WO2004079087A1 - Bleaching of cellulose pulp in a first chlorine dioxide bleaching step - Google Patents
Bleaching of cellulose pulp in a first chlorine dioxide bleaching step Download PDFInfo
- Publication number
- WO2004079087A1 WO2004079087A1 PCT/SE2004/000303 SE2004000303W WO2004079087A1 WO 2004079087 A1 WO2004079087 A1 WO 2004079087A1 SE 2004000303 W SE2004000303 W SE 2004000303W WO 2004079087 A1 WO2004079087 A1 WO 2004079087A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- pulp
- bleaching
- chlorine dioxide
- phase
- minutes
- Prior art date
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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
- D21C9/12—Bleaching ; Apparatus therefor with halogens or halogen-containing compounds
- D21C9/14—Bleaching ; Apparatus therefor with halogens or halogen-containing compounds with ClO2 or chlorites
- D21C9/142—Bleaching ; Apparatus therefor with halogens or halogen-containing compounds with ClO2 or chlorites with ClO2/Cl2 in a multistage process involving ClO2/Cl2 exclusively
Definitions
- the present invention concerns a method for bleaching cellulose pulp in a first chlorine dioxide step.
- a typical bleaching sequence of several steps can be: D 0 (EO)D 1 D 2 , Do(EOP)D ⁇ D 2 or solely Do(EOP)D ⁇ with washes between the steps, where the first chlorine dioxide step is equivalent to the Do-step and where the bleaching sequence is normally preceded by oxygen gas delignification, O 2 .
- Other bleaching agents can sometimes be used, such as ozone, Z, which can be batchwise added before or after Do, either with or without an intermediate wash.
- a step using pure peroxide, P may be used as a final bleaching step.
- US;A;3.745.065 reveals a chlorine dioxide bleaching stage for cellulose pulp with a tower with upward flow and an immediately subsequent tower with downward flow.
- the process is controlled in this case such that the pulp is processed in these towers at a temperature in the range 60-85 °C (140-185 °F) and where the pulp has a retention time in the tower with upward flow of 25 minutes and a retention time in the tower with downward flow of 2-3 hours.
- US;A;3.745.065 concerns, more specifically, how the addition of bleaching chemicals is controlled by measuring residual gases at the highest point at the transition between the tower with upward flow and that with downward flow, where the pressure is lowest and gases are expelled. It is here specified that the tower with downward flow is normally completely filled, with a pulp level just below the top of the tower with downward flow.
- Kvaerner Pulping AB (previously Kamyr AB) marketed during the 1980s special bleaching towers in which the tower with upward flow was arranged concentrically within a larger surrounding tower of downward flow. The pulp was thus fed into the bottom of the tower of upward flow (in actuality a coarse pulp pipe), after which the pulp flowed out of the tower of upward flow, which opened just under the top of the larger surrounding tower of downward flow, in order subsequently to sink downwards to an outlet at the bottom of the tower of downward flow.
- This tower design allowed a compact bleaching step to be achieved and simultaneously allowed heat from the tower of upward flow to radiate out into the tower of downward flow.
- WO;A;01/96656 (with date of priority 13 June, 2000) reveals that the known combination of tower of upward flow and tower of downward flow in one chlorine dioxide step can be adapted to different cellulose pulps. It is specified here that when the chlorine dioxide bleaching step is adapted to softwood (SW) pulp, the retention time can be longer, specified as 2-4 hours, than the retention time can be for hardwood (HW) pulp, specified as 10 minutes-2.5 hours, although in certain cases they may be identical (overlapping). With respect to the temperature, this may be lower for softwood pulps, 50-70 °C, and for hardwood pulps 60-85 °C, but it thus is not necessarily lower for softwood pulps. It is specified in this adaptation strategy that the conditions specified are also to be suitable for a first, second or third chlorine dioxide step (the D 0 -, D and D 2 -steps, respectively).
- this first D 0 -step is in a first phase to be carried out at a conventional low temperature of 60+10 °C with very short retention time, and then subsequently to be carried out in a second phase at a considerably increased temperature 90+10 °C and with a long retention time.
- This method allows an intrinsic viscosity improved by 20-30 units (measured in dm 3 /kg), relative to a modified first D 0 -step at raised temperature that has been adapted in order to destroy the undesired inorganic acids to be obtained.
- a first chlorine dioxide step also known as a Do step
- a chlorine multiple of at least 1.0 is used, i.e. at least 1 kg of active chlorine added batchwise for each kappa unit of the input pulp, or, alternatively, that a total amount of active chlorine added in batches that exceeds 10 kg/BDMT (Bone Dry Metric Tonne) of pulp, and where no preceding step with the batchwise addition of active chlorine in excess of these levels is used in the bleaching sequence.
- the principal aim of the invention is to achieve an improved D 0 -step in which the highest possible pulp strength is obtained while at the same time the pulp is readily bleached to the desired final whiteness in subsequent bleaching steps.
- Figure 1 shows suitable process equipment in which hardwood pulp is bleached with chlorine dioxide according to the invention
- Figure 2 shows the improved viscosity that is obtained with a short, cold first phase at 60 °C for 3, 6, or 12 minutes, before a step lasting 120 minutes at 90 °C.
- FIG. 1 Detailed Description of Preferred Embodiments Process equipment is shown in Figure 1 in which the method according to the invention can be applied.
- Bleaching of cellulose pulp here takes place at a mean consistency of 7-22%, preferably between 10-14%, in a first bleaching step with chlorine dioxide.
- the pulp 1 is fed in from a preceding sulphate cooking step, and often from a preceding oxygen gas delignification stage, to a pulp chute 2.
- the pulp for the bleaching stage has an input kappa value that exceeds 7.0.
- Heating can take places in the pulp chute using steam STi.
- a pulp level is established in the pulp chute, and an MC pump 3 is arranged at the bottom of the chute.
- the pulp is pressurised by the pump 3 to an excess pressure of at least 2 bar (2 atmospheres), preferably with an excess pressure of 4-8 bar.
- the pulp is subsequently led to a second heating means 4 and a mixer 5 placed in series, where chlorine dioxide CIO 2 is mixed into the pulp using the mixer once the pulp has been given the correct temperature in the heating means.
- the temperature of the pulp at this position is to be maintained at a low level, in the range 60+10 °C.
- the pulp is subsequently led to the reactor 6 at the established reaction temperature, which reactor comprises a tower of upward flow 6a and a tower of downward flow 6b connected in series after each other.
- the tower of upward flow 6a is in this case a coarse pulp pipeline which gives a retention time/ascension time in the tower of upward flow of 1-30 minutes during normal production.
- the pulp is, according to the invention, to be bleached in a first phase in the tower of upward flow at low temperature during a retention time that is shorter than 30 minutes, and directly after this first phase is to be heated by at least 10 °C without an intermediate wash, after which the pulp is given a retention time at this raised temperature in a second step in the range 60-200 minutes, preferably 100-180 minutes and typically approximately 120 minutes. Therefore, the pulp can, as is shown in the drawing, be heated in the transition between the tower of upward flow 6a and the tower of downward flow 6b, with at least one heating means, preferably a steam mixer 12. It is appropriate that the retention time during the first phase does not exceed 20 minutes and it is even more preferable that it does not exceed 10 minutes.
- the retention time in the first phase should amount to at least 30 seconds and preferably at least 1 minute.
- This minimum retention time provides a clear distinction from any batchwise addition of chlorine dioxide in which the heating may take place immediately after the mixing in of the chlorine dioxide. It is conventional, however, that the "correct" or the desired reaction temperature is usually established before the chlorine dioxide is mixed into the pulp.
- the first phase can be established in a pipeline of a few tens of meters, which pipeline in the form of a U-bend can be located in a single horizontal plane, or in a vertical plane, possibly followed by a second phase at an increased temperature in a reactor of upward flow.
- the increase in temperature obtained with the heater/mixer 12 before the second phase is in the range 10-30 °C, which gives a starting temperature for the second step in the range 90 ⁇ 10 °C .
- the tower of downward flow has a volume that, when hydraulically filled with pulp, gives a retention time of 60-200 minutes during normal production.
- the retention time of the pulp in the tower of downward flow in the reactor can be controlled by adjusting the level in the tower of downward flow to the desired level by the level sensor, the differential pressure-sensor, which is connected to the output pump 9.
- a rotating scraper 8 is located at the bottom of the tower of downward flow 6b in order to facilitate output from the tower.
- the pulp is led, after pumping out, through the pump 9 to a wash press, in which the pulp is washed with cleaner process water PW.
- This process water can preferably, in closed bleaching plant in which the process water is led in a countercurrent flow relative to the flow of pulp, be a filtrate from the subsequent washing steps (not shown in the drawing).
- the second heating means 4 and the heating means 12 can be constituted by at least one static (shown in the drawing) or dynamic steam mixer, through which pulp flows during the addition of steam directly to the pulp.
- a slit mixer with locally reduced area of pulp flow at the addition of steam can be used in a static mixer, or a conventional static mixer in which the steam is added to a plug flow in the pulp pipeline.
- a dynamic mixer may be of the type equivalent to a simple wisp mixer, or it may be a multizone slit mixer of a type equivalent to a DUALDMIX (previously known as an MC- mixer).
- the second heating means 4 and the heating means 12 can, as is shown in the drawing, be supplemented with, or be solely constituted by, a fluid mixer through which pulp flows during the addition of pressurised superheated process fluid through a pump 30. A somewhat higher degree of dilution of the pulp concentration occurs when using such heating.
- This process fluid can preferably be filtered WF from a washing arrangement 10 arranged to wash the pulp following the chlorine dioxide step, which filtrate has been heated to the desired temperature of the process fluid by steam ST 2 in an indirect heat exchanger 31.
- Figure 2 reveals the surprising result of experiments.
- the initial pulp for the bleaching in the experiments has been hardwood pulp with a kappa value of 11.4, and the (EOP)-step has been maintained identical, with the same consumption of peroxide, 3 kg/BDMT, the same batch of alkali, 15 kg/BDMT, and the same final pH, 11.0.
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- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Wood Science & Technology (AREA)
- Paper (AREA)
Abstract
Description
Claims
Priority Applications (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2006507938A JP2006519939A (en) | 2003-03-07 | 2004-03-04 | Cellulose pulp bleaching method in the first chlorine dioxide bleaching step |
US10/547,038 US20060118260A1 (en) | 2003-03-07 | 2004-03-04 | Bleaching of cellulose pulp in a first chlorine dioxide bleaching step |
EP04717335A EP1604061A1 (en) | 2003-03-07 | 2004-03-04 | Bleaching of cellulose pulp in a first chlorine dioxide bleaching step |
BRPI0408171-4A BRPI0408171A (en) | 2003-03-07 | 2004-03-04 | method for bleaching pulp pulp in a first chlorine dioxide bleaching step |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
SE0300608-7 | 2003-03-07 | ||
SE0300608A SE524896C2 (en) | 2003-03-07 | 2003-03-07 | Bleaching of cellulose pulp with chlorine dioxide in two phases with heating between the phases |
Publications (1)
Publication Number | Publication Date |
---|---|
WO2004079087A1 true WO2004079087A1 (en) | 2004-09-16 |
Family
ID=20290593
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/SE2004/000303 WO2004079087A1 (en) | 2003-03-07 | 2004-03-04 | Bleaching of cellulose pulp in a first chlorine dioxide bleaching step |
Country Status (6)
Country | Link |
---|---|
US (1) | US20060118260A1 (en) |
EP (1) | EP1604061A1 (en) |
JP (1) | JP2006519939A (en) |
BR (1) | BRPI0408171A (en) |
SE (1) | SE524896C2 (en) |
WO (1) | WO2004079087A1 (en) |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2008076268A2 (en) * | 2006-12-18 | 2008-06-26 | International Paper Company | A process in a (d) stage bleaching of hardwood pulps in a presence of mg(oh)2 |
EP2006441A1 (en) | 2007-06-18 | 2008-12-24 | Andritz, Inc. | Processes and systems for the bleaching of lignocellulosic pulps following cooking with soda and anthraquinone |
US7976676B2 (en) | 2006-12-18 | 2011-07-12 | International Paper Company | Process of bleaching softwood pulps in a D1 or D2 stage in a presence of a weak base |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20050173082A1 (en) * | 1998-08-24 | 2005-08-11 | Arbozon Oy Ltd. | Bleaching of medium consistency pulp with ozone without high shear mixing |
Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3745065A (en) * | 1971-09-07 | 1973-07-10 | Cons Paper Inc | Control of chlorine dioxide bleaching |
WO1991005909A1 (en) * | 1989-10-19 | 1991-05-02 | North Carolina State University | High efficiency chlorine dioxide pulp bleaching process |
EP0940498A1 (en) * | 1998-03-06 | 1999-09-08 | Ahlstrom Machinery Oy | Method for treatment of pulp |
WO2001096656A1 (en) * | 2000-06-13 | 2001-12-20 | Valmet Fibertech Ab | Bleaching of pulp |
Family Cites Families (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20050051288A1 (en) * | 2003-09-09 | 2005-03-10 | Caifang Yin | Extended retention and medium consistency pulp treatment |
-
2003
- 2003-03-07 SE SE0300608A patent/SE524896C2/en not_active IP Right Cessation
-
2004
- 2004-03-04 JP JP2006507938A patent/JP2006519939A/en active Pending
- 2004-03-04 BR BRPI0408171-4A patent/BRPI0408171A/en not_active IP Right Cessation
- 2004-03-04 WO PCT/SE2004/000303 patent/WO2004079087A1/en active Application Filing
- 2004-03-04 US US10/547,038 patent/US20060118260A1/en not_active Abandoned
- 2004-03-04 EP EP04717335A patent/EP1604061A1/en not_active Withdrawn
Patent Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3745065A (en) * | 1971-09-07 | 1973-07-10 | Cons Paper Inc | Control of chlorine dioxide bleaching |
WO1991005909A1 (en) * | 1989-10-19 | 1991-05-02 | North Carolina State University | High efficiency chlorine dioxide pulp bleaching process |
EP0940498A1 (en) * | 1998-03-06 | 1999-09-08 | Ahlstrom Machinery Oy | Method for treatment of pulp |
WO2001096656A1 (en) * | 2000-06-13 | 2001-12-20 | Valmet Fibertech Ab | Bleaching of pulp |
Non-Patent Citations (1)
Title |
---|
LACHENAL D. ET AL.: "High temperature chlorine dioxide delignification: a breakthrough in ECF bleaching of hardwood kraft pulps", PULPING CONFERENCE, 1998, pages 601 - 604, XP002905597 * |
Cited By (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2008076268A2 (en) * | 2006-12-18 | 2008-06-26 | International Paper Company | A process in a (d) stage bleaching of hardwood pulps in a presence of mg(oh)2 |
WO2008076268A3 (en) * | 2006-12-18 | 2008-09-18 | Int Paper Co | A process in a (d) stage bleaching of hardwood pulps in a presence of mg(oh)2 |
US7976676B2 (en) | 2006-12-18 | 2011-07-12 | International Paper Company | Process of bleaching softwood pulps in a D1 or D2 stage in a presence of a weak base |
US7976677B2 (en) | 2006-12-18 | 2011-07-12 | International Paper Company | Process of bleaching hardwood pulps in a D1 or D2 stage in a presence of a weak base |
EP2006441A1 (en) | 2007-06-18 | 2008-12-24 | Andritz, Inc. | Processes and systems for the bleaching of lignocellulosic pulps following cooking with soda and anthraquinone |
AU2008202566B2 (en) * | 2007-06-18 | 2011-11-03 | Andritz Inc. | Processes and Systems for the Bleaching of Lignocellulosic Pulps Following Cooking with Soda and Anthraquinone |
US8262856B2 (en) | 2007-06-18 | 2012-09-11 | Andritz Inc. | Processes and systems for the bleaching of lignocellulosic pulps following cooking with soda and anthraquinone |
Also Published As
Publication number | Publication date |
---|---|
SE0300608L (en) | 2004-09-08 |
BRPI0408171A (en) | 2006-03-21 |
US20060118260A1 (en) | 2006-06-08 |
SE0300608D0 (en) | 2003-03-07 |
JP2006519939A (en) | 2006-08-31 |
EP1604061A1 (en) | 2005-12-14 |
SE524896C2 (en) | 2004-10-19 |
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