CA2154076A1 - Method for chlorine-free bleaching of pulp with acetic acid as acidifying agent - Google Patents
Method for chlorine-free bleaching of pulp with acetic acid as acidifying agentInfo
- Publication number
- CA2154076A1 CA2154076A1 CA 2154076 CA2154076A CA2154076A1 CA 2154076 A1 CA2154076 A1 CA 2154076A1 CA 2154076 CA2154076 CA 2154076 CA 2154076 A CA2154076 A CA 2154076A CA 2154076 A1 CA2154076 A1 CA 2154076A1
- Authority
- CA
- Canada
- Prior art keywords
- pulp
- peroxide
- acid
- bleaching
- acetic acid
- 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.)
- Abandoned
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
- D21C9/16—Bleaching ; Apparatus therefor with per compounds
- D21C9/166—Bleaching ; Apparatus therefor with per compounds with peracids
-
- 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
- D21C9/1005—Pretreatment of the pulp, e.g. degassing the pulp
-
- 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
- D21C9/16—Bleaching ; Apparatus therefor with per compounds
- D21C9/163—Bleaching ; Apparatus therefor with per compounds with peroxides
Landscapes
- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Wood Science & Technology (AREA)
- Paper (AREA)
Abstract
A method of bleaching pulp of cellulosic fibre material without the use of chlorine when manufacturing chemical pulp is described, wherein the pulp entering is fed continuously in a bleaching line and is treated with a sequestering agent in the presence of an acid in order to adjust the pH to a value below 7 and is thereafter bleached in a sequence of several stages consisting of peroxide, at least one organic per-acid and peroxide. According to the invention it is suggested that in the treatment with the sequestering agent the pulp is acidified with acetic acid.
Description
W094/17~9 21~ 4 n 7 6 PCT/SE94/00054 -Method for chlorine-free bleaching of pulp with acetic acid as acidifying agent.
The present invention relates to a method of bleaching pulp of cellulosic fibre material without the use of chlorine when manufacturing chemical pulp, wherein the pulp entering is fed continuously in a bleaching line and is treated with a sequestering agent in the presence of at least one acid in order to adjust the pH to a value below 7 and is thereafter bleached in a sequence of several stages consisting of peroxide, one or more organic per-acids and peroxide.
The strict environmental requirements concerning the use of bleaching agents containing chlorine for bleaching pulp have resulted in extensive research work to find other bleaching agents that are not detrimental to the environment in the way the chlorine-containing bleaching agents are which form chlorinated organic compounds.
Thus, it has been proposed to bleach pulp using ozone and peroxide in various sequences preceded by treatment with sequestering agent such as those described in SE-A-9101300-3, for instance. However, the use of ozone involves a number of drawbacks. Ozone has a decomposing effect on the cellulose, and the equipment for producing and supplying ozone in connection to the bleaching process is vast and expensive. US-A-3,867,246 corresponding to SE-B-405130 describes another bleaching process without the use of chlorine, including the sequence peroxide, peracetic acid and peroxide, the first peroxide stage being preceded by treatment with sequestering agent in the presence of an acid in order to adjust a low pH value. The acid used is generally sulphuric acid. However, like ozone, also peracetic acid has a strongly decomposing effect on the cellulose.
The object of the present invention is to solve the drawback in bleaching pulp without the use of chlorine, WO94/17~9 PCTISE94/00054 21S~07~i 2 using peracetic acid in combination with peroxide in the bleaching sequence PPaP preceded by treatment with a sequestering agent (Q) in tha presence of an acid, so that a ready-bleached pulp is obtained that has acceptable viscosity and strength properties and a brightness of 85-90% ISO requested by the market.
The method according to the invention is characterised in that during the treatment with the sequestering agent the pulp is acidified with acetic acid.
The pulp entering is preferably produced by means of a digestion process giving a low Kappa number, and is thereafter subjected to delignification with oxygen gas to that the pulp obtains a Kappa number of about 12 or less and a viscosity of at least about lOOO dm3/kg.
The peroxide used is preferably hydrogen peroxide.
The second bleaching stage, following the first peroxide stage, is performed using performic acid, peracetic acid or perpropionic acid, preferably peracetic acid or a mixture of at least two of said per-acids.
According to a suitable embodiment acetic acid is added in such an amount that the pH value is below 6, preferably below 5.
The temperature during all bleaching stages should be 30 80C or above, preferably 9OC.
Each peroxide stage is suitably performed in alkaline solution.
The peracetic acid stage is preferably performed in acid solution.
WO94/17~9 21 5 4 n 7 6 PCT/SE94/00054 Acetic acid and peracetic acid, or other suitable per--acids are preferably manufactured on site.
The consistency of the pulp during the various treatment stages is about 8-16%, preferably 9-11%.
The following example illustrates the invention further and shows its unexpected results.
Example A number of experiments were performed using a sulphate pulp of softwood which had been delignified with oxygen gas and washed. The delignified pulp had a Kappa number of 12.1, brightness 33.7% ISO and a viscosity of 1020 dm3/kg. It was supplied into the bleaching line in a consistency of lO~ and this was maintained during the treatment with the sequestering agent EDTA and all the bleaching stages. In experiments 1 and 2 sulphuric acid was used as acidifying agent in the Q-stage, whereas acetic acid was used in experiments 3 and 4 in accordance with the present invention.
WO94117~9 PCT/SE94100054 215~0~
Experiments 1-4 l. Additives Bleaching sequence 2. Conditions OPPaP OPPaP
The present invention relates to a method of bleaching pulp of cellulosic fibre material without the use of chlorine when manufacturing chemical pulp, wherein the pulp entering is fed continuously in a bleaching line and is treated with a sequestering agent in the presence of at least one acid in order to adjust the pH to a value below 7 and is thereafter bleached in a sequence of several stages consisting of peroxide, one or more organic per-acids and peroxide.
The strict environmental requirements concerning the use of bleaching agents containing chlorine for bleaching pulp have resulted in extensive research work to find other bleaching agents that are not detrimental to the environment in the way the chlorine-containing bleaching agents are which form chlorinated organic compounds.
Thus, it has been proposed to bleach pulp using ozone and peroxide in various sequences preceded by treatment with sequestering agent such as those described in SE-A-9101300-3, for instance. However, the use of ozone involves a number of drawbacks. Ozone has a decomposing effect on the cellulose, and the equipment for producing and supplying ozone in connection to the bleaching process is vast and expensive. US-A-3,867,246 corresponding to SE-B-405130 describes another bleaching process without the use of chlorine, including the sequence peroxide, peracetic acid and peroxide, the first peroxide stage being preceded by treatment with sequestering agent in the presence of an acid in order to adjust a low pH value. The acid used is generally sulphuric acid. However, like ozone, also peracetic acid has a strongly decomposing effect on the cellulose.
The object of the present invention is to solve the drawback in bleaching pulp without the use of chlorine, WO94/17~9 PCTISE94/00054 21S~07~i 2 using peracetic acid in combination with peroxide in the bleaching sequence PPaP preceded by treatment with a sequestering agent (Q) in tha presence of an acid, so that a ready-bleached pulp is obtained that has acceptable viscosity and strength properties and a brightness of 85-90% ISO requested by the market.
The method according to the invention is characterised in that during the treatment with the sequestering agent the pulp is acidified with acetic acid.
The pulp entering is preferably produced by means of a digestion process giving a low Kappa number, and is thereafter subjected to delignification with oxygen gas to that the pulp obtains a Kappa number of about 12 or less and a viscosity of at least about lOOO dm3/kg.
The peroxide used is preferably hydrogen peroxide.
The second bleaching stage, following the first peroxide stage, is performed using performic acid, peracetic acid or perpropionic acid, preferably peracetic acid or a mixture of at least two of said per-acids.
According to a suitable embodiment acetic acid is added in such an amount that the pH value is below 6, preferably below 5.
The temperature during all bleaching stages should be 30 80C or above, preferably 9OC.
Each peroxide stage is suitably performed in alkaline solution.
The peracetic acid stage is preferably performed in acid solution.
WO94/17~9 21 5 4 n 7 6 PCT/SE94/00054 Acetic acid and peracetic acid, or other suitable per--acids are preferably manufactured on site.
The consistency of the pulp during the various treatment stages is about 8-16%, preferably 9-11%.
The following example illustrates the invention further and shows its unexpected results.
Example A number of experiments were performed using a sulphate pulp of softwood which had been delignified with oxygen gas and washed. The delignified pulp had a Kappa number of 12.1, brightness 33.7% ISO and a viscosity of 1020 dm3/kg. It was supplied into the bleaching line in a consistency of lO~ and this was maintained during the treatment with the sequestering agent EDTA and all the bleaching stages. In experiments 1 and 2 sulphuric acid was used as acidifying agent in the Q-stage, whereas acetic acid was used in experiments 3 and 4 in accordance with the present invention.
WO94117~9 PCT/SE94100054 215~0~
Experiments 1-4 l. Additives Bleaching sequence 2. Conditions OPPaP OPPaP
3. Result l 2 3 4 O-stage lO l. EDTA, kg/BDMT 2.0 2.0 H2SO4, kg/BDMT 6.2 Acetic acid, kg/BDMT - 15.0 2. Initial pH value 4.7 4.8 Time, min. 60 60 Temperature, C 70 70 P-sta~e l. H22, kg/BDMT 35 35 MgSO4, kg/BDMT 3.0 3.0 NaOH, kg/BDMT 25 25 2. Time, min 240 240 Temperature,C 90 90 Final pH value lO.9 ll.O
3. Consumed H2O2, kg/BDMT 18 16 Kappa number 5.1 4.9 Viscosity, dm3/kg 9lO 9ll Brightness, % ISO77. 3 77.0 Pa-stage l. Peracetic acid calculated as total H2O2, kg/BDMT 20 30 20 30 2. pH, buffer solution (sodium acetate) 4.3 4.3 4.3 4.3 Time, min. 240 240 240 240 Temperature, C 90 90 90 90 Cont.
_ WO94tl7~9 21 S 4 n 7 G PCT/SE94/00054 1. Additives Bleaching sequence 2. Conditions OPPaP OPPaP
~ 5 3. Result 1 2 3 4 3. Consumed peracetic acid as H2O2, kg/BDMT 11.6 17.9 9.9 14.2 Kappa number 1.1 0.7 1.2 0.9 Viscosity, dm3/kg 842 814 852 841 Brightness, % ISO84.4 87.4 84.4 86.8 P-sta~e 1. H202, kg/BDMT 4.0 4.0 4.0 4.0 MgS04, kg/BDMT 3.0 3.0 3.0 3.0 NaOH, kg/BDMT 7.0 7.0 7.0 7.0 2. Time, min. 180 180 180 180 Temperature, C 90 90 90 90 Final pH value 10.3 10.4 10.6 10.5 3. Consumed H202, kg/BDMT1.5 1.3 0.9 1.1 Kappa number 0.8 0.5 1.1 0.7 Viscosity, dm3/kg 808 778 834 828 Brightness, % ISO88,1 89,3 87,8 89,2 The results show that surprisingly the pulps pre-treated and bleached in accordance with the invention have significantly improved viscosity, which in turn indicates improved strength properties as compared with the pulps pre-treated and bleached according to Examples 1 and 2.
Using equal quantities of peracetic acid (Pa) in the second bleaching stage, 20 kg in Examples l and 3 and 30 kg in Examples 2 and 4, the use of acetic acid instead of sulphuric acid as acidifying agent in the Q-stage results in an increase in viscosity by 26 and 50 units, respectively.
WO94/17~9 PCT/SE94/00054 215407~ 6 As mentioned above, acetic acid and peracetic acid or other suitable per-acids are ~referably produced on site.
Acetic acid, for instance, can be recovered from the black liquor in quantities up to 50 kg per ton of pulp when manufacturing pulp. Peracetic acid, for instance, can be produced in known manner from the acetic acid recovered. Consequently the method according to the invention can be performed in an extremely advantageous manner from the economical point of view.
3. Consumed H2O2, kg/BDMT 18 16 Kappa number 5.1 4.9 Viscosity, dm3/kg 9lO 9ll Brightness, % ISO77. 3 77.0 Pa-stage l. Peracetic acid calculated as total H2O2, kg/BDMT 20 30 20 30 2. pH, buffer solution (sodium acetate) 4.3 4.3 4.3 4.3 Time, min. 240 240 240 240 Temperature, C 90 90 90 90 Cont.
_ WO94tl7~9 21 S 4 n 7 G PCT/SE94/00054 1. Additives Bleaching sequence 2. Conditions OPPaP OPPaP
~ 5 3. Result 1 2 3 4 3. Consumed peracetic acid as H2O2, kg/BDMT 11.6 17.9 9.9 14.2 Kappa number 1.1 0.7 1.2 0.9 Viscosity, dm3/kg 842 814 852 841 Brightness, % ISO84.4 87.4 84.4 86.8 P-sta~e 1. H202, kg/BDMT 4.0 4.0 4.0 4.0 MgS04, kg/BDMT 3.0 3.0 3.0 3.0 NaOH, kg/BDMT 7.0 7.0 7.0 7.0 2. Time, min. 180 180 180 180 Temperature, C 90 90 90 90 Final pH value 10.3 10.4 10.6 10.5 3. Consumed H202, kg/BDMT1.5 1.3 0.9 1.1 Kappa number 0.8 0.5 1.1 0.7 Viscosity, dm3/kg 808 778 834 828 Brightness, % ISO88,1 89,3 87,8 89,2 The results show that surprisingly the pulps pre-treated and bleached in accordance with the invention have significantly improved viscosity, which in turn indicates improved strength properties as compared with the pulps pre-treated and bleached according to Examples 1 and 2.
Using equal quantities of peracetic acid (Pa) in the second bleaching stage, 20 kg in Examples l and 3 and 30 kg in Examples 2 and 4, the use of acetic acid instead of sulphuric acid as acidifying agent in the Q-stage results in an increase in viscosity by 26 and 50 units, respectively.
WO94/17~9 PCT/SE94/00054 215407~ 6 As mentioned above, acetic acid and peracetic acid or other suitable per-acids are ~referably produced on site.
Acetic acid, for instance, can be recovered from the black liquor in quantities up to 50 kg per ton of pulp when manufacturing pulp. Peracetic acid, for instance, can be produced in known manner from the acetic acid recovered. Consequently the method according to the invention can be performed in an extremely advantageous manner from the economical point of view.
Claims (8)
1. A method of bleaching pulp of cellulosic fibre material without the use of chlorine when manufacturing chemical pulp, wherein the pulp entering is fed continuously in a bleaching line and is treated with a sequestering agent in the presence of at least one acid in order to adjust the pH to a value below 7 and is thereafter bleached in a sequence of several stages consisting of peroxide, one or more organic per-acids and peroxide, characterized in that in the treatment with the sequestering agent the pulp is acidified with acetic acid.
2. A method as claimed in claim 1, characterized in that the peroxide used is hydrogen peroxide.
3. A method as claimed in claims 1 or 2, characterized in that the one or more organic per-acids used is/are performic acid, peracetic acid or perpropionic acid, preferably peracetic acid or a mixture of at least two of said per-acids.
4. A method as claimed in any of claims 1-3, characterized in that acetic acid, is added in such an amount that the pH value is below 6, preferably below 5.
5. A method as claimed in any of claims 1-4, characterized in that each peroxide stage is performed in alkaline solution.
6. A method as claimed in any of claims 1-5, characterized in that the consistency of the pulp during the treatment with sequestering agent and during said bleaching sequence is about 6-16%, preferably 9-11%.
7. A method as claimed in any of claims 1-6, characterized in that the pulp entering has been treated with oxygen gas and has a Kappa number of about 14 or less, preferably 12 or less and most preferably 10 or less.
8. The use of acetic acid, as acidifying agent when treating a chemical pulp with a sequestering agent in the bleaching of pulp without the use of chlorine, wherein the pulp entering is fed continuously in a bleaching line and is treated with a sequestering agent in the presence of acetic acid, in order to adjust the pH value to a value below 7, and is thereafter bleached in a sequence of several stages consisting of peroxide, one or more organic per-acids and peroxide.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| SE9300277-2 | 1993-01-29 | ||
| SE9300277A SE501325E (en) | 1993-01-29 | 1993-01-29 | Process for chlorine-free bleaching of pulp, wherein the pulp is acidified with acetic acid in the treatment with complexing agents |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2154076A1 true CA2154076A1 (en) | 1994-08-04 |
Family
ID=20388704
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2154076 Abandoned CA2154076A1 (en) | 1993-01-29 | 1994-01-26 | Method for chlorine-free bleaching of pulp with acetic acid as acidifying agent |
Country Status (10)
| Country | Link |
|---|---|
| EP (1) | EP0681624A1 (en) |
| JP (1) | JPH08505907A (en) |
| CN (1) | CN1117301A (en) |
| AU (1) | AU675291B2 (en) |
| BR (1) | BR9406193A (en) |
| CA (1) | CA2154076A1 (en) |
| FI (1) | FI111387B (en) |
| NO (1) | NO305763B1 (en) |
| SE (1) | SE501325E (en) |
| WO (1) | WO1994017239A1 (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1050642C (en) * | 1996-06-25 | 2000-03-22 | 华南理工大学 | Everyday production 30-150 ton high concentration paper pulp bleaching method by using hydrogen peroxide |
| CN103726382B (en) * | 2013-12-31 | 2016-08-17 | 安徽泾县千年古宣宣纸有限公司 | A kind of pure straw Chinese art paper and chloride-free bleaching production process thereof |
| EP3882380B1 (en) * | 2020-03-16 | 2022-04-27 | Re:NewCell AB | One stage method for acid metal removal and bleach |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2219505C3 (en) * | 1972-04-21 | 1974-10-17 | Deutsche Gold- Und Silber-Scheideanstalt Vormals Roessler, 6000 Frankfurt | Chlorine-free multi-stage bleaching of cellulose |
| DE2841013C2 (en) * | 1978-09-21 | 1984-06-07 | Degussa Ag, 6000 Frankfurt | Process for full bleaching of pulp |
| DE402335T1 (en) * | 1989-06-06 | 1992-04-09 | Eka Nobel Ab, Surte, Se | METHOD FOR BLEACHING LIGNOCELLULOSE-CONTAINING CELLS. |
| SE468355B (en) * | 1991-04-30 | 1992-12-21 | Eka Nobel Ab | CHEMISTRY OF CHEMICAL MASS THROUGH TREATMENT WITH COMPLEX PICTURES AND OZONE |
-
1993
- 1993-01-29 SE SE9300277A patent/SE501325E/en not_active IP Right Cessation
-
1994
- 1994-01-26 AU AU59820/94A patent/AU675291B2/en not_active Expired - Fee Related
- 1994-01-26 CN CN 94191058 patent/CN1117301A/en active Pending
- 1994-01-26 JP JP6516930A patent/JPH08505907A/en active Pending
- 1994-01-26 WO PCT/SE1994/000054 patent/WO1994017239A1/en active IP Right Grant
- 1994-01-26 EP EP94905899A patent/EP0681624A1/en not_active Ceased
- 1994-01-26 BR BR9406193A patent/BR9406193A/en not_active IP Right Cessation
- 1994-01-26 CA CA 2154076 patent/CA2154076A1/en not_active Abandoned
-
1995
- 1995-07-24 NO NO952935A patent/NO305763B1/en not_active IP Right Cessation
- 1995-07-27 FI FI953589A patent/FI111387B/en active
Also Published As
| Publication number | Publication date |
|---|---|
| EP0681624A1 (en) | 1995-11-15 |
| SE501325E (en) | 1999-06-09 |
| FI953589A (en) | 1995-07-27 |
| WO1994017239A1 (en) | 1994-08-04 |
| FI111387B (en) | 2003-07-15 |
| BR9406193A (en) | 1996-01-09 |
| SE501325C2 (en) | 1995-01-16 |
| AU675291B2 (en) | 1997-01-30 |
| NO952935L (en) | 1995-09-13 |
| SE9300277D0 (en) | 1993-01-29 |
| AU5982094A (en) | 1994-08-15 |
| NO952935D0 (en) | 1995-07-24 |
| JPH08505907A (en) | 1996-06-25 |
| CN1117301A (en) | 1996-02-21 |
| SE9300277L (en) | 1994-07-30 |
| NO305763B1 (en) | 1999-07-19 |
| FI953589A0 (en) | 1995-07-27 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| FZDE | Dead |