JPS63169557A - Hydrazine concentration measuring instrument - Google Patents

Abstract

PURPOSE:To quickly measure hydrazine by heating a liquid mixture contg. the hydrazine, color forming reagent, etc. to bring the liquid into reaction so that the liquid forms a color, measuring the light absorptivity with a flow cell and specifying the capacities of respective apparatus to specific sizes. CONSTITUTION:The hydrazine, color forming reagent (p-dimethylaminobenzaldehyde) and diluent are put into a mixer 3 and are mixed. The liquid mixture is fed to a reaction tube 13 and is brought into reaction so that the liquid forms the color. The absorbancy is measured by the flow cell 19 and the hydrazine concn. is analyzed. The reaction is accelerated by heating the mixer 3 and the reaction tube 13 to about 40 deg.C at this time. The relations between the liquid capacity VM of the mixer 3, the capacity VR of the reaction tube 13, the capacity VC of the flow cell 19 and the discharge rate VP of a fixed delivery pump are specified to VM>VP VR>=5VC. Since these capacities are related in the above-mentioned manner, the cleaning of the mixer 3 during the reaction in the reaction tube 13 is possible. The liquid mixture can be admitted into the flow cell 19 while the flow passage 20 thereof is jointly cleaned. Since reaction is carried out at the high temp. and the capacities of the apparatus are specified to the specific sizes, the hydrazine concn. is quickly measured.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hydrazine concentration measuring device, and more specifically, to a device for measuring hydrazine concentration, and more specifically, to continuously measure the hydrazine concentration in startup wastewater at the exit of a startup wastewater treatment equipment of a thermal power plant boiler unit. The present invention relates to a measuring device particularly suitable for use in measurements.

Conventionally, at the Muwazasa thermal power plant, hydrazine is injected into the boiler when the unit is stopped to prevent corrosion of the evaporator pipes, but since the start-up wastewater has a high COD (chemical oxygen demand),
Hydrazine is decomposed in the activated wastewater treatment equipment before being discharged. In this case, it is necessary to inject an equivalent amount of the decomposer that reacts with hydrazine, and for this purpose, the hydrazine concentration in the waste water must be detected in advance.

Therefore, in the operational management of startup wastewater treatment equipment, it is necessary to constantly measure the hydrazine concentration in the startup wastewater, and for this reason, the hydrazine concentration in the startup wastewater is measured based on the p-dimethylaminobenzaldehyde colorimetric method specified in JIS. Conventionally, it has been measured by manual analysis or by using an ORP meter.

Problems to be Solved by the Invention However, the above-mentioned method using manual analysis lacks speed, and the method using an RP meter has the disadvantage that accurate measured values cannot be obtained. Therefore, the reality is that these methods cannot fully and satisfactorily manage the operation of the activated wastewater treatment equipment.

For this reason, there is a need for a means to automatically measure the hydrazine concentration in startup wastewater accurately and in a short time based on the p-dimethylaminobenzaldehyde method specified in JIS, but no satisfactory proposal has yet been found. The reality is that nothing has been done.

In view of the above circumstances, the inventors of the present invention conducted various studies in order to obtain an automatic measuring device based on the above-mentioned JIS method, and as a result, the following findings were made.

That is.

(2) In the JIS method, it takes 10 minutes for color development to stabilize after adding a coloring reagent, which does not satisfy the analysis time requirements.

On the other hand, when we investigated the change in absorbance over time while changing the reaction temperature in the range of 10 to 40°C, we found that the coloring reaction takes 10 minutes at room temperature, but completes in 3 minutes at 40°C, as described below. I discovered that. However, although this results in a decrease in sensitivity, there is no problem since there is a large sensitivity margin in the measurement of start-up wastewater and a large amount of dilution is performed.On the other hand, JIS does not mention the necessity of temperature control.

■ Under the conditions of ■ above, the color reaction takes 3 minutes, but when measuring by batch method, the time required to inject sample water and reagents into the reaction container, the time to drain the liquid after the reaction, and the time required to drain the reaction container. Washing time is required, and if these are added, an additional 2 minutes or more is required, so analysis can only be performed at intervals of 5 minutes or more.In contrast, the sample water and reagent mixing section and the reaction section are separated, The above time can be shortened by sending the mixed solution to the reaction section and cleaning the mixing section while it is being reacted in the reaction section so that it can receive the next sample water. It has been found that analysis can be performed at intervals of about minutes.

When the mixing part and the reaction part are separated as in ■■, the reaction part will be co-washed with the mixed liquid, so one reaction part should have a structure that makes it easy to wash together, and the inside of the mixing part and reaction part should be The mixed solution is heated and maintained at, for example, 40°C. In addition, the absorbance measurement cell is a flow cell, which also has a structure that allows easy co-washing.

Furthermore, a metering pump that operates at the desired measurement time interval is connected to this flow cell, and the operation of this metering pump transfers the mixed liquid from the mixing section to the reaction section to continue and complete the reaction, and then the next metering pump is activated. The mixed liquid is transferred from the reaction part to the flow cell while washing the flow cell together with the flow cell, and the absorbance is measured in the flow cell.In this case, the liquid volume in the mixing part is made larger than the capacity of the reaction part.
The capacity of the reaction section is approximately equal to the discharge amount per unit operation of the metering pump, and the capacity of the reaction section is 5 times the capacity of the flow cell.
It has been found that by making the size more than double the size, the reaction section and the flow cell can be washed together well, and accurate analysis can be performed.

That is, heating the liquid mixture and maintaining it at, for example, 40°C;
The mixing section and the reaction section are formed separately.

By sequentially connecting the mixing section 1 reaction section, the flow cell, and the metering pump and setting their capacities in the above-mentioned relationship, it has been shown that the hydrazine concentration can be measured accurately and in a short time (for example, at short intervals of 3 minutes) using the JIS method. This is what I found out.

Therefore, in the present invention, a sample solution containing hydrazine, a dilution solution, and a coloring reagent that develops color by reacting with hydrazine are injected,
A mixing cell to be mixed, a mixing cell equipped with a heat retention mechanism to keep the test liquid in the mixing container in a heated state, a reaction tube through which the test liquid flows, and a reaction tube to heat the test liquid in the reaction tube. It consists of a reaction cell equipped with a heat retention mechanism that maintains the temperature, a flow cell that has a flow path for the test liquid inside and measures the absorbance of the test liquid flowing through this flow path, and a metering pump that are connected in sequence. By operating this metering pump at predetermined time intervals, the test liquid in the mixing container is sequentially transferred to the reaction tube and the flow cell, and the liquid in the mixing container 11t V
M, the capacity VR of the reaction tube, the capacity Vc of the sample liquid flow path of the flow cell, and the discharge amount by one unit operation of the metering pump ■P are set in the relationship shown by the following formula (1)% formula % (1) An object of the present invention is to provide a hydrazine concentration measuring device characterized by the following.

In the apparatus of the present invention, the mixed liquid in the mixing cell and the reaction cell is kept in a heated state, for example at approximately 40°C, so that the color development reaction time is shortened to a short time of, for example, 3 minutes. Since the mixing cell and the reaction cell are formed separately so that the mixing cell can be cleaned while the reaction is being carried out in one reaction cell, the time required for these steps can be saved. Therefore, it is possible to accurately measure the hydrazine concentration in a short measurement cycle.The present invention will be specifically explained by referring to Examples, but the present invention is not limited to the following Examples. 111 1 Figure 1 shows a hydrazine concentration measuring device according to an embodiment of the present invention.

In the figure, 1 is a mixing cell in which a mixing container 3 is inserted into a substantially cylindrical water tank 2. The mixing container 3 of this mixing cell 1 contains a sample water flow pipe 4, a diluting/washing water inflow pipe 5, and a coloring water container 3. One end of the reagent inflow tubes 6 are in communication with each other, and sample water, dilution/washing water, and coloring reagent (p-dimethylaminobenzaldehyde) are respectively injected into the mixing container 3 under the control of a control unit (not shown). It has become so. In addition, 7 is a stirring bar whose tip is inserted into the mixing container 3, 8 is a rotary motor connected to this stirring bar 7, 9 is a discharge pipe connected to the discharge port 3a at the lower end of the mixing container 3, and 10 is a stirring bar connected to the stirring bar 7. This is a solenoid valve installed in the discharge pipe 9.

Reference numeral 11 denotes a reaction cell in which a reaction tube 13 formed by coiling a fluororesin tube with an inner diameter of about 2 to 3 m is disposed inside a cylindrical water jacket 12, and an inflow end 13a of the reaction tube 13 has an inlet end 13a. One end of the communication pipe 14 communicates with the mixing container 3, and the other end of the communication pipe 14 is connected to the mixing vessel 3.

Note that 15 and 16 are first and second circulation pipes that communicate the water jacket 2 of the mixing cell 1 and the water jacket 12 of the reaction cell 11, respectively. Circulation pumps 18 are interposed in each case, and the operation of the pumps 18 opens the circulation channel A consisting of the first circulation pipe 15, the water jacket 12 of the reaction cell 11, the second circulation pipe 16, and the water jacket 2 of the mixing cell 1. Insulated water adjusted to a predetermined temperature by a constant temperature water tank 17 is circulated to maintain the inside of the mixing container 3 and the reaction tube 13 at approximately 40°C.

Further, 19 has a test liquid flow path 2o formed therein.

This flow cell for measuring absorbance measures the absorbance of the test liquid flowing through the flow path 20, and one end thereof is connected to the inflow end 20a of the test liquid flow path 20 of this flow cell 19.
The other end of the communicating tube 21 is connected to the outlet end 13b of the first reaction tube 13.

Further, 22 has one end connected to the test liquid flow path 2 of the flow cell 19.
This discharge pipe 2 is connected to the outflow end 20b of 0.
2 includes a check valve 2 having a pair of valve bodies 23a and 23b.
3 is interposed, and the valve bodies 23a, 23
A metering pump 25 (a syringe pump that operates at intervals equal to the analysis interval time and whose discharge amount per unit operation is accurate) is connected between b and a connecting pipe 24. Each time, the test liquid in the mixing container 3 is transferred to the reaction tube 13. The liquid is sequentially transferred to the flow cell 19 and further discharged through the discharge pipe 22.

Here, in the above device, the liquid amount VM in the mixing container 3,
Capacity VR of reaction tube 13, test liquid flow path 2 of flow cell 19
0 capacity Vc and the discharge amount vP by one unit operation of the metering pump are expressed by the above formula (1), that is, V M > V p Iso V
R≧5■c - Old: The relationship shown in (1) is set. In addition, the discharge amount VP due to one unit operation of the pump
There are cases where the amount is discharged in one operation of the pump and cases where it is discharged in multiple operations, but in either case, it is considered as one unit operation.

When measuring the hydrazine concentration in the startup wastewater of a thermal power plant boiler using the hydrazine concentration measuring device, the circulation pump 18 is operated and the water jacket 2 of the mixing cell 1 is
Insulating water is passed through the water jacket 12 of the reaction cell 11, and sampled startup wastewater, dilution water, and coloring water are supplied into the mixing container 3 from the sample water flow pipe 4, dilution/wash water flow pipe 5, and coloring reagent inflow pipe 6. A predetermined amount of each reagent (p-dimethylaminobenzaldehyde) is injected.

Note that these liquids are stirred by a stirring rod 7.

In this case, in this device, we focused on the fact that the absorption characteristics of the colorimetric method have linearity at a hydrazine concentration of 3.4 or less, and the dilution of the sample water is performed when the hydrazine concentration in the sample water is 0 to 20. A method is adopted that automatically dilutes 10 times and 100 times when diluting from 20 to 200. In addition,
As the dilution water, it is preferable to use demineralized water to which hydrochloric acid has been added in order to prevent a decrease in the hydrazine concentration due to oxidation of dissolved oxygen, but demineralized water alone may be used without any practical problems.

The mixed liquid in the mixing container 3 is maintained at 40°C by the action of the water jacket 2, and the liquid mixture in the mixing container 3 is maintained at 40°C by the action of the water jacket 2.
The reaction tube 13 of the reaction cell 11 flows into the reaction tube 13 of the reaction cell 11 through the communication tube 14' by the operation of
The coloring reaction is completed during the stay at 3.

Thereafter, at the timing of operation of the primary metering pump 25, this mixed liquid passed through the communication pipe 21 and flowed into the test liquid flow path 20 of the flow cell 19 while washing this flow path 2o, and the absorbance was measured here. Thereafter, it is discharged through the discharge pipe 22 at the next timing when the pump 25 operates.

On the other hand, while the coloring reaction is being carried out in the reaction cell 11, the excess liquid in the mixing container 3 is first discharged from the discharge pipe 9, and then washing water is poured into the mixing container 3 from the dilution/washing water flow pipe 5. After the water is injected and the container 3 is washed, this washing water is discharged from the discharge pipe 9, and the mixing container 3 becomes ready to receive the next sample water. Then, new sample water, diluent and reagent are added to the mixing container 3 in the same manner as above.
The metering pump 25 operates at regular intervals to send the sample to the reaction cell 11 and flow cell 19 for measurement.

Therefore, according to the above device, the mixing container 3 and the reaction tube 13
Since the mixed liquid inside the chamber was kept at 40°C, the color reaction was completed in 3 minutes, and the mixing cell 1 and reaction cell 11 were formed separately to allow color development and mixing as shown in Figure 2. - By adopting a method in which washing and cleaning are performed in parallel, that is, a method in which new samples are taken in one after another while moving the liquid sequentially in the three parts shown in Figure 2, the time required for mixing and washing can be saved. Therefore, the hydrazine concentration can be measured quickly and accurately at a time interval approximately equal to the reaction time, that is, at a measurement period of approximately 3 minutes. Also, a mixing container 3, a reaction tube 13. The capacity of the flow path 2o of the flow cell 19 and the pump 25 are set to the relationship expressed by the above equation (1), that is, the liquid volume in the mixing container 3 is larger than the capacity of the reaction tube 13, and the capacity of the reaction tube 13 is set to be larger than the capacity of the reaction tube 13. By setting the capacity of the reaction tube 13 to be approximately equal to the discharge amount by one unit operation of 25 and at least five times the capacity of the flow cell channel 20, when performing continuous measurement, the inside of the reaction tube 13 and the flow cell channel 2 are
o is sufficiently co-washed with the new mixed solution, the inside of the reaction tube 13 and the flow cell flow path 20 are completely replaced with the new mixed solution, and therefore measurement without error can be performed without being affected by the previous mixed solution. It is something that can be done.

Note that in the above apparatus, a water jacket was used to keep the mixing container 3 and reaction tube 13 warm.

The heat retention mechanism is not limited to this, and other mechanisms may be adopted. Further, although a coiled fluororesin tube with an inner diameter of approximately 2 to 3 mm was used as the reaction tube 13, other materials and shapes may be used, and other configurations may also be used. Various changes may be made without departing from the gist.

Next, the effects of the present invention will be specifically illustrated by experimental examples.

The change in absorbance over time when p-dimethylaminobenzaldehyde was added to a sample solution containing 1μ1L of hydrazine was calculated by
Each reaction temperature of 0°C, 20°C, 30°C, and 40°C was investigated. The results are shown in Figure 3.

As a result, when the reaction temperature was set to 40°C, the coloring reaction was completed in about 3 minutes.
It is recognized that the apparatus of the example, which is kept at a temperature of .degree. C., allows rapid measurement.

u''Δ In the apparatus shown in FIG. 1, the flow cell 19 is filled with a liquid having an absorbance of about 2, and one reaction tube 13 is filled with clean water, and the metering pump 25 is operated to flow this clean water into the flow cell 19 while adjusting the absorbance. As a result of measurement, the relationship between the magnification of the amount of liquid passed through the flow cell 19 and the absorbance was as shown in FIG. 4.

From the results shown in FIG. 4, if the above magnification is 5 times, the flow cell 19 will be sufficiently co-washed and there will be no carryover of the previous sample.
It is recognized that the analyzer of the example set as shown in the formula can perform accurate measurements without being influenced by the previous sample. It should be noted that the relationship between the liquid volume vM in the mixing container 3 and the capacity vR of the reaction tube 13 only requires that there is a surplus liquid volume, so there is no problem if vM is made larger than vR, especially twice or more.

In order to judge the applicability of the device shown in Figure 1 as a practical instrument, measurements were carried out using start-up wastewater from a thermal power plant.

The results are shown in Figure 5.

The measurement results were found to have good linearity and reproducibility, and were in good agreement with manual analysis.

As explained above, the hydrazine concentration measuring device of the present invention is capable of rapidly and accurately continuously automatically measuring the hydrazine concentration in a sample liquid based on the colorimetric method specified in JIS. It is effectively used to measure the hydrazine concentration in the start-up wastewater at the exit of the start-up wastewater treatment equipment of a boiler unit.

This contributes to appropriate operational management of the startup wastewater treatment equipment.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing a hydrazine concentration measuring device according to an embodiment of the present invention, Fig. 2 is a flow diagram of measurement by the same device, and Fig. 3 shows various reactions when a coloring reagent is added to a hydrazine-containing liquid. A graph showing the change in absorbance over time at different temperatures. Figure 4 is a graph showing the results of investigating the effect of co-washing in an experimental example. Figure 5 shows the correlation between the values measured by the device shown in Figure 1 and the manual analysis values. This is a graph showing. DESCRIPTION OF SYMBOLS 1...Mixing cell, 2...Water jacket, 3...Mixing container, 4...Sample water inflow pipe 5...Dilution/washing water inflow pipe. 6... Coloring reagent inflow tube, 11... Reaction cell, 12... Water jacket, 13...
...Reaction tube, 19...Measurement flow cell, 20...
Test liquid flow path, 25... metering pump. Applicant Chubu Electric Power Co., Ltd. (and 1 other person) Agent
Patent Attorney Takashi Kojima Time (minutes) 01234'567 Passage liquid volume magnification Figure 5 0 40 so 120 160 200 Manual analysis value (■/l >

Claims (1)

[Scope of Claims] 1. A mixing container into which a sample solution containing hydrazine, a diluent solution, and a coloring reagent that develops color by reacting with hydrazine are injected and mixed, and a test solution in this mixing container are maintained in a heated state. A mixing cell equipped with a heat retention mechanism, a reaction tube through which a test liquid flows, a reaction cell equipped with a heat retention mechanism that maintains the test liquid in the reaction tube in a heated state, and a test liquid flow path inside. A flow cell for measuring the absorbance of the test liquid flowing through this flow path and a metering pump are sequentially connected, and by operating the metering pump at predetermined time intervals, the test liquid in the mixing container is is sequentially transferred to the reaction tube and flow cell, and the liquid volume V_M in the mixing container and the capacity V_ of the reaction tube are
R, the capacity V_C of the flow cell sample liquid flow path and the discharge amount V_P per unit operation of the metering pump are expressed by the following formula (1) V_M>V_P≠V_R≧5V_C... (1)
A hydrazine concentration measuring device characterized by being set to the relationship shown in the following.