JPH07284623A - Method for treating and recovering concentrated gaseous hydrocarbon contained in discharged gas - Google Patents

Abstract

PURPOSE:To discharge a gas contg. <=1vol.% hydrocarbons into the atmosphere and simultaneously to recover the hydrocarbons by treating the discharged gas contg. concentrated hydrocarbons. CONSTITUTION:The well-known absorption method or gas separation membrane method and adsorption method are jointly used in this case. A pressure and temperature swing adsorption method (PTSA method) is used as the adsorption method. Concretely, the discharged gas contg. about 40vol.% gasoline vapor is introduced into an absorption tower 3, and a gas (exhaust gas 8) contg. 2-5vol.% gasoline vapor is discharged. The exhaust gas 8 is then sent to an adsorption tower 11 (12) to remove the residual gasoline vapor by adsorption, and the exhaust gas contg. <=1vol.% gasoline is discharged into the atmosphere. The heat of the tower 11 (12) is removed by water, the vacuum of the water is linked to the temp. in the adsorption bed, and the bed is cooled to about 60 deg.C in the PTSA method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a treatment of a gas which is diffused while containing a rich gaseous hydrocarbon, and a method for collecting and recovering the gaseous hydrocarbon. In particular, the present invention relates to an industrial means for reducing the concentration of gaseous hydrocarbons, which is one of the causative substances of photochemical smocks, to 1 vol% or less and releasing them into the atmosphere. Regarding hydrogen treatment / recovery method.

[0002]

BACKGROUND OF THE INVENTION It photochemical smog which is one of the causes of air pollution caused by the reaction of the NO _X and gaseous hydrocarbons are known in the art. For this reason, Japan, the United States, Europe and other developed countries, recently Taiwan,
Even in Mexico, China, South Korea, etc., the emission concentrations of NO _X and volatile hydrocarbons contained in the atmosphere, which are the sources of the emission sources, are strictly regulated legally, and in order to clear this regulation value. Many industrial-scale devices are installed in various places.

By the way, what is particularly problematic as a source of generation of gaseous hydrocarbons is emitted gas generated from a storage tank or an oil tanker at the time of unloading or unloading when storing volatile hydrocarbons. In addition, it is a gas emitted from the roll truck when it is loaded on the tank roll.

As a method for treating and recovering the emission gas containing such a gaseous hydrocarbon, the following methods have been widely used: (1) Japanese Patent Publication No. 54-8632, Japanese Patent Publication No. 54-5789, Absorption method by means described in JP-A-58-022503, (2) Method using gas separation membrane (gas separation membrane method), (3)
Liquefaction by deep cooling to -60 to -70 ° C, (4) adsorption method using activated carbon or synthetic zeolite.

Among the above methods (1) to (4), the method for treating and recovering the emission gas containing gaseous hydrocarbons by the absorption method (1) is
This is the most widely used method in Japan. The processing / recovery method by this absorption method will be described below.
In this method, a gaseous hydrocarbon-containing emission gas is introduced into the absorption tower, and the emission gas and the absorption liquid of the organic liquid are brought into countercurrent gas-liquid contact, and the gaseous hydrocarbon in the emission gas is absorbed into the absorption liquid. A step of releasing the gas after absorption into the atmosphere from the top of the absorption tower, a flashing of the absorbing liquid that has absorbed the gaseous hydrocarbon into a vacuum container, and a gaseous hydrocarbon from the absorbing liquid. Separated
A step of recovering, and a step of returning the absorption liquid after separation / recovery to the absorption tower again and circulating it (see JP-B-58-022503 mentioned above).

[0006]

[Problems to be Solved by the Invention] In the above-mentioned (1) "Method of treating and recovering gaseous emissions containing gaseous hydrocarbons by absorption method", the concentration of gaseous hydrocarbons released from the top of the absorption tower into the atmosphere Is determined by the vacuum degree of the vacuum container. Therefore, in order to reduce the concentration of gaseous hydrocarbons released into the atmosphere from the top of the absorption tower to 5 vol% or less based on the pollution prevention regulations established by each prefecture of Japan, for example, maintain a vacuum degree of 30 mmHg or less. There is a need.

By the way, Western countries except Japan, Taiwan,
In countries such as Mexico, it is obligatory that the emission concentration is 1 VOL% or less (38 mg / L or less) set by the US Environmental Protection Agency (EPA). In order to clear this regulation value, if the absorption method of (1) is taken as an example, it is necessary to set the vacuum degree of the vacuum container to 7 mmHg or less, and especially considering the resistance loss of the absorbing liquid flowing in the piping. Then it should be 2mmHg or less.

However, when operating at such a vacuum degree, the absorbing liquid itself also partially evaporates, and cannot be circulated. On the other hand, a high vacuum of about 2 mmHg and 100 to 2000
There is no vacuum pump that handles a large amount of m ³ / Hr of emitted gas. Therefore, with the absorption method of (1) above, it is extremely difficult to reduce the hydrocarbon concentration in the emitted gas to 1 VOL% or less,
It has not been realized yet.

Further, the method using the gas separation membrane of the above (2)
The same applies to the (gas separation membrane method), and the technology for reducing the concentration of hydrocarbons in the emitted gas to 1 vol% or less has not been completed yet.

On the other hand, in the method (3) of deep cooling to liquefy by -60 to -70 ° C., gaseous hydrocarbons are not liquefied until the dew point is reached. For example, the concentration of hydrocarbons in the emitted gas is 50
In the case of ~ 100VOL%, if the light components such as methane, ethane, propane, etc. are in small amount, if it is deep-cooled to -70 ° C or below, the dew point is barely reached except methane and ethane, and 1VOL%
There is a possibility that the

However, the hydrocarbon concentration in the stripped gas is usually 5 to 50 VOL% in the case of storing or shipping the hydrocarbon (gasoline etc.). And in the case of gasoline, 1V is required unless it is deeply cooled to near -100 ° C.
I can't keep the level below OL%. It should be noted that methyl chloride can be used as a refrigerant at about −70 ° C., but its toxicity has recently become a problem, and no refrigerant that can achieve −100 ° C. can be economically used.

Therefore, the hydrocarbon concentration in the stripped gas is adjusted to 1 VO
At present, as a method capable of keeping the L% or less,
Although this is an adsorption method using activated carbon or synthetic zeolite of (4), this method also has the following problems. That is, the heat of adsorption when adsorbing gaseous hydrocarbons using activated carbon is, for example, 10 to 15 KCAL in the case of gasoline vapor.
/ Mol, and if this gas amount (gasoline amount) is large, the heat of adsorption generated will be enormous. For this reason, the temperature of the activated carbon adsorption tower rises, and an accident that often ignites occurs.

As a means for preventing this accident, (A) air is mixed with the desorption gas introduced into the adsorption tower to reduce the heat of adsorption per unit time, and the temperature rise of the adsorption tower is kept within about 60 ° C. It is possible to do it. However, it is uneconomical to dilute the emission gas with air, and the size of the adsorption tower and ancillary equipment increases in proportion to the increase in the amount of gas to be treated due to the mixing of air, which is not economically feasible.

It is also conceivable that (B) the adsorption tower is cooled with water to remove heat, but even if cooling water is used, only the latent heat of this water can be utilized, and so much cooling effect cannot be expected. is there. In addition, it is not economical to increase the cooling area or to increase the size of the adsorption tower more than necessary simply because of the cooling effect.

Further, (C) a heat removal method using a non-flammable refrigerant having a low boiling point such as carbon tetrachloride can be considered, but if this method is adopted, the heat of adsorption is taken to evaporate carbon tetrachloride into the atmosphere. This carbon tetrachloride vapor could not be released.
Is required to be returned to the original liquid carbon tetrachloride by cooling to below the boiling point, and this method is not economical either.

On the other hand, as a heat removal means for an activated carbon adsorption tower, a method of using a liquid hydrocarbon having a large latent heat of vaporization (for example, liquid gasoline) as a refrigerant has been developed and widely adopted in various countries. In this method, a liquid hydrocarbon passage is provided inside and outside the adsorption tower, and liquid hydrocarbon is passed through the passage.
The latent heat of vaporization is used to remove heat, and the vaporized hydrocarbon gas is washed with the same type of liquid hydrocarbon and recovered.

The above method is superior in cooling effect to the case of using cooling water, but if the passage of the liquid hydrocarbon is damaged, it may lead to a fire accident. It has the drawback of having to be installed far away. This method is not permitted in Japan.

As a method of operating the adsorption tower, it is general to operate by alternately switching the adsorption step and the desorption step. As this method, a PSA (Pressure Swing Adsorption) cycle method and a TSA (Temperature Swing Adsorption) cycle method have been conventionally known.

The PSA cycle method is a method in which a steam is used as a purge gas in the desorption process. However, the disadvantage of this method is that continuous countercurrent contact is difficult, so that the operation becomes unsteady, and the operation is not stable. Part of N ₂ and O ₂ in the digas are adsorbed and the adsorbability is lowered, and as a result, work is performed only in a part of the adsorption zone, which is inefficient. Also, with this method, it can be installed in the field as it is,
It also has the drawback of not being able to do so-called "skit mounts".

T which is an improved version of the PSA cycle system
The SA cycle method is a method of heating by using electrothermal heating or the like as the desorption means, but in this method, since desorption is performed by heating, the result is heating and cooling of the entire adsorption tower, resulting in heat loss. Many have the disadvantage that it takes a long time to transfer heat.

By the way, the concentration of gaseous hydrocarbon is 1 VOL.
As for the treatment method of dilute emission gas of less than 10%, the adsorption method using known activated carbon or synthetic zeolite is effective, and this adsorption method is generally used as a treatment method of such low concentration emission gas, but 100 m ³ / Hr or more of emission gas containing various gaseous hydrocarbons is treated, hydrocarbons are efficiently recovered from the gas, and the residual concentration in the gas discharged into the atmosphere is 1 VO
There is currently no economical way to reduce L% or less.

The present invention has been made in view of the above points, and an object thereof is to process a concentrated gaseous hydrocarbon-containing emission gas and collect and recover the gaseous hydrocarbon, Treatment of a rich gaseous hydrocarbon-containing emission gas that can efficiently recover hydrocarbons from the emission gas and reduce the residual concentration in the gas discharged into the atmosphere to 1 vol% or less.
It is to provide a recovery method. Another object of the present invention is to provide an industrial means for releasing the concentration of gaseous hydrocarbon, which is one of the causative substances of photochemical smock, at 1 VOL% or less.

[0023]

In order to achieve the above-mentioned object, the present invention uses a novel vacuum heating regeneration adsorption method (PTSA) as an adsorption method when the known adsorption method or gas separation membrane method is used in combination with the adsorption method. Method) is adopted.

That is, according to the present invention, in the method of treating the emission gas containing a rich gaseous hydrocarbon and recovering the gaseous hydrocarbon, an absorption method or a gas separation membrane method and a vacuum heating regeneration adsorption method are used. The method is a method for treating and recovering a rich gaseous hydrocarbon contained in the emitted gas, which is characterized by being combined. "

The present invention also provides the vacuum heating regeneration adsorption method.
In adopting (PTSA method), as an adsorbing device: -using an adsorbing device in which an inner cylinder, a tube or a coil for introducing decompressed water into the adsorbing layer is embedded, and / or-a coil is wound around a jacket or Using an adsorption device for supplying the reduced pressure water into the jacket, and the reduced pressure water having a vapor pressure of atmospheric pressure or less (desirably about 150 mmHg), the temperature inside the adsorption layer is 80 ° C. or less (desirably Was maintained at about 60 ° C).

Further, according to the present invention, as a means for controlling the temperature rise inside the adsorption layer caused by the generation of heat of adsorption, a vacuum device is disposed in the circulation path of the circulating water, and the vapor pressure of the circulating water, that is, The degree of vacuum was changed arbitrarily.

The present invention, which has been difficult to realize by the above-mentioned constitution, treats the "emission gas containing rich gaseous hydrocarbons, and the residual hydrocarbon concentration in the gas discharged into the atmosphere is 1 vol% or less. Can be performed easily and with a small device.

The present invention will be described in detail below. The present inventors have advantages of the absorption method or the gas separation membrane method, which is widely used for the separation of rich gaseous hydrocarbons, and the adsorption method, which is widely used for the separation of dilute gaseous hydrocarbons. The present invention has been completed as a result of earnestly researching the technical problem of overcoming the drawbacks while taking the above into consideration.

That is, the known absorption method or gas separation membrane method is
It is suitable for treating the emission gas containing rich gaseous hydrocarbons, but as described above, the technique for reducing the concentration of hydrocarbons in the emission gas to 1 VOL% or less has not been completed. According to this absorption method or gas separation membrane method, the concentration in the gas released into the atmosphere after the treatment is usually 2 to 5 VOL%.

On the other hand, the advantage of the known adsorption method is that it is effective in treating a desorbed gas containing a dilute gaseous hydrocarbon which generates little heat of adsorption, and in this case, the concentration at the inlet is usually the same.
Below 1 VOL%, the concentration at the outlet is on the order of PPM. The disadvantage of this adsorption method is that, as mentioned above, a large amount of heat of adsorption is generated when treating a stripped gas containing a rich gaseous hydrocarbon.

A method using liquid hydrocarbon (for example, liquid gasoline) having a large latent heat of vaporization as a refrigerant for removing the heat of adsorption has been developed, but it involves danger as described above.
It is also possible to use water or a low boiling point nonflammable carbon tetrachloride or the like as the refrigerant, but as described above, in the case of water, the desired cooling effect cannot be expected, and in the case of carbon tetrachloride or the like, It is not economical because it is not possible to release the vaporized carbon tetrachloride and the like by absorbing the heat of adsorption to the atmosphere, and it is necessary to cool it to the boiling point or lower and return it to the original liquid again.

Therefore, the present invention is effective as an absorption method or a gas separation membrane method that is effective as a treatment method for a desorbed gas containing rich gaseous hydrocarbons, and an effective method as a treatment method for a desorbed gas containing dilute gaseous hydrocarbons. It is intended to be used together with the adsorption method. And in constructing a system that uses this absorption method or gas separation membrane method and adsorption method together, in order to take advantage of this combined use, in the case of the absorption method, the degree of vacuum of the vacuum container is reduced and gas separation is also performed. In the case of the membrane method, the pressure of the emitted gas applied to the membrane is reduced so that the hydrocarbon concentration in the gas introduced into the adsorption tower in the next step does not approach 1 VOL%.
By setting the hydrocarbon concentration to a relatively high level of about 5 VOL%, the process of treating the emission gas by the absorption method or the gas separation membrane method is extremely simplified and the processing apparatus becomes small.

Treatment step by adsorption method following the above treatment step
In (hereinafter referred to as "adsorption step"), the concentration of hydrocarbons in the gas introduced into the adsorption tower is 1 VOL% or less, which is usually carried out.
Since it is considerably darker than the (inlet concentration), the temperature of the adsorption layer rises. However, the present invention employs a novel vacuum heat regeneration adsorption method (PTSA method) proposed by the present inventors to remove the heat of adsorption, thereby simplifying the adsorption step,
Moreover, it is possible to make it into a small device, which has been difficult to achieve until now by treating the emission gas containing rich gaseous hydrocarbons and reducing the residual hydrocarbon concentration in the gas discharged to the atmosphere to 1 vol. % Or less ”can be easily implemented with a small device, and a very economically advantageous system can be constructed.

Here, the novel vacuum heating regeneration adsorption method (PTSA method: Pressure and Temperature Swing Ads) adopted in the present invention is used.
The adsorption heat removal method by the orption method will be described. The present inventors have used water as a refrigerant for removing the heat of adsorption, and set the degree of vacuum of cooling water to control the temperature in the adsorption layer, which is endlessly increased by the heat of adsorption, within a safe temperature range. The inventors have found a method in which the temperature in the adsorption layer can be set arbitrarily by linking with the temperature, and the cooling water can be circulated and used without being discharged.

Specifically, it is an adsorption tower containing an adsorbent, which uses an adsorption tower in which an inner cylinder for supplying water as a refrigerant, a pipe or a coil is embedded inside the adsorption tower, and / or Or, using an adsorption tower in which a coil is wound around the jacket or water as a refrigerant is supplied into the jacket,
This is a method to circulate water as a refrigerant in a pipe, a coil, and a jacket to remove heat of adsorption. At this time, the temperature in the adsorption layer is controlled by linking the vacuum degree of cooling water with the temperature in the adsorption layer. It can be set arbitrarily.

In the case of an adsorption tower having an inner cylinder embedded therein as the adsorption tower, one or more inner cylinders may be provided on the outer side of the adsorption tower so as to cross or cross the adsorption tower. An adsorption tower in which an adsorbent is inserted inside and outside the inner cylinder can be used. Further, in the case of an adsorption tower having a tube embedded therein as the adsorption tower, the adsorption tower is one in which one or more tubes are arranged so as to cross or cross the adsorption tower, and the outside of the tube. An adsorption tower in which an adsorbent is inserted can be used.

The temperature of the adsorption layer in the adsorption tower is measured by a programmable indicator TIC (Temperature Indicator Contro
ller) signal and PIC (Pressure Indicator Controller) signal are compared, and the PIC valve is controlled so that the TIC set value (for example, 60 ° C) is constantly kept and the vacuum degree is adjusted. (See FIG. 2 below).

As is well known, the boiling point of water is determined by the degree of vacuum, and if a safe temperature of about 60 ° C. is appropriate, 150 mmH
By circulating water under a reduced pressure of g, latent heat of vaporization (> 540Kcal / Kg) based on the boiling point of water at 60 ° C is taken from the adsorption layer and vaporized by itself. The vaporized water vapor (steam) is sucked into the upper part of the circulating water storage tank by using a vacuum pump or a steam ejector, discharged into the atmosphere, and discharged outside the system.

Further, according to the vacuum heating regeneration adsorption method (PTSA method) adopted in the present invention, the boiling point of water can be arbitrarily set by changing the degree of vacuum. The temperature in the adsorption layer can be kept within a safe range by changing the temperature and the circulating amount of the reduced pressure water.

The reason why the vacuum heating regeneration adsorption method (PTSA method) is selected in the adsorption step of the present invention is as follows. That is, in the conventional vacuum regeneration adsorption method (PSA method), the hydrocarbon in the desorbed gas is adsorbed on the activated carbon or synthetic zeolite to carry out the substitution purge, and then the hydrocarbon is desorbed by the vacuum pump. Thus, the hydrocarbon in the stripped gas can be recovered at a high concentration, but the replacement purge (N ₂ , O as a pretreatment before being sucked by the vacuum pump).
_As the replacement gas in ₂ ), the product gas, that is, the gaseous hydrocarbon sucked by the vacuum pump is used.

However, since the amount of this purge gas is several times that of the product gas, the power required to circulate the gas becomes very large. Therefore, in the present invention, the above-mentioned PT
By using the SA method, the adsorption layer is heated after the completion of adsorption by using a heater or a heat exchanger to desorb high-concentration hydrocarbons in the adsorbent, and therefore the substitution purge step is omitted. It has the significant advantage of being able to.

In the present invention, the adsorbent used is not limited, but synthetic zeolite, particularly activated silica is preferable. The present invention also includes, but is not limited to, the treatment of diffused gas containing gasoline vapor.
It is suitable for recovery and can be applied to other emission gases containing low boiling point hydrocarbons such as benzene, acetone and methanol, which are also included in the present invention.

[0043]

Embodiments of the present invention will be described below with reference to FIGS. FIG. 1 shows a hydrocarbon treatment / recovery device for explaining an embodiment of the present invention, and is a diagram in the case where an absorption method is used in the preceding stage. Further, FIG. 2 shows the vacuum heating regeneration adsorption method (PTSA) of the present invention for removing heat from the adsorption tower.
FIG.

As shown in FIG. 1, hydrocarbons (gasoline)
40 vol% of gasoline vapor discharged from the storage tank 1 of the above enters the absorption tower 3 via the conduit 2. At the top of the absorption tower 3, a heavy non-volatile absorption liquid 4 is sprayed, and the gasoline vapor is absorbed therein.

The absorption liquid 4 ′ containing gasoline discharged from the bottom of the absorption tower 3 enters the vacuum tank 5. The tank 5 is kept at a vacuum degree of about 30 mmHg by a vacuum pump 6. In the vacuum tank 5, the absorption liquid 4 obtained by evaporating and separating gasoline is returned to the top of the absorption tower 3 again by a pump (not shown), and is recycled.

On the other hand, the gasoline vapor sucked by the vacuum pump 6 is introduced into the recovery tower 7 at a concentration close to 100 VOL%. On the top of the recovery tower 7, fresh liquid gasoline is sprayed from a separately provided gasoline tank (not shown), and the gasoline vapor is melted into this and returned to the original gasoline tank for recovery. .

Exhaust gas 8 discharged from the top of the absorption tower 3
Contains 2 to 5 VOL% of gasoline vapor, and this gas is passed through a blower 9 and a cooler 10 with water to an adsorption tower.
Send to 11, 12. The adsorption towers 11 and 12 are operated by alternately switching the adsorption process and the desorption process. This switching time is
3 to 10 minutes.

After the adsorption step is completed, the adsorption towers 11 and 12 are heated to a safe temperature range by a heating exchanger, and further desorbed by sucking with a vacuum pump 13. The desorbed gasoline vapor is returned to the recovery tower 7 and recovered as liquid gasoline. The clean dry gas discharged from the top of the adsorption tower 11 (the adsorption tower 12 after switching to the desorption step) is released into the atmosphere as humid air containing 1 vol% or less of gasoline vapor.

FIG. 2 is a diagram showing an example of the vacuum heating regeneration adsorption method (PTSA method) of the present invention for removing heat from the adsorption tower. In FIG. 2, a coil 21 is embedded inside an adsorption tower 20 containing an adsorption layer 22, and decompressed water 23
Circulates while having a boiling point of 50 to 60 ° C., and this reduced pressure water 23 is stored in a vacuum container 24.

The vacuum container 24 is maintained at a constant degree of vacuum by sucking with a vacuum pump 25. Since the gas discharged from the vacuum pump 25 is water vapor, it may be released into the atmosphere. The temperature of the adsorption layer 22 can be measured by TI
C (Temperature Indicator Controller) signal and PIC (Pre
ssure Indicator Controller)
Always keep the TIC set value (for example, 60 ° C) so that the PIC
Control the V (PIC valve) to adjust the vacuum level.

Further, the vacuum container 24 has a LI (Level Indicato
r) is provided, and a water supply port 26 is provided in the middle of the circulating water (reduced pressure water 23).

[0052]

As described above in detail, the present invention is characterized in that when the known gas separation membrane method or absorption method is used in combination with the adsorption method, a novel vacuum heating regeneration adsorption method is adopted as the adsorption method. , Which has been difficult to realize until now, "to process the emission gas containing rich gaseous hydrocarbons,
The residual hydrocarbon concentration in the gas discharged into the atmosphere is 1 VOL%
The effect that "the following" can be performed easily and can be performed by a small device is produced.

Further, according to the present invention, in the method of treating and recovering gaseous hydrocarbons which are air pollutants, the environmental protection in the United States which could not be achieved at all by the absorption method or the gas separation membrane method which has been conventionally used. 1VOL% established by the Bureau (EPA)
It is possible to construct a system that can completely clear the following regulation values and can sufficiently cope with the regulation values that are expected to become stricter.

[Brief description of drawings]

FIG. 1 is a diagram showing a hydrocarbon treatment / recovery device for explaining an embodiment of the present invention, and is a diagram in the case where an absorption method is used in the preceding stage.

FIG. 2 is a diagram showing an example of the vacuum heating regeneration adsorption method (PTSA method) of the present invention for removing heat from an adsorption tower.

[Explanation of symbols]

 1 Storage Tank 2 Conduit 3 Absorption Tower 4, 4'Absorption Liquid 5 Vacuum Tank 6 Vacuum Pump 7 Recovery Tower 8 Exhaust Gas 9 Blower 10 Cooler 11, 12 Adsorption Tower 13 Vacuum Pump 20 Adsorption Tower 21 Coil 22 Adsorption Layer 23 Decompressed Water 24 Vacuum Container 25 Vacuum Pump 26 Water Supply Port

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Claims (4)

[Claims] 1. A method for recovering the above-mentioned gaseous hydrocarbon by treating an emission gas containing rich gaseous hydrocarbon,
A method for treating and recovering a rich gaseous hydrocarbon contained in a released gas, which is characterized by combining an absorption method or a gas separation membrane method and a vacuum heating regeneration adsorption method. 2. In the vacuum heating regeneration adsorption method, an inner cylinder, pipe or coil for introducing decompressed water having a vapor pressure below atmospheric pressure is embedded in the adsorption layer and / or a coil is wound around a jacket or in a jacket. The treatment and recovery of the rich gaseous hydrocarbon contained in the desorbed gas according to claim 1, characterized in that an adsorption device for supplying the reduced pressure water is used to maintain the temperature inside the adsorption layer at 80 ° C or lower. Method. 3. As a means for controlling the temperature rise inside the adsorption layer caused by the generation of heat of adsorption, a vacuum device is provided in the circulation path of the circulating water, and the vapor pressure of the circulating water, that is, the degree of vacuum is arbitrarily set. The method for treating and recovering the rich gaseous hydrocarbon contained in the emitted gas according to claim 1, wherein 4. The rich gaseous hydrocarbon contained in the stripped gas according to claim 1, wherein the hydrocarbon concentration in the clean gas discharged from the adsorption tower to the atmosphere is 1 vol% or less. How to process and recover.