Organic solvent recovery system

Abstract

Provided is an organic solvent recovery system comprising: a plurality of treatment vessels each of which has a first adsorbent capable of absorbing and desorbing an organic solvent and which alternately perform an adsorption treatment for adsorbing an organic solvent contained in an introduced gas of interest with a first adsorbent to discharge a first treatment gas and a desorption treatment for desorbing the organic solvent from the first adsorbent with introduced water vapor to discharge a desorbed gas; a water vapor supply unit which introduces water vapor into a treatment vessel selected from the plurality of treatment vessels; a plurality of organic solvent recovery devices each of which is provided with an outlet flow path through which the first treatment gas is discharged from the treatment vessel; and an organic solvent condensation device which has a second adsorbent capable of absorbing and desorbing an organic solvent, adsorbs the organic solvent contained in the first treatment gas discharged from the organic solvent recovery device to discharge a second treatment gas and then desorbs the adsorbed organic solvent from the second adsorbent to discharge the organic solvent as a condensed gas. In the organic solvent recovery system, when the adsorption treatment and the desorption treatment of the treatment vessels are switched from each other in one organic solvent recovery device, the operation is performed so as to simultaneously avoid the switching between the adsorption treatment and the desorption treatment of the treatment vessel in the other organic solvent recovery devices.

Description

Organic Solvent Recovery System

[0001] The present invention relates to an organic solvent recovery system.

[0002] As a system for recovering an organic solvent from a gas containing the organic solvent, for example, Patent Document 1 discloses a gas treatment device including three treatment tanks, a treated gas supply unit, a connecting flow path, a water vapor supply unit, and a dilution gas supply path. Also, Patent Document 2 discloses an organic solvent recovery system including a first adsorption / desorption device having two treatment tanks and a second adsorption / desorption device that recovers an organic solvent contained in a treated gas discharged from one of the treatment tanks of the first adsorption / desorption device.

[0003] In the gas treatment device described in Patent Document 1, the adsorption process is carried out continuously in two treatment tanks, thereby increasing the removal rate of the organic solvent. In the organic solvent recovery system described in Patent Document 2, the adsorption process is carried out continuously in one of the treatment tanks of the first adsorption / desorption device and the first treatment section of the second adsorption / desorption device, thereby increasing the removal rate of the organic solvent.

[0004] JP 2014-147863 A JP 2014-240052 A

[0005] In recent years, there has been a need for an organic solvent recovery system with a higher organic solvent removal rate. To meet this need, for example, a system has been considered in which an adsorption process is performed continuously in two treatment tanks as described in Patent Document 1, and then an adsorption process is further performed in a second adsorption / desorption device as described in Patent Document 2. In this case, the treated gas containing the organic solvent desorbed from the second adsorption / desorption device is returned to the flow path that supplies the treated gas (raw gas) to the treatment tank.

[0006] However, in such a system, steam mist (hereinafter referred to as white smoke) generated immediately after switching between the adsorption and desorption processes in the treatment tank of the first adsorption / desorption device may be mixed into the gas to be treated, even for several tens of seconds, immediately after switching. When high-temperature, high-humidity gas containing white smoke is supplied to the second adsorption / desorption device after the adsorbent of the second adsorption / desorption device has adsorbed a certain amount of organic solvent from the gas to be treated (i.e., the adsorption process of the second adsorption / desorption device has been performed for several minutes), the increase in the temperature of the gas to be treated and the adsorption of moisture by the adsorbent of the second adsorption / desorption device slow down the adsorption rate of the organic solvent, resulting in the discharge of organic solvent gas into the treatment gas at a concentration greater than the designed outlet concentration of the second adsorption / desorption device. Furthermore, the adsorption of moisture by the white smoke also increases the thermal energy required for the desorption process of the second adsorption / desorption device. One way to deal with the effects of such white smoke is to cool and dehumidify the gas to be treated, but this requires larger cooling equipment, which in turn increases the size of the device.

[0007] In addition, in the first adsorption / desorption device, the concentration of organic solvent gas contained in the process gas immediately before switching from the adsorption process to the desorption process is generally relatively high compared to the concentration of organic solvent gas contained in the process gas at the start of the adsorption process. This is because the adsorbent of the first adsorption / desorption device sufficiently adsorbs the organic solvent gas, and the unused adsorption capacity gradually decreases, resulting in a decrease in the adsorption rate. Therefore, a design capable of treating this high organic solvent gas concentration is required, which results in a problem of an increased device size.

[0008] Furthermore, there is a need to treat a large volume of gas using an organic solvent recovery system, but in this case, multiple organic solvent recovery systems are required, which increases the size of the equipment.

[0009] In view of the above problems, the present invention has an object to provide an organic solvent recovery system that does not reduce the treatment performance and can prevent the system from becoming large in size.

[0010] As a result of extensive research, the present inventors have found that the above problems can be solved by the following means, and have arrived at the present invention. That is, the present invention has the following configuration.

[0011] The organic solvent recovery system of the present invention comprises: a plurality of treatment tanks each having a first adsorbent capable of adsorbing and desorbing an organic solvent, the treatment tank alternately performing an adsorption process in which the organic solvent contained in an introduced gas to be treated is adsorbed by the first adsorbent and a first treatment gas is discharged; and a desorption process in which introduced water vapor desorbs the organic solvent from the first adsorbent and a desorbed gas is discharged; a plurality of organic solvent recovery devices each including a water vapor supply unit that introduces the water vapor into a treatment tank selected from the plurality of treatment tanks; and an organic solvent concentration device having a second adsorbent capable of adsorbing and desorbing the organic solvent, the organic solvent contained in the first treatment gas discharged from the organic solvent recovery device, the second treatment gas is discharged; and the adsorbed organic solvent is desorbed from the second adsorbent and a concentrated gas is discharged, When the treatment tank of one of the organic solvent recovery devices switches between adsorption treatment and desorption treatment, the remaining organic solvent recovery devices are operated so that the treatment tanks do not switch between adsorption treatment and desorption treatment at the same time.

[0012] The organic solvent recovery system may include three or more treatment tanks and a connecting flow path that connects a selected number of the treatment tanks from all of the treatment tanks in series in multiple stages, performing the adsorption treatment in the multiple treatment tanks connected in series in multiple stages to discharge the first treatment gas, and performing the desorption treatment using the water vapor in the remaining treatment tanks, and further including a dilution gas supply flow path that supplies a dilution gas to the connecting flow path.

[0013] The organic solvent recovery system may include a return flow path that returns the concentrated gas desorbed from the second adsorbent to the dilution gas supply flow path.

[0014] The organic solvent recovery system may include a return flow path that returns the concentrated gas desorbed from the second adsorbent to a treated gas supply flow path that introduces the treated gas into the organic solvent recovery device.

[0015] In the organic solvent recovery system, the second adsorbent may be made of a material containing at least one of granular activated carbon, activated carbon fiber, and zeolite.

[0016] The organic solvent recovery system may use heated air for desorption in the second adsorbent.

[0017] The organic solvent recovery system may include a connecting flow path that introduces a portion of the second treatment gas into the second adsorbent for use in desorbing the organic solvent from the second adsorbent, and a heating unit provided in the connecting flow path.

[0018] According to the present invention, by configuring a system in which treated gas from multiple organic solvent recovery units is treated in an organic solvent concentrator, it is possible to reduce the size of the organic solvent recovery system. Furthermore, by operating the system so that the adsorption and desorption process switching in the treatment tank of one organic solvent recovery unit and the adsorption and desorption process switching in the treatment tank of the other organic solvent recovery unit do not occur simultaneously, when one organic solvent recovery unit discharges treated gas containing white smoke, the other unit discharges treated gas not containing white smoke, and the treated gases join together and are introduced into the organic solvent concentrator. As a result, it is possible to level out the large amount of moisture contained in the white smoke and the rise in the temperature of the treated gas, and not only can the cooling equipment for cooling the white smoke be made smaller, but also because when the treated gas from one organic solvent recovery device is discharged at a relatively high concentration, the treated gas from the other organic solvent recovery device is discharged at a low concentration, the treated gas from the organic solvent recovery devices that is introduced into the organic solvent concentration device is merged and leveled, stabilizing the concentration of the treated gas, making it possible to downsize the organic solvent concentration device and thereby achieving a downsized organic solvent recovery system.

[0019] 1 is a diagram showing an example of the configuration of an organic solvent recovery system according to an embodiment of the present invention; 2 is a diagram showing an example of the configuration of an organic solvent recovery system according to an embodiment of the present invention; 3 is a table showing the temperature of the gas to be treated containing white smoke introduced into the organic solvent concentrating device and the difference in the temperature required for cooling in Examples and Comparative Examples; 4 is a table showing the dichloromethane concentration in the gas to be treated introduced into the organic solvent concentrating device and the dichloromethane concentration in the gas treated by the organic solvent concentrating device in Examples and Comparative Examples;

[0020] Hereinafter, an embodiment of the present invention will be described in detail with reference to FIG.

[0021] 1 and 2 are schematic diagrams illustrating the configuration of organic solvent recovery systems 1A and 1B according to one embodiment of the present invention. The following description will be given assuming that two organic solvent recovery apparatuses 100 are provided. The organic solvent recovery systems 1A and 1B each include an organic solvent recovery apparatus 100, an organic solvent concentration apparatus 200 (200A, 200B), a feed flow path 300, and a return flow path 400. The organic solvent recovery systems 1A and 1B are configured to remove and recover organic solvent from a gas to be treated containing the organic solvent in the organic solvent recovery apparatus 100, and then further remove and concentrate the organic solvent from a first treated gas discharged from the organic solvent recovery apparatus 100 in the organic solvent concentration apparatus 200 (200A, 200B). The concentrated gas discharged from the organic solvent concentration apparatus 200 (200A, 200B) is returned to the organic solvent recovery apparatus 100 via the return flow path 400.

[0022] Each component will be explained below.

[0023] The organic solvent recovery apparatus 100 is an apparatus for removing and recovering an organic solvent from a gas to be treated. The gas to be treated is supplied to the organic solvent recovery apparatus 100 from a gas to be treated supply source provided outside the system of the organic solvent recovery apparatus 100. The organic solvent recovery apparatus 100 has three treatment tanks 101 to 103, a gas to be treated supply flow path L110, connecting flow paths L121 to L123, extraction flow paths L131 to L133, steam supply flow paths L141 to L143, organic solvent recovery flow paths L151 to L153, ​​a separator 120, a re-supply flow path L160, and a dilution gas supply flow path L170.

[0024] Each treatment tank 101-103 has a first adsorbent 101A-103A capable of adsorbing and desorbing organic solvents. Examples of the first adsorbent 101A-103A include granular activated carbon, zeolite, honeycomb-shaped activated carbon, zeolite, and activated carbon fiber, with activated carbon fiber being preferred. Each treatment tank 101-103 has an open / close damper V101-V103 that switches between supplying and not supplying the treated gas to the treated gas supply port, and an open / close damper V104-V106 that switches between discharging and not discharging the treated gas from the discharge port after passing through the first adsorbent 101A-103A.

[0025] In each of the treatment tanks 101-103, adsorption of the organic solvent by the first adsorbents 101A-103A and desorption of the organic solvent from the first adsorbents 101A-103A are alternately performed. That is, in one of the three treatment tanks 101-103, a first adsorption step is performed in which the first adsorbent adsorbs the organic solvent from the gas to be treated supplied from the gas to be treated source. In another of the three treatment tanks 101-103, a second adsorption step is performed in which the first adsorbent adsorbs the organic solvent from the gas to be treated after treatment in the treatment tank used in the first adsorption step (hereinafter referred to as the first adsorption step gas) and discharges the first treatment gas. Meanwhile, in the remaining treatment tank, a desorption step is performed in which the organic solvent is desorbed from the first adsorbent. In each of the treatment tanks 101-103, the desorption step, the second adsorption step, the first adsorption step, and the desorption step are repeatedly performed in this order.

[0026] The treated gas supply flow path L110 is a flow path for supplying the treated gas to each of the treatment tanks 101 to 103. The upstream end of the treated gas supply flow path L110 is connected to a treated gas supply source. The treated gas supply flow path L110 is provided with a cooler C1 and a heater H1 for adjusting the temperature and humidity of the treated gas flowing into each of the treatment tanks 101 to 103.

[0027] The treated gas supply flow path L110 has branch flow paths L111 to L113 that supply the treated gas to each of the treatment tanks 101 to 103. The branch flow path L111 is provided with an on-off valve V111. The branch flow path L112 is provided with an on-off valve V112. The branch flow path L113 is provided with an on-off valve V113. The branch flow paths L111 to L113 are connected to the treated gas supply ports of each of the treatment tanks 101 to 103.

[0028] Each of the discharge flow paths L181 to L183 is connected to each of the three treatment tanks 101 to 103. The gas to be treated introduced into the treatment tank 101 undergoes a first adsorption process and is discharged from the discharge flow path L181 as a first adsorption process gas. The discharged first adsorption process gas is transported to the connecting flow path L121 via the dilution gas supply flow path L170 and the merging path L120. The connecting flow path L121 is connected to the branch flow path 112, and the first adsorption process gas is introduced into the gas to be treated supply port of the treatment tank 102, where the second adsorption process is performed. Similarly, when the first adsorption process is performed in the treatment tank 102, the first adsorption process gas is discharged from the discharge flow path L182 and transported through the connecting flow path L122 to the treatment tank 103, where the second adsorption process is performed. When the first adsorption step is performed in the treatment tank 103, the first adsorption step gas is discharged from the discharge flow path L183 and passes through the connecting flow path L123 to the treatment tank 101 where the second adsorption step is performed.

[0029] Each of the connecting flow paths L121 to L123 has a junction path L120 where they merge with one another. An on-off valve V121 is provided at the portion of the connecting flow path L121 where it branches off again from the junction path L120. An on-off valve V122 is provided at the portion of the connecting flow path L122 where it branches off again from the junction path L120. An on-off valve V123 is provided at the portion of the connecting flow path L123 where it branches off again from the junction path L120.

[0030] The extraction flow paths L131 to L133 are flow paths for extracting a first treatment gas, which is a treatment gas after being adsorbed in each of the treatment tanks 101 to 103. The extraction flow paths L131 to L133 are connected to the treatment gas exhaust ports of each of the treatment tanks 101 to 103. An on-off valve V131 is provided in the extraction flow path L131. An on-off valve V132 is provided in the extraction flow path L132. An on-off valve V133 is provided in the extraction flow path L133. The extraction flow paths L131 to L133 have a confluence flow path L130 where they converge with each other.

[0031] The water vapor supply flow paths L141 to L143 are flow paths for supplying water vapor to the treatment tanks 101 to 103, for desorbing the organic solvent adsorbed in the first adsorbents 101A to 103A from the first adsorbents 101A to 103A.

[0032] The water vapor supply flow path L141 connects the water vapor supply source and the treatment tank 101, and is provided with an on-off valve V141. The water vapor supply flow path L142 connects the water vapor supply source and the treatment tank 102, and is provided with an on-off valve V142. The water vapor supply flow path L143 connects the water vapor supply source and the treatment tank 103, and is provided with an on-off valve V143. The water vapor supply flow paths L141 to L143 each have a water vapor supply flow path L140 that joins with each other.

[0033] The organic solvent recovery flow paths L151 to L153 are flow paths for recovering water vapor (desorbed gas) containing the organic solvent desorbed from the first adsorbents 101A to 103A. Each of the organic solvent recovery flow paths L151 to L153 is connected to each of the treatment tanks 101 to 103. Each of the organic solvent recovery flow paths L151 to L153 has a confluence path L150. A condenser 122 is provided in the confluence path L150. The condenser 122 condenses the desorbed gas by cooling the desorbed gas flowing through the confluence path L150, and discharges the condensed liquid (a mixture of water produced by condensation of the desorbed gas and liquid-phase organic solvent).

[0034] The separator 120 is provided downstream of the confluence flow path L150. After the condensate flows into the separator 120, the condensate undergoes phase separation into a liquid phase of separated wastewater and a liquid phase of recovered solvent within the separator 120, and the recovered solvent is removed from the organic solvent recovery system 100. A space (vent gas) containing a trace amount of organic solvent is formed above the separator 120.

[0035] The re-supply passage L160 is a passage that connects the separator 120 and the treated gas supply passage L110. The vent gas in the separator 120 is supplied again to each of the treatment tanks 101 to 103 through the re-supply passage L160 and the treated gas supply passage L110.

[0036] The wastewater treatment equipment 130 is equipment that removes organic solvents contained in the separated wastewater. It is supplied from the liquid phase of the separated wastewater from the separator 120, removes the organic solvents from the separated wastewater, and discharges treated water outside the system. Specific examples of the wastewater treatment equipment 130 include an aeration equipment that aerates the separated wastewater to volatilize the organic solvents contained in the separated wastewater and separates it into an aeration gas containing the organic solvents and treated water. The aeration gas is connected to the treated gas supply flow path L110 upstream of the cooler C1 via an aeration gas supply flow path L161. The aeration gas supply flow path may be provided with a dehumidification means for removing moisture from the aeration gas.

[0037] The dilution gas supply flow path L170 is a flow path for supplying a dilution gas to the connecting flow paths L121 to L123 to promote drying of the first adsorbents 101A to 103A after the desorption step. The dilution gas is composed of a gas containing at least one of outside air, instrument air, nitrogen gas, and argon gas.

[0038] The organic solvent concentrating apparatus 200 will be described using 200A in Fig. 1 and 200B in Fig. 2. The organic solvent concentrating apparatus 200A provided in the organic solvent recovery system 1A shown in Fig. 1 is equipment that further removes organic solvent from the first treated gas discharged from the organic solvent recovery apparatus 100. The organic solvent concentrating apparatus 200A has a rotor-type adsorption / desorption treatment device including a second adsorbent 201C that adsorbs and desorbs the organic solvent, and the second adsorbent 201C is divided into an adsorption zone that adsorbs the organic solvent and a desorption zone that desorbs the adsorbed organic solvent.

[0039] The first treated gas discharged from the two organic solvent recovery units 100 passes through the feed flow path 300, cooler C2, and heater H2 and through the adsorption zone of the second adsorbent 201C, thereby discharging a second treated gas, which is a clean gas from which the organic solvent has been further removed. At the same time, in the desorption zone, a heated gas with a smaller flow rate than the first treated gas is passed through the desorption zone to desorb the organic solvent adsorbed by the adsorbent, thereby discharging a concentrated gas in which the organic solvent has been concentrated. The concentrated gas is returned to the organic solvent recovery unit 100 through the dilution gas supply flow path L170 connected to the return flow path 400.

[0040] The second adsorbent 201C is an adsorbent having a substantially cylindrical outer shape or an adsorbent arranged to form a substantially cylindrical shape. For example, the organic solvent concentration apparatus 200A is provided with a motor, and when the motor is driven, the second adsorbent 201C rotates in the tangential direction, and any part of the second adsorbent 201C moves alternately between the adsorption zone and the desorption zone over time to perform adsorption and desorption processing.

[0041] The second adsorbent 201C is made of an adsorbent containing any one of activated alumina, silica gel, activated carbon, and zeolite, but activated carbon and zeolite in granular, powder, honeycomb, or other shapes are preferred.

[0042] The organic solvent concentrating apparatus 200A discharges the second treated gas discharged from the adsorption zone of the second adsorbent 201C to the outside through the cleaned gas discharge passage L220.

[0043] The organic solvent concentrating device 200A includes a connecting flow path L230 and a heater H3.

[0044] The connection flow path L230 connects the clean gas discharge flow path L220 to the downstream of the adsorption zone, and a part of the second process gas is used for desorption. Alternatively, the outside air may be used for desorption.

[0045] The organic solvent concentrating apparatus 200B provided in the organic solvent recovery system 1B shown in FIG. 2 is equipment for further removing organic solvent from the first treated gas discharged from the organic solvent recovery apparatus 100. The organic solvent concentrating apparatus 200B has at least two or more treatment tanks. To explain the two cases, the treatment tanks 201 and 202 each have second adsorbents 201A and 202A capable of adsorbing the organic solvent contained in the first treated gas discharged from the branched flow paths L211 and L212 via the confluence flow path L130. In the treatment tank 201, the second adsorbent 201A adsorbs the organic solvent contained in the first treated gas, while the treatment tank 202 desorbs the organic solvent in the first treated gas adsorbed by the second adsorbent 202A. The treatment tanks 201 and 202 alternate between the adsorption and desorption processes and perform them sequentially. By passing the first treated gas through the treatment tank, the organic solvent is further removed, and the resulting clean second treated gas can be discharged from the connecting flow paths L221, 222 connected to the treatment tanks 201, 202, respectively. After adsorption is complete, a heated gas with a smaller flow rate than the first treated gas is passed through to desorb the organic solvent adsorbed to the adsorbent, thereby discharging a concentrated gas in which the organic solvent is concentrated. The concentrated gas is returned to the organic solvent recovery system 100 from the dilution gas supply flow path L170 connected to the return flow path 400.

[0046] The branch flow path L211 is provided with an on-off valve V211. The branch flow path L212 is provided with an on-off valve V212.

[0047] The connecting flow path L221 is provided with an on-off valve V221. The connecting flow path L222 is provided with an on-off valve V222.

[0048] Each treatment tank 201, 202 has a second adsorbent 201A, 202A capable of adsorbing and desorbing organic solvents. Examples of the second adsorbent 201A, 202A include granular activated carbon, zeolite, honeycomb-shaped activated carbon, zeolite, and activated carbon fiber, with activated carbon fiber being preferred. Each treatment tank 201, 202 has an open / close damper V201, V202 that switches between supplying and not supplying the treated gas to the treated gas supply port, and an open / close damper V203, V204 that switches between discharging and not discharging the treated gas from the discharge port after passing through the second adsorbent 201A, 202A.

[0049] The organic solvent concentrating device 200B discharges the second treated gas discharged from the treatment tank to the outside through the cleaned gas discharge passage L220.

[0050] The organic solvent concentrating device 200B includes a connecting flow path L230 and a heater H3.

[0051] The connection flow path L230 connects the clean gas exhaust flow path L220 and the treatment tank, and uses a portion of the second treatment gas for desorption. Alternatively, outside air may be used for desorption. The connection flow path L230 branches into connection flow paths L231 and L232, which are connected to the treatment tanks 201 and 202, respectively. The connection flow path L231 is provided with an on-off valve V231. The connection flow path L232 is provided with an on-off valve V232.

[0052] The organic solvent recovery flow paths L241, L242 are flow paths for recovering water vapor (desorbed gas) containing the organic solvent desorbed from the second adsorbents 201A, 202A. Each of the organic solvent recovery flow paths L241, L242 is connected to each of the treatment tanks 201, 202. Each of the organic solvent recovery flow paths L241, L242 has a return flow path 400 where they merge with each other.

[0053] The feed flow path 300 is a flow path for feeding the gas to be treated from the organic solvent recovery device 100 to the organic solvent concentration device 200. The feed flow path 300 is provided with a cooler C2 and a heater H2 for adjusting the temperature and humidity of the first treated gas to be introduced into the organic solvent concentration device 200.

[0054] The return flow path 400 is a flow path for returning the concentrated gas from the organic solvent concentrating device 200 to the organic solvent recovery device 100. The return flow path 400 is connected to the diluted gas supply flow path L170.

[0055] The two organic solvent recovery units 100 may be provided with damper control devices as needed to prevent simultaneous switching of the treatment tanks.

[0056] The organic compounds contained in the gas to be treated by the organic solvent recovery systems 1A and 1B of this embodiment are not particularly limited, and include aldehydes such as formaldehyde, acetaldehyde, propionaldehyde, and acrolein; ketones such as methyl ethyl ketone, diacetyl, methyl isobutyl ketone, and acetone; esters such as 1,4-dioxane, 2-methyl-1,3-dioxolane, 1,3-dioxolane, tetrahydrofuran, methyl acetate, ethyl acetate, propyl acetate, and butyl acetate; alcohols such as ethanol, n-propyl alcohol, isopropyl alcohol, and butanol. Examples of suitable organic compounds include phenols, glycols such as ethylene glycol, propylene glycol, diethylene glycol, and triethylene glycol, organic acids such as acetic acid and propionic acid, phenols, aromatic organic compounds such as toluene, xylene, and cyclohexane, ethers such as diethyl ether and allyl glycidyl ether, nitriles such as acrylonitrile, chlorine-containing organic compounds such as dichloromethane, 1,2-dichloroethane, trichloroethylene, and epichlorohydrin, and organic compounds such as N-methyl-2-pyrrolidone, dimethylacetamide, and N,N-dimethylformamide. The gas to be treated may contain one or more of these compounds.

[0057] The solvent recovery system according to the present invention, which has been described in the above embodiment, will be further described in detail using the following examples, but the present invention is not limited to these examples.

[0058] Example 1 The following treatment was carried out using the organic solvent recovery system 1A shown in FIG. 1 described above. An organic solvent-containing gas, which is an example of the gas to be treated, containing 26,000 ppm of dichloromethane at 25°C was treated at a flow rate of 5.3 Nm３ / min (per organic solvent recovery device), and the design concentration of dichloromethane discharged outside the organic solvent recovery system was set to 5 ppm or less.

[0059] First, the gas to be treated was treated in two organic solvent recovery devices 100. Activated carbon fiber was used as the first adsorbent. Air volume: 5.3 Nm 3 The gas was then sent to the treatment tank 101, which was in the first adsorption step, at a flow rate of 9.5 Nm / min (per organic solvent recovery device). The first adsorption step gas discharged from the treatment tank 101 was then sent to the treatment tank 102, which was in the second adsorption step. 3 The temperature was adjusted with the dilution gas and the concentrated gas to a rate of 1 / min and 45°C. The gas treated in the treatment tank 102 was discharged as the first treatment gas and sent to the organic solvent concentrating device 200 through the feed flow path 300. When the dichloromethane concentration of the first adsorption step gas discharged from the treatment tank 101 reached 100 ppm, the steps were switched. At this time, the switching between the steps of the two organic solvent concentrating devices was adjusted so that the timing of the switching was shifted by half the time of the adsorption step.

[0060] While treatment tank 101 was performing the first adsorption step and treatment tank 102 was performing the second adsorption step, desorption steam was introduced into treatment tank 103 to perform the desorption step. At this time, white smoke was present for one minute immediately after switching between adsorption tanks, and after the two first treatment gases were joined, the gas temperature was 50°C, the humidity was 100%, and the maximum concentration of dichloromethane in the first treatment gas was 50 ppm.

[0061] The second adsorbent 201A of the organic solvent concentrating device 200A was made of activated carbon fiber.

[0062] The first treated gas discharged from the organic solvent recovery system 100 was passed through the adsorption zone, and a second treated gas was discharged. A portion of the second treated gas was supplied to the heater H3 via L230, heated to 130°C, and supplied to the desorption zone, where concentrated gas was discharged. The entire amount of concentrated gas was supplied to the dilution gas supply line L170 of the organic solvent recovery system 100 through the return line 400. The dichloromethane concentration in the second treated gas at this time was 5 ppm or less.

[0063] The amount of activated carbon fiber used as the first adsorbent in the organic solvent recovery unit 100 was 3.8 kg / tank, and the amount of activated carbon fiber used as the first adsorbent in the organic solvent concentration unit 200A was 0.8 kg / unit.

[0064] Comparative Example The same gas to be treated as in the Example was treated in the organic solvent recovery apparatus 100 and the organic solvent concentration apparatus 200A in the same manner as in the Example, except that the switching between the processes of the two organic solvent recovery apparatuses 100 was adjusted to occur at the same time.

[0065] At this time, white smoke was present for one minute immediately after the adsorption tank was switched, and the gas temperature after the two first treated gases were joined was 60°C, the humidity was 100%, and the maximum concentration of dichloromethane in the first treated gas was 100 ppm. Also, the dichloromethane concentration in the second treated gas at this time was 5 ppm or less.

[0066] The temperature of the first treated gas containing white smoke introduced into the organic solvent concentrating device and the difference in temperature required for cooling are shown in FIG. 3, and the maximum concentration of dichloromethane in the second treated gas is shown in FIG. 4 in the examples and comparative examples.

[0067] Compared to the comparative example using conventional technology, the example prevents simultaneous switching of the treatment tanks of the two organic solvent concentration devices, thereby suppressing the rise in gas temperature due to the inflow of white smoke. This reduces the temperature required to cool the gas, making it possible to downsize the cooling equipment. Furthermore, it shows that the maximum concentration of dichloromethane in the first treated gas can be suppressed by leveling, making it possible to downsize the organic solvent concentration device.

[0068] The above-disclosed embodiments, modifications, and examples are all illustrative and not restrictive. Furthermore, appropriate combinations of the embodiments, modifications, and examples are also included within the scope of the present invention. In other words, the technical scope of the present invention is defined by the claims, and includes all changes, modifications, substitutions, etc. within the meaning and scope of the claims.

[0069] The present invention can make a significant contribution to industry by controlling the switching of the processes of multiple organic solvent recovery devices in an organic solvent recovery system so that they do not occur simultaneously, thereby making it possible not only to reduce the size of the cooling equipment used to prevent white smoke, but also to reduce the size of the organic solvent concentration device in the system.

[0070] 1A, 1B: organic solvent recovery system, 100: organic solvent recovery device, 101 to 103: treatment tank, 101A to 103A: first adsorbent, 120: separator, 122: condenser, 130: wastewater treatment equipment, 200, 200A, 200B: organic solvent concentration device, 201, 202: treatment tank, 201A, 202A, 201C: second adsorbent, 300: feed flow path, 400: return flow path, H1 to H3: heater (heating section), C1, C2: cooler, L110: treated gas supply flow path, L111 to L113, L211, L212: branch flow paths, L120, L130, L150: merging path, L121 to L123, L2 21, L222: connecting flow path, L131 to L133: extraction flow paths, L140 to L143: steam supply flow path, L151 to L153, ​​L241, L242: organic solvent recovery flow path, L160: re-supply flow path, L161: aeration gas supply flow path, L170: dilution gas supply flow path, L181 to L183: discharge flow path, L220: clean gas discharge flow path, L230 to L232: connecting flow paths, V111 to V113, V121 to V123, V131 to V133, V141 to V143, V211, V212, V221, V222, V231, V232: on-off valves, V101 to V106, V201 to V204: on-off dampers

Claims

1. a plurality of organic solvent recovery devices each including a plurality of treatment tanks each having a first adsorbent capable of adsorbing and desorbing an organic solvent, the treatment tank alternately performing an adsorption process in which the organic solvent contained in an introduced gas to be treated is adsorbed by the first adsorbent and a first treatment gas is discharged, and a desorption process in which the organic solvent is desorbed from the first adsorbent by introduced water vapor and a desorbed gas is discharged, the treatment tank comprising: a water vapor supply unit which introduces the water vapor into a treatment tank selected from the plurality of treatment tanks; and an extraction flow path which discharges the first treatment gas from the treatment tank; an organic solvent concentration device having a second adsorbent capable of adsorbing and desorbing the organic solvent, adsorbing the organic solvent contained in the first treated gas discharged from the organic solvent recovery device, discharging a second treated gas, and desorbing the adsorbed organic solvent from the second adsorbent and discharging it as a concentrated gas, An organic solvent recovery system in which, when the treatment tank of one of the organic solvent recovery apparatuses is switched between adsorption treatment and desorption treatment, the remaining organic solvent recovery apparatuses are operated so that the treatment tanks of the remaining organic solvent recovery apparatuses do not simultaneously switch between adsorption treatment and desorption treatment.

2. a connecting flow path that connects a selected number of the treatment tanks from among all of the treatment tanks in series in multiple stages, the adsorption treatment is performed in the multiple treatment tanks connected in series in multiple stages to discharge the first treatment gas, and the desorption treatment is performed in the remaining treatment tanks using the water vapor, The organic solvent recovery system according to claim 1 , further comprising a dilution gas supply passage for supplying a dilution gas to the connecting passage.

3. 3. The organic solvent recovery system according to claim 2, further comprising a return flow passage for returning the concentrated gas desorbed from the second adsorbent to the dilution gas supply flow passage.

4. 2. The organic solvent recovery system according to claim 1, further comprising a return flow path for returning the concentrated gas desorbed from the second adsorbent to a treated gas supply flow path for introducing the treated gas into the organic solvent recovery device.

5. 3. The organic solvent recovery system according to claim 1, wherein the second adsorbent is made of a material containing at least one of granular activated carbon, activated carbon fiber, and zeolite.

6. 3. The organic solvent recovery system according to claim 1, wherein heated air is used for desorption in the second adsorbent.

7. 3. The organic solvent recovery system according to claim 1, further comprising: a connecting flow path that introduces a portion of the second treatment gas into the second adsorbent for use in desorbing the organic solvent from the second adsorbent; and a heating section provided in the connecting flow path.

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