JPS60127448A - Cod measuring method and apparatus therefor - Google Patents

Abstract

PURPOSE:To make it possible to detect COD in a solution rapidly and continuously, by mixing a solution to be measured, an oxidizing agent solution and a liquid rising in its temp. upon the mixing with water to react the same and measuring the redox potential of the reacted solution. CONSTITUTION:A solution to be measured (e.g., waste water), an oxidizing agent (KMnO4) solution and a liquid rising in its temp. upon the mixing with water (e.g., concn. sulfuric acid) are respectively supplied to the upper reaction tube of a heat insulating container in a reactor 1 through supply tubes 41, 42, 43 and mixed to raise the temp. of the resulting mixture. Subsequently, the reaction mixture is sent to a reaction promotion pipe and passed through a cooler 5 from the outtake port thereof to be sent to a detection container 6 where the redox potential of the reacted solution is detected by using an electrode 6a of a temp. and redox potential detector (recorder) 7 and converted to COD which is, in turn, recorded. When the COD value is equal to or more than a set value, an alarm is issued from an alarm 8. The detector 7 is constituted so as to also detect the temp. of the reaction tube. By this method, even a solution containing a hardly oxidized org. component, for example, glycol can be subjected to the measurement of COD rapidly, continuously and precisely.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for measuring COD contained in a solution and an apparatus used for carrying out the method.

[Prior art]

Specified workplaces in designated areas subject to total water quality regulations are required to measure and record pollution loads, and the measurement method is based on JIS K 0102 Factory Effluent Test Methods, Section 17, Oxygen consumption (COD) by potassium manganate is specified. This specified COD measurement method requires that a flask containing waste water, sulfuric acid, and potassium permanganate solution be heated in a boiling water bath for 30 minutes to cause the υ1 water and potassium permanganate to react. Allow approximately 40 minutes for measurement. For this reason, in addition to measuring and recording water quality using a single-point quantitative measurement method, it is important to monitor water quality so that it can be rapidly and continuously measured.

When monitoring and managing water quality, for example, if it dissolves in water extremely well and its state is colorless and transparent, it can be visually inspected or
When monitoring and managing water, glycol-based water-soluble hydraulic fluids, etc. that cannot be confirmed by B1 and have a high COO, the following problems arise.

r! 11th, COD: 97 ppm wastewater with added thorium oxalate as a representative of easily oxidized substances,
Figure 1 is obtained by using waste water containing glycol added with COD: 89 ppm and directly heating it and measuring the COO value by varying the heating time after boiling the waste water.

FIG. 1 is a graph showing the measurement results, with the horizontal axis representing the heating time after boiling (minutes) and the vertical axis representing the direct flame type simple CotJ needle indication value (ppm). As can be understood from this figure, the C0O value of wastewater to which oxidized thorium oxalate was added (black circle) does not change when heated for 1 to 2 minutes after boiling, but remains constant; however, for wastewater to which glycol has been added ( With white circles), the temperature is not constant even after heating for about 5 minutes. That is, when measuring a water-glycol type aqueous working fluid, heating for 5 minutes or more is required at a temperature of about 100°C, making rapid measurement impossible.

For this reason, it is most important to be able to quickly measure water-glycol-based aqueous working fluids in monitor measurements.

On the other hand, water quality measuring instruments include a COO meter, which is an automated version of the specified GO[) measurement method, and other instruments that can continuously measure the contamination status of organic substances, such as a TOC meter.
There are T0n meters, uvtl, fluorometers, etc. Naturally, the COO meter uses a specified measurement method and is not suitable for rapid measurement. And TOC meter, Toil meter is COD
Although it has excellent measurement speed, it is expensive, and although it is possible to use a fluorometer, it is not common because, like uvRl, the detection substance is selective and its uses are limited.

The inventors of the present application obtained the following knowledge in the process of researching a method for rapidly measuring the COO of a solution.

In other words, the COD with sodium oxalate added is 79p.
COD with pm wastewater and glycol added or 37ppm
Two types of wastewater were used, each with a temperature of 95%.
The reaction was carried out at 120°C, 130°C, and 140°C, and the oxidation-reduction potential (ORP) of the reaction solution was measured.

Figure 2 is a graph showing the measurement results, with the case of terium oxalate added on the upper side and the case of glycol added wastewater on the ) side, and the horizontal axis is Ol? II value (V) and reaction l7jr degrees (°C), and the time based on the recording paper feeding speed is taken in the direction corresponding to the vertical axis.

In the figure, the solid line indicates the OR+'' value, the dashed-dotted line indicates the reaction temperature, and the bottom right of the figure indicates the recording paper feeding speed for one hour.

As can be understood from this figure, as the reaction temperature increases, the ORP value of the wastewater from sawdust to which sodium oxalate has been added approaches the ORP value of the wastewater to which glycol has been added, and the reaction temperature is 130°C to 140°C. Then, the level corresponds to each COD concentration. Therefore, it has been found that lowering the reaction temperature is effective for rapid analysis when determining wastewater containing poorly reactive glycols and the like.

〔the purpose〕

The present invention has been made based on such knowledge, and its purpose is to provide a COO measurement method that allows reaction to occur at a higher temperature than conventional methods and allows rapid continuous measurement, and an inexpensive COO measurement device used for carrying out the method. It is in.

[Configuration of the present invention]

The COD measurement method according to the present invention is a method of measuring the C01] of the solution to be measured by reacting the solution to be measured/8 with an oxidizing agent solution by raising the temperature. The method is characterized in that the oxidation-reduction potential of the reacted reaction solution is detected by mixing the reaction solution with a liquid that reacts by increasing the temperature, and the COD of the liquid to be measured/8 is measured based on the detection result.

〔Example〕 The present invention will be specifically explained below based on the drawings.

FIG. 3 is a schematic diagram showing the implementation state of the present invention, and in the figure 1
indicates a reactor. The reactor 1 has three feed pipes, namely a waste water feed pipe 41. Feed pipe 42 for potassium permanganate solution
．． A concentrated sulfuric acid feed pipe 43 is attached to the tip side, and a drainage pump 31. Potassium permanganate/8 liquid pump 32. A pump 33 for sulfuric acid is interposed, and the proximal end of the pump 33 is connected to a three-way switching cock 21, 22, 23, and one side of each feed pipe 41, 42, 43 is connected to a drain pipe (not shown), and permanganate. Potassium solution storage tank 11. a to the sulfuric acid storage tank 12, and the other to the water supply pipes 51, 52, and 53, respectively.
It is connected to the clean water storage tank 13 at.

Switching of three-way switching cocks 21, 22, 23 and pump 31,
32. Drainage, potassium permanganate/
8 liquid.

Concentrated sulfuric acid and clean water are selectively introduced into reactor 1.

For reaction 191, uL water, J potassium manganate solution.

The liquids are mixed as concentrated sulfuric acid is fed. At this time, the concentrated sulfuric acid is diluted by the water component and generates heat of dilution. For this reason, the other two types of υ1 water.

The temperature of the potassium permanganate solution is also raised, and this generates reaction heat, causing the wastewater and potassium permanganate to react. Reaction/11! The temperature is detected by a temperature sensor 16 such as a thermocouple whose tip is located in the reactor 1.
16 is detected by the temperature/redox potential detector 7 connected to the base end.

A portion of the three types of mixed liquids (hereinafter referred to as reaction liquids) is overflowed and sent to the cooler 4, cooled while flowing through the cooler 4, and sent to the waste liquid tank 14-1.

The reaction of the reaction liquid that has reacted by raising the temperature is accelerated while passing through the reactor J, and is then sent to the reaction liquid cooler 5 where it is cooled, and is further cooled by a pump 34 that can adjust the flow rate. It is sucked and sent to the oxidation-reduction potential detection container 6. The reaction liquid sent to the detection container 6 is caused to overflow and sent to the waste liquid tank 14. The tip of the redox electrode 6a is immersed in the reaction solution in the detection container 6, and the electrode 6a
The 8-oxidation reduction potential of the reaction solution is detected by a temperature/oxidation-reduction potential detector 7 to which the base end of the reaction solution is connected. The COD of wastewater is reduced by converting the detected oxidation-reduction potential (ORP) into COD.

The detector 7 also has a recording function, recording the reaction temperature and the redox potential of the reaction liquid, and if the value of the redox potential falls below the set value, an alarm 8 will be issued as field lightning. to emit.

Then, by switching the three-way switching cocks 2], 22, and 23, clean water is supplied to the reactor 1, thereby reactor 11 reaction liquid cooler 5. Detection container 6 and each piping 41.42
．． 43 etc. are cleaned.

Next, the reactor 1 suitable for the present invention will be explained.

4 is an enlarged view of the structure of the reactor 1, and FIG. 5 is a horizontal 111 view taken along the line V--V in FIG. 4.

The reactor 1 is almost entirely made of heat-resistant glass such as borosilicate glass;
The air release hole installed at the bottom end is 1 except 112.
It is a J-stopped cylinder, and a fixing part 100a is formed on the circumferential surface of the reactor 1 so as to protrude in an annular shape at a position of about 115 mm from the upper end, and the reactor 1 is mounted on a fixing stand (not shown) by the fixing part 100a. .

A test bamboo-shaped reaction tube 101 is installed on the upper surface of the heat insulating container 100 with its lower half extending toward the heat insulating container 100 and its upper end protruding above the thermal container 100. Approximately at the center of the circumferential surface of the reaction tube +01 in the vertical direction, there is -.gl of the reaction liquid.
(Overflow pipe 10 for overflowing
4 or 1tli The overflow pipe 104 is protruded outward from above the fixed part 100a of the heat container 100, and the overflow pipe 104 is bent downward in the middle of the protrusion, and has a hemispherical shape with a larger diameter than the overflow pipe 104 at the tip. An outlet 105 is formed, and this outlet 105 is joined to the inlet side of the cooler 4. A coiled reaction promoting tube 102 is connected to the lower end of the reaction tube 101.
The outlet side of the tube 2 protrudes outward from the lower end of the circumferential surface of the heat insulating container 100, and a hemispherical outlet 103 with a diameter larger than that of the reaction promoting tube 102 is formed at the outlet end, and this outlet 103 is used for cooling the reaction liquid. It is joined to the inlet side of the vessel 5. of reaction tube 101.”
The diameter of the end of the unit is reduced slightly below it, and the diameter is reduced by 1tit.
A plug body 106 made of heat-resistant glass and processed into a common sliding fit-1 is fitted and locked into the diameter portion.

Two pairs of spring locking parts LO1a, 101a and 106a, 106a are provided at the lower end of the circumferential surface of the reaction tube 101 and the stopper 106.
are formed, and two pairs of spring locking parts 101a, 10
1a and 106a.

106a each has a spring 120'+120 attached to the stopper 10.
6 is stretched over the reaction tube 101 so as to be elastically retained therein.

At the axial center of the stopper 106, there are a thermometer tube attachment portion 117 and three injection tube attachment portions 118a and 118 equally spaced around the temperature measurement tube attachment portion 117.
11. In 118, there are also injection pipe attachment parts 118b, 118.
An air discharge pipe attachment portion 119 is provided between the portions c. Injection tube receptacle section 118a, ll8b, ll8c
an injection tube 108a whose distal end Qi is bent into a lock-shape, and whose proximal end is slightly bent in the direction opposite to the bending direction of the distal end;
]08b, l08c first I/i! The t+ openings are each taken so as to face the axis of the reaction tube I01 (marked with -1), and the feed tubes 41, 42, and 43 are connected to the injection tubes 108a, 108b, and 108c, respectively. Waste water, potassium permanganate solution, and concentrated sulfuric acid are in the reaction tube 101.
It is ejected towards the axis of the machine and mixed. Temperature measuring tube (=J
Part 117 has a closed tip/I! ! A tube 107 is attached with its tip positioned near the tips of the injection tubes 108a, 108b, and 108c, and the temperature measuring tube 10
A temperature sensor 16 such as a thermocouple is inserted in 7.

A steam release pipe 109 is attached to the steam release pipe section 119 with its tip substantially aligned with the bottom surface of the stopper 106, so that the steam heated and evaporated by the heat of dilution is discharged from the steam release pipe. 109, the pressure inside the reaction tube 101 is made equal to atmospheric pressure, and the flows of the pumps 31, 32, and 33 are prevented from interfering with each other.

Note that the heat insulating container 100 and the reaction tube 1011 reaction promoting tube 1
The air in the air insulation part 1a formed by 02 is heated and expanded as a result of the reaction.
It is discharged from 1L 112, and together with this, the reaction tube 101 and the reaction promoting tube 102 are insulated from the outside air temperature and kept warm.

When such a reactor is used, the structure can be simplified because the reaction can be carried out by simply mixing three types of liquids.

〔effect〕

Next, the effects of the present invention will be explained based on Examples. COD measured by specified measurement method is 35ppm, 79pp
m.

Using waste water and tap water to which 5 levels of glycol of 96 ppm and 190 ppm were added, the feed line was first purged before measurement, and 96 ppm-190 ppm-96 ppm was added.
Switch between pm Nijosui - 190ppm and COD level, then 79ppm - 35ppm - Josui → 35ppm 1
The ORP value and the reaction temperature were detected according to the present invention under conditions such that the reaction temperature was approximately 130 to 140'C by switching from 79ppm to 35ppm to 35ppm to 5ppm.

Figures 6 and 7 are graphs showing the detection results, with the horizontal axis showing the ORP value (V) and reaction temperature (°C), and the vertical axis showing the time based on the recording paper feeding speed of the detector 7. is taking. In the figure, the solid line shows the ORP value, the dashed-dotted line shows the reaction temperature, the upper left shows the recording paper feed rate per hour, and the right shows the measurement period of waste water and clean water.

Figures 6 and 7 show examples when the mixing ratio of the three types of liquids is changed, and as is clear from the figures, under the conditions of Figure 6 (flow rate ratio and concentration of potassium permanganate), the COD O of
ppm (water supply), 96 ppm and 190 ppm can be distinguished. Also, in the ff17 diagram, COD's 09
It can be seen that it is possible to identify pm+35ppm and 79ppm. In this way, the pumps 41, 42.
The dilution ratio of concentrated sulfuric acid is changed by adjusting the flow rate nTta of 43,
The reaction temperature can be adjusted #IfJ. Alternatively, the COD detection level can be freely set by changing the mixing ratio of wastewater and the concentration of the oxidizing agent.

Therefore, since the reaction temperature can be set to 100 DEG C. or higher according to the present invention, GOI+ can be quickly measured even in the case of a water-glycol water-soluble working fluid with poor reactivity. Furthermore, it is clear that the measured values can be freely matched with the measured values by the designated measuring method, and that accurate and continuous measurement is possible.

Therefore, the present invention can be applied as a monitor for water quality control.

However, as a fate of the method of the present invention, the reaction temperature is influenced by the outside temperature and temperature, but as shown in Figure 7, if the atmospheric temperature near the reactor 1 is raised in the middle of this measurement, the reaction will occur. Although the temperature increased by about 10°C to about 140°C as shown by A in the figure, there was no problem with the detection accuracy within the range of room temperature changes caused by lightning strikes.

In this way, the present invention continuously supplies the three types of liquids to the reactor 1 and the detection container 6, so continuous measurement is possible. Furthermore, since the present invention measures COD based on the oxidation-reduction potential of the reaction solution, it is possible to measure COD in the case of turbid wastewater or colored wastewater. Furthermore, since the present invention uses a self-heating method, it can be started quickly, and since the overheating of the reaction is limited depending on the type of oxidizing agent, there is no risk of overheating (also, the reaction can be carried out at temperatures of 100°C or higher under atmospheric pressure). This method can be realized and is highly safe.Furthermore, the response time can be changed by adjusting the flow rate of the pump 34.

In addition, in the description given in the North, concentrated sulfuric acid is used as the liquid whose temperature increases when water is added, but the present invention is not limited to this, and when water is added, heat is generated and the boiling point rises (to 100°C or more), and υ1 water and potassium permanganate/ Of course, it is also possible to use a liquid that reacts with the 8 liquid and does not cause an error in the COD measurement value. Furthermore, the present invention is not limited to the wastewater ζ, assuming that the melt to be measured is 11. Of course, COD can be measured even in Ik bodies.

As described in detail above, the COO measuring method according to the present invention involves mixing and reacting a solution to be measured, an oxidizing agent/g liquid, and a liquid whose temperature increases, and based on the oxidation-reduction potential of the reaction liquid, C01
], the three types of liquids are continuously fed into the reactor, and deviations can be measured rapidly and continuously. Also, external heating is not required and overheating does not occur, making it highly safe. It can also be measured in the case of a solution to be measured. When using the present invention, the measuring operation is simple, and therefore an inexpensive monitoring device can be provided, and the present invention has excellent effects.

[Brief explanation of the drawing]

Figure 1 is a graph showing the differences in oxidation reactions depending on the substance. , FIG. 3 is a diagram showing an embodiment of the present invention, FIG. 4 1 is a vertical cross-sectional view showing the structure of the reactor, and y of FIG.
-V-line cross-sectional view, Figures 6 and 7 (showing the measurement results according to the present invention are rough) 1... Reactor 6... Redox potential detection sound 2 Draw 6a
...Redox electrode 7...Temperature/Redox type (I)
"Moxibustion 11" Device Patent Applicant Sumitomo Metal Industries Co., Ltd. Agent Patent Attorney Norio Kono Figure 4 Figure 5 °C) No. G Fig.0RP(!(V) 上□□□□----"0 100 2ω ηO Reaction 7! ('C)

Claims (1)

[Scope of Claims] 1. In a method of measuring the COD of a solution to be measured by raising the temperature of a constant solution of ij++1 and an oxidizing agent solution to cause a reaction, a liquid that warms the stomach by adding water to the solution to be measured and the oxidizing agent solution A method for measuring COD, which comprises: detecting the oxidation-reduction potential of a reaction solution that has reacted by heating the mixture, and measuring the COD of the solution to be measured based on the detection result. 2. Raise the temperature of the solution to be measured and the oxidizing agent solution to cause a reaction.
In an apparatus for measuring the COD of a solution to be measured, a feeding means for feeding the solution to be measured, an oxidizing agent solution, and a liquid that is dissolved by adding water; 1. A Cot1 measuring device comprising a reactor and a detector for measuring the redox potential of a reacted liquid, and measuring the COD of a solution to be measured based on the detection result.