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WO1988001661A1 - Procede de blanchiment de pulpes - Google Patents

Procede de blanchiment de pulpes Download PDF

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Publication number
WO1988001661A1
WO1988001661A1 PCT/US1987/002130 US8702130W WO8801661A1 WO 1988001661 A1 WO1988001661 A1 WO 1988001661A1 US 8702130 W US8702130 W US 8702130W WO 8801661 A1 WO8801661 A1 WO 8801661A1
Authority
WO
WIPO (PCT)
Prior art keywords
pulp
chlorine
range
bleaching
chlorine dioxide
Prior art date
Application number
PCT/US1987/002130
Other languages
English (en)
Inventor
John K. Rogers
Ronald K. Baysden
Original Assignee
James River-Norwalk, Inc.
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 James River-Norwalk, Inc. filed Critical James River-Norwalk, Inc.
Priority to FI881930A priority Critical patent/FI881930L/fi
Publication of WO1988001661A1 publication Critical patent/WO1988001661A1/fr
Priority to NO881599A priority patent/NO881599D0/no

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
    • 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

Definitions

  • This invention relates to a multistage process for bleaching alkaline digested cooked pulps. such as wood pulps prepared by the kraft. alkaline sulphite and soda precesses.
  • the process ot this invention comprises a sequence of delighification and bleaching stages in which the initial stage involves treatment with chlorine (C) or chlorine and chlorine dioxide (C D ) and in which the final stage comprises a chlorine diixide
  • C D bleaching stage is followed sequentially by a combined alkali extraction/oxygen bleaching step (E O ) and a hot hypochlorite extraction step (H*/E), followed by chlorine dioxide (D) bleaching.
  • E O alkali extraction/oxygen bleaching step
  • H*/E hot hypochlorite extraction step
  • chlorine dioxide bleaching is combined with the hot hypochlorite treatment (H*/ED).
  • a typical bleaching sequence in present practice involves the sequence of steps C D EHD wherein C D represents treatment of an aqueous slurry of wood pulp with a mixture of chlorine and chlorine dioxide, E represents an alkali extraction step (usually with sodium hydroxide) , H represents a hypochlorite treatment step, and D represents treatment with chlorine dioxide.
  • the conversion of wood chips into wood pulp sui table for the manufacture of paper products generally consists of a series of chemical treatments necessary for the separation of relatively pure cellulose fibers from the various non-cellulosic components of the wood, most notably lignins.
  • lignins In the manufacture of high grade paper products, particularly highly absorbent tissue and the like, it i s necessary to separate the lignin ini ti ally combined with wood fibers f rom the cellulose fibers with minimal degradation of the cellulose fibers.
  • raw wood either softwood or hardwood, is first reduced to chips, loaded into a pressure vessel and digested or cooked in an aqueous chemical solution under conditions of elevated temperature and pressure dissolving at least a part of the lignin and liberating the wood fibers.
  • the cellulose fibers are dark in color due to the presence of lignin which has not been removed completely from the fibers by the digestion process.
  • the pulp resulting from digestion is referred to as unbleached pulp.
  • unbleached pulp may be used directly in the manufacture of kraft paper useful in the production of paper bags, corrugated board, and the like.
  • the first step in a multistage bleaching process is usually a chlorination step in which pulp from a kraft digestion process, after water washing, is contacted with chlorine at a temperature in the range of about 20 to 60C for a period of time within the range of about 10 to 60 minutes at a pulp consistency ranging from 3 to 10 weight percent.
  • the initial chlorination step by chlorinating, oxidizing or otherwise solubilizing the lignins, aids in the subsequent removal of lignin from the pul p from the chlorination system and in a subsequent alkaline extraction step.
  • the chlorination step may comprise treatment with a mixture of chlorine and chlorine dioxide and is usually followed by caustic extraction with a sodium hydroxide solution at a pulp consistency in the range of 8 to 14 weight percent for one hour or longer at a temperature in the range of 50 to 70C.
  • a hypochlorite treatment step in which the pulp is treated with sodium hypochlorite at about the same pulp consistency and a temperature in the range of 35 to 40C commonly follows the caustic extraction step, and sometimes is combined with the caustic extraction step.
  • chlorine dioxide bleaching at 75 to 85C is commonly used with kraft pulps to bring the brightness to the range of about 85 to 90% GE.
  • Brightness of the pulp is a measure of the reflectance of light in the blue range (457 m ⁇ ) compared with magnesium oxide as a standard. Brightness standard scales vary in different countries depending upon the standard light meter employed in determining brightness. In the united States, the General Electric meter is standard and brightness is reported as percent GE. For very high quality tissue, a pulp brightness of 85% GE or higher is desirable.
  • the Kappa number is a standard measure of lignin content.
  • the Kappa number is determined by the amount of potassium permanganate consumed by a standard sample of pulp and represents a measurement of its retained lignin content. Higher Kappa numbers indicate the presence of greater amounts of lignin and vice versa.
  • the extent of delignification which occurs in a bleaching step may be evaluated by comparison of Kappa numbers of samples taken before and after the bleaching step. Kappa numbers are commonly used as a measure of the lignin content of the cooked pulp prior to bleaching and of preoxidized and chlorine treated pulps.
  • Brightness numbers are more generally used to determine the extent of removal of color bodies, including lignins and their degradation compounds, in the later stages of a bleaching sequence.
  • Chlorine dioxide bleaching is a highly desirable process step in that it results in a high brightness coupled with good color stability without significantly deteriorating pulp strength.
  • Chlorine dioxide is essentially non-degrading to cellulose and is capable of producing very bright pulp without degrading the cellulose or hemlcelluloses. Due to the highly corrosive and toxic nature of chlorine dioxide, it is generated at the pulp mill as a gas and then absorbed in water. The resulting solution is then brought in contact with the pulp.
  • the reaction is conducted at a temperature in the range of 60 to 80C for two to six hours at a pH of about 4 and a pulp consistency of about 8 to 14 percent.
  • a second caustic extraction followed by second chlorine dioxide stage is employed to bring kraft pulp brightness to the desired level.
  • a chlorine dioxide bleaching step may be used as the first step in the bleaching sequence, but more commonly, it is used in the first step in combination with chlorination and is usually followed by caustic extraction or a hypochlorite treatment.
  • Oxygen bleaching usually has been employed as a prebleach stage before chlorination, oxygen bleaching being compatible with spent liquors from the kraft recovery system.
  • oxygen bleaching being compatible with spent liquors from the kraft recovery system.
  • pulp consistencies 10 to 35 weight percent and 2 to 4 weight percent concentration sodium hydroxide (on pulp) at 85 to 125C for a period of 20 to 40 minutes
  • the lignin content of soft wood kraft pulp may be reduced from about 6 weight percent to about 3 weight percent.
  • Oxygen bleaching is usually carried out in the presence of a magnesium salt, e.g. magnesium carbonate, to prevent oxidative degradation of the pulp.
  • alkaline pulps such as kraft pulps
  • C D a mixture of chlorine and chlorine dioxide
  • H*/E hot hypochlorite/sodium hydroxide treatment
  • H*/ED hot hypochlorite/sodium hydroxide treatment
  • chlorine dioxide is employed in connection with hot hypochlorite/sodium hydroxide treatment (H*/ED) as the final step in the bleaching sequence C D E O (H*/ED).
  • the extraction step and hypochlorite bleaching steps common in existing bleaching sequences are modified to achieve chemical and energy savings as well as savings in capital expenditures through the use of lower dosages of reagents and shorter treating time sequences while maintaining pulp strength.
  • improved pulp brightness may be obtained as well.
  • Fig. 1 is a flow diagram illustrating one embodiment of the present invention.
  • Fig. 2 is a flow diagram illustrating another embodiment of this invention.
  • unbleached kraft pulp at a consistency of about 3 weight percent wood fibers on an air dried basis is supplied from make-up tank 4 to chlorine-chlorine dioxide bleaching tower 5 by pump 6.
  • Chlorine and chlorine dioxide are introduced into the bleaching tower 5 from line 7.
  • Bleaching conditions in tower 5 are preferably 15 to 30 minutes residence time at a temperature in the range of
  • pulp stream from tower 5 is passed through line 9 to washer 10.
  • pulp from washer 10 is passed through line 11 to chemical/steam mixer 12 where it is heated and mixed with an aqueous solution of sodium hydroxide from line 13.
  • sodium hydroxide is the preferred alkaline agent and in this stage is employed in an amount within the range of 2 to 5 weight percent basis the air dried (a.d.) weight of the pulp, at a pulp consistency of about 12 weight percent.
  • the alkaline pulp slurry from chemical/steam mixer 12 is passed through line 14 to a high shear mixing device 16.
  • Oxygen in an amount equivalent to about 0.5 weight percent basis air dried pulp is supplied to the mixing device 16 from line 18 and thoroughly dispersed in the alkaline slurry.
  • the resulting oxygenated alkaline pulp slurry is passed through transfer line reactor 19 to tower 20 where further delignification of the pulp takes place.
  • Preferred conditions in the E O stage are a minimum of 3 minutes at 20 psig or greater in transfer line reactor 19, followed by 60 to 120 minutes of retention time at 50 to 65C in the extraction tower 20.
  • Pulp slurry is withdrawn from the bottom of the alkaline extraction tower 20 and passed by pump 21 through line 22 to washer 23.
  • Washed pulp from washer 23 is passed through line 24, mixed with aqueous sodium hydroxide and sodium hypochlorite from line 26, heated by means not illustrated and passed by pump 27 through reaction tube 28 where further amounts of lignin are removed from the cellulose by a hot caustic hypochlorite extraction.
  • Preferred reaction conditions in the H*/E stage reaction tube 28 are in the ranges of 70 to 75C (160 to 17 OF) for a period of about 10 minutes with from about 0.7 to about 1.1 weight percent sodium hypochlorite and 0.4 to 0.6 weight percent sodium hydroxide basis air dried pulp.
  • the delignified pulp is passed through line 29 to washer 30.
  • Washed delignified pulp from washer 30 is passed through line 31, mixed with chlorine dioxide from line 32, and passed to tower 40 where the final chlorine dioxide (D) bleach takes place.
  • Preferred operating conditions in bleach tower 40 include a pulp consistency of about 12 weight percent, a holding time of 120 to 180 minutes at about 70C, and a dosage of chlorine dioxide in the range of 0.35 to 0.9 weight percent basis the air dried weight of the pulp, optionally including up to about 0.2 weight percent sodium hydroxide.
  • the bl eached pulp sl urry from the chlor ine dioxide (D ) bleach stage is withdrawn from the top of tower 40 and passed by pump 41 through l ine 42 to washer 43 .
  • Bleached pulp is discharged from washer 43 through l ine 44 to pump 45 and passed through l ine 46 to storage , not illustrated.
  • Hot hypochlorite mixture from line 51, and the mixture pumped directly into the bottom of tower 52 where the hot hypochlorite/chlorine dioxide bleaching (H*/ED) operation takes place.
  • Preferred operating conditions in tower 52 include a temperature of about 70C and a holding time of 120 to 180 minutes with from 0.5 to 0.9 weight percent sodium hypochlorite, 0.2 to0.4 weight percent sodium hydroxide, and about 0.4 weight percent chlorine dioxide basis on the air dried weight of the pulp in the charge to the tower.
  • Bleached pulp is discharged from the top of tower 52 through line 53, washed in washer 54, and discharged by pump 55 through line 56 to storage, not illustrated.
  • Sequence A Samples of softwood pulp, having Kappa number of 29.9, and a 0.5% CED viscosity of 26.9 mPa.s were bleached in a conventional sequence (Sequence A) in Example 1, and by sequences of this invention. Sequence B in Example 2 and Sequence C in Example 3. The treatment steps and process conditions for these examples are shown in Table I. In the examples. Sequence C differs from
  • Sequence B in omitting washing between stages H*/E and D, effectively combining these stages into a single H*/ED stage.
  • the unbleached pulp had a Kappa number of 29.9 and a viscosity of 26.9 mPa.s. Results of the tests are summarized in Table II.
  • Samples of hardwood pulp having a Kappa number of 14.8 were bleached in a conventional mill sequence (Sequence A) and by methods of this invention (Sequences B and
  • Sequence C differs from Sequence B in omitting the wash step between stages H*/E and D. Treatment steps and process conditions for these examples are shown in Table III with results of the tests reported in Table IV, Examples 4 to 7.
  • Sequence B of Example 5 produces pulp of significantly improved brightness as compared with Sequence A of Example 4 with a savings in both sodium hypochlorite requirements and in time of treatment.
  • Example 6 demonstrates that, for equivalent pulp brightness, less chlorine dioxide is required also even when the wash step between H*/E and D is omitted.
  • Example 7 demonstrates that Sequence C is capable of producing a pulp brightness comparable to that of Sequence B (Example 5) with a small increase in the sodium hypochlorite requirement in the H*/E stage while still saving approximately half that required in Sequence A (Example 4).

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

Abstract

Un procédé à étapes multiples de blanchiment de pulpes comprend au moins trois étapes de blanchiment comprenant l'extraction à l'oxygène (20) dans un milieu alcalin (EO) d'une étape de blanchiment (5) au chlore (C) ou une étape de blanchiment (5) au chlore/dioxyde de chlore (CD) suivie par un traitement avec un hypochlorite alcalin chaud (H*/E) (28) ou suivie d'un traitement au dioxyde de chlore (D) avec traitement simultané au dioxyde de chlore (H*/ED) dans la séquence (EO H*/ED) ou (EO(H*/ED). Ces nouvelles séquences de blanchiment se traduisent par des économies significatives en temps et en coûts de fonctionnement par rapport aux séquences de blanchiment conventionnelles et permettent d'obtenir des produits de brillance comparable.
PCT/US1987/002130 1986-08-28 1987-08-25 Procede de blanchiment de pulpes WO1988001661A1 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
FI881930A FI881930L (fi) 1986-08-28 1987-08-25 Massablekningsfoerfarande.
NO881599A NO881599D0 (no) 1986-08-28 1988-04-13 Fremgangsmaate for bleking av tremasse.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US90099286A 1986-08-28 1986-08-28
US900,992 1986-08-28

Publications (1)

Publication Number Publication Date
WO1988001661A1 true WO1988001661A1 (fr) 1988-03-10

Family

ID=25413427

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US1987/002130 WO1988001661A1 (fr) 1986-08-28 1987-08-25 Procede de blanchiment de pulpes

Country Status (3)

Country Link
EP (1) EP0279845A4 (fr)
FI (1) FI881930L (fr)
WO (1) WO1988001661A1 (fr)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1991000386A1 (fr) * 1989-06-30 1991-01-10 Nekoosa Papers, Inc. Procede de blanchiment de pate a papier kraft avec un melange d'oxygene et de peroxyde
WO2008076268A3 (fr) * 2006-12-18 2008-09-18 Int Paper Co Procédé de blanchiment en une étape (d) de pâte de feuillus en présence de mg(oh)2
US7976676B2 (en) 2006-12-18 2011-07-12 International Paper Company Process of bleaching softwood pulps in a D1 or D2 stage in a presence of a weak base
US9057156B2 (en) 2010-12-22 2015-06-16 Skzo Nobel Chemicals International B.V. Process for improving chlorine dioxide bleaching of pulp

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103266519A (zh) * 2013-05-14 2013-08-28 昆明理工大学 一种漂白草浆的制备方法

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SU874813A1 (ru) * 1980-01-31 1981-10-23 Всесоюзное научно-производственное объединение целлюлозно-бумажной промышленности Способ отбелки целлюлозы дл химической переработки
US4451332A (en) * 1979-05-11 1984-05-29 Sca Development Aktiebolag Method for delignification of ligno-cellulose containing fiber material with an alkali-oxygen extraction stage
US4568420A (en) * 1984-12-03 1986-02-04 International Paper Company Multi-stage bleaching process including an enhanced oxidative extraction stage

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4238281A (en) * 1979-04-30 1980-12-09 Canadian International Paper Company Simplified bleaching process

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4451332A (en) * 1979-05-11 1984-05-29 Sca Development Aktiebolag Method for delignification of ligno-cellulose containing fiber material with an alkali-oxygen extraction stage
SU874813A1 (ru) * 1980-01-31 1981-10-23 Всесоюзное научно-производственное объединение целлюлозно-бумажной промышленности Способ отбелки целлюлозы дл химической переработки
US4568420A (en) * 1984-12-03 1986-02-04 International Paper Company Multi-stage bleaching process including an enhanced oxidative extraction stage
US4568420B1 (en) * 1984-12-03 1999-03-02 Int Paper Co Multi-stage bleaching process including an enhanced oxidative extraction stage

Non-Patent Citations (3)

* Cited by examiner, † Cited by third party
Title
Pulp & Paper Canada, Volume 81, No. 11 issued November 1980, HISTED, "Bleachery Simplification in CIP", (See paragragh bridging pages T299-T300. *
Pulp & Paper Canada, Volume 87, No. 8, issued August 1986, LIEBERGOTT et al, "Oxidative Bleaching -A Review Part I -Delignification", see page T303 column 1. *
See also references of EP0279845A4 *

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1991000386A1 (fr) * 1989-06-30 1991-01-10 Nekoosa Papers, Inc. Procede de blanchiment de pate a papier kraft avec un melange d'oxygene et de peroxyde
WO2008076268A3 (fr) * 2006-12-18 2008-09-18 Int Paper Co Procédé de blanchiment en une étape (d) de pâte de feuillus en présence de mg(oh)2
US7976677B2 (en) 2006-12-18 2011-07-12 International Paper Company Process of bleaching hardwood pulps in a D1 or D2 stage in a presence of a weak base
US7976676B2 (en) 2006-12-18 2011-07-12 International Paper Company Process of bleaching softwood pulps in a D1 or D2 stage in a presence of a weak base
US9057156B2 (en) 2010-12-22 2015-06-16 Skzo Nobel Chemicals International B.V. Process for improving chlorine dioxide bleaching of pulp

Also Published As

Publication number Publication date
FI881930A7 (fi) 1988-04-25
FI881930A0 (fi) 1988-04-25
EP0279845A4 (en) 1991-01-09
EP0279845A1 (fr) 1988-08-31
FI881930L (fi) 1988-04-25

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