EP0687321B1 - Method of bleaching pulp with chlorine-free chemicals - Google Patents

Method of bleaching pulp with chlorine-free chemicals Download PDF

Info

Publication number
EP0687321B1
EP0687321B1 EP93910051A EP93910051A EP0687321B1 EP 0687321 B1 EP0687321 B1 EP 0687321B1 EP 93910051 A EP93910051 A EP 93910051A EP 93910051 A EP93910051 A EP 93910051A EP 0687321 B1 EP0687321 B1 EP 0687321B1
Authority
EP
European Patent Office
Prior art keywords
stage
pulp
recited
bleaching
ozone
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
EP93910051A
Other languages
German (de)
English (en)
French (fr)
Other versions
EP0687321A1 (en
Inventor
Kaj Henricson
Bertil Stromberg
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.)
Andritz Oy
Original Assignee
Andritz Oy
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
Family has litigation
First worldwide family litigation filed litigation Critical https://patents.darts-ip.com/?family=8537491&utm_source=google_patent&utm_medium=platform_link&utm_campaign=public_patent_search&patent=EP0687321(B1) "Global patent litigation dataset” by Darts-ip is licensed under a Creative Commons Attribution 4.0 International License.
Application filed by Andritz Oy filed Critical Andritz Oy
Priority to EP98113684A priority Critical patent/EP0884415B1/en
Priority to AT98113684T priority patent/ATE228181T1/de
Publication of EP0687321A1 publication Critical patent/EP0687321A1/en
Application granted granted Critical
Publication of EP0687321B1 publication Critical patent/EP0687321B1/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

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
    • D21C9/02—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
    • D21C9/1036—Use of compounds accelerating or improving the efficiency of the 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
    • D21C9/1026—Other features in bleaching processes
    • D21C9/1042—Use of chelating 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
    • D21C9/1057—Multistage, with compounds cited in more than one sub-group D21C9/10, D21C9/12, D21C9/16
    • 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
    • D21C9/147—Bleaching ; Apparatus therefor with oxygen or its allotropic modifications
    • 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
    • D21C9/147—Bleaching ; Apparatus therefor with oxygen or its allotropic modifications
    • D21C9/153—Bleaching ; Apparatus therefor with oxygen or its allotropic modifications with ozone
    • 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
    • D21C9/163—Bleaching ; Apparatus therefor with per compounds with peroxides

Definitions

  • the present invention relates to a method of bleaching kraft pulp containing heavy metals like manganese by using chlorine-free chemicals.
  • the invention is especially related to ozone bleaching of pulp without first actually removing heavy metals.
  • Typical bleaching sequences by which pulp has earlier been bleached are, for example, OOAZEZPZ, OAZEZPZ, OOAZEZP and OAZEZP. These sequences thus include one or more oxygen bleaching stages (O), an A-stage (acid washing), an ozone stage (Z), an extraction stage (E), a second ozone stage (Z) and a peroxide stage (P), and possibly a third ozone stage (Z).
  • the extraction stage (E) may be an oxidizing peroxide extraction stage or a conventional oxidizing extraction stage.
  • the ozone bleaching stages are preferably carried out with pulp having the consistency of about 5-18%.
  • washing stages in other words bleaching stages alternate with washing stages, i.e. washers, by which the chemicals separated from the fibers as reaction products or otherwise in each bleaching stage are removed from the suspension. Since the washers form a considerable part of the investment costs in a bleaching plant, the number of the washers should, of course, be limited as much as possible, if it is only possible without risking the quality of the final product.
  • EP-A-0 426 652 teaches in Example 7 a first bleaching stage with ozone, followed by a bleaching with peroxide and oxygen, then a further bleaching with ozone. In the final stage a peroxide treatment is performed.
  • the treated pulp is a kraft pulp.
  • the first bleaching stage encompasses the removal of metals.
  • EP-A-0 402 335 describes the treatment of a pulp with a complexing agent before the peroxide step to remove metals.
  • EP-A-0 512 978 the pulp is first treated with enzymes, followed by a treatment with oxygen. In a further stage the treatment with peroxide is performed.
  • EP-A-0 426 652 discloses several bleaching sequences where ozone has been used in combination with peroxide and oxygen. For instance, sequences like EOP-Z-PE-Z-PE, EOP-Z-PE, O-Z-EO-Z-P, O-Z-EOP-Z-P and O-Z-EO-Z-D were discussed. However, the publication does not take into account the presence of heavy metals in the pulp in spite of the fact that at least one of the examples discusses bleaching of kraft pulp by means of a peroxide containing compound.
  • EP-A-0 512 978 discloses a multi-stage bleaching process using both ozone and peroxide for bleaching pulp. The document does not pay any attention to the removal of heavy metals from pulp before bleaching with peroxide.
  • EP-A-0 402 335 discloses a process for bleaching lignocellulose-containing pulps by means of peroxide containing substance.
  • the main teaching of the document is to alter the trace metal profile of the pulp by means of a separate treatment with a complexing agent.
  • the document teaches the importance of treating pulp prior to a peroxide stage in a separate metal removing stage.
  • the treatment comprises a washing stage between the treatment with complex formers and the peroxide stage.
  • a conventional bleaching + screening plant has thus included four or five bleaching stages and one screening and/or vortex cleaning stage, which the washing stage separates from each other.
  • the present invention compresses these five to six stages into three stages and thus almost halves the investment costs of a bleaching plant and a screening plant.
  • pulp is bleached with a sequence beginning with ozone and without first actually removing heavy metals preceding the ozone stage.
  • kraft pulp is bleached with a three-stage sequence (ZT) (EOP) (ZP) without an actual removal of heavy metals preceding the sequence, in which
  • the Z portion of the ZT stage employs ozone as a primary bleaching chemical and the T portion represents the actual metal removal by the use of chelating agents.
  • a bleaching sequence is provided using a high consistency pulp tower 10, from which pulp is discharged and fed, for example, with an MC® (i.e. fluidizing) pump 12 into an ozone reactor 14, from which kraft pulp is preferably discharged by means of a gas separator 16 into a first reaction tower 18.
  • Pulp is preferably discharged from tower 18 into a washer 22 by means of an MC® pump 20.
  • the washer may be a conventional DRUM DISPLACERTM washer or a conventional pressure diffuser. Pulp is preferably pumped from washer 22 by an MC® pump 24 into can oxygen reactor 26, and from reactor 26 into a second reaction tower 28.
  • a second washer 32 preferably a DRUM DISPLACERTM washer
  • ozone in a carrier gas
  • oxygen may be mixed prior to the oxygen reactor 26 with mixer 62 and the mixture of ozone and carrier gas prior to the second ozone reactor 36.
  • the mixers 60, 62 and 64 are preferably AHLMIXERTM type fluidizing mixers, which are able to mix very large amounts of gas into fiber suspensions, including medium consistency suspensions.
  • Fig. 1 teaches how, in order to adjust the pH value of the pulp for the first ozone stage and the removal of heavy metals subsequent thereto, acid may be supplied into the pulp, for example, in the pump 12.
  • complex formers such as EDTA, and/or alkali may be added to the pulp. If too much magnesium is removed from the pulp by washer 22, it may be added, for example, with the alkali either in pump 24 and/or in the discharge from the oxygen reactor 26, or in any other appropriate way.
  • Another possibility to adjust the pH of the pulp for the second ozone treatment is to feed acid subsequent to the second washer 32 in pump 34 or in some other suitable way.
  • peroxide and/or magnesium may be added into the pulp, as illustrated in Fig. 1.
  • All the reaction towers 18, 28 and 40 in Fig. 1 are shown as of the down flow type. Alternatively, they may be of the up flow type, as is shown in Fig. 2.
  • the only significant difference between Figs. 1 and 2 is the flow direction of the reaction towers.
  • components functionally equivalent to or the same as the components in the Fig. 1 embodiment are illustrated by the same reference numeral, only preceded by a "1".
  • pumps 20, 30 and 42 of Fig. 1 are replaced by pumps 120', 130' and 142 of Fig. 2, because they have been relocated at the other side of the reaction tower, in other words instead of feeding washers 22, 32 and 44 as illustrated in Fig. 1 they feed pulp to the reaction towers 118, 128 and 140 in the embodiments of Fig. 2.
  • pulp is cooked, for example with a continuous EMCC digester, sold by Kamyr Inc., of Glens Falls, New York, to a low kappa number, whereafter the kappa number is further decreased by oxygen bleaching to a value of about 14 or below.
  • a continuous EMCC digester sold by Kamyr Inc., of Glens Falls, New York
  • oxygen bleaching to a value of about 14 or below.
  • hot alkali extraction and oxygen bleaching a kappa range of 14 - 5 is obtained both with soft wood and birch.
  • a kappa number of 14 is sufficient in order to carry out the final bleaching with chlorine-free bleaching chemicals and yet reach a full brightness defined by ISO 86 (preferably ISO 88).
  • ISO 86 preferably ISO 88
  • the kraft pulp is bleached subsequent to the pulp washing and according to the invention without a separate removal of heavy metals, for example, with a sequence in accordance with Fig. 1, which is described more in detail below.
  • Pulp may be treated, if so required, with enzymes prior to the sequence in accordance with the present invention.
  • Pulp is brought from the high consistency pulp tower 10 to the first bleaching stage, which is a (ZT) stage.
  • the first bleaching stage which is a (ZT) stage.
  • pulp is bleached with ozone, the dosing being about 2-10 kg/adt, pH about 2- 7, and temperature about 40-70°C.
  • the pH value of pulp is adjusted by adding acid to the bottom of the high consistency tower 10, pump 12 (or the discharge to pump 12 as seen in Fig. 1), or chemical mixer 60.
  • the ozone having reacted, the residual gas is removed from the pulp preferably in a gas separator 16 and the treatment of heavy metals begins in the first reaction tower 18 in the T portion
  • a way to carry out the T portion of the (ZT) stage is to use complex formers, for example, EDTA.
  • the T portion of the (ZT) stage is then carried out in the pH range of about 4-7 and it is advantageous also to have the pH of Z portion of the (ZT) stage preceding T portion above 4.
  • manganese which is harmful in the oxygen stages
  • Filtrate S 1 of the washer 22 subsequent to the (ZT) stage may be brought to pulp washing prior to the (ZT) stage, or passed to the sewer or to the recovery of cooking chemicals.
  • the (ZT) stage is followed in Fig. 1 by an (EOP) stage.
  • the oxygen dose is about 2-6 kg/adt and the peroxide dose about 10-20 kg/adt. In some special cases it is possible to run the process completely without oxygen.
  • Temperature in the (EOP) stage is about 60-95°C, pH about 9-12, and the duration is about 2-8 hours. If required, magnesium may be added as a protective chemical.
  • the (EOP) stage is followed by washing, which gives filtrate S 2 .
  • the filtrate S 2 may be taken to pulp washing prior to or subsequent to the (ZT) stage, to sewer, or to recovery of chemicals.
  • the (EOP) stage is followed in Fig. 1 by a second ozone bleaching stage, i.e. an (ZP) stage.
  • the ozone portion of the (ZP) stage is normally carried out in the processes in accordance with the prior art in cold, acid conditions in order to have the ozone react properly.
  • the P portion of the (ZP) stage is carried out according to the teachings of the prior art in hot, alkali conditions in order to have the peroxide react properly.
  • the ozone dose is small, below 3 kg/adt and the purpose of the ozone is only to activate. Although disadvantageous conditions are used and a part of the ozone reacts poorly, this is insignificant, because the dose is small. Ozone is thus mainly used for the activation of the bleaching stage.
  • the temperature in the ozone stage may be 50-80°C, preferably, for example, 60-70°C.
  • the pH is 4-10, preferably about 6- 10.
  • the dose in the P portion of the (ZP) stage is also small, usually less than 10 kg/adt. Normally about 3-7 kg/adt is sufficient.
  • the temperature in the peroxide stage may be dropped to the range of 60-80°C, preferably to 70-80°C.
  • the pH is 9-11, preferably about 10.
  • the duration is about 1-6 hours.
  • the pulp is washed and a filtrate S 3 is obtained.
  • the filtrate S 3 may be used for the washing of pulp in connection with the earlier bleaching stages, discharged to the sewer, or led to the recovery of cooking chemicals.
  • a vortex cleaner 66 and/or a screening plant may be added according to Fig. 3 to the last stage of the bleaching plant to precede the thickener/washer 68, which in this case does not have to be an MC® washer, as in the earlier embodiments.
  • Pulp is diluted to the consistency range of about 0.5-1.5 % after the P-tower 140, when vortex cleaning or screening with a slotted screen is used. On the other hand, when screening with a perforated screen, a dilution to about 2-4% is usually sufficient.
  • the pulp is thickened and washed - usually with a suction filter 68. Previously pulp had to be diluted after washing to a screening consistency and thickened again after screening to a medium consistency.
  • FIG. 5 illustrates an oxygen delignification stage 80, which is followed by a two-stage washing 82. Pulp is transferred from the washing stage to the (ZT) stage 83, and from there via washing 84 to (EOP) stage 85, and from there via washing 86 to the (ZP) stage 87, which is followed by a washing stage 88.
  • the amount of effluent, which is brought to the effluent clarification, discharge channel 90, is 0-5 m3/adt. Part of the effluent may alternatively be transferred to the manufacture of cooking chemicals, via discharge channel 92, to be used instead of fresh water. Thus the amount of effluent that must be treated is minimized.
  • the present invention also includes a new method of arranging the screening subsequent to the pulp bleaching in such a way that a separate washing between the last washing stage and screening/vortex cleaning is unnecessary, but only dilution to screening/cleaning consistency is needed.
EP93910051A 1993-03-03 1993-05-25 Method of bleaching pulp with chlorine-free chemicals Expired - Lifetime EP0687321B1 (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
EP98113684A EP0884415B1 (en) 1993-03-03 1993-05-25 Method of washing pulp in connection with bleaching
AT98113684T ATE228181T1 (de) 1993-03-03 1993-05-25 Verfahren zum waschen von zellstoff beim bleichen

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
FI930954 1993-03-03
FI930954A FI93232C (fi) 1993-03-03 1993-03-03 Menetelmä massan valkaisemiseksi kloorivapailla kemikaaleilla
PCT/FI1993/000222 WO1994020673A1 (en) 1993-03-03 1993-05-25 Method of bleaching pulp with chlorine-free chemicals

Related Child Applications (1)

Application Number Title Priority Date Filing Date
EP98113684A Division EP0884415B1 (en) 1993-03-03 1993-05-25 Method of washing pulp in connection with bleaching

Publications (2)

Publication Number Publication Date
EP0687321A1 EP0687321A1 (en) 1995-12-20
EP0687321B1 true EP0687321B1 (en) 1999-02-17

Family

ID=8537491

Family Applications (2)

Application Number Title Priority Date Filing Date
EP98113684A Expired - Lifetime EP0884415B1 (en) 1993-03-03 1993-05-25 Method of washing pulp in connection with bleaching
EP93910051A Expired - Lifetime EP0687321B1 (en) 1993-03-03 1993-05-25 Method of bleaching pulp with chlorine-free chemicals

Family Applications Before (1)

Application Number Title Priority Date Filing Date
EP98113684A Expired - Lifetime EP0884415B1 (en) 1993-03-03 1993-05-25 Method of washing pulp in connection with bleaching

Country Status (13)

Country Link
EP (2) EP0884415B1 (ru)
JP (1) JP3276083B2 (ru)
AT (2) ATE176808T1 (ru)
AU (1) AU5370594A (ru)
BR (1) BR9307858A (ru)
CA (1) CA2157109C (ru)
DE (2) DE69323566T2 (ru)
ES (2) ES2130260T3 (ru)
FI (3) FI93232C (ru)
NO (1) NO953444L (ru)
PT (1) PT884415E (ru)
RU (1) RU2126471C1 (ru)
WO (1) WO1994020673A1 (ru)

Families Citing this family (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FI89516B (fi) 1989-05-10 1993-06-30 Ahlstroem Oy Foerfarande foer blekning av cellulosamassa med otson
FI103818B1 (fi) * 1995-02-21 1999-09-30 Ahlstrom Machinery Oy Menetelmä massan valkaisemiseksi
US20080110584A1 (en) * 2006-11-15 2008-05-15 Caifang Yin Bleaching process with at least one extraction stage
FR2910027B1 (fr) * 2006-12-13 2009-11-06 Itt Mfg Enterprises Inc Procede de blanchiment des pates papeteries chimiques par traitement final a l'ozone a haute temperature
AU2010253926B2 (en) 2009-05-28 2016-02-18 Gp Cellulose Gmbh Modified cellulose from chemical kraft fiber and methods of making and using the same
WO2012170183A1 (en) 2011-05-23 2012-12-13 Gp Cellulose Gmbh Softwood kraft fiber having improved whiteness and brightness and methods of making and using the same
BR112014017164A8 (pt) 2012-01-12 2017-07-04 Gp Cellulose Gmbh método para produzir polpa kraft oxidada e fibras kraft de madeira macia
CN106968127B (zh) 2012-04-18 2019-03-01 Gp纤维素股份有限公司 用于粘胶溶液的针叶木牛皮纸浆
WO2014122533A2 (en) 2013-02-08 2014-08-14 Gp Cellulose Gmbh Softwood kraft fiber having an improved a-cellulose content and its use in the production of chemical cellulose products
CA2901665A1 (en) 2013-03-14 2014-09-18 Gp Cellulose Gmbh A method of making highly functional, low viscosity kraft fiber using an acidic bleaching sequence and a fiber made by the process
CN108049234B (zh) 2013-03-15 2020-12-08 Gp 纤维素股份有限公司 一种经化学改性的牛皮纸纤维
FR3007044B1 (fr) * 2013-06-13 2016-01-15 Air Liquide Procede de traitement des pates papetieres chimiques par traitement a l'ozone en presence d'ions magnesium
AT515152B1 (de) * 2013-11-26 2015-12-15 Chemiefaser Lenzing Ag Verfahren zum Vorbehandeln von rückgewonnenen Baumwollfasern zur Verwendung bei der Herstellung von Formkörpern aus regenerierter Cellulose
US10865519B2 (en) 2016-11-16 2020-12-15 Gp Cellulose Gmbh Modified cellulose from chemical fiber and methods of making and using the same
SE545759C2 (en) * 2022-06-20 2024-01-02 Valmet Oy Method for bleaching pulp from recycled textile material

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0402335A2 (en) * 1989-06-06 1990-12-12 Eka Nobel Ab Process for bleaching lignocellulose-containing pulps
EP0512590A1 (en) * 1991-04-30 1992-11-11 Eka Nobel Ab Process for bleaching of lignocellulose-containing material

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NO144711C (no) * 1978-04-04 1981-10-21 Myrens Verksted As Fremgangsmaate til bleking av oksygendelignifiserte celluloseholdige masser med ozon
US4310384A (en) * 1979-01-11 1982-01-12 Weyerhaeuser Company Reducing chemical transfer between treatment stages
FI74752C (fi) * 1986-03-20 1992-12-01 Ahlstroem Oy Foerfarande och anordning foer tvaettning av cellulosa
AU636173B2 (en) * 1989-10-30 1993-04-22 Lenzing Aktiengesellschaft Method for the chlorine-free bleaching of pulps
US5567262A (en) * 1991-04-16 1996-10-22 Ahlstrom Machinery Inc. Two stage pressure diffuser
AT400153B (de) * 1991-05-02 1995-10-25 Voest Alpine Ind Anlagen Verfahren zum bleichen von xylan- und lignocellulosehältigen materialien

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0402335A2 (en) * 1989-06-06 1990-12-12 Eka Nobel Ab Process for bleaching lignocellulose-containing pulps
EP0512590A1 (en) * 1991-04-30 1992-11-11 Eka Nobel Ab Process for bleaching of lignocellulose-containing material

Also Published As

Publication number Publication date
FI93232C (fi) 1995-03-10
FI954093A (fi) 1995-10-17
ES2186948T3 (es) 2003-05-16
PT884415E (pt) 2003-03-31
RU2126471C1 (ru) 1999-02-20
WO1994020673A1 (en) 1994-09-15
CA2157109A1 (en) 1994-09-15
NO953444D0 (no) 1995-09-01
EP0687321A1 (en) 1995-12-20
DE69332508T2 (de) 2003-07-03
FI930954A (fi) 1994-09-04
FI934036A (fi) 1994-09-04
ES2130260T3 (es) 1999-07-01
ATE228181T1 (de) 2002-12-15
BR9307858A (pt) 1996-02-27
EP0884415A1 (en) 1998-12-16
FI93232B (fi) 1994-11-30
EP0884415B1 (en) 2002-11-20
AU5370594A (en) 1994-09-26
FI930954A0 (fi) 1993-03-03
DE69332508D1 (de) 2003-01-02
JP3276083B2 (ja) 2002-04-22
DE69323566T2 (de) 1999-07-15
ATE176808T1 (de) 1999-03-15
FI98223B (fi) 1997-01-31
FI934036A0 (fi) 1993-09-15
CA2157109C (en) 2002-09-03
DE69323566D1 (de) 1999-03-25
JPH08509781A (ja) 1996-10-15
NO953444L (no) 1995-10-19
FI954093A0 (fi) 1995-08-30

Similar Documents

Publication Publication Date Title
US6010594A (en) Method of bleaching pulp with chlorine-free chemicals wherein a complexing agent is added immediately after an ozone bleach stage
EP0687321B1 (en) Method of bleaching pulp with chlorine-free chemicals
AU670659B2 (en) Process for delignification of lignocellulose-containing pulp
US20010020521A1 (en) Acid treatment of pulp at high temperature in connection with bleaching
RU2148118C1 (ru) Двустадийная делигнификация лигноцеллюлозной массы кислородом
CA2031848C (en) Method of bleaching pulp
RU95122814A (ru) Способ производства целлюлозы без применения хлорных химикатов
WO1995009945A1 (en) Method of treating chemical paper pulp without using chlorine-containing chemicals
AU665461B2 (en) Method of treating process water
CA2031850C (en) Method of bleaching pulp
EP1644574B1 (en) Method for treating pulp in connection with the bleaching of chemical pulp
EP0557112A1 (en) Chlorine free bleaching and pulping process
US20020056533A1 (en) Method of treating chemical cellulose pulp
WO1994029512A1 (en) Method of bleaching pulp without using chlorine chemicals
WO1995008021A1 (en) Eop stage for chlorine free bleaching
EP0846199B1 (en) Treatment of pulp with chelating agent in at least two mixing steps without intermediate washing
JPH05247864A (ja) セルロースパルプの漂白法
US6375797B1 (en) Bleaching chemical pulp in a PkDQ-Po Sequence
EP0951599B1 (en) Treatment of pulp with a chelating agent without using a bleaching tower
WO1998014657A1 (en) Oxidation of disturbing metal ions in bleaching processes
CA2179700A1 (en) Method and apparatus for treating pulp
WO2007108760A1 (en) Final bleaching of cellulose pulp with ozone

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

17P Request for examination filed

Effective date: 19950829

AK Designated contracting states

Kind code of ref document: A1

Designated state(s): AT DE ES FR PT SE

17Q First examination report despatched

Effective date: 19951215

RAP1 Party data changed (applicant data changed or rights of an application transferred)

Owner name: AHLSTROM MACHINERY OY

GRAG Despatch of communication of intention to grant

Free format text: ORIGINAL CODE: EPIDOS AGRA

GRAG Despatch of communication of intention to grant

Free format text: ORIGINAL CODE: EPIDOS AGRA

GRAG Despatch of communication of intention to grant

Free format text: ORIGINAL CODE: EPIDOS AGRA

GRAH Despatch of communication of intention to grant a patent

Free format text: ORIGINAL CODE: EPIDOS IGRA

GRAH Despatch of communication of intention to grant a patent

Free format text: ORIGINAL CODE: EPIDOS IGRA

GRAA (expected) grant

Free format text: ORIGINAL CODE: 0009210

AK Designated contracting states

Kind code of ref document: B1

Designated state(s): AT DE ES FR PT SE

REF Corresponds to:

Ref document number: 176808

Country of ref document: AT

Date of ref document: 19990315

Kind code of ref document: T

ET Fr: translation filed
REF Corresponds to:

Ref document number: 69323566

Country of ref document: DE

Date of ref document: 19990325

REG Reference to a national code

Ref country code: PT

Ref legal event code: SC4A

Free format text: AVAILABILITY OF NATIONAL TRANSLATION

Effective date: 19990218

REG Reference to a national code

Ref country code: ES

Ref legal event code: FG2A

Ref document number: 2130260

Country of ref document: ES

Kind code of ref document: T3

PLBI Opposition filed

Free format text: ORIGINAL CODE: 0009260

PLBF Reply of patent proprietor to notice(s) of opposition

Free format text: ORIGINAL CODE: EPIDOS OBSO

26 Opposition filed

Opponent name: EKA CHEMICALS AB PATENT DEPARTMENT

Effective date: 19991116

PLBF Reply of patent proprietor to notice(s) of opposition

Free format text: ORIGINAL CODE: EPIDOS OBSO

PLBF Reply of patent proprietor to notice(s) of opposition

Free format text: ORIGINAL CODE: EPIDOS OBSO

PLBO Opposition rejected

Free format text: ORIGINAL CODE: EPIDOS REJO

PLBN Opposition rejected

Free format text: ORIGINAL CODE: 0009273

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: OPPOSITION REJECTED

27O Opposition rejected

Effective date: 20011009

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: AT

Payment date: 20030408

Year of fee payment: 11

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: FR

Payment date: 20030411

Year of fee payment: 11

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: PT

Payment date: 20030507

Year of fee payment: 11

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: ES

Payment date: 20040510

Year of fee payment: 12

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: AT

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20040525

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: PT

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20041125

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: FR

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20050131

REG Reference to a national code

Ref country code: PT

Ref legal event code: MM4A

Effective date: 20041125

REG Reference to a national code

Ref country code: FR

Ref legal event code: ST

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: ES

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20050526

REG Reference to a national code

Ref country code: ES

Ref legal event code: FD2A

Effective date: 20050526

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: DE

Payment date: 20080425

Year of fee payment: 16

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: SE

Payment date: 20080421

Year of fee payment: 16

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: DE

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20091201

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: SE

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20090526