US3884752A - Single vessel wood pulp bleaching with chlorine dioxide followed by sodium hypochlorite or alkaline extraction - Google Patents

Single vessel wood pulp bleaching with chlorine dioxide followed by sodium hypochlorite or alkaline extraction Download PDF

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Publication number
US3884752A
US3884752A US398165A US39816573A US3884752A US 3884752 A US3884752 A US 3884752A US 398165 A US398165 A US 398165A US 39816573 A US39816573 A US 39816573A US 3884752 A US3884752 A US 3884752A
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Prior art keywords
pulp
chlorine dioxide
bleaching
treatment
tower
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Expired - Lifetime
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US398165A
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English (en)
Inventor
Robert T Campbell
Laurence B Ritter
Jr Joseph G Land
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International Paper Co
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International Paper Co
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Application filed by International Paper Co filed Critical International Paper Co
Priority to US398165A priority Critical patent/US3884752A/en
Priority to NO740054A priority patent/NO740054L/no
Priority to SE7400192A priority patent/SE408069B/xx
Priority to JP49010043A priority patent/JPS5058302A/ja
Priority to FR7402954A priority patent/FR2245817B1/fr
Priority to IT67249/74A priority patent/IT1004819B/it
Priority to BE140434A priority patent/BE810468A/xx
Priority to DE19742407542 priority patent/DE2407542A1/de
Priority to LU69421A priority patent/LU69421A1/xx
Priority to FI1051/74A priority patent/FI105174A/fi
Priority to CA204,529A priority patent/CA1019906A/en
Priority to BR7461/74A priority patent/BR7407461D0/pt
Application granted granted Critical
Publication of US3884752A publication Critical patent/US3884752A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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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
    • D21C9/10—Bleaching ; Apparatus therefor
    • D21C9/1026—Other features in bleaching processes

Definitions

  • the process disclosed herein generally relates to the manufacture of wood pulp and more particularly, to a specific process used in the manufacture of wood pulp, viz. the bleaching of wood pulp.
  • wood pulp basically entails the alteration of the chemical constituents of wood. That is to say, wood is primarily comprised of cellulose fibers and a complex chemical generically referred to as lig nin. From the point of view of providing a wood pulp useful in the manufacture of paper, the pulp maker desires to retain the cellulose fibers and either dispose of the lignin initially combined therewith or alter its chemical form so as to yield desired properties. Thus, the initial steps in the production of wood pulp usually comprise the reduction of the wood to chips and the subsequent chemical treatment of the chips thus formed.
  • the chips are loaded into a vessel and mixed with various chemicals, usually under conditions of elevated pressure and temperature, whereby the chemicals act upon the lignin and dissolve a portion thereof.
  • this process of initial delignification is referred to as digesting.
  • the resulting material is generally a dark colored cellulose fiber.
  • the dark color is attributable to the fact that not all of the lignin has been removed in the digesting process and, as a result of the digestion, the residual lignin is darker than in its natural state,
  • the pulp thus provided is referred to as unbleached pulp and may pass directly to the paper making operation for use in the manufacture of paper which does not have to be white or colored other than the dark color of the pulp, e.g. Kraft paper for paperbags, paper for use in manufacturing corrugated board, etc.
  • the common measure or index thereof is brightness and, more specifically, the so-called GE brightness number.
  • pulp supplied directly from a Kraft digestion process, after washing commonly has a GE brightness of 15 to 30 whereas highly bleached pulp has a GE brightness in the range of to 90.
  • chlorination is commonly the first step in multiple-step bleaching processes.
  • the unbleached pulp is mixed with a chlorine and water combination which has the effect of chlorinating, oxidizing, or otherwise solubilizing the lignin either in the acid chlorination system or a subsequent alkaline extraction process.
  • Alkaline extraction is a process which is commonly used in the bleaching of pulp and most commonly is used as a second step following an initial treatment such as chlorination.
  • an alkaline extraction process the pretreated pulp is contacted with a basic solution which is commonly a sodium hydroxide solution. The effect of this operation is the further removal of lignin.
  • alkaline extraction may be used as a first step in a bleaching process, it is most expeditiously used subsequent to a step such as chlorination since the chlorination step causes the lignin to be particularly soluble in an alkaline solution. More over, the alkaline extraction step removes a significant amount of material which would impede the bleaching action of subsequent steps, e.g. subsequent oxidative bleaching steps.
  • hypochlorite bleaching A third bleaching process is referred to as hypochlorite bleaching.
  • This bleaching technique is one of the oldest forms of chemical bleaching of pulp and is attractive to the manufacturer of pulp because the associated chemicals are effective and economical.
  • hypochlorite bleaching was used alone, the more common practice today is to use it after chlorination and alkaline extraction.
  • Hypochlorite bleaching is particularly useful with pulp that contains a significant amount of lignin since, at the start of the hypochlorite stage, the hypochlorite will react faster with lignin than the cellulose and normally most of the hypochlorite will be consumed before cellulose degradation commences to a substantial degree.
  • Typical hypochlorites utilized are calcium hypochlorite and sodium hypochlorite.
  • chlorine dioxide is first generated as a gas and is then absorbed in water. The resulting solution is then brought in contact with the pulp resulting in the oxidation and chlorination of lignin into water soluble compounds. In some instances, chlorine dioxide is used together with chlorine as a first bleaching step.
  • a chlorination step is designated by the letter C
  • an alkaline extraction step is designated by the letter E
  • a hypochlorite bleaching step is designated by the letter H
  • a chlorine dioxide bleaching step is designated by the letter D
  • a combined chlorine and chlorine dioxide treatment is designated as C
  • CEDED a typical bleaching sequence
  • An improved pulp bleaching process employing chlorine dioxide bleaching and alkaline extraction or hypochlorite treatment is the field to which this invention pertains.
  • the pulp slurry-chlorine dioxide mixture Upon discharging from the pulp mixer 12, the pulp slurry-chlorine dioxide mixture enters a first chlorine dioxide bleaching apparatus or unit generally indicated as 20.
  • the unit 20 is representative of modern, chlorine dioxide bleaching units and includes an upflow, preretention tube 13 and a downflow tower 14. Further, the downflow tower 14 is generally divided into two sections, an upper section 15 referred to as the retention zone and a lower section 16 referred to as the dilution zone.
  • Chlorine dioxide bleaching towers such as shown in FIG. 1 are known to those skilled in the art to which this invention pertains and, as well, are described in existing literature, e.g. The Bleaching of Pulp, Tappi Monograph Series No. 27. However, the tower could be downflow without a preretention tube, or upflow without a preretention tube.
  • the pulp supplied to the tower is subjected to a chlorine dioxide bleaching action while in the preretention tube 13 and in the retention zone 15 of the downflow tower 14 or in some other form of retention vessel.
  • water or other liquid is generally added thereto, as at 18, in order to reduce the consistency from approximately 8 to 14 percent to approximately 2 to 4 percent.
  • One of the purposes of the consistency change achieved in the dilution zone is to permit the use of a fan type pump 17 in lieu of a more expensive thick stock pump.
  • the low consistency (approximately 24 percent) pulp slurry is pumped to a washer 19, which is typically a drum type washer.
  • the filtrate from a down stream washer e.g. the D filtrate
  • sodium hydroxide is added to the pulp slurry as it exits from the washer 19.
  • Sodium hydroxide is added at this point to raise the pH of the pulp slurry being discharged from the washer 19 to a pH in the range of approximately 10 to 13 which is required for the following alkaline extraction treatment.
  • the pulp slurry at a consistency of 8 to 14 percent and a pH of 10 to l3 is pumped to the extraction tower 22.
  • washer filtrate is again added to the pulp slurry as at 23 in order to once again reduce the consistency.
  • the pulp slurry exits from the caustic extraction tower and is pumped by pump 24 to washer 25.
  • the pulp is then supplied to thick stock pump 27.
  • the pulp is subjected to a second chlorine dioxide treatment (the D stage), as indicated.
  • an alkaline extraction treatment or a hypochlorite treatment is conducted in the downstream portion of a chlorine dioxide bleaching apparatus. In this manner, a separate alkaline extraction unit or hypochlorite stage unit and a washer are not required. Additionally, the cost and operating expense of a washer and an alkaline extraction tower or a hypochlorite tower is avoided.
  • FIG. 1 is a schematic representation of a DED. prior art bleaching process.
  • FIG. 2 is a schematic representation of the process disclosed herein.
  • FIG. 3 shows an apparatus arrangement for practicing the process of the instant invention.
  • FIG. 2 there is shown therein a schematic representation of different embodiments of our invention.
  • a number of process units shown therein are identical to corresponding units shown in FIG. 1.
  • the thick stock pumps 11 and 27, the chlorine dioxide pulp mixers and the two chlorine dioxide towers 20 and 40 are the same as shown in FIG. 1.
  • sodium hydroxide is added to the pulp slurry at the beginning of the dilution zone 16.
  • sufficient alkaline material for example sodium hydroxide
  • sodium hydroxide is added to raise the pH of the pulp slurry to a pH of at least about 10.
  • the pH is raised to approximately to 13, and preferably within the range of, approximately, 10 to 12.
  • alkaline material for example sodium hydroxide
  • a conventional chlorine dioxide tower i.e. at the beginning of the retention zone, as indicated by the dotted line representation 30.
  • alkaline material is added in an amount sufficient to raise the pH of the pulp slurry to a pH in the range of, approximately, 10-13 and preferably, ap-
  • a pulp mixer not shown in the drawings, should be included at the top of the tower.
  • the need for a subsequent alkaline extraction tower and an intermediate washer is obviated while nevertheless obtaining an overall bleaching action which is equivalent to the prior art practice.
  • the chlorine dioxide bleaching apparatus is otherwise operated in accordance with prior art procedures, e.g. a dilution stream is added at the beginning of the dilution zone to reduce the consistency of the pulp slurry to approximately 2-4 percent.
  • the consistency of the pulp slurry in the preretention tube 13 and the retention zone 15 of the downflow tower 14 may be maintained in the range of, approximately, 8 to 14 percent.
  • an alkaline material such as sodium hydroxide
  • Sufficient alkaline material is added to raise the pH of the pulp slurry to a pH in the range of, approximately, 10 to 13 and, preferably, approximately lO-l2.
  • sodium hypochlorite is also added to the wood pulp slurry at the top of the dilution zone 16.
  • hypochlorite treatment occurs in the dilution zone 16 of the downflow tower 14 to achieve a DH" bleaching sequence and thus obviate the need for a subsequent hypochlorite tower.
  • the precise amount of sodium hypochlorite which must be added to a wood pulp slurry in order to achieve hypochlorite bleaching action cannot be predicted since the required amount depends upon such diverse factors as the initial brightness of the pulp, the previous bleaching treatments to which the pulp has been subjected, the temperature of the pulp slurry in the hypochlorite stage and the desired final brightness.
  • the amount of sodium hypochlorite added is generally empirically determined. Typically, however, the amount of sodium hypochlorite added is in the range of 0.1 to 0.6 percent and preferably 0.2 to 0.4 percent as available chlorine based on oven dry pulp.
  • the need for raising the pH of the pulp slurry when conducting a hypochlorite treatment as described above arises from the fact that the temperature of the pulp slurry in the downflow portion 14 of a conventional chlorine dioxide bleaching apparatus is generally approximately to F and, at these temperatures, a high pH is necessary in order to avoid fiber degradation during a hypochlorite treatment.
  • a hypochlorite treatment cannot be commenced at the top of the downflow portion 14 unless temperature is significantly reduced because, in such event, an extended residence time would be encountered and the combination of the high temperature and the hypochlorite treatment would result in prohibitive attack upon the cellulose fibers.
  • the relatively short residence time of the pulp in the dilution zone for example approximately ten minutes, apparently permits a rapid hypochlorite bleaching to occur without a corresponding attack upon the cellulose fibers.
  • Chlorine dioxide 1.03 1.03 0.73 NaOH (includes amount combined with hypo) 1.56 1.32 1.49 NaOCl as available chlorine 0.00 0.00 0.25
  • the initial brightness for the D/E and D/H treatments corresponds favorably to the initial brightness obtained from the conventional DED treatment.
  • the reverted brightness for the D/E and D/H treatments compared favorably with the reverted brightness of the pulp from the conventional DED treatment.
  • the pulp treated in the D/E process had a higher reverted brightness than the pulp treated in the conventional DED process.
  • the Post Color Number indicated in Table l is an index of brightness stability wherein a lower Post Color Number indicates increased color stability.
  • Table l reflects still another fact of considerable interest, viz. the reduced chemical use associated with either the D/ED sequence or the D/l-ID sequence compared to the DED sequence.
  • the bleaching sequences in accordance with our invention should provide a reduced chemical operating cost.
  • the chlorine dioxide bleaching towers shown in FIGS. 1 and 2 are commonly used in the industry and include a preretention tube which may be of the upflow type. Although the use of a preretention tube is often desirable, the prior art has recognized that pulp may be subjected to a chlorine dioxide bleaching treatment in a tower which does not include a preretention tube and which may be either an upflow tower or a downflow tower.
  • An upflow chlorine dioxide bleaching tower which does not include a preretention tube is shown in FIG. 3.
  • a chlorine dioxide bleaching tower without a preretention tube may also be used to practice our invention.
  • the tower 49 includes an upstream portion 50 and a downstream portion 52.
  • the tower 49 of FIG. 3 is shown as an upflow tower wherein a pulp slurry passes through a thick stock pump 11, is mixed with chlorine dioxide, passed through a mixer 12 and enters the tower 49 at the bottom. After entering the tower 49, the pulp-chlorine dioxide mixture passes up through the upstream portion or retention zone 50. Thereafter, the mixture passes through the downstream portion or dilution zone 52.
  • either an alkaline extraction or a hypochlorite treatment may be effected in the downstream portion 52 of the tower 49.
  • sufficient aklaline material e.g.
  • sodium hydroxide is added to the pulp entering the dilution zone to raise the pH of the pulp slurry to a pH in the range of approximately, 10 to 13 and preferably 10 to 12. If it is desired to perform a hypochlorite treatment, the pH of the pulp slurry is raised to a pH in the range of approximately lO to 13 or preferably ID to 12 and a sufficient amount of sodium hypochlorite is also added. In either event, a diluent, such as the filtrate from a washer, is also added in an amount sufficient to lower the consistency of the pulp slurry to, approximately, 2 to 4 percent. After passing through the downstream potion 52, wherein the residence portion may be approximately 10 minutes, the treated pulp exits from the tower 49 and may be supplied to other units for further processng.
  • a pulp bleaching process which includes the steps of mixing a pulp slurry with chlorine dioxide in a conventional chlorine dioxide treatment, passing the pulp slurry-chlorine dioxide mixture through a bleaching tower having a preretention tube and downflow tower portion which includes a dilution zone and, without draining the pulp, subjecting the pulp slurry to an alkaline extraction treatment, the improvement which comprises conducting said alkaline extraction step in the downflow portion of said bleaching tower after substantially all of said chlorine dioxide has been consumed.
  • a pulp bleaching process which includes the steps of mixing a pulp slurry with chlorine dioxide in a conventional dioxide treatment, passing the pulp slurry-chlorine dioxide mixture through a bleaching tower having a preretention tube and a downflow tower portion which includes a dilution zone and, without draining the pulp, subjecting the pulp slurry to a hypochlorite treatment, the improvement which comprises conducting said hypochlorite treatment in the dilution zone of said bleaching tower after substantially all of said chlorine dioxide has been consumed.

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  • Engineering & Computer Science (AREA)
  • Wood Science & Technology (AREA)
  • Paper (AREA)
US398165A 1973-09-17 1973-09-17 Single vessel wood pulp bleaching with chlorine dioxide followed by sodium hypochlorite or alkaline extraction Expired - Lifetime US3884752A (en)

Priority Applications (12)

Application Number Priority Date Filing Date Title
US398165A US3884752A (en) 1973-09-17 1973-09-17 Single vessel wood pulp bleaching with chlorine dioxide followed by sodium hypochlorite or alkaline extraction
NO740054A NO740054L (it) 1973-09-17 1974-01-08
SE7400192A SE408069B (sv) 1973-09-17 1974-01-08 Sett vid blekning av massa med klordioxid
JP49010043A JPS5058302A (it) 1973-09-17 1974-01-22
FR7402954A FR2245817B1 (it) 1973-09-17 1974-01-29
IT67249/74A IT1004819B (it) 1973-09-17 1974-01-30 Procedimento perfezionato per la sbianca della pastalegno
BE140434A BE810468A (fr) 1973-09-17 1974-01-31 Procede ameliore de blanchiment de la pate a papier
DE19742407542 DE2407542A1 (de) 1973-09-17 1974-02-16 Verfahren zum bleichen von pulpe
LU69421A LU69421A1 (it) 1973-09-17 1974-02-19
FI1051/74A FI105174A (it) 1973-09-17 1974-04-05
CA204,529A CA1019906A (en) 1973-09-17 1974-07-10 Pulp bleaching process
BR7461/74A BR7407461D0 (pt) 1973-09-17 1974-09-09 Processo aperfeicoado para branqueamento de polpa

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US398165A US3884752A (en) 1973-09-17 1973-09-17 Single vessel wood pulp bleaching with chlorine dioxide followed by sodium hypochlorite or alkaline extraction

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JP (1) JPS5058302A (it)
BE (1) BE810468A (it)
BR (1) BR7407461D0 (it)
CA (1) CA1019906A (it)
DE (1) DE2407542A1 (it)
FI (1) FI105174A (it)
FR (1) FR2245817B1 (it)
IT (1) IT1004819B (it)
LU (1) LU69421A1 (it)
NO (1) NO740054L (it)
SE (1) SE408069B (it)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4274912A (en) * 1978-08-01 1981-06-23 Groupement Europeen De La Cellulose Process for bleaching preoxidized paper pulp
US4543155A (en) * 1983-01-31 1985-09-24 The Boc Group, Inc. Method for bleaching wood pulp including dissolving oxygen into the dilution water of an extraction stage
US4944842A (en) * 1987-03-26 1990-07-31 Kamyr, Inc. Method for reducing contamination in pulp processing
US5268075A (en) * 1989-10-19 1993-12-07 North Carolina State University High efficiency two-step, high-low pH chlorine dioxide pulp bleaching process
WO2007113381A1 (en) * 2006-03-31 2007-10-11 Oy Lännen Tutkimus - Western Research Inc Bleaching process of chemical pulp
WO2018134525A1 (fr) * 2017-01-23 2018-07-26 Centre Technique De L'industrie Des Papiers, Cartons Et Celluloses Procede de blanchiment d'une pate a papier

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS60244287A (ja) * 1984-05-21 1985-12-04 Res Assoc Petroleum Alternat Dev<Rapad> セルラ−ゼ生産用基質の製造法
JPS62106999U (it) * 1985-12-21 1987-07-08
JPH076147B2 (ja) * 1988-12-16 1995-01-30 新王子製紙株式会社 リグノセルロース物質の漂白方法

Citations (13)

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Publication number Priority date Publication date Assignee Title
US2001268A (en) * 1932-09-21 1935-05-14 Hooker Electrochemical Co Pulp treating process
US2031485A (en) * 1931-05-20 1936-02-18 Paper Patents Co Method of bleaching pulp
US2477631A (en) * 1945-02-21 1949-08-02 Ecusta Paper Corp Catalytic bleaching with chlorites
US2558054A (en) * 1949-03-16 1951-06-26 Celanese Corp Purification of cellulosic materials
US2587064A (en) * 1949-03-09 1952-02-26 Int Paper Canada Method of bleaching wood pulp
US3120424A (en) * 1956-09-19 1964-02-04 Fmc Corp Continuous bleaching method with an alkali metal chlorite containing an activator salt
US3294624A (en) * 1962-01-24 1966-12-27 Ass Pulp & Paper Mills Bleaching treated wood chips
US3313678A (en) * 1962-02-14 1967-04-11 Svenska Cellulose Aktiebolaget Bleaching of cellulose pulp in towers in completely filled and closed system
US3433702A (en) * 1965-06-28 1969-03-18 Hooker Chemical Corp Woodpulp bleaching process
US3501374A (en) * 1968-12-26 1970-03-17 Hooker Chemical Corp Sequential bleaching of kraft pulp with chlorine dioxide and chlorine
US3595743A (en) * 1969-02-28 1971-07-27 Anglo Paper Prod Ltd Five stage woodpulp bleaching process
US3622444A (en) * 1969-04-14 1971-11-23 Canadian Ind Pulp bleaching process
US3630828A (en) * 1968-05-13 1971-12-28 Pulp Paper Res Inst Bleaching of a low-density, substantially uncompacted, porous fluffed cellulosic pulp

Patent Citations (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2031485A (en) * 1931-05-20 1936-02-18 Paper Patents Co Method of bleaching pulp
US2001268A (en) * 1932-09-21 1935-05-14 Hooker Electrochemical Co Pulp treating process
US2477631A (en) * 1945-02-21 1949-08-02 Ecusta Paper Corp Catalytic bleaching with chlorites
US2587064A (en) * 1949-03-09 1952-02-26 Int Paper Canada Method of bleaching wood pulp
US2558054A (en) * 1949-03-16 1951-06-26 Celanese Corp Purification of cellulosic materials
US3120424A (en) * 1956-09-19 1964-02-04 Fmc Corp Continuous bleaching method with an alkali metal chlorite containing an activator salt
US3294624A (en) * 1962-01-24 1966-12-27 Ass Pulp & Paper Mills Bleaching treated wood chips
US3313678A (en) * 1962-02-14 1967-04-11 Svenska Cellulose Aktiebolaget Bleaching of cellulose pulp in towers in completely filled and closed system
US3433702A (en) * 1965-06-28 1969-03-18 Hooker Chemical Corp Woodpulp bleaching process
US3630828A (en) * 1968-05-13 1971-12-28 Pulp Paper Res Inst Bleaching of a low-density, substantially uncompacted, porous fluffed cellulosic pulp
US3501374A (en) * 1968-12-26 1970-03-17 Hooker Chemical Corp Sequential bleaching of kraft pulp with chlorine dioxide and chlorine
US3595743A (en) * 1969-02-28 1971-07-27 Anglo Paper Prod Ltd Five stage woodpulp bleaching process
US3622444A (en) * 1969-04-14 1971-11-23 Canadian Ind Pulp bleaching process

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4274912A (en) * 1978-08-01 1981-06-23 Groupement Europeen De La Cellulose Process for bleaching preoxidized paper pulp
US4543155A (en) * 1983-01-31 1985-09-24 The Boc Group, Inc. Method for bleaching wood pulp including dissolving oxygen into the dilution water of an extraction stage
US4944842A (en) * 1987-03-26 1990-07-31 Kamyr, Inc. Method for reducing contamination in pulp processing
US5268075A (en) * 1989-10-19 1993-12-07 North Carolina State University High efficiency two-step, high-low pH chlorine dioxide pulp bleaching process
WO2007113381A1 (en) * 2006-03-31 2007-10-11 Oy Lännen Tutkimus - Western Research Inc Bleaching process of chemical pulp
US20090242152A1 (en) * 2006-03-31 2009-10-01 Oy Lannen Tutkimus - Western Research Inc Bleaching process of chemical pulp
CN101460676B (zh) * 2006-03-31 2013-04-10 奥伊兰南塔特基莫斯-维斯特恩研究股份有限公司 化学纸浆的漂白方法
US8524038B2 (en) 2006-03-31 2013-09-03 Oy Lannen Tutkimus—Western Research Inc. Bleaching process of chemical pulp
WO2018134525A1 (fr) * 2017-01-23 2018-07-26 Centre Technique De L'industrie Des Papiers, Cartons Et Celluloses Procede de blanchiment d'une pate a papier
FR3062138A1 (fr) * 2017-01-23 2018-07-27 Centre Technique De L'industrie Des Papiers, Cartons Et Celluloses Procede de blanchiment d'une pate a papier
CN110177909A (zh) * 2017-01-23 2019-08-27 纸、纸板和纤维素工业技术中心 用于漂白纸浆的方法
RU2747664C2 (ru) * 2017-01-23 2021-05-11 Сантр Текник Де Л'Индустри Де Папье, Картон И Селлюлоз Способ отбеливания бумажной массы
US11384480B2 (en) 2017-01-23 2022-07-12 Centre Technique De L'industrie Des Papiers, Cartons Et Celluloses Method for bleaching paper pulp

Also Published As

Publication number Publication date
NO740054L (it) 1975-04-14
BR7407461D0 (pt) 1975-07-22
JPS5058302A (it) 1975-05-21
CA1019906A (en) 1977-11-01
FR2245817B1 (it) 1978-03-17
FR2245817A1 (it) 1975-04-25
DE2407542A1 (de) 1975-04-24
IT1004819B (it) 1976-07-20
SE408069B (sv) 1979-05-14
BE810468A (fr) 1974-07-31
SE7400192L (it) 1975-03-18
LU69421A1 (it) 1975-05-21
FI105174A (it) 1975-03-18

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