JPH0515934Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] This invention efficiently removes solvents from solvent-containing processing gases generated from cleaning equipment, painting plants, printing plants, chemical plants, semiconductor plants, dry cleaning plants, etc. This invention relates to a solvent recovery device that adsorbs and recovers solvents.

[Prior Art] Conventionally, various solvent recovery devices have been used to prevent environmental pollution and to effectively utilize organic solvents. FIG. 4 is a schematic diagram of a conventional solvent recovery apparatus, in which a plurality of adsorption towers are arranged in parallel to alternately adsorb and desorb organic solvents in a process gas.

The plurality of adsorption towers 31a and 31b have an adsorption unit 33 equipped with adsorption filters 32a and 32b therein.
a, 33b, and a discharge port 3 at the top.
4a and 34b are formed. A processing gas supply line 36 for supplying an organic solvent-containing processing gas by a blower 35 is branched, and the branched processing gas supply lines 36a, 36b are connected to each adsorption tower 31a, 31b. In addition, each processing gas supply line 36
First electromagnetic valves 37a and 3 are provided in a and 36b, respectively.
7b is provided.

This solvent recovery device also has a heating medium supply line 38 for desorption such as water vapor. This heating medium supply line 38 branches, and the branched heating medium supply lines 38a and 38b are connected to each adsorption tower 3, respectively.
1a, 31b, and a second electromagnetic valve 3 is connected to each heating medium supply line 38a, 38b.
9a and 39b are provided.

An air cylinder 42 is connected to the upper part of the adsorption towers 31a and 31b via support rods 40a and 40b.
a, 42b are provided, and this air cylinder 42
Valve bodies 41a and 41b that close the discharge ports 34a and 34b are fixed to a and 42b. Further, the lower part of the device is covered with a frame (not shown). Each adsorption tower 31a, 31b has a recovery line 44 provided with a third electromagnetic valve 43a, 43b, respectively.
a and 44b are connected. This collection line 4
4a and 44b are joined together and connected to a condenser 45 cooled with a refrigerant such as cooling water. The organic solvent liquefied in the condenser 45 and the heating medium are separated by a separator 46, and the organic solvent is recovered. Further, the gaseous organic solvent that has not been liquefied in the condenser 45 is recycled to the processing gas supply line 36 through a recycling line 47.

The adsorption/desorption operation in the above solvent recovery device is performed as follows.

During the adsorption treatment of the process gas, the process gas is supplied to one of the adsorption towers 31a, 31b through the process gas supply lines 36a, 36b by opening and closing the first electromagnetic valves 37a, 37b, and then the process gas is supplied to one of the adsorption towers 31a, 31b by the adsorption filters 32a, 32b. The gas purified by the adsorption treatment is discharged from the discharge ports 34a and 34b.

On the other hand, in the desorption process, the discharge ports 34b and 34a of the other adsorption tower 31b and 31a after the adsorption process are
The valve bodies 41b, 4 of the air cylinders 42b, 42a
It is occluded at 1a. Also, the second solenoid valves 39b, 39
a and the third solenoid valves 43b, 43a, the heating medium for desorption is supplied to the heating medium supply lines 38b, 38.
The other adsorption tower 31b, 3 after adsorption treatment through a
1a, the adsorption filter 32
The organic solvent adsorbed on b and 32a is desorbed. Then, the desorbed gaseous organic solvent is liquefied in a condenser 45 and separated and recovered in a separator 46.

In this way, the first to third solenoid valves 37a, 3
By controlling the opening and closing of the lines 7b, 39a, 39b, 43a, and 43b and the opening and closing of the exhaust ports 34a and 34b by the valve bodies 41a and 41b, adsorption and desorption operations of the process gas are performed alternately.

At this time, the gaseous organic solvent that has not been liquefied in the condenser 45 is recycled to the process gas supply line 36, thereby increasing the recovery rate of the organic solvent.

[Problems to be solved by the invention] However, the above-mentioned solvent recovery device still has insufficient adsorption efficiency and recovery efficiency for organic solvents.
Requires excess adsorbent. More specifically, the suction filters 32a and 32b are connected to the suction portions 33a and 33b.
Even if the space is filled with air, air still exists within the space. In particular, fibrous activated carbon has a higher adsorption rate for organic solvents than granular activated carbon and has excellent adsorption ability, but its bulk density is small and the packing density cannot be increased, so a considerable amount of air is present in the adsorption parts 33a and 33b. Therefore, when a heating medium such as water vapor is sprayed in the desorption step, the organic solvent is desorbed and immediately discharged to the condenser 45 together with the air in the adsorption sections 33a and 33b.

On the other hand, even if the gas containing the organic solvent is cooled by the condenser 45, the amount of organic solvent corresponding to the vapor pressure cannot be liquefied because the liquefaction of the gaseous organic solvent depends on the vapor pressure at the cooling temperature. Further, an organic solvent corresponding to the saturated vapor pressure is present in the gas phase of the condenser 45 and separator 46 and in the recycle line 47. The concentration of this organic solvent is much higher than that of the source gas, ie the process gas. In the desorption process, when recycled gas mixes into the processing gas supply line 36, the concentration of the organic solvent in the processing gas supply line 36 temporarily increases from several thousand ppm to several thousand ppm.
increase to a certain extent. Note that the highly concentrated process gas flows out into the recycle line usually for about 1 to 2 minutes after the start of the desorption operation. Therefore, conventional solvent recovery devices cannot reliably adsorb organic solvents that have temporarily become highly concentrated, resulting in a decrease in recovery efficiency.
In addition, the amount of solvent adsorbed by activated carbon increases as the solvent concentration increases, so if a gas containing a high concentration of solvent is initially adsorbed and then a gas containing a low concentration of solvent is passed through the activated carbon, the adsorbed solvent will be re-desorbed. . Further, as the adsorption efficiency decreases, organic solvents are detected in the purified gas exhausted from the exhaust port, polluting the environment. on the other hand,
To cope with the high concentration of solvent-containing gas recycled from the recycle line 47, the adsorbent must be overfilled even when the concentration of solvent in the source gas, ie, the process gas, is low.

The purpose of this invention is to prevent recycled gas containing a high concentration of organic solvent from entering the processing gas supply line, and to efficiently adsorb and recover the solvent in the processing gas without using excessive adsorbent. An object of the present invention is to provide a solvent recovery device.

[Means for Solving the Problems] The present invention provides an adsorption tower that houses an adsorption filter and has an outlet that can be opened and closed, a processing gas supply line that supplies a solvent-containing adsorption gas to the adsorption tower, and A heating medium supply line that supplies a heating medium for desorption, a condensation section that condenses the solvent desorbed by the heating medium, a separation section that separates the condensed solvent, and a gas phase of the separation section to the processing gas supply line. In the solvent recovery device having a recycle line for merging, a pressure buffer section whose capacity is variable in response to pressure fluctuations in the line is provided in the line between the condensation section and the separation section, the separation section, or the recycle line. The above-mentioned problem is solved by the solvent recovery device.

[Operation] According to the present invention, gas containing a highly concentrated organic solvent can be stored in the pressure buffer section whose capacity is variable in response to pressure fluctuations in the line, and pressure fluctuations in the line can be suppressed. Furthermore, since the recycle line becomes under negative pressure as the processing gas is supplied, the gas containing a highly concentrated organic solvent stored in the pressure buffer section is gradually supplied to the processing gas supply line in accordance with the line pressure.

[Example] Hereinafter, an example of the present invention will be described in detail based on the accompanying drawings.

FIG. 1 is a schematic configuration diagram showing one embodiment of the present invention, FIG. 2 is a partially cutaway schematic front view of the solvent recovery device shown in FIG. 1, and FIG. 3 is a schematic plan view of FIG. 2. be. In the following description, the features of the present invention will be explained in more detail.

A plurality of adsorption towers 1a, 1 of the solvent recovery device of the present invention
b has suction parts 3a, 3b provided with suction filters 2a, 2b, and discharge ports 4a, 4b, as described above. A processing gas supply line 6 for supplying the organic solvent-containing processing gas by the blower 5 is branched and connected to the lower portions of the adsorption towers 1a and 1b. Further, the branched processing gas supply lines 6a, 6b are provided with first electromagnetic valves 7a, 7b, respectively. Heating medium supply line 8 that supplies heating medium for desorption
is branched in the middle and connected to the upper part of each adsorption tower 1a, 1b. Further, the branched heating medium supply lines 8a and 8b are provided with second solenoid valves 9a and 8b, respectively.
9b is provided.

Air cylinders 13a and 13b as actuators for opening and closing operations are attached to the upper portions of the adsorption towers 1a and 1b via support rods 10a and 10b. Also, air cylinders 13a, 13b
There are valve bodies 12a, 1 that close the discharge ports 4a, 4b.
2b is fixed. Also, the lower part of the device is the frame 1
Covered by 1.

In order to recover the gaseous organic solvent desorbed by the heating medium, recovery lines 15a and 15b each provided with a third electromagnetic valve 14a and 14b are connected to the lower part of each adsorption tower 1a and 1b, respectively. . The recovery lines 15a and 15b merge, and the merged recovery line 15 is connected to a condensing section 16 such as a condenser cooled with a refrigerant such as cooling water. The organic solvent liquefied in the condensing section 16 and the heating medium are separated by specific gravity separation in a separating section 17 such as a decanter, and the organic solvent is recovered. Further, in the same manner as described above, the gaseous organic solvent that has not been liquefied in the condensing section 16 and the gas phase in the separating section 17 are recycled to the processing gas supply line 6 through the recycling line 18.

A pressure buffer section 20 whose capacity is variable in response to pressure fluctuations in the line is connected to the recycle line 18 via a pipe 19. As shown in FIG. 2, this pressure buffer section 20 is composed of a gas reservoir bag 21 housed in a case 22.

By providing such a variable capacity pressure buffer section 20, even if gas containing a high concentration of solvent flows into the recycle line 18 during the desorption process, etc., the gas can be stored in the bag body 21, and pressure fluctuations in the line can be prevented. can be suppressed. Further, as the processing gas is supplied, the recycle line 18 becomes under negative pressure, so the gas containing the highly concentrated organic solvent stored in the bag body 21 is gradually supplied to the processing gas supply line 6 according to the line pressure. . Furthermore, since the bag body 21 is housed in the case 22, the bag body 21 does not expand excessively and damage to the bag body 21 can be prevented, and by adjusting the volume of the case 22, the bag body The amount of gas that can be stored within 21 can be adjusted. Therefore, even if gas containing a high concentration of organic solvent flows into the recycle line 18, the concentration of the solvent in the treated gas supply line 6 can be averaged, and the organic solvent can be removed by the adsorption filters 2a and 2b of the adsorption towers 1a and 1b. can be reliably absorbed. Further, by alternately supplying the processing gas continuously generated from the generation source to the plurality of adsorption towers 1a and 1b, the adsorption/desorption process can be performed continuously and the solvent can be recovered.

Note that the bag only needs to have the ability to expand and contract in response to pressure fluctuations in the line, particularly pressure fluctuations during the attachment/detachment process. Accordingly, the bag can be made of stretchable or non-stretchable materials. Further, the pressure buffer is not limited to the above-mentioned bag, and may be any other material whose capacity can be varied in response to pressure fluctuations. For example, it may be configured with a cylinder and a sliding member that slides within the cylinder in response to pressure fluctuations. In this case, by adjusting the volume of the cylinder and the weight of the sliding member, the amount of gas that can be stored in the cylinder and the discharge speed of the stored gas can be adjusted. Therefore, pressure fluctuations in the line can be absorbed by the sliding member's own weight, and the concentration of organic solvent in the gas in the recycle line can be made uniform.

Note that the pressure buffer section may be constituted by a suction and discharge mechanism such as a cylinder and a piston, and the gas in the recycle line may be sucked and discharged in conjunction with the attachment/detachment operation. At this time, the operation and stopping of the suction and discharge mechanism may be controlled based on a detection signal from a pressure sensor. Also, normally, gas containing a high concentration of organic solvent flows into the recycle line about 1 to 2 minutes after the start of the desorption operation, so after the start of the desorption operation, the
Activation and stopping of the suction and discharge mechanism may be controlled.

Further, the variable capacity pressure buffer section may be provided not only in the recycle line 18 but also in the line 15c between the condensation section 16 and the separation section 17 or the separation section 17.

Note that the solvent recovery device of the present invention can be applied not only to a plurality of adsorption towers but also to one adsorption tower. That is, in FIGS. 1 to 3, one adsorption tower 1b
is omitted, and the other adsorption tower 1a is connected to a process gas supply line 6 having a solenoid valve 7a, a heating medium supply line 8 having a solenoid valve 9a, and a recovery line 15 having a solenoid valve 14a. It may also be a solvent recovery device. This one-column solvent recovery equipment is
Capable of processing discontinuously generated solvent-containing gas.
For example, in the case of a dry cleaning machine, gas containing solvents such as perchlorethylene generated during the deodorizing process and the process of loading and unloading the laundry is transferred to the process gas supply line 6.
By supplying it to the adsorption tower 1a, it can be adsorbed by the adsorption filter 1a. On the other hand, by supplying a heating medium from the heating medium supply line 8 to the adsorption tower 1a in the same manner as described above during a process in which a solvent-containing gas is not generated, such as a washing process or a drying process,
Adsorbed solvent can be desorbed. Also collection line 1
5. The organic solvent can be recovered in the separation section 17 via the condensation section 16. In this one-column solvent recovery device, similarly to the above, the pressure buffer section 20 temporarily stores high-concentration solvent-containing gas and prevents it from flowing into the processing gas supply line 6, allowing it to be used in the next adsorption step. In the pressure buffer section 20, the highly concentrated solvent-containing gas is sent to the adsorption tower 1a. In this way, the single-column solvent recovery equipment can efficiently adsorb and recover solvents without using excessive amounts of adsorbent, and allows recycled gas containing highly concentrated solvents to be discharged outside the equipment. Leakage can be prevented.

The solvent recovery device of the present invention is useful for recovering solvents from gases containing solvents such as fluorocarbons, trichlorethylene, and various organic solvents generated in various processes. In particular, it is suitable for a solvent recovery device using fibrous activated carbon with a small bulk density as an adsorbent.

[Effects of the invention] As described above, according to the solvent recovery device of the invention, a pressure buffer section with a variable capacity whose capacity changes according to pressure fluctuations in the line is provided. It is possible to prevent recycled gas from entering the process gas supply line. Moreover, the adsorption efficiency and recovery efficiency for the solvent in the process gas can be increased without using an excessive amount of adsorbent.

[Experimental Examples] The present invention will be described in more detail below based on experimental examples.

Comparative Experimental Example As shown in Figure 1, a solvent recovery device (Osaka Gas Engineering Co., Ltd. ) manufactured by ESR-3F) and 2000ppm of Freon R-113 as a solvent gas.
The processing gas containing the gas was processed at a processing air flow rate of 3 m ³ /min. As a result, the concentration of CFCs in the process gas, including recycled gas, decreases at the beginning of the desorption cycle.
It rose to around 7000ppm. Following the change in concentration at the entrance to the adsorption tower, the fluorocarbon gas concentration at the outlet also varied greatly. This situation is shown in FIG.

Experimental Example A gas storage bag with an internal capacity of 20 was provided in the recycling line of the solvent recovery device, and the treated gas was treated in the same manner as in the comparative experimental example.

As a result, the average CFC concentration at the entrance to the adsorption tower was 3000 ppm, and fluctuations in concentration were significantly suppressed. In addition, the fluorocarbon gas concentration on the outlet side was also averaged, and the fluorocarbon concentration did not rise temporarily. This situation is shown in FIG.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention;
FIG. 2 is a partially cutaway schematic front view of the solvent recovery device shown in FIG. 1, FIG. 3 is a schematic plan view of FIG. 2, FIG. 4 is a schematic configuration diagram of a conventional solvent recovery device, and FIG. FIG. 6 is a graph showing the results of the experimental example, and FIG. 6 is a graph showing the results of the comparative experimental example. 1a, 1b...Adsorption tower, 2a, 2b...Adsorption filter, 4a, 4b...Discharge port, 6, 6a, 6b
... Processing gas supply line, 8, 8a, 8b ... Heating medium supply line, 16 ... Condensation section, 17 ... Separation section, 18 ... Recycle line, 20 ... Pressure buffer section.

Claims (1)

[Scope of utility model registration request] an adsorption tower that houses an adsorption filter and has an outlet that can be opened and closed; a processing gas supply line that supplies a solvent-containing processing gas to the adsorption tower; a heating medium supply line that supplies a heating medium for desorption to the adsorption tower; In a solvent recovery device having a condensation section that condenses the solvent desorbed by a heating medium, a separation section that separates the condensed solvent, and a recycle line that joins the gas phase of the separation section to the processing gas supply line, A solvent recovery device characterized in that a line between a condensation section and a separation section, a separation section, or the recycling line is provided with a pressure buffer section whose capacity is variable in response to pressure fluctuations in the line.