EP0846199B1 - Traitement d'une pate a papier avec un agent chelatant en au moins deux etapes de melange, sans lavage intermediaire - Google Patents

Traitement d'une pate a papier avec un agent chelatant en au moins deux etapes de melange, sans lavage intermediaire Download PDF

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Publication number
EP0846199B1
EP0846199B1 EP96928765A EP96928765A EP0846199B1 EP 0846199 B1 EP0846199 B1 EP 0846199B1 EP 96928765 A EP96928765 A EP 96928765A EP 96928765 A EP96928765 A EP 96928765A EP 0846199 B1 EP0846199 B1 EP 0846199B1
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EP
European Patent Office
Prior art keywords
pulp
chelating agent
mixing steps
mixing
bleaching
Prior art date
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Expired - Lifetime
Application number
EP96928765A
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German (de)
English (en)
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EP0846199A1 (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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Publication date
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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
    • D21C9/1026—Other features in bleaching processes
    • D21C9/1042—Use of chelating agents

Definitions

  • This invention relates to the bleaching of chemical pulp with chlorine-free bleaching chemicals.
  • the invention more precisely, refers to the treatment of pulp by chelating agents in connection with the bleaching.
  • Totally chlorine-free bleaching (TCF) of chemical papermaking pulp has become a very great success, and the making of chlorine-free pulp in the world will soon have reached five million tons per year, which is a highly exceptional development considering that this bleaching method was introduced less than five years ago.
  • Bleaching is carried out in most cases by first treating the papermaking pulp to be bleached 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 would affect the bleaching result negatively if they remain in the pulp.
  • the chelating agent step usually is designated by the letter Q.
  • the pulp is washed to eliminate the exposed metal ions from the pulp as completely as possible. Thereafter follows the bleaching, which normally is carried out with hydrogen peroxide, at times in combination with other bleaching steps and intermediate washing steps where ozone or peracids can be used. Hydrogen peroxide steps usually are designated by the letter P. According to a thumb rule, the more harmful metal ions are eliminated from the pulp in the Q-step, the more effective the subsequent bleaching will be.
  • a method, at which the pulp is treated in a Q-step and thereafter in a P-step, usually is called the "Lignox"-method, as disclosed, for example, in EP-A-402 335.
  • the original pulp normally is oxygen delignified to a relatively low kappa number prior to the QP-bleaching.
  • a low kappa number implies that the obtainable maximum brightness increases and the bleaching chemical demand decreases.
  • the QP-bleaching is carried out in mills most often in such a way, that the pulp first is passed through a pump, which pumps the pulp suspension through the treatment steps. Thereafter the chelating agent is admixed homogenously to the pulp in a mixer. The next step is a bleaching tower where the pulp without additional activation slowly passes through and where all remaining reaction takes place. The pulp finally is directed to a washing step where the exposed and complexed metal ions are washed out. The exposed 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 stay-time of 1-2 hours, a pulp concentration of 10-14%, a pH of 5-7 and a charge of chelating agent of 1-3 kg/ton pulp.
  • the Q-step from a strict bleaching point of view, actually is an unnecessary treatment step, because no increase in brightness takes place here.
  • the Q-treatment is necessary for a successful chlorine-free bleaching, as appears from above. If the Q-step could be simplified without thereby reducing the efficiency of metal elimination, great savings could be made, because a complete bleaching step with bleaching tower is expensive.
  • the present invention is directed to a solution of the aforesaid problems.
  • the Q-step is made more efficient by eliminating the metals effectively at the same time as the Q-step is simplified, resulting in reduced investment costs in relation to a conventional Q-step.
  • the invention is based on the surprising discovery that the efficiency of the Q-step is affected considerably less by increased reaction temperature than by increased retention time. This indicates, according to classic chemical kinetics, that the Q-step is controlled by diffusion and not by reaction. The Q-step, consequently, should be carried out so that diffusion is facilitated. If this is done effectively, the total retention time can thereby be reduced considerably.
  • the best way of reducing the diffusion resistance is by decreasing the diffusion distance for active reactants and released reaction products.
  • the retention time in the Q-step can be reduced by repeated effective mixing.
  • the number of mixing steps should be at least two, preferably at least three. For economic reasons, however, the number of mixing steps, and thereby the number of mixers, must be held on a reasonable level. A suitable number can be 2-4 steps.
  • a certain retention time between the mixing steps is of good use, but this time need not be long, because the diffusion rate without mixing still is much slower than what is obtainable by mixing, for example in a mixer.
  • the stay-time between the mixing steps thus, shall be short, less than 15 minutes, suitably less than 10 minutes, and preferably less than 5 minutes.
  • the mixing steps should 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 after the last mixing step.
  • the chelating agent preferably is of the type EDTA (ethylene diamine tetraacetic acid) or DTPA (diethylene triamine pentaacetic acid), but other types of chelating agent can be used, for example NTA (nitrilotriacetic acid) or DTPMP (diethylene triamine pentamethylene phosphonic acid).
  • the total amount of added chelating agent should be 0,5-5 kg/t pulp (counted as pure chelating agent), preferably 1-3 kg/ t pulp.
  • the entire charge of chelating agent can be added in the first mixing step, whereby subsequent mixing steps bring about only repeated mixing.
  • the chelating agent can be added in several of the mixing steps.
  • the charging then should be made substantially in the first step, and in subsequent steps the added amount should be less than 2 kg/ t pulp per step.
  • the temperature in the mixing steps should be above 70°C and suitably above 80°C. A preferable temperature interval is 80-120°C.
  • the pressure in the entire Q-step preferably should be 1-10 bar.
  • An especially effective admixture can be achieved by uisng highly intensive mixers, which break-up the fiber network in the pulp and bring about close contact between fibers and chelating agent.
  • the invention is not restricted to the embodiments described above, but can be varied within the scope of the invention idea.

Landscapes

  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Wood Science & Technology (AREA)
  • Paper (AREA)
  • Cosmetics (AREA)
  • Chemical Or Physical Treatment Of Fibers (AREA)
  • Treatments For Attaching Organic Compounds To Fibrous Goods (AREA)
  • Detergent Compositions (AREA)

Claims (9)

  1. Procédé de blanchiment sans chlore d'une pâte à papier dans lequel les métaux sont éliminés au moyen d'un agent chélatant, caractérisé en ce que l'agent chélatant est mélangé à la pâte à papier sans utiliser une tour de blanchiment en, au moins, deux étapes de mélange consécutives sans lavage, en ce que le temps de séjour entre les étapes de mélange est inférieur à 15 minutes, et en ce que la pâte à papier est lavée après la dernière étape de mélange.
  2. Procédé selon la revendication 1, caractérisé en ce que toute la charge d'agent chélatant est apportée dans la première étape de mélange, de sorte que les étapes de mélange consécutives entrainent seulement un mélange répété.
  3. Procédé selon la revendication 1, caractérisé en ce que la charge d'agent chélatant est ajoutée en plusieurs étapes de mélange.
  4. Procédé selon l'une quelconque des revendications précédentes, caractérisé en ce que toute la charge d'agent chélatant s'évalue entre 0,5 et 5 kg par tonne de pâte à papier, de préférence entre 1 et 3 kg par tonne de pâte.
  5. Procédé selon l'une quelconque des revendications précédentes, caractérisé en ce que la température des étapes de mélange est de 70° C environ.
  6. Procédé selon l'une quelconque des revendications précédentes, caractérisé en ce que l'agent chélatant est du type EDTA ou DTPA.
  7. Procédé selon l'une quelconque des revendications 1 à 5, caractérisé en ce que l'agent chélatant est du type NTA ou DTPMP.
  8. Procédé selon l'une quelconque des revendications précédentes, caractérisé en ce que le mélange de l'agent chélatant est effectué par des mélangeurs très puissants, qui cassent le réseau de fibres dans la pâte et entrainent un contact étroit entre les fibres et l'agent chélatant.
  9. Procédé selon l'une quelconque des revendications précédentes, caractérisé en ce que les étapes de mélange sont réalisées sous une pression de 1 à 10 bars.
EP96928765A 1995-08-24 1996-08-09 Traitement d'une pate a papier avec un agent chelatant en au moins deux etapes de melange, sans lavage intermediaire Expired - Lifetime EP0846199B1 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
SE9502962 1995-08-24
SE9502962A SE504803C2 (sv) 1995-08-24 1995-08-24 Behandling av massa med komplexbildare i minst två blandningssteg utan mellanliggande tvätt
PCT/SE1996/000996 WO1997008380A1 (fr) 1995-08-24 1996-08-09 Traitement d'une pate a papier avec un agent chelatant en au moins deux etapes de melange, sans lavage intermediaire

Publications (2)

Publication Number Publication Date
EP0846199A1 EP0846199A1 (fr) 1998-06-10
EP0846199B1 true EP0846199B1 (fr) 2001-01-24

Family

ID=20399294

Family Applications (1)

Application Number Title Priority Date Filing Date
EP96928765A Expired - Lifetime EP0846199B1 (fr) 1995-08-24 1996-08-09 Traitement d'une pate a papier avec un agent chelatant en au moins deux etapes de melange, sans lavage intermediaire

Country Status (11)

Country Link
EP (1) EP0846199B1 (fr)
AT (1) ATE198916T1 (fr)
AU (1) AU6839996A (fr)
BR (1) BR9610199A (fr)
CA (1) CA2229212A1 (fr)
DE (1) DE69611680T2 (fr)
ES (1) ES2153593T3 (fr)
NO (1) NO980753L (fr)
PT (1) PT846199E (fr)
SE (1) SE504803C2 (fr)
WO (1) WO1997008380A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8361571B2 (en) 2008-06-20 2013-01-29 International Paper Company Composition and recording sheet with improved optical properties

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SE508239C2 (sv) * 1997-01-03 1998-09-21 Sunds Defibrator Ind Ab Behandling av massa med komplexbildare i minst ett blandningssteg, utan användning av blektorn

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
ATE97179T1 (de) * 1989-06-06 1993-11-15 Eka Nobel Ab Verfahren zum bleichen von lignocellulose enthaltenden zellstoffen.
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

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8361571B2 (en) 2008-06-20 2013-01-29 International Paper Company Composition and recording sheet with improved optical properties
US8906476B2 (en) 2008-06-20 2014-12-09 International Paper Company Composition and recording sheet with improved optical properties

Also Published As

Publication number Publication date
DE69611680D1 (de) 2001-03-01
SE504803C2 (sv) 1997-04-28
EP0846199A1 (fr) 1998-06-10
PT846199E (pt) 2001-06-29
WO1997008380A1 (fr) 1997-03-06
NO980753D0 (no) 1998-02-23
SE9502962D0 (sv) 1995-08-24
ATE198916T1 (de) 2001-02-15
SE9502962L (sv) 1997-02-25
NO980753L (no) 1998-02-24
CA2229212A1 (fr) 1997-03-06
AU6839996A (en) 1997-03-19
DE69611680T2 (de) 2001-05-10
ES2153593T3 (es) 2001-03-01
BR9610199A (pt) 1998-08-04

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