WO1994010375A1 - Traitement de la pate de cellulose avec deplacement du chelate - Google Patents

Traitement de la pate de cellulose avec deplacement du chelate Download PDF

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Publication number
WO1994010375A1
WO1994010375A1 PCT/US1993/009212 US9309212W WO9410375A1 WO 1994010375 A1 WO1994010375 A1 WO 1994010375A1 US 9309212 W US9309212 W US 9309212W WO 9410375 A1 WO9410375 A1 WO 9410375A1
Authority
WO
WIPO (PCT)
Prior art keywords
pulp
wash liquid
stage
recited
metals
Prior art date
Application number
PCT/US1993/009212
Other languages
English (en)
Inventor
J. R. Prough
Brian F. Greenwood
W. E. Wiley
Victor L. Bilodeau
C. B. Stromberg
Original Assignee
Kamyr, Inc.
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 Kamyr, Inc. filed Critical Kamyr, Inc.
Publication of WO1994010375A1 publication Critical patent/WO1994010375A1/fr

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Classifications

    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
    • D21C9/10—Bleaching ; Apparatus therefor
    • D21C9/1005—Pretreatment of the pulp, e.g. degassing the pulp
    • 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
    • D21C9/1026—Other features in bleaching processes
    • D21C9/1042—Use of chelating agents

Definitions

  • a method which effects removal of the majority of metals from the pulp prior to any bleaching or extended (e.g., oxygen) "delignification thereof so as to maximize the effectiveness of the subsequent bleaching and/or oxygen delignification stages, thereby facilitating the elimination, or minimization, of chlorine bleaching chemicals.
  • any bleaching or extended (e.g., oxygen) "delignification thereof so as to maximize the effectiveness of the subsequent bleaching and/or oxygen delignification stages, thereby facilitating the elimination, or minimization, of chlorine bleaching chemicals.
  • a method of creating cellulose pulp, particularly chemical pulp (and more particularly kraft pulp) having metals therein, prior to bleaching or oxygen delignification comprises the following steps: (a) In a first stage, washing cellulose pulp with a first wash liquid, including an amount of chelating agent and chemicals required (if necessary) to properly adjust pH, collectively effective to ultimately effect removal of the majority of the metals from the pulp, to produce pulp with a chelate. (b) In a second stage, after the first stage, washing the pulp from step (a) with a second wash liquid to displace the chelate from the pulp, to produce a washed pulp having the majority of the metals removed therefrom. And, (c) oxygen delignifying and/or bleaching the washed pulp from step (b) with no or minimal chlorine, to produce a bleached pulp.
  • step (c) is practiced without the use of any chlorine, e.g., using a plurality of stages selected from the group consisting essentially of O, __ , P, A and E ( v e.g., Eo or Eop stages), e.g., OOAZEZP.
  • Spent wash liquid is preferably extracted during the practice of step (a) and is used in an earlier pulp treatment step.
  • at least one additional washing step, after the second wash stage may be provided to effect further removal of chelate (and metals) from the pulp prior to step (c).
  • the chelating agent is preferably EDTA or DTPA although other chelating agents may be utilized.
  • the invention also preferably comprises the further step of recirculating part of the spent wash liquid from step (b) to step (a) to provide a part of the first wash liquid, and sewering another part of the spent wash liquid from step (b), with chelate therein.
  • the proportion of spent wash liquid from step (b) being sewered or recirculated may be dependent upon the concentration of metals therein.
  • the method is preferably practiced at medium consistency (e.g., about 6-15%, preferably about 8-12%).
  • a method of treating cellulose pulp having metals therein, prior to bleaching or oxygen delignification thereof comprises the steps of (a) In a first stage, washing chemical cellulose pulp at a consistency of about 8-12% with a first wash liquid, including an amount of chelating agent effective to ultimately effect removal of the majority of the metals from the pulp, to produce pulp with a chelate. (b) In a second stage, after the first stage, washing the pulp from step (a) with a second wash liquid to displace the chelate from the pulp, to produce a washed pulp having the majority of the metals removed therefrom.
  • step (c) recirculating part of the spent wash liquid from step (b) to step (a) to provide a part of the first wash liquid.
  • step (c) recirculating part of the spent wash liquid from step (b) to step (a) to provide a part of the first wash liquid.
  • step (b) may also be the further step of sewering a part of the spent wash liquid, with chelate therein, from step (b) and controlling the proportions of spent wash liquid from step (b) being sewered or recirculated depending upon the concentration of the metals therein.
  • FIGURE 1 is a schematic view showing a method of removing metals from cellulose pulp prior to bleaching, according to the invention.
  • FIGURE 2 is a schematic view showing the method of FIGURE 1 in association with bleaching and pretreatment stages.
  • Pulp in line 11 from a preceding process stage (such as chemical pulp -- e.g., kraft pulp -- from a continuous digester, which has gone through a first wash, or storage stage) is fed to a first wash stage 12 according to the invention.
  • the equipment utilized in the stage 12 may be any suitable equipment for effecting "washing", specifically equipment for washing medium consistency pulp (e.g., a consistency of about 6-15%, typically about 8-12%) .
  • the washer 12 may be a conventional atmospheric or pressure diffusion washer such as available from Kamyr, Inc., of Glens Falls, New York, a drum washer such as available from A. Ahlstro Corporation of Roswell, Georgia, or other types of washers.
  • Wash liquid is supplied to the stage 12 in line 13 from a wash liquid source 14.
  • the wash liquid 14 is typically primarily water.
  • a chelating agent -- such as DTPA, EDTA, NTA, or their derivatives (or equivalents) -- is added to the wash liquid in line 13, as indicated by reference numeral 15 in FIGURE 1.
  • Added with the chelating agent to the wash liquid are -- if necessary -- chemicals to adjust pH to make the chelating agents most effective. Examples of such pH adjusting chemicals are NaOH and H ? SO..
  • the amount of chelating agent added is effective (at a given pH) to ultimately effect removal of the majority of the metals from the pulp in line 11 to produce a substantially metal-free pulp.
  • the amount of chelating agent will depend upon the particular chelating agent utilized, the particular type of pulp, the metal content of the pulp, and a number of other parameters.
  • Spent liquid from the first wash stage 12 is extracted as indicated at 16 in FIGURE 1.
  • the pulp with chelate from the first wash stage 12 passes in line 17 to a second wash stage 18.
  • the equipment for the wash stage 18 may be the same as for the stage 12, or any other type of conventional wash equipment.
  • Wash liquid such as water
  • the second wash liquid, from source 19 and in the stage 18, displaces the chelate from the pulp.
  • the spent wash liquid, with chelate, from stage 18 is withdrawn in lines 22, 23 from the second stage 18, preferably passing through valves 24, 25, respectively, controlled by a controller 26 (such as a computer) .
  • That amount of the spent wash liquid from the second stage 18 that passes through the valve 24 is recirculated to the line 13 to provide part of the wash liquid for the first stage 12, while that part of the spent wash liquid in line 23 flowing through valve 25 is sewered (e.g., disposed of, or treated to reclaim the metals, or to make the effluent environmentally acceptable).
  • the valves 24, 25 can be controlled by controller 26 depending upon a wide variety of process conditions, including the concentration, of metals in the liquid withdrawn from the stage 18.
  • Washed pulp having the majority of the metals removed therefrom passes in line 27 to subsequent stages.
  • one or more additional optional wash stages 28 may be provided to effect further removal of chelate (including metals) therefrom, until ultimately, pulp with metals removed therefrom in line 29 passes to subsequent bleach or extended delignification stages, such as oxygen delignification, peroxide, ozone, caustic extraction, or even chlorine dioxide stages.
  • FIGURE 2 shows a metal removal method illustrated schematically at 10 in FIGURE 1 in association with other process stages. As illustrated in FIGURE 2, the extract 16 from the first wash stage 12 may be used in a preceding process stage, such as an earlier wash stage 32 in which no chelate is used.
  • the pulp in line 29 passes to a plurality of subsequent oxygen delignification or bleach stages 33 through 35.
  • Stages 33 through 35 are designed to effectively bleach the pulp with a minimum use of chlorine, and preferably use no chlorine whatsoever. That is, preferably the subsequent bleaching stages 33 through 35 are selected from the group consisting essentially of 0, Z, P, A and E (e.g., E or E ).
  • one or more oxygen delignification stages are utilized first, followed by ozone, peroxide and/or caustic extraction stages.
  • one of the sequences disclosed in copending application Serial No. 07/839,389 may be employed (e.g., OOAZEZP).
  • the final product produced -- illustrated schematically at 36 in FIGURE 2 -- is a bleached cellulose pulp, which has been produced utilizing a minimum of chlorine, yet has sufficient brightness (e.g., at least 90 ISO) so that it may be used as a commercial grade bleached pulp, such as for the manufacture of bond paper, or the like.
  • the consistency of the pulp during the practice of the method 10 is typically medium consistency, e.g., about 6-15%, preferably about 8-12%. Even during the bleaching stages 30-35, etc., the pulp may be maintained at medium consistency.

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  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Wood Science & Technology (AREA)
  • Paper (AREA)

Abstract

L'on traite la pâte de cellulose, telle que la pâte kraft, comportant des métaux, avant son blanchiment ou sa délignification à l'oxygène de sorte que l'on puisse la blanchir de manière efficace sans chlore, ou avec une quantité minimum de chlore. Dans une première étape, on lave la pâte avec un premier liquide de lavage, renfermant une quantité d'agent chélatant (tel que EDTA, DTPA ou NTA) efficace pour retirer la majorité des métaux de la pâte, afin d'obtenir une pâte avec un chélate. On peut aussi ajouter, si nécessaire, des agents chimiques pour ajuster le niveau de pH. Dans une seconde étape, à la suite de la première, on lave la pâte avec un second liquide de lavage afin de retirer le chélate de la pâte et d'obtenir une pâte épurée dont on a retiré la majorité des métaux. On peut également effectuer d'autres étapes de lavage. La pâte sans métaux est ensuite soumise à la délignification à l'oxygène et/ou au blanchiment, de préférence sans utiliser de chlore d'aucune sorte (tel qu'en effectuant une pluralité d'étapes O, Z, P, A et/ou E). On peut faire recirculer une partie du liquide de lavage usé provenant de la seconde étape pour obtenir une partie du liquide de lavage de la première étape alors que l'on évacue une partie du liquide de lavage usé provenant de la seconde étape. L'on peut réguler les proportions de liquide de lavage usé que l'on a évacué ou que l'on a fait recirculer en fonction de la concentration des métaux dans le liquide de lavage usé. Le lavage se fait de préférence à une consistence moyenne.
PCT/US1993/009212 1992-10-26 1993-09-28 Traitement de la pate de cellulose avec deplacement du chelate WO1994010375A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US96674592A 1992-10-26 1992-10-26
US966,745 1992-10-26

Publications (1)

Publication Number Publication Date
WO1994010375A1 true WO1994010375A1 (fr) 1994-05-11

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1998016683A1 (fr) * 1996-10-11 1998-04-23 Solvay Interox (Societe Anonyme) Procede de delignification et de blanchiment de pate a papier chimique
WO1999020829A1 (fr) * 1997-10-17 1999-04-29 Solvay (Societe Anonyme) Fabrication de pate a papier chimique
WO1999020830A1 (fr) * 1997-10-17 1999-04-29 Solvay (Societe Anonyme) Fabrication de pate a papier chimique
US5985097A (en) * 1994-05-24 1999-11-16 Aga Aktiebolag Method for suppressing undesired effects of transition and alkaline metal compounds during bleaching

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2502330A (en) * 1943-03-01 1950-03-28 Clarence E Libby Washing paper pulp to remove coloring matter
US4946556A (en) * 1989-04-25 1990-08-07 Kamyr, Inc. Method of oxygen delignifying wood pulp with between stage washing
EP0554965A1 (fr) * 1991-04-30 1993-08-11 Eka Nobel Ab Procédé de blanchiment de matériaux contenant de la lignocellulose

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2502330A (en) * 1943-03-01 1950-03-28 Clarence E Libby Washing paper pulp to remove coloring matter
US4946556A (en) * 1989-04-25 1990-08-07 Kamyr, Inc. Method of oxygen delignifying wood pulp with between stage washing
EP0554965A1 (fr) * 1991-04-30 1993-08-11 Eka Nobel Ab Procédé de blanchiment de matériaux contenant de la lignocellulose

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
DATABASE WPI Section Ch Week 8151, Derwent World Patents Index; Class F09, AN 81-94305D *

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5985097A (en) * 1994-05-24 1999-11-16 Aga Aktiebolag Method for suppressing undesired effects of transition and alkaline metal compounds during bleaching
WO1998016683A1 (fr) * 1996-10-11 1998-04-23 Solvay Interox (Societe Anonyme) Procede de delignification et de blanchiment de pate a papier chimique
BE1010679A3 (fr) * 1996-10-11 1998-11-03 Solvay Interox Procede de delignification et de blanchiment de pate a papier chimique.
WO1999020829A1 (fr) * 1997-10-17 1999-04-29 Solvay (Societe Anonyme) Fabrication de pate a papier chimique
WO1999020830A1 (fr) * 1997-10-17 1999-04-29 Solvay (Societe Anonyme) Fabrication de pate a papier chimique
BE1011503A3 (fr) * 1997-10-17 1999-10-05 Solvay Interox Fabrication de pate a papier chimique.
BE1011504A3 (fr) * 1997-10-17 1999-10-05 Solvay Interox Fabrication de pate a papier chimique.

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