JPS6261694A - Electrodyalitic method for desalting seawater - Google Patents

Abstract

PURPOSE:To reduce electric energy to a large extent, by using a solar cell in a part of the power source of an electrodyalitic cell and preheating supplied seawater by a heat exchanger and a solar heater. CONSTITUTION:Seawater is guided to the cooler 10 for a solar cell 9 through a conduit 12 by a main pump to cool the solar cell 9 and preheated. The preheated seawater is guided to a heat exchanger 14 through a branched pipe 12a and further preheated through the heat-exchange with the high temp. fresh water discharged from an electrodyalitic cell 1. The preheated seawater is guided to a solar heater 11 and further preheated to 40-60 deg.C to be supplied to the electrodyalitic cell 1 and electrodyalized by the DC current obtained by utilizing the solar cell 9 as a part of a power source while fresh water is discharged through a conduit. By this method, installation cost and operation cost can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a seawater desalination method using electrodialysis.

[Prior art and its problems]

Reverse osmosis and electrodialysis are known as seawater desalination methods using membranes. The reverse osmosis method uses seawater to 1001
This is a method of obtaining fresh water by permeating it through a reverse osmosis membrane at a pressure of about 1/d. However, this method requires complicated pretreatment of the seawater in order to prevent the reverse osmosis membrane from clogging due to water scale and microbial moss contained in the seawater, and is difficult to handle. However, there is an intermediate layer where equipment costs are high due to pre-treatment equipment, etc.

In the electrodialysis method, seawater is passed through an electrodialysis tank in which cation-exchange membranes and anion-exchange membranes are arranged alternately, and a direct current is applied to the tank to remove constituent ions of salts through the membrane. This is the way to obtain. According to this method,
Although it does not require complicated pretreatment of seawater like reverse osmosis, there is a problem in that it requires a large amount of electricity compared to reverse osmosis. 20
Seawater with a relatively low concentration of about 00ppm to 200ppm
It is used for desalination to a certain degree.

[Purpose of the invention]

Therefore, the purpose of this invention is to provide a method for economically desalinating seawater with a high concentration of salinity (TDS') of approximately 30,000 ppm or more by electrodialysis without requiring a large amount of electricity. The purpose is to provide a method.

[Summary of the invention]

This invention introduces seawater into an electrodialysis tank having a cation exchange membrane and an anion exchange membrane, and passes a direct current through the seawater through an anode and a cathode provided in the electrodialysis tank. In an electrodialysis seawater desalination method in which salt is removed by the cation exchange membrane and the anion exchange membrane, a solar cell is used as a part of the power source for the direct current, and the direct current is guided to the electrodialysis tank. sea water,
exchanging heat with high temperature fresh water discharged from the electrodialysis tank,
Furthermore, the electrodialysis tank is characterized in that preheating is performed by a solar heater provided on the entrance side of the electrodialysis tank.

[Structure of the invention]

Next, 1 this invention will be explained with reference to the drawings.

FIG. 1 is an explanatory diagram of essential parts showing one embodiment of the present invention. As shown in the drawing, the electrodialysis tank 1 includes cation exchange membranes 2 and anion exchange membranes 3, which are high temperature resistant and are arranged alternately at a predetermined interval in a tank body 1a, and a cation exchange membrane 3. 2 and an anion exchange membrane 3, respectively.

Each of the anode 4 and the cathode 5 is a conductive wire 8a.

8bK is connected to the positive and negative electrodes of the battery 6. 7 is a charger for charging the battery 6.

The negative pole of the solar cell 9 is connected to the positive pole of the battery 6 by a conductive wire 10a, and the glass pole of the solar cell 9 is connected to the negative pole of the battery 6 by a conductive wire 10b. 1o is a cooler for cooling the solar cell 9.

A conduit 12 for guiding seawater to the electrodialysis tank 1 is connected to a solar cell cooler 10 in the middle, and a solar warmer 11 is connected in the middle of the conduit 12 on the outlet side of the solar cell cooler 10. It is provided. A heat exchanger 14 is provided in the middle of a conduit 13 that guides the high temperature fresh water discharged from the electrodialysis tank 1.

A branch pipe 12a branched from the conduit 12 passes through the heat exchanger 14 to lead the seawater to the solar warmer 11 without passing through the solar cell cooler 10. '
The seawater is preheated by hot fresh water with a temperature of approximately 40-60°C discharged through 13.

FIG. 2 is a system diagram showing one embodiment of the present invention. In FIG. 2, 12b and 12c are conduits for directly guiding seawater to the electrodialysis tank IK in order to improve the conductivity in the electrodialysis tank I and protect the cation exchange membrane 2 and anion exchange M3. It is a branch pipe branching from 12,
Reference numeral 15 denotes a circulation conduit having a circulation pump 16 in the middle thereof for circulating the seawater led through the conduit 12b to the electrodialysis tank l. 17 is a conduit for discharging salt-rich water 19 (water) separated from seawater in the electrodialysis tank 1; 18 is a conduit for circulating a part of the reduced water to the electrodialysis tank 1; 20 is a circulation conduit having a pump 7'19.
It is a cartridge filter installed in the middle of 2.
21 is a variable pulp provided in the middle of each conduit, 22 is an opening/closing pulp, 23 is a flow rate adjusting pulp, and 24 is a main pump provided in the middle of the conduit 12.

The seawater is guided by a main pump 24 through a conduit 12 to a solar cell cooler 10 VC to cool and preheat the solar cells, and is also led to a heat exchanger 14 through a branch pipe 12a to be removed from the electrodialysis tank 1. It is preheated by heat exchange with the discharged high temperature fresh water.

The seawater thus preheated is led to the solar warmer 11 where it is further preheated, raised to a temperature of about 40 to 60°C, and then supplied to the electrodialysis tank 1.

The seawater supplied to the electrodialysis tank 1
It is electrodialyzed by direct current as part of the source, and the salts are separated into fresh water, which is discharged through conduit 13.

On the other hand, the salt-rich l' separated by the electrodialysis tank 1
, :<The water is discharged through conduit 17.

In addition, as a power source for the driving DC motor of the pump etc. for flowing seawater through each conduit, a part or all of it is equipped with a solar battery 9.
may be used.

〔Effect of the invention〕

As described above, according to the present invention, a solar cell is used as a part of the power source of the electrodialysis tank, and the seawater supplied into the electrodialysis tank is preheated by a heat exchanger, a solar heater, etc. Therefore, the amount of electricity required for electrodialysis in the electrodialysis tank 1 can be significantly reduced, and the amount of salt (TD
S) from seawater with 30,000 ppm or more, 500 p
Fresh water below pm can be produced economically. In addition, since seawater pretreatment requires only filtration, the equipment costs and operating costs required for seawater pretreatment can be reduced to approximately 50% or less compared to reverse osmosis, and furthermore, the operation is simple. Many excellent effects are brought about.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of essential parts showing one embodiment of the present invention, and FIG. 2 is a system diagram. In the drawings, 1... Electrodialysis tank, 1a... Tank body, 2...
Cation exchange membrane, 3... Anion exchange membrane, 4... Anode, 5... Cathode, 6... Battery,
7...N charger, 9...Solar battery, 10
...Solar cell cooler, 11...Solar warmer, 1
4... Heat exchanger, 16.19... Circulation pump, 20... Cartridge filter, 21... Variable valve, 22... Open/close valve, 23
...Flow rate adjustment valve, 24...Main inlet.

Claims (1)

[Scope of Claims] Seawater is introduced into an electrodialysis tank having a cation exchange membrane and an anion exchange membrane, and a direct current is passed through the seawater through an anode and a cathode provided in the electrodialysis tank, In an electrodialysis seawater desalination method for removing salt in seawater using the cation exchange membrane and the anion exchange membrane, a solar cell is used as a part of the power source for the direct current, and the electrodialysis The seawater introduced into the tank is heat-exchanged with high-temperature fresh water discharged from the electrodialysis tank, and is further preheated by a solar heater installed on the inlet side of the electrodialysis tank. Electrodialysis seawater desalination method.