JP2521215Y2 - COD automatic measuring device - Google Patents

Description

[Detailed description of the device]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a COD automatic measuring device.

[0002]

2. Description of the Related Art As one of the standards for the quality of industrial wastewater,
There is a chemical oxygen demand (hereinafter referred to as COD). COD
Is the amount of oxygen (ppm) corresponding to the amount of the oxidizable substance in the wastewater, which is mainly consumed by the organic substance when the wastewater is oxidized by the oxidant.

The COD is measured by, for example, the acidic potassium permanganate method. Usually, the following COD is used.
Use automatic measuring equipment. The COD automatic measurement device includes, for example, a reaction tank section, a measuring section, a storage section, and a measurement / control section. The reaction tank part is composed of a reaction tank and a heating tank for accommodating the reaction tank, such as a water bath or an oil bath. As shown in FIG. 3, a metal electrode 8 for potentiometric titration is provided inside the reaction tank 86.
The reference electrode 1 and the reference electrode 82 are attached in parallel with each other and their tips are located near the bottom of the reaction tank 86. The metal electrode 81 and the comparison electrode 82 are electrically connected to a potentiometer 84 incorporated inside the measurement / control unit. A stirrer 83 is inserted inside the reaction tank 86.

In the reaction tank portion having such a constitution, a predetermined amount is supplied from a storage tank for storing various reagents such as sample water, sulfuric acid test solution, silver nitrate test solution, sodium oxalate test solution and potassium permanganate test solution. The measuring unit having a plurality of measuring pipes for measuring the sample water and various reagent solutions is connected, and the measured sample water and various reagent solutions are injected into the reaction tank 86. Further, the reaction tank 86 is connected to a titration reagent injector for injecting a potassium permanganate test solution used in a titration operation described later. Furthermore, the reaction tank 86
Is connected to a tap water storage tank that supplies tap water for cleaning and dilution.

Using the COD automatic measuring apparatus as described above, COD is measured as follows. First, a predetermined amount of sample water is injected into the reaction tank 86, and then tap water is injected from the tap water storage tank to a total volume of 100 ml. Next, 5 ml of silver nitrate test solution (20% by weight / volume) and sulfuric acid test solution [sulfuric acid:
Water = 1: 2 (weight ratio)] 10 ml are added. Furthermore, N
/ 40 After adding 10 ml of potassium permanganate test solution,
This mixed solution is heated in a heating tank for 30 minutes to oxidize the substance to be oxidized in the sample water with potassium permanganate. Then, 10 ml of N / 40 sodium oxalate reagent is added dropwise to react with the remaining potassium permanganate. Then, the excess sodium oxalate is titrated with N / 40 potassium permanganate reagent by potentiometric titration. That is,
While dropping the N / 40 potassium permanganate test solution, the potential difference between the metal electrode and the reference electrode is measured, and the measurement / control unit determines the end point of the titration from the change in the potential difference. The COD of the sample water is calculated by the measurement / control unit from the amount of the N / 40 potassium permanganate test solution dropped at this time.
In this COD measurement operation, various test solutions are measured using a measuring tube.

[0006]

[Problems to be Solved by the Invention] As described above,
In the conventional COD automatic measuring device, as shown in FIG. 3, the metal electrode 81 and the reference electrode 82 have a reaction tank 86 at the tip thereof.
Is arranged so as to be located near the bottom of the. Therefore, 100 ml of sample water and diluted water, 10 ml of silver nitrate test solution, 10 ml of sulfuric acid test solution, and N / 40 potassium permanganate test solution 1
When 0 ml is supplied, the liquid surface is at the position 87 in the figure, and the tips of the metal electrode 81 and the comparison electrode 82 are immersed in the reaction solution. Furthermore, after the heating reaction, N / 4
When 10 ml of 0 sodium oxalate solution is injected, the liquid level of the reaction solution becomes the position indicated by 88 in the figure. In this way, the tip portions of the metal electrode 81 and the reference electrode 82 are in a state of being constantly immersed in the reaction liquid from a relatively early point of the measurement operation described above.

On the other hand, for example, in communication represented by optical fibers, production of optical parts, and production of silicon semiconductors, chlorine-containing compounds such as silicon tetrachloride are used as vapor phase raw materials. Vaporized chlorine-containing compounds are contained in the waste gas in such various manufacturing processes. When this chlorine-containing compound undergoes a hydrolysis reaction, hydrogen chloride is generated. In order to remove this hydrogen chloride, conventionally, a waste gas and a cleaning liquid are brought into contact with each other to absorb and remove the hydrogen chloride. The wastewater after purifying the cleaning liquid used for such waste gas treatment contains chlorine ions at a higher concentration than normal wastewater. For example, it contains 300 to 20,000 ppm of chlorine ions.

When the COD of the wastewater containing a high concentration of chlorine ions is measured by the COD automatic measuring device, the chlorine ions react with the silver nitrate in the reaction solution, and silver chloride reacts with the metal electrode 81 and the reference electrode. It adheres to the surface of 82. When silver chloride adheres to the electrode surface as described above, the accuracy of COD measurement is reduced. In the conventional COD automatic measurement device, the tip portions of the metal electrode 81 and the reference electrode 82 are arranged at positions where they are constantly immersed in the reaction solution, so that the adhesion of silver chloride to the electrode surface is remarkable. For this reason, it is necessary to remove the metal electrode 81 and the reference electrode 82 from time to time to wash the electrode surface, which requires time and effort for maintenance of the electrode. Further, in the worst case, there is a problem that the life of the electrode is shortened.

The present invention has been made in view of the above point, and provides an automatic COD measuring device which can reduce the adhesion of silver chloride or the like to the electrode surface and easily extend the life of the electrode. Is.

[0010]

The present invention is directed to a sample water injection section for injecting sample water into a reaction tank, a diluted water injection section for injecting diluted water into the reaction tank, a silver nitrate test solution, a sulfuric acid test solution, and permanganese. A reagent solution supply unit for sequentially injecting a predetermined amount of a potassium acid reagent solution and a sodium oxalate reagent solution, a titration reagent solution injection unit for injecting a potassium permanganate titration reagent solution into the reaction tank, and a heating means for heating the reaction tank. A metal electrode inserted into the reaction chamber, a reference electrode spaced apart from the metal electrode and inserted into the reaction chamber, and a measuring unit for measuring a potential difference between the metal electrode and the reference electrode. When,
A COD automatic measurement device comprising: a calculation unit that calculates the COD of sample water from the measurement value measured by the measurement unit,
The tip of the metal electrode and the reference electrode is higher than the liquid surface when the sample water in the reaction tank, the diluted water, the silver nitrate reagent, the sulfuric acid reagent and the potassium permanganate reagent are injected, Further, the present invention provides a COD automatic measuring device, which is arranged at a position lower than a liquid surface when the sodium oxalate reagent is injected.

[0011]

According to the COD automatic measuring apparatus of the present invention, when the sample water, the diluting water, the silver nitrate test solution, the sulfuric acid test solution and the potassium permanganate test solution are injected into the reaction tank, the tips of the metal electrode and the reference electrode are It is not immersed in these reaction solutions. Then, when the sodium oxalate reagent is further injected, it is first immersed in the reaction liquid. This allows the tips of both electrodes to be immersed in the reaction solution only when the metal and reference electrodes are needed for potentiometric titration. Therefore, the contact time between the tip of the electrode and the reaction solution is significantly shortened as compared with the conventional case.

[0012]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is an explanatory view showing a main part of one embodiment of the COD automatic measuring device of the present invention. FIG.
FIG. 3 is an explanatory view showing an embodiment of the COD automatic measuring device of the present invention.

As shown in FIG. 2, the COD automatic measuring device 20 of the present invention comprises a reaction tank portion 21, a measuring portion 30, and a reservoir portion 40.
And a measurement / control unit 51, an instruction / recording external output unit 52, and a titration reagent solution injection unit 60.

The reaction tank section 21 comprises a reaction tank 27 housed in a heating tank 26 having a heater 24. Heating tank 26
Is, for example, a water bath or an oil bath. The reaction tank 27 includes an electrode unit 22 including a metal electrode and a reference electrode, and a stirrer 2.
3 is inserted. A drain pipe 25 is attached so that the waste liquid is drained to the outside from the bottom of the reaction tank 27 via the opening / closing valve 25a. A measurement / control unit 51 is electrically connected to the electrode unit 22, and an instruction / recording external output unit 52 is electrically connected to the measurement / control unit 51.

The measurement / control unit 51 includes a potentiometer 17 for measuring the potential difference of the sample water, an arithmetic unit for calculating the COD of the sample water from the measurement value measured by the potentiometer 17, and the supply and waste liquid of various test solutions. Built-in control unit to control the discharge of.

The structure of the reaction tank portion 21 will be described in more detail with reference to FIG. 1. In the reaction tank 27, the metal electrode 11 and the reference electrode 12 are inserted separately from each other. Further, the tip portions of the metal electrode 11 and the reference electrode 12 have a liquid surface of the reaction liquid when the sample water, the diluted water, the silver nitrate reagent solution, the sulfuric acid reagent solution and the potassium permanganate reagent solution are injected by the measuring unit 30 described later (Fig. It is arranged at a position lower than the liquid level (indicated by 14 in the figure) of the reaction solution when the sodium oxalate reagent is injected. The position adjustment of the tip portions of the electrodes is performed by the raising members 15 and 16 which are fitted and inserted into the portions of the metal electrode 11 and the comparison electrode 12 protruding from the reaction tank 27.
Further, the metal electrode 11 and the comparison electrode 12 are electrically connected to a potentiometer 17 incorporated in the measurement / control unit 51, respectively.

Into such a reaction tank 27, the sample and various reagent solutions weighed by the measuring unit 30 including the measuring pipes 31 to 35 for measuring the sample water and various reagent solutions in a predetermined amount are injected. . Here, the measuring pipe 31 includes an opening / closing valve 31.
Sample water is supplied via a.

The reservoir 40 is a reservoir 41 for storing tap water used as diluting water or washing water, a reservoir 42 for storing a sulfuric acid test solution, a reservoir 43 for storing a silver nitrate test solution,
It comprises a reservoir 44 for storing the sodium carbonate reagent and a reservoir 45 for storing the potassium permanganate reagent. A tap water supply source (not shown) is connected to the storage section 41 via an on-off valve 41a so that a fixed amount of tap water is always stored. Further, tap water is supplied from the reservoir 41 to the reaction tank 27.

The reservoirs 42 to 44 are respectively provided with the on-off valve 3
The measuring pipes 32 to 34 are connected via 2a to 35a. The reservoir 45 is connected to the measuring pipe 35 via an opening / closing valve 35 a, and a titration reagent injection unit 60 for injecting the stored potassium permanganate reagent into the reaction tank 27.
It is connected to the.

Although not shown, the on-off valves 31a to 35a and 41a and the titration reagent injection unit 60 are electrically connected so as to be controlled by an output signal from the measurement / control unit 51. .

The COD measuring device 2 having such a configuration
With 0, COD is measured as follows. First, measure
The on-off valve 31 a is opened and closed according to the output signal from the control unit 51, an appropriate amount of sample is measured by the measuring pipe 31, and the sample is injected into the reaction tank 27. Next, tap water is poured from the reservoir 41 to bring the total amount to 1
Make up to 00 ml. The following opening and closing of the on-off valve is similarly performed by the output signal from the measurement / control unit 51.

After that, the opening / closing valve 32a is opened / closed to open the reservoir 4
2 to sulfuric acid test solution [sulfuric acid: water = 1: 2 (weight ratio)] 10 ml
Is measured with a measuring pipe 32 and injected into the reaction tank 27. Similarly, the opening / closing valve 33a is opened / closed from the reservoir 43 to 20 w / v.
5 ml of a 5% silver nitrate solution is weighed with a measuring pipe 33 and poured into the reaction tank 27. Further, the opening / closing valve 35a is opened / closed to open the storage tank 45.
10 ml of N / 40 potassium permanganate test solution is weighed with a measuring pipe 35 and injected into the reaction tank 27. At this time, the reaction liquid injected into the reaction tank 27 is continuously stirred by the stirrer 23,
The stirring is performed similarly in the subsequent steps.

Thereafter, the reaction tank 27 is heated by the heating tank 26, and the reaction liquid in the reaction tank 27 is boiled for 30 minutes. As a result, the substance to be oxidized such as an organic substance in the sample water is oxidized by the potassium permanganate, and the potassium permanganate corresponding to the substance to be oxidized is consumed.

After the reaction, the opening / closing valve 34a is opened / closed from the storage tank 44, and 10 ml of the N / 40 sodium oxalate solution is measured by the measuring pipe 34 and injected into the reaction solution. As a result, the residual potassium permanganate in the reaction solution reacts with the corresponding amount of sodium oxalate.

Thereafter, the N / 40 potassium permanganate test solution is gradually added dropwise into the reaction solution by the titration test solution injection section 60 from the storage section 45, and the remaining sodium oxalate is titrated by potentiometric titration. That is, the potential difference between the metal electrode 11 and the reference electrode 12 when the N / 40 potassium permanganate test solution is dropped is measured by the measurement / control unit 51, and the end point of titration is determined from the change in the potential difference. Then, the measurement / control unit 51 calculates the COD of the sample water from the amount of the dropped potassium permanganate at the titration end point. The calculated COD of the sample water is measured and controlled by the measurement / control unit 5.
The instruction / recording external output unit 52 according to the output signal from
Is displayed on the display means.

Finally, the reaction liquid after the titration is completed is opened and closed by the on-off valve 2.
5a is opened and drained through the drain pipe 25. After this,
Tap water is poured into the reaction tank 27 from the reservoir 41, and the reaction tank 2
Wash 7. The waste water after cleaning is similarly discharged from the drain pipe 25.

As described above, according to the COD automatic measuring device 20, the sample water and the diluted water 100 are placed in the reaction tank 27.
When 5 ml, silver nitrate reagent 5 ml, sulfuric acid reagent 10 ml and N / 40 potassium permanganate reagent 10 ml (125 ml in total) were injected, the tips of the metal electrode 11 and the reference electrode 12 were not immersed in the reaction liquid. Then, when 10 ml of N / 40 sodium oxalate test solution is further injected, the solution is first immersed in the reaction solution. Thereby, the tip portions of both electrodes are immersed in the reaction solution only when the metal electrode 11 and the reference electrode 12 are required for potentiometric titration. As a result, for example, when the COD automatic measurement device 20 is used to continuously perform COD measurement, the contact time between the reaction solution and the electrode is about 5 minutes per hour, and the contact time is constant during conventional COD measurement operation. In contrast to this, the contact time between the tip of the electrode and the reaction solution is significantly shortened. Therefore, for example, even when measuring the COD of wastewater containing a high concentration of chlorine ions generated in the manufacturing process of an optical fiber, the adhesion of silver chloride to the electrode surface can be significantly reduced. As a result, the labor required for cleaning the electrodes can be reduced, and the lifespan of the metal electrode and the reference electrode can be easily extended.

[0028]

As described above, according to the COD automatic measuring apparatus of the present invention, the metal electrode and the reference electrode are immersed in the reaction solution only when necessary. As a result, the adhesion of silver chloride or the like to the surface of each electrode is significantly reduced. As a result, with an extremely simple structure, the maintenance work of the electrodes can be reduced, and the life of each electrode can be easily extended.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a main part of an embodiment of a COD automatic measuring device of the present invention.

FIG. 2 is an explanatory view showing the COD automatic measuring device of the embodiment.

FIG. 3 is an explanatory diagram showing a main part of an embodiment of a conventional COD automatic measuring device.

[Explanation of symbols]

11 ... Metal electrode, 12 ... Reference electrode, 15, 16 ... Raising member, 17 ... Potentiometer, 20 ... COD automatic measuring device,
21 ... Reaction tank part, 22 ... Electrode part, 23 ... Stirrer, 26 ...
Heating tank, 27 ... Reaction tank, 30 ... Measuring unit, 31, 32, 3
3, 34, 35 ... Measuring tube, 40 ... Reservoir section, 41, 41,
43, 44, 45 ... Reservoir, 51 ... Measurement / control section, 52
... Instruction / recording external output unit, 60 ... Titration reagent injection unit.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kunio Sanpei Kunio Sampei 2-6-1, Marunouchi, Chiyoda-ku, Tokyo Furukawa Electric Co., Ltd. (56) Bibliography Sho 53-87193 (JP, U)

Claims (1)

(57) [Scope of utility model registration request] 1. A sample water injection part for injecting sample water into a reaction tank, a diluted water injection part for injecting diluted water into the reaction tank, a silver nitrate reagent solution, a sulfuric acid reagent solution, a potassium permanganate reagent solution and a sodium oxalate reagent solution. , A titration reagent injection part for injecting potassium permanganate titration reagent into the reaction tank, a heating means for heating the reaction tank, and an insertion inside the reaction tank. Metal electrode,
A reference electrode which is separated from the metal electrode and is inserted into the reaction tank, a measuring unit which measures a potential difference between the metal electrode and the reference electrode, and sample water from the measurement value measured by the measuring unit. And a calculation unit that calculates the COD of
D is an automatic measuring device, wherein the tip ends of the metal electrode and the reference electrode are the sample water, the diluted water, and
The silver nitrate test solution, the sulfuric acid test solution, and the potassium permanganate test solution are arranged at a position higher than the liquid level when injected and further lower than the liquid level when the sodium oxalate test solution is injected. C characterized by
OD automatic measuring device.