JPS5942694Y2 - Residual chlorine meter - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a residual chlorine meter that is equipped with a so-called diaphragm battery type sensor that is filled with an electrolyte and has a diaphragm that partially transmits hypochlorous acid and chloramine.

For example, chlorine is used to sterilize drinking water, and the degree of sterilization is determined by the concentrations of hypochlorous acid HOCl, hypochlorite ion 0C1-, and chloramine NH2Cl.

Therefore, knowing the sum of these three concentrations is important in the chlorine sterilization process.

Since then, there have been methods to measure these components by continuously injecting reagents, and methods that require special sampling equipment.

A residual chlorine meter using a diaphragm battery type sensor can perform continuous measurements without using reagents.

However, with this method, it was not possible to distinguish between the components, that is, hypochlorous acid and chloramine, and it was not possible to measure hypochlorite ions.

As shown in FIG. 1, a conventional residual chlorine meter using a diaphragm cell/sensor is constructed with a diaphragm 12 which is a part of a container 11, and which serves as a bottom plate in the figure, which allows hypochlorous acid and chloramine to pass therethrough.

As the diaphragm 12, a porous polytetraflora ethylene membrane having a pore size o, t of about 0.3 μm can be used.

Inside the container 11, an electrolytic solution 13, which is a mixture of, for example, 0.1 mol of potassium chloride and a pH buffer solution (for example, a phosphate buffer solution) having a pH of 7, is sealed.

Inside this, a cathode 14 is disposed close to the diaphragm 12 and an anode 15 is disposed in an intermediate position, which are connected via a cable 18 to an operational amplifier 17 constituting a transducer 16.

In order to compensate for the temperature % characteristic of the permeability coefficient of the diaphragm 12,
A temperature-sensitive resistance element 19 with a negative temperature coefficient is attached to 1 and is also connected to a part of the feedback circuit of the operational amplifier 17.

In this conventional residual chlorine meter, the diaphragm 12 allows hypochlorous acid and chloramine to pass through, and an output corresponding to the sum of these concentrations is obtained at the output 21 of the converter 16.

Therefore, it was not possible to distinguish between the concentrations of hypochlorous acid and chloramine.

From this point of view, this idea takes advantage of the fact that in conventional residual chlorine meters with diaphragm battery sensors, the output changes depending on the voltage between the anode and cathode even if the chlorine concentration is the same, and it is possible to calculate the difference between the two values between the anode and cathode. The present invention provides a residual chlorine meter that measures at least one of the concentrations of hypochlorous acid and chloramine by calculation using two measurement outputs.

In the conventional residual chlorine meter shown in FIG. 1, when a certain amount of hypochlorous acid HOCIL is not present in the test liquid, the output of the terminal 21 with respect to the voltage V between the cathode 14 and the anode 15 is the curve 22 shown in FIG. become that way.

On the other hand, if only a certain amount of chloramine NH2Cl is present in the test liquid, the curve will be like 23, and if a certain amount of hypochlorous acid and chloramine are present, the curve will be like 24.

Gold was used as the cathode, silver was used as the anode 15, and the electrolyte 13 was 0.1 mol of potassium chloride, pH 7.
buffer solution was added.

If the amount of chloramine and the amount of hypochlorous acid in curve 24 are the values for curves 22 and 23, respectively, then curve 24 is the sum of curves 22 and 23.

When the voltage FEAI between the cathode and the anode is V□, the output e1 of the terminal 21 of the converter becomes e1=a CHOCI ] +b CNH2C1], and the output e2 of the terminal 21 when the voltage V between the cathode and the anode is v2 becomes e2=d[HOCl]+cCNH2Cl].

These [ ] indicate the concentration of the component shown inside.

Each output is the sum of the concentration of that component multiplied by constants a and b, or by constants d and c.

Therefore, if these constants a-d are measured in advance for the reference liquid, the predetermined electric potential FEv1. The output e1se2 of the terminal 21 for v2 is measured, and the concentrations of hypochlorous acid and chloramine, which are two unknown quantities, can be calculated from the above two simultaneous equations.

For example, as shown in FIG. 3, in the conventional residual chlorine meter shown in FIG.
6, the power supply 27 is switched to alternately supply the voltages V1 and sV2, thereby setting the voltage of the cyanode 15 to v1 or V2.

By introducing the output of the terminal 21 at that time into the arithmetic unit 28 and solving the simultaneous equations based on the two equations mentioned above, for example, the measured value of the concentration of hypochlorous acid can be input to the terminal 31, and the concentration of chloramine can be input to the terminal 31. terminal 30.

These are connected to the switching of the switch 26, and the switches 33 and 34 are temporarily closed for each calculation, and each of these is stored in the capacitor 35 and 36, and each measured concentration stored in the capacitor 35 and 36 is stored in the amplifier. 37.38 to output terminals 41.42.

When measuring a concentration that changes, a timer 43 is provided to control the switches 26, 33, 34 and the calculator 28 to perform periodic measurements, and in the next measurement 1, the measured value is sent to the terminals 41, 42. It is possible to hold the

In this way, each concentration of hypochlorous acid and chloramine can be measured by a residual chlorine meter using a diaphragm battery type sensor.

The concentration of hypochlorite ions also affects the sterilization effect.

Hypochlorite ions cannot be detected with conventional residual chlorine meters.

However, it is known that the following relationship exists between the pH of the liquid to be measured and hypochlorous acid.

K(T5 is a dissociation constant and is a function of temperature T.

Therefore, by measuring the dipH and temperature based on this relationship, the concentration of hypochlorite ions can also be determined by calculation from these values and the hypochlorous acid concentration.

For example, in FIG. 3, a measuring section 44 for measuring the pH of the test liquid and a measuring section 45 for measuring the temperature are provided, and from the measured outputs of these and the concentration of hypochlorous acid obtained at the terminal 41, a calculator 26
The hypochlorite ion having the above-mentioned relationship is calculated and outputted to the output terminal 47.

By adding the outputs of the terminals 41, 42, and 47 at the adder 48 and outputting the result to the terminal 49, the overall effective sterilization degree can be determined.

When measuring pH and temperature as well, for example, as shown in FIG.
2 is provided, a cathode 14 is placed near it, and an anode 15 is also provided corresponding thereto.

A pH sensor 51 is provided at the axial center position inside the container, a part of which protrudes from one end of the container 11, and the protruding end serves as a glass electrode 52, and a liquid introduction part between the reference electrode and the glass electrode, 53 also protrudes from the container 11.

The protruding portion is protected by a protection tube 54 attached to the outer periphery of the container 11.

A temperature sensitive resistance element 55 for temperature measurement is provided on a part of the side wall of the container, and is electrically connected to the outside through the cable 18 at the other end of the container 11.

It is possible to use such an integrated sensor.

In the above, two value measurement outputs were obtained by switching the voltage between the anode and cathode, but two sensors were used for each, and different values were given as the voltage between the anode and cathode of these sensors. Each measurement output from the sensor may be supplied to the computing unit 28.

In this way, each concentration of hypochlorous acid and chloramine can be obtained accurately and continuously.

Note that one of the two voltages applied between the anode and cathode is 0.
It is easy to see from Figure 2 that it may be an electric tomoe.

As described above, according to the residual chlorine meter of this invention, the concentrations of hypochlorous acid and chloramine can be measured separately using a conventional diaphragm battery type sensor.

In addition, the hypochlorous acid concentration obtained as necessary and the p of the test solution
Hypochlorite ions can also be measured from H and temperature.

Therefore, it becomes possible to perform sterilization control accurately.

Furthermore, continuous measurements can be performed.

[Brief explanation of the drawing]

Figure 1 is a route map showing a conventional residual chlorine meter, Figure 2 is an output characteristic curve diagram for the anode-cathode electric motor, Figure 3 is a route map showing an example of a residual chlorine meter based on this invention, and Figure 4
The figure is a cross-sectional view showing an example of a sensor suitable for also measuring hypochlorite ions. 11: Container, 12: Diaphragm, 13: Electrolyte, 14: Cathode, 15 Near node, 16: Converter, 18 Two cables,
19: Temperature sensitive resistance element, 21: Output terminal, 28: Arithmetic unit,
41: pH detection unit, 45: temperature detection unit, 46: hypochlorite ion calculator.

Claims (1)

[Scope of utility model registration request] Regarding the different values of the voltage between the anode and cathode in a diaphragm-type residual chlorine meter that is equipped with a sensor in which an electrolyte is sealed and a diaphragm that permeates hypochlorous acid and chloramine in two parts, and an anode and a cathode are housed inside. A residual chlorine meter comprising means for calculating the hypochlorous acid concentration and the chloramine concentration from the two measured outputs.