CA2136165C - Process and installation for removing solvent vapor from exhaust air - Google Patents
Process and installation for removing solvent vapor from exhaust air Download PDFInfo
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- CA2136165C CA2136165C CA002136165A CA2136165A CA2136165C CA 2136165 C CA2136165 C CA 2136165C CA 002136165 A CA002136165 A CA 002136165A CA 2136165 A CA2136165 A CA 2136165A CA 2136165 C CA2136165 C CA 2136165C
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- 239000002904 solvent Substances 0.000 title claims abstract description 45
- 238000000034 method Methods 0.000 title claims abstract description 32
- 238000009434 installation Methods 0.000 title claims abstract description 31
- 230000008569 process Effects 0.000 title claims abstract description 25
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 35
- 230000008929 regeneration Effects 0.000 claims abstract description 25
- 238000011069 regeneration method Methods 0.000 claims abstract description 25
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 17
- 238000001035 drying Methods 0.000 claims abstract description 13
- 230000003750 conditioning effect Effects 0.000 claims description 13
- 238000001816 cooling Methods 0.000 claims description 13
- 238000004140 cleaning Methods 0.000 claims description 9
- 238000001179 sorption measurement Methods 0.000 claims description 9
- 239000000203 mixture Substances 0.000 claims description 6
- 230000001143 conditioned effect Effects 0.000 claims description 5
- 238000010438 heat treatment Methods 0.000 claims description 5
- 230000009471 action Effects 0.000 claims description 3
- 238000011010 flushing procedure Methods 0.000 claims description 2
- 238000002156 mixing Methods 0.000 claims 2
- 238000003912 environmental pollution Methods 0.000 abstract description 2
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 description 12
- 238000011017 operating method Methods 0.000 description 7
- 230000000694 effects Effects 0.000 description 5
- 238000004064 recycling Methods 0.000 description 4
- 239000002826 coolant Substances 0.000 description 3
- 230000002035 prolonged effect Effects 0.000 description 3
- 239000002699 waste material Substances 0.000 description 3
- 230000008859 change Effects 0.000 description 2
- 239000000428 dust Substances 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- 239000000976 ink Substances 0.000 description 2
- 230000007246 mechanism Effects 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 239000013557 residual solvent Substances 0.000 description 2
- 229920006395 saturated elastomer Polymers 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- 238000011144 upstream manufacturing Methods 0.000 description 2
- 241000320892 Clerodendrum phlomidis Species 0.000 description 1
- 238000005299 abrasion Methods 0.000 description 1
- 230000004075 alteration Effects 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 238000011068 loading method Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
Classifications
-
- 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
- B01D53/02—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 by adsorption, e.g. preparative gas chromatography
- B01D53/04—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 by adsorption, e.g. preparative gas chromatography with stationary adsorbents
- B01D53/0454—Controlling adsorption
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2253/00—Adsorbents used in seperation treatment of gases and vapours
- B01D2253/10—Inorganic adsorbents
- B01D2253/102—Carbon
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2259/00—Type of treatment
- B01D2259/40—Further details for adsorption processes and devices
- B01D2259/40003—Methods relating to valve switching
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2259/00—Type of treatment
- B01D2259/40—Further details for adsorption processes and devices
- B01D2259/40083—Regeneration of adsorbents in processes other than pressure or temperature swing adsorption
- B01D2259/40088—Regeneration of adsorbents in processes other than pressure or temperature swing adsorption by heating
- B01D2259/4009—Regeneration of adsorbents in processes other than pressure or temperature swing adsorption by heating using hot gas
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2259/00—Type of treatment
- B01D2259/40—Further details for adsorption processes and devices
- B01D2259/402—Further details for adsorption processes and devices using two beds
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2259/00—Type of treatment
- B01D2259/40—Further details for adsorption processes and devices
- B01D2259/404—Further details for adsorption processes and devices using four beds
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Analytical Chemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Treating Waste Gases (AREA)
- Separation Of Gases By Adsorption (AREA)
- Cleaning By Liquid Or Steam (AREA)
- Cleaning Or Drying Semiconductors (AREA)
- Encapsulation Of And Coatings For Semiconductor Or Solid State Devices (AREA)
Abstract
In a process and installation for removing solvent vapor from exhaust air sucked from a working space, the air is fed to at least two parallel activated carbon adsorbers. Each adsorber can be switched to and fro between a charging mode in which it adsorbs solvent vapors from the exhaust air flowing through the adsorber, and a regeneration mode in which it is separated from the flow of exhaust air and flushed with water vapor and desorbed. To save energy and to reduce environmental pollution, at the end of the regeneration period each adsorber has a drying phase in which exhaust air from the working space flows through the adsorber, the air thereafter being fed to an adsorber which is operating in the charging mode. In the periods in which an adsorber is operating in the charging mode, it firstly has an initial phase followed by a main phase wherein air flows from adsorbers which are in the main phase are returned directly into the working space while the air flow from an adsorber which is in the initial phase is kept separate from the first-mentioned air flows.
Description
,2136165 The present invention concerns a process arKl an installation for removing solvent vapors fran exhaust or waste air.
There are various situations in which there is a need for solvent vapor to be removed from exhaust or waste air, for example inter alia in printing works where, in particular in the area of rotary intaglio printing, toluene which is used as a solvent for the printing inks and which in operation of the printing machine is discharged into the air in the working space not only has to be removed frccn the vaorking space but also separated out of the exhaust air which is sucked out of the working space, and recycled so that the toluene can be used again. A process and installation for performing those operations are to be found for example in 'Haas der Technik' lecture publications 404 (1978), pages 98 ff.
The above-described operating procedure is effected by means of activated carbon adsorbers fran which the cleaned exhaust air issues in a practically solvent-free condition. In actual fact the residual solvent content in the exhaust air, at about 20 mg/m3, is so far below the limit value of 100 mg/m3 which is required by the present statutory provi.sians in the Federal Republic of Gex~nany (such air being referred to as TA-air), that it is readily permissible for that exhaust air to be discharged into the atmosphere by way of a chirtaiey or the like.
As an activated carbon adsorber can rave impurities fran the exhaust air which flows therethrough and which requires cleaning therein, only until its loading of such impurities has reached a Z5 certain limit value, the .adsorber must switch between two operating modes. The one operating mode is the above-described charging mode during , wh?.ch ,the "cQntamina~ec~ , exhaust air flows through , the ;adsorber in an upward direction, the solvent vapors being adsorptively bound by the activated carbon layers. t~lhen the adsorption capacity of the activated carbon is fully used up, the adsorber is autanatically separated from the flow of exhaust sir and switched over into a regeneration mode in which saturated water vapor or steam is fed to the adsorber by way of a valve so that the vapor flows through the activated carbon in a downward direction, during which time the activated carbon bed is heated and the adsorptively bound solvent is desorbed. The mixture of vapors which is gra3uced in that case is condensed and fed to a piece of equignent in which the solvent is separated fran the water and thus maintained in such a pure condition that it can be re-used.
When the adsorber has been regenerated, the feed of water vapor is terminated and the adsorber is put back into the charging mode condition again in which the exhaust air to be cleaned flows through it.
When this operating procedure is used in the context of printing, in order not to disturb continuous operation of the printing machines by virtue of the fact that solvent adsorption is not possible during the regeneration period, the installation involved in carrying out the operating procedure usually has a plurality of adsorbpxs which are operated in parallel and the number of which is so great that, when one of the adsorbers is operating in the regeneration mode, the adsorption capacity or cleaning capacity of the other adsorbers is sufficient to produce the required cleaning effect for the exhaust air which is to be sucked out of the working space in which the printing equi~xnent is disposed, for x~aval of the solvent vapors produced by the machines. In that situation the adsorbers are operated in opposite relationship at least fran time to time, in such a way that at least one of the adsorbers is in the regeneration mode while at least one other adsorber is operating in the charging mode.
30, . In order to, keep the, concentration of solvent at the working location~below the prescribed values, a considerable amount 'of air must be rerroved from a printing roan in which one or even a plurality of rotary intaglio printing machines are operating, and that amount zl ~s~ ss of air, per printing machine, may ba of the order of magnitude of up to 150,000 m3/hour. AdCnittedly, the air is not sucked away directly in the printing roan itself, but rather the air is sucked out of the machine hoods which cover over the rotary intaglio printing machines, or from the drying devices of the printing mechanisms, which however are open on their feed flow side to the printing room. So that the slight reduced pressure which is desired in relation to the outside air is maintained within the printing roan, the printing roan must be supplied with an amount of conditioned fresh air which corresponds to the amount of air that is sucked out of the printing roan. The fresh air is air which is sucked in out of the surrounding atmosphere. That air must be filtered to separate off dust and other solid particles, heated or cooled to the required temperature, and possibly also adjusted to a desired value in respect of its moisture content or humidity. So that those conditioning operations can be carried out for the large amounts of air indicated above, the equipment involved requires correspondingly large fresh air blowers and conditioning installations, and operation thereof involves a considerable level of energy expenditure.
In accordance with a first aspect of the present invention there is provided a process for rgnoving solvent vapor fran exhaust air which is sucked out of a working space, wherein the air is cleaned by being passed through at least two activated carbon adsorbers which are in mutually parallel relationship and each of which runs through operating cycles which each canprise. a charging. period in which the exhaust air flows through the adsorber and the adsorber adsorbs the solvent vapor contained in the exhaust air and a regeneration period in which the adsorber is separated fran the flow of exhaust air and water vapor flows through the adsorber to desorb and flush out the previously adsorbed solvent; wherein the working cycles of the at least two adsorbers are displaced relative to each other in respect of time ~in such a~ way that ~at least one of the ' adsorbers is' always working in the charging mode, thereby to achieve a continuous zl3s~s~
adsorption. procesuret wherein each regeneration period includes a concluding drying phase in which, instead of water vapor, exhaust air from the working space flows through the adsorber in question, the exhaust air after leaving said adsorber being fed to the at least one adsorber which in that period is working in the charging mode: and wherein each charging period includes an initial phase and a subsequent main phase, which are determined by virtue of the fact that the air flow issuing fran an adsorber which is in the initial phase of a charging period is fed to a separate treatment while the air flow issuing fran an adsorber which is in the main phase of a charging period is returned directly into the working space.
It will be noted hereinafter that the process for removing solvent vapors fran exhaust air in accoxriance with the invention can afford an at least reasonable reduction in the level of apparatus expenditure and energy costs, in conjunction with an enhanced level of reliability and efficiency in solvent removal, giving better operating results in tee of the solvent x~nrnred and the air fran which the solvent is rerioved. The pxncess can be used more specifically for removing solvent vapor fran exhaust air fran printing equipment, thus permitting the cleaned air to be recycled.
In accordance with a further aspect of the present invention there is provided an installation for x~naving solvent vapor from exhaust air, comprising:
- blower means for sucking the exhaust air out of a working space, - at least first and second activated carbon adsorbers arranged in mutually parallel relationship, .
- a control means, - a control arrangement which is controllable by said control 30~ means and which, ~~for each' of the adsorbers, includes an inlet vale means which in the opened condition cocm~unicates it with the associated blower means; a main flow path; and an outlet valve means which in the opened condition passes air issuing fran the adsorber into said main flow path; the arranggnent being such that each of the adsorbers is switchable to and fm between a charging mode in which exhaust air to be cleaned flows through the adsorber and the adsorber adsorbs solvent contained in the exhaust air and a regeneration mode in which the adsorber is separated fran the flow of exhaust a9r and water vapor can flow through the adsorber for desorbing and flushing out the adsorbed solvent, the switching action between the charging and the regeneration modes occurring alternately in such a way that at least one of the adsorbers is always operating in the charging mode, and - a discharge means by means of which air which has flowed through one of the adsorbers can be expelled into the surrounding atmosphere, wherein the contml arranggnent further includes the following, for each adsorber:
- a second outlet valve means and a conduit which in the open condition of the second outlet valve means is communicated thereby with the adsorber and by way of which air issuing from the adsorber can be returned to the flow path leading fxnm the working space to the adsorbers so that. air fran the working space which. flows through..
an adsorber in a drying phase which concludes the adsorber regeneration period when the inlet valve means is open and the first outlet valve means is closed can be fed by way of the opened second outlet valve means to the at least one adsorber which iss operating in the charging mode, and - an auxiliary outlet valve means and an auxiliary flow path which in the open condition of~the auxiliary outlet valve means is carmunicated thereby with the adsorber so that air firm the working space which flows through the adsorber in an initial phase of its charging period when the inlet valve means is open and the first and second outlet valve means are closed can be fed by way of said auxiliary flow path to a separate treatment, and the main flow path is canrnmicated with the working space so that air fran the working space which flows through the adsorber in a main phase following the initial phase of its charging period can be returned into the working space after cleaning of said air.
As will be seen fran the following description of a preferred embodiment of the invention, the invention is based on the following considerations:
In the previous operating procedure as discussed above, recycling of the cleaned exhaust air issuing from the adsorbers to the working area or space is not meaningful in econanic terms . That is because in that procedure all air flows issuing from the adsorbers are mixed together irm~ediately downstream of the adsorbers. As a result, the very k:ot and very moist fl~v of air issuing fxnm an adsorber which is in the initial phase of a charging mode is admittedly considerably cooled. At the same time haaever, it so greatly heats up the total air flow coming fran the adsorbers, and introduces into that air flow such a large amount of mixture, that the expenditure which has to be made to provide a cooling action and to remove moisture fran the total air flow in order to condition it to such an extent that it can be recycled to the working space, is considerably greater than the expenditure required for conditioning the fresh air which is sucked in fran the ambient atmosphere. Accordingly, in that prior procedure,., it vas,, leas expensive, for the ,cleaned exhaust air to be completely discharged into the atmosphere and replaced by fresh air which was drawn from the atmosphere at another location.
There are various situations in which there is a need for solvent vapor to be removed from exhaust or waste air, for example inter alia in printing works where, in particular in the area of rotary intaglio printing, toluene which is used as a solvent for the printing inks and which in operation of the printing machine is discharged into the air in the working space not only has to be removed frccn the vaorking space but also separated out of the exhaust air which is sucked out of the working space, and recycled so that the toluene can be used again. A process and installation for performing those operations are to be found for example in 'Haas der Technik' lecture publications 404 (1978), pages 98 ff.
The above-described operating procedure is effected by means of activated carbon adsorbers fran which the cleaned exhaust air issues in a practically solvent-free condition. In actual fact the residual solvent content in the exhaust air, at about 20 mg/m3, is so far below the limit value of 100 mg/m3 which is required by the present statutory provi.sians in the Federal Republic of Gex~nany (such air being referred to as TA-air), that it is readily permissible for that exhaust air to be discharged into the atmosphere by way of a chirtaiey or the like.
As an activated carbon adsorber can rave impurities fran the exhaust air which flows therethrough and which requires cleaning therein, only until its loading of such impurities has reached a Z5 certain limit value, the .adsorber must switch between two operating modes. The one operating mode is the above-described charging mode during , wh?.ch ,the "cQntamina~ec~ , exhaust air flows through , the ;adsorber in an upward direction, the solvent vapors being adsorptively bound by the activated carbon layers. t~lhen the adsorption capacity of the activated carbon is fully used up, the adsorber is autanatically separated from the flow of exhaust sir and switched over into a regeneration mode in which saturated water vapor or steam is fed to the adsorber by way of a valve so that the vapor flows through the activated carbon in a downward direction, during which time the activated carbon bed is heated and the adsorptively bound solvent is desorbed. The mixture of vapors which is gra3uced in that case is condensed and fed to a piece of equignent in which the solvent is separated fran the water and thus maintained in such a pure condition that it can be re-used.
When the adsorber has been regenerated, the feed of water vapor is terminated and the adsorber is put back into the charging mode condition again in which the exhaust air to be cleaned flows through it.
When this operating procedure is used in the context of printing, in order not to disturb continuous operation of the printing machines by virtue of the fact that solvent adsorption is not possible during the regeneration period, the installation involved in carrying out the operating procedure usually has a plurality of adsorbpxs which are operated in parallel and the number of which is so great that, when one of the adsorbers is operating in the regeneration mode, the adsorption capacity or cleaning capacity of the other adsorbers is sufficient to produce the required cleaning effect for the exhaust air which is to be sucked out of the working space in which the printing equi~xnent is disposed, for x~aval of the solvent vapors produced by the machines. In that situation the adsorbers are operated in opposite relationship at least fran time to time, in such a way that at least one of the adsorbers is in the regeneration mode while at least one other adsorber is operating in the charging mode.
30, . In order to, keep the, concentration of solvent at the working location~below the prescribed values, a considerable amount 'of air must be rerroved from a printing roan in which one or even a plurality of rotary intaglio printing machines are operating, and that amount zl ~s~ ss of air, per printing machine, may ba of the order of magnitude of up to 150,000 m3/hour. AdCnittedly, the air is not sucked away directly in the printing roan itself, but rather the air is sucked out of the machine hoods which cover over the rotary intaglio printing machines, or from the drying devices of the printing mechanisms, which however are open on their feed flow side to the printing room. So that the slight reduced pressure which is desired in relation to the outside air is maintained within the printing roan, the printing roan must be supplied with an amount of conditioned fresh air which corresponds to the amount of air that is sucked out of the printing roan. The fresh air is air which is sucked in out of the surrounding atmosphere. That air must be filtered to separate off dust and other solid particles, heated or cooled to the required temperature, and possibly also adjusted to a desired value in respect of its moisture content or humidity. So that those conditioning operations can be carried out for the large amounts of air indicated above, the equipment involved requires correspondingly large fresh air blowers and conditioning installations, and operation thereof involves a considerable level of energy expenditure.
In accordance with a first aspect of the present invention there is provided a process for rgnoving solvent vapor fran exhaust air which is sucked out of a working space, wherein the air is cleaned by being passed through at least two activated carbon adsorbers which are in mutually parallel relationship and each of which runs through operating cycles which each canprise. a charging. period in which the exhaust air flows through the adsorber and the adsorber adsorbs the solvent vapor contained in the exhaust air and a regeneration period in which the adsorber is separated fran the flow of exhaust air and water vapor flows through the adsorber to desorb and flush out the previously adsorbed solvent; wherein the working cycles of the at least two adsorbers are displaced relative to each other in respect of time ~in such a~ way that ~at least one of the ' adsorbers is' always working in the charging mode, thereby to achieve a continuous zl3s~s~
adsorption. procesuret wherein each regeneration period includes a concluding drying phase in which, instead of water vapor, exhaust air from the working space flows through the adsorber in question, the exhaust air after leaving said adsorber being fed to the at least one adsorber which in that period is working in the charging mode: and wherein each charging period includes an initial phase and a subsequent main phase, which are determined by virtue of the fact that the air flow issuing fran an adsorber which is in the initial phase of a charging period is fed to a separate treatment while the air flow issuing fran an adsorber which is in the main phase of a charging period is returned directly into the working space.
It will be noted hereinafter that the process for removing solvent vapors fran exhaust air in accoxriance with the invention can afford an at least reasonable reduction in the level of apparatus expenditure and energy costs, in conjunction with an enhanced level of reliability and efficiency in solvent removal, giving better operating results in tee of the solvent x~nrnred and the air fran which the solvent is rerioved. The pxncess can be used more specifically for removing solvent vapor fran exhaust air fran printing equipment, thus permitting the cleaned air to be recycled.
In accordance with a further aspect of the present invention there is provided an installation for x~naving solvent vapor from exhaust air, comprising:
- blower means for sucking the exhaust air out of a working space, - at least first and second activated carbon adsorbers arranged in mutually parallel relationship, .
- a control means, - a control arrangement which is controllable by said control 30~ means and which, ~~for each' of the adsorbers, includes an inlet vale means which in the opened condition cocm~unicates it with the associated blower means; a main flow path; and an outlet valve means which in the opened condition passes air issuing fran the adsorber into said main flow path; the arranggnent being such that each of the adsorbers is switchable to and fm between a charging mode in which exhaust air to be cleaned flows through the adsorber and the adsorber adsorbs solvent contained in the exhaust air and a regeneration mode in which the adsorber is separated fran the flow of exhaust a9r and water vapor can flow through the adsorber for desorbing and flushing out the adsorbed solvent, the switching action between the charging and the regeneration modes occurring alternately in such a way that at least one of the adsorbers is always operating in the charging mode, and - a discharge means by means of which air which has flowed through one of the adsorbers can be expelled into the surrounding atmosphere, wherein the contml arranggnent further includes the following, for each adsorber:
- a second outlet valve means and a conduit which in the open condition of the second outlet valve means is communicated thereby with the adsorber and by way of which air issuing from the adsorber can be returned to the flow path leading fxnm the working space to the adsorbers so that. air fran the working space which. flows through..
an adsorber in a drying phase which concludes the adsorber regeneration period when the inlet valve means is open and the first outlet valve means is closed can be fed by way of the opened second outlet valve means to the at least one adsorber which iss operating in the charging mode, and - an auxiliary outlet valve means and an auxiliary flow path which in the open condition of~the auxiliary outlet valve means is carmunicated thereby with the adsorber so that air firm the working space which flows through the adsorber in an initial phase of its charging period when the inlet valve means is open and the first and second outlet valve means are closed can be fed by way of said auxiliary flow path to a separate treatment, and the main flow path is canrnmicated with the working space so that air fran the working space which flows through the adsorber in a main phase following the initial phase of its charging period can be returned into the working space after cleaning of said air.
As will be seen fran the following description of a preferred embodiment of the invention, the invention is based on the following considerations:
In the previous operating procedure as discussed above, recycling of the cleaned exhaust air issuing from the adsorbers to the working area or space is not meaningful in econanic terms . That is because in that procedure all air flows issuing from the adsorbers are mixed together irm~ediately downstream of the adsorbers. As a result, the very k:ot and very moist fl~v of air issuing fxnm an adsorber which is in the initial phase of a charging mode is admittedly considerably cooled. At the same time haaever, it so greatly heats up the total air flow coming fran the adsorbers, and introduces into that air flow such a large amount of mixture, that the expenditure which has to be made to provide a cooling action and to remove moisture fran the total air flow in order to condition it to such an extent that it can be recycled to the working space, is considerably greater than the expenditure required for conditioning the fresh air which is sucked in fran the ambient atmosphere. Accordingly, in that prior procedure,., it vas,, leas expensive, for the ,cleaned exhaust air to be completely discharged into the atmosphere and replaced by fresh air which was drawn from the atmosphere at another location.
The present invention therefore now provides as a first step that, just before the termination of each regeneration period of an adsorber, the adsorber, instead of being supplied with water vapor or steam, is supplied with exhaust air frcm the working space, during a drying phase which lasts for only a few minutes. Because the level of adsorption efficiency of the ~sorber which is hot and moist throughout is still very low at that time, the air, after issuing fran that adsorber, is not ~ only very hot and charged with water vapor, but it is also charged with solvent vapors. It is therefore not mixed with the air which is discharged from the adsorbers that are operating in the charging mode. On the contrary, after the air has preferably been cooled down and moisture rsnoved therefrom by means of a condenser, in which operation the toluene contained therein cannot be separated therefran, the air is returned to the flow path leading from the working space to the adsorbers which are operating in the charging mode and by which the air is purified of solvent vapors in the necessary fashion.
In that drying step the exhaust air already flows through the adsorber in an upward direction, that is to say in the direction in which it also flows in the subsequent charging mode. In flowing through the adsorber in that way, it already dries and cools the lowexrriost layers of the adsorber bed, to such an extent that, after a short time, the installation can be switched over to the charging mode. Although a totally sufficient cleaning effect in respect of the exhaust air is already achieved at the beginning of that charging mode, by virtue of the above-mentioned lawennost layers of the adsorber bed, the upper layers of the adsorber bed still impart a very large, anount of heat and moisture to the air flowing through ~,, ;~ ; ,,: .;, , ,~
the adsoib~er.
In that drying step the exhaust air already flows through the adsorber in an upward direction, that is to say in the direction in which it also flows in the subsequent charging mode. In flowing through the adsorber in that way, it already dries and cools the lowexrriost layers of the adsorber bed, to such an extent that, after a short time, the installation can be switched over to the charging mode. Although a totally sufficient cleaning effect in respect of the exhaust air is already achieved at the beginning of that charging mode, by virtue of the above-mentioned lawennost layers of the adsorber bed, the upper layers of the adsorber bed still impart a very large, anount of heat and moisture to the air flowing through ~,, ;~ ; ,,: .;, , ,~
the adsoib~er.
It is here that, in a second step, the invention now makes use of the fact that the exhaust air is at the above-mentioned high temperature and moisture values, only for an initial phase which is short in canparison with the overall duration of the charging period, and the invention also makes use of the fact that in particular the relative moisture content of the exhaust air has already fallen fran about 100 to a readily acceptable value, between about 10 and 12 minutes after the beginning of a new charging phase. The value to which the relative moisture content falls approximately corresponds to that of the air which is discharged by adsorbers which have already been operating in the charging mode for a prolonged period of time.
If therefore, during that initial phase of each new charging period, the cleaned air which is discharged by the respective adsorber is kept separate fran the air flows fxrm the other adsorbers which are already operating in the main phase of the charging mode, then the exhaust air thereof can be recycled to tha working space without the need for special conditioning thereof.
The hot moist exhaust air flow which is kept separate and from which solvent has been satisfactorily removed can either be discharged directly into the 2mbient atmosphere or it can be conditioned for it to be recycled to the working space, at a cost which is considerably lower than the cost involved in corresponding conditioning of the total air flow when immediately mixed after leaving the adsorbers. In particular the process according to the invention pexmtts a highly flexible operating procedure. Thus for exanple at high outside t~peratures the hot moist air fran the initial phase can be discharged directly to the ambient atmosphere ~, ~ , ,. ;
while, at lower outside t~peratures, ~it is recycled to the ~uorkirig space, aftex c~aratively little cooling, so that the residual heat contained in the air serves for heating purposes.
It will be seen that, by virtue of the procedure and apparatus according to the invention, the working space has to be supplied with only a fraction of the amount of fresh air which is required in accordance with the above-discussed prior procedure. The input of energy permanently required and also the level of apparatus expenditure required for conditioning the air that is fed to the working space are also correspondingly lower. Another particular advantage of the process and installation accorriing to the invention lies in their effects in terms of reducing environmental pollution.
Such effects provide that the recycling of the major part of the exhaust air means that even less solvent is discharged to the environment. On the other hand the considerably reduced level of energy expenditure also contributes to protecting the envizronment.
The duration of the initial phase, after the beginning of a new charging period, during which phase the air issuing fran a respective adsorber is discharged to the exterior ail thus into the open air, can basically be established by means of a time control arrangement. Fbr that purpose, it is possible to ascertain empirically for a given adsorber the length of the period of time after which the above-mentioned clear drop in temperature and in particular relative air humidity has reliably occurred. Taking that tine value as a basis, the procedure can then be autanatically switched over fran feeding the air issuing fran the adsorber into the auxiliary flow path, to feeding the air into the main flow path for direct recycling to the working space. It will be appreciated that a necessary condition for that operating procedure is that the properties of the adsorber change only very slightly.
Preferably the tature'of the cleaned 'exhaust air issuing fran the adsorber is to be measured and the operating procedure is to be switched over fran a feed of air into the auxiliary flow path to direct recycling to the working space, when the measured t~perature has fallen below a predetermined limit value.
Further preferred features of the process and installation according to the invention for carzying out the process are set forth in the accartpanying claims.
An embodiment of the process and installation according to the present invention will now be described by way of example with reference to the accar~panying drawing in which the single Figure is a diagrammatic view of an exhaust air cleaning installation.
Referring now to the drawing, shown therein is a diagranmtic view of an exhaust air cleaning installation for carrying out a process for removing solvent vapors fran exhaust air which is sucked out of a working space, for example in a printing works. In the illustrated installation accordingly solvent vapors which in a printing situation are generally toluene vapors are produced in a printing roan 1 and in particular in the printing mechanism driers 3 of a rotary intaglio printing machine, the driers being disposed under a machine hood 2. The solvent vapors are to be removed frcm the exhaust or waste air fran the driers, and recovered for further use thereof.
Fbr that purpose the exhaust air cleaning installation includes four blowers 5 which, by way of a trolling belt filter 6 which sezves to retain ink dust and other solid particles, suck the air out of the driers 3 and, by way of same, also out of the machine hood 2.
Disposed downstream of each of the blowers 5 is a respective heat exchanger 8. Heat can be removed fx~cm the exhaust air which is ,2136165 sucked in by the blowers 5, by means of the respective heat exchangers 8, in order to reduce the tenperature of the air from about 45°C to about 30°C. In that way the level of adsorption efficiency of the subsequent activated carbon adsorbers 10 - 13 is considerably increased.
The heat exchangers 8 are arranged in parallel relationship with each other, both in regard to the exhaust air fran the machinery and also in regard to their respective coolant circuit.
The coolant is passed by means of a pump 16 through an open cooling tower 17 in which it can discharge the heat which is re~r~aved fran the exhaust air fran the machinery. Disposed between the manifold conduit 9 whicr_ connects the outlets of the heat exchangers 8 together and each of the adsorbers 10 - 13 is a controllable inlet flap 18, by means of which the respective adsorber 10 - 13 'can be completely separated from the exhaust air flow caning fran the filter 6.
Each of the adsorbers 10 - 13 has two air outlet conduits 22 , 23. The first conduit 22 serves to caTTy away the air which issues fran its adsorber in the charging mode and fran which solvent vapors have been very substantially removed. In order to be able to measure the temperature of that air, the first conduits 22 each have a respective temperature-rtieasuring sensor 20.
Each of the first conduits 22 is branched in a Y-shape. One of the arms of the respective Y-shape branching is camn~nicated by way of a first controllable outlet flap 24 with a return conduit 26 which serves as a msin flow path, while the other of the two arnis of the Y=shaped branch cattnunicates by way of a controllable auxiliary outlet flap 27 with an auxiliary flow path 28.
The~~ second air outlet ~ conduits 23 are each' cannunicated' with''a conduit 19 by way of a second controllable outlet flap 25 and serve a to cariy air which flows through the associated adsorber during a drying phase concluding the regeneration period, by way of the above-mentioned conduit 19 and a condenser 29 between the filter 6 and the blowers 5, back into the flow path which leads fran the working space 2 to the adsorbexs 10 - 13.
Each of the adsorbers 10 - 13 has a vapor inlet valve 14 and an outlet valve 15 which are opened during the main part of the regeneration period so that the adsorber can be steamed out with steam or water vapor which flows through the adsorber in the opposite direction to the direction of flow of the exhaust air to be cleaned. The inlet valves 14 are fed by a steam or vapor supply apparatus (not shown) while the outlet valves 15 are camwnicated by way of a conduit (not shown) with a solvent recovery apparatus of which only the condenser 29 is illustrated in the drawing.
The return conduit 26 has a Y-shaped branching 30 of which one arm is communicated by way of a controllable flap 31 with a discharge conduit 32 while the other arm of the branching arrangement goes by way of a controllable flap 33 and a filter 34 which serves to filter out any carbon which is entrained in the return conduit 26 by virtue of attrition and abrasion in the adsorbers 10 - 13, and leads back into the printing roan 1 and therein by way of a further controllable flap 35 into the machine hood 2 in which the return conduit 26 terminates in an open condition.
The auxiliary flow path 28 leads by way of an optional heat exchanger 37 and a heat exchanger 38 which is always provided to a Y-shaped branching location 40 of which one arm is oartnunicated by way of a controllable flap, ,42, with the return conduit 26 while the n ~ ;~ .
other aim of the Y-shape arrangementlis camnnicated ~by way of~a controllable flap 43 with the discharge conduit 32 which is connected to a chimney 45, through which air flowing into the conduit 32 can be discharged into the ambient atmosphere. The coolant circuit of the heat exchanger 38 also goes by way of the cooling tower 17 and is driven by a planp 46.
The installation further includes a blower 48 which serves to suck in by way of a filter 50 fresh air from the surrounding atmosphere. The fresh air is blown under the control of tc~~
controllable flaps 52 and 53 either into the return conduit 26 ~n which it is mixed with the air that is returned fi:~an the adsort~ers J.0 - 13 and then fed to the machine hood 2 , or the air wh ~_ch is sucked in by way of the filter 50 is passed directly to the printing roan 1 by way of a heat exchange assgnbly 55, 56. The heat exchange assgnbJy 55, 56 includes two heat exchangers of which one serves fc~r selectively cooling the fresh air that is sucked in through tt~e filter 50, while the other serves for selectively heating the fresh air. The last-mentioned heat exchanger 56 can be connected together with the heat exchanger 37 in the auxiliary flow path 28 to provide a heat exchange medium circuit. The heat which the heat exchanger 37 removes from the exhaust ai.r flowing through the auxiliary flow path 28 can however also be used otherwise than for heating the fresh ai.r.
which is sucked in by way of the filter 50.
Arranged on the return conduit 26, upstream and dowrrstrearn of the region at which the fresh air conduit 58 caning from tloe blower.
48 opens into the conduit 26, are respective moisture and terl~peraturP
measuring sensors 60, 61 and 62, 63 respectively. The fresh air conduit 58 also has a moisture and a temperature measuring sensor 64 and 65 respectively, immediately upstream of the location at which it connects to the return conduit 26.
The structure of the .illustrated installation Having been described, the preferred mode of operation thereof is now set out as follows::
_2136165 Out of the four adsorbers 10 - 13 which are operatively disposed in mutually parallel relationship, in any given situation three thereof, for exa~r~ple the adsorbers 10 - 12, can be in the condition of the charging mode while at the same time the fourth adsorber 13 is being regenerated. Fbr that purpose the air flow fran the associated blower 5 is distributed by way of the manifold conduit 9 to the adsorbers 10 - 12 and the controllable inlet flap 18 leading to the adsorber 13 which is to be regenerated is closed so that the adsorber 13 is separated fran the flow of exhaust air caning fran the filter 6.
The controllable flaps 24, 25 and 27 on the outlet side of the adsorber 13 are also closed. In order to desorb the solvent residues which are adsorbed on the activated carbon in the adsorber 13, the adsorber 13 is supplied by way of the vapor inlet valve 14 with saturated steam or water vapor which flows through the activated carbon from above in a downward direction therethrough. In that part of the procedure the water vapor or steam heats the activated carbon bed and desorbs the solvent. The solvent/water mixture which is produced in that case and which condenses beneath the activated carbon bed is fed by way of the outlet valve 15 and a discharge conduit (not shown) to a separation apparatus in which the solvent is separated fran the water so that the solvent can be used again.
During that regeneration operation the activated carbon fill in the adsorber 13 is heated to about 120°C and greatly saturated with steam. If the installation were to be switched over to the charging mode without any transitional phase after closure of the valves 14 and 15, the adsorber 13 would initially have an extrelriely poor adsorption efficiency.
,~ ~ ~ .,. , " , , In'order to avoid that, each regeneration period is concluded by a drying phase, during which the inlet flap 18 and the second outlet flap 25 are opened but the outlet flaps 24 and 27 remain closed. In that way exhaust air which has been sucked out of the working space 2 can flow through the adsorber as a drying medium.
Because of the poor level of efficiency of the adsorber, due to the high temperature involved, that air, after issuing from the adsorber, is not only hot and moist but it is also still heavily charged with solvent vapors. Although the air is cooled and moisture is removed therefran in the condenser 29, there is nonetheless only an immaterial reduction in its solvent content. It is therefore returned to the flow path which goes fran the working space 2 to the adsorbers 10 - 12 which are operating in the charging mode. There, that air is cleaned with the other exhaust air caning fran the working space 2, in such a way that the first-mentioned air can be totally harmlessly fed into the main flow path 26 which leads back to the working sapce 2.
4~hen the drying phase is concluded by closure of the second controllable outlet flap 25, the exhaust air which is fed to the adsorber 13 is initially always still very greatly heated and charged with moisture.
It is therefore not possible for that air to be recycled directly to the working space 2. The p~r~cess described herein provides however that this air can be kept separate from the floras of air issuing fran the other adsorbers 10 - 12 which have already been in l~he charging mode for a prolonged period of tune and which are therefore alre~y discharging air which is sufficiently cool and dry that it can be recycled to the working space 2 without the need for further conditioning, possibly after just filtering.
It is possible to deal in various ways with the air which ,, ", ., ~ . i ,, ;, ; , , , -issues firom the adsorber 13 that is, in the ~.nitial phase of ~a charging mode condition. In every case the associated first outlet flap 24 initially remains closed and the corresponding controllable auxiliary outlet flap 27 is opened so that the above-mentioned hot and moist air flows through the auxiliary flow path 28. By means of the heat exchanger 37, a part of the heat contained in that air can be recovered and put to further use.
Thereafter, that air can be passed directly into the discharge conduit 32 and through same into the chimney 45 which discharges it to the ambient atmosphere. If only that mode of operation is wanted, the heat exchanger 38, the branching arrangement 40 and the controllable flaps 42, 43 can be omitted.
In order to achieve a higher level of flexibility however those elgnents can be used to provide that the air which, in the initial phase of each charging mode condition of one of the adsorbers 10 -13, flows through the auxiliary flow path 28 is cooled down in the heat exchanger 38 to such an extent that it can be fed into the return conduit 26 when the controllable flap 42 is open and the controllable flap 43 is closed.
The two options just described above are ~t mutually exclusive, in other words, a part of the air which flows through the auxiliary flow path 28 can also be discharged to the ambient atmosphere and the remainder, after suitable conditioning, can be fed into the return conduit 26. Finally, it is also possible for a part of the sufficiently cool and dry air caning fxnm the adsorbers 10 -12 which have already been operating in the charging mode for a prolonged period of time, which air flows in the return conduit 26, to be branched off at the branching arrangement 30 and passed into the discharge conduit 32. For that purpose, the flow resistance in the conduit 26 is increased by means of the controllable flap 33 and the contirollable ~ flap 31~~ is correspondingly opened wide. That is effected, for the purposes of maintaining a constant balance sheet in _2136165 respect of the amounts of air involved, when a particularly large amount of fresh air is to be fed to the printing roan 1 or the machine hood 2.
After a certain period of time, the initial phase of the charging period is terminated, in other words, the cleaned exhaust air which issues from the adsorber 13 and which has a residual solvent content of for example about 20 mg/an3 has, of its own accord, reached such a low temperature and such a low rmisture content that it can be readily recycled to the working space, in particular the machine hood 2 of the rotary intaglio printing machine. At that time which is determined either by way of a time control or preferably by means of the te~r~perature measuring sensor 20 disposed downstream of the adsorber 13, the appropriate auxiliary outlet flap 27 is closed and instead the associated first outlet flap 24 is opened so that the cleaned exhaust air issuing fran the adsorber 13 is recycled to the working space 2 by way of the return conduit 26.
A corresponding situation also applies in xto the other ~oy~rs 10 - 12 ; when the abrnre-described adsorber 13 is switched over fran the regeneration mode into the charging mode, one of the other adsorbers 10 - 12 can change fran the charging mode to the regeneration mode and can perform. the same steps as have been described above.
The controllable flaps 33; 52 and 53 serve to feed the fresh air' which is sucked in by means of the blower 48 directly to the printingroan 1, in which case the air can be cooled by means of the heat exchanger 55 or heated by the heat exchanger 56, or the flaps 33 , , 5z anal 53. serve tq m~c , fit, .east a ,part of that fresh, sir with the cleaned exhaust'air flowing in the conduit 26.
z~3sls5 The measuring sensors 60, 61; 64, 65; and 62, 63 serve to measure the moisture content and the temperature of the cleaned exhaust air, the fresh air which is supplied fran the exterior and the mixture which is produced from those two air flows. Those measursnent values can then be used to alter the ratio of the constituents of the mixture in such a way that the air which is returned to the machine hood 2 is set at the appropriately required values.
It will be seen from the foregoing that the process and the installation according to the invention can also be employed when the exhaust air which is sucked out of the working space 1, 2 is cleaned by means of more or fewer than four adsorbers. The only important consideration in this respect is that each adsorber provided, at the end of each regeneration period, performs the described drying phase to achieve the required level of adsorption efficiency and then, when it has been switched over fxnm the regeneration mode to the charging mode, for the above-defined initial phase the exhaust air which has been cleaned by the adsorber is fed into the auxiliary flow path 28 from which it can be passed as required into the discharge conduit 32 leading to the chimney 45 or after suitable cooling and re~naval of moisture therefrom by way of the heat exchanger 38 into the return conduit 26. After tern~ination of the initial phase, that is to say when the exhaust air issuing fran the respective adsorber has reached appropriately advantageous values, it is then fed directly into the return conduit 26.
It will be appreciated that the above-described process and installation according to the invention have been set forth solely by way of e~samp~e ands i.~.lustfa~ion ; of the principles ,thereof and that various modifications and alterations may be made therein without thereby departing from the spirit and scope of the invention.
It will further be noted at this point that the reference numerals contained in the appended claims serve for ease of interpretation thereof and are not intended to have restrictive effect.
If therefore, during that initial phase of each new charging period, the cleaned air which is discharged by the respective adsorber is kept separate fran the air flows fxrm the other adsorbers which are already operating in the main phase of the charging mode, then the exhaust air thereof can be recycled to tha working space without the need for special conditioning thereof.
The hot moist exhaust air flow which is kept separate and from which solvent has been satisfactorily removed can either be discharged directly into the 2mbient atmosphere or it can be conditioned for it to be recycled to the working space, at a cost which is considerably lower than the cost involved in corresponding conditioning of the total air flow when immediately mixed after leaving the adsorbers. In particular the process according to the invention pexmtts a highly flexible operating procedure. Thus for exanple at high outside t~peratures the hot moist air fran the initial phase can be discharged directly to the ambient atmosphere ~, ~ , ,. ;
while, at lower outside t~peratures, ~it is recycled to the ~uorkirig space, aftex c~aratively little cooling, so that the residual heat contained in the air serves for heating purposes.
It will be seen that, by virtue of the procedure and apparatus according to the invention, the working space has to be supplied with only a fraction of the amount of fresh air which is required in accordance with the above-discussed prior procedure. The input of energy permanently required and also the level of apparatus expenditure required for conditioning the air that is fed to the working space are also correspondingly lower. Another particular advantage of the process and installation accorriing to the invention lies in their effects in terms of reducing environmental pollution.
Such effects provide that the recycling of the major part of the exhaust air means that even less solvent is discharged to the environment. On the other hand the considerably reduced level of energy expenditure also contributes to protecting the envizronment.
The duration of the initial phase, after the beginning of a new charging period, during which phase the air issuing fran a respective adsorber is discharged to the exterior ail thus into the open air, can basically be established by means of a time control arrangement. Fbr that purpose, it is possible to ascertain empirically for a given adsorber the length of the period of time after which the above-mentioned clear drop in temperature and in particular relative air humidity has reliably occurred. Taking that tine value as a basis, the procedure can then be autanatically switched over fran feeding the air issuing fran the adsorber into the auxiliary flow path, to feeding the air into the main flow path for direct recycling to the working space. It will be appreciated that a necessary condition for that operating procedure is that the properties of the adsorber change only very slightly.
Preferably the tature'of the cleaned 'exhaust air issuing fran the adsorber is to be measured and the operating procedure is to be switched over fran a feed of air into the auxiliary flow path to direct recycling to the working space, when the measured t~perature has fallen below a predetermined limit value.
Further preferred features of the process and installation according to the invention for carzying out the process are set forth in the accartpanying claims.
An embodiment of the process and installation according to the present invention will now be described by way of example with reference to the accar~panying drawing in which the single Figure is a diagrammatic view of an exhaust air cleaning installation.
Referring now to the drawing, shown therein is a diagranmtic view of an exhaust air cleaning installation for carrying out a process for removing solvent vapors fran exhaust air which is sucked out of a working space, for example in a printing works. In the illustrated installation accordingly solvent vapors which in a printing situation are generally toluene vapors are produced in a printing roan 1 and in particular in the printing mechanism driers 3 of a rotary intaglio printing machine, the driers being disposed under a machine hood 2. The solvent vapors are to be removed frcm the exhaust or waste air fran the driers, and recovered for further use thereof.
Fbr that purpose the exhaust air cleaning installation includes four blowers 5 which, by way of a trolling belt filter 6 which sezves to retain ink dust and other solid particles, suck the air out of the driers 3 and, by way of same, also out of the machine hood 2.
Disposed downstream of each of the blowers 5 is a respective heat exchanger 8. Heat can be removed fx~cm the exhaust air which is ,2136165 sucked in by the blowers 5, by means of the respective heat exchangers 8, in order to reduce the tenperature of the air from about 45°C to about 30°C. In that way the level of adsorption efficiency of the subsequent activated carbon adsorbers 10 - 13 is considerably increased.
The heat exchangers 8 are arranged in parallel relationship with each other, both in regard to the exhaust air fran the machinery and also in regard to their respective coolant circuit.
The coolant is passed by means of a pump 16 through an open cooling tower 17 in which it can discharge the heat which is re~r~aved fran the exhaust air fran the machinery. Disposed between the manifold conduit 9 whicr_ connects the outlets of the heat exchangers 8 together and each of the adsorbers 10 - 13 is a controllable inlet flap 18, by means of which the respective adsorber 10 - 13 'can be completely separated from the exhaust air flow caning fran the filter 6.
Each of the adsorbers 10 - 13 has two air outlet conduits 22 , 23. The first conduit 22 serves to caTTy away the air which issues fran its adsorber in the charging mode and fran which solvent vapors have been very substantially removed. In order to be able to measure the temperature of that air, the first conduits 22 each have a respective temperature-rtieasuring sensor 20.
Each of the first conduits 22 is branched in a Y-shape. One of the arms of the respective Y-shape branching is camn~nicated by way of a first controllable outlet flap 24 with a return conduit 26 which serves as a msin flow path, while the other of the two arnis of the Y=shaped branch cattnunicates by way of a controllable auxiliary outlet flap 27 with an auxiliary flow path 28.
The~~ second air outlet ~ conduits 23 are each' cannunicated' with''a conduit 19 by way of a second controllable outlet flap 25 and serve a to cariy air which flows through the associated adsorber during a drying phase concluding the regeneration period, by way of the above-mentioned conduit 19 and a condenser 29 between the filter 6 and the blowers 5, back into the flow path which leads fran the working space 2 to the adsorbexs 10 - 13.
Each of the adsorbers 10 - 13 has a vapor inlet valve 14 and an outlet valve 15 which are opened during the main part of the regeneration period so that the adsorber can be steamed out with steam or water vapor which flows through the adsorber in the opposite direction to the direction of flow of the exhaust air to be cleaned. The inlet valves 14 are fed by a steam or vapor supply apparatus (not shown) while the outlet valves 15 are camwnicated by way of a conduit (not shown) with a solvent recovery apparatus of which only the condenser 29 is illustrated in the drawing.
The return conduit 26 has a Y-shaped branching 30 of which one arm is communicated by way of a controllable flap 31 with a discharge conduit 32 while the other arm of the branching arrangement goes by way of a controllable flap 33 and a filter 34 which serves to filter out any carbon which is entrained in the return conduit 26 by virtue of attrition and abrasion in the adsorbers 10 - 13, and leads back into the printing roan 1 and therein by way of a further controllable flap 35 into the machine hood 2 in which the return conduit 26 terminates in an open condition.
The auxiliary flow path 28 leads by way of an optional heat exchanger 37 and a heat exchanger 38 which is always provided to a Y-shaped branching location 40 of which one arm is oartnunicated by way of a controllable flap, ,42, with the return conduit 26 while the n ~ ;~ .
other aim of the Y-shape arrangementlis camnnicated ~by way of~a controllable flap 43 with the discharge conduit 32 which is connected to a chimney 45, through which air flowing into the conduit 32 can be discharged into the ambient atmosphere. The coolant circuit of the heat exchanger 38 also goes by way of the cooling tower 17 and is driven by a planp 46.
The installation further includes a blower 48 which serves to suck in by way of a filter 50 fresh air from the surrounding atmosphere. The fresh air is blown under the control of tc~~
controllable flaps 52 and 53 either into the return conduit 26 ~n which it is mixed with the air that is returned fi:~an the adsort~ers J.0 - 13 and then fed to the machine hood 2 , or the air wh ~_ch is sucked in by way of the filter 50 is passed directly to the printing roan 1 by way of a heat exchange assgnbly 55, 56. The heat exchange assgnbJy 55, 56 includes two heat exchangers of which one serves fc~r selectively cooling the fresh air that is sucked in through tt~e filter 50, while the other serves for selectively heating the fresh air. The last-mentioned heat exchanger 56 can be connected together with the heat exchanger 37 in the auxiliary flow path 28 to provide a heat exchange medium circuit. The heat which the heat exchanger 37 removes from the exhaust ai.r flowing through the auxiliary flow path 28 can however also be used otherwise than for heating the fresh ai.r.
which is sucked in by way of the filter 50.
Arranged on the return conduit 26, upstream and dowrrstrearn of the region at which the fresh air conduit 58 caning from tloe blower.
48 opens into the conduit 26, are respective moisture and terl~peraturP
measuring sensors 60, 61 and 62, 63 respectively. The fresh air conduit 58 also has a moisture and a temperature measuring sensor 64 and 65 respectively, immediately upstream of the location at which it connects to the return conduit 26.
The structure of the .illustrated installation Having been described, the preferred mode of operation thereof is now set out as follows::
_2136165 Out of the four adsorbers 10 - 13 which are operatively disposed in mutually parallel relationship, in any given situation three thereof, for exa~r~ple the adsorbers 10 - 12, can be in the condition of the charging mode while at the same time the fourth adsorber 13 is being regenerated. Fbr that purpose the air flow fran the associated blower 5 is distributed by way of the manifold conduit 9 to the adsorbers 10 - 12 and the controllable inlet flap 18 leading to the adsorber 13 which is to be regenerated is closed so that the adsorber 13 is separated fran the flow of exhaust air caning fran the filter 6.
The controllable flaps 24, 25 and 27 on the outlet side of the adsorber 13 are also closed. In order to desorb the solvent residues which are adsorbed on the activated carbon in the adsorber 13, the adsorber 13 is supplied by way of the vapor inlet valve 14 with saturated steam or water vapor which flows through the activated carbon from above in a downward direction therethrough. In that part of the procedure the water vapor or steam heats the activated carbon bed and desorbs the solvent. The solvent/water mixture which is produced in that case and which condenses beneath the activated carbon bed is fed by way of the outlet valve 15 and a discharge conduit (not shown) to a separation apparatus in which the solvent is separated fran the water so that the solvent can be used again.
During that regeneration operation the activated carbon fill in the adsorber 13 is heated to about 120°C and greatly saturated with steam. If the installation were to be switched over to the charging mode without any transitional phase after closure of the valves 14 and 15, the adsorber 13 would initially have an extrelriely poor adsorption efficiency.
,~ ~ ~ .,. , " , , In'order to avoid that, each regeneration period is concluded by a drying phase, during which the inlet flap 18 and the second outlet flap 25 are opened but the outlet flaps 24 and 27 remain closed. In that way exhaust air which has been sucked out of the working space 2 can flow through the adsorber as a drying medium.
Because of the poor level of efficiency of the adsorber, due to the high temperature involved, that air, after issuing from the adsorber, is not only hot and moist but it is also still heavily charged with solvent vapors. Although the air is cooled and moisture is removed therefran in the condenser 29, there is nonetheless only an immaterial reduction in its solvent content. It is therefore returned to the flow path which goes fran the working space 2 to the adsorbers 10 - 12 which are operating in the charging mode. There, that air is cleaned with the other exhaust air caning fran the working space 2, in such a way that the first-mentioned air can be totally harmlessly fed into the main flow path 26 which leads back to the working sapce 2.
4~hen the drying phase is concluded by closure of the second controllable outlet flap 25, the exhaust air which is fed to the adsorber 13 is initially always still very greatly heated and charged with moisture.
It is therefore not possible for that air to be recycled directly to the working space 2. The p~r~cess described herein provides however that this air can be kept separate from the floras of air issuing fran the other adsorbers 10 - 12 which have already been in l~he charging mode for a prolonged period of tune and which are therefore alre~y discharging air which is sufficiently cool and dry that it can be recycled to the working space 2 without the need for further conditioning, possibly after just filtering.
It is possible to deal in various ways with the air which ,, ", ., ~ . i ,, ;, ; , , , -issues firom the adsorber 13 that is, in the ~.nitial phase of ~a charging mode condition. In every case the associated first outlet flap 24 initially remains closed and the corresponding controllable auxiliary outlet flap 27 is opened so that the above-mentioned hot and moist air flows through the auxiliary flow path 28. By means of the heat exchanger 37, a part of the heat contained in that air can be recovered and put to further use.
Thereafter, that air can be passed directly into the discharge conduit 32 and through same into the chimney 45 which discharges it to the ambient atmosphere. If only that mode of operation is wanted, the heat exchanger 38, the branching arrangement 40 and the controllable flaps 42, 43 can be omitted.
In order to achieve a higher level of flexibility however those elgnents can be used to provide that the air which, in the initial phase of each charging mode condition of one of the adsorbers 10 -13, flows through the auxiliary flow path 28 is cooled down in the heat exchanger 38 to such an extent that it can be fed into the return conduit 26 when the controllable flap 42 is open and the controllable flap 43 is closed.
The two options just described above are ~t mutually exclusive, in other words, a part of the air which flows through the auxiliary flow path 28 can also be discharged to the ambient atmosphere and the remainder, after suitable conditioning, can be fed into the return conduit 26. Finally, it is also possible for a part of the sufficiently cool and dry air caning fxnm the adsorbers 10 -12 which have already been operating in the charging mode for a prolonged period of time, which air flows in the return conduit 26, to be branched off at the branching arrangement 30 and passed into the discharge conduit 32. For that purpose, the flow resistance in the conduit 26 is increased by means of the controllable flap 33 and the contirollable ~ flap 31~~ is correspondingly opened wide. That is effected, for the purposes of maintaining a constant balance sheet in _2136165 respect of the amounts of air involved, when a particularly large amount of fresh air is to be fed to the printing roan 1 or the machine hood 2.
After a certain period of time, the initial phase of the charging period is terminated, in other words, the cleaned exhaust air which issues from the adsorber 13 and which has a residual solvent content of for example about 20 mg/an3 has, of its own accord, reached such a low temperature and such a low rmisture content that it can be readily recycled to the working space, in particular the machine hood 2 of the rotary intaglio printing machine. At that time which is determined either by way of a time control or preferably by means of the te~r~perature measuring sensor 20 disposed downstream of the adsorber 13, the appropriate auxiliary outlet flap 27 is closed and instead the associated first outlet flap 24 is opened so that the cleaned exhaust air issuing fran the adsorber 13 is recycled to the working space 2 by way of the return conduit 26.
A corresponding situation also applies in xto the other ~oy~rs 10 - 12 ; when the abrnre-described adsorber 13 is switched over fran the regeneration mode into the charging mode, one of the other adsorbers 10 - 12 can change fran the charging mode to the regeneration mode and can perform. the same steps as have been described above.
The controllable flaps 33; 52 and 53 serve to feed the fresh air' which is sucked in by means of the blower 48 directly to the printingroan 1, in which case the air can be cooled by means of the heat exchanger 55 or heated by the heat exchanger 56, or the flaps 33 , , 5z anal 53. serve tq m~c , fit, .east a ,part of that fresh, sir with the cleaned exhaust'air flowing in the conduit 26.
z~3sls5 The measuring sensors 60, 61; 64, 65; and 62, 63 serve to measure the moisture content and the temperature of the cleaned exhaust air, the fresh air which is supplied fran the exterior and the mixture which is produced from those two air flows. Those measursnent values can then be used to alter the ratio of the constituents of the mixture in such a way that the air which is returned to the machine hood 2 is set at the appropriately required values.
It will be seen from the foregoing that the process and the installation according to the invention can also be employed when the exhaust air which is sucked out of the working space 1, 2 is cleaned by means of more or fewer than four adsorbers. The only important consideration in this respect is that each adsorber provided, at the end of each regeneration period, performs the described drying phase to achieve the required level of adsorption efficiency and then, when it has been switched over fxnm the regeneration mode to the charging mode, for the above-defined initial phase the exhaust air which has been cleaned by the adsorber is fed into the auxiliary flow path 28 from which it can be passed as required into the discharge conduit 32 leading to the chimney 45 or after suitable cooling and re~naval of moisture therefrom by way of the heat exchanger 38 into the return conduit 26. After tern~ination of the initial phase, that is to say when the exhaust air issuing fran the respective adsorber has reached appropriately advantageous values, it is then fed directly into the return conduit 26.
It will be appreciated that the above-described process and installation according to the invention have been set forth solely by way of e~samp~e ands i.~.lustfa~ion ; of the principles ,thereof and that various modifications and alterations may be made therein without thereby departing from the spirit and scope of the invention.
It will further be noted at this point that the reference numerals contained in the appended claims serve for ease of interpretation thereof and are not intended to have restrictive effect.
Claims (22)
1. A process for removing solvent vapor firm exhaust air which is sucked out of a working space, wherein the air is cleaned by being passed through at least two activated carbon adsorbers which are in mutually parallel relationship and each of which runs through operating cycles which each comprise a charging period in which the exhaust air flows through the adsorber and the adsorber adsorbs the solvent vapor contained in the exhaust air and a regeneration period in which the adsorber is separated from the flow of exhaust air and water vapor flows through the adsorber to desorb and flush out the previously adsorbed solvent; wherein the working cycles of the at least two adsorbers are displaced relative to each other in respect of time in such a way that at least one of the adsorbers is always working in the charging mode, thereby to achieve a continuous adsorption procedure: wherein each regeneration period includes a concluding drying phase in which, instead of water vapor, exhaust air from the working space flows through the adsorber in question, the exhaust air after leaving said adsorber being fed to the at least one adsorber which in that period is working in the charging mode: and wherein each charging period includes an initial phase and a subsequent main phase, which are determined by virtue of the fact that the air flow issuing from an adsorber which is in the initial phase of a charging period is fed to a separate treatment while the air flow issuing from an adsorber which is in the main phase of a charging period is returned directly into the working space.
2. A process as set forth in claim 1 wherein the length of the initial phase of the charging period is established by means of a time control.
3. A process as set forth in claim 1 wherein the temperature of the air flow issuing from an adsorber which is operating in the charging mode is measured and the initial phase of the charging period is terminated when said temperature falls below a predeterminable limit value.
4. A process as set forth in claim 1 wherein the separate treatment provides that at least a part of the air flow which issues from an adsorber in the initial phase of the charging period and which is kept separate is cooled and thereafter returned into the working space.
5. A process as set forth in claim 1 wherein the separate treatment provides that at least a part of the air flow which issues from an adsorber in the initial phase of the charging period and which is kept separate is expelled into the surrounding atmosphere.
6. A process as set forth in claim 5 wherein the air expelled into the surrounding atmosphere firstly passes through a heat exchanger to recover a part of the heat contained in the air.
7. A process as set forth in claim 5 wherein an amount of fresh air which approximately corresponds to the amount of air expelled into the surrounding atmosphere is sucked in out of the surrounding atmosphere, conditioned and fed to the working space.
8. A process as set forth in claim 7 wherein heat which is taken from the air expelled into the surrounding atmosphere is used to heat the fresh air which is sucked in from the surrounding atmosphere.
9. A process as set forth in claim 7 wherein the conditioned fresh air which is sucked in out of the surrounding atmosphere is directly fed to the working space.
10. A process as set forth in claim 7 wherein the fresh air which is sucked in out of the surrounding atmosphere, is at least partially mixed with the air which is returned from the adsorbers and said air mixture is fed to the working space.
11. A process as set forth in claim 7 wherein the air which is returned from the adsorbers is fed to a region of the working space;
that is different from the region to which conditioned fresh air is fed.
that is different from the region to which conditioned fresh air is fed.
12. An installation for removing solvent vapor from exhaust air, comprising:
- blower means (5) for sucking the exhaust air out of a working space (2), - at least first and second activated carbon adsorbers (10, 11, 12, 13) arranged in mutually parallel relationship, - a control means, - a control arrangement which is controllable by said control means and which, for each of the adsorbers (10, 11, 12, 13), includes an inlet valve means (18) which in the opened condition communicates it with the associated blower means (5); a main flow path (26); and an outlet valve means (24) which in the opened condition passes air issuing from the adsorber (10, 11, 12, 13) into said main flow path (26); the arrangement being such that each of the adsorbers (10, 11, 12, 13) is switchable to and fro between a charging mode in which exhaust air to be cleaned flows through the adsorber and the adsorber adsorbs solvent contained in the exhaust air and a regeneration mode in which the adsorber is separated from the flow of exhaust air and water vapor can flow through the adsorber for desorbing and flushing out the adsorbed solvent, the switching action between the charging and the regeneration modes occurring alternately in such a way that at least one of the adsorbers (10, 11, 12, 13) is always operating in the charging mode, and - a discharge means (32, 45) by means of which air which has flowed through one of the adsorbers (10, 11, 12, 13) can be expelled into the surrounding atmosphere, wherein the control arrangement further includes the following, for each adsorber (10, 11, 12, 13):
- a second outlet valve means (25) and a conduit (19) which in the open condition of the second outlet valve means (25) is communicated thereby with the adsorber (10, 11, 12, 13) and by way of which air issuing from the adsorber (10, 11, 12, 13) can be returned to the flow path leading from the working space (2) to the adsorbers (10, 11, 12,
- blower means (5) for sucking the exhaust air out of a working space (2), - at least first and second activated carbon adsorbers (10, 11, 12, 13) arranged in mutually parallel relationship, - a control means, - a control arrangement which is controllable by said control means and which, for each of the adsorbers (10, 11, 12, 13), includes an inlet valve means (18) which in the opened condition communicates it with the associated blower means (5); a main flow path (26); and an outlet valve means (24) which in the opened condition passes air issuing from the adsorber (10, 11, 12, 13) into said main flow path (26); the arrangement being such that each of the adsorbers (10, 11, 12, 13) is switchable to and fro between a charging mode in which exhaust air to be cleaned flows through the adsorber and the adsorber adsorbs solvent contained in the exhaust air and a regeneration mode in which the adsorber is separated from the flow of exhaust air and water vapor can flow through the adsorber for desorbing and flushing out the adsorbed solvent, the switching action between the charging and the regeneration modes occurring alternately in such a way that at least one of the adsorbers (10, 11, 12, 13) is always operating in the charging mode, and - a discharge means (32, 45) by means of which air which has flowed through one of the adsorbers (10, 11, 12, 13) can be expelled into the surrounding atmosphere, wherein the control arrangement further includes the following, for each adsorber (10, 11, 12, 13):
- a second outlet valve means (25) and a conduit (19) which in the open condition of the second outlet valve means (25) is communicated thereby with the adsorber (10, 11, 12, 13) and by way of which air issuing from the adsorber (10, 11, 12, 13) can be returned to the flow path leading from the working space (2) to the adsorbers (10, 11, 12,
13) so that air from the working space (2) which flows through an adsorber (10, 11, 12, 13) in a drying phase which concludes the adsorber regeneration period when the inlet valve means (18) is open and the first outlet valve means (24) is closed can be fed by way of the opened second outlet valve means (25) to the at least one adsorber (10, 11, 12, 13) which is operating in the charging mode, and - an auxiliary outlet valve means (27) and an auxiliary flow path (28) which in the open condition of the auxiliary outlet valve means (27) is communicated thereby with the adsorber (10, 11, 12, 13) so that air from the working space (2) which flows through the adsorber (10, 11, 12, 13) in an initial phase of its charging period when the inlet valve means (18) is open and the first and second outlet valve means (24, 25) are closed can be fed by way of said auxiliary flow path (28) to a separate treatment, and the main flow path (26) is communicated with the working space (2) so that air from the working space (2) which flows through the adsorber (10, 11, 12, 13) in a main phase following the initial phase of its charging period can be returned into the working space (2) after cleaning of said air.
13. An installation as set forth in claim 12 wherein each said valve means comprises a flap.
13. An installation as set forth in claim 12 wherein each said valve means comprises a flap.
14. An installation as set forth in claim 12 wherein the control means includes a time control operable to predetermine the length of the initial phase.
15. An installation as set forth in claim 12 wherein for each adsorber (10, 11, 12, 13) the control means includes a temperature measuring device (20) for measuring the temperature of the cleaned air issuing therefrom, said device terminating the initial phase when the temperature of the issuing air falls below a predeterminable limit value.
16. An installation as set forth in claim 12 including a discharge chimney (45), a first cooling means (38) in the auxiliary flow path (28), and a change-over switching device (42, 43) which is connected to the auxiliary flow path and by means of which air flowing through it can be at least partially fed after suitable cooling into the main flow path (26) and at least partially passed to the discharge chimney (45).
17. An installation as set forth in claim 16 including a second cooling means (37) in the auxiliary flow path (28).
18. An installation as set forth in claim 12 including a suction and conditioning means (48, 50, 55, 56) for sucking fresh air from the surrounding atmosphere and conditioning it, said suction and conditioning means being adapted to feed the working space (2) with an amount of fresh air which at least substantially corresponds to the amount of air which is discharged.
19. An installation as set forth in claim 18 wherein the suction and conditioning means (48, 50, 55, 56) includes a heat exchanger (56) for heating the sucked-in fresh air.
20. An installation as set forth in claim 18 wherein the suction and conditioning means (48, 50, 55, 56) includes a heat exchanger (55) for cooling the sucked-in fresh air.
21. An installation as set forth in claim 19 including a first cooling means (38) in the auxiliary flow path (28); and including a second cooling means (37) in the auxiliary flow path (28); and including a common heat exchange medium circuit communicating the heat exchanger (56) for heating the sucked-in fresh air with one of the first or second cooling means (37, 38) of the auxiliary flow path (28).
22. An installation as set forth in claim 17 including a mixing means (33, 52, 53) for mixing at least a part of the fresh air sucked in from the surrounding atmosphere with air which is returned from the adsorbers (10, 11, 12, 13).
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DEP4339422.1 | 1993-11-18 | ||
| DE4339422 | 1993-11-18 | ||
| DEP4409622.4 | 1994-03-21 | ||
| DE19944409622 DE4409622A1 (en) | 1994-03-21 | 1994-03-21 | Process and solvent absorber device which can be regenerated and dried using air drawn from working space |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2136165A1 CA2136165A1 (en) | 1995-05-19 |
| CA2136165C true CA2136165C (en) | 2005-02-08 |
Family
ID=25931334
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002136165A Expired - Fee Related CA2136165C (en) | 1993-11-18 | 1994-11-18 | Process and installation for removing solvent vapor from exhaust air |
Country Status (10)
| Country | Link |
|---|---|
| US (1) | US5542965A (en) |
| EP (1) | EP0654295B1 (en) |
| JP (1) | JP2750507B2 (en) |
| AT (1) | ATE149866T1 (en) |
| CA (1) | CA2136165C (en) |
| CZ (1) | CZ289836B6 (en) |
| DE (1) | DE59402050D1 (en) |
| FI (1) | FI109579B (en) |
| HU (1) | HU217021B (en) |
| PL (1) | PL176902B1 (en) |
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| RU2159706C1 (en) * | 2000-05-04 | 2000-11-27 | Кутьев Анатолий Анатольевич | Method of and device for charcoal regeneration |
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| JP2004181672A (en) * | 2002-11-29 | 2004-07-02 | Fuji Photo Film Co Ltd | Image recorder |
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| CN103111084A (en) * | 2013-01-23 | 2013-05-22 | 海湾环境科技（北京）股份有限公司 | Condensation-adsorption combined process capable of improving the service life of oil vapor recovery system equipment |
| CN103277982B (en) * | 2013-05-21 | 2015-06-17 | 南京九思高科技有限公司 | Technology and device for circulating recycling of volatile organic compound in coating printing industry |
| JP6099487B2 (en) * | 2013-06-03 | 2017-03-22 | 住友理工株式会社 | Processing method of printing plate developer |
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| CN107998877A (en) * | 2017-11-28 | 2018-05-08 | 江苏科威环保技术有限公司 | More component organic exhaust gas recycle abatement technique |
| CN108895465B (en) * | 2018-07-17 | 2020-06-02 | 福建兴业东江环保科技有限公司 | High-efficient environmental protection waste disposal system |
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1994
- 1994-11-14 AT AT94117945T patent/ATE149866T1/en not_active IP Right Cessation
- 1994-11-14 DE DE59402050T patent/DE59402050D1/en not_active Expired - Fee Related
- 1994-11-14 EP EP94117945A patent/EP0654295B1/en not_active Expired - Lifetime
- 1994-11-16 FI FI945384A patent/FI109579B/en active
- 1994-11-16 CZ CZ19942812A patent/CZ289836B6/en not_active IP Right Cessation
- 1994-11-17 US US08/341,077 patent/US5542965A/en not_active Expired - Fee Related
- 1994-11-18 PL PL94305906A patent/PL176902B1/en not_active IP Right Cessation
- 1994-11-18 JP JP6309611A patent/JP2750507B2/en not_active Expired - Fee Related
- 1994-11-18 CA CA002136165A patent/CA2136165C/en not_active Expired - Fee Related
- 1994-11-18 HU HU9403314A patent/HU217021B/en not_active IP Right Cessation
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|---|---|
| CZ289836B6 (en) | 2002-04-17 |
| CZ281294A3 (en) | 1995-07-12 |
| FI945384A (en) | 1995-05-19 |
| FI945384A0 (en) | 1994-11-16 |
| CA2136165A1 (en) | 1995-05-19 |
| US5542965A (en) | 1996-08-06 |
| EP0654295A2 (en) | 1995-05-24 |
| HUT72819A (en) | 1996-05-28 |
| EP0654295B1 (en) | 1997-03-12 |
| EP0654295A3 (en) | 1995-11-29 |
| ATE149866T1 (en) | 1997-03-15 |
| JPH07213853A (en) | 1995-08-15 |
| HU9403314D0 (en) | 1995-01-30 |
| JP2750507B2 (en) | 1998-05-13 |
| FI109579B (en) | 2002-09-13 |
| DE59402050D1 (en) | 1997-04-17 |
| PL305906A1 (en) | 1995-05-29 |
| PL176902B1 (en) | 1999-08-31 |
| HU217021B (en) | 1999-11-29 |
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