CA1065105A - Method for bleaching of material containing cellulose - Google Patents
Method for bleaching of material containing celluloseInfo
- Publication number
- CA1065105A CA1065105A CA215,743A CA215743A CA1065105A CA 1065105 A CA1065105 A CA 1065105A CA 215743 A CA215743 A CA 215743A CA 1065105 A CA1065105 A CA 1065105A
- Authority
- CA
- Canada
- Prior art keywords
- pulp
- bleaching
- oxidizing gas
- pressure
- pulp suspension
- 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
-
- 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
- D21C9/1036—Use of compounds accelerating or improving the efficiency of the processes
Abstract
ABSTRACT OF THE DISCLOSURE
An improved method of bleaching cellulosic material with an oxidizing gas in an alkaline environment in which a pulp suspension is treated with an alkali solution at an elevated temperature and pressure in the presence of an oxidizing gas to effect removal of lignin wherein the improvement comprises transforming the pulp suspension into a stable foam in the presence of a foaming agent.
An improved method of bleaching cellulosic material with an oxidizing gas in an alkaline environment in which a pulp suspension is treated with an alkali solution at an elevated temperature and pressure in the presence of an oxidizing gas to effect removal of lignin wherein the improvement comprises transforming the pulp suspension into a stable foam in the presence of a foaming agent.
Description
10tj5105 The present invention relates to a method of bleaching ~ cellulosic containing material with an oxidizing gas, par-,; ticularly oxygen gas, in an alkaline envirament, particularly in connection with production of pulp according to the sulphate method.
Up until the present teachings, oxygen gas bleaching of pulp was usually carried out in order that after washing ~ and pressing to remove the liquid from the fibers of the pulp,- 10 the iber concentration of the pulp was approximately 30%.
, Subsequently, the amount of alkali (NaOH solution) which -~ is requiréd for bleaching is added and the pulp stirred '' which results in a concentration decrease down to approximately ~! 25%. The pulp i~ then fed into a reactor and disintegrated by a shredder which is located at the upper part of the reactor in accordance with the method as outlined in Swedish patent 333,498.
The earlier proposed method has certain drawbacks which the present invention will eliminate as described in more detail as follows.
In accordance with the present teachings, oxygen is used in the bleaching in place of chlorine in order to ~- act on the lignin in the wood fibers so that the lignin may be eliminated. As the bleaching agent also effects the cellulose of the material, but at a slower rate, it is ; desirable that the reaction take place as selectively as , possible, that is, so that the lignin is eliminated as .~ quickly as possible and the cellulose is effected as little as possible.
.'' ~
: ~. . . , -: , ~ :
The oxygen gas bleaching involves a process employing alkali, water, heat and oxygen in order to delignify cellulose fibers. The amount of reagents (2~ NaOH) which is transferred to the fiber is directly dependent on the size of the phase surface, which at a maximum can be the outer surface of the fiber~ This presupposes that the fibers are detached from each other. If on the other hand the fibers are flocculated together, the total contact surface of the fibers becomes smaller and the required reaction time for release of the lignin from the fibers located in the interior of the 10ck thereby becomes longer. This may result in over bleaching of the fibers taking place at the outer surface of the flocks where even the cellulose in the fiber may be effected and the bleaching becomes uneven. When the fibers are detached from each other, a homogeneous bleaching result is attained.
Pulp with a high fiber concentration is difficult to process and problems are encountered in mixing the required amount of alkali into the pulp and because of this the alkali becomes unevenly distributed. Pulp with high fiber concen-trations are also difficult to transport to the reaction vessel. With the presently known operations, it was previously impossible to feed the pulp into the reaction vessel in forms other than flocks.
The known methods for oxygen bleaching till now required, due to the presence of flocks, longer reaction times which results in the reactor having to be of larger size.
-~ The ,nnermost and outermost fibers in the fiber flock have - different strengths and viscosities and as the alkali may become unevenly distributed, the desired bleaching is not completed in some areas.
The amount of oxygen needed for removal of lignin from cellulose fibers is about 1 to I.S~ by weight of the pulp.
A reactor which has a volume of 1 m3 contains approximately 100 kg of wet fluffy pulp which is approximately 25% fiber concentration or 25 kg dry cellulose. If the reaction takes '~ place under a pressure of 10 kp/cm2, the amount of oxygen : .~
.,, ~,.~, ;:.. ,: ,. : . :
,:
:
.. :: . :. . :.: . , 10~i5105 required is approximately 10 kg, i.e. more than 30 times the quantity required thus the reaction requires a very large excess of oxygen.
In contrast, and in accordance with the present method, the amount of oxygen may now be revised so that it corresponds - to the quality which is actually required. According to prior methods, it was not possible to mix into the pulp as much gas as would be needed as the gas forms a continuous phase andthe pulp-alkali-water a dispersed phase. In accordance with the present teachings, the proportion is in the reverse, with the gas forming the dispersed phase and the pulp-alkali-water the continuous phase.
The purpose of the present invention is to eliminate the drawbacks of the prior art processes whereby bleaching will now take place in the presence of surface active agents which act to make small oxygen gas bubbles to form a stable foam whereby the fibers are dispersed.
In accordance with a preferred embodiment of the present teachings, the foaming agent is added to the pulp suspension before it is ~rought into contact with the oxygen gas thus the oxygen gas feed may be utilized to effect the foaming .
I In accordance with the present procedure, reduction of pressure may be effected before bleaching whereby the bubbles of oxygen gas in the stable foam are expanded.
At times, no foaming agent is required to be added particularly if the pulp suspension after the digestion is permitted to retain, after washing, a sufficient quantity of lye which will act as foaming agent. A sufficient quantity of foaming agent is 1 kg/ton pulp.
Thus, in accordance with the present teachings, an improvement is provided in a method of bleaching cellulosic material with an oxidizing gas in an alkaline enviroment in [:
~ which a pulp suspension which has a maximum consistency of ;:~
15% is treated with an alkali solution and the oxidizing gas for effecting removal of lignin from the cellulosic material such treatment being effected at elevated temperature and pressure, wherein the improvement aomprises transforming ','',' ~:~,' . ; .
:
',' '`': ' , ~ .' ',' ' ' ', , : , .
': ''` .` ' '' . ', ~ :: .. .: ' ,`', : ,: . `':. ' ... ,, :' ' , , '' ~ : ~ ' :
10~51~5 the pulp suspension into a stable foam in the presence of 21 foaming agent.
In the following, the present invention is described in ~ore detail with reference to the drawings wherein Figures 1 and 2 show alternative embodiments for application of the present process in accordance with the teachings.
With respect to Figure 1, reference numeral 1 indicates a digester which is provided with a washing zone, wherein the lye, after diges.ion is removed from the pulp with the pulp being conducted through a blow pipe 2 to a mixer 3.
The mixer may be a defibrator. Alkali is added through pipe 4 to the pulp with oxygen being introduced through 5 and a foaming agent via 6. From the mixer 3, the pulp flows through pipe 7 into the bleaching reactor 8. A portion of lS the oxygen gas as well as the foaming agent is added before or into the mixture with the remaining oxygen and alkali solution being added into the reactor, preferably so that percolation ; and circulation may take place. From the reactor 8, the pulp , passes through line 9 to a washing diffuser 10 wherein the pulp may be washed with additional alkali. Between the bleaching and the washing, the pressure is reduced and the ; pulp degassified in apparatus 11. Between the mixer and the reactor, a pressure reducing valve may be installed whereby the pressure in the reactor may be regulated to be at a lower value than that of the digester. Because of the reduced pressure, the bubbles expand in the foamy pulp.
If necessary, steam may also be added to the pulp in order to raise the temperature. To bring about foam formation, the lye remaining in the pulp after digestion and washing may be utilized and/or synthetic foaming agents may be added , such as polyoxyalkylene-condensates, dodecylbenzenesulphonate and octylphenoxypolyethoxyethanol.
In accordance with prior art teachings, foam formation in pulp had been attempted to be avoided as causing an inconvenience and because of this any lye which was present was washed away and removed as much as possible. In accordance with the present teachings, foam is employed for dispersion '' ~.,.,'~
,., . . . -. . . ~
.. . ..
- 10~5105 of the fibers and the foam has been found to facilitate the transport of the pulp. Inhibitors may be fed in before or after the mixer.
In place of oxygen gas, air or other gases as for example ozone C12, C12 + C102 or gaseous mixtures may be used. In accordance with the present teachings, the reaction time is considerably shortened and requires about 10 to 20 minutes in comparison to the prior methods which require 30 to 60 minutes. It is thus seen that the volume of the bleaching reactor may be considerably smaller and for example may even be a pipe which has a suitable length.
The tests which were carried out show that the method may be employed at fiber concentrations of approximately up to 15~. In cellulose production, in a continuous digester, the pulp may have a concentration amounting to approximately 10% which is a value suitable for application of the present concept, The method is illustrated by the following examples.
Example 1 ~ A test reactor was filled with pulp which had been ; impregnated with oxygen gas and heated with steam. A
NaOH solution was allowed to percolate through the pulp during circulation. Bleaching tests were performed under the same conditions with pulp containing 1% TEEPOL (Shell's trade mark), a synthetic washing detergent, which was foamed in a mixture, as well as ordinary pulp.
~ Before the tests, the kappa-figure and viscosity of - the pulp where:
K = 29.3 ;~ n = 1086 After percolation with NaOH solution with the following prerequisites:
- alkali charge 6~
pressure 4 ato temperature 110C
:
pulp consistency 8%
time 15 min.
' . , . ; : .: -,; : . . .. .
. ,, : . .. ~ . - , .;
, 5J,(JS
the kappa-figure and viscosity of the pulp were Test 1: with foam Test 2: without foam = 16.5 K = 22.4 n =985 It is difficult to obtain a lower kappa-figure than 20 without foam and without increasing the consistency to over 10%. When the pulp consistency is increased, the bleaching results were uneven.
In tests wherein no foam was employed and with an alkali charge of over 10% with the same prerequisites as in previous tests, the following results were obtained:
Test 3: without foam K = 21.2 n = soo A comparison between the results of test 1 and test 3 clearly indicates that with the same viscosity, a lower kappa-figure was obtained when foam was employed. Treatment without foam requires higher alkali charge.
:' ~!!!e~
Sulphate cellulose pulp which has a fiber concentration ; of 10% was treated in an apparatus in accordance with that ~; shown in Figure 2. The pulp suspension was blown out of the digester 1, at a pressure of 15 kp/cm2 and at a temper-ature of 90C. In the blow pipe 2, and before the mixer, via pipe 4 there was added to the pulp about 30 kg of NaOH/ton ~; ce~lulose and via pipe 6 a foaming agent containing polyoxyalkylene-condensate as well as octylphenoxypolyethoxyethanol to approximately 0.5 kg/ton cellulose and through pipe 5 was ~ added approximately 10 kg oxygen/ton cellulose. The mixture -~ 30 was than mixed in mixer 3 at a temperature of 120C whereby -- stable foam is obtained which was fed via pipe 7 into reactor 8. The pressure had been reduced to a pressure of 3 kp/cm through i valve 12 in pipe 7. Apparatus 11 acts to decrease the pressure -~ to 1 kp/cm2. After removal of the liquid containing unused chemical, such liquid may be recycled through return pipes ~i 13 and 14 to the reactor and to the digester respectfully.
The pulp is finally washed in diffuser 10 whereby a pulp having ~;i a viscosity of 900 cm3/g and a kappa-figure equal to 14 was '': ~"~
: , : , . ,,,, - . , : :
','",,'',, ' ', ',: . ~- ' ''. :
lV5 obtained while the corresponding value after the digester l were 1080 cm /g and 29. It is thus readily seen that the viscosity of the pulp had not decreased to any appreciable extent however on the other hand considerable decrease in the kappa-figure of the pulp was experienced.
, 10 ~,~
.~ .
i, .
:
~, ., , , .
.
.
Up until the present teachings, oxygen gas bleaching of pulp was usually carried out in order that after washing ~ and pressing to remove the liquid from the fibers of the pulp,- 10 the iber concentration of the pulp was approximately 30%.
, Subsequently, the amount of alkali (NaOH solution) which -~ is requiréd for bleaching is added and the pulp stirred '' which results in a concentration decrease down to approximately ~! 25%. The pulp i~ then fed into a reactor and disintegrated by a shredder which is located at the upper part of the reactor in accordance with the method as outlined in Swedish patent 333,498.
The earlier proposed method has certain drawbacks which the present invention will eliminate as described in more detail as follows.
In accordance with the present teachings, oxygen is used in the bleaching in place of chlorine in order to ~- act on the lignin in the wood fibers so that the lignin may be eliminated. As the bleaching agent also effects the cellulose of the material, but at a slower rate, it is ; desirable that the reaction take place as selectively as , possible, that is, so that the lignin is eliminated as .~ quickly as possible and the cellulose is effected as little as possible.
.'' ~
: ~. . . , -: , ~ :
The oxygen gas bleaching involves a process employing alkali, water, heat and oxygen in order to delignify cellulose fibers. The amount of reagents (2~ NaOH) which is transferred to the fiber is directly dependent on the size of the phase surface, which at a maximum can be the outer surface of the fiber~ This presupposes that the fibers are detached from each other. If on the other hand the fibers are flocculated together, the total contact surface of the fibers becomes smaller and the required reaction time for release of the lignin from the fibers located in the interior of the 10ck thereby becomes longer. This may result in over bleaching of the fibers taking place at the outer surface of the flocks where even the cellulose in the fiber may be effected and the bleaching becomes uneven. When the fibers are detached from each other, a homogeneous bleaching result is attained.
Pulp with a high fiber concentration is difficult to process and problems are encountered in mixing the required amount of alkali into the pulp and because of this the alkali becomes unevenly distributed. Pulp with high fiber concen-trations are also difficult to transport to the reaction vessel. With the presently known operations, it was previously impossible to feed the pulp into the reaction vessel in forms other than flocks.
The known methods for oxygen bleaching till now required, due to the presence of flocks, longer reaction times which results in the reactor having to be of larger size.
-~ The ,nnermost and outermost fibers in the fiber flock have - different strengths and viscosities and as the alkali may become unevenly distributed, the desired bleaching is not completed in some areas.
The amount of oxygen needed for removal of lignin from cellulose fibers is about 1 to I.S~ by weight of the pulp.
A reactor which has a volume of 1 m3 contains approximately 100 kg of wet fluffy pulp which is approximately 25% fiber concentration or 25 kg dry cellulose. If the reaction takes '~ place under a pressure of 10 kp/cm2, the amount of oxygen : .~
.,, ~,.~, ;:.. ,: ,. : . :
,:
:
.. :: . :. . :.: . , 10~i5105 required is approximately 10 kg, i.e. more than 30 times the quantity required thus the reaction requires a very large excess of oxygen.
In contrast, and in accordance with the present method, the amount of oxygen may now be revised so that it corresponds - to the quality which is actually required. According to prior methods, it was not possible to mix into the pulp as much gas as would be needed as the gas forms a continuous phase andthe pulp-alkali-water a dispersed phase. In accordance with the present teachings, the proportion is in the reverse, with the gas forming the dispersed phase and the pulp-alkali-water the continuous phase.
The purpose of the present invention is to eliminate the drawbacks of the prior art processes whereby bleaching will now take place in the presence of surface active agents which act to make small oxygen gas bubbles to form a stable foam whereby the fibers are dispersed.
In accordance with a preferred embodiment of the present teachings, the foaming agent is added to the pulp suspension before it is ~rought into contact with the oxygen gas thus the oxygen gas feed may be utilized to effect the foaming .
I In accordance with the present procedure, reduction of pressure may be effected before bleaching whereby the bubbles of oxygen gas in the stable foam are expanded.
At times, no foaming agent is required to be added particularly if the pulp suspension after the digestion is permitted to retain, after washing, a sufficient quantity of lye which will act as foaming agent. A sufficient quantity of foaming agent is 1 kg/ton pulp.
Thus, in accordance with the present teachings, an improvement is provided in a method of bleaching cellulosic material with an oxidizing gas in an alkaline enviroment in [:
~ which a pulp suspension which has a maximum consistency of ;:~
15% is treated with an alkali solution and the oxidizing gas for effecting removal of lignin from the cellulosic material such treatment being effected at elevated temperature and pressure, wherein the improvement aomprises transforming ','',' ~:~,' . ; .
:
',' '`': ' , ~ .' ',' ' ' ', , : , .
': ''` .` ' '' . ', ~ :: .. .: ' ,`', : ,: . `':. ' ... ,, :' ' , , '' ~ : ~ ' :
10~51~5 the pulp suspension into a stable foam in the presence of 21 foaming agent.
In the following, the present invention is described in ~ore detail with reference to the drawings wherein Figures 1 and 2 show alternative embodiments for application of the present process in accordance with the teachings.
With respect to Figure 1, reference numeral 1 indicates a digester which is provided with a washing zone, wherein the lye, after diges.ion is removed from the pulp with the pulp being conducted through a blow pipe 2 to a mixer 3.
The mixer may be a defibrator. Alkali is added through pipe 4 to the pulp with oxygen being introduced through 5 and a foaming agent via 6. From the mixer 3, the pulp flows through pipe 7 into the bleaching reactor 8. A portion of lS the oxygen gas as well as the foaming agent is added before or into the mixture with the remaining oxygen and alkali solution being added into the reactor, preferably so that percolation ; and circulation may take place. From the reactor 8, the pulp , passes through line 9 to a washing diffuser 10 wherein the pulp may be washed with additional alkali. Between the bleaching and the washing, the pressure is reduced and the ; pulp degassified in apparatus 11. Between the mixer and the reactor, a pressure reducing valve may be installed whereby the pressure in the reactor may be regulated to be at a lower value than that of the digester. Because of the reduced pressure, the bubbles expand in the foamy pulp.
If necessary, steam may also be added to the pulp in order to raise the temperature. To bring about foam formation, the lye remaining in the pulp after digestion and washing may be utilized and/or synthetic foaming agents may be added , such as polyoxyalkylene-condensates, dodecylbenzenesulphonate and octylphenoxypolyethoxyethanol.
In accordance with prior art teachings, foam formation in pulp had been attempted to be avoided as causing an inconvenience and because of this any lye which was present was washed away and removed as much as possible. In accordance with the present teachings, foam is employed for dispersion '' ~.,.,'~
,., . . . -. . . ~
.. . ..
- 10~5105 of the fibers and the foam has been found to facilitate the transport of the pulp. Inhibitors may be fed in before or after the mixer.
In place of oxygen gas, air or other gases as for example ozone C12, C12 + C102 or gaseous mixtures may be used. In accordance with the present teachings, the reaction time is considerably shortened and requires about 10 to 20 minutes in comparison to the prior methods which require 30 to 60 minutes. It is thus seen that the volume of the bleaching reactor may be considerably smaller and for example may even be a pipe which has a suitable length.
The tests which were carried out show that the method may be employed at fiber concentrations of approximately up to 15~. In cellulose production, in a continuous digester, the pulp may have a concentration amounting to approximately 10% which is a value suitable for application of the present concept, The method is illustrated by the following examples.
Example 1 ~ A test reactor was filled with pulp which had been ; impregnated with oxygen gas and heated with steam. A
NaOH solution was allowed to percolate through the pulp during circulation. Bleaching tests were performed under the same conditions with pulp containing 1% TEEPOL (Shell's trade mark), a synthetic washing detergent, which was foamed in a mixture, as well as ordinary pulp.
~ Before the tests, the kappa-figure and viscosity of - the pulp where:
K = 29.3 ;~ n = 1086 After percolation with NaOH solution with the following prerequisites:
- alkali charge 6~
pressure 4 ato temperature 110C
:
pulp consistency 8%
time 15 min.
' . , . ; : .: -,; : . . .. .
. ,, : . .. ~ . - , .;
, 5J,(JS
the kappa-figure and viscosity of the pulp were Test 1: with foam Test 2: without foam = 16.5 K = 22.4 n =985 It is difficult to obtain a lower kappa-figure than 20 without foam and without increasing the consistency to over 10%. When the pulp consistency is increased, the bleaching results were uneven.
In tests wherein no foam was employed and with an alkali charge of over 10% with the same prerequisites as in previous tests, the following results were obtained:
Test 3: without foam K = 21.2 n = soo A comparison between the results of test 1 and test 3 clearly indicates that with the same viscosity, a lower kappa-figure was obtained when foam was employed. Treatment without foam requires higher alkali charge.
:' ~!!!e~
Sulphate cellulose pulp which has a fiber concentration ; of 10% was treated in an apparatus in accordance with that ~; shown in Figure 2. The pulp suspension was blown out of the digester 1, at a pressure of 15 kp/cm2 and at a temper-ature of 90C. In the blow pipe 2, and before the mixer, via pipe 4 there was added to the pulp about 30 kg of NaOH/ton ~; ce~lulose and via pipe 6 a foaming agent containing polyoxyalkylene-condensate as well as octylphenoxypolyethoxyethanol to approximately 0.5 kg/ton cellulose and through pipe 5 was ~ added approximately 10 kg oxygen/ton cellulose. The mixture -~ 30 was than mixed in mixer 3 at a temperature of 120C whereby -- stable foam is obtained which was fed via pipe 7 into reactor 8. The pressure had been reduced to a pressure of 3 kp/cm through i valve 12 in pipe 7. Apparatus 11 acts to decrease the pressure -~ to 1 kp/cm2. After removal of the liquid containing unused chemical, such liquid may be recycled through return pipes ~i 13 and 14 to the reactor and to the digester respectfully.
The pulp is finally washed in diffuser 10 whereby a pulp having ~;i a viscosity of 900 cm3/g and a kappa-figure equal to 14 was '': ~"~
: , : , . ,,,, - . , : :
','",,'',, ' ', ',: . ~- ' ''. :
lV5 obtained while the corresponding value after the digester l were 1080 cm /g and 29. It is thus readily seen that the viscosity of the pulp had not decreased to any appreciable extent however on the other hand considerable decrease in the kappa-figure of the pulp was experienced.
, 10 ~,~
.~ .
i, .
:
~, ., , , .
.
.
Claims (8)
1. In a method of bleaching cellulosic material with an oxidizing gas in an alkaline material, in which a pulp suspension having a maximum consistency of 15% is treated with an alkali solution and an oxidizing gas for removal of lignin from the cellulosic material at elevated temperature and pressure, the improvement comprising transforming the pulp suspension into a stable foam in the presence of a foaming agent.
2. The method of Claim 1, wherein the foaming agent is added to the pulp suspension before it is brought into contact with the oxidizing gas.
3. The method of Claim 1, wherein the oxidizing gas is added to the pulp suspension before it is brought into contact with the alkali solution.
4. The method of Claim 1, in which the bleaching is carried out at a pressure which is lower than the pressure at which the oxidizing gas is added in order to expand the oxidizing gas in the foaming pulp suspension.
5. The method of Claim 4, wherein the stable foam is formed by agitation, the pressure at the agitation being controlled to approximately 15 kp/cm2 and reduced to approximately 3 kp/cm2 before the bleaching.
6. The method of Claim 1, wherein as foaming agent is used at least one agent selected from waste liquor and synthetic foaming agents.
7. The method of Claim 6 wherein said foaming agent is selected from the group of polyoxyalkylene-condensate, dodecyl-benzene-sulphonate and octyl-phenoxy-polyethoxy-ethanol.
8. The method of Claim 1, wherein oxygen gas is used as bleaching agent.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| SE7317221A SE390549C (en) | 1973-12-20 | 1973-12-20 | SET TO BLOW CELLULOSIC MATERIAL WITH ACID OR FREE ACID CONTAINING GAS IN ALKALIC ENVIRONMENT |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1065105A true CA1065105A (en) | 1979-10-30 |
Family
ID=20319462
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA215,743A Expired CA1065105A (en) | 1973-12-20 | 1974-12-11 | Method for bleaching of material containing cellulose |
Country Status (12)
| Country | Link |
|---|---|
| JP (1) | JPS524643B2 (en) |
| BR (1) | BR7410652D0 (en) |
| CA (1) | CA1065105A (en) |
| DE (1) | DE2460144B2 (en) |
| FI (1) | FI52878C (en) |
| FR (1) | FR2255419B1 (en) |
| GB (1) | GB1452710A (en) |
| IT (1) | IT1027773B (en) |
| NO (1) | NO142128C (en) |
| SE (1) | SE390549C (en) |
| SU (1) | SU850019A3 (en) |
| ZA (1) | ZA747918B (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0397308A2 (en) * | 1989-05-10 | 1990-11-14 | A. Ahlstrom Corporation | Method of bleaching cellulose pulp with ozone |
| US5460696A (en) * | 1993-08-12 | 1995-10-24 | The Boc Group, Inc. | Oxygen delignification method incorporating wood pulp mixing apparatus |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS563214Y2 (en) * | 1978-05-15 | 1981-01-24 | ||
| US4209359A (en) * | 1978-10-23 | 1980-06-24 | International Paper Company | Process for removing residual oxygen from oxygen-bleached pulp |
| SE462919B (en) * | 1979-05-11 | 1990-09-17 | Sunds Defibrator Ind Ab | PROCEDURE TO PERFORM ALKALIE EXTRACTION OF CELLULOSAMASS IN THE PRESENCE OF ACID |
| US4574032A (en) * | 1979-10-15 | 1986-03-04 | Westvaco Corporation | Process for delignification of lignocellulosic material in the presence of anthraquinone in solution with white and black liquors |
| SE452896B (en) * | 1985-01-24 | 1987-12-21 | Aga Ab | METHOD OF TREATING CELLULOSAMASSOR |
| SE460202B (en) * | 1987-03-13 | 1989-09-18 | Aga Ab | SEATED AS TREATMENT OF A MATERIAL WITH A GAS IN A SCIENCE |
-
1973
- 1973-12-20 SE SE7317221A patent/SE390549C/en unknown
-
1974
- 1974-12-11 CA CA215,743A patent/CA1065105A/en not_active Expired
- 1974-12-12 ZA ZA00747918A patent/ZA747918B/en unknown
- 1974-12-13 GB GB5403874A patent/GB1452710A/en not_active Expired
- 1974-12-19 SU SU742090807A patent/SU850019A3/en active
- 1974-12-19 FI FI743702A patent/FI52878C/en active
- 1974-12-19 NO NO744609A patent/NO142128C/en unknown
- 1974-12-19 BR BR10652/74A patent/BR7410652D0/en unknown
- 1974-12-19 JP JP49146650A patent/JPS524643B2/ja not_active Expired
- 1974-12-19 DE DE19742460144 patent/DE2460144B2/en not_active Ceased
- 1974-12-19 IT IT70687/74A patent/IT1027773B/en active
- 1974-12-20 FR FR7442400A patent/FR2255419B1/fr not_active Expired
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0397308A2 (en) * | 1989-05-10 | 1990-11-14 | A. Ahlstrom Corporation | Method of bleaching cellulose pulp with ozone |
| EP0397308B1 (en) * | 1989-05-10 | 1996-10-09 | A. Ahlstrom Corporation | Method of bleaching cellulose pulp with ozone |
| US6547923B1 (en) * | 1989-05-10 | 2003-04-15 | Andritz Oy | Process for bleaching medium consistency pulp with ozone using a pressurized fluidizing mixer |
| US6579411B1 (en) * | 1989-05-10 | 2003-06-17 | Andritz Oy | Bleaching medium consistency pulp with ozone |
| US5460696A (en) * | 1993-08-12 | 1995-10-24 | The Boc Group, Inc. | Oxygen delignification method incorporating wood pulp mixing apparatus |
| US5591308A (en) * | 1993-08-12 | 1997-01-07 | The Boc Group, Inc. | Wood pulp reactor |
Also Published As
| Publication number | Publication date |
|---|---|
| ZA747918B (en) | 1975-12-31 |
| SE7317221L (en) | 1975-06-23 |
| FI370274A (en) | 1975-06-21 |
| FI52878C (en) | 1987-09-24 |
| NO744609L (en) | 1975-07-14 |
| IT1027773B (en) | 1978-12-20 |
| NO142128B (en) | 1980-03-24 |
| FR2255419B1 (en) | 1979-06-01 |
| BR7410652D0 (en) | 1975-09-02 |
| SE390549C (en) | 1985-10-17 |
| FI52878B (en) | 1977-08-31 |
| GB1452710A (en) | 1976-10-13 |
| FR2255419A1 (en) | 1975-07-18 |
| JPS5094202A (en) | 1975-07-26 |
| DE2460144B2 (en) | 1977-03-03 |
| NO142128C (en) | 1980-07-02 |
| SE390549B (en) | 1976-12-27 |
| SU850019A3 (en) | 1981-07-23 |
| DE2460144A1 (en) | 1975-07-03 |
| JPS524643B2 (en) | 1977-02-05 |
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