JPH09239365A - Method for generating strongly acidic water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To generate a strongly acidic water contg. an absolute minimum of residual chlorine in accordance with its use and free from problems with chlorine gas and corrosion. SOLUTION: Raw water is passed through an electrolytic cell having the cathode compartment and anode compartment divided by an ion-permeable diaphragm and electrolyzed to generate a strongly acidic water. In this case, sodium chloride or potassium chloride and sodium sulfate or potassium sulfate are added to the raw water which is then electrolyzed, the sodium chloride or potassium chloride is added to decrease the chlorine ion concn. of the raw water to 10-500mg/l, and the sodium sulfate or potassium sulfate is added so that the conductivity of the raw water is controlled to 1500-2000μS/cm. The electrolyzing current strength applied in the electrolytic cell is controlled to 5-20A per liter of the flow rate of the generated strongly acidic water per minute.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing strongly acidic water, and more particularly to a method for producing strongly acidic water having a strong sterilizing power and used for sterilization and washing.

[0002]

2. Description of the Related Art In recent years, attention has been paid to the fact that electrolyzed acidic water has various properties such as strong sterilizing power among various functional waters. The sterilizing power of acidic water produced by diaphragm electrolysis of dilute saline depends on its pH, ORP and residual chlorine. Acidic water with the minimum required residual chlorine is desired depending on the purpose of use. Conventionally, by adding sodium chloride or potassium chloride to tap water and subjecting it to diaphragm electrolysis, a pH of 2.5 to
3.0, ORP 1000 mV or more, residual chlorine 20-60
There is a technique of producing mg / liter of strongly acidic water and using it for sterilization and washing. However, when the strongly acidic water is produced, chlorine gas is generated from the electrolyzer and the strongly acidic water produced, and it is harmful to the human body, or the strongly acidic water has a high concentration of chlorine ions and residual chlorine, There were problems such as showing strong corrosiveness to stainless steel.

[0003]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems of the prior art and is capable of producing a strong acid water having a minimum residual chlorine content required according to the purpose of use of the strong acid water. It is an object of the present invention to provide a method for producing strongly acidic water that does not generate gas or corrosiveness.

[0004]

In order to solve the above problems, in the present invention, raw water is passed through an electrolytic cell having a cathode chamber and an anode chamber partitioned by an ion-permeable diaphragm to electrolyze. In the method for producing strongly acidic water according to 1., sodium chloride or potassium chloride and sodium sulfate or potassium sulfate are added to the raw water for electrolysis. In the production method, sodium chloride or potassium chloride has a chlorine ion concentration of raw water of 10 to 500 m.
It is added so that the concentration is within the range of g / liter, and sodium sulfate or potassium sulfate has a raw water conductivity of 15
It is advisable to add it so that it is from 00 to 2000 μS / cm. Further, the electrolysis tank is preferably loaded with an electrolysis current value within a range of 5 to 20 amperes per 1 liter / min of a strongly acidic water generation flow rate, and a chlorine generation type insoluble electrode as an anode is provided in the anode chamber. Good to use.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention has been completed based on the following findings. The bactericidal power of strongly acidic water depends on its pH, ORP and residual chlorine. Usually, sodium chloride or potassium chloride is added for the purpose of improving the conductivity of raw water in the production of strongly acidic water, supplying counter ions of the acid and alkali produced, and supplying chlorine ions for chlorine generation. In the present invention, the conductivity improvement and the counter ion supply are shared by the addition of sodium sulfate or potassium sulfate, and the chloride ion supply is shared by the addition of sodium chloride or potassium chloride. Raw water has a chloride ion concentration of 10 to 500 mg
Sodium chloride or potassium chloride is added so that the raw water conductivity becomes
Sodium sulfate or potassium sulfate is added so as to be 1500 to 2000 μS / cm. For example, the amount of sodium chloride added is in the range of 15 to 750 mg / liter,
The addition amount of sodium sulfate is preferably in the range of 0 to 1200 mg / liter.

The electrolysis current value applied per 1 liter / minute of the strongly acidic water production flow rate is set to a range of 5 to 20 amperes. A chlorine-generating electrode is used as the anode. As described above, the chlorine ion concentration of raw water is 10 to 500.
The range of mg / liter is desirable. Chloride concentration is 1
When it is 0 mg / liter or less, the residual chlorine concentration of strongly acidic water is 2 mg / liter or less, and the ORP is 1000 mV.
In some cases, sufficient bactericidal power cannot be obtained. If the chlorine ion concentration is 500 mg / liter or more, the chlorine gas generation problem and the corrosive problem become remarkable.

Further, it is desirable to add sodium sulfate or potassium sulfate so that the conductivity of the raw water adjusted to a predetermined chlorine ion concentration by adding sodium chloride or potassium chloride is 1500 to 2000 μS / cm. . When the electrical conductivity is 1500 μS / cm or less, the electrolysis voltage for maintaining the required electrolysis current increases, and the energy efficiency decreases. On the other hand, when the conductivity is 2000 μS / cm or more, the amount of sodium sulfate or potassium sulfate added increases, and the chemical cost increases. Sodium sulfate and potassium sulfate are preferable because they are inexpensive and do not decompose in electrolysis, but sodium sulfate is more preferable because it is certified as a food additive. Generation flow rate of strongly acidic water 1 liter /
The electrolytic current value per minute is preferably in the range of 5 to 20 amperes. If the current value per 1 liter / min of the strongly acidic water generation flow rate is 5 amperes or less, it is difficult to reduce the pH of the acidic water to 3.0 or less. On the other hand, if the current value is 20 amperes or more, there arises a problem that the amount of strongly acidic water produced per unit amount of electricity decreases and a problem that electrolysis efficiency decreases.

It is desirable to use a chlorine-generating insoluble electrode as the anode. The chlorine-generating insoluble anode having a high anodic oxidation efficiency of chlorine ions can produce the same residual chlorine concentration in acidic water with a lower concentration of raw water chloride ions as compared with other types of anodes. Match. Any insoluble electrode having a high chlorine generation efficiency may be used. For example, an electrode formed by firing a ruthenium oxide film on a titanium base material is preferable. In the above condition range, the residual chlorine concentration [Cl] of the strongly acidic water produced is directly proportional to the chlorine ion concentration [Cl ⁻ ] of the raw water and the electrolytic current (I), and is inverse to the strongly acidic water production flow rate (Q). A proportional relationship is established. [Cl] = K [Cl ⁻ ] I / Q Here, K is a constant determined by the characteristics of the electrode.
Chlorine-generating electrodes have higher K values than other types of electrodes.

[0009]

The present invention will be described below in more detail with reference to examples. Example 1 FIG. 1 shows a block diagram of an experimental apparatus used in the method for producing strongly acidic water of the present invention. In FIG. 1, 1 is a raw water tank, 2 is a raw water pump, 3 is a wash water tank, 4 is a wash water pump, 5 is an acidic water electrolysis tank, 6 is a wash water electrolysis tank, and 7 is a DC power supply. Thus, in FIG. 1, the electrolytic cleaning method is adopted as the cathode scale removing mechanism. That is,
At the time of cleaning, the acidity stored in the tank is further electrolyzed by a diaphragm in another electrolytic cell to increase its acidity and temperature. Then, this acidic hot water is used for cleaning the cathode scale.

Cylindrical electrolytic cells of 12 cells and 2 cells were used as the electrolytic cell for producing acidic water and the electrolytic cell for producing washing water, respectively.
Usually, in the electrolytic production of acidic water, salt is added for the purpose of improving the electric conductivity of raw water, supplying counter ions of the generated acid and alkali, and supplying chlorine ions for chlorine generation. Here, how to generate the acid water residual chlorine required minimum in accordance with the intended use, the supply of the electric conductivity increased and the counter ions Na ₂ SO ₄ addition, sharing the supply of chlorine ions in NaCl added I went there. Specifically, NaCl is added to adjust chlorine ion in the raw water to 10 to 50.
Acidic water electrolysis was carried out by adding Na ₂ SO ₄ so that the electric conductivity of raw water was 1.6 mS / cm or more while changing the range of 0 mg / liter.

The results are shown in the graphs of FIGS. 2 and 3. Fig. 2 shows that, in the case of strongly acidic water having a pH of 3.0 or less, the same electrolytic strength (current value (A) per unit flow rate of acidic water (liter / min)) is acidic with respect to the chlorine ion concentration (mg / liter) of raw water. Residual chlorine concentration in water (mg / liter)
It was plotted, and a direct proportional relationship was obtained for both.
Further, FIG. 3 is a plot of the residual chlorine concentration against the product of the chlorine ion concentration and the electrolytic strength. The data of different electrolytic strengths are plotted on almost the same straight line, and the residual chlorine concentration is expressed by the following empirical formula. I was able to. [Cl] = 0.012 [Cl ^-] I / Q (1)

[0012]

EFFECT OF THE INVENTION By using the method for producing strong acidic water according to the present invention, residual chlorine in acidic water can be reliably controlled according to the purpose of use, and chlorine gas and chlorine ions can be suppressed to the minimum necessary. Therefore, the safety of the strongly acidic water can be increased and the corrosiveness can be suppressed.

[Brief description of drawings]

FIG. 1 is an example 1 used in the method for producing strongly acidic water of the present invention.
Diagram of the experimental device.

FIG. 2 is a graph showing the relationship between the residual chlorine concentration in acidic water and the chlorine ion concentration in raw water.

FIG. 3 is a graph showing the relationship between the product of chloride ion and electrolytic strength and the residual chlorine concentration in acidic water.

[Explanation of symbols]

1: Raw water tank, 2: Raw water pump, 3: Wash water tank,
4: Wash water pump, 5: Acidic water electrolyzer, 6: Wash water electrolyzer, 7: DC power supply,

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Ryoji Tsukii 11-1 Haneda Asahi-cho, Ota-ku, Tokyo Inside EBARA CORPORATION

Claims (4)

[Claims] 1. A method for producing strong acid water by passing raw water through an electrolytic cell having a cathode chamber and an anode chamber partitioned by an ion-permeable diaphragm to electrolyze the raw water, wherein sodium chloride or chloride is added to the raw water. A method for producing strongly acidic water, which comprises adding potassium and sodium sulfate or potassium sulfate to perform electrolysis. 2. The sodium chloride or potassium chloride is added so that the chlorine ion concentration in the raw water is in the range of 10 to 500 mg / liter, and sodium sulfate or potassium sulfate has a raw water conductivity of 1500 to 200.
The method for producing strongly acidic water according to claim 1, wherein the method is added so that the concentration becomes 0 μS / cm. 3. The strong acid water according to claim 1 or 2, wherein the electrolytic cell is loaded with an electrolysis current value within a range of 5 to 20 amperes per 1 liter / min of a strongly acidic water generation flow rate. How to generate. 4. The method for producing strong acidic water according to claim 1, wherein a chlorine-generating insoluble electrode is used as an anode in the anode chamber.