EP0517689A1 - Liqueurs avec quantités de sulfure à plusieurs niveaux - Google Patents

Liqueurs avec quantités de sulfure à plusieurs niveaux Download PDF

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Publication number
EP0517689A1
EP0517689A1 EP92890125A EP92890125A EP0517689A1 EP 0517689 A1 EP0517689 A1 EP 0517689A1 EP 92890125 A EP92890125 A EP 92890125A EP 92890125 A EP92890125 A EP 92890125A EP 0517689 A1 EP0517689 A1 EP 0517689A1
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EP
European Patent Office
Prior art keywords
cooking
liquor
white liquor
pulp
stages
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.)
Granted
Application number
EP92890125A
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German (de)
English (en)
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EP0517689B1 (fr
Inventor
Jian E.C/O Kamyr Inc. Jiang
Joe R. C/O Kamyr Inc Phillips
Brian F. c/o Kamyr Inc. Greenwood
Robert J. C/O Kamyr Inc. Prough
c/o Kamyr Inc. Henrickson Kaj
Bertil C. C/O Kamyr Inc. Stromberg
Rolf Ryham
James W. Smith
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.)
Ahlstrom Machinery Inc
Original Assignee
Kamyr Inc
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Filing date
Publication date
Priority claimed from GB919111256A external-priority patent/GB9111256D0/en
Application filed by Kamyr Inc filed Critical Kamyr Inc
Publication of EP0517689A1 publication Critical patent/EP0517689A1/fr
Application granted granted Critical
Publication of EP0517689B1 publication Critical patent/EP0517689B1/fr
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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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
    • D21C11/00—Regeneration of pulp liquors or effluent waste waters
    • D21C11/0064—Aspects concerning the production and the treatment of green and white liquors, e.g. causticizing green liquor
    • 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
    • D21C3/022—Pulping cellulose-containing materials with inorganic bases or alkaline reacting compounds, e.g. sulfate processes in presence of S-containing 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
    • D21C3/22—Other features of pulping processes
    • D21C3/26—Multistage processes

Definitions

  • the concepts described above are utilized in a practical manner to provide kraft pulp that has an optimum viscosity/kappa ratio, and/or good strength properties, and with good yield.
  • the invention is applicable to a wide variety of different kraft cooking processes, both batch and continuous.
  • the invention can be utilized in continuous digesters having an impregnation zone, or in cooking systems utilizing a separate impregnation vessel from the continuous digester, or in batch digesters.
  • the invention can also be utilized in association with co-current movements of white liquor with the pulp, or countercurrent movements, such as are provided in the commercial digesting process marketed by Kamyr, Inc. of Glens Falls, New York under the trademark "MCC".
  • White liquor is that treatment liquid in a kraft process which contains the active cooking chemicals, sodium hydroxide (NaOH) and sodium sulfide (Na2S); or white liquor in an extreme situation may contain substantially only NaOH as active ingredient.
  • the white liquor cooking sulfur content is maintained in the range of 25-35% (this overall sulfur content ratio is the amount of sodium sulfide to the sum of sodium sulfide and sodium hydroxide applied to the whole cooking process), and according to standard practice in the art, a sulfur content level below 15% results in a deterioration in the cooking rate and pulp quality.
  • the present invention it has been found that by making two (or more) supplies or streams of white liquor, with different sulfur contents, and applying them to different portions in the kraft cycle, significantly improved results can be achieved.
  • Practicing the invention it is possible to optimize the viscosity/kappa ratio of the produced pulp for any given level of sulfur content, and/or to optimize pulp strength properties.
  • the increase can be dramatic, easily on the order of 25% for conventional cooks with multiple white liquor additions (co-current), about the same increase for modified continuous cooking (MCCTM), and 15% or more for extended modified continuous cooking (EMCCTM). Comparable increases occur for batch treatment too.
  • a method of producing kraft pulp from cellulosic comminuted fibrous material utilizing white liquor comprises the following steps: (a) Making at least two streams of white liquor, including a second stream having relatively low sulfur content, and a first stream having relatively high sulfur content, substantially higher than the sulfur content of the second stream. (b) Impregnating the cellulosic comminuted fibrous material with the first stream of white liquor. (c) Cooking the cellulosic comminuted fibrous material under kraft cooking conditions, in a cooking zone with cooking chemicals to produce kraft pulp. (d) Supplying the second stream of white liquor to the cooking zone as cooking chemicals. And, (e) washing the kraft pulp produced.
  • a method of producing kraft pulp comprising the following steps: (a) Treating a slurry of cellulosic fibrous material in a plurality of consecutive stages with white liquor, including at least first and second stages, using a first supply of white liquor to the first stage and a second supply to the second stage. (b) Subjecting the material treated with white liquor to cooking conditions in at least one stage of the stages to effect kraft cooking thereof, and producing black liquor. (c) Recovering sulfur from the black liquor. And, (d) adding the recovered sulfur to the first supply of white liquor to significantly increase the sulfur content thereof so that it is greater than the sulfur content of the second supply.
  • a method of producing kraft pulp comprising the steps of: (a) Treating cellulosic comminuted fibrous material in a first stage with a first supply of white liquor. (b) Treating the material in a second stage with a second supply of white liquor. And, (c) controlling the relative sulfur contents of the first and second supplies of white liquor so as to optimize the viscosity/kappa ratio and/or physical strength properties of the kraft pulp produced.
  • any lignin reaction enhancing or carbohydrate degradation slowing chemicals are targeted to one or more specific parts of the cook, such as the impregnation, co-current, or countercurrent stages.
  • the invention is applicable not just to kraft white liquor, but to sulfite process cooking liquors (containing a cationic base), anthraquinone, derivatives of or equivalents to anthraquinone, or the like.
  • the anthraquinone may replace all or some of the sodium sulfide in a cooking liquor containing NaOH, or may be used in other liquor compositions.
  • a method of treating comminuted cellulosic fibrous material with cooking liquor to obtain cellulosic pulp comprises the following steps: (a) Providing at least first and second cooking liquors, including a first cooking liquor having a first concentration of lignin enhancing or carbohydrate degradation slowing chemical, and a second cooking liquor having a second concentration of that lignin enhancing or carbohydrate degradation slowing chemical, the second concentration being from zero to much less than the first concentration. (b) Cooking the comminuted cellulosic fibrous material in several cook stages. (c) Targeting the first cooking liquor to one or more, but less than all, of the cook stages, to provide cooking liquor for that one or more stages; and (d) utilizing the second cooking liquor in at least one cook stage in which the first cooking liquor is not utilized.
  • the cooking liquor utilized above may be a kraft cooking liquor, sulfite cooking liquor, or the like. It may contain a cationic base, sodium sulfide, anthraquinone or its derivatives or equivalents, or the like, and the first liquor may be targeted to an impregnation stage, co-current cook stage, or countercurrent cook stage.
  • FIGURE 1 is a schematic view of exemplary apparatus for practicing an exemplary method according to the present invention.
  • FIGURE 1 illustrates exemplary apparatus for use in a kraft pulping process.
  • the invention is applicable to other processes for the production of paper pulp from comminuted cellulosic fibrous material in which any lignin reaction enhancing or carbohydrate degradation slowing chemicals are targeted to one or more specific parts of the cook, such as the impregnation, co-current, or countercurrent stages.
  • a digester 12 which preferably is a continuous digester such as that sold by Kamyr, Inc. of Glens Falls, New York, but may be a batch digester -- has a stream of off gases 13, and black liquor (residual white liquor containing the reaction products of lignin solubilization) is withdrawn at an intermediate position as indicated at 14, while the kraft pulp produced is discharged at 15.
  • black liquor in line 14 When the black liquor in line 14 is discharged, it may be passed directly to black liquor evaporators, and preferably it is subjected, somewhere in the evaporator chain, to a heat treatment process at step 17 to produce off gases in line 18.
  • the heat treatment of block 17 is preferably that described in U.S.
  • the off gases in line 18 which may include only those from the heat treatment 17, or also those from the digester line 13, only and from the black liquor evaporators in line 20, or a combination of any two of them -- are preferably first subjected to a drying or absorption stage (as indicated schematically at 27 in FIGURE 1) in order to remove a majority of the water vapor.
  • the removal of the water vapor increases the concentration of organic sulfur gases.
  • Step 27 is accomplished by drying the gas stream by any conventional means and/or by absorbing or adsorbing the organic portion of the gas onto a solid, or additionally by absorbing the off gas into one of any non-polar liquids (e.g. kerosene or mineral oil).
  • Treatment may be provided of a liquid mixture, but preferably according to the invention further treatment is of the concentrated gas.
  • the next steps in the treatment of the off gases as illustrated in FIGURE 1 are to add hydrogen, and then pass the gas in the presence of the added hydrogen past a hydrogen desulfurization catalyst.
  • This may be accomplished, for example, in the hydrogen desulfurization (HDS) unit 28, with the hydrogen gas from line 29 added to the unit 28 along with the gas in line 18.
  • the hydrogen gas in line 29 can come from any source (e.g. be purchased , from water electroylsis, etc.).
  • the hydrogen desulfurization catalyst consist essentially of a transition metal-molybdenum alloy, particularly a nickel molybdenum or cobalt molybdenum alloy.
  • the product gas stream in line 30 is further acted upon.
  • the gas stream in line 30 contains primarily methane, and hydrogen sulfide, with hydrogen also present.
  • the hydrogen sulfide is then separated out from the gas in stream 30.
  • the hydrogen sulfide may be separated as a gas and then used in its gaseous form in conventional pulping techniques, it may be fed to a scrubber 32 in which it is brought into contact with a caustic solution, preferably kraft white liquor, which contains sodium hydroxide and most likely at least some sodium sulfide. While in the preferred embodiment illustrated in the drawings white liquor is utilized, under some circumstances green liquor may be advantageously utilized, with white liquor subsequently made from the green liquor.
  • White liquor from line 24 is passed into inlet 33 of scrubber 32, the hydrogen sulfide being absorbed in the white liquor and thereby significantly enhancing its sulfur content.
  • the significantly enhanced sulfur content white liquor then passes through the outlet 34 of the scrubber into line 35, to be used in the pulping process.
  • the white liquor in line 35 passes through a polysulfide treatment stage, as illustrated at 36, and then to the impregnation vessel 37 (if a separate impregnation vessel is used) or the like, to be utilized in the pulping cycle.
  • Elemental sulfur may be added at 36 instead of polysulfide.
  • the gas stream that remains, in line 38, contains primarily methane, but also some hydrogen. Ultimately, the gas in line 38 may become the source of the hydrogen for line 29.
  • the high sulfur content white liquor in line 35 is provided at an early stage of the cook, e. g. at the beginning of the impregnation vessel 37, or impregnation stage if impregnation takes place in the digester 12 itself, or at multiple-places in the impregnation zone and/or vessel 37.
  • a countercurrent impregnation flow may be provided, in which case the higher sulfur content liquor is added near the end of the impregnation stage.
  • Part of the sulfide depleted white liquor in line 24 is passed into line 41, and it is then introduced into the cook, preferably at multiple locations, as indicated at 42 and 43 in FIGURE 1.
  • the low sulfur content white liquor in line 41 may vary widely.
  • it may be added to the middle of the impregnation vessel 37, at one, two, or more co-current stages in the digester 12, or at one, two, or more countercurrent stages in the digester 12 (e.g. for modified continuous cooking, or extended modified continuous cooking).
  • the liquor in line 41 may also be utilized in a batch process.
  • While the drawing illustrates only two streams or supplies of white liquor, 35, 41, having different sulfur content, as many different sulfur content streams as desired may be produced.
  • two series connected units 32 may be utilized, the first producing the highest sulfur content level white liquor, while the second produces an intermediate (between lines 35 and 41) sulfur content level white liquor.
  • the intermediate sufidity white liquor is added earlier in the cook than the white liquor in line 41.
  • the relative amount of sulfur content of the white liquor added at various stages within the kraft cycle may also be varied widely according to the invention.
  • the kraft pulping process is to be a multi-level conventional cook, that is white liquor is added at two or more points in the cook and flows co-currently with the pulp, then about 60% of the total cooking chemical is added to the impregnation vessel (e.g. in line 35), while about 25% is added to the first co-current stage (e.g. at 42) and about 15% to the second co-current stage (e.g. at 43).
  • the amount of sulfide provided in line 35 is about 60-90%, and if practical may be almost 100% of the total sulfide in all of the white liquor streams, that is the white liquor in stream 41 is substantially fully sulfide depleted.
  • the stream in line 35 in this embodiment may be made by manufactured by passing 35-65% of the total volume of white liquor through the unit 32, the remaining 65-35% of the white liquor being added through line 41.
  • about 35% of the total volume of white liquor is passed through unit 32, and this high sulfur content white liquor is then added to the top circulation in the conventional impregnation vessel 37.
  • the sulfide-depleted white liquor in line 41 is added to middle circulation in the vessel 37 in the amount of about 25-35% of the total cooking chemical from white liquor, while about 20-25% of the total cooking chemical, in the sulfide depleted white liquor in line 41, is added to the continuous digester 12 first cooking circulation.
  • the low sodium sulfide content liquor in line 41 may also be added at 44 to an oxygen delignification or bleaching stage 45 as a source of sodium hydroxide.
  • the viscosity to kappa ratio may be increased by about 0.2-0.3 units if almost all sulfide is added to the impregnation stage (e.g. in line 35 to vessel 37).
  • the total sulfur content is added in the impregnation stage (line 35), the total volume of white liquor added in line 35 being about 40-65% of the total volume of white liquor used in the pulping process.
  • polysulfide is added to the white liquor.
  • this can be done by the MOXY (TM) process in which some of the sodium sulfide in the white liquor is partially oxidized to produce polysulfide, or by other known polysulfide processes.
  • polysulfide from an external source may merely be introduced into the white liquor, e.g. polysulfide produced by reacting elemental sulfur with sulfide ions in an aqueous solution under proper conditions; or elemental sulfur may be added to the white liquor instead of polysulfide.
  • the amount of polysulfide produced, or added, in stage 36 is about 0.5%-8% on wood, expressed as elemental sulfur. Typically, about 2% polysulfide is desirable. If 2% polysulfide is used in conjunction with extended modified continuous cooking, a kraft pulp with a kappa of about 12.5, a viscosity of about 33.7 cp, and a yield of about 44.6% can be made. This yield is equal to that of a conventional cook or extended modified continuous cook pulp at a kappa of about 18-20 without polysulfide, and the viscosity is equivalent to that of a conventional cook pulp at kappa 26, or an extended modified continuous cook pulp at kappa 17.
  • a slurry of wood chips is treated in a plurality of consecutive stages (e.g. impregnation stage, first and second co-current or countercurrent cooking stages) with white liquor using first and second supplies, differing in the sulfur content thereof.
  • the chips are treated with white liquor under cooking conditions (e.g. in digester 12) in at least one stage, to effect kraft cooking thereof.
  • Black liquor is withdrawn (at 14) and sulfur is recovered from the black liquor, as by heating treating it (at 17) according to the process of US Patent 4,929,307, evaporating it (in 19), etc. (see 22 and 23 in FIGURE 1).
  • the recovered sulfur is added to the first supply of white liquor, as in unit 32, to significantly increase the sulfur content thereof, so that the sulfur content of the liquor in line 35 is substantially greater than that in line 24 (which is sulfur depleted, and may be near zero).
  • the relative sulfur contents of the white liquors in lines 35 and 24 are controlled so as to optimize the viscosity/kappa ratio and/or physical strength properties.
  • the invention allows advantageous production of kraft pulp to be practiced on an industrial scale -- that is, larger production than reasonably possible in a laboratory, with complete chemical recovery.
  • the invention may be illustrated by various examples.
  • Tables IA-IE provide the results of laboratory batch cooks using split white liquor streams with variable sulfur content, according to the invention, and conventional cooks for comparison purposes.
  • CK means conventional kraft cooking
  • MCK means kraft cooking with multiple introductions of white liquor, with more than one co-current cooking stage
  • MCC refers to Kamyr, Inc.'s trademarked modified continuous cooking process in which multiple introductions of white liquor are provided
  • EMCC refers to Kamyr, Inc.'s trademarked extended modified continuous cooking process in which a second countercurrent cook is provided.
  • Table II illustrates the advantages achieved when polysulfide is used.
  • the liquid to wood ratio for all cooks in Table II is 4/1.
  • “Sulfidity” refers to sodium sulfide content.
  • the method according to the invention optimizes the viscosity/kappa ratio and/or strength properties of kraft pulp produced, and achieves other advantageous results.
  • the utilization of polysulfide or elemental sulfur as part of the sulfide content of the white liquor also significantly increases yield.
  • the invention is applicable to other cooking processes and cooking liquors for the production of paper pulp.
  • sulfite cooking liquor and when using other lignin reaction enhancing or carbohydrate degradation slowing chemicals, such as anthraquinone or its derivatives or equivalents, or the like, significant increases in viscosity/kappa ratio or pulp strength properties can be obtained by targeting one cooking liquor to a specific stage (or stages) of the cook, while another cooking liquor is used in other portions.
  • a method in which comminuted cellulosic fibrous material is treated with cooking liquor to obtain cellulosic pulp in the following steps: (a) Providing at least first and second cooking liquors, including a first cooking liquor having a first concentration of lignin enhancing or carbohydrate degradation slowing chemical (e.g. in line 35) , and a second cooking liquor (e.g. in line 41) having a second concentration of that lignin enhancing or carbohydrate degradation slowing chemical, the second concentration being from zero to much less than the first concentration. (b) Cooking the comminuted cellulosic fibrous material in several cook stages (e.g. in vessels 12, 37).

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  • Chemical & Material Sciences (AREA)
  • Inorganic Chemistry (AREA)
  • Paper (AREA)
  • Transition And Organic Metals Composition Catalysts For Addition Polymerization (AREA)
  • Artificial Filaments (AREA)
  • Catalysts (AREA)
EP92890125A 1991-05-24 1992-05-25 Un procédé de fabrication de pâte kraft Expired - Lifetime EP0517689B1 (fr)

Applications Claiming Priority (6)

Application Number Priority Date Filing Date Title
GB919111256A GB9111256D0 (en) 1991-05-24 1991-05-24 Pulping process
GB9111256 1991-05-24
US75684991A 1991-09-10 1991-09-10
US78815191A 1991-11-05 1991-11-05
US756849 1991-11-05
US788151 1991-11-05

Publications (2)

Publication Number Publication Date
EP0517689A1 true EP0517689A1 (fr) 1992-12-09
EP0517689B1 EP0517689B1 (fr) 1997-07-16

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EP92890125A Expired - Lifetime EP0517689B1 (fr) 1991-05-24 1992-05-25 Un procédé de fabrication de pâte kraft

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EP (1) EP0517689B1 (fr)
JP (1) JPH05163690A (fr)
AT (1) ATE155540T1 (fr)
DE (1) DE69220853D1 (fr)
FI (1) FI921254A0 (fr)
NO (1) NO920692L (fr)

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1995023256A1 (fr) * 1994-02-28 1995-08-31 Valtion Teknillinen Tutkimuskeskus Procede de production et d'utilisation de produits chimiques supplementaires destines a la reduction en pate dans un procede du type kraft
WO1996002698A1 (fr) * 1994-07-18 1996-02-01 Pulp And Paper Research Institute Of Canada Cuisson de pate kraft en deux etapes
WO1996006217A1 (fr) * 1994-08-18 1996-02-29 Kamyr, Inc. Ameliorations de la reduction du bois en pate avec elimination des solides dissous
WO1996007787A1 (fr) * 1994-09-02 1996-03-14 Kamyr, Inc. Cuisson de matieres cellulosiques avec pretraitement a l'aide de la liqueur epuisee
WO1996007786A1 (fr) * 1994-09-02 1996-03-14 Kamyr, Inc. Procede de cuisson continue de pate kraft avec pretraitement de la liqueur noire
EP0903436A2 (fr) * 1997-09-18 1999-03-24 Kvaerner Pulping Ab Procédé pour l'imprégnation et digestion de matériaux lignocellulosiques
US6132556A (en) * 1993-05-04 2000-10-17 Andritz-Ahlstrom Inc. Method of controlling pulp digester pressure via liquor extraction
EP1052326A1 (fr) * 1999-05-11 2000-11-15 Air Products And Chemicals, Inc. Utilisation de liqueur blanche oxidée dans un procédé Kraft de cuisson
WO2018211175A1 (fr) * 2017-05-16 2018-11-22 Andritz Oy Procédé de production de pâte chimique

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20070240837A1 (en) * 2006-04-13 2007-10-18 Andritz Inc. Hardwood alkaline pulping processes and systems
WO2008088077A1 (fr) * 2007-01-15 2008-07-24 Nihon Cellulose Co., Ltd. Procédé de production de pâte
KR20120125488A (ko) * 2010-01-05 2012-11-15 바스프 에스이 다황화물에 기초한, 극고온을 위한 열 전달 유체 및 열 저장 유체

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR1375278A (fr) * 1962-09-15 1964-10-16 Dominion Tar & Chemical Co Perfectionnements à la fabrication de pâtes cellulosiques
EP0407370A2 (fr) * 1989-06-28 1991-01-09 Kamyr Ab Cuisson de pâte à papier à haute sulfidité, en procédant à une sulfonisation à la liqueur noire des copeaux traités à la vapeur

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AU1765892A (en) * 1991-02-06 1992-09-07 A. Ahlstrom Corporation A method of recovering energy and chemicals from black liquor

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR1375278A (fr) * 1962-09-15 1964-10-16 Dominion Tar & Chemical Co Perfectionnements à la fabrication de pâtes cellulosiques
EP0407370A2 (fr) * 1989-06-28 1991-01-09 Kamyr Ab Cuisson de pâte à papier à haute sulfidité, en procédant à une sulfonisation à la liqueur noire des copeaux traités à la vapeur

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
ABSTRACT BULLETIN OF THE INSTITUTE OF PAPER CHEMISTRY. vol. 56, no. 11, May 1986, APPLETON US page 1366; ANDREWS, E.K. ET AL.: 'Extended delignification kraft pulping of softwoods.-Effect of treatments on chips and pulp with sulfide-containing liquors.' *
WORLD PATENTS INDEX Week 8038, Derwent Publications Ltd., London, GB; AN 80-66836C & JP-A-55 103 386 (SANYO KOKUSAKO PULP) 8 August 1980 *

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5575890A (en) * 1993-05-04 1996-11-19 Kamyr, Inc. Method for selectively increasing the sulfide ion concentration and sulfidity of kraft cooking liquor during kraft cooking of wood
US6132556A (en) * 1993-05-04 2000-10-17 Andritz-Ahlstrom Inc. Method of controlling pulp digester pressure via liquor extraction
WO1995023256A1 (fr) * 1994-02-28 1995-08-31 Valtion Teknillinen Tutkimuskeskus Procede de production et d'utilisation de produits chimiques supplementaires destines a la reduction en pate dans un procede du type kraft
WO1996002698A1 (fr) * 1994-07-18 1996-02-01 Pulp And Paper Research Institute Of Canada Cuisson de pate kraft en deux etapes
WO1996006217A1 (fr) * 1994-08-18 1996-02-29 Kamyr, Inc. Ameliorations de la reduction du bois en pate avec elimination des solides dissous
WO1996007787A1 (fr) * 1994-09-02 1996-03-14 Kamyr, Inc. Cuisson de matieres cellulosiques avec pretraitement a l'aide de la liqueur epuisee
US5660686A (en) * 1994-09-02 1997-08-26 Ahlstrom Machinery Inc. Cooking with spent liquor pretreatment of cellulose material
WO1996007786A1 (fr) * 1994-09-02 1996-03-14 Kamyr, Inc. Procede de cuisson continue de pate kraft avec pretraitement de la liqueur noire
EP0903436A2 (fr) * 1997-09-18 1999-03-24 Kvaerner Pulping Ab Procédé pour l'imprégnation et digestion de matériaux lignocellulosiques
EP0903436A3 (fr) * 1997-09-18 1999-09-01 Kvaerner Pulping Ab Procédé pour l'imprégnation et digestion de matériaux lignocellulosiques
EP1052326A1 (fr) * 1999-05-11 2000-11-15 Air Products And Chemicals, Inc. Utilisation de liqueur blanche oxidée dans un procédé Kraft de cuisson
WO2018211175A1 (fr) * 2017-05-16 2018-11-22 Andritz Oy Procédé de production de pâte chimique
US11473241B2 (en) 2017-05-16 2022-10-18 Andritz Oy Method of producing chemical pulp

Also Published As

Publication number Publication date
EP0517689B1 (fr) 1997-07-16
NO920692L (no) 1992-11-25
DE69220853D1 (de) 1997-08-21
NO920692D0 (no) 1992-02-21
ATE155540T1 (de) 1997-08-15
FI921254A0 (fi) 1992-03-24
JPH05163690A (ja) 1993-06-29

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