CA1073187A - Process for the removal of sulphur dioxide from a flue gas stream by means of a solid acceptor - Google Patents
Process for the removal of sulphur dioxide from a flue gas stream by means of a solid acceptorInfo
- Publication number
- CA1073187A CA1073187A CA220,642A CA220642A CA1073187A CA 1073187 A CA1073187 A CA 1073187A CA 220642 A CA220642 A CA 220642A CA 1073187 A CA1073187 A CA 1073187A
- Authority
- CA
- Canada
- Prior art keywords
- acceptor
- reaction zone
- regeneration
- flue gas
- auxiliary
- 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
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B17/00—Sulfur; Compounds thereof
- C01B17/48—Sulfur dioxide; Sulfurous acid
- C01B17/50—Preparation of sulfur dioxide
- C01B17/60—Isolation of sulfur dioxide from gases
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/34—Chemical or biological purification of waste gases
- B01D53/46—Removing components of defined structure
- B01D53/48—Sulfur compounds
- B01D53/50—Sulfur oxides
- B01D53/508—Sulfur oxides by treating the gases with solids
Abstract
ABSTRACT
In the removal of sulphur dioxide, from a flue gas stream it is known to use a solid acceptor which is regenerated using reducing or strip-ping gas. However, the time required for regenerating the acceptor is less than that required for loading the acceptor. As a result there is a discon-tinuous demand for reducing or stripping gas which consequentially places a high demand upon the unit generating the reducingly stripping gas and the unit for treating this gas subsequent to regeneration of the acceptor. The present invention overcomes the drawbacks associated with a discontinuous demand for reducing or stripping gas by providing a process for the removal of sulphur dioxide from a flue gas stream by means of a solid acceptor on which the sulphur dioxide is accepted and from which it is subsequently recovered by regeneration of the loaded acceptor with a reducing gas, which process is carried out in two or three equally large main reaction zones com-prising the said acceptor, of which zones at least one and at most two is/are invariably connected to the flue gas stream and said main zones being alter-nately subjected to a regeneration treatment with the exclusion of the flue gas stream, characterized in that an auxiliary reaction zone with acceptor is applied, which auxiliary reaction zone is of shorter length than the said main reaction zones, and which auxiliary zone is subjected to a regeneration treatment during the short intervals which are maintained between the subse-quent regeneration treatments of the main reaction zones.
In the removal of sulphur dioxide, from a flue gas stream it is known to use a solid acceptor which is regenerated using reducing or strip-ping gas. However, the time required for regenerating the acceptor is less than that required for loading the acceptor. As a result there is a discon-tinuous demand for reducing or stripping gas which consequentially places a high demand upon the unit generating the reducingly stripping gas and the unit for treating this gas subsequent to regeneration of the acceptor. The present invention overcomes the drawbacks associated with a discontinuous demand for reducing or stripping gas by providing a process for the removal of sulphur dioxide from a flue gas stream by means of a solid acceptor on which the sulphur dioxide is accepted and from which it is subsequently recovered by regeneration of the loaded acceptor with a reducing gas, which process is carried out in two or three equally large main reaction zones com-prising the said acceptor, of which zones at least one and at most two is/are invariably connected to the flue gas stream and said main zones being alter-nately subjected to a regeneration treatment with the exclusion of the flue gas stream, characterized in that an auxiliary reaction zone with acceptor is applied, which auxiliary reaction zone is of shorter length than the said main reaction zones, and which auxiliary zone is subjected to a regeneration treatment during the short intervals which are maintained between the subse-quent regeneration treatments of the main reaction zones.
Description
~C~7~37 The invention relates to the removal of sulphur dioxide from a flue gas stream by means of a solid acceptor on which the sulphur dioxide is accepted. This sulphur dioxide is subsequently recovered during the regeneration o~ the loaded acceptor with a reducing gas.
In such a process the intention is that invariabl~ the total ~eed of sulphur dioxide-containing flue gas be entirely trea-ted in one or more reactors, so that no untreated flue gas is discharged into the atmosphere. It should further be ensured th~t substantially the same number of reactors is invariably available for treating the flue gas stream. The reactors should, therefore, be subjected to regeneration treatment alternately.
When flue gas is desulphurized using reducing gas for the regeneration, the time required for regenerating a reactor con- ;
taining loaded acceptor is shorter than the time elaps;ng during the loading of that acceptor. Hence, in the event of two reactors in total being used, this fact alone means that some time elapses between the regeneration treatments of the respective reactors. When three re actors are used, with only one reactor being re6enerated per treatment, `
at least two reactors are thus continuously connected to the flue gas stream, and when the regeneration time is less than half the acceptance time, this also will cause a substantial period to elapse between the regen3~tion treatments of the subsequent reactors.
With a view to the operation Or the unit from which the flue gas emanates, it is moreover desirable that - simultaneously with the closure of the valve in the flue gas line to the reac-tor of which the loaded acceptor has been regenerated - the valve should be opened in the fl~e gas line to the reactor of which the acceptor has just been regener-ated. Since opening and closing of these valves take some time, there will invariably be short intervals between the subsequent regeneration treatments of the various reactors.
~he regeneration usually comprises a purging period with inert gas, followed by a period in which a reducing gas is passed through the re actor which gas entrains the sulphur dioxide recovered, whereupon the reactor is purged for an additional time with an inert gas. The purging before and after the passage of the reducing gas also causes some time .. . , . . , . ................ . . . ........... I ~ .
. : : ; ~ , 1C~73~L~7 ~
to elapse between subsequent periods in which a sulphur dioxide-containing gas becomes available during regeneration Although in some processes the sulphur d;oxide can only be recovered from the acceptor with a reducing gas, other processes are conceivable in which this sulphur dioxide could be stripped with an inert gas~ thus rendering;purging unnecessary. However, also in the latter case the character of the regeneration remains discontinuous owing to the opaning and closing of the valves.
The discontinuous character of khe regeneration is disadvantageous for two reasons, namely because the demand or reducing gas or stripping gas is discontinuous and because the production of regeneration off-gas with a high sulphur dioxide content is also discontinuous. This makes particularly heavy demands on the unit for the preparation of the required reducing gas or stripping gas on the one hand and on the unit for the furthe~ processing of the sulphur dioxide-containing regeneration off-gas `
on the other hand.
The object of the present invention is to remove the above disadvantages and provide a method to eliminate the discontinuous character of the demand for reducing gas or stripping gas and of the production of regeneration off-gas for the process for desulphurizing flue gases.
The present invention therefore concerns a process for the removal of sulphur dioxide from a flue gas stream by means of a solid acceptor on which the sulphur dioxide is accepted and from which it is subsequently recovered by regneration of the loaded acceptor with a reducing gas, which process is carried out in two or three equally sized main reaction zones comprising the said acceptor, of which zones at least one and at most two is/are invariably connected to the flue gas stream and said main reaction zones being alternately subjected to a regeneration treatment with the exclusion of the flue gas stream, charact0rized in that an auxiliary reaction zone with acceptor is applied, which aux:iliary reaction ~ _ 3 _ , ,~) ,~
1073~87 ,- -zone is of shorter length than the said main reaction zones, and is connected to the flue gas stream in front of a main reactor zone during an acceptance period, said auxiliary zone being subjected to a regeneration treatment during the short intervals between the sequential regeneration . . :~
treatments of the main reaction zones in such a manner that the said regeneration treatment o the auxiliary reaction zone is continued for a short period at the beginning of the regeneration treatment of the next main reaction zone.
;. - 3a. ~
~, .
. ~73~137 ,. .
In this connection it is noted that the frequency with which the auxiliary reaction zone is regenerated is higher than that with which the main reaction zones are regenerated, because the acceptance time of the ;~
auxiliary reaction zone is shorter, the length of the said zone being shorter.
The provision according to the invention results in one reaction zone of the total zones being continuously subjectecl to a regeneration treat-ment. The demand for reducing gas or stripping gas, as well as the production of sulphur dioxide-containing regeneration off-gas, can thus be rendered continuous.
It is noted that the required length of the auxiliary reaction zone will depend on the duration of the interval to be bridged between the regeneration treatments of subsequent main reaction zones. Since in practice the frequency of regeneration and acceptance will usually vary in dependence on the quantity of flue gas to be desulphurized, a safe length will have to be chosen. In many cases the length of the auxiliary reaction zone will be between 10% and 90% of the length of a main reaction zone.
Preferably, according to the invention - when the auxiliary ~ ~
reaction zone is in its acceptance period - the flue gas stream is invariably -first passed through this auxiliary reaction zone and then through a main reaction zone. The auxiliary reaction zone can thus be kept so short that, in the period of time available, the quantity of acceptor present in the said auxiliary zone is loaded as completely as possible. In this case the auxiliary reaction zone and the main reaction zone arranged thereafter should be considered as one unit. The sulphur dioxide slipping through the auxiliary reaction zone is accepted in the main reaction zone.
It will be clear that at the end of the relatively short accept-ance period of the auxiliary reaction zone the flue gas stream is no longer passed therethrough, bu~ passed direc~ly to the main reaction zone which is arranged after the auxiliary reaction zone.
~ 73~7 According to the invention the connection of a main reaction zone to the flue gas stream is preferably effected invariably simultaneously with the disconnection of the flue gas stream to another main reaction zone. The main reaction zones are in this case connected to branch ~lines of a flue gas duct. These latter lines contain valves, and simultaneously with the opening of the valve to the main reaction zone to be connected to the flue gas stream, the valve to the zone of which the supply of flue gas has to be discontinued, is closed. In ~ this way the total quantity of flue gas keeps flowing freely and minimal additional decrease or increase in the pressure drop occurs, so that the unit from which the flue gas emanates~ is not affected at all by the change-over to another main reaction zone.
In a preferred embodiment of the invention the regeneration treat-mentis preceded and followed by purging with steam or another inert gas.
During this purging no sulphur dioxide is removed from the ac-...
ceptor and the purging of the reaction zones serves to prevent the formation of explosive gas mixtures during -the transition from the acceptance - under oxidizing conditions - to the regeneration under reducing conditions.~It will be obvious that purging applied for safety reasons, also contributes to the fact that some time elapses between the periods in which reducing eas is passed through subsequent main reaction zones, assuming that these zones have subsequent ac-ceptance periods. The invention is therefore also of importance in particular under these conditions.
In the above embodiment the regeneration of t,he auxiliary reaction zone i5 preferably already started during the purging of the main re-action zone which has been regenerated immediately be~ore and is ~ ~ continued for some time during the purging of the main reaction zone to be regenerated immediately thereafter. In this way the continuity of the demand for reducing gas and of the supply of sulphur dioxi~e-containing regeneration off-gas is guaranteed in spite of the purgin of the main reaction zones.
According to the invention the regeneration of the acceptor in the auxiliary reaction zone is preferably continued for a short period ~o~3~87 `: ' at the beginning of the regeneration of the acceptor present in a main reaction zone. Unlike the acceptor in the auxiliary reaction ;~
zone, which i5 loaded with sulphur dioxide over the full length of the said zone at the end of the acceptance period, the acceptor in a main reaction zone is substantially fully loaded over only part of the zone length at the end of the ~cceptance period and for the .:
rest the degree of the load decreases in the direction of flow.
The choice of the length of the acceptance period of the main re-action zone such that at the end thereof the acceptor in this main zone is not fully loaded as indicated,prevents that too much sulphur dioxide will slip throuKh the main reaction zone. The foregoing implies, however, that at the beginning of the regeneration of the acceptor in such a main reaction zone the sulphur dioxide content in the regeneration oPf-gas will be low. This phenomenon, known as re-acceptance, may be explained from the fact that sulphur dioxide recovered in the first ~rt of the acceptor bed during regeneration i9 re-accepted in ano-ther part of the bed. By supplying further regeneration off-gas from the auxiliary reaction zone in the period of re-acceptance during regeneration, the sulphur dioxide content 20 ~ of the total quantity of regeneration off-gas liberated will still be as constant as possible.
Consequently, the acceptance and regeneration periods of the invention are preferably so selected that at the end of the relevant acceptance period the acceptor in the auxiliary reaction zone is loaded as fully as possible with sulphur dioxide over the entire length of the said zone, whereas the acceptor in the main reaction zone is not - yet fully loaded over the entire length o~ the saidnain reaction zone~ in such a way that in regenerating the acceptor in the said main reaction zone, the sulphur dioxide initially recovered in the reducing gas is re-accepted further on in the as yet unregenerated part of the main reaction zone. It will further be obvious that the acceptance period of the auxiliary reaction zone terminates at an-other point of time than the acceptance period of each of the main reaction zones. Under these conditions the applica~ion o~ the auxiliary reaction zone according to the invention will haYe its greatest effect.
~ : ' :
..;..
~ 73~L87 : .~
In a preferred embodiment of the invention the acceptor consists of a ceramic carrier on which one or more metals, including copper, have been deposited, aDd acceptance and regener~tion are carried out at a temperature between 200 C and 600 C. Under these conditions the invention is advantageous especially because the regeneration ;
~riod is significantly shorter than the acceptance period.
The inven-tion may be applied adYantageously, inter alia, where the flue gas contains less than 2% by volume of sulphur dioxide and at least an equal portion of oxygen and the reducing gas contains at least 50% by volume of steam and/or another inert gas and at most ~
50% by volume of hydrogen, carbon monoxide and/or hydrocarbons.
In ~eneral, flue gas originating from the complete combustion of sulphur-conkaining hydrocarbon-based fuel or coal contains the said percentages of sulphur dioxide and oxygen. Oxygen, which is usually supplied as air when the combustion takes place in a furnace, is usually provided in a slight excess quantity in order to ensure -~
complete combustion without a soot-forming flame. When a copper-containing acceptor is used the presence of oxygen in the flue gas is important, since the sulphur dioxide is accepted as sulphate.
In addition, it is, of course, possible to oxidize the acceptor after regeneration in a separate step. Under the above conditions and in particular at the said composition of the reducing gas, reasonably short regeneration times are possible withou-t the temperature of the acceptor rising to values which are unacceptable in view of thermal stability.
~ According to the invention when use is made of three main re-action zones, the regeneration time for a main reaction zone is preferably less than half the acceptance time. In particular in the latter case some time will elapse between the regeneration treatments of subsequent main reaction zones, so that the application of an auxiliary reaction zone is very useful. This, o~ course, also applies when~ in the event of three main reaction zones being used, the time required for purging, regeneration and repurging of a main reaction zone is less than half the acceptance time.
.
:
~C~73~87 Aft~r r~moval of the c~xcess water va~)our the r~gcrleration off-gas comprising sulphur d;oxide i5 passed direct:Ly to a sulphur re-covery plant of the Claus type for the prepara-tion o~ element~1 sulphur.
~5 Under the above conditions the provision according to the in~
vention is of importance especially since it is essential for a ~
Claus plant that the concentration of sulphur compounds in -the feed -gas should be as constant as possible. In this connection it should be borne in mind that thelreparation of elemental sulphur proceeds }0 in principle via the Claus reaction:
In such a process the intention is that invariabl~ the total ~eed of sulphur dioxide-containing flue gas be entirely trea-ted in one or more reactors, so that no untreated flue gas is discharged into the atmosphere. It should further be ensured th~t substantially the same number of reactors is invariably available for treating the flue gas stream. The reactors should, therefore, be subjected to regeneration treatment alternately.
When flue gas is desulphurized using reducing gas for the regeneration, the time required for regenerating a reactor con- ;
taining loaded acceptor is shorter than the time elaps;ng during the loading of that acceptor. Hence, in the event of two reactors in total being used, this fact alone means that some time elapses between the regeneration treatments of the respective reactors. When three re actors are used, with only one reactor being re6enerated per treatment, `
at least two reactors are thus continuously connected to the flue gas stream, and when the regeneration time is less than half the acceptance time, this also will cause a substantial period to elapse between the regen3~tion treatments of the subsequent reactors.
With a view to the operation Or the unit from which the flue gas emanates, it is moreover desirable that - simultaneously with the closure of the valve in the flue gas line to the reac-tor of which the loaded acceptor has been regenerated - the valve should be opened in the fl~e gas line to the reactor of which the acceptor has just been regener-ated. Since opening and closing of these valves take some time, there will invariably be short intervals between the subsequent regeneration treatments of the various reactors.
~he regeneration usually comprises a purging period with inert gas, followed by a period in which a reducing gas is passed through the re actor which gas entrains the sulphur dioxide recovered, whereupon the reactor is purged for an additional time with an inert gas. The purging before and after the passage of the reducing gas also causes some time .. . , . . , . ................ . . . ........... I ~ .
. : : ; ~ , 1C~73~L~7 ~
to elapse between subsequent periods in which a sulphur dioxide-containing gas becomes available during regeneration Although in some processes the sulphur d;oxide can only be recovered from the acceptor with a reducing gas, other processes are conceivable in which this sulphur dioxide could be stripped with an inert gas~ thus rendering;purging unnecessary. However, also in the latter case the character of the regeneration remains discontinuous owing to the opaning and closing of the valves.
The discontinuous character of khe regeneration is disadvantageous for two reasons, namely because the demand or reducing gas or stripping gas is discontinuous and because the production of regeneration off-gas with a high sulphur dioxide content is also discontinuous. This makes particularly heavy demands on the unit for the preparation of the required reducing gas or stripping gas on the one hand and on the unit for the furthe~ processing of the sulphur dioxide-containing regeneration off-gas `
on the other hand.
The object of the present invention is to remove the above disadvantages and provide a method to eliminate the discontinuous character of the demand for reducing gas or stripping gas and of the production of regeneration off-gas for the process for desulphurizing flue gases.
The present invention therefore concerns a process for the removal of sulphur dioxide from a flue gas stream by means of a solid acceptor on which the sulphur dioxide is accepted and from which it is subsequently recovered by regneration of the loaded acceptor with a reducing gas, which process is carried out in two or three equally sized main reaction zones comprising the said acceptor, of which zones at least one and at most two is/are invariably connected to the flue gas stream and said main reaction zones being alternately subjected to a regeneration treatment with the exclusion of the flue gas stream, charact0rized in that an auxiliary reaction zone with acceptor is applied, which aux:iliary reaction ~ _ 3 _ , ,~) ,~
1073~87 ,- -zone is of shorter length than the said main reaction zones, and is connected to the flue gas stream in front of a main reactor zone during an acceptance period, said auxiliary zone being subjected to a regeneration treatment during the short intervals between the sequential regeneration . . :~
treatments of the main reaction zones in such a manner that the said regeneration treatment o the auxiliary reaction zone is continued for a short period at the beginning of the regeneration treatment of the next main reaction zone.
;. - 3a. ~
~, .
. ~73~137 ,. .
In this connection it is noted that the frequency with which the auxiliary reaction zone is regenerated is higher than that with which the main reaction zones are regenerated, because the acceptance time of the ;~
auxiliary reaction zone is shorter, the length of the said zone being shorter.
The provision according to the invention results in one reaction zone of the total zones being continuously subjectecl to a regeneration treat-ment. The demand for reducing gas or stripping gas, as well as the production of sulphur dioxide-containing regeneration off-gas, can thus be rendered continuous.
It is noted that the required length of the auxiliary reaction zone will depend on the duration of the interval to be bridged between the regeneration treatments of subsequent main reaction zones. Since in practice the frequency of regeneration and acceptance will usually vary in dependence on the quantity of flue gas to be desulphurized, a safe length will have to be chosen. In many cases the length of the auxiliary reaction zone will be between 10% and 90% of the length of a main reaction zone.
Preferably, according to the invention - when the auxiliary ~ ~
reaction zone is in its acceptance period - the flue gas stream is invariably -first passed through this auxiliary reaction zone and then through a main reaction zone. The auxiliary reaction zone can thus be kept so short that, in the period of time available, the quantity of acceptor present in the said auxiliary zone is loaded as completely as possible. In this case the auxiliary reaction zone and the main reaction zone arranged thereafter should be considered as one unit. The sulphur dioxide slipping through the auxiliary reaction zone is accepted in the main reaction zone.
It will be clear that at the end of the relatively short accept-ance period of the auxiliary reaction zone the flue gas stream is no longer passed therethrough, bu~ passed direc~ly to the main reaction zone which is arranged after the auxiliary reaction zone.
~ 73~7 According to the invention the connection of a main reaction zone to the flue gas stream is preferably effected invariably simultaneously with the disconnection of the flue gas stream to another main reaction zone. The main reaction zones are in this case connected to branch ~lines of a flue gas duct. These latter lines contain valves, and simultaneously with the opening of the valve to the main reaction zone to be connected to the flue gas stream, the valve to the zone of which the supply of flue gas has to be discontinued, is closed. In ~ this way the total quantity of flue gas keeps flowing freely and minimal additional decrease or increase in the pressure drop occurs, so that the unit from which the flue gas emanates~ is not affected at all by the change-over to another main reaction zone.
In a preferred embodiment of the invention the regeneration treat-mentis preceded and followed by purging with steam or another inert gas.
During this purging no sulphur dioxide is removed from the ac-...
ceptor and the purging of the reaction zones serves to prevent the formation of explosive gas mixtures during -the transition from the acceptance - under oxidizing conditions - to the regeneration under reducing conditions.~It will be obvious that purging applied for safety reasons, also contributes to the fact that some time elapses between the periods in which reducing eas is passed through subsequent main reaction zones, assuming that these zones have subsequent ac-ceptance periods. The invention is therefore also of importance in particular under these conditions.
In the above embodiment the regeneration of t,he auxiliary reaction zone i5 preferably already started during the purging of the main re-action zone which has been regenerated immediately be~ore and is ~ ~ continued for some time during the purging of the main reaction zone to be regenerated immediately thereafter. In this way the continuity of the demand for reducing gas and of the supply of sulphur dioxi~e-containing regeneration off-gas is guaranteed in spite of the purgin of the main reaction zones.
According to the invention the regeneration of the acceptor in the auxiliary reaction zone is preferably continued for a short period ~o~3~87 `: ' at the beginning of the regeneration of the acceptor present in a main reaction zone. Unlike the acceptor in the auxiliary reaction ;~
zone, which i5 loaded with sulphur dioxide over the full length of the said zone at the end of the acceptance period, the acceptor in a main reaction zone is substantially fully loaded over only part of the zone length at the end of the ~cceptance period and for the .:
rest the degree of the load decreases in the direction of flow.
The choice of the length of the acceptance period of the main re-action zone such that at the end thereof the acceptor in this main zone is not fully loaded as indicated,prevents that too much sulphur dioxide will slip throuKh the main reaction zone. The foregoing implies, however, that at the beginning of the regeneration of the acceptor in such a main reaction zone the sulphur dioxide content in the regeneration oPf-gas will be low. This phenomenon, known as re-acceptance, may be explained from the fact that sulphur dioxide recovered in the first ~rt of the acceptor bed during regeneration i9 re-accepted in ano-ther part of the bed. By supplying further regeneration off-gas from the auxiliary reaction zone in the period of re-acceptance during regeneration, the sulphur dioxide content 20 ~ of the total quantity of regeneration off-gas liberated will still be as constant as possible.
Consequently, the acceptance and regeneration periods of the invention are preferably so selected that at the end of the relevant acceptance period the acceptor in the auxiliary reaction zone is loaded as fully as possible with sulphur dioxide over the entire length of the said zone, whereas the acceptor in the main reaction zone is not - yet fully loaded over the entire length o~ the saidnain reaction zone~ in such a way that in regenerating the acceptor in the said main reaction zone, the sulphur dioxide initially recovered in the reducing gas is re-accepted further on in the as yet unregenerated part of the main reaction zone. It will further be obvious that the acceptance period of the auxiliary reaction zone terminates at an-other point of time than the acceptance period of each of the main reaction zones. Under these conditions the applica~ion o~ the auxiliary reaction zone according to the invention will haYe its greatest effect.
~ : ' :
..;..
~ 73~L87 : .~
In a preferred embodiment of the invention the acceptor consists of a ceramic carrier on which one or more metals, including copper, have been deposited, aDd acceptance and regener~tion are carried out at a temperature between 200 C and 600 C. Under these conditions the invention is advantageous especially because the regeneration ;
~riod is significantly shorter than the acceptance period.
The inven-tion may be applied adYantageously, inter alia, where the flue gas contains less than 2% by volume of sulphur dioxide and at least an equal portion of oxygen and the reducing gas contains at least 50% by volume of steam and/or another inert gas and at most ~
50% by volume of hydrogen, carbon monoxide and/or hydrocarbons.
In ~eneral, flue gas originating from the complete combustion of sulphur-conkaining hydrocarbon-based fuel or coal contains the said percentages of sulphur dioxide and oxygen. Oxygen, which is usually supplied as air when the combustion takes place in a furnace, is usually provided in a slight excess quantity in order to ensure -~
complete combustion without a soot-forming flame. When a copper-containing acceptor is used the presence of oxygen in the flue gas is important, since the sulphur dioxide is accepted as sulphate.
In addition, it is, of course, possible to oxidize the acceptor after regeneration in a separate step. Under the above conditions and in particular at the said composition of the reducing gas, reasonably short regeneration times are possible withou-t the temperature of the acceptor rising to values which are unacceptable in view of thermal stability.
~ According to the invention when use is made of three main re-action zones, the regeneration time for a main reaction zone is preferably less than half the acceptance time. In particular in the latter case some time will elapse between the regeneration treatments of subsequent main reaction zones, so that the application of an auxiliary reaction zone is very useful. This, o~ course, also applies when~ in the event of three main reaction zones being used, the time required for purging, regeneration and repurging of a main reaction zone is less than half the acceptance time.
.
:
~C~73~87 Aft~r r~moval of the c~xcess water va~)our the r~gcrleration off-gas comprising sulphur d;oxide i5 passed direct:Ly to a sulphur re-covery plant of the Claus type for the prepara-tion o~ element~1 sulphur.
~5 Under the above conditions the provision according to the in~
vention is of importance especially since it is essential for a ~
Claus plant that the concentration of sulphur compounds in -the feed -gas should be as constant as possible. In this connection it should be borne in mind that thelreparation of elemental sulphur proceeds }0 in principle via the Claus reaction:
2 H2S ~ S02 ~ 3 S ~ ~2 and that the sulphur dioxide originating from the flue gas formation must, therefore, react in some manner with or be partially converted into the stoichiometrically required quantity of hydrogen sulphide.
The in~ention will now be further illustrated with reference to the appertaining drawings, in which: ;
Fi~g. 1 is a diagram of the manner in which two main reactors `
and one suxiliary reactor for flue gas desulphurization are connected to the lines for the supply and disch~rge of Plue gas and regener-ation gas;
Fig. 2 is a diagram showing the sequence in which the three reactors o~ Fig. 1 can be operated; and Fig. 3 is a diagram of the sequence in which three main reactors and one auxiliary reactor can be operated in a flue gas desulphur-ization appsratus according to the invention.
Fig. 1 shows two long reaction zones I and II, namely the "main reactors", of the same length and identical design, and a short ` reaction zone III, "the auxiliary reactor", of considerably shorter length. Each reactor contains a bed of acceptor material, for example, copper on an alumina carrier, which is suitable to bind sulphur di- ;
oxide under oxidizing conditions and to release it under reducing conditions.
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,, .
~3LC973~37 :
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_9_ :. .
The three reactors are connected in a special way to a supply line ~1) for flue gas to be desulphurized, to a discharge line (2) for desulphurized flue gas, to supply lines (3) and (19) for re-ducing gas for the regeneration of the loaded acceptor and for purge gas for purgirlg the reactors, and to a discharge line 4 for regeneration off-gas originating from the regeneration of loaded acceptor with the reducing gas.
The purge gas is also supplied and discharged through the ~
system of lines for the reducing gas. ~ ;
o B ~ Flue gas supply line (1) bifurcates into a line (5) with a valve (6) to auxiliary reactor ~ and a line (7) with a valve (8) which may be considered as a by-pass around main reactor I and ;is y connectel~to flue gas discharge line (9) with valve (10) of ~d~}
reactor ~. Downstream of valve (10) line (7) debouches into line (9).
Line (9) bifurcates into lines (11) and (12) with valves (13) and , i (14) for the suppIy of flue gas to main reactors I And II.
Discharge line (2) for desulphurized flue gas is connected to ` ~i main reactors I and II through lines (15) and (16) with valves (17) and (18), respectively.
Supply line (19) for reducing gas and purge gas has a valve (20) and leads to auxiliary reactor III. Supply line (3) for re- ;~
ducing gas and purge gas divides into lines (22) and (23) with ~alves (24) and (25) to main reactors I and II.
Discharge line (4) for regeneration off-gas is connected to reactors I, II and III through lines (26), (27) and (28) with valves (29), (30) and (31), respectively.
The operation of the system shown in Fig. 1 is as follows:
at any moment flue gas is pasæed through one of the ~wo main re- ;
actors I or II. Assuming this at a certain moment to be reactor I, the relevant valves (13) and (17) in flue gas lines (11) and (15) of reactor I are opened and valves (14) and (18) in flue gas lines (12) and (16) of reactor II are closed. Valves (24) and (29) of the regeneration gas lines (22) and (26) of reactor I are then closed and valves (25) and (30) of the regeneration gas lines (23) and (27) of reactor II are opened. Reactor II, through which no flue gas is .; ~
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~07311~7 .~
flowing at this moment, can be regenerated or purged by supplying and discharging regerlera~n gas or purge gas through ]ines (23) and t27).
- - At the end of the acceptance period of reactor I, valves (13) and (17) in the flue gas lines to this reactor I are closed and simultaneously valves (14) and (18) in the flue gas lines to the ~regenerated reactor II are opened. Opening and closing of the valves in the flue gas lines generally takes some minutes, owing to the large dimensions of the valves.
The time schedule of Fig. 2 shows from left to right the sequence -of operations with respect to the apparatus of Fig. 1 chronologically for a period of about three hours. The upper band relates to main reactor I, the middle band to main reactor II and the lower band to auxiliary reactor III~ The hatched parts indicate the regeneration periods, the long blank parts the acceptance periods and the short ;~
blank linking~parts indicate the purging-periods. Opening and closing of the valves in the flue gas lines ha~ been incorporated in the acceptance periods. Thus, the acceptance period (32) of reactor I
is followed by a purging period (33) and subsequently by a regener-ation period (34), then a purging period (35) and thereafter a sub-sequent acceptance period (36), etc.
As shown in Fig. 2, the regeneration period (37~ of reactor II
is terminated before the acceptance period (32) of reactor I. This is necessary to ensure that at the end of the purging period (38) -~hich follows the period (37j - the acceptance period (39) can co~mence in good time, i.e.~ periods (32) and (39) should overlap each other for the duration of the simultaneous opening of the valves (14) and (18) in the flue gas lines of reactor II and closing o~ the valves (13) and (17) in the flue gas lines of reactor I.
This ensures that the flue gas supply can invaria~ly be treated.
Fig. 2 shows th~tthe regeneration periods of main reactors I~ and II are no-t linked. In order nevertheless to ensure a continuous demand for reducing gas nd a continuous supply of sulphur dioxide-.
containing regeneration off-gas,according to the invention auxiliary r reactor III is used. As appears from Fig. 23 this reactor III i5 oper-, --/0 ~ :
,,-~73~L8~ ~
ated at a frequency which is double that o~ reactors I and II. The length o~ auxiliary reactor III is shorter, so that the acceptance period and regeneration period are also shorter.
The regeneration period (40) is so chosen that it lin~s up `~
with the end of the regeneration period (37) of a main reactor, but overlaps the beginning of the regeneration period (34) of the next reactor. As already stated, the sulphur dioxide content of ; the regeneration off-gas of a main reactor at the beginning of the regeneration period is low owing to the re-acceptance. Subsequently, this content remains at an approximately constant, relatively high level until the end of the regeneration period. In regeneratin~
auYiliary reactor III, on the other hand, which reactor contains acceptor that is loaded as completely as possi~le at the end of its acceptance period, the sulphur dioxide content in the regeneration o~f-gas thereof is high during substantially the entire regener-ation period. In this way the supply of sulphur dioxide through line (4) of the apparatus ~ Fig. 1 is substantially constant in the course of time.
As stated above, the degree of load is substantially constant over the length of the acceptor bed of auxiliary reactor III, since this reactor is always connected in front of a main reactor during the acceptance period and, therefore, behaves as the front part of this main reactor. Hence, during the acceptance period a quantity of sulphur dioxide invariably slips from auxiliary reactor III to the main reactor connected thereafter.
In the left-hand part of Fig. 2 auxiliary reactor III is in the acceptance period (41), which coincides with the acceptance period ~32) of main reactor I. In Fig. 1 this ~eans that valves (6) and (10) in ~lue gas supply lines (5) and (9) are opened and that valve (8) in by-pass line (7) is closed. At the end of the ac-ceptance period (41) (see Fig. 2) valve (8) is opened and ; simultaneously valves (6) and (10) are closed.
Valves (20) and (31) in the supply and discharge lines ~or regeneration eas are closed during the acceptance ~riod (41) (see Fig. 2) and are opened at the end of that period, whereupon purge ' `' ;:
1~73~1L87 _12-`~
gas iB supplied through the line (19) dur;ng the purging period (42) (see Fig. 2). Fig. 2 shows clearly that the beginning of the regener-ation period (40) of reactor III coincides with the end of the regeneration period (37) of main reactor II and that this period ~40) ~ -terminates after the beginning of the regeneration period (34) of main reactor I.
The regeneration period (40) is followed by a purging period (43), in which purge gas is again supplied through line (19) as shown ~ ;
in Fig. 1. At the end of -the period (43) valves (20) and (31) are ~ -closed and subsequently valves (6) and (10) are opened simultaneously with the closure of valve (8), thus commencing the acceptance period ~4).
; Fig. 3 shows a chronological dia8ram in accordance with Fig. 2, showing the course o~ acceptance, purging and regeneration with an apparatus comprising three main reactors A, B and C and one auxiliary reactor D.
Since the regeneration period (45) together with the two purging periods (46) and (47) covers less than half the acceptance period (48), some time will elapse bet~een subsequent regeneration periods (45), (49) and (50~ of the three main reactors A, B and C. The acceptance period (48) of one rea¢tor commences some time before the end of the acceptance period (51) of one of the two other reactors. As is known, this time is used for the simultaneous opening and ~osing of the relevant valves in th~ flue gas lines. As is shown in Fig. 3, in-variably two reactors simultaneously accept sulphur dioxide from the flue gas. ~he three reactors are regenerated alternately.
During the time elapsing between the regeneration of subsequent main reactors the auxiliary reactor D is regenerated. As in Fig. 2 the regeneration of the auxiliary reactor is now commenced st the end ;;~
of the regeneration of a main reactor and stopped after the beginning of the regeneration of the next main reactor. r During the acceptance period ~52) of auxiliary reactor D flue gas i8 invarl~bly passed through, which flue gas is ~ubsequently passed to main long reactor A of which the acceptance period (48) commenced during the preceding regeneraton period (53) of auxiliary reactor D.
,"
',: .
' ' /,~_ ; ~ "
. ' '
The in~ention will now be further illustrated with reference to the appertaining drawings, in which: ;
Fi~g. 1 is a diagram of the manner in which two main reactors `
and one suxiliary reactor for flue gas desulphurization are connected to the lines for the supply and disch~rge of Plue gas and regener-ation gas;
Fig. 2 is a diagram showing the sequence in which the three reactors o~ Fig. 1 can be operated; and Fig. 3 is a diagram of the sequence in which three main reactors and one auxiliary reactor can be operated in a flue gas desulphur-ization appsratus according to the invention.
Fig. 1 shows two long reaction zones I and II, namely the "main reactors", of the same length and identical design, and a short ` reaction zone III, "the auxiliary reactor", of considerably shorter length. Each reactor contains a bed of acceptor material, for example, copper on an alumina carrier, which is suitable to bind sulphur di- ;
oxide under oxidizing conditions and to release it under reducing conditions.
'` ;
,, .
~3LC973~37 :
"
_9_ :. .
The three reactors are connected in a special way to a supply line ~1) for flue gas to be desulphurized, to a discharge line (2) for desulphurized flue gas, to supply lines (3) and (19) for re-ducing gas for the regeneration of the loaded acceptor and for purge gas for purgirlg the reactors, and to a discharge line 4 for regeneration off-gas originating from the regeneration of loaded acceptor with the reducing gas.
The purge gas is also supplied and discharged through the ~
system of lines for the reducing gas. ~ ;
o B ~ Flue gas supply line (1) bifurcates into a line (5) with a valve (6) to auxiliary reactor ~ and a line (7) with a valve (8) which may be considered as a by-pass around main reactor I and ;is y connectel~to flue gas discharge line (9) with valve (10) of ~d~}
reactor ~. Downstream of valve (10) line (7) debouches into line (9).
Line (9) bifurcates into lines (11) and (12) with valves (13) and , i (14) for the suppIy of flue gas to main reactors I And II.
Discharge line (2) for desulphurized flue gas is connected to ` ~i main reactors I and II through lines (15) and (16) with valves (17) and (18), respectively.
Supply line (19) for reducing gas and purge gas has a valve (20) and leads to auxiliary reactor III. Supply line (3) for re- ;~
ducing gas and purge gas divides into lines (22) and (23) with ~alves (24) and (25) to main reactors I and II.
Discharge line (4) for regeneration off-gas is connected to reactors I, II and III through lines (26), (27) and (28) with valves (29), (30) and (31), respectively.
The operation of the system shown in Fig. 1 is as follows:
at any moment flue gas is pasæed through one of the ~wo main re- ;
actors I or II. Assuming this at a certain moment to be reactor I, the relevant valves (13) and (17) in flue gas lines (11) and (15) of reactor I are opened and valves (14) and (18) in flue gas lines (12) and (16) of reactor II are closed. Valves (24) and (29) of the regeneration gas lines (22) and (26) of reactor I are then closed and valves (25) and (30) of the regeneration gas lines (23) and (27) of reactor II are opened. Reactor II, through which no flue gas is .; ~
:.: .
.
: `
~07311~7 .~
flowing at this moment, can be regenerated or purged by supplying and discharging regerlera~n gas or purge gas through ]ines (23) and t27).
- - At the end of the acceptance period of reactor I, valves (13) and (17) in the flue gas lines to this reactor I are closed and simultaneously valves (14) and (18) in the flue gas lines to the ~regenerated reactor II are opened. Opening and closing of the valves in the flue gas lines generally takes some minutes, owing to the large dimensions of the valves.
The time schedule of Fig. 2 shows from left to right the sequence -of operations with respect to the apparatus of Fig. 1 chronologically for a period of about three hours. The upper band relates to main reactor I, the middle band to main reactor II and the lower band to auxiliary reactor III~ The hatched parts indicate the regeneration periods, the long blank parts the acceptance periods and the short ;~
blank linking~parts indicate the purging-periods. Opening and closing of the valves in the flue gas lines ha~ been incorporated in the acceptance periods. Thus, the acceptance period (32) of reactor I
is followed by a purging period (33) and subsequently by a regener-ation period (34), then a purging period (35) and thereafter a sub-sequent acceptance period (36), etc.
As shown in Fig. 2, the regeneration period (37~ of reactor II
is terminated before the acceptance period (32) of reactor I. This is necessary to ensure that at the end of the purging period (38) -~hich follows the period (37j - the acceptance period (39) can co~mence in good time, i.e.~ periods (32) and (39) should overlap each other for the duration of the simultaneous opening of the valves (14) and (18) in the flue gas lines of reactor II and closing o~ the valves (13) and (17) in the flue gas lines of reactor I.
This ensures that the flue gas supply can invaria~ly be treated.
Fig. 2 shows th~tthe regeneration periods of main reactors I~ and II are no-t linked. In order nevertheless to ensure a continuous demand for reducing gas nd a continuous supply of sulphur dioxide-.
containing regeneration off-gas,according to the invention auxiliary r reactor III is used. As appears from Fig. 23 this reactor III i5 oper-, --/0 ~ :
,,-~73~L8~ ~
ated at a frequency which is double that o~ reactors I and II. The length o~ auxiliary reactor III is shorter, so that the acceptance period and regeneration period are also shorter.
The regeneration period (40) is so chosen that it lin~s up `~
with the end of the regeneration period (37) of a main reactor, but overlaps the beginning of the regeneration period (34) of the next reactor. As already stated, the sulphur dioxide content of ; the regeneration off-gas of a main reactor at the beginning of the regeneration period is low owing to the re-acceptance. Subsequently, this content remains at an approximately constant, relatively high level until the end of the regeneration period. In regeneratin~
auYiliary reactor III, on the other hand, which reactor contains acceptor that is loaded as completely as possi~le at the end of its acceptance period, the sulphur dioxide content in the regeneration o~f-gas thereof is high during substantially the entire regener-ation period. In this way the supply of sulphur dioxide through line (4) of the apparatus ~ Fig. 1 is substantially constant in the course of time.
As stated above, the degree of load is substantially constant over the length of the acceptor bed of auxiliary reactor III, since this reactor is always connected in front of a main reactor during the acceptance period and, therefore, behaves as the front part of this main reactor. Hence, during the acceptance period a quantity of sulphur dioxide invariably slips from auxiliary reactor III to the main reactor connected thereafter.
In the left-hand part of Fig. 2 auxiliary reactor III is in the acceptance period (41), which coincides with the acceptance period ~32) of main reactor I. In Fig. 1 this ~eans that valves (6) and (10) in ~lue gas supply lines (5) and (9) are opened and that valve (8) in by-pass line (7) is closed. At the end of the ac-ceptance period (41) (see Fig. 2) valve (8) is opened and ; simultaneously valves (6) and (10) are closed.
Valves (20) and (31) in the supply and discharge lines ~or regeneration eas are closed during the acceptance ~riod (41) (see Fig. 2) and are opened at the end of that period, whereupon purge ' `' ;:
1~73~1L87 _12-`~
gas iB supplied through the line (19) dur;ng the purging period (42) (see Fig. 2). Fig. 2 shows clearly that the beginning of the regener-ation period (40) of reactor III coincides with the end of the regeneration period (37) of main reactor II and that this period ~40) ~ -terminates after the beginning of the regeneration period (34) of main reactor I.
The regeneration period (40) is followed by a purging period (43), in which purge gas is again supplied through line (19) as shown ~ ;
in Fig. 1. At the end of -the period (43) valves (20) and (31) are ~ -closed and subsequently valves (6) and (10) are opened simultaneously with the closure of valve (8), thus commencing the acceptance period ~4).
; Fig. 3 shows a chronological dia8ram in accordance with Fig. 2, showing the course o~ acceptance, purging and regeneration with an apparatus comprising three main reactors A, B and C and one auxiliary reactor D.
Since the regeneration period (45) together with the two purging periods (46) and (47) covers less than half the acceptance period (48), some time will elapse bet~een subsequent regeneration periods (45), (49) and (50~ of the three main reactors A, B and C. The acceptance period (48) of one rea¢tor commences some time before the end of the acceptance period (51) of one of the two other reactors. As is known, this time is used for the simultaneous opening and ~osing of the relevant valves in th~ flue gas lines. As is shown in Fig. 3, in-variably two reactors simultaneously accept sulphur dioxide from the flue gas. ~he three reactors are regenerated alternately.
During the time elapsing between the regeneration of subsequent main reactors the auxiliary reactor D is regenerated. As in Fig. 2 the regeneration of the auxiliary reactor is now commenced st the end ;;~
of the regeneration of a main reactor and stopped after the beginning of the regeneration of the next main reactor. r During the acceptance period ~52) of auxiliary reactor D flue gas i8 invarl~bly passed through, which flue gas is ~ubsequently passed to main long reactor A of which the acceptance period (48) commenced during the preceding regeneraton period (53) of auxiliary reactor D.
,"
',: .
' ' /,~_ ; ~ "
. ' '
Claims (4)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1 A process for the removal of sulphur dioxide from a flue gas stream by means of a solid acceptor on which the sulphur dioxide is accepted and from which it is subsequently recovered by regeneration of the loaded acceptor with a reducing gas, which process is carried out in two or three equally sized main reaction zones comprising the said acceptor, of which zones at least one and at most two is/are invariably connected to the flue gas stream and said main reaction zones being alternately subjected to a regeneration treatment with the exclusion of the flue gas stream, character-ized in that an auxiliary reaction zone with acceptor is applied, which auxiliary reaction zone is of shorter length than the said main reaction zones, and is connected to the flue gas stream in front of a main reactor zone during an acceptance period, said auxiliary zone being subjected to a re-generation treatment during the short intervals between the sequential regeneration treatments of the main reaction zones in such a manner that the said regeneration treatment of the auxiliary reaction zone is continued for a short period at the beginning of the regeneration treatment of the next main reaction zone.
2. A process as claimed in claim 1, wherein the flue gas stream is invariably first passed through the auxiliary reaction zone and then through a main reaction zone during an acceptance period of the auxiliary reaction zone
3. A process as claimed in claim 1 or claim 2, wherein the regeneration treatment of the auxiliary reaction zone is already started during purging with steam or another inert gas of the main reaction zone which has been regenerated immediately before and is continued for some time during purging with steam or another inert gas of the main reaction zone to be regenerated immediately thereafter,
4, A process as claimed in claim 1, wherein the acceptance and regeneration periods of the main reaction zones are so selected that at the end of its acceptance period the acceptor in the auxiliary reaction zone is loaded as fully as possible with sulphur dioxide over the entire length of the said auxiliary zone, whereas the acceptor in the main reaction zone following the auxiliary reaction zone is not yet fully loaded over the entire length of the said main reaction zone,
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| NL7403073A NL177085C (en) | 1974-03-07 | 1974-03-07 | METHOD AND DEVICE FOR THE REMOVAL OF SULFUR DIOXIDE FROM FLUE GAS USING A FIXED ACCEPTOR. |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1073187A true CA1073187A (en) | 1980-03-11 |
Family
ID=19820905
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA220,642A Expired CA1073187A (en) | 1974-03-07 | 1975-02-24 | Process for the removal of sulphur dioxide from a flue gas stream by means of a solid acceptor |
Country Status (7)
| Country | Link |
|---|---|
| JP (1) | JPS5846336B2 (en) |
| BE (1) | BE826323A (en) |
| CA (1) | CA1073187A (en) |
| DE (1) | DE2509573C2 (en) |
| FR (1) | FR2263023B1 (en) |
| GB (1) | GB1503693A (en) |
| NL (1) | NL177085C (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2840357A1 (en) * | 1978-09-16 | 1980-04-03 | Linde Ag | ADIABATIC ADSORPTION METHOD FOR GAS PURIFICATION OR SEPARATION |
| JPS58128123A (en) * | 1982-01-26 | 1983-07-30 | Taiyo Sanso Kk | Separation of gas and its device |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| NL170379C (en) * | 1970-12-02 | 1983-04-18 | Shell Int Research | METHOD FOR PREPARING CATALYSTS AND / OR ACCEPTORS FOR THE REMOVAL OF SULFUR OXIDES FROM GASES CONTAINING THEM, AND PREPARED PRODUCTS, CONTAINING ANY METHOD / CONCRETE AND CONCRETED. |
-
1974
- 1974-03-07 NL NL7403073A patent/NL177085C/en not_active IP Right Cessation
-
1975
- 1975-02-24 CA CA220,642A patent/CA1073187A/en not_active Expired
- 1975-03-05 GB GB913775A patent/GB1503693A/en not_active Expired
- 1975-03-05 JP JP50026103A patent/JPS5846336B2/en not_active Expired
- 1975-03-05 BE BE154032A patent/BE826323A/en not_active IP Right Cessation
- 1975-03-05 DE DE19752509573 patent/DE2509573C2/en not_active Expired
- 1975-03-05 FR FR7506845A patent/FR2263023B1/fr not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5846336B2 (en) | 1983-10-15 |
| GB1503693A (en) | 1978-03-15 |
| BE826323A (en) | 1975-09-05 |
| FR2263023A1 (en) | 1975-10-03 |
| DE2509573C2 (en) | 1984-11-15 |
| DE2509573A1 (en) | 1975-10-02 |
| NL177085B (en) | 1985-03-01 |
| FR2263023B1 (en) | 1979-04-27 |
| NL7403073A (en) | 1975-09-09 |
| NL177085C (en) | 1985-08-01 |
| JPS50122472A (en) | 1975-09-26 |
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