WO1998023810A1 - Method for controlling oxygen delignification of pulp - Google Patents

Method for controlling oxygen delignification of pulp Download PDF

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Publication number
WO1998023810A1
WO1998023810A1 PCT/SE1997/001852 SE9701852W WO9823810A1 WO 1998023810 A1 WO1998023810 A1 WO 1998023810A1 SE 9701852 W SE9701852 W SE 9701852W WO 9823810 A1 WO9823810 A1 WO 9823810A1
Authority
WO
WIPO (PCT)
Prior art keywords
delignification
pulp
stage
kappa number
kappa
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.)
Ceased
Application number
PCT/SE1997/001852
Other languages
French (fr)
Inventor
Monica BOKSTRÖM
Jan-Erik HÄGGQVIST
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
Family has litigation
First worldwide family litigation filed litigation Critical https://patents.darts-ip.com/?family=20404765&utm_source=google_patent&utm_medium=platform_link&utm_campaign=public_patent_search&patent=WO1998023810(A1) "Global patent litigation dataset” by Darts-ip is licensed under a Creative Commons Attribution 4.0 International License.
Priority to AU51413/98A priority Critical patent/AU723369B2/en
Priority to CA002270598A priority patent/CA2270598C/en
Priority to JP52459098A priority patent/JP4535515B2/en
Priority to BR9713143-1A priority patent/BR9713143A/en
Priority to DE69737603T priority patent/DE69737603T2/en
Application filed by Sunds Defibrator Industries AB filed Critical Sunds Defibrator Industries AB
Priority to EP97946194A priority patent/EP0941381B1/en
Priority to NZ335724A priority patent/NZ335724A/en
Priority to US09/308,820 priority patent/US6238517B1/en
Publication of WO1998023810A1 publication Critical patent/WO1998023810A1/en
Priority to NO19992491A priority patent/NO325724B1/en
Anticipated expiration legal-status Critical
Ceased 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
    • D21C9/1052—Controlling the process
    • 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

Definitions

  • This invention relates to the control of a method for oxygen delignification of lignocellulosic material in two steps at medium consistency, i.e. 8-16%.
  • the chemicals can be distributed between the stages so as to create optimum conditions in each stage.
  • Other conditions could also be optimized for each stage.
  • the object of the present invention is a method of controlling oxygen delignification in such a manner, that a lower kappa number is obtained without deterioration of the pulp properties.
  • the total delignification can amount to 50-85% of the lignin content (kappa number) of unbleached pulp.
  • the method is carried out at medium consistency in two subsequent steps.
  • cooked pulp is pumped at medium consistency, i.e. 8-16%, by a first pump 1 from the brown pulp washing to oxygen delignification. Alkali is charged to the pulp ahead of the first pump 1. After this pump 1 a first mixer
  • the pulp is used for admixing oxygen to the pulp.
  • the pulp is thereafter supplied into a first reactor 3, in which the first delignification stage is carried out.
  • the pulp is moved from there, possibly by means of a second pump 4, via a second mixer 5 for admixing steam and possibly more oxygen and alkali to a second reactor 6 for the second delignification stage.
  • the pulp is moved to a blow tank 7 and further to subsequent processing stages.
  • the method thus implies that the delignification is carried out in two subsequent stages.
  • a high alkali addition as well as a high oxygen addition are made.
  • the oxygen charge should be 10- 50 kg/ton pulp, preferably 10-30 kg/ton.
  • the retention time in the reactor 3 should be relatively short, 5-30 min, preferably 15-25 min.
  • the pressure in the first reactor 3 should be 4-15 bar.
  • the rate of the cellulose degradation is held on a low level due to the relatively low temperature and the short retention time.
  • the temperature in the second reactor 6 should be higher than in the first reactor 3.
  • the temperature difference shall be less than 20°C, preferably 10-15°C.
  • steam is supplied to the second mixer 5.
  • the pressure in the second reactor should be 2-5 bar and lower than in the first reactor 3.
  • the retention time should be relatively long, 45-180 min, preferably 60-120 min.
  • the second delignification stage is primarily a long extraction stage, where, in relation to the first step, the in ⁇ creased temperature and extended retention time give extended delignification. At temperatures above 90°C, thus, good extraction/leaching rate is obtained.
  • the entire or main part of the chemical addition is made to the first stage.
  • a very small or no addition of alkali or oxygen should be made, not even for compensating for the consumption in the first stage.
  • the alkaliness of the pulp can thereby be held relatively low in the second stage.
  • cellulose degradation is substantially avoided, in spite of high temperature and long retention time.
  • the charge of alkali and oxygen to the second stage, respectively, can be up to 5 kg/ton pulp.
  • control of the oxygen delignification according to the invention is based on forward control, which means it implies the least possible back feed coupling.
  • the control is carried out as follows.
  • the kappa number of the ingoing pulp is measured and compared to the desired value (set value) of the kappa number of the pulp after the oxygen delignification.
  • the reduction of the kappa number thus determined is used for adjusting the chemical addition (oxygen, alkali) to the first stage.
  • a greater kappa number reduction implies higher charge, calculated per reduced kappa number unit.
  • the level of the kappa number of the ingoing pulp is also used for adjusting the chemical charge, so that a higher ingoing kappa number implies a lower charge, calculated per reduced kappa number unit.
  • a kappa number reduction of about 60% implies an alkali charge measured in kg NaOH/ton pulp of about 2.2 times (ingoing kappa minus outgoing kappa).
  • a delignification of 50% from kappa 25 to kappa 12,5 implies an alkali charge of 2.0 times (ingoing kappa minus outgoing kappa) .
  • a delignification of 50% from kappa 20 to kappa 10 implies an alkali charge of 2.2 times (ingoing kappa minus outgoing kappa) .
  • the exact factor is corrected in each individual case by means of obtained kappa number in relation to final pH value. If the final pH is somewhat high and the kappa number somewhat low the alkali charge is adjusted somewhat downwards. If the final pH is somewhat low and the kappa number somewhat high the alkali charge is adjusted somewhat upwards .
  • Oxygen is charged in the relation 1:1 to the alkali charge, but with a maximum oxygen charge of 25-30 kg/ton pulp.
  • the degree of delignification is higher, i.e. when the alkali charge exceeds 25-30 kg NaHO/ton pulp, the ratio between oxygen and alkali charge is reduced. Thereby it is possible to avoid gas channeling as a result of large gas amounts.
  • the temperature level in the second stage is controlled partly in the usual way by the production level, so-called kappa factor control, and partly by the chemical addition to the first stage, so that a higher chemical charge to the first stage should result in a higher temperature in the second stage.
  • the temperature is controlled so that a final pH of 10.5-11.5, preferably 10.7-11.0, is obtained.
  • the factor between a change in chemical charge and the temperature level is adjusted manually by means of a final pH as mentioned above.
  • the increase in temperature between the first and second stage should always be less than 20°C, preferably 10-15°C, in order to avoid too large cellulose degradation due to high temperature.
  • control of the oxygen delignification according to the invention implies that a high delignification degree with good selectivity can be obtained.
  • a low and even kappa number and an even pH-value can be obtained after the second delignification stage.

Landscapes

  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Wood Science & Technology (AREA)
  • Paper (AREA)
  • Chemical And Physical Treatments For Wood And The Like (AREA)
  • Investigating Or Analyzing Non-Biological Materials By The Use Of Chemical Means (AREA)
  • Detergent Compositions (AREA)

Abstract

A method of controlling oxygen delignification of pulp, i.e. reduction of the kappa number of the pulp, where the delignification is carried out in two stages, and the main portion of the chemicals required for the delignification is added to the first stage. The ingoing kappa number of the pulp prior to the delignification and the reduction of the kappa number of the pulp during the total delignification in the two stages are used for adjusting the chemical addition to the first stage. The control is carried out so that higher ingoing kappa number yields lower charge and higher kappa number reduction yields higher charge, calculated per reduced kappa number unit. Said chemical addition to the first stage in its turn is used for control the temperature in the second stage.

Description

METHOD FOR CONTROLLING OXYGEN DELIGNIFICATION OF PULP
This invention relates to the control of a method for oxygen delignification of lignocellulosic material in two steps at medium consistency, i.e. 8-16%.
Since the introduction of oxygen delignification at medium consistency, not much development work has been invested in this process. When chlorine free bleaching and closure of bleach plants came into being, the interest in extended delignification, i.e. further reduction of the kappa number with oxygen, has increased. Extended delignification with oxygen in one or several stages, however, can result in deteriorated pulp quality. Application of proper conditions, however, can bring about several advantages.
With extended oxygen delignification the pulp yield could also be maintained better than at extended cooking, i.e. cooking to lower kappa number.
At a multi-stage method, the chemicals can be distributed between the stages so as to create optimum conditions in each stage. Other conditions could also be optimized for each stage.
The object of the present invention is a method of controlling oxygen delignification in such a manner, that a lower kappa number is obtained without deterioration of the pulp properties. By using the extended delignification according to the invention, the total delignification can amount to 50-85% of the lignin content (kappa number) of unbleached pulp. The method is carried out at medium consistency in two subsequent steps. The characterizing features of the invention are defined in the attached claims.
The invention is described in greater detail in the following, with reference to the accompanying Figure, which schematically shows a plant for carrying out the method according to the invention.
In the plant shown cooked pulp is pumped at medium consistency, i.e. 8-16%, by a first pump 1 from the brown pulp washing to oxygen delignification. Alkali is charged to the pulp ahead of the first pump 1. After this pump 1 a first mixer
2 is used for admixing oxygen to the pulp. The pulp is thereafter supplied into a first reactor 3, in which the first delignification stage is carried out. The pulp is moved from there, possibly by means of a second pump 4, via a second mixer 5 for admixing steam and possibly more oxygen and alkali to a second reactor 6 for the second delignification stage. After the second reactor 6 the pulp is moved to a blow tank 7 and further to subsequent processing stages.
The method thus implies that the delignification is carried out in two subsequent stages. To the first reaktor 3 a high alkali addition as well as a high oxygen addition are made. This means a charge of 10-50 kg alkali (NaOH) per ton pulp, preferably 10-35 kg/ton. The oxygen charge should be 10- 50 kg/ton pulp, preferably 10-30 kg/ton.
The temperature of the pulp at its feed to the reactor
3 shall be below 90°C, preferably 75-90°C. The retention time in the reactor 3 should be relatively short, 5-30 min, preferably 15-25 min.
The pressure in the first reactor 3 should be 4-15 bar. The high pressure, together with the high alkaliness of the pulp and the high oxygen charge, result in a high delignification rate. At the same time, the rate of the cellulose degradation is held on a low level due to the relatively low temperature and the short retention time.
After the first delignification stage in the first reactor 3 the pulp is moved to the second delignification stage in the second reactor 6. The temperature in the second reactor 6 should be higher than in the first reactor 3. The temperature difference, however, shall be less than 20°C, preferably 10-15°C. In order to bring about the necessary increase in temperature, steam is supplied to the second mixer 5.
The pressure in the second reactor should be 2-5 bar and lower than in the first reactor 3. The retention time should be relatively long, 45-180 min, preferably 60-120 min.
The second delignification stage is primarily a long extraction stage, where, in relation to the first step, the in¬ creased temperature and extended retention time give extended delignification. At temperatures above 90°C, thus, good extraction/leaching rate is obtained.
The entire or main part of the chemical addition is made to the first stage. To the second stage preferably a very small or no addition of alkali or oxygen should be made, not even for compensating for the consumption in the first stage. The alkaliness of the pulp can thereby be held relatively low in the second stage. Hereby cellulose degradation is substantially avoided, in spite of high temperature and long retention time.
The charge of alkali and oxygen to the second stage, respectively, can be up to 5 kg/ton pulp.
The control of the oxygen delignification according to the invention is based on forward control, which means it implies the least possible back feed coupling. The control is carried out as follows.
The kappa number of the ingoing pulp is measured and compared to the desired value (set value) of the kappa number of the pulp after the oxygen delignification. The reduction of the kappa number thus determined is used for adjusting the chemical addition (oxygen, alkali) to the first stage. A greater kappa number reduction implies higher charge, calculated per reduced kappa number unit. The level of the kappa number of the ingoing pulp is also used for adjusting the chemical charge, so that a higher ingoing kappa number implies a lower charge, calculated per reduced kappa number unit. For instance, a kappa number reduction of about 60%, such as from kappa 25 to kappa 10, implies an alkali charge measured in kg NaOH/ton pulp of about 2.2 times (ingoing kappa minus outgoing kappa). A delignification of 50% from kappa 25 to kappa 12,5 implies an alkali charge of 2.0 times (ingoing kappa minus outgoing kappa) . A delignification of 50% from kappa 20 to kappa 10 implies an alkali charge of 2.2 times (ingoing kappa minus outgoing kappa) . The exact factor is corrected in each individual case by means of obtained kappa number in relation to final pH value. If the final pH is somewhat high and the kappa number somewhat low the alkali charge is adjusted somewhat downwards. If the final pH is somewhat low and the kappa number somewhat high the alkali charge is adjusted somewhat upwards .
Oxygen is charged in the relation 1:1 to the alkali charge, but with a maximum oxygen charge of 25-30 kg/ton pulp. When the degree of delignification is higher, i.e. when the alkali charge exceeds 25-30 kg NaHO/ton pulp, the ratio between oxygen and alkali charge is reduced. Thereby it is possible to avoid gas channeling as a result of large gas amounts.
The temperature level in the second stage is controlled partly in the usual way by the production level, so-called kappa factor control, and partly by the chemical addition to the first stage, so that a higher chemical charge to the first stage should result in a higher temperature in the second stage. The temperature is controlled so that a final pH of 10.5-11.5, preferably 10.7-11.0, is obtained. The factor between a change in chemical charge and the temperature level is adjusted manually by means of a final pH as mentioned above. However, the increase in temperature between the first and second stage should always be less than 20°C, preferably 10-15°C, in order to avoid too large cellulose degradation due to high temperature.
Normally, however, no compensation takes place of the temperature in the first stage to the chemical addition and production level. The pulp ingoing to the first stage is not heated, but it might need some cooling, so that a temperature suitably low for the process is obtained, below 90°C.
The control of the oxygen delignification according to the invention implies that a high delignification degree with good selectivity can be obtained. A low and even kappa number and an even pH-value can be obtained after the second delignification stage.

Claims

Claims
1. A method of controlling oxygen delignification of pulp, i.e. reduction of the kappa number of the pulp, where the delignification is carried out in two stages, and the main portion of the chemicals required for the delignification is added to the first step, characterized in that the ingoing kappa number of the pulp prior to the delignification and the reduction of the kappa number of the pulp during the total delignification in the two stages are used for adjusting the chemical addition to the first stage, so that a higher ingoing kappa number yields lower charge and greater kappa number reduction yields higher charge, calculated per reduced kappa number unit, and that said chemical addition to the first stage in its turn is used for control of the temperature in the second stage.
2. A method as defined in claim 1, characterized in that the temperature in the second stage is controlled so that a final pH of 10.5-11.5 is obtained.
3. A method as defined in claim 1 or 2 characterized in that the entire chemical addition required for the delignification is made in the first stage.
PCT/SE1997/001852 1996-11-26 1997-11-06 Method for controlling oxygen delignification of pulp Ceased WO1998023810A1 (en)

Priority Applications (9)

Application Number Priority Date Filing Date Title
US09/308,820 US6238517B1 (en) 1996-11-26 1997-11-06 Method for controlling oxygen delignification of pulp
CA002270598A CA2270598C (en) 1996-11-26 1997-11-06 Method for controlling oxygen delignification of pulp
JP52459098A JP4535515B2 (en) 1996-11-26 1997-11-06 Control method for oxygen delignification of pulp
BR9713143-1A BR9713143A (en) 1996-11-26 1997-11-06 Process to control pulp delignification with oxygen.
DE69737603T DE69737603T2 (en) 1996-11-26 1997-11-06 METHOD FOR CONTROLLING THE OXYGEN DETECTION OF PULP
AU51413/98A AU723369B2 (en) 1996-11-26 1997-11-06 Method for controlling oxygen delignification of pulp
EP97946194A EP0941381B1 (en) 1996-11-26 1997-11-06 Method for controlling oxygen delignification of pulp
NZ335724A NZ335724A (en) 1996-11-26 1997-11-06 Method for controlling oxygen delignification of pulp in two stages
NO19992491A NO325724B1 (en) 1996-11-26 1999-05-25 Method for regulating oxygen delignification of pulp

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE9604350-0 1996-11-26
SE9604350A SE510740C2 (en) 1996-11-26 1996-11-26 Oxygen delignification control

Publications (1)

Publication Number Publication Date
WO1998023810A1 true WO1998023810A1 (en) 1998-06-04

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ID=20404765

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/SE1997/001852 Ceased WO1998023810A1 (en) 1996-11-26 1997-11-06 Method for controlling oxygen delignification of pulp

Country Status (17)

Country Link
US (1) US6238517B1 (en)
EP (1) EP0941381B1 (en)
JP (1) JP4535515B2 (en)
CN (1) CN1103833C (en)
AT (1) ATE359392T1 (en)
AU (1) AU723369B2 (en)
BR (1) BR9713143A (en)
CA (1) CA2270598C (en)
DE (1) DE69737603T2 (en)
ES (1) ES2281110T3 (en)
ID (1) ID19277A (en)
NO (1) NO325724B1 (en)
NZ (1) NZ335724A (en)
PT (1) PT941381E (en)
SE (1) SE510740C2 (en)
WO (1) WO1998023810A1 (en)
ZA (1) ZA9710422B (en)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1067237A1 (en) * 1999-07-06 2001-01-10 Kvaerner Pulping Ab System and process for the oxygen delignification of pulp consisting of lignocellulose-containing material
WO2001020075A1 (en) * 1999-09-16 2001-03-22 Aga Aktiebolag Oxidised white liquor in an oxygen delignification process
EP1834034A4 (en) * 2004-12-30 2012-12-19 Kvaerner Pulping Tech Method for oxygen delignification of cellulose pulp by mixing of chemicals

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SE526000C2 (en) * 2003-11-26 2005-06-14 Kvaerner Pulping Tech Method and system for controlling the addition of oxygen and alkali in oxygen delignification

Citations (5)

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Publication number Priority date Publication date Assignee Title
CA1057906A (en) * 1974-06-14 1979-07-10 Oy Nokia Ab Method for automatic control of the dosageing of two chemicals
US4419184A (en) * 1980-08-26 1983-12-06 Kamyr Ab Method for control of chemicals during gas treatment of suspensions
US4840703A (en) * 1984-11-08 1989-06-20 Rauma-Repola Oy Method for controlling an oxygen bleaching
US5217575A (en) * 1988-10-18 1993-06-08 Kamyr Ab Process for oxygen bleaching using two vertical reactors
WO1997015715A1 (en) * 1995-10-23 1997-05-01 Sunds Defibrator Industries Ab Oxygen delignification of lignocellulosic pulp in two steps

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SE373395B (en) * 1972-12-19 1975-02-03 Mo Och Domsjoe Ab PROCEDURE FOR THE PRODUCTION OF CELLULOSA MASS WITH HIGH LIGHTNESS BY DISTRIBUTING WOOD WITH ACID GAS UNDER PRESSURE IN THE PRESENCE OF A COCK
JPS5789690A (en) * 1980-11-21 1982-06-04 Toyo Pulp Co Ltd Alkali oxygen delignification of fiber substance
JPH0672386B2 (en) * 1988-04-26 1994-09-14 新王子製紙株式会社 Oxygen delignification and bleaching method for cellulose pulp
SE467582B (en) * 1988-10-18 1992-08-10 Kamyr Ab OXYGEN WHITING
US4946556A (en) * 1989-04-25 1990-08-07 Kamyr, Inc. Method of oxygen delignifying wood pulp with between stage washing
US5034095A (en) * 1989-06-01 1991-07-23 Oji Paper Co., Ltd. Apparatus and process for the delignification of cellulose pulp
JPH04272289A (en) * 1991-02-21 1992-09-29 Mitsubishi Paper Mills Ltd Method for oxygen bleaching of cellulosic pulp
US5672247A (en) * 1995-03-03 1997-09-30 Union Camp Patent Holding, Inc. Control scheme for rapid pulp delignification and bleaching

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA1057906A (en) * 1974-06-14 1979-07-10 Oy Nokia Ab Method for automatic control of the dosageing of two chemicals
US4419184A (en) * 1980-08-26 1983-12-06 Kamyr Ab Method for control of chemicals during gas treatment of suspensions
US4840703A (en) * 1984-11-08 1989-06-20 Rauma-Repola Oy Method for controlling an oxygen bleaching
US5217575A (en) * 1988-10-18 1993-06-08 Kamyr Ab Process for oxygen bleaching using two vertical reactors
WO1997015715A1 (en) * 1995-10-23 1997-05-01 Sunds Defibrator Industries Ab Oxygen delignification of lignocellulosic pulp in two steps

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1067237A1 (en) * 1999-07-06 2001-01-10 Kvaerner Pulping Ab System and process for the oxygen delignification of pulp consisting of lignocellulose-containing material
US6391152B1 (en) * 1999-07-06 2002-05-21 Kvaerner Pulping Ab Process for the oxygen delignification of pulp in two stages with higher pressure in the second stage
JP2003504526A (en) * 1999-07-06 2003-02-04 クヴアナ・パルピング・アクチボラグ System for oxygen delignification of pulp comprising lignocellulose-containing material
JP2003504525A (en) * 1999-07-06 2003-02-04 クヴアナ・パルピング・アクチボラグ Apparatus and method for oxygen delignification of pulp made of lignocellulose-containing material
WO2001020075A1 (en) * 1999-09-16 2001-03-22 Aga Aktiebolag Oxidised white liquor in an oxygen delignification process
US6691358B1 (en) 1999-09-16 2004-02-17 Aga Aktiebolag Oxidized white liquor in an oxygen delignification process
EP1834034A4 (en) * 2004-12-30 2012-12-19 Kvaerner Pulping Tech Method for oxygen delignification of cellulose pulp by mixing of chemicals

Also Published As

Publication number Publication date
AU723369B2 (en) 2000-08-24
SE510740C2 (en) 1999-06-21
CN1103833C (en) 2003-03-26
PT941381E (en) 2007-04-30
EP0941381A1 (en) 1999-09-15
JP4535515B2 (en) 2010-09-01
SE9604350D0 (en) 1996-11-26
US6238517B1 (en) 2001-05-29
ES2281110T3 (en) 2007-09-16
NO992491D0 (en) 1999-05-25
ATE359392T1 (en) 2007-05-15
SE9604350L (en) 1998-05-27
AU5141398A (en) 1998-06-22
EP0941381B1 (en) 2007-04-11
NZ335724A (en) 1999-09-29
NO992491L (en) 1999-05-25
NO325724B1 (en) 2008-07-07
ID19277A (en) 1998-06-28
DE69737603D1 (en) 2007-05-24
CA2270598C (en) 2005-05-03
DE69737603T2 (en) 2007-07-26
JP2001504558A (en) 2001-04-03
CA2270598A1 (en) 1998-06-04
BR9713143A (en) 2000-02-08
ZA9710422B (en) 1998-06-10
CN1238817A (en) 1999-12-15

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