CA1101884A - Method for the production of urea from pure co.sub.2 and nh.sub.3 - Google Patents
Method for the production of urea from pure co.sub.2 and nh.sub.3Info
- Publication number
- CA1101884A CA1101884A CA299,501A CA299501A CA1101884A CA 1101884 A CA1101884 A CA 1101884A CA 299501 A CA299501 A CA 299501A CA 1101884 A CA1101884 A CA 1101884A
- Authority
- CA
- Canada
- Prior art keywords
- absorber
- ammonia
- reactor
- carbon dioxide
- urea
- 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
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C273/00—Preparation of urea or its derivatives, i.e. compounds containing any of the groups, the nitrogen atoms not being part of nitro or nitroso groups
- C07C273/02—Preparation of urea or its derivatives, i.e. compounds containing any of the groups, the nitrogen atoms not being part of nitro or nitroso groups of urea, its salts, complexes or addition compounds
- C07C273/04—Preparation of urea or its derivatives, i.e. compounds containing any of the groups, the nitrogen atoms not being part of nitro or nitroso groups of urea, its salts, complexes or addition compounds from carbon dioxide and ammonia
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
AND NH3 . -ABSTRACT OF THE DISCLOSURE:
In a process for producing urea with pure ammonia and carbon dioxide as the starting materials, the improvement consisting in that liquid ammonia is fed partly to the con-denser. Preferred molar ratios of ammonia to carbon dioxide are from 2 to 4 in the absorber and from 2.5 to 7 in the reactor. Film absorbers are preferred.
In a process for producing urea with pure ammonia and carbon dioxide as the starting materials, the improvement consisting in that liquid ammonia is fed partly to the con-denser. Preferred molar ratios of ammonia to carbon dioxide are from 2 to 4 in the absorber and from 2.5 to 7 in the reactor. Film absorbers are preferred.
Description
This invention relates to a method or the production of urea starting from pure carbon dioxide and ammonia.
In a Eew of the methods known heretofore, ca.rbon dioxide was reacted with the yaseous ammonia as produced by the splitting of the ammon~um carbamate, the gaseous ammonia having previously been exploited as thestrippin~ agent of the urea solution.
The gaseous mixture thus obtained, which was composed by the dissociated gases, carbon dioxide and ammniar was cooled by circulation of water so as to form carbamate .
to be sent to the reactor used for the synthesis in order to carry out the dehydration to urea. From the reactor, the mixture to be used for the syn~hesis was sent to the stripper for s-tripping carbon dioxide and ammonia (as formed by the thermal splitting of the carbamate~, such stripping being carried into effect in a dissociation apparatus, through the bottom of which gaseous ammonia was introduced, whereas the mixture for the synthesis was introduced at the top~ Two 20 streams emerged from the dissociation apparatus, viz. one stream composed by the solution of urea which still contained a certain quantity of carbamate, and the other stream composed by the dissociated gases and ammonia, which, as outlined above, were fed to the condenser.
The most conspicuous drawback of this kin.d of procedure was the high concentration of ammonium carbamate which was experienced in the as produce solution, the result :
being a decreased urea yield. This shortcoming was due to the requirement of operating with constant NH3 to CO2 ratios, 30 both for the condenser and the reactor.
It has surprisingly been found, according to the present invention, that urea can be produced from ammonia and ?
;?~ 2 ~
carbon dioxide with improved ~ields by usin~ instead of thé
condensation coil, a film absorber, the operation of which will be described : . . . . . .
,-, ... . :' ' ` ', ' , ' ' ; ' ~
, ~ , o, , .. . .
' : ~, . :. '. . .
... . , ~ .
' : . ' ' . .: ' `~' ' ," '~, . ~ '',,; ' .
, . . . . . . . ..
': . . : . .
:: ~ :
. ` '; ' , .
~ ` ' . .
, . :
, .
hereinafter and by sending, i~ addition to gaseous ammonia at the bottom o~ the stripper, liquid ammonia, partly to the absorbed and partly to the synthesis reactor, so as to obtain in bo-th such apparatus difEerent molar ratios oE NH3 to CO2 and, more detailedly, a ratio of from 2.5 to 7 in the reactor, and of from 2 to 4 in the absorber, and by reacting adiabatically C2 and NH3 at the bottom of said absorber.
Assuming that P is the total pressure and taking a certain H2O to CO2 ratio as the basis, and setting a ratio of NH3 to CO2, which must be comparatively high in the reactor and the stripper and comparatively low in the absorber, it is now possible to begin to describe the improved method according to the present in~ention.
~ he single FIGU~E of the accompanying drawing is a plant layout intencled to illustrate the method according to this invention.
All the carbon dioxide is fed to the bottom o an absorber, 1, together with a portion of liquid ammonia via the line 4~ whereas at the top of the absorber, via the line 5, the recycle absorbing solution is fed, which is composed by an aqueous ammoniacal solution of ammonium carbonate.
The overall NE[3 to CO2 ratio is regulated by governing the rate of flow of the liquid ammonia at the absorber bottom.
In the lower section of the absorber 1, the carbon dioxide reacts with the ammonia adiabatically, to produce ammonium carbamate. The built-up heat rises the temperature oE the mixture to higher or less high values consisten-tly with the total pressure P, the contents of water and the NH3 to CO2 ratio.
The gases which are evolved from the adiabatic bath and which are in chemicaI equilibrium therewith at that temper-ature, are absorbed partly by the recycle solution which falls !l 81~
filmwise from the top section. The part of the gas which has not been absorbed, exits the absorber l and, via the line 6, is combined with the stream 7 which carries gaseous ammonia to the stripper.
The absorption heat is communicated to water which flows through the absorber jacket and, inasmuch as the compo-sitions of the gas and the absorbing liquor in equilibrium through the entire absorber have such an N~13 to CO2 ratio as to have the evolution of heat taking place at a high temperature, it is possible to produce from -the water coolant, steam having a thermal level which is high enough as to be used for subsequent requirements of the installation.
The carbamate is then passed, via the line 8, to the reactor 2, in which the dehydration to urea takes place. The NH3 to CO2 ratio and the reactor temperature axe adjusted by feeding liquid ammonia, a small fraction indeed, through the bottom via the line 9 and gaseous ammonia, predominant1y, with gases emerging from the stripper 3 via the line lO.
; The NH3 to CO2 ratio in the reactor 2 is kept at a higher rating than in the absorber l, the conversion yields o~
C2 to urea being thereby increased.
The N~13 to CO2 ratios, the temperature and the yields are so selected as to have the absorption condensation heat of the gas from the stripper 3 enabling the thermal balance of the reactor 2 at the preselected total pressure to be kept constant.
By so doing, it becomes possible to increase the ~ -yields in the reactor while abating the consumption of steam for the str1pper and raising the thermal level of the steam produced by the absorber~
Inasmuch as the pressure in the reactor-stripper ~ sys-tem is virtually the same, it is regulated by discharging ; from the reactor top the inert gases coming from the stripper ,~ ?~
` ` ' :
88~
bottom and rom the absorber for carbon dioxide. Such a pressure can be either heavier or lighter than the pressure obtaining in the absorber, according to whether the ~ransfer of the caxbamate takes place either by barometric pull or by the agency of pumps.
Inasmuch as the conversion yields in the reactor are outstandingly high and on.taking into account the physicochemical properties o the solution which exits the reactor.
.. . .
.
: . .
.~ . ... . . .
:. .. , . , . . ~ . .. .
..... ..
..... : .
. . . ~. , . , - . . ~
''~ '' "'' " ' ' ' -,' '........... . ' ' : ' :
'~. : i ': ' ' ~:
.
1 . .
..... i . . . ~ . . . .
. . . . .
through the line ll, carbon dioxide.and water separated in the stripper are a small amount as compared with the ~uantity of ammonia. In addition to this particular reason, the heat to be administered to the system is not a great deal, since the solution of urea is already close to its critical con-ditions, whereby ammonia can easily be distilled. ~ :
The critical temperature is decreased as the NH3to CO2 ratio is increased and as the water contents is decreased. This circumstance is such that exchange surfaces in the stripper are required, which are lesser than the sur~
faces required for the conventional strippers and, in addition, lower heat-exchanger temperatures are necessary, which enable steam at a lower thermal level to be used, the running costs ~ ;
being thereby reduced.
An example will now be reported in order better to elucidate the invention without, however, limiting it ~ .
: anyhow.
E X A M P L E
To produce 72,550 kilograms an hour oE urea, the absorber 1 is fed with :
53,167 kilograms an hour of CO2 at the temperature of 150~C
32~853 kilograms an hour of NH3 at the temperature of 50C
along with the recycle carbonate which is sent to the top of the absorber l at a temperature of 76C and with the following composition : ~
NH3 27,323 kilograms an hour 47.62% by weight ~ ;
C2 lO/127 17,65% " ~ ;
; 30 H2O 19,926 " " 34.73~ "
The absorber:works under the pressure of the entire urea-synthesis loop which tpressure drops allowed for) is 180 kiloyrams/s~. centimeters. CO2 and NH3 react in the absorber and the reaction heat is remo~ed for producing steam.
From the bottom of the absorbf~r a carbamate solution emerges at the temperature of 180C and has the following composition :
NH3 50,794 kilograms an hour 42.23% by weight C2 50~794 kilograms an hour 42.23%
H20 18,699 " ~ 15.54% "
Said solution is sent to the reactor 2.
The uncondensed vapors exit the top of the - absorber 1 at the temperature of 180C and have the following composition :
NH3 9,382 kilograms an hour 40,60% by weight C2 12,500 " " 54.09% 1l .
H20 1,227 ~ - 5.31%
Said vapors are fed to the bottom of the stripper 3.
The reactor 2 is fed, in addition to the solution of carbamate, with 47,840 kilograms an hour of ammonia at 100C and with the vapors exiting the stripped 3, which have a temperature of 190C and the following composition :
NH3 50,218 kilograms an hour 59.10% by weight C2 26,259 " " 30.90% "
H2O '3,497 ~ .. 10.00% 17 The solution exiting the reactor is sent -to the stripper 3 at a temperature of 185C and has the following composition :
Urea 72,500 kilograms an hour 28.64% by weight NH3107,768 " " 42.58% "
C223,886 " " 9.44% "
H2O48~946 " " 19.34%
`~
' ~ . ,~ , . .
38~
Through the stripper bott~m exist a stream at 210C which is sent to a conventional concentration section, and has the ~ollowing composition : .
~rea 72,500 kilograms an hour 37~91% by weight NH3 66,932 ~: ~ C2 10,127 " " 5.30~ .
H2O 41,676 " " 21.79%
. . . .
. . . . .
, ~ . . .. ~
, . . . ~ .
. ~ : : . :
,: : : :: . . , . . , . . :
.
: . :
~` : , ;: :
: , `:. ' .: . . : ~ : : '.
In a Eew of the methods known heretofore, ca.rbon dioxide was reacted with the yaseous ammonia as produced by the splitting of the ammon~um carbamate, the gaseous ammonia having previously been exploited as thestrippin~ agent of the urea solution.
The gaseous mixture thus obtained, which was composed by the dissociated gases, carbon dioxide and ammniar was cooled by circulation of water so as to form carbamate .
to be sent to the reactor used for the synthesis in order to carry out the dehydration to urea. From the reactor, the mixture to be used for the syn~hesis was sent to the stripper for s-tripping carbon dioxide and ammonia (as formed by the thermal splitting of the carbamate~, such stripping being carried into effect in a dissociation apparatus, through the bottom of which gaseous ammonia was introduced, whereas the mixture for the synthesis was introduced at the top~ Two 20 streams emerged from the dissociation apparatus, viz. one stream composed by the solution of urea which still contained a certain quantity of carbamate, and the other stream composed by the dissociated gases and ammonia, which, as outlined above, were fed to the condenser.
The most conspicuous drawback of this kin.d of procedure was the high concentration of ammonium carbamate which was experienced in the as produce solution, the result :
being a decreased urea yield. This shortcoming was due to the requirement of operating with constant NH3 to CO2 ratios, 30 both for the condenser and the reactor.
It has surprisingly been found, according to the present invention, that urea can be produced from ammonia and ?
;?~ 2 ~
carbon dioxide with improved ~ields by usin~ instead of thé
condensation coil, a film absorber, the operation of which will be described : . . . . . .
,-, ... . :' ' ` ', ' , ' ' ; ' ~
, ~ , o, , .. . .
' : ~, . :. '. . .
... . , ~ .
' : . ' ' . .: ' `~' ' ," '~, . ~ '',,; ' .
, . . . . . . . ..
': . . : . .
:: ~ :
. ` '; ' , .
~ ` ' . .
, . :
, .
hereinafter and by sending, i~ addition to gaseous ammonia at the bottom o~ the stripper, liquid ammonia, partly to the absorbed and partly to the synthesis reactor, so as to obtain in bo-th such apparatus difEerent molar ratios oE NH3 to CO2 and, more detailedly, a ratio of from 2.5 to 7 in the reactor, and of from 2 to 4 in the absorber, and by reacting adiabatically C2 and NH3 at the bottom of said absorber.
Assuming that P is the total pressure and taking a certain H2O to CO2 ratio as the basis, and setting a ratio of NH3 to CO2, which must be comparatively high in the reactor and the stripper and comparatively low in the absorber, it is now possible to begin to describe the improved method according to the present in~ention.
~ he single FIGU~E of the accompanying drawing is a plant layout intencled to illustrate the method according to this invention.
All the carbon dioxide is fed to the bottom o an absorber, 1, together with a portion of liquid ammonia via the line 4~ whereas at the top of the absorber, via the line 5, the recycle absorbing solution is fed, which is composed by an aqueous ammoniacal solution of ammonium carbonate.
The overall NE[3 to CO2 ratio is regulated by governing the rate of flow of the liquid ammonia at the absorber bottom.
In the lower section of the absorber 1, the carbon dioxide reacts with the ammonia adiabatically, to produce ammonium carbamate. The built-up heat rises the temperature oE the mixture to higher or less high values consisten-tly with the total pressure P, the contents of water and the NH3 to CO2 ratio.
The gases which are evolved from the adiabatic bath and which are in chemicaI equilibrium therewith at that temper-ature, are absorbed partly by the recycle solution which falls !l 81~
filmwise from the top section. The part of the gas which has not been absorbed, exits the absorber l and, via the line 6, is combined with the stream 7 which carries gaseous ammonia to the stripper.
The absorption heat is communicated to water which flows through the absorber jacket and, inasmuch as the compo-sitions of the gas and the absorbing liquor in equilibrium through the entire absorber have such an N~13 to CO2 ratio as to have the evolution of heat taking place at a high temperature, it is possible to produce from -the water coolant, steam having a thermal level which is high enough as to be used for subsequent requirements of the installation.
The carbamate is then passed, via the line 8, to the reactor 2, in which the dehydration to urea takes place. The NH3 to CO2 ratio and the reactor temperature axe adjusted by feeding liquid ammonia, a small fraction indeed, through the bottom via the line 9 and gaseous ammonia, predominant1y, with gases emerging from the stripper 3 via the line lO.
; The NH3 to CO2 ratio in the reactor 2 is kept at a higher rating than in the absorber l, the conversion yields o~
C2 to urea being thereby increased.
The N~13 to CO2 ratios, the temperature and the yields are so selected as to have the absorption condensation heat of the gas from the stripper 3 enabling the thermal balance of the reactor 2 at the preselected total pressure to be kept constant.
By so doing, it becomes possible to increase the ~ -yields in the reactor while abating the consumption of steam for the str1pper and raising the thermal level of the steam produced by the absorber~
Inasmuch as the pressure in the reactor-stripper ~ sys-tem is virtually the same, it is regulated by discharging ; from the reactor top the inert gases coming from the stripper ,~ ?~
` ` ' :
88~
bottom and rom the absorber for carbon dioxide. Such a pressure can be either heavier or lighter than the pressure obtaining in the absorber, according to whether the ~ransfer of the caxbamate takes place either by barometric pull or by the agency of pumps.
Inasmuch as the conversion yields in the reactor are outstandingly high and on.taking into account the physicochemical properties o the solution which exits the reactor.
.. . .
.
: . .
.~ . ... . . .
:. .. , . , . . ~ . .. .
..... ..
..... : .
. . . ~. , . , - . . ~
''~ '' "'' " ' ' ' -,' '........... . ' ' : ' :
'~. : i ': ' ' ~:
.
1 . .
..... i . . . ~ . . . .
. . . . .
through the line ll, carbon dioxide.and water separated in the stripper are a small amount as compared with the ~uantity of ammonia. In addition to this particular reason, the heat to be administered to the system is not a great deal, since the solution of urea is already close to its critical con-ditions, whereby ammonia can easily be distilled. ~ :
The critical temperature is decreased as the NH3to CO2 ratio is increased and as the water contents is decreased. This circumstance is such that exchange surfaces in the stripper are required, which are lesser than the sur~
faces required for the conventional strippers and, in addition, lower heat-exchanger temperatures are necessary, which enable steam at a lower thermal level to be used, the running costs ~ ;
being thereby reduced.
An example will now be reported in order better to elucidate the invention without, however, limiting it ~ .
: anyhow.
E X A M P L E
To produce 72,550 kilograms an hour oE urea, the absorber 1 is fed with :
53,167 kilograms an hour of CO2 at the temperature of 150~C
32~853 kilograms an hour of NH3 at the temperature of 50C
along with the recycle carbonate which is sent to the top of the absorber l at a temperature of 76C and with the following composition : ~
NH3 27,323 kilograms an hour 47.62% by weight ~ ;
C2 lO/127 17,65% " ~ ;
; 30 H2O 19,926 " " 34.73~ "
The absorber:works under the pressure of the entire urea-synthesis loop which tpressure drops allowed for) is 180 kiloyrams/s~. centimeters. CO2 and NH3 react in the absorber and the reaction heat is remo~ed for producing steam.
From the bottom of the absorbf~r a carbamate solution emerges at the temperature of 180C and has the following composition :
NH3 50,794 kilograms an hour 42.23% by weight C2 50~794 kilograms an hour 42.23%
H20 18,699 " ~ 15.54% "
Said solution is sent to the reactor 2.
The uncondensed vapors exit the top of the - absorber 1 at the temperature of 180C and have the following composition :
NH3 9,382 kilograms an hour 40,60% by weight C2 12,500 " " 54.09% 1l .
H20 1,227 ~ - 5.31%
Said vapors are fed to the bottom of the stripper 3.
The reactor 2 is fed, in addition to the solution of carbamate, with 47,840 kilograms an hour of ammonia at 100C and with the vapors exiting the stripped 3, which have a temperature of 190C and the following composition :
NH3 50,218 kilograms an hour 59.10% by weight C2 26,259 " " 30.90% "
H2O '3,497 ~ .. 10.00% 17 The solution exiting the reactor is sent -to the stripper 3 at a temperature of 185C and has the following composition :
Urea 72,500 kilograms an hour 28.64% by weight NH3107,768 " " 42.58% "
C223,886 " " 9.44% "
H2O48~946 " " 19.34%
`~
' ~ . ,~ , . .
38~
Through the stripper bott~m exist a stream at 210C which is sent to a conventional concentration section, and has the ~ollowing composition : .
~rea 72,500 kilograms an hour 37~91% by weight NH3 66,932 ~: ~ C2 10,127 " " 5.30~ .
H2O 41,676 " " 21.79%
. . . .
. . . . .
, ~ . . .. ~
, . . . ~ .
. ~ : : . :
,: : : :: . . , . . , . . :
.
: . :
~` : , ;: :
: , `:. ' .: . . : ~ : : '.
Claims (3)
1. A method for the production of urea starting from pure carbon dioxide and ammonia, comprising reacting both reactants, decomposing the ammonium carbamate contained in the solution of urea exiting the synthesis reactor, stripping the decomposition products with gaseous ammonia and condensing the decomposition products and the stripping ammonia, characterized in that liquid ammonia is partly sent to the bottom of the condenser which is a film absorber, together with all the carbon dioxide, and partly to the synthesis reactor, the NH3 to CO2 molar ratio in the absorber being from 2 to 4 and being from 2.5 to 7 in the reactor, and the reaction of CO2 and NH3 takes place adiabatically at the bottom of said absorber.
2. A method according to claim 1, characterized in that to the top of said film absorber is sent a recycle solution composed by an aqueous ammoniacal solution of ammonium carbonate.
3. A method according to claim 1, wherein the gaseous ammonia exploited as a stripping medium is partly obtained as a head product of the carbon dioxide absorber.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| IT21904/77A IT1075371B (en) | 1977-03-31 | 1977-03-31 | PROCESS FOR THE PRODUCTION OF UREA STARTING FROM CO2 AND PURE NH3 |
| IT21904A/77 | 1977-03-31 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1101884A true CA1101884A (en) | 1981-05-26 |
Family
ID=11188506
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA299,501A Expired CA1101884A (en) | 1977-03-31 | 1978-03-22 | Method for the production of urea from pure co.sub.2 and nh.sub.3 |
Country Status (20)
| Country | Link |
|---|---|
| JP (1) | JPS53149929A (en) |
| AR (1) | AR214002A1 (en) |
| AU (1) | AU519725B2 (en) |
| BE (1) | BE865585A (en) |
| BR (1) | BR7802007A (en) |
| CA (1) | CA1101884A (en) |
| CH (1) | CH632240A5 (en) |
| CS (1) | CS204026B2 (en) |
| DD (1) | DD134223A5 (en) |
| DE (1) | DE2813528C3 (en) |
| DK (1) | DK140378A (en) |
| ES (1) | ES469090A1 (en) |
| FR (1) | FR2385690A1 (en) |
| GB (1) | GB1586629A (en) |
| IE (1) | IE46700B1 (en) |
| IT (1) | IT1075371B (en) |
| LU (1) | LU79340A1 (en) |
| NL (1) | NL7803338A (en) |
| PL (1) | PL108056B1 (en) |
| SE (1) | SE7803685L (en) |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| BE790015A (en) * | 1971-10-19 | 1973-04-12 | Mavrovic Ivo | UREA SYNTHESIS WITH IMPROVED CONVERSION AND HEAT RECOVERY |
-
1977
- 1977-03-31 IT IT21904/77A patent/IT1075371B/en active
-
1978
- 1978-03-20 AU AU34291/78A patent/AU519725B2/en not_active Expired
- 1978-03-21 GB GB11243/78A patent/GB1586629A/en not_active Expired
- 1978-03-22 CA CA299,501A patent/CA1101884A/en not_active Expired
- 1978-03-28 AR AR271575A patent/AR214002A1/en active
- 1978-03-28 ES ES469090A patent/ES469090A1/en not_active Expired
- 1978-03-29 NL NL7803338A patent/NL7803338A/en not_active Application Discontinuation
- 1978-03-29 DE DE2813528A patent/DE2813528C3/en not_active Expired
- 1978-03-29 CH CH335878A patent/CH632240A5/en not_active IP Right Cessation
- 1978-03-29 PL PL1978205651A patent/PL108056B1/en unknown
- 1978-03-30 IE IE636/78A patent/IE46700B1/en unknown
- 1978-03-30 FR FR7809361A patent/FR2385690A1/en not_active Withdrawn
- 1978-03-30 LU LU79340A patent/LU79340A1/en unknown
- 1978-03-30 DK DK140378A patent/DK140378A/en unknown
- 1978-03-30 CS CS782044A patent/CS204026B2/en unknown
- 1978-03-31 BR BR7802007A patent/BR7802007A/en unknown
- 1978-03-31 SE SE7803685A patent/SE7803685L/en unknown
- 1978-03-31 BE BE186482A patent/BE865585A/en not_active IP Right Cessation
- 1978-03-31 DD DD78204529A patent/DD134223A5/en unknown
- 1978-03-31 JP JP3695778A patent/JPS53149929A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| AU519725B2 (en) | 1981-12-17 |
| ES469090A1 (en) | 1978-11-16 |
| DK140378A (en) | 1978-10-01 |
| DE2813528A1 (en) | 1978-10-12 |
| GB1586629A (en) | 1981-03-25 |
| DD134223A5 (en) | 1979-02-14 |
| IE46700B1 (en) | 1983-08-24 |
| BR7802007A (en) | 1979-04-03 |
| DE2813528C3 (en) | 1980-03-20 |
| AR214002A1 (en) | 1979-04-11 |
| IT1075371B (en) | 1985-04-22 |
| CH632240A5 (en) | 1982-09-30 |
| FR2385690A1 (en) | 1978-10-27 |
| LU79340A1 (en) | 1978-07-13 |
| NL7803338A (en) | 1978-10-03 |
| PL108056B1 (en) | 1980-03-31 |
| AU3429178A (en) | 1979-09-27 |
| DE2813528B2 (en) | 1979-07-26 |
| SE7803685L (en) | 1978-10-01 |
| CS204026B2 (en) | 1981-03-31 |
| IE780636L (en) | 1978-11-30 |
| PL205651A1 (en) | 1978-12-04 |
| JPS53149929A (en) | 1978-12-27 |
| BE865585A (en) | 1978-10-02 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |