WO1995008666A1 - Chlorine-free bleaching of chemical pulp involving a two stage treatment with chelating agent - Google Patents

Chlorine-free bleaching of chemical pulp involving a two stage treatment with chelating agent Download PDF

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Publication number
WO1995008666A1
WO1995008666A1 PCT/SE1994/000758 SE9400758W WO9508666A1 WO 1995008666 A1 WO1995008666 A1 WO 1995008666A1 SE 9400758 W SE9400758 W SE 9400758W WO 9508666 A1 WO9508666 A1 WO 9508666A1
Authority
WO
WIPO (PCT)
Prior art keywords
pulp
bleaching
chelating agent
ozone
treated
Prior art date
Application number
PCT/SE1994/000758
Other languages
French (fr)
Inventor
Mårten DAHL
Solveig NORDÉN
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
Application filed by Sunds Defibrator Industries Ab filed Critical Sunds Defibrator Industries Ab
Priority to AU77923/94A priority Critical patent/AU7792394A/en
Priority to EP94928521A priority patent/EP0720675A1/en
Priority to BR9407555A priority patent/BR9407555A/en
Priority to JP7509711A priority patent/JPH09503028A/en
Priority to CA002168445A priority patent/CA2168445A1/en
Publication of WO1995008666A1 publication Critical patent/WO1995008666A1/en
Priority to FI961279A priority patent/FI961279A/en
Priority to NO961139A priority patent/NO961139L/en

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
    • D21C9/1026—Other features in bleaching processes
    • D21C9/1042—Use of chelating agents
    • 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
    • D21C9/16—Bleaching ; Apparatus therefor with per compounds
    • D21C9/163—Bleaching ; Apparatus therefor with per compounds with peroxides

Definitions

  • This invention relates to the bleaching of lignocellulose- -containing fiber material in the form of chemical pulp without using chloric bleaching agents.
  • the invention more precisely, relates to ozone bleaching of the pulp and sub ⁇ sequent peroxide bleaching.
  • the pulp is first treated with a chelating agent, for example DTPA or EDTA.
  • a chelating agent for example DTPA or EDTA.
  • metal ions are solved out of the pulp and are removed by dewatering the pulp prior to the ozone bleaching.
  • the pulp bleached with ozone still contains metals, which partially are absorbed on the fibers and partially solved in surrounding liquid. These metals must be removed for being able to bleach with peroxide in a subsequent step.
  • a treatment with chelat ⁇ ing agent is carried out at a pulp concentration of 1-10% for 1-60 minutes at a temperature of 20-70°C and a pH value of 2-5.
  • the pulp is thereafter dewatered and bleached with ozone. After the ozone bleaching the pulp is washed and dewatered, whereafter a peroxide bleaching takes place.
  • an additional treatment with chelating agent is carried out after the washing and de ⁇ watering. This treatment with chelating agent usually is carried out for 30-120 minutes at 60-90°C. The pulp must thereafter again be washed and dewatered prior to the peroxide bleaching.
  • FIG. 1 is an example of a flow chart for a method accord ⁇ ing to the invention.
  • Fig. 2 is a diagram showing the brightness as a function of the hydroperoxide charge, for known methods and, resp. , for a method according to the invention.
  • chemical pulp first is fed to a first chelating step 10 for treatment with EDTA or DTPA.
  • the pulp concentration should be 1-10% and the treatment be carried out for 1-60 minutes, preferably 5-30 minutes.
  • the temperature should be 20-70°C, preferably 20-40°C, and the pH value 2-5.
  • the pulp is washed and dewatered, for example in a washing press 11, for the removal of solved metal ions.
  • the pulp is directed therefrom to an ozone step 12 for ozone bleaching.
  • the pulp is diluted to a concentration of 1-10% and fed to a second chelating step 13.
  • chelating agent preferably DTPA or EDTA
  • the amount of charged DTPA or EDTA preferably can be up to 0,5 kg/ton pulp.
  • washing and dewatering is carried out to a concentration of 8-40% in a second washing step 14, whereafter the pulp is directed to a peroxide step 15 for peroxide bleaching.
  • the pulp can be bleached to a brightness exceeding 83% ISO.
  • Curve 1 relates to a conventional method with peroxide bleaching after the ozone-bleached pulp is only washed and dewatered .
  • Curve 2 relates to peroxide bleaching of ozone-bleached pulp, which in known manner had been washed, dewatered, treated with chelating agent and again be washed and dewater ⁇ ed prior to the peroxide bleaching.
  • Curve 3 relates to a method according to the invention.

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

Abstract

A method for bleaching lignocellulose-containing fiber material in the form of chemical pulp without using chloric bleaching agents where the pulp is treated with chelating agent and is bleached with ozone and peroxide. Immediately after the ozone bleaching the pulp is treated with chelating agent in a second chelating step at a pulp concentration of 1-10 % for 1-30 minutes at the temperature of 20-90 °C and the pH value 1,5-5. The pulp thus treated is washed and dewatered to a concentration of 8-40 % prior to the peroxide bleaching.

Description

Chlorine-free bleaching of chemical pulp involving a two stage treatment with chelating agent
This invention relates to the bleaching of lignocellulose- -containing fiber material in the form of chemical pulp without using chloric bleaching agents. The invention, more precisely, relates to ozone bleaching of the pulp and sub¬ sequent peroxide bleaching.
For rendering ozone bleaching of the pulp to take place more selectively, the pulp is first treated with a chelating agent, for example DTPA or EDTA. Hereby metal ions are solved out of the pulp and are removed by dewatering the pulp prior to the ozone bleaching.
The pulp bleached with ozone still contains metals, which partially are absorbed on the fibers and partially solved in surrounding liquid. These metals must be removed for being able to bleach with peroxide in a subsequent step.
According to a conventional method, a treatment with chelat¬ ing agent is carried out at a pulp concentration of 1-10% for 1-60 minutes at a temperature of 20-70°C and a pH value of 2-5. The pulp is thereafter dewatered and bleached with ozone. After the ozone bleaching the pulp is washed and dewatered, whereafter a peroxide bleaching takes place. Alternatively, an additional treatment with chelating agent is carried out after the washing and de¬ watering. This treatment with chelating agent usually is carried out for 30-120 minutes at 60-90°C. The pulp must thereafter again be washed and dewatered prior to the peroxide bleaching.
According to the firstmentioned one of the above known methods, no satisfactory ISO-brightness is obtained, and according to the alternative method extra treatment steps are required which complicate the process and make it more expensive. According to the present invention, these problems are elim¬ inated in that the method is relati ely simple and at the same time yields a high ISO brightness of the pulp. The characterizing features of the invention are apparent from the attached claims.
The invention is described in greater detail in the follow¬ ing with reference to the accompanying drawing, in which Fig. 1 is an example of a flow chart for a method accord¬ ing to the invention, and
Fig. 2 is a diagram showing the brightness as a function of the hydroperoxide charge, for known methods and, resp. , for a method according to the invention.
According to the flow chart in Fig. 1, chemical pulp first is fed to a first chelating step 10 for treatment with EDTA or DTPA. The pulp concentration should be 1-10% and the treatment be carried out for 1-60 minutes, preferably 5-30 minutes. The temperature should be 20-70°C, preferably 20-40°C, and the pH value 2-5.
After the first chelating step 10 the pulp is washed and dewatered, for example in a washing press 11, for the removal of solved metal ions. The pulp is directed therefrom to an ozone step 12 for ozone bleaching. Immediately after the ozone step 12 the pulp is diluted to a concentration of 1-10% and fed to a second chelating step 13. There it is treated with chelating agent, preferably DTPA or EDTA, for 1-30 minutes, preferably 5-20 minutes, at the temperature 20-90°C, preferably 40-80°C and the pH value 1,5-5. The amount of charged DTPA or EDTA preferably can be up to 0,5 kg/ton pulp.
After this second chelating step 13 washing and dewatering is carried out to a concentration of 8-40% in a second washing step 14, whereafter the pulp is directed to a peroxide step 15 for peroxide bleaching. According to this method, the pulp can be bleached to a brightness exceeding 83% ISO.
In the diagram in Fig. 2 the brightness is shown as a funct¬ ion of the peroxide charged at different types of treatment between ozone and peroxide step.
Curve 1 relates to a conventional method with peroxide bleaching after the ozone-bleached pulp is only washed and dewatered .
Curve 2 relates to peroxide bleaching of ozone-bleached pulp, which in known manner had been washed, dewatered, treated with chelating agent and again be washed and dewater¬ ed prior to the peroxide bleaching. Curve 3 relates to a method according to the invention.
It appears from Fig. 2 that the bleaching according to the invention (Curve 3) yields a considerably better result than conventional bleaching according to Curve 1. It further appears that the bleaching according to the invention yields a result which substantially corresponds to the result of the bleaching according to Curve 3, in spite of the fact that the method according to the invention is very much simpler. Experiences made in mill environment also prove that the difference between the two lastmentioned methods (Curve 2 and 3) is very small.
The invention, of course, is not restricted to the embodiment shown, but can be varied within the scope of the invention idea .

Claims

Claims
1. A method for bleaching lignocellulose-containing fiber material inthe form of chemical pulp without using chloric bleaching agents, at which method the pulp is treated with chelating agent and is bleached with ozone and peroxide, c h a r a c t e r i z e d i n that the pulp immediately after the ozone bleaching is treated with chelating agent in a second chelating step at a pulp concentration of 1-10% for 1-30 minutes, where the temperature is 20-90°C and the pH value 1,5-5, and that the pulp thus treated is washed and dewatered to a concentration of 8-40% prior to the peroxide bleaching.
2. A method as defined in claim 1, c h a r a c t e r ¬ i z e d i n that as chelating agent in the second chelating step DTPA or EDTA is used, which is added in an amount of up to 0,5 kg per ton of pulp.
3. A method as defined in claim 1 or 2, 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.
PCT/SE1994/000758 1993-09-21 1994-08-22 Chlorine-free bleaching of chemical pulp involving a two stage treatment with chelating agent WO1995008666A1 (en)

Priority Applications (7)

Application Number Priority Date Filing Date Title
AU77923/94A AU7792394A (en) 1993-09-21 1994-08-22 Chlorine-free bleaching of chemical pulp involving a two stage treatment with chelating agent
EP94928521A EP0720675A1 (en) 1993-09-21 1994-08-22 Chlorine-free bleaching of chemical pulp involving a two stage treatment with chelating agent
BR9407555A BR9407555A (en) 1993-09-21 1994-08-22 Process for bleaching fiber material containing lignocellulose in the form of chemical pulp without using chlorine bleaching agents
JP7509711A JPH09503028A (en) 1993-09-21 1994-08-22 Chlorine-free bleaching of chemical pulp including two-step treatment with chelating agents
CA002168445A CA2168445A1 (en) 1993-09-21 1994-08-22 Chlorine-free bleaching of chemical pulp involving a two stage treatment with chelating agent
FI961279A FI961279A (en) 1993-09-21 1996-03-20 Chlorine-free chemical pulp bleaching comprising a two-stage treatment with chelating agent
NO961139A NO961139L (en) 1993-09-21 1996-03-20 Chlorine-free chemical pulp bleaching by two-stage bleaching with chelating agent

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE9303066A SE501836C2 (en) 1993-09-21 1993-09-21 Bleaching of chemical pulp whereby the pulp is treated with complexing agents before and after an ozone step
SE9303066-6 1993-09-21

Publications (1)

Publication Number Publication Date
WO1995008666A1 true WO1995008666A1 (en) 1995-03-30

Family

ID=20391160

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/SE1994/000758 WO1995008666A1 (en) 1993-09-21 1994-08-22 Chlorine-free bleaching of chemical pulp involving a two stage treatment with chelating agent

Country Status (9)

Country Link
EP (1) EP0720675A1 (en)
JP (1) JPH09503028A (en)
AU (1) AU7792394A (en)
BR (1) BR9407555A (en)
CA (1) CA2168445A1 (en)
FI (1) FI961279A (en)
NO (1) NO961139L (en)
SE (1) SE501836C2 (en)
WO (1) WO1995008666A1 (en)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1997008380A1 (en) * 1995-08-24 1997-03-06 Sunds Defibrator Industries Ab Treatment of pulp with chelating agent in at least two mixing steps without intermediate washing
WO1998029597A1 (en) * 1997-01-03 1998-07-09 Sunds Defibrator Industries Ab Treatment of pulp with a chelating agent without using a bleaching tower
CN102587186A (en) * 2012-03-20 2012-07-18 昆明理工大学 Method for bleaching dendrocalamus giganteus chemical pulp
RU2634586C1 (en) * 2016-08-01 2017-10-31 федеральное государственное бюджетное образовательное учреждение высшего образования "Пермский национальный исследовательский политехнический университет" Method of bleaching hardwood sulphate cellulose

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1992012289A1 (en) * 1991-01-03 1992-07-23 Union Camp Patent Holding, Inc. Chlorine-free process for bleaching lignocellulosic pulp
EP0512590A1 (en) * 1991-04-30 1992-11-11 Eka Nobel Ab Process for bleaching of lignocellulose-containing material

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1992012289A1 (en) * 1991-01-03 1992-07-23 Union Camp Patent Holding, Inc. Chlorine-free process for bleaching lignocellulosic pulp
EP0512590A1 (en) * 1991-04-30 1992-11-11 Eka Nobel Ab Process for bleaching of lignocellulose-containing material

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1997008380A1 (en) * 1995-08-24 1997-03-06 Sunds Defibrator Industries Ab Treatment of pulp with chelating agent in at least two mixing steps without intermediate washing
WO1998029597A1 (en) * 1997-01-03 1998-07-09 Sunds Defibrator Industries Ab Treatment of pulp with a chelating agent without using a bleaching tower
AU726599B2 (en) * 1997-01-03 2000-11-16 Valmet Fibertech Ab Treatment of pulp with a chelating agent without using a bleaching tower
CN1103832C (en) * 1997-01-03 2003-03-26 瑞典商顺智公司 Treatment of pulp with a chelating agent without using a bleaching tower
CN102587186A (en) * 2012-03-20 2012-07-18 昆明理工大学 Method for bleaching dendrocalamus giganteus chemical pulp
CN102587186B (en) * 2012-03-20 2015-03-11 昆明理工大学 Method for bleaching dendrocalamus giganteus chemical pulp
RU2634586C1 (en) * 2016-08-01 2017-10-31 федеральное государственное бюджетное образовательное учреждение высшего образования "Пермский национальный исследовательский политехнический университет" Method of bleaching hardwood sulphate cellulose

Also Published As

Publication number Publication date
SE9303066L (en) 1995-03-22
FI961279A0 (en) 1996-03-20
SE9303066D0 (en) 1993-09-21
BR9407555A (en) 1996-12-31
EP0720675A1 (en) 1996-07-10
FI961279A (en) 1996-03-20
AU7792394A (en) 1995-04-10
NO961139D0 (en) 1996-03-20
SE501836C2 (en) 1995-05-22
JPH09503028A (en) 1997-03-25
CA2168445A1 (en) 1995-03-30
NO961139L (en) 1996-03-20

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