JP2015055565A - Magnetic oxygen analysis method and magnetic oxygen analyzer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic oxygen analyzer capable of measuring an oxygen concentration of a measurement gas with high sensitivity while allowing reduction in device cost.SOLUTION: The magnetic oxygen analyzer comprises: a sample flow passage 3; a measurement gas inlet 4 and a measurement gas outlet 5 formed on both ends of the sample flow passage; a first auxiliary gas flow inlet 6 and a second auxiliary gas flow inlet 7 provided on the sample flow passage on a measurement gas outlet side so as to oppose each other; an auxiliary gas flow passage 8 connected to the first and second auxiliary gas flow inlets; a bypass flow passage 11 communicating the auxiliary gas flow passage on a first auxiliary gas flow inlet side with the auxiliary gas flow passage on a second auxiliary gas flow inlet side; and a hot-wire sensor 12 disposed in the bypass flow passage. A gas (at least one kind of gases among Xe, Kr, COand Ar) as an auxiliary gas, which has low heat conductivity and large specific weight in comparison with reference gases, including N, Oand air, that are selected depending on the concentration of the measurement gas, is used.

Description

  The present invention relates to a magnetic oxygen analysis method and a magnetic oxygen analyzer.

The measurement principle of the magnetic oxygen analyzer will be described with reference to FIGS. 3A to 3C (see, for example, Patent Document 1).
FIG. 3A shows the relationship between oxygen molecules and a magnetic field when a means (magnet) for generating a magnetic field is provided in a gas containing oxygen. As shown in FIG. 3 (B), a force that attracts oxygen acts on a portion where the magnetic field is strong and the strength changes (the end of the magnetic pole that is a non-uniform magnetic field), and the end of the magnetic pole The right force and the left force are pressed against each other and balanced, and oxygen molecules are attracted by the influence of the magnetic field and move into the magnetic field (magnet gap). As a result, as shown in FIG. 3C, the pressure (concentration) of the attracted oxygen is higher in the magnetic field than in the magnetic field.

As a magnetic oxygen analyzer adopting the above-described measurement principle, for example, an apparatus described in Patent Document 2 is known.
The magnetic oxygen analyzer described in Patent Document 2 is formed in an annular shape, and a magnetic field application region is provided in the measurement side sample flow path and the comparison side sample flow path of the divided measurement gas and the measurement side sample flow path. Magnetic field generating means to be formed; first and second auxiliary gas flow paths for flowing the same amount of auxiliary gas conducted to opposite positions of the measurement side and comparison side sample flow paths; and the first and second Each of the first and second flow paths that are branched in the same parallel direction from the auxiliary gas inlet, and each of the first and second flow paths that are branched in the same parallel direction. It is an apparatus provided with the arrange | positioned 1st and 2nd heat ray sensor, 1st flow path, and the detection means which detects oxygen concentration based on the signal obtained from the 1st and 2nd heat ray sensor.

And this apparatus flows so that the measurement gas introduce | transduced from the measurement gas introduction port may be diverted into two directions, a measurement side sample flow path and a comparison side sample flow path, and it may merge with a measurement gas outlet.
Further, the auxiliary gas introduced from the auxiliary gas introduction port passes through the first and second auxiliary flow paths where the first and second heat ray sensors are arranged, and passes through the first and second auxiliary gas flow paths. The measurement gas flows through the measurement side sample flow path and the comparison side sample flow path and flows to the measurement gas outlet.

Under such circumstances, when oxygen molecules are not included in the measurement gas, the output signal obtained from the first heat ray sensor is the same as the output signal obtained from the second heat ray sensor, and the detection means is Output when the oxygen concentration in the measurement gas is “0” (zero).
On the other hand, when oxygen molecules are contained in the measurement gas, the oxygen molecules in the measurement gas are attracted by the magnetic force action of the magnetic field application region formed in the measurement-side sample flow path, and a partial flow is generated. For this reason, a difference occurs between the flow rate of the auxiliary gas passing through the first heat ray sensor and the flow rate of the auxiliary gas passing through the second heat type flow rate sensor 18b, and the output signal of the first heat ray sensor and the second The output signals of the hot wire sensors are not the same, and the detection means shows a value corresponding to the molecular weight of oxygen in the measurement gas.

FIG. 3 of JP 2004-325098 A 1 and 2 of JP 2004-325368 A

By the way, although the measurement range put into practical use in the magnetic oxygen analyzer is 1 to 2%, in recent years, in order to measure low concentration oxygen such as purity monitoring of a produced gas or process gas, The demand for measuring oxygen concentration with high sensitivity is increasing.
In order to increase the measurement sensitivity of oxygen concentration, improve the magnetic properties of the magnetic material of the magnetic field generation means, increase the number of turns of the coil to increase the magnetic field strength of the magnetic field application area, the drive current and frequency of the detection means Although optimization etc. can be considered, if it does in this way, there exists a possibility that apparatus cost may rise by the rise of components, the enlargement of an apparatus, etc.

  The present invention has been made in view of the above circumstances, and provides a magnetic oxygen analyzer and a magnetic oxygen analyzer capable of measuring the oxygen concentration in a measurement gas with high sensitivity while reducing the apparatus cost. The purpose is to do.

  In order to achieve the above object, a magnetic oxygen analysis method according to an aspect of the present invention includes a sample channel, a measurement gas inlet and a measurement gas outlet formed at both ends of the sample channel, and the measurement gas outlet. A first auxiliary gas inlet and a second auxiliary gas inlet provided opposite to each other on the side of the sample flow path, an auxiliary gas flow path connected to the first and second auxiliary gas inlets, A bypass channel communicating the auxiliary gas channel on the first auxiliary gas inlet side and the auxiliary gas channel on the second auxiliary gas inlet side, and a heat ray sensor disposed in the bypass channel, A change in the flow rate of the bypass channel caused by supplying the auxiliary gas from an intermediate position of the auxiliary gas channel and applying a magnetic field to the sample channel near the first auxiliary gas inlet is detected by the hot wire sensor. By doing In the magnetic oxygen analysis method for calculating the oxygen concentration contained in the measurement gas, as the auxiliary gas, a gas having a low thermal conductivity and a large specific gravity compared to a reference gas selected according to the concentration of the measurement gas Is used.

In the magnetic oxygen analysis method according to one embodiment of the present invention, it is preferable that the auxiliary gas includes at least one gas selected from Xe, Kr, CO ₂ , and Ar.
Here, the reference gas is N ₂ , O ₂ , Air (air).
According to the magnetic oxygen analysis method according to one aspect of the present invention, the thermal conductivity is low and the specific gravity is large as compared with the reference gas (N ₂ , O ₂ , Air, etc.) selected according to the concentration level of the measurement gas. When at least one kind of gas of Xe, Kr, CO ₂ , and Ar is used as an auxiliary gas, the output value of the heat ray sensor becomes high even when detecting low concentration oxygen in the measurement gas.

Further, the auxiliary gas having a specific gravity larger than that of the reference gas such as N ₂ , O ₂ , Air (air), etc., is less likely to cause flow rate fluctuations even when subjected to vibration from a plant or the like disposed around.
The magnetic oxygen analyzer according to one aspect of the invention includes a sample flow path, a measurement gas inlet and a measurement gas outlet formed at both ends of the sample flow path, and the sample flow path on the measurement gas outlet side. A first auxiliary gas inlet and a second auxiliary gas inlet provided opposite to each other, an auxiliary gas flow path connected to the first and second auxiliary gas inlets, and the first auxiliary gas inlet side A bypass passage communicating the auxiliary gas passage and the auxiliary gas passage on the second auxiliary gas inlet side, and a heat ray sensor disposed in the bypass passage, By detecting the flow rate change of the flow path of the bypass flow path caused by supplying the auxiliary gas from a position and applying a magnetic field to the sample flow path near the first auxiliary gas inlet, In the measurement gas The magnetic oxygen analyzer for calculating the Murrell oxygen concentration, as the auxiliary gas, the compared with a reference gas selected by the concentration of the measurement gas low thermal conductivity, was used and the specific gravity is larger gas.

In the magnetic oxygen analyzer according to one embodiment of the present invention, it is preferable that the auxiliary gas includes at least one gas selected from Xe, Kr, CO ₂ , and Ar.
According to the magnetic oxygen analyzer of one aspect of the present invention, the oxygen concentration in the measurement gas can be measured with high sensitivity, and the magnetic field strength in the magnetic field generation region is increased in order to increase the measurement sensitivity of the oxygen concentration. Alternatively, no mechanism or device for increasing the accuracy of the detection circuit is used, and an increase in the number of components and an increase in the size of the device can be suppressed.

According to the magnetic oxygen analysis method of the present invention, a gas having a low thermal conductivity and a large specific gravity is used as an auxiliary gas compared to a reference gas selected according to the concentration level of the measurement gas. Even when a low concentration of oxygen is detected, the output value of the heat ray sensor becomes high, and the oxygen concentration in the measurement gas can be measured with high sensitivity.
Further, according to the magnetic oxygen analyzer of the present invention, the oxygen concentration in the measurement gas can be measured with high sensitivity, and the magnetic field strength in the magnetic field generation region is increased in order to increase the measurement sensitivity of the oxygen concentration. Alternatively, no mechanism or device for increasing the accuracy of the detection circuit is used, and an increase in the number of parts and an increase in the size of the device are suppressed, so that the device cost can be reduced.

1 is a schematic configuration diagram showing a magnetic oxygen analyzer according to an embodiment of the present invention. It is a graph shown about the characteristic of the kind of auxiliary gas used with the magnetic oxygen analyzer of one embodiment concerning the present invention. It is a figure which shows the measurement principle of a magnetic oxygen analyzer.

DESCRIPTION OF EMBODIMENTS Hereinafter, modes for carrying out the present invention (hereinafter referred to as embodiments) will be described in detail with reference to the drawings.
FIG. 1 shows a magnetic oxygen analyzer according to an embodiment of the present invention. A sample cell 1 having a flow path for flowing a measurement gas, and a hot wire sensor 12 installed in the sample cell 1 are shown. It comprises a detection circuit 2 for detecting the oxygen concentration contained in the measurement gas by a signal.

  The sample cell 1 includes a cylindrical sample flow path 3, a measurement gas introduction port 4 provided in communication with one end side in the axial direction of the sample flow path 3, and the other end side in the axial direction of the sample flow path 3. The first auxiliary gas provided in communication with the measurement gas outlet 5 and the sample channel 3 on the measurement gas outlet 5 side and provided opposite to each other from the radial direction perpendicular to the axial direction of the sample channel 3 The auxiliary gas flowing into the gas inlet 6 and the second auxiliary gas inlet 7 and the auxiliary gas supply flow path 8 is supplied at the same flow rate from the first auxiliary gas inlet 6 and the second auxiliary gas inlet 7 to the sample flow path 3. The pole piece (() forms the region of the magnetic field Mf in the vicinity of the first auxiliary gas branch flow path 9 and the second auxiliary gas branch flow path 10 to be supplied with the first auxiliary gas inlet 6 of the sample flow path 3 communicates (Not shown), the first auxiliary gas branch channel 9 and the second auxiliary gas branch channel It includes a bypass flow path 11 communicating, to 0.

And the heat ray sensor 12 is arrange | positioned in the intermediate position of the bypass flow path 11, and the detection circuit 2 is connected to this heat ray sensor 12. FIG.
The heat ray sensor 12 changes in voltage according to a resistance change accompanying a temperature change due to contact with the auxiliary gas in the bypass flow path 11, and outputs a signal of the voltage change to the detection circuit 2. The detection circuit 2 detects the oxygen concentration contained in the measurement gas by receiving and amplifying the voltage signal from the hot wire sensor 12.

  In the magnetic oxygen analyzer having the above configuration, the measurement gas introduced from the measurement gas inlet 4 of the sample cell 1 flows toward the measurement gas outlet 5. In addition, the auxiliary gas supplied from the auxiliary gas supply flow path 8 is divided into the first auxiliary gas branch flow path 9 and the second auxiliary gas branch flow path 10, and the first auxiliary gas inlet 6 and the second auxiliary gas flow. It flows into the sample channel 3 from the inlet 7, merges with the measurement gas, and flows to the measurement gas outlet 5. Further, a part of the auxiliary gas that is branched from the auxiliary gas supply flow path 8 to the first auxiliary gas branch flow path 9 and the second auxiliary gas branch flow path 10 is a bypass flow path that is connected to the first auxiliary gas branch flow path 9. 11 flows from the bypass flow path 11 connected to the second auxiliary gas branch flow path 10 toward the flow sensor 12.

  And when oxygen molecules are not contained in the measurement gas, even if the magnetic field Mf is applied in the vicinity of the first auxiliary gas inlet 6 of the sample flow path 3, oxygen molecules are not attracted, The pressure does not increase. Thereby, the fluid resistance when the auxiliary gas flows out from each of the first auxiliary gas branch flow path 9 and the second auxiliary gas branch flow path 10 to the sample flow path 3 becomes the same, and the first auxiliary gas branch flow path 9 The flow rate of the auxiliary gas passing through the flow rate sensor 12 in the bypass flow path 11 is the same as the flow rate of the auxiliary gas passing through the flow rate sensor 12 in the bypass flow path 11 from the second auxiliary gas branch flow path 10. Thereby, the signal of the flow sensor 12 is not obtained, and the detection circuit 2 does not detect the oxygen concentration.

  On the other hand, when oxygen molecules are contained in the measurement gas, when the magnetic field Mf is applied in the vicinity of the first auxiliary gas inlet 6 of the sample flow path 3, the oxygen molecules are attracted to that portion (see FIG. 5 (C)), the pressure increases due to the cohesive pressure of oxygen. Therefore, the fluid resistance when the auxiliary gas flows out from the first auxiliary gas branch flow path 9 to the sample flow path 3 increases, and the outflow amount decreases. On the contrary, in the vicinity of the second auxiliary gas inlet 7 of the sample flow path 3, the magnetic resistance Mf is not applied since the magnetic field Mf is not applied, so that the fluid resistance does not increase. Outflow increases.

  Thereby, the auxiliary gas is the first auxiliary gas at the point P0 (hereinafter referred to as the branch point P0) where the auxiliary gas supply flow path 8 branches to the first auxiliary gas branch flow path 9 and the second auxiliary gas branch flow path 10. The diversion ratio at the time of branching to the branch channel 9 and the second auxiliary gas branch channel 10 changes, and the flow rate of the auxiliary gas from the first auxiliary gas branch channel 9 via the flow sensor 12 in the bypass channel 11 A difference occurs in the flow rate of the auxiliary gas passing through the flow rate sensor 12 in the bypass flow channel 11 from the second auxiliary gas branch flow channel 10, and the flow rate sensor 12 obtains a signal of change in the flow rate of the auxiliary gas. Detects the oxygen concentration of the measurement gas.

Here, with reference to FIG. 2, the kind of auxiliary gas of this embodiment is demonstrated.
In a conventional magnetic oxygen analyzer, N ₂ , O ₂ , and Air (air) are used as auxiliary gases. These N ₂ , O ₂ , and Air are gases selected according to the concentration level of the measurement gas, and are hereinafter referred to as reference gases.
In the present embodiment, as shown in FIG. 2, at least one gas of Xe (xenon), Kr (krypton), CO ₂ (carbon dioxide), and Ar (argon) is used as an auxiliary gas.

These Xe, Kr, CO ₂ , and Ar are gases having a lower thermal conductivity and a higher specific gravity (specific gravity with respect to air 1) than a reference gas (for example, N ₂ is a reference gas). Although not shown in FIG. 2, the thermal conductivity of O ₂ is 0.0229 (W / (m · K)), the specific gravity is about 1.1053, and the thermal conductivity of Air is 0.0241 (W / (M · K)) and the specific gravity is 1.
As described above, when the gas having a low thermal conductivity and a large specific gravity is used as the auxiliary gas, for example, when CO ₂ and Ar are used as the auxiliary gas, the output of the heat ray sensor 12 is twice that of the reference gas. A value can be obtained, and when Xe is used as an auxiliary gas, the output value of the hot wire sensor 12 can be obtained three times that of the reference gas.

As described above, when Xe, Kr, CO ₂ , and Ar having a low thermal conductivity and a large specific gravity are used as auxiliary gas, it is easy to take a lot of heat from the heat ray sensor 12, so that the output value of the heat ray sensor 12 is high. It becomes.
In addition, the auxiliary gas having a specific gravity larger than that of the reference gas such as N ₂ , O ₂ , Air (air), etc., is less likely to cause fluctuations in flow rate even when subjected to vibration from a plant or the like disposed around.

Here, the measurement gas inlet according to the present invention corresponds to the measurement gas inlet 4, the measurement gas outlet according to the present invention corresponds to the measurement gas outlet 5, and the auxiliary gas flow path according to the present invention is the first auxiliary gas. It corresponds to the branch channel 9 and the second auxiliary gas branch channel 10.
Next, the effect of this embodiment is demonstrated.
According to the present embodiment, Xe, Kr, CO ₂ , and Ar are low in thermal conductivity and large in specific gravity as compared with a reference gas (N ₂ , O ₂ , Air, etc.) selected according to the concentration level of the measurement gas. If at least one kind of gas is used as an auxiliary gas, the output value of the heat ray sensor 12 becomes high even when detecting low concentration oxygen in the measurement gas, so the oxygen concentration in the measurement gas is measured with high sensitivity. can do.

In addition, the auxiliary gas having a specific gravity larger than that of the reference gas such as N ₂ , O ₂ , Air (air), etc., is less likely to generate flow rate fluctuations even when subjected to vibration from a plant or the like disposed around it. It is possible to measure the oxygen concentration of the measurement gas with high accuracy.
Furthermore, in order to increase the measurement sensitivity of the oxygen concentration, the magnetic field strength in the region of the magnetic field Mf is increased, or no mechanism or device for increasing the accuracy of the detection circuit is used. Since the increase in size is suppressed, the cost of the apparatus can be reduced.

DESCRIPTION OF SYMBOLS 1 ... Sample cell, 2 ... Detection circuit, 3 ... Sample flow path, 4 ... Measurement gas inlet, 5 ... Measurement gas outlet, 6 ... 1st auxiliary gas inlet, 7 ... 2nd auxiliary gas inlet, 8 ... Auxiliary gas supply channel, 9 ... first auxiliary gas branch channel, 10 ... second auxiliary gas branch channel, 11 ... bypass channel, 12 ... heat ray sensor

Claims (4)

A sample flow path, a measurement gas inlet and a measurement gas outlet formed at both ends of the sample flow path, and a first auxiliary gas flow inlet and a first gas flow path provided opposite to the sample flow path on the measurement gas outlet side 2 auxiliary gas inlets, auxiliary gas passages connected to the first and second auxiliary gas inlets, the auxiliary gas passages on the first auxiliary gas inlet side, and the second auxiliary gas inlet side A bypass passage communicating with the auxiliary gas passage and a heat ray sensor disposed in the bypass passage, supplying the auxiliary gas from an intermediate position of the auxiliary gas passage, and supplying the first auxiliary gas flow In the magnetic oxygen analysis method for calculating the oxygen concentration contained in the measurement gas by detecting a change in the flow rate of the bypass flow path caused by applying a magnetic field to the sample flow path near the inlet with the heat ray sensor. ,
A magnetic oxygen analysis method characterized in that a gas having a low thermal conductivity and a large specific gravity is used as the auxiliary gas as compared with a reference gas selected according to the concentration of the measurement gas. The magnetic oxygen analysis method according to claim 1, wherein the auxiliary gas includes at least one kind of gas selected from Xe, Kr, CO ₂ and Ar. A sample flow path, a measurement gas inlet and a measurement gas outlet formed at both ends of the sample flow path, and a first auxiliary gas flow inlet and a first gas flow path provided opposite to the sample flow path on the measurement gas outlet side 2 auxiliary gas inlets, auxiliary gas passages connected to the first and second auxiliary gas inlets, the auxiliary gas passages on the first auxiliary gas inlet side, and the second auxiliary gas inlet side A bypass passage communicating with the auxiliary gas passage and a heat ray sensor disposed in the bypass passage, supplying the auxiliary gas from an intermediate position of the auxiliary gas passage, and supplying the first auxiliary gas flow Magnetic oxygen analysis for calculating the oxygen concentration contained in the measurement gas by detecting a change in the flow rate of the bypass channel caused by applying a magnetic field to the sample channel near the inlet by the heat ray sensor In total Stomach,
A magnetic oxygen analyzer characterized in that a gas having a low thermal conductivity and a large specific gravity is used as the auxiliary gas as compared with a reference gas selected according to the concentration of the measurement gas. The magnetic oxygen analyzer according to claim 3, wherein the auxiliary gas contains at least one kind of gas selected from Xe, Kr, CO ₂ and Ar.

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