JPH03224614A - Solvent recovery apparatus - Google Patents

Abstract

PURPOSE:To improve the condensation efficiency in a condensation cooler, even when the solvent concn. in the gas which contains the solvent and is introduced into the device from an outer system is low, and to recover the solvent with extremely high efficiency by passing the gas contg. the solvent through the concn. process of two stages consisting of a main adsorption tower and an auxiliary adsorption tower. CONSTITUTION:The solvent concd. gas of middle concn. having the solvent desorbed in the solvent desorption process in a 1st or a 2nd main adsorption tower 1, 2 is passed through a 1st or a 2nd auxiliary adsorption tower 10, 11, and then cooled in the condensation cooler 7 in which the solvent is condensed and separated from the gas. In this case, the solvent concd. gas of middle concn. discharged from the main adsorption tower 1, 2 desorbs CFC adsorbed by the adsorbent in the auxiliary adsorption tower 10, 11 by a pressure swing desorption effect, and is further concentrated resulting in the gas contg. high concn. solvent, and sucked and introduced into the condensation cooler 7.

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. There is.

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 CFCs 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 for

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 is designed to heat the adsorbent with 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. This adsorbent 41 is a monolith molded body such as a honeycomb molded body. Then, the seat heater 42 is energized to generate resistance heat, thereby causing the adsorbent 41 in contact with the seat heater 42 to
It is designed to heat up. 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 is connected to the first and second adsorption towers 1, 1, 2, and 3 by means of a pipe 23 and pipes 23a and 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 and 2. Cooling water is supplied to the cooler 4 to pre-cool the fluorocarbon-containing air sent into the adsorption tower 1.2. In addition, the piping 23a, 2
3b is provided with on-off valves vl and V3, respectively.

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.

Each of the pipes 24a and 24b has an on-off valve V2.
V4 is installed.

Further, the pipe 24 is connected to one end of each of the first and second adsorption towers 1 and 2 via a pipe 28 a + 27 a and pipes 2E3b and 27b. Piping 28a,
Air release valves Ve and Ve are installed in the pipes 26b, respectively, and carrier air flow rate regulating valves VIO and V12 are installed in the pipes 27a and 27b, respectively. At the other end of each of the first and second adsorption towers 1 and 2, piping 25a is provided.
, 25b and piping 28a, 28b are connected. Piping 25a.

25b joins the pipe 25, and 17) the pipe 25 is connected to the pipe 22. A cooling blower 5 is installed in the pipe 25 to suck air from the adsorption towers 1 and 2 through the pipes 25a and 25b.
are provided with on-off valves V5 and V7, respectively.

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. Open the on-off valve VI5. v
Close e and Ve. The flow rate adjustment valve VIO is set to allow a predetermined flow rate of regeneration gas to flow through during depressurization in the next step. Further, the on-off valves V31, V4+V7+V8 are closed, the on-off valve V11 is opened, and the flow rate adjustment valve V12 is set to a predetermined opening degree to allow a predetermined flow rate of regeneration gas to flow through the flow rate adjustment valve V12. 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 pipes 23 and 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 2B and 28b, and the purified air flowing through the pipe 24 is supplied to a predetermined level through the flow rate adjustment valve V1°. introduced at a flow rate.

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 on the adsorbent 41 are desorbed, and the fluorocarbons desorbed from the adsorbent 41 are transferred to the vacuum pump using the purified air introduced into the adsorption tower 2 through the flow rate adjustment valve V1 as a carrier gas. 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 become 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 step to the cooling step while the first adsorption tower 1 remains in the adsorption step. to be transferred to That is, the valves VllV2, VB, Ve, V
e and valve V3. V4 is left as is, opening/closing valve v8 is opened, and opening/closing valve V11 is closed.

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. Let V be open.

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.

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 towers 1 and 2 increases, in the adsorption tower 1.2, -
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 that is supplied from the outside system, is reduced. This is extremely inefficient. For example, in Freon 113, even if it is cooled to 5°C in the cooler 7 and condensed and separated, the theoretical value is 1 in the carrier gas.
It contains a high concentration of uncondensed fluorocarbons of 8%, in fact 30%, and is returned to the inlet 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. Since the amount of uncondensed fluorocarbons in the return air is large as described above, there is a drawback that the concentration process using the adsorption towers 1 and 2 is not effectively used for concentrating 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 that house adsorbents whose component is activated carbon and through which exhaust gases from the first and second main adsorption towers flow, and the first or second main adsorption towers; a solvent-containing gas flow means for selectively passing a solvent-containing processing gas through the auxiliary adsorption tower to obtain a clean gas; It is characterized by having a condensing cooler for condensing the solvent therein, and an uncondensed gas flow means for selectively flowing the uncondensed gas from the condensing cooler to the first or second auxiliary adsorption tower. shall be.

In this case, the adsorbent may be in the form of a monolith molded body or pellets. When the adsorbent is a monolith molded body, the heating means can use a heat supply member that comes into contact with the adsorbent. A specific example of this heat supply member is a seat heater that generates resistance heat when energized.

Furthermore, in the case of a sheet-like monolith molded body in which a bent wavy sheet is sandwiched between flat sheets, the bending wavy sheets are arranged so as to intersect at 90 degrees, and hot air is passed in one direction. Can be heated.

[Function] In the present invention, the solvent concentrated gas containing the solvent desorbed in the solvent desorption step in the first (second) main adsorption tower (
After passing through the first (second) auxiliary adsorption tower, the medium concentration gas is cooled in a condensing cooler, and the solvent is condensed and separated from the gas. In this case, the solvent concentrated gas (medium concentration gas) discharged from the main adsorption tower is further concentrated and highly concentrated by desorbing the fluorocarbons adsorbed on the adsorbent in the auxiliary adsorption tower due to the pressure swing desorption effect. After becoming a concentrated solvent-containing gas, it is sucked and introduced into a condensing cooler.

Therefore, even if the solvent-containing gas supplied from the outside to the main adsorption tower has a relatively low concentration, the solvent-concentrated gas introduced into the condenser cooler is further concentrated in the auxiliary adsorption tower outside the main adsorption tower. Since it has a high concentration, extremely high condensation efficiency can be obtained in the condensing cooler.

The gas containing some uncondensed solvent after condensation and separation is supplied to the second (first) auxiliary adsorption tower by the uncondensed gas flow means, and the uncondensed solvent is adsorbed and removed.

In this way, the low-concentration solvent-containing gas to be treated is repeatedly subjected to adsorption and desorption processes due to temperature and pressure swings in an equilibrium state at a relatively low concentration in the main adsorption tower, and is then discharged from the main adsorption tower. The medium-concentration solvent-containing gas is repeatedly subjected to adsorption and desorption steps by pressure swings in an equilibrium state at a relatively high concentration in the auxiliary adsorption tower. Therefore,
Since the solvent-containing gas introduced into the condensing cooler is the highly concentrated solvent-containing gas discharged from the auxiliary adsorption tower, the solvent is condensed with extremely high efficiency, and little solvent remains in the uncondensed gas. Further, this uncondensed gas is supplied to the auxiliary adsorption tower, and the uncondensed solvent is adsorbed by the adsorbent in the auxiliary adsorption tower. Therefore, since the main adsorption tower is effectively used for concentrating the solvent-containing gas introduced from the outside system, the amount of adsorbent required in the main adsorption tower is small, and the equipment cost is low.

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

FIG. 1 is a block diagram showing a solvent recovery device according to an embodiment of the present invention. In FIG. 1, the same parts as in FIG. 2 are given the same reference numerals, and detailed explanation thereof will be omitted.

An adsorbent 40 shown in FIG. 3 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, Freon is desorbed from the adsorbent and the adsorbent is regenerated. On the other hand, the first and second auxiliary adsorption towers 10.11 are filled with activated carbon pellets, and the activated carbon pellets adsorb and remove freon from the air flowing through the auxiliary adsorption towers.

The first main adsorption tower 1 is connected to the first auxiliary adsorption tower 10 via a pipe 28a. Further, the second main adsorption tower 2 is connected to the auxiliary adsorption tower 11 via a pipe 28b. Pipes 30a and 3ob are connected to the gas discharge ports of these auxiliary adsorption towers 10 and 11, respectively, and a pipe 30 where these pipes 30a and 30b join is connected to the condensing cooler 7. The pipes 30a and 30b each have an on-off valve v,
3゜Vyu. is interposed therein, and a vacuum pump 6 is interposed in the piping 30. The fluorocarbon liquid and water condensed in the condensing cooler 7 are then supplied to the separator 8.

The air containing uncondensed fluorocarbons is transferred from the separator 8 to the pipe 31.
and a pipe 31a branched from this pipe 31.

31b to the respective auxiliary adsorption columns 10.11. The pipes 31a and 31b each have on-off valves V15. V
B2 is interposed. The fluorocarbon liquid separated by specific gravity in the separator 8 is collected and stored in a solvent tank 9.

In addition, the main adsorption towers 1 and 2 are provided with pipes 29a and 29b each having an on-off valve v17°Via interposed therein.
, 29b are connected to a cooler 32 via a cooling fan 5. A pipe 25 is connected to the gas outlet of the cooler 32, and the cooler 32 is connected to the main adsorption towers 1 and 2 through pipes 25a and 25b branched from the pipe 25, respectively. The pipes 25a and 25b each have an on-off valve V5. V7 is installed.

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 valves V, , V2. V, , open the on-off valve V5. Ve, close V13. Flow rate adjustment valve VI
O is adjusted so that a predetermined amount of air flows when the adsorption tower is depressurized. Also, on-off valve V31V4+V7+V B +
Close V1B, open on-off valve V14, and set flow rate adjustment valve 1° to a predetermined opening. Then, the vacuum pump 6 is driven, and the processing blower 3 is always driven.

Then, the fluorocarbon-containing air is supplied to the cooler 4 by the processing blower 3 and cooled, becoming low-temperature air with high adsorption efficiency, and then sent into the first main adsorption tower 1. This fluorocarbon-containing air flows through the adsorbent of the adsorbent 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 that a small amount of purified air is transferred to the second adsorption tower via the flow rate adjustment valve V12. It is installed in tower 2. The fluorocarbons desorbed from the adsorbent in the second main adsorption tower 2 are sucked by the vacuum pump 6 and supplied into the auxiliary adsorption tower 11 using the purified air as carrier air. This carrier air is heated while passing through the high temperature adsorbent 40 in the second main adsorption tower 2 and therefore has a relatively high temperature. The high-temperature fluorocarbon-concentrated air containing a medium concentration of fluorocarbons is then
is sent to the activated carbon pellet adsorbent in the auxiliary adsorption tower 11. Since the inside of this auxiliary adsorption tower 11 is suctioned by the vacuum pump 6, the adsorbent in the auxiliary adsorption tower 11 placed under reduced pressure desorbs fluorocarbons due to the pressure swing and becomes air containing higher concentration of fluorocarbons. It is sucked into the vacuum pump 6 and supplied to the condensing cooler 7. The fluorocarbons and water contained in this discharged air are cooled and condensed by the condensing cooler 7 to become a fluorocarbon liquid and water, which are then supplied to the 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 cooler 7 is supplied from the separator 8 to the first auxiliary adsorption tower 10 via the pipes 31 and 31a, and the uncondensed fluorocarbons are fed into the first auxiliary adsorption tower 10. It is adsorbed by the adsorbent material. Further, the air discharged from the auxiliary adsorption tower 10 flows through the first main adsorption tower 1 together with the treated air (air containing fluorocarbons) introduced via the pipe 21, and the remaining fluorocarbons are transferred to the first main adsorption tower 1. Adsorbed by the adsorbent in the adsorption tower 1,
It becomes clean air and is emitted into the atmosphere.

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, the on-off valve V 141 vlel is closed, the on-off valve v8 is opened, the inside of the adsorption tower is brought to normal pressure, and then the on-off valve v8 is closed again. Then, the vacuum pump 6 is stopped, the on-off valve V 71 V ta is opened, and the driving of the cooling blower 5 and the cooling of the cooler 32 are started.

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 through 9.25b and 25 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. That is, close the on-off valves V11 V21 V51 Ve+Vi5, and close the on-off valves V
Open 13. In addition, on-off valve V3 + V4 + V
Open □e, open/close valve V7 + Vs + VI41V18
close. Then, the vacuum pump 6 is driven and the cooling blower 5 is stopped. Further, the seat heater 42 of the adsorbent 40 housed in the first main adsorption tower 1 is energized to heat the adsorbent 41, thereby desorbing fluorocarbons from the adsorbent 41 in the first main adsorption tower 1.

As a result, the first main adsorption tower 1 performs the desorption process, and the second main adsorption tower 2 performs the adsorption process. After the adsorbent in the first main adsorption tower 1 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, and the on-off valves V, 3. V□6 is closed, on-off valve v6 is opened, and after the main adsorption tower 1 is brought to normal pressure, on-off valve v6 is closed again. Further, the vacuum pump 6 is stopped, the on-off valve V51V17 is opened, and the processing blower 5 is started to be driven. This results in
Purified air is introduced into the first main adsorption tower 1, and the adsorbent in the first main adsorption tower 1, which has been heated in the previous desorption step, is cooled by the flow of purified air.

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 9.

In this example, air containing fluorocarbons introduced into the apparatus from the outside system passes through the main adsorption towers 1 and 2, and the fluorocarbons contained therein are adsorbed and removed by the adsorbent in the main adsorption towers 1 and 2. . Then, by applying electricity to the seat heater and heating the adsorbent, the fluorocarbons adsorbed by the adsorbent are desorbed. In this case, if the concentration of fluorocarbons in the fluorocarbon-containing air introduced into this device is low, the concentration of fluorocarbons in the fluorocarbon-enriched air desorbed from the main adsorption tower 1.2 is not concentrated. However, the condensation efficiency is at a low level. However, this medium-concentration CFC enriched air is transferred to the auxiliary adsorption tower 10.1.
The air is concentrated to an even higher concentration through a concentration process using the adsorbent in the auxiliary adsorption towers io and it, and high-concentration freon-concentrated air is supplied to the condensing cooler 7 from the auxiliary adsorption towers io and it. Therefore, even if the concentration of the air containing fluorocarbons introduced into the apparatus is low, the condensation efficiency in the condenser cooler 7 is extremely high, and fluorocarbons are recovered with high efficiency. In addition, the air containing uncondensed fluorocarbons that was not condensed in the condensation cooler 7 is passed through the auxiliary adsorption tower 10.11, and the fluorocarbons contained therein are adsorbed and removed.
Next, the air is passed through the main adsorption towers 1 and 2 to further adsorb and remove fluorocarbons, and then is discharged as clean air. Therefore, very little of the fluorocarbons adsorbed and removed by the main adsorption towers 1 and 2 are circulated within the system, and are mainly 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.

In addition, the main adsorption towers 1 and 2 perform temperature and pressure swing adsorption (Temperature & Pressure) on the low concentration side.
SvjngAdsorptlon: TPS A
), and the auxiliary adsorption tower 10.11 performs pressure swing adsorption (Pressure Swing Ads) on the high concentration side.
Orption: PSA) is carried out. For this reason, even if the inlet concentration is as low as 200 ppm and the conventional solvent recovery device shown in Figure 2 does not condense, the CFCs will only circulate inside the device.
In the apparatus of this embodiment, the chlorofluorocarbons are sufficiently condensed in the condensing cooler because they undergo two stages of concentration: concentration in the main adsorption tower and concentration in the auxiliary adsorption tower. Therefore,
In the apparatus of this embodiment, fluorocarbons can be recovered with high efficiency from air containing fluorocarbons at a temperature of 1 degree.

Note that the present invention is of course applicable not only to the recovery of fluorocarbons but also to the recovery of various other solvents.

Further, in the above-described embodiment, an adsorbent 40 shown in FIG. 3 is inserted into the main adsorption tower 1°2. As described above, this adsorbent 40 is configured so that a monolithic adsorbent 41 is heated by a sheet heater 42 that is in contact with this adsorbent 41.
Of course, the configuration of the adsorbent inserted therein is not limited to the above embodiment. For example, the adsorbent may be heated not only by a sheet heater but also by energizing a coiled heater. In addition, as an adsorbent,
A monolith molded body such as a honeycomb molded body, a corrugated sheet body interposed between a plurality of cylindrical sheets, or a pellet shape may be used. When this pellet-like adsorbent is used, it is preferable to use a coil-shaped heater rather than a sheet-shaped heater.

Furthermore, since the auxiliary adsorption tower is supplied with a gas containing a relatively high concentration of solvent, even if the auxiliary adsorption tower is of the PSA type, the solvent can be concentrated with sufficiently high efficiency. However, it goes without saying that a TPSA type adsorption tower may be used for this auxiliary adsorption tower as well as for the main adsorption tower.

[Effects of the Invention] According to the present invention, the solvent-containing gas undergoes a two-stage concentration process of the main adsorption tower and the auxiliary adsorption tower, so that the solvent in the solvent-containing gas introduced into the apparatus from the external system is Even at low concentrations, the condensation efficiency in the condenser cooler is high and the solvent is recovered with extremely high efficiency. 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 equipment cost can be reduced.In this way, 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 a solvent recovery device according to an embodiment of the present invention, FIG. 2 is a block diagram showing a conventional solvent recovery device, and FIG. 3 is a schematic perspective view showing an adsorbent that does not use steam. be. 1.2; Main adsorption tower, 3; Processing blower, 4: Cooler, 5;
Cooling blower, 6; Vacuum pump, 7: Condensing cooler, 8; Separator, 9; Solvent tank, 10, 11: Auxiliary adsorption tower, 32
;Cooler

Claims (5)

[Claims] (1) First and second main adsorption towers each containing an adsorbent whose main component is activated carbon and a heating means for heating the adsorbent; A process gas containing a solvent is selectively passed through the first and second auxiliary adsorption towers through which the exhaust gas from the second main adsorption tower flows, and the first or second main adsorption tower. a solvent-containing gas flow means for obtaining clean gas; a condensing cooler that introduces and cools the exhaust gas from the first and second auxiliary adsorption towers and condenses the solvent in the exhaust gas; and the condensing cooler. and uncondensed gas flow means for selectively flowing uncondensed gas from the first or second auxiliary adsorption tower to the first or second auxiliary adsorption tower. (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) Any one of claims 1 to 4, further comprising introducing means for introducing exhaust gas from the first and second auxiliary adsorption towers into the first and second main adsorption towers, respectively. Solvent recovery equipment as described in Section.