JPH03270710A - Solvent recovery apparatus - Google Patents

Abstract

PURPOSE:To reduce the requirement of an adsorbent and the cost of the title apparatus by executing a regenerating process by the adsorbent of one main adsorbing tower and that of an auxiliary tower and condensing and separating a solvent from gas after regeneration and introducing gas containing the non- condensed solvent into the other auxiliary adsorbing tower to adsorb and remove the solvent. CONSTITUTION:An adsorbent is received in main adsorbing towers 1, 2 and heated by supplying a current to sheet heaters and fluorocarbon is desorbed from the adsorbent to regenerate the adsorbent. Auxiliary adsorbing towers 10, 11 are packed with activated carbon pellets and fluorocarbon is adsorbed and removed from the air flowing through the auxiliary adsorbing towers. The carrier gas in the main adsorbing tower 2 is sucked by a vacuum pump 6 to be supplied to a condensing cooler 7 and the non-condensed gas not condensed by the condensing cooler 7 is supplied to the auxiliary adsorbing tower 10 to be adsorbed and removed by the adsorbent in the auxiliary adsorbing tower 10.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a batch-type solvent recovery device for recovering a solvent from a process gas containing a solvent such as fluorocarbons, and in particular, a method for recovering a solvent without using water vapor during regeneration. It is related to the device.

[Prior Art] Recently, there has been an increased interest in environmental pollution, and regulations have been tightened from the standpoint of environmental conservation, and there is a tendency to prohibit the release of carbon waste into the atmosphere. In particular, air pollution caused by fluorocarbon gases containing chlorine is attracting attention as a serious problem on a global scale, and for this reason, regulations on the emission of fluorocarbon gases are being implemented.

Although these fluorocarbon gas emission regulations call for the complete discontinuation of the use of fluorocarbon gas in the future, during the current period until a replacement product is developed, the fluorocarbon gas that was previously released into the atmosphere will be removed from the system. The next best option is to collect and reuse the waste so that it is not discharged into the environment. For this reason, various fluorocarbon gas recovery devices have been developed.

In conventional batch-type fluorocarbon gas recovery equipment, fluorocarbon-containing gas is selectively and alternately passed through multiple adsorption towers storing adsorbent material, and the fluorocarbons are adsorbed by the adsorbent material in the adsorption towers. clean gas is obtained. Then, high-temperature steam is passed through the adsorbent in the adsorption tower after adsorbing fluorocarbons, and the vapor heats the adsorbent to desorb the fluorocarbons from the adsorbent and regenerate the adsorbent. In this way, by alternately repeating adsorption and desorption in multiple adsorption towers,
CFCs are removed from CFC-containing air to obtain clean air. If necessary, a cooling gas at room temperature or other low temperature is passed through the adsorption tower after the desorption process to cool the adsorbent and increase its adsorption efficiency before moving on to the adsorption process. ing.

However, such conventional fluorocarbon gas recovery apparatuses have the disadvantage that generation of acid cannot be avoided because steam is used to regenerate the adsorbent. That is, when fluorocarbons remain adsorbed on activated carbon for a long time under conditions where they are exposed to steam, a portion of the fluorocarbons decomposes, generating hydrochloric acid and hydrofluoric acid. This causes problems such as a decrease in the purity of fluorocarbons in the recovered fluorocarbons and the mixing of acids into waste water and purified gas. In addition, when recovering azeotropic fluorocarbons containing alcohol, the alcohol dissolves in water and most of it is discharged with the large amount of wastewater, so measures must be taken to prevent BOD and COD in the wastewater. There are also problems such as the need to

Therefore, the inventor proposed a solvent recovery device that does not use steam to regenerate adsorbents (Japanese Patent Application No. 1-144987).
. This solvent recovery device heats the adsorbent using a sheet heater, and an example thereof is shown in FIG.

That is, in the two adsorption towers 1 and 2, the adsorbent 4 shown in FIG.
0 is stored.

This adsorbent 40 has a sheet heater 42 interposed between a plurality of activated carbon adsorbents 41. and,
By energizing this seat heater 42, it generates resistance heat, thereby causing the adsorbent 41 in contact with the seat heater 42 to
It is designed to add By stopping the power supply to the seat heater 42, the adsorbent 42 is allowed to cool.

Freon-containing air is supplied to the processing blower 3 via piping 21. The processing blower 3 is connected to a cooler 4 via a pipe 22, and the cooler 4 connects the first and second adsorption towers 1, 1, 2, 3, 3, 4, 3, 3, 3, 4 to 4 using a pipe 23 and pipes 23a, 23b branched from this pipe 23, respectively. It is connected to 2. Freon-containing air is transferred to piping 22, 23.23a by processing blower 3.
, 23b to the first and second adsorption towers 1.2. Cooling water is supplied to the cooler 4, which cools the fluorocarbon-containing air sent into the adsorption towers 1 and 2 in advance. In addition, the piping 23a, 2
3b, on-off valves V, , V, respectively.

is interposed.

The purified air discharged from the first and second adsorption towers 1 and 2 is discharged into the atmosphere via pipes 24a and 24b and a main pipe 24 to which these pipes 24a and 24b are connected.

Opening/closing valves V2 and V4 are installed in the pipes 24a and 24b, respectively.

Further, the pipe 24 is connected to the first and second adsorption towers 1 through pipes 26 a + 27 a and pipes 26 b and 27 b, respectively.
, 2 are connected to one end of each. Piping 26a, 2
Air release valves Ve and Va are interposed in the pipes 8b, respectively, and carrier air flow rate regulating valves vlol VI2 are interposed in the pipes 27a and 27b, respectively. At the other end of each of the first and second adsorption towers 1 and 2, piping 25 is provided.
a, 25b and piping 28a, 28b are connected.

Piping 25a.

25b joins the pipe 25, and this pipe 25 is connected to the pipe 22. Then, the pipe 25 has a pipe 25
A cooling blower 5 is interposed to suck air from the adsorption towers 1 and 2 through pipes 25a and 25b, and on-off valves V5. V7 is installed.

Furthermore, the pipes 28a and 28b merge into a pipe 28, and are connected to the separator 8 via this pipe 28.

A vacuum pump 6 and a cooler 7 are interposed in this pipe 28, and the air inside the adsorption towers 1 and 2 is sucked by the vacuum pump 6 through the pipes 28a, 28b, and 28, and the air inside the adsorption towers 1 and 2 is sucked into the cooler 7. After cooling this suction air, it is sent to the separator 8.

Chill cooling water is supplied to the cooler 7, and the air containing fluorocarbons in the adsorption towers 1 and 2 sucked by the vacuum pump 6 is cooled by this chill cooling water, and the fluorocarbons and water in the air containing fluorocarbons are condensed. , these fluorocarbon liquids and water are supplied to the separator 8 together with air containing uncondensed fluorocarbons.

In the separator 8, water and fluorocarbon liquid are separated, and the fluorocarbon liquid is collected in a tank 9 for recovery.

Moisture is discharged from separator 8. On the other hand, the air containing uncondensed fluorocarbons is returned to the pipe 21 via the pipe 29 and subjected to the adsorption and desorption process again together with the treated air.

Next, the operation of the fluorocarbon recovery device configured as described above will be explained.

First, the adsorbent stored in the first adsorption tower 1 has been regenerated and is in an active state, and the adsorbent stored in the second adsorption tower 2 has been adsorbed and has sufficiently adsorbed fluorocarbons. Suppose we are in a state where Therefore, the first adsorption tower 1 carries out the adsorption process, and the second adsorption tower 2 carries out the desorption process.

In this case, the on-off valve V1. V2 open, on/off valve V
5. Close Ve and V8. Flow rate adjustment valve V 10
is set so that a predetermined flow rate of regeneration gas is passed through during depressurization in the next step. In addition, the on-off valve V 3 r v,t
I V7 rV8 is closed, the on-off valve V 11 is opened, and the flow rate regulating valve VL2 is set to a predetermined opening degree to allow a predetermined flow rate of regeneration gas to flow through this flow rate regulating valve V I 2. Further, the processing blower 3 is always driven, and the vacuum pump 6 and the cooling cleaning blower 5 are selectively driven.

Note that at the beginning of this process, the vacuum pump 6 is in an operating state, and the cooling cleaning blower 5 is in an inoperative state.

Then, the fluorocarbon-containing air is sucked by the blower 3 through the piping 21, and is supplied to the cooler 4 through the piping 22, where it is cooled. As a result, the fluorocarbon-containing air is cooled to a low temperature at which the adsorption efficiency of the adsorbent is high, and then sent into the first adsorption tower 1 by the blower 3 via the piping 23.23a. An adsorbent 40 is housed in the adsorption tower 1,
The air containing fluorocarbons passes through the adsorbent 41 of the adsorbent 40, and the fluorocarbons contained therein are adsorbed by the adsorbent 41. The clean air from which Freon has been removed is supplied to the pipe 24a.

24 to the atmosphere.

On the other hand, in the second adsorption tower 2, the inside of the adsorption tower 2 is sucked by the vacuum pump 6 through the pipes 28, 28b, and the purified air flowing through the pipe 24 is adjusted to a predetermined flow rate through the flow rate regulating valve VI2. will be introduced in

In the adsorbent 40 in the adsorption tower 2, electricity is supplied to the sheet heater 42 to cause the sheet heater 42 to generate resistance heat, and the adsorbent 40 in contact with the sheet heater 42
Heat 1. As a result, the fluorocarbons adsorbed by the adsorbent 41 are desorbed, and the fluorocarbons desorbed from the adsorbent 41 are vacuumed using the purified air introduced into the adsorption tower 2 through the flow rate adjustment valve V1□ as a carrier gas. It is sucked by the pump 6 and supplied to the cooler 7. The air discharged from the adsorption tower 2 in which the fluorocarbons are concentrated is cooled by chilled water in the cooler 7, and the fluorocarbons and water in the discharged air are condensed to form a fluorocarbon liquid and water, which are then supplied to the separator 8. Air containing uncondensed fluorocarbons is sent from the separator 8 to the pipe 2 via the pipe 29.
1 and introduced into the first adsorption tower 1 where an adsorption process is being carried out by the processing blower 3 together with the fluorocarbon-containing air sent through the pipe 21. Therefore, the air containing uncondensed fluorocarbons after condensing fluorocarbons and moisture from the fluorocarbon-concentrated air in the cooler 8 is supplied to the first adsorption tower 1, where the uncondensed fluorocarbons are adsorbed and removed.

In the separator 8, the Freon liquid and water are separated by specific gravity,
The water is discharged and the fluorocarbon liquid is collected in the tank 9.

Next, after sufficiently desorbing fluorocarbons from the adsorbent in the second adsorption tower 2, the second adsorption tower 2 is transferred from the desorption process to the cooling process while the first adsorption tower l remains in the adsorption process. to be transferred to That is, valve VI+V2. V6. V, ,Ve and valve V3. Leave V4 as is, open on-off valve V8, and open on-off valve V.
Close H.

By doing so, air is supplied through the pipe 26b into the adsorption tower 2, which had been under reduced pressure until then, and the pressure becomes normal. Next, close the on-off valve V8 while leaving the other on-off valves as they are.
Open/close valve V4. Open V7.

Further, the vacuum pump 6 stops its operation, and the cooling cleaning blower 5 starts its operation. Then, the purified air flowing through the pipe 24 is sucked into the cooling cleaning blower 5 and introduced into the second adsorption tower 2 via the pipe 26b. After this purified air cools the adsorbent in the second adsorption tower 2 as a cooling gas, it is returned to the pipe 22 via the pipes 25b and 25, and is supplied to the first adsorption tower 1 together with the fluorocarbon-containing air. As a result, the fluorocarbons mixed into the cooling gas when flowing through the second adsorption tower 2 are adsorbed by the adsorbent in the first adsorption tower 1 and removed.

Thereafter, the first adsorption tower 1 is switched to the desorption process, and the second adsorption tower 2 is switched to the adsorption process, and thereafter, such operations are alternately repeated to recover fluorocarbons from the fluorocarbon-containing air.

In this way, the adsorbent can be regenerated without the use of steam, which may generate acids.

[Problems to be Solved by the Invention] However, the above-described fluorocarbon recovery device has the following drawbacks. Note that this drawback does not occur in a specific case where the gas is chlorofluorocarbons, but occurs in general with solvents such as fluorocarbons.

Hereinafter, to simplify the explanation, a case where the solvent is fluorocarbon will be explained.

When the fluorocarbon concentration in the fluorocarbon-containing air to be treated is low, the fluorocarbon concentration in the fluorocarbon concentrated gas sucked by the vacuum pump 6 and sent to the cooler 7 is also low. the result,
The cooling condensation efficiency in the cooler 7 becomes low, and the air returned from the separator 8 to the pipe 21 contains a large amount of uncondensed fluorocarbon. Therefore, in the adsorption towers 1 and 2, in addition to the fluorocarbons in the fluorocarbon-containing air sent into the device via the piping 21, it is also necessary to adsorb and treat the fluorocarbons in the return air that is circulated within the device. Since the amount of fluorocarbon in the return air is relatively large, the required amount of adsorbent to be stored in the adsorption tower increases. Therefore, there is a drawback that the device cost is high.

In addition, since the amount of return air returned from the separator 8 to the adsorption tower L2 increases, in the adsorption towers 1 and 2, -
The ratio of highly concentrated air being reconcentrated as return air increases, resulting in a wasteful concentration (adsorption and desorption) process.

Then, the adsorbent is used to adsorb and recover the fluorocarbons in this return air, and the proportion of the adsorbent that should be used to treat the fluorocarbon-containing air that should originally be adsorbed and recovered, that is, the fluorocarbon-containing air supplied from the outside system, is reduced. This is extremely inefficient. For example, in Freon 113, the cooler 7 has a temperature of 5°C.
Even if the carrier gas is cooled and condensed and separated, the carrier gas will contain a high concentration of uncondensed chlorofluorocarbons, theoretically 18%, and actually 30%, and will be returned to the inlets of the adsorption towers 1 and 2. The Freon 11 contains an even higher concentration of uncondensed Freon, about 53%, and is returned to the inlets of the adsorption towers 1 and 2. Because of this large amount of uncondensed CFC in the return air,
There is a drawback that the concentration process using the adsorption towers 1 and 2 is not effectively used to condense the fluorocarbon-containing air introduced from the outside system.

The present invention has been made in view of such problems, and includes:
It is an object of the present invention to provide a solvent recovery device that can improve the efficiency of a concentration process using an adsorption tower, and can reduce the amount of adsorbent required and the cost of the device.

[Means for Solving the Problems] A solvent recovery device according to the present invention includes first and second main adsorption towers each having an adsorbent whose main component is activated carbon and a heating means for heating the adsorbent; first and second auxiliary adsorption towers containing adsorbents whose component is activated carbon;
a solvent-containing gas flow means for selectively passing a processing gas containing a solvent through the main adsorption tower to obtain a clean gas;
or a condensing cooler that introduces and cools the regenerated gas from the second main adsorption tower and the regenerated gas from the first or second auxiliary adsorption tower to condense the solvent in the regenerated gas; uncondensed gas flow means for selectively flowing uncondensed gas from the condensation cooler to the first or second auxiliary adsorption tower; supplying processing gas to the first and second main adsorption towers; control means for selectively and alternately discharging the post-regeneration gas, and selectively and alternately discharging the post-regeneration gas and supplying the uncondensed gas to the first and second auxiliary adsorption towers; It is characterized by having.

In this case, the adsorbent may be a monolith molded body such as a honeycomb molded body, or a pellet-like material.

When the adsorbent is a monolith molded body, a heat supply member that comes into contact with the adsorbent can be used as the heating means. Specifically, this heat supply member includes:
There are sheet-shaped heaters that generate resistance heat when energized. Furthermore, when the adsorbent is in the form of pellets,
A coil-shaped heater or the like can be used as the heating means. This coil-shaped heater may be arranged so as to surround the adsorbent.

[Operation] In the present invention, when the adsorbent charged in one of the first (second) main adsorption towers is heated by the heating means, the adsorbent absorbs the solvent adsorbed in the previous adsorption step. is desorbed by the temperature-pressure swing desorption effect. Also, one of the first
The adsorbent charged in the (second) auxiliary adsorption tower is also undergoing a regeneration process, and the first (second) main adsorption tower and the first
The regenerated gas discharged from the (second) auxiliary adsorption tower is cooled in a condensing cooler, and the solvent it contains is condensed and separated from the gas. Then, the gas containing the uncondensed solvent that is not condensed in this condensing cooler is transferred to the other second (first)
) is introduced into the auxiliary adsorption tower where the contained solvent is adsorbed and removed, yielding semi-clean gas. Also, the other second (first
) A solvent-containing gas (processing gas) is introduced from the outside into the main adsorption tower, and the second (first) main adsorption tower adsorbs and removes the solvent in the processing gas to obtain clean gas. Then, the first and second main adsorption towers alternate between adsorption and regeneration (desorption) processes of the treated gas. In addition, the first and second auxiliary adsorption towers also carry out the adsorption process and regeneration (desorption) of uncondensed solvent-containing gas.
Alternate with the process.

In this way, the main adsorption tower adsorbs and removes the solvent in the treated gas, and during regeneration, the concentration of this solvent is concentrated and the solvent-containing gas (medium concentration gas) is desorbed, while the condensation cooler does not condense it. The uncondensed solvent-containing gas containing uncondensed solvent is introduced into an auxiliary adsorption tower, and most of the uncondensed solvent is removed by this auxiliary adsorption tower. Therefore, because the solvent concentration in the solvent-containing gas supplied from the external system is low, the solvent may not be sufficiently condensed in the condensing cooler and a relatively large amount of uncondensed solvent may be discharged from the condensing cooler. However, according to the present invention, this uncondensed solvent can be sufficiently removed by the auxiliary adsorption tower, so even if the semi-clean gas discharged from the auxiliary adsorption tower is returned to the entrance of the main adsorption tower, Since the amount and concentration of the solvent contained in the returned gas is low, the main adsorption tower is effectively used exclusively for the solvent concentration process by adsorption and desorption of the process gas introduced from the outside system.

Therefore, the solvent-containing gas can be concentrated with extremely high efficiency in the main adsorption tower.

[Example code] Examples of the present invention will be specifically described below.

FIG. 1 is a block diagram showing the principle of the present invention.

However, the solvent recovery device shown in this block diagram is for recovering fluorocarbons. In FIG. 1, the same parts as in FIG. 3 are given the same reference numerals.

An adsorbent 40 shown in FIG. 4 is housed in the main adsorption towers 1 and 2, and when the sheet heater 42 is energized, the sheet heater 42 generates heat and the adsorbent 41 is heated. As a result, fluorocarbons are desorbed from the adsorbent 41 and the adsorbent is regenerated. On the other hand, the first and second auxiliary adsorption towers 10.1
1 is filled with activated carbon pellets, and these activated carbon pellets adsorb and remove fluorocarbons from the air flowing through the auxiliary adsorption tower.

In the process shown in FIG. 1, the main adsorption tower works performs an adsorption process, and the main adsorption tower 2 performs a desorption process (regeneration process). Then, solvent-containing air is introduced into the main adsorption tower 1 by a processing blower 3 as a processing gas. In addition, the main adsorption tower 2
A carrier gas is introduced to transport the desorbed solvent. In this desorption process of the main adsorption tower 2, the main adsorption tower 2
The adsorbent material 41 inside is heated by a sheet heater 42 that generates resistance heat when energized. The carrier gas in the main adsorption tower 2 is sucked by a vacuum pump 6 and supplied to a condensing cooler 7. The uncondensed gas containing the uncondensed solvent that has not been condensed in the condensing cooler 7 is supplied to the auxiliary adsorption tower 10. This uncondensed gas undergoes adsorption of the solvent contained in the adsorbent in the auxiliary adsorption tower 10, becomes a semi-clean gas, and is returned to the upstream side of the processing blower 3. This returned gas is again subjected to solvent adsorption by the main adsorption tower 1, and is discharged into the atmosphere as a clean gas.

On the other hand, the inside of the auxiliary adsorption tower 11 is sucked by the vacuum pump 11, and the adsorbent in the auxiliary adsorption tower 11 is reduced in pressure to a vacuum, thereby desorbing the solvent that has been adsorbed up to that point.

This desorption solvent is carried by the carrier gas and introduced into the condensing cooler 7, where the solvent is adsorbed and removed together with the regenerated gas discharged from the main adsorption tower 2. The condensate of the solvent condensed in the condensing cooler 7 is recovered in a recovery tank.

After the adsorbent in the main adsorption tower 1 is saturated with fluorocarbons,
Or just before saturation, the main adsorption tower 1 moves to the desorption process, the main adsorption tower 2 to the adsorption process, the auxiliary adsorption tower 10 to the desorption process, and the auxiliary adsorption tower 11 to the adsorption process.

Thereafter, the adsorption and desorption steps are repeated alternately in the same manner to recover the fluorocarbons in the process gas.

In particular, in the main adsorption tower 1.2, when moving from the desorption step to the adsorption step, a cooling step for cooling the adsorbent may be provided in the middle. Thereby, after the adsorbent whose temperature has risen due to heating in the desorption step is cooled and its adsorption ability is restored, the adsorption step can be started.

In the present invention described above, the adsorbent in the main adsorption tower 2 is regenerated, and the regenerated gas containing a high concentration of fluorocarbons is sucked by the vacuum pump 6 and supplied to the condensing cooler 7. 7, the Freon is condensed and recovered. Further, the regenerated gas containing a high concentration of fluorocarbons by regenerating the adsorbent in the auxiliary adsorption tower 11 is similarly condensed in the condensing cooler 7.

The uncondensed gas remaining in the gas without being condensed and recovered in the condensing cooler 7 is supplied from the condensing cooler 7 to the auxiliary adsorption tower 10 and is adsorbed by the adsorbent in this auxiliary adsorption tower 10. removed. Therefore, after the fluorocarbons contained in this uncondensed gas are removed by the auxiliary adsorption tower 10, they are returned to the entrance of the main adsorption tower 1 with an extremely low concentration of fluorocarbons. Concentration processing may be performed by adsorption and desorption of fluorocarbons contained in the processing gas introduced from the processing gas. Therefore, even when the concentration of fluorocarbons in the processing gas introduced from the outside system is low, the processing efficiency in the main adsorption tower is high and its size can be reduced.

The regenerated gas discharged from the main adsorption towers 2 and 1 is directly introduced into the auxiliary adsorption tower 10.11.
It is also conceivable to further condense some of the fluorocarbons by 0.11, and then introduce this highly concentrated fluorocarbon-containing gas into the condenser cooler 7 to condense and recover the fluorocarbons. However, in the processing gas introduced from the outside system, moisture is present in addition to fluorocarbons. Then, the fluorocarbon concentration in the processing gas is, for example, IQOOppm.
When the main adsorption towers 1 and 2 concentrate the fluorocarbons in the treated gas to, for example, 80%, that is, 800 times, water is similarly concentrated, although the concentration ratio is different.

Therefore, the main adsorption towers 1 and 2 discharge high concentration, high temperature, and high humidity post-regeneration gas.

In addition, since this regenerated gas contains supersaturated water,
Some of it is discharged as water droplets.

In this case, if a highly humid gas is introduced into the auxiliary adsorption tower 10.11 as described above, the adsorbent activated carbon in the auxiliary adsorption tower 10.11 will be wetted by moisture or water droplets, and its fluorocarbon adsorption capacity will deteriorate. There is a possibility that

However, as in the present invention, the regenerated gas discharged from the main adsorption tower 2゜1 is first cooled by the condensing cooler 7 to condense and recover the fluorocarbons, and after condensing and removing moisture, the uncondensed gas is By configuring the uncondensed gas containing fluorocarbons to be introduced into the auxiliary adsorption tower 10.11, the auxiliary adsorption tower 10.11 is supplied with dry uncondensed gas containing little moisture, so that the auxiliary adsorption is performed by water droplets. The adsorbent in the column 10.11 is not wetted and its adsorption capacity deteriorates.

In the example shown in FIG. 1, the main adsorption towers 1 and 2 are equipped with a heating source such as a sheet heater 42 to desorb the adsorbent 41 using temperature and pressure.
ture Pressure Swing Adsor
ption). Auxiliary adsorption tower 10
．． 11 is the so-called PSA (P
Ressure Swing Adsorption
). By the way, the auxiliary adsorption tower 10.
11 may also adsorb and desorb fluorocarbons using TPSA. However, the uncondensed gas discharged from the condensing cooler 7 contains fluorocarbon at a relatively high concentration of about 30%. Therefore, even if the concentration ratio of the auxiliary adsorption towers 10 and 11 is 3 times, the regenerated gas discharged from the auxiliary adsorption towers 10 and 11 and given to the condensing cooler 7 will contain fluorocarbons at a concentration of 90%. A high concentration of fluorocarbon-containing gas is supplied to the condensing cooler 7. Therefore, the auxiliary adsorption tower 10.1
1, adsorption and desorption using the PSA method is sufficient.

In addition, as mentioned above, the main adsorption towers 1 and 2 are composed of an activated carbon adsorbent made of a monolith molded body such as honeycomb activated carbon, and a heat supply member such as a sheet heater that contacts the adsorbent and supplies heat. It is not limited to those who have the means.

For example, the adsorbent may be in the form of pellets. When this pellet-like adsorbent is used, it is preferable to use a heating means that can heat the adsorbent without contact, such as a coil heater.

Furthermore, as a carrier gas introduced into the main adsorption towers 1 and 2 to transport fluorocarbons during regeneration of the main adsorption towers 1 and 2,
Outside air may be used, or a portion of the clean gas discharged from the main adsorption tower of the adsorption step may be used. As for the auxiliary adsorption tower 10.11, the carrier gas may be outside air or may be a semi-clean gas discharged from the auxiliary adsorption tower in the adsorption step. When outside air is used as a carrier gas in the auxiliary adsorption tower, activated carbon can be sufficiently normalized and activated. On the other hand, if outside air is used as the carrier gas for the auxiliary adsorption tower, although the cleaning (regeneration) of activated carbon is slightly inferior,
The amount of return gas returned to the inlet of main adsorption tower 1 is
．． 2 (for example, 417 minutes), and this return gas amount is reduced. That is, if the auxiliary adsorption towers 10 and 11 also use outside air as a carrier gas, the carrier gas amount (3.51/min) plus the gas is returned to the entrance of the main adsorption tower as a return gas. When the carrier gas is supplied from the outlet of the auxiliary adsorption tower 10.11, the amount of return gas is small, so this is particularly suitable for recovering a low boiling point solvent-containing gas.

Next, an embodiment in which the above-described invention is applied to the recovery of fluorocarbons will be described with reference to FIG.

Note that in FIG. 2, the same parts as in FIG. 1 or 3 are designated by the same reference numerals, and detailed explanation thereof will be omitted.

The first and second main adsorption towers 1 and 2 are connected to piping 28a +
Piping 28 where 28b and these pipings 28a and 28b merge
It is connected to the vacuum pump 6 via. Further, a pipe 30 is connected to this pipe 28 (28b), and this pipe 30 is connected to the auxiliary adsorption tower 10.11 via branch pipes 30a and 30b, respectively. Therefore, the first
The second main adsorption tower 1.112 and the first and second auxiliary adsorption towers 10.11 are both directly connected to the vacuum pump 6. The piping 28 includes a vacuum pump 6 and a condensing cooler 7.
and a specific gravity separator 8 are connected in series. For example, chilled water of O'C flows through the condensing cooler 7, and the supplied gas is cooled by the chilled water.

As a result, the gas sucked and discharged from the multi-column by the vacuum pump 6 is supplied to the condensing cooler 7, and after being cooled in the condensing cooler 7 and condensing and separating fluorocarbons and water, this liquid bone is It is supplied to the separator 8. Also, separator 8
A solvent tank 9a and a drain tank 9b are connected to. As a result, the solvent and water separated by specific gravity in the specific gravity separator 8 are separated into a solvent tank 9a and a drain tank 9b, respectively.
will be collected.

Note that the pipes 28a and 28b are provided with on-off valves Ve+V+, respectively.
+ is inserted. Moreover, the piping 30a.

30b is provided with on-off valves V131 and V14, respectively.

The main adsorption towers 1 and 2 each have on-off valves V l 7+ V l
Pipes 29a and 29b with pipes 8 interposed therein are provided.
A pipe 29 where 9a and 29b join is connected to a cooler 32 via a cooling blower 5. A pipe 25 is connected to the gas outlet of the cooler 32, and the cooler 32 is connected to the main adsorption tower 1.2 by pipes 25a and 25b branched from the pipe 25, respectively. An on-off valve V51v7 is installed in each of the pipes 25a and 25b.

Further, the uncondensed gas containing uncondensed fluorocarbons that is not condensed in the condensing cooler 7 is transferred to the auxiliary adsorption tower 10.
11. Further, each of the auxiliary adsorption towers 10 and 11 is provided with a pipe 33a.

33b are connected, and both of these pipes 33a and 33b are connected to the pipe 2 on the upstream side of the processing blower 3 via the pipe 33.
1. An on-off valve V 19+V2O is installed in each of the pipes 33a and 33b. Furthermore,
The auxiliary adsorption towers 10 and 11 each have a flow rate regulating valve V171.
A pipe 32a with a VIB interposed therein.

32b are connected, and these pipes 32a, 32b merge into the pipe 32, and these pipes 32°32a, 3
The semi-clean gas flowing through the pipe 33 via the auxiliary adsorption tower 10.
It is set to be introduced in 11.

Next, the operation of the solvent recovery device configured as described above will be explained.

First, it is assumed that the first main adsorption tower 1 carries out an adsorption process, and the second main adsorption tower 2 carries out a desorption process. Therefore, the adsorbent in the first main adsorption tower 1 is in an active state, and the adsorbent in the second main adsorption tower 2 is adsorbing fluorocarbons in a saturated state or a state close to it.

In this case, first, the on-off valve V l + VQ + +
Vll+V1°+ V+5+ V1O1V14 is opened, and on-off valve V5. V, □.

Ve+ Ve+ V71 Vlllll VO2V41
Va+V 131 V 18+ V 20 is closed. The flow rate regulating valve Vlo+V1°+V171 VlO is adjusted so that a predetermined amount of air flows during depressurization of the adsorption tower. However, in this process, on-off valves V1□, ■, 4
Since only the flow rate adjustment valves V1° and VlO are open, a predetermined large amount of gas flows through only the flow rate adjustment valves V1° and VlO. Then, the vacuum pump 6 is driven, and the processing blower 3 is always driven.

Then, the fluorocarbon-containing air is transferred to the first
into the main adsorption tower 1. Then, this fluorocarbon-containing air passes through the adsorbent 41 of the adsorbent 40 housed in the first main adsorption tower 1, and after the fluorocarbons are adsorbed and removed,
It is discharged into the atmosphere as clean air.

On the other hand, in the second main adsorption tower 2, the adsorbent 41 is heated by energizing the sheet heater 42 of the adsorbent 40, and the adsorbent 41 desorbs the fluorocarbons adsorbed in the previous adsorption process. . The second main adsorption tower 2 and the second auxiliary adsorption tower 11 are sucked by the vacuum pump 6 and placed under negative pressure, so a small amount of purified air is pumped into the second adsorption tower through the flow rate adjustment valve V1□. In addition to being introduced into the main adsorption tower 2, a small amount of semi-purified air is also introduced into the second auxiliary adsorption tower 11 via the flow rate adjustment valve V□8. The fluorocarbons desorbed from the adsorbents in the second main adsorption tower 2 and the second auxiliary adsorption tower 11 are sucked by the vacuum pump 8 using the purified air and semi-purified air as carrier gas, and are supplied to the condensing cooler 7. . This fluorocarbon concentrated air containing a medium concentration of fluorocarbons is cooled in a condensing cooler 7, and the fluorocarbons and water contained in this concentrated air are condensed to become a fluorocarbon liquid and water, which are then supplied to a separator 8. The fluorocarbon liquid and water are separated by specific gravity in a separator 8, and the fluorocarbon liquid is collected and stored in a solvent tank 9.

The air containing uncondensed fluorocarbons discharged from the condensing cooler 7 is transferred to the first auxiliary adsorption tower 10 via a pipe 31.31a.
The uncondensed freon is adsorbed by the adsorbent in the first auxiliary adsorption tower 10. Furthermore, the air discharged from the auxiliary adsorption tower 10 is returned to the upstream side of the processing blower 3 via the pipes 33a and 33, and is passed through the first main adsorption tower 1 together with the processing air (air containing fluorocarbons). The remaining fluorocarbons are adsorbed by the adsorbent in the first main adsorption tower 1, and are discharged into the atmosphere as clean air.

Next, after the adsorbent in the second main adsorption tower 2 has been sufficiently desorbed, the second main adsorption tower 2 moves to a step of cooling the adsorbent. That is, after closing the on-off valve V□1 and opening the on-off valve V8 to bring the inside of the adsorption tower to normal pressure, the on-off valve V8 is closed again. Then, the on-off valve v7°ViB is opened to start driving the cooling blower 5 and start cooling by the cooler 32. Further, the power supply to the seat heater 42 of the adsorbent 40 housed in the second main adsorption tower 2 is stopped.

As a result, inside the second main adsorption tower 2, the pipes 29b, 2
The purified air sucked into the cooling blower 5 via the cooling blower 5 through the cooling blower 5 flows as cooling air, and the adsorbent in the second main adsorption tower 2, which has been heated in the previous desorption process, is cooled. While this cooling air flows through the second main adsorption tower 2,
The fluorocarbons in the second main adsorption tower 2 will be mixed into the cooling air, but after the cooling air discharged from the second main adsorption tower 2 is cooled by the cooler 32 to a temperature range where it can be adsorbed,
It is supplied to the second main adsorption tower 2 and adsorbed again. As a result, the mixed Freon is adsorbed and removed by the adsorbent in the second main adsorption tower 2.

Next, after the adsorbent in the first main adsorption tower 1 is saturated or in a state close to it, the first main adsorption tower 1 undergoes a desorption process.
The second main adsorption tower 2 moves to the adsorption step. Further, the auxiliary adsorption tower 10 moves to the desorption process, and the auxiliary adsorption tower 11 moves to the adsorption process.

That is, the on-off valve V r + V2 v V5 + Ver
Close VI7 and open on-off valve V8. In addition, the on-off valve V31V4 is opened, and the on-off valve V 71 Va + V ll
+V Leave 1s idle. Furthermore, the on-off valve V13 is opened, and the on-off valve V5. V and 9 are closed, and the on-off valve V
Open l l+ V 20 and close on-off valve V 14. Then, the driving of the cooling blower 5 is stopped. Also, the first
The seat heater 42 of the adsorbent 40 housed in the first main adsorption tower 1 is heated to heat the adsorbent 41, and the first main adsorption tower 1 is heated.
Freon is desorbed from the adsorbent 41 inside.

As a result, the first main adsorption tower 1 and the first auxiliary adsorption tower 1
0 carries out the desorption process, and the second main adsorption tower 2 and the second auxiliary adsorption tower 11 carry out the adsorption process. And the first main adsorption tower 1
After the adsorbent therein has sufficiently desorbed fluorocarbons, the first main adsorption tower 1 moves to a cooling process. That is, the power supply to the seat heater 42 is stopped, the on-off valve V9 is left idle, and the on-off valve V8 is turned off.
After opening the main adsorption tower 1 to normal pressure, open the on-off valve v again.
6 is closed. And the on-off valves V,,V,. Open the
Driving of the processing blower 5 is started. As a result, purified air cooled by the cooler 32 is introduced into the first main adsorption tower 1, and the adsorbent in the first main adsorption tower 1, which had been heated in the previous desorption process, is converted into purified air. It is cooled by the flow of water.

After that, the first main adsorption tower 1 and the second main adsorption tower 2 alternately repeat the adsorption process and the desorption and cooling process, and the first main adsorption tower 1 performs the adsorption process (or desorption process). In case, the first
When the auxiliary adsorption tower 10 performs the adsorption step (or desorption step) and the second main adsorption tower 2 performs the desorption step (or adsorption step), the second auxiliary adsorption tower 11 performs the desorption step (or adsorption step). )
Implement. As a result, the fluorocarbon-containing air is continuously adsorbed and clean air is obtained, and the condensed and separated fluorocarbon liquid is collected into the solvent tank 9a.

In this way, Freon is recovered as a liquid.

In this case, the fluorocarbons adsorbed and removed by the main adsorption tower 1.2 are:
There are very few substances that are circulated within the system, and only those that are introduced into the apparatus from outside the system.

For this reason, the main adsorption towers 1 and 2 are used exclusively for adsorption treatment of air containing fluorocarbons, which should be removed by adsorption, and can adsorb fluorocarbons extremely effectively, so the amount of adsorbent material required in the main adsorption towers is small. suffice, and the equipment cost can be reduced.

Further, the main adsorption towers 1 and 2 perform temperature pressure swing adsorption (TPSA) on the low concentration side, and the auxiliary adsorption towers 10 and 11 perform pressure swing adsorption (PSA) on the high concentration side. For this reason, even if the inlet concentration is as low as 200 ppm and the conventional solvent recovery device shown in Figure 3 does not condense as the fluorocarbons circulate inside the device,
In this example device, after being concentrated in the main adsorption tower, the uncondensed gas generated from the condensing cooler is condensed in the auxiliary adsorption tower, making it possible to recover the solvent in the treated gas with extremely high efficiency. can. Therefore, in the apparatus of this embodiment, fluorocarbons can be recovered with high efficiency from air containing low concentrations of fluorocarbons.

Note that the present invention is not limited to the recovery of fluorocarbons, but can of course be applied to the recovery of various other solvents.

[Effects of the Invention] According to the present invention, an auxiliary adsorption tower is provided outside the main adsorption tower for adsorbing and removing the solvent in the uncondensed gas of the condensing cooler, and in addition to the main adsorption tower concentrating the solvent-containing gas. Since the uncondensed gas is adsorbed and desorbed by the auxiliary adsorption tower, the solvent can be recovered with extremely high efficiency even when the solvent concentration in the solvent-containing gas introduced into the device from this external system is low. can.

In addition, the gas containing uncondensed solvent is introduced into the auxiliary adsorption tower, and the uncondensed solvent is adsorbed and removed by the adsorbent in the auxiliary adsorption tower. The amount of uncondensed solvent (solvent circulated within the device) that must be removed by adsorption is extremely small. Therefore, only a small amount of adsorbent is required in the main adsorption tower, and the cost of the apparatus can be reduced.

In this manner, by providing dedicated adsorption towers for the low concentration side and the high concentration side, the present invention can improve the solvent recovery efficiency and reduce the equipment cost.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the principle of the present invention, Fig. 2 is a block diagram showing a solvent recovery device according to an embodiment of the present invention, and Fig. 3 is a block diagram showing the principle of the present invention.
The figure is a block diagram showing a conventional solvent recovery device, and FIG. 4 is a schematic perspective view showing an adsorbent that does not use steam.

Claims (9)

[Claims] (1) First and second main adsorption towers equipped with an adsorbent whose main component is activated carbon and heating means for heating and regenerating this adsorbent; and a first adsorption tower containing the adsorbent whose main component is activated carbon. and a second auxiliary adsorption tower, a solvent-containing gas flow means for selectively passing a solvent-containing processing gas through the first and second main adsorption towers to obtain a clean gas, A condensing cooler that introduces and cools the gas after adsorbent regeneration from the second main adsorption tower and the gas after regeneration of the adsorbent from the first or second auxiliary adsorption tower, and condenses the solvent in the regenerated gas. and an uncondensed gas flow means for selectively flowing the uncondensed gas from the condensation cooler to the first or second auxiliary adsorption tower, and a process gas for the first and second main adsorption towers. control to selectively and alternately supply uncondensed gas and discharge post-regeneration gas to the first and second auxiliary adsorption towers and to discharge post-regeneration gas selectively and alternately. A solvent recovery device comprising: means. (2) The solvent recovery device according to claim 1, wherein the adsorbent is a monolith molded body, and the heating means is a heat supply member that comes into contact with the adsorbent. (3) The solvent recovery device according to claim 1, wherein the adsorbent is in the form of pellets. (4) After cooling the adsorbent in the first and second main adsorption towers by flowing cooling gas, the exhaust gas is cooled and introduced again into the adsorption tower from which the cooling gas was discharged. 4. The solvent recovery apparatus according to claim 1, further comprising a cooling gas flow means having an annular gas flow system. (5) The semi-clean gas obtained after the uncondensed gas selectively flows through the first and second auxiliary adsorption towers is transferred to the first
The solvent recovery device according to any one of claims 1 to 4, further comprising a return means for returning the treated gas to the inlet of the second main adsorption tower. (6) The gas used for regenerating the adsorbent in the main adsorption tower is a part of the clean gas discharged from the other main adsorption tower. Solvent recovery equipment. (7) The solvent recovery apparatus according to claim 5, wherein the gas used for regenerating the adsorbent of the auxiliary adsorption tower is a part of the semi-clean gas discharged from the other auxiliary adsorption tower. (8) The solvent recovery device according to any one of claims 1 to 5, wherein the gas used for regenerating the adsorbent in the main adsorption tower is outside air. (9) Any one of claims 1 to 5, wherein the gas used for regenerating the adsorbent in the auxiliary adsorption tower is outside air.
Solvent recovery equipment as described in Section.