JP3028666B2 - Water purification method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[Object of the invention]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for producing purified water from water containing impurities such as tap water and seawater.

[0002]

2. Description of the Related Art Since tap water contains various impurity components, it is desirable to purify tap water for use as drinking water. Conventional household water purifiers are based on a filtration and adsorption system, and use a filter made of an organic membrane or activated carbon. However, it is considered that it is difficult for conventional water purifiers to sufficiently remove trihalomethane, which is contained in tap water and is called a carcinogen. Further, in the filtration type water purifier, the filter has a limited life due to clogging, so that periodic maintenance such as replacement of the filter is required.

On the other hand, as a seawater desalination technique, an evaporation method and a freezing method using LNG (liquefied natural gas) are known. The evaporation method is a technique in which seawater is heated by a boiler or the like, and the generated steam is condensed with the seawater or the like to obtain fresh water. However, in this method, the heat of vaporization of water is 5
Since it is as high as 40 cal / g, high energy is required. On the other hand, in the freezing method, seawater is cooled by using low-temperature LNG, crystallized ice is separated from the residual liquid, and the ice is melted to obtain fresh water. The heat of fusion of water is 80c
Since it is al / g, there is an advantage that fresh water can be obtained with lower energy than the evaporation method. However, the freezing method is LNG
Must be available.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method and an apparatus for producing purified water capable of removing impurities more completely.

Another object of the present invention is to provide a method and an apparatus for producing purified water with high efficiency which require no maintenance.

Another object of the present invention is to provide a water purification method which can be easily implemented and an apparatus which can be easily manufactured.

Another object of the present invention is to provide a water purification apparatus which has a simple structure, is compact, and does not generate noise or vibration.

[0008]

Configuration of the Invention

The method and apparatus according to the present invention are basically based on the principle of the freezing method, and are used for freezing water containing impurities (for example, tap water or seawater). It is based on the principle that ice with less impurities crystallizes first.

[0009] The feature of the present invention is that ice is crystallized,
In addition, a thermoelectric element is used to melt the crystallized ice. Thermoelectric elements are known for consuming electrical energy and transferring heat. Today's high-performance thermoelectric elements are generally made of a compound semiconductor, and are formed by joining a p-type semiconductor and an n-type semiconductor to form a thermocouple. When a direct current is passed through the pn junction, an endothermic heat generation phenomenon (Peltier effect) occurs at both ends. In the present invention, the water to be treated is cooled by utilizing the heat absorbing action of the thermoelectric element, and the water to be treated is partially frozen. The ice crystallized in this way is melted using the heat generation effect of the same thermoelectric element,
Purified water is obtained.

More specifically, in the method and apparatus of the present invention, a thermoelectric element having a pair of heat-absorbing and heating surfaces is used, and both sides of the thermoelectric element are associated with a first water tank and a second water tank in relation to each working surface. And water to be treated (tap water, seawater, etc.) is introduced into these water tanks. The water to be treated may be brought into direct contact with the working surface of the thermoelectric element, or may be brought into indirect contact with heat transfer.

When a direct current is supplied to the thermoelectric element in one direction, one working surface (first working surface) is cooled and the other working surface (second working surface) is heated. When the temperature of the first working surface on the cooling side falls below the freezing point, ice composed of relatively pure water is crystallized along the first working surface, and impurities are concentrated in the liquid phase in the first water tank. The liquid phase in which the impurities are concentrated is discharged from the first water tank.

Next, when a current is supplied to the thermoelectric element in the opposite direction, the first working surface is heated and the second working surface is cooled. By heating, the ice crystallized on the first working surface is melted, and the obtained purified water is collected in a purified water storage container. At the same time, ice is now similarly crystallized on the second working surface on the cooling side, and impurities are concentrated in the liquid phase of the second water tank. The liquid phase in which the impurities are concentrated is discharged from the second water tank. When the current is reversed again, the ice crystallized on the second working surface is melted, and the obtained purified water is collected in a purified water storage container. By repeating the above steps, purified water is stored in the purified water storage container.

As described above, in the method of the present invention, since purified water is obtained using the thermoelectric element, maintenance such as filter replacement is not required.

Further, in the apparatus of the present invention, water tanks are arranged on both sides of the thermoelectric element, and ice is crystallized and melted in each of the water tanks. Therefore, purified water is efficiently produced by an extremely compact and simple structure. can do.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the accompanying drawings showing embodiments of the present invention.

FIG. 1 schematically shows an embodiment of an apparatus for performing the method of the present invention. In the illustrated embodiment, the water purification device 10 has one freeze / thaw unit 12, a water purification tank 14, and a drainage tank 16. The freezing and thawing unit 12 has a housing 18, and a thermoelectric element module 20 is disposed in the center of the housing. Details of the thermoelectric element module 20 will be described later with reference to FIG. The thermoelectric element module 20 has a heat absorbing / generating action surface 22 (first action surface) and 24 (second action surface). 26 and second water tank 28
Are formed. In the illustrated embodiment, the heat absorbing / heating surfaces 22 and 24 of the thermoelectric element module 20 also serve as side walls of the water tanks 26 and 28, respectively.
The heat absorbing and heat generating surfaces 22 and 24 are in direct contact with the water to be treated in the water tank so as to effectively transfer heat to the water to be treated in the water tanks 28 and 28. It is also possible to arrange the inner side wall of the housing 18.

FIG. 2 is an enlarged view of a part of a commercially available thermoelectric element module 20 which can be suitably used in the present invention.
Referring to FIG. 2, this thermoelectric element module 20
p-type semiconductor 30 made of i-Te compound semiconductor and n
A plurality of thermoelectric elements 36 formed by joining the mold semiconductor 32 to a thermocouple via a metal plate 34;
These thermoelectric elements are arranged in an array. That is, adjacent thermoelectric elements 36 in the same row are electrically connected to each other in series by the metal terminal 38, and the front and rear rows are connected in series to each other at the end of the row by, for example, the metal terminal 40. In this way, the 100's are arranged so as to be electrically in series with each other and parallel to the heat flow.
One thermoelectric element module 20 is constituted by the pair of thermoelectric elements 36 described above. Each thermoelectric element 36 is supported by electrically insulating and thermally conductive ceramic substrates 22 and 24. When a direct current is passed through the pn junction of each thermoelectric element, heat is transferred between the two ends by the Peltier effect, and one end exhibits an endothermic phenomenon and the other end exhibits a heat generation phenomenon. In the illustrated thermoelectric module 20, heat is transferred between the ceramic substrates 22 and 24, and the pair of substrates 22 and 24 is
It acts as a zero heat absorbing / heating surface. Which of the above absorbs heat and which generates heat depends on the direction of the current passing through the pn junction.

Referring again to FIG. 1, the electric power from the AC power supply 42 is converted to DC by the DC power supply 44, and the thermoelectric element module 20 is connected through the leads 46 and 48.
Supplied to The control circuit 5 is connected to the leads 46 and 48.
A relay switch 52 controlled by 0 is arranged to interrupt the current supplied to the module 20 and to reverse the direction of the current.

Each of the water tanks 26, 28 has an inlet pipe 54,
The to-be-treated water is supplied through a to-be-treated water supply pipe 58 provided with 56. The supply of the water to be treated is controlled by an electromagnetic three-way valve 60 controlled by the control circuit 50.

The water tanks 26 and 28 are also provided with an outlet conduit 6.
2, 64 are connected respectively. The outlet conduit 62 of the first water tank 26 is connected to a water purification pipe 68 and a drainage pipe 70 via an electromagnetic three-way valve 66 controlled by the control circuit 50. The outlet conduit 64 of the second water tank 28 is also connected to a water purification pipe 68 and a drain pipe 70 via a similar three-way valve (not shown).

Next, the process of the water purification method of the present invention and the operation of the water purification apparatus will be described with reference to FIG. First, water to be treated is supplied from the water supply pipe 58 to each of the water tanks 26 and 28 (FIG. 3A). Next, when electricity is supplied to the thermoelectric element module 20 in the direction of the arrow, the first working surface 22 is cooled and the second working surface 22 is cooled.
The working surface 24 generates heat (FIG. 3B). First with cooling
When the temperature of the working surface 22 falls below the freezing point, ice 72 starts to crystallize from the water to be treated in the first water tank 26. Since the freezing point of water falls in accordance with the amount of impurities contained therein, the ice 72 initially crystallized has few impurity components. With the crystallization of ice, impurities are concentrated in the residual liquid 74.

When the crystallization of the ice 72 has progressed to some extent, the power supply to the module 20 is stopped, and the three-way valve 66 is operated to leave the remaining water from the first water tank 26 to the drain tank 16 via the drain pipe 70. Drain the liquid (Fig. 3
(C)).

Next, when power is supplied in the opposite direction, the first working surface 22 is heated and the second working surface 24 is cooled (FIG. 3).
(D)). As a result, the ice in the first water tank 26 is melted and purified water is obtained in the first water tank 26, and at the same time, the second water tank 28
Inside, ice begins to crystallize along the second working surface 24. The obtained purified water is sent to the purified water tank 14 via the pipe 68 by the operation of the three-way valve 66 and stored.

Next, the power supply is stopped, fresh water is injected into the first water tank 26, and the remaining liquid in the second water tank 28 is discharged (FIG. 3 (E)). When the direction of the current is reversed again and the current is supplied (FIG. 3 (F)), the ice in the second water tank 28 is melted and purified water is obtained. This purified water is also sent to the purified water tank 14. At the same time, ice begins to crystallize along the first working surface 22 in the first water tank 26.

By repeating the above steps, purified water is produced from the water to be treated. By treating the purified water thus obtained again in the freezing / thawing unit 12, the purity of the purified water can be further increased.

Although a specific embodiment of the present invention has been described above, the present invention is not limited to this, and various modifications can be made. For example, the water purification device 10 is 1
Although described as having one freeze / thaw unit 12, the capacity of the device can be increased by arranging a plurality of units. In addition, thermoelectric element module 2
Although 0 is described as having a plurality of elements, in order to achieve the object of the present invention, one thermoelectric element may be used. Conversely, a multi-layered thermoelectric element module can be used.

[0027]

Since the method of the present invention uses the principle of the freezing method, it is possible to more completely remove impurities such as trihalomethane, which were difficult to remove in the prior art.

In another aspect, the heat of vaporization of water is 540
Given the cal / g and the heat of fusion of 80 cal / g, the method of the invention is clearly advantageous from an energy consumption point of view compared to the evaporation method.

In yet another aspect, the method and apparatus of the present invention does not utilize filters or activated carbon, and thus requires no maintenance.

In another aspect, water tanks are arranged on both sides of the thermoelectric element, and the crystallization and melting of ice are performed while utilizing the endothermic action and the exothermic action that occur simultaneously at both ends of the thermoelectric element. Thus, a compact device can be realized.

Further, since the apparatus of the present invention has no moving parts such as a compressor, no noise or vibration is generated.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing one embodiment of an apparatus for performing the method of the present invention.

FIG. 2 is an enlarged view showing a part of the thermoelectric element module.

FIG. 3 is a schematic view showing various steps of the method of the present invention.

[Explanation of symbols]

 10: Water purification device 12: Freezing / thawing unit 14: Water purification tank 16: Drainage tank 20: Thermoelectric element module 22, 24: Heat absorbing / heating action surface of thermoelectric element module 36: Thermoelectric element 44: DC power supply 58: Water supply pipe

──────────────────────────────────────────────────の Continuation of the front page (51) Int.Cl. ⁷ identification code FI F25B 21/02 F25B 21/02 B (58) Investigated field (Int.Cl. ⁷ , DB name) C02F 1/22 B01D 9 / 02 F25B 21/02

Claims (4)

(57) [Claims] 1. A method for obtaining purified water from water containing impurities, comprising: arranging a heat absorbing / heating surface of a thermoelectric element in a heat transfer relationship with the water containing impurities, and applying a direct current to the thermoelectric element in one direction. Supplying and cooling the working surface to a temperature below the freezing point to crystallize ice in association with the working surface, and supplying a direct current in the opposite direction to the thermoelectric element to heat the working surface, Melting the ice thus crystallized, and collecting only the purified water obtained by melting the ice; 2. A method for producing purified water from water containing impurities, comprising: supplying impurity-containing water in a heat transfer relationship with respect to the working surface of the thermoelectric element having a working surface that absorbs and generates heat by the Peltier effect; By supplying a direct current to the thermoelectric element in one direction to cool the working surface to a temperature below freezing, ice composed of relatively pure water is crystallized in association with the working surface, and impurities are added to the liquid phase. Concentrating, separating the liquid phase in which the impurities are concentrated from the crystallized ice, supplying a direct current to the thermoelectric element in the opposite direction to heat the working surface, thereby melting the ice, A method for producing purified water, comprising recovering purified water obtained by melting. 3. A method for desalinizing seawater, comprising: supplying seawater in a heat transfer relationship with respect to a heat-absorbing / heating action surface of a thermoelectric element; and supplying a direct current to the thermoelectric element in one direction to lower the action surface below freezing. By cooling to the temperature described above, ice composed of fresh water is crystallized in association with the working surface, salt in seawater is concentrated to a liquid phase, and the liquid phase in which the salt is concentrated from the crystallized ice is removed. Separating and supplying a direct current to the thermoelectric element in the opposite direction to heat the working surface to melt the ice and convert it to fresh water, and recover the fresh water obtained by melting the ice. Seawater desalination method. 4. An apparatus for producing purified water from water containing impurities, comprising a pair of first and second heat-absorbing surfaces which cooperate with each other to participate in the transfer of heat by the Peltier effect. A thermoelectric element having, when a direct current is supplied, one of the first and second working surfaces absorbing heat and the other working surface generating heat according to the direction of the current; A first and a second water tank independent of each other, which are disposed in association with the first and second working surfaces of the thermoelectric element, and a supply of treated water containing impurities to each of the water tanks. Means, a current supply means for supplying a direct current to the thermoelectric element so as to generate the Peltier effect, a drainage means for discharging water from each of the water tanks, and a purified water storage container, the current supply means comprising: Current to the thermoelectric element in a predetermined direction To cool one working surface of the first and second working surfaces to a temperature below freezing, thereby crystallizing ice in association with the one working surface, and forming the other working surface Heating; draining means for draining residual liquid phase treated water from a water tank associated with the one working surface when ice has at least partially crystallized in relation to the one working surface;
The current supply means then supplies a current to the thermoelectric element in the opposite direction to heat the one working surface,
Melting ice crystallized in relation to said one working surface and cooling said other working surface to a temperature below freezing to crystallize ice in relation to said other working surface;
The drainage means introduces purified water obtained by melting of ice into the purified water storage vessel; ice crystallized in relation to the other working surface is similarly melted after discharging remaining water to be treated; Is a water purification production device, which is introduced into the water purification storage container.