Organic solvent recovery system

Abstract

An organic solvent recovery system comprising a recovery device (1), a dehydration device (2), and a return device (3). The dehydration device (2) includes: a dehydration material (202) for coming into contact with a recovered solvent (113B) to thereby absorb moisture contained in the recovered solvent (113B); one or more dehydration treatment tanks (203) in which the dehydration material (202) is stored; and a discharge mechanism for supplying the recovered solvent (113B), which is separated by a separator (113), to the one or more dehydration treatment tanks (203) and discharging, from the one or more dehydration treatment tanks (203), a dehydrated solvent (E) obtained through dehydration from the recovered solvent (113B) by the dehydration material (202). When returning the recovered solvent (113B) within the one or more dehydration treatment tanks (203) to the separator (113), the return device (3) sends the recovered solvent (113B) to a recovered-solvent (113B) layer of the separator (113). This organic solvent recovery system makes it possible to discharge a dehydrated solvent from which moisture is sufficiently removed even upon restarting of the system.

Description

Organic Solvent Recovery System

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

[0002] The organic solvent recovery system includes a pair of treatment tanks that use an adsorbent to adsorb the organic solvent in the gas to be treated, a treatment gas supply device and a desorption gas supply device for each treatment tank, and employs a mechanism for switching between an adsorption process in which the treatment gas is supplied to the treatment tank and a desorption process in which the desorption gas is supplied.

[0003] For example, activated carbon fiber (ACF) (hereinafter referred to as ACF) is used as an adsorbent in gas treatment devices. ACF has an excellent function of adsorbing low-concentration organic solvent-containing gases and is used as an adsorbent. For example, Japanese Patent Laid-Open Publication No. 2014-147864 (Patent Document 1) discloses a gas treatment device in which an ACF is fixed to a support or configured into a cylindrical shape that is self-supporting and vertically arranged within a core material.

[0004] JP 2014-147864 A

[0005] The recovered solvent recovered from the adsorbent may contain moisture. When the recovered solvent is reused in production equipment, it must be dehydrated (moisture removal). One known method for this is to bring the recovered solvent into contact with a dehydrating material such as zeolite. The recovered solvent is dehydrated by passing it through a dehydration device that has a dehydration treatment tank filled with the dehydrating material.

[0006] However, if the dehydration equipment is stopped or the organic solvent load in the treated gas is lower than designed, the recovered solvent may remain in the dehydration tank for a long time. In this case, water is released from the dehydrating material in the dehydration tank, returning water to the recovered solvent, and when the dehydration equipment is restarted, dehydrated solvent with insufficient water removal is discharged. Another issue is that the organic solvent contained in the dehydration tank volatilizes through the piping outlet of the dehydration equipment, reducing the amount of organic solvent recovered.

[0007] The present disclosure aims to solve the above problems, and a first object of the present disclosure is to provide an organic solvent recovery system that can discharge dehydrated solvent from which water has been sufficiently removed even when the system is restarted. A second object of the present disclosure is to provide an organic solvent recovery system that can suppress the evaporation of organic solvent contained in a dehydration treatment tank through the piping outlet of a dehydration device, thereby suppressing a decrease in the amount of recovered organic solvent.

[0008] The organic solvent recovery system of the present disclosure is an organic solvent recovery system including a recovery device, a dehydration device, and a return device, and has the following configuration.

[0009] The recovery apparatus includes an adsorbent that adsorbs an organic solvent that is poorly soluble in water and has a specific gravity greater than that of water upon contact with a gas to be treated containing the organic solvent and desorbs the organic solvent upon contact with water vapor, two or more treatment tanks containing the adsorbent, an adsorption step of supplying the gas to be treated to the treatment tank, causing the organic solvent to be adsorbed and removed by the adsorbent, and discharging a clean gas, a desorption step of supplying water vapor to the treatment tank, desorbing the recovered solvent from the adsorbent, and discharging a desorbed gas, a step of sequentially repeating the adsorption step and the desorption step for the two or more treatment tanks, a condenser that cools and condenses the desorbed gas and discharges a desorbed liquid, and a separator that separates the desorbed liquid into a layer of separated water and a layer of the recovered solvent.

[0010] The dehydration device includes a dehydrating material that comes into contact with the recovered solvent to adsorb moisture contained in the recovered solvent, one or more dehydration treatment tanks that house the dehydrating material, and a discharge mechanism that supplies the recovered solvent separated by the separator to the dehydration treatment tank and discharges the dehydrated solvent that has been dehydrated from the recovered solvent by the dehydrating material from the dehydration treatment tank.

[0011] The return device sends the recovered solvent to the layer of the recovered solvent in the separator when returning the recovered solvent in the dehydration treatment tank to the separator.

[0012] In the organic solvent recovery system, the return device has a return flow path that discharges the recovered solvent out of the dehydration treatment tank and returns the recovered solvent to the separator when the dehydration device stops supplying the recovered solvent to the dehydration treatment tank.

[0013] In the organic solvent recovery system, the dehydration device includes a speed adjusting device that adjusts the speed at which the recovered solvent is returned to the separator.

[0014] In the organic solvent recovery system, the speed adjusting device uses a portion of the treated gas or the clean gas to pressurize the inside of the dehydration treatment tank, thereby discharging the recovered solvent out of the dehydration treatment tank.

[0015] The organic solvent recovery system has three or more treatment tanks, one of which performs the desorption step, and the remaining treatment tanks are connected in series in multiple stages and perform the adsorption step.

[0016] According to the present disclosure, it is possible to provide an organic solvent recovery system that can discharge dehydrated solvent from which moisture has been sufficiently removed even when restarting the system. Preferably, it is possible to provide an organic solvent recovery system that can suppress the evaporation of organic solvent contained in the dehydration treatment tank through the piping outlet of the dehydration device, thereby suppressing a decrease in the amount of recovered organic solvent.

[0017] Fig. 1 is a diagram showing the configuration of an organic solvent recovery system according to a first embodiment. Fig. 2 is a cross-sectional view taken along the line II-II in Fig. 1. Fig. 3 is a diagram showing the configuration of an organic solvent recovery system according to a second embodiment. Fig. 4 is a diagram showing the configuration of an organic solvent recovery system according to a third embodiment. Fig. 5 is a diagram showing the configuration of an organic solvent recovery system according to a fourth embodiment. Fig. 6 is a diagram showing the configuration of an organic solvent recovery system according to another embodiment. Fig. 7 is a diagram showing the configuration of an organic solvent recovery system according to yet another embodiment.

[0018] The organic solvent recovery system according to each embodiment of the present disclosure will be described below with reference to the drawings. In the embodiments described below, when reference is made to the number, amount, etc., the scope of the present invention is not necessarily limited to the number, amount, etc., unless otherwise specified. The same reference numerals are used for the same or equivalent parts, and redundant descriptions may not be repeated. It is intended from the beginning that the configurations in the embodiments may be used in appropriate combinations.

[0019] The organic solvent used in this disclosure refers to an organic solvent that is poorly soluble in water and has a higher specific gravity than water. Specific examples include 1,2,4-trichlorobenzene, 1,1,1-trichloroethane, trichloroethylene, perchloroethylene, methylene chloride, carbon tetrachloride, chloroform, ethylene chloride, dimethyl carbonate, 1-bromopropane, o-dichlorobenzene, nitrobenzene, 1,2-dichloropropane, epichlorohydrin, monochlorobenzene, 1,2-dichloroethane, 1,1,2-trichloroethane, 1,2-dichloroethylene, 1,1,2-trichloroethane, 1,1,2,2-tetrachloroethane, pentachloroethane, 1,1-dichloroethylene, methyl bromide, and hydrofluorocarbons such as Freon 11, Freon 12, Freon 225, decafluoropentane, and ethyl nonafluorobutyl ether. Organic solvents other than those listed here may also be treated.

[0020] [Embodiment 1: Organic Solvent Recovery System 1000] An organic solvent recovery system 1000 according to this embodiment will be described with reference to Figures 1 and 2. Figure 1 is a diagram showing the configuration of the organic solvent recovery system 1000, and Figure 2 is a cross-sectional view taken along line II-II in Figure 1.

[0021] The organic solvent recovery system 1000 includes a recovery device 1, a dehydration device 2, and a return device 3. The detailed configuration of each of these devices will be described below.

[0022] (Recovery Apparatus 1) The recovery apparatus 1 includes a first treatment tank 104A and a second treatment tank 104B. The first treatment tank 104A includes a cylindrical first adsorbent 105A, and the second treatment tank 104B includes a cylindrical second adsorbent 105B. The gas A to be treated passes through the first adsorbent 105A and the second adsorbent 105B from the outside to the inside to perform an adsorption process, and water vapor passes through the first adsorbent 105A and the second adsorbent 105B from the inside to the outside to perform a desorption process. For example, ACF is used for the first adsorbent 105A and the second adsorbent 105B.

[0023] The first treatment tank 104A and the second treatment tank 104B are connected to the treated gas inlet line 103 and the desorption gas line 110. To open and close communication with the treated gas inlet line 103 and the desorption gas line 110, the first treatment tank 104A and the second treatment tank 104B are provided with a first automatic lower damper 107A and a second automatic lower damper 107B, respectively.

[0024] A first automatic upper damper 106A and a second automatic upper damper 106B for controlling the flow of the gas A to be treated are provided above the first treatment tank 104A and the second treatment tank 104B, respectively.

[0025] A condenser 111 is connected to the desorption gas line 110. The condenser 111 has a condenser inlet 111B to which the desorption gas line 110 is connected and a condenser outlet 111C to which the desorbed liquid line 112 is connected. The condenser 111 contains a cooling water pipe 111A having a cooling water inlet 111E and a cooling water outlet 111F.

[0026] A separator 113 is connected to a desorption liquid line 112 connected to the condenser outlet 111C. The separator 113 separates the desorption liquid sent from the desorption liquid line 112 into a layer of separated water 113A and a layer of recovered solvent 113B. The separated water 113A may be aerated in an aeration device and then discharged (see the aeration device 800 of the organic solvent recovery system 1000D in FIG. 6 ).

[0027] Here, the configuration of aerating the separated water 113A in the aeration device and then discharging the separated water 113A refers to, for example, aerating the separated water 113A while heating it to vaporize and remove the organic solvent in the separated water 113A. By combining this with the organic solvent recovery system 1000 of the present embodiment, the organic solvent in the separated water 113A can be removed and purified.

[0028] Since the gas A to be treated contains an organic solvent that is poorly soluble in water and has a higher specific gravity than water, recovered solvent 113B accumulates in the lower layer and separated water 113A accumulates in the upper layer inside separator 113. As a result, recovered solvent 113B is covered by separated water 113A, preventing the recovered solvent 113B from volatilizing outside the system. A recovered solvent level monitor 115 is provided inside separator 113 to detect the liquid level of the layer of recovered solvent 113B.

[0029] A return gas line 114 is connected to the return gas outlet 111D of the condenser 111 and the gas phase region 113D of the separator 113. The return gas line 114 is introduced into the gas line 101 to be treated. The gas returned from the return gas line 114 to the gas line 101 to be treated is preferably introduced so as to form a counterflow with respect to the flow direction of the gas A to be treated.

[0030] A treated gas blower 102 is provided on the treated gas line 101. The treated gas A delivered by the treated gas blower 102 is sent through a treated gas introduction line 103 to a first treatment tank 104A and a second treatment tank 104B.

[0031] Steam C is supplied to the first treatment tank 104A and the second treatment tank 104B through a steam line 108. The first treatment tank 104A is connected to the steam line 108, which is provided with a first steam on-off valve 109A. The second treatment tank 104B is connected to the steam line 108, which is provided with a second steam on-off valve 109B.

[0032] In the recovery apparatus 1 having the above-described configuration, the operation and opening / closing of the first automatic upper damper 106A, the second automatic upper damper 106B, the first automatic lower damper 107A, the second automatic lower damper 107B, the first steam on-off valve 109A, the second steam on-off valve 109B, the condenser 111, the separator 113, the recovered solvent liquid level monitoring device 115, and the treated gas blower 102 are appropriately controlled by a control device (not shown) so as to realize the gas treatment method described below.

[0033] (Gas Treatment Method) A description will be given of a gas treatment method using the recovery apparatus 1 having the above configuration. In Fig. 1, the first treatment tank 104A of the recovery apparatus 1 performs a desorption process, and the second treatment tank 104B performs an adsorption process.

[0034] (Adsorption step in second treatment tank 104B) The treated gas A containing an organic solvent-containing gas is sent from the treated gas line 101 to the second treatment tank 104B, which is undergoing an adsorption step, by the treated gas blower 102. The second automatic lower damper 107B is controlled to open the treated gas inlet line 103 and close the desorption gas line 110.

[0035] The second automatic upper damper 106B is controlled to an open state that allows the gas A to flow through the second adsorbent 105B.

[0036] The gas is adsorbed in the second adsorbent 105B of the second treatment tank 104B, and the resulting gas is discharged to the outside of the system as purified gas B. The second steam on-off valve 109B of the water vapor line 108 is controlled to be in a closed state.

[0037] (Desorption step in first treatment tank 104A) No gas A to be treated is sent to the first treatment tank 104A, and the first automatic lower damper 107A controls the gas to be treated introduction line 103 to be closed and the desorption gas line 110 to be open. The first automatic lower damper 107A blocks gas flow from the outside to the inside of the first adsorbent 105A. Water vapor C to be desorbed is introduced through the water vapor line 108 to allow flow from the inside to the outside of the first adsorbent 105A. The first water vapor on-off valve 109A of the water vapor line 108 is controlled to be open.

[0038] In the first treatment tank 104A, water vapor is ejected, and the organic solvent adsorbed by the first adsorbent 105A is desorbed from the first adsorbent 105A. A desorption gas G containing the desorbed organic solvent is sent to a condenser 111 through a desorption gas line 110.

[0039] The desorbed gas G and water vapor C are condensed in a condenser 111. A desorbed liquid H containing a high concentration of organic solvent is sent to a separator 113 through a desorbed liquid line 112. The desorbed liquid H is separated into a layer of separated water 113A and a layer of recovered solvent 113B in the separator 113. As described above, inside the separator 113, the recovered solvent 113B accumulates in the lower layer, and the separated water 113A accumulates in the upper layer.

[0040] The return gas J remaining in the condenser 111 and the separator 113 is pushed out by the desorbed gas G and introduced into the treated gas line 101 through the return gas line 114, where it is mixed with the treated gas A. The treated gas A and the return gas J introduced from the treated gas line 101 are sent to the second treatment tank 104B.

[0041] The above steps are repeated, and the recovered solvent 113B is sent to the dehydrator 2 through the recovered solvent line 210 connected to the layer of the recovered solvent 113B in the separator 113.

[0042] After a certain time has passed, the adsorption process and the desorption process are switched over, with the first treatment tank 104A performing the adsorption process and the second treatment tank 104B performing the desorption process. In this way, the recovery device 1 continuously recovers the recovered solvent 113B through a continuous process in which the adsorption process and the desorption process are alternately performed.

[0043] (Dehydrator 2) Next, in the dehydrator 2, the recovered solvent 113B recovered in the recovery apparatus 1 is dehydrated. The configuration of the dehydrator 2 will be described below. The dehydrator 2 includes a dehydrating material 202 that comes into contact with the recovered solvent 113B separated by the separator 113 to adsorb moisture contained in the recovered solvent 113B, and a dehydration treatment tank 203 that stores the dehydrating material 202. For example, zeolite or the like is used as the dehydrating material 202. Activated alumina, ion exchange resin, activated carbon, or the like may also be used.

[0044] The separator 113 and the dehydration treatment tank 203 are connected by a recovered solvent line 210. One end of the recovered solvent line 210 is connected to a tank for recovered solvent 113B separated by the separator 113. The other end of the recovered solvent line 210 is connected to the lower end of the dehydration treatment tank 203.

[0045] A pump 201 is provided in a midstream region of the recovered solvent line 210. The pump 201 sends the recovered solvent 113B to a dehydration treatment tank 203. A check valve 205 is provided in the recovered solvent line 210 downstream of the pump 201. The check valve 205 prevents the recovered solvent 113B from flowing back from the dehydration treatment tank 203 toward the pump 201.

[0046] A dehydrating solvent discharge line 113C is provided above the dehydration treatment tank 203. A dehydrating solvent valve 401 is provided on the dehydrating solvent discharge line 113C. Furthermore, a flow rate control valve 402 capable of introducing a predetermined gas is connected to the dehydrating solvent valve 401. The operation and opening / closing of the pump 201, the dehydrating solvent valve 401, and the flow rate control valve 402 are appropriately controlled by a control device (not shown) so as to achieve the dehydration treatment described below.

[0047] (Dehydration Treatment) The recovered solvent 113B fed from the lower side of the dehydration treatment tank 203 by operation of the pump 201 is dehydrated by contact with the dehydrating material 202 and is discharged to the outside of the system through the dehydration solvent discharge line 113C as the dehydration solvent E. At least the recovered solvent line 210, the pump 201, the dehydration, and the dehydration solvent discharge line 113C constitute a discharge mechanism that discharges the dehydration solvent E from the dehydration treatment tank 203.

[0048] (Returning Device 3) When the dehydration device 2 stops, or when the organic solvent load in the gas to be treated is lower than designed, the recovered solvent 113B continues to remain in the dehydration treatment tank 203 for a long time. At this time, water is desorbed from the dehydrating material 202 in the dehydration treatment tank 203, returning water to the recovered solvent 113B, and when the dehydration device 2 is restarted, there is a risk that dehydrated solvent E from which water has been insufficiently removed will be discharged. Furthermore, there is a risk that the organic solvent contained in the dehydration treatment tank 203 will volatilize through the piping outlet of the dehydration device 2, thereby reducing the amount of organic solvent recovered.

[0049] Therefore, when the dehydration device 2 stops or when the organic solvent load in the gas to be treated is lower than designed, the return device 3 operates to return the recovered solvent 113B in the dehydration treatment tank 203 to the separator 113. Specifically, the return device 3 is configured to return the recovered solvent 113B to the layer of recovered solvent 113B in the separator 113.

[0050] 2, a partition plate 116 is provided inside the separator 113 of this embodiment. The partition plate 116 defines an independent space with its upper and lower ends open to the internal space of the separator 113. The lower end of the partition plate 116 reaches the tank for the recovered solvent 113B. The upper end of the partition plate 116 is configured to be open to the gas phase region 113D. When operating the organic solvent recovery system 1000, it is necessary to store a predetermined amount of recovered solvent 113B in advance inside the separator 113 to a height that exceeds the lower end of the partition plate 116.

[0051] 1 , a return line 301 branching off from the recovered solvent line 210 is provided downstream of the check valve 205 of the recovered solvent line 210 that communicates with the dehydration treatment tank 203. This return line 301 is a flow path that discharges the recovered solvent 113B out of the dehydration treatment tank 203 and returns the recovered solvent 113B to the separator 113 when the dehydration device 2 stops supplying the recovered solvent 113B to the dehydration treatment tank 203, for example. An open / close valve 302 is provided in the return line 301.

[0052] The operation and opening / closing of the on-off valve 302, the dehydration solvent valve 401, and the flow rate control valve 402 are appropriately controlled by a control device (not shown) so as to realize the return process of the recovered solvent 113B in the dehydration treatment tank 203 to the separator 113 as described below.

[0053] (Returning Process of Recovered Solvent 113B) When the recovered solvent 113B is to be discharged outside the dehydration treatment tank 203, the on-off valve 302 is opened, the dehydration solvent valve 401 is closed, and a predetermined gas is introduced through the flow rate adjustment valve 402. This increases the internal pressure of the dehydration treatment tank 203, and the recovered solvent 113B remaining inside the dehydration treatment tank 203 can be returned to the separator 113.

[0054] Here, the predetermined gas may be outside air, but it is also preferable to use, for example, the gas to be treated A or the clean gas B. Furthermore, by controlling the amount and speed of these gases fed using the flow rate control valve 402, it is possible to avoid introducing the gas all at once and to introduce the gas gradually. This makes it possible to adjust the amount and speed of the recovered solvent 113B fed back to the separator 113. As a result, the organic solvent contained in the gas to be treated A can be efficiently recovered. This is particularly economical when the organic solvent is expensive.

[0055] The recovered solvent 113B returned to the separator 113 is sent to a space separated by a partition plate 116 within the separator 113. As a result, the recovered solvent 113B returned to the separator 113 is directly returned to the layer of recovered solvent 113B within the separator 113. Therefore, the recovered solvent 113B is not mixed again with the separated water 113A.

[0056] As described above, according to the organic solvent recovery system 1000 of this embodiment, when the dehydration device 2 stops or when the organic solvent load amount in the gas A to be treated is lower than designed, in order to prevent the recovered solvent 113B from remaining in the dehydration treatment tank 203 for a long period of time, operation control is performed to return the recovered solvent 113B in the dehydration treatment tank 203 to the separator 113 as described above.

[0057] This makes it possible to discharge the dehydrated solvent E, from which water has been sufficiently removed, outside the organic solvent recovery system 1000, even when the dehydration device 2 is restarted. Furthermore, it is possible to prevent the organic solvent contained in the dehydration treatment tank 203 from volatilizing through the piping outlet of the dehydration device 2. As a result, improvement in the recovery of organic solvent can be expected for the organic solvent recovery system 1000 as a whole.

[0058] When the dehydration device 2 is stopped (the pump 201 is stopped), the recovered solvent 113B can be prevented from remaining in the dehydration treatment tank 203 for a long period of time by fully closing the inlet and outlet of the dehydration treatment tank 203 using a valve or the like. However, if a portion of the recovered solvent 113B volatilizes in the dehydration treatment tank 203 due to the outside air temperature or the like, the internal pressure may increase. Furthermore, if the recovered solvent 113B is kept in the dehydration treatment tank 203 for a long period of time, the dehydrated water may be desorbed from the dehydration material 202. Therefore, as shown in the above embodiment, it is preferable to perform operation control such that the recovered solvent 113B in the dehydration treatment tank 203 is returned to the separator 113.

[0059] In addition, a configuration may be adopted that includes a temperature control means for adjusting the recovered solvent 113B contained inside one or more of the separator 113, the dehydration device 2, the return device 3, and the dehydration treatment tank 203 to a predetermined temperature.

[0060] [Embodiment 2: Organic Solvent Recovery System 1000A] An organic solvent recovery system 1000A according to this embodiment will be described with reference to Fig. 3. Fig. 3 is a diagram showing the configuration of the organic solvent recovery system 1000A.

[0061] The basic configuration of the organic solvent recovery system 1000A is the same as that of the organic solvent recovery system 1000 described in the first embodiment. The difference lies in the configuration of the dehydration device 2. In the dehydration device 2 of this embodiment, a recovered solvent line 210 is connected to the upper side of the dehydration treatment tank 203, and a dehydrated solvent discharge line 113C is connected to the lower side of the dehydration treatment tank 203. Therefore, the recovered solvent 113B flows from above downward.

[0062] This configuration also provides the same effects as those of the organic solvent recovery system 1000 in the first embodiment.

[0063] [Embodiment 3: Organic Solvent Recovery System 1000B] An organic solvent recovery system 1000B according to this embodiment will be described with reference to Fig. 4. Fig. 4 is a diagram showing the configuration of the organic solvent recovery system 1000B.

[0064] The basic configuration of the organic solvent recovery system 1000B is the same as that of the organic solvent recovery system 1000 described in the first embodiment. The difference lies in the configuration of the separator 113. The separator 113 in this embodiment is not provided with the partition plate 116, and is directly connected to the tank of the recovered solvent 113B of the separator 113.

[0065] This configuration also provides the same effects as those of the organic solvent recovery system 1000 in the first embodiment.

[0066] [Embodiment 4: Organic Solvent Recovery System 1000C] An organic solvent recovery system 1000C according to this embodiment will be described with reference to Fig. 5. Fig. 5 is a diagram showing the configuration of the organic solvent recovery system 1000C.

[0067] The basic configuration of organic solvent recovery system 1000C is the same as that of organic solvent recovery system 1000 described in the first embodiment. The difference is that first dehydration treatment tank 203A and second dehydration treatment tank 203B are provided as dehydration treatment tanks in the configuration of dehydration device 2. By operating one dehydration treatment tank while the other dehydration treatment tank is operating, dehydration device 2 can be operated continuously.

[0068] This configuration also provides the same effects as those of the organic solvent recovery system 1000 in the first embodiment.

[0069] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims.

[0070] In the recovery device 1 disclosed above, the organic solvent recovery process is described as using the first treatment tank 104A and the second treatment tank 104B as treatment tanks and alternately performing the adsorption process and the desorption process, but the recovery process is not limited to using these two treatment tanks.

[0071] For example, as shown in Figure 7, as a modification of the organic solvent recovery system 1000 of the first embodiment, an organic solvent recovery system 1000E as disclosed in Japanese Patent Application Laid-Open No. 2014-147863 may be employed, which employs three treatment tanks: a first treatment tank 104A, a second treatment tank 104B, and a third treatment tank 104C, with one of the treatment tanks performing the desorption step and the remaining treatment tanks connected in series in multiple stages to perform the adsorption step. In Figure 7, the dehydrator 2, the return device 3, the condenser 111, and the separator 113 are not shown. Note that the number of treatment tanks may be three or more. This can further increase the organic solvent recovery efficiency.

[0072] 1 Recovery device, 2 Dehydration device, 3 Return device, 101 Treated gas line, 102 Treated gas blower, 103 Treated gas introduction line, 104A First treatment tank, 104B Second treatment tank, 104C Third treatment tank, 105A First adsorbent, 105B Second adsorbent, 105C Third adsorbent, 106A First automatic upper damper, 106B Second automatic upper damper, 106C Third automatic upper damper, 107A First automatic lower damper, 107B Second automatic lower damper, 107C Third automatic lower damper, 108 Water vapor line, 109A First water vapor on-off valve, 109B Second steam on-off valve, 110 Desorption gas line, 111 Condenser, 111A Cooling water piping, 111B Condenser inlet, 111C Condenser outlet, 111D Gas outlet, 111E cooling water inlet, 111F cooling water outlet, 112 desorption liquid line, 113 separator, 113A separated water, 113B recovered solvent, 113C dehydrated solvent discharge line, 113D gas phase region, 114 gas line, 115 recovered solvent liquid level monitor, 116 partition plate, 201 pump, 202 dehydration material, 203 dehydration treatment tank, 203A first dehydration treatment tank, 203B second dehydration treatment tank, 205 check valve, 210 recovered solvent line, 301 return line, 302 on / off valve, 401 dehydrated solvent valve, 402 flow rate adjustment valve, 800 aeration tank, 1000, 1000A, 1000B, 1000C organic solvent recovery system, A treated gas, B cleaned gas, C water vapor, E Dehydrated solvent, G desorbed gas, H desorbed liquid, J return gas.

Claims

1. An organic solvent recovery system comprising a recovery device, a dehydration device, and a return device, wherein the recovery device comprises: an adsorbent that adsorbs an organic solvent that is poorly soluble in water and has a specific gravity greater than that of water upon contact with a gas to be treated containing the organic solvent, and desorbs the organic solvent upon contact with water vapor; two or more treatment tanks containing the adsorbent; an adsorption step in which the gas to be treated is supplied to the treatment tank, the organic solvent is adsorbed and removed by the adsorbent, and a clean gas is discharged; a desorption step in which water vapor is supplied to the treatment tank, the recovered solvent is desorbed from the adsorbent, and a desorbed gas is discharged; a step of sequentially repeating the adsorption step and the desorption step for two or more treatment tanks; a condenser that cools and condenses the desorbed gas and discharges a desorbed liquid; and a separator that separates the desorbed liquid into a layer of separated water and a layer of the recovered solvent, and the dehydration device comprises: a dehydrator that adsorbs water contained in the recovered solvent upon contact with the recovered solvent, an organic solvent recovery system comprising: one or more dehydration treatment tanks containing the dehydrating material; and a discharge mechanism that supplies the recovered solvent separated by the separator to the dehydration treatment tank and discharges the dehydrated solvent dehydrated from the recovered solvent by the dehydrating material from the dehydration treatment tank, wherein the return device sends the recovered solvent to a layer of the recovered solvent in the separator when returning the recovered solvent in the dehydration treatment tank to the separator.

2. The organic solvent recovery system according to claim 1, wherein the return device has a return flow path that discharges the recovered solvent out of the dehydration treatment tank and returns the recovered solvent to the separator when the dehydration device stops supplying the recovered solvent to the dehydration treatment tank.

3. The organic solvent recovery system according to claim 2, wherein the dehydration device includes a speed adjusting device for adjusting the speed at which the recovered solvent is returned to the separator.

4. An organic solvent recovery system as described in claim 3, wherein the speed adjusting device uses a portion of the treated gas or the clean gas to pressurize the inside of the dehydration treatment tank and discharge the recovered solvent outside the dehydration treatment tank.

5. An organic solvent recovery system as described in any one of claims 1 to 4, having three or more treatment tanks, one of which performs the desorption process, and the remaining treatment tanks are connected in series in multiple stages and perform the adsorption process.

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