JPH0663941B2 - Concentration control method of trace components in aqueous solution by reverse osmosis membrane method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a system for concentrating a trace amount of reactor water or boiler water in a nuclear power plant, a thermal power plant, etc., and more specifically, not only in a laboratory but also in particular. The present invention relates to a control method capable of exerting an effect online, which concentrates a trace component in an aqueous solution in a stable state.

[Conventional technology]

Conventionally, a method such as a boiling concentration method or an ion exchange resin adsorption concentration method has been adopted to treat an aqueous solution such as reactor water or boiler water in a nuclear power plant or a thermal power plant to concentrate its trace components.

In the boiling concentration method, the aqueous solution in the flask is heated and boiled with a burner or a heater to evaporate the mother liquor, thereby concentrating the concentration several to several tens of times. However, this method changes the concentration amount (concentration ratio) per time depending on the volume of the flask, changes the temperature and pressure conditions according to the solution conditions and target trace components, and requires pretreatment.
Further, it has a drawback that it requires manual work.

On the other hand, in the ion exchange resin adsorption method, the solution is passed through the ion exchange resin tower to adsorb the target component onto the resin, and then the adsorbed component is desorbed and eluted from the resin tower by the eluent, and then the desorbed resin is removed. This is a method in which the resin is repeatedly reused after being regenerated with a regeneration solution. This method can be performed by using multiple ion-exchange resin towers in parallel, but there is a limit to the adsorption capacity and ion-exchange capacity for the target component, and the resin type can be changed depending on the anion component or the cation component, or the anion-type ion-exchange resin can be used. Both a resin and a cation-type exchange resin are required, elution of the adsorbed component requires special chemicals and special technology according to the component, and slippage occurs on the resin during adsorption, resulting in instability of the concentration degree (background It has various drawbacks of causing instability), and this method is mainly a technique close to manual work.

[Problems to be solved by the invention]

The present invention eliminates the drawbacks associated with the above-mentioned conventional techniques, and can concentrate trace components in an aqueous solution in a stable state, and does not require complicated and troublesome treatments such as pretreatment with chemicals, elution, and regeneration. It is an object of the present invention to provide a concentration control method that can exert an effect online.

[Means for solving problems]

In order to achieve the above-mentioned object, the method for controlling the concentration of trace components in an aqueous solution by the reverse osmosis membrane method according to the present invention, a nuclear plant, a thermal power plant, etc. An aqueous solution containing a predetermined component to be concentrated is passed through, and this aqueous solution and a calibration standard solution of a predetermined concentration for confirming the concentration efficiency of the reverse osmosis membrane are periodically switched and supplied through a solenoid valve. Then, the aqueous solution or standard solution is pressurized to a required pressure of the reverse osmosis membrane by a booster pump, and the temperature of the aqueous solution or standard solution is cooled to a required temperature by a cooler and supplied to the reverse osmosis membrane unit. In a method for controlling the concentration of a trace component in an aqueous solution by a reverse osmosis membrane method for concentrating a trace component to be concentrated, a suspended matter is passed through the filter. The aqueous solution obtained by removing the water is flowed through the first solenoid valve to the circulation tank serving as the supply tank while the instantaneous total flow meter is flowed, and the total accumulated amount is recorded to flow into the circulation tank by a predetermined amount. The aqueous solution in the inside is allowed to flow out through a second solenoid valve to a concentrated liquid circulating thread in which a booster pump, a cooler, a flow meter and a reverse osmosis membrane unit are connected in series, and the permeated water obtained in the reverse osmosis membrane unit is recovered. And the concentrated liquid obtained in the reverse osmosis membrane unit is circulated to the circulation tank via a constant flow rate adjusting valve, and then the second electromagnetic valve is switched to pump the concentrated liquid in the circulation tank by a constant amount. , A concentration detector and a flow meter are connected in series to the concentrated liquid recovery system to collect a concentrated liquid of a predetermined concentration.

In the present invention configured as described above, individual members and instruments used in the system, such as a filter, a solenoid valve, a booster pump, a cooler, a flow meter, a reverse osmosis membrane unit, a constant flow rate regulating valve, a concentration detector, etc. Each of those known or known to those skilled in the art can be used for the purpose of the present invention.

A characteristic of the concentration control method of the present invention is that a circulation system and a recovery system for the concentrated solution are provided, and concentration is circulated repeatedly in the circulation system until a predetermined concentration is reached, and the concentrated solution having a predetermined concentration is recovered. By switching between the two systems via the solenoid valve, it is possible to appropriately collect in a batch system.

In addition, the sample water solution supplied to the circulation tank is supplied in a fixed amount for each batch and circulated and concentrated by the cooperation of the instantaneous integration flowmeter and the level control, and it is possible to concentrate with an efficiency of about 70% or more. It has been found. The concentration ratio can be expressed by the following equation. : As can be seen from the above formula, the concentration control method of the present invention is particularly suitable for high-concentration concentration, because the concentration ratio increases as the amount of liquid after concentration is made constant and the amount of aqueous solution supplied increases. During this circulation concentration cycle, the set pressure by the booster pump and the control temperature by the cooler can be set to optimum values according to factors such as the type and concentration of the trace components in the aqueous solution, and the desired degree of concentration. Can be determined by a simple preliminary test.

Further, the calibration standard solution can be flowed into the path by switching the solenoid valve, and the degree of concentration in the reverse osmosis membrane unit or the concentration of the final concentrated solution can be appropriately controlled and controlled.

[Operation] According to the present invention, by arranging the circulation system of the concentrated solution and the recovery system to be switched by the solenoid valve, the predetermined high concentration rate is reached after the concentration of the trace components in the aqueous solution by the reverse osmosis membrane is repeatedly circulated. The concentrated liquid can be recovered from the concentrated liquid recovery system by switching the solenoid valve. Thus, although it is a batch method, it is possible to stably concentrate a trace amount of components at a high magnification.

Furthermore, since a reverse osmosis membrane is used, complicated operations such as pretreatment with chemicals, elution, and regeneration, which accompany the conventional ion exchange resin adsorption method, are unnecessary, which is advantageous in terms of maintenance management.

〔Example〕

Hereinafter, embodiments of the present invention will be further described with reference to the accompanying drawings.

In the present invention, a reverse osmosis membrane conventionally used in a seawater desalination apparatus or a pure water apparatus is used as its reverse use for concentration of molecules larger than NaCl, and each component to be concentrated (ion) About filter (ultrafiltration membrane)
By selectively using the functions of the reverse osmosis membrane and the reverse osmosis membrane, they can be individually adapted to nuclear power plants and thermal power plants, and not only trace analysis but also trace component recovery method and trace sampling (dilution) in high-concentration liquid
It can be used in a range different from the usual field of use of a reverse osmosis membrane.

In FIG. 1, reference numeral 10 is a filter having a mesh size larger than that of a component to be concentrated contained in an aqueous solution such as reactor water or boiler water, which is momentarily integrated flow meter FQI through a solenoid valve M _1. Connect to. The electromagnetic valve M ₁ is also connected to a path for flowing the calibration standard solution. The instantaneous flow rate integrator FQI is equipped with a circulating talc 1 via the control valve 12 as needed.
Connected to 4. The circulation tank 14 is provided with a level sensor LC, which is linked with the instantaneous integration flow meter FQI and the control valve 12.
The supply amount of the supply aqueous solution to the circulation tank 14 is controlled. The outlet dew of the circulation tank 14 is branched via a solenoid valve M ₂ so that one is configured as a circulation system and the other is configured as a concentrated liquid recovery system.

In the circulation system, the booster pump P is connected to an ordinary controllable cooler 16, and this booster pump P is connected to the level sensor LC (that is, the level control system) in cooperation with the liquid level in the circulation tank 14 to boost the pressure. The pressure increase of the aqueous solution by the pump P can be maintained in a predetermined relationship.

The pump P pressurizes the aqueous solution or standard solution to the required pressure in the reverse osmosis membrane, while the cooler 16 controls the aqueous solution or standard solution to a temperature optimum for the efficiency of the reverse osmosis membrane.

Next, the cooler 16 is connected to the reverse osmosis membrane unit 20 via the flow meter 18, and then the permeated water side is connected to the recovery path via the flow meter 22 while the concentrated liquid side is adjusted to a constant pressure type constant flow rate. It communicates with the circulation tank 14 via a valve 24. On the other hand, in the concentrated liquid recovery system, the metering pump 26, the concentration detector E, and the flowmeter 28 are sequentially arranged in series and then connected to the concentrated liquid recovery path.

In the present invention, the feature that the reverse osmosis membrane has a stable permeated water amount under a constant temperature and a constant pressure condition can be used to adjust the concentration degree by the ratio of the total water permeated amount to the permeated water amount. The concentration is calibrated by periodically passing a standard solution of a predetermined concentration through the above path, and the constant flow rate control valve 24 automatically corrects it so that the standard solution is positive and the concentration on the outlet side of the concentrated solution is constant. can do.

The operation of the apparatus configured as described above will be described below.

First, an aqueous solution such as reactor water or boiler water is first passed through a filter 10 having a mesh size larger than the trace components contained therein to remove suspended matter (prevention of clogging of reverse osmosis membrane), and then electromagnetic After passing through the instantaneous integrating flow meter FQI via the valve M ₁ to record the total amount of the supply water accumulated, it is allowed to flow into the circulation tank 14 (which also functions as a sample water supply tank) via the control valve 12. The aqueous solution flowing out from the circulation tank 14 according to the command of the level control system (composed of the instantaneous integration flow meter FQI, the control valve 12 and the level sensor LC) is then subjected to the reverse osmosis membrane by the booster pump P via the solenoid valve M _2. After the pressure is increased to the required pressure, the temperature is adjusted to a constant temperature by the cooler 16, and then the reverse osmosis membrane unit 20 is processed through the flow meter 18 for processing. The permeated water of the reverse osmosis membrane unit 20 is recovered via the flow meter 22, while the concentrated liquid of the reverse osmosis membrane unit 20 is circulated to the circulation tank 14 with its flow rate adjusted by the constant flow rate adjusting valve 24.

This circulation circuit is maintained by the solenoid valve M ₂ for a predetermined time or until a concentrated liquid having a predetermined concentration is obtained, and when the concentration reaches a predetermined value, the electromagnetic valve M ₂ is immediately switched to the circulating tank 14 in the concentrated liquid recovery system. The concentrated liquid having a predetermined concentration is collected through the metering pump 26, the concentration detector E, and the flowmeter 28 in communication with each other. The supply of the aqueous solution to the circulation tank (sample aqueous solution supply tank) 14 is controlled by a level control system, and a fixed amount is supplied for each batch by the integrating flow meter FQI and is circulated and concentrated. It can be controlled to obtain a desired concentration ratio according to the purpose of use.

Hereinafter, a concentration test using the reverse osmosis membrane unit according to the above circulation concentration control method of the present invention will be described.

Chloride standard solution with three different concentrations is put in the sample supply tank (circulation tank) 14 and the level of the aqueous solution in the tank is 1/7.
As a result of circulating concentration until the concentration reached, a good linear relationship was obtained between the concentration before and after the concentration, and it was confirmed that the concentration was about 5 times (7 times when the concentration efficiency was 100%). .

As a result of this test, by using a reverse osmosis membrane, from 1 ppb
It has been confirmed that chlorine ions up to 20 ppb can be concentrated with a concentration efficiency of about 70% or more, and a mechanism that keeps the water recovery rate constant, that is, a constant flow rate system is required for stable concentration with a reverse osmosis membrane. It turned out to be

〔The invention's effect〕

According to the present invention, trace components contained in an aqueous solution such as reactor water or boiler water can be concentrated in a stable state without delay, and complicated and troublesome maintenance management and operation such as pretreatment with chemicals, elution, regeneration, etc. Since it is not necessary, a concentration control method is obtained which is effective not only for laboratory use but also for online use in particular.

[Brief description of drawings]

FIG. 1 is a schematic system diagram showing an embodiment of a system for carrying out the method for controlling the concentration of trace components in an aqueous solution by the reverse osmosis membrane method according to the present invention. 10 …… Filter, M …… Solenoid valve 12 …… Control valve, 14 …… Circulation tank FQI …… Instantaneous flow meter P …… Boost pump, 16 …… Cooler 18 …… Flow meter, 20 …… Reverse osmosis membrane Unit 22 …… Flowmeter, 24 …… Constant flow adjustment valve E …… Concentration detector, 26 …… Quantitative pump 28 …… Flowmeter, LC …… Level sensor

Front page continuation (56) References JP-A-60-212286 (JP, A) JP-A-59-156402 (JP, A) JP-A-58-55779 (JP, A) Practical application JP-A-55-49353 ( Micro film (JP, U) of Japanese Utility Model Sho 56-151951) Micro film (JP, U) of Japanese Patent Application 59-162680 (Japanese Utility Model Sho 61-76341)

Claims (1)

[Claims] 1. An aqueous solution containing a predetermined component to be concentrated is passed through a filter having a mesh size larger than the component to be concentrated in the aqueous solution in a nuclear power plant, a thermal power plant, etc., and the aqueous solution and the reverse osmosis membrane are concentrated. A standard solution for calibration having a predetermined concentration for confirming the efficiency is periodically switched and supplied through a solenoid valve, and then the aqueous solution or standard solution is pressurized to a required pressure of the reverse osmosis membrane by a booster pump,
Furthermore, the temperature of the aqueous solution or the standard solution is cooled to a required temperature by a cooler and supplied to the reverse osmosis membrane unit so that the trace elements to be concentrated in the aqueous solution are concentrated. In the method of controlling concentration, the aqueous solution obtained by removing the suspended matter through the filter is passed through a first solenoid valve to a circulation tank as a supply tank while passing an instantaneous integrating flow meter, The total accumulated amount is recorded and a predetermined amount is flown in, and then the aqueous solution in the circulation tank is flown out through a second solenoid valve to a concentrated liquid circulation system in which a booster pump, a cooler, a flow type and a reverse osmosis membrane unit are connected in series. The permeated water obtained in the reverse osmosis membrane unit is led to a recovery system, and the concentrated liquid obtained in the reverse osmosis membrane unit is transferred to the circulation tank via a constant flow rate adjusting valve. After being circulated, the second solenoid valve is switched to cause the concentrated liquid in the circulation tank to flow out to a concentrated liquid recovery system in which a metering pump, a concentration detector and a flow meter are connected in series to obtain a concentrated liquid having a predetermined concentration. A method for controlling the concentration of trace components in an aqueous solution by the reverse osmosis membrane method, which comprises recovering.