JP4332608B2 - Method for treating solvent-containing gas - Google Patents

Description

  The present invention relates to a method for treating a solvent-containing gas. Specifically, in the method for treating a solvent-containing gas in which the solvent in the solvent-containing gas is removed by alternately performing an adsorption process for adsorbing the solvent on the adsorbent and a desorption process using water vapor, the water vapor in the adsorption tank after the start of the adsorption process. The present invention relates to a method for treating a solvent-containing gas that prevents white gas from being blown out.

  Since exhaust gas containing a solvent causes environmental pollution if released into the atmosphere as it is, the solvent is removed. Conventionally, the solvent is removed by adsorbing the solvent on an adsorbent such as activated carbon to capture the solvent in the solvent-containing gas. When the adsorption of the solvent to the adsorbent reaches a certain amount, the adsorbent breaks through and the solvent leaks out. Therefore, it is necessary to regenerate the adsorbent by performing a desorption process at an appropriate time.

  Examples of a method for desorbing the solvent from the adsorbent include a method for reducing the adsorbent and a method using a high-temperature inert gas or water vapor as a known method, but a method using water vapor because the cost is low. It is common.

  An example of a processing apparatus for a solvent-containing gas using water vapor for the desorption process is shown in FIG. A solvent-containing gas is supplied to the adsorption tank 1a to perform an adsorption process, and water vapor is supplied to the adsorption tank 1b to perform a desorption process. In this apparatus, the adsorption process and the desorption process are alternately repeated in the adsorption tanks 1a and 1b installed in parallel in the two tanks, whereby the solvent-containing gas is continuously processed.

  In the desorption process using water vapor, the adsorption tank immediately after the desorption process is filled with water vapor, so the water vapor remaining in the adsorption tank when switching from the desorption process to the adsorption process is pushed by the exhaust gas and discharged. There is a problem that white smoke is emitted from the exit into the atmosphere. For example, the following method is used as a method for preventing the white smoke.

(1) A method of providing a mist trap in an exhaust pipe that releases gas from the adsorption tank to the atmosphere (2) A method of heating the gas released from the adsorption tank to the atmosphere (3) Outside air after blowing water vapor into the adsorption tank To push water vapor remaining in the adsorption tank into a condenser (Patent Document 1)
All of these methods have the following problems.

  In the method (1), the mist contained in the white smoke can be removed, but since the water vapor is not sufficiently captured, the white smoke cannot be completely prevented.

  The method (2) is a method in which a gas containing water vapor exhausted from the adsorption tank is heated and discharged as dry steam. Although the white smoke prevention effect is sufficiently obtained, the cost of energy required for heating increases. There is a problem.

  In the method (3), after the desorption of the solvent from the adsorbent is completed, the outside air is introduced into the adsorption tank by a blower as shown in FIG. 4 and the water vapor remaining in the adsorption tank is pushed out into the condenser. This is a method of removing water vapor from the water. In this method, the white smoke prevention effect can be sufficiently obtained, but there is a problem that control of introduction of water vapor and outside air into the adsorption tank is required, and the processing apparatus becomes complicated.

3 and 4, 1a and 1b are adsorption tanks, 2a and 2b are exhaust valves, 3a and 3b are intake valves, 4a and 4b are exhaust ports, 5a and 5b are adsorbents, and 6a and 6b are intake ports. , 30 and 33 are blowers, 31 is a condenser, and 32 is a tank.
Japanese Patent Publication No. 6-34897 (Claims)

  An object of the present invention is to provide a method for easily treating a solvent-containing gas without producing white smoke resulting from the discharge of water vapor remaining in the adsorption tank to the outside when switching from the desorption process to the adsorption process. There is.

  The inventor installs a blower at the rear stage of the condenser connected to the outlet side of the adsorption tank, opens the exhaust outlet of the adsorption tank between the desorption process and the adsorption process, and operates the blower attached at the rear stage of the condenser. Then, a patent application was filed based on the finding that the introduction of outside air into the adsorption tank can easily prevent white smoke from being generated by the ejection of water vapor remaining in the adsorption tank (Japanese Patent Application No. 2003-142306).

  Furthermore, as a result of earnest research, the present inventor has found that two paths connecting the outlet side and the inlet side of the adsorption tank, that is, a path for condensing and recovering the solvent and water vapor desorbed from the adsorbent, and the inside of the adsorption tank The amount of return of the solvent to the adsorption tank can be reduced by performing a desorption step and a step of replacing the water vapor remaining in the adsorption tank with the outside air by using a separate path. It was found that the solvent-containing gas can be treated more advantageously because it can be reduced, and the present invention has been completed.

  That is, this invention which solves the said subject is described below.

  [1] Gas after removal of the solvent by supplying the solvent-containing gas into the adsorption tank filled with the adsorbent by an inlet-side fan connected to the inlet side of the adsorption tank to adsorb the solvent in the solvent-containing gas to the adsorbent. Is condensed by a first condenser connected to the outlet side of the adsorption tank, with an adsorption step of discharging the gas from the exhaust port of the adsorption tank, and a mixed gas of water vapor blown into the adsorption tank and desorbed from the adsorbent In the method for treating a solvent-containing gas, in which the solvent and water are recovered and the desorption process of returning the uncondensed gas in which the solvent remains to the inlet side of the adsorption tank is alternately repeated, the outlet side of the adsorption tank and the inlet side blower The first condenser is interposed between the first condenser and the inlet side of the suction tank, and the second condenser and the return fan are interposed between the outlet side of the adsorption tank and the inlet side of the inlet fan. A second path is provided, and the desorption step The mixed gas of the solvent and water vapor passes through the first path to condense and remove the solvent with the first condenser, and return the non-condensed gas to the inlet side of the inlet side blower. Further, the desorption step and the adsorption step In the meantime, the exhaust port of the adsorption tank that has completed the desorption process is opened, and the return blower installed in the second path is operated to bring the water vapor remaining in the adsorption tank together with the outside air introduced into the adsorption tank into the second path. A method for treating a solvent-containing gas, comprising adding a step of introducing and condensing water vapor with a second condenser.

  [2] A gas cooler and an inlet-side fan are connected to the inlet side of the adsorption tank filled with the adsorbent, and the solvent-containing gas cooled by the gas cooler is supplied into the adsorption tank by the inlet-side fan. The adsorbent adsorbs the solvent and releases the gas after removal of the solvent from the exhaust port of the adsorption tank, and the mixed gas of the solvent and water vapor desorbed from the adsorbent by blowing water vapor into the adsorption tank. Solvent-containing gas that alternately repeats the desorption step of collecting the solvent and water by condensing with the first condenser connected to the outlet side of the adsorption tank and returning the uncondensed gas in which the solvent remains to the inlet side of the adsorption tank In the processing method, the first path in which the first condenser is interposed between the outlet side of the adsorption tank and the inlet side of the gas cooler or the inlet side blower is connected to the outlet side of the adsorption tank and the inlet side of the gas cooler. The return blower And a mixed gas of solvent and water vapor is passed through the first path to condense and remove the solvent with the first condenser and uncondensed gas is removed from the gas cooler or the inlet side blower. In addition, the exhaust port of the adsorption tank that has completed the desorption process is opened between the desorption process and the adsorption process, and the return blower installed in the second path is operated and introduced into the adsorption tank. A method for treating a solvent-containing gas, comprising a step of sending water vapor remaining in the adsorption tank together with the outside air to the inlet side of the gas cooler.

  [3] The method for treating a solvent-containing gas according to [1] or [2], wherein an aeration direction of outside air supplied to the adsorbent is a direction opposite to an aeration direction of the solvent-containing gas in the adsorption step.

  According to the present invention, the solvent can be easily removed from the solvent-containing gas without producing white smoke resulting from the discharge of water vapor when switching from the desorption process to the adsorption process. In the present invention, a first path for condensing and collecting the solvent desorbed in the desorption process and a second path for replacing the water vapor remaining in the adsorption tank after the desorption process with outside air are provided separately. Since the desorption process and the process of replacing the water vapor in the adsorption tank after the desorption process with the outside air are performed using different paths, the return amount of the solvent to the adsorption tank can be reduced.

  A block diagram of an example of a processing apparatus used in the present invention is shown in FIG. Hereinafter, the present invention will be specifically described with reference to FIG.

  The adsorption tanks 1a and 1b have intake ports 6a and 6b having intake valves 3a and 3b, respectively, and are connected to the inlet side blower 25 through the intake ports 6a and 6b. Further, the adsorption tanks 1a and 1b have exhaust ports 4a and 4b provided with exhaust ports 7a, 7b, 8a and 8b and exhaust valves 2a and 2b. The exhaust ports 7a and 7b are connected to one end of the path B, and the exhaust ports 8a and 8b are connected to one end of the path A. A is the first path, capacitor 20, B is the second path, and condenser 22 and fan 24 are interposed, and the other ends of paths A and B are connected to the inlet side of inlet side fan 25. .

  In FIG. 1, the adsorption tank 1a shows the state of the adsorption process, and the adsorption tank 1b shows the state of the desorption process. The solvent-containing gas is introduced into the adsorption tank 1a from the intake port 6a by the inlet side fan 25. The solvent contained in the solvent-containing gas is adsorbed by the adsorbent 5a filled in the adsorption tank 1a when passing through the adsorption tank 1a. The gas purified through the adsorption tank 1a passes through the exhaust valve 2a and is released into the atmosphere from the exhaust port 4a.

  On the other hand, the solvent is adsorbed to the adsorbent 5b filled in the adsorption tank 1b. With the exhaust valve 2b, the intake valve 3b, and the valve 10b closed, the valves 12b and 11b are opened, water vapor is introduced into the adsorption tank 1b, and the solvent adsorbed on the adsorbent 5b is desorbed. The mixed gas of the desorbed solvent and water vapor is pushed out of the adsorption tank 1b and introduced into the path A, and is cooled and condensed by the condenser 20. The solvent and water condensed in the condenser 20 are collected in the tank 21.

  The solvent contained in the mixed gas is cooled by the condenser 20 and most of the solvent is condensed and liquefied, but remains as a slight gas. The gas containing a small amount of solvent discharged from the condenser 20 is sent to the inlet side of the inlet side fan 25 and processed in the adsorption tank 1a.

  After the desorption process is completed in the adsorption tank 1b, the valves 12b and 11b are closed, the exhaust valve 2b and the valve 10b of the adsorption tank 1b are opened, and at the same time, the return blower 24 installed in the path B is operated to operate the adsorption tank from the exhaust port 4b. Outside air is introduced into 1b. The water vapor remaining in the adsorption tank 1b passes through the adsorbent 5b together with the outside air and is introduced into the second condenser 22 connected to the front stage of the return blower 24 and cooled. The water condensed in the second condenser 22 is collected in the tank 23. Since the gas discharged from the second condenser 22 also contains a trace amount of solvent, it is sent to the inlet side of the inlet side fan 25 and processed in the adsorption tank 1a.

  Thereafter, the intake valve 3a, the exhaust valve 2a, and the valve 10b are closed, and the intake valve 3b and the valves 11a and 12a are opened, and the desorption process is performed in the adsorption tank 1a and the adsorption process is performed in the adsorption tank 1b as described above.

  As described above, the present invention removes the solvent from the adsorbent by blowing water vapor into the adsorption tank as described above, and then opens the exhaust port of the adsorption tank and operates the return blower 24 to introduce outside air into the adsorption tank. The concentration of water vapor is reduced, thereby preventing white smoke generated when switching from the desorption process to the adsorption process. By introducing outside air after completion of the desorption process, the solvent adsorbed and remaining on the adsorbent moves from the inside to the outside of the cylindrical adsorbent, and the residual solvent concentration inside the adsorbent is low. If the process proceeds to the adsorption step in this state, the solvent-containing gas is supplied from the outside of the cylindrical adsorbent inward (opposite to the direction of the outside air flow), so that the amount of solvent leaking from the adsorbent is extremely small.

  The processing apparatus of FIG. 1 is provided with a first path A for condensing and collecting the solvent desorbed in the desorption process, and a second path B for replacing water vapor remaining in the adsorption tank with the outside air at the end of the desorption process. ing. Since there are many condensed or uncondensed solvents in the path A, when the process of replacing the water vapor in the adsorption tank with the outside air is performed by the path A, the solvent existing in the path A is removed from the inlet of the adsorption tank. Will return to the side. Therefore, the return amount of the solvent to the adsorption tank can be reduced by providing the first path A and the second path B separately as in the processing apparatus described above. In particular, when the amount of replacement air in the outside air is large, the return amount of the solvent increases. Therefore, the effect of reducing the return amount of the solvent by providing two paths becomes remarkable.

  The adsorbent filled in the adsorption tank is not particularly limited as long as it is usually used as an adsorbent, and examples thereof include activated carbon, activated carbon fiber, and zeolite.

It is preferable that the air volume at the time of introducing outside air into the adsorption tank is 0.1 to 0.4 m ³ per 1 kg of the adsorbent. If it is less than 0.1 m ³ , the effect is not sufficient, and if it exceeds 0.4 m ³ , the outside air returned to the adsorption tank tends to increase and the solvent removal efficiency tends to decrease.

  Another example of the processing apparatus used in the present invention is shown in FIG.

  The processing apparatus is provided with two adsorption tanks 1a and 1b as in FIG. 1, and an adsorption process is performed in the adsorption tank 1a and a desorption process is performed in the adsorption tank 1b.

  In the processing apparatus shown in FIG. 2, operations similar to those in FIG. 1 are performed. 2 is different from FIG. 1 in that a gas cooler 26 is connected to the front stage of the inlet-side blower 25 and the gas cooled by the gas cooler 26 is introduced into the adsorption tank 1a. Further, only the return blower 24 is installed in the path B, and the water vapor discharged from the adsorption tank 1b is liquefied by the gas cooler 26 instead of the second condenser 22 in FIG. .

  Since the other points are the same as those in FIG. 1, the same reference numerals are given to the same parts and the description thereof is omitted.

  In FIG. 2, although the case where the gas discharged | emitted from the 1st condenser 20 installed in the path | route A is returned to the inlet side of the gas cooler 26 was shown, between the gas cooler 26 and the inlet side air blower 25 (inlet side air blower). 25 may be returned.

  In the above description, the case of using two adsorption tanks has been described as an example. However, the present invention is not limited to this, and the same applies to the case of one adsorption tank and the case of using three or more adsorption tanks.

  Hereinafter, the present invention will be described in more detail with reference to examples.

Example 1 and Comparative Example 1
The solvent (methylene chloride) contained in the exhaust gas was recovered under the conditions shown below using the processing apparatus shown in FIG. The results are shown in Table 1. FIG. 5 shows the change over time of the solvent concentration in the exhaust gas discharged from the apparatus.
Adsorption tank type: GS-2 type (2 cans alternate switching, water vapor desorption system)
Filler: Activated carbon fiber 5 kg / tank Filling operation condition:
(1) Solvent inlet solvent concentration: approx. 2500 ppm (amount of supplied solvent: 2.8 kg / h)
(2) Gas throughput 5Nm ³ / min
(3) Gas temperature 25 ° C
(4) Desorption steam volume 10kg / h

比較例１では脱着工程から吸着工程への切り替え時に吸着槽からの排気が白煙を生じたが、実施例１においては白煙の噴出は見られなかった。

In Comparative Example 1, the exhaust from the adsorption tank produced white smoke when switching from the desorption process to the adsorption process, but no white smoke was ejected in Example 1.

It is a block diagram which shows an example of the processing apparatus used for this invention. It is a block diagram which shows the other example of the processing apparatus used for this invention. It is a block diagram which shows an example of the conventional processing apparatus. It is a block diagram which shows the other example of the conventional processing apparatus. It is a figure which shows the time-dependent change of the solvent density | concentration in the waste gas discharged | emitted from the processing apparatus in an Example.

Explanation of symbols

1a, 1b Adsorption tank 2a, 2b Exhaust valve 3a, 3b Intake valve 4a, 4b, 7a, 7b, 8a, 8b Exhaust port 5a, 5b Adsorbent 6a, 6b Intake port 10a, 10b, 11a, 11b, 12a, 12b Valve 20 First condenser 22 Second condenser 21, 23, 27 Tank 24 Return blower 25 Inlet blower 26 Gas cooler A, B Route

Claims (3)

A solvent-containing gas is supplied into an adsorption tank filled with the adsorbent by an inlet-side blower connected to the inlet side of the adsorption tank so that the solvent in the solvent-containing gas is adsorbed by the adsorbent, and the gas after solvent removal is adsorbed to the adsorption tank. An adsorption process for discharging from the exhaust port of the tank, and a solvent obtained by condensing a mixed gas of solvent and water vapor blown into the adsorption tank and desorbed from the adsorbent by a first condenser connected to the outlet side of the adsorption tank In the method for treating a solvent-containing gas by alternately repeating a desorption step of recovering water and water and returning the uncondensed gas in which the solvent remains to the inlet side of the adsorption tank, the outlet side of the adsorption tank and the inlet side of the inlet side fan And a second path for interposing a second condenser and a return blower between the outlet side of the adsorption tank and the inlet side of the inlet side blower. Providing a route, and in the desorption step The vapor mixed gas is passed through the first path to condense and remove the solvent by the first condenser, and the uncondensed gas is returned to the inlet side of the inlet side blower, and further, between the desorption step and the adsorption step. The exhaust port of the adsorption tank after the desorption process is opened and the return blower installed in the second path is operated to introduce the water vapor remaining in the adsorption tank together with the outside air introduced into the adsorption tank into the second path. And adding a step of condensing the water vapor with the second condenser. A gas cooler and an inlet-side fan are connected to the inlet side of the adsorption tank filled with the adsorbent, and the solvent-containing gas cooled by the gas cooler is supplied into the adsorption tank by the inlet-side fan to remove the solvent in the solvent-containing gas. An adsorption process for adsorbing to the adsorbent and releasing the gas after removal of the solvent from the exhaust port of the adsorption tank, and a mixed gas of the solvent and water vapor desorbed from the adsorbent by blowing water vapor into the adsorption tank A method for treating a solvent-containing gas by alternately repeating a desorption step of collecting a solvent and water by condensing with a first condenser connected to the outlet side and returning an uncondensed gas in which the solvent remains to the inlet side of the adsorption tank A first path including a first condenser between the outlet side of the adsorption tank and the inlet side of the gas cooler or the inlet side blower, between the outlet side of the adsorption tank and the inlet side of the gas cooler. Install a return blower In the desorption process, the mixed gas of the solvent and water vapor is passed through the first path to condense and remove the solvent with the first condenser, and the uncondensed gas is removed from the gas cooler or the inlet side of the inlet side blower. In addition, the exhaust port of the adsorption tank that has completed the desorption process is opened between the desorption process and the adsorption process, and the return blower installed in the second path is operated and the outside air introduced into the adsorption tank A method for treating a solvent-containing gas, comprising a step of sending water vapor remaining in the adsorption tank to the inlet side of the gas cooler. The method for treating a solvent-containing gas according to claim 1 or 2, wherein the direction of ventilation of the outside air supplied to the adsorbent is opposite to the direction of ventilation of the solvent-containing gas in the adsorption step.

Images