JPH0857247A - Recovery of solvent - Google Patents

Abstract

PURPOSE: To sufficiently desorb a solvent from an adsorbent by preventing a foaming phenomenon,while keeping the adsorbing efficiency of the solvent high after desorption in a solvent recovering method. CONSTITUTION: In the solvent recovering method using an apparatus equipped with a solvent adsorbing column 1, the steam generator 5 provided to the lower part of the solvent adsorbing column, the condenser 10 provided to the solvent adsorbing column and the specific gravity separator 16 connected to the condeser 10 through first piping 14 and connected to the steam generator through second pipings 17, 19, 20 and supplying the water separated from a solvent by the specific gravity separator 16 to the steam generator 5 through the second pipings 17, 19, 21, a defoaming agent is added to the separated water.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic solvent generated from a solvent vapor generating section such as dry cleaning, metal washing, fiber washing, etc., particularly water-insoluble organic solvent such as trichlorethylene, perchlorethylene, trichlorethane,
A method for recovering a solvent such as Freon 113, toluene, xylene,
In particular, the present invention relates to a solvent recovery method capable of preventing the forming phenomenon of separated water.

[0002]

2. Description of the Related Art As a conventional method of recovering a solvent of this kind, there is a method described in JP-A-6-23230 previously proposed by the applicant of the present invention. In this conventional method, as shown in FIG. 1, the specific gravity separator 16 separates the solvent from the water, and the separated water is sent directly to the steam generator 5 through the pipes 17 and 19 and the separated water is steam. In the generator 5, the solvent is heated and evaporated to become vapor, which is sent to the solvent adsorption tower 1 to recover the solvent from the adsorbent again and repeatedly used.

[0003]

By the way, in the above conventional method, a trace amount of components such as fats and oils contained in the raw gas is accumulated in the separated water separated by the specific gravity separator 16,
By increasing the surface tension of the separated water, the steam generator 5
In the case of generating steam, a phenomenon of water bubbling (hereinafter referred to as a forming phenomenon) may occur. When this forming phenomenon occurs, the liquid surface of the steam generator 5 becomes bubbly. The bubbles break on the surface of the liquid and become droplets that move with the vapor, so that the temperature of the vapor decreases and the desorption of the solvent adsorbed by the adsorbent becomes insufficient, resulting in a decrease in the solvent adsorption efficiency. There was a problem.

Therefore, the present invention solves the above-mentioned conventional problems, prevents the forming phenomenon, and allows the solvent to be sufficiently desorbed from the adsorbent, resulting in high solvent adsorption efficiency after desorption. It is an object of the present invention to provide a method for recovering a solvent that can be maintained.

[0005]

In order to achieve the above object, the invention of claim 1 provides a solvent adsorption tower, a vapor generator provided under the solvent adsorption tower, and a condenser provided in the solvent adsorption tower. And a specific gravity separator connected to the condenser via the first pipe and connected to the steam generator via the second pipe, and the separated water separated from the solvent by the specific gravity separator is In the solvent recovery method of supplying the steam to the steam generator through the second pipe, an antifoaming agent is added to the separated water.

According to the invention of claim 2, in claim 1, a separation water tank is provided in the middle of the second pipe, and an antifoaming agent is added to the separation water in the separation water tank. According to the invention of claim 3, in claim 1, an aeration tank and an ion exchange tank are provided in the middle of the second pipe so that the aeration tank is closer to the specific gravity separator than the ion exchange tank. An antifoaming agent is added to the separated water in the tank.

[0007]

Since the defoaming agent is added to the separated water separated by the specific gravity separator as described above, the defoaming agent is added to the steam generator to send the separated water whose surface tension is suppressed to a low level. Therefore, when the steam is generated in the steam generator, the forming phenomenon does not occur.

[0008]

FIG. 1 is a partially cutaway front view showing an embodiment of the present invention. The apparatus of this embodiment has almost the same configuration as the apparatus of the conventional method. That is, in FIG. 1, 1 is an adsorption tower in which an adsorbent a such as activated carbon
And is installed on the leg 2. 3 is a dust filter, 4 is a fan connected to the dust filter 3, and this fan 4 is installed in communication with the upper space of the adsorbent a accommodated in the adsorption tower 1.

Reference numeral 5 denotes a steam generator directly connected to the lower part of the adsorption tower 1. The steam generator 5 has a housing 6, and an upper heating electrothermal coil 7 is provided in the upper space of the housing 6. An electric heating coil 8 for steam generation is arranged in the water.

A condenser 10 composed of an inner and outer double pipe is wound around the upper periphery of the adsorption tower 1. The inner tube of the condenser 10 is provided with an inlet 11 for supplying cooling water and an outlet 12 for discharging water. One end of the outer pipe is connected to an introduction pipe 13 opened in the upper space of the adsorbent a housed in the adsorption tower 1, and the other end is a drain pipe.
Connected to 14. 16 is connected to drain pipe 14 and adsorption tower 1
The separator 16 is provided with a specific gravity separator, and a separator water tank 18 is connected to the separator 16 via a pipe 17, and the lower portion of the tank is a valve.
It is connected to a makeup water pipe 21 connected to the casing 6 of the steam generator 5 via a pipe 19 having 20. In this embodiment, the drain pipe 14 constitutes the first pipe, and the pipes 17 and 19 and the makeup water pipe are provided.
21 forms the second pipe.

Reference numeral 25 is a gas introducing damper, 26 is an air exhausting damper, and 27 and 28 are temperature controllers. The temperature controller 27 has a steam generating electrothermal coil 8 which is always underwater exposed on the water surface in case of an accident. The temperature controller 28 is provided so as to switch off the coil when the power is turned on while the coil is turned on or off when the heating coil 7 for overheating becomes below or above the set temperature. Has been. 30 is the case 6
A water level gauge for maintaining the water level in the inside at a constant water level, 31 is a solenoid valve, 32 is an exhaust pipe, and 33 is a solvent extraction pipe. Reference numeral 35 is an antifoaming agent inlet pipe provided in the separated water tank 18.

The operation of the above embodiment will be described. Damper 25,
26 is opened, and the raw gas containing the solvent vapor is introduced into the dust filter 3 by the activation of the fan 4. The raw gas is supplied with static air pressure by the fan 4 into the adsorption tower 1 and the adsorbent a The solvent vapor in the gas is adsorbed by the adsorbent a while passing through the exhaust gas, and the air purified by this is released into the atmosphere through the exhaust pipe 32.

After the adsorbent a has adsorbed a predetermined amount, the dampers 25 and 26 are closed, and the steam generated in the casing 6 of the steam generator 5 is sent to the adsorbent a, whereby the adsorbent a is adsorbed. The used solvent is desorbed.

The desorbed solvent vapor and water vapor are introduced into the introduction pipe 13
Is guided to the condenser 10 via, and is condensed while passing through a passage in the outer pipe constituting the condenser in a countercurrent direction with the cooling water, becomes a liquid and flows into the separator 16 through the drain pipe 14, Here, they are separated by the difference in specific gravity. At this time, cooling water flows in through the inlet 11 to cool the solvent vapor and water vapor, and is discharged through the outlet 12.

The solvent separated in the separator 16 is recovered from the conduit 33, and the separated water separated is introduced into the separated water tank 18 via the pipe 17, where a small amount of defoaming agent is introduced from the defoaming agent inlet pipe 41. After the agent is charged, it is supplied into the casing 6 of the steam generator 5 through the pipe 19 and the makeup water pipe 21. Therefore, the specific gravity separator 16
Even if a component that causes a forming phenomenon is accumulated in the separated water separated in step 1, the foaming phenomenon in which water foams due to the addition of the defoaming agent that is a low surface tension substance causes the case 6 of the steam generator 5 to have a foaming phenomenon. It does not occur within.

When the desorption is completed, the dampers 25 and 26 are opened, the fan 4 is activated and the cooling gas (generally the atmosphere) is introduced, and the adsorbent a is dried and cooled.

FIG. 2 shows another embodiment of the present invention. The difference between this embodiment and the above embodiment is that instead of the separation water tank 18, an aeration tank 41 and a cation tank 46 and anion tank 47 as ion exchange tanks, and the aeration tank 41 is a specific gravity separator.
A point provided in series so as to be located close to 16 and two adsorption towers 1 having the same structure described above are installed in parallel, and the specific gravity separator 16 and the steam generator 51 are shared by these adsorption towers. It is a point that one is installed as a thing.

That is, the specific gravity separator 16 is provided so as to be connected to the condensers 10 of the No. 1 adsorption tower 1 and No. 2 adsorption tower 1 by pipes 54 and 55. It should be noted that each condenser 10 may be independent of each adsorption tower 1 and may be shared by each adsorption tower. Further, the steam generator 51 is provided by connecting the lower portions of the No. 1 adsorption tower 1 and the No. 2 adsorption tower 1 with pipes 56, 57, and the pipes 56, 57.
A three-way valve 58 is installed at the connection part of. Specific gravity separator 16
The aeration tank 41 is connected to the pipe 61, the cation tank 46 and the anion tank 47 are sequentially connected to the aeration tank, and the pipe 62 of the steam generator 51 is connected to the anion tank 47. A blower 44 is connected to the aeration tank 41. A pipe 52 is connected between the aeration tank 41 and the pipe 53 of the fan 4. 64
65 in the pump and steam generator 51 installed in the pipe 62
Indicates a steam generating chamber, and a steam overheating coil 66 and a steam generating heating coil 67 as electric heaters are vertically arranged in the chamber. 68 is a liquid level gauge (controller), 70 is a blanking prevention thermometer, and 71 is an overheat prevention thermometer. 72 is a defoaming agent inlet pipe provided in the anion tank 47. In this embodiment, the pipes 54 and 55 form a first pipe, and the pipes 61 and 62 form a second pipe.
The piping of is configured.

73 is a solvent recovery tank connected to the specific gravity separator 16 through a pipe 74, and 76 and 77 are No. 1 adsorption tower 1 and No. 2 adsorption tower 1.
An exhaust pipe 78 connected to the exhaust pipe 32 of FIG. 1 is a cooling water supply pipe 78, and valves 80 and 81 are provided near each adsorption tower 1. Reference numeral 83 is a cooling water return pipe. The No. 1 adsorption tower 1 and the No. 2 adsorption tower 1 can be alternately switched between running and stopping by a control member (not shown).

An example of the operation of this example will be described below. In this example, the raw gas containing the solvent is supplied into the No. 1 adsorption tower 1 through a duct filter (not shown) when the dampers 25, 26 of the No. 1 adsorption tower 1 are opened, and the fan 4 is activated. Only the solvent is adsorbed by the adsorbent a in 1 and the cleaned air is discharged into the atmosphere through the exhaust pipes 32 and 76. And 1
When the adsorption time by the adsorption tower 1 becomes long, the amount of the solvent in the adsorbent a increases, and the solvent is gradually exhausted from the outlet of the adsorption tower. The breakthrough point is 10% concentration), but before this breakthrough time, the control member stopped the operation of No. 1 adsorption tower 1,
Operation is switched to No. 2 adsorption tower 1. When the adsorption by the No. 1 adsorption tower 1 is completed, the solvent is desorbed from the adsorbent a, so that steam (105 ° C. to 110 ° C.) passes from the steam generator 51 through the pipe 56 and the three-way valve 58 to the No. 1 adsorption tower 1. Sent to. The steam and the solvent desorbed by the steam are cooled in the condenser 10 and liquefied. The liquefied mixed liquid (solvent and water) is sent to the specific gravity separator 16 through the pipe 54, separated into the solvent and the separated water by the specific gravity separation, and the solvent is recovered in the recovery tank 73 and reused. On the other hand, the separated water is sent to the aeration tank 41 through the pipe 61. This separated water contains a trace amount of dissolved solvent and trace components such as fats and oils.

The separated water that has flowed into the aeration tank 41 has a small amount of solvent removed by the fine bubbles stirred in the tank as described above, and the separated water from which this solvent has been removed is further cation tank 46.
Ions that cause scales are removed when passing through the anion tank, chlorine ions that cause metal corrosion are removed when passing through the anion tank 47, and a small amount of defoaming agent is introduced from the defoaming agent inlet pipe 72. After being charged, it flows into the steam generator 51 through the pipe 62. The foaming phenomenon does not occur in the casing 6 of the steam generator 5 due to the introduction of the defoaming agent as in the above-described embodiment.

FIG. 3 shows the relationship between the outlet concentration of the solvent (trichlorethylene) and the adsorption time in both the above examples. In the figure, the line A shows the change with time in the case where the defoaming agent was not added, and is the case where the solvent was desorbed by the vapor in which the forming phenomenon occurred.
Line B shows the change with time when an antifoaming agent was added.
This is a case where after the experiment of the line A is performed, the defoaming agent is added and the solvent is desorbed by the vapor which prevents the forming phenomenon. The concentration of the solvent in the raw gas flowing into the solvent recovery device was about 600 ppm in all cases. As a defoaming agent, a silicone type defoaming agent is well known, and among them, an emulsion type is the most general. In both examples, a silicone type antifoaming agent manufactured by Toshiba Silicone Co., Ltd. was used as an emulsion type (product name = TSA737F), and an extremely small amount of about 3 cc was added per 100 liters of separated water.

[0023]

According to the present invention, the defoaming agent is added when the separated water separated from the solvent by the specific gravity separator is supplied to the steam generator through the second pipe. , The surface tension of the separated water is reduced, and the forming phenomenon can be prevented from occurring when steam is generated in the steam generator,
There is an excellent effect that the solvent can be sufficiently desorbed from the adsorbent by the steam at a high temperature (generally 105 ° C to 110 ° C), and the adsorption efficiency of the solvent after the desorption can be maintained high.

[Brief description of drawings]

FIG. 1 is a partially cutaway front view showing an embodiment of the present invention.

FIG. 2 is a piping system diagram showing another embodiment.

FIG. 3 is a graph showing the relationship between the solvent outlet concentration and the adsorption time.

[Explanation of symbols]

 1 Adsorption tower 3 Dust filter 4 Fan 5 Steam generator 10 Condenser 16 Specific gravity separator 18 Separation water tank 35,72 Defoaming agent inlet pipe 41 Aeration tank 46 Cation tank 47 Anion tank

Claims (3)

[Claims] 1. A solvent adsorption tower, a vapor generator provided in the lower part of the solvent adsorption tower, a condenser provided in the solvent adsorption tower, and a connection with the condenser via a first pipe, A method for recovering a solvent, comprising: a steam generator and a specific gravity separator connected through a second pipe; and separating water separated from the solvent by the specific gravity separator into the steam generator through a second pipe. A method for recovering a solvent, which comprises adding an antifoaming agent to the separated water. 2. The method for recovering a solvent according to claim 1, wherein a separation water tank is provided in the middle of the second pipe, and an antifoaming agent is added to the separation water in the separation water tank. 3. An aeration tank and an ion exchange tank are provided in the middle of the second pipe so that the aeration tank is located closer to the specific gravity separator than the ion exchange tank, and the separated water in the ion exchange tank is consumed. The solvent recovery method according to claim 1, wherein a foaming agent is added.