JPH03184000A - Method and device for processing waste liquid of nuclear power plant - Google Patents

Abstract

PURPOSE:To maintain the purirty of condensed water by passing waste liquid through a film vaporizing and condensing device after a surface active agent is removed and measuring its conductivity with time, interrupting waste liquid processing when a specific value is reached, and cleaning a film and restarting the waste liquid processing. CONSTITUTION:If solid matter and the surface active agent are mixed with the waste liquid, they sticks on the external surface of the tubular film 16, which is contaminated gradually. If the waste liquid leaks on a cooling water side owing to the contamination of the film 17, its conductivity rises, so when the value exceeds the specific value, a detection end 13 detect and a detector 13A generates a signal to interrupt the processing of the waste liquid. Then the contamination film of the film 17 is reproduc tion. For the preproduction, a valve 12 is opened first and the waste liquid in the film vaporizing and concentrating container 2 is discharged and returned to a storage tank 7 through a circulation system 7 through a circulation system B. Then valves 22, 24, 26, and 27 are closed and valves 32 and 25 are opened; and the pump 15 is operated from the storage tank 14 and cleaning liquid is supplied to the flow passage 19 in the film 17. Then H2SO4, oxalate, alcohol, etc., which is adjusted to specific concentration.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method and device for treating waste liquid in a nuclear power plant, and in particular, a membrane evaporation concentrator using a hydrophobic porous membrane on the evaporation surface to treat waste liquid containing salts. Concerning a waste liquid treatment method and device for evaporating and concentrating waste liquid and obtaining highly pure condensed water [Prior art] Membrane evaporation concentration using a hydrophobic porous membrane on the evaporation surface of an evaporation chamber containing a solution containing salts As a vessel, for example, Tokuko Sho 49
There is a structure shown in No.-45461.

3- Also, as a waste liquid treatment method incorporating a membrane evaporation concentrator,
For example, there is a method disclosed in Japanese Patent Application Laid-open No. 164195/1983.

Since these membrane evaporation concentrators use a membrane for the evaporation surface, the evaporation surface can be freely set, and the device can be easily miniaturized. Furthermore, since steam can be generated from waste liquid at medium humidity and normal pressure, polymeric materials that are relatively resistant to corrosion can be used as structural materials. In the above points, membrane evaporative concentrators have many advantages over conventional evaporator concentrators made of metal materials.

[Problem to be solved by the invention]

By the way, what about waste liquid from nuclear power plants?

In addition to salts, solids and surfactants may be included. The waste liquid mixed with such impurities, especially surfactants, makes the hydrophobic porous membrane used on the evaporation surface of the membrane evaporation concentrator hydrophilic, causing the waste liquid to leak from the membrane and reduce the purity of the condensed water. As described above, there is a problem in that a membrane evaporative concentrator in which the membrane is made hydrophilic cannot treat waste liquid, and this problem has not been solved by conventional methods. SUMMARY OF THE INVENTION Therefore, an object of the present invention is to maintain the purity of condensed water and to regenerate the contaminated membrane in a case where the membrane of a 4-membrane evaporation concentrator becomes contaminated and becomes hydrophilic.

Further, in the regeneration treatment of contaminated membranes, there is a problem in that waste liquid is generated secondary due to the treatment reagent, and another object of the present invention is to reduce the amount of reagent used for the regeneration treatment.

Furthermore, there is a problem in that the operating rate of the membrane evaporation concentrator is reduced due to the interruption of waste liquid treatment due to the regeneration treatment of contaminated membranes.Another object of the present invention is to reduce the frequency of regeneration treatment of contaminated membranes. be.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a waste liquid treatment method using a membrane evaporation concentrator, in which a waste liquid from which a surfactant has been removed in advance is passed through the membrane evaporation concentrator, and the conductivity of condensed water obtained from the apparatus is measured over time. When the conductivity value reaches a predetermined value, the waste liquid treatment by the membrane evaporation concentrator is stopped, the membrane is washed with acid and alcohol, and finally it is dried and adhered to the membrane. The waste liquid treatment is restarted after removing the liquid material.

Further, in order to achieve the above-mentioned other objects, in the alcohol cleaning in the regeneration treatment of the contaminated membrane, the alcohol solution is heated to a temperature of 35° C. or more and the boiling point or less and brought into contact with the contaminated membrane.

Furthermore, in order to achieve the other objects mentioned above, the waste liquid is subjected to surfactant removal treatment in advance, and then treated in the membrane evaporation concentration device.

In order to implement the method, the apparatus of the present invention may be configured as follows. That is, the waste liquid containing salts generated in the atomic couplant is introduced into the outer cylinder of the membrane evaporative concentrator, and the vapor of the waste liquid generated in the outer cylinder is passed through a hydrophobic porous tubular membrane provided in the outer cylinder. In a waste liquid treatment apparatus for concentrating salts and obtaining condensed water, the apparatus includes a means for measuring the conductivity of the condensed water flowing through the tubular membrane, and an acid cleaning solution and alcohol inside the tubular membrane. A waste liquid treatment apparatus incorporating a membrane evaporation concentrator is provided with means for regenerating a contaminated membrane, which includes means for supplying a cleaning liquid and means for supplying warm air into a tubular membrane.

Furthermore, in order to carry out the other method, the present invention provides the following (a)
) to (f).

(a) Storage tank for waste liquid containing salts and surfactants.

(b) A foam separator that blows fine bubbles into the waste liquid sent from the storage tank.

(c) A storage tank for foam generated in the foam separator and containing concentrated surfactant.

(d) The waste liquid treatment device 6 that processes the waste liquid generated in the foam separator and from which the surfactant has been removed. (e) A storage tank for concentrated waste liquid generated in the waste liquid treatment device.

(f) A dryer for converting the foam and concentrated waste liquid stored in each storage tank into dry powder.

In order to solve the above problem, we investigated the effect on the conductivity of condensed water when a salt solution containing a surfactant is treated as a raw solution (equivalent to waste liquid) in a membrane evaporation concentrator.

As a result, as shown in Figure 5, a surfactant (D
It was found that the conductivity of condensed water increases after a predetermined period of time when BS, sodium dodecyl bene 7-zene sulfonate) is contained. They also found that the time it takes for the electrical conductivity of condensed water to increase is inversely proportional to the surfactant concentration, and that the higher the concentration, the faster the electrical conductivity of condensed water increases. As a result of research on a method for regenerating a membrane contaminated by the raw solution, in which the conductivity of condensed water increases as described above, the present invention was achieved.

[Effect]

The waste liquid treatment method of the present invention (in this case, the conductivity of the condensed water obtained from the membrane evaporation concentrator is measured over time. As a result, if the membrane is contaminated and the waste liquid leaks to the condensed water side, the condensed water The degree of membrane contamination of the membrane evaporation concentrator can be detected because the conductivity of the membrane has increased.

In addition, the conductivity of condensed water is a predetermined value of 10 to 100 μs/aw.
When this is reached, the waste liquid treatment by the membrane evaporation concentrator is interrupted, thereby preventing the waste liquid from leaking to the condensed water side due to membrane contamination, and the condensed water can be maintained at a high purity. Also,
By washing the contaminated membrane with acid and alcohol, and finally drying it to remove the liquid matter adhering to the membrane, restarting the waste liquid treatment, the contaminated membrane can be regenerated and the membrane can be evaporated and concentrated again. Enables waste liquid treatment by the device.

Furthermore, in alcohol cleaning during the regeneration treatment of contaminated membranes, by heating the alcohol solution to a temperature above 35°C and below the boiling point and bringing it into contact with the contaminated membrane, the same cleaning effect can be achieved with a relatively lower concentration alcohol solution than at room temperature. You can get

Furthermore, by subjecting the waste liquid to a surfactant removal process in advance and then treating it in the membrane evaporation concentrator, the progress of membrane contamination by the waste liquid can be delayed and the time required for the waste liquid to leak from the membrane can be lengthened.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a waste liquid treatment apparatus 1 according to the present invention incorporating a membrane evaporative concentrator 2. As shown in FIG. The waste liquid processing bag w1 has a waste liquid circulation system 3, 3A centered around the membrane evaporation concentrator 2.

Cooling water circulation system 4, 4A, cleaning liquid circulation system 5゜5A
and a dry air supply system 6. The waste liquid circulation system 3, 3A includes a storage tank 7 for storing waste liquid. A heater 8 such as a heater for heating waste liquid and a circulation pump 9 for waste liquid are provided. The cooling water circulation system 4, 4A includes a cooling water storage tank 10. Cooler 11. A circulation pump 12 and a detection end 13 of a detector 13A for detecting the conductivity of condensed water are provided. In addition, the cleaning liquid circulation system 5 includes a cleaning liquid storage tank 1.
4 and a cleaning liquid circulation pump 15 are provided. The dry air supply system 6 is provided with a warm air supply device 16 . Each circulation system is provided with valves 21 to 30 for switching between a waste liquid treatment operation and a contaminated membrane regeneration operation.

The membrane evaporative concentrator 2 is composed of a tubular membrane module 17 and an outer cylinder 18 that houses the module.The inside of the tubular membrane is a cooling water flow path 19, and the outside of the tubular membrane is a waste liquid flow path. Form 20. The tubular membrane 17 is made of polytetrafluoroethylene or polyethylene.

It is a porous tubular membrane made of hydrophobic materials such as polypropylene and polysulfone. The pore size of the membrane is 0.05-1
μm and a porosity of 50 to 85% is used.

Next, the waste liquid treatment method of the present invention will be explained using the waste liquid treatment apparatus 1. The waste liquid stored in the storage tank 7 is transferred to the heater 8.
The liquid is heated to a predetermined temperature by the pump 9, is supplied to the waste liquid flow path 20 of the membrane evaporator 2 through the circulation system 3, and is circulated through the circulation system 3A. On the other hand, the pure water stored in the storage tank 10 is cooled to a predetermined temperature, and is supplied by the pump 12 through the circulation system 4 to the cooling water flow path 19 in the tubular membrane 17 of the membrane evaporator concentrator 2, and is then circulated through the circulation system 4A. be done. Here, the high-temperature waste liquid in the flow path 20 and the low-temperature cooling water in the flow path 19 exist through the membrane wall of the tubular membrane 17.

Since the tubular membrane 17 uses a hydrophobic porous membrane, only the water vapor generated from the waste liquid passes through the pores of the membrane and is directly condensed on the cooling water inside the tubular membrane to become condensed water. The condensed water thus obtained is transferred to the circulation system 4, 4A, for example, in the storage tank 10 by the amount increased.
is discharged from. Through this treatment operation, the salts in the waste liquid are concentrated, and at the same time, highly pure condensed water is obtained.
Waste liquid can be treated.

11- By the way, if solid content and surfactant are mixed into the waste liquid,
These adhere to the outer surface of the tubular membrane 17, and if their concentration is high, the membrane will be contaminated over time. If the membrane becomes hydrophilic due to membrane contamination, the waste liquid will leak into the cooling water side where steam condenses, making it impossible to obtain high-purity condensed water, and the waste liquid treatment operation by the membrane evaporator concentrator 2 will have to be stopped. I have no choice but to.

Therefore, in the present invention, a detector 13 for measuring the conductivity of condensed water over time is installed in the cooling water circulation system 4A from which condensed water is obtained.
A detection end 13 was provided. If the waste liquid leaks to the cooling water side due to membrane contamination, its conductivity will increase, so if the value exceeds a predetermined value (10 to 100 μS/an), the detection end 13 detects this, A signal is generated by the detector 13A to interrupt the waste liquid treatment. Thereby, the influence of leakage of waste liquid from the tubular membrane 17 can be reduced, and highly purified condensed water can be maintained.

Next, after interrupting the waste liquid treatment, the contaminated membrane of the tubular membrane 17 is regenerated. In this case, first open the valve 21, and then open the membrane evaporator concentrator 2.
The waste liquid inside is extracted and returned to the storage tank 7 via the circulation system 12-3B. Next, valve 22゜24.2
6 and 27, open the valves 23 and 25, and operate the pump 15 to supply the cleaning liquid from the cleaning liquid storage tank 14 to the tubular membrane 17.
It is supplied to the flow path 19 inside.

The cleaning liquid is an acid cleaning liquid and an alcohol cleaning liquid.

As the acid cleaning solution, HasOa, oxalic acid, etc. prepared to a predetermined concentration are used. Further, as the alcohol cleaning solution, it is preferable to use an aqueous solution of a lower alcohol such as methanol or ethanol prepared to a concentration that can make the membrane hydrophilic.

Here, the cleaning liquid, particularly the alcohol cleaning liquid, is heated to a temperature above 35° C. and below the boiling point, preferably below the heat resistance temperature of the membrane, and is brought into contact with the contaminated membrane of the tubular membrane 17 for cleaning.

This increases the cleaning effect of the cleaning liquid, reduces the amount of acid and alcohol used, and suppresses secondary generation of waste liquid. Furthermore, it is preferable that the cleaning liquid containing a surfactant obtained by cleaning the contaminated film be brought into contact with, for example, activated carbon to remove the surfactant and be regenerated. As a result, the cleaning liquid can be used repeatedly, and secondary generation of waste liquid can be suppressed.

Next, after removing contaminants adhering to the inside and outside of the tubular membrane, the cleaning liquid is extracted from the membrane evaporator concentrator 2. Then valve 27
, 28 and 30 are opened, and hot air at a predetermined temperature is supplied from the hot air supply device 16 to remove the liquid matter adhering to the membrane.

By this regeneration operation of the contaminated membrane, the solid matter and surfactant adhering to the tubular membrane t7 can be removed, and the hydrophobicity of the membrane can be restored.

As described above, in regenerating the contaminated membrane of the tubular membrane 17 in the membrane evaporation concentrator 2, it is necessary to wash the contaminated membrane to remove contaminants from the membrane, and then finally dry the membrane.

On the other hand, in the case of conventional water treatment filtration devices, regeneration of membrane contamination requires only cleaning to remove contaminants from the membrane, and there is no need to finally dry the membrane. This is because the evaporation process by the membrane evaporation concentrator 2 is performed in a state where the tubular membrane 17 is made hydrophobic, that is, in a state where no liquid exists in the pores of the membrane. In order to confirm the effect of drying the membrane after cleaning, the results of a comparative experiment are shown in FIG. Figure 3 shows A as it is after cleaning the membrane, and B
2 shows the change over time in the electrical conductivity of condensed water when the membrane was further dried and then the N a Z S O 4 solution was supplied again for evaporation and concentration treatment. As a result, in A, the conductivity of the condensed water immediately increased after starting to supply the Na 2 SO 4 solution.

This indicates that the hydrophobic state of the membrane has not been recovered. On the other hand, in B, the conductivity of condensed water did not increase over a long period of time. This shows the importance of finally drying the contaminated membrane after cleaning it in regenerating the contaminated membrane in the membrane evaporation concentrator 2.

Next, FIG. 4 shows changes in the dry state of the membrane during the drying process. Immediately after cleaning the membrane, as shown in FIG. 4 (1), the pores 17A are filled with liquid material 40, and the membrane is in a hydrophilic state. FIG. 3 shows that such a membrane cannot be used for membrane evaporation. When the membrane is dried, the liquid substance 40 adhering to the pores 17A of the tubular membrane 17 is removed as shown in FIG. 4 (2).
When the film is completely dried, the state shown in FIG. 4 (4) is reached. Among these, Fig. 4 (2) shows a state in which only the surface of the membrane is dry and a liquid substance 40 remains inside the pores 17A of the membrane. , the liquid substance 40 accumulates inside the pores of the membrane, making it easy for the waste liquid to leak. In addition, it takes a long time to dry to the completely dry state shown in FIG. 4 (4). Therefore, it is preferable to dry the membrane in the state (3) in which a very small amount of a liquid substance in almost equilibrium with natural air is attached to the pores 17A of the membrane.

Therefore, valves 23, 25, 28.30 are closed, valves 22, 26, 24, 27.29 are opened, and circulation system 3,
4, the waste liquid and cooling water are supplied to the membrane evaporator concentrator 2, and the waste liquid treatment is started again.

By the above waste liquid treatment method, contamination of waste liquid into condensed water can be suppressed as much as possible and the condensed water can be maintained at a high purity. Furthermore, the amount of secondary waste liquid generated by the cleaning liquid during contaminated membrane regeneration can be reduced.

Next, a waste liquid treatment system in which the waste liquid treatment apparatus 1 of the present invention is combined with a surfactant removal process will be described with reference to FIG. This system is intended, for example, for the treatment of highly conductive waste liquids generated in nuclear power plants. The waste liquid supplied from the storage tank 7 containing the waste liquid is sent to the pretreatment device 31 .

16- The pretreatment device 31 is, for example, a foam separator, which allows the waste liquid to stay there for a predetermined period of time and blows fine bubbles into the waste liquid. Since the surfactant is concentrated in the generated foam, the foam is separated from the waste liquid and sent to storage tank 32. The waste liquid that remains in the pretreatment device 31 for a predetermined period of time and from which the surfactant has been removed is transferred to the membrane evaporation concentrator 2.
The waste liquid is supplied to the waste liquid treatment device 1 incorporating the waste liquid and is treated therein. In addition, in case the concentration of surfactant in the liquid supplied to the waste liquid treatment device 1 suddenly increases due to an unexpected situation, the concentration of surfactant in the liquid supplied is measured, and when the value reaches a predetermined value, It is desirable to install a preliminary pretreatment device (not shown) that bypasses the activated carbon layer provided separately and then supplies the waste liquid to the wastewater treatment device 1 (not shown). The waste liquid treated and concentrated by the waste liquid treatment device 1 is sent to the storage tank 33. The waste liquid stored in the storage tank 32 and the storage tank 33 is supplied to the dryer 34, dried and powdered, and further formed into solidified pellets in the assimilation machine 35 and sent to the storage tank 36.
will be stored in.

On the other hand, the condensed water obtained by the waste liquid treatment device 1 is further treated in a demineralizer 37, stored in a storage tank 38, and reused as condensate make-up water. Here, if the membrane of the membrane evaporator concentrator 2 becomes contaminated due to long-term waste liquid treatment, the electrical conductivity of the condensed water increases, and its value increases to a predetermined value (10 to 100 μm).
When S/a11) is reached, waste liquid treatment is interrupted. Furthermore, after removing contaminants from the contaminated membrane by the above-mentioned cleaning method and drying it to recover the hydrophobicity of the membrane, the waste liquid is again supplied to the membrane evaporation concentrator 2 and the waste liquid treatment is restarted.

The above waste liquid treatment system delays the progress of membrane contamination and improves the operating rate of the waste liquid treatment apparatus 1.

〔Effect of the invention〕

According to the method of the present invention, mixing of waste liquid into condensed water can be prevented and the recovered condensed water can be maintained at a high purity, which has the effect of reducing the load on the demineralizer, which is the next treatment step. In addition, the amount of reagents required for cleaning contaminated membranes can be reduced, and secondary generation of waste liquid can be suppressed.

This has the effect of simplifying waste liquid treatment. moreover,
This has the effect of slowing down the progress of membrane contamination and improving the operating rate of waste liquid treatment equipment.

Furthermore, according to the apparatus of the present invention that carries out the above method, it is possible to accurately detect the degree of hydrophilization of the tubular membrane due to membrane contamination by measuring the conductivity of condensed water flowing within the tubular membrane of membrane evaporation concentration. At the same time, when regenerating a contaminated membrane, acid cleaning solution, alcohol cleaning solution, and hot air are sequentially supplied into the tubular membrane, and this series of operations cleans the inside of the pores of the membrane and removes any liquid remaining in the pores. can be quickly removed and hydrophobicized, and waste liquid treatment can be restarted in a short time.

Furthermore, according to the wastewater treatment system of the present invention, by incorporating each element including the foam separator into the line, the operating rate of the wastewater treatment apparatus can be improved and efficient treatment can be performed.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of a waste liquid treatment device according to an embodiment of the present invention, Fig. 2 is a diagram of a waste liquid treatment system according to an embodiment of the present invention, and Fig. 3 shows the effect of a membrane drying operation after cleaning a contaminated membrane. Graph of experimental data shown in Figure 4 (1). (2) and (3) are enlarged cross-sectional views showing the dry state of the membrane;
The figure is a graph of experimental data showing changes in the conductivity of condensed water when a waste liquid containing a surfactant is subjected to membrane evaporation concentration19- treatment. 1... Waste liquid treatment device, 2... Membrane evaporation concentrator, 3, 3
A... Waste liquid circulation system, 4, 4A... Cooling water circulation, 5
゜5A...Cleaning liquid circulation system, 6...Warm air supply system,
13... Conductivity detection end, 13A... Conductivity detector,
3rd stage: Pre-treatment equipment.

Claims (1)

[Claims] 1. Waste liquid containing salts and surfactants generated in a nuclear power plant is treated with a membrane evaporation concentrator using a hydrophobic porous membrane on the evaporation surface to concentrate salts and In the waste liquid treatment method for obtaining condensed water, the conductivity of the condensed water is measured after removing the surfactant in the waste liquid, and when the value reaches a predetermined value, the waste liquid treatment by the membrane evaporation concentrator is interrupted. A method for treating waste liquid in a nuclear power plant, characterized in that the porous membrane is washed with acid and alcohol, and then dried to remove liquid matter adhering to the porous membrane, and then the waste liquid treatment is restarted. . 2. The method for treating waste liquid in a nuclear power plant according to claim 1, wherein the alcohol cleaning is performed by heating an alcohol solution to a temperature of 35° C. or higher and lower than the boiling point and bringing it into contact with the porous membrane. 3. Waste liquid treatment that processes waste liquid containing salts and surfactants generated in nuclear power plants using a membrane evaporation concentrator that uses a hydrophobic porous membrane on the evaporation surface to concentrate salt and obtain condensed water. In the method, the waste liquid is subjected to surfactant removal treatment in advance before being supplied to the membrane evaporation concentrator, and the conductivity of the condensed water is measured, and the value reaches a predetermined value of 10 to 100 μS/cm. If so, the waste liquid treatment by the membrane evaporation concentrator is interrupted, the porous membrane is washed with acid and alcohol, and then the liquid substance adhering to the porous membrane is removed by drying, and then the waste liquid treatment is started. A waste liquid treatment method in a nuclear power plant characterized by restarting. 4. The method for treating waste liquid in a nuclear power plant according to claim 3, wherein the alcohol cleaning is performed by heating an alcohol solution to a temperature of 35° C. or higher and lower than the boiling point and bringing it into contact with the porous membrane. 5. Waste liquid containing salts and surfactants generated in nuclear power plants is introduced into the outer cylinder of the membrane evaporative concentrator, and the vapor of the waste liquid generated in the outer cylinder is transferred to a hydrophobic membrane installed in the outer cylinder. In a waste liquid treatment device that permeates a porous tubular membrane and introduces it into the interior to concentrate salts and obtain condensed water, a surfactant in the waste liquid is removed before the waste liquid is introduced into the membrane evaporation concentrator. It consists of a means for removing in advance, a means for measuring the conductivity of condensed water flowing through the tubular membrane, a means for supplying an acid cleaning solution and an alcohol cleaning solution into the tubular membrane, and a means for supplying hot air into the tubular membrane. A waste liquid treatment device for a nuclear power plant, characterized in that it incorporates a membrane evaporation concentrator equipped with means for regenerating contaminated membranes. 6. A waste liquid treatment system in a nuclear power plant comprising the following elements (a) to (f). (a) Storage tank for waste liquid containing salts and surfactants. (b) A foam separator that blows fine bubbles into the waste liquid sent from the storage tank. (c) A storage tank for foam generated in the foam separator and containing concentrated surfactant. The waste liquid treatment apparatus according to claim 5, wherein (d) the waste liquid generated in the foam separator and from which the surfactant has been removed is treated. (e) A storage tank for concentrated waste liquid generated in the waste liquid treatment device. (f) A dryer that converts the foam and concentrated waste liquid stored in each storage tank into dry powder.