AU3412593A - Bleaching of sulphate pulp - Google Patents

Bleaching of sulphate pulp

Info

Publication number
AU3412593A
AU3412593A AU34125/93A AU3412593A AU3412593A AU 3412593 A AU3412593 A AU 3412593A AU 34125/93 A AU34125/93 A AU 34125/93A AU 3412593 A AU3412593 A AU 3412593A AU 3412593 A AU3412593 A AU 3412593A
Authority
AU
Australia
Prior art keywords
pulp
bleaching
complexing agent
consistency
peroxide
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
AU34125/93A
Other versions
AU653467B2 (en
Inventor
Marten Dahl
Lars-Ake Lindstrom
Solveig Norden
Lars Sjodin
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.)
Valmet AB
Original Assignee
Sunds Defibrator Industries AB
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
Family has litigation
First worldwide family litigation filed litigation Critical https://patents.darts-ip.com/?family=20385065&utm_source=google_patent&utm_medium=platform_link&utm_campaign=public_patent_search&patent=AU3412593(A) "Global patent litigation dataset” by Darts-ip is licensed under a Creative Commons Attribution 4.0 International License.
Application filed by Sunds Defibrator Industries AB filed Critical Sunds Defibrator Industries AB
Publication of AU3412593A publication Critical patent/AU3412593A/en
Application granted granted Critical
Publication of AU653467B2 publication Critical patent/AU653467B2/en
Anticipated expiration legal-status Critical
Ceased 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
    • D21C9/147—Bleaching ; Apparatus therefor with oxygen or its allotropic modifications
    • D21C9/153—Bleaching ; Apparatus therefor with oxygen or its allotropic modifications with ozone
    • 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
    • D21C9/147—Bleaching ; Apparatus therefor with oxygen or its allotropic modifications
    • 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
    • D21C9/16—Bleaching ; Apparatus therefor with per compounds
    • D21C9/163—Bleaching ; Apparatus therefor with per compounds with peroxides

Abstract

A method of bleaching sulphate pulp without using chlorine-containing bleaching agents. The sulphate pulp is oxygen delignified and can possibly also be ozone delignified to a kappa number below 9.5. Thereafter a pretreatment with complexing agent is carried out for 1-60 minutes, at which the pulp consistency is 1-15 %, the temperature 70-110 DEG C and pH 5-7. The pulp thus pretreated is washed and dewatered to a consistency of 18-40 %. Thereafter peroxide bleaching in alkaline environment takes place in the presence of silicate or an organic complexing agent of the type phosphonic or carboxylic acid.

Description

Bleaching of chemical pulp
This invention relates to the bleaching of sulphate pulp without using bleaching agents containing chlorine. The technique of bleaching chemical pulps is now developing rapidly, because the bleaching chemicals heretofore mainly used, CI2, ClO2, and hypochl-orite, are feared to give rise to products being a risk for the environment and health.
Until now, the discussions have been concentrated on the emissions of chlorinated organic substance to the recipient. The majority of the countries in the world have now established limit values for these emissions, which normally are measured as AOX (Adsorbable organic halogens). As a new trend, the customers require to an ever increasing degree paper with a low content of chlorinated organic substance.
Conventional bleaching with Cl2 disappears now more and more, and CI2 is replaced primarily by ClO2. Bleaching with CIO2 causes substantially lower AOX-emissions to the recipient, but the amount of chlorinated substance in the pulp is affected only insignificantly.
In recent years, the use of hydroperoxide at the bleaching of chemical pulps has increased considerably. Hydroperoxide can replace part of the chlorine chemicals.
In patent application SE 89 02058-0, a method is described at which the pulp is pretreated with complexing agent under neutral conditions. By this process, coniferous sulphate pulp can be bleached with peroxide-containing bleaching agents to 70-75% ISO at about 10% pulp consistency. In order to achieve fully bleached pulp qualities., with higher ISO-brightness (above 83% ISO), this process can be combined with final bleaching with CIO2. As a result, th-is final bleaching then yields emission of AOX from the bleach plant and chlorinated organic susbstance in the bleached pulp. Other known methods of reducing emissions of chlorinated organic substance to the recipient are to extend the delignification further in the closed part of the mill, i.e. in the digester house and/or oxygen step.
Extended digestion with maintained pulp quality can be achieved by impregnating the chips with black liquor in the initial phase of the cook, as described in Finnish patent application 90 0663. This method renders it possible to digest pulp down to a kappa number of about 10 and obtain strength properties equal to or better than with pulp digested to conventional level, kappa number 25-30. Combined with oxygen delignification, kappa numbers as low as 5-6 can be obtained for.further bleaching.
By combining conventional digestion, oxygen delignificat- ion and ozone bleaching in acid environment, kappa numbers lower than 10 can be obtained.
It has, however, not been possible to produce fully bleached pulp qualities without final bleaching with ClO2.
The present invention implies, that fully bleached pulp with a brightness above 83% ISO can be made without the use of chlorine-containing bleaching agents.
At the start of the bleaching, the pulp shall have a kappa number below 9.5. This can be achieved by conventional or extended digestion followed by O2-delignification, alternatively by conventional or extended digestion followed by O2- and O3-delignification. The bleaching is initiated by a pretreatment step with complexing agent followed by treatment with hydroperoxide in alkaline environment in the presence of silicate or an organic complexing agent of the type phosphonic or carboxylic acid. The characterizing features of the invention are apparent from the attached claims.
The pulp digested and delignified with oxygen and possibly ozone according to above shall have a kappa number below 9.5. This can be achieved by known methods of digestion and delignification. The pulp shall thereafter be pretreated with complexing agent, for example EDTA or DTPA, at a pulp consistency of 1-15% for 1-60 minutes, preferably 5-30 minutes. The temperature shall be 70-100°C, preferably 80-100°C, and the pH-value 5-7.
The pulp thus pretreated is washed and dewatered to a consistency of 18-4.0%, preferably 20-30%. The pH-value is increased to alkaline level, and hydroperoxide is added together with silicate, for example sodium silicate, alternatively together with an organic complexing agent of the type phosphonic or carboxylic acid. The dwell time of the pulp in this hydroperoxide step shall be 1/2 - 5 hours, preferably 1-4 hours, and the temperature 70-100°C, preferably 80-100°C. The silicate charge shall be 2-30 kg/ton pulp, preferably 5-15 kg/ton pulp, expressed as SiO2.
Alternatively, the charge of the organic complexing agent shall be 0.5-5 kg/ton pulp.
Fig. 1 is a diagram, in which the brightness of the pulp is plotted as a function of the pulp consistency at the peroxide bleaching,partly at conventional peroxide bleaching and partly at bleaching according to the invention.
The starting pulp was oxygen-delignified coniferous wood sulphate pulp with kappa number 6.5 (10.5 after digestion). Curve 1 showg. conventional peroxide bleaching, with a consumption of H2O2 of 20 kg/ton pulp. Curve 2 and, respectively, 3 refer to bleaching according to the invention with silicate addition and a consumption of H2O2 of 20 and, respectively, 30 kg/ton pulp. It appears from the diagram how the brightness, after bleaching according to the invention and, respectively, after conventional bleaching, depends on the pulp consistency. At about 12% pulp consistency, the brightness obtained is" equal in both cases, but at increased pulp consistency in the peroxide step an increased brightness is obtained according to the invention, while conventional peroxide bleaching results in a deteriorated bright- ness.
The following examples have the object to additionally elucidate the invention and its advantages.
Example 1
An oxygen-delignified coniferous wood sulphate pulp
(Scandinavian fir/pine) with kappa number 6.4 (10.5 after digestion according to above Finnish patent application 90 0663), brightness 43% ISO, intrinsic viscosity 605 dur/kg, was pretreated with complexing agent and peroxide bleached according to the invention.
Pretreatment
Pulp consistency % 5
Time min 15
Temperature °C 90
EDTA kg/ton 2
Final pH 6.1
Peroxide step
Pulp consistency % 25
Time min 240
Temperature °C 90
SiO2 kg/ton 10
H2O2 consumption kg/ton 13.5 32.0
Final pH 10.2 10.3
Brightness % ISO 79.6 84.2
Intrinsic viscosity dm3/kg 520 447 Example 2
A coniferous wood sulphate pulp with kappa number 13.3 (digested of Scandinavian fir/pine according to Finnish patent application 90 0663), oxygen delignified to kappa number 8.3 and ozone bleached in acid environment to kappa number 3.2, brightness 61% ISO, intrinsic viscosity 582 dm3/kg, was bleached according to the invention.
Pretreatment as in Example 1
Peroxide bleaching
Pulp consistency % 25
Time min 24.0
Temperature °C 90
SiO2 kg/ton 10
H2O2 consumption kg/ton 7.3 14.2 30.1
Final pH 8.9 9.5 10.1
Brightness % ISO 85.3 88.4 90.4
Intrinsic viscosity dm3/kg 536 498 420
Example 3
An oxygen delignified coniferous wood sulphate pulp
(digested of Pinus taeda according to Finnish patent application 90 0663) with kappa number 9.9, ozone bleached to kappa number 4.8, brightness 54.5% ISO, intrinsic viscosity 607 dm3/kg was pretreated and bleached according to the invention.
Pretreatment as in Example 1
Peroxide bleaching
Pulp consistency % 25
Time min 240
Temperature °C 90
SiO2 kg/ton 10
H2O2 consumption kg/ton 7.9 14.6 29.6
Final pH 10.2 10.4 10.6 Brightness % ISO 81.3 85.3 87.8
Intrinsic viscosity dm3/kg 570 534 459
Example 4
An oxygen delignified birch sulphate pulp with kappa number 9.0, brightness 59.4% ISO and intrinsic viscosity 996 dm3/kg was bleached according to the invention.
Pretreatment as in Example 1
Peroxide bleaching
Pulp consistency % 25
Time min 240
Temperature °C 90
SiO2 kg/ton 10
H2O2 consumption kg/ton 8.5 17.5 35
Final pH 10.2 10.4 10.5
Brightness % ISO 82.2 85.5 86.5
Intrinsic viscosity dm3/kg 903 975 822
The invention is not restricted to the embodiments set forth above , but can be varied within the scope of the invention idea.

Claims (6)

Claims
1. A method of bleaching sulphate pulp without using chlorine-containing bleaching agents, comprising oxygen delignification and possibly ozone delignification of the pulp to a kappa number below 9.5 and subsequent
peroxide bleaching, c h a r a c t e r i z e d i n
that the pulp directly after the delignification is
pretreated with complexing agent for 1-60 minutes,
the pulp consistency being 1-15%, the temperature 70-110°C and pH 5-7, and that the pulp thus pretreated is washed and dewatered to a consistency of 18-40% and thereafter peroxide bleached in alkaline environment in the presence of silicate or an organic. complexing agent of the type phosphonic or carboxylic acid.
2. A method as defined in claim 1, c h a r a c t e r i z e d i n that the peroxide bleaching is carried out for 1/2-5 hours at the temperature 70-110°C.
3. A method as defined in claim 1 or 2, c h a r a c te r i z e d i n that as complexing agent at the
pretreatment EDTA or DTPA is used.
4. A method as defined in any one of the preceding claims, c h a r a c t e r i z e d i n that at the peroxide bleaching silicate is added in an amount of
2-30 kg/ton pulp, expressed as SiO2.
5. A method as defined in any one of the claims 1-3, c h a r a c t e r i z e d i n that at the peroxide bleaching an organic complexing agent of the type phosphonic acid or carboxylic acid is added in an amount of
0.5-5 kg/ton pulp.
6. A method as defined in any one of the preceding claims, c h a r a c t e r i z e d i n that the
bleaching is carried out to a brightness exceeding 83% ISO.
AU34125/93A 1992-01-21 1993-01-12 Bleaching of sulphate pulp Ceased AU653467B2 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
SE9200152 1992-01-21
SE9200152A SE469842C (en) 1992-01-21 1992-01-21 Bleaching of chemical pulp with peroxide
PCT/SE1993/000012 WO1993014262A1 (en) 1992-01-21 1993-01-12 Bleaching of chemical pulp

Publications (2)

Publication Number Publication Date
AU3412593A true AU3412593A (en) 1993-08-03
AU653467B2 AU653467B2 (en) 1994-09-29

Family

ID=20385065

Family Applications (1)

Application Number Title Priority Date Filing Date
AU34125/93A Ceased AU653467B2 (en) 1992-01-21 1993-01-12 Bleaching of sulphate pulp

Country Status (14)

Country Link
EP (1) EP0621915B1 (en)
JP (1) JPH07503042A (en)
AT (1) ATE151826T1 (en)
AU (1) AU653467B2 (en)
BR (1) BR9305761A (en)
CA (1) CA2124088A1 (en)
DE (1) DE69309893T2 (en)
ES (1) ES2102008T3 (en)
FI (1) FI943431A (en)
NO (1) NO942718D0 (en)
NZ (1) NZ246713A (en)
SE (1) SE469842C (en)
WO (1) WO1993014262A1 (en)
ZA (1) ZA93317B (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AU660301B2 (en) * 1991-03-11 1995-06-22 Solvay Interox Process for bleaching a chemical paper pulp

Families Citing this family (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
BE1006056A3 (en) * 1992-07-06 1994-05-03 Solvay Interox Method of laundering of chemical pulp.
SE500616C2 (en) * 1993-06-08 1994-07-25 Kvaerner Pulping Tech Bleaching of chemical pulp with peroxide at overpressure
SE501253E8 (en) * 1993-06-08 1994-12-19 Chlorine-free bleaching of chemical pulp
JPH09502229A (en) * 1993-09-02 1997-03-04 ユニオン キャンプ パテント ホールディング インコーポレイテッド Improved bleaching method for lignocellulosic pulp
BE1007757A3 (en) * 1993-11-10 1995-10-17 Solvay Interox Method of laundering of chemical pulp.
FR2719854B1 (en) * 1994-05-11 1996-06-21 Atochem Elf Sa Process for the preparation of delignified and bleached chemical paper pulps.
SE514697C2 (en) * 1994-08-31 2001-04-02 Valmet Fibertech Ab Elimination of metal ions in pulp bleaching

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB8620222D0 (en) * 1986-08-20 1986-10-01 Abitibi Price Inc Peroxide bleaching
US4732650A (en) * 1986-09-15 1988-03-22 The Dow Chemical Company Bleaching of cellulosic pulps using hydrogen peroxide
ATE97179T1 (en) * 1989-06-06 1993-11-15 Eka Nobel Ab PROCESS FOR BLEACHING LIGNOCELLULOSE CONTAINING PULP.
FI93866B (en) * 1990-02-09 1995-02-28 Sunds Defibrator Rauma Oy Method for preparing sulphate pulp

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AU660301B2 (en) * 1991-03-11 1995-06-22 Solvay Interox Process for bleaching a chemical paper pulp

Also Published As

Publication number Publication date
WO1993014262A1 (en) 1993-07-22
EP0621915B1 (en) 1997-04-16
CA2124088A1 (en) 1993-07-22
NO942718L (en) 1994-07-20
DE69309893D1 (en) 1997-05-22
ATE151826T1 (en) 1997-05-15
FI943431A0 (en) 1994-07-20
ZA93317B (en) 1993-08-19
SE9200152L (en) 1993-07-22
EP0621915A1 (en) 1994-11-02
SE9200152D0 (en) 1992-01-21
ES2102008T3 (en) 1997-07-16
SE469842C (en) 1995-09-22
FI943431A (en) 1994-07-20
NO942718D0 (en) 1994-07-20
AU653467B2 (en) 1994-09-29
DE69309893T2 (en) 1997-11-06
BR9305761A (en) 1997-01-28
NZ246713A (en) 1995-04-27
SE469842B (en) 1993-09-27
JPH07503042A (en) 1995-03-30

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