JP2011177695A - Method for producing pervaporation membrane, pervaporation membrane and organic solvent recovery system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pervaporation membrane which can suppress production of byproducts and to provide a method for producing the pervaporation membrane. <P>SOLUTION: The pervaporation membrane is used for separating water from an organic solvent, is made of a carbon membrane and respective contents of specific impurity elements contained in the carbon membrane are 100 ppm or less. The method for producing the pervaporation membrane made of the carbon membrane comprises a process of film-making a carbon precursor, a process of heating the film-made carbon precursor to perform infusibilizing treatment to give thermal stability, a process of heating the thermally stabilized carbon precursor in an inert atmosphere to perform carbonization treatment to form the carbon membrane, a process of washing the carbon membrane with an acid and a process of washing the pickled carbon membrane with water and then drying the carbon membrane. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a pervaporation membrane used for separating an organic solvent and water, a method for producing the permeation vaporization membrane, and an organic solvent recovery system in which the permeation vaporization membrane is incorporated.

  Conventionally, there has been known an organic solvent recovery system that removes the organic solvent from the gas to be processed containing the organic solvent, purifies and discharges the gas to be processed, and concentrates and recovers the removed organic solvent to a high concentration. ing. The organic solvent recovery system is widely used for the treatment of industrial exhaust gas discharged from various factories, research facilities, etc., and the recovered organic solvent is generally reused from the viewpoint of economy and environment. It is.

  This type of organic solvent recovery system generally contains a high-concentration organic solvent by bringing the gas to be treated into contact with the adsorbent material to adsorb the organic solvent, and blowing high-temperature heating gas onto it to desorb the organic solvent. An adsorption / desorption treatment device that discharges as a desorption gas, and a desorption gas containing a high-concentration organic solvent discharged from the adsorption / desorption treatment device is condensed and separated in a separation tank so that water is a main component. And a condensing / recovering device that collects a liquid containing a high concentration organic solvent as a recovered liquid (for example, (See Japanese Utility Model Publication No. 7-2028 (Patent Document 1), Japanese Utility Model Publication No. 7-2029 (Patent Document 2), Japanese Utility Model Publication No. 7-2030 (Patent Document 3), etc.).

  In the recovery liquid mainly composed of the organic solvent recovered by using the organic solvent recovery system, in addition to the organic solvent, water or organic solvent derived from a heating gas such as water vapor used for desorption treatment is usually used. Decomposed products are included. Therefore, in general, the recovered liquid is separated by performing a distillation treatment in a distillation column using the boiling point difference of each component contained, thereby purifying the organic solvent. In many cases, the recovery liquid containing an organic solvent, water and a trace component dissolved in these is an azeotropic mixture, and the distillation treatment requires an azeotropic distillation operation.

  However, the distillation process using a distillation tower is not preferable as equipment attached to an organic solvent recovery system because it requires not only high capital investment but increases initial cost and also increases the installation area of the equipment. . In addition, the facility requires enormous energy for its operation, which increases running costs and causes air pollution, which is not preferable from the viewpoint of environmental conservation.

  From such a viewpoint, a membrane separation process based on a pervaporation separation method (pervaporation method) has attracted attention as a purification method that replaces the distillation treatment using a distillation column. The pervaporation separation method is a separation method suitable for separating an azeotropic mixture, and can be suitably used for separation of an organic solvent and water. Here, as a separation membrane used for the membrane separation treatment, a permeation vaporization membrane composed of a carbon membrane, a zeolite membrane as an inorganic membrane, a polysulfone membrane as a polymer membrane, a silicon membrane, a polyamide membrane, a polyimide membrane, or the like. Can be mentioned.

  As an organic solvent recovery system provided with a membrane separation apparatus based on such a pervaporation separation method, there is one disclosed in, for example, Japanese Patent Application Laid-Open No. 2009-66530 (Patent Document 4). The organic solvent recovery system disclosed in Patent Document 4 has a configuration in which a membrane separation device based on a pervaporation separation method is further added to the downstream side of the condensation recovery device of the conventional organic solvent recovery system described above, The liquid containing the high-concentration organic solvent recovered by the condensation recovery apparatus is further introduced into the membrane separation apparatus based on the pervaporation separation method, and water is further added from the liquid containing the high-concentration organic solvent. By separating and removing the organic solvent, the organic solvent is purified.

Japanese Utility Model Publication No. 7-2028 Japanese Utility Model Publication No. 7-2029 Japanese Utility Model Publication No. 7-2030 JP 2009-66530 A

  By the way, in the organic solvent recovery system equipped with the adsorption / desorption processing apparatus as described above, when a gas to be processed containing a component that generates an acid by reacting with water is processed, the component is converted into the gas to be processed. Acid is generated by reacting with water vapor contained therein, water vapor contained in the heating gas introduced in the adsorption / desorption treatment apparatus described above, or water after the water vapor has condensed. For example, when the gas to be treated contains an acetate ester, a hydrolysis reaction takes place, so that a portion of the acetate ester is decomposed to generate acetic acid.

  Here, when the organic solvent recovery system is equipped with a membrane separation device based on the above-described pervaporation separation method, a concentrated liquid containing an acid generated by reacting with water is introduced into the membrane separation device. It will be. As described above, any of the carbon membrane, the inorganic membrane and the polymer membrane is used as the pervaporation membrane provided in the membrane separation device, but the introduced concentrated liquid contains an acid. Considering this, it is not preferable to use an inorganic film that is weak against acid or a polymer film that swells when contacted with a concentrated liquid, and it can be said that the use of a carbon film is particularly preferable.

  However, the carbon film may contain a large amount of impurity elements derived from the raw material itself or processing in its manufacturing process. Examples of the impurity element include alkali metals and alkaline earth metals, but when a carbon film containing a large amount of the impurity element is used as a separation film, the impurity element decomposes the organic solvent and causes a side reaction. There is a problem that an object is generated. When such a problem occurs, the side reaction product is contained in the recovered liquid, resulting in a problem that the yield is lowered, and the reuse of the recovered liquid is hindered.

  Accordingly, the present invention has been made to solve the above-mentioned problems, and its object is to provide a pervaporation membrane capable of suppressing the formation of by-products, a method for producing the same, and an organic An object of the present invention is to provide an organic solvent recovery system capable of recovering a solvent in high concentration and high yield.

  The method for producing a pervaporation membrane based on the present invention is a method for producing a permeation vaporization membrane comprising a carbon membrane, which is used for separating an organic solvent and water, and forms a carbon precursor into a membrane. A carbonization treatment by heating the carbon precursor that has been heat-stabilized in a inert atmosphere, and a step of heat-stabilizing the carbon precursor by heating the film-precipitated carbon precursor. Forming a carbon film, washing the carbon film with an acid, and washing the carbon film washed with the acid, followed by drying.

  In the method for producing a pervaporation membrane based on the present invention, in the step of forming the carbon precursor into a membrane, the membrane having a hollow membrane structure is obtained by attaching the carbon precursor to the surface of the porous support. It is preferable to do.

  In the method for producing a pervaporation membrane based on the present invention, the carbon precursor is formed into a film using any one of a wet method, a dry method, and a dry and wet method in the step of forming the carbon precursor into a film. It is good also as a film | membrane which has a hollow fiber structure by this.

  In the method for producing a pervaporation membrane based on the present invention, hydrochloric acid is preferably used as the cleaning acid in the step of cleaning the carbon membrane using an acid.

  The pervaporation membrane according to the present invention is a permeation vaporization membrane made of a carbon membrane used to separate an organic solvent and water, and is a group 1 element as an impurity element contained in the carbon membrane (Li, Na, K, Rb, Cs, Fr), Group 2 elements (Be, Mg, Ca, Sr, Ba, Ra), Group 12 elements (Zn, Cd, Hg), Group 17 elements (F , Cl, Br, I, At), phosphorus (P), sulfur (S) and transition elements such as chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), The content of each element of copper (Cu) is 100 ppm or less in a state before the pervaporation process is started.

  In the pervaporation membrane based on the present invention, the carbon membrane preferably has a hollow membrane structure or a hollow fiber structure.

  An organic solvent recovery system according to the present invention recovers an organic solvent from a gas to be treated containing an organic solvent, and includes an adsorption / desorption treatment device, a condensate / separation device, and a membrane separation device. The adsorption / desorption treatment apparatus includes an adsorption element that adsorbs an organic solvent by contacting a gas to be treated and desorbs the adsorbed organic solvent by contacting a heated gas, and supplies the gas to be treated to the adsorption element. Then, the organic solvent is adsorbed on the adsorption element and discharged as a processing gas. By supplying a heating gas to the adsorption element, the organic solvent is desorbed from the adsorption element and discharged as a desorption gas containing the organic solvent. Is. The condensing / separating apparatus condenses by cooling the desorption gas discharged from the adsorption / desorption treatment apparatus, and separates the condensed liquid based on the difference in specific gravity, thereby concentrating liquid and water containing an organic solvent. Is separated into a separation liquid containing as a main component. The membrane separation device includes a pervaporation membrane that selectively permeates and separates water contained in the concentrate by contacting the concentrate, and the permeate vaporizes the concentrate discharged from the condensate separator. By supplying it to the membrane, it is separated into a recovered liquid containing an organic solvent at a high concentration and a permeated liquid containing water as a main component. Here, the pervaporation film is made of a carbon film, and includes Group 1 elements (Li, Na, K, Rb, Cs, Fr) and Group 2 elements (Be as impurity elements contained in the carbon film. Mg, Ca, Sr, Ba, Ra), Group 12 elements (Zn, Cd, Hg), Group 17 elements (F, Cl, Br, I, At), phosphorus (P), sulfur (S) and Among the transition elements, the content of each element of chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu) is before the pervaporation process is started. In this state, it is 100 ppm or less.

  In the organic solvent recovery system according to the present invention, it is preferable that the pervaporation membrane has a hollow membrane structure or a hollow fiber structure.

  In the organic solvent recovery system according to the present invention, the adsorbing element is preferably an activated carbon fiber.

  In the organic solvent recovery system according to the present invention, the heating gas is preferably water vapor.

  The organic solvent recovery system according to the present invention is particularly preferably used when the gas to be treated includes a component that generates an acid by reacting with water. Here, as a component which generates an acid by reacting with water, for example, an acetate ester or a basic compound is raised.

  According to the present invention, it is possible to provide a pervaporation membrane that can suppress the formation of by-products, and by using the organic solvent recovery system that includes the pervaporation membrane, the organic solvent can be produced in a high concentration and high yield. It becomes possible to collect.

It is a system configuration figure of an organic solvent recovery system in an embodiment of the invention. It is a schematic cross section of the membrane separation apparatus with which the organic solvent collection | recovery system in embodiment of this invention is equipped. It is a flowchart which shows an example of the manufacturing method of the pervaporation film | membrane in embodiment of this invention. It is a flowchart which shows the other example of the manufacturing method of the pervaporation film | membrane in embodiment of this invention. It is a table | surface which shows the result of having confirmed experimentally the content of the impurity element contained in each step of a manufacture process of the pervaporation membrane which has the hollow membrane structure manufactured according to the flow shown in FIG. It is a table | surface which shows the result of a verification test.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In the following embodiments, an organic solvent recovery system provided with an osmosis vaporization membrane according to the present invention will be described prior to the description of the osmosis vaporization membrane and the manufacturing method thereof according to the present invention.

  FIG. 1 is a system configuration diagram of an organic solvent recovery system according to an embodiment of the present invention, and FIG. 2 is a schematic cross-sectional view of the membrane separation apparatus shown in FIG. First, with reference to these FIG. 1 and FIG. 2, the structure of the organic solvent collection | recovery system in this Embodiment is demonstrated.

  As shown in FIG. 1, the organic solvent recovery system 1 in the present embodiment includes an adsorption / desorption treatment device 100, a condensate / separation device 200, and a separation / recovery device 300. The organic solvent recovery system 1 in the present embodiment treats the gas to be processed by removing the organic solvent from the gas to be processed containing the organic solvent, and purifies and recovers the removed organic solvent. . Examples of gas to be treated containing an organic solvent to be treated include those containing acid, those containing no acid, but containing a component that generates acid by reacting with water (for example, acetate ester, basic compound, etc.), etc. Is mentioned.

  The adsorption / desorption treatment apparatus 100 includes a first treatment tank 110 and a second treatment tank 120 in which adsorbents 111 and 121 as adsorption elements are accommodated, respectively. The adsorbents 111 and 121 adsorb the organic solvent contained in the gas to be processed by contacting the gas to be processed. Therefore, in the adsorption / desorption processing apparatus 100, the organic solvent is adsorbed by the adsorbents 111 and 121 by supplying the gas to be treated to the adsorbents 111 and 121, whereby the gas to be treated is cleaned and discharged as the process gas. Will be. The adsorbents 111 and 121 desorb the adsorbed organic solvent by bringing water vapor as a heating gas into contact therewith. Therefore, in the adsorption / desorption processing apparatus 100, by supplying water vapor to the adsorbents 111 and 121, the organic solvent is desorbed from the adsorbents 111 and 121, whereby the water vapor is discharged as a desorption gas containing the organic solvent. become. Note that as the heated gas introduced into the adsorption / desorption treatment apparatus 100 for desorption of the organic solvent, a high-temperature inert gas or the like can be used in addition to water vapor.

  Piping lines L1, L2, L3, and L4 are connected to the first processing tank 110 and the second processing tank 120, respectively. The piping line L1 is a piping line for supplying a gas to be processed containing an organic solvent to the first processing tank 110 and the second processing tank 120, and the first processing tank 110 and the second processing tank by valves V101 and V102. The connection / disconnection state for 120 is switched. The piping line L2 is a piping line for supplying water vapor to the first processing tank 110 and the second processing tank 120, and is connected / disconnected to the first processing tank 110 and the second processing tank 120 by valves V103 and V104. Is switched. The piping line L3 is a piping for discharging the processing gas from the first processing tank 110 and the second processing tank 120, and is connected / disconnected to the first processing tank 110 and the second processing tank 120 by valves V105 and V106. Is switched. The piping line L4 is a piping line for discharging desorption gas from the first processing tank 110 and the second processing tank 120, and is connected / disconnected to the first processing tank 110 and the second processing tank 120 by valves V101 and V102. The state is switched.

  The first treatment tank 110 and the second treatment tank 120 function alternately as an adsorption tank and a desorption tank by operating the above-described opening and closing of the valves V101 to V106. Specifically, the first treatment tank 110 is adsorbed. When functioning as a tank, the second processing tank 120 functions as a desorption tank, and when the first processing tank 110 functions as a desorption tank, the second processing tank 120 functions as an adsorption tank. . That is, the adsorption / desorption processing apparatus 100 according to the present embodiment is configured such that the adsorption tank and the desorption tank are alternately switched over time. The piping line L1 is connected to a tank functioning as an adsorption tank among the first processing tank 110 and the second processing tank 120 and supplies a gas to be processed to the adsorption tank. Among the 1 treatment tank 110 and the 2nd treatment tank 120, it connects with the tank which is functioning as a desorption tank, and supplies water vapor | steam to the said desorption tank. The piping line L3 is connected to a tank functioning as an adsorption tank among the first processing tank 110 and the second processing tank 120 and discharges the processing gas from the adsorption tank. The piping line L4 is connected to the first processing tank 110 and the second processing tank 120. The processing tank 110 and the second processing tank 120 are connected to a tank functioning as a desorption tank and discharge the desorption gas.

  The adsorbents 111 and 121 are made of a member containing at least one of activated carbon, activated carbon fiber, and zeolite. Preferably, the adsorbents 111 and 121 are activated carbon or zeolite in the form of particles, granules or honeycombs, but more preferably activated carbon fibers. Since the activated carbon fiber has a fibrous structure having micropores on the surface, the activated carbon fiber has high contact efficiency with gas and is a member that can realize high adsorption efficiency as compared with other adsorption elements.

  The condensing and separating apparatus 200 includes a condenser 210 and a separation tank 220. The condenser 210 is an apparatus that condenses and liquefies the desorption gas discharged from the adsorption / desorption treatment apparatus 100 using cooling water or the like, and the separation tank 220 divides the liquid obtained by liquefying the desorption gas with a specific gravity difference. Is separated into a concentrated liquid containing an organic solvent at a high concentration and a separating liquid containing water as a main component.

  The condenser 210 is connected to the piping lines L4 and L5, respectively, and the separation tank 220 is connected to the piping lines L5, L6, L7, and L8, respectively. The piping line L4 is a piping line for supplying the desorption gas discharged from the above-described adsorption / desorption processing apparatus 100 to the condenser 210, and the piping line L5 supplies the liquid obtained in the condenser 210 to the separation tank 220. It is a piping line for supplying. The piping line L6 is a piping line for discharging the separation liquid separated in the separation tank 220 from the separation tank 220, and the piping line L7 is a non-condensed gas remaining in the separation tank 220 in an uncondensed state. It is piping returned to the piping line L1. The piping line L8 is a piping line for discharging the concentrated liquid separated in the separation tank 220 from the separation tank 220. The piping line L8 is provided with a valve V107, and the valve V107 switches a connection / disconnection state via the piping line L8 between the separation tank 220 and a buffer tank 310 described later.

  The separation / recovery device 300 includes a buffer tank 310, a preliminary heater 320, a membrane separation device 330, a condenser 340, and a recovery tank 350. The buffer tank 310 is a tank for temporarily storing the concentrated liquid discharged from the condensing / separating apparatus 200, and the auxiliary heater 320 uses the high temperature steam or the like to concentrate the liquid discharged from the buffer tank 310. It is an apparatus for heating as needed. The membrane separation device 330 is a device for selectively permeating and separating water contained in the concentrated liquid based on a so-called pervaporation separation method. The condenser 340 is a device for condensing the permeated component discharged from the membrane separation device 330 using cooling water or the like and discharging it as a permeate, and the recovery tank 350 is a high-pressure device discharged from the membrane separation device 330. It is a tank for storing a liquid containing an organic solvent having a concentration as a recovered liquid.

  The buffer tank 310 is connected to the piping lines L8, L9, L14, and the preliminary heater 320 is provided in the middle of the piping line L9. The membrane separator 330 is connected to the piping lines L9, L10, L12, and L14, respectively. The condenser 340 is connected to the piping lines L10 and L11, respectively, and the recovery tank 350 is connected to the piping lines L12 and L13.

  The piping line L8 is a piping line for supplying the concentrated liquid discharged from the condensing and separating apparatus 200 described above to the buffer tank 310, and the piping line L9 is a membrane separating apparatus for concentrating the liquid stored in the buffer tank 310. This is a piping line for supplying to 330. The piping line L10 is a piping line for supplying the permeated component separated and discharged by the membrane separator 330 to the condenser 340, and the piping line L11 is a permeation obtained by condensing in the condenser 340. It is a piping line for discharging the liquid from the condenser 340. The piping line L12 is a piping line for supplying the recovered liquid separated and discharged by the membrane separator 330 to the recovery tank 350, and the piping line L13 is configured to supply the recovered liquid stored in the recovery tank 350 to the outside. It is a piping line for discharging. The piping line L14 is a piping line for returning the non-permeated liquid separated and discharged by the membrane separation device 330 to the buffer tank 310. In addition, the valve V108 is provided in the piping line L12, and the valve V108 switches the connection / disconnection state between the membrane separator 330 and the recovery tank 350 via the piping line L12. In addition, a valve V109 is provided in the piping line L14, and the valve V109 switches a connection / disconnection state between the membrane separation device 330 and the buffer tank 310 via the piping line L14. The membrane separation device 330 may be constituted by a single unit as shown in the figure, but may be constituted by arranging a plurality of units in parallel or in series.

  As shown in FIG. 2, the membrane separation device 330 includes a shell 331 serving as an outer shell, a tube element 332 accommodated in the shell 331, and a suction pipe connected so as to communicate with the hollow interior of the tube element 332. 334. The tube element 332 includes a porous support 332a as a base material and a pervaporation membrane 332b that covers the outer peripheral surface of the porous support 332a. Here, the pervaporation membrane 332b is a membrane that selectively permeates water contained in the concentrated liquid by contacting the concentrated liquid and separates it from other components contained in the concentrated liquid. In the organic solvent recovery system 1 according to the present embodiment, a carbon membrane is used as the pervaporation membrane 332b, and details thereof will be described later.

  The shell 331 is connected to the piping line L9 and connected to the inlets 335 for introducing the concentrated liquid discharged from the condensing and separating apparatus 200 into the shell 331 and the piping lines L12 and L14. It has an outlet 336 for leading the concentrated liquid after passing through the inside of the shell 331 from the shell 331 as a non-permeate liquid or a recovered liquid. One end of the pervaporation membrane 332b is supported by the support member 333a, and the other end is supported by the support member 333b and connected to the suction pipe 334. The suction pipe 334 is connected to a vacuum pump and a condenser 340 (not shown) by being connected to the piping line L10.

  Next, with reference to FIG. 1, the details of the processing performed in the organic solvent recovery system 1 in the present embodiment will be described. The following description is based on the state in which the first treatment tank 110 of the adsorption / desorption treatment apparatus 100 functions as an adsorption tank and the second treatment tank 120 functions as a desorption tank. The same process is also performed when the desorption tank is replaced.

  As shown in FIG. 1, the gas to be treated is introduced into the adsorption / desorption treatment apparatus 100 via a piping line L1. The introduced gas to be treated is sent to the first treatment tank 110 and comes into contact with the adsorbent 111, and the organic solvent contained in the gas to be treated is adsorbed by the adsorbent 111. The gas after the organic solvent is adsorbed by the adsorbent 111 is introduced into the piping line L3 and discharged from the adsorption / desorption processing apparatus 100 as a processing gas.

  On the other hand, water vapor is introduced into the adsorption / desorption treatment apparatus 100 via the piping line L2 in parallel with the introduction of the gas to be treated. The introduced water vapor is sent to the second treatment tank 120 and comes into contact with the adsorbent 121 to desorb the organic solvent adsorbed on the adsorbent 121. The water vapor containing the organic solvent desorbed from the adsorbent 121 is introduced into the piping line L4 and discharged from the adsorption / desorption processing apparatus 100 as a desorption gas.

  The desorption gas discharged from the adsorption / desorption processing apparatus 100 is sent to the condensing / separating apparatus 200 via the piping line L4. The desorption gas sent to the condensing / separating apparatus 200 is introduced into the condenser 210 and cooled to condense, and the condensed liquid is sent to the separation tank 220 via the piping line L5. The liquid introduced into the separation tank 220 is separated in the separation tank 220 based on the specific gravity difference, and separated into a concentrated liquid containing an organic solvent at a high concentration and a separation liquid containing water as a main component. The separation liquid mainly composed of water is introduced into the piping line L6 and discharged from the condensing / separating apparatus 200, and the concentrated liquid containing the organic solvent at a high concentration is introduced into the piping line L8 by opening the valve V107. And discharged from the condensate / separation apparatus 200. The uncondensed gas remaining in the uncondensed state in the separation tank 220 is returned to the piping line L1 via the piping line L7.

  The concentrate discharged from the condensing / separating apparatus 200 is sent to the separation and recovery apparatus 300 via the piping line L8. The concentrated liquid sent to the separation / recovery device 300 is temporarily stored in the buffer tank 310, and then introduced into the piping line L9 and heated by the preliminary heater 320 as necessary to raise the temperature to a predetermined temperature. Introduced into the membrane separator 330. Here, the reason why the concentrated liquid introduced into the membrane separation device 330 is heated to a predetermined temperature is to increase the separation performance of the pervaporation separation process in the membrane separation device 330 described later, and this makes it efficient. The pervaporation separation process is performed.

  In the membrane separator 330, the concentrated liquid is introduced from the piping line L8 through the introduction port 335 provided in the shell 331, and the introduced concentrated liquid passes through the inside of the shell 331 to the pervaporation membrane 332b. Contact. At this time, due to the action of a vacuum pump (not shown), the water contained in the concentrate passes through the pervaporation membrane 332b, passes through the porous support 332a, and is introduced into the hollow interior of the tube element 332. As a result of the above, it is discharged to the outside of the membrane separation device 330 through the suction pipe 334. The permeated component discharged from the membrane separation device 330 is supplied to the condenser 340 via the piping line L10, and is condensed by being cooled by the condenser 340, and becomes a permeated liquid, via the piping line L11. Discharged. On the other hand, the non-permeated liquid after passing through the inside of the shell 331 is discharged from the outlet 336 provided in the shell 331, is introduced into the piping line L14 by opening the valve V109, and is discharged from the membrane separator 330. The The non-permeated liquid discharged from the membrane separation device 330 is returned to the buffer tank 310 via the piping line L14.

  In the separation and recovery apparatus 300, the above-described operation is continued for a predetermined time. As a result, impurities other than the organic solvent are gradually separated and removed by the membrane separator 330 from the concentrated liquid temporarily stored in the buffer tank 310. Then, after a predetermined time has elapsed, the valve V109 is closed and the valve V108 is opened instead, so that the concentrated liquid discharged from the outlet 336 provided in the shell 331 is introduced into the piping line L12 and collected. The liquid is discharged from the membrane separation device 330 and stored in the recovery tank 350. Thereafter, the recovered liquid stored in the recovery tank 350 is discharged to the outside of the organic solvent recovery system 1 via the piping line L13 when a predetermined amount is stored.

  Next, the details of the pervaporation membrane 332b in the present embodiment described above will be described. As described above, the pervaporation membrane 332b in the present embodiment is made of a carbon membrane. In general, as a pervaporation membrane made of a carbon membrane, a membrane having a hollow membrane structure and a membrane having a hollow fiber structure can be used. Here, the membrane having a hollow membrane structure is a membrane as provided in the tube element described above, and is a non-self-supporting hollow provided so as to coat the surface of the tubular porous support. It means a membrane. On the other hand, a membrane having a hollow fiber structure means a self-supporting hollow membrane having no support.

  Whether the membrane having the above-described hollow membrane structure or the membrane having the above-described hollow fiber structure is used as the pervaporation membrane made of the carbon membrane is appropriately selected based on the processing conditions and the like. Examples of the raw material for the carbon film (namely, the carbon precursor) include acrylic resins, polyimide resins, cellulose resins, polyphenylene oxide resins, polyfurfuryl alcohol, and phenol resins. It is not something.

  Here, the reason why the carbon membrane is used as the pervaporation membrane 332b is a result of considering that the concentrate is a relatively high-temperature liquid and that the acid may be contained in the concentrate slightly. This is because the life of the membrane separation device 330 can be extended by using a carbon membrane having excellent heat resistance and acid resistance. In addition to the carbon membrane, an inorganic membrane or a polymer membrane may be used as the pervaporation membrane 332b. However, when an inorganic membrane is used as the pervaporation membrane 332b, an acid is added to the concentrated liquid to be treated. Therefore, when the polymer membrane is used as the pervaporation membrane 332b, since the treatment target is liquid, the polymer membrane is Swelling causes deformation, and there is a concern that the film may be broken or leaked. Therefore, their use should be avoided.

  Further, when the above-described membrane having the hollow fiber structure is used as the pervaporation membrane 332b, the surface area per unit volume of the pervaporation membrane can be increased. The membrane separation device 330 can be reduced in size, cost, and energy can be reduced.

  Usually, the carbon film contains a large amount of impurity elements derived from the raw material itself and the processing in its manufacturing process. Examples of the impurity element include a group 1 element (lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), francium (Fr)), a group 2 element (beryllium). (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), radium (Ra)), group 12 elements (zinc (Zn), cadmium (Cd), mercury (Hg)) , Group 17 elements (fluorine (F), chlorine (Cl), bromine (Br), iodine (I), astatine (At)), phosphorus (P), sulfur (S) and transition element chromium (Cr ), Manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu) and the like. When such a pervaporation film made of a carbon film containing a large amount of impurity elements is used, there is a problem in that the impurity elements decompose the organic solvent and produce side reaction products. When such a problem occurs, the side reaction product is contained in the recovered liquid, resulting in a problem that the yield is lowered, and the reuse of the recovered liquid is hindered.

  In particular, ethyl acetate, which is assumed to be treated in the organic solvent recovery system 1 in the present embodiment described above, is hydrolyzed both acidic and basic in all salts having ionicity in the presence of water. Showing gender. Therefore, when the pervaporation film made of a carbon film contains a large amount of the above-mentioned elements as impurity elements, acetic acid and ethanol as by-products are contained in a large amount in the recovered liquid, resulting in a decrease in yield. At the same time, acetic acid odor is generated, causing problems such as deterioration of the workplace environment and acetic acid odor adhering to the product. In particular, a pervaporation membrane made of a carbon membrane is used as an impurity, such as chloride, sulfide, phosphate, hydroxide (chromium (Cr), manganese (Mn), iron (Fe), cobalt ( Co), nickel (Ni), zinc (Zn), etc.), alkalis, and alkaline earth elements require attention from the viewpoint of the hydrolyzability of ethyl acetate described above.

  Therefore, in the membrane separation apparatus 330 of the organic solvent recovery system 1 in the present embodiment, the pervaporation membrane 332b is in a state before the pervaporation treatment is started (that is, before the permeation vaporization membrane 332b is used). In the stage), each of the above-described impurity elements contained in the carbon film is suppressed to 100 ppm or less. More specifically, as the pervaporation film 332b, the carbon film was previously washed with an acid to elute the impurity element, and the content of the impurity element contained thereby was suppressed to 100 ppm or less. I am using it. By using such a pervaporation membrane 332b, it is possible to greatly suppress the occurrence of a problem such as generation of a side reaction product, and the side reaction product is contained in the recovered liquid. We are trying to solve the problem that the rate drops.

  FIG. 3 and FIG. 4 are flowcharts showing an example and another example of the method for producing a pervaporation membrane in the present embodiment. Here, FIG. 3 shows a production flow in the case of producing a membrane having a hollow membrane structure as the pervaporation membrane in the present embodiment, and FIG. 4 shows a hollow fiber as the pervaporation membrane in the present embodiment. The manufacturing flow in the case of manufacturing what has a structure is shown.

  As shown in FIG. 3, when producing a pervaporation membrane having a hollow membrane structure based on the method for producing a pervaporation membrane in the present embodiment, first, a phenol resin, a polyimide precursor resin (by heating or the like) Polyimide)), silicon carbide precursor (organosilicon polymer, polycarbosilane, polymethylsilane, etc.), lignin resin, wood tar, polyvinyl chloride, polyfurfuryl alcohol, acrylic resin, cellulose resin, polyphenylene oxide By immersing the porous support in a carbon precursor such as resin or other thermosetting resin, the carbon precursor is attached to the surface of the porous support in the form of a thin film, thereby forming a hollow membrane made of the carbon precursor. A porous structure including the same is manufactured (step S101). Here, as the porous support, for example, a ceramic porous support such as a porous alumina support can be used.

  Next, the produced porous structure is heated in the air to infusibilize the hollow membrane (step S102). Here, the infusibilization treatment is also referred to as flame resistance treatment or heat stabilization treatment, and is a heat treatment for pre-stabilizing the hollow membrane before performing the carbonization treatment described later. The heat treatment as the infusibilization treatment is performed for about 30 minutes to 300 minutes under a temperature condition of about 180 ° C. to 500 ° C., for example. In addition to the heat treatment described above, various methods such as a method of adding a chemical such as a flame retardant and a method of using the addition of the chemical and heat treatment can be applied to the infusibilization treatment. Some carbon precursor species do not require infusibility treatment itself. Therefore, the infusibilization treatment may be performed by selecting an optimum method from various methods in consideration of the carbon precursor species.

  Next, carbonization is performed by heating the porous structure including the infusible hollow membrane in an inert atmosphere (step S103). Here, the carbonization treatment is a heat treatment for carbonizing the infusible carbon precursor by further heating to form a carbon film. The heat treatment as the carbonization treatment is performed for about 5 minutes to 180 minutes under a temperature condition of about 500 ° C. to 1000 ° C., for example.

  Here, in this manufacturing flow, in order to repair and prevent defects (pinholes, cracks, etc.) that are likely to be formed on the surface of the hollow membrane, the processes from step S101 to step S103 described above are repeated a plurality of times as necessary. You may do it.

  Next, an acid cleaning process is performed by immersing the porous structure including the carbonized hollow membrane in an acid (step S104). Hydrochloric acid is preferably used as the acid used, but is not limited thereto. The acid cleaning treatment is performed, for example, by immersing the porous structure including the hollow membrane in a container in which hydrochloric acid having a concentration of about 1 mol / l is stored at room temperature for about several hours to several tens of hours. Thereby, the impurity element contained in the carbon film is eluted into hydrochloric acid, and the impurity element is removed. In addition, in order to promote the elution of an impurity element, it is good also as stirring hydrochloric acid during the said immersion, or heating hydrochloric acid.

  Next, pH adjustment is performed by subjecting the acid-cleaned porous structure to water washing using running water or distilled water (step S105). The pH after adjustment is around neutral. Thereafter, the washed porous structure is dried (step S106). Thereby, the pervaporation membrane which has the hollow membrane structure in this Embodiment is obtained.

  Moreover, as shown in FIG. 4, when manufacturing the pervaporation membrane which has a hollow fiber structure based on the manufacturing method of the pervaporation membrane in this Embodiment, first, acrylic resin, polyimide precursor resin ( Hollow fibers are produced by thinning carbon precursors such as those made of polyimide by heating, etc.), cellulose resins, polyphenylene oxide resins, etc. using various methods such as dry methods, wet methods, and dry and wet methods ( Step S201).

  Next, the infusibilization process is performed by heating the produced hollow fiber in the air (step S202). This infusibilization treatment is performed by performing a heat treatment for about 30 minutes to 300 minutes under a temperature condition of about 180 ° C. to 500 ° C., for example. As described above, in addition to the heat treatment described above, various methods such as a method of adding a chemical such as a flame retardant, a method of using the addition of the chemical and heat treatment in addition to the heat treatment described above are applied to the infusible treatment. Can do. Some carbon precursor species do not require infusibility treatment itself. Therefore, the infusibilization treatment may be performed by selecting an optimum method from various methods in consideration of the carbon precursor species.

  Next, carbonization is performed by heating the infusible hollow fiber in an inert atmosphere (step S203). This carbonization treatment is performed by performing heat treatment for about 5 minutes to 180 minutes under a temperature condition of about 500 ° C. to 1000 ° C.

  Next, an acid cleaning process is performed by immersing the carbonized hollow fiber in an acid (step S204). In addition, as an acid to be used, although hydrochloric acid is used suitably, it is not restricted to this. The acid cleaning treatment is performed, for example, by immersing the hollow fiber in a container in which hydrochloric acid having a concentration of about 1 mol / l is stored at room temperature for about several hours to several tens of hours. Thereby, the impurity element contained in the carbon film is eluted into hydrochloric acid, and the impurity element is removed. In order to promote the elution of impurity elements, hydrochloric acid may be stirred during the immersion, or hydrochloric acid may be heated.

  Next, the pH is adjusted by subjecting the acid-washed hollow fiber to water washing using running water or distilled water (step S205). The pH after adjustment is around neutral. Thereafter, the washed hollow fiber is dried (step S206). Thereby, the pervaporation film | membrane which has the hollow fiber structure in this Embodiment is obtained.

  FIG. 5 is a table showing results of experimentally confirming the content of impurity elements contained in each stage of the manufacturing process of the pervaporation membrane having a hollow membrane structure manufactured according to the flow shown in FIG.

  As the impurity element species contained in the carbon precursor (here, phenol resin) as a raw material, as shown in FIG. 5, sodium (Na), aluminum (Al), silicon (Si), phosphorus (P), There are sulfur (S), chlorine (Cl), potassium (K), calcium (Ca), iron (Fe), cobalt (Co), bromine (Br), and the like. Among these, when the content of impurity elements other than sulfur (S) and bromine (Br) contained in the carbon precursor as a raw material was confirmed, although the content varies, it is approximately several ppm to several thousands. ppm.

  Next, the content of impurity elements other than sulfur (S) and bromine (Br) contained in the carbon film before acid cleaning (that is, carbon film after carbonization treatment) was confirmed. Although it decreased, it was approximately several ppm to several hundred ppm.

  Next, when the content of the impurity element contained in the carbon film after the acid cleaning was confirmed, the content was surely reduced and was about several ppm to several tens of ppm.

  From the above results, it was experimentally confirmed that the content of each impurity element contained in the carbon film as the pervaporation film to be manufactured is surely suppressed to 100 ppm or less by adding the acid cleaning treatment. It was.

  As described above, by using the pervaporation membrane in the present embodiment, it is possible to provide a pervaporation membrane that can suppress the generation of by-products even when the liquid to be treated containing acid is treated. By using the organic solvent recovery system provided with the pervaporation membrane, it becomes possible to recover the organic solvent at a high concentration and in a high yield.

  In the following, the verification test conducted to verify the effect of the present invention will be described in detail. In this verification test, as an example, the organic solvent recovery system according to the present embodiment described above was prototyped, and the hollow membrane structure manufactured by performing the acid cleaning process as described above on the membrane separation device of this organic solvent recovery system The pervaporation membrane consisting of a carbon membrane with a gas is set to process the gas to be treated, and the components of the recovered liquid obtained as a result are measured. As a comparative example, in a similar organic solvent recovery system, a membrane separation device The pervaporation membrane consisting of a carbon membrane with a hollow membrane structure manufactured without acid cleaning treatment was set on the gas to be treated, and the components of the recovered liquid obtained as a result were measured. The effects of the present invention were verified by comparing the above. FIG. 6 is a table showing the results of this verification test.

In this verification test, a gas to be treated at 40 ° C. containing ethyl acetate at a concentration of 2000 ppm was used as the organic solvent, and this was introduced into the organic solvent recovery system according to the example and the organic solvent recovery system according to the comparative example, respectively. The process was performed. Here, the same adsorption / desorption treatment apparatus is used in any organic solvent recovery system. As the adsorbent, the average pore diameter is 17.4 mm, the BET specific surface area is 1650 m ² / g, and the total pore volume is 0. 66 cm ³ / g of activated carbon fiber was used.

First, the gas to be treated is adsorbed by blowing air at a flow rate of 100 Nm ³ / min for 9 minutes to one treatment tank of an adsorption / desorption treatment device using a blower (not shown), and the gas to be treated is cleaned to obtain a treatment gas. As discharged. In that case, the concentration of ethyl acetate contained in the processing gas discharged from the adsorption / desorption processing apparatus is 20 ppm in both the organic solvent recovery system according to the example and the organic solvent recovery system according to the comparative example. It was confirmed that ethyl acetate was removed by the adsorption / desorption treatment apparatus at a removal rate of 99%.

  After the above-mentioned 9 minutes of blowing, the valve was switched to switch the one processing tank to the desorption tank, and the remaining processing tank was used as an adsorption tank. In the desorption tank, the adsorbent was desorbed by introducing water vapor, and in the adsorption tank, the adsorption process was performed under the same conditions as described above. This operation of adsorption treatment and desorption treatment was repeated alternately in each treatment tank.

  The desorption gas discharged at 100 ° C. from the desorption tank of the adsorption / desorption treatment apparatus described above is introduced into the condensing / separating apparatus, cooled with a condenser using 32 ° C. cooling water, and then separated in the separation tank. As a result, a concentrate containing high-concentration ethyl acetate and a separation liquid mainly composed of water were obtained. Here, in both of the organic solvent recovery system according to the example and the organic solvent recovery system according to the comparative example, the ethyl acetate concentration of the concentrated liquid separated in the separation tank is 96.5 wt%, and the amount thereof. Was found to be 35 kg / hr.

  Subsequently, the concentrated liquid discharged from the condensing and separating apparatus is introduced into the separation and recovery apparatus, temporarily stored in the buffer tank, and then the concentrated liquid is heated using a preliminary heater, and has a hollow membrane structure as a separation membrane. It was introduced into a membrane separator equipped with a carbon membrane and subjected to pervaporation separation. At this time, the permeated component separated by the membrane separator was condensed by a condenser and discharged as a permeated liquid, and the non-permeated liquid was returned to the buffer tank. After a predetermined time, the non-permeated liquid discharged from the membrane separator was introduced into the recovery tank as a recovery liquid.

  Here, as shown in FIG. 6, the concentration of ethyl acetate in the recovered solution recovered in the organic solvent recovery system according to the example is 99.85 wt%, the concentration of acetic acid is 300 ppm, and the concentration of ethanol is 150 ppm. It was confirmed that the water concentration was 0.1 wt%. On the other hand, the concentration of ethyl acetate in the recovered liquid recovered in the organic solvent recovery system according to the comparative example is 99.75 wt%, the concentration of acetic acid is 1000 ppm, the concentration of ethanol is 500 ppm, and the concentration of water is 0. .1 wt% was confirmed.

  From the above results, by making the organic solvent recovery system according to the example, compared with the organic solvent recovery system according to the comparative example, while suppressing the generation of acetic acid and ethanol, ethyl acetate has a high concentration and a high yield. It was confirmed that it can be recovered at the same time.

  In the organic solvent recovery system 1 in the above-described embodiment, the description has been made without necessarily showing all the components such as the fluid transporting means such as the pump and the fan and the fluid storing means such as the storage tank. What is necessary is just to arrange | position a component in an appropriate position as needed.

  Moreover, in the organic solvent collection | recovery system 1 in this Embodiment mentioned above, as the adsorption / desorption processing apparatus 100, two treatment tanks in which the adsorbent is accommodated are provided, and these adsorption tanks and desorption tanks alternately with time. However, if it is not always necessary to process the gas to be processed, the adsorption / desorption process is performed. You may comprise the apparatus 100 with what comprised the single processing tank. Further, when it is necessary to continuously process the gas to be treated, a part of the adsorbent is used as an adsorption treatment zone instead of the above-described switching type adsorption / desorption treatment apparatus 100, and the remaining portion of the adsorbent is used. Is used as a desorption treatment zone, and an adsorption / desorption treatment device equipped with a rotary adsorbent configured such that the adsorption treatment zone and the desorption treatment zone gradually move as the adsorbent rotates. Also good.

  Further, in the organic solvent recovery system 1 in the above-described embodiment, the concentrated liquid is sent from the buffer tank 310 to the membrane separation device 330 through the piping line L9 and the preliminary heater 320, and the pervaporation process is performed. A non-permeated liquid discharged from the membrane separation device 330 is configured to return to the buffer tank 310 again via the piping line L14, whereby impurities are gradually removed from the concentrated liquid by repeating the pervaporation process. However, depending on the required processing conditions, the purpose may be achieved by a single pervaporation process. In the case of adopting the above, it is sufficient to discharge to the recovery tank 350 as it is without returning to the buffer tank 320. It is also possible to configure the organic solvent recovery system so no ring circuit.

  Further, in the organic solvent recovery system 1 according to the present embodiment described above, the case where only one stage of the membrane separation device 330 is provided has been described, but the membrane separation device 330 is connected in series or in parallel depending on the processing amount. It can also be provided in multiple stages.

  Thus, the one embodiment disclosed this time is illustrative in all respects and is not restrictive. The technical scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  DESCRIPTION OF SYMBOLS 1 Organic solvent recovery system, 100 Adsorption / desorption processing apparatus, 110 1st processing tank, 111 Adsorbent, 120 2nd processing tank, 121 Adsorbent, 200 Condensation liquid separation apparatus, 210 Condenser, 220 Separation tank, 300 Separation / recovery apparatus , 310 buffer tank, 320 preliminary heater, 330 membrane separator, 331 shell, 332 tube element, 332a porous support, 332b pervaporation membrane, 333a, 333b support member, 334 suction pipe, 335 inlet, 336 outlet, 340 condenser, 350 collection tank, L1-L14 piping line, V101-V109 valve.

Claims (12)

A method for producing a pervaporation membrane comprising a carbon membrane, used to separate an organic solvent and water,
Forming a carbon precursor into a film;
A step of heat-stabilizing the carbon precursor formed into a film by infusibilizing by heating,
Forming a carbon film by carbonizing the thermally stabilized carbon precursor by heating in an inert atmosphere;
Cleaning the carbon film with an acid;
A method for producing a pervaporation membrane, comprising: a step of washing the carbon membrane washed with an acid with water, followed by drying.   The method for producing a pervaporation membrane according to claim 1, wherein in the step of forming the carbon precursor into a membrane, the membrane is made to have a hollow membrane structure by attaching the carbon precursor to the surface of the porous support.   2. The permeation according to claim 1, wherein in the step of forming the carbon precursor into a membrane, the carbon precursor is formed into a membrane using any one of a wet method, a dry method, and a dry and wet method to form a membrane having a hollow fiber structure. A method for producing a vaporized film.   The method for producing a pervaporation membrane according to any one of claims 1 to 3, wherein hydrochloric acid is used as a cleaning acid in the step of cleaning the carbon membrane with an acid. A pervaporation membrane made of a carbon membrane used to separate an organic solvent and water,
Group 1 elements (Li, Na, K, Rb, Cs, Fr), Group 2 elements (Be, Mg, Ca, Sr, Ba, Ra), 12th as impurity elements contained in the carbon film. Group elements (Zn, Cd, Hg), Group 17 elements (F, Cl, Br, I, At), phosphorus (P), sulfur (S), and chromium (Cr), manganese (Mn) among transition elements Permeation vaporization film | membrane whose content of each element of iron (Fe), cobalt (Co), nickel (Ni), and copper (Cu) is 100 ppm or less in the state before the pervaporation process is started.   The pervaporation membrane according to claim 5, wherein the carbon membrane has a hollow membrane structure or a hollow fiber structure. An organic solvent recovery system for recovering the organic solvent from the gas to be treated containing the organic solvent,
It includes an adsorbing element that adsorbs an organic solvent by contacting a gas to be treated, and desorbs the adsorbed organic solvent by bringing a heated gas into contact with the organic solvent. An adsorption / desorption treatment apparatus that adsorbs the adsorption element and discharges it as a processing gas, and supplies a heating gas to the adsorption element to desorb the organic solvent from the adsorption element and discharge it as a desorption gas containing the organic solvent;
The desorption gas discharged from the adsorption / desorption treatment device is condensed by cooling, and the condensed liquid containing the organic solvent and the separation liquid mainly composed of water are separated by separating the condensed liquid based on the specific gravity difference. A condensate separator that separates into
Including a pervaporation membrane that selectively permeates and separates water contained in the concentrate by contacting the concentrate, and supplying the concentrate discharged from the condensate separator to the pervaporation membrane A membrane separation device that separates a recovered liquid containing an organic solvent at a high concentration into a permeate containing water as a main component,
The pervaporation membrane is a carbon membrane,
Group 1 elements (Li, Na, K, Rb, Cs, Fr), Group 2 elements (Be, Mg, Ca, Sr, Ba, Ra), 12th as impurity elements contained in the carbon film. Group elements (Zn, Cd, Hg), Group 17 elements (F, Cl, Br, I, At), phosphorus (P), sulfur (S), and chromium (Cr), manganese (Mn) among transition elements , Iron (Fe), cobalt (Co), nickel (Ni), copper (Cu) content of each element is 100 ppm or less in the state before the pervaporation process is started.   The organic solvent recovery system according to claim 7, wherein the pervaporation membrane has a hollow membrane structure or a hollow fiber structure.   The organic solvent recovery system according to claim 7 or 8, wherein the adsorption element is activated carbon fiber.   The organic solvent recovery system according to claim 7, wherein the heated gas is water vapor.   The organic solvent recovery system according to any one of claims 7 to 10, wherein the gas to be treated includes a component that generates an acid by reacting with water.   The organic solvent recovery system according to claim 11, wherein the component is an acetate ester or a basic compound.

Images