JP2001347126A - Gas treating device and gas treating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the adsorption ability of active carbon fiber materials more effectively utilizable than heretofore and to enhance the recovering efficiency of an organic solvent from the gas to be treated. SOLUTION: The gas treating device for alternately switching an adsorption treating state and a desorption state using the active carbon fiber materials as adsorption elements is constituted by connecting a discharge pipe (vessel drain line) at the bottom of an adsorption vessel and piping (recovering liquid line) for discharging the condensate from a cooling section independently or confluently from or with a solvent recovering section in such a manner that the aggregated drain does not flow backward in desorption, by which the wetting of the active carbon fiber materials by the back flow of the condensate is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas adsorbing / desorbing apparatus and a gas adsorbing / desorbing apparatus capable of adsorbing an organic substance and desorbing the adsorbed organic substance using fiber activated carbon (hereinafter referred to as ACF) as an adsorbent. The present invention relates to a processing method using.

[0002]

2. Description of the Related Art In recent years, regulations on the emission concentration of harmful air pollutants have been strengthened, and it has been desired to reduce the concentration of exhaust gas from a gas treatment device.

Conventionally, the above-mentioned gas treatment apparatus comprises one or more pairs of adsorption tanks for adsorbing an organic solvent of a gas to be treated (that is, exhaust gas) with an activated carbon fiber material, a gas supply means for each adsorption tank, and a gas supply for desorption. And a switching means for switching between an adsorption processing state in which a gas to be treated is supplied to the adsorption tank and a desorption processing state in which a desorption gas is supplied to the adsorption tank.

[0004] The above gas processing apparatus uses an ACF. ACF has an excellent function of adsorbing a low concentration of organic gas, and has been used as an adsorbent for a long time. For example, A
An apparatus in which a CF is fixed to a support or formed in a cylindrical shape by self-support and arranged in a vertical form in a core material is disclosed in JP-A-51-3.
No. 8278, and Japanese Patent Publication No. 64-11326. In addition, actual fairness 7-2028, 2029, 203
A similar adsorption / desorption device is also proposed for No. 0. They are,
In each case, steam is blown out to the core material containing the ACF,
The organic substance adsorbed on the ACF is desorbed.

[0005] The water content of ACF greatly affects the adsorption capacity of ACF. As the water content increases, the adsorption capacity decreases extremely. For this reason, various proposals have been made in the above-mentioned proposal, for example, from the upper or lower direction of the steam ejection, or from the center inside direction of the core material. However, there is a problem in that the drain in the jetted steam is scattered to the ACF below the core material at the start of operation and the ACF contains moisture, thereby lowering the gas adsorption ability.

Furthermore, in the gas treatment apparatus using the gas adsorption element described above, it has been difficult to stably operate the adsorption and desorption continuously for a long period of time. In other words, in the case where the gas is adsorbed on the element and the vapor is ejected and the adsorbed gas is desorbed alternately and repeatedly used, especially low-boiling solvents are significantly affected by the temperature of the outside air and the like, and piping connected to the solvent recovery section is used. Condensate often flows back from Due to this backflow, the condensed liquid comes into contact with the ACF in the gas treatment element, and there is a problem that the adsorbing capacity is greatly reduced, which also hinders the continuous operation.

[0007]

SUMMARY OF THE INVENTION The present invention relates to a gas adsorption / desorption apparatus capable of continuously and efficiently absorbing and desorbing an organic gas, particularly a solvent having a low boiling point, using ACF. .

[0008]

The liquid condensed in the adsorption tank during the desorption is discharged to the separator through the tank drain line at the bottom of the adsorption tank, and the uncondensed vapor and the solvent pass through the desorption gas line. After condensing after going to the condenser, it joins the tank drain line and the solvent recovery section (hereinafter referred to as separator)
Is discharged to For example, the condensed liquid passes through the tank drain line 8 from the lower part of the adsorption tank B in FIG. 1 (for continuous operation, when the tank A is operated as the adsorption tank, the tank B is a desorption tank), and the separator passes through the tank drain line 8. At this time, the solvent boiling in the tank drain line 8 is heated to heat the solvent remaining in the tank drain line 8, and condensate containing the solvent flows backward. This tendency becomes remarkable when the outside air temperature is low and the gas to be treated is a low-boiling solvent.

According to the present invention, in order to prevent the backflow of the condensed liquid, the condensed liquid containing the high-concentration solvent discharged from the condenser is prevented from flowing into the tank drain line through the collected liquid line. To prevent the condensed liquid from flowing back into the tank. Conventionally, the recovery liquid line is connected at the lowermost end of the tank drain line, and then rises upward for the purpose of liquid sealing, and is connected to the separator. The merging is performed by mixing the condensate in the high-temperature tank drain line and the condensate in the relatively low-temperature recovery liquid line cooled by the condenser to lower the temperature of the condensate flowing into the separator as a whole. This was for suppressing the volatilization of the solvent inside. However, when the solvent to be recovered has a boiling point lower than that of water, a high-condensate in which the high-concentration solvent flowing from the recovery line into the tank drain line condenses in the adsorption tank flows from the tank drain line, and this solvent This causes boiling due to heating, and the condensed liquid in the tank drain line was caused to flow back into the adsorption tank. As shown in FIG. In this way, the backflow of the condensate was prevented.

FIG. 3 shows a case where the temperature of the solvent in the separator is increased due to the high temperature of the condensate in the recovery liquid line, and the concentration of the gas returned to the processing gas inlet may be increased. By connecting the recovery liquid line after the rise of the tank drain line, the concentration of the returned gas can be suppressed. Due to these pipe route changes, the solvent concentration in the tank drain line becomes only a trace amount in the high-temperature condensate condensed from the adsorption tank, it does not boil and does not cause backflow, and the ACF does not wet with the liquid to be treated. , Enabling continuous operation.

As an organic gas, its effect is particularly remarkable for a solvent having a low boiling point. Usually, these gases are discharged to the outside of the core together with the vapor, but outside the core, upon cooling, separation occurs into two layers of a water layer and a solvent layer. In general, the specific gravity of the organic solvent is larger, and the organic solvent is stored below the two layers. Therefore, when a backflow of the condensed liquid occurs from the gas outlet at the lower part of the core material, the ACF is wetted by the condensed liquid, so that the adsorption capacity is reduced.

The organic gas referred to here is methylene chloride,
Trichloroethane, trichloroethylene, carbon tetrachloride,
Refers to an organic solvent such as chloroform. In the present invention, a low-boiling solvent such as methylene chloride is particularly suitable.

[0013] This change in the recovery liquid line also eliminates the wetting of the ACF by the condensate, makes it possible to keep the ACF dry at all times, facilitates the control of the temperature and relative humidity in the adsorption / desorption tank, and improves the adsorption efficiency. Was further improved.

Further, since the ACF of the core material does not always come into contact with moisture and maintains the adsorption capacity, it is possible to continuously switch between the adsorption tank and the desorption tank. As a result, the device of the present invention is able to continuously absorb and desorb the organic gas, smoothly operate at the time of operation and stoppage, and is excellent in operability, and can be operated for a long period.

In the present invention, ACF means acrylonitrile (PAN) -based fiber, rayon-based, coal pitch-based, phenolic resin-based, petroleum pitch-based raw material fiber, and the specific surface area of 300 to 3,000 m. ² /
g, fiber diameter is about 2 to 30 μm, fiber length is 0.5 to
It is preferable to use fibrous activated carbon having a diameter of about 10 mm and a pore radius of about 8 to 20 °.

According to this measure, the steam outlet may be located at any position above or below the core material or at the center of the core material.
The upper case is excellent from the viewpoint of the spontaneous fall of steam, the lower case is excellent in that the ACF under the ACF has little wetting, and the center is excellent in that the steam is easily distributed uniformly, and is free depending on the arrangement conditions of the apparatus. It became possible to choose.

[0017]

Next, an example of an embodiment of the present invention will be described with reference to FIG. A solvent mixed gas (a gas to be treated) X containing an organic solvent is supplied to a pre-filter 1 (a condenser 1).
0, the gas remaining in the separator 12 is * 3, * 4
After passing through the pre-filter 1 again, the air is passed through the adsorption tank 3 by the blower 2 (in this case, the adsorption tank 4 is not sent to the solvent mixed gas, but is closed by the automatic damper 6. In the tank 4, steam is blown out and sent to a state in which the gas already adsorbed by the adsorption element 5 is being desorbed. The gas is adsorbed by the adsorption element 5, and as the clean air Y, 3 is discharged out of the system through the exhaust port 14. The condensate is sent to the separator 12 through the tank drain line 8 below the adsorption tank 4. Uncondensed vapor and solvent pass through the desorption gas line 9 and pass through the condenser 1
Sent to 0. From the condenser 10, a condensate containing a high-concentration organic solvent passes through the recovery liquid line 11, joins the tank drain line 8, and is sent to the separator 12.

At this time, in the case of a mixed gas containing a low-boiling solvent, particularly, the lower the external temperature is, the larger the amount of the gas flowing into the tank drain line 8 is. Becomes noticeable and squirts into the adsorption tank 4,
Wet the ACF. For this reason, the present invention prevents the backflow of the condensed liquid to the lower part of the adsorption tanks 3 and 4 by disconnecting the recovery liquid line 11 from the tank drain line 8 and connecting it to the separator 12 alone.

FIGS. 2 and 3 show enlarged piping diagrams of the condenser and the separator.

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

The solvent adsorbed on the adsorption element 5 causes the vapor W1 to be ejected to the element in the adsorption tank 4 to desorb the solvent. The amount of steam is controlled by a steam control automatic valve 7. This vapor is blown into the adsorption tank 4 from above or below (dotted line in FIG. 1).

As a result, the solvent mixed gas X is released out of the system as clean air Y and is recovered as the solvent Z. The steam W1 for desorption is recovered as recovered water W2.

Examples will be described below. 90 methylene chloride
A solvent mixed gas containing 40 ppm at 40 ° C. and an air volume of 70 Nm
Air was blown from the blower 2 to the adsorption tank 3 at a rate of ³ / min. 8 in adsorption tank 4
After desorption for a minute, the air flow to the adsorption tank 3 was blocked by the automatic damper 6, and then steam was blown 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 gas adsorption was performed in the adsorption tank 4 this time. This operation of adsorption and desorption was repeated 10 times or more. The concentration of the gas discharged out of the system was measured using a measuring device of a total hydrocarbon meter manufactured by Shimadzu Corporation.

The same conditions were used when the recovered liquid line was connected to the lowermost end of the tank drain line. The exhaust gas concentrations during continuous operation are shown in FIGS.

As can be seen from the graphs of FIGS. 4 and 5, it is clear that the concentration of gas discharged out of the system is stable and low even in the operation of alternately switching the adsorption tanks 3 and 4. There is almost no change in the gas concentration even if it is operated continuously.

[0026]

As described above, by changing the piping route of the recovery liquid line so that the condensate of the recovery liquid line does not flow into the tank drain line, the adsorption and desorption of the mixed gas containing the low boiling point solvent can be continuously performed. It is possible to stably and efficiently perform the above, which greatly contributes to the industry.

[Brief description of the drawings]

FIG. 1 is an example of a basic processing flow diagram of a gas adsorption processing apparatus.

FIG. 2 shows an example of a single connection of the recovery liquid line 11

FIG. 3 shows an example of a junction connection of the recovery liquid line 11

FIG. 4 shows the exhaust gas concentration when the recovery liquid line 11 is conventionally connected

FIG. 5: Exhaust gas concentration when the recovery liquid line 11 is connected alone

[Explanation of symbols]

 1: Pre-filter 2: Blower 3: Adsorption tank (when 4 functions as adsorption tank) 4: Desorption tank (when 3 functions as adsorption tank) 5: Adsorption element 6: Automatic damper 7: Automatic steam control valve 8 : Tank drain line 9: Desorption gas line 10: Condenser 11: Recovered liquid line 12: Separator 13: Return gas line 14: Exhaust port 15: Steam line X: Solvent mixed gas (gas to be treated) Y: Clean air Z: Recovery Solvent W1: Steam W2: Recovered water W3: Cooling water

Claims (3)

[Claims] An adsorption tank for adsorbing a gas to be treated with an activated carbon fiber material is provided. A gas supply means for the adsorption tank and a gas supply means for desorption are provided to the adsorption tank. In a gas treatment apparatus provided with a switching means between an adsorption treatment state for supplying and a desorption treatment state for supplying a desorption gas, a pipe (tank drain line) for discharging condensed liquid from a lower portion of the adsorption tank and a cooling unit A gas adsorption treatment apparatus characterized in that a pipe (recovery liquid line) for discharging condensate is connected to the solvent recovery section independently or in a combined manner. 2. A gas processing apparatus according to claim 1, wherein a gas adsorbing element having a steam outlet at an upper portion, a lower portion, or a central portion of the cylindrical core material is used. 3. A method for treating an organic agent-containing gas using the gas treatment apparatus according to claim 1.