JP2000298097A - Chemoluminescence type nitrogen oxide meter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform measurement reduce in error by rapidly stabilizing an indication value after the changeover of a flow channel passing through an NO2/NO converter and a flow channel not passing therethrough. SOLUTION: When a pump 32 is operated, measuring gas is sucked from a measuring gas inlet 2 and sucked toward a reaction tank 16 while dust in the gas is removed by a filter 4, and moisture in the gas is removed by a duhumidifier 6. The measuring gas is guided to a reaction tank 14 through a converter 8 when a flow channel changeover device 10 is connected to a flow channel 9a, and guided thereto through a resistance pipe 38 without being passed through the converter 8 when the flow channel changeover device 10 is connected to a flow channel 9b. At this time, though the flow channel changeover device 10 is connected to either one of the flow channels 9a, 9b, the measuring gas passed through the converter 8 is sucked to a branched flow channel 9d. By this constitution, the measuring gas always flows through the converter 8. The measuring gas sucked to the branched flow channel 9d is guided to an ozone generator 24 through an activated carbon column 22.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for measuring a concentration of nitric oxide based on the intensity of chemiluminescence generated during a chemical reaction between ozone and nitric oxide by introducing a measurement gas into a reaction tank of a detector. A flow path for guiding the measurement gas to the reaction vessel, a flow path changer, a reduction flow path passing through the nitrogen dioxide reduction catalyst,
The present invention relates to a chemiluminescent nitrogen oxide meter capable of quantifying the concentration of nitrogen dioxide by introducing a measurement gas into a reaction tank by switching to a bypass flow path not passing through a nitrogen dioxide reduction catalyst. The chemiluminescent nitrogen oxide meter is used, for example, for measuring or monitoring the concentration of nitrogen oxide in the atmosphere or flue gas, measuring the concentration of nitrogen oxide for medical diagnosis, or a test field related thereto.

[0002]

2. Description of the Related Art Nitrogen oxides (NO) that are harmful to the human body and are contained in exhaust gas from combustion furnaces of factories and automobile engines.
While x) is a problem, one of the devices for measuring the concentration of nitrogen oxides in the atmosphere or exhaust gas is a chemiluminescent nitrogen oxide meter. The intensity of chemiluminescence generated when a measurement gas and an ozone gas (O ₃ ) are brought into contact with each other in a reaction tank of a measurement device and a chemical reaction occurs between nitrogen monoxide (NO) and O ₃ in the measurement gas. Is quantitatively measured by detecting the NO content in the measurement gas by detecting the NO. In a chemiluminescent nitrogen oxide meter, only NO can be measured due to the measurement principle. Therefore, when measuring nitrogen dioxide (NO ₂ ), a catalyst for reducing NO ₂ to NO is passed through, and the indicated value and catalyst at that time are passed. N from the indicated value when not passing
Convert the O ₂ concentration.

FIG. 1 is a schematic flow chart showing a conventional chemiluminescent nitrogen oxide meter. The flow path from the measurement gas inlet 2 that supplies the measurement gas is connected to a dehumidifier 6 that removes moisture via a filter 4 that removes dust and the like in the measurement gas. The flow path from the dehumidifier 6 is branched into two flow paths, one flow path 9a is via a NO ₂ / NO converter 8 for converting NO ₂ in the measurement gas into NO, and the other flow path 9b is a converter. It is connected to a flow path switching device 10 composed of a three-way solenoid valve without passing through the same. A common outlet of the flow path switching device 10 is connected via a resistance tube 12 to a reaction tank 14 for generating chemiluminescence by a reaction between NO and O ₃ .
By switching the flow path switching device 10, the measurement gas is sent to the reaction tank 14 via the converter 8 or not.
The reaction tank 14 is combined with a photoelectric measurement unit 28 that detects chemiluminescence generated in the reaction tank 14.

A flow path from an air inlet 16 for supplying air as an ozone source gas includes a filter 18 for removing dust and the like in the air, a dehumidifier 20 for removing moisture, for example, a high-concentration sulfur oxide and an organic solvent. Is connected to an ozone generator 24 that generates O ₃ from oxygen in the air via an activated carbon column 22 that removes substances that interfere with ozone generation. The flow path from the ozone generator 24 is connected to the reaction tank 14 via a resistance tube 26. The flow path from the reaction tank 14 is connected to a suction pump 32 via an ozone decomposer 30 for decomposing O ₃ . The exhaust side of the pump 32
The gas is led to an exhaust port 36 via a NOx adsorber 34 that absorbs nitrogen oxides.

When the NO concentration of the measurement gas is measured, the flow path 9 b is connected to the reaction tank 14 by the flow path switch 12, and the measurement gas is led to the reaction tank 14 without passing through the converter 8. N
When measuring the O ₂ concentration, the flow path 9 a is connected to the reaction vessel 14 by the flow path switching device 12, NO ₂ in the measurement gas is converted into NO by the converter 8, and then the measurement gas is supplied to the reaction vessel 14. Lead. The measurement gas contains NO due to NO ₂
And NO originally present, and the total of those NO concentrations corresponds to the NOx concentration. Then, NOx concentration and NO
The NO ₂ concentration is calculated by calculating the difference between the concentrations.
During the operation of this conventional example, the flow passages 9a and 9b are alternately switched every 15 seconds, for example, by the flow passage switching device 10 and connected to the reaction tank 14.

[0006]

Since the flow path 9a passing through the NO ₂ / NO converter 8 and the flow path 9b not passing through are alternately switched, when the flow path 9b is connected to the reaction tank 14, There is a state in which the measurement gas remains in the converter 8. Therefore, the measurement gas delivered to the reaction vessel 14 immediately after being switched to the channel 9a side is the measured gas flowing during the previous flow path 9a-side connection, particularly if NO ₂ concentration changes in the measured gas large, the flow path 9a is the reaction tank 14
And the measurement gas is sent from the converter 8 to the reaction tank 14, the stability of the indicated value is delayed, and a measurement error may occur.

Accordingly, the present invention provides a chemiluminescent nitrogen oxide capable of quickly stabilizing an indicated value after switching between a flow path that passes through a NO ₂ / NO converter and a flow path that does not pass, and performing measurement with less error. The purpose is to provide a total.

[0008]

According to the present invention, a measurement gas is introduced into a reaction vessel of a detector, and the concentration of nitric oxide is determined from the intensity of chemiluminescence generated during a chemical reaction between ozone and nitric oxide. At the same time, the flow path that leads the measurement gas to the reaction tank is
The flow path switcher switches between a reduction flow path that passes through the nitrogen dioxide reduction catalyst and a bypass flow path that does not pass through the nitrogen dioxide reduction catalyst, and guides the measurement gas to the reaction tank so that the concentration of nitrogen dioxide can be determined. A light-emitting nitrogen oxide meter, wherein a flow path switching device is disposed downstream of the nitrogen dioxide reduction catalyst, and a branch flow path is provided in a flow path between the nitrogen dioxide reduction catalyst and the flow path switching device; The measurement gas always flows through the nitrogen dioxide reduction catalyst even when the device is connected to the bypass flow path to the reaction tank.

Even when the bypass flow path is connected to the reaction tank by the flow path switching device, the measurement gas is discharged from the nitrogen dioxide reduction catalyst through the branch flow path, so that the measurement gas is stored in the nitrogen dioxide reduction catalyst. , The measurement gas does not remain in the nitrogen dioxide reduction catalyst, and the indicated value after the flow path switch is connected to the reduction flow path side can be quickly stabilized.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Before supplying a measurement gas to a nitrogen dioxide reduction catalyst, dust and moisture in the measurement gas are removed. Before supplying an ozone source gas to an ozone generator that generates ozone from oxygen, dust and moisture in the ozone source gas are removed. Therefore, in another aspect of the present invention, it is preferable that the branch channel is connected to a channel connected to an ozone generator, and the measurement gas flowing out of the branch channel is used as an ozone source gas. As a result, dust and moisture in the measurement gas supplied as the ozone source gas have been removed, and it is possible to omit a separate device for removing dust and moisture in the ozone source gas. Further, the flow path configuration can be simplified.

[0011]

FIG. 2 is a schematic flow chart showing one embodiment of a chemiluminescent nitrogen oxide meter to which the present invention is applied. The same parts as those in FIG. 1 are denoted by the same reference numerals, and detailed description is omitted. The flow path from the measurement gas inlet 2 for supplying the measurement gas is a filter 4
Is connected to the dehumidifier 6 via the
The flow path is branched into two flow paths, one flow path 9a is connected via a NO ₂ / NO converter 8 and the other flow path 9b is connected to a flow path switching device 10 without passing through a converter 8, and the flow path switching device 10
Are connected to a reaction tank 14 via a resistance tube 12. The reaction tank 14 is combined with a photoelectric measurement unit 28. The flow path from the air inlet 16 passes through a filter 18, a dehumidifier 20, and an activated carbon column 22 through an ozone generator 24.
The flow path from the ozone generator 24 is connected to the reaction tank 14 via a resistance tube 26. Reaction tank 1
The flow path from the suction pump 3 through the ozone decomposer 30
2 and the exhaust side of the pump 32 is connected to the NOx adsorber 34
Through the exhaust port 36. The configuration so far is the same as that of FIG. In this embodiment, a branch channel 9c provided with a resistance tube 38 is connected to a channel between the converter 8 and the channel switch 10, and the branch channel 9c is connected to the ozone decomposer 30 and the pump 32. And is always sucked.

When the pump 32 is operated, the measurement gas is sucked from the measurement gas inlet 2 and the air is sucked from the air inlet 16. The measurement gas sucked from the measurement gas inlet 2 is
After being dust-removed by the filter 4 and dehumidified by the dehumidifier 6, it is sucked into the reaction tank 16 side. When the flow path switch 10 is connected to the flow path 9a side, the measurement gas passes through the converter 8, and when the flow path switch 10 is connected to the flow path 9b side, without passing through the converter 8, the measurement gas further flows through the resistance tube 38. Then, it is led to the reaction tank 14. At this time, the flow path switch 10
Is connected to either of the flow paths 9a and 9b,
The measurement gas that has passed through the converter 8 is sucked into the branch channel 9c. Thus, no matter which flow path 9a or 9b the flow path switching device 10 is connected to, the measurement gas continues to flow into the converter 8 to prevent the old measurement gas from staying therein and to perform a new measurement in the converter 8. Replace with gas.
When the flow path switch 10 is switched and the converter 8 is connected to the reaction tank 14, the measurement gas to be measured is immediately introduced into the reaction tank 14.

On the other hand, the air sucked from the air inlet 16 is dust-removed by the filter 18, dehumidified by the dehumidifier 20, and the ozone generation obstructing substance is removed by the activated carbon column 22, and then guided to the ozone generator 24. . In the ozone generator 24, O ₃ is generated from oxygen in the air. The air containing O ₃ from the ozone generator 24 is led to the reaction tank 14 via the resistance tube 26. The measurement gas introduced into the reaction tank 14 and the air containing O ₃ are mixed,
The generated chemiluminescence is detected by the photoelectric measurement unit 8, and the NO concentration is calculated based on the detected intensity. Thereafter, the mixed gas of the measurement gas and the air containing O ₃ in the reaction tank 14 is guided to the ozone decomposer 30 to decompose O ₃ , and then merges with the measurement gas from the branch channel 9 c to form the pump 32. Is sucked. The mixed gas discharged from the pump 32 is discharged from the exhaust port 36 after nitrogen oxides are removed by the NOx adsorber 34.

FIG. 3 is a schematic flow chart showing another embodiment.
You. The flow path from the sample gas inlet 2 is removed via the filter 4.
The dehumidifier 6 is connected to the humidifier 6 and has two flow paths.
The flow paths 9a and 9b are branched, and one of the flow paths 9a is NO. _Two/
Via the NO converter 8, the other flow path 9b is converted
Connected to the flow path switching device 10 without passing through the
The common outlet of the path changer 10 is connected to the reaction vessel 1 through the resistance tube 12.
4 is connected. A photoelectric measurement unit 28 is provided in the reaction tank 14.
Are combined. The flow path from the reaction tank 14 has an ozone
Connected to a suction pump 32 through a dissociator 30;
The exhaust side 2 is led to an exhaust port 36 via a NOx adsorber 34.
Have been. The above configuration is the same as the embodiment of FIG.

In the embodiment shown in FIG. 2, an air inlet 16 for generating ozone is separately provided, whereas in this embodiment, a branch passage 9 is provided in a passage between the converter 8 and the passage switch 10.
d is connected, and the branch flow path 9c is connected to the activated carbon column 22.
Through the ozone generator 24. The flow path from the ozone generator 24 is connected to the reaction tank 14 via a resistance tube 40. The flow path between the filter 4 and the dehumidifier 6 is connected to the reaction tank 14 and the ozone decomposer 3 through a pressure regulator 42.
It is connected to a flow path between zero and the pressure regulator 42 adjusts the degree of pressure reduction in the reaction tank 14 by the pump 32. Although the flow path including the pressure regulator 42 is not provided in FIG. 2, it may be provided similarly.

When the pump 32 is operated, the measurement gas is sucked from the measurement gas inlet 2. The measurement gas sucked from the measurement gas inlet 2 is dust-removed by the filter 4, dehumidified by the dehumidifier 6, and then sucked into the reaction tank 16. When the flow path switch 10 is connected to the flow path 9a side, the measurement gas passes through the converter 8, and when the flow path switch 10 is connected to the flow path 9b side, without passing through the converter 8, the measurement gas further flows through the resistance tube 38. Then, it is led to the reaction tank 14. At this time, regardless of which of the flow paths 9a and 9b the flow path switch 10 is connected to, the measurement gas that has passed through the converter 8 is sucked into the branch flow path 9d. Then, the measurement gas is led to the ozone generator 24 via the activated carbon column 22. The air containing O ₃ from the ozone generator 24 is led to the reaction tank 14 via the resistance tube 26.

In this embodiment, a measurement gas guided to a branch passage 9d for constantly flowing a measurement gas to the converter 8 is supplied to the ozone generator 24 as an ozone source gas. Since the measurement gas guided to the branch channel 9d is dedusted by the filter 4 and dehumidified by the dehumidifier 6, it is not necessary to separately provide a device for removing dust and moisture in the ozone source gas. it can. Further, the flow path configuration can be simplified.

[0018]

According to the chemiluminescent nitrogen oxide meter of the present invention,
A flow path switch is arranged downstream of the nitrogen dioxide reduction catalyst, a branch flow path is provided in a flow path between the nitrogen dioxide reduction catalyst and the flow path switch, and a flow path in which the flow path switch does not pass through the nitrogen dioxide reduction catalyst. Even when the flow path is connected to the reaction tank, the measurement gas is made to always flow through the nitrogen dioxide reduction catalyst, so that the measurement gas does not remain in the nitrogen dioxide reduction catalyst, and the flow path switch is reduced. The indication value after connection to the flow path side can be quickly stabilized, and measurement with less error can be performed. Furthermore, by connecting the branch flow path to a flow path leading to the ozone generator and using the measurement gas flowing out of the branch flow path as an ozone source gas, dust and moisture in the measurement gas supplied as the ozone source gas are removed. Therefore, it is not necessary to separately provide a device for removing dust and moisture in the ozone source gas, and the flow path configuration can be simplified.

[Brief description of the drawings]

FIG. 1 is a schematic flow path configuration diagram showing a conventional chemiluminescent nitrogen oxide meter.

FIG. 2 is a schematic flow chart showing one embodiment.

FIG. 3 is a schematic flow chart showing another embodiment.

[Explanation of symbols]

2 Sample gas inlet 4,18 filter 6,20 dehumidifier 8 NO ₂ / NO converter 9a reduction passage 9b bypass passage 9c, 9d branch channel 10 the channel changer 12,26,38,40 resistance tube 14 reaction vessel Reference Signs List 16 air inlet 22 activated carbon column 24 ozone generator 28 photoelectric measurement unit 30 ozone decomposer 32 suction pump 34 NOx adsorber 36 exhaust port 42 pressure regulator

Continued on the front page F term (reference) 2G042 AA01 BB07 CA01 CB01 DA03 DA09 FA09 FA11 2G054 AA01 CA06 CE01 CE08 EA01 FA10 FA50

Claims (2)

[Claims] 1. A measuring gas is introduced into a reaction tank of a detector to determine a concentration of nitric oxide from the intensity of chemiluminescence generated during a chemical reaction between ozone and nitric oxide. The flow path leading to the tank is switched by a flow path switch between a reduction flow path passing through the nitrogen dioxide reduction catalyst and a bypass flow path not passing through the nitrogen dioxide reduction catalyst, and the measurement gas is led to the reaction tank. In a chemiluminescent nitrogen oxide meter that can also determine the concentration, the flow path switching device is disposed downstream of the nitrogen dioxide reduction catalyst, and a flow path between the nitrogen dioxide reduction catalyst and the flow path switching device. A branch flow path is provided, and even when the flow path switch connects the bypass flow path to the reaction tank, the measurement gas always flows through the nitrogen dioxide reduction catalyst. Chemiluminescence Nitrogen oxides meter. 2. The chemiluminescent nitrogen oxide meter according to claim 1, wherein the branch channel is connected to a channel connected to an ozone generator, and a measurement gas flowing out of the branch channel is used as an ozone source gas. .