JP3336384B2 - Method and apparatus for measuring the concentration of two types of gas mixtures - Google Patents

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 the concentration of a mixed gas composed of two types of gases, and more particularly to a device for measuring the concentration of a mixed gas without depending on the pressure of the gas to be measured and without decomposing the gas during measurement. Further, the present invention relates to a method for measuring the concentration so that the air-fuel mixture to be measured is not discarded after the measurement, and an apparatus for executing the method.

[0002]

2. Description of the Related Art Conventionally, when measuring the concentration of a mixed gas composed of two kinds of gases, for example, when measuring the ozone concentration in an ozone-oxygen mixed gas, it is specified that ozone is absorbed in ultraviolet rays but oxygen is hardly absorbed. There is known an ultraviolet absorbance measuring method in which a mixed gas is selected, the mixture is irradiated with the mixed gas, and the concentration is determined by measuring the absorptivity of ultraviolet.

[0003]

In such concentration measurement, the pressure of the mixed gas generally used is atmospheric pressure, and concentration measurement at other pressures has hardly been expected. Therefore, for example, when the ultraviolet absorption method is used for an ozone-oxygen mixture gas as described above, if the pressure of the mixture gas decreases, the ultraviolet absorbance decreases even if the ozone concentration is the same. Could not be measured accurately.

That is, for example, as in the case of the above example, when the mixed gas is measured by ultraviolet absorbance, when the concentration ratio of the mixed gas changes, the indicated value changes correspondingly, and the concentration and the physical property indicated value are changed. There is a correlation between Therefore, the concentration of the mixed gas can be obtained from the indicated value.
A schematic relationship between the indicated value and the gas mixture is shown by a curve p1 in FIG. However, a curve showing this correlation generally has pressure dependency, and when the pressure of the mixed gas changes, the correlation curve also changes as shown by p2 and p3 in FIG. Therefore, when the pressure fluctuated, the concentration could not be obtained.

[0005] Further, in the concentration measurement method by the light absorption method as described above, a light source such as a lamp is required. However, this lamp has a finite life, requires regular replacement, and requires maintenance. It was troublesome. Further, in the method of measuring concentration using the absorbance of the ultraviolet light, since the absorption wavelength is different for each type of gas, it is impossible to handle a plurality of mixed gases with one ultraviolet lamp, In some cases, there is no light source that generates a necessary light wavelength, and thus lacks versatility.

On the other hand, there is a measuring method utilizing the principle of measuring the decomposition rate of a gas mixture by adding heat or light in the concentration measuring method. However, in such a measuring method, explosion occurs when heat or light is added. -There was a risk of explosion or ignition when measuring the concentration of a flammable gas mixture. For example,
If the ozone concentration exceeds 50% in an ozone-oxygen gas mixture at atmospheric pressure, there is a risk of explosion when ignited. Therefore, there is a danger in the measurement of high-concentration ozone gas in the ultraviolet absorption method involving ozone decomposition by light irradiation. there were.

In the above-described measuring method based on the principle of measuring the decomposition rate by applying heat or light, for example, in the case of an ozone-oxygen mixed gas, ozone in the sampled mixed gas is decomposed by irradiation of ultraviolet rays. Since it becomes oxygen, the ozone concentration in the mixed gas decreases. For this reason, a high-accuracy concentration measurement requires a large amount of sampling of the mixed gas so that a change in the mixed gas concentration due to ozonolysis can be ignored. In addition, since the concentration of the gas mixture to be measured changes depending on the measurement, a means for discarding the sampled gas and not mixing it with the non-measured gas is required.

Further, there is a method of performing chemical analysis at another place after extracting a part of the gas mixture. In this case, since the gas concentration changes with time, it is necessary to know the concentration in real time. In some cases, this was inconvenient in terms of immediacy.

Therefore, the present invention can accurately measure the concentration even if the pressure changes, does not require an ultraviolet lamp having a specific wavelength, is easy to maintain, and can apply heat or light. Since there is no danger of explosive ignition as in the method of measurement and there is no decomposition of the gas to be measured, there is no need to prepare a large amount of sampling gas, and it is not necessary to dispose of it. It is an object of the present invention to provide a method for measuring the concentration of a mixture of two kinds of gases and a concentration measuring device for performing the method, wherein the concentration can be measured immediately.

[0010]

Means for Solving the Problems In order to solve the above-mentioned conventional problems, the invention according to claim 1 of the present application is directed to a method for measuring the concentration of a mixed gas in which two types of mixed gases are known in advance. Obtain physical property value data corresponding to the concentration, measure the pressure of the gas mixture to be measured by a pressure measuring device sensitive to the physical property value, and simultaneously measure the pressure of the gas by a pressure measuring device that is not affected by the physical property value Then, a physical property value of the mixed gas is obtained from the measured values of the two pressures, and a concentration is obtained from the physical property values.

Further, according to a second aspect of the present invention, as the pressure measuring device sensitive to the physical property value, a plurality of pressure measuring devices having different characteristics are simultaneously used to simultaneously measure the pressure of the mixed gas to be measured, and each pressure measurement is performed. 2. The method for measuring the concentration of a mixed gas of two types according to claim 1, wherein a physical property value of the mixed gas is determined from the measured value and a measured value of a pressure measuring device which is not affected by the physical property value.

Further, in the invention according to claim 3, the physical property value is viscous, a quartz friction vacuum gauge or a spinning rotor gauge is used as a pressure measuring device sensitive to the physical property value, and the pressure measurement is not affected by the physical property value. 3. The device according to claim 1, wherein a diaphragm gauge is used as the device.
This is a method for measuring the concentration of a mixed gas.

According to a fourth aspect of the present invention, there is provided an apparatus for measuring the concentration of a mixture of two kinds of gases, the constituent gases of which are known in advance, a pressure measuring apparatus which is sensitive to physical properties, and which is not affected by the physical properties. A pressure measuring device, and a concentration calculating means for inputting the pressure values from the two pressure measuring devices to obtain a physical property value and for obtaining a concentration based on data of a physical property value corresponding to a concentration previously obtained from the physical property value. This is a device for measuring the concentration of two types of mixed gas.

The invention according to claim 5 is characterized in that a plurality of pressure measuring devices having different characteristics from each other are provided as the pressure measuring device sensitive to the physical property value. Is a concentration measuring device.

The invention according to claim 6 uses a quartz friction vacuum gauge or a spinning rotor gauge as the pressure measuring device sensitive to the physical property value, and uses a diaphragm gauge as a pressure measuring device not affected by the physical property value. An apparatus for measuring the concentration of a mixture of two kinds of gases according to claim 4 or claim 5.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The basic principle of the present invention is to measure the physical properties of a gas mixture as a function of viscosity, thermal conductivity, density, molecular weight, and the like, and to determine the properties of a gas based on the physical properties inherent in a pure gas. This adopts a method of calculating the concentration. More specifically, the probe A is sensitive to pressure and physical property values such as viscosity.
And, by simultaneously measuring the target gas mixture using the probe B sensitive only to pressure, and calculating the physical property values of the mixed gas, such as viscosity, by removing the influence of the pressure by arithmetic processing, according to the physical property values This is to determine the concentration of the mixed gas.

The measuring pressure range can be further expanded by adding a measuring element C corresponding to a range other than the target pressure range of the measuring element A to the measuring element A and the measuring element B. In addition, concentration calibration is performed by mixing two kinds of pure gases constituting the mixed gas at a known ratio in advance to prepare standard gases of various concentrations, and actually measuring the standard gases with the concentration measuring device to obtain a calibration curve. hand,
The calibration can be performed by recording this calibration curve in a concentration calculator.

Examples of the measuring element used in the present invention include:
For example, a liquid column differential gauge, compression gauge, diaphragm gauge, Bourdon tube gauge, etc., which are sensitive only to pressure, change depending on pressure, and change the frictional force that a moving solid receives from gas. A pressure gauge can be used which changes any of the physical quantities such as the change in thermal conductivity to the heat and the heat generated by decomposition when the gas reacts near the solid surface.

Examples of the pressure gauge whose physical quantity changes as the pressure changes include, for example, a quartz friction gauge and a spinning rotor gauge using viscosity (friction), a thermocouple gauge and a Pirani gauge using heat conduction, and others. A Knudsen vacuum gauge or the like can be used, and for example, a hot cathode ionization vacuum gauge, a cold cathode ionization vacuum gauge, a radiation ionization vacuum gauge, or the like utilizing an ionization phenomenon can be used. These probes can be used properly depending on the properties of gas such as flammability and explosiveness, the concentration and pressure of the target mixed gas.

FIG. 1 shows an outline of an apparatus for implementing the present invention. As shown in the figure, a communication pipe is connected to a pipe 4 to which a mixed gas to be measured is supplied, and an absolute pressure at which a measured value does not change due to physical properties such as viscosity and molecular density of the mixed gas is applied to the communication pipe. An absolute pressure measuring element 1 that can be measured, and a pressure measuring element whose display pressure changes due to physical properties such as viscosity of a gas and whose characteristics are known in advance;
That is, the pressure / physical property measuring element 2 is connected. Further, the data of the absolute pressure gauge 1 and the pressure / physical gauge 2 are inputted, and based on the physical property values inherent to the pure gas, the concentration of the mixed gas and the data showing the relationship between the displayed pressure changed by the physical property values are used. Is provided.

Based on the above-described basic principle of the concentration measurement according to the present invention, the measurement can be performed by a specific apparatus as shown in FIG. 2, for example. In the device shown in FIG.
It is an embodiment of a measurement device for ozone oxygen mixed gas,
A diaphragm gauge 5 is used as an absolute pressure gauge. The diaphragm gauge 5 can obtain the absolute value of the gas pressure irrespective of the physical property value, and thereby can measure the absolute value of the gas pressure irrespective of the type of gas.

A quartz friction vacuum gauge 6 is used as a pressure / physical property measuring element. FIG. 3 shows the characteristics of the quartz friction vacuum gauge 6. This indicates that, as shown in Table 1, for example, the indication value of the quartz friction vacuum gauge indicates an apparently different pressure depending on the difference between the molecular weight and the viscosity coefficient of the gas. The reason for this is that the frictional force between the quartz crystal vibrator and the quartz crystal vibrator in contact with the gas is proportional to the 1/2 power of the product of the molecular weight of the gas and the viscosity coefficient of the gas when the pressure is in the viscous flow range. It arises from doing This quartz friction vacuum gauge operates at normal temperature, and the contact surface to gas is gold, quartz,
Only stainless steel, there is no factor to decompose ozone.

[Table 1]

FIG. 4 shows the results of actual measurements used to create a calibration curve for calibrating the measuring device, which was obtained by measuring a standard gas of ozone / oxygen mixture concentration (ozone concentration 5%, oxygen concentration 95%) with the measuring device. is there. When the pressure of the mixed gas is measured, the quartz friction vacuum gauge apparently has a larger pressure indication value than the pure oxygen pressure measurement due to the mixing of ozone gas having a large viscosity and a high molecular weight. A calibration curve is created based on the measured values, stored in a concentration calculator, and the concentration is calculated. Such calibration curve data can be measured in advance according to each mixing ratio, and the mixing ratio is determined based on the measured value of the diaphragm gauge pressure indicating the absolute pressure and the indicated pressure value of the quartz friction gauge. Obtainable.

FIG. 5 shows an apparatus of the embodiment shown in FIG.
Further, an embodiment of a concentration measuring device constituted by three kinds of vacuum gauges by connecting a spinning rotor gauge 13 to a communicating pipe of a pipe 15 will be described. As described above, the diaphragm vacuum gauge 11 measures the absolute pressure irrespective of the type of gas, and the quartz friction vacuum gauge 2 is sensitive to both the physical properties of the viscosity and molecular weight of the gas and the pressure. ⁻² pa to 10 ⁵ pa, and the spinning rotor gauge 13 is sensitive to both the physical property value of the viscosity and molecular weight of gas and the pressure similarly to the quartz friction vacuum gauge 12, and the working pressure range is 10 ⁻⁵ Pa to 10 ⁻⁵ Pa. 1 Pa. FIG. 6 shows the characteristics of the spinning rotor gauge 5,
This probe can measure a region having a higher degree of vacuum than the quartz friction vacuum gauge.

Therefore, in the concentration calculator 14 shown in FIG.
3, the concentration can be calculated based on the display value of the quartz friction vacuum gauge 12 in a low region, so that more accurate concentration calculation can be performed. Use both values in the valid range of values,
By calculating and removing the influence of the pressure to obtain the physical property value of the gas, the concentration of the gas can be calculated more accurately.

[0027]

According to the present invention, the above-described measuring method is adopted and the measuring apparatus is used. Therefore, even when the pressure of the mixed gas is other than the atmospheric pressure, and even when the pressure changes, an accurate concentration is always obtained. Can be measured. In addition, since a method that does not irradiate heat or light can be adopted, even a mixed gas that explodes due to stimulation by heat or light can be safely measured. In addition, maintenance is easy without the need for an ultraviolet lamp or the like having a specific wavelength, and the concentration can be measured immediately in response to a change in gas concentration.

In the case where a plurality of pressure measuring devices having different characteristics are used as pressure measuring devices sensitive to the physical property values, the physical property values are obtained by using the most appropriate portions of the respective characteristics, thereby obtaining the mixing ratio. So that
A more accurate concentration measuring device can be obtained.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a measuring instrument for explaining a measuring principle of the present invention.

FIG. 2 is a configuration diagram of a measuring instrument according to a first embodiment of the present invention.

FIG. 3 is a graph showing characteristics of a quartz friction vacuum gauge used in an example of the present invention.

FIG. 4 is a graph showing an example of a difference between indicated values of a diaphragm gauge and a quartz friction gauge used in an embodiment of the present invention.

FIG. 5 is a configuration diagram of a measuring instrument according to a second embodiment of the present invention.

FIG. 6 is a characteristic diagram of a spinning rotor gauge used in an example of the present invention.

FIG. 7 is a characteristic diagram showing pressure dependency of a conventional densitometer.

[Explanation of symbols]

 Reference Signs List 1 Absolute pressure gauge 2 Pressure / physical property gauge 3 Concentration calculator 4 Piping 5 Diaphragm gauge 6 Quartz friction gauge 13 Spinning rotor gauge

────────────────────────────────────────────────── ─── Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01N 7/00 G01L 21/00 JICST file (JOIS)

Claims (6)

(57) [Claims] 1. A method for measuring the concentration of a mixture of two kinds of gases in which constituent gases are known, wherein data of physical property values corresponding to the concentration of the mixed gas is obtained, and measured by a pressure measuring device sensitive to the physical property values. Measure the pressure of the mixed gas, simultaneously measure the pressure of the same gas with a pressure measuring device that is not affected by the physical property values, obtain the physical property value of the mixed gas from both the measured pressure values, and obtain the concentration from the physical property values A method for measuring the concentration of two types of mixed gas, characterized by the following. 2. As a pressure measuring device sensitive to the physical property value, a plurality of pressure measuring devices having different characteristics are simultaneously used to simultaneously measure the pressure of the mixed gas to be measured, and each pressure measured value and the physical property value are affected. 2. The physical property value of a gas mixture is determined from a measured value of a pressure measuring device that does not receive the pressure.
The method for measuring the concentration of two kinds of mixed gases described in the above. 3. The physical property value is made viscous, a quartz friction vacuum gauge or a spinning rotor gauge is used as a pressure measuring device sensitive to the physical property value, and a diaphragm gauge is used as a pressure measuring device not affected by the physical property value. 3. The method for measuring the concentration of two types of gas mixtures according to claim 1 or 2, characterized in that: 4. A concentration measuring device for a mixture of two kinds of gases in which constituent gases are known, a pressure measuring device sensitive to a physical property value, a pressure measuring device not affected by the physical property value, Concentration calculating means for obtaining a physical property value by inputting a pressure value from the apparatus and obtaining a concentration based on data of a physical property value corresponding to a density obtained in advance from the physical property value. Device for measuring the concentration of mixed gas. 5. The apparatus for measuring the concentration of a mixture of two kinds of gases according to claim 4, wherein a plurality of pressure measuring apparatuses having different characteristics are provided as the pressure measuring apparatus sensitive to the physical property values. 6. A quartz friction vacuum gauge or a spinning rotor gauge is used as a pressure measuring device sensitive to the physical property value,
6. The apparatus for measuring the concentration of a mixture of two kinds of gases according to claim 4, wherein a diaphragm gauge is used as a pressure measuring apparatus which is not affected by physical properties.