EP1223245A2 - Process for cleaning a pulp of primary fibres - Google Patents

Process for cleaning a pulp of primary fibres Download PDF

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Publication number
EP1223245A2
EP1223245A2 EP02000753A EP02000753A EP1223245A2 EP 1223245 A2 EP1223245 A2 EP 1223245A2 EP 02000753 A EP02000753 A EP 02000753A EP 02000753 A EP02000753 A EP 02000753A EP 1223245 A2 EP1223245 A2 EP 1223245A2
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EP
European Patent Office
Prior art keywords
bleaching
flotation
pulp
suspension
solids
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.)
Granted
Application number
EP02000753A
Other languages
German (de)
French (fr)
Other versions
EP1223245A3 (en
EP1223245B1 (en
Inventor
Volker Dr. Gehr
Peter Respondek
Martin Kemper
Peter Schweiss
Thomas Martin
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.)
Voith Paper Fiber and Environmental Solutions GmbH and Co KG
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Voith Paper Fiber Systems GmbH and Co KG
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Publication date
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Application filed by Voith Paper Fiber Systems GmbH and Co KG filed Critical Voith Paper Fiber Systems GmbH and Co KG
Publication of EP1223245A2 publication Critical patent/EP1223245A2/en
Publication of EP1223245A3 publication Critical patent/EP1223245A3/en
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Publication of EP1223245B1 publication Critical patent/EP1223245B1/en
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    • 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
    • D21C9/001—Modification of pulp properties
    • D21C9/007—Modification of pulp properties by mechanical or physical means
    • 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

Definitions

  • the invention relates to a method according to the preamble of claim 1.
  • Primary fiber is understood to mean e.g. B. chemically produced pulp, mechanically produced wood pulp or mixed forms, such as. B. TMP, CTMP, etc. During generation These primary fibers are made from wood by boiling and bleaching originating lignin components essentially removed. Nevertheless, often remain undesirable, solid, colloidally dissolved or dissolved components, such as. B. resins, Bark particles or small fragments. These components are already being tried at least in part through highly effective sorting and cleaning processes remove; however, such procedures are complex on the one hand and on the other Page not always completely satisfactory. Therefore, it often has to be accepted that the primary fiber materials are not clean, i.e. the paper made from them Has dirt spots or that this results in poor paper machine runability results.
  • EP 0 522 334 A1 describes a method for the treatment of CTMP production known waste water.
  • this procedure serves to increase the yield of production, i.e. fiber and fine material losses to reduce.
  • extensive chemical treatment is required proposed, which leads to the coagulation of all substances to be obtained, so this then separated from the remaining clear water in a microflotation can be.
  • the flotation sludge therefore contains substances that are processed further and are not to be regarded as interfering substances.
  • the invention is based on the object of a method of the type specified create with which it is possible to reliably remove residual impurities from the to remove suspension containing primary fibers.
  • the purpose of the pulp produced are qualitatively improved and / or the production process becomes more economical let it be designed.
  • the flotation is particularly advantageous in the Primary fiber generation used, for. B. left over in pulp boiling or bleaching to remove remaining interfering components.
  • the fiber behave such impurities hydrophobic. It is also possible to use chemical To make treatment hydrophobic.
  • the diagram shows an example of the application of the method Details of primary pulp production have not been entered as they are known to those skilled in the art are already known and a variety of different processes is possible.
  • the Raw material R is added to a pulp cooker 1, in which it is thermally and chemically is converted to pulp P.
  • the cooking process is followed by a thickening stage 2 Partial return of the washed-out lye to the cellulose cooker 1.
  • the thickened Pulp P ' is now in a cleaning stage 3, which is indicated here as a sorting stage, freed from disruptive components. This cleaning level can also be used with others work on known separation processes.
  • the pulp comes in one Bleaching level 4 or a bleaching sequence that can consist of several bleaching levels, where only 4 'is given here as a further one.
  • the substance is diluted with water W and collected in a chest 6.
  • a further mechanical separation of the Pulp fibers required in the suspension It is usually superfluous to have one To carry out treatment in which the fiber itself is changed.
  • the Primary fiber now comes as a suspension S in a thickening stage 9, the filtrate in the flotation 7 is carried out. It can be subjected to further cleaning , for which purpose highly effective cleaners can be used, e.g. With work at least 100 times gravitational acceleration.
  • the thickening stage can be advantageous aim for optimal washing effect.
  • the clear water 11 of the flotation can e.g. to the Thinning can be used again.
  • the thickened suspension contains the cleaned one Primary fiber and is collected in the chest 8. He is after another Treatment suitable for paper production.
  • the flotation can advantageously be carried out neutral or in an acidic environment.

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  • Engineering & Computer Science (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Wood Science & Technology (AREA)
  • Mechanical Engineering (AREA)
  • Paper (AREA)
  • Polysaccharides And Polysaccharide Derivatives (AREA)
  • Chemical Or Physical Treatment Of Fibers (AREA)
  • Yarns And Mechanical Finishing Of Yarns Or Ropes (AREA)
  • Manufacture, Treatment Of Glass Fibers (AREA)

Abstract

After bleaching (4') a process remove impurities from a suspension (S) of primary cellulose. The process employs a thickening or washing stage (9) surrendering to a filter and a subsequent micro-floatation stage (7). The vast majority of impurities are solids liberated by boiling cellulose and removed by micro-floatation in a neutral or acid zone. The individual cellulose fibres are separated by a 100G hydro-cyclone between the bleaching (4') and floatation (7) stages.

Description

Die Erfindung bezieht sich auf ein Verfahren gemäß dem Oberbegriff des Anspruchs 1.The invention relates to a method according to the preamble of claim 1.

Unter Primärfaserstoff versteht man z. B. chemisch erzeugten Zellstoff, mechanisch erzeugten Holzschliff oder Mischformen, wie z. B. TMP, CTMP usw. Bei der Erzeugung dieser Primärfaserstoffe werden durch Kochen und Bleichen die aus dem Holz stammenden Ligninbestandteile im Wesentlichen entfernt. Dennoch verbleiben oft unerwünschte, feste, kolloidal gelöste oder gelöste Bestandteile, wie z. B. Harze, Rindenpartikel oder kleine Splitter. Zwar wird bereits versucht, diese Bestandteile wenigstens teilweise durch hochwirksame Sortier- und Reinigungsverfahren zu entfernen; solche Verfahren sind aber auf der einen Seite aufwendig und auf der anderen Seite nicht immer vollständig befriedigend. Daher muss oft in Kauf genommen werden, dass die Primärfaserstoffe nicht sauber sind, also das aus ihnen erzeugte Papier Schmutzpunkte aufweist oder dass daraus eine schlechte Papiermaschinen-Runability resultiert.Primary fiber is understood to mean e.g. B. chemically produced pulp, mechanically produced wood pulp or mixed forms, such as. B. TMP, CTMP, etc. During generation These primary fibers are made from wood by boiling and bleaching originating lignin components essentially removed. Nevertheless, often remain undesirable, solid, colloidally dissolved or dissolved components, such as. B. resins, Bark particles or small fragments. These components are already being tried at least in part through highly effective sorting and cleaning processes remove; however, such procedures are complex on the one hand and on the other Page not always completely satisfactory. Therefore, it often has to be accepted that the primary fiber materials are not clean, i.e. the paper made from them Has dirt spots or that this results in poor paper machine runability results.

Aus der EP 0 522 334 A1 ist ein Verfahren zur Behandlung von bei der CTMP-Produktion anfallendem Abwasser bekannt. Dieses Verfahren dient jedoch dazu, die Ausbeute der Produktion zu erhöhen, also Faser- und Feinstoffverluste zu reduzieren. Um das zu erreichen, wird eine umfangreiche chemische Behandlung vorgeschlagen, die zur Koagulation aller zu gewinnenden Stoffe führt, so dass diese anschließend in einer Mikroflotation vom zurückbleibenden Klarwasser abgetrennt werden können. Der Flotationsschlamm enthält daher Stoffe, die weiter verarbeitet werden und nicht als Störstoffe anzusehen sind.EP 0 522 334 A1 describes a method for the treatment of CTMP production known waste water. However, this procedure serves to increase the yield of production, i.e. fiber and fine material losses to reduce. To achieve this, extensive chemical treatment is required proposed, which leads to the coagulation of all substances to be obtained, so this then separated from the remaining clear water in a microflotation can be. The flotation sludge therefore contains substances that are processed further and are not to be regarded as interfering substances.

Der Erfindung liegt die Aufgabe zu Grunde, ein Verfahren der angegebenen Art zu schaffen, mit dem es gelingt, restliche Verunreinigungen zuverlässig aus der primärfaserstoffhaltigen Suspension zu entfernen. Dadurch soll der erzeugte Faserstoff qualitativ verbessert werden und/oder sich das Erzeugungsverfahren wirtschaftlicher gestalten lassen.The invention is based on the object of a method of the type specified create with which it is possible to reliably remove residual impurities from the to remove suspension containing primary fibers. The purpose of the pulp produced are qualitatively improved and / or the production process becomes more economical let it be designed.

Diese Aufgabe wird durch die Kennzeichen des Anspruchs 1 erfüllt.This object is achieved by the features of claim 1.

Verbesserungen des Verfahrens lassen sich erzielen, wenn die Maßnahmen der Unteransprüche benutzt werden.Process improvements can be achieved if the measures taken by Subclaims are used.

Es ist an sich bekannt, Flotationsverfahren bei der Aufbereitung von Altpapier einzusetzen. Dabei werden jedoch solche Bestandteile aus der Altpapiersuspension entfernt, die nicht vom Faserstoff oder Papier her stammen. Vielmehr sind sie als Verunreinigungen angefallen, die ursächlich mit dem Gebrauch des Papieres zusammenhängen, also erst nach dessen Erzeugung hinzugekommen sind. Derartige Verunreinigungen sind z. B. die Druckfarben von graphischen Altpapieren, Verunreinigungen, die aus dem sonstigen Gebrauch des Papiers stammen oder auch Kleberücken, um nur einige zu nennen.It is known per se, flotation processes in the processing of waste paper use. However, such components become from the waste paper suspension removed that do not come from the pulp or paper. Rather, they are as Impurities accumulated that are caused by the use of the paper connected, that is, only added after its creation. such Impurities are e.g. B. the printing inks of graphic waste paper, Impurities that originate from the other use of the paper or also Adhesive backing, just to name a few.

Erfindungsgemäß wird die Flotation mit besonderem Vorteil bei der Primärfasererzeugung eingesetzt, um z. B. bei der Zellstoffkochung oder Bleiche übrig gebliebene störende Bestandteile zu entfernen. Im Gegensatz zur Faser verhalten sich solche Verunreinigungen hydrophob. Es ist auch möglich, sie durch chemische Behandlung hydrophob zu machen.According to the invention, the flotation is particularly advantageous in the Primary fiber generation used, for. B. left over in pulp boiling or bleaching to remove remaining interfering components. In contrast to the fiber behave such impurities hydrophobic. It is also possible to use chemical To make treatment hydrophobic.

Ein weiterer Vorteil des Verfahrens ergibt sich bei der Betrachtung der Gesamtökonomie der Faserstofferzeugungsanlage, in der das Verfahren angewendet wird. Da durch die genannten Möglichkeiten zur besseren Entferung unerwünschter, feiner Bestandteile die Anforderungen an den eigentlichen Herstellungs- und Bleichprozeß geringer gehalten werden können, ergibt sich gesamthaft betrachtet die Möglichkeit einer preisgünstigen Primärfaserstofferzeugung. Ein ähnlicher Gesichtspunkt liegt im Folgenden: Zur Primärfaserstofferzeugung werden diverse natürliche, gewachsene Rohstoffe verwendet, die auch in derselben Charge in Abhängigkeit von Herkunft, Gattung, Art, Klima, biologischen Gegebenheiten usw. recht unterschiedliche Eigenschaften haben können. In vielen Fällen ist es daher nur mit großem Aufwand oder gar nicht möglich, z. B. den Kochprozess zur Primärfaserstofferzeugung so abzustimmen, dass dieser heterogene Rohstoff optimal aufbereitet werden kann, wobei in diesem Zusammenhang die Freiheit von unerwünschten Bestandteilen gemeint ist. Schließlich müssen bei der Primärfaserstofferzeugung auch andere wichtige Forderungen, wie z. B. Festigkeit, Faserlänge etc. berücksichtigt werden, was zu einem sehr komplexen Herstellungsverfahren führt. Diese Probleme können mit Hilfe des erfindungsgemäßen Verfahrens sehr viel leichter gelöst werden.Another advantage of the process is that of considering the overall economy the pulp production plant in which the process is used. Because through the mentioned possibilities for better removal of unwanted, fine components Requirements for the actual manufacturing and bleaching process kept lower considered overall, there is the possibility of an inexpensive Primary pulp production. A similar point of view lies below: Zur Primary fiber production becomes various natural, grown raw materials used in the same batch depending on origin, genus, type, Climate, biological conditions, etc. have quite different properties can. In many cases it is therefore only possible with great effort or not at all, e.g. B. to coordinate the cooking process for primary fiber production so that this heterogeneous raw material can be processed optimally, in this context freedom from undesirable components is meant. After all, at the Primary fiber production also other important requirements, such as. B. strength, Fiber length etc. are taken into account, which becomes a very complex Manufacturing process leads. These problems can be solved with the help of the invention Procedure can be solved much easier.

Die Erfindung wird erläutert anhand eines figürlich dargestellten Anlagenschemas.The invention is explained on the basis of a figurative system diagram.

Das Schema stellt ein Beispiel für die Anwendung des Verfahrens dar. Dabei wird auf die Details der Primärfaserstoff-Erzeugung nicht eingegangen, da sie dem Fachmann ohnehin bekannt sind und eine Vielzahl von verschiedenen Prozessen möglich ist. Der Rohstoff R wird in einen Zellstoffkocher 1 zugegeben, in dem er thermisch und chemisch zur Pulpe P umgesetzt wird. Dem Kochprozess folgt eine Eindickstufe 2 mit Teilrückführung der ausgewaschenen Lauge in den Zellstoffkocher 1. Die eingedickte Pulpe P' wird nun in einer Reinigungsstufe 3, die hier als Sortierstufe angedeutet ist, von störenden Bestandteilen befreit. Diese Reinigungsstufe kann aber auch mit anderen an sich bekannten Trennverfahren arbeiten. Als nächstes kommt die Pulpe in eine Bleichstufe 4 oder eine Bleichsequenz, die aus mehreren Bleichstufen bestehen kann, wobei hier mit 4' lediglich eine weitere angegeben ist. Am Ende der Bleichsequenz wird der Stoff mit Wasser W verdünnt und in einer Bütte 6 gesammelt. Eventuell ist an dieser Stelle des Verfahrens auch eine weitere mechanische Vereinzelung der Zellstoffasern in der Suspension erforderlich. Dabei ist es meist überflüssig, eine Behandlung vorzunehmen, bei der der Faserstoff selbst verändert wird. Der Primärfaserstoff gelangt nun als Suspension S in eine Eindickstufe 9, deren Filtrat in die Flotation 7 geführt wird. Dabei kann er einer weiteren Reinigung unterzogen werden, wozu mit Vorteil hochwirksame Cleaner verwendet werden können, die z.B. mit mindestens 100-facher Erdbeschleunigung arbeiten. Die Eindickstufe kann mit Vorteil auf optimalen Wascheffekt zielen. Das Klarwasser 11 der Flotation kann z.B. zum Verdünnen wieder verwendet werden. Die eingedickte Suspension enthält den gereinigten Primärfaserstoff und wird in der Stoffbütte 8 gesammelt. Er ist nach weiterer Behandlung zur Papiererzeugung geeignet.The diagram shows an example of the application of the method Details of primary pulp production have not been entered as they are known to those skilled in the art are already known and a variety of different processes is possible. The Raw material R is added to a pulp cooker 1, in which it is thermally and chemically is converted to pulp P. The cooking process is followed by a thickening stage 2 Partial return of the washed-out lye to the cellulose cooker 1. The thickened Pulp P 'is now in a cleaning stage 3, which is indicated here as a sorting stage, freed from disruptive components. This cleaning level can also be used with others work on known separation processes. Next, the pulp comes in one Bleaching level 4 or a bleaching sequence that can consist of several bleaching levels, where only 4 'is given here as a further one. At the end of the bleaching sequence the substance is diluted with water W and collected in a chest 6. Maybe is on this point of the method also a further mechanical separation of the Pulp fibers required in the suspension. It is usually superfluous to have one To carry out treatment in which the fiber itself is changed. The Primary fiber now comes as a suspension S in a thickening stage 9, the filtrate in the flotation 7 is carried out. It can be subjected to further cleaning , for which purpose highly effective cleaners can be used, e.g. With work at least 100 times gravitational acceleration. The thickening stage can be advantageous aim for optimal washing effect. The clear water 11 of the flotation can e.g. to the Thinning can be used again. The thickened suspension contains the cleaned one Primary fiber and is collected in the chest 8. He is after another Treatment suitable for paper production.

Die Flotation kann mit Vorteil neutral oder im sauren Milieu durchgeführt werden.The flotation can advantageously be carried out neutral or in an acidic environment.

Claims (7)

Verfahren zur Reinigung einer Suspension aus gebleichten Primärfaserstoffen,
dadurch gekennzeichnet, dass die Suspension (S) nach der Bleichstufe (4') oder im Anschluss an eine Bleichsequenz (4, 4') einer Eindickung oder Wäsche zugeführt wird und das dabei anfallende Filtrat in einer Flotation (7), vorzugsweise einer Mikroflotation, behandelt wird, in der der überwiegende Teil der Feststoffe ausflotiert wird.Process for cleaning a suspension of bleached primary fibers,
characterized in that the suspension (S) after the bleaching stage (4 ') or following a bleaching sequence (4, 4') is fed to a thickening or washing and the resulting filtrate in a flotation (7), preferably a microflotation, is treated in which the majority of the solids are floated out. Verfahren nach Anspruch 1,
dadurch gekennzeichnet, dass die ausflotierten Feststoffe Störstoffe sind.Method according to claim 1,
characterized in that the flotated solids are contaminants. Verfahren nach Anspruch 2,
dadurch gekennzeichnet, dass die ausflotierten Feststoffe bei der Zellstoffkochung oder Bleiche übrig gebliebene störende Bestandteile sind.Method according to claim 2,
characterized in that the flotated solids are residual constituents left over during cellulose boiling or bleaching. Verfahren nach Anspruch 1, 2 oder 3,
dadurch gekennzeichnet, dass die Flotation (7) im neutralen Bereich durchgeführt wird.The method of claim 1, 2 or 3,
characterized in that the flotation (7) is carried out in the neutral range. Verfahren nach Anspruch 1, 2 oder 3,
dadurch gekennzeichnet, dass die Flotation (7) im sauren Bereich durchgeführt wird.The method of claim 1, 2 or 3,
characterized in that the flotation (7) is carried out in the acidic range. Verfahren nach einem der voranstehenden Ansprüche,
dadurch gekennzeichnet, dass zwischen der Bleichstufe (4') bzw. der Bleichsequenz (4) und der Flotation (7) eine mechanische Vereinzelung der Zellstofffasern erfolgt, ohne dass die Fasern selbst verändert werden.Method according to one of the preceding claims,
characterized in that between the bleaching stage (4 ') or the bleaching sequence (4) and the flotation (7) the pulp fibers are mechanically separated without the fibers themselves being changed. Verfahren nach einem der voranstehenden Ansprüche,
dadurch gekennzeichnet, dass die Suspension (S) zwischen Bleichstufe (4') bzw. Bleichsequenz (4, 4') und Flotation (7) im Hydrozyklon mit mindestens hundertfacher Erdbeschleunigung gereinigt wird.Method according to one of the preceding claims,
characterized in that the suspension (S) between the bleaching stage (4 ') or bleaching sequence (4, 4') and flotation (7) is cleaned in the hydrocyclone with at least a hundred times the acceleration due to gravity.
EP02000753A 1996-09-05 1997-07-15 Process for cleaning a pulp of primary fibres Revoked EP1223245B1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
DE19635967A DE19635967A1 (en) 1996-09-05 1996-09-05 Process for cleaning a suspension of primary fiber
DE19635967 1996-09-05
EP97112005A EP0828026B1 (en) 1996-09-05 1997-07-15 Process for cleaning a pulp of primary fibres

Related Parent Applications (1)

Application Number Title Priority Date Filing Date
EP97112005A Division EP0828026B1 (en) 1996-09-05 1997-07-15 Process for cleaning a pulp of primary fibres

Publications (3)

Publication Number Publication Date
EP1223245A2 true EP1223245A2 (en) 2002-07-17
EP1223245A3 EP1223245A3 (en) 2004-06-02
EP1223245B1 EP1223245B1 (en) 2005-10-26

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ID=7804657

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EP97112005A Expired - Lifetime EP0828026B1 (en) 1996-09-05 1997-07-15 Process for cleaning a pulp of primary fibres
EP02000753A Revoked EP1223245B1 (en) 1996-09-05 1997-07-15 Process for cleaning a pulp of primary fibres

Family Applications Before (1)

Application Number Title Priority Date Filing Date
EP97112005A Expired - Lifetime EP0828026B1 (en) 1996-09-05 1997-07-15 Process for cleaning a pulp of primary fibres

Country Status (3)

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EP (2) EP0828026B1 (en)
AT (2) ATE307923T1 (en)
DE (3) DE19635967A1 (en)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN107700263B (en) * 2016-08-08 2020-10-09 迅普精工株式会社 Deinking device and waste paper recycling device
CN109629300B (en) * 2018-12-28 2021-08-24 四川凤生纸业科技股份有限公司 Efficient pulping system for paper pulp production line and pulp washing process

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0522334A1 (en) * 1991-07-12 1993-01-13 Nalco Chemical Company A method of treating BCTMP/CTMP wastewater
DE4317466A1 (en) * 1993-05-26 1994-12-01 Degussa Improved process for bleaching wood pulp
WO1996006978A1 (en) * 1994-08-31 1996-03-07 Hoffman Environmental Systems, Inc. Method of papermaking having zero liquid discharge

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE310554C (en) *

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0522334A1 (en) * 1991-07-12 1993-01-13 Nalco Chemical Company A method of treating BCTMP/CTMP wastewater
DE4317466A1 (en) * 1993-05-26 1994-12-01 Degussa Improved process for bleaching wood pulp
WO1996006978A1 (en) * 1994-08-31 1996-03-07 Hoffman Environmental Systems, Inc. Method of papermaking having zero liquid discharge

Also Published As

Publication number Publication date
DE59708425D1 (en) 2002-11-14
DE19635967A1 (en) 1998-03-12
EP0828026B1 (en) 2002-10-09
DE59712461D1 (en) 2005-12-01
ATE307923T1 (en) 2005-11-15
ATE225878T1 (en) 2002-10-15
EP0828026A1 (en) 1998-03-11
EP1223245A3 (en) 2004-06-02
EP1223245B1 (en) 2005-10-26

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