JP2003053131A - Apparatus and method for treating gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus and a method for treating gas in which the adsorbing capacity of an activated carbon fiber material can be used more effectively than usual and the recovery efficiency of an organic solvent from the gas to be treated is enhanced. SOLUTION: This gas treating apparatus for treating the gas to be treated by using the activated carbon fiber material as an adsorbing element and changing the adsorbing state of the activated carbon fiber material and the desorbing state alternately has a baffle arranged at the inlet of a discharge pipe at the bottom of an adsorbing tank so that the drain condensed when desorbed does not flow backward and consequently the activated carbon fiber material can be prevented from being wetted owing to the backward flow of the condensed liquid.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas treatment device which uses activated carbon fiber (hereinafter referred to as ACF) as an adsorbent to adsorb a gas containing an organic solvent and at the same time to desorb and recover the adsorbed organic solvent, and The present invention relates to a processing method using an apparatus.

[0002]

2. Description of the Related Art In recent years, emission concentration regulations for harmful air pollutants have been strengthened, and when treating harmful air pollutants with a gas treatment device, the concentration of harmful air pollutants at the gas treatment device outlet is reduced as much as possible. Is desired.

Conventionally, the above-mentioned gas treatment device has one or more pairs of adsorption tanks for adsorbing a gas to be treated (that is, an exhaust gas such as a gas containing an organic solvent) with an activated carbon fiber material, and a means for supplying a gas to be treated to each adsorption tank. And a desorption gas supply means, and means for switching between an adsorption treatment state in which the gas to be treated is supplied to the adsorption tank and a desorption state in which the gas to be treated adsorbed by the desorption gas is desorbed. It was

Conventionally, the above-mentioned gas treatment device uses AC as the adsorbent.
Although F and granular activated carbon are generally used, ACF has a specific surface area of 1000 to 2000 m ² / m compared to granular activated carbon.
It has a large g and a large number of micropores effective for gas adsorption on the surface of the adsorbent and has an extremely high adsorption / desorption rate. Therefore, it is known and used as the most general method in the field of organic solvent recovery. For example, by fixing the ACF to a support,
Alternatively, a device in which it is formed into a cylindrical shape by self-support and arranged in a vertical mold in a core material is proposed in JP-A-51-38278 and JP-A-64-11326. Also, fairness 7
No. 2028, 2029, 2030 proposes a gas device for performing similar adsorption and desorption. These are all
Water vapor is jetted onto the core material containing the ACF to desorb and collect the organic solvent adsorbed on the ACF.

Generally, the ability of ACF to adsorb organic solvent is
It is easily affected by moisture, and when the water content of ACF is high, the adsorption capacity is extremely reduced. For this reason, in the above-mentioned proposal, various ideas have been devised such that the direction of jetting water vapor to the core material, that is, the adsorption element is from above or below, or from the center inside direction. However, when the operation is started, there is a problem that the adsorbing element is wetted due to the scattering of the drain of the jetted water vapor and the reverse flow of the condensate, which wets the adsorbing element and reduces the adsorbing ability of the organic solvent of ACF.

Further, in the gas treatment device using the above-described gas adsorption element, it has been difficult to carry out stable continuous adsorption / desorption for a long period of time. That is,
When water vapor is jetted to the element to which the organic solvent is adsorbed and the adsorbed organic solvent is desorbed alternately and repeatedly, the low boiling point solvent is significantly affected by the temperature of the outside air, etc. (Separated)
Condensate often flows back from the pipe leading to. Due to this backflow, there is a problem that the condensate comes into contact with the ACF in the gas treatment element, greatly lowering the adsorption capacity, which has also hindered continuous operation.

[0007]

DISCLOSURE OF THE INVENTION The present invention relates to a gas treatment apparatus capable of continuously adsorbing and desorbing an organic solvent-containing gas, particularly a low boiling point solvent, using ACF with high efficiency. is there.

In the continuous operation of the gas treatment apparatus using the adsorption element, in the desorption process, the desorption gas, steam, and the desorbed desorption gas become a condensate in the adsorption tank at the initial stage of supplying the desorption gas. It is discharged to the separator through the tank drain line at the bottom. On the other hand, the uncondensed water vapor and the organic solvent pass through the desorption gas line, condense in the cooling unit (hereinafter referred to as a condenser), merge with the tank drain line, and are discharged to the separator. For example, the condensate from the lower part of the adsorption tank 4 in FIG. 1 (because of continuous operation, it becomes a desorption tank when another tank is operating as an adsorption tank) passes through the tank drain line 8 and the separator 12 However, the condensate retained in the tank drain line 8 at this time is heated by the condensate from the lower part of the adsorption tank 4 to be boiled gas and flow backward. This tendency becomes remarkable when the outside air temperature is low, the condensate is large, and the gas to be treated contains a low boiling point solvent.

[0009]

According to the present invention, a baffle is installed at the outlet of the adsorption tank to the tank drain line to prevent wetting of the adsorption element by the backflow of the condensate into the tank. The baffle, as shown in FIG. 2 by way of example, is one in which a pillar is erected on a flat plate and mounted on the discharge port. Water vapor, the gas to be treated and the condensate can freely pass between these columns, and they do not affect the pressure balance in the tank or the flow of gas. Even if the outside air temperature decreases and the amount of condensate in the adsorption tank increases and flows back into the adsorption tank, the baffle can prevent the condensate from scattering to the adsorption element. Therefore, continuous operation is possible without wetting the adsorption element with the condensate.

The shape of the baffle may be an umbrella shape or a hemispherical shape other than the above, and a conical shape or a flared shape with respect to the discharge port is preferable. Further, it is installed by a pillar so as to be located above the discharge port. Any material may be used as long as it does not dissolve in the organic solvent contained in the gas to be treated. In addition, it is installed so that it can be detached from the adsorption tank by the column, and it can be detached and easily operated for cleaning.

In the case of a gas treatment apparatus in which an organic solvent is continuously treated by desorption of water vapor using an adsorption element, this effect is remarkable especially in a low boiling point solvent. Normally, the organic solvent is discharged together with water vapor out of the adsorption element. However, in the case of an organic solvent that is difficult to dissolve in water, cooling occurs outside the adsorption element to cause separation into two layers, a water layer and a solvent layer. Generally, the specific gravity of the organic solvent is large, and the organic solvent is separated into the lower two layers, so that the organic solvent is likely to be stored in the lowermost part of the drain line of the tank, and the reverse flow due to boiling becomes remarkable. Therefore, when a backflow of the condensate is generated from the lower part of the adsorption tank, the condensate wets the adsorbing element, thereby lowering the adsorption capacity.

The organic solvent referred to here is methylene chloride,
Trichloroethane, trichlorethylene, carbon tetrachloride,
It refers to an organic solvent such as chloroform, and in particular, a solvent such as methylene chloride having a lower boiling point than water and a specific gravity heavier than water is suitable in the present invention. By installing this baffle, wetting of the adsorption element by the condensate is eliminated, the temperature and relative humidity inside the adsorption / desorption tank are easily controlled, and the adsorption efficiency is further improved.

Further, since the adsorption element does not always come into contact with moisture and the adsorption ability is maintained,
The adsorption tank and desorption tank can be continuously switched. As a result, the device of the present invention is capable of adsorbing and desorbing the organic solvent-containing gas continuously along with smooth operation at the time of operation and stoppage, and is excellent in operability, and can be operated for a long period of time.

The ACF used in the present invention means a specific surface area of 1000 obtained by treating a raw material fiber such as acrylonitrile (PAN) type fiber, rayon type, coal pitch type, phenol resin type and petroleum pitch type by an existing method. ~ 2000m
² / g, the fiber diameter is about ² to 30 μm, and the fiber length is 0.
Any may be used as long as it has a pore radius of 5 to 10 mm and a pore radius of 5 to 20 Å.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Next, an example of an embodiment of the present invention will be described with reference to FIG. Organic solvent-containing gas (process gas)
X passes through the pre-filter 1 (gas * 3, * 4 staying in the condenser 10 and the separator 12 is returned to the pre-filter 1 again through the return gas line 13), and the adsorption tank 3 is blown by the blower 2. (At this time, the organic solvent-containing gas is not sent to the adsorption tank 4 and is blocked by the automatic damper 6. In the adsorption tank 4, steam is jetted to remove the gas already adsorbed by the adsorption element 5. (In a desorbed state), the adsorption element 5 adsorbs the gas, and is discharged as clean air Y from the exhaust port 14 of the adsorption tank 3 to the outside of the system. The condensate is sent to the separator 12 through the tank drain line 8 below the adsorption tank 4. The uncondensed water vapor and the organic solvent are sent to the condenser 10 through the desorption gas line 9. A condensate containing a high-concentration organic solvent flows from the condenser 10 through the recovery liquid line 11 to the tank drain line 8 and is sent to the separator 12.

At this time, in the case of the mixed gas in which the low boiling point solvent is mixed, the amount of the condensate flowing back to the adsorption tank increases because the amount of the gas flowing into the tank drain line 8 increases as the external temperature decreases. Becomes noticeable and jets out into the adsorption tank 4,
Wet the adsorption element.

FIG. 2 shows an enlarged view of the baffle in the adsorption tank (desorption tank) and above the tank drain line. In particular, even if the outside air temperature decreases and the amount of the condensed liquid in the adsorption tank increases and flows back into the adsorption tank, the baffle can prevent the condensed liquid from scattering to the adsorption element. Therefore, continuous operation became possible without wetting the adsorption element with the condensate.

As a result, even if the adsorption tanks 3 and 4 are switched and continuously operated, the concentration of the organic solvent gas constantly discharged outside the system can be kept low and constant.

The organic solvent adsorbed by the adsorption element 5 is ejected from the water vapor W1 in the adsorption tank 4 through the automatic valve 7 to the adsorption element in the adsorption tank to desorb the organic solvent. The amount of water vapor is controlled by the vapor adjustment automatic valve 7.
In addition, this water vapor is either above or below the adsorption tank 4 (see FIG.
It is ejected from the inside (dotted line).

As a result, the organic solvent-containing gas X is discharged to the outside of the system as clean air Y, and the desorbed uncondensed organic solvent gas and water vapor are cooled by the condenser 10 and condensed to be collected in the separator 12. To be done. The liquid that is difficult to dissolve in water is collected as the heavy specific gravity liquid Z and the light specific gravity liquid W2 due to the specific gravity. For example, organic solvent gas has a specific gravity of 1.3 (2
In the case of methylene chloride (0/4 ° C.), the heavy gravity liquid Z is recovered as methylene chloride, and the light gravity liquid W2 is recovered as steam condensed water.

[0021]

Example 1 Using the gas treatment apparatus shown in FIG. 1 equipped with the baffle of the present invention, an organic solvent-containing gas containing 9000 ppm of methylene chloride at a temperature of 40 ° C. was blown with an air volume of 70 Nm ³ /
The air was blown from the blower 2 to the adsorption tank 3 in minutes. Desorption was performed in the adsorption tank 4 for 8 minutes, and then the air blow to the adsorption tank 3 was blocked by the automatic damper 6, and then steam was jetted into the adsorption element 5 of the adsorption tank 3. At the same time as this treatment, the automatic damper 6 of the adsorption tank 4 was opened, and this time, gas adsorption was performed in this adsorption tank 4. This operation of adsorption and desorption was repeated 10 times or more. An enlarged view of the baffle is shown in FIG. The concentration of the gas discharged outside the system is the total hydrocarbon meter HCM- manufactured by Shimadzu Corporation.
The measurement was performed at the confluence of the outlet of the blower 2 and the outlets of the adsorption tanks 3 and 4 using the measuring instrument of 1B. The gas concentrations at the inlet and outlet of the gas treatment device during continuous operation are shown in FIG.

[0022]

Comparative Example 1 FIG. 1 except that the baffle of the present invention is not installed.
The same conditions were used for the case of using an apparatus equivalent to. The gas concentration during continuous operation is shown in FIG.

As can be seen by comparing the graphs of FIGS. 3 and 4, the concentration of gas discharged to the outside of the system by using the method of the embodiment of the invention is stable even in the alternate switching operation of the adsorption tanks 3 and 4. And it is clear that the concentration is low. There is almost no change in gas concentration even during continuous operation.

[0024]

As described above, by installing the baffle so that the condensate in the recovery liquid line does not flow into the tank drain line, the adsorption and desorption of the organic solvent-containing gas containing the low boiling point solvent can be continuously stabilized. It will be possible to perform with high efficiency, which will greatly contribute to the industrial world.

[Brief description of drawings]

FIG. 1 Example of basic processing flow diagram of gas adsorption processing device

FIG. 2 is an example of an enlarged view of the baffle 16.

FIG. 3 is an exhaust gas concentration when a baffle 16 is provided (Example)

FIG. 4 Exhaust gas concentration without baffle 16 (comparative example)

[Explanation of symbols]

1: Pre-filter 2: Blower 3: Adsorption tank (desorption tank when 4 functions as an adsorption tank) 4: Desorption tank (adsorption tank when 3 functions as a desorption tank) 5: Adsorption element 6: Automatic Damper 7: Automatic steam control valve 8: Tank drain line 9: Desorption gas line 10: Condenser 11: Recovery liquid line 12: Separator 13: Return gas line 14: Exhaust port 15: Steam line 16: Baffle (general name for 17, 18) ) 17: Support 18: Backflow prevention plate X: Organic solvent-containing gas (gas to be treated) Y: Clean air Z: Heavy specific gravity liquid W1: Water vapor W2: Light specific gravity liquid W3: Cooling water

Claims (4)

[Claims] 1. An adsorption element of an activated carbon fiber material for adsorbing a gas to be treated is provided in an adsorption tank, and means for supplying a gas to be treated and a desorption gas supply means for the adsorption tank and a desorption gas supply means. In the gas processing device provided with means for cooling and recovering the desorbed gas desorbed by
A gas adsorption treatment device, characterized in that a baffle is provided at an inlet (lower part of the adsorption tank) of a pipe (tank drain line) connecting from a lower part of the adsorption tank to a solvent recovery section (separator). 2. A means for switching between an adsorption treatment state for adsorbing a gas to be treated and a desorption treatment state for desorbing a gas to be treated adsorbed by a desorption gas, wherein two or more adsorption tanks are provided. 1. The gas processing device according to 1. 3. The gas treatment apparatus according to claim 1, wherein the desorption gas supply means is arranged at an upper part, a lower part or a central part of the core material of the adsorption element in the adsorption tank. 4. A method for treating a gas containing an organic solvent by using the gas treatment apparatus according to claim 1.