JPH06249809A - Gas concentration measuring device - Google Patents

Abstract

PURPOSE:To carry out only the measurement of concentration of various gases at a low cost without providing a function of qualitative analysis by utilizing changes of reflectance and transmissivity due to condensation of a measured gas component. CONSTITUTION:A standard gas wherein measured gas component concentration is already known as C1 is flown in a gas pipe 14 and a plane mirror 11 is cooled by a temperature regulator 13, and temperature of the plane mirror 11 in which reflectance reaches a predetermined value R1 is represented by T1. Similarly, with respect to respective standard gases having concentration C2, C3,..., temperature T2, T3,... are found when reflectance reaches the value R1 and an analytical curve in relation to the reflectance R1 is obtained. In the case of measuring a gas whose concentration is unknown, the measured gas whose concentration is unknown is flown in the gas pipe 14. A control and calculating device 16 regulates temperature of the plane mirror it through the temperature regulator 13 so that reflectance of the plane mirror 11 may reach R1. In the control and calculating device 16, temperature T' of the plane mirror 11 at that time is found and gas concentration C' is obtained in accordance with the retained analytical curve.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for measuring a gas to be measured flowing through a gas pipe in a plant or a gas concentration of the gas to be measured in a gas cell.

[0002]

2. Description of the Related Art There are various gas concentration measuring methods for measuring the concentration of gas flowing through a gas pipe and other gases.
For example, the method using a semiconductor detector can inexpensively and easily measure the gas concentration, but since the semiconductor detector has selectivity depending on the kind of gas, the kind of gas that can be measured by each detector It is fixed or constrained, and each dedicated detector is required depending on the type of gas.

Other measuring methods include an infrared spectrophotometer and a gas chromatograph. Infrared spectrophotometers and gas chromatographs are general-purpose analyzers for various gases, and qualitative and quantitative measurements of various gases are possible. However, these measuring devices are bulky and expensive.

[0004]

Since the type of gas flowing through the gas pipe in the plant is known in advance, a measuring device having a qualitative analysis function such as an infrared spectrophotometer or a gas chromatograph is not necessary. Therefore, an object of the present invention is to provide a gas concentration measuring device that does not have a qualitative analysis function and can inexpensively perform quantitative measurement of various gases, that is, only concentration measurement.

[0005]

According to the present invention, light is used to measure the concentration of a gas to be measured by utilizing changes in reflectance and transmittance due to condensation of a gas component to be measured. The gas concentration measuring device of the present invention, a glass surface arranged to be in contact with the gas to be measured, a temperature adjusting means for changing the temperature of the glass surface,
An optical system including at least a light source section for irradiating the glass surface with the measurement light and a photodetector for detecting reflected light or transmitted light of the measurement light by the glass surface, and the glass surface at a predetermined reflectance or transmittance Maintaining the relationship between the temperature and the concentration of the gas to be measured, taking in the output of the photodetector so that the reflectance or transmittance of the measuring light based on the output of the photodetector becomes the predetermined reflectance or transmittance. While adjusting the temperature of the glass surface through the temperature adjusting means,
The control / calculation means for applying the adjusted glass surface temperature to the above relationship between the glass surface temperature and the measured gas concentration to obtain the measured gas concentration.

[0006]

When the temperature of the glass surface in contact with the gas to be measured is lowered, the gas component to be measured is condensed on the glass surface when the concentration of the gas to be measured reaches the saturated vapor pressure at the temperature of the glass surface. Condensation of the gas component on the glass surface reduces the reflectance and the transmittance of the measuring light by the glass surface.

Prior to the measurement of the gas to be measured, a standard gas whose concentration of the gas to be measured is known is brought into contact with the glass surface, condensation occurs on the glass surface, and the reflectance or the transmittance of the glass surface is predetermined. The temperature of the glass surface when the value is reached is measured. By performing this measurement on a plurality of standard samples having different concentrations of the gas component to be measured, the relationship between the concentration of the gas component to be measured and the glass surface temperature at a predetermined reflectance or transmittance can be obtained. This relationship becomes a calibration curve.

In the measurement of the gas to be measured, the gas to be measured whose concentration is unknown comes into contact with the glass surface, and the temperature adjusting means is set so that the reflectance or the transmittance on the glass surface becomes the value when the calibration curve was created. The temperature of the glass surface is adjusted via. The gas concentration is obtained from the temperature at that time using a calibration curve.

[0009]

Embodiment FIG. 1 shows an embodiment. 14
Is a gas pipe in the plant, through which the measured gas 15 flows. The gas pipe 14 is made of transparent glass in a portion where the measuring device is installed, or a window plate made of transparent glass is provided at least in a portion where the measurement light is transmitted. The measurement side plane mirror 11 is provided on a part of the wall surface of the gas pipe 14.
Is mounted so that its mirror surface is exposed in the gas pipe 14 and is in direct contact with the gas 15 flowing in the gas pipe 14. A temperature controller 1 such as a Peltier device is provided on the back surface of the plane mirror 11.
3 is attached to adjust the temperature of the plane mirror 11. The reference side plane mirror 12 is provided on the wall surface of the other part of the gas pipe 14.
Is mounted so that its mirror surface is exposed in the gas pipe 14 and is in direct contact with the gas 15 flowing in the gas pipe 14.

An optical system for measuring the light reflected by the plane mirrors 11 and 12 and detecting the reflectance is provided on the opposite side of the plane mirrors 11 and 12 across the gas pipe 14. Reference numeral 1 denotes a white light source, and a collimator lens 2 is arranged in order to convert the measurement light from the light source 1 into a parallel light flux. In order to separate the measurement light into the measurement-side plane mirror 11 side and the reference-side plane mirror 12 side, the semitransparent mirror 4 is arranged in the optical path of the measurement light, and the measurement light transmitted through the semitransparent mirror 4 passes through the gas pipe 14. The optical system is arranged so that the light enters the measurement-side plane mirror 11 and is reflected by the plane mirror 11. In order to guide the reflected light from the plane mirror 11 to the measurement side photodetector 9, a semitransparent mirror 5 is arranged in the optical path, and a condensing lens for condensing the measurement light reflected by the semitransparent mirror 5 on the photodetector 9. 7 are arranged.

On the other hand, in order to change the direction of the measurement light reflected by the semi-transparent mirror 4 and make it enter the reference plane mirror 12, the semi-transparent mirror 6 is arranged, and the measurement light reflected by the plane mirror 12 is used as the reference side photodetector. A condensing lens 8 is arranged in order to lead to 10.

The detection output of the measurement side photodetector 9 and the detection output of the reference side photodetector 10 are fetched by the control / calculation device 16. The control / arithmetic unit 16 calculates the reflectance of the reflected light from the plane mirror 11 using the reflected light intensity from the plane mirror 12 as the reference light. The control / arithmetic unit 16 also controls the temperature controller 13 to change the temperature of the measuring-side flat mirror 11 and detect the temperature of the measuring-side flat mirror 11.

Next, the operation of the embodiment shown in FIG. 1 will be described. A standard gas having a known concentration of the gas component to be measured is flowed through the calibration curve creating gas pipe 14. The plane mirror 12 is at the gas temperature, and the plane mirror 12
The measured gas component does not condense on the top. The temperature of the plane mirror 11 is lowered by the temperature controller 13, the gas component is condensed on the plane mirror 11, and the plane mirror 11 becomes cloudy. The temperature at which the gas component is condensed on the plane mirror 11 is a temperature at which the concentration of the gas in the gas pipe 14 becomes the saturated vapor pressure of the component or a temperature below the temperature.

In the optical system, the light emitted from the light source 1 is collimated by the collimator lens 2 and a part of the light is reflected by the measurement side plane mirror 11 in the gas pipe, and the semitransparent mirror 5 changes its direction to change the direction of the condenser lens 7. After that, it reaches the photodetector 9. The measuring light reflected by the semi-transparent mirror 4 changes its direction by the semi-transparent mirror 6, is reflected by the plane mirror 12 which is not temperature-controlled, passes through the semi-transparent mirror 6 as it is, and the condensing lens 8
To reach the photodetector 10. As a result, the plane mirror 1
The reflectance (R of the plane mirror 11 using the light reflected by 2 as the reference light)
%) Is calculated by the control / arithmetic unit 16.

Now, when a known standard gas having a measured gas component concentration of C ₁ is flown through the gas pipe 14, when the plane mirror 11 is cooled by the temperature controller 13 and the reflectance reaches a predetermined value R _1. The temperature of the plane mirror 11 is T ₁ . Similarly, for the standard gases having different concentrations C ₂ , C ₃ , ..., Similarly, the temperatures T ₂ , T ₃ , ... Of the plane mirror 11 when the reflectance becomes R ₁ .
Ask for ... Thus, the standard gas measurement yields a calibration curve for a given reflectance R ₁ as shown in FIG. The reflectivity can be set to other values. The data of the obtained calibration curve is held in the control / calculation device 16.

Measurement of measured gas Next, the case of measuring a measured gas whose concentration is unknown will be described. A gas under measurement whose concentration is unknown is passed through the gas pipe 14. The controller / arithmetic unit 16 adjusts the temperature of the plane mirror 11 via the temperature controller 13 so that the reflectance of the plane mirror 11 becomes R ₁ . In the control / arithmetic unit 16, the plane mirror 1 at that time
The temperature T'of 1 is obtained, and the gas concentration C'is obtained as shown in FIG. 3 according to the calibration curve held.

In the embodiment, the control / calculation device 16 is made to perform the calculation operation for creating the calibration curve and calculating the concentration of the gas to be measured using the calibration curve, so that the measurement is easy. However, the operator may perform this calculation operation.

In the embodiment of FIG. 1, the plane mirror 11 is brought into direct contact with the gas to be measured, but as shown in FIG. 4, for example, a transparent glass window plate 17 is attached to the gas pipe 14 to condense the gas to be measured. May be generated on the surface of the window plate 17, and the plane mirror 11 may be arranged outside the window plate 17. In that case, since the temperature of the window plate 17 is changed, the temperature controller 13 is arranged around the window plate 17. In this case, the gas concentration is measured using the transmittance (absorption rate) of the window plate 17 as a parameter. Also, FIG.
In the embodiment, the measurement-side condenser lens 7 and the photodetector 9 may be arranged at the position of the plane mirror 11.

In order to improve the stability of the device and facilitate installation, the plane mirrors 11 and 12 in FIG. 1 may be replaced by corner cubes. Depending on the gas to be measured, if the measurement light is not white light and light in a limited wavelength range is advantageous, or if only a certain gas in the gas of a plurality of components is selectively measured, the plane mirror 11 or In order to irradiate the measuring light peculiar to the gas component condensed on the window plate 17,
In the optical system of FIG. 1, the bandpass filter 3 may be provided on the optical path between the collimator lens 2 and the semitransparent mirror 4. Further, when it is convenient to use light having a specific single wavelength according to the gas component to be measured as the measurement light, a laser can be used instead of the light source 1. Although the embodiment shows an embodiment in which the concentration of the gas to be measured flowing through the gas pipe 14 is measured, the present invention can be applied to measure the gas to be measured in the gas cell instead of the gas pipe 14. .

[0020]

As described above, according to the present invention, the gas concentration is measured by utilizing the relationship between the condensation temperature and the gas concentration of the gas component in the gas to be measured. Therefore, it is possible to use the conventional gas chromatograph and infrared spectrophotometer. It is not necessary to use a large-scale device,
With a simple structure, the gas concentration can be continuously monitored. This measuring device is particularly effective in monitoring the gas concentration flowing through the gas pipe in a continuously operated plant. Further, since a detector specific to gas is not used, various gases can be supported. Furthermore, if a spectral filter is added, it can be applied to the concentration measurement of multi-component gas.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment.

FIG. 2 is a diagram showing a calibration curve in the present invention.

FIG. 3 is a diagram showing a method of measuring a gas concentration using a calibration curve.

FIG. 4 is a schematic front sectional view of an essential part showing another embodiment.

[Explanation of symbols]

 1 light source 2 collimator lens 3 bandpass filter 4,5,6 semi-transparent mirror 7,8 condenser lens 9,10 photodetector 11, 12 plane mirror 13 temperature controller 14 gas pipe 15 flow of measured gas 16 control / calculation device

Claims (1)

[Claims] 1. A glass surface arranged in contact with a gas to be measured, temperature adjusting means for changing the temperature of the glass surface, a light source unit for irradiating the glass surface with measurement light, and measurement by the glass surface. An optical system including at least a photodetector that detects reflected light or transmitted light, and holds the relationship between the glass surface temperature and the measured gas concentration at a predetermined reflectance or transmittance, and the photodetector. While adjusting the temperature of the glass surface via the temperature adjusting means so that the reflectance or the transmittance of the measurement light based on the output of the photodetector becomes the predetermined reflectance or the transmittance. And a control / calculation means for determining the measured gas concentration by applying the adjusted glass surface temperature to the relationship between the glass surface temperature and the measured gas concentration. Place