EP0561786A1 - Blanchiment de pate chimique au moyen de chlore/dioxyde de chlore puis d'ozone - Google Patents

Blanchiment de pate chimique au moyen de chlore/dioxyde de chlore puis d'ozone

Info

Publication number
EP0561786A1
EP0561786A1 EP91916878A EP91916878A EP0561786A1 EP 0561786 A1 EP0561786 A1 EP 0561786A1 EP 91916878 A EP91916878 A EP 91916878A EP 91916878 A EP91916878 A EP 91916878A EP 0561786 A1 EP0561786 A1 EP 0561786A1
Authority
EP
European Patent Office
Prior art keywords
pulp
chlorine
chlorine dioxide
stage
bleaching
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP91916878A
Other languages
German (de)
English (en)
Other versions
EP0561786A4 (en
EP0561786B1 (fr
Inventor
Ted Yuan Tsai
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.)
International Paper Co
Original Assignee
International Paper Co
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
Application filed by International Paper Co filed Critical International Paper Co
Publication of EP0561786A1 publication Critical patent/EP0561786A1/fr
Publication of EP0561786A4 publication Critical patent/EP0561786A4/en
Application granted granted Critical
Publication of EP0561786B1 publication Critical patent/EP0561786B1/fr
Anticipated expiration legal-status Critical
Expired - Lifetime 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
    • D21C9/12—Bleaching ; Apparatus therefor with halogens or halogen-containing compounds
    • D21C9/14—Bleaching ; Apparatus therefor with halogens or halogen-containing compounds with ClO2 or chlorites
    • 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
    • D21C9/12—Bleaching ; Apparatus therefor with halogens or halogen-containing compounds
    • D21C9/14—Bleaching ; Apparatus therefor with halogens or halogen-containing compounds with ClO2 or chlorites
    • D21C9/144—Bleaching ; Apparatus therefor with halogens or halogen-containing compounds with ClO2 or chlorites with ClO2/Cl2 and other bleaching agents in a multistage 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
    • D21C9/153—Bleaching ; Apparatus therefor with oxygen or its allotropic modifications with ozone

Definitions

  • the present invention relates to delignification and bleaching of chemical cellulosic wood pulp fibers for use in papermaking and to the production of a pulp having reduced halogen concentrations, and good brightness and vis ⁇ cosity.
  • Chlorine-based chemicals such as chlorine, chlo ⁇ rine dioxide, and hypochlorite, have been used in pulp bleaching for several decades, and continue to be used for removing lignin and bleaching the pulp to high brightness.
  • the extent of bleaching hence the degree of brightness obtained, is determined by the type of pulp being bleached and the proposed end use of the paper product.
  • kraft pulps intended for use in making fine writing papers require different bleaching circumstances which will produce the desired brightness in the final paper product.
  • chlorine-based bleaching agents have been employed in the prior art, there are produced chlorinated organics and organic halogens (i.e. chlorides).
  • the compounds are gener ⁇ ally insoluble in an aqueous medium and substantial quanti ⁇ ties are swept from the pulp with the effluent from one or more of the stages of the bleaching sequence. A relatively smaller percentage of such chlorinated organics and organic chlorides remain in the pulp and eventually appear in the paper product.
  • the "C” factor of the pulp is employed as a measure of the chlorina- tion charge required for a specific pulp.
  • the "C” factor refers to the effective chlorination charge and is equal to the chlorine dioxide plus the chlorine in the charge (expressed in terms of effective chlorine) , divided by the Kappa number of the pulp.
  • a "C” factor of 0.22 provides maximum brightness in a pulp without unacceptable degrada ⁇ tion of the cellulosic fibers (e.g. reduced strength) .
  • Another option to reduce the discharge of chlori ⁇ nated organic compounds is to reduce the chlorine usage in the first stage of the bleaching process.
  • Two alternatives that produce no significant degradation of pulp properties have been commercialized for this purpose. These are (a) extended delignification in the cooking stage and (b) oxygen delignification. These alternatives, with proper extrac ⁇ tion, reduce the lignin content of brown stock going into the bleach plant. They do not, however, reduce the chlori ⁇ nated organic compounds in the bleached pulp and effluent to sufficiently low levels.
  • a third option to reduce the generation of chlori ⁇ nated organics in a bleaching process is to substitute chlorine dioxide for chlorine.
  • Chlorine dioxide is a rela ⁇ tively strong oxidant compared to chlorine; to achieve the same degree of delignification, it requires only about thirty-eight weight percent chlorine dioxide on the pulp compared with one hundred weight percent of chlorine.
  • these prior art processes are of the DEDED type wherein the chlorination stage (D) is followed by the con ⁇ ventional extraction (E) and additional chlorination (D) stages.
  • the pulp and the discharge effluents resulting from this prior art option contain higher concentrations of chlorinated organics than are acceptable and/or desirable. Processes using both oxygen delignification and chlorine dioxide substitution have been suggested but do not achieve the regulated concentrations of chlorine-containing residues in either the pulp or the effluent. Summary of the Invention
  • the present invention comprises a method for the treatment of kraft pulp in preparation for its use in paper- making including the steps of contacting the pulp while dispersed in an aqueous medium with an initial charge of a chlorine-based bleaching agent selected from the group consisting of chlorine dioxide, and mixtures of chlorine dioxide and chlorine, wherein the total chlorine dioxide p esent in the charge represents between about 100% and about 50% of the total charge, expressed as effective chlorine, the remainder of the charge being chlorine, the bleaching agent producing a substantial quantity of chlorine- containing moieties that are insoluble in an acid 5 medium,
  • a chlorine-based bleaching agent selected from the group consisting of chlorine dioxide, and mixtures of chlorine dioxide and chlorine
  • a cellulosic kraft pulp suitable for papermaking purposes the pulp being bleached through the use of chlorine dioxide or a mixture of chlorine dioxide and chlorine, being essentially free of tetrachlorodibenzodioxin or tetradibenzofuran,
  • a chemical cellulosic wood pulp e.g. a kraft pulp
  • chlorine dioxide may initially contain up to about 50% chlorine, based on effective chlorine, or in this initial bleaching stage, up to about 50% chlorine may be added to the chlorine dioxide as a substitute for the chlorine dioxide, also based on effective chlorine.
  • the pulp is processed through an ozonation stage.
  • the pulp is processed through the custom ⁇ ary extraction, further bleaching, etc. stages.
  • the ozona- tion takes place immediately following chlorination and prior to extraction. It has been recognized heretofore that ozone as a strong oxidant tends to degrade the pulp. Also, the art teaches the _ any use of ozone on pulp should be preceded with an acid wash, for example to remove heavy metals known to be harmful to the stability of ozone and/or decomposition products that may cause low pulp properties (e.g. strength) .
  • the present inventor has found that the ozonation can take place immedi ⁇ ately following an initial chlorine dioxide/chlorine (D c ) bleaching stage as defined hereinabove.
  • D c initial chlorine dioxide/chlorine
  • This washing is not deemed to be a "stage", but rather is in the nature of a dilution of the aqueous phase of the pulp.
  • the quantity of water commonly used provides a dilution factor of between about 1 and about 3. It has been found that the wash water need not be "clean” or "fresh” water. For example, recirculated water which contains considerable residues from previous usage has been used successfully.
  • the ozone treatment not only provides delignification and bleaching but also oxidizes substantial quantities of the chlorinated lignin residues left over from the chlorination stage.
  • This oxidative activity converts substantial quantities of the insoluble chlorinated organics to inorganic chlorine- containing compounds and/or to chlorinated organics that are soluble in the acid liquor present in the ozonation stage.
  • the oxidation of these chlorinated residues by the ozone thus not only reduces the chlorinated organic content in the wood pulp, but also reduces the adsorbed chlorinated organ ⁇ ics discharged in the effluent.
  • These converted inorganic chlorides generally, are not environmentally hazardous and/or are recoverable.
  • the result is a pulp having good brightness, acceptable viscosity, and reduced chlorinated organic content.
  • desirable results are ob ⁇ tained by employing as few as four stages in the bleaching sequence, and employing lower total effective chlorine charges in the chlorination stage than heretofore known to be possible.
  • the present inventors using their improved method, have produced wood pulp which has less than 200 ppm total organic chloride (T0C1) residue.
  • TOC1 refers to the total organically bound chlorine content of the pulp resulting from the bleaching sequence unless indicated otherwise.
  • T0C1 is essentially insoluble.
  • the effluent discharge from the bleaching process of the disclosed method has less than 2.0 kg adsorbed organic halogens (AOX) per ton of wood pulp.
  • AOX refers to the sum of the AOX, i.e. adsorbed organic halogens, of the several stages of bleaching, i.e. AOX of the D c stage plus AOX of the Z stage plus AOX of the E stage and plus AOX of further D stages, unless indicated otherwise.
  • the pulp produced by the present invention has a brightness and viscosity that meet or exceed the requirements of industrial papermaking.
  • AOX adsorbed organic ha- lides
  • FIGURES 1-5 are graphic representations, computer- generated from mathematical models depicting the relation ⁇ ship of ozone charge and chlorination factor in obtaining various values of the brightness, viscosity and total chlo ⁇ ride on pulp.
  • an aqueous slurry of cellulosic wood fibers as is commonly produced by conventional digestion means in the papermaking industry is processed through sequential stages of a bleach ⁇ ing operation.
  • Softwoods, hardwoods or mixtures thereof may be processed employing the present invention.
  • the slurry preferably is processed directly to the bleaching sequence disclosed herein. If desired, it may be subjected to such treatment as oxygenation, ozonation or other oxidation prior to entering the present sequence, but with attendant increased expense.
  • the pulp slurry is treated with a chlorine-based agent, i.e. chlorine dioxide or a mixture of chlorine dioxide and chlo ⁇ rine.
  • the oxidant is principally chlorine dioxide.
  • D is employed to represent a bleaching stage employing chlorine dioxide.
  • D-L is used to represent the first D stage of a sequence.
  • D c represents a stage employing chlorine dioxide plus chlorine.
  • the chlorine may be present in the chlorine dioxide, i.e. a mixture, or the chlorine dioxide may be first added to the pulp and after a brief time period the chlorine is added.
  • D ⁇ C is at times used to represent this latter chlorine substitution, but herein, the term D c is deemed to encompass both the mixture and the chlorine sub ⁇ stitution procedures unless indicated otherwise.
  • the pulp of the present invention is processed through an ozonation stage, Z.
  • ozone tends to be decom ⁇ posed by certain of the heavy metal components of the pulp that conventionally are removed by an additional acid treat- ment stage that comprises subjecting the pulp to an acidic medium.
  • the pulp moves from the D- ⁇ stage which is an acidic stage directly to the Z stage without an acidic treatment stage.
  • the acid pulp is contacted with ozone in a reaction tower, for exam- pie, for a period of time and employing sufficient ozone to effect oxidation of substantial quantities of the chlorinat ⁇ ed lignins and/or other chlorinated components of-the pulp, in addition to the contribution of the ozone toward further delignification.
  • Many of the oxidized chlorine-based moie- ties are soluble in the environment of the Z stage. Thus, these oxidized chlorine-based moieties are solubilized into the liquor and extracted from the pulp during washing fol ⁇ lowing the Z stage.
  • Other of the oxidized compounds are soluble in an alkaline solution such as is present in an E stage.
  • Extraction with an alkaline medium following the Z stage thus serves to remove alkaline-soluble oxidized chlo ⁇ rine-based moieties from the pulp.
  • a preferred complete sequence will include an extraction stage following the ozonation stage.
  • Such extraction stage may be enhanced with oxygen, E 0 , or peroxide, E p , a combination of oxygen and peroxide, E 0+p , or other enhancer.
  • the pulp may be further processed through any of several selected stages.
  • the extraction stage is followed by a further bleaching stage. Chlorine dioxide, i.e. a D 2 stage is preferred as such further bleaching stage.
  • washes may be employed between selected stages, e.g. between the E and D 2 stages.
  • D c stage In the sequential chlorine dioxide substitution stage, D ⁇ C, chlorine dioxide was added to the pulp and mixed; after 20 seconds, chlorine was added and the pulp was well mixed; this stage was conducted in a reactor for 40 min. at 50°C with a consistency of 3-10%. In those instances where the chlorine was present in the chlorine dioxide as a mixture, the chlorine was introduced simultane ⁇ ously with the chlorine dioxide.
  • C stage Chlorination was conducted in a reactor for 30 to 40 min. at 45°C with a consistency of 3%, with chlorine of the desired charge.
  • D stage Chlorine dioxide addition was conducted at 50 to 70°C with a consistency of 10%;
  • E 0 stage Extraction enhanced with oxygen was conducted under conditions similar to the E stage with an initial oxygen pressure of 40-50 psig that was gradually reduced to 0 psig;
  • Examples 6-13 the pulp employed was the same as in Examples 1-5.
  • Examples 6-13 involved bleaching sequences using an ozone bleaching stage. Table 2 shows the proper- ties of the pulps of these Examples.
  • Examples 8 and 9 employed 20% and 7% less chlorine dioxide than Example 11 (DZEDED) plus the fact that the DZED sequence with its fewer stages yielded better viscosity values and almost equal brightness values. Fur ⁇ ther, the brightness obtained by the DZED sequence is almost equal to the brightness obtained in the more costly prior art CEDED sequence (cf. Ex. 10 and Ex. 5) .
  • the DZED (Ex. 8) produced better results than that of ZDED (Ex. 10) at same chemical charge.
  • the DZED produced 84.7% GZ brightness while ZDED produced only 79.0% GZ. The same result has been experienced in the DZEDED (Ex. 11) and ZDEDED (Ex. 12) examples.
  • the DZ sequence also generated less T0C1 than that of ZD sequence.
  • Examples 14-16 employed Southern softwood kraft pulp having a Kappa number of 27.3.
  • Table 3 shows certain properties of the resultant bleached pulps. From Table 3 it is noted that enhancement of the extraction stage (e.g. E 0 , p , or E 0+p in the DZED bleaching sequence permits the use of less chlorine dioxide in the D stage and produces a pulp of substantially equivalent brightness and viscosity to the pulp produced using a DZED sequence without such enhance- ment.
  • the extraction stage e.g. E 0 , p , or E 0+p in the DZED bleaching sequence permits the use of less chlorine dioxide in the D stage and produces a pulp of substantially equivalent brightness and viscosity to the pulp produced using a DZED sequence without such enhance- ment.
  • Examples 17-19 employed Southern hardwood kraft pulp having a Kappa of 14.9. Table 3 also shows the proper ⁇ ties of the resultant bleached pulps of these examples. These pulps showed high viscosity and good brightness values as well as relatively low TOCl values employing total chlo ⁇ rine dioxide amounts less than the total chlorine dioxide amounts employed in obtaining substantially equivalent brightness and viscosity values for softwood pulp. For either softwood or hardwood pulps, the total chlorine diox- ide employed in these Examples 14-19 is substantially less than the total chlorine dioxide employed to obtain equiva ⁇ lent brightness and viscosity values without employing ozone after chlorination.
  • Table 5 shows the adsorbed organic halogens (AOX) generated in the bleaching stages of the sequences of Exam ⁇ ples 1-3, 9, 11 and 14.
  • Examples 1 and 2 showed AOX levels in excess of the desired 2.0 kg per ton of wood pulp.
  • a pre-delignification stage, as in Example 3, produced efflu ⁇ ent within the 2.0 kg level, but Example 3 had high levels of chloride in the wood pulp (see Table 2).
  • Examples 9, 11 and 14 involved stages of chlorine dioxide bleaching fol ⁇ lowed by ozonation.
  • Example 9 represented a DZED sequence, and produced effluent well below the targeted AOX level.
  • Example 14 showed that pre-delignification with oxygen can improve the AOX level, but at the expense of the cost asso ⁇ ciated with the additional stage (0) .
  • the present invention provides for a method of preparation of kraft cellulosic wood pulp fibers for use in papermaking that reduces the total chloride residue in the wood pulp to less than 200 ppm and the AOX discharge per ton of wood pulp to less than 2.0 kg.
  • the wood pulp has a bright ⁇ ness greater than 85% GE and a viscosity above about 14 centipoises.
  • the method is economical and readily adaptable to the current papermaking industry.
  • the percentage of ozone, based on oven dry weight of pulp, employed varies as a function of the "C" factor, the effec ⁇ tive ratio of "C" factor to % ozone being between about 0.11 and 0.6, and preferably between about 0.2 and 0.6 for mini ⁇ mizing the TOCl and AOX values while maximizing the bright- ness and viscosity values of the pulp.
  • EXAMPLES 55-58 In Tabl' 6, there are shown the results of two runs in which the dioxin content of the pulp and effluent was determined. Southern pine kraft pulp, with 1% reject from cooking, having a Kappa No. of 30.3 and a viscosity of 35 cP was employed in all examples.
  • Example 55 a con ⁇ trol run indicative of prior art bleaching sequences that do not employ ozone, but which do include oxygen and peroxide enhanced extraction, there was no detectable tetrachlorodi ⁇ benzodioxin (TCDD) in the final bleached pulp. In this example, there was detected 2.5 ppt of tetrachlorodibenzofu- ran (TCDF) . In the effluent from this run there was detect ⁇ ed 2.5 ppt and 30.3 ppt of TCDD and TCDF, respectively,
  • Example 58 a D C ZE 0 D sequence in accordance with the present invention, there were no dioxins (TCDD or TCDF) detected in either the pulp or the effluent.
  • Eo E 0+p was conducted in Quantum Reactor at 10% CSC, 75'C for 1 hour at 45 psig 0 2 pressure, gradually reduced to 0 psig.
  • Table 7 presents the results of a bleaching se ⁇ quence in accordance with the present invention in which the ozonated pulp at a pH of 12.7 was processed directly to an alkaline extraction stage (enhanced with oxygen) without an intervening water washing (ZE 0 ) .
  • the GE brightness of the pulp and its viscosity were lower than when the pulp was washed with water between the Z and E stages, but these parameter values were still in a range that is acceptable for certain pulps.
  • the simplification of this process can lead to a capital reduction.
  • the TOCl of the pulp was 128 ppm, well below present regulated stand ⁇ ards.

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  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Wood Science & Technology (AREA)
  • Paper (AREA)

Abstract

L'invention concerne des améliorations dans la préparation de pâte chimique de bois cellulosique utilisée dans la fabrication du papier, et en particulier l'amélioration de la qualité d'une pâte kraft qui a été soumise à un blanchiment au dioxyde de chlore/chlore puis à une ozonation avant de passer dans un étage d'extraction dans la séquence de blanchiment. La pâte améliorée de la présente invention se caractérise par une réduction des restes de chlore liés organiquement dans la pâte de bois et des halogénures organiques adsorbés (AOX) dans l'effluent, et posséde une bonne brillance et une bonne viscosité. Les avantages de la présente invention peuvent être obtenus au moyen d'une séquence de blanchiment qui utilise un minimum d'étages, à savoir (D->C)ZED ou DcZED qui s'accompagne d'investissements relativement plus faibles que ceux qui étaient nécessaires jusqu'à présent.
EP91916878A 1990-08-14 1991-08-14 Blanchiment de pate chimique au moyen de chlore/dioxyde de chlore puis d'ozone Expired - Lifetime EP0561786B1 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
US56740990A 1990-08-14 1990-08-14
US567409 1990-08-14
PCT/US1991/005834 WO1992003609A1 (fr) 1990-08-14 1991-08-14 Blanchiment de pate chimique au moyen de chlore/dioxyde de chlore puis d'ozone

Publications (3)

Publication Number Publication Date
EP0561786A1 true EP0561786A1 (fr) 1993-09-29
EP0561786A4 EP0561786A4 (en) 1995-11-15
EP0561786B1 EP0561786B1 (fr) 1997-11-26

Family

ID=24267030

Family Applications (1)

Application Number Title Priority Date Filing Date
EP91916878A Expired - Lifetime EP0561786B1 (fr) 1990-08-14 1991-08-14 Blanchiment de pate chimique au moyen de chlore/dioxyde de chlore puis d'ozone

Country Status (7)

Country Link
EP (1) EP0561786B1 (fr)
JP (1) JP3093263B2 (fr)
CA (1) CA2089477A1 (fr)
DE (1) DE69128287T2 (fr)
ES (1) ES2109273T3 (fr)
FI (1) FI930625A (fr)
WO (1) WO1992003609A1 (fr)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
ZA93224B (en) * 1992-01-22 1993-08-18 Olin Corp Gas phase delignification of lignocellulosic material.
US6174409B1 (en) 1997-09-19 2001-01-16 American Air Liquide Inc. Method to improve final bleached pulp strength properties by adjusting the CI02:03 ration within a single (D/Z) stage of the bleaching process

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1990013705A1 (fr) * 1989-05-05 1990-11-15 International Paper Company Traitement a l'ozone de pate a papier chloree avec du chlore/dioxyde de chlore

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4568420B1 (en) * 1984-12-03 1999-03-02 Int Paper Co Multi-stage bleaching process including an enhanced oxidative extraction stage

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1990013705A1 (fr) * 1989-05-05 1990-11-15 International Paper Company Traitement a l'ozone de pate a papier chloree avec du chlore/dioxyde de chlore

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See also references of WO9203609A1 *

Also Published As

Publication number Publication date
EP0561786A4 (en) 1995-11-15
DE69128287D1 (de) 1998-01-08
WO1992003609A1 (fr) 1992-03-05
JPH06503857A (ja) 1994-04-28
JP3093263B2 (ja) 2000-10-03
FI930625A (fi) 1993-03-25
CA2089477A1 (fr) 1992-02-15
EP0561786B1 (fr) 1997-11-26
FI930625A0 (fi) 1993-02-12
ES2109273T3 (es) 1998-01-16
DE69128287T2 (de) 1998-03-19

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