JPH07246309A - Separation - Google Patents

Abstract

PURPOSE:To prevent he quantity of drainage contg. insoluble materials from increasing, after cooling and condensing insoluble material distilled vapor, by recovering the insoluble materials in a separation tank, returning a water phase to a distillation device, and on the other hand, treating the drainage by a reverse osmosis membrane to discharge the permeated liquid, and returning the concrete to the separation tank or the distillation device. CONSTITUTION:A desorbed gas (d) discharged from an adsorption tank 1 or 2 is conducted to a distillation device 3, where it is separated into (e) insoluble material distilled vapor in which insoluble materials are concentrated and (i) diluted drainage. The insoluble material distilled vapor (e) is condensed and liquefied in a cooling condenser 4, and the condensate is separated by differential specific gravity in a separation tank 5, and an insoluble material phase (h) is discharged to outside the system as a recovered solvent and a water phase (g) is timely transferred to the distillation device 3. On the other hand, after the drainage (i) in the distillation device 3 is cooled by a cooler 6, it is fed to a reverse osmosis membrane 9 through a circulating tank 7. At this time, the insoluble materials contained in a reverse osmosis membrane feeding liquid (i) is very small and is cooled, allowing the load to the reverse osmosis membrane 9 to be decreased. A permeated liquid (m) is discharged to outside the system, and a concentrate (k) is returned to the separation tank 5 or the distillation device 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of desorbing a hardly soluble substance to be adsorbed by an adsorbent by a steam desorption method to regenerate the adsorbent and separating and recovering the desorbed hardly soluble substance.

[0002]

2. Description of the Related Art Conventionally, an absorption method, a condensation method, an adsorption method or the like has been generally used as a method for separating exhaust gas containing a hardly soluble substance vapor generated from various factories or treatment plants. The optimal method is selected from the economical point of view of the processing equipment depending on the amount of processing.

That is, the absorption method and the adsorption method are suitable for separating a large amount of treatment, and the condensation method is suitable for a small amount of treatment. The absorption method and the condensation method are suitable for high concentration vapor, and the adsorption method is suitable for low concentration vapor. The law is suitable. Therefore, the adsorption method is selected as the most suitable method when a large throughput / low concentration vapor separation is targeted. For example, the adsorption method has been conventionally used for deodorizing air containing low-concentration solvent vapor generated from a solvent handling factory such as a coating factory. Also, steam desorption method, heated air desorption method, nitrogen gas desorption method, etc. are used to regenerate the adsorbent that has adsorbed the hardly soluble substance. Used.

[0004]

However, in this steam desorption method, steam is liquefied during the condensation liquefaction which is a step after desorption and becomes waste water containing a hardly soluble substance. There is a problem of equipment such as new construction or expansion of wastewater treatment facilities to avoid.

As a method for solving the above problems, a method of treating condensed liquefied wastewater by a pervaporation method or a vapor separation (vapor permeation) method before condensation and liquefaction is used to form a sparingly soluble substance vapor and steam. However, these membrane separation methods are not practical because the operation cost is high and the current separation membrane lacks reliability in heat resistance and solvent resistance. Has the drawback. A method has also been proposed in which condensed liquefied wastewater is directly treated with a reverse osmosis membrane without introducing it to a distiller, but at the current technical level where the reverse osmosis membrane has poor solvent resistance, wastewater containing a high concentration of solvent is proposed. It is difficult to directly treat the lactic acid with a reverse osmosis membrane.

The present invention has been made to solve the above-mentioned problems of the prior art, and does not cause a problem of wastewater treatment such as an increase in the amount of wastewater containing a hardly soluble substance, and the operating cost. It is an object of the present invention to provide a separation method that includes an adsorbent regeneration step that does not increase the amount of adsorbent, and that can separate and collect desorbed hardly soluble substances.

[0007]

The method for desorbing an adsorbent of the present invention is a desorption method comprising a step of desorbing a hardly soluble substance to be adsorbed on an adsorbent in an adsorption tank with water vapor. The desorption gas, which is a mixture of the sparingly soluble substance vapor and steam sometimes discharged from the adsorption tank, is introduced into a distiller and separated into a concentrated sparingly soluble substance distilled gas and a diluted wastewater, and the sparingly soluble substance distilled gas is cooled. After condensing, it is introduced into a separation tank and separated into a hardly soluble substance phase and an aqueous phase to recover the hardly soluble substance, and the aqueous phase is returned to the distiller again. The liquid is discharged and the concentrated liquid is returned to the separation tank or the distiller.

[0008]

Embodiments will be described below with reference to embodiments of the present invention. FIG. 1 is an explanatory diagram showing an example of a separation method used in the embodiment of the present invention. In FIG. 1, a is a hardly soluble substance-containing gas, and the hardly soluble substance-containing gas a is supplied to the adsorption tank 1 or 2 by the adsorption gas blower 11.
The hardly soluble substance gas is adsorbed by the adsorbent, and the adsorbed exhaust gas b is discharged from the adsorption tank 1 or 2 as a gas containing no hardly soluble substance. The above-mentioned sparingly soluble refers to a property that is difficult to dissolve in water, and for example, as a sparingly soluble substance, toluene, xylene, hexane, heptane, cyclohexane, diethyl ether,
Examples include benzene.

After the adsorption operation is carried out for a certain time, the desorption operation is started. Usually, the adsorption tank is provided with two or more tanks so that the gas a containing the hardly soluble substance can be constantly received and adsorbed, that is, even during the desorption operation, the adsorption operation can be performed simultaneously. Specifically, in the case of two tanks, the adsorption tank 2 completes the desorption / regeneration operation during the adsorption operation of the adsorption tank 1,
During the adsorption operation, the adsorption tank 1 completes the desorption regeneration operation.

In the desorption process, the desorption operation is carried out by injecting steam into the adsorption tank 1 or 2. When water vapor is injected, the hardly soluble substance adsorbed by the adsorbent is desorbed from the adsorbent, mixed with the water vapor, and discharged as desorption gas d from the adsorption tank 1 or 2. The water vapor used in the present invention is
Although it is appropriately selected depending on the heat resistance of the adsorbent and the physical properties and amount of the hardly soluble substance, steam having a pressure of 7 kgf / cm ² or less is usually used.

The discharged desorbed gas d is guided to the distiller 3 where the heat of the steam used for desorption is used to cause the refractory substance and water to concentrate the refractory substance by vapor-liquid equilibrium. It is separated into soluble substance distilled gas e and diluted wastewater i. Incidentally, when the hardly soluble substance is a component having a lower boiling point than water, ordinary distillation is carried out, and when the hardly soluble substance is a component having a higher boiling point than water, the region exceeding the azeotropic point, that is, the hardly soluble substance is at a dilute concentration. Distillation is performed and separated. Insoluble substance distilled gas e
Is indirectly cooled to a temperature equal to or lower than the saturated vapor pressure temperature of the hardly soluble substance in the cooling condenser 4, and is condensed and liquefied to form a condensed liquid f in which water and the hardly soluble substance are mixed, and flows into the separation tank 5. In the separation tank 5, water and the sparingly soluble substance are separated by specific gravity difference, and the sparingly soluble substance phase h is discharged out of the system as a recovery solvent, and is recovered as necessary. The aqueous phase g accumulated in the separation tank 5 is appropriately transferred to the distiller 3.

On the other hand, the waste water i in the distiller 3 is cooled by the cooler 6, then guided to the circulation tank 7, and supplied to the reverse osmosis membrane 9 by the circulation pump 8. Since most hardly soluble substances are separated by the distiller 3 and cooled by the cooler 6, the reverse osmosis membrane feed liquid j containing a trace amount of hardly soluble substances supplied to the reverse osmosis membrane 9 is reversed. The load on the permeable membrane 9 is reduced. A pressure regulating valve 10 is provided at the outlet of the reverse osmosis membrane 9, and the permeated liquid m is obtained by pressurizing the supply liquid. The permeated liquid m is discharged out of the system as a liquid having a concentration of the hardly soluble substance lower than that of the reverse osmosis membrane supply liquid j, and the concentration of the hardly soluble substance in the concentrated liquid k is contained in the aqueous phase g accumulated in the separation tank 5. If the concentration is higher than that of the above, the concentrated liquid k is returned to the separation tank 5, and if it is lower than that, it is returned to the distiller 3.

The equipment used in the present invention is not limited as long as it is resistant to the properties of the gas to be handled and can be operated efficiently, but in order to avoid contamination of impure components and third component in the handled gas as much as possible, The blower 11 is a dry type, while the indirect heat exchanger is suitable for the cooling condenser 4 and the cooler 6.

The reverse osmosis membrane 9 used in the present invention is not limited as long as it has a high blocking rate for a slightly soluble substance slightly dissolved in water and can be efficiently treated. The module type of the reverse osmosis membrane 9 is not limited at all, and various modules such as spiral type, hollow fiber type, plate & frame type can be used. For example, spiral type polyamide reverse osmosis membrane module manufactured by Nitto Denko Corporation (Product name:
NTR-759HR) is suitable.

The adsorbent filled in the adsorption tank used in the present invention is capable of efficiently adsorbing a sparingly soluble substance as a target adsorbed substance, resistance to the supplied sparingly soluble substance-containing gas a, and desorption treatment. It is appropriately selected based on the heat resistance including. Examples of the adsorbent include granular activated carbon, fiber activated carbon, zeolite and the like.

Hereinafter, the present invention will be described in more detail with reference to Examples of the present invention. Example 1 It was carried out as follows according to the system explanatory view shown in FIG. This example is an example in which an apparatus including an adsorption tank for adsorbing a local exhaust outlet gas which is a toluene-containing exhaust gas from an adhesive coating section of an adhesive tape manufacturing plant is assembled and the separation method of the present invention is applied. In FIG. 1, adsorption tanks 1 and 2 each have an inner diameter of 500 mm, an effective height of 400 mm, and an activated carbon filling amount of 20 kg / tank made of SUS304, and a distiller 3 has an inner diameter of 300 mm and a height of 350 mm. , Cooling condenser 4 has cooling tower circulating water 32 ° C (water pressure 2 Kg / cm ² G) as utility cooling water.
SUS304 multi-tube type indirect heat exchanger (heat transfer area; 2
m ² ), the separation tank 5 is a square tank having a width of 200 mm, a depth of 400 mm, and a height of 400 mm, and the cooler 6 serves as cooling water for the purpose of cooling water circulating in a cooling tower at 32 ° C. (water pressure 2 Kg / cm ² G)) SUS304 multi-tube indirect heat exchanger (heat transfer area: 2 m ² )
The circulation tank 7 has an inner diameter of 250 mm and a height of 400 mm, the circulation pump 8 is a 0.75 Kw centrifugal pump, and the reverse osmosis membrane 9 is a polyamide composite membrane spiral type which is a separation membrane manufactured by Nitto Denko Corporation. Module NTR-759HR-S2
(Membrane area = 1.8 m ² / piece) One, reverse osmosis treatment pressure is 10 kgf / cm ^{2 on} average, reverse osmosis membrane supply flow rate is 5 L / min, and adsorption gas blower 11 uses 0.75 Kw turbo blower Then, by repeating adsorption and desorption of the adsorption tanks 1 and 2, the toluene in the toluene-containing exhaust gas was recovered.

The repetition time of adsorption / desorption is 4 hours for adsorption and 2
For time desorption, the adsorption tanks 1 and 2 were switched every 4 hours. Specifically, the adsorption gas blower 11 makes 1000
Gas containing a sparingly soluble substance at about 40 ° C, which is a mixed gas of ppm toluene vapor and 1.6vol% steam and air a
(Toluene-containing exhaust gas) 300 m ³ / h was supplied to the adsorption tank 1, and toluene vapor was adsorbed on the activated carbon as an adsorbent.
After 4 hours, the piping was switched and the toluene-containing exhaust gas 3
00 m ³ / h was supplied to the adsorption tank 2, and the adsorption tank 1 was switched from the adsorption operation to the desorption operation. In the desorption operation, 30 kg of water vapor is added to the adsorption amount of toluene of 4.5 kg per adsorption tank.
By supplying / h and performing desorption in the above order,
The recovery rate of toluene was 95% or more, the toluene concentration of the reverse osmosis membrane feed liquid j was 50 ppm, and the toluene concentration of the reverse osmosis membrane permeate liquid m was 5 ppm. The average power consumption of the device was 1.5kw (200V, 3 phase).

[0018]

EFFECTS OF THE INVENTION According to the present invention, the problem of wastewater treatment such as increase in the amount of wastewater containing a hardly soluble substance does not occur.
It is possible to regenerate the adsorbent and recover the desorbed hardly soluble substance by a method that does not increase the operating cost.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an example of a separation method used in the present invention.

[Explanation of sign]

 1 Adsorption tank 2 Adsorption tank 3 Distiller 4 Cooling condenser 5 Separation tank 6 Cooler 7 Circulation tank 8 Circulation pump 9 Reverse osmosis membrane 10 Pressure regulating valve 11 Adsorbed gas blower a Adsorbed gas containing gas b Adsorbed exhaust gas c Water vapor d Desorption Gas e Slightly soluble substance Distilled gas f Condensate g Water phase h Slightly soluble substance phase i Waste water j Reverse osmosis membrane feed liquid k Concentrate m Permeate

Claims (1)

[Claims] 1. A method of separation comprising a step of desorbing a sparingly soluble substance to be adsorbed on an adsorbent in an adsorption tank with water vapor, wherein a mixture of a sparingly soluble substance vapor and water vapor discharged from the adsorption tank during desorption. The desorption gas is introduced into the still,
Separated into concentrated insoluble substance distilled air and diluted wastewater,
The sparingly soluble substance distilled gas is cooled and condensed, then introduced into a separation tank and separated into a sparingly soluble substance phase and a water phase to return the sparingly soluble substance to the water phase again to the distiller, while the drainage is A separation method comprising treating with a reverse osmosis membrane to discharge the permeated liquid, and returning the concentrated liquid to a separation tank or a distiller.