JPS6034787A - Electrodialytic water making device and operating process thereof - Google Patents

Abstract

PURPOSE:To reduce installation cost and operation cost by providing >=2 circulation tank 5 in a desalting chamber to enable changeover operation at the stage of actuation of an electrodialytic cell, a stage for water discharge and supply alternately by a changeover valve provided to a circulation system in the desalting chamber. CONSTITUTION:Supply of raw water 12 to a tnak A is commenced by opening a raw water feed valve 34. After the water level is detected to have reached high level by a water gauge A44, a raw water feed valve A is closed and the operation is held in the waiting state until dialysis of raw water 39 in the tank B31 is completed. When the concn. of salt attains specified concn. by the dialysis, the passage of flow is changed again by an outlet changeover valve 32 and a return changeover valve 33 of a salt water circulation tank so as to flow the raw water 38 in the tank A through the passage. The dialysis of the raw water 38 in the tank A 30 is thus commenced again, and the process is transferred to the dialysis process of the raw water 39 in the tank B 31 when the dialysis of the raw water 38 is finished. By repeating this procedure, operation of the electrodialysis cell is continued without suspending actuation of the cell.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrodialysis water generation device and a method of operating the same, and particularly relates to an electrodialysis water generation device that has a simple structure and can reduce equipment costs and operating costs, and a method of operating the same. It is.

Cation exchange membranes and anion exchange membranes are arranged alternately between the anode and the cathode, and a demineralization chamber and a concentration chamber are formed between these membranes by applying electricity, and demineralized water and concentrated water are obtained from these chambers, respectively. The processing methods of dialysis water generators can be roughly divided into batch processing and transient processing.

FIG. 1 and Table 1 show a system diagram of a conventional batch processing system and an operation time chart thereof. In the figure, raw water 12 is supplied into the desalinated water circulation tank 2 via the raw water supply valve 7, and after the water is filled, water supply is stopped, and raw water 13 is also supplied to the concentrated water circulation tank 3. Then,
The desalinated water circulation pump 5 and the concentrated water pump 6 are driven, and dialysis is started by applying electricity. Raw water 1 entering dialysis tank 1
4.15 is desalted and concentrated, and then returned to the respective desalted water circulation tank 2 and concentrated water circulation tank 3 by circulation pumps 5 and 6, respectively. The raw water 14 in the desalinated water circulation tank 2 is repeatedly circulated until it reaches a predetermined concentration. After the desalination is completed, the desalinated water circulation pump 5 is stopped, and the desalted water in the desalted water circulation pump 2 is discharged to the outside through the discharge valve 8. In the figure, 9 indicates a salt concentration needle, 10 indicates a voltmeter, and 11 indicates an ammeter.

Table 1 In the above conventional method, the steps of water supply to the dialysis tank, dialysis, and drainage are repeated, but since the electricity to the dialysis tank is stopped during the water supply and drainage steps, the actual amount of water produced decreases. do. For this reason, conventional batch-processing electrodialysis water generation equipment requires a dialysis tank with a water generation capacity larger than the amount of water produced by the equipment, and this dialysis tank is mainly composed of an expensive ion exchange membrane. This has the disadvantage of increasing production costs.

Next, Figures 2 to 4 show system diagrams of conventional electrodialysis equipment using a transient treatment method, of which Figure 2 shows a partial circulation -
FIG. 2 is a system diagram of an over-processing system.

Raw water 12 is supplied in a constant amount during lightning to a desalinated water circulation pump 2 that has circulating desalinated water 16 inside, and is mixed with desalinated water 16, and this desalted water 16 is transferred into the dialysis tank 1 by a desalinated water circulation pump 5. and desalted by dialysis. An equal amount of water is always extracted from this desalted circulating water to obtain produced water 17. In this partial circulation-overtreatment method,
Since the raw water is diluted and desalted, the electrical resistance of the dialysis tank increases, resulting in high power consumption and high operating costs.

FIG. 3 shows a system diagram of the conventional multi-stage series-overtreatment system, and this system has a plurality of dialysis tanks 18.
~20 are provided. The raw water 12 is divided into two systems 21 and 22, desalinated water and concentrated water, and these dialysis tanks 18 to 2
0 in series.

When leaving the final dialysis tank 20, the raw water in the desalinated water system becomes produced water 17 that has been desalted to a predetermined salt concentration.

This multistage series-overtreatment system has the disadvantage that it is difficult to operate because it is necessary to strictly control the salt concentration, temperature, and flow rate of the raw water 12. In addition, while the raw water 12 is divided into a desalinated water system 21 and a concentrated water system 22 and flows through a long channel in the dialysis tank, a pressure difference is created between the two systems 21 and 22, and this pressure difference causes a pressure difference in the dialysis tank. Dialysis membranes 18 to 20 may move. When this movement of the dialysis membrane occurs, water decomposition occurs, causing scaling problems and making stable operation difficult.

FIG. 4 shows a system diagram of a transient processing method that combines multi-stage series and partial circulation. In order to prevent scaling problems caused by the long flow path, which is a disadvantage of the multi-stage series system shown in Figure 3, this combination of temporary treatment systems uses desalinated water circulation tanks 27 to 29 for each dialysis tank, Circulation pumps 23 to 25 are additionally installed, and it also improves the drawback of the partial circulation type dialysis tank shown in FIG. 2, which has a large electrical resistance. However, this combination of over-treatment methods requires a large number of desalinated water circulation pumps 23 to 25, desalted water circulation tanks 27 to 29, piping, etc., and therefore has the disadvantage of high equipment cost.

An object of the present invention is to eliminate the drawbacks of the prior art described above, and to provide an electrodialytic water generating apparatus and a method for operating the same, which have a relatively simple structure and good operating efficiency.

The present invention provides a batch treatment type electrodialysis water generation device that is equipped with at least two desalted water circulation tanks and a valve for switching these tanks, and that immediately after desalination of raw water in one desalted water circulation tank is completed. By shifting to the treatment of raw water in another desalinated water circulation tank, the dialysis tank can be used with electricity constantly on. That is, the present invention provides an electrodialysis tank in which a desalination chamber and a concentration chamber are formed between an anode and a cathode via an ion exchange membrane, raw water is supplied to the desalination chamber and concentration chamber, and electrodialysis is performed. In an electrodialysis water generation apparatus, the desalination water and concentrated water are temporarily stored in respective circulation tanks and then circulated to the electrodialysis tank. At least two salt chamber circulation tanks are provided, and a switching valve provided in the circulation system of the desalination chamber is configured to alternately switch between energization of the electrodialysis tank, draining water, and water supply.

Further, in the method of operating an electrodialysis apparatus of the present invention, when operating an electrodialysis apparatus in which switching valves are provided at the outlet and inlet of the demineralization chamber circulation tank, the outlet It is characterized by operating the switching valve and the inlet switching valve with a certain period of time shift.

Hereinafter, the present invention will be explained in more detail with reference to the drawings.

FIG. 5 is a system diagram of an electrodialysis water generation apparatus showing one embodiment of the present invention. In this example, there are two demineralized water circulation tanks (tank A30, tank B5) for one dialysis tank.
1) It is installed. In order to select the desalinated water circulation tank A or B (hereinafter simply referred to as tanks A and B) leading to the dialysis tank 1, the desalinated water circulation tank outlet switching valve 32 is installed on the outlet side of the tank, and the desalinated water circulation tank is installed on the return side of the tank. Return switching valve 33
is installed. In order to detect the desalination state of raw water, a salt concentration needle (or conductivity meter) 9 is installed in the desalinated water circulation system 41, and a water level gauge 44.45 is installed in the desalinated water circulation tank 31.32 to detect the water level. is set up. In addition, in the figure,
34.35 are raw water supply valves for tanks A and B, respectively;
36.37 are desalinated water discharge valves provided in tanks A and B, respectively, 38.39 is raw water in tanks A and B, 4o is a desalinated water system, 42.43 is a concentrated water system, and 46 is concentrated water.

Table 2 shows a time chart showing how the above device is operated.

Table 2 in the margin below To operate this electrodialysis water generator, first, start with the raw water supply valve 3.
4 and transfer raw water 12 to desalinated water circulation tank A (tank A).
After detecting that the water level has reached a high level using the water level gauge A44, the raw water supply valve A34 is closed. Also,
The flow paths of the desalted water circulation tank outlet switching valve 32 and the desalted water circulation tank return switching valve 33 are switched so that the raw water 38 in the tank A flows into the dialysis tank 1. In the concentrated water system, water 13 is supplied into the concentrated water circulation tank 3, and an amount of concentrated water 26 corresponding to the supplied amount is discharged. Next, the desalinated water circulation pump 5, the concentrated water circulation pump 6, etc. are driven and energization is started.

As a result, the raw water 38 in the tank A30 can be completely introduced into the demineralization chamber of the dialysis tank 1 through the demineralized water circulation outlet switching valve 32. Further, the concentrated water 46 in the concentrated water circulation tank 3 is introduced into the i-tub chamber of the dialysis tank 1. The raw water 38 and concentrated water 46 that have entered the dialysis tank 1 are dialyzed, the salts in the raw water 38 move to the concentrated water 46, and the salt concentration of the raw water 38 is reduced. The raw water 38 leaving the dialysis tank 1 has its salt concentration measured by a concentration meter 9, passes through a desalinated water circulation tank return switching valve 33, and enters the original tank A30. The concentrated water 46 that has left the dialysis tank returns to the concentrated water circulation tank 3. Raw water 38 in tank A30
By circulating through this dialysis tank 1, the salt concentration gradually decreases.

While the raw water 38 in the tank A30 is being desalinated by dialysis, the raw water supply valve B35 is opened to supply the raw water 12 into the tank B31, and after the water level gauge 845 detects a high water level,
Close the raw water supply valve B35 and wait until the dialysis of the raw water in the tank A30 is completed.

The dialysis of the raw water 38 in the tank A30 continues until the low salt concentration 9 indication reaches a predetermined concentration. When a predetermined concentration is reached, the flow paths of the outlet switching valve 32 and the return switching valve 33 of the desalinated water circulation tank are changed so that the raw water 39 in the tank B flows. By changing the flow path, the raw water 3 in the tank B31 is replaced by the raw water 3 in the tank A30 in the dialysis tank 1.
9 begins to flow, this raw water 39 is also subjected to dialysis treatment, its salt concentration is detected, and after passing through the desalted water circulation tank return switching valve 33, it is introduced into tank B31. This tank B31
Similarly to the raw water 38 in the tank A30, the salt concentration of the raw water 39 in the tank A30 gradually decreases as it circulates through the dialysis tank 1. While the raw water 39 in the tank B31 is being desalinated by dialysis, the desalinated product water in the tank A30 is discharged to the outside of the water generator by opening the desalted water discharge valve A36. When the water level gauge A44 detects that the water level has become low due to the discharge of this desalinated water, the desalted water discharge valve A36 is closed. Next, the raw water supply valve A34 is opened and the raw water 12 starts to be supplied to the tank A30, and after the water level gauge A44 detects that the water level has reached a high level, the raw water supply valve A34 is closed and the raw water 39 in the tank B31 is dialyzed. Wait until it completes. Dialysis of the raw water 39 in Kunku B31 is performed using a salt concentration meter 9.
This instruction continues until the predetermined concentration is reached. When the predetermined concentration is reached, the flow paths of the outlet switching valve 32 and return switching valve 33 of the desalinated water circulation tank are changed so that the raw water 38 in the tank A30 flows again. By changing the flow path, the dialysis of the raw water 38 in the tank A30 is started again, and when the dialysis is completed, the process shifts to the dialysis of the raw water 39 in the tank B31. Thereafter, by repeatedly performing this operation, efficient operation is possible without stopping the electricity supply to the electrodialysis tank.

According to the above embodiment, compared to the batch processing method shown in FIG. 1, the dialysis tank 1 can be energized at the same time, so there is no substantial decrease in the amount of water produced, and therefore there is no need to increase the size of the dialysis tank. It disappears. Regarding the apparatus, although the number of demineralized water tanks increases from one to two, there is no increase in the number of expensive ion exchange membranes, so the overall cost of the apparatus can be reduced.

Compared to the partial circulation-overtreatment method shown in FIG. 2, the raw water 12 is not mixed with the desalinated water 16 for dialysis, so the electrical resistance of the dialysis tank does not increase, thus reducing operating costs. can.

Furthermore, compared to the one-time treatment system that combines multi-stage series and partial circulation as shown in FIG. 4, the number of desalted water circulation tanks and desalted water circulation tanks to be installed can be reduced, resulting in the effect of reducing equipment costs.

As another embodiment of the present invention, as shown in FIG. 6, instead of the outlet switching valve 32 and return switching valve 33 of the desalinated water circulation tanks A and B, a desalinated water circulation tank is installed in each tank A and B. outlet valves A47, B48, and return valves A49,
By providing the same B50, the raw water in the desalinated water circulation tank A30 can be alternately subjected to dialysis treatment in the same way. That is, when dialyzing raw water in tank A30, open outlet valve A47 and return valve A49 of the desalinated water circulation tank, and open outlet valve 848.
By closing the return valve A50, an effect similar to that of the switching valves 32 and 33 in FIG. 5 can be obtained. In addition, as the salt concentration needle 9, in the embodiment shown in FIG. It may also be an instrument that measures physical properties such as

In the embodiment shown in FIG. 5 and Table 2, the flow path change of the outlet switching valve 32 and the return switching valve 33 of the desalted water circulation tank is not performed at the same time, and the flow path change time of the return switching valve 33 is delayed for a certain period of time. As a result, more desalinated water in the desalinated water system (the desalinated chamber in the dialysis tank and the desalted water system 40.41) can be recovered, which has the effect of reducing operating costs. The flow path change of this desalinated water circulation tank outlet switching valve 32 is performed using the salt concentration needle 917! Using the signal that the indication reaches a predetermined concentration, the desalination water circulation tank return switching valve 3
For the flow path change in step 3, it is preferable to use a signal or the like in which the indication of the salt concentration needle 9 suddenly changes to a higher salt concentration. The amount of water held between the outlet switching valve 32 and the return switching valve 33 of the desalinated water circulation tank reaches approximately 10% of the amount of water held in the desalted water circulation tank in a device in which the -times of dialysis time is 2 hours. Being able to recover this much amount is extremely advantageous in terms of operating costs. Note that if these valves are switched at the same time, the desalinated water between these switching valves 32 and 33 will be mixed with the raw water that will be subjected to the next dialysis treatment, diluting the raw water, but such dilution will Although it is possible to reduce the current applied to the dialysis tank, it increases the electrical resistance, which increases power consumption.

As mentioned above, by shifting the flow path change times of the outlet switching valve 32 and return switching valve 33 of the desalinated water circulation tank, the amount of recovered desalted water can be increased, which has the effect of further reducing operating costs. is obtained.

In the above embodiment, the signal for changing the flow path of the demineralized water circulation tank return valve 33 includes, in addition to an increase in the indicated value of the salt concentration needle 9, an increase in the applied current in the dialysis tank, a change in the pH of the demineralized water, etc. Can be used for signals. That is, since the current applied to the dialysis tank is normally operated at a constant voltage, when the salt concentration of the desalinated water in the dialysis tank changes, the electrical resistance changes and the current value changes. Therefore, after completion of desalination, when raw water with a high salt concentration newly flows into the dialysis tank, the current value increases. By using this change in current value as a signal for changing the flow path of the desalinated water circulation tank return valve 33, it is possible to increase the recovery rate of desalinated water as in the case of concentration detection. Also, the pH of desalinated water
can be used as a signal for changing the flow path of the desalted water circulation tank return valve 33 in the same way as a change in salt concentration when the pH of the desalted water and the raw water are different. Furthermore, if the circulation amount of desalinated water is constant, the time for desalinated water to be pushed out can be set, so the difference in flow path change time between the desalted water circulation tank outlet valve 32 and the desalted water circulation tank return valve 33 can be adjusted. can be determined. Therefore, the flow path change time of the desalinated water circulation tank return valve 32 can be set after a certain period of time after the desalination completion signal using the timer, and the same effect can be obtained.

Furthermore, in the present invention, the electrical resistance of the dialysis tank 1 can be reduced by configuring the structure of the demineralized water circulation tanks 30 and 31 in FIG. can be reduced. FIG. 7 shows an example of the structure of a desalinated water circulation tank that prevents mixing of liquids in the tank, in which the desalinated water tank 2 is divided into a plurality of parts by a partition plate 51 in a direction perpendicular to the flow. be. If there is no partition plate, the liquid in the demineralized water circulation tank 2 will be diluted by the liquid returned from the dialysis tank, but by installing the partition plate 51, dilution of the liquid in the demineralized water circulation tank 2 is prevented. As described above, the electrical resistance of the dialysis tank 1 can be reduced. For example, T, D, 3.500 from seawater
In an electrodialysis water generator that produces 2 ppm of domestic water per batch in 2 hours, the electrical resistance of the dialysis tank can be reduced by 30%.

As a method of preventing dilution due to the return liquid in this desalinated water circulation tank, instead of providing a partition plate, the tank itself may be constructed with a long pipe 52 as shown in FIG. 8, and even better results can be obtained. can be obtained.

As described above, according to the present invention, by providing at least two desalted water circulation tanks and creating a piping system in which these tanks are alternately partitioned to supply and discharge raw water and circulate desalted water, the operation of the electrodialysis tank can be controlled. This can be done continuously, improving operational efficiency and reducing equipment costs.

[Brief explanation of the drawing]

Figure 1 is a system diagram of a conventional electrodialysis water generation system in batch processing mode, Figure 2 is a system diagram of a conventional partial circulation-overtreatment system, and Figure 3 is a system diagram of a conventional multi-stage series-overtreatment system. FIG. 4 is a system diagram of a conventional one-time treatment system that combines multi-stage series and partial circulation, and FIG. 5 is a system diagram of an electrodialysis water generator showing an embodiment of the present invention. Fig. 6 is a system diagram showing another embodiment of the switching valve in the above embodiment, Fig. 7 is a sectional view showing an embodiment of the desalinated water circulation tank used in the present invention, and Fig. 8 is a pipe shape FIG. 2 is an explanatory diagram showing a desalinated water circulation tank. 1... Dialysis tank, 2... Desalinated water circulation tank, 3...
Concentrated water circulation tank, 4... DC power supply, 5... Desalinated water circulation pump, 6... Circulating water circulation pump, 7... Raw water supply valve, 8... Desalinated water discharge valve, 9... Salt concentration needle, 1
0... Voltage needle, 11... Current needle, 12.13.14
．． 15... Raw water, 16... Desalinated water, 17... Produced water, 30... Desalinated water circulation tank (tank A), 31...
...Demineralized water circulation tank (tank B), 32...Demineralized water circulation tank outlet switching valve, 33...Demineralized water circulation tank return switching valve, 34...Raw water supply valve A, 35...Raw water supply Valve B, 36...Demineralized water discharge valve A, 37...Demineralized water discharge valve B, 38.39...Raw water, 40.41...Demineralized water system, 42.43...Concentrated water system , 46... Concentrated water. Agent Patent Attorney Takenaga KawakitaFigure 1Figure 3Figure 4Figure 5Figure 6Figure 7Figure 8

Claims (1)

[Scope of Claims] (1) An electrodialysis tank in which a demineralization chamber and a concentration chamber are formed via an ion exchange membrane between an anode and a cathode, and raw water is supplied to the demineralization chamber and concentration chamber, In an electrodialysis water generation apparatus having a circulation system for desalinated water and concentrated water, which performs electrodialysis, temporarily stores the obtained desalted water and concentrated water in respective circulation tanks, and then circulates them to the electrodialysis tank. , characterized in that at least two circulation tanks are provided in the demineralization chamber, and a switching valve provided in the circulation system of the demineralization chamber can be alternately switched when energizing the electrodialysis tank and when draining and supplying water. Electrodialysis water generator. (2. Claim 1, characterized in that the demineralized water circulation tank is provided with a flow path formed by connecting a plurality of straight and convergent flow path portions with a plurality of bent flow path portions. (3) An electrodialysis tank in which a demineralization chamber and a concentration chamber are formed via an ion exchange membrane between an anode and a cathode, and raw water is supplied to the demineralization chamber and concentration chamber. and a circulation system for desalinated water and concentrated water that performs electrodialysis, temporarily stores the obtained desalted water and concentrated water in respective circulation tanks, and then circulates them to the electrodialysis tank, At least two circulation tanks are provided in the demineralization chamber, and switching valves are provided at the outlet and inlet of the demineralization chamber circulation tank, respectively, so that switching can be performed alternately when the electrodialysis tank is energized, drained, and water is supplied. In the operation of the electrodialysis type water supply device, the operation of the outlet switching valve and the inlet switching valve of the desalination chamber circulation tank is shifted by a certain period of time so that desalinated water does not remain in the circulation tank when the switching valve is operated. (4) In claim 3, the operation of the switching valve is performed based on a measurement signal of the salt concentration of desalinated water or a physical property value corresponding thereto. 1. A method of operating an electrodialysis water generator, characterized in that: