EP0847460A1 - Verfahren zur verhinderung der metallanhäufung in einem geschlossenen verfahren zur zellstoffbleichung - Google Patents

Verfahren zur verhinderung der metallanhäufung in einem geschlossenen verfahren zur zellstoffbleichung

Info

Publication number
EP0847460A1
EP0847460A1 EP96929609A EP96929609A EP0847460A1 EP 0847460 A1 EP0847460 A1 EP 0847460A1 EP 96929609 A EP96929609 A EP 96929609A EP 96929609 A EP96929609 A EP 96929609A EP 0847460 A1 EP0847460 A1 EP 0847460A1
Authority
EP
European Patent Office
Prior art keywords
bleaching
pulp
metals
peracetic acid
value
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.)
Withdrawn
Application number
EP96929609A
Other languages
English (en)
French (fr)
Inventor
Ulf Germgard
Jonas Lindquist
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 AB
Original Assignee
Sunds Defibrator Industries 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 Sunds Defibrator Industries AB filed Critical Sunds Defibrator Industries AB
Publication of EP0847460A1 publication Critical patent/EP0847460A1/de
Withdrawn legal-status Critical Current

Links

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
    • D21C9/1026—Other features in bleaching processes
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
    • D21C9/10—Bleaching ; Apparatus therefor
    • D21C9/16—Bleaching ; Apparatus therefor with per compounds
    • D21C9/166—Bleaching ; Apparatus therefor with per compounds with peracids

Definitions

  • This invention relates to chlorine-free bleaching of pulp from ligno- cellulosic fiber material comprising bleaching with peracetic acid.
  • TCF bleaching mostly is carried out with oxygen gas, hydrogen peroxide ozone and/or some type of peracids such as peracetic acid (Paa) . Due to the fact that neither chlorine nor chlorine dioxide are used as bleaching chemical, chloride ions are prevented from accumulating at the chemical recovery when the bleach plant is closed, and thereby the risk of corrosion attacks a.o. in the soda recovery boiler is reduced substantially.
  • a chelating agent treatment is carr ⁇ ied out in a separate step before the hydrogen peroxide step (so-called Q-step) .
  • the Q-step is carried out in such a way that the pulp is treated with a chelating agent of the type EDTA or DTPA, whereafter the pulp is washed in order to eliminate released metals.
  • the conditions normally applied in the Q-step are 70-90 C, 1-2 hours, 10-14% pulp concentration, pH 5-7 and charge of chelating agent mostly of the magnitude 1-3 kg/;;.
  • a Paa-step bleaches the pulp much inferior when the pH is increased above pH 7, which renders it difficult to carry out an alkaline TCF bleaching containing peracetic acid.
  • the present invention has the object to solve the aforesaid problems. It implies that the peracetic acid bleaching can be carried out under optimum pH conditions for the bleaching while at the same time the metals are bound in the pulp and thereby can follow along out of the bleach plant, so that the bleaching process can be closed.
  • the Paa-step is carried out at a temperature of at least 70°C, preferably 80-120°C, for 1-2 hours at pH 5-7, preferably 5-6.
  • the Paa-step can be pressurized. This means optimum pH conditions for the peracetic acid bleaching, but also that metals such as calcium and manganese are released.
  • the pulp is washed before it is transferred to the next step in the bleaching sequence.
  • the pH value is increased to at least 9, preferably 9-12, in the final phase of the Paa-step in order thereby to effect a rebinding of the metals to the fibers in the pulp.
  • the bleaching process can thereby be closed in counterflow without risk of accumulation of the metals.
  • the pH value should be increased 1-10 preferably 2-5 minutes before the washing. This can be made with help of alkali, which preferably is added in the form of alkaline white water from other parts of the bleaching process.

Landscapes

  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Wood Science & Technology (AREA)
  • Paper (AREA)
EP96929609A 1995-08-30 1996-08-09 Verfahren zur verhinderung der metallanhäufung in einem geschlossenen verfahren zur zellstoffbleichung Withdrawn EP0847460A1 (de)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
SE9503004A SE9503004L (sv) 1995-08-30 1995-08-30 Blekning av massa
SE9503004 1995-08-30
PCT/SE1996/000997 WO1997008381A1 (en) 1995-08-30 1996-08-09 Method for preventing accumulation of metals in a closed pulp bleaching process

Publications (1)

Publication Number Publication Date
EP0847460A1 true EP0847460A1 (de) 1998-06-17

Family

ID=20399329

Family Applications (1)

Application Number Title Priority Date Filing Date
EP96929609A Withdrawn EP0847460A1 (de) 1995-08-30 1996-08-09 Verfahren zur verhinderung der metallanhäufung in einem geschlossenen verfahren zur zellstoffbleichung

Country Status (7)

Country Link
EP (1) EP0847460A1 (de)
AU (1) AU6892696A (de)
BR (1) BR9610198A (de)
CA (1) CA2229893A1 (de)
NO (1) NO980872D0 (de)
SE (1) SE9503004L (de)
WO (1) WO1997008381A1 (de)

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SE509444C2 (sv) * 1997-05-14 1999-01-25 Mo Och Domsjoe Ab Förfarande för minimering av kalcium orsakat inkrustproblem vid framställning av blekt cellulosamassa
SE511794C2 (sv) * 1997-06-30 1999-11-29 Sunds Defibrator Ind Ab Sätt att reducera halten kalcium i vätskefasen i en pappersmassasuspension
AU5657098A (en) * 1997-11-25 1999-06-15 Amylum Belgium N.V. Improvements to the bleaching process for chemical pulp and intermediate pulp dispersions
FI117337B (fi) * 2004-12-16 2006-09-15 Kemira Oyj Menetelmä mangaanin poistamiseksi vedestä

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SE9301160L (sv) * 1992-08-28 1994-03-01 Sunds Defibrator Ind Ab Förfarande för behandling av processvatten
AU671337B2 (en) * 1992-11-27 1996-08-22 Eka Nobel Ab Process for bleaching of lignocellulose-containing pulp
US5554259A (en) * 1993-10-01 1996-09-10 Union Camp Patent Holdings, Inc. Reduction of salt scale precipitation by control of process stream Ph and salt concentration

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO9708381A1 *

Also Published As

Publication number Publication date
BR9610198A (pt) 1999-06-29
NO980872L (no) 1998-02-27
SE9503004L (sv) 1997-03-01
SE9503004D0 (sv) 1995-08-30
WO1997008381A1 (en) 1997-03-06
CA2229893A1 (en) 1997-03-06
NO980872D0 (no) 1998-02-27
AU6892696A (en) 1997-03-19

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