JP2009066530A - Voc recovery apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a VOC (volatile organic compound) recovery apparatus capable of recovering the VOC of high purity and further enhancing a yield in the recovery apparatus for recovering the VOC for recycling from a gas to be treated containing the VOC. <P>SOLUTION: The VOC recovery apparatus is mainly constituted by an adsorption apparatus (1) for capturing the VOC in the gas to be treated by an adsorbent, a condenser (2) for condensing the desorption gas containing the VOC, a separation tank (3) for separating the condensate to a liquid to be treated containing the VOC as a main component and water by difference of specific gravity, and a membrane separation apparatus (6) for further separating the liquid to be treated to a permeation liquid containing a moisture content and a concentration liquid removed with the moisture content by a separation membrane. The permeation liquid separated in the membrane separation apparatus (6) is returned to the separation tank (3), and the concentration liquid separated by the membrane separation apparatus (6) is recovered. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a recovery device for volatile organic compounds (hereinafter referred to as “VOC”), and more specifically, so that VOC can be reused from laminates, printing, coating, exhaust gas from coating equipment, and the like. The present invention relates to a VOC recovery device.

  In equipment for laminating, printing, coating, painting, etc., VOC used as a solvent is released as a gas. Therefore, as a countermeasure for the working environment, it is essential to prevent the VOC from diffusing into the atmosphere and to disassemble or collect it. It has become. Typically, VOC is typically benzene, cyclohexanone, toluene, dichloromethane, methyl isobutyl ketone, methyl ethyl ketone, methyl acetate, ethyl acetate, methanol, ethanol, propyl alcohol, acetone or the like.

As a method for decomposing VOC, direct combustion method, heat storage combustion method, catalytic combustion method, etc. are used. However, since CO ₂ emission is small and no auxiliary fuel is required, there are various VOC recovery methods. It is being considered. For example, as a method of recovering VOCs, a process of absorbing VOC in exhaust gas into water with a scrubber, and water containing VOCs are freeze-concentrated with a freeze concentrator and separated into water and ice containing high concentrations of VOCs. An “exhaust gas recovery method” has been proposed, which includes a step of separating water containing high-concentration VOC into VOC and water using a distiller.
JP 2001-259356 A

Further, as a technique for first extracting VOC from exhaust gas, a technique for recovering by a adsorption process using an adsorbent or an absorbent is common. As a technique using an adsorbent, for example, an adsorption rotor carrying an adsorbent is used, and a VOC-containing gas is passed through a part of the aeration processing region of the adsorption rotor to adsorb the VOC and heated. A “volatile organic compound concentrating device” has been proposed in which an inert gas is passed through another part of the desorption process region of the adsorption rotor to desorb and recover VOC.
JP 2007-44687 A

Furthermore, as a technique using an adsorbent, three or more adsorption towers filled with an adsorbent and a cooling condensation means are used, and moisture and VOC are reduced in one adsorption tower from air containing moisture and VOC. The adsorption step, the step of regenerating the adsorbent by desorbing moisture in the other one adsorption tower, and the step of regenerating the adsorbent by desorbing VOC in the other single adsorption tower are sequentially performed for each adsorption tower. A “volatile organic compound recovery process” that efficiently recovers VOC by switching is proposed.
JP 2007-50378 A

  By the way, from the viewpoint of effective utilization of resources, it is desirable to collect and recycle VOC. However, the recovered VOC can be reused if it is a single component, but must be treated as waste if it is a mixed component. Therefore, in order to reuse the VOC, it is necessary to recover a higher purity VOC. Moreover, in order to recycle, it is necessary to further increase the recovery rate and reduce the processing cost.

  The present invention has been made in view of the above circumstances, and its purpose is a recovery device that recovers VOC from a gas to be processed containing VOC for recycling, and can recover higher-purity VOC. An object of the present invention is to provide a VOC recovery device that can further increase the yield.

  In order to solve the above-mentioned problems, in the present invention, an adsorbent is used in the adsorption device to mainly collect VOC from the gas to be treated, condense it with a condenser, and VOC is mainly collected with a specific gravity difference in a separation tank. After removing the water by separating it into the liquid to be treated as the component and water, a separation membrane is further used in the membrane separation device, and water is separated from the liquid to be treated mainly as a permeated liquid. Purity VOC was obtained. The yield was increased by returning the permeate separated by the membrane separator to the separation tank.

  That is, the gist of the present invention is a recovery device that recovers VOC from a gas to be processed containing VOC, adsorbs the VOC in the gas to be processed with an adsorbent, and vents the adsorbed VOC with water vapor or an inert gas. , A condenser for condensing a desorption gas containing VOC desorbed by the adsorption apparatus, a liquid to be treated and water containing VOC as a main component with a specific gravity difference between the condensed liquid condensed by the condenser. A separation tank that separates the liquid into the separation tank, and a membrane separation device that separates the liquid to be treated separated in the separation tank into a permeate containing moisture and a concentrated liquid from which moisture has been removed by a separation membrane, The VOC recovery device is configured to return the permeate separated by the membrane separation device to the separation tank and collect the concentrated solution separated by the membrane separation device.

  According to the VOC recovery apparatus of the present invention, the VOC collected from the gas to be treated in the adsorption device is condensed by the condenser, and separated into the liquid to be treated and water mainly composed of VOC by the specific gravity difference in the separation tank. After the water is removed, the water is further removed by the separation membrane in the membrane separation device, so that reusable higher-purity VOC can be recovered as a concentrate and the permeate separated by the membrane separation device is separated. Since it returns to the tank, the yield can be further increased.

  An embodiment of a VOC recovery device (hereinafter abbreviated as “recovery device”) according to the present invention will be described with reference to the drawings. FIG. 1 is a flowchart showing main components of a VOC recovery apparatus according to the present invention. In the figure, illustration of the blower, pump, and valves is omitted.

  The recovery device of the present invention is a recovery device that recovers VOC for recycling from a gas to be processed containing VOC. Examples of the gas to be treated include gas exhausted from the above-described facilities for laminating, printing, coating, painting, and the like, and include air containing VOC used as a solvent and nitrogen for sealing. The concentration of VOC in the gas to be treated is preferably about 500 to 3000 ppm.

  As shown in FIG. 1, the recovery device of the present invention includes an adsorption device (1) that adsorbs VOC in a gas to be treated with an adsorbent and desorbs the adsorbed VOC by passing water vapor or inert gas, and the adsorption device. A condenser (2) that condenses the desorbed gas containing VOC desorbed by the apparatus, and a separation tank that separates the condensate condensed by the condenser into a liquid to be treated and water mainly composed of VOC by specific gravity difference ( 3) and a membrane separation device (6) that separates the liquid to be treated separated in the separation tank into a permeate containing moisture and a concentrated solution from which moisture has been removed by the separation membrane. .

  Examples of the adsorption device (1) include a device using a granular adsorbent such as activated carbon, silica gel and zeolite, a device using a fibrous adsorbent such as activated carbon fiber, and a rotary rotor having a honeycomb ventilation structure. Various adsorbing devices such as a device utilizing the above can be used.

  For example, as an adsorption device using activated carbon fibers as an adsorbent, a cylindrical adsorption tank loaded with a cylindrical adsorbent unit made of activated carbon fibers, a blower for introducing a gas to be treated, adsorption / desorption The apparatus is provided with a flow path for switching operation, and in the adsorption operation, the gas to be treated supplied to the adsorption tank is vented from the outer peripheral portion of the adsorbent unit to the inner peripheral portion, thereby allowing the activated carbon fiber to VOC. In the desorption operation, the water vapor supplied from the upper part of the adsorption tank is vented from the inner peripheral part to the outer peripheral part of the adsorbent unit, so that the VOC adsorbed on the activated carbon fiber is desorbed, and from the adsorption tank An apparatus configured to take out a VOC can be used.

  In the above-described adsorption apparatus, one adsorption tank is divided into two chambers, each chamber is loaded with an adsorbent unit, and the adsorption / desorption operation is switched alternately for each chamber, or two or more Adsorbent units are installed in each tank, and the adsorption / desorption operation is switched alternately or sequentially in units of tanks. These are products manufactured by Toyobo Co., Ltd. It is known as a VOC adsorption / recovery device using an adsorbent unit called “K Filter” or a trade name “Solvent Rika” manufactured by Toho Chemical Corporation.

  In addition, as an adsorption device using granular activated carbon as an adsorbent, the inside of the tower is divided into an upper half adsorption section and a lower half desorption section, and the adsorption section is arranged in multiple stages in the adsorption section. An apparatus provided with a perforated plate, a desorption tube for circulating water vapor arranged in the desorption unit in a state where a large number of vertical tubes are arranged, and an activated carbon transfer tube inserted through the tower bottom to the upper part of the adsorption unit It is done.

  In the above-described apparatus, in the adsorption operation, a fluidized bed is formed on each porous plate by activated carbon supplied to the adsorption unit, and a gas to be treated introduced from an inlet at a lower portion of the adsorption unit is brought into countercurrent contact with the activated carbon. By adsorbing the VOC to the activated carbon, in the desorption operation, the activated carbon dropped from the adsorption unit is allowed to pass through the gap of the desorption tube of the desorption unit, and the desorption aeration gas is introduced and desorbed from the gas introduction port below the desorption unit. By circulating the steam for heating through the tube, the VOC adsorbed on the activated carbon is desorbed, and the VOC is taken out together with the desorption gas (for example, nitrogen) from the gas outlet at the top of the desorption section. The adsorbent from which the adsorbate has been desorbed in the desorption section is again conveyed to the adsorption section by an activated carbon conveyance pipe.

  The above adsorption apparatus has an adsorption part and a desorption part in one treatment tower, or uses two treatment towers, the adsorption part is constituted by one treatment tower and the other one The desorption part is constituted by the processing towers, and the adsorbent is continuously conveyed by air flow between the processing towers, and these are referred to as “Gas stack” (registered trademark) manufactured by Kureha Engineering Co., Ltd. It is known as a solvent recovery / deodorization device or as the trade name “Soldax” manufactured by Daikin Industries.

As shown in FIG. 1, the adsorption device (1) is supplied with the gas to be treated through the pipe (11), and an inert gas such as water vapor or nitrogen at 100 to 200 ° C. is supplied through the pipe (12). A gas to be treated, which is supplied as a desorption gas and from which VOC has been almost removed by adsorption, is exhausted from the pipe (13) as an exhaust gas, and includes a desorption gas (water vapor or inert gas) and a desorbed VOC. The gas is extracted from the pipe (14). In the adsorber (1), for example, the type of adsorbent, the amount used, and the amount of adsorbent are 10 to 1500 Nm ³ / min when ethyl acetate is mixed and the concentration is 1000 ppm. An adsorption / desorption mechanism is designed.

  A condenser (2) is disposed downstream of the adsorption device (1). The condenser (2) is, for example, a corrugated fin type in which a gas inlet is provided at the top and a condensate outlet is provided at the bottom, and a coolant such as cooling water is circulated in the container. A so-called condenser comprising a heat exchanger of the above type or a serpentine type heat exchanger, and by condensing the desorption gas introduced into the container through the pipe (14) by circulating the refrigerant through the heat exchanger, Is taken out from the pipe (15) at the bottom of the container.

A separation tank (3) is disposed downstream of the condenser (2). The condensate extraction pipe (15) is connected to the top of the separation tank (3), the pipe (16) for discharging the separated water is attached to the bottom, and the top is attached to the top. A pipe (18) for taking out the separated liquid (liquid to be treated) is attached. The separation tank (3) separates the condensate introduced through the pipe (15) with a specific gravity difference, takes out the liquid to be treated mainly composed of VOC having a small specific gravity from the pipe (18), and pipes water with a large specific gravity. It is comprised so that it may discharge from (16). The internal volume of the separation tank (3) is about 0.1 to 0.5 m ³ .

  A drainage storage tank (4) and a VOC storage tank (5) are disposed downstream of the separation tank (3). The drainage storage tank (4) is a tank for temporarily storing the water separated in the separation tank (3), and is provided for inspecting drainage standards and draining the pump at an appropriate timing. The pipe (16) is inserted in the upper part of the drainage storage tank (4), and the pipe (17) for drainage is attached to the bottom. On the other hand, the VOC storage tank (5) is a tank for temporarily storing the liquid to be processed separated in the separation tank (3), and is provided for pumping the liquid to be processed to the membrane separation device (6). It is done. The pipe (18) is connected to the top of the VOC storage tank (5), and the pipe (19) for supplying the liquid to be treated to the membrane separation device (6) is attached to the bottom.

  A small amount of water is mixed in the liquid to be treated separated in the separation tank (3), and it is necessary to further increase the purity in order to reuse this as a solvent. Therefore, in the recovery device of the present invention, the membrane separation device (6) is disposed on the downstream side of the VOC storage tank (5), and is configured to further separate and remove trace moisture in the liquid to be treated.

  The membrane separation device (6) is composed of a membrane module (a separation membrane device that is a constituent unit of the membrane separation device), a pump for feeding and circulating a liquid to be treated, a heater for heating, a cooler, a condenser, and the like. The In such a membrane separation device (6), usually, a plurality of membrane modules, for example, 2 to 10 membrane modules, are arranged in parallel or in series in consideration of fluctuations in throughput and convenience of maintenance management. The element structure of the membrane module (shape and assembly of the separation membrane) and the material of the separation membrane (membrane) can be appropriately selected as long as moisture can be selectively separated from the liquid to be treated containing VOC. From the viewpoint of chemical resistance and separation performance, a tubular pervaporation membrane made of a porous inorganic membrane is preferably used.

Specifically, the membrane module of the membrane separation device (6) is configured by accommodating a membrane element in, for example, a cylindrical outer container. The membrane element has about 10 to 100 hollow tubes (tubes), which are porous inorganic membranes sealed at the tip, arranged in parallel and in parallel, and the open proximal ends of these hollow tubes are flanged partitions. It is configured to be inserted into the plate in an inserted state. The porous inorganic membrane (hollow tube) is obtained by forming a zeolite membrane on the outer surface of a tube made of porous ceramic by a hydrothermal reaction. Note that the membrane area of one porous inorganic membrane (hollow tube) is 0.02 to 0.05 m ² , and the total membrane area of one membrane module is 0.2 to ⁵ m ² .

On the other hand, the outer casing of the membrane module is configured by providing an inlet for the liquid to be treated at one end and an outlet for the concentrated liquid at the peripheral surface on the other end. The inner volume of the outer container is 0.001 to 0.3 m ³ . Then, the membrane module is loaded with the membrane element from the other open end of the outer casing so that the sealed end of the hollow tube is positioned at one end of the outer casing, and the outer casing is covered with the partition plate of the membrane element. The other end of the container is sealed, and a lid is attached to the other end of the outer container. Such a lid covers the partition plate of the membrane element and forms a permeate (water) recovery space on the other end side of the mantle container, and a permeate discharge port is provided at the top of the lid. In addition, as said membrane module, it is available as a brand name "Ceramic membrane module" by Mitsui & Co., Ltd.

  The membrane separator (6) is connected to the above-mentioned pipe (19) for supplying the liquid to be treated, the pipe (21) for extracting the concentrate, and the pipe (20) for discharging the permeate, and the membrane separator In (6), the liquid to be treated sent by the pipe (19) is supplied to each membrane module via the liquid feed pump, and the concentrated liquid separated by each membrane module is taken out through the pipe (21). The permeate separated in each membrane module is discharged through the pipe (20).

The recovery device of the present invention is configured to recover the concentrated liquid separated by the membrane separation device (6) as a recycled VOC for recycling. Specifically, a recovery VOC storage tank (8) for storing the concentrated liquid taken out through the pipe (21) is provided on the downstream side of the membrane separation device (6). Then, through the pipe (23) attached to the recovered VOC storage tank (8), the stored concentrated liquid can be supplied as a recycled VOC to a solvent use facility for laminating and the like. Alternatively, the concentrate can be filled into the portable container through the pipe (23). The internal volume of the recovered VOC storage tank (8) is about 0.05 to ³⁰ m ³ .

  Further, in the recovery device of the present invention, the permeate (water) separated by the membrane separation device (6) can be returned to the separation tank (3) in order to further increase the VOC recovery rate. . That is, said piping (20) is connected to the upper part of the above-mentioned separation tank (3). A small amount of VOC accompanying the permeate is obtained by connecting the permeate discharge pipe (20) of the membrane separator (6) to the separation tank (3) and returning the permeate (water) to the separation tank (3). Can be collected, and the collection rate can be improved.

  Furthermore, in a preferred embodiment of the present invention, in order to further purify the concentrated liquid separated and recovered by the membrane separator (6), the downstream side of the membrane separator (6) and the upstream side of the recovered VOC storage tank (8) are provided. A purification device (7) for purifying the concentrated liquid separated by the membrane separation device (6) by distillation is provided. Specifically, the pipe (21) is connected to the purification device (7), and the concentrated liquid can be supplied to the purification device (7).

  The purification device (7) includes, for example, a jacket in which steam for heating flows, a tube-type heat exchanger, a coil-type heat exchanger, and the like, and a distillation column that distills the VOC vapor by boiling a concentrated liquid (VOC). And a cooling condenser such as a multi-tube type for bringing the vapor of the VOC separated by distillation into contact with the refrigerant pipe to liquefy it. And the refinement | purification apparatus (7) is provided with the piping (22) for extraction | purification of purified VOC for collect | recovering the concentrate (distillate) refined | purified by distillation to the above-mentioned collection | recovery VOC storage tank (8).

When the concentrated solution is further purified by distillation using the refining device (7), trace amounts of impurities such as ionic dissolved substances, particles, and insoluble substances mixed in the concentrated liquid can be reliably removed, and the recovered VOC. Quality can be further improved. In addition, the processing capacity of the refiner | purifier (7) (distillation apparatus) shall be about 0.02-15m < ³ > / day. Moreover, although not shown in figure, the concentrated waste liquid extracted from the bottom part of the evaporation kettle is exhausted or returned to the VOC storage tank (5).

  Next, a VOC recovery method using the above recovery device will be described. In the recovery of the VOC, first, a gas to be processed such as air or nitrogen containing VOC is supplied to the adsorption device (1) through the pipe (11). In the adsorption operation in the adsorption device (1), VOC in the gas to be treated is adsorbed by the adsorbent, and the exhaust gas from which VOC has been adsorbed and removed is exhausted from the pipe (13). In the desorption operation, Alternatively, the adsorbed VOC is desorbed by passing an inert gas through the adsorbent, and the desorbed gas containing VOC is supplied to the condenser (2) through the pipe (14).

  Next, the desorption gas is condensed in the condenser (2), and the obtained condensate is supplied to the separation tank (3) through the pipe (15). In the separation tank (3), the condensate is separated into a liquid to be processed mainly composed of VOC and water with a specific gravity difference, and the liquid to be processed separated in the upper part of the separation tank (3) is passed through the pipe (18). Supplied to the VOC storage tank (5) and temporarily stored in the VOC storage tank. Further, the water separated at the bottom of the separation tank (3) is supplied to the drainage storage tank (4) through the pipe (16) to be drained.

  Subsequently, the liquid to be treated stored in the VOC storage tank (5) is supplied to the membrane separation device (6) through the pipe (19). In the membrane separation device (6), the liquid to be treated is introduced into the membrane module, and the separation membrane separates the permeate containing moisture and the concentrated solution from which moisture has been removed. And the isolate | separated concentrate is collect | recovered through a piping (21). The separated permeate is returned to the separation tank (3) again through the pipe (20), mixed with the condensate, and subjected to a separation operation.

  As described above, the concentrated liquid obtained by separation in the membrane separation device (6) needs to be further purified and impurities removed depending on the required specifications. In this case, the pipe (21) The concentrate is supplied to the purifier (7) through Then, the concentrate is purified by distillation in the purification device (7), and the distillate is supplied to the recovery VOC storage tank (8) through the pipe (22). Thereby, the refined VOC can be supplied from the recovered VOC storage tank (8) to the solvent-using facility through the pipe (23).

  As described above, in the recovery device of the present invention, the VOC is mainly collected from the gas to be treated in the adsorption device (1), condensed in the condenser (2), and the specific gravity difference in the separation tank (3). After removing the water by separating it into a liquid to be treated mainly composed of VOC and water, the membrane separation device (6) further uses a separation membrane to separate and remove mainly water as a permeate from the liquid to be treated. Therefore, the reusable higher-purity VOC can be recovered as a concentrate, and the permeate containing the water separated by the membrane separator (6) is returned to the separation tank (3). It can be further enhanced. When the concentrated solution obtained by the membrane separation device (6) is further purified by distillation using the purification device (7), impurities such as ionic dissolved substances can be reliably removed, and the recovered VOC is recovered. Quality can be further improved.

In this connection, the ethyl acetate was recovered by treating the ethyl acetate-containing air (exhaust gas) discharged from the laminating equipment using the recovery device shown in FIG. The concentration of ethyl acetate in the exhaust gas was 934 ppm, and the exhaust gas throughput was 981 Nm ³ / min. When the adsorption device (1) adsorbs ethyl acetate and the desorption gas taken out from the adsorption device (1) is liquefied by the condenser (2), a condensate of 96.6 wt% ethyl acetate and 3.4 wt% water is obtained. Obtained at a flow rate of 180 kg / h. And, as a result of separating the obtained ethyl acetate (liquid to be treated) in the separation tank (3) and further treating in the membrane separation device (6), a concentrated solution of ethyl acetate 99.9 wt% and water 0.1 wt% was obtained. Obtained.

It is a flowchart which shows the main components of the collection device of VOC concerning the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1: Adsorption apparatus 2: Condenser 3: Separation tank 4: Drainage storage tank 5: VOC storage tank 6: Membrane separation apparatus 7: Purification apparatus 8: Recovery VOC storage tank 11-23: Piping

Claims (3)

  A recovery device that recovers VOC from a gas to be treated containing a volatile organic compound (hereinafter referred to as “VOC”), adsorbs the VOC in the gas to be treated with an adsorbent, and converts the adsorbed VOC into water vapor or An adsorption device desorbed by aeration of inert gas, a condenser for condensing desorption gas containing VOC desorbed by the adsorption device, and a condensate condensed by the condenser as a main component of VOC with a specific gravity difference. A separation tank that separates the liquid to be treated and water, and a membrane separation device that separates the liquid to be treated separated in the separation tank into a permeate containing moisture and a concentrated liquid from which moisture has been removed by a separation membrane. The VOC is mainly configured and configured to return the permeate separated by the membrane separator to the separation tank and collect the concentrate separated by the membrane separator. Recovery device.   The VOC recovery apparatus according to claim 1, further comprising a purification apparatus for distilling and purifying the concentrated liquid separated by the membrane separation apparatus.   The VOC recovery device according to claim 1 or 2, wherein the separation membrane of the membrane separation device is a pervaporation membrane.

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