CA1081908A - Method of improving the homogenity at periodical digestion of ligno-cellulose containing material - Google Patents
Method of improving the homogenity at periodical digestion of ligno-cellulose containing materialInfo
- Publication number
- CA1081908A CA1081908A CA249,635A CA249635A CA1081908A CA 1081908 A CA1081908 A CA 1081908A CA 249635 A CA249635 A CA 249635A CA 1081908 A CA1081908 A CA 1081908A
- Authority
- CA
- Canada
- Prior art keywords
- digester
- boiling
- circulation
- digestion
- minutes
- 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
- 238000000034 method Methods 0.000 title claims abstract description 33
- 230000029087 digestion Effects 0.000 title claims abstract description 17
- 229920002678 cellulose Polymers 0.000 title claims abstract description 5
- 239000001913 cellulose Substances 0.000 title claims abstract description 5
- 239000000463 material Substances 0.000 title claims abstract description 5
- 230000004087 circulation Effects 0.000 claims abstract description 40
- 238000010438 heat treatment Methods 0.000 claims abstract description 22
- 239000007788 liquid Substances 0.000 claims abstract description 17
- 238000010411 cooking Methods 0.000 claims abstract description 11
- 238000012856 packing Methods 0.000 claims description 5
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 7
- 229910052801 chlorine Inorganic materials 0.000 description 7
- 239000000460 chlorine Substances 0.000 description 7
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 6
- 239000002023 wood Substances 0.000 description 5
- 239000003513 alkali Substances 0.000 description 4
- 238000009835 boiling Methods 0.000 description 3
- 238000012216 screening Methods 0.000 description 3
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 2
- 238000001816 cooling Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000009434 installation Methods 0.000 description 2
- 229910021653 sulphate ion Inorganic materials 0.000 description 2
- 230000007423 decrease Effects 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 230000008092 positive effect Effects 0.000 description 1
- 238000004537 pulping Methods 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
- D21C3/00—Pulping cellulose-containing materials
- D21C3/22—Other features of pulping processes
Landscapes
- Paper (AREA)
- Dry Formation Of Fiberboard And The Like (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A method of improving homogeneity in batch digestion of ligno-cellulose containing material in a digester, the circulation system of which is designed so that the cooking liquid is drawn off from the digester via a strainer girdle, heated in a calorisator and returned to the top and bottom, respectively, of the digester. During the heating phase the digester is subjected to boiling-up brought about by periodically heating only from below by a substantial supply of heat via the bottom circulation with a cooking liquid flow of 1-15m3/minute, preferably .3-8m3/minute, at the same time as the top circulation is held closed and pressure drop in the digester is prevented. The number of the boilings-up and the time intervals are adjusted to the digestion schedule in question, so that the greatest possible heat homogeneity in the digester is obtained during the entire part of the digesting process when delignification takes place.
A method of improving homogeneity in batch digestion of ligno-cellulose containing material in a digester, the circulation system of which is designed so that the cooking liquid is drawn off from the digester via a strainer girdle, heated in a calorisator and returned to the top and bottom, respectively, of the digester. During the heating phase the digester is subjected to boiling-up brought about by periodically heating only from below by a substantial supply of heat via the bottom circulation with a cooking liquid flow of 1-15m3/minute, preferably .3-8m3/minute, at the same time as the top circulation is held closed and pressure drop in the digester is prevented. The number of the boilings-up and the time intervals are adjusted to the digestion schedule in question, so that the greatest possible heat homogeneity in the digester is obtained during the entire part of the digesting process when delignification takes place.
Description
l~Bl~O~
This invention relates to a method of obtaining homogenous pulping in batch digestion of a ligno-cellulose containing material in a digester, the circulation system of which is so designed, that the cooking liquld is drawn off from the digester, heated in a calorisator and returned to the top and bottom, respectively, of the digester.
Uniform digestion is of great importance at all pulp manufacturing processes, both with respect to economy and to the quality of the pulp. The causes of non-uniform digestion vary with the type of process. In Swedish . ~or* 0~7e i~
patent specification 345 885 the most important factors influencing~n~fflege~ty in batch digestion are listed, and a method is disclosed which has the object of eliminating negative effects of the commonest dominating factor, via. the cooking liquid circulation.
The technique applied according to the method, i.e. heat boiling-up, according to operating experience in a mill installation has very positive effects on the homogenity at the digestion. According to this method, the boilings-up are carried out by rapid decreases in pressure in order to effect upward flows and thereby temperature balance in the digester. This takes place either by violent gassing or by the intake of cooling liquor at the digester top.
From continued experiments for developing the boiling method, a new method has been worked out. According to the present invention, there is pro-~ o~o9 vided a method of improving the-~me~cnit~ in batch digestion of ligno-cellulose containing material in a digester having a circulation system wherein cooking liquid is drawn off from the digester via a strainer girdle, heated in a calorisator and returned to the top and bottom, respectively, of the digester, wherein the digester during the heating phase is subjected to boiling-up, brought about by periodically providing heating at only the bottom of the digester by supplying the bottom circulation with a cooking liquid flow of 1-15m3/minute, at the same time as the top circulation is held closed and - 1 - ~ ' 1~8~
pressure drop in the digester is prevented. ~leating from below results in boiling-up, which ensures that heat is also distributed to poorly heated 7ones.
This heating, if it is to be carried out within a reasonable time and without risk of extra incrustration in the calorisator, requires a rela-tively large diameter bottom circulation conduit, so that a sufficiently great circulation flow during the boiling-up is provided.
One advantage of the new method is, that its installation is simpler and cheaper than in the case of the previously known boiling method, and at the same time a very uniformly digested pulp with a low shives content is obtained.
The first boiling-up preferably is carried out at the time when the chlorine number of the pulp is 30-20, i.e. at the time when delignification is becoming substantial, but before much delignification has actually taken place. The number of boilings-up and the time intervals between them should be adjusted to the digestion schedule in question, so that for the duration of the boiling process when delignification takes place the greatest possible ~ n~og~
heat ~homog~ity in the digester is obtained.
The duration of each boiling-up can vary, but should be at least 10 seconds. A normal duration is 1-30 minutes, suitably 2-20 minutes, and prefer-ably 4-10 minutes.
In order to obtain efficient boiling-up, the bottom circulation conduit should be so dimensioned that the bottom circulation flow at the boilings-up is l-lSm3/min, suitably 2~12m3/min and preferably 3-8m3/min.
The digester, furthermore, should be well degassed when the boilings-up are carried out.
By periodically closing the bottom circulation after boiling-up, an increase of the top circulation immediately after boiling-up is brought about, which is favourable to the digesting process.
In order to reduce packing of the digester content, the top circula-. ~ , .
.
- ~819~
tion can periodically be limited prior and/or subsequent to the boilings-up.
The characterizing features of the invention will be apparent from the claims.
The invention will further be described, by way of example only, with reference to the accompanying Figure which shows an apparatus for carrying out the method according to the invention.
The digester 1 is provided with a circulation system for indirect heating. The circulation system comprises a strainer girdle 2, which is con-nected to a circulation pump 3 for drawing off liquid from the digester. The liquid is passed through a calorisator 4 for heating, and from the calorisator the liquid is circulated to the top and bottom of the digester through conduits 5 and 6, respectively. In the top circulation conduit 5 a valve 7 is provided which preferably is controlled automatically by a timer and/or by temperature impulses.
The invention is further illustrated by the following examples.
Example No. 1 Digestion was carried out in a batch sulphate digester with the volume 140m3 which was provided with a circulation system for indirect heating according to the Figure. The digester was charged with about 25 tons bone-dry chips by means of a liquor packing method. White liquor and black liquor were charged in such an amount, that the alkali charge was 220 kg active alkali (NaOH) per ton absolutely dry wood, and the wood: liquid ratio was 1:3.5.
During the charging of chips the circulation pump 3 was started and sucked liquid out of the digester 1 through the strainer girdle 2. The cooking liquor was circulated through the calorisator 4 for heating, and after the heating ~ 7 distributed so that 70% of the volume flow was passed to the top of the digest-er via the conduit 5 and the remaining 30~ was passed to the bottom of the digester via the conduit 6.
The digester was heated to 170 C within 70 minutes indirectly by 1(~81~
means of steam in the calorisator 4. When the temperature in the top circula-tion conduit 5 during the heating of the charge had reached 155 C, a period of boiling-up was started. This was effected by the valve 7 being automatic-ally closed by a timer which started at the beginning of the digestion. Thus the top circulation was closed, and the digester, thus, was heated only from below by the bottom circulation. This heating from below caused a boiling-up to take place which spread heat to poorly heated zones in the digester. After 10 minutes the valve 7 was again opened, and the heating of the charge could continue in the normal manner.
The charge was held at the maximum temperature 170 C for about 50 minutes and was finished with a strong top gassing for 10 minutes before the blow-off. The blow-off time was 15 minutes. The chlorine number of the pulp was 6, and the shives content at screening of an average sample from the charge in the Wennberg screen with a slit width 0.20mm was 1.5%. For a charge to which the method in question was not applied, the shives content was 4.5% at the chlorine number 6.
Example No. 2 Digestion was carried out in the same type of digester as in Example No. 1 and at the same charge conditions, with one exception, viz. that the wood:liquid ratio was 1:3.0 instead of 1:3.5. The charge was also heated in the same way as in Example No. 1 up to 145 C, at which point the top circula-tion was reduced by about 15% by partially closing the valve 7. When the tem-perature in the top circulation 5 during the heating of the charge had reached 155 C, a boiling-up was carried out. This was brought about by closing the top circulation by means of the valve 7, so that the charge was heated only from below by means of the bottom circulation. After 8 minutes the valve 7 was again opened to the position it had been in before the boiling-up, i.e.
partially closed position. During continued digestion this throttling of the top circulation was maintained in order to reduce packing of the chip-bed.
L91~8 The charge was held at the maximum temperature 170 C for about 50 minutes and was finished with a strong top gassing for 10 minutes prior to the blow-off. The blow-off time was 15 minutes. The chlorine number of the pulp was 5.5, and the shi~es content at the screening of an average sample from the charge in a Wennberg screen with the slit width 0.20 mm was 1.4%. For a charge to which the method here concerned was not applied, the shives content was 6.5 at the chlorine number 5.5.
Fxample No.3 Digestion was carried out in a batch sulphate digester with the volume 125m , which was provided with a circulation system for indirect heating according to the Figure. The digester was charged with about 23 tons of bone-dry chips by a liquor packing method. White liquor and black liquor were charged in such an amount that the alkali charging was 200 kg active alkali (NaOH) per ton absolutely dry wood, and the wood:liquid ratio was 1:3.5.
During the chip charging the circulation pump 3 was started which sucked out liquid from the digester through the strainer girdle 2.
The cooking liquid was circulated through the calorisator 3 for heating, and distributed after heating so that 75% of the volume flow was passed to the top of the digester via conduit 6 and the remaining 25% was passed to the bottom of the digester ~ia conduit 6.
~ eating to 170 C took place within 150 minutes by indirect heating with steam in the calorisator 4. When the temperature in the top circulation conduit 5 during ~he heating of the charge had reached 135 C, a first boiling-up was carried out. This was brought about by closing the valve 7 to terminate top circulation, and the digester, thus, was heated only from below by means of the bottom circulation. After 8 minutes the valve 7 was again opened, and heating of the charge could continue in a normal way. A second boiling-up was carried out at 163 C with the same boiling-up time as for the first, i.e. 8 minutes. The charge was held at the maximum temperature 170 C for one hour.
,:, ' ~ ' ' :
101~:~90~;~
After the intake of about 10 m cooling liquor the charge was blown off. The blow-off time was 25 minutes.
The chlorine number of the pulp was 5.9, and the shives content at screening of an average sample from the charge in a Wennberg screen with the slit width 0.20 mm was 1.0%. For a charge to which the above method was not applied the shives content was ~.7% at the chlorine number 5.9.
This invention relates to a method of obtaining homogenous pulping in batch digestion of a ligno-cellulose containing material in a digester, the circulation system of which is so designed, that the cooking liquld is drawn off from the digester, heated in a calorisator and returned to the top and bottom, respectively, of the digester.
Uniform digestion is of great importance at all pulp manufacturing processes, both with respect to economy and to the quality of the pulp. The causes of non-uniform digestion vary with the type of process. In Swedish . ~or* 0~7e i~
patent specification 345 885 the most important factors influencing~n~fflege~ty in batch digestion are listed, and a method is disclosed which has the object of eliminating negative effects of the commonest dominating factor, via. the cooking liquid circulation.
The technique applied according to the method, i.e. heat boiling-up, according to operating experience in a mill installation has very positive effects on the homogenity at the digestion. According to this method, the boilings-up are carried out by rapid decreases in pressure in order to effect upward flows and thereby temperature balance in the digester. This takes place either by violent gassing or by the intake of cooling liquor at the digester top.
From continued experiments for developing the boiling method, a new method has been worked out. According to the present invention, there is pro-~ o~o9 vided a method of improving the-~me~cnit~ in batch digestion of ligno-cellulose containing material in a digester having a circulation system wherein cooking liquid is drawn off from the digester via a strainer girdle, heated in a calorisator and returned to the top and bottom, respectively, of the digester, wherein the digester during the heating phase is subjected to boiling-up, brought about by periodically providing heating at only the bottom of the digester by supplying the bottom circulation with a cooking liquid flow of 1-15m3/minute, at the same time as the top circulation is held closed and - 1 - ~ ' 1~8~
pressure drop in the digester is prevented. ~leating from below results in boiling-up, which ensures that heat is also distributed to poorly heated 7ones.
This heating, if it is to be carried out within a reasonable time and without risk of extra incrustration in the calorisator, requires a rela-tively large diameter bottom circulation conduit, so that a sufficiently great circulation flow during the boiling-up is provided.
One advantage of the new method is, that its installation is simpler and cheaper than in the case of the previously known boiling method, and at the same time a very uniformly digested pulp with a low shives content is obtained.
The first boiling-up preferably is carried out at the time when the chlorine number of the pulp is 30-20, i.e. at the time when delignification is becoming substantial, but before much delignification has actually taken place. The number of boilings-up and the time intervals between them should be adjusted to the digestion schedule in question, so that for the duration of the boiling process when delignification takes place the greatest possible ~ n~og~
heat ~homog~ity in the digester is obtained.
The duration of each boiling-up can vary, but should be at least 10 seconds. A normal duration is 1-30 minutes, suitably 2-20 minutes, and prefer-ably 4-10 minutes.
In order to obtain efficient boiling-up, the bottom circulation conduit should be so dimensioned that the bottom circulation flow at the boilings-up is l-lSm3/min, suitably 2~12m3/min and preferably 3-8m3/min.
The digester, furthermore, should be well degassed when the boilings-up are carried out.
By periodically closing the bottom circulation after boiling-up, an increase of the top circulation immediately after boiling-up is brought about, which is favourable to the digesting process.
In order to reduce packing of the digester content, the top circula-. ~ , .
.
- ~819~
tion can periodically be limited prior and/or subsequent to the boilings-up.
The characterizing features of the invention will be apparent from the claims.
The invention will further be described, by way of example only, with reference to the accompanying Figure which shows an apparatus for carrying out the method according to the invention.
The digester 1 is provided with a circulation system for indirect heating. The circulation system comprises a strainer girdle 2, which is con-nected to a circulation pump 3 for drawing off liquid from the digester. The liquid is passed through a calorisator 4 for heating, and from the calorisator the liquid is circulated to the top and bottom of the digester through conduits 5 and 6, respectively. In the top circulation conduit 5 a valve 7 is provided which preferably is controlled automatically by a timer and/or by temperature impulses.
The invention is further illustrated by the following examples.
Example No. 1 Digestion was carried out in a batch sulphate digester with the volume 140m3 which was provided with a circulation system for indirect heating according to the Figure. The digester was charged with about 25 tons bone-dry chips by means of a liquor packing method. White liquor and black liquor were charged in such an amount, that the alkali charge was 220 kg active alkali (NaOH) per ton absolutely dry wood, and the wood: liquid ratio was 1:3.5.
During the charging of chips the circulation pump 3 was started and sucked liquid out of the digester 1 through the strainer girdle 2. The cooking liquor was circulated through the calorisator 4 for heating, and after the heating ~ 7 distributed so that 70% of the volume flow was passed to the top of the digest-er via the conduit 5 and the remaining 30~ was passed to the bottom of the digester via the conduit 6.
The digester was heated to 170 C within 70 minutes indirectly by 1(~81~
means of steam in the calorisator 4. When the temperature in the top circula-tion conduit 5 during the heating of the charge had reached 155 C, a period of boiling-up was started. This was effected by the valve 7 being automatic-ally closed by a timer which started at the beginning of the digestion. Thus the top circulation was closed, and the digester, thus, was heated only from below by the bottom circulation. This heating from below caused a boiling-up to take place which spread heat to poorly heated zones in the digester. After 10 minutes the valve 7 was again opened, and the heating of the charge could continue in the normal manner.
The charge was held at the maximum temperature 170 C for about 50 minutes and was finished with a strong top gassing for 10 minutes before the blow-off. The blow-off time was 15 minutes. The chlorine number of the pulp was 6, and the shives content at screening of an average sample from the charge in the Wennberg screen with a slit width 0.20mm was 1.5%. For a charge to which the method in question was not applied, the shives content was 4.5% at the chlorine number 6.
Example No. 2 Digestion was carried out in the same type of digester as in Example No. 1 and at the same charge conditions, with one exception, viz. that the wood:liquid ratio was 1:3.0 instead of 1:3.5. The charge was also heated in the same way as in Example No. 1 up to 145 C, at which point the top circula-tion was reduced by about 15% by partially closing the valve 7. When the tem-perature in the top circulation 5 during the heating of the charge had reached 155 C, a boiling-up was carried out. This was brought about by closing the top circulation by means of the valve 7, so that the charge was heated only from below by means of the bottom circulation. After 8 minutes the valve 7 was again opened to the position it had been in before the boiling-up, i.e.
partially closed position. During continued digestion this throttling of the top circulation was maintained in order to reduce packing of the chip-bed.
L91~8 The charge was held at the maximum temperature 170 C for about 50 minutes and was finished with a strong top gassing for 10 minutes prior to the blow-off. The blow-off time was 15 minutes. The chlorine number of the pulp was 5.5, and the shi~es content at the screening of an average sample from the charge in a Wennberg screen with the slit width 0.20 mm was 1.4%. For a charge to which the method here concerned was not applied, the shives content was 6.5 at the chlorine number 5.5.
Fxample No.3 Digestion was carried out in a batch sulphate digester with the volume 125m , which was provided with a circulation system for indirect heating according to the Figure. The digester was charged with about 23 tons of bone-dry chips by a liquor packing method. White liquor and black liquor were charged in such an amount that the alkali charging was 200 kg active alkali (NaOH) per ton absolutely dry wood, and the wood:liquid ratio was 1:3.5.
During the chip charging the circulation pump 3 was started which sucked out liquid from the digester through the strainer girdle 2.
The cooking liquid was circulated through the calorisator 3 for heating, and distributed after heating so that 75% of the volume flow was passed to the top of the digester via conduit 6 and the remaining 25% was passed to the bottom of the digester ~ia conduit 6.
~ eating to 170 C took place within 150 minutes by indirect heating with steam in the calorisator 4. When the temperature in the top circulation conduit 5 during ~he heating of the charge had reached 135 C, a first boiling-up was carried out. This was brought about by closing the valve 7 to terminate top circulation, and the digester, thus, was heated only from below by means of the bottom circulation. After 8 minutes the valve 7 was again opened, and heating of the charge could continue in a normal way. A second boiling-up was carried out at 163 C with the same boiling-up time as for the first, i.e. 8 minutes. The charge was held at the maximum temperature 170 C for one hour.
,:, ' ~ ' ' :
101~:~90~;~
After the intake of about 10 m cooling liquor the charge was blown off. The blow-off time was 25 minutes.
The chlorine number of the pulp was 5.9, and the shives content at screening of an average sample from the charge in a Wennberg screen with the slit width 0.20 mm was 1.0%. For a charge to which the above method was not applied the shives content was ~.7% at the chlorine number 5.9.
Claims (10)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method of improving the homogeneity in batch digestion of ligno-cellulose containing material in a digester having a circulation system wherein cooking liquid is drawn off from the digester via a strainer girdle, heated in a calorisator and returned to the top and bottom, respectively, of the digester,wherein the digester during the heating phase is subjected to boiling-up, brought about by periodically providing heating at only the bottom of the digester by supplying the bottom circulation with a cooking liquid flow of 1-15m3/minute, at the same time as the top circulation is held closed and pressure drop in the digester is prevented.
2. A method according to claim 1, wherein said cooking liquid flow is from 3 to 8 m3/minute.
3. A method according to claim 1 or 2, wherein the number of the boilings-up and the time intervals are adjusted to a predetermined digestion schedule, so that the greatest possible heat homogeneity in the digester is obtained during all the time when delignification takes place in the digesting process.
4. A method according to claim 1, wherein the duration of the boiling-up is 1-30 minutes.
5. A method according to claim 1 wherein the duration of the boiling-up is 2-20 minutes.
6. A method according to claim 1 wherein the duration of the boiling-up is 4 to 10 minutes.
7. A method according to claim 1, 2 or 4, wherein the digesten is well degassed when boiling-up is carried out.
8. A method according to claim 1, 2 or 4, wherein boiling-up is carried out by means of automatic valves in the top circulation conduit which are controlled by timer and/or by temperature impulses.
9. A method according to claim 1, 2 or 4, wherein bottom circulation is closed periodically after boiling-up, in order to obtain an increase in the top circulation flow.
10. A method according to claim 1, 2 or 4, wherein the top circulation is limited periodically prior and/or subsequent to boiling-up in order to reduce packing of the chip-bed.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| SE7504526A SE403308B (en) | 1975-04-18 | 1975-04-18 | WAY TO IMPROVE HOMOGENITY BY PERIODIC COOKING OF LIGNOCELLULOSE-MATERIAL |
| SE7504526-0 | 1975-04-18 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1081908A true CA1081908A (en) | 1980-07-22 |
Family
ID=20324340
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA249,635A Expired CA1081908A (en) | 1975-04-18 | 1976-04-06 | Method of improving the homogenity at periodical digestion of ligno-cellulose containing material |
Country Status (5)
| Country | Link |
|---|---|
| CA (1) | CA1081908A (en) |
| FI (1) | FI62688C (en) |
| FR (1) | FR2307911A1 (en) |
| NO (1) | NO146960C (en) |
| SE (1) | SE403308B (en) |
-
1975
- 1975-04-18 SE SE7504526A patent/SE403308B/en unknown
-
1976
- 1976-03-30 FI FI760847A patent/FI62688C/en not_active IP Right Cessation
- 1976-04-06 CA CA249,635A patent/CA1081908A/en not_active Expired
- 1976-04-08 FR FR7610228A patent/FR2307911A1/en active Granted
- 1976-04-09 NO NO761240A patent/NO146960C/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| NO146960B (en) | 1982-09-27 |
| SE7504526L (en) | 1976-10-19 |
| SE403308B (en) | 1978-08-07 |
| FI62688B (en) | 1982-10-29 |
| FI62688C (en) | 1983-02-10 |
| NO146960C (en) | 1983-01-05 |
| FR2307911B1 (en) | 1979-06-29 |
| FR2307911A1 (en) | 1976-11-12 |
| FI760847A7 (en) | 1976-10-19 |
| NO761240L (en) | 1976-10-19 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |