WO2002016691A1 - Chemical method - Google Patents
Chemical method Download PDFInfo
- Publication number
- WO2002016691A1 WO2002016691A1 PCT/SE2001/001710 SE0101710W WO0216691A1 WO 2002016691 A1 WO2002016691 A1 WO 2002016691A1 SE 0101710 W SE0101710 W SE 0101710W WO 0216691 A1 WO0216691 A1 WO 0216691A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- pulp
- aqueous liquid
- reducing
- bleached
- sulfur compound
- Prior art date
Links
- 238000000034 method Methods 0.000 title claims abstract description 22
- 239000000126 substance Substances 0.000 title description 8
- 150000003464 sulfur compounds Chemical class 0.000 claims abstract description 30
- 239000007788 liquid Substances 0.000 claims abstract description 21
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 claims abstract description 20
- 239000000460 chlorine Substances 0.000 claims abstract description 20
- 229910052801 chlorine Inorganic materials 0.000 claims abstract description 20
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 claims abstract description 11
- 239000003546 flue gas Substances 0.000 claims abstract description 11
- 230000007423 decrease Effects 0.000 claims abstract description 3
- OSVXSBDYLRYLIG-UHFFFAOYSA-N dioxidochlorine(.) Chemical compound O=Cl=O OSVXSBDYLRYLIG-UHFFFAOYSA-N 0.000 claims description 17
- LSNNMFCWUKXFEE-UHFFFAOYSA-M Bisulfite Chemical compound OS([O-])=O LSNNMFCWUKXFEE-UHFFFAOYSA-M 0.000 claims description 10
- 239000004155 Chlorine dioxide Substances 0.000 claims description 8
- 235000019398 chlorine dioxide Nutrition 0.000 claims description 8
- 238000010411 cooking Methods 0.000 claims description 5
- LSNNMFCWUKXFEE-UHFFFAOYSA-N Sulfurous acid Chemical compound OS(O)=O LSNNMFCWUKXFEE-UHFFFAOYSA-N 0.000 claims description 4
- 239000007789 gas Substances 0.000 claims description 4
- -1 metabisulfite ions Chemical class 0.000 claims description 4
- 239000000203 mixture Substances 0.000 claims description 4
- KZBUYRJDOAKODT-UHFFFAOYSA-N Chlorine Chemical compound ClCl KZBUYRJDOAKODT-UHFFFAOYSA-N 0.000 claims description 3
- 150000008044 alkali metal hydroxides Chemical class 0.000 claims description 3
- 238000002485 combustion reaction Methods 0.000 claims description 2
- QBWCMBCROVPCKQ-UHFFFAOYSA-N chlorous acid Chemical compound OCl=O QBWCMBCROVPCKQ-UHFFFAOYSA-N 0.000 claims 1
- RAHZWNYVWXNFOC-UHFFFAOYSA-N Sulphur dioxide Chemical compound O=S=O RAHZWNYVWXNFOC-UHFFFAOYSA-N 0.000 description 12
- GEHJYWRUCIMESM-UHFFFAOYSA-L sodium sulfite Chemical compound [Na+].[Na+].[O-]S([O-])=O GEHJYWRUCIMESM-UHFFFAOYSA-L 0.000 description 8
- 238000010521 absorption reaction Methods 0.000 description 5
- 229910001868 water Inorganic materials 0.000 description 5
- 235000010265 sodium sulphite Nutrition 0.000 description 4
- LSNNMFCWUKXFEE-UHFFFAOYSA-L sulfite Chemical compound [O-]S([O-])=O LSNNMFCWUKXFEE-UHFFFAOYSA-L 0.000 description 4
- 238000005406 washing Methods 0.000 description 4
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
- 229910052783 alkali metal Inorganic materials 0.000 description 3
- 239000007864 aqueous solution Substances 0.000 description 3
- 238000004061 bleaching Methods 0.000 description 3
- 229920002678 cellulose Polymers 0.000 description 3
- 239000001913 cellulose Substances 0.000 description 3
- 230000006378 damage Effects 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 2
- 150000001340 alkali metals Chemical class 0.000 description 2
- 239000007844 bleaching agent Substances 0.000 description 2
- WBZKQQHYRPRKNJ-UHFFFAOYSA-L disulfite Chemical compound [O-]S(=O)S([O-])(=O)=O WBZKQQHYRPRKNJ-UHFFFAOYSA-L 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- 230000002829 reductive effect Effects 0.000 description 2
- 235000010267 sodium hydrogen sulphite Nutrition 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 1
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 1
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 description 1
- 229920001131 Pulp (paper) Polymers 0.000 description 1
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- 238000003915 air pollution Methods 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 239000000706 filtrate Substances 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 239000002480 mineral oil Substances 0.000 description 1
- 235000010446 mineral oil Nutrition 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 229910052700 potassium Inorganic materials 0.000 description 1
- 239000011591 potassium Substances 0.000 description 1
- 238000004537 pulping Methods 0.000 description 1
- 238000000746 purification Methods 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 239000011734 sodium Substances 0.000 description 1
- 229910052708 sodium Inorganic materials 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 239000004071 soot Substances 0.000 description 1
- 239000011593 sulfur Substances 0.000 description 1
- 229910052717 sulfur Inorganic materials 0.000 description 1
- 150000003568 thioethers Chemical class 0.000 description 1
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
Definitions
- the present invention relates to a process for reducing the content of residual active chlorine in bleached and/or delignified pulp by treating said pulp with an aqueous liquid obtained by absorbing at least on sulfur compound from flue gas.
- Chlorine based chemicals particularly chlorine dioxide, are often used for bleaching or delignifying cellulose pulp, which then generally contains some residual active chlorine.
- At least partial removal of the active chlorine can be effected by washing with sulfur dioxide water, as described in e.g. TAPPI, "Bleach Plant Operations Short
- the invention thus concerns a processes for reducing the content of residual active chlorine in bleached and/or delignified pulp comprising the steps:
- step (a) contacting flue gas comprising at least one sulfur compound with an aqueous liquid to at least partially absorb said at least one sulfur compound, such as SO 2 , and yield one or more reducing sulfur compounds in said aqueous liquid; and, (b) contacting the bleached and/or delignified pulp with the aqueous liquid obtained in step (a), wherein said reducing sulfur compound reacts with the active chlorine in the pulp and decreases the content thereof.
- the gaseous substances normally include organic or inorganic sulfur compounds such as mercaptanes and sulfides, and will in this description be referred to as pulp cooking exhaust gases.
- these gases can be combusted in a destruction furnace, optionally together with any suitable fuel, preferably derived from the pulping process, but also mineral oil or the like can be used.
- the flue gas- obtained from the combustion normally comprises SO 2 and/or other water soluble sulfur compounds, so when this flue gas is contacted with an aqueous liquid, for example in a scrubber, such water soluble sulfur compounds are absorbed to yield one or more reducing sulfur compound, suitably in a total amount from about 0.1 to about 700 g/litre, preferably up to about 400 g/litre most preferably from about 50 to about 400 g/litre.
- Reducing sulfur compounds refers to compounds where the sulfur has an oxidation number of not more than V, preferably not more than IV.
- reducing sulfur compounds examples include sulfite (SO 3 2" ), bisulfite (HSO 3 ' ) and metabisulfite (S 2 O 5 2" ) ions, or mixtures thereof.
- the aqueous liquid used for the absorption is suitably alkaline, preferably with a pH from about 7 to about 15, and preferably comprises alkali metal hydroxide, for example in an amount from about 0.1 to about 60 wt%, preferably from about 10 to about 50 wt%. It is also possible to use white liquor, i.e. the aqueous liquid used in alkaline cooking of cellulose pulp, which liquor as a main component contains alkali metal hydroxide in an amount within the above range.
- the aqueous liquid obtained by the absorption of sulfur compounds from flue gas thus suitably contains alkali metal sulfite, bisulfite or metabisulfite, or mixtures thereof, suitably in a total amount from about 0.1 to about 700 g/litre, preferably up to about 400 g/litre, most preferably from about 50 to about 400 g/litre.
- the pH is from about 1 to about 14, most preferably from about 2 to about 10. In most cases a suitable pH is obtained after completed absorption.
- the liquid obtained by the absorption for the presence of any impurities such as soot particles, which may disturb the process or damage the pulp. If such impurities are detected, the liquid should not be used for reducing the active chlorine, but rather be transferred to the cooking chemicals recovery system.
- the pulp in most cases contains from about 0.1 to about 2 kg active chlorine per tonne pulp, typically from about 0.5 to about 1 kg active chlorine per tonne pulp, which active chlorine normally comprises CIO 2 and/or Cl 2 .
- active chlorine normally comprises CIO 2 and/or Cl 2 .
- CIO 2 and Cl 2 particularly CIO 2
- the active chlorine is reduced, normally to mainly yield chloride and sulfate ions, or other substantially harmless species. This is exemplified with following formulas showing the reactions of chlorine dioxide with sulfite and bisulfite, respectively:
- Alkali metal in this description refer to any alkali metal such as sodium, potassium or mixtures thereof.
- the process of the invention is particularly useful for treating cellulose pulp, e.g. chemical pulp, bleached and/or delignified in a sequence including at least one step using chlorine dioxide.
- the treatment of the pulp is performed at the end of or immediately after a chlorine dioxide based bleaching and/or delignification step.
- the treatment may, for example, be performed in a washing step.
- at least about stochiometric amounts of the reducing sulfur compound is added, while the upper limit is not critical and is only determined by the availability of reducing sulfur compounds.
- the reducing sulfur compound is used in an excess from about 0 to about 1000 %, preferably from about 0 to about 100 % above stochiometric amounts.
- the temperature critical it may for example be from about 10 to about 150°C, preferably from about 40 to about 90°C.
- EXAMPLE 1 At a pulp mill 38 tonnes/h of sulfate pulp was produced and bleached in a sequence comprising a chlorine dioxide step. Flue gas from a destruction furnace for cooking exhaust gases was scrubbed in aqueous sodium hydroxide to yield 350 litre/h of an aqueous solution containing 70 g/litre of SO 3 2" and HSO 3 " , and having a pH of 7.0. By treating the bleached pulp with the sodium sulfite and bisulfite containing solution at a temperature of 73°C the content of active chlorine was decreased from 0.49 kg/tonne pulp to 0.12 kg/tonne pulp.
- EXAMPLE 2 At the pulp mill of Example 1 pulp filtrate from the last chlorine dioxide bleaching step was taken out and four samples of 100 ml were treated with various amounts of a sodium sulfite and bisulfite containing aqueous solution obtained by absorption of flue gas as in Example 1.
- the aqueous solution contained 0.81 moles/litre of SO 3 2' and HSO 3 " , and had a pH of 6.78. The results appear in the table below:
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- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Wood Science & Technology (AREA)
- Treating Waste Gases (AREA)
Abstract
The invention relates to a processes for reducing the content of residual active chlorine in bleached and/or delignified pulp comprising the steps:(a) contacting flue gas comprising at least one sulfur compound with an aqueous liquid to at least partially absorb said at least one sulfur compound and yield one or more reducing sulfur compounds in said aqueous liquid; and,(b) contacting the bleached and/or delignified pulp with the aqueous liquid obtained in step (a), wherein said reducing sulfur compound reacts with the active chlorine in the pulp and decreases the content thereof.
Description
CHEMICAL METHOD The present invention relates to a process for reducing the content of residual active chlorine in bleached and/or delignified pulp by treating said pulp with an aqueous liquid obtained by absorbing at least on sulfur compound from flue gas. Chlorine based chemicals, particularly chlorine dioxide, are often used for bleaching or delignifying cellulose pulp, which then generally contains some residual active chlorine. At least partial removal of the active chlorine can be effected by washing with sulfur dioxide water, as described in e.g. TAPPI, "Bleach Plant Operations Short
Course" March 20-24, 1994, Course Notes p. 213 - 215. However, the handling of sulfur dioxide is unpleasant and may also be dangerous for the process operators. Although washing of bleached pulp with acidified sodium sulfite is suggested in Appita Vol. 30. No.
2, Sept. 1976, Operation of a DcED ED2 bleach plant with no washing after the D-t stage", p. 143-147, such acidified sodium sulfite is normally prepared from sulfur dioxide.
It is an object of the present invention to provide a process for reducing the amount of active chlorine in pulp without the need for handling sulfur dioxide or other reductive chemicals from external sources. It is another object of the invention to reduce the amount of active chlorine with chemicals readily available at a pulp mill.
It has now been found that aqueous liquids obtained from purification of flue gas containing sulfur compound can be used. The invention thus concerns a processes for reducing the content of residual active chlorine in bleached and/or delignified pulp comprising the steps:
(a) contacting flue gas comprising at least one sulfur compound with an aqueous liquid to at least partially absorb said at least one sulfur compound, such as SO2, and yield one or more reducing sulfur compounds in said aqueous liquid; and, (b) contacting the bleached and/or delignified pulp with the aqueous liquid obtained in step (a), wherein said reducing sulfur compound reacts with the active chlorine in the pulp and decreases the content thereof.
At pulp mills it is common that various gaseous substances are withdrawn from the process. The gaseous substances normally include organic or inorganic sulfur compounds such as mercaptanes and sulfides, and will in this description be referred to as pulp cooking exhaust gases. In order to avoid air pollutions and bad smell, these gases can be combusted in a destruction furnace, optionally together with any suitable fuel, preferably derived from the pulping process, but also mineral oil or the like can be used. It has been found that the flue gas- obtained from the combustion normally comprises SO2 and/or other water soluble sulfur compounds, so when this flue gas is contacted with an aqueous liquid, for example in a scrubber, such water soluble sulfur compounds are absorbed to yield one or more reducing sulfur compound, suitably in a total amount from about 0.1 to about 700 g/litre, preferably up to about 400 g/litre most
preferably from about 50 to about 400 g/litre. Reducing sulfur compounds refers to compounds where the sulfur has an oxidation number of not more than V, preferably not more than IV. Examples of such reducing sulfur compounds are sulfite (SO3 2"), bisulfite (HSO3 ') and metabisulfite (S2O5 2") ions, or mixtures thereof. The aqueous liquid used for the absorption is suitably alkaline, preferably with a pH from about 7 to about 15, and preferably comprises alkali metal hydroxide, for example in an amount from about 0.1 to about 60 wt%, preferably from about 10 to about 50 wt%. It is also possible to use white liquor, i.e. the aqueous liquid used in alkaline cooking of cellulose pulp, which liquor as a main component contains alkali metal hydroxide in an amount within the above range.
The aqueous liquid obtained by the absorption of sulfur compounds from flue gas thus suitably contains alkali metal sulfite, bisulfite or metabisulfite, or mixtures thereof, suitably in a total amount from about 0.1 to about 700 g/litre, preferably up to about 400 g/litre, most preferably from about 50 to about 400 g/litre. Preferably the pH is from about 1 to about 14, most preferably from about 2 to about 10. In most cases a suitable pH is obtained after completed absorption. Before treating the pulp it is also advisable to analyse the liquid obtained by the absorption for the presence of any impurities such as soot particles, which may disturb the process or damage the pulp. If such impurities are detected, the liquid should not be used for reducing the active chlorine, but rather be transferred to the cooking chemicals recovery system.
Before the treatment according to the invention the pulp in most cases contains from about 0.1 to about 2 kg active chlorine per tonne pulp, typically from about 0.5 to about 1 kg active chlorine per tonne pulp, which active chlorine normally comprises CIO2 and/or Cl2. In most cases, CIO2 and Cl2, particularly CIO2, are the main components. Upon contact with a reducing sulfur compound the active chlorine is reduced, normally to mainly yield chloride and sulfate ions, or other substantially harmless species. This is exemplified with following formulas showing the reactions of chlorine dioxide with sulfite and bisulfite, respectively:
2 CIO2 + 5 SO3 2' + H20 2 Cr + 5 SO4 2" + 2 H+ 2 CIO2 + 5 HSO3 " + H2O → 2 Ci + 5 SO4 2" + 7 H+
Alkali metal in this description refer to any alkali metal such as sodium, potassium or mixtures thereof.
The process of the invention is particularly useful for treating cellulose pulp, e.g. chemical pulp, bleached and/or delignified in a sequence including at least one step using chlorine dioxide. Preferably the treatment of the pulp is performed at the end of or immediately after a chlorine dioxide based bleaching and/or delignification step. The treatment may, for example, be performed in a washing step. Suitably at least about
stochiometric amounts of the reducing sulfur compound is added, while the upper limit is not critical and is only determined by the availability of reducing sulfur compounds. In most cases the reducing sulfur compound is used in an excess from about 0 to about 1000 %, preferably from about 0 to about 100 % above stochiometric amounts. Neither is the temperature critical, it may for example be from about 10 to about 150°C, preferably from about 40 to about 90°C.
The invention will now be further described in connection with the following Examples which, however, not should be interpreted to limit the scope of the invention. If not otherwise stated, all parts and percentages refer to parts and percent by weight. EXAMPLE 1: At a pulp mill 38 tonnes/h of sulfate pulp was produced and bleached in a sequence comprising a chlorine dioxide step. Flue gas from a destruction furnace for cooking exhaust gases was scrubbed in aqueous sodium hydroxide to yield 350 litre/h of an aqueous solution containing 70 g/litre of SO3 2" and HSO3 ", and having a pH of 7.0. By treating the bleached pulp with the sodium sulfite and bisulfite containing solution at a temperature of 73°C the content of active chlorine was decreased from 0.49 kg/tonne pulp to 0.12 kg/tonne pulp.
EXAMPLE 2: At the pulp mill of Example 1 pulp filtrate from the last chlorine dioxide bleaching step was taken out and four samples of 100 ml were treated with various amounts of a sodium sulfite and bisulfite containing aqueous solution obtained by absorption of flue gas as in Example 1. The aqueous solution contained 0.81 moles/litre of SO3 2' and HSO3 ", and had a pH of 6.78. The results appear in the table below:
It was thus shown that residual chlorine dioxide can be efficiently removed even when only stochiometric amounts of sulfite is added (i.e. 0% excess).
Claims
1. Process for reducing the content of residual active chlorine in bleached and/or delignified pulp comprising the steps.
(a) contacting flue gas comprising at least one sulfur compound with an aqueous liquid to at least partially absorb said at least one sulfur compound and yield one or more reducing sulfur compounds in said aqueous liquid; and,
(b) contacting the bleached and/or delignified pulp with the aqueous liquid obtained in step (a), wherein said reducing sulfur compound reacts with the active chlorine in the pulp and decreases the content thereof.
2. A process as claimed in claim 1, wherein the flue gas is obtained by combustion of pulp cooking exhaust gases.
3. A process as claimed in any one of the claims 1-2, wherein the flue gas comprises SO2.
4. A process as claimed in any one of the claims 1-3, wherein the reducing sulfur compound comprises sulfite, bisulfite or metabisulfite ions, or mixtures thereof.
5. A process as claimed in any one of the claims 1-4, wherein the aqueous liquid used to at least partially absorb said at least one sulfur compound in step (a) comprises alkali metal hydroxide.
6. A process as claimed in any one of the claims 1-5, wherein the aqueous liquid containing one or more reducing sulfur compounds obtained in step (a) has a pH from about 1 to about 14.
7. A process as claimed in any one of the claims 1-6, wherein the aqueous liquid obtained in step (a) contains from about 0.1 to about 400 g/litre of reducing sulfur compounds.
8. A process as claimed in claim 7, wherein the aqueous liquid obtained in step
(a) contains from about 50 to about 400 g/litre of reducing sulfur compounds.
9. A process as claimed in any one of the claims 1-8, wherein the pulp has been bleached and/or delignified in a sequence including at least one step using chlorine dioxide.
10. A process as claimed in any one of the claims 1-9, wherein the active chlorine comprises ClO2 and/or Cl2.
11. A process as claimed in any one of the claims 1-10, wherein the bleached and/or delignified pulp contains from about 0.1 to about 2 kg/tonne of active chlorine.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AU2001284569A AU2001284569A1 (en) | 2000-08-25 | 2001-08-06 | Chemical method |
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US22782700P | 2000-08-25 | 2000-08-25 | |
| US60/227,827 | 2000-08-25 | ||
| EP00850142 | 2000-08-25 | ||
| EP00850142.1 | 2000-08-25 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| WO2002016691A1 true WO2002016691A1 (en) | 2002-02-28 |
Family
ID=26074204
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| PCT/SE2001/001710 WO2002016691A1 (en) | 2000-08-25 | 2001-08-06 | Chemical method |
Country Status (2)
| Country | Link |
|---|---|
| AU (1) | AU2001284569A1 (en) |
| WO (1) | WO2002016691A1 (en) |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US1780943A (en) * | 1927-04-19 | 1930-11-11 | Brown Co | Fiber liberating and bleaching process |
| US5041237A (en) * | 1983-09-08 | 1991-08-20 | Stora Kopparbergs Berglags Ab | Aqueous solution containing sulphur dioxide and sodium in high percentages, its manufacture and use |
| FI913688A (en) * | 1991-03-14 | 1992-09-15 | Metsae Sellu Oy | FOERFARANDE FOER BINDNING AV FOERENINGAR I ETT AKTIVA KLORCELLULOSABLEKERI OCH MOTSVARANDE PROCESSAPPARATUR |
| WO1993015264A1 (en) * | 1992-01-22 | 1993-08-05 | Olin Corporation | Gas phase delignification of lignocellulosic material |
| WO1998000602A1 (en) * | 1996-06-28 | 1998-01-08 | Sunds Defibrator Industries Ab | Pressurized chlorine dioxide bleaching with recovery of chlorine dioxide |
-
2001
- 2001-08-06 WO PCT/SE2001/001710 patent/WO2002016691A1/en active Application Filing
- 2001-08-06 AU AU2001284569A patent/AU2001284569A1/en not_active Abandoned
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US1780943A (en) * | 1927-04-19 | 1930-11-11 | Brown Co | Fiber liberating and bleaching process |
| US5041237A (en) * | 1983-09-08 | 1991-08-20 | Stora Kopparbergs Berglags Ab | Aqueous solution containing sulphur dioxide and sodium in high percentages, its manufacture and use |
| FI913688A (en) * | 1991-03-14 | 1992-09-15 | Metsae Sellu Oy | FOERFARANDE FOER BINDNING AV FOERENINGAR I ETT AKTIVA KLORCELLULOSABLEKERI OCH MOTSVARANDE PROCESSAPPARATUR |
| WO1993015264A1 (en) * | 1992-01-22 | 1993-08-05 | Olin Corporation | Gas phase delignification of lignocellulosic material |
| WO1998000602A1 (en) * | 1996-06-28 | 1998-01-08 | Sunds Defibrator Industries Ab | Pressurized chlorine dioxide bleaching with recovery of chlorine dioxide |
Also Published As
| Publication number | Publication date |
|---|---|
| AU2001284569A1 (en) | 2002-03-04 |
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