CA1249904A - Oxygen alkali extraction of cellulosic pulp - Google Patents
Oxygen alkali extraction of cellulosic pulpInfo
- Publication number
- CA1249904A CA1249904A CA000474986A CA474986A CA1249904A CA 1249904 A CA1249904 A CA 1249904A CA 000474986 A CA000474986 A CA 000474986A CA 474986 A CA474986 A CA 474986A CA 1249904 A CA1249904 A CA 1249904A
- Authority
- CA
- Canada
- Prior art keywords
- pulp
- oxygen
- alkali
- consistency
- pressurized
- 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.)
- Expired
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
Abstract
OXYGEN ALKALI EXTRACTION OF CELLULOSIC PULP
Abstract of the Disclosure An aqueous solution of alkali and oxygen gas is added to chlorinated and washed pulp and the pulp is retained in a retention apparatus from one to five minutes to remove lignin from the pulp. The pulp is fed directly to a pressing and washing apparatus from the retention apparatus where the pulp is pressed to a consistency ranging from about 16 percent to 40 percent and then washed to a con-sistency ranging from about 9 percent to about 15 percent.
Abstract of the Disclosure An aqueous solution of alkali and oxygen gas is added to chlorinated and washed pulp and the pulp is retained in a retention apparatus from one to five minutes to remove lignin from the pulp. The pulp is fed directly to a pressing and washing apparatus from the retention apparatus where the pulp is pressed to a consistency ranging from about 16 percent to 40 percent and then washed to a con-sistency ranging from about 9 percent to about 15 percent.
Description
~730-Ir~-~'A
This invention relates to oxygen alkali extraction of wood pulp. More particularly this invention is a new oxygen alkali process and system for extracting lignin from, and bleaching wood pulp.
One method of removing chlorinated and oxidized lignin from pulp is to add an alkali in aqueous solution to the pulp. This method is called "alkali extraction" Another method of removing chlorinated and oxidized lignin from pulp is to not only add the al~ali in aqueous solution to the pulp, but also add oxygen gas. This method may be called "oxygen alkali extraction". The treatment of wood pulp using both the alkali and the oxygen gas results in a pulp which is whiter and has a lower Kappa number when compared to the whiteness and Kappa number of the resulting pulp when 15 only alkali is added to the wood pulp starting with the same type of wood. Therefore, to obtain the removal of more lignin from the wood and obtain brighter pulp it is better to add oxygen to the system in addition to the alkali.
In a commercial conventional oxygen alkali extraction bleach plant, a series of bleaching stages are used. The equipment for each bleaching stage in the series usually consists of a chemical and/or steam mixer, followed by a large tower, followed by a washer, such as for example a rotary drum vacuum filter washer. A conventional oxygen
This invention relates to oxygen alkali extraction of wood pulp. More particularly this invention is a new oxygen alkali process and system for extracting lignin from, and bleaching wood pulp.
One method of removing chlorinated and oxidized lignin from pulp is to add an alkali in aqueous solution to the pulp. This method is called "alkali extraction" Another method of removing chlorinated and oxidized lignin from pulp is to not only add the al~ali in aqueous solution to the pulp, but also add oxygen gas. This method may be called "oxygen alkali extraction". The treatment of wood pulp using both the alkali and the oxygen gas results in a pulp which is whiter and has a lower Kappa number when compared to the whiteness and Kappa number of the resulting pulp when 15 only alkali is added to the wood pulp starting with the same type of wood. Therefore, to obtain the removal of more lignin from the wood and obtain brighter pulp it is better to add oxygen to the system in addition to the alkali.
In a commercial conventional oxygen alkali extraction bleach plant, a series of bleaching stages are used. The equipment for each bleaching stage in the series usually consists of a chemical and/or steam mixer, followed by a large tower, followed by a washer, such as for example a rotary drum vacuum filter washer. A conventional oxygen
2~ alkali system is described in U.S. Patent 3,832,276, iss~ed August 27, 1974.
The large tower is a very large and expensive structure. For example, in a plant of about 800 tons per day, the extraction tower may be 16 feet in diameter by 60 30 feet high. The tower must be constructed of corrosion-resistant materials, for example, a tile lining inside a steel cylinder, and equipped at the bottom with dilution and -mixing equipment to effect controlled removal of the pulp to the washer.
Also, in the conventional commercial oxygen alkali extraction plant, it is often required that the ~ixture of pulp, alkali, and oxygen gas be retained in the large expensive tower for from 40 to 90 minutes before diluting 2 ~ 0~ 973 and washing. of course, the actual residence time of the pulp in the tower varies depending upon the pressure on the system, the degree of bleaching required, and the particular pulp employed. However, from 40 to 90 minutes residence time is generally required to remove significant amounts of lignin from most pulp.
This invention is a new continuous oxygen alkali extraction method and system for bleaching and delignifying wood pulp which does not require the large expensive bleaching tower and does not require the long reaction time required by the conventional oxygen alkali extraction systems and methods.
~ riefly described, the invention comprises a pressurized pulp retention apparatus adapted to retain pulp for a sufficient pre-determined time period for the extraction of chlorinated lignin by the alkali and oxygen gas. Fluid conduits are provided for feeding the pulp containing the alkali, and oxygen gas into the pressurized retention apparatus. A pulp pressing and washing apparatus for pressin~ the pulp into a pulp mat having a consistency ranging from about 16 percent to 40 percent and washing the pulp mat to a consistency ranging from about 9 percent to about 15 percent is also included. The pulp, after the lignin has been extracted, is fed from the retention apparatus to the pressing and washing apparatus.
In practicing my new method of continuous oxygen alkali extraction of chlorinated lignin from wood pulp, an aqueous solution of alkali is mixed into chlorinated and washed pulp and also pressurized oxygen gas in the form of fine bubbles is also mixed with the pulp. As soon as the alkali and oxygen have reacted with the pulp for a sufficient time to significantly remove lignin from the pulp and to bleach the pulp, the pulp is pressed to a consistency ranging from about 1~ percent to about 40 percent and washed to a con-sistency ranging from about 9 percent to about 15 percent.
~ he invention as well as its many advantages may befurther understood by reference to the following detailed description and drawing in which:
~ 97~C~
Fig~ 1 is a flow diagram illustrating one embodiment of the present invention; and Fig. 2 is a flow diagram il]ustrating another embodi-ment of the present invention.
In the various figures, like parts are referre~ to by like numbers~
Bleaching is a continuation of the cooking process in which the ligneous material and coloring matter which remain in the pulp are removed selectively with as little degradation of the pulp fiber as possible. The bleaching is done in several stages. A stage constitutes a phase starting with the addition and reaction of a chemical and/or steam with a pulp and ends with the washing of the pulp.
Chlorination, which comprises the first stage of most bleaching sequences, results in chlorinated lignin, some of which, is soluble in water and removed in the wash follo~ing chlorination. Additional chlorinated lignin may be removed - in one or more stages after the chlorination s,age or stages by methods such as oxygen alkali extraction. This invention is an improved oxygen alkali extraction method and system.
Complete removal of the chlorinated lignin is accomplished in stages following the oxygen alkali stage or stages.
Referring to the drawings and more pa~ticularly to Fig.
1, the pulp from a previous chlorination stage, is fed through conduit 10 to the pulp slurry pressing and washing apparatus 12. In the oxygen alkali extraction stage of this invention, the pulp from the apparatus 12 is conducted by means of centrifugal pump 14 to the retention apparatus 16 by means of fluid conduit 18.
In the embodiment of Fig. 1 the retention apparatus 16 is a pressurized agitated reactor vessel. The pressurized agitated reactor vessel 16 is constructed to retain pulp for a pre-determined time period and react the alkali and oxygen gas with the pulp to delignify and bleach the pulp.
The retention time in reactor lS ranges from one to five minutesO The pulp consistency in reactor 16 ranges from 0.5 percent to 4.0 percent.
The aqueous solution sf alkali is introduced into the 9730~ PA
recirculation conduit 20. The recirculation conduit 20 leads to the repulping portion of the apparatus 12. Usually sodium hydroxide at a concentration of 0.~ percent to 5.0 percent by weight of the pulp is used as the ;3lkali although 5 other suitable alkalis may be used.
Oxygen gas ranging in amount from 0.1 percent to 2.0 percent by weight of the pulp is dispersed 2S fine bubbles into the conduit 18 utilizing a venturi ejector 22 to mix the oxygen with washer f iltrate recirculated back to the 10 pressurized reactor 16 by means of conduit 24. The oxygen is at a pressure ranging froM 10 psig to 40 psig.
The pulp f rom the agitated reac~or vessel 16 is directly fed to the pulp pressing and washing apparatus 26 by means of the fluid conduit 28 ~hich directly intercon-15 nects the reactor 16 and the pressing and washing apparatus26.
The pressing and washing apparatus 26 has a structure ' similar to the structure of the pressing and washing filter described in U.S. Patent 3,772,144 patented November 13, 20 1973 by Oscar Luthi and Lawrence A. Carlsmith and entitled "Apparatus and Method for Thickening and Washing Suspensions (~ontaining Fibrous NaterialU. The pulp slurry passes into the pressurized :Eeed box 30 of the apparatus 26 and is pressed under the resilient baffle 32 to a consistency 25 ranging from about 16 percent to about 40 percent. After the pulp mat adhering to the washer drum 34 emerges from underneath the bafr'le 32 it is washed with water or recirculated filtrate and discharged from the apparatus 26 by means of high consistency stock pump 35 and pulp outlet 30 conduit 36 to a subsequent bleaching stage. In general, the pulp leaving the pressing and washing apparatus 26 has a consistency ranging from about 9 percent to about 15 per-cent.
The filtrate from the pressing and washing apparatus 26 35 is fed into the rotatable drum 34, and then through conduit line 38 into the retainer vessel 4~ from which the filtrate is pumped through line 24 to the conduit 18 by means of pump 42. A portion of the washer filtrate from line 24 is ~ 3û~ P
recirculated back to the pressing and washing apparatus 12 by means of line 20 which branches off from line 24.
In the embodiment of Fig. 2 oxygen gas is mixed with pulp having a consistency ranging from 9 percent to 15 percent. The pulp at the consistency ranging from 9 percent to 15 percent is fed by means of line 50 to the high consistency stock pump 52. The aqueous solution of alkali may be added to the line 50 ahead of the stock pump 52. The stock pump 52 discharges the pulp through pipe 54 into the high consistency mixer 56. In the embodiment of Fig. 2, the retention apparatus comprises a short length of pipe 60 extending from the high consistency pulp mixer 56. The oxygen gas is dispersed in finely divided bubbles thro~lghout the pulp. The pulp pa~ses through the short length of pipe 60 which is adapted to provide a retention time of 1 minute to 5 minutes after which the pressure of 10 psig to 40 psig is reduced through a valve 62 and the pulp is discharged - into a low consistency mixing tank 64 in which it is diluted to a consistency of about 2 to 4 percent utilizing filtrate from the pressing and washing apparatus 26. The oilute pulp is pumped by pump 6~ from the mixing tank 64 by means of fluid conduit 70 into the inlet 30 of the pressing and washing apparatus 26 where it is formed into a mat on the drum 34 of the apparatus 26 and pressed under the resilient baffle 32 to a consistency ranging from about 16 percent to about 40 percent. After emerging from underneath the baffle 32, the mat adhering to the drum 3~ is washed with water and discharged at a consistency ranging from 9 percent to 15 percent to a subsequent bleaching stage by means of high consistency stock p~mp 35 and pulp outlet conduit 36.
A laboratory experiment was conducted to produce the results shown in the table. A sample of chlorinated softwood kraft pulp of Kappa NoO 25.3 was mixed with 3 percent of sodium hydroxide by weight and a pulp consistency of 12 percent at a temperature of 160 degrees F. The pulp was placed in an agitated autoclave and treated with oxygen gas at 20 psig for three min~tes, removed and diluted to 4 percent consistency using recycled filtrate from previous 9730-iR-PA
runs to simulate countercurrent conditions, then within 2 minutes pressed to 16 percent pulp consistency and then washed with water.
A comparable experiment was made utilizing the conventional oxygen alkali extraction with 90 minutes total retention by the long retention method. -The data in the table show that the press oxygen alkaIi -extraction achieves substantially the same ~appa number as 10 the conventional oxygen alkali extraction method and that the press oxygen alkali extraction method achieves sub-stantially the same reduction in Kappa number as the conventional method.
. .
-I~LE~ -Oxygen Alkali Extraction of Softwood Rraft Pulp ~r Unbleached Rappa No. 25.3 Viscosity 29.8mPa(0.5% CED) E
-Chlorination conditions: 5.1% Chlorine on pulp including 0.5% Chlorine Dioxide :
2.7% consistency 45 minutes at 125 F
Washed by dilution and pressing -~
Conventional OxyaenPress Oxvaen ~kali ExtractionAlkali Ext~action Conditions12% Consistency12~ Consistency
The large tower is a very large and expensive structure. For example, in a plant of about 800 tons per day, the extraction tower may be 16 feet in diameter by 60 30 feet high. The tower must be constructed of corrosion-resistant materials, for example, a tile lining inside a steel cylinder, and equipped at the bottom with dilution and -mixing equipment to effect controlled removal of the pulp to the washer.
Also, in the conventional commercial oxygen alkali extraction plant, it is often required that the ~ixture of pulp, alkali, and oxygen gas be retained in the large expensive tower for from 40 to 90 minutes before diluting 2 ~ 0~ 973 and washing. of course, the actual residence time of the pulp in the tower varies depending upon the pressure on the system, the degree of bleaching required, and the particular pulp employed. However, from 40 to 90 minutes residence time is generally required to remove significant amounts of lignin from most pulp.
This invention is a new continuous oxygen alkali extraction method and system for bleaching and delignifying wood pulp which does not require the large expensive bleaching tower and does not require the long reaction time required by the conventional oxygen alkali extraction systems and methods.
~ riefly described, the invention comprises a pressurized pulp retention apparatus adapted to retain pulp for a sufficient pre-determined time period for the extraction of chlorinated lignin by the alkali and oxygen gas. Fluid conduits are provided for feeding the pulp containing the alkali, and oxygen gas into the pressurized retention apparatus. A pulp pressing and washing apparatus for pressin~ the pulp into a pulp mat having a consistency ranging from about 16 percent to 40 percent and washing the pulp mat to a consistency ranging from about 9 percent to about 15 percent is also included. The pulp, after the lignin has been extracted, is fed from the retention apparatus to the pressing and washing apparatus.
In practicing my new method of continuous oxygen alkali extraction of chlorinated lignin from wood pulp, an aqueous solution of alkali is mixed into chlorinated and washed pulp and also pressurized oxygen gas in the form of fine bubbles is also mixed with the pulp. As soon as the alkali and oxygen have reacted with the pulp for a sufficient time to significantly remove lignin from the pulp and to bleach the pulp, the pulp is pressed to a consistency ranging from about 1~ percent to about 40 percent and washed to a con-sistency ranging from about 9 percent to about 15 percent.
~ he invention as well as its many advantages may befurther understood by reference to the following detailed description and drawing in which:
~ 97~C~
Fig~ 1 is a flow diagram illustrating one embodiment of the present invention; and Fig. 2 is a flow diagram il]ustrating another embodi-ment of the present invention.
In the various figures, like parts are referre~ to by like numbers~
Bleaching is a continuation of the cooking process in which the ligneous material and coloring matter which remain in the pulp are removed selectively with as little degradation of the pulp fiber as possible. The bleaching is done in several stages. A stage constitutes a phase starting with the addition and reaction of a chemical and/or steam with a pulp and ends with the washing of the pulp.
Chlorination, which comprises the first stage of most bleaching sequences, results in chlorinated lignin, some of which, is soluble in water and removed in the wash follo~ing chlorination. Additional chlorinated lignin may be removed - in one or more stages after the chlorination s,age or stages by methods such as oxygen alkali extraction. This invention is an improved oxygen alkali extraction method and system.
Complete removal of the chlorinated lignin is accomplished in stages following the oxygen alkali stage or stages.
Referring to the drawings and more pa~ticularly to Fig.
1, the pulp from a previous chlorination stage, is fed through conduit 10 to the pulp slurry pressing and washing apparatus 12. In the oxygen alkali extraction stage of this invention, the pulp from the apparatus 12 is conducted by means of centrifugal pump 14 to the retention apparatus 16 by means of fluid conduit 18.
In the embodiment of Fig. 1 the retention apparatus 16 is a pressurized agitated reactor vessel. The pressurized agitated reactor vessel 16 is constructed to retain pulp for a pre-determined time period and react the alkali and oxygen gas with the pulp to delignify and bleach the pulp.
The retention time in reactor lS ranges from one to five minutesO The pulp consistency in reactor 16 ranges from 0.5 percent to 4.0 percent.
The aqueous solution sf alkali is introduced into the 9730~ PA
recirculation conduit 20. The recirculation conduit 20 leads to the repulping portion of the apparatus 12. Usually sodium hydroxide at a concentration of 0.~ percent to 5.0 percent by weight of the pulp is used as the ;3lkali although 5 other suitable alkalis may be used.
Oxygen gas ranging in amount from 0.1 percent to 2.0 percent by weight of the pulp is dispersed 2S fine bubbles into the conduit 18 utilizing a venturi ejector 22 to mix the oxygen with washer f iltrate recirculated back to the 10 pressurized reactor 16 by means of conduit 24. The oxygen is at a pressure ranging froM 10 psig to 40 psig.
The pulp f rom the agitated reac~or vessel 16 is directly fed to the pulp pressing and washing apparatus 26 by means of the fluid conduit 28 ~hich directly intercon-15 nects the reactor 16 and the pressing and washing apparatus26.
The pressing and washing apparatus 26 has a structure ' similar to the structure of the pressing and washing filter described in U.S. Patent 3,772,144 patented November 13, 20 1973 by Oscar Luthi and Lawrence A. Carlsmith and entitled "Apparatus and Method for Thickening and Washing Suspensions (~ontaining Fibrous NaterialU. The pulp slurry passes into the pressurized :Eeed box 30 of the apparatus 26 and is pressed under the resilient baffle 32 to a consistency 25 ranging from about 16 percent to about 40 percent. After the pulp mat adhering to the washer drum 34 emerges from underneath the bafr'le 32 it is washed with water or recirculated filtrate and discharged from the apparatus 26 by means of high consistency stock pump 35 and pulp outlet 30 conduit 36 to a subsequent bleaching stage. In general, the pulp leaving the pressing and washing apparatus 26 has a consistency ranging from about 9 percent to about 15 per-cent.
The filtrate from the pressing and washing apparatus 26 35 is fed into the rotatable drum 34, and then through conduit line 38 into the retainer vessel 4~ from which the filtrate is pumped through line 24 to the conduit 18 by means of pump 42. A portion of the washer filtrate from line 24 is ~ 3û~ P
recirculated back to the pressing and washing apparatus 12 by means of line 20 which branches off from line 24.
In the embodiment of Fig. 2 oxygen gas is mixed with pulp having a consistency ranging from 9 percent to 15 percent. The pulp at the consistency ranging from 9 percent to 15 percent is fed by means of line 50 to the high consistency stock pump 52. The aqueous solution of alkali may be added to the line 50 ahead of the stock pump 52. The stock pump 52 discharges the pulp through pipe 54 into the high consistency mixer 56. In the embodiment of Fig. 2, the retention apparatus comprises a short length of pipe 60 extending from the high consistency pulp mixer 56. The oxygen gas is dispersed in finely divided bubbles thro~lghout the pulp. The pulp pa~ses through the short length of pipe 60 which is adapted to provide a retention time of 1 minute to 5 minutes after which the pressure of 10 psig to 40 psig is reduced through a valve 62 and the pulp is discharged - into a low consistency mixing tank 64 in which it is diluted to a consistency of about 2 to 4 percent utilizing filtrate from the pressing and washing apparatus 26. The oilute pulp is pumped by pump 6~ from the mixing tank 64 by means of fluid conduit 70 into the inlet 30 of the pressing and washing apparatus 26 where it is formed into a mat on the drum 34 of the apparatus 26 and pressed under the resilient baffle 32 to a consistency ranging from about 16 percent to about 40 percent. After emerging from underneath the baffle 32, the mat adhering to the drum 3~ is washed with water and discharged at a consistency ranging from 9 percent to 15 percent to a subsequent bleaching stage by means of high consistency stock p~mp 35 and pulp outlet conduit 36.
A laboratory experiment was conducted to produce the results shown in the table. A sample of chlorinated softwood kraft pulp of Kappa NoO 25.3 was mixed with 3 percent of sodium hydroxide by weight and a pulp consistency of 12 percent at a temperature of 160 degrees F. The pulp was placed in an agitated autoclave and treated with oxygen gas at 20 psig for three min~tes, removed and diluted to 4 percent consistency using recycled filtrate from previous 9730-iR-PA
runs to simulate countercurrent conditions, then within 2 minutes pressed to 16 percent pulp consistency and then washed with water.
A comparable experiment was made utilizing the conventional oxygen alkali extraction with 90 minutes total retention by the long retention method. -The data in the table show that the press oxygen alkaIi -extraction achieves substantially the same ~appa number as 10 the conventional oxygen alkali extraction method and that the press oxygen alkali extraction method achieves sub-stantially the same reduction in Kappa number as the conventional method.
. .
-I~LE~ -Oxygen Alkali Extraction of Softwood Rraft Pulp ~r Unbleached Rappa No. 25.3 Viscosity 29.8mPa(0.5% CED) E
-Chlorination conditions: 5.1% Chlorine on pulp including 0.5% Chlorine Dioxide :
2.7% consistency 45 minutes at 125 F
Washed by dilution and pressing -~
Conventional OxyaenPress Oxvaen ~kali ExtractionAlkali Ext~action Conditions12% Consistency12~ Consistency
3~ NaOH, 160 F3~ NaOH, 160 F
3 minutes at 203 minutes at 20 :
psig Oxygen psig Oxygen 87 minutes retention2 minutes retention Procedurewash with waterdilute at 4% con-sistency press to 16~ con-. sistency wash with water Results Kappa number 3.1 3.4 Viscosity26.1 26.5 -Final pH10.7 10.3 -
3 minutes at 203 minutes at 20 :
psig Oxygen psig Oxygen 87 minutes retention2 minutes retention Procedurewash with waterdilute at 4% con-sistency press to 16~ con-. sistency wash with water Results Kappa number 3.1 3.4 Viscosity26.1 26.5 -Final pH10.7 10.3 -
Claims (9)
1. A continuous oxygen alkali extraction method of bleaching and delignifying wood pulp comprising the steps of mixing chlorinated and washed pulp with an aqueous solution of an alkali, and with pressurized oxygen gas in the form of fine bubbles; reacting the alkali and oxygen with the pulp for a predetermined time period of from 1 to 5 minutes for removal of lignin which can be removed by the alkali and oxygen; in a pressing and washing apparatus, pressing the pulp slurry to a consistency ranging from about 16% to about 40%, and then washing the pulp slurry to a consistency ranging from about 9% to about 15%.
2. The method of claim 1 wherein the aqueous solution of an alkali is first mixed with the chlorinated and washed pulp and thereafter the pressurized oxygen gas is mixed with the pulp.
3. The method of claim 2 wherein the pressurized oxygen is mixed with the pulp at a pulp consistency ranging from 0.5% to 4.0%.
4. The method of claim 2 wherein the pressurized oxygen is mixed with the pulp at a pulp consistency ranging from 9% to 15%.
5. The method of claim 3 wherein the aqueous solution of alkali has a concentration of 0.5% to 5% by weight of the pulp, the oxygen is at a pressure ranging from 10 psig to 40 psig and the amount of oxygen introduced ranges from 0.1%
to 2% by weight of the pulp.
to 2% by weight of the pulp.
6. The method of claim 4 wherein the aqueous solution of alkali. has a concentration of 0.5% to 5% by weight of the pulp, the oxygen is at a pressure ranging from 10 psig to 40 psig and the amount of oxygen introduced ranges from 0.1% to 2% by weight of the pulp.
7. An oxygen alkali extraction system for bleaching and delignifying wood pulp comprising a pressurized pulp retention apparatus adapted to retain pulp for a sufficient predetermined time period of from 1 to 5 minutes for the extraction of chlorinated lignin by an alkali and oxygen gas;
means for feeding pulp with the alkali, and oxygen gas into the pressurized pulp retention apparatus; a pulp pressing and washing apparatus for pressing the pulp into a pulp mat having a consistency ranging from about 16% to 40% and then washing said pulp mat to a consistency ranging from about 9 to about 15%; and means for feeding the pulp from the retention apparatus to the pressing and washing apparatus after the lignin has been extracted.
means for feeding pulp with the alkali, and oxygen gas into the pressurized pulp retention apparatus; a pulp pressing and washing apparatus for pressing the pulp into a pulp mat having a consistency ranging from about 16% to 40% and then washing said pulp mat to a consistency ranging from about 9 to about 15%; and means for feeding the pulp from the retention apparatus to the pressing and washing apparatus after the lignin has been extracted.
8. An oxygen alkali extraction system in accordance with claim 7 wherein the pressurized pulp retention apparatus is an agitated reactor vessel for mixing the oxygen with pulp having a consistency of from 0.5% to 4.0%.
9. An oxygen alkali extraction system in accordance with claim 7 wherein a mixer is used for mixing the oxygen gas directly with the pulp at a consistency of from 9% to 15%; and a length of pipe connected to the mixer is adapted to retain the pulp for the said period of from 1 to 5 minutes.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US63513584A | 1984-07-27 | 1984-07-27 | |
| US635,135 | 1984-07-27 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1249904A true CA1249904A (en) | 1989-02-14 |
Family
ID=24546587
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000474986A Expired CA1249904A (en) | 1984-07-27 | 1985-02-22 | Oxygen alkali extraction of cellulosic pulp |
Country Status (6)
| Country | Link |
|---|---|
| JP (1) | JPS6141385A (en) |
| BR (1) | BR8501918A (en) |
| CA (1) | CA1249904A (en) |
| FI (1) | FI852910L (en) |
| NO (1) | NO851038L (en) |
| SE (1) | SE8501032L (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| SE0300276L (en) * | 2003-01-31 | 2003-12-09 | Kvaerner Pulping Tech | Method for bleaching cellulose pulp and bleaching line for this |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FI48486C (en) * | 1973-01-24 | 1977-07-29 | Ahlstroem Oy | Process for bleaching a pulp. |
| JPS5126302A (en) * | 1974-08-22 | 1976-03-04 | Hitachi Shipbuilding Eng Co | Sansoganjugasunyoru seruroosubutsushitsuno shorihoho |
| JPS5789690A (en) * | 1980-11-21 | 1982-06-04 | Toyo Pulp Co Ltd | Alkali oxygen delignification of fiber substance |
| JPS5940398A (en) * | 1982-08-30 | 1984-03-06 | Toshiba Corp | Memory control system |
-
1985
- 1985-02-22 CA CA000474986A patent/CA1249904A/en not_active Expired
- 1985-03-04 SE SE8501032A patent/SE8501032L/en not_active Application Discontinuation
- 1985-03-15 NO NO851038A patent/NO851038L/en unknown
- 1985-04-23 BR BR8501918A patent/BR8501918A/en unknown
- 1985-04-26 JP JP60089090A patent/JPS6141385A/en active Pending
- 1985-07-26 FI FI852910A patent/FI852910L/en not_active Application Discontinuation
Also Published As
| Publication number | Publication date |
|---|---|
| FI852910A0 (en) | 1985-07-26 |
| SE8501032L (en) | 1986-01-28 |
| JPS6141385A (en) | 1986-02-27 |
| FI852910L (en) | 1986-01-28 |
| SE8501032D0 (en) | 1985-03-04 |
| BR8501918A (en) | 1986-05-06 |
| NO851038L (en) | 1986-01-28 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US4806203A (en) | Method for alkaline delignification of lignocellulosic fibrous material at a consistency which is raised during reaction | |
| US3832276A (en) | Delignification and bleaching of a cellulose pulp slurry with oxygen | |
| US4298426A (en) | Method and apparatus for treating pulp with oxygen in a multi-stage bleaching sequence | |
| US4248662A (en) | Oxygen pulping with recycled liquor | |
| JPS61138793A (en) | Reinforcing oxidation extraction method | |
| US4295926A (en) | Method and apparatus for treating pulp with oxygen | |
| EP0060104B1 (en) | Drying wood pulp | |
| US4310384A (en) | Reducing chemical transfer between treatment stages | |
| EP0056263B1 (en) | A method for improving the washing of cellulose pulps produced from lignocellulosic material | |
| US4295927A (en) | Method and apparatus for treating pulp with oxygen and storing the treated pulp | |
| CA1207503A (en) | Processes for bleaching wood pulp | |
| EP0106609A1 (en) | Apparatus and method for oxygen extraction of lower consistency pulp | |
| US4406735A (en) | Process for alkaline oxygen gas bleaching of cellulose pulp | |
| JPH06184974A (en) | Method for bleaching of rignocellulose pulp and method for recovering of oxygen-enriched gas | |
| CA1249904A (en) | Oxygen alkali extraction of cellulosic pulp | |
| CA1147909A (en) | Method for delignifying and/or bleaching cellulose pulp | |
| CA1275759C (en) | Method and apparatus for alkaline delignification of lignocellulosic fibrous material | |
| CA2484557A1 (en) | Low consistency oxygen delignification process | |
| US3992250A (en) | Method for bleaching of high consistency cellulosic pulp | |
| JPH05247864A (en) | Bleaching of cellulose pulp | |
| KR100194405B1 (en) | Chlorine-Free Bleaching Method of Wood Pulp | |
| EP0087412B1 (en) | Method and apparatus for mixing pulp with gases | |
| EP0720676A1 (en) | Improved method for bleaching lignocellulosic pulp | |
| US6315863B1 (en) | Chlorine dioxide pulp bleaching process having reduced barium scaling by recycling post-chlorination waste filtrate | |
| AU647485B2 (en) | Pulp alkali addition process for high consistency oxygen delignification |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |