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EP0951599B1 - Zellstoffbehandlung mit einem komplexbildner ohne verwendung eines bleichturms - Google Patents

Zellstoffbehandlung mit einem komplexbildner ohne verwendung eines bleichturms Download PDF

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Publication number
EP0951599B1
EP0951599B1 EP97912616A EP97912616A EP0951599B1 EP 0951599 B1 EP0951599 B1 EP 0951599B1 EP 97912616 A EP97912616 A EP 97912616A EP 97912616 A EP97912616 A EP 97912616A EP 0951599 B1 EP0951599 B1 EP 0951599B1
Authority
EP
European Patent Office
Prior art keywords
pulp
chelating agent
stage
mixing
bleaching
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.)
Expired - Lifetime
Application number
EP97912616A
Other languages
English (en)
French (fr)
Other versions
EP0951599A1 (de
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
Valmet Fibertech 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 Fibertech AB filed Critical Valmet Fibertech AB
Publication of EP0951599A1 publication Critical patent/EP0951599A1/de
Application granted granted Critical
Publication of EP0951599B1 publication Critical patent/EP0951599B1/de
Anticipated expiration legal-status Critical
Expired - Lifetime 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
    • 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
    • D21C9/02—Washing ; Displacing cooking or pulp-treating liquors contained in the pulp by fluids, e.g. wash water or other pulp-treating agents
    • 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

  • This invention relates to the bleaching of chemical pulp with chlorine-free chemicals.
  • the invention more precisely, refers to a method of pretreating the pulp with chelating agents in combination with the bleaching.
  • Bleaching is carried out in most cases by treating the papermaking pulp to be bleached with chlorine-free chemicals first with a chelating agent of the type EDTA or DTPA.
  • the chelating agent has the object to remove from the pulp certain metal ions, particularly manganese, copper, iron a.o., which affect the bleaching result negatively, if they remain in the pulp.
  • the chelating agent usually is designated by the letter Q.
  • the pulp is washed after the Q-step, so that the exposed metal ions are eliminated from the pulp as completely as possible. Thereafter the bleaching takes place, which normally is carried out with hydrogen peroxide, at times in combination with oxygen. Hydrogen peroxide steps are designated with the letter P, and P-steps reinforced with oxygen are designated with OP or PO where the dominating chemical is mentioned first.
  • P Hydrogen peroxide steps
  • OP P-steps reinforced with oxygen
  • the original pulp normally is oxygen delignified to a relatively low kappa number prior to the QP-bleaching.
  • a low kappa number before the bleaching implies that the obtainable maximum bleaching result increases in the subsequent step, and that the bleaching chemical demand is reduced.
  • the QP-bleaching most often is carried out in such a way, that the pulp first is passed through a pump, which pumps the pulp suspension through the treatment steps. Thereafter follows a mixer where the chelating agent is added to the pulp. The next step is a bleaching tower, where the pulp without additional agitation slowly passes through and where all remaining reaction takes place. The pulp finally passes to a washing step where the exposed and complexed metal ions are washed out. The freed liquid enriched on metal ions most often is discharged.
  • the conditions normally applied in a Q-step are a temperature of 70-90°C, a retention time of 1-2 hours, a pulp consistency of 10-14%, a pH of 5-7 and a charge of chelating agent of 1-3 kg per ton pulp.
  • a very good metal separation can be achieved, which is necessary if subsequent bleaching is carried out on pulp with low lignin content (the kappa number is below about 5) and if a large amount of hydrogen peroxide is used in the stage (more than 15 kg/t). If, however, the pulp still contains a considerable amount of lignin (kappa number above about 5), and the hydrogen peroxide charge in the subsequent step is limited to about 5-10 kg/t, the demand for a complete metal elimination is less critical.
  • the Q-step per se is an unnecessary treatment step, because no proper bleaching takes place there.
  • the Q-treatment is necessary for a following successful P- or PO-bleaching, as appears from the aforesaid. If the Q-step could be simplified without reducing the effectiveness in the elimination of metals, great savings could be made, because a complete bleaching stage is expensive.
  • the present invention is directed to a simplification of the Q-step, especially for pulps with kappa number above about 5, and for chelating agent treatments which require less than 60% metal reduction.
  • the simplification implies, that the investment cost decreases in relation to a conventional Q-step.
  • the invention is based on the surprising observation, that the effectiveness of the Q-step is considerably less affected by increased reaction temperature than by increased retention time. This indicates, according to classical chemical cinetics, that the Q-step is diffusion controlled and not reaction controlled. This means, that the Q-step should be carried out so that the diffusion is facilitated, and if this is made effectively, the total retention time can thereby be reduced substantially.
  • the best method to reduce the diffusion resistance is to decrease the diffusion distance for active reactants and released reaction products. On a technical scale this is made by effective mixing, for example in a mixer with long retention time. Thus, by effective mixing, the retention time in the Q-step can be shortened.
  • the number of mixing steps is not critical, but the total mixing time must be above a certain critical level, alternatively at least two mixing apparatuses shall be used. For economic reasons, however, the number of mixing steps must be held on a reasonable level. For a pulp with kappa number above about 5, which shall be bleached further with at maximum about 5-10 kg hydrogen peroxide exclusive possible oxygen, a suitable number of mixing steps is 1-2. The same applies, if the metal reduction to be achieved in the chelating agent step is limited and need not be above 60%.
  • the stay-time between the mixing steps shall be short, less than 10 minutes and preferably less than 5 minutes.
  • the mixing steps then shall be carried out one after the other without intermediate washing.
  • the washing required for removing the metals from the pulp suspension shall be carried out less than 15 minutes after the last mixing step.
  • the entire charge of chelating agent shall be added in the first mixing step, and subsequent mixing steps bring about only a renewed mixing.
  • the chelating agent preferably is of the type EDTA (ethylene diamine tetraacetic acid) or DTPA (diethylene triamine pentaacetic acid), but also other types of chelating agent can be used, for example NTA (nitrilotriacetic acid) or DTPMP (diethylene triamine pentamythylene phosphoric acid).
  • the total amount of added chelating agent should be 0.5-3 kg per ton pulp (calculated as pure chelating agent), preferably 1-2 kg per ton pulp.
  • the temperature in the Q-step should be above 75°C, suitably over 80°C and more preferably over 85°C.
  • a preferred temperature interval is 85-110°C.
  • the desired pH interval is pH 5 to pH 11.
  • the pulp consistency should be between 2 and 16%.
  • An especially effective mixing can be achieved by using high-intensity mixers or with another type of mixer, where the mixing is effective and the retention time is sufficient, so that a homogenous mixture of fibres and chelating agent is obtained.
  • the starting pulp was oxygen bleached and of coniferous sulphate type with kappa number 10.1, viscosity 975 dm 3 /t and brightness 43.0% ISO.
  • the bleaching was carried out according to Q(OP) with 10 kg H 2 O 2 /t.

Landscapes

  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Wood Science & Technology (AREA)
  • Paper (AREA)
  • Detergent Compositions (AREA)
  • Chemical And Physical Treatments For Wood And The Like (AREA)
  • Hybrid Cells (AREA)
  • Noodles (AREA)

Claims (10)

  1. Verfahren zum chlorfreien Bleichen von Pulpe, in der Metalle mittels eines chelatbildenden Mittels eliminiert werden, die Kappa-Zahl der Pulpe vor dem Chelationsschritt über 5 und die erwünschte Metallreduktion in der Chelationsstufe weniger als 60% ist, wobei das chelatbildende Mittel mit der Pulpe ohne Verwendung eines Bleichturms in wenigstens einer effektiven Mischstufe unter Verwendung eines hochintensiven Mischers bei einem pH-Wert zwischen 5 und 11 gemischt wird, die Pulpe weniger als 15 Minuten nach der letzten Mischstufe gewaschen wird und die Pulpe danach in einer chlorfreien Bleichstufe gebleicht wird.
  2. Verfahren nach dem vorhergehenden Anspruch,
    dadurch gekennzeichent, dass die Kappa-Zahl der Pulpe vor der Chelationsstufe über 5 ist oder dass die gewünschte Metallreduktion in der Chelationsstufe weniger als 60% ist.
  3. Verfahren nach einem der vorhergehenden Ansprüche,
    dadurch gekennzeichnet, dass die gesamte Zugabe des chelatbildenden Mittels bis 0,5 - 3kg pro Tonne Pulpe, vorzugsweise 1-2 kg pro Tonne Pulpe beträgt.
  4. Verfahren nach einem der vorhergehenden Ansprüche,
    dadurch gekennzeichnet, dass die Temperatur in der Chelationsstufe über 75° C und maximal 110°C beträgt.
  5. Verfahren nach einem der vorhergehenden Ansprüche,
    dadurch gekennzeichnet, dass die Pulpenkonsistenz in der Chelationsstufe 2-16% ist.
  6. Verfahren nach einem der vorhergehenden Ansprüche,
    wobei wenigstens zwei Mischstufen verwendet werden,
    dadurch gekennzeichnet, dass die gesamte Zugabe des chelatbildenden Mittels in der ersten Mischstufe ausgeführt wird und dass die nachfolgenden Mischstufen nur ein erneutes Mischen ergeben.
  7. Verfahren nach Anspruch 6,
    dadurch gekennzeichnet, dass das chelatbildende Mittel in verschiedenen Mischstufen zugegeben wird.
  8. Verfahren nach einem der vorhergehenden Ansprüche,
    dadurch gekennzeichnet, dass das chelatbildende Mittel vom Typ EDTA oder DTPA ist.
  9. Verfahren nach einem der vorhergehenden Ansprüche,
    dadurch gekennzeichnet, dass das chelatbildende Mittel vom Typ NTA oder DTPMP ist.
  10. Verfahren nach einem der vorhergehenden Ansprüche,
    dadurch gekennzeichnet, dass die hochintensiven Mischer die Faservernetzung in der Pulpe aufbrechen und einen engen Kontakt zwischen den Fasern und dem chelatbildenden Mittel ergeben.
EP97912616A 1997-01-03 1997-11-06 Zellstoffbehandlung mit einem komplexbildner ohne verwendung eines bleichturms Expired - Lifetime EP0951599B1 (de)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
SE9700030A SE508239C2 (sv) 1997-01-03 1997-01-03 Behandling av massa med komplexbildare i minst ett blandningssteg, utan användning av blektorn
SE9700030 1997-01-03
PCT/SE1997/001853 WO1998029597A1 (en) 1997-01-03 1997-11-06 Treatment of pulp with a chelating agent without using a bleaching tower

Publications (2)

Publication Number Publication Date
EP0951599A1 EP0951599A1 (de) 1999-10-27
EP0951599B1 true EP0951599B1 (de) 2003-05-28

Family

ID=20405369

Family Applications (1)

Application Number Title Priority Date Filing Date
EP97912616A Expired - Lifetime EP0951599B1 (de) 1997-01-03 1997-11-06 Zellstoffbehandlung mit einem komplexbildner ohne verwendung eines bleichturms

Country Status (16)

Country Link
EP (1) EP0951599B1 (de)
JP (1) JP2001508837A (de)
CN (1) CN1103832C (de)
AT (1) ATE241725T1 (de)
AU (1) AU726599B2 (de)
BR (1) BR9714252A (de)
CA (1) CA2275257A1 (de)
DE (1) DE69722445T2 (de)
ES (1) ES2195123T3 (de)
ID (1) ID20003A (de)
NO (1) NO993290L (de)
NZ (1) NZ336204A (de)
PT (1) PT951599E (de)
SE (1) SE508239C2 (de)
WO (1) WO1998029597A1 (de)
ZA (1) ZA9710418B (de)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101446054B (zh) * 2008-12-23 2010-04-14 华南理工大学 年产5万吨以上纸浆生产线的全无氯漂白方法

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SE9201477L (sv) * 1992-05-11 1993-06-28 Kamyr Ab Saett vid blekning av massa utan anvaendning av klorkemikalier
SE502665C2 (sv) * 1993-06-11 1995-12-04 Kvaerner Pulping Tech Sätt och reaktor för ozonblekning
SE501836C2 (sv) * 1993-09-21 1995-05-22 Sunds Defibrator Ind Ab Blekning av kemisk massa varvid massan behandlas med komplexbildare före och efter ett ozonsteg
SE504803C2 (sv) * 1995-08-24 1997-04-28 Sunds Defibrator Ind Ab Behandling av massa med komplexbildare i minst två blandningssteg utan mellanliggande tvätt

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101446054B (zh) * 2008-12-23 2010-04-14 华南理工大学 年产5万吨以上纸浆生产线的全无氯漂白方法

Also Published As

Publication number Publication date
CN1103832C (zh) 2003-03-26
JP2001508837A (ja) 2001-07-03
ZA9710418B (en) 1998-06-10
NO993290L (no) 1999-09-02
ID20003A (id) 1998-09-10
CA2275257A1 (en) 1998-07-09
WO1998029597A1 (en) 1998-07-09
ATE241725T1 (de) 2003-06-15
SE9700030D0 (sv) 1997-01-03
SE508239C2 (sv) 1998-09-21
AU4974197A (en) 1998-07-31
ES2195123T3 (es) 2003-12-01
DE69722445D1 (de) 2003-07-03
EP0951599A1 (de) 1999-10-27
DE69722445T2 (de) 2004-01-15
CN1242060A (zh) 2000-01-19
PT951599E (pt) 2003-10-31
AU726599B2 (en) 2000-11-16
BR9714252A (pt) 2000-04-18
NO993290D0 (no) 1999-07-02
NZ336204A (en) 1999-11-29
SE9700030L (sv) 1998-07-04

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