EP0408803A1 - Procedure for the bleaching of sulphate pulp - Google Patents

Procedure for the bleaching of sulphate pulp Download PDF

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Publication number
EP0408803A1
EP0408803A1 EP89117234A EP89117234A EP0408803A1 EP 0408803 A1 EP0408803 A1 EP 0408803A1 EP 89117234 A EP89117234 A EP 89117234A EP 89117234 A EP89117234 A EP 89117234A EP 0408803 A1 EP0408803 A1 EP 0408803A1
Authority
EP
European Patent Office
Prior art keywords
pulp
bleaching
procedure
chlorine
oxidation
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
EP89117234A
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German (de)
French (fr)
Other versions
EP0408803B1 (en
Inventor
Marja Vaheri
Kari Miikki
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Stora Enso Oyj
Original Assignee
Enso Gutzeit Oy
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Application filed by Enso Gutzeit Oy filed Critical Enso Gutzeit Oy
Priority to AT89117234T priority Critical patent/ATE100157T1/en
Publication of EP0408803A1 publication Critical patent/EP0408803A1/en
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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
    • D21C9/1057—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
    • D21C5/00—Other processes for obtaining cellulose, e.g. cooking cotton linters ; Processes characterised by the choice of cellulose-containing starting materials
    • D21C5/005—Treatment of cellulose-containing material with microorganisms or enzymes

Definitions

  • the present invention relates to a procedure for the bleaching of pulp, in which procedure an oxidating bleaching chemical containing chlorine is used.
  • Especially pulp obtained from a sulphate pulping process is of brown colour, which is mainly due to the lignin remaining in the pulp.
  • Lignin is removed from the pulp by bleaching, which is generally a process consisting of several stages. During this process, the pulp is treated alternately with oxidizing, lignin-degrading chemicals and chemicals dissolv­ing the degradation products. Oxidizing agents commonly used are chlorine-containing chemicals and oxygen, whereas alkali solutions are used for eliminating the degradation products.
  • the spent bleach liquors causing the worst environmental pollution load are produced in the washing stages following the first chlorination and the first alkali treatment in the bleaching process.
  • various methods have been employed, including the use of chlorine dioxide instead of chlorine gas, the use of oxygen as an oxidating chemical in the first bleaching stage, and bio­logical purification of the spent bleach liquor.
  • these methods have not yielded completely satisfactory re­sults.
  • the amounts of chlorophenols and other toxic chlorine compounds in the spent bleach liquor have been significantly reduced by using chlorine dioxide and employ­ ing oxygen bleaching, it has not been possible to achieve a sufficient reduction in the chemical oxygen demand values of the effluents. Therefore, the methods referred to have re­quired the employment of efficient biological purification.
  • the object of the present invention is to achieve a pulp bleaching procedure that enables the toxic content and chemical oxygen demand of the spent bleach liquor to be reduced so as to reduce the need for purification of the liquor.
  • the invention is characterized in that, in conjunc­tion with or before oxidation, the pulp is subjected to an enzyme treatment using an oxidation-reduction enzyme modi­fying lignin.
  • a treatment with a suitable redox enzyme reduces the amount of chlorine chemicals required for bleaching, thereby also reducing the amounts of organic chlorine compounds left in the spent bleach liquor.
  • the redox potential of the enzymatic reaction should be below 400 mV, preferably below 250 mV.
  • Suitable redox enzymes are e.g. phenoloxidases, such as the lactase produced by the white-rot fungus.
  • the bleaching of pulp by the procedure of the invention can be performed in the con­ventional manner by employing alternate oxidation and alkali stages and washing the pulp after each of these stages to remove the bleaching chemicals and degradation products.
  • the enzyme treatment as taught by the invention is preferivelyably carried out in a temperature range of 10-90 °C, the most suitable range being 40-80 °C, with pH values in the range 3.0-10.0, preferably 4.0-8.0.
  • the enzyme used is a lignin-modifying oxidation-reduction enzyme, e.g. a lactase as mentioned above.
  • the invention also concerns the use of a lignin-modifying enzyme, e.g. the lactase produced by the white-rot fungus, in the bleaching of pulp using an oxidating bleaching chemical containing chlorine.
  • a lignin-modifying enzyme e.g. the lactase produced by the white-rot fungus
  • a diluted enzyme mixture of lactase produced by the Trametes hirsuta white-rot fungus was added to 220 g of dry matter obtained from pine sulphate pulp (with a dry matter content of 30%) so that a mixture with a consistency of 10% and a lactase activity of 60 U/kg of pulp dry matter was obtained.
  • the temperature in the enzyme treatment was 55 °C and the duration of treatment 2 h. After the enzyme treatment the pulp was filtered in a Buchner funnel and the pulp cake obtained was washed with ion-exhange-treated water so that a wash ratio of 20 was obtained.
  • both the pulp quantity which had undergone enzyme treatment and the reference portion were bleached by a process consisting of five successive stages of oxidation and leaching.
  • the chemicals used were chlorine (90%) and chlorine dioxide (10%), in the second stage sodium hydroxide, in the third stage chlorine dioxide, in the fourth stage sodium hydroxide and in the fifth stage chlorine dioxide.

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  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Wood Science & Technology (AREA)
  • Chemical & Material Sciences (AREA)
  • Biochemistry (AREA)
  • Microbiology (AREA)
  • Paper (AREA)
  • Noodles (AREA)
  • Investigating Or Analysing Biological Materials (AREA)
  • Hard Magnetic Materials (AREA)
  • Agricultural Chemicals And Associated Chemicals (AREA)
  • Silver Salt Photography Or Processing Solution Therefor (AREA)
  • Cereal-Derived Products (AREA)
  • Table Devices Or Equipment (AREA)

Abstract

The invention concerns a procedure for the bleaching of pulp, in which procedure an oxidating bleaching chemical containing chlorine is used. The essential feature of the invention is that the pulp is treated, either in conjunction with or before oxidation, with a lignin-modifying oxidation-­reduction enzyme, such as the lactase produced by the white-­rot fungus. The oxidating bleaching chemical used in the procedure may be chlorine dioxide or a mixture of chlorine dioxide and chlorine gas. The use of said enzyme reduces the amount of chlorophenols and other forms of organically bound chlorine in the spent bleach liquor, simultaneously lowering its chemical oxygen demand.

Description

  • The present invention relates to a procedure for the bleaching of pulp, in which procedure an oxidating bleaching chemical containing chlorine is used.
  • Especially pulp obtained from a sulphate pulping process is of brown colour, which is mainly due to the lignin remaining in the pulp. Lignin is removed from the pulp by bleaching, which is generally a process consisting of several stages. During this process, the pulp is treated alternately with oxidizing, lignin-degrading chemicals and chemicals dissolv­ing the degradation products. Oxidizing agents commonly used are chlorine-containing chemicals and oxygen, whereas alkali solutions are used for eliminating the degradation products.
  • In the reactions occurring in bleaching using chlorine-con­taining chemicals, lignin is converted into organic chlorine compounds, which remain in the spent bleach liquor. Spent bleach liquors are a problem in regard of environmental protection because of the possible toxic nature of the organic chlorine compounds contained in the liquors. More­over, the chemical oxygen demand in spent bleach liquors reaches detrimental levels.
  • The spent bleach liquors causing the worst environmental pollution load are produced in the washing stages following the first chlorination and the first alkali treatment in the bleaching process. To reduce the pollution load, various methods have been employed, including the use of chlorine dioxide instead of chlorine gas, the use of oxygen as an oxidating chemical in the first bleaching stage, and bio­logical purification of the spent bleach liquor. However, these methods have not yielded completely satisfactory re­sults. Although the amounts of chlorophenols and other toxic chlorine compounds in the spent bleach liquor have been significantly reduced by using chlorine dioxide and employ­ ing oxygen bleaching, it has not been possible to achieve a sufficient reduction in the chemical oxygen demand values of the effluents. Therefore, the methods referred to have re­quired the employment of efficient biological purification.
  • The object of the present invention is to achieve a pulp bleaching procedure that enables the toxic content and chemical oxygen demand of the spent bleach liquor to be reduced so as to reduce the need for purification of the liquor. The invention is characterized in that, in conjunc­tion with or before oxidation, the pulp is subjected to an enzyme treatment using an oxidation-reduction enzyme modi­fying lignin.
  • It has been observed in earlier investigations that by using enzymes degrading hemicellulose it is possible to separate lignin and/or hemicellulose from cellulose and thus make the pulp more easily bleachable in the subsequent bleaching stages. This effect has not been observed before in conjunc­tion with the use of lignin-degrading enzymes.
  • According to the invention, it has now been observed that a treatment with a suitable redox enzyme reduces the amount of chlorine chemicals required for bleaching, thereby also reducing the amounts of organic chlorine compounds left in the spent bleach liquor.
  • According to the invention, the redox potential of the enzymatic reaction should be below 400 mV, preferably below 250 mV. Suitable redox enzymes are e.g. phenoloxidases, such as the lactase produced by the white-rot fungus.
  • Except for the enzyme treatment, the bleaching of pulp by the procedure of the invention can be performed in the con­ventional manner by employing alternate oxidation and alkali stages and washing the pulp after each of these stages to remove the bleaching chemicals and degradation products.
  • The enzyme treatment as taught by the invention is prefer­ably carried out in a temperature range of 10-90 °C, the most suitable range being 40-80 °C, with pH values in the range 3.0-10.0, preferably 4.0-8.0. The enzyme used is a lignin-modifying oxidation-reduction enzyme, e.g. a lactase as mentioned above.
  • The invention also concerns the use of a lignin-modifying enzyme, e.g. the lactase produced by the white-rot fungus, in the bleaching of pulp using an oxidating bleaching chemical containing chlorine.
  • In the following, the invention is described in greater detail by the aid of examples of embodiments based on laboratory experiments.
    • Example 1
  • A diluted enzyme mixture of lactase produced by the Trametes hirsuta white-rot fungus was added to 220 g of dry matter obtained from pine sulphate pulp (with a dry matter content of 30%) so that a mixture with a consistency of 10% and a lactase activity of 60 U/kg of pulp dry matter was obtained. The temperature in the enzyme treatment was 55 °C and the duration of treatment 2 h. After the enzyme treatment the pulp was filtered in a Buchner funnel and the pulp cake obtained was washed with ion-exhange-treated water so that a wash ratio of 20 was obtained.
  • For reference, a corresponding portion of pulp was treated in the same way except that no enzyme was added.
  • Next, both the pulp quantity which had undergone enzyme treatment and the reference portion were bleached by a process consisting of five successive stages of oxidation and leaching. In the first stage, the chemicals used were chlorine (90%) and chlorine dioxide (10%), in the second stage sodium hydroxide, in the third stage chlorine dioxide, in the fourth stage sodium hydroxide and in the fifth stage chlorine dioxide.
  • The consumption of bleaching chemicals and the analysis results representing the quality of the bleached pulp are presented in Table 1.
  • The experiment shows that by using a lignin-modifying enzyme, i.e. lactase, a substantial reduction in the amount of chlorine has been achieved. TABLE 1
    Enzyme treatment, pine sulphate pulp, kappa 27.4 Final pH Viscosity Kappa Yield%
    Reference portion 8.70 1020 26.4 100.84
    Enzyme-treated pulp 8.60 1045 26.5 100.63
    Experiment continues with bleaching sequence D/C-E-D-E-D
    Phase D/C 10/90 Reference Enzyme-treated pulp
    D/C 2* kappa
    D/C dosage % 5.28 5.30
    consumption % 5.28 5.30
    pH 1.65 1.55
    consistency 3.5 3.5
    temperature °C 55 55
    duration min. 45 45
    Phase E
    E 0.9*kappa
    E dosage % 2.38 2.39
    pH 11.65 11.3
    kappa 9.6 8.2
    yield % 96.13 96.81
    Phase D
    dosage % 3.0 3.0
    consumption % 3.0 3.0
    pH 1.9 1.8
    consistency % 10 10
    temperature °C 70 70
    duration min. 180 180
    Phase E2
    dosage % 1.0 1.0
    pH 11.2 11.3
    consistency % 10 10
    temperature °C 60 60
    duration min. 90 90
    Phase D2
    dosage % 1.0 1.5
    consumption % 1.5 1.42
    pH 2.2 2.2
    consistency % 10 10
    temperature °C 75 75
    duration min. 240 240
    acidation pH 4.2 3
    yield % 97.96 98.18
    total yield % 94.96 95.65
    degree of bleaching 83.8 87.1
    viscosity
    TCl mg/kg 345 265
    DKM extract %

Claims (9)

1. Procedure for the bleaching of pulp, said procedure using an oxidating bleaching chemical containing chlorine, characterized in that, in connection with or before oxidation, the pulp is subjected to an enzyme treat­ment in which a lignin-modifying oxidation-reduction enzyme is used.
2. Procedure according to claim 1, character­ized in that the redox potential of the enzymatic reaction is below 400 mV, preferably below 250 mV.
3. Procedure according to claim 1 or 2, character­ized in that the enzyme used is a lignin-modifying phenoloxidase, such as the lactase produced by the white-rot fungus.
4. Procedure according to any one of the preceding claims, characterized in that the pulp is treated with a phenoloxidase, e.g. lactase, and washed before the first oxidation phase.
5. Procedure according to any one of the preceding claims, characterized in that the bleaching chemical used in the oxidation phases is chlorine dioxide or a mixture of chlorine dioxide and chlorine gas, and that between the oxidation phases the pulp is treated with an alkali.
6. Procedure according to any one of the preceding claims, characterized in that the enzyme treatment is carried out in a temperature range of 10-90 °C, preferably 40-80 °C, with pH values in the range 3.0-10.0, preferably 4.0-8.0.
7. Procedure according to any one of the preceding claims, characterized in that the procedure is used for the bleaching of softwood pulp, e.g. pine sulphate pulp.
8. Use of a lignin-modifying oxidation-reduction enzyme in a pulp bleaching process using an oxidating bleaching chemical containing chlorine.
9. Use of a phenoloxidase, e.g. the lactase produced by the white-rot fungus, in a pulp bleaching process using an oxidating bleaching chemical containing chlorine.
EP89117234A 1989-07-10 1989-09-18 Procedure for the bleaching of sulphate pulp Expired - Lifetime EP0408803B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT89117234T ATE100157T1 (en) 1989-07-10 1989-09-18 METHOD OF BLEACHING SULFATE PULP.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FI893338A FI88316C (en) 1989-07-10 1989-07-10 Process for bleaching cellulose pulp
FI893338 1989-07-10

Publications (2)

Publication Number Publication Date
EP0408803A1 true EP0408803A1 (en) 1991-01-23
EP0408803B1 EP0408803B1 (en) 1994-01-12

Family

ID=8528744

Family Applications (1)

Application Number Title Priority Date Filing Date
EP89117234A Expired - Lifetime EP0408803B1 (en) 1989-07-10 1989-09-18 Procedure for the bleaching of sulphate pulp

Country Status (8)

Country Link
EP (1) EP0408803B1 (en)
JP (1) JP2831048B2 (en)
AT (1) ATE100157T1 (en)
CA (1) CA1335184C (en)
DE (1) DE68912322D1 (en)
ES (1) ES2061857T3 (en)
FI (1) FI88316C (en)
NO (1) NO175105C (en)

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5369024A (en) * 1992-03-25 1994-11-29 The United States Of America As Represented By The Secretary Of Agriculture Xylanase from streptomyces roseiscleroticus NRRL-11019 for removing color from kraft wood pulps
WO1995007988A1 (en) * 1993-09-17 1995-03-23 Novo Nordisk A/S PURIFIED pH NEUTRAL RHIZOCTONIA LACCASES AND NUCLEIC ACIDS ENCODING SAME
US5498534A (en) * 1992-03-25 1996-03-12 The United States Of America As Represented By The Secretary Of Agriculture Method of removing color from wood pulp using xylanase from streptomyces roseiscleroticus NRRL B-11019
US5591304A (en) * 1991-05-07 1997-01-07 Von Kreisler Selting Werner Method for the use of enzymes in bleaching paper pulp
US5691193A (en) * 1993-02-25 1997-11-25 Pulp And Paper Research Institute Of Canada Non-chlorine bleaching of kraft pulp
US6824646B2 (en) 1999-03-23 2004-11-30 Oji Paper Co., Ltd. Process for oxygen bleaching and enzyme treating lignocellulosic pulp with liquid treatment and recovery
ES2221529A1 (en) * 2002-07-10 2004-12-16 Instituto Nacional De Investigacion Y Tecnologia Agraria Y Alimentaria (Inia) Delignification of cellulose pastes comprises enzymatic treatment e.g. with laccase, in the presence of a mediator, and washing with water
US6942754B2 (en) 1999-03-23 2005-09-13 Oji Paper Co., Ltd. Process for producing xylooligosaccharide from lignocellulose pulp
CN109537343A (en) * 2018-11-29 2019-03-29 崔雪柯 A kind of paper pulp gas-water separation technique

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FI113879B (en) 2000-05-23 2004-06-30 Valtion Teknillinen A new coating enzyme

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3636208A1 (en) * 1986-10-24 1988-05-05 Call Hans Peter METHOD FOR DELIGNIFYING AND WHICH BLEACHING LIGNICELLULOSE-CONTAINING OR LIGNINAL MATERIAL OR LIGNIN BY ENZYMATIC TREATMENT

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3636208A1 (en) * 1986-10-24 1988-05-05 Call Hans Peter METHOD FOR DELIGNIFYING AND WHICH BLEACHING LIGNICELLULOSE-CONTAINING OR LIGNINAL MATERIAL OR LIGNIN BY ENZYMATIC TREATMENT

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
TAPPI, vol. 67, no. 10, October 1984, pages 31-33; R. FARRELL: "Biocatalysts hold promise of better pulp quality" *

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5591304A (en) * 1991-05-07 1997-01-07 Von Kreisler Selting Werner Method for the use of enzymes in bleaching paper pulp
US5369024A (en) * 1992-03-25 1994-11-29 The United States Of America As Represented By The Secretary Of Agriculture Xylanase from streptomyces roseiscleroticus NRRL-11019 for removing color from kraft wood pulps
US5498534A (en) * 1992-03-25 1996-03-12 The United States Of America As Represented By The Secretary Of Agriculture Method of removing color from wood pulp using xylanase from streptomyces roseiscleroticus NRRL B-11019
US5834301A (en) * 1992-03-25 1998-11-10 The United States Of America As Represented By The Secretary Of Agriculture Method of removing color from kraft wood pulps
US5691193A (en) * 1993-02-25 1997-11-25 Pulp And Paper Research Institute Of Canada Non-chlorine bleaching of kraft pulp
WO1995007988A1 (en) * 1993-09-17 1995-03-23 Novo Nordisk A/S PURIFIED pH NEUTRAL RHIZOCTONIA LACCASES AND NUCLEIC ACIDS ENCODING SAME
US5480801A (en) * 1993-09-17 1996-01-02 Novo Nordisk A/S Purified PH neutral Rhizoctonia laccases and nucleic acids encoding same
US6824646B2 (en) 1999-03-23 2004-11-30 Oji Paper Co., Ltd. Process for oxygen bleaching and enzyme treating lignocellulosic pulp with liquid treatment and recovery
US6942754B2 (en) 1999-03-23 2005-09-13 Oji Paper Co., Ltd. Process for producing xylooligosaccharide from lignocellulose pulp
ES2221529A1 (en) * 2002-07-10 2004-12-16 Instituto Nacional De Investigacion Y Tecnologia Agraria Y Alimentaria (Inia) Delignification of cellulose pastes comprises enzymatic treatment e.g. with laccase, in the presence of a mediator, and washing with water
CN109537343A (en) * 2018-11-29 2019-03-29 崔雪柯 A kind of paper pulp gas-water separation technique

Also Published As

Publication number Publication date
ATE100157T1 (en) 1994-01-15
FI893338A (en) 1991-01-11
NO893715L (en) 1991-01-11
JP2831048B2 (en) 1998-12-02
FI88316C (en) 1993-04-26
JPH03130485A (en) 1991-06-04
DE68912322D1 (en) 1994-02-24
ES2061857T3 (en) 1994-12-16
CA1335184C (en) 1995-04-11
NO175105C (en) 1994-08-31
FI88316B (en) 1993-01-15
EP0408803B1 (en) 1994-01-12
NO893715D0 (en) 1989-09-18
FI893338A0 (en) 1989-07-10
NO175105B (en) 1994-05-24

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