JP2000009677A - Hypochlorous acid measuring apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a hypochlorous acid measuring apparatus in which the indicator electrode of a polarograph is used as a fixed electrode, whose size is miniaturized and whose installation direction is made arbitrary. SOLUTION: Water L to be inspected is jetted, along an indicator electrode 2, by the pressurization force of a pump 26 from a ring-shaped water passage which is formed between a nozzle 23 and the indicator electrode 2. Its jet amount is held at a set flow rate in such a way that the pump 26 is microcomputer-controlled by a control part by using a flow-rate sensor 25. In a hypochlorous acid measuring apparatus which is constituted in this manner, the thickness of a diffusion layer which is formed in the boundary face between the face of the indicator electrode 2 and the water L, to be inspected, in an electrolytic operation can be made thin to be a set thickness at the same level as a rotating electrode due to a jet flow. Consequently, the sensitivity of a diffusion current to be detected can be made at the same level as the rotating electrode while the indicator electrode 2 is kept fixed. In addition, the pressurization pump 26 is provided at the apparatus, the apparatus can be miniaturized, and its installation direction can be made arbitrary.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for measuring the concentration of hypochlorous acid using drinking well water and tap water as water to be measured.

[0002]

2. Description of the Related Art Conventionally, chlorine is generally used for sterilizing drinking water. When chlorine is dissolved in water, it becomes hypochlorous acid, and since this hypochlorous acid has a strong sterilizing power, chlorine is put into water and sterilized as hypochlorous acid to convert it into drinking water. However, if the chlorine input is too large, the excess chlorine will combine with other substances and become harmful to the human body,
Since problems such as chlorine odor occur, it is necessary to accurately grasp the required concentration of chlorine and also to grasp and manage the concentration of hypochlorous acid as a result of the introduction.

[0003] Therefore, in order to control the hypochlorous acid concentration in the final treatment step of a water purification plant, an apparatus for measuring hypochlorous acid concentration called a polarograph capable of continuously measuring without a reagent has been put to practical use. This polarograph is a hypochlorous acid concentration measurement device that utilizes the fact that the diffusion current due to microelectrolysis is proportional to the hypochlorous acid concentration, with the gold or platinum rotating electrode as the indicator electrode and the silver electrode as the counter electrode. is there.

[0004] As a conventional technique, a first example of the polarograph practically used in a final treatment step of a water purification plant and the like will be described.

FIG. 3 is a cross-sectional view showing the configuration of a conventional hypochlorous acid measuring apparatus. The hypochlorous acid measuring apparatus includes an indicator electrode 2 that is driven to rotate by a motor 4 in a liquid tank 1 in which a test water L is placed, as shown in FIG.
And a bead 10 for washing the indicator electrode 2. The rotor 6 connected to the indicator electrode 2 above the indicator electrode 2 is in electrical contact with a mercury contact 7. The beads 10 are in the test water L.

The measuring section 8 contains a power supply 11 for applying a voltage to the indicator electrode 2 and the counter electrode 3, a voltmeter 9 and an ammeter 10. The lead 16 is connected to the indicator electrode 2, and the lead 17 is connected to the counter electrode 3.
Is electrically connected to

In the drawing, reference numeral 5 denotes an inlet for allowing the test water to flow into the liquid tank 1, reference numeral 12 denotes a storage tank for storing the flow of the test water, and reference numeral 13 denotes a required height of the test water in the storage tank 12. A drain for discharging test water overflowing from the weir 13, and an outlet 15 in the liquid tank 1.

In the hypochlorous acid measuring apparatus having such a configuration, first, the test water L flows into the storage tank 12 from the inlet 5,
The test water L overflowing from the weir 13 is discharged from the drain port 14, while a certain flow rate flows into the liquid tank 1 due to the head H with the liquid level of the liquid tank 1, and further overflows there, and the outlet 15. More outflow.

A voltage is applied to the indicator electrode 2 and the counter electrode 3 by the power supply 11 of the measuring unit 8, and the voltage between the indicator electrode 2 and the test water L is calculated based on the oxidation-reduction potential of hypochlorous acid contained in the test water L. When the potential becomes high, hypochlorous acid is reduced, and the electrolytic current flowing at this time is governed by the diffusion rate of hypochlorous acid and has a plateau, which is called a diffusion current. By measuring the diffusion current, the concentration of hypochlorous acid that is proportional to the value is known.

In order to improve the measurement accuracy of the diffusion current, the indicator electrode 2 is rotated at a constant speed by the motor 4 to reduce the thickness of the diffusion layer formed at the boundary between the indicator electrode 2 and the test water L, and , To keep the thickness constant to increase the sensitivity. And
The beads 10 are induced by the rotational movement of the indicator electrode 2 to constantly perform the washing and polishing operations of the indicator electrode 2 to keep the electrolytic current diffusion-controlled.

As a second example of the prior art polarograph, the one disclosed in Japanese Utility Model Laid-Open Publication No. 63-129861 will be described.

FIG. 4 is a cross-sectional view showing the configuration of another conventional hypochlorous acid measuring apparatus. The same parts as those in FIG. 3 are denoted by the same reference numerals, and description thereof will be omitted.

In this hypochlorous acid measuring apparatus, an internal tank 19 is placed in the liquid tank 1 in which the test water L is stored, and the internal tank 19 has a large number of holes 20 for liquid junctions on its surface. Then, beads 10 for washing are housed inside. A motor 4 is disposed outside the liquid tank 1, and a second gear 4 b rotated by the motor 4 meshes with a first gear 4 a integrally formed with the internal tank 19.

The indicator electrode 2 is inserted into the internal tank 19 so that its axis coincides with the center of rotation of the internal tank 19.

A conduit 18 for guiding the test water is connected to the liquid tank 1. Specifically, the conduit 18 passes through the center of the gear 4 a from the bottom of the liquid tank 1, and passes through the inner tank 19. Connected to bottom hole. The conduit 18 is connected to the gear 4a.
Also serves as a rotation center axis.

In the hypochlorous acid measuring apparatus having such a configuration,
First, the test water L is introduced from the conduit 18 into the liquid tank 1. Next, the internal tank 19 is rotated in the liquid tank 1 by rotating the motor 4. At the same time, a voltage is applied between the indicator electrode 2 and the counter electrode 3,
The diffusion current, which is the electrolysis current of hypochlorous acid, is measured. Here, since the indicator electrode 2 is fixed, the lead wire 16
And no electrical contacts such as mercury contacts are required.

[0017]

In the above-described hypochlorous acid measuring apparatus of the first example, the thickness of the diffusion layer formed at the boundary between the indicator electrode 2 and the test water L is made small and constant. As a means for maintaining and improving the measurement accuracy of the diffusion current, since the indicator electrode 2 is rotationally driven by the motor 4, an electrical contact using a metal fluid such as a mercury contact 7 is required, and the structure is complicated and handling is difficult. And there are many basic safety issues in the handling of mercury.

In the second conventional hypochlorous acid measuring apparatus, the internal tank 1 is replaced with the rotation of the indicator electrode 2 in the first example.
9 is rotated to eliminate electrical contacts such as the mercury contact of the first example, but instead requires driving gears 4a and 4b in the inner tank 9, Since a shaft sealing device is also required between the pipe and the conduit 18, the structure remains complicated. In addition, since the gear is newly rotated in the test water, there is also a restriction that the gear must use a material that does not affect the original measuring device.

The present invention has been made in consideration of the above-mentioned conventional problems, and eliminates the rotating structure of the indicator electrode, which is a means for improving the measurement accuracy of the diffusion current. Therefore, an intractable electrical contact such as a mercury contact is not required. It is another object of the present invention to provide a hypochlorous acid measuring apparatus that does not require a constant flow rate structure using a weir, can reduce the size of the apparatus itself, and can easily adjust the sensitivity.

[0020]

According to the present invention, an indicator electrode and a counter electrode are provided in a liquid tank, water to be measured flows into the liquid tank, and a voltage is applied to the indicator electrode and the counter electrode. Is a hypochlorous acid measuring device for detecting a diffusion current flowing between the two electrodes to measure a concentration of an electrolyte contained in the test water, wherein the test water is jetted from a nozzle along the indicator electrode. And flow into the liquid tank.

According to the present invention, it is possible to obtain a means for improving the accuracy of measuring the diffusion current which does not require a rotating structure of the indicator electrode or an unwieldy electrical contact such as a mercury contact, and the apparatus itself can be miniaturized. An acid measuring device can be realized.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the first aspect of the present invention, an indicator electrode and a counter electrode are provided in a liquid tank, and test water flows at a constant speed from a nozzle into the liquid tank. Apparatus for measuring the concentration of hypochlorous acid contained in the test water by applying a voltage to the counter electrode and detecting the diffusion current of hypochlorous acid flowing between the two electrodes, wherein the test water from the nozzle is Injection along the indicator electrode, a hypochlorous acid measuring device in which the diffusion tank formed on the indicator electrode surface is made thinner, by reducing the thickness of the diffusion layer formed on the surface of the indicator electrode. This has the effect of increasing the sensitivity of the diffusion current to improve the measurement accuracy.

According to a second aspect of the present invention, there is provided the hypochlorous acid measuring apparatus according to the first aspect, wherein the indicator electrode has a rotating body shape and is inserted concentrically from the end of the nozzle, and the water to be measured is The test water is rectified by flowing through the ring-shaped water passage, and the flow becomes a stable laminar flow on the surface of the indicator electrode, and is diffused. It also has the effect of stabilizing the current sensitivity.

According to a third aspect of the present invention, in the hypochlorous acid measuring apparatus according to the second aspect, the indicator electrode surface has a width of 5 to 10 times the width of the water passage (however, the flow velocity injected from the nozzle). Is protruded from the nozzle end into the liquid tank by a length of 0.2 to 0.6 m / sec), and the indicator electrode surface is arranged so as to be limited to within the influence range of the jet flow from the nozzle. As a result, the sensitivity of the diffusion current flowing by the electrolytic reaction is further stabilized.

According to a fourth aspect of the present invention, in the hypochlorous acid measuring apparatus according to the first aspect, a pump for injecting the test water from the nozzle along the indicator pole surface, and Since the control unit has a control unit for performing the constant flow rate operation, the operation water amount is controlled by the microcomputer of the control unit by receiving the signal of the flow rate sensor to converge to a preset value and is constantly controlled to a constant water amount. , The flow path of the test water of the measuring device becomes an opening and closing path, and there is no restriction on the installation direction of the measuring device,
This has the effect of enabling downsizing.

According to a fifth aspect of the present invention, there is provided the hypochlorous acid measuring apparatus according to the second aspect, further comprising an adjusting section for changing a width between the indicator electrode and the nozzle. Has the effect of facilitating the sensitivity adjustment of the measuring device.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. (Embodiment 1) FIG. 1 is a cross-sectional view showing a configuration of a hypochlorous acid measuring apparatus according to Embodiment 1 of the present invention, and FIG. 2 is an applied voltage-electrolysis current which is a measurement result of the hypochlorous acid measuring apparatus. It is a characteristic diagram. In FIG. 1, the same components as those of the conventional technique are denoted by the same reference numerals as those of the conventional technique, and the description thereof will be omitted.

In the hypochlorous acid measuring apparatus according to the first embodiment, the indicator electrode 2 and the counter electrode 3 are provided in the liquid tank 1, the test water L flows into the liquid tank 1, and the indicator electrode 2 and the counter electrode 3 In a hypochlorous acid measuring device for measuring a concentration of hypochlorous acid contained in the test water L by detecting a diffusion current flowing between the two electrodes by applying a voltage, the test water L is passed from the nozzle along the indicator electrode 2. It is characterized in that it is injected into the liquid tank 1 and flows into the liquid tank 1.

That is, as shown in FIG. 1, the liquid tank 1 containing the test water L is formed by a lower liquid tank case 21 and an upper liquid tank cover 22. The nozzle 23 is inserted from above and the nozzle 23 is fixed to the liquid tank cover 22 with a fixing nut 24 screwed to the screw portion 28 to form an adjusting portion. A pump 26 is connected to the inlet 5 of the nozzle 23 serving as the inlet of the liquid tank 1.
A flow sensor 25 is connected to the outlet of the liquid tank 1,
There is a control unit that receives the output signal and operates the pump 26 at a constant flow rate.

The nozzle 23 is formed such that its diameter gradually increases toward the nozzle end port 23a, that is, it has a trumpet shape. An indicator pole holder 27 attached to a truncated cone-shaped indicator electrode 2 is provided inside the liquid tank 1, and the hemispherical tip portion and the cone shape of the indicator electrode 2 continue smoothly, and the nozzle The nozzle 23 and the indicator electrode 2 are concentrically inserted into the nozzle 23 from the end 23a to form a ring-shaped water passage having a water passage width S. The indicator electrode 2 projects from the nozzle end 23a into the liquid tank 1 by a length of 5 to 10 times the width S of the water passage. On the other hand, the counter electrode 3 is formed in a cylindrical shape,
The indicator electrode 2 and the counter electrode 3 are mounted on the inner surface of the liquid tank case 21 and electrically connected to the measuring unit 8 by the lead wires 16 and 17, respectively.
Connected to the electrolysis power supply. The beads 10 are sealed in the liquid tank 1.

In the hypochlorous acid measuring apparatus according to the first embodiment configured as described above, first, the test water L passes through the nozzle 23 by the pump 26 and the water passage width S = 0.5 mm. The constant flow rate operation of the pump 26 allows the ring-shaped water passage to pass through the water passage.
It passes through at a constant flow rate of 3 m / sec and is injected from the nozzle end 23a into the liquid tank 1 along the pole surface of the indicator electrode 2 and flows therethrough. Therefore, the thickness of the hypochlorous acid diffusion tank formed on the pole surface of the indicator electrode 2 is reduced by the jet flow over the entire pole surface, and the sensitivity of the diffusion current is improved. Then, the beads 10 in the vicinity wash and polish the indicator electrode 2 by the flow 29 induced by the jet flow, increase the charge transfer speed on the electrode surface, and maintain the electrolytic current to be a diffusion current governed by diffusion.

Here, the water passage width S is preferably as small as possible for the purpose of reducing the required flow rate of the test water L, but is set in the range of 0.2 mm to 2 mm due to accuracy restrictions. The flow velocity at the water passage width S is about 0.2 to 0.6 m / sec, which is about the same as the peripheral speed of the designated polar surface of the conventional rotary electrode type polarograph.
c.

The flow rate of the test water L at the nozzle end 23a is set to 0.
When a voltage is applied to the indicator electrode 2 and the counter electrode 3 by the electrolytic power source of the measuring unit 8 for the test water L having the three types of hypochlorous acid concentrations, set to 3 m / sec, the applied voltage as shown by the solid line in FIG. Voltage-current characteristics can be obtained. In the graph of the applied voltage-current characteristics, the plateau portion shows the rate at which hypochlorous acid in the test water L is reduced at the indicator electrode 2, that is, the electrolytic current is governed by the diffusion rate of hypochlorous acid. It indicates that Since the diffusion speed is proportional to the concentration, the concentration of hypochlorous acid can be known by measuring the diffusion current at the potential Vp of the plateau.

Here, the characteristic shown by the broken line is the applied voltage-current characteristic at a hypochlorous acid concentration of 0.3 ppm when the peripheral surface speed of the rotating electrode system shown in the first example of the prior art is 0.3 m / sec. Have the same characteristics as the present invention. The two-dot chain line is a characteristic of the present invention when the flow velocity is set to 0.1 m / sec. The diffusion current is reduced, and the sensitivity of the indicator electrode 2 is reduced.

When the predetermined sensitivity to the diffusion current cannot be obtained, the nozzle 23 is slid with the screw portion 28 formed on the outer cylinder of the nozzle 23, and the indicator electrode holder on which the indicator electrode 2 is mounted. The sensitivity of the diffusion current is adjusted by changing the distance between 27 and the nozzle end 23a.

[0036]

As is apparent from the above description, according to the present invention, an indicator electrode and a counter electrode are provided in a liquid tank, test water flows into the liquid tank, and a voltage is applied to the indicator electrode and the counter electrode. A hypochlorous acid measuring device for detecting a diffusion current flowing between the two electrodes and measuring a concentration of an electrolyte contained in the test water, wherein the test water is supplied at a constant flow rate from a nozzle end along the indicator electrode. The structure in which the indicator electrode is rotated by means for improving the measurement accuracy of the diffusion current because the diffusion layer of hypochlorous acid is kept thin and has a constant thickness because it is injected and flows into the liquid tank. And
Elimination of cumbersome electrical contacts such as mercury contacts is eliminated.

Further, since a constant flow device is constructed by incorporating a flow sensor and a pump, a constant flow structure using a weir becomes unnecessary, the device itself can be reduced in size, and the installation direction is not restricted. The sensitivity can be easily adjusted by changing the position of the nozzle with a screw, and the effect is large.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a configuration of a hypochlorous acid measuring device according to a first embodiment of the present invention.

FIG. 2 is an applied voltage-electrolysis current characteristic diagram which is a measurement result of the same hypochlorous acid measuring device.

FIG. 3 is a cross-sectional view showing a configuration of a conventional example of a hypochlorous acid measuring device.

FIG. 4 is a cross-sectional view showing the configuration of another example of a conventional hypochlorous acid measuring apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Liquid tank 2 Indicator electrode 3 Counter electrode 5 Inlet 8 Measuring part 15 Outlet 16 Lead wire 17 Lead wire 21 Liquid tank case 22 Liquid tank cover 23 Nozzle 23a Nozzle end 24 Fixed nut 25 Flow rate sensor 26 Pump 27 Indicator electrode holder 28 Screw part

Claims (5)

[Claims] An indicator electrode and a counter electrode are provided in a liquid tank, and test water flows from the nozzle into the liquid tank at a constant speed, and a voltage is applied to the indicator electrode and the counter electrode to flow between the two electrodes. An apparatus for measuring the concentration of hypochlorous acid contained in the test water by detecting the diffusion current of chloric acid, injecting the test water from the nozzle along the indicator electrode, forming the indicator electrode surface. A hypochlorous acid measuring apparatus characterized in that a diffusion tank to be used is made thin. 2. The hypochlorite according to claim 1, wherein the indicator electrode has a rotating body shape and is inserted concentrically from a nozzle end to form a ring-shaped water passage through which the test water flows. Acid measuring device. 3. The indicator electrode surface is 5 to 10 times the width of the water passage (provided that the flow velocity jetted from the nozzle is 0.2 to 0.6 m / sec.
3. The hypochlorous acid measuring device according to claim 2, wherein the device protrudes from the nozzle end into the liquid tank by the length of c). 4. The hypochlorous acid according to claim 1, further comprising a pump for injecting the test water from the nozzle along the indicator pole surface, and a control unit for causing the pump to perform a constant flow rate operation. measuring device. 5. The hypochlorous acid measuring apparatus according to claim 2, further comprising an adjusting unit for changing a width between the indicator electrode and the nozzle.