US20090008263A1

US20090008263A1 - Method and apparatus for production of electrolyzed water

Info

Publication number: US20090008263A1
Application number: US11/822,327
Authority: US
Inventors: Nobuo Achiwa
Original assignee: Hoshizaki Electric Co Ltd
Current assignee: Hoshizaki Electric Co Ltd
Priority date: 2007-07-05
Filing date: 2007-07-05
Publication date: 2009-01-08

Abstract

An electrolyzed water production apparatus including an electrolytic cell the interior of which is subdivided into an anode chamber and a cathode chamber by means of a partition member in the form of a water permeable membrane, wherein flow quantity control means is disposed in a discharge conduit to cause the flow of electrolyzed alkaline water from the cathode chamber into the anode chamber through the partition membrane.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to a method of simultaneously producing electrolyzed alkaline water and acidic water by electrolysis of diluted solution of inorganic salt in an electrolytic cell with a partition membrane and to an electrolyzed water production apparatus for carrying out the production method of electrolyzed water.
2. Discussion of the Prior Art
Disclosed in Japanese Patent Publication No. 4-42077 is an apparatus for carrying out the production method of electrolyzed water described above. In the electrolytic cell used in the electrolyzed water production apparatus, a neutral ion-permeable membrane of non-water permeability is used as a partition membrane to subdivide the interior of the cell into an anode chamber and a cathode chamber. Disclosed in Japanese Patent Laic-open Publication No 2002-210466 is an electrolyzed water production apparatus including an electrolytic cell in which an anode-ion exchange membrane of non-water permeability is used to subdivide the interior of the cell into an anode chamber and a cathode chamber.
In the electrolytic cell with the neutral partition member of non-water permeability, a strong acid water of less than pH 2.7 and a strong alkaline water of more than pH 11.3 are produced at the same time. The pH of electrolyzed water is adjusted in accordance with the purpose of use. In the pH adjustment of the electrolyzed water, the electrolyzed acid water is mixed with the water to be electrolyzed or the electrolyzed alkaline water.
The main purpose of pH adjustment of the electrolyzed acid water is to enhance the pH of the electrolyzed strong acid water. In the electrolyzed strong acidic water, chlorine component is vaporized as chlorine gas, causing pollution of the surrounding environment, particularly corrosion of appliances of the production apparatus. Accordingly, the pH of electrolyzed acid water is adjusted to restrain the occurrence of chlorine gas in an extent capable of avoiding damage of germicidal resolution.
In the electrolytic cell with the partition membrane, however, the electrolyzed strong acid water is inevitably produced and conditioned to vaporize chlorine gas until the pH of electrolyzed water is adjusted. For this reason, it is difficult to sufficiently solve the problem caused by vaporization of chlorine gas. As the partition membrane forming the electrolytic chambers in the cell is non-water permeable, the electric resistance between the electrodes becomes large, and high voltage is required to flow an electric current between the electrodes. As a result, the source of electricity becomes large in size.
In the electrolytic cell with the anode ion exchange membrane, the electrolyzed alkaline water produced in the cathode chamber is maintained in a condensed condition to reduce a discharge amount thereof. The electrolytic cell is used without any recognition for use of the electrolyzed alkaline water.
In the electrolytic cell with the anode ion exchange membrane, the pH of electrolyzed acid water in the anode chamber is increased by condensation of the electrolyzed alkaline water. This is effective to greatly decrease a vapor amount of chlorine gas. However, as the ion exchange membrane is substantially non water permeable, it is needed to apply high voltage to the anode and cathode electrodes to cause the flow of an electric current between them. As a result, the source of electricity becomes large in size. Additionally, as the electrolyzed alkaline water in the cathode chamber does not flow, scale will accumulate in the cathode chamber and on the ion exchange membrane.

SUMMARY OF THE INVENTION

It is, therefore, an object of the present invention to solve the problems in the conventional production method and apparatus of electrolyzed water discussed above.
A production method of electrolyzed water in accordance with the present invention is characterized by use of an electrolytic cell the interior of which is subdivided into an anode chamber and a cathode chamber by means of a partition membrane in the form of a water permeable membrane. With this method, it is able to simultaneously produce electrolyzed acid water of high germicidal resolution and electrolyzed alkaline water of high washing resolution. In this method, a portion of electrolyzed alkaline water produced in the cathode chamber flows into the anode chamber through the partition membrane. In a practical embodiment, it is preferable that means for controlling an amount of electrolyzed alkaline water discharged from the cathode chamber is provided to cause the flow of electrolyzed alkaline water from the cathode chamber into the anode chamber.
An electrolyzed water production apparatus in accordance with the present invention is characterized in that an electrolytic cell adapted to the apparatus is provided with a partition membrane in the form of a water permeable membrane for subdividing the interior of the cell into an anode chamber and a cathode chamber and that flow quantity control means for controlling an amount of electrolyzed alkaline water discharged from the cathode chamber is provided to cause the flow of electrolyzed alkaline water into the anode chamber from the cathode chamber.
In the method and apparatus for producing electrolyzed water, the electrolytic cell is controlled at a first mode of operation in such a manner as to supply the same amount of solution of inorganic salt into the electrolytic chambers and to discharge the same amount of electrolyzed water from the electrolytic chambers. The electrolytic cell is controlled at a second mode of operation in such a manner as to supply the same amount of diluted solution of inorganic salt into the electrolytic chambers and to reduce an amount of electrolyzed water discharged from the cathode side chamber less than that from the anode side chamber.
At the first mode of operation, the electrolyzed water does not flow through the water permeable membrane from one of the electrolytic chambers to the other because of no difference in pressure between the electrolytic chambers. Thus, the electrolyzed strong acid water from the anode side chamber is discharged without being adjusted its pH. When the electrodes in the electrolytic chambers are applied with an electric current at the same value at the first mode of operation, it is not required to apply high voltage to the electrodes. Thus, the amount of electricity can be reduced to enhance the electric efficiency in operation.
In operation of the electrolytic cell at the first mode, chloride ion and hydroxide ion react on the surface of the anode side electrode. If the voltage between the electrodes is excessive in operation as in a conventional electrolytic cell, the reaction of chloride ion becomes less than that of hydroxide ion. As a result, the effective chlorine concentration of electrolyzed acid water is enhanced more than that of electrolyzed acid water produced in a conventional manner.
At the second mode of operation, the discharge amount of electrolyzed alkaline water from the cathode side chamber is reduced less than that from the anode side chamber. Thus, a portion of the electrolyzed alkaline water from the cathode side chamber flows into the anode side chamber through the water permeable membrane and is mixed with the electrolyzed acid water in the anode side chamber to adjust the pH of electrolyzed acid water to be discharged for use. Accordingly, the electrolyzed strong alkaline water and the electrolyzed strong acid water are simultaneously produced at the second mode of operation. In this instance, it is preferable that the pH of electrolyzed acid water is adjusted by mixture with the electrolyzed alkaline water to an extent of 3.7˜7.0, desirably to an extent of 4.0˜6.0. The electrolyzed acid water of pH adjusted in the extent contains a chlorine component effective to sterilization in a stable condition. In other words, at the second mode of operation, the electrolyzed acid water can be produced as germicidal water of high effective chlorine concentration superior in germicidal resolution.

BRIEF DESCRIPTION OF THE DRAWING

In the drawing:

FIG. 1 is a schematic illustration of an embodiment of an electrolyzed water production apparatus in accordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention relates to a method of simultaneously producing electrolyzed alkaline and acidic water by electrolysis of diluted solution of inorganic salt in an electrolytic cell with a partition membrane and to an electrolyzed water production apparatus for carrying out the production method of electrolyzed water. In FIG. 1, there is schematically illustrated an embodiment of an electrolyzed water production apparatus in accordance with the present invention.
The electrolyzed water production apparatus includes an electrolytic cell 10 of the type which is composed of a cell housing 10, a partition membrane 12 disposed within the cell housing 10 to subdivide the interior of cell housing 10 into a pair of electrolytic chambers R1, R2, and electrodes 13 a, 13 b arranged within the electrolytic chambers. The electrolytic chambers R1, R2 of electrolytic cell 10 are respectively connected at their upstream sides to water supply conduits 21 a,21 b and at their downstream sides to discharge conduits 22 a, 22 b. Flow quantity control valves 23 a, 23 b are respectively disposed in the discharge conduits 23 a, 23 b, and pressure reduction valves 24 a, 24 b are respectively disposed in the water supply conduits 21 a, 21 b.
In the electrolyzed water production apparatus, diluted solution of inorganic salt, such as table salt is supplied into the electrolytic chambers R1, R2 through water supply conduits 21 a, 21 b. In operation, a predetermined amount of the diluted solution is continually supplied to the electrolytic chambers R1, R2, and the electrodes 13 a, 13 b in electrolytic chambers R1, R2 are applied with an electric current of predetermined voltage to electrolyze the diluted solution under the electric current. In the case that the electrolytic chamber R1 is an anode chamber while the electrolytic chamber R2 is a cathode chamber, electrolyzed acid water produced in the electrolytic chamber R1 is discharged through the conduit 22 a while electrolyzed alkaline water produced in the electrolytic chamber R2 is discharged through the conduit 22 b. Thus, the electrolyzed acid water and alkaline water are simultaneously produced in the electrolytic cell.
In the electrolytic cell, the partition membrane 12 is in the form of a water permeable membrane made of a meshed thin fabric or knit of polyester filament. For example, the water permeable membrane is a thin membrane of 70 in mesh (70 stitches/inch, space stitches 233 μm, linear radius 130 μm). In a condition where a difference in pressure exists between the electrolytic chambers R1 and R2 subdivided by the partition membrane 12, electrolyzed water produced in the electrolytic chamber at a high pressure side flows into the electrolytic chamber at a low pressure side through the partition membrane 12.
The electrolytic cell is controlled at a first mode of operation in such a manner as to supply the same amount of diluted solution of inorganic water into the electrolytic chambers R1, R2 and to discharge the same amount of electrolyzed water from the electrolytic chambers R1, R2. The electrolytic cell is also controlled at a second mode of operation in such a manner as to supply the same amount of diluted solution of inorganic salt into both the electrolytic chambers and to reduce the amount of electrolyzed water discharged from the cathode side chamber less than that from the anode side chamber.
At the first mode of operation, the electrolyzed water does not flow through the water permeable membrane 12 from one of the electrolytic chambers to the other because of no difference in pressure between the electrolytic chambers. Thus, the electrolyzed strong acid water from the anode side chamber R1 is discharged through the conduit 23 a without being adjusted at its pH. As the electrodes 13 a, 13 b are applied with the electric current of the same value at the first mode of operation, the amount of electricity required for operation at the first mode can be reduced to enhance the electric efficiency in operation.
In operation of the electrolytic cell at the first mode, chloride ion and hydroxide ion react on the surface of the anode side electrode 13 a, respectively. If the voltage between the electrodes 13 a, 13 b is excessive in operation as in a conventional electrolytic cell, the reaction of chloride ion becomes less than that of hydroxide ion. As the voltage between the electrodes is lowered at the first mode of operation as described above, the reaction of chloride ion becomes effective as the reaction of hydroxide ion to increase the effective chlorine concentration of electrolyzed acid water. This means that the electric efficiency of the electrolytic cell is enhanced at the first mode of operation.
At the second mode of operation, the discharge amount of electrolyzed water from the cathode side chamber R2 is reduced less than that from the anode side chamber R1 under control of the flow quantity control valves 23 a, 23 b. The difference in discharge amount of electrolyzed water causes a difference in pressure between the electrolytic chambers R1 and R2 to permit the flow of a portion of electrolyzed alkaline water from the cathode side chamber R2 into the anode side chamber R1 through the water permeably membrane 12. Thus, the electrolyzed alkaline water from the cathode side chamber R2 is mixed with the electrolyzed acid water in the anode side chamber R1 to adjust the pH of electrolyzed acid water to be discharged through the conduit 23 a. In such an instance, the electrolyzed alkaline water from the cathode side chamber R2 is discharged as strong alkaline water through the conduit 23 b without being adjusted at its pH.
Accordingly, the electrolyzed strong alkaline water of high washing resolution and the electrolyzed acid water of high germicidal resolution are simultaneously produced at the second mode of operation. In this instance, it is preferable that the pH of electrolyzed acid water is adjusted by mixture with the electrolyzed alkaline water to an extent of 3.0˜7.0, desirably to an extent of 4.0˜60. The electrolyzed acid water of pH adjusted in the extent contains a chlorine component effective to sterilization in a stable condition more than volatile chlorine component. In other words, the electrolyzed acid water can be produced as germicidal water of high effective chlorine concentration superior in germicidal resolution.
Experiments:
In a first experiment, the electrolyzed water production apparatus shown in FIG. 1 was used to produce electrolyzed water at the first mode of operation and the second mode of operation. In the electrolytic cell shown in FIG. 1, the water permeable membrane 12 was in the form of a thin membrane of 70 in mesh (70 stitches/inch, space stitches 233 μm, linear radius 130 μm). A solution of 0.1 weight % salt was used as the solution of inorganic salt, and the electrolytic chambers R1, R2 were set as anode and cathode side chambers, respectively. The temperature of the solution of salt was 20° C.
In operation at the first mode, the supply amount of the solution into the electrolytic chambers R1, R2 was set in 2 L/min, and the discharge amount of electrolyzed acid and alkaline water from the electrolytic chambers R1, R2 was set in 2 L/min. In a second experiment for comparison with the first experiment, a conventional electrolytic cell with a neutral membrane of non-water permeability was used as the partition membrane forming the electrolytic chambers. A result of the experiments is shown in the following table 1.

TABLE 1

Experiments at the first mode of operation:

	First experiment	Second experiment

Electrolytic current	10 A	10 A
Electrolytic voltage	3 V	12 V

	pH	2.7	2.6
OX	ACC	35 (mg/kg)	30 (mg/kg)
	Production amount	2 (L/min)	2 (L/min)
	pH	11.4	11.5
RED	Production amount	2 (L/min)	2 (L/min)

Note:
Electrolytic voltage: Voltage required for maintaining an electrolytic current of 10 A.
OX: Electrolyzed acid water
ACC: Effective chlorine concentration
RED: Electrolyzed alkaline water

At the second mode of operation, the supply amount of the solution into the electrolytic chambers R!, R2 was set in 2 L/min, and the discharge amount of electrolyzed alkaline water from cathode side chamber R2 was controlled less than that of electrolyzed acid water from the anode chamber R1. In addition, the electrolytic current was set at 10 A, and the electrolytic voltage for maintaining the electrolytic current was set at 3V. A result of the experiments is shown in the following table 2.

TABLE 2

Experiments at the second mode of operation:

	Discharge amount		ACC
Electrolyzed water	(L/min)	pH	(mg/kg)

1	OX	3	6.3	23
	RED	1	11.9	—
2	OX	2.5	4.0	29
	RED	1.5	11.6	—
3	OX	2.0	2.7	35
	RED	2.0	11.4	—

Note:
OX:: Electrolyzed acid water
ACC:: Effective chlorine concentration
RED:: Electrolyzed alkaline water
Discharge amount:: Production amount

Claims

1. A method of simultaneously producing electrolyzed acid water and alkaline water by electrolysis of diluted solution of inorganic salt in an electrolytic cell, wherein a partition membrane subdividing the interior of the electrolytic cell into a anode chamber and a cathode chamber is in the form of a water permeable member capable of permitting the flow of electrolyzed water between the anode and cathode chambers.

2. A production method of electrolyzed water as claimed in claim 1, wherein the solution of inorganic salt is electrolyzed in a condition where a portion of electrolyzed alkaline water produced in the cathode chamber flows into the anode chamber through the partition membrane.

3. A production method of electrolyzed water as claimed in claim 2, wherein means for controlling an amount of electrolyzed alkaline water discharged from the cathode chamber is provided to cause the flow of electrolyzed alkaline water from the cathode chamber into the anode chamber.

4. An apparatus for simultaneously producing electrolyzed acid water and alkaline water by electrolysis of a diluted solution of inorganic salt in an electrolytic cell, wherein a partition membrane subdividing the interior of the electrolytic cell into a anode chamber and a cathode chamber is in the form of a water permeable member capable of permitting the flow of electrolyzed water therethrough.

5. A production apparatus of electrolyzed acid water and alkaline water as claimed in claim 4, wherein means for controlling an amount of electrolyzed alkaline water discharged from the cathode chamber is provided to cause the flow of electrolyzed alkaline water from the cathode chamber into the anode chamber.