JPH095239A - Apparatus for measuring concentration of nitrogen oxide - Google Patents

Abstract

PURPOSE: To provide an accurate nitrogen oxide concentration-measuring apparatus which can catch a chemiluminescence with a high sensitivity in a relatively simple constitution. CONSTITUTION: A reaction tank 1 is arranged, which has a reaction chamber 1a at the center. Photosensors 3, 3 are set at both sides of the reaction tank 1 to face each other via the reaction chamber 1a. Filters 2, 2 are held at both sides of the reaction tank 1 in some cases. The amount of light of a wavelength band passing through the filters 2 is analyzed thereby to measure a concentration of a nitrogen oxide.

Description

Detailed Description of the Invention

[0001]

This invention relates to nitric oxide (NO).
The present invention relates to a nitrogen oxide concentration measuring device capable of efficiently receiving chemiluminescence generated when a nitrogen oxide reacts with ozone (O ₃ ) and detecting the concentration of nitrogen oxide.

[0002]

2. Description of the Related Art When measuring the concentration of a relatively low concentration of nitrogen oxides such as nitric oxide (NO) in the atmosphere, concentration analysis is often performed using a nitrogen oxide concentration measuring device.
This device for measuring the concentration of nitrogen oxides utilizes the fact that the amount of light emitted by the chemical reaction of nitric oxide (NO) and ozone (O ₃ ) is proportional to the concentration. ing. That is, this apparatus is assembled with the reaction tank 1, the filter 2, and the detector 4. In this case, the reaction chamber 1a is provided on one side of the reaction tank 1 and is located at a position facing the reaction chamber 1a. Through the filter 2 to the detector 4
The optical sensor 3 on the side is arranged. In the reaction chamber 1a of the reaction tank 1, nitric oxide (NO) and ozone (O) are supplied from one side.
₃ ) and are separately introduced and reacted, and the reaction product gas is discharged to the other side. Then, the chemiluminescence generated by the reaction between nitric oxide (NO) and ozone (O ₃ ) in the reaction chamber 1a is detected by the optical sensor 3 to amplify the change of this signal to increase the concentration of nitric oxide (NO). It is designed to measure. In addition, there is also a conventional nitrogen oxide concentration measuring device for recognizing a light emission phenomenon by disposing two optical sensors on one side because the reaction chamber becomes large in order to obtain complete light emission when the reaction gas flow rate is large. . In that case, noise may be included in only one of the optical sensors, for example, radiation such as cosmic rays may occasionally jump in, so that a circuit for cutting noise may be incorporated.

[0003]

When nitrogen oxides are analyzed by the nitrogen oxides concentration measuring device having the above-mentioned structure, the photosensor 3 of the detector 4 is arranged on one side of the reaction chamber 1a, so that the light generated by the light emission is emitted. Means that only the light emitted from one side of the reaction chamber 1a is received. That is, reaction tank 1
Is usually made of a chemically stable substance such as Teflon, and a part of the emitted light hits the side wall of the reaction chamber 1a and is diffusely reflected and enters the optical sensor 3, but most of the light projected in the wall direction is lost. Will be there.

It is also conceivable to install a mirror on the side wall of the reaction chamber 1a as a means for receiving a large amount of light generated in the reaction chamber 1a by the optical sensor 3 installed on one side of the reaction chamber 1a. However, the processing work becomes complicated, the number of parts increases, or a chemically extremely unstable substance such as ozone (O ₃ ) is used, which may cause a chemical reaction other than a reaction internally required. Not really.

The present invention has been made in view of the above problems, and provides a highly accurate nitrogen oxide concentration measuring device capable of capturing chemiluminescence generated with a relatively simple structure with high sensitivity. Is intended.

[0006]

That is, in order to solve the above problems, the present invention provides a nitrogen oxide concentration measuring device,
An optical sensor is arranged on both sides of the reaction chamber provided with the reaction chamber so as to face both sides of the reaction chamber.
Alternatively, a filter is arranged on both sides of a reaction chamber provided with a reaction chamber, the reaction chamber is sandwiched, and an optical sensor is arranged outside these filters so as to face both sides of the reaction chamber. And

[0007]

When the nitrogen oxide concentration measuring device is used as the above means, the light generated by the chemical reaction is received by the two photosensors and added as a predetermined signal by the addition circuit via the amplifier (not shown). The concentration is displayed in (). Therefore, according to this device, twice as many signals can be taken in as compared with the conventional one, so that the light emission can be captured with high sensitivity, and the measurement accuracy is improved accordingly.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of the present invention will be described below with reference to the drawings. Note that the same reference numerals as those described in the conventional art are used for the same components to avoid redundant description. FIG. 1 is a sectional view showing the structure of a nitrogen oxide concentration measuring apparatus of the present invention, and FIG. 2 is a sectional view taken along the line AA of FIG. In this apparatus, a reaction tank 1 having a reaction chamber 1a in the center is arranged, filters 2 and 2 are arranged and sandwiched on both sides of the reaction tank 1, and the reaction chambers are provided outside the filters 2 and 2. The detectors 4 and 4 in which the optical sensors 3 and 3 are disposed so as to face each other on both sides of 1a are arranged. That is,
The reaction chamber 1a of the reaction tank 1 is opened on both sides, and the reaction chamber 1a is arranged so as to be sandwiched by the two optical sensors 3 and 3.

The reaction chamber 1a of the reaction tank 1 has an inlet 1b for introducing ozone (O ₃ ) and a nitric oxide (N) on one side.
An inlet 1c for introducing O) and an outlet 1d for discharging the reaction product gas are provided. In the reaction chamber 1a, the nitric oxide (NO) and ozone (O ₃ ) react well with each other. There are sine curves and complicated maze-like curves. Various shapes have been considered as the shape of the reaction chamber 1a in order to increase the reaction time, but the optimum shape is determined by the flow rate and the concentration. In addition, the optical sensors 3, 3
Is formed into a space that covers the entire reaction chamber 1a from both sides.

Next, the detector 4 has the optical sensor 3 arranged inside the case 4a, and the space 4b is filled with a dry gas such as nitrogen gas. Further, the photosensors 3 are arranged on both sides of the reaction chamber 1a, but if the two photosensors 3 are arranged in this way, the light emission can be received with high sensitivity. That is, the optical sensor 3 is a semiconductor element, and when the area is increased, the internal capacitance is increased and the noise in the amplifier is increased, but by using the two optical sensors 3, the area of one optical sensor 3 is not increased so much. In addition, if the same signal is used, the sensitivity can be improved by dividing the two signals and adding them.

The filters 2 and 2 are for taking in light of a specific wavelength band out of the light emitted by the chemical reaction and cutting off the other light. The concentration of nitrogen oxides is measured by analyzing the amount of light in the wavelength band transmitted by the filter 2. The filter 2 simultaneously physically separates the reaction chamber 1a and the optical sensor 3 (particularly from ozone).
Has a role to do.

The nitrogen oxide concentration measuring device of the present invention has the above-mentioned structure, and the light generated by the chemical reaction is transmitted through the filters 2 and 2 and is received by the two photosensors 3 and 3 to receive a predetermined signal. Is added by the adding circuit 6 via the amplifiers 5 and 5, and the density is displayed on the display device (not shown). Therefore, according to this device, twice as many signals can be taken in as compared with the conventional one, so that the light emission can be captured with high sensitivity, and the measurement accuracy is improved accordingly.

In the above embodiment, the photosensors 3 and 3 of the detectors 4 and 4 may be cooled in order to reduce noise due to heat. Further, the filters 2 and 2 may be omitted if necessary, or may be resin or the like as long as they are not deteriorated by simple transparent glass or ozone (O ₃ ).

[0014]

As described in detail above, according to the nitrogen oxide concentration measuring apparatus of the present invention, since the reaction chamber of the reaction vessel is sandwiched by the optical sensors of the two detectors, nitric oxide (NO) and ozone (O) are used. ₃ ) The luminescence generated by the chemical reaction with can be detected from two directions. Further, since the same light emission phenomenon is received by the photosensors of the two detectors, a signal that is almost twice as large as that of the conventional device can be obtained, and therefore, highly sensitive analysis can be performed. Further, in the conventional nitrogen oxide concentration measuring device, two optical sensors are arranged on one side because the reaction chamber becomes large, and in that case, one of the optical sensors is sensitive to noise such as cosmic rays and the analysis result It could have an adverse effect.
For this reason, a conventional circuit was constructed to cut off any noise such as cosmic rays, but such a circuit can be used as it is even when optical sensors are arranged on both sides of the reaction chamber of the present invention.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing the configuration of a nitrogen oxide concentration measuring device of the present invention.

FIG. 2 is a sectional view taken along the line AA of FIG.

FIG. 3 is a cross-sectional view showing the configuration of a conventional nitrogen oxide concentration measuring device.

[Explanation of symbols]

 1 Reaction Tank 1a Reaction Chamber 2 Filter 3 Optical Sensor 4 Detector

Claims (2)

[Claims] 1. A nitrogen oxide concentration measuring device comprising a photosensor arranged on both sides of a reaction chamber provided with a reaction chamber so as to face both sides of the reaction chamber. 2. A filter is arranged on both sides of a reaction tank provided with a reaction chamber to sandwich the reaction tank, and an optical sensor is arranged outside these filters so as to face both sides of the reaction chamber. A nitrogen oxide concentration measuring device characterized by the above.