JP2541993Y2 - Chemiluminescence gas analyzer - Google Patents

Description

[Detailed description of the invention] [Industrial application field] The invention is an analyzer that analyzes gas contained in the atmosphere, exhaust gas, and the like. A chemiluminescent gas analyzer (Chemical Luminescence Dete) that detects the light emitted when the excited component transitions to an excited state and analyzes the gas.
cter, hereinafter referred to as CLD).

[Conventional technology]

FIG. 3 schematically shows a conventional CLD. In the figure, reference numeral 1 denotes a reaction tank, and a sample gas inlet 2 for introducing a sample gas containing NO (nitrogen monoxide) and the like, and a reaction gas as a reaction gas. An ozone inlet 3 for introducing ozone and a gas outlet 4 are provided, and a light transmitting window 5 is formed on one side. Reference numeral 6 denotes a photodetector such as a photocell provided so as to cover substantially the entire light transmitting window 5, reference numeral 7 denotes a cooling element such as a thermo module for cooling the photodetector 6, and reference numeral 8 denotes a photodetector. Reference numeral 6 denotes a preamplifier for amplifying the output signal, and reference numeral 9 denotes an output terminal. The ozone is generated, for example, by an ozone generator (not shown) and supplied via an ozone line.

In the chemiluminescence gas analyzer configured as described above, when a sample gas and ozone are respectively introduced into the reaction tank 1, NO and ozone as the components to be measured in the sample gas react to emit light. . Then, this light is detected by the photodetector 6, and the NO in the sample gas is determined based on the amount of light.
Is measured.

[Problems to be solved by the invention]

Thus, in the above CLD, in order to obtain an indication excellent in linearity and stability, the NOx in the sample gas with respect to the ozone concentration is
Must be kept at a certain ratio or less, and in high-concentration measurement, depending on the generated concentration and flow rate in the ozone line,
It is necessary to limit the flow rate of the sample gas. Then, when measuring low concentrations such as 1/100 or less under these conditions,
The output signal was sometimes too small.

By the way, in order to increase the output signal, it is sufficient to increase the light emission amount. One method of increasing the light emission amount is to increase the flow rates of the sample gas and ozone, but in this case, the reaction tank 1 is not enlarged. Then, output characteristics such as linearity and stability deteriorate due to light emission outside the tank. And if the reaction tank 1 is enlarged, unless the light receiving area of the photodetector 6 is increased,
Background effects increase. Further, since the photodetector 6 having a large light receiving area is special, the cost increases accordingly.

On the other hand, it is conceivable to prepare a plurality of detection units (including the reaction tank 1) corresponding to the conditions of the sample gas.
Also in this case, there is a problem that the cost is increased and the output characteristics of the individual detection units are not uniform.

The present invention has been made in consideration of the above, and an object of the present invention is to provide a chemiluminescent gas analyzer capable of accurately measuring a wide range from a low concentration to a high concentration. It is in.

[Means for solving the problem]

In order to achieve the above object, the chemiluminescence gas analyzer according to the present invention is provided with a sample gas inlet and an ozone inlet at an upstream end of a reaction tank, and a gas outlet at a downstream end,
In a chemiluminescence gas analyzer in which a sample gas and ozone are introduced into a reaction vessel and light emitted in the reaction vessel is detected, a plurality of light beams are transmitted along a light transmission window formed in the reaction vessel. Detectors are provided, and further, these photodetectors are arranged from the upstream side where the sample gas and the ozone merge to the downstream side,
Further, the light receiving surfaces of these photodetectors are provided so as to cover substantially the entire surface of the light transmitting window, and adders are provided for adding the outputs of the photodetectors. Further, the outputs of the photodetectors and the outputs of the adders are provided. This is characterized in that an abnormality determiner for determining whether or not there is an abnormality in each photodetector by inputting is input.

[Action]

For example, when two photodetectors are provided for the reaction tank, the output of the photodetector provided on the upstream side where the reaction between the sample gas and ozone is performed relatively quickly is shown in FIG. )
, And the output of the photodetector provided on the downstream side is as shown in FIG. Then, when the outputs of these two photodetectors are added, as shown in FIG.
An output with excellent linearity can be obtained in a wide range from low density to high density. Further, an adder for adding the outputs of the respective photodetectors is provided, and the respective outputs of the respective photodetectors and the output of the adder are input to the abnormality determiner. Can be detected.

〔Example〕

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a configuration example of a chemiluminescence gas analyzer according to the present invention. In this figure, the same reference numerals as those shown in FIG. 3 denote the same or corresponding components, and a description thereof will be omitted.

In FIG. 1, reference numerals 10 and 11 denote photodetectors such as photocells provided outside the light transmission window 5, which are provided along the flow of gas in the reaction tank 1. One photodetector 10 is provided to correspond to the vicinity of the sample gas inlet 2 and the ozone inlet 3 where the reaction between the sample gas and ozone occurs relatively quickly in the reaction tank 1.
The other photodetector 11 is provided so as to correspond to a region downstream of the photodetector 10. And these photodetectors 10, 11
The light receiving surface covers substantially the entire surface of the light transmission window 5.

12 is a cooling element provided commonly to the photodetectors 10 and 11,
For example, it consists of a thermo module. 13, 14 are photodetectors 10,
A preamplifier provided on each output side of 11, an adder 15 for adding the outputs of the preamplifiers 13 and 14, and an output terminal 16 are provided. Reference numeral 17 denotes an abnormality determiner, to which the outputs of the preamplifiers 13 and 14 and the output of the adder 15 are respectively input, and by comparing the outputs of the preamplifiers 13 and 14, the photodetectors 10 and 11 are used. It can be determined whether or not an abnormality has occurred.

Thus, in the chemiluminescent gas analyzer having the above configuration, when the sample gas and ozone are respectively introduced into the reaction tank 1, the NO and ozone as the components to be measured in the sample gas react to emit light. This light is received by the photodetectors 10 and 11, respectively. In this case, in the vicinity of the sample gas inlet 2 and the ozone inlet 3, the reaction between the sample gas and the ozone is promptly performed, so that the output from the photodetector 10 provided at a position corresponding to this region is , The curve a in FIG. 2 (A). Further, on the downstream side in the reaction tank 1, the two gases react slowly with a slight delay from the reaction, and the output from the photodetector 11 provided at a position corresponding to this region is shown in FIG. B)
Is as shown by the curve b. Then, by adding the outputs from the two photodetectors 10 and 11 in the adder 15, an output as shown by a curve c that is substantially linear in FIG.

That is, according to the above configuration, output characteristics with excellent linearity and stability can be obtained over a wide range from a low concentration to a high concentration, and these high ranges can be accurately measured.

Further, in the above configuration, since the respective outputs of the photodetectors 10 and 11 and the output of the adder 15 are input to the abnormality determiner 17, whether an abnormality has occurred in the photodetectors 10 and 11 or not. Can be detected. For example, as one method, based on the final density output, the individual outputs of the photodetectors 10 and 11 are compared with the respective signal amounts to be output, and when each exceeds a certain range, the photodetectors 10 and 11 are used. 11 is determined to be abnormal. Another approach is to use a photodetector
The correlation curves of the outputs of 10 and 11 are stored in the abnormality determiner 17 in advance, and the output of the photodetector 10 is compared with the output of the photodetector 11, or the output of the photodetector 11 is For example, when the correlation exceeds a certain range, it is determined that the photodetectors 10 and 11 are abnormal.

Therefore, in this type of conventional CLD, even if an abnormality occurs in the photodetector 6 or the reaction tank 1, the abnormality may not be discovered until calibration is performed periodically, and the indication failure may continue. Although the measurement is sometimes performed, according to the above-described configuration, such a situation is prevented beforehand, and an indication defect due to an abnormality of the photodetectors 10 and 11 can be effectively eliminated.

The present invention is not limited to the above embodiment. For example, three or more light detectors may be provided in the reaction tank 1. Needless to say, the present invention can be applied to a case where a gas other than nitric oxide is measured.

[Effect of the invention]

As described above, according to the present invention, since it is only necessary to add the outputs of the plurality of photodetectors with the adder, the configuration is simple and inexpensive, but the wide range from low density to high density can be obtained. It can be measured accurately.

That is, in the vicinity of the sample gas inlet and the ozone inlet, that is, in the upstream region of the reaction tank, the reaction between the sample gas and ozone is rapidly performed, so that the gas is provided at a position corresponding to this region. The output from the photodetector
For example, it is as shown by a curve a in FIG. Further, in the downstream region in the reaction vessel, the sample gas and ozone react slowly and slightly later than the upstream region, so the output from the photodetector provided at a position corresponding to this downstream region is: For example, it becomes as shown by a curve b in FIG. 2 (B). Then, by adding the outputs from these photodetectors in the adder, an output as shown by a curve c that is substantially linear in FIG. 2 (C) is obtained. Therefore, as in the past, when the low concentration measurement was performed, the output signal was too small,
To increase the output signal, the sample flow rate is increased to increase the luminescence, but on the other hand, the linearity in the high concentration range deteriorates, and the necessity of increasing the size of the reaction tank leads to an increase in cost, Various problems such as the necessity of preparing a plurality of tanks can be solved at once.

Further, since the output of each photodetector and the output of the adder are input to the abnormality determiner, it is possible to detect whether or not each photodetector is abnormal.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an example of a chemiluminescence gas analyzer according to the present invention, and FIG. 2 is a characteristic diagram showing a relationship between concentration and output. FIGS. (C) is an output characteristic diagram after adding the outputs of the two photodetectors. FIG. 3 is a configuration diagram showing a conventional example. 1 ... Reaction tank, 2 ... Sample gas inlet, 3 ... Ozone inlet, 4 ... Gas outlet, 5 ... Light transmission window, 10, 11 ...
Photodetector, 15: Adder, 17: Abnormality detector.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-50-147794 (JP, A) JP-A-57-53646 (JP, A) JP-A-60-2288941 (JP, A) JP-A-58-1983 160850 (JP, A)

Claims (1)

(57) [Scope of request for utility model registration] A sample gas inlet and an ozone inlet are provided at an upstream end of a reaction tank, and a gas outlet is provided at a downstream end of the reaction tank. A sample gas and ozone are introduced into the reaction tank. In a chemiluminescence gas analyzer configured to detect light emitted in the above, a plurality of light detectors are provided along a light transmission window formed in the reaction tank, and these light detectors are further combined with a sample gas and ozone. From the upstream side to the downstream side where they merge, and provided so as to cover substantially the entire surface of the light transmitting window by the light receiving surfaces of these photodetectors, and an adder for adding the output of each photodetector is provided. A chemiluminescence gas analyzer, comprising: an abnormality determiner that receives an output of a photodetector and an output of an adder to determine whether each photodetector is abnormal.