JP2007038071A - System for recovering organic solvent - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an adsorption/desorption type apparatus and a method for recovering an organic solvent, in each of which activated carbon is used and the organic solvent in a gas, which is to be treated and contains the organic solvent of high concentration, is removed efficiently and stably. <P>SOLUTION: The gas which is to be treated and contains the organic solvent of high concentration is diluted by the air dehumidified by a dehumidification mechanism 13, which is then introduced into the activated carbon-used adsorption/desorption type apparatus 3 for recovering the organic solvent. Since the diluting air is dehumidified, activated carbon can be dried satisfactorily, the wetted state, a hindrance factor of adsorptivity, of activated carbon can be restrained and activated carbon can keep high removal performance. The treated gas discharged from the adsorption/desorption type apparatus 3 for recovering the organic solvent is introduced into the dehumidification mechanism 13 and dehumidified, which is then used circularly as diluting air. As a result, the high removal performance of activated carbon can be kept and the amount of the organic solvent to be discharged to the atmosphere can be reduced. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an organic solvent recovery apparatus capable of recovering the organic solvent to the maximum while minimizing the scattering of the organic solvent to the atmosphere.

  Conventionally, two or more adsorption tanks filled with activated carbon fibers or granular activated carbon as adsorbents are provided as a processing apparatus for recovering and reusing organic solvents and preventing the organic solvents from being released to the outside air. In addition, a means for supplying a gas to be treated containing an organic solvent to each adsorption tank and a desorption means for ejecting water vapor are provided, and an adsorption process for desorbing the gas to be treated in the adsorption tank and a desorption means for desorption. The structure provided with the means to switch alternately with the desorption process which performs is employ | adopted (for example, refer patent document 1).

  In such a configuration, since the adsorbent is desorbed with water vapor, it is necessary to dry the adsorbent before the next desorption in order to maintain the adsorption performance in a long-term operation once the adsorbent gets wet. There is. If this drying is insufficient, as the long-term operation proceeds, the portion of the adsorbent that gets wet spreads and the adsorption performance is greatly reduced.

  When activated carbon fibers are used as the adsorbent, drying is performed much faster than granular activated carbon. Therefore, the adsorption process also serves as drying from the viewpoint of recovery efficiency.

  However, in the conventional solvent recovery apparatus, when the organic solvent concentration of the gas to be treated is high, it is necessary to increase the amount of adsorbent in order to keep the solvent concentration to be discharged low. This increases the amount of adsorbent, resulting in insufficient drying of the adsorbent and lowers the adsorption performance. In addition, in the case of adsorption at a high concentration, the temperature of the adsorbent rises due to the heat of adsorption, but if the amount of adsorbent per processing air volume increases, the degree of heat release by the processing gas will be small, and the adsorption performance will be significantly reduced by the heat of adsorption. Become.

In recent years, regulations on emission concentrations for harmful air pollutants have been strengthened, and it is desired to minimize the concentration of organic solvents in exhaust gas from organic solvent recovery equipment at a higher level. The device could not meet these requirements when the organic solvent concentration was high.
Therefore, when the concentration of the organic solvent to be processed is high, a method of reducing the concentration of the organic solvent to be processed by mixing the gas to be processed and the outside air has been studied, but sufficient performance has not been obtained. Currently, there is no solvent recovery system that can meet market demands.
JP-A-4-66605

  The present invention has been made against the background of the problems of the prior art, and even when the concentration of the organic solvent in the gas to be treated is high, the organic solvent is effectively recovered, so that the organic solvent in the exhaust gas can be recovered at a very high level. An object of the present invention is to provide an organic solvent recovery system that can reduce the solvent concentration.

As a result of intensive studies to solve the above problems, the present inventors have finally completed the present invention. That is, the present invention is (1) a batch-type organic solvent treatment apparatus that has an adsorption / desorption tank for adsorbing and desorbing a gas to be treated with an adsorbent, and diluting the gas to be treated with dilution air and introducing it into the organic solvent treatment apparatus. An organic solvent recovery system having a dehumidifying device capable of continuously absorbing and desorbing moisture contained in the diluted air; and (2) a processing gas of the organic solvent recovering device is circulated in the diluted air. And (3) the organic solvent recovery system according to (1), wherein the organic solvent recovery system comprises: a dehumidifying device configured to continuously absorb and desorb moisture contained in the processing gas. (1) The organic solvent recovery system according to (2), wherein the adsorbent of the solvent recovery device is activated carbon fiber, (4) the adsorbent of the dehumidifying device is activated carbon, zeolite, silica gel, The organic solvent recovery system according to any one of (1) to (3), wherein the adsorbent of the dehumidifying device has at least one selected from an exchange resin and activated alumina. (1) The organic solvent recovery system according to any one of (1) to (3), which is an ion exchange resin, and (6) the adsorbent of the dehumidifying device is processed into a honeycomb shape The organic solvent recovery system according to any one of (1) to (5).

  According to the organic solvent recovery system of the present invention, by continuously dehumidifying the outside air dilution air, the relative humidity of the adsorbed air is lowered, and the adsorbent is sufficiently dried, so that a stable and high removal process can be performed continuously. Yes. Furthermore, the total amount of exhausted solvent can be greatly reduced by adsorbing a small amount of solvent contained in the adsorption processing air again by circulating the adsorption processing air to the dilution air.

The present invention is described in detail below.
The organic solvent recovery system according to the present invention has an adsorption / desorption tank that absorbs and desorbs a gas to be treated with an adsorbent, and dilutes the gas to be treated with dilution air and introduces it into an organic solvent recovery device. The apparatus preferably includes a dehumidifying apparatus capable of continuously performing moisture absorption / desorption treatment on moisture contained in the diluted air.
This is based on the finding of the present inventors that the humidity of the diluted air taken in greatly affects the solvent processing performance of the solvent recovery system. By installing the dehumidifying device, it is possible to ensure extremely high solvent recovery performance.

  The organic solvent recovery system according to the present invention is preferably configured to circulate a part of the processed gas of the organic solvent recovery apparatus as dilution air of the gas to be processed in order to dilute the gas to be processed. This is because a trace amount of the solvent component contained in the treated gas can be re-adsorbed and recovered by the organic solvent recovery device, and the amount of the exhausted solvent of the processed gas can be reduced.

  The type of adsorbent used for the dehumidifying mechanism is preferably one that adsorbs moisture and does not adsorb organic solvents. Combined with a dehumidifying mechanism that consists of an adsorbent that selectively adsorbs only the moisture contained in the treated gas, the organic solvent contained in the treated gas can be adsorbed to the adsorbent of the dehumidifying mechanism without adsorbing it. It is because the solvent discharged | emitted from this system can be reduced by making it adsorb | suck to a solvent collection | recovery apparatus again. If a material that adsorbs the adsorbent of the dehumidifying mechanism is selected, the solvent is continuously adsorbed and desorbed by the dehumidifying mechanism, and a trace amount of solvent contained in the processing gas of the organic solvent recovery device is removed from the dehumidifying mechanism. Since it is discharged by the desorption operation, it is preferable to adsorb only moisture as the adsorbent of the dehumidifying mechanism. However, even in the adsorbent that adsorbs organic solvents, by selecting an adsorbent with high moisture adsorption capacity, Since the relative humidity of the air circulating to the solvent recovery device can be further reduced and the adsorbent of the organic solvent recovery device is sufficiently dried, continuous high removal treatment can be performed. This is because the amount of the solvent discharged from the desorption / regeneration zone of the dehumidifying mechanism can be reduced. Examples of the adsorbent that selectively adsorbs only moisture contained in the gas include ion exchange resins and ion exchange fibers.

  In addition, the treated gas contains moisture and a small amount of solvent-containing gas. In particular, in the case of moisture, a large amount of moisture adsorbed or adhered to the adsorbent is released at the moment of switching from the desorption process to the adsorption process. Therefore, although it affects the moisture adsorption performance of the dehumidifying mechanism of the continuous processing system, it is also preferable to attach an adsorbent for a buffer that can adsorb and hold moisture and release it over time. The adsorbent for the buffer is selected from those capable of adsorbing moisture, and mainly includes granular activated carbon, zeolite, ion exchange resin, ion exchange fiber, silica gel, and activated alumina. By installing these adsorbents between the treated gas line and the dehumidifying mechanism, the moisture generated at the moment of switching from the desorption process to the adsorption process is once adsorbed, and then the adsorption process and desorption process are switched. It is possible to stabilize the amount of moisture introduced into the dehumidifying mechanism by gradually desorbing the moisture once adsorbed in the meantime by adsorption concentration equilibrium.

  It is preferable that the dehumidifying mechanism is a rotor of a rotary adsorbent having a honeycomb structure including an adsorbent and capable of continuous adsorption / desorption treatment.

  As a result, the system of the present invention can continuously remove a high-concentration organic solvent-containing gas with high efficiency, and is extremely excellent in operability and can maintain high performance over a long period of time. It is.

  A preferred embodiment of the present invention is illustrated in FIG. The gas A to be treated is sent to the adsorption tank 6 in the adsorption process by opening and closing the automatic dampers 4 and 5 by the blower 2, and the organic solvent is adsorbed while passing through the adsorbent 7 in the adsorption tank 6 and has been processed. Gas is sent to the circulation duct D. The treated gas is introduced into the buffer adsorbent 12 from the circulation duct D, and after adsorbing and holding moisture and a small amount of organic solvent, it is introduced into the dehumidifying mechanism 13 and uses an adsorbent that carries the ion exchange tree. Then, only the moisture in the treated gas is selectively adsorbed in the adsorption zone 14 to become a dehumidified gas F containing a small amount of organic solvent. A part G of the dehumidifying gas F is heated by the heating mechanism 15 and introduced into the desorption zone 16 of the dehumidifying mechanism, and the adsorbed moisture is desorbed and regenerated and then released to the atmosphere. The remainder of the dehumidified gas F becomes a dehumidified gas H containing a small amount of organic solvent, becomes diluted air of the solvent-containing gas, and repeats adsorption again.

On the other hand, the organic solvent adsorbed on the adsorbent 7 in the adsorption tank 6 which is in the desorption process by opening and closing the automatic damper is desorbed by the water vapor introduced from the water vapor introduction line 8 and introduced into the condenser 10 through the recovery line 9. The condensed organic solvent is obtained as the recovered solvent 11.

[Example 1]
In the organic solvent recovery system using the organic solvent recovery system shown in FIG. 1 as a basic flow, using activated carbon fiber as the adsorbent 7 of the organic solvent recovery device, and using zeolite as the adsorbent of the dehumidifier, the following examples The to-be-processed gas containing the organic solvent was cleaned under the conditions shown in the above, and the organic solvent was recovered.

The 20 ° C. of the solvent gas mixture containing 50000ppm methylene chloride, flow rate 1 Nm ³ / min, mixed with air 9 Nm ³ / min dehumidified by dehumidifier outside air and to be treated diluted gas, cooling and heating means 1, The blower 2, the adsorption tank 6, and the adsorbent 7 were flowed in this order to perform the adsorption treatment of the dilution gas to be treated. Switching was performed at an adsorption time of 10 minutes and a desorption time of 7 minutes, and the methylene chloride and water vapor desorbed by the water vapor 8 were sent to the condenser 10 and condensed in the condenser 10 to recover methylene chloride.

By diluting the gas to be treated with the dehumidifying device adsorption outlet gas, the amount of adsorption air is 10 Nm ³ / min, the methylene chloride concentration is 5000 ppm, the temperature is 30 ° C., and the dew point is −10 ° C. The temperature is 20 ° C. and the dew point is −10 ° C. Then, it was introduced into a blower and subjected to an adsorption treatment. The methylene chloride outlet concentration in the adsorption process outlet was 10 ppm on average (removal rate 99.8%), the exhaust air volume was 10 Nm ³ / min, and the exhaust solvent quantity was 23 g / h.

[Example 2]
The organic solvent recovery system shown in FIG. 2 is applied flow, and the organic solvent recovery system using activated carbon fiber as the adsorbent 7 of the organic solvent recovery device and ion exchange resin as the adsorbent of the dehumidifying device is as follows. The to-be-treated gas containing the organic solvent was cleaned under the conditions shown in the examples, and the organic solvent was recovered.
Air volume of 20 ° C. of the solvent gas mixture containing 50000ppm methylene chloride 1 Nm ³ / min, the treated gas of the organic solvent recovery apparatus was mixed with 9 Nm ³ / min of the circulating gas as a dilution air, diluted gas of the process gas Then, the cooling or heating means 1, the blower 2, the adsorption tank 6, and the adsorbent 7 were flowed in this order to perform the adsorption treatment of the gas to be treated. Switching was performed at an adsorption time of 10 minutes and a desorption time of 7 minutes, and the methylene chloride and water vapor desorbed by the water vapor 8 were sent to the condenser 10, cooled and condensed, and methylene chloride was recovered.

By dehumidifying the solvent-adsorbed gas and mixing it with the gas to be treated, the adsorption air volume is 10 Nm ³ / min, the temperature is 30 ° C., and the dew point is 5 ° C. The temperature is 20 ° C. and the dew point is 5 ° C. by cooling or heating means. And was subjected to an adsorption treatment. The concentration of methylene chloride at the exit of the adsorption process is 12 ppm on average (removal rate 99.8%) introduced into the dehumidifier, and 12 ppm of methylene chloride is not adsorbed by the adsorbent using an ion exchange resin that can selectively adsorb only water. The dehumidifying operation is performed by passing through and becomes dehumidified and diluted diluted air, and the methylene chloride is 12 ppm and the air volume is 9 m ³ / min. A methylene chloride concentration of 12 ppm and an air volume of 1 m ³ / min are used as desorption air for the dehumidifier and discharged. The discharged methylene chloride concentration was 12 ppm, the discharged air volume was 1 m ³ / min, and the discharged solvent volume was 3 g / h.

[Comparative Example 1]
In the organic solvent recovery device using activated carbon fiber as the adsorbent 7 of the organic solvent recovery device, the gas to be treated containing the organic solvent was cleaned under the conditions shown in the following examples, and the organic solvent was recovered. A gas to be treated at 20 ° C. containing 50000 ppm of methylene chloride, an air volume of 1 Nm ³ / min, and an outside air of 9 Nm ³ / min are mixed to form a gas to be treated to be diluted, and cooling or heating means 1, blower 2, adsorption tank 6, adsorption The material 7 was flowed in order and the treatment dilution gas was adsorbed. Switching was performed at an adsorption time of 10 minutes and a desorption time of 7 minutes, and the methylene chloride and water vapor desorbed by the water vapor 8 were sent to the condenser 10, cooled and condensed, and methylene chloride was recovered.

By diluting the gas to be treated 1Nm ³ / min with outside air, the air volume becomes 10 Nm ³ / min, the methylene chloride concentration is 5000 ppm, the temperature is 30 ° C., and the dew point is 21 ° C. The temperature is 30 ° C. and the dew point is 21 ° C. by cooling or heating means. It was introduced into a blower and subjected to adsorption treatment. The concentration of methylene chloride at the outlet of the adsorption process was 50 ppm on average (removal rate 99.0%), and the amount of solvent discharged was 114 g / h.

The processing results of Example 1, Example 2, and Comparative Example are shown in Table 1 below.

  From Table 1, it can be seen that the amount of solvent discharged by the organic solvent recovery system according to the present invention is extremely small.

  The organic solvent recovery system of the present invention increases the solvent recovery efficiency, makes it possible to reduce the amount of solvent discharged, and contributes greatly to the industry.

It is a basic processing flowchart of Example 1 of an organic solvent recovery system. It is a basic processing flow figure of Example 2 of an organic solvent recovery system.

Explanation of symbols

1: Cooling and heating means 2: Blower 3: Organic solvent recovery device 4: Automatic damper A
5: Automatic damper B
6: Adsorption tank 7: Adsorption element 8: Water vapor line 9: Desorption gas 10: Condenser 11: Recovery solvent line 12: Adsorption means 13: Dehumidification device 14: Heating means 15: Dehumidification device adsorbent A: Processed gas B: Subject Processed diluted gas C: Adsorption inlet gas D: Organic solvent recovery apparatus processed gas E: Dehumidifier adsorption inlet gas F: Dehumidifier adsorption outlet gas G: Dehumidifier desorption inlet gas H: Dehumidified diluted air I: Exhaust gas

Claims (6)

  In a batch-type organic solvent processing apparatus that has an adsorption / desorption tank for adsorbing and desorbing a gas to be processed with an adsorbent, and diluting the gas to be processed with dilution air and introducing it into the organic solvent processing apparatus, An organic solvent recovery system comprising a dehumidifier capable of continuously performing adsorption / desorption treatment. A dehumidifying device configured to circulate the processing gas of the organic solvent recovery device in the diluted air and capable of continuously absorbing and desorbing moisture contained in the processing gas. Item 10. The organic solvent recovery system according to Item 1. The organic solvent recovery system according to claim 1 or 2, wherein the adsorbent of the organic solvent recovery device is activated carbon fiber. The organic solvent recovery according to any one of claims 1 to 3, wherein the adsorbent of the dehumidifying device has at least one selected from activated carbon, zeolite, silica gel, ion exchange resin, and activated alumina. system. The organic solvent recovery system according to claim 1, wherein an adsorbent of the dehumidifying device is an ion exchange resin. 6. The organic solvent recovery system according to claim 1, wherein the adsorbent of the dehumidifying device is processed into a honeycomb shape.