阅读说明：本技术 有机溶剂回收系统 (Organic solvent recovery system ) 是由 冈田武将 于 2020-03-27 设计创作，主要内容包括：本发明涉及一种能够从含有机溶剂的待处理气体中分离回收有机溶剂的有机溶剂回收系统,其具有：能够使载气循环流通的循环通路；具有吸脱附元件的、交替执行从导入的上述待处理气体中吸附有机溶剂以及通过导入上述载气来脱附上述有机溶剂的吸脱附处理装置；设置在上述循环通路上的上述吸脱附处理装置下游的、将从该吸脱附处理装置排出的上述载气冷却,冷凝回收该载气中含有的有机溶剂的冷凝回收装置；和设置在上述循环通路上的上述吸脱附处理装置上游的、加热上述冷凝回收装置中排出的上述低温状态的载气的加热部；上述冷凝回收装置调节从该冷凝回收装置排出的载气的温度,以使从该冷凝回收装置排出的载气中含有的有机溶剂的蒸气压为规定值以下。(The present invention relates to an organic solvent recovery system capable of separating and recovering an organic solvent from a gas to be treated containing the organic solvent, the system comprising: a circulation path through which the carrier gas can circulate; an adsorption/desorption processing device having an adsorption/desorption element for alternately performing adsorption of the organic solvent from the introduced gas to be processed and desorption of the organic solvent by introducing the carrier gas; a condensation recovery device provided downstream of the adsorption/desorption processing device in the circulation path, for cooling the carrier gas discharged from the adsorption/desorption processing device and condensing and recovering an organic solvent contained in the carrier gas; and a heating unit provided upstream of the adsorption/desorption processing unit in the circulation passage and configured to heat the carrier gas in the low-temperature state discharged from the condensation recovery unit; the condensation recovery device adjusts the temperature of the carrier gas discharged from the condensation recovery device so that the vapor pressure of the organic solvent contained in the carrier gas discharged from the condensation recovery device is equal to or lower than a predetermined value.)

1. An organic solvent recovery system for separating and recovering an organic solvent from a gas to be treated containing the organic solvent, comprising:

a circulation path through which the carrier gas can circulate;

adsorption and desorption treatment device: having an adsorption-desorption element, alternately performing adsorption of the organic solvent by introducing the gas to be treated and desorption of the organic solvent by introducing the carrier gas;

condensation recovery unit: a cooling unit disposed downstream of the adsorption/desorption processing unit in the circulation passage, for cooling the carrier gas discharged from the adsorption/desorption processing unit, and condensing and recovering an organic solvent contained in the carrier gas;

a heating section: the carrier gas in the low-temperature state discharged from the condensation recovery device is heated upstream of the adsorption/desorption treatment device provided in the circulation path;

the condensation recovery device adjusts the temperature of the carrier gas discharged from the condensation recovery device so that the vapor pressure of the organic solvent contained in the carrier gas discharged from the condensation recovery device is equal to or lower than a predetermined value.

2. The organic solvent recovery system according to claim 1, having a temperature measuring unit that measures a temperature of the carrier gas discharged from the condensation recovery apparatus;

the condensation recovery device adjusts the temperature of the discharged carrier gas so that the water vapor pressure becomes a predetermined value or less based on the measured value of the temperature measuring means.

3. The organic solvent recovery system according to claim 1, comprising a vapor pressure measuring means for measuring a vapor pressure of the carrier gas discharged from the condensation recovery device;

the condensation recovery device adjusts the temperature of the discharged carrier gas so that the vapor pressure becomes a predetermined value or less based on the measured value of the vapor pressure measuring means.

4. The organic solvent recovery system according to any one of claims 1 to 3, wherein the condensation recovery device cools the carrier gas by indirect cooling using a refrigerant.

5. The organic solvent recovery system according to claim 4, wherein the refrigerant is any one of water, ethylene glycol, propylene glycol, glycerol, ethanol, or a mixture thereof.

Technical Field

The present invention relates to an organic solvent recovery system that separates an organic solvent from a gas to be treated containing the organic solvent, purifies and discharges the gas to be treated, and simultaneously recovers the separated organic solvent using a carrier gas.

Background

Conventionally, the following organic solvent-containing gas treatment systems are known: the gas to be treated containing an organic solvent is subjected to adsorption treatment and desorption treatment of the organic solvent using an adsorbent, and purification of the gas to be treated and recovery of the organic solvent are made possible by transferring the organic solvent from the gas to be treated to a carrier gas.

Such an organic solvent recovery system generally includes an adsorption/desorption processing device for alternately bringing a gas to be processed containing an organic solvent and a carrier gas in a high-temperature state into contact with an adsorbent with time, and a condensation recovery device for condensing and recovering the organic solvent by cooling the carrier gas discharged from the adsorption/desorption processing device.

As one of such organic solvent recovery systems, patent document 1 discloses an organic solvent-containing gas treatment system using water vapor as a carrier gas.

Further, recently, there has been a demand for a low-drainage organic solvent recovery system for the purpose of improving the quality of recovered organic solvents and simplifying the drainage treatment process. Patent document 2 discloses an organic solvent recovery system for supplying a carrier gas to a high-temperature adsorbent indirectly heated at a high temperature.

Documents of the prior art

Patent document

[ patent document 1] Japanese Utility model patent application publication "Kaiping 3-32924"

[ patent document 2] Japanese laid-open patent publication "Japanese patent application laid-open No. Hei 7-68127"

Disclosure of Invention

Problems to be solved by the invention

In such an organic solvent recovery system, in order to improve the purification capability of the gas to be treated and the recovery efficiency of the organic solvent, it is necessary to sufficiently perform desorption of the organic solvent at the time of desorption treatment, that is, regeneration of the adsorbent.

In order to control the running cost of the organic solvent recovery system, it is preferable that the used carrier gas is recycled in the organic solvent recovery system.

However, in the condensation recovery apparatus, it is difficult to completely separate the organic solvent from the carrier gas, and therefore, the carrier gas discharged from the condensation recovery apparatus contains the organic solvent that has not been condensed. Therefore, in the configuration in which the carrier gas is circulated and returned to the adsorption and desorption treatment apparatus, the adsorbent may not be regenerated sufficiently, and there is a natural limitation in the purification capacity of the gas to be treated and the recovery efficiency of the organic solvent.

Accordingly, the present invention has been made to solve the above problems, and an object of the present invention is to provide an organic solvent recovery system that improves the purification capability of a gas to be treated and the recovery efficiency of an organic solvent while controlling the operation cost.

Means for solving the problems

As a result of intensive studies, the present inventors have found a method for solving the above problems by the following method, and have completed the present invention. That is, the present invention is constituted as follows.

1. An organic solvent recovery system for separating and recovering an organic solvent from a gas to be treated containing the organic solvent, comprising: a circulation path through which the carrier gas can circulate; an adsorption/desorption element for alternately performing adsorption of the organic solvent by introducing the gas to be treated and desorption of the organic solvent by introducing the carrier gas; a condensation recovery device provided downstream of the adsorption/desorption processing device in the circulation path, for cooling the carrier gas discharged from the adsorption/desorption processing device and condensing and recovering an organic solvent contained in the carrier gas; and a heating unit provided upstream of the adsorption/desorption processing unit in the circulation passage and configured to heat the carrier gas in the low-temperature state discharged from the condensation recovery unit; the condensation recovery device adjusts the temperature of the carrier gas discharged from the condensation recovery device so that the vapor pressure of the organic solvent contained in the carrier gas discharged from the condensation recovery device is equal to or lower than a predetermined value.

According to the above configuration, the concentration of the organic solvent in the discharged carrier gas can be made equal to or lower than a certain value by adjusting the temperature so that the vapor pressure of the organic solvent contained in the carrier gas discharged from the condensation recovery device becomes equal to or lower than a predetermined value, and further, it is not necessary to provide another adsorption device for adsorbing and removing the organic solvent in the carrier gas between the condensation recovery device and the adsorption/desorption treatment device. Therefore, the architecture is simplified and miniaturized.

2. The organic solvent recovery system according to 1, comprising a temperature measuring means for measuring the temperature of the carrier gas discharged from the condensation recovery apparatus; the condensation recovery device adjusts the temperature of the discharged carrier gas so that the water vapor pressure becomes a predetermined value or less based on the measured value of the temperature measuring means.

3. The organic solvent recovery system described in the above 1, comprising a vapor pressure measuring means for measuring a vapor pressure of the carrier gas discharged from the condensation recovery device; the condensation recovery device adjusts the temperature of the discharged carrier gas so that the vapor pressure becomes a predetermined value or less based on the measured value of the vapor pressure measuring means.

4. The organic solvent recovery system according to any one of items 1 to 3, wherein the condensation recovery device cools the carrier gas by indirect cooling using a refrigerant.

5. In the organic solvent recovery system according to item 4 above, the refrigerant is any one of water, ethylene glycol, propylene glycol, glycerol, and ethanol, or a mixture thereof.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, since the vapor pressure of the organic solvent contained in the carrier gas discharged from the condensation and recovery device is adjusted to a predetermined value or less by adjusting the temperature, the concentration of the organic solvent in the discharged carrier gas can be reduced to a certain level or less, and therefore, it is not necessary to provide a separate adsorption device for adsorbing and removing the organic solvent in the carrier gas between the condensation and recovery device and the adsorption and desorption processing device, and the purification capability can be ensured. Therefore, the system structure is simplified and miniaturized. Thus, according to the present invention, there is provided an organic solvent recovery system capable of improving the purification ability of a gas to be treated and the recovery efficiency of an organic solvent while controlling the running cost

Drawings

Fig. 1 is a diagram showing a structure of an organic solvent recovery system according to an embodiment.

Fig. 2 is a diagram showing a time chart of switching between the adsorption process and the desorption process using a pair of adsorption and desorption elements in the organic solvent recovery system according to the embodiment.

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, in the following embodiments, the same or common portions in the drawings are denoted by the same reference numerals, and the description thereof will not be repeated.

As shown in fig. 1, the organic solution recovery system 100A according to the present embodiment includes a circulation path L1 through which a carrier gas can circulate, a suction/desorption treatment device 10 provided in the circulation path L1, a condensation recovery device 20, a circulation blower 40, and a gas blower 50 to be treated. As the carrier gas, various gases such as water vapor, heated air, and an inert gas heated to a high temperature can be used. In particular, if a moisture-free inactive gas is used, the configuration of the organic solvent recovery system 100A may be simpler.

The circulation passage L1 includes piping lines L4 to L7 shown in the figure. The circulation blower 40 is a blower unit for circulating the carrier gas through the circulation passage L1, and the gas-to-be-treated blower 50 is a blower unit for supplying the gas-to-be-treated from the piping line L2 to the adsorption and desorption processing apparatus 10.

The adsorption and desorption processing apparatus 10 has an adsorption and desorption tank a11 and an adsorption and desorption tank B12, and a heater 30 as a temperature adjustment unit. The adsorption and desorption tank a11 is filled with an adsorption and desorption element a13 for adsorbing and desorbing an organic solvent, and the adsorption and desorption tank B12 is filled with an adsorption and desorption element B14 for adsorbing and desorbing an organic solvent. In the present embodiment, 2 adsorption/desorption tanks are provided, but 1 tank may be provided, or 3 or more tanks may be provided.

The heater 30 is used to adjust the carrier gas supplied to the adsorption and desorption tank a11 or the adsorption and desorption tank B12 to a high temperature state. More specifically, the heater 30 adjusts the temperature of the carrier gas discharged from the condensation and recovery device 20 and passed through the circulation blower 40 to a high temperature, and then supplies the adjusted carrier gas to the adsorption and desorption tank a11 or the adsorption and desorption tank B12. Here, the heater 30 adjusts the temperature of the carrier gas introduced into the adsorption and desorption tank a11 and the adsorption and desorption tank B12 so that the adsorption and desorption element a13 and the adsorption and desorption element B14 are maintained at a predetermined desorption temperature.

The adsorption and desorption element a13 and the adsorption and desorption element B14 adsorb the organic solvent contained in the gas to be treated by contacting the gas to be treated. Therefore, in the desorption apparatus 10, if the gas to be treated is introduced into the adsorption/desorption tank a11 or the adsorption/desorption tank B12, the organic solvent is adsorbed by the adsorption/desorption element a13 or the adsorption/desorption element B14, the organic solvent is removed from the gas to be treated, the gas to be treated is purified, and the purified gas is discharged as a clean gas from the adsorption/desorption tank a11 or the adsorption/desorption tank B12.

Further, the adsorption and desorption element a13 and the adsorption and desorption element B14 desorb the adsorbed organic solvent by contacting the carrier gas in a high temperature state. Therefore, in the adsorption and desorption processing apparatus 10, if the carrier gas in a high temperature state is introduced into the adsorption and desorption tank a11 or the adsorption and desorption tank B12, the organic solvent is desorbed from the adsorption and desorption element a13 or the adsorption and desorption element B14, and the carrier gas containing the organic solvent is discharged from the adsorption and desorption tank a11 or the adsorption and desorption tank B12.

The adsorption and desorption element a13 and the adsorption and desorption element B14 are constituted by an adsorbent containing any one of granular activated carbon, activated carbon fiber, zeolite, silica gel, porous polymer, and metal organic structure. Activated carbon such as granular, powdery, or honeycomb form, or zeolite is preferably used, and activated carbon fiber is more preferably used. Since the activated carbon fibers have a fibrous structure with micropores on the surface thereof and have a high contact rate with gas, higher adsorption efficiency and desorption efficiency can be achieved as compared with other adsorbent materials.

The piping lines L2 and L3 are connected to the adsorption and desorption processing apparatus 10, respectively. The piping line L2 is a piping line for supplying the gas to be treated containing the organic solvent to the adsorption and desorption tank a11 or the adsorption and desorption tank B12 by the gas blower 40 to be treated. The piping line L2 can be switched between the connected and disconnected states of the suction/desorption tank a11 by the valve V1 and between the connected and disconnected states of the suction/desorption tank B12 by the valve V3. The piping line L3 is a piping line for discharging the clean gas from the adsorption and desorption tank a11 or the adsorption and desorption tank B12. The piping line L3 can be switched between the connected and disconnected states of the suction/desorption tank a11 by the valve V2 and between the connected and disconnected states of the suction/desorption tank B12 by the valve V4.

Further, the piping lines L5 and L6 are connected to the adsorption and desorption processing apparatus 10, respectively. The piping line L5 is a piping line for supplying the carrier gas to the adsorption and desorption tank a11 or the adsorption and desorption tank B12 via the heater 30. The piping line L5 can be switched between the connected and disconnected states of the suction/desorption tank a11 by the valve V5 and between the connected and disconnected states of the suction/desorption tank B12 by the valve V7. The piping line L6 is a piping line for discharging the carrier gas from the adsorption/desorption tank a11 or the adsorption/desorption tank B12. The piping line L6 can be switched between the connected and disconnected states of the adsorption tank a11 by the valve V6 and between the connected and disconnected states of the adsorption tank B12 by the valve V8.

According to the switching operation of the valves V1-V8, the gas to be treated and the carrier gas in a high temperature state are supplied alternately to the adsorption and desorption tank a11 and the adsorption and desorption tank B12, respectively, in time. Thus, the adsorption/desorption tank a11 and the adsorption/desorption tank B12 function to operate as an adsorption tank and a desorption tank alternately in time, and the organic solvent can be transferred from the gas to be treated to the carrier gas in a high temperature state. Further, specifically, during the period when the adsorption-desorption tank a11 performs the function of the adsorption tank, the adsorption-desorption tank B12 performs the function of the desorption tank, and during the period when the adsorption-desorption tank a11 performs the function of the desorption tank, the adsorption-desorption tank B12 performs the function of the adsorption tank.

The condensation recovery device 20 includes a condenser (condenser)21 and a recovery tank 22. The condenser 21 is a device for condensing the organic solvent contained in the carrier gas discharged from the adsorption/desorption tank a11 or the adsorption/desorption tank B12 in a high-temperature state by adjusting the temperature to a low-temperature state. Specifically, the condenser 21 liquefies the organic solvent by indirectly cooling the carrier gas using a refrigerant. The recovery tank 22 is a device for storing the organic solvent liquefied by the condenser 21 as a condensate.

The refrigerant may be any one of water, primary alcohol, secondary alcohol, tertiary alcohol, hydrochlorofluorocarbon, hydrofluorocarbon, ammonia, or a mixture thereof, and particularly, when any one of water, ethylene glycol, propylene glycol, glycerin, and ethanol, or a mixture thereof is used, the configuration of the organic solvent recovery system 100A may be simpler.

The condensation recovery apparatus 20 is connected to the pipe lines L6 and L7, respectively. The piping line L6 is a piping line for supplying the carrier gas discharged from the adsorption and desorption processing apparatus 10 to the condenser 21. The piping line L7 is a piping line for discharging the carrier gas from the condenser 21.

Further, a piping line L9 is connected to the condenser 21. The piping line L9 is a piping line for introducing the organic solvent condensed by the condenser 21 into the recovery tank 22.

Fig. 2 shows a time chart of the adsorption process using the adsorption-desorption element a13 and the adsorption element B14 and the time-wise switching of the desorption process in the organic solvent recovery system 100A shown in fig. 1. Next, referring to fig. 2, the treatment of the gas to be treated using the organic solvent recovery system 100A of the present embodiment will be described in detail, taking as an example a case where an inert gas is used as a carrier gas.

The organic solvent recovery system 100A continuously treats the gas to be treated by repeating 1 cycle as shown in fig. 2 as a unit cycle.

In the first half of the above-described 1 cycle (between the time period t0 to t2 shown in fig. 2), the adsorption process is performed in the adsorption-desorption tank a11 of the adsorption-desorption process apparatus 10 filled with the adsorption-desorption element a 13. Meanwhile, in the adsorption and desorption tank B12 of the adsorption and desorption processing apparatus 10 filled with the adsorption and desorption element B14, after the replacement purge processing is performed with the inert gas in the adsorption and desorption tank B12 (between the time period t0 and t1 shown in fig. 2), the desorption processing is performed (between the time period t1 and t2 shown in fig. 2).

In the latter half of the 1 cycle (between the time periods t2 to t4 shown in fig. 2), the adsorption process is performed in the adsorption/desorption tank B12 of the adsorption/desorption processing apparatus 10 filled with the adsorption/desorption element B14, and at the same time, the desorption process is performed in the adsorption/desorption tank a11 of the adsorption/desorption processing apparatus 10 filled with the adsorption/desorption element a13 (between the time periods t2 to t3 shown in fig. 2) after the replacement purge process with the inert gas is performed in the adsorption/desorption tank a11 (between the time periods t3 to t4 shown in fig. 2).

In the condensation and recovery apparatus 20, the carrier gas containing the organic solvent discharged from the adsorption and desorption apparatus 10 is indirectly cooled by the condenser 21, and the organic solvent is condensed by adjusting the temperature to a low temperature state, thereby recovering the organic solvent.

The condensation and recovery device 20 adjusts the temperature so that the vapor pressure of the carrier gas containing the organic solvent discharged from the condenser 21 becomes a predetermined value or less. For example, a temperature adjusting unit (not shown) for adjusting the temperature of condenser 21 may be provided. By adjusting the temperature of the condenser 21, the vapor pressure of the organic solvent contained in the exhaust gas is lower than a predetermined value, and thereby the concentration of the organic solvent in the exhaust gas can be kept at a constant value or lower. Therefore, the organic solvent adsorbed on the adsorption/desorption element can be effectively desorbed.

For example, according to the embodiment described later, when the organic solvent is paraxylene, in the condensation treatment, the vapor pressure of the organic solvent contained in the carrier gas discharged from the condenser 21 is preferably adjusted to 11.4mmHg or less by adjusting the temperature of the carrier gas, and more preferably adjusted to 6.1mmHg or less. When the vapor pressure of the organic solvent contained in the carrier gas discharged from the condenser 21 is 11.4mmHg or less, the vapor pressure of the organic solvent contained in the carrier gas cyclically contacting the adsorption and desorption element a13 and the adsorption and desorption element B14 is sufficiently low, and therefore, the regeneration effect of the adsorption and desorption element a13 and the adsorption and desorption element B14 can be effectively promoted. On the other hand, when the vapor pressure of the organic solvent contained in the carrier gas discharged from the condenser 21 is greater than 11.4mmHg, the vapor pressure of the organic solvent contained in the carrier gas cyclically contacting the adsorption and desorption element a13 and the adsorption and desorption element B14 is high, and therefore, the adsorption and desorption element a13 and the adsorption and desorption element B14 are difficult to sufficiently regenerate, and the performance as a system is degraded. The numerical values of 11.4mmHg and 6.1mmHg are derived from the test results in examples described later.

The condensation and recovery apparatus 20 can adjust the vapor pressure of the organic solvent contained in the carrier gas discharged from the condenser 21 to a predetermined value or less by adjusting the temperature, and can adjust the concentration of the organic solvent in the discharged carrier gas to a predetermined value or less, and it is not necessary to separately provide an adsorption apparatus for adsorbing and removing the organic solvent in the carrier gas between the condenser 21 and the adsorption and desorption processing apparatus 10, and the configuration of the organic solvent recovery system 100A can be simplified and downsized.

The condensation and recovery device 20 may also have a temperature measuring device (not shown) for measuring the temperature of the carrier gas discharged from the condenser 21. The condensation and recovery device 20 adjusts the temperature of the carrier gas discharged from the condenser 21 based on the value measured by the temperature measuring device so that the vapor pressure of the organic solvent contained in the carrier gas becomes a predetermined value or less, and the configuration of the organic solvent recovery system 100A is simplified.

The condensation and recovery device 20 may also have a water vapor pressure measuring device (not shown) for measuring the vapor pressure of the carrier gas discharged from the condenser 21. The condensation and recovery device 20 adjusts the temperature of the carrier gas discharged from the condenser 21 so that the vapor pressure of the organic solvent contained in the carrier gas is equal to or lower than a predetermined value, based on the value measured by the water vapor pressure measuring instrument, and the configuration of the organic solvent recovery system 100A is simplified. The method for measuring the vapor pressure of the carrier gas is not particularly limited, and examples thereof include a hydrogen flame ionization detection method, a catalytic oxidation-non-dispersive infrared absorption method, a photoionization detection method, a detection method using a semiconductor sensor, an interference amplification reflection method, and a detection method using a detection tube.

By using the organic solvent recovery system 100A of the present embodiment in the above description, the regeneration of the adsorption and desorption element a13 and the adsorption and desorption element B14 in the desorption process is promoted, and thereafter, the organic solvent can be adsorbed and removed more efficiently from the gas to be treated when the adsorption process is performed. Therefore, by using the organic solvent recovery system 100A, the purification capability of the gas to be treated and the recovery efficiency of the organic solvent are improved, and a high-performance and simple constitution system is realized as compared with the conventional one.

In addition, the organic solvent recovery system 100A of the present embodiment has excellent economical efficiency because the carrier gas can be recycled by constructing the circulation passage. Therefore, when an inert gas such as nitrogen is used as the carrier gas, the effect of reducing the running cost can be obtained particularly.

(examples)

In the following examples, the treatment gas was treated using the organic solvent recovery system 100A in the above-described embodiment of the present invention.

In the examples, a gas containing p-xylene as an organic solvent at a concentration of 1500ppm and having a relative humidity of 50% RH at 40 ℃ was used as a gas to be treated. Nitrogen at 120 ℃ was used as carrier gas. Further, as the adsorption and desorption element A12 and the adsorption and desorption element B14, a BET specific surface area of 1500mg/m was used²The activated carbon fiber of (3) uses water of 5 ℃ as a refrigerant.

First, the flow rate of the gas to be treated is fed to one of the adsorption and desorption tanks a12 and B13 of the adsorption and desorption apparatus 10 by the blower 50 for the gas to be treated, and the flow rate is adjusted to 10Nm³The air is supplied for 10 minutes per min, so that the adsorption and desorption tank on one side performs the function of the adsorption tank, and the adsorption treatment is performed.

After the adsorption treatment is completed, a valve switching operation is performed to switch the one adsorption/desorption tank to the desorption tank, and the other adsorption/desorption tank is set as the adsorption tank. In the desorption tank, after the nitrogen replacement purge treatment was performed in the desorption tank, the flow rate was 1.5Nm³The desorption treatment was performed on the adsorption/desorption element by introducing nitrogen gas heated to 120 ℃ by the heater 30. In the adsorption tank, the adsorption treatment was performed under the same conditions as described above. The condensation recovery device 20 condenses p-xylene by adjusting the amount of refrigerant supplied in the condenser 21 while maintaining the temperature of the p-xylene-containing nitrogen gas discharged from the desorption tank at 10 c,recovered in the recovery tank 22.

The above-described 1 cycle was continuously repeated, and it was confirmed that the concentration of xylene contained in the clean gas discharged from the adsorption/desorption treatment apparatus 10 was reduced to about 10 ppm. That is, in the examples, xylene could be removed at a removal rate as high as about 99%.

In the desorption treatment, it was confirmed that the vapor pressure of paraxylene contained in the nitrogen gas flowing through the piping line L6 introduced into the part of the condensation/recovery apparatus 20 increased to an average of 13.0mmHg, and that the vapor pressure of paraxylene contained in the nitrogen gas flowing through the piping line L7 discharged from the part of the condensation/recovery apparatus 20 continued to decrease to 3.6 mmHg. In the present example, the temperature of the nitrogen gas was adjusted by changing the temperature of the refrigerant, and the vapor pressure of paraxylene contained in the nitrogen gas flowing through the piping line L7 was always 3.6mmHg or less.

The above disclosed embodiments and examples are illustrative in all respects and are not to be construed as limiting the invention. The technical scope of the present invention is defined by the scope of the claims, and includes all modifications that are equivalent in meaning to and within the scope of the description of the claims.

Industrial applicability of the invention

The present invention can be effectively used, for example, in a system for treating a gas to be treated containing an organic solvent discharged from a factory or a building.

Description of the symbols

10 inhale desorption processing apparatus

11 adsorption and desorption tank A

12 adsorption and desorption tank B

13 adsorption and desorption element A

14 adsorption and desorption element B

20 condensation recovery device

21 condenser

22 recovery tank

30 heater

40 circulation blower

50 blower for gas to be treated

100A organic solvent recovery system

L1 circulation path

L2-L11 piping line

V1-V8 valve