EP0951599B1 - Traitement de pate avec un chelateur sans utiliser de tour de blanchiment - Google Patents

Traitement de pate avec un chelateur sans utiliser de tour de blanchiment 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
German (de)
English (en)
Other versions
EP0951599A1 (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
Valmet Fibertech AB
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Filing date
Publication date
Application filed by Valmet Fibertech AB filed Critical Valmet Fibertech AB
Publication of EP0951599A1 publication Critical patent/EP0951599A1/fr
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Publication of EP0951599B1 publication Critical patent/EP0951599B1/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
    • D21C9/02—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. Procédé de blanchiment de pâte à papier exempt de chlore où des métaux sont éliminés au moyen d'un agent chélatant, l'indice kappa de la pâte à papier avant l'étape de chélation étant supérieur à 5 et la réduction métallique souhaitée dans l'étape de chélation étant inférieure à 60%, dans lequel l'agent chélatant est mélangé avec la pâte à papier, sans utiliser do tour do blanchiment, dans au moins une étape de blanchiment efficace en utilisant des mélangeurs à intensité élevée à un pH compris entre 5 et 11, la pâte à papier est lavée moins de 15 minutes après la dernière étape de mélange, et la pâte à papier est ensuite blanchie dans une étape de blanchiment exempte de chlore.
  2. Procédé selon la revendication précédente, caractérisé en ce que l'indice kappa de la pâte à papier avant l'étape de l'agent chélatant est supérieur à 5, ou en ce que la réduction du métal souhaitée dans l'étape de l'agent chélatant est inférieure à 60%.
  3. Procédé selon l'une quelconque des revendications précédentes, caractérisé en ce que l'addition complète des quantités d'agent chélatant s'élève entre 0,5 et 3 kg par tonne de pâte à papier, de préférence entre 1 et 2 kg par tonne de pâte à papier.
  4. Procédé selon l'une quelconque des revendications précédentes, caractérisé en ce que la température dans l'étape mettant en oeuvre l'agent chélatant est supérieure à 75°C et est au maximum de 110°C.
  5. Procédé selon l'une quelconque des revexidications précédentes, caractérisé en ce que la consistance de la pâte à papier dans l'étape mettant en oeuvre l'agent chélatant est comprise entre 2 et 16%.
  6. Procédé selon l'une quelconque des revendications précédentes, dans lequel au moins deux étapes de mélange sont utilisées, caractérisé en ce que l'addition complète de l'agent chélatant est réalisée dans la première étape de mélange, et en ce que les étapes de mélange ultérieures n'entraínent qu'un mélange renouvelé.
  7. Procédé selon la revendication 6, caractérisé en ce que l'agent chélatant est ajouté en plusieurs étapes de mélange.
  8. Procédé selon l'une quelconque des revendications précédentes, caractérisé en ce que l'agent chélatant est du type EDTA ou DTPA.
  9. Procédé selon l'une quelconque des revendications précédentes, caractérisé en ce que l'agent chélatant est du type NTA ou DTPMP.
  10. Procédé selon l'une quelconque des revendications précédentes, caractérisé en ce que les mélangeurs à intensité élevée rompent le réseau fibreux dans la pâte à papier et provoquent un contact étroit entre les fibres et l'agent chélatant.
EP97912616A 1997-01-03 1997-11-06 Traitement de pate avec un chelateur sans utiliser de tour de blanchiment Expired - Lifetime EP0951599B1 (fr)

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 (fr) 1997-01-03 1997-11-06 Traitement de pate avec un chelateur sans utiliser de tour de blanchiment

Publications (2)

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

Family

ID=20405369

Family Applications (1)

Application Number Title Priority Date Filing Date
EP97912616A Expired - Lifetime EP0951599B1 (fr) 1997-01-03 1997-11-06 Traitement de pate avec un chelateur sans utiliser de tour de blanchiment

Country Status (16)

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

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
SE469387B (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
DE69722445D1 (de) 2003-07-03
SE9700030L (sv) 1998-07-04
NZ336204A (en) 1999-11-29
AU4974197A (en) 1998-07-31
ES2195123T3 (es) 2003-12-01
ID20003A (id) 1998-09-10
BR9714252A (pt) 2000-04-18
NO993290D0 (no) 1999-07-02
CA2275257A1 (fr) 1998-07-09
EP0951599A1 (fr) 1999-10-27
WO1998029597A1 (fr) 1998-07-09
SE508239C2 (sv) 1998-09-21
JP2001508837A (ja) 2001-07-03
SE9700030D0 (sv) 1997-01-03
PT951599E (pt) 2003-10-31
ZA9710418B (en) 1998-06-10
CN1242060A (zh) 2000-01-19
ATE241725T1 (de) 2003-06-15
NO993290L (no) 1999-09-02
AU726599B2 (en) 2000-11-16
DE69722445T2 (de) 2004-01-15

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