JPS61114704A - Desalting apparatus by electrodialytic method - Google Patents

Abstract

PURPOSE:To obtain a desalting apparatus conserved in energy and showing high desalting effect, by providing a heat pump for recovering the heat of a liquid after desalting treatment and heating a liquid requiring desalting and bringing an electrodialytic tank to a multistage structure. CONSTITUTION:Seawater passing through a filter 1 and a storage tank 2 is heated in a heat exchanger 4 by the heat exchange with the liquid after desalting treatment and further heated by the heat recovered from the liquid after desalting treatment by a heat pump 5. The heated seawater is sent to a first dialytic tank 9A through a filter 8 and a storage tank 6 while the liquid with intermediate concn. issued from the desalting chamber D of the tank 9A is sent to the concn. chamber C and desalting chamber D of the second dialytic tank 9B in a rear stage side. The final desalted water issued from the tank 9B is sent to the heat exchanger 4 and the heat pump 5 along with conc. water from the first dialytic tank 9A to contribute to the heating of new seawater. The desalted water insufficient in desalting in the second dialytic tank 9B is refluxed to the first dialytic tank 9A to successively perform desalting.

Description

Detailed Description of the Invention (Industrial Application Field) This invention is a desalination method using an electrodialysis method in which salt ions are electrically moved and separated by utilizing the selective permeability of an ion exchange membrane in an electrodialysis tank. It is related to the device.

(Prior Art) This type of desalination apparatus has conventionally been used to desalinate seawater by passing it through an electrodialysis tank.

The above-mentioned electrodialysis tank consists of a multi-chamber electrodialysis tank in which cation exchange membranes that pass only cations and anion exchange membranes that pass only anions are arranged alternately. When a DC voltage is applied to , cations move to the cathode side and anions to the anode side due to the potential difference. During this movement process, cations move to the anion exchange membrane,
Further, the movement of anions is blocked by the cation exchange membrane. As a result, by the electrodialyzer mentioned above.

A concentration chamber in which ions are concentrated and a desalination chamber in which ions are desalinated or diluted (hereinafter simply referred to as "desalination") are generated alternately, and fresh water is extracted from the area where the salt content is low.

The voltage of the electrodialysis tank consists of the voltage applied to the anode and cathode, and the voltage due to the electrical resistance of the ion exchange membrane and seawater, and the voltage due to the electrical resistance of the seawater is approximately 50% of the sliding voltage.
Therefore, it is known that lowering the electrical resistance of seawater is effective in saving energy in electrodialysis.

On the other hand, as shown in FIG. 2, it is known that the electrical conductivity of seawater increases by about 10% when the temperature of seawater with a salinity of 3.5% and a temperature of 20° C. increases by 10° C., for example.

As described above, as the temperature of seawater increases, not only the electrical conductivity of the seawater itself increases, that is, the electrical resistance of the seawater decreases, but also the electrical resistance of the ion exchange membrane can be expected to decrease.

Therefore, attempts have been made to heat seawater by direct heating using engine exhaust heat, solar heat, heaters, etc., but when using engine exhaust heat,
The presence of the engine itself is necessary, and in the case of using solar heat, the collector for collecting solar heat becomes large, and direct heating with a heater etc. has the disadvantage of too much energy loss. there were.

Furthermore, since the conventional electrodialysis tank consists of one dialysis tank, when trying to increase the concentration ratio of raw water and desalinated water, the concentration ratio between the C condensation chamber and the demineralization chamber increases. ,
There was a drawback that the diffusion of salt ions from the concentration chamber to the desalination chamber became significant, and the original movement of ions due to electric current was canceled out.

(Purpose of the Invention) This invention was made to improve the above-mentioned drawbacks, and can contribute to energy saving with less energy loss. The purpose is to provide a desalination device using the dialysis method.

(Structure of the Invention) In order to achieve the above object, the present invention provides a heat pump that recovers liquid heat after desalination treatment and heats a liquid that requires desalination, and a heat pump that desalinates the liquid heated by the heat pump. Equipped with an electrodialysis tank for

This electrodialysis tank is composed of a plurality of dialysis tanks, which are connected so that the intermediate concentration liquid obtained in the previous dialysis tank flows into the concentration chamber and desalination chamber of the subsequent dialysis tank.

By connecting in this way, it is possible to suppress the concentration ratio between the concentration chamber and the desalination chamber to a certain value or less in a particularly large dialysis tank, while increasing the concentration ratio between the raw water and the finally obtained desalinated water. can.

Since the heat pump described above has extremely high heat recovery efficiency of liquid heat, it can effectively heat a liquid that requires desalination, and can contribute to energy saving.

In addition, the electrodialysis tank is composed of multiple dialysis tanks, and the desalted water that has not been sufficiently desalinated in the first stage dialysis tank is returned to the subsequent stage dialysis tank to sequentially perform desalination again. , the desalination effect of the liquid that undergoes desalination, such as seawater, is sufficient, and the desired desalinated water can be obtained.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

In Figure 1, 1 is a filter that purifies seawater, 2 is a storage tank that temporarily stores the purified seawater, 3 is a pump that takes out the purified seawater from the storage tank 2, and 4 is the pump that removes the seawater. A heat exchanger 5 heats the seawater by heat exchange with the liquid after salt treatment, and 5 is a heat pump that further heats the seawater heated by the heat exchanger.This heat pump 5 recovers the heat of the liquid after the desalination treatment. The above seawater is further heated.

6 is a storage tank that temporarily stores the seawater heated by the heat pump 5, 7 is a pump that takes out the heated seawater from the storage tank 6, and 8 is a filter that purifies the heated seawater.

9 is an electrodialysis tank for desalinating heated seawater, and this electrodialysis tank 9 is composed of first and second dialysis tanks 9A and 9B, and the desalination in the first dialysis tank 9A is They are connected so that insufficiently desalinated water is refluxed to the second dialysis tank 9B on the downstream side to sequentially perform desalination. In addition, 10 is a pump, and this pump 10 is used to cause a current to flow from the concentration chamber C of the dialysis tank 9B to the demineralization chamber of the first dialysis tank 9A on the previous stage side. 11 is a storage tank that temporarily stores desalinated water.

Next, the operation of the above configuration will be explained.

The seawater purified by the filter 1 is temporarily stored in a storage tank 2, and then sent to a heat exchanger 4 by a pump 3, where it is heated by heat exchange with the desalinated liquid. The seawater heated by the heat exchanger 4 is further heated by the heat pump 5 using the heat recovered from the liquid heat after the desalination treatment.

The seawater heated by the heat pump 5 is stored in a storage tank 6.
After being temporarily stored in the storage tank 6, it is taken out from the storage tank 6 by a pump 7, purified by a filter 8, and sent to an electrodialysis tank 9.

The seawater sent to this electrodialysis tank 9 is first sent to the first dialysis tank 9A. The intermediate concentration liquid discharged from the same type of desalination chamber is sent to the concentration chamber C and the desalination chamber in the second dialysis tank 9B on the downstream side, and the final desalted water discharged from the same type of desalination chamber is Together with the concentrated water from the first dialysis tank 9A, it is sent to the aforementioned heat exchanger 4 and heat pump 5, contributing to the heating of new seawater. As a result, new seawater is heated with the heat recovered from the liquid heat after the desalination process, and each dialysis M9A
, 9B can reduce power consumption in the desalination process, contributing to energy saving.

Desalinated water that has not been sufficiently desalinated in the second dialysis tank 9B is returned to the first dialysis tank 9A on the previous stage side to sequentially perform desalination.

In the above embodiment, desalination is carried out in two dialysis tanks 9A and 9B, but desalination may be carried out sequentially in more dialysis tanks, and desalination is not limited to seawater. It goes without saying that the present invention may also be used in desalination equipment for other liquids that require salt.

(Effects of the Invention) As explained above, according to the present invention, the liquid that requires desalination is heated by a heat pump that has extremely high heat recovery efficiency of liquid heat, which contributes to energy saving in heating the liquid. In addition, by using an electrodialysis tank composed of multiple dialysis tanks, desalination water that has not been sufficiently desalinated in the first stage dialysis tank is returned to the subsequent stage dialysis tank, and desalination is performed sequentially. As a result, the desalination effect of liquids that require desalination, such as seawater, is sufficient, and desired desalinated water can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a schematic piping system diagram showing an example of a desalination apparatus using an electrodialysis method according to the present invention, and FIG. 2 is a temperature-dedicated conductivity characteristic diagram of seawater. 4...Heat exchanger, 5...Heat pump, 9-gas dialysis tank, C...Concentration chamber, D...Demineralization chamber. one

Claims (1)

[Claims] (1) A heat exchanger that heats the liquid that requires desalination through heat exchange between the liquid that requires desalination and the liquid that has undergone desalination treatment, and a heat exchanger that heats the liquid that requires desalination and recovers the heat of the desalted liquid to perform the desalination process. It is equipped with a heat pump that heats the required liquid and an electrodialysis tank that desalinates the liquid heated by the heat pump. 1. A desalination apparatus using an electrodialysis method, characterized in that a concentrated solution is connected to flow into a concentration chamber and a desalination chamber of a downstream dialysis tank, and desalination is performed sequentially.