • Addition of liquid such as water H 2 O is an option, which may be preferable if a liquid prehydrolysis is sought for, for example in a continuous cooking system.
  • Another option is to add an acidifier Ac if a lower temperature is sought for in the prehydrolysis.
  • the inventive process is a distinct ending of the prehydrolysis implemented by adding a strong and cold alkali chock charge WL COLD with a volume and at a temperature that will reduce the temperature of the cellulosic material by at least 10% in comparison to the temperature in the prehydrolysis stage, preferably at least 12o C if the prehydrolyse temperature is about 120 oC and at least 18o C if the prehydrolyse temperature is about 180o C.
  • This will establish an alkaline treatment liquor which after this charge establishes a residual effective alkali concentration above 20 g/l EA as NaOH.
  • the prehydrolyzed material is maintained in an alkaline pre extraction stage Ex for a sufficient time in the alkaline pre-extraction stage to reduce the alkali concentration by at least 10 g/l EA as NaOH but not to a concentration below 5 g/l EA as NaOH.
  • the dissolved carbohydrates as well as any lignin dissolved in the prehydrolysis are maintained dissolved during this alkaline pre-extraction stage and further carbohydrates and lignin are dissolved from the cellulosic material.
  • the cellulosic material is transferred from the alkaline pre-extraction stage Ex to a kraft cooking stage Co.
  • the kraft cook Before transfer to the kraft cooking stage is preferably a large part of the spent alkaline treatment liquor withdrawn to recovery and a fresh charge of alkali WL is added to start of cook.
  • the kraft cook may be implemented in any kind of known kraft cooking method for batch or continuous cooking such as, Compact Cooking, Lo-Solids cooking, ITC-cooking, MCC cooking, EAPC cooking as examples.
  • the kraft cook is then finished by a wash stage Wa, which may be implemented in any kind of known wash equipment, such as a countercurrent wash zone in bottom of a digester or using a pressure diffuser wash or filter wash after the cook.
  • FIG 3a is disclosed schematically the pH profile trough a wood chip as exposed to the alkali chock charge after a prehydrolysis.
  • the pH level at the core of the chips is as low as established in the prehydrolysis while the outer surface of the chip is exposed to the alkaline treatment liquor established.
  • reaction rate i.e. consumption rate
  • the reaction rate is doubled for each increase in temperature by 8oC. If one starts with a typical cooking temperature of 140oC this temperature corresponds to a reaction rate which establishes a base reference at 100%. If the cooking temperature is reduced in steps by 8oC to 132, 126, 118 and 110oC the reaction rate would decrease in steps to 50%, 25%, 12.5% and 6.25% respectively.
  • FIG 4 is shown the schematic difference in established pH level inside a wood chip if a diffusion of alkali is made into prehydrolysed wood material using either hot or cold alkaline treatment liquor, i.e. T HOT and T COLD respectively.
  • T HOT hot or cold alkaline treatment liquor
  • T COLD the pH level reached after treatment in the cold alkaline liquor
  • T COLD the dotted line, much higher in the core of the cellulose material than if hot alkaline treatment liquor T HOT was used. The reason is due to the reduced alkali consumption rate during the diffusion process.
  • FIG. 5 An even pH profile is of outmost importance for the subsequent cook which is shown in figure 5 , where schematically the kappa number through the cooked wood chips is disclosed with the dotted line for hot respectively cold alkaline treatment.
  • the kappa number higher in the core i.e. is undercooked UC
  • the surface has much lower kappa number, i.e. is overcooked OC. This result in high reject amount from core parts and alkali degradation of the cellulose at the surface.
  • the right hand picture is shown a more even delignification with less difference between surface and core of wood material due to leveled out pH profile.
  • Both left and right hand pictures resulting in same average kappa number H AV but the cook conducted after treating with cold alkaline will result in a pulp containing higher alpha cellulose.
  • FIG 6 a three vessel continuous cooking system for prehydrolysis and cooking.
  • the chips are first fed to a chip bin 1 and subsequent steaming vessel 2 during addition of steam ST for purging the chips from bound air.
  • the steamed chips falls into a liquid filled chute above a high pressure sluice feeder 3, which pressurize the steamed chips and feed the formed slurry of chips in a feed flow 4 to the prehydrolysis vessel 10.
  • the prehydrolysis vessel is in form of a steam-liquid phase digester having an inverted top separator 11 withdrawing a part of the transport liquid from line 4 back to start of feeding via A.
  • steam ST added to top of vessel 10, and optionally could also acid be added from source Ac.
  • bottom of the prehydrolysis vessel 10 is the cold and strong alkali charge added from source WL. This could be done by mixing in the alkali to the return flow B.
  • the prehydrolysed wood material in its now alkaline treatment liquor is fed in line 14 to a succeeding pre extraction vessel 20, here in form of a hydraulically filled vessel with a downward feeding top separator 21.
  • the alkaline wood material is fed to steam-liquid phase digester 30 via line 24, and excess transport fluid is withdrawn by an inverted top separator 31 and sent to C, which is added to bottom of the pre extraction vessel 20 as part of the transfer circulation.
  • the kraft cook is established in the digester 30 and finally the prehydrolysed and cooked pulp is washed in a pressure diffuser 40.
  • FIG 7 a two vessel continuous cooking system for prehydrolysis and cooking.
  • the pre extraction vessel 20 is implemented as a first stage in the vessel 30, between the top separator 31 and a screen section from where a substantial part of the used alkaline treatment liquor is withdrawn to recovery REC1.
  • Fresh white liquor for the subsequent cooking phase is added via a central pipe at the level of this withdrawal screen.
  • FIGS 8a to 8d are shown how the inventive method may be implemented in a batch digester in a 4 step sequence.
  • a steam prehydrolysing phase shown in figure 8a , where the steam phase is filling the vessel at the prehydrolyse temperature T HYD .
  • T HYD prehydrolyse temperature
  • FIG 8b At ending of the prehydrolysis phase is cold white liquor added to the bottom and as shown in figure 8b which added white liquor catch the acidic condensate on the wood material as a layer PC in front of the rising cold white liquor level.
  • FIG 8c is shown the later phase of the displacement of the cold white liquor trough the vessel, and here is also a larger volume of a mixture MX of cold white liquor and acidic condensate formed between the acidic condensate PC and the rising cold white liquor.
  • the liquid level When the liquid level reaches an upper screen, it could be circulated back to the bottom as shown in figure 8d , and at least a part of the acidic condensate PC could be returned, either in the mixed fraction MX or also as a part of the acidic condensate. However, some or all of the acidic condensate PC may be sent to recovery as the purer fraction PC, while only the acidic condensate as contained in the mixture MX may be circulated.
  • the switching from withdrawal to recirculation could be controlled by a pH sensor and/or a temperature sensor..

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Claims (13)

  1. Verfahren zur Herstellung von Zellstoff aus Lignin-enthaltenden zellulosischem Material, umfassend,
    Vorhydrolysieren des zellulosischen Materials in einer Vorhydrolysestufe bei einer Temperatur zwischen 120 ° und 180 °C und während wenigstens 20 Minuten, um ein vorhydrolysiertes zellulosisches Material und ein saures Hydrolysat herzustellen ,
    Zufügen einer starken Alkali Bremsgabe dem Gemisch des vorhydrolysierten zellulosischen Materials und des sauren Hydrolysats in solch einem Ausmaß, dass die Restalkalikonzentration nach der Neutralisierung des sauren Hydrolysats über 20 g/l EA als NaOH liegt, eine alkalische Behandlungslauge ausgebildet wird,
    Halten des vorhydrolysierten zellulosischen Materials in der alkalischen Behandlungslauge für ausreichend Zeit in einer alkalischen Vorextraktionsstufe, um die Alkali Konzentration um wenigstens 10g/l EA als NaOH zu reduzieren, aber nicht auf eine Konzentration unter 5g/l EA als NaOH, wobei die gelösten Kohlenhydrate wie auch jedes in der Vorhydrolysestufe gelöste Lignin gelöst aufrechterhalten werden während der alkalischen Vorextraktionsstufe und weitere Kohlenhydrate und Lignin von dem zellulosischem Material in der alkalischen Vorextraktionsstufe gelöst werden,
    danach Übertragen des zellulosischen Materials von der alkalischen Vorextraktionsstufe auf eine Kraft Kochstufe, wobei das starke Alkalilademittel aus Laugenvolumen gemacht wird, welches die Temperatur der resultierenden alkalischen Behandlungslauge für das vorhydrolsierte Material um wenigstens 10% reduziert, im Vergleich zu der Temperatur in der Vorhydrolysestufe, vorzugsweise wenigstens 12°C, falls die Vorhydrolyse Temperatur ungefähr 120 °C und wenigstens 18 °C ist, falls die Vorhydrolysetemperatur ungefähr 180 °C ist, um den Alkaliverbrauch während des kochchemikalischen Diffusionsprozess zu reduzieren, in welchem die alkalische Behandlungslauge zu dem Kern des Lignin-enthaltenden zellulosischem Material vordringt.
  2. Verfahren gemäß Anspruch 1, wobei die Säurebildung der Vorhydrolyse nur durch Erhitzen und optionales Hinzufügen von Wasser, und ohne Hinzufügen eines externen Säuremittels, nur durch Verwenden eines Holzsäuregehalts eingestellt wird, der während des Erhitzens freigesetzt wird, wobei ein pH Wert unterhalb 5 während der Vorhydrolyse erreicht wird.
  3. Verfahren gemäß Anspruch 2, wobei die Säurebildung der Vorhydrolyse durch eine flüssigkeitsgefüllte Phase eingestellt wird.
  4. Verfahren gemäß Anspruch 3, wobei die Temperatur am Ende der Vorhydrolyse in einem Bereich von 150-180°C liegt.
  5. Verfahren gemäß Anspruch 4, wobei die Temperatur der resultierenden alkalischen Behandlungslauge für das vorhydrolysierte Material unter 130 °C liegt.
  6. Verfahren gemäß Anspruch 1, wobei die Säurebildung der Vorhydrolyse, welche durch Erhitzen und Hinzufügen des externen Säuremittels eingestellt wird, wodurch während der Vorhydrolyse ein pH Wert unter 3 erreicht wird.
  7. Verfahren gemäß Anspruch 6, wobei die Säurebildung der Vorhydrolyse in einer flüssigkeitsgefüllten Phase eingestellt wird.
  8. Verfahren gemäß Anspruch 7, wobei die Temperatur am Ende der Vorhydrolyse in einem Bereich von 120-165°C liegt.
  9. Verfahren gemäß Anspruch 8, wobei die Temperatur der resultierenden alkalischen Behandlungslauge für das vorhydrolysierte Material unter 125 °C liegt.
  10. Verfahren gemäß Anspruch 2 oder 5, wobei der Schritt des Haltens des vorhydrolysierten zellulosischen Materials in der alkalischen Behandlungslauge für einen bestimmten Zeitraum von ungefähr 10 bis 90 Minuten ausgeführt wird.
  11. Verfahren gemäß Anspruch 2 oder 5, wobei wenigstens 1 m3/ton von Holz OD der verwendeten alkalischen Behandlungslauge von der alkalischen Vorextraktionsstufe mit seinem Inhalt an gelösten Kohlenhydraten und Lignin vor dem Beginn der Kraft Kochstufe entfernt wird, und danach Alkali zu der Kraft Kochstufe hinzugefügt wird.
  12. Verfahren gemäß Anspruch 1, wobei das Verfahren in einem kontinuierlichen Zellstoffkochersystem durchgeführt wird, welches wenigstens ein Gefäß für die Vorhydrolyse und ein Gefäß für die alkalische Extraktionsstufe und die Kraft Kochstufe verwendet.
  13. Verfahren gemäß Anspruch 12, wobei die alkalische Vorextraktionsstufe in einem separaten Gefäß und die Kraft Kochstufe in einem anderen separaten Gefäß durchgeführt werden.
EP11865841.8A 2011-05-13 2011-05-13 Kompaktes verfahren zur herstellung von vorhydrolysiertem zellstoff Active EP2707539B1 (de)

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PCT/SE2011/050610 WO2012158075A1 (en) 2011-05-13 2011-05-13 Compact process for producing prehydrolyzed pulp

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CA (1) CA2837277C (de)
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US8951388B2 (en) 2011-04-08 2015-02-10 Pec-Tech Engineering And Construction Pte Ltd Method and system for efficient production of dissolving pulp in a kraft mill producing paper grade pulp with a continuous type digester
SE539706C2 (en) 2014-11-07 2017-11-07 Valmet Oy Method for recovering hydrolyzate
SE538454C2 (en) 2014-11-27 2016-07-12 Valmet Oy Method for displacement in batch digesters
ES2959654T3 (es) * 2016-05-27 2024-02-27 Fibratech Pte Ltd Un método y un sistema para la producción de lignina de alto peso molecular
SE541646C2 (en) * 2017-07-04 2019-11-19 Valmet Oy Method for operating a continuous vertical reactor comprising a prehydrolysis zone and the reactor design as such
EP3673110A4 (de) * 2017-08-25 2021-05-12 Valmet AB Verbessertes kompaktes verfahren zur herstellung von vorhydrolysiertem zellstoff
FI130070B (fi) * 2018-03-07 2023-01-31 Andritz Oy Menetelmä liukosellun valmistamiseksi
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SE542991C2 (en) * 2019-03-29 2020-09-22 Valmet Oy A method and a system for extracting hydrolyzate in a continuous cooking process for producing pulp
FI129760B (en) * 2020-07-06 2022-08-15 Amppc Finland Oy HIGH YIELD COOKING METHOD
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CN112048929B (zh) * 2020-08-18 2021-06-29 福建农林大学 一种低固形预水解分离木、竹材原料半纤维素的方法
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WO2012158075A1 (en) 2012-11-22
EP2707539A4 (de) 2014-11-19
RU2546497C1 (ru) 2015-04-10
ES2737432T3 (es) 2020-01-14
EP2707539A1 (de) 2014-03-19
PT2707539T (pt) 2019-06-27
CA2837277C (en) 2017-06-27
CN103687990A (zh) 2014-03-26
CA2837277A1 (en) 2012-11-22
CN103687990B (zh) 2016-03-30

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