JPH0452892B2 - - Google Patents

Description

[Detailed Description of the Invention] (a) Industrial Application Field The present invention relates to a chemiluminescence spectrometer that analyzes the concentration of nitrogen monoxide contained in, for example, automobile exhaust gas or flue gas by chemiluminescence analysis. In particular, the present invention relates to a chemiluminescent analyzer that measures luminescence when nitrogen monoxide reacts with ozone and nitrogen dioxide in an electronically excited state shifts to the ground state.

(b) Prior Art For example, methods using infrared absorption method and chemiluminescence method are used to measure the concentration of nitrogen monoxide contained in automobile exhaust gas, flue gas, etc.

Analyzers based on chemiluminescence have excellent selective properties for nitric oxide and are attracting great interest. This analyzer reacts with nitric oxide (NO) and ozone (O ₃ ) in its chemiluminescent reaction chamber (NO+O ₃ →NO ₂ *+O ₂ ), and the electronically excited state of nitrogen dioxide ( The amount of nitrogen monoxide is measured by measuring the intensity of the light emission (hν) that occurs when NO ₂ *) transitions to the ground state (NO ₂ *→NO ₂ + hν).

A typical conventional example of a chemiluminescence reaction chamber used in this analyzer is explained with reference to FIG. 1. 1 is a chemiluminescence reaction chamber made of stainless steel to block the incidence of light from the outside, and 2 is a chemiluminescence reaction chamber made of stainless steel to block the incidence of light from the outside. A pipe 3 introduces ozone into the chemiluminescence reaction chamber 1, and a pipe 3 similarly introduces a gas containing nitrogen monoxide to be measured into the chemiluminescence reaction chamber 1. The ends of these pipes 2 and 3 are bent inward so that ozone and nitrogen monoxide discharged from these pipes come into contact and mix. 6 is a glass window, and the chemiluminescence reaction chamber 1 has a glass window 7.
It is fixed via a fixing member such as a screw shown below. At a position facing this glass window 6,
A photomultiplier tube 4 is provided so that the streamline 5' of ozone discharged from the pipe 2 for introducing ozone and the streamline 5 of nitrogen monoxide discharged from the pipe 3 for introducing nitric oxide come into contact. 9000 generated by
Detects near-infrared light with a spectrum of ~30000Å.

In the chemiluminescence reaction chamber 1 with this configuration,
Experiments have shown that since the streamlines 5 and 5' of ozone and nitric oxide intersect, the probability of contact between the two is insufficient and the linearity, which is a characteristic of chemiluminescence spectrometry, deteriorates. confirmed. More specifically, when the chemiluminescence reaction chamber is kept at normal pressure and emitted light, nitric oxide is 0.
Linearity is obtained in the concentration range of ~500 ppm, but linearity deteriorates in the concentration range of 500 ppm or more.

In order to deal with these drawbacks, conventional methods have been to reduce the flow rate of ozone and nitrogen monoxide into the chemiluminescence reaction chamber, increase the volume of the chemiluminescence reaction chamber, or increase the length of the chemiluminescence reaction chamber.
A photomultiplier tube with a larger light-receiving area was used, but this increased the volume of the analyzer itself.
This went against the demands of the times for more compact equipment, and since photomultiplier tubes have an inherently short lifespan, they had to be replaced, resulting in high maintenance costs.

On the other hand, semiconductor optical sensors have appeared, but although these sensors have a long life and can meet the demands for miniaturization of devices, the light receiving area is small, resulting in poor linearity, making them unsuitable for practical use. It was hot.

(c) Purpose The present invention eliminates the drawbacks of the prior art described above, and provides a chemiluminescence analyzer equipped with a completely new chemiluminescence reaction chamber that eliminates the drawbacks of semiconductor optical sensors and takes advantage of its advantages. The purpose is to provide.

(D) Structure The present invention forms a double pipe structure with a pipe for introducing a gas containing nitrogen monoxide into a chemiluminescence reaction chamber and an ozone introduction pipe surrounding the pipe, so that nitrogen monoxide is produced by the flow of ozone. The gas flow is laminar, the mixing and contact of ozone and nitrogen monoxide is ideal, and complete luminescence occurs within the ozone introduction tube, and this is ensured at the discharge end of the ozone introduction tube. It can be detected by semiconductor optical sensors facing each other at right angles.

(E) Example An example of the chemiluminescent analyzer of the present invention will be explained with reference to FIG.

In the figure, 1 is a chemiluminescence reaction chamber made of stainless steel, and 1' is an exhaust section from which nitrogen dioxide and oxygen that have completed the luminescence reaction in the chemiluminescence reaction chamber 1 are discharged. 2 is a pipe for introducing ozone,
The wall 1a of the chemiluminescence reaction chamber 1 is bent at a right angle at the center thereof, inserted into the chemiluminescence reaction chamber 1, and extends close to the glass window 6. A pipe 3 introduces a gas containing nitrogen monoxide to be measured, and is inserted into the ozone introduction pipe 2 through the hole 2' of the ozone introduction pipe 2 to form a double pipe section. The inner diameter a of the pipe 3 for introducing gas containing nitrogen monoxide is, for example, 0.5 mm, and the pipe 3
The inner diameter b of the ozone introducing pipe 2 which contains the ozone and reaches near the glass window 6 is, for example, 4 mm. 6
is a glass window, which is fixed to the flange 5 of the chemiluminescence reaction chamber 1 via a packing 7 with a fixing member such as a screw (not shown). 4 is, for example, a 10 mm square semiconductor optical sensor, which is arranged at a position opposite to the tip 2'' of the ozone introduction pipe 2. The distance c from the tip 2'' of the ozone introduction pipe 2 to the inner surface of the glass window 6 is is, for example, 5 mm, and the distance d from the inner surface of the glass window 6 to the tip 3' of the pipe 3 into which the gas containing nitrogen monoxide is introduced is, for example, 40 mm. l ₁
indicates the flow of gas containing nitric oxide discharged from pipe 3, and l ₂ located outside it indicates pipe 2
This shows the flow of ozone emitted from the

In this configuration, the stream l 2 of ozone 3 exiting pipe ₂ flows outside the stream l ₁ of gas containing nitric oxide exiting pipe 3, thereby imparting ideal laminar flow to stream l _1. Let it form. this flow
l ₁ and l ₂ , that is, nitrogen monoxide and ozone contained in the gas, are sufficiently contacted and mixed from the tip 3' of the pipe 3 to the glass window, and the chemical reaction is 100%.
After hitting the inner surface of the glass window 6, it is reflected and exhausted from the exhaust section 1'. Since the reaction area where the chemical reaction described above takes place is limited to the inner diameter of the ozone discharge pipe 3, for example,
The light source is narrowed down to a small light emitting light source that can receive enough light for the small semiconductor photosensor 4 of about 10 mm square, and therefore this is used as the small semiconductor photosensor 4.
can be completely detected.

As explained above, the double-pipe structure allows for ideal mixing and contact between nitric oxide and ozone, making it possible to lower the ozone concentration, in other words, allowing a large flow of ozone to flow. As a result, the quenching effect that occurs when NO ₂ * in an excited state collides with CO ₂ can be removed, and the interference of carbon dioxide on measurement results can be halved compared to conventional methods.

According to experiments conducted by the inventors, ozone is absorbed at 1.75% per minute.
liter of gas containing nitric oxide per minute.
It was found that the linearity was the best at a flow rate of 300c.c. The interference of carbon dioxide in the analysis results at this time was 1.8% for 10Vol.% carbon dioxide, compared to the conventional interference of 7% to
This was much lower than 8%, and could be ignored in terms of measurement precision.

(f) Effects As explained above, according to the present invention, an ozone introduction pipe is provided outside the introduction pipe for gas containing nitrogen monoxide to form a double pipe structure, and ozone is introduced near the glass window of the chemiluminescence reaction chamber. Stretch the pipe,
Since the semiconductor optical sensor is arranged at the right angle in front of this ozone introduction pipe, the flow of gas containing nitrogen monoxide is formed into a laminar flow by the flow of ozone flowing outside, and the glass surface of the chemiluminescence reaction chamber is The mixture of ozone and nitric oxide,
When the contact is complete, the amount of light emitted at that time can be detected by a semiconductor optical sensor, and it is possible to obtain linearity even in the region of 500 ppm or more, which was not possible with conventional methods, and also to improve the relationship between the two. By ideally carrying out the catalytic reaction, the ozone concentration can be lowered, and therefore the interference of carbon dioxide can be lowered than in the conventional case.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a conventional chemiluminescent analyzer, and FIG. 2 is a sectional view of an embodiment of the chemiluminescent analyzer of the present invention. In the figure, 1 is a chemiluminescence reaction chamber, 2 is a pipe for introducing ozone, 3 is a pipe for introducing gas containing nitrogen monoxide, 4 is a semiconductor optical sensor, 5 is a flange, 6 is a glass window, 7 is a packing, l ₁ indicates the flow of gas containing nitric oxide, l ₂ indicates the flow of ozone.

Claims (1)

[Scope of Claims] 1. A gas introduction tube inserted from one side of the chemiluminescence reaction chamber and introducing a gas containing nitric oxide;
An ozone introduction pipe inserted outside this introduction pipe,
A semiconductor optical sensor is provided facing the ozone introduction tube outside the glass window provided on the other side of the chemiluminescence reaction chamber, and gas containing nitrogen monoxide is generated by the flow of ozone flowing through the ozone introduction tube. A chemiluminescence analyzer that generates light in the ozone introduction tube by making the flow a laminar flow. 2 The inner diameter of the ozone introduction tube described above is 4 mm, the inner diameter of the gas introduction tube that introduces the gas containing nitrogen monoxide is 0.5 mm, and the distance from the tip of the ozone introduction tube to the inner surface of the glass window is 5 mm. 2. The chemiluminescent analyzer according to claim 1, wherein the distance from the tip of the gas introduction tube through which the gas containing nitrogen monoxide is introduced to the inner surface of the glass window is 40 mm.