Organic solvent recovery device and organic solvent recovery system

Abstract

Provided is an organic solvent recovery device that removes an organic solvent via adsorption and discharges a first treatment gas, wherein the organic solvent recovery device is characterized by comprising: a water vapor supply flow path via which water vapor is introduced, using, as a desorption treatment tank, a treatment tank for performing a desorption treatment from among at least four treatment tanks in which an adsorption treatment for removing the organic solvent via adsorption, a desorption treatment in which the organic solvent is desorbed, and a drying treatment for discharging dried outlet gas using a drying gas are performed in the stated order; a drying gas supply flow path via which the drying gas is introduced, using, as a drying treatment tank, a treatment tank for performing the drying treatment from among the remaining treatment tanks; and a linking flow path via which a plurality of treatment tanks other than the desorption treatment tank and the drying treatment tank are connected in series and in multiple stages as adsorption treatment tanks, the upstream end of the adsorption treatment tank being connected to a path for supplying a gas to be treated, the downstream end of the adsorption treatment tank being connected to an extraction flow path, and said organic solvent recovery device comprising a control unit that introduces water vapor to the drying treatment tank in the first portion of a period during which water vapor has been introduced to the desorption treatment tank and supplying the drying gas to the drying treatment tank in the remaining portion of the period during which the water vapor has been introduced to the desorption treatment tank.

Description

Organic solvent recovery device and organic solvent recovery system

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

[0002] Conventionally, systems for recovering organic solvents from gases containing organic solvents have been known. For example, Patent Document 1 discloses a gas treatment device having three treatment tanks, in which an adsorption process is performed continuously in two treatment tanks, while a desorption process is performed in the remaining treatment tank. In this device, the adsorption process is performed continuously in the two treatment tanks, thereby increasing the organic solvent removal rate. Furthermore, for example, 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 organic solvents contained in a gas to be treated discharged from one of the treatment tanks of the first adsorption / desorption device. The concentrated gas discharged from the second adsorption / desorption treatment device is returned to a flow path that supplies the gas to be treated to each treatment tank of the first adsorption / desorption device.

[0003] As an example of an adsorption / desorption device, Patent Document 3 discloses an organic solvent concentration device configured with adsorption elements containing an adsorbent that adsorbs organic solvents. In this device, the adsorption elements are arranged in the circumferential direction to form a cylindrical rotating body, and the arranged adsorption elements are divided into an adsorption zone and a desorption zone. The adsorption and desorption processes are carried out continuously by rotating the rotating body in the circumferential direction on which the adsorption elements are arranged.

[0004] There is a need for an even higher organic solvent removal rate in the organic solvent recovery system described above. To meet this need, for example, Patent Document 4 discloses an organic solvent recovery system in which an adsorption step is continuously performed in two treatment tanks as described in Patent Document 1, and then an additional adsorption step is performed using the device described in Patent Document 3. In this system, concentrated gas containing organic solvent discharged from the organic solvent concentration device in the subsequent stage is returned to a flow path that supplies the gas to be treated to the treatment tank of the organic solvent recovery device in the previous stage.

[0005] JP 2014-147863 A JP 2014-240052 A International Publication No. 2017 / 170207 International Publication No. 2020 / 158442

[0006] However, the organic solvent recovery apparatus and organic solvent recovery system described in Patent Document 4 suffer from a first problem: the apparatus and system become large. To address this problem, a method for miniaturizing an organic solvent recovery apparatus is to configure the cycle time between the adsorption and desorption processes to switch between short intervals, i.e., to perform the adsorption and desorption processes using a small amount of adsorbent, thereby reducing the size of the treatment tank and the apparatus. However, a shorter adsorption process also means that the desorption process is shorter than before. In such an apparatus, the adsorbent is generally heated for a sufficient period of time to desorb the organic solvent adsorbed on the adsorbent and regenerate the adsorption capacity of the adsorbent. Therefore, if the cycle time is configured to switch between short intervals, the adsorbent will not desorb sufficiently, resulting in a decrease in treatment performance.

[0007] A second problem is that in the organic solvent recovery apparatus and organic solvent recovery system described in Patent Document 4, when switching from the desorption process to the adsorption process, the water vapor remaining in the adsorption tank is suddenly cooled and condensed by the gas to be treated, causing the adsorbent to become temporarily wet, temporarily reducing the adsorption performance until the adsorbent dries. While it is possible to suppress the performance degradation caused by such adsorbent wetting by increasing the length of the adsorbent layer in the ventilation direction, this increases the amount of adsorbent, resulting in an increase in the size of the organic solvent recovery apparatus.

[0008] Furthermore, the condensed water vapor mist (hereinafter referred to as white smoke) described above is mixed into the gas to be treated discharged from the treatment tank of the organic solvent recovery system and supplied to the organic solvent concentration system for several tens of seconds immediately after switching between the adsorption and desorption processes in the treatment tank. When high-temperature and high-humidity gas containing white smoke is supplied to the adsorbent of the organic solvent concentration system, the increase in the gas temperature and adsorption of moisture into the adsorbent slows the organic solvent adsorption rate, resulting in the discharge of organic solvent gas into the treated gas at concentrations greater than the designed outlet concentration of the organic solvent concentration system. Furthermore, moisture adsorption by the white smoke increases the thermal energy required for the desorption process of the adsorbent of the organic solvent concentration system. One solution to the impact of white smoke is to cool and dehumidify the gas to be treated, but this increases cooling costs. While it is possible to address the slower adsorption rate by increasing the adsorbent bed length to minimize degradation of treatment performance, this increases the size of the organic solvent concentration system due to the increased amount of adsorbent.

[0009] Therefore, in consideration of the above-mentioned problems, the present invention has an object to reduce the size of the organic solvent recovery device and the organic solvent concentrating device in an organic solvent recovery system equipped with the organic solvent recovery device and the organic solvent concentrating device, and to reduce the running costs of the system.

[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] 1. An organic solvent recovery apparatus for adsorbing and removing organic solvents contained in a gas to be treated and discharging a first treated gas, comprising: at least four treatment tanks having a first adsorbent, each treatment tank sequentially performing an adsorption treatment in which the organic solvent is adsorbed and removed from the gas to be treated by the first adsorbent, a desorption treatment in which the organic solvent is desorbed from the first adsorbent with water vapor, and a drying treatment in which the first adsorbent is dried with a dry gas and a dried outlet gas is discharged; a water vapor supply flow path for introducing water vapor into one of the at least four treatment tanks that performs the desorption treatment, the treatment tank being a desorption treatment tank; a dry gas supply flow path for introducing dry gas into one of the remaining treatment tanks that performs the drying treatment, the treatment tank being a drying treatment tank; and a connecting flow path for connecting a plurality of the treatment tanks other than the desorption treatment tank and the drying treatment tank in series and in multiple stages as adsorption treatment tanks, the adsorption treatment tank being connected upstream to a treated gas supply flow path for supplying the gas to be treated, and downstream to an extraction flow path for discharging the first treated gas; and an organic solvent recovery apparatus comprising: a control unit that introduces the water vapor into the drying treatment tank during an early period of the period in which the water vapor is being introduced into the desorption treatment tank, and that supplies the dry gas to the drying treatment tank during a later period of the period in which the water vapor is being introduced into the desorption treatment tank. 2. The organic solvent recovery apparatus described in above 1, characterized in that the dry outlet gas is discharged to the outside of the system. 3. The organic solvent recovery apparatus described in above 1, characterized in that it includes a flow path that returns the dry outlet gas to the treated gas supply flow path or the connecting flow path. 4. An organic solvent recovery system comprising the organic solvent recovery apparatus described in any one of above 1 to 3 and an organic solvent concentrating device, wherein the organic solvent concentrating device has a second adsorbent, and uses the second adsorbent to adsorb and remove the organic solvent from the first treatment gas introduced from a feed flow path connected to the extraction flow path, thereby discharging a second treatment gas, and also desorbs the organic solvent adsorbed by the second adsorbent with a desorption gas, thereby discharging a concentrated gas. 5. The organic solvent recovery system described in above 4, characterized in that it includes a return flow path that returns the concentrated gas to the connecting flow path. 6. 6. The organic solvent recovery system according to claim 4 or 5, further comprising a return flow path for returning the concentrated gas to the treated gas supply flow path of the organic solvent recovery device.7. The organic solvent recovery system according to any one of claims 4 to 6, further comprising a connecting flow path for introducing a portion of the second treated gas as the desorption gas into the organic solvent concentrating device. 8. The organic solvent recovery system according to any one of claims 4 to 7, further comprising a flow path for introducing a portion of the second treated gas as the dry gas into the organic solvent recovery device. 9. The organic solvent recovery system according to any one of claims 4 to 8, further comprising: feeding the dry outlet gas to the feed flow path. 10. The organic solvent recovery system according to any one of claims 4 to 9, further comprising: a first adsorbent and a second adsorbent made of a material containing at least one of granular activated carbon, activated carbon fiber, and zeolite. 11. The organic solvent recovery system according to any one of claims 4 to 10, further comprising: heated air or nitrogen as the desorption gas.

[0012] According to the present invention, by introducing water vapor into the drying tank during the early period of the period in which water vapor is introduced into the desorption tank and supplying the dry gas to the drying tank during the later period of the period in which water vapor is introduced into the desorption tank, it is possible to sufficiently desorb and regenerate the adsorbent even when switching between each process in a short span, and the total amount of activated carbon fiber in the organic solvent recovery apparatus can be reduced in volume, thereby reducing the size of the organic solvent recovery apparatus. Furthermore, by discharging the dry gas after the desorption and drying processes to the outside of the system, it is possible to suppress a decrease in performance of the organic solvent concentrator due to the inflow of white smoke, thereby increasing the concentration ratio of the concentrated gas in the organic solvent concentrator and reducing the volume of the returned concentrated gas. This not only reduces the running costs for heating the desorbed gas, but also achieves a reduction in the size of the entire organic solvent recovery system by reducing the volume of the organic solvent recovery apparatus and the processing air volume of the organic solvent concentrator.

[0013] It is a diagram showing an example of the configuration of an organic solvent recovery system according to an embodiment of the present invention. It is a diagram showing an example of the configuration of an organic solvent recovery system of a comparative example. It is a diagram showing an example of a time chart for switching processes in each treatment tank of an organic solvent recovery apparatus according to an embodiment of the present invention. It is a table showing the treatment air volume, total amount of activated carbon, and concentration ratio introduced into an organic solvent recovery apparatus and an organic solvent concentrating apparatus in Examples and Comparative Examples.

[0014] Hereinafter, an embodiment of the present invention will be described in detail with reference to FIG.

[0015] (Embodiment 1) Figure 1 is a diagram schematically illustrating the configuration of an organic solvent recovery system according to one embodiment of the present invention. Here, the case will be described in which one organic solvent recovery apparatus and one organic solvent concentrating apparatus are used. The organic solvent recovery system includes an organic solvent recovery apparatus 100, an organic solvent concentrating apparatus 200, a feed flow path 300, and a return flow path 400. The organic solvent recovery system removes and recovers the organic solvent from a gas to be treated containing the organic solvent in the organic solvent recovery apparatus 100, and then further removes and concentrates the organic solvent from a first treated gas discharged from the organic solvent recovery apparatus 100 in the organic solvent concentrating apparatus 200, and returns the concentrated gas discharged from the organic solvent concentrating apparatus 200 to the organic solvent recovery apparatus 100 via the return flow path 400.

[0016] Each component will be described below. The organic solvent recovery apparatus 100 is an apparatus that adsorbs, removes, and recovers 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 includes four treatment tanks 101-104, a gas to be treated supply flow path L110, connecting flow paths L121-L124, extraction flow paths L131-L134, steam supply flow paths L140-L144, organic solvent recovery flow paths L151-L154, a separator 120, a wastewater treatment facility 130, a re-supply flow path L160, an aeration gas supply flow path L161, a dry gas supply flow path L170, connecting flow paths L171-L174, dry outlet gas extraction flow paths L181-L184, and a control unit 190.

[0017] Each treatment tank 101-104 has a first adsorbent 101A-104A capable of adsorbing and desorbing organic solvents. Granular activated carbon, granular zeolite, honeycomb-shaped activated carbon, honeycomb-shaped zeolite, activated carbon fiber, or the like can be used as the first adsorbent 101A-104A, but activated carbon fiber is preferred. Each treatment tank 101-104 has an open / close damper V101-V104 that switches between supplying and not supplying the treated gas to the treated gas supply port, and an open / close damper V105-V108 that switches between discharging and not discharging the treated gas from the discharge port after passing through the first adsorbent 101A-104A.

[0018] In each of the treatment tanks 101 to 104, adsorption of the organic solvent by the first adsorbents 101A to 104A, desorption of the organic solvent from the first adsorbents 101A to 104A, and a drying process for drying the first adsorbents 101A to 104A are alternately performed. That is, in one of the four treatment tanks 101 to 104, a first adsorption process (first adsorption treatment) 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 and a first adsorption process gas is discharged. Simultaneously, in one of the remaining treatment tanks, a second adsorption process (second adsorption treatment) is performed in which the first adsorbent adsorbs the organic solvent from the discharged first adsorption process gas and a first treatment gas is discharged. Furthermore, in one of the remaining treatment tanks, a desorption process (desorption treatment) is performed in which the organic solvent is desorbed from the first adsorbent. Furthermore, in the remaining treatment tank, water vapor is introduced in the early period of the period during which water vapor is introduced in the desorption process, and a desorption / drying process (desorption / drying treatment) is performed to dry the first adsorbent in the later period of the period during which water vapor is introduced in the desorption process. The treatment tanks performing the first adsorption process and the second adsorption process are sometimes referred to as adsorption treatment tanks, the treatment tank performing the desorption process is sometimes referred to as desorption treatment tank, and the treatment tank performing the desorption / drying process is sometimes referred to as drying treatment tank. In this embodiment, the drying treatment tank performs the desorption process in the early period and the drying process in the later period. In each of the treatment tanks 101 to 104, the desorption process, desorption / drying process, second adsorption process, and first adsorption process are repeatedly performed in this order. Figure 2 shows an example of a time chart for switching processes in each tank.

[0019] The treated gas supply flow path L110 is a flow path for supplying the treated gas to each of the treatment tanks 101 to 104. 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 104.

[0020] The treated gas supply flow path L110 has branch flow paths L111 to L114 that supply the treated gas to each of the treatment tanks 101 to 104. 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 path L114 is provided with an on-off valve V114.

[0021] The connecting flow paths L121 to L124 are connected so that the organic solvent is adsorbed in the first adsorbent of a first adsorption treatment tank among the four treatment tanks 101 to 104, and the discharged first adsorption process gas is introduced into the treated gas supply port of a second adsorption treatment tank that is different from the first adsorption treatment tank among the four treatment tanks 101 to 104. In other words, the first adsorption treatment tank and the second adsorption treatment tank are connected in series in multiple stages by the connecting flow paths.

[0022] Each of the connecting flow paths L121 to L124 has a confluence flow path L120 where they merge with one another. An on-off valve V121 is provided at the location of the first connecting flow path L121 where it branches off again from the confluence flow path L120. An on-off valve V122 is provided at the location of the second connecting flow path L122 where it branches off again from the confluence flow path L120. An on-off valve V123 is provided at the location of the third connecting flow path L123 where it branches off again from the confluence flow path L120. An on-off valve V124 is provided at the location of the fourth connecting flow path L124 where it branches off again from the confluence flow path L120.

[0023] The extraction flow paths L131 to L134 are flow paths for extracting a first process gas, which is a process gas after being adsorbed in each of the treatment tanks 101 to 104. The extraction flow paths L131 to L134 are connected to the process gas exhaust ports of each of the treatment tanks 101 to 104. An on-off valve V131 is provided in the first extraction flow path L131. An on-off valve V132 is provided in the second extraction flow path L132. An on-off valve V133 is provided in the third extraction flow path L133. An on-off valve V134 is provided in the fourth extraction flow path L134. The extraction flow paths L131 to L134 have a confluence flow path L130 where they converge with each other.

[0024] The water vapor supply flow paths L141 to L144 are flow paths for supplying water vapor to the treatment tanks 101 to 104, for desorbing the organic solvent adsorbed in the first adsorbents 101A to 104A from the first adsorbents 101A to 104A.

[0025] The first water vapor supply passage L141 connects the water vapor supply source and the first treatment tank 101, and is provided with an on-off valve V141. The second water vapor supply passage L142 connects the water vapor supply source and the second treatment tank 102, and is provided with an on-off valve V142. The third water vapor supply passage L143 connects the water vapor supply source and the third treatment tank 103, and is provided with an on-off valve V143. The fourth water vapor supply passage L144 connects the water vapor supply source and the fourth treatment tank 104, and is provided with an on-off valve V144.

[0026] The organic solvent recovery flow paths L151 to L154 are flow paths for recovering water vapor (recovered gas) containing the organic solvent desorbed from the first adsorbents 101A to 104A. Each of the organic solvent recovery flow paths L151 to L154 is connected to each of the treatment tanks 101 to 104. Each of the organic solvent recovery flow paths L151 to L154 has a confluence path L150. A condenser 121 is provided in the confluence path L150. The condenser 121 condenses the recovered gas by cooling the recovered gas flowing through the confluence path L150, and discharges the condensed liquid (a mixture of water produced by condensation of the recovered gas and liquid-phase organic solvent).

[0027] 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) in which the gaseous organic solvent exists is formed above the separator 120.

[0028] 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 104 through the re-supply passage L160 and the treated gas supply passage L110.

[0029] The wastewater treatment equipment 130 is equipment for removing 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 upstream side of the cooler C1 of the treated gas supply flow path L110 via an aeration gas supply flow path L161. A dehumidification means for removing moisture from the aeration gas may be provided in the aeration gas supply flow path.

[0030] The dry gas supply flow path L170 is a flow path for supplying a dry gas to the connecting flow paths L171 to L174 to promote drying of the first adsorbents 101A to 104A after the desorption step. The connecting flow paths L171 to L174 are connected to the treated gas supply ports of the treatment tanks 101 to 104. The connecting flow path L171 is provided with an on-off valve V161. The connecting flow path L172 is provided with an on-off valve V162. The connecting flow path L173 is provided with an on-off valve V163. The connecting flow path L174 is provided with an on-off valve V164. The dry gas is composed of a gas containing at least one of outside air, instrument air, nitrogen gas, argon gas, and the second treatment gas discharged from the organic solvent concentrating apparatus 200.

[0031] The dryer outlet gas extraction flow paths L181 to L184 are flow paths for extracting dryer outlet gas discharged after the drying process is performed using dry gas in each of the treatment tanks 101 to 104. The dryer outlet gas extraction flow paths L181 to L184 are connected to the treatment gas exhaust ports in each of the treatment tanks 101 to 104. The dryer outlet gas extraction flow path L181 is provided with an on-off valve V151. The dryer outlet gas extraction flow path L182 is provided with an on-off valve V152. The dryer outlet gas extraction flow path L183 is provided with an on-off valve V153. The dryer outlet gas extraction flow path L184 is provided with an on-off valve V154. The dryer outlet gas extraction flow paths L181 to L184 are connected to the confluence flow path L180 where they converge with each other.

[0032] The dried outlet gas discharged after the drying step in each of the treatment tanks 101 to 104 may be discharged outside the system or returned to either the treated gas supply flow path L110 or the treated gas supply flow path for the second adsorption step. Discharge outside the system is more preferable. The dried outlet gas may contain high-humidity white smoke, and returning this to the supply flow path within the system would reduce the treatment performance of the adsorbent. However, discharging it outside the system prevents this reduction in treatability.

[0033] The control unit 190 is a device for controlling switching between the desorption process, the desorption / drying process, the second adsorption process, and the first adsorption process in the treatment tanks 101 to 104.

[0034] The organic solvent concentration apparatus 200 is equipment that further removes organic solvent from the first treated gas discharged from the organic solvent recovery apparatus 100. The organic solvent concentration apparatus 200 has a rotor-type adsorption / desorption treatment apparatus equipped with a second adsorption / desorption element 201 containing a second adsorbent that adsorbs and desorbs organic solvent, and the rotor is divided into an adsorption zone that adsorbs the organic solvent and a desorption zone that desorbs the adsorbed organic solvent. In this embodiment, the rotor-type adsorption / desorption treatment apparatus is illustrated as being of a horizontal (disc) type, but is not limited to this and may be of a vertical (cylinder) type. Furthermore, adsorption / desorption treatment apparatuses other than rotor-type may also be used.

[0035] The first process gas discharged from the organic solvent recovery apparatus 100 passes through the feed flow path 300, cooler C2, and heater H2 and through the adsorption zone of the second adsorption / desorption element 201, thereby discharging a second process 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 process 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 apparatus 100 through the return flow path 400.

[0036] The organic solvent concentrating device 200 has an adsorbent having a substantially cylindrical outer shape or a second adsorption / desorption element 201 arranged to have a substantially cylindrical shape. The organic solvent concentrating device 200 is equipped with a motor, and when the motor is driven, the second adsorption / desorption element 201 rotates in the tangential direction, and any part of the second adsorption / desorption element 201 moves alternately between the adsorption zone and the desorption zone over time to perform the adsorption / desorption process.

[0037] The second adsorption / desorption element is made of an adsorbent material containing any one of activated alumina, silica gel, activated carbon, and zeolite, with activated carbon and zeolite in granular, powder, honeycomb, or other shapes being preferred.

[0038] The organic solvent concentrating device 200 discharges the second treated gas, which is the cleaned gas discharged from the adsorption zone, to the outside of the system through a cleaned gas discharge line L210.

[0039] The organic solvent concentrating apparatus 200 further includes a connecting flow path L220 and a heater H3. The connecting flow path L220 connects the clean gas discharge flow path L210 to the adsorption zone, and a portion of the second process gas is used as a desorption gas. Alternatively, outside air may be used as the desorption gas.

[0040] 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 treatment gas to be introduced into the organic solvent concentration device 200.

[0041] 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 confluence flow path L120. The return flow path 400 may also be connected to the treated gas supply flow path L110.

[0042] The organic compounds contained in the gas to be treated by the organic solvent recovery system of this embodiment are not particularly limited, but 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; and alcohols such as ethanol, n-propyl alcohol, isopropyl alcohol, and butanol. Examples of suitable organic compounds include 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.

[0043] The organic 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, although the present invention is not limited to these examples.

[0044] [Example 1] The following treatment was carried out using the organic solvent recovery system shown in Figure 1 described above. An organic solvent-containing gas, which is an example of the gas to be treated, containing 40,000 ppm of dichloromethane at 25°C was treated at a flow rate of 5.3 Nm ３The design concentration of dichloromethane discharged outside the organic solvent recovery system was set to 2 ppm or less. First, the gas to be treated was treated in the organic solvent recovery device 100. Activated carbon fiber was used as the first adsorbent. The air volume was 5.3 Nm ３ The gas discharged from the first treatment tank 101 was then sent to the second treatment tank 102, which was in the second adsorption step. At this time, the gas sent to the second treatment tank was a total of 6.1 Nm3, which was the first adsorption step gas and the concentrated gas from the organic solvent concentration device 200. ３ / min and 40°C. The gas treated in the second 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 treatment gas discharged from the second treatment tank 102 reached 100 ppm, the respective processes were switched. At this time, the cycle time for each treatment process was 6 min, and the third treatment tank 103 performed the desorption process for 6 min, and the fourth treatment tank 104 performed desorption for 2 min in the early stage of the desorption / drying process and then sent drying gas for 4 min in the later stage of the drying process to dry the gas.

[0045] Activated carbon fiber was used for the second adsorption / desorption element 201 of the organic solvent concentration device 200. The gas sent to the organic solvent concentration device 200 was the first treated gas 6.1 Nm ３ A portion of the second process gas discharged from the organic solvent concentrating device 200 was supplied to the heater H3 through the connecting flow path L220, heated to 130°C, and supplied to the desorption zone as a desorption gas, where the concentrated gas was discharged. At this time, a flow rate of 0.76 Nm was supplied to the organic solvent concentrating device 200. ３ The concentrated gas was supplied to the confluence flow path L120 of the organic solvent recovery unit 100 through the return flow path 400. At this time, the concentration of dichloromethane in the concentrated gas was 800 ppm.

[0046] At this time, the dichloromethane concentration in the second treated gas discharged to the outside of the system was 2 ppm or less. The amount of activated carbon fiber used in the organic solvent recovery device 100 was 56 kg in total.

[0047] Comparative Example 1 Figure 2 shows an organic solvent recovery system using conventional technology. The organic solvent recovery system shown in Figure 2 has an organic solvent recovery apparatus 100A and an organic solvent concentrating apparatus 200. The organic solvent recovery apparatus 100A shown in Figure 2 has three treatment tanks and does not have the drying treatment tank of the organic solvent recovery apparatus 100 in the organic solvent recovery system shown in Figure 1. The configuration of the organic solvent concentrating apparatus 200 shown in Figure 2 is the same as the configuration of the organic solvent concentrating apparatus 200 shown in Figure 1.

[0048] As Comparative Example 1, the following treatment was carried out using the organic solvent recovery system shown in Figure 2. An example of the gas to be treated was an organic solvent-containing gas containing 40,000 ppm of dichloromethane at 25°C, and the gas was passed through a gas flow rate of 5.3 Nm3. ３ The design concentration of dichloromethane discharged outside the system was set to 2 ppm or less. First, the gas to be treated was treated in the organic solvent recovery device 100. Activated carbon fiber was used as the first adsorbent. The air volume was 5.3 Nm ３ The gas discharged from the first treatment tank 101 was then sent to the second treatment tank 102, which was in the second adsorption process. At this time, the gas sent to the second treatment tank was a mixture of the first adsorption process gas, concentrated gas from the organic solvent concentration device 200, and diluted gas, at a flow rate of 7.9 Nm3. ３ / min and 40°C. The gas treated in the second 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 treatment gas discharged from the second treatment tank 102 reached 100 ppm, each process was switched. At this time, the cycle time for each treatment process was 8 minutes, and the desorption process in the third treatment tank 103 was performed for 8 minutes.

[0049] Activated carbon fiber was used for the second adsorption / desorption element 201 of the organic solvent concentration device 200. The gas sent to the organic solvent concentration device 200 was the first treated gas 7.9 Nm ３A part of the second treated gas discharged from the organic solvent concentrating device 200 was supplied to the heater H3 via L220, heated to 130°C, and supplied to the desorption zone as a desorption gas, where the concentrated gas was discharged. At this time, a flow rate of 1.58 Nm was supplied to the organic solvent concentrating device 200. 3 The concentrated gas was supplied to the diluted gas supply line L170 of the organic solvent recovery unit 100 through the return line 400. At this time, the concentration of dichloromethane in the concentrated gas was 500 ppm.

[0050] At this time, the dichloromethane concentration in the second treated gas discharged to the outside of the system was 2 ppm or less. The amount of activated carbon fiber used in the organic solvent recovery device 100 was 72 kg in total.

[0051] The treatment air volume (air volume of the gas to be treated) and the total amount of activated carbon of the organic solvent recovery apparatus 100, as well as the treatment air volume (air volume of the first treatment gas) and concentration ratio of the organic solvent concentrating apparatus 200 in Example 1 and Comparative Example 1 are shown in Figure 4. The concentration ratio was calculated using the following formula: Concentration ratio [times] = treatment air volume / desorption gas volume Here, the treatment air volume is the volume of the first treatment gas introduced into the organic solvent concentrating apparatus 200, and the desorption gas volume is the volume of the gas used for desorption in the organic solvent concentrating apparatus 200.

[0052] 4, it can be seen that, compared to Comparative Example 1 using conventional technology, Example 1 was able to reduce the treated air volume of the organic solvent recovery device by approximately 23% and the treated air volume of the organic solvent concentrating device 200 by approximately 23%. It can also be seen that the total amount of activated carbon used in the organic solvent recovery device was able to be reduced by approximately 23%.

[0053] Here, the treatment tanks of the organic solvent recovery apparatus shown in FIG. 1 (the system of Example 1) and FIG. 2 (the system of Comparative Example 1) are approximately the same size. However, because the total volume of activated carbon in Example 1 can be reduced, each treatment tank in Example 1 and, therefore, the organic solvent recovery apparatus 100 can be made smaller. Furthermore, the second adsorption / desorption elements shown in FIGS. 1 and 2 are approximately the same size. However, because the volume of the treated air volume of the organic solvent concentrator in Example 1 can be reduced, the organic solvent concentrator can be made smaller. Furthermore, the concentration ratio of the organic solvent concentrator 200 is improved by 1.6 times compared to Comparative Example 1, which uses conventional technology, thereby achieving a reduction in the energy required to heat the desorbed gas. Therefore, the configuration shown in Example 1 demonstrates that the overall organic solvent recovery system can be made smaller and its running costs reduced.

[0054] 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.

[0055] The present invention is configured to introduce steam into the drying tank during the early period of the period during which steam is introduced into the desorption tank, and to supply dry gas to the drying tank during the later period of the period during which steam is introduced into the desorption tank. Therefore, even when switching between processes over a short time span, sufficient desorption and regeneration of the adsorbent is possible, and the total volume of activated carbon fiber in the organic solvent recovery system can be reduced, resulting in a more compact organic solvent recovery system. Furthermore, the present invention is configured to discharge the dry gas after the desorption and drying processes outside the system, thereby suppressing performance degradation of the organic solvent concentrator due to the inflow of white smoke. This increases the concentration ratio of the concentrated gas in the organic solvent concentrator, thereby reducing the volume of the returned concentrated gas. This not only reduces the running costs for heating the desorbed gas, but also achieves a more compact organic solvent recovery system as a whole by reducing the volume of the organic solvent recovery system and the volume of the processed airflow in the organic solvent concentrator. This contributes greatly to the industry.

[0056] 100: organic solvent recovery apparatus, 101 to 104: first to fourth treatment tanks, 101A to 104A: first adsorbent, 120: separator, 121: condenser, 130: wastewater treatment equipment, L110: treated gas supply flow path, L111 to L114: branch flow paths, L120, L130, L150, L180: confluence flow paths, L121 to L124, L171 to L174: connection flow paths, L131 to L134: extraction flow paths, L140 to L144: steam supply flow paths, L151 to L154: organic solvent recovery flow path, L160: re-supply flow path, L16 1: aeration gas supply flow path, L170: dry gas supply flow path, L181 to L184: dry outlet gas extraction flow path, 190: control unit, V101 to V108: on-off dampers, V111 to V114, V121 to V124, V131 to V134, V141 to V144, V151 to V154, V161 to V164: on-off valves, 200: organic solvent concentration device, 201: second adsorption / desorption element, L210: clean gas discharge flow path, L220: connection flow path, 300: feed flow path, 400: return flow path, H1 to H3: heater, C1, C2: cooler.

Claims

1. In an organic solvent recovery apparatus that adsorbs and removes an organic solvent contained in a gas to be treated and discharges a first treated gas, the apparatus has a first adsorbent, and performs an adsorption treatment of adsorbing and removing the organic solvent from the gas to be treated with the first adsorbent, a desorption treatment of desorbing the organic solvent from the first adsorbent with steam, and a drying treatment of drying the first adsorbent with a dry gas and discharging a dried outlet gas, in at least four treatment tanks in sequence; a steam supply passage for introducing the steam into a treatment tank that performs the desorption treatment among the at least four treatment tanks as a desorption treatment tank; a dry gas supply passage for introducing the dry gas into a treatment tank that performs the drying treatment among the remaining treatment tanks as a drying treatment tank; and a connection passage for connecting a plurality of the treatment tanks other than the desorption treatment tank and the drying treatment tank in series and in multiple stages as adsorption treatment tanks. The upstream of the adsorption treatment tank is connected to a gas to be treated supply passage for supplying the gas to be treated, and the downstream is connected to a take-out passage for discharging the first treated gas. Further, a control unit that introduces the steam into the drying treatment tank in the first half of the period during which the steam is introduced into the desorption treatment tank and supplies the dry gas to the drying treatment tank in the second half of the period during which the steam is introduced into the desorption treatment tank. An organic solvent recovery apparatus characterized by comprising the above.

2. The organic solvent recovery apparatus according to claim 1, characterized in that the dried outlet gas is discharged outside the system.

3. The organic solvent recovery apparatus according to claim 1, characterized by comprising a passage for returning the dried outlet gas to the gas to be treated supply passage or the connection passage.

4. An organic solvent recovery system comprising the organic solvent recovery apparatus according to any one of claims 1 to 3 and an organic solvent concentration apparatus. The organic solvent concentration apparatus has a second adsorbent, adsorbs and removes an organic solvent from the first treated gas introduced from a feed passage connected to the take-out passage with the second adsorbent and discharges a second treated gas, and desorbs the organic solvent adsorbed by the second adsorbent with a desorption gas and discharges a concentrated gas. An organic solvent recovery system characterized by the above.

5. The organic solvent recovery system according to claim 4, characterized by comprising a return passage for returning the concentrated gas to the connection passage.

6. The organic solvent recovery system according to claim 4, characterized by comprising a return passage for returning the concentrated gas to the gas to be treated supply passage of the organic solvent recovery apparatus.

7. The organic solvent recovery system according to claim 4, comprising a connection channel for introducing a part of the second processing gas as the desorption gas into the organic solvent concentrator.

8. The organic solvent recovery system according to claim 4, comprising a channel for introducing a part of the second processing gas as the drying gas into the organic solvent recovery device.

9. The organic solvent recovery system according to claim 4, characterized in that the dried outlet gas is sent to the feed channel.

10. The organic solvent recovery system according to claim 4, characterized in that the first adsorbent and the second adsorbent are made of a material containing at least one of granular activated carbon, activated carbon fiber, and zeolite.

11. The organic solvent recovery system according to claim 4, characterized in that heated air or nitrogen is used for the desorption gas.

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