JP7388269B2 - gas detection device - Google Patents

Description

The present invention relates to a gas detection device.

BACKGROUND ART A non-dispersive infrared absorption (NDIR) gas analyzer that measures the concentration of sulfur dioxide, nitrogen oxides, etc. in flue gas is known (for example, see Patent Document 1). The gas analyzer described in Patent Document 1 includes a light source that irradiates infrared rays, a sample cell and a compensation cell to which infrared rays are alternately incident, a detector that detects the intensity of infrared rays, and a concentration sensor for target gas components (for example, sulfur dioxide). and an indicator that detects.

The compensation cell is filled with nitrogen gas that does not absorb infrared rays, and the intensity of infrared rays that pass through it is not attenuated. On the other hand, a measurement gas containing a target gas component can pass through the sample cell, and the intensity of the infrared rays transmitted through the sample cell is attenuated as a part of the infrared rays is absorbed by the target gas component. A structure in which gas can be introduced into the sample cell and the compensation cell independently in this manner is hereinafter referred to as a "two-system structure." Compensation cells are also provided to increase the stability of continuous measurements (eg, reduce drift and ambient temperature change effects).
Further, the gas analyzer described in Patent Document 1 includes an interference cell having two chambers. In the gas analyzer described in Patent Document 1, a differential pressure sensor can be provided between the two chambers of the interference cell.

Japanese Patent Application Publication No. 2003-014591

For example, if the measurement gas is a gas containing sulfur dioxide and methane whose wavelength bands that absorb infrared rays partially overlap, it is possible to fill an interference cell with methane and use the gas analyzer described in Patent Document 1. However, it may be difficult to accurately detect the concentration of sulfur dioxide.

An object of the present invention is to provide a gas detection device that can detect the concentration of a first gas with a simple configuration.

Aspects of the present invention include a light source that irradiates infrared rays, and a first gas that is disposed on the optical path of the infrared rays irradiated from the light source, through which the infrared rays pass, and that absorbs infrared rays in a first wavelength band of the infrared rays. a first chamber through which a sample gas containing the sample gas passes; and a second wavelength band of the infrared rays, which is disposed downstream of the first chamber on the optical path, through which infrared rays pass, and which partially overlaps with the first wavelength band of the infrared rays. a second chamber filled with a second gas that absorbs the infrared rays; a received light amount detection section that receives the infrared rays that have passed through the first chamber and the second chamber in order and detects the amount of the received light; A pressure detection unit that detects the pressure of the gas existing in the chamber; and a calculation unit that calculates the concentration of the first gas in the sample gas based on the amount of light received, the calculation unit configured to detect the pressure The present invention relates to a gas detection device that corrects the concentration of the first gas based on.

According to the present invention, the concentration of the first gas in the sample gas can be accurately detected regardless of the magnitude of the concentration of the second gas in the sample gas. Further, the gas detection device does not have a two-system structure as described above, but has a simple configuration.

FIG. 1 is a schematic configuration diagram showing a first embodiment of a gas detection device of the present invention. FIG. 2 is a block diagram of the gas detection device shown in FIG. 1. FIG. 3 is an example of a calibration curve showing the relationship between the pressure in the second chamber and the concentration of the second gas contained in the sample gas. FIG. 4 is an example of a calibration curve showing the relationship between the concentration of the second gas contained in the sample gas and the correction value for the concentration of the first gas calculated by the calculation unit. FIG. 5 is a graph showing a first wavelength band of infrared rays absorbed by the first gas and a graph showing a second wavelength band of infrared rays absorbed by the second gas. FIG. 6 is a schematic configuration diagram showing a second embodiment of the gas detection device of the present invention. FIG. 7 is an example of a calibration curve showing the relationship between the pressure in the second chamber (effective value of pressure fluctuation) and the concentration of the second gas contained in the sample gas. FIG. 8 is an example of a calibration curve showing the relationship between the concentration of the second gas contained in the sample gas and the correction value for the concentration of the first gas calculated by the calculation section.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The gas detection device of the present invention will be described in detail below based on preferred embodiments shown in the accompanying drawings.
<First embodiment>
A first embodiment of the gas detection device of the present invention will be described below with reference to FIGS. 1 to 5. In the following, for convenience of explanation, in FIG. 1 (the same applies to FIG. 6), the X-axis, Y-axis, and Z-axis are set to be perpendicular to each other, and the XY plane is parallel to the horizontal plane, and the Z-axis direction is vertical. parallel to the direction. Further, the upper side in FIG. 1 (the same applies to FIG. 6) may be referred to as "upper", the lower side as "lower", the left side as "left", and the right side as "right". Furthermore, the calibration curves shown in FIGS. 3 and 4 are schematic diagrams.

The gas detection device 1 shown in FIG. 1 is an infrared gas analyzer specified in "JIS K0151:1983", and uses non-dispersive infrared absorption method (NDIR) to detect specific gases contained in sample gas GS0. The concentration of one gas GS1 can be measured.
The flue gas contains, for example, sulfur dioxide ( _SO2 ) such as sulfur oxides, and various other gas components such as nitrogen oxides ( _NOx ) and carbon monoxide (CO). In this embodiment, the flue gas is the sample gas GS0, and the sulfur dioxide gas is the first gas GS1. Therefore, in this embodiment, the gas detection device 1 is used as a sulfur dioxide concentration measuring device. Further, the flue gas may also contain methane gas, and this methane gas is referred to as the second gas GS2.

As shown in FIG. 1, the gas detection device 1 includes a light source 2, a sector 3, a rotation drive section 4, a first chamber 5, a first gas supply section 6, a second chamber 7, and a second gas supply section 6. It includes a supply section 8 , a received light amount detection section 9 , a pressure detection section 10 , an operation section 11 , a display section 12 , and a control section 13 .
The light source 2 can emit infrared IF toward the positive side in the X-axis direction. The light source 2 is not particularly limited, and has, for example, a nichrome wire, and is configured to be able to emit infrared rays by energizing the nichrome wire.

A sector 3 is arranged on the positive side of the light source 2 in the X-axis direction. Sector 3 is a switching unit that switches between irradiation (projection) of infrared IF on the positive side in the X-axis direction and stop of irradiation (shielding). The sector 3 is composed of a disc-shaped member, and has a slit 31 at a position eccentric from the center. The slit 31 is formed to penetrate the sector 3 in the thickness direction (X-axis direction).

Further, a rotation drive unit 4 is connected to the sector 3 . The rotation drive unit 4 includes, for example, a motor. By operating this motor, the sector 3 can be rotated around its central axis. As a result, when the slit 31 faces the light source 2, that is, in a state where it faces the light source 2, the infrared IF passes through the slit 31, and irradiation of the infrared IF toward the positive side in the X-axis direction is performed. Furthermore, when the sector 3 rotates and the slit 31 is displaced from the light source 2, that is, in a retracted state, the infrared IF is blocked and irradiation of the infrared IF to the positive side in the X-axis direction is stopped.

A first chamber 5 is arranged on the positive side of the sector 3 in the X-axis direction. The first chamber 5 has a chamber body 51, a supply port 52, and a discharge port 53.
The chamber body 51 is arranged on the optical path LP of the infrared ray IF emitted from the light source 2 along the X-axis direction. The chamber main body 51 is, for example, formed of a hollow rectangular parallelepiped, and has a window through which infrared IF passes through a wall on the positive side in the X-axis direction and a wall on the negative side in the X-axis direction, which face each other via an internal space (space 512). It has a section 511. Thereby, the infrared IF can pass through (transmit) the chamber main body 51 through the window 511 on the negative side in the X-axis direction, the space 512, and the window 511 on the positive side in the X-axis direction in this order. Note that the window portion 511 is preferably made of calcium fluoride (CaF ₂ ) or the like.

A tubular supply port 52 is formed protruding from the negative side of the chamber body 51 in the X-axis direction. Supply port 52 communicates with space 512. Then, the sample gas GS0 from the first gas supply section 6 can be supplied to the chamber body 51 via the supply port 52.
A tubular discharge port 53 is formed protruding from the positive side of the chamber body 51 in the X-axis direction. The discharge port 53 communicates with the space 512. The sample gas GS0 within the chamber body 51 is exhausted via the exhaust port 53. Thereby, the sample gas GS0 can pass through the chamber body 51 from the supply port 52 toward the discharge port 53, that is, along the X-axis direction.

The first gas supply unit 6 includes a supply source 61 , a connecting pipe 62 , and a switching valve 63 .
The supply source 61 includes, for example, a tank filled with sample gas GS0.
The connecting tube 62 connects the supply source 61 and the supply port 52 of the first chamber 5 . Thereby, the supply source 61 and the first chamber 5 are communicated with each other.

A switching valve 63 is provided in the middle of the connecting pipe 62. The switching valve 63 opens and closes the connection pipe 62. In the open state, the sample gas GS0 in the supply source 61 can be supplied to the first chamber 5. In the closed state, the supply of sample gas GS0 to the first chamber 5 can be stopped. Note that the switching valve 63 may be omitted.

A second chamber 7 is arranged on the positive side of the first chamber 5 in the X-axis direction. The configuration of the second chamber 7 will be described later.

A received light amount detection section 9 is arranged on the positive side of the second chamber 7 in the X-axis direction. The received light amount detection section 9 includes, for example, a photoconductive element. The photoconductive element can receive infrared IF that has passed through the chamber body 51 of the first chamber 5 and the chamber body 71 of the second chamber 7 in order. The photoconductive element detects the amount of infrared IF received by utilizing the photoconductive effect. Further, the amount of light received by the infrared IF is stored in the storage unit 132 of the control unit 13. Note that since the infrared IF is non-dispersive, the light reception and detection section 9 is sensitive only to the infrared absorption wavelength of the target gas component (first component).

As shown in FIG. 1, in the gas detection device 1, a received light amount detection section 9, a control section 13, an operation section 11, and a display section 12 are integrated into a unit, and constitute a control unit 14.
As shown in FIG. 2, the control section 13 includes a light source 2, a rotation drive section 4, a first gas supply section 6, a second gas supply section 8, a received light amount detection section 9, a pressure detection section 10, an operation section 11, and a display. It is electrically connected to the section 12 and can control the operation of each section. The control unit 13 includes a CPU 131 and a storage unit 132. For example, the CPU 131 can execute a control program stored in advance in the storage unit 132. Further, the CPU 131 also has a function as a calculation section 133 that calculates the concentration of the first gas GS1 in the sample gas GS0 based on the amount of infrared IF light received by the received light amount detection section 9. The storage unit 132 can store various information such as a control program and a calibration curve CC1 (see FIG. 3) and a calibration curve CC2 (see FIG. 4), which will be described later.

The operation unit 11 is a part that receives input from a user who operates and uses the gas detection device 1. The operation unit 11 is not particularly limited, and examples thereof include a keyboard, a mouse, and the like.
The display unit 12 can display, for example, the measurement conditions for measuring the concentration of the first gas GS1, the concentration of the first gas GS1, and the like. The display section 12 is not particularly limited, and may be constructed of, for example, liquid crystal, organic EL, or the like.

As described above, in this embodiment, the flue gas is the sample gas GS0, and the sulfur dioxide gas contained in the flue gas is the first gas GS1. Further, the flue gas may also contain methane gas, and this methane gas is referred to as the second gas GS2.
As shown in FIG. 5, the first gas GS1 has a characteristic of absorbing infrared IF in the first wavelength band among infrared IF. When the first gas GS1 is sulfur dioxide gas, the first gas GS1 has an absorption peak of infrared IF having a wavelength of 7.4 μm, and absorbs infrared IF of a wavelength within a range before and after that.

Furthermore, the second gas GS2 has a characteristic of absorbing infrared IF in a second wavelength band that partially overlaps with the first wavelength band. When the second gas GS2 is methane gas, the second gas GS2 has an absorption peak at an infrared IF having a wavelength of 7.6 μm, and absorbs infrared IF having a wavelength within a range before and after that.

In the overlapping wavelength band where the first wavelength band and the second wavelength band overlap, there is a peak wavelength of infrared IF that is maximally absorbed by the first gas GS1, and a peak wavelength of infrared IF that is maximally absorbed by the second gas GS2. and included. Although each peak wavelength is included in the overlapping wavelength band in this embodiment, the peak wavelength is not limited to this, and may fall outside the overlapping wavelength band depending on the type of the first gas GS1 and the second gas GS2, for example. .

The amount of received light detection section 9 detects the amount of received light of the infrared IF depending on the amount of absorption of the infrared IF. For example, when the amount of absorption is large, the amount of received light is detected as small. Conversely, when the amount of absorption is small, the amount of received light is detected as large.
Furthermore, the calculation unit 133 calculates the concentration of the first gas GS1 in the sample gas GS0 based on the amount of light received by the infrared IF.

When the second gas GS2 is mixed in the sample gas GS0, in the first chamber 5, the overlapping wavelength band of the infrared IF is absorbed not only by the first gas GS1 but also by the second gas GS2. That will happen. Therefore, the amount of light received by the received light amount detection section 9 is also affected by the amount absorbed by the second gas GS2. As a result, the concentration (actually measured value) of the first gas GS1 calculated based on the amount of received light includes the concentration of the second gas GS2, which causes an error corresponding to the concentration and becomes inaccurate.
Further, when the gas detection device 1 has the above-mentioned two-system structure, the device configuration of the gas detection device 1 becomes complicated accordingly.

Therefore, the gas detection device 1 is configured to be able to eliminate such problems. This configuration and operation will be explained below. In addition, below, the part comprised by the 2nd chamber 7, the 2nd gas supply part 8, and the pressure detection part 10 may be called the "correction unit 15."
A second chamber 7 is arranged between the first chamber 5 and the received light amount detection section 9. The second chamber 7 has a chamber body 71 and a supply port 72. Note that the second chamber 7 may be in a sealed state filled with the second gas GS2 in advance.
The chamber body 71 is disposed on the optical path LP on the downstream side of the chamber body 51 of the first chamber 5, that is, on the positive side in the X-axis direction. The chamber body 71 is, for example, formed of a hollow rectangular parallelepiped.

The second chamber 7 also includes a partition portion 74 that vertically partitions the inside of the chamber body 71 (second chamber 7) into two spaces, and a communication portion 75 that communicates the two spaces. Hereinafter, one (lower) of the two spaces will be referred to as the "first space 712," and the other (upper) space will be referred to as the "second space 713." The partition portion 74 has a plate shape, and the communication portion 75 is formed of a through hole that penetrates the partition portion 74 in the thickness direction (Z-axis direction).

The chamber main body 71 has a window 711 through which infrared IF passes through a wall on the positive side in the X-axis direction and a wall on the negative side that face each other with a first space 712 interposed therebetween. Thereby, the infrared IF can pass through the chamber body 71 in this order: the window 711 on the negative side in the X-axis direction, the first space 712, and the window 711 on the positive side in the X-axis direction. Note that, like the window portion 511, the window portion 711 is preferably made of calcium fluoride or the like.

Note that the cross-sectional shape of the first space 712 along the Y-axis direction and the cross-sectional shape of the space 512 in the first chamber 5 along the Y-axis direction are preferably the same. It is preferable that cross-sectional area S712 and cross-sectional area S512 of space 512 be the same. Thereby, the infrared IF can sufficiently reach the received light amount detection section 9.

Further, the second space 713 has a smaller volume than the first space 712, and the pressure detection unit 10 is disposed therein. By arranging the pressure detection unit 10 in the second space 713, when the infrared IF passes through the first space 712, the pressure detection unit 10 can be prevented from interfering with the infrared IF. Thereby, the received light amount detecting section 9 can sufficiently receive the infrared IF.

A tubular supply port 72 is formed protruding from the negative side of the chamber body 71 in the X-axis direction. The supply port 72 communicates with the second space 713. Then, the second gas GS2 from the second gas supply section 8 can be supplied into the chamber body 71 via the supply port 72. Thereby, the chamber main body 71, that is, the first space 712 and the second space 713 can be filled with the second gas GS2.

The second gas supply section 8 includes a supply source 81 , a connecting tube 82 , and a switching valve 83 .
The supply source 81 includes, for example, a tank filled with the second gas GS2.
The connecting pipe 82 connects the supply source 81 and the supply port 72 of the second chamber 7 . Thereby, the supply source 81 and the second chamber 7 are communicated with each other.

A switching valve 83 is provided in the middle of the connecting pipe 82. The switching valve 83 opens and closes the connecting pipe 82 . In the open state, the second gas GS2 in the supply source 81 can be supplied to the second chamber 7. In the closed state, the supply of the second gas GS2 to the second chamber 7 can be stopped.
Although the gas detection device 1 is configured to include the second gas supply section 8 in this embodiment, it is not limited to this, and for example, the second gas supply section 8 (supply port 72) may be omitted. It may be configured as follows. In this case, the second chamber 7 is sealed and filled with the second gas GS2 in advance.

The pressure detection unit 10 is arranged in the second space 713 of the second chamber 7 . The pressure detection unit 10 detects the pressure of the gas present in the second chamber 7 (hereinafter simply referred to as "pressure" or "pressure in the second chamber 7"). This pressure is actually the effective value of the pressure change.
As shown in FIG. 2, the pressure detection section 10 includes a piezoelectric conversion section 101 that electrically detects changes in pressure. The piezoelectric conversion unit 101 is not particularly limited, and examples thereof include sensors such as a capacitor microphone and a flow sensor (for example, a comb-shaped hot wire microsensor).

When infrared IF is emitted from the light source 2 and passes through the second chamber 7, the second gas GS2, which is methane gas, absorbs the infrared IF in the second wavelength band. As a result, the temperature inside the second chamber 7 rises, and the pressure also rises accordingly, that is, the pressure changes. The pressure detection unit 10 can detect a change in pressure using the piezoelectric conversion unit 101 and accurately detect the pressure inside the second chamber 7 during infrared irradiation.

Note that the length LX512 along the X-axis direction within the space 512 of the first chamber 5 is preferably about 200 mm, for example. Moreover, it is preferable that the length LX712 along the X-axis direction (optical path LP) in the first space 712 of the second chamber 7 is 5 mm or more and 50 mm or less.
Further, the concentration of the second gas GS2 in the second chamber 7 is preferably 20 g/Nm ³ or more and 700 g/Nm ³ or less, more preferably 40 g/Nm ³ or more and 300 g/Nm ³ or less.

With such a numerical range, when the infrared IF passes through the second chamber 7, the second gas GS2 in the second chamber 7 can absorb just the right amount of infrared IF in the second wavelength band. Thereby, the pressure inside the second chamber 7 can be changed to such an extent that the pressure inside the second chamber 7 can be detected more accurately.

The storage unit 132 stores in advance a calibration curve CC1 shown in FIG. 3 and a calibration curve CC2 shown in FIG. 4.
The calibration curve CC1 is a graph showing the relationship between the pressure in the second chamber 7 (effective value of pressure fluctuation) and the concentration of the second gas GS2 contained in the sample gas GS0, that is, in the first chamber 5. . As mentioned above, the calibration curve CC1 is just a schematic diagram. Note that the pressure within the second chamber 7 tends to be constant at the base (usually atmospheric pressure). Further, in accordance with the intermittent irradiation of infrared IF (infrared light), the same frequency slightly fluctuates. As the concentration of the second gas GS2 in the first chamber 5 increases, the amplitude (effective value) of the slight fluctuation in pressure decreases.
The calibration curve CC2 is a graph showing the relationship between the concentration of the second gas GS2 contained in the sample gas GS0 and the correction value for the concentration (actually measured value) of the first gas GS1.

Note that the calibration curve CC1 and the calibration curve CC2 are determined in advance, for example, experimentally or by simulation.
Further, although the calibration curve CC1 and the calibration curve CC2 are graphs in this embodiment, they are not limited to this, and may be, for example, a table or a mathematical formula.

The calculation unit 133 calculates the concentration of the first gas GS1 in the sample gas GS0 based on the amount of infrared IF received by the received light amount detection unit 9.
As mentioned above, if the second gas GS2 (methane gas) is mixed in the sample gas GS0 (flue gas), there is a risk that an error will occur in the actual measured value of the concentration of the first gas GS1 based on the amount of light received. be. The calculation unit 133 can eliminate this error and correct the density to an accurate density.

Specifically, the calculation unit 133 corrects the concentration of the first gas GS1 based on the pressure. In particular, in this embodiment, the calculation unit 133 corrects the concentration of the first gas GS1 based on the calibration curve CC1 and the calibration curve CC2.
In the gas detection device 1, first, the concentration of the first gas GS1 is calculated based on the amount of light received by the amount of received light detection section 9. Thereby, an actual measured value of the concentration of the first gas GS1 is obtained.

Moreover, at this time, the pressure inside the second chamber 7 is detected by the pressure detection section 10. The calculation unit 133 uses the calibration curve CC1 to determine the concentration of the second gas GS2 corresponding to the pressure detected by the pressure detection unit 10. For example, as shown in FIG. 3, when the pressure detected by the pressure detection unit 10 is "pressure P", the concentration of the second gas GS2 is determined as "concentration Q" using the calibration curve CC1.

Next, the calculation unit 133 uses the calibration curve CC2 to determine a correction value for the concentration of the first gas GS1 corresponding to the concentration of the second gas GS2 determined above. For example, as shown in FIG. 4, when the concentration of the second gas GS2 is "concentration Q", the correction value is determined as "correction value R" using the calibration curve CC2.

Next, the calculation unit 133 calculates a value that reflects, or takes into account, the correction value R on the actually measured value of the concentration of the first gas GS1. Thereby, the concentration of the first gas GS1 is corrected to an accurate value. The concentration of the first gas GS1 after this correction is displayed on the display section 12. Thereby, the accurate concentration of the first gas GS1 can be confirmed.

For example, sample gas GS0 contains sulfur dioxide gas (first gas GS1) with a concentration of 26 mg/Nm ³ and methane gas (second gas GS2) with a concentration of 300 mg/Nm ³ . An example of an experiment in this case will be described. Note that the concentration of sulfur dioxide gas and the concentration of methane gas in the sample gas GS0 are both known.

When gas detection device 1 was used, the concentration of sulfur dioxide gas was detected at 26 mg/Nm ³ . This detection result is the same as the known value.
On the other hand, when the correction unit 15 was omitted from the gas detection device 1, the concentration of sulfur dioxide gas was detected at 66 mg/Nm ³ . This detection result deviates significantly from known values.

As described above, the gas detection device 1 uses the correction unit 15 to accurately detect the concentration of the first gas GS1 in the sample gas GS0, regardless of the magnitude of the concentration of the second gas GS2 in the sample gas GS0. be able to. Further, the gas detection device 1 does not have a two-system structure, but has a simple configuration.

<Second embodiment>
The second embodiment of the gas detection device of the present invention will be described below with reference to FIGS. 6 to 8, but the explanation will focus on the differences from the above-described embodiment, and the explanation of similar matters will be omitted. .
This embodiment is similar to the first embodiment except that the configuration of the correction unit is different.

As shown in FIG. 6, in this embodiment, the second chamber 7 further includes a discharge port 73 in addition to a chamber body 71 and a supply port 72.
The discharge port 73 has a tubular shape and is formed to protrude toward the negative side of the chamber body 71 in the X-axis direction. The discharge port 73 communicates with the second space 713.

Further, the correction unit 15 (gas detection device 1) includes an adjustment section 16 that adjusts the concentration of the second gas GS2 in the second chamber 7. The adjustment section 16 includes a connection pipe 161 and a switching valve 162.
The connecting tube 161 is connected to the discharge port 73. Thereby, the connecting tube 161 and the chamber body 71 communicate with each other via the discharge port 73.

A switching valve 162 is provided in the middle of the connecting pipe 161. The switching valve 162 opens and closes the connection pipe 161. Then, by adjusting the opening degree of the switching valve 162, the second gas GS2 in the chamber body 71 can be discharged from the connection tube 161, and the inside of the chamber body 71 can be opened to the atmosphere. Thereby, the concentration of the second gas GS2 can be adjusted in stages (for example, in three stages).

The storage unit 132 also stores calibration curve CC1-1, calibration curve CC1-2, and calibration curve CC1-3 shown in FIG. 7, and calibration curve CC2-1, calibration curve CC2-2, and calibration curve CC2 shown in FIG. -3 is stored in advance.
The calibration curve CC1-1 to the calibration curve CC1-3 are graphs showing the relationship between the pressure in the second chamber 7 and the concentration of the second gas GS2 contained in the sample gas GS0, that is, the second gas GS2 in the first chamber 5. Yes, and can be used depending on the concentration of the second gas GS2.

The calibration curve CC2-1 to the calibration curve CC2-3 are graphs showing the relationship between the concentration of the second gas GS2 contained in the sample gas GS0 and the correction value for the concentration (actually measured value) of the first gas GS1. Similar to the curve CC1-1 to the calibration curve CC1-3 , they can be used depending on the concentration of the second gas GS2.

When detecting the concentration of the first gas GS1, for example, when the calibration curve CC1-1 is used, the calibration curve CC2-1 is used. Furthermore, when the calibration curve CC1-2 is used, the calibration curve CC2-2 is used. Furthermore, when the calibration curve CC1-3 is used, the calibration curve CC2-3 is used.
In this manner, the gas detection device 1 selects one of the calibration curves CC1-1 to CC1-3 depending on the concentration of the second gas GS2, and also selects one of the calibration curves CC2-1 to CC1-3 . One of CC2-3 can be selected and used. Thereby, the concentration of the first gas GS1 can be detected more accurately.

Although the gas detection device of the present invention has been described above with reference to the illustrated embodiment, the present invention is not limited to this, and each part constituting the gas detection device can be configured in any arbitrary configuration that can perform the same function. It can be replaced with that of . Moreover, arbitrary components may be added.
Further, the gas detection device of the present invention may be a combination of any two or more configurations (features) of the above embodiments.

Further, in each of the embodiments, sulfur dioxide gas is used as the first gas GS1, and methane gas is used as the second gas GS2, but the present invention is not limited thereto. For example, nitrogen oxide or carbon monoxide may be used as the first gas GS1, and carbon dioxide may be used as the second gas GS2.
Further, the first chamber 5 may be configured to suck the sample gas GS0 with a pump and continuously circulate the sample gas through the chamber body 51.

Further, the positional relationship between the first chamber 5 and the second chamber 7 is such that the first chamber 5 is placed on the upstream side and the second chamber 7 is placed on the downstream side in the above embodiment, but it is not limited to this. For example, the second chamber 7 may be placed on the upstream side and the first chamber 5 may be placed on the downstream side.

[Mode]
It will be appreciated by those skilled in the art that the exemplary embodiments described above are specific examples of the following aspects.

(Section 1) The gas detection device according to one embodiment includes:
a light source that emits infrared rays;
a first chamber disposed on the optical path of the infrared rays emitted from the light source, through which the infrared rays pass and a sample gas containing a first gas that absorbs the infrared rays in a first wavelength band of the infrared rays;
a second chamber disposed on the optical path and filled with a second gas through which infrared rays pass and which absorbs infrared rays in a second wavelength band that partially overlaps with the first wavelength band;
a received light amount detection unit that receives infrared rays that have passed through the first chamber and the second chamber in order, and detects the amount of the received light;
a pressure detection unit that detects the pressure of gas existing in the second chamber;
a calculation unit that calculates the concentration of the first gas in the sample gas based on the amount of received light;
The calculation unit corrects the concentration of the first gas based on the pressure.

According to the gas detection device described in item 1, the concentration of the first gas in the sample gas can be accurately detected regardless of the magnitude of the concentration of the second gas in the sample gas. Further, the gas detection device does not have a two-system structure as described above, but has a simple configuration.

(Section 2) In the gas detection device according to Section 1,
comprising a storage unit that stores a calibration curve indicating the relationship between the pressure and the concentration of the second gas contained in the sample gas;
The calculation unit corrects the concentration of the first gas based on the calibration curve.

According to the gas detection device described in item 2, the concentration of the first gas can be accurately detected with a simple configuration that uses a calibration curve.

(Section 3) In the gas detection device according to Item 1 or 2,
The second chamber has a partition portion that partitions the inside of the second chamber into two spaces, and a communication portion that communicates the two spaces,
Infrared rays pass through one of the two spaces, and the pressure detection section is arranged in the other space.

According to the gas detection device described in item 3, when the infrared rays pass through one of the spaces, it is possible to prevent the pressure detection section from interfering with the infrared rays, so that the received light amount detection section sufficiently receives the infrared rays. can do.

(Section 4) In the gas detection device according to any one of Items 1 to 3,
The length along the optical path within the second chamber is 5 mm or more and 50 mm or less.

According to the gas detection device described in item 4, when infrared rays pass through the second chamber, the second gas in the second chamber can absorb just the right amount of infrared rays in the second wavelength band. Thereby, the pressure inside the second chamber can be changed to such an extent that the pressure inside the second chamber can be detected more accurately.

(Section 5) In the gas detection device according to any one of Items 1 to 4,
The concentration of the second gas in the second chamber is 20 g/Nm ³ or more and 700 g/Nm ³ or less.

According to the gas detection device described in item 5, when infrared rays pass through the second chamber, the second gas in the second chamber can absorb just the right amount of infrared rays in the second wavelength band. Thereby, the pressure inside the second chamber can be changed to such an extent that the pressure inside the second chamber can be detected more accurately.

(Section 6) In the gas detection device according to any one of Items 1 to 5,
The pressure detection section includes a piezoelectric conversion section that electrically detects changes in the pressure.

According to the gas detection device described in item 6, pressure can be accurately detected with a simple configuration that uses a piezoelectric conversion section.

(Section 7) In the gas detection device according to any one of Items 1 to 6,
An adjustment unit is provided that adjusts the concentration of the second gas in the second chamber.

According to the gas detection device described in item 7, it is possible to use different calibration curves depending on the concentration of the second gas, for example.

(Section 8) In the gas detection device according to any one of Items 1 to 7,
The first gas is sulfur dioxide gas, and the second gas is methane gas.

According to the gas detection device described in item 8, the gas detection device can be used as a sulfur dioxide concentration measuring device that measures the concentration of sulfur dioxide gas.

1 Gas detection device 2 Light source 3 Sector 31 Slit 4 Rotation drive section 5 First chamber 51 Chamber body 511 Window section 512 Space 52 Supply port 53 Discharge port 6 First gas supply section 61 Supply source 62 Connection pipe 63 Switching valve 7 Second Chamber 71 Chamber body 711 Window section 712 First space 713 Second space 72 Supply port 73 Discharge port 74 Partition section 75 Communication section 8 Second gas supply section 81 Supply source 82 Connection tube 83 Switching valve 9 Received light amount detection section 10 Pressure detection Section 101 Piezoelectric conversion section 11 Operation section 12 Display section 13 Control section 131 CPU
132 Storage section 133 Calculation section 14 Control unit 15 Correction unit 16 Adjustment section 161 Connection tube 162 Switching valve CC1 Calibration curve CC1-1 Calibration curve CC1-2 Calibration curve CC1-3 Calibration curve CC2 Calibration curve CC2-1 Calibration curve CC2-2 Calibration curve CC2-3 Calibration curve GS0 Sample gas GS1 1st gas GS2 2nd gas IF Infrared LP Optical path LX512 Length LX712 Length P Pressure Q Concentration R Correction value S512 Cross-sectional area S712 Cross-sectional area

Claims (8)

a light source that emits infrared rays;
a first chamber disposed on the optical path of the infrared rays emitted from the light source, through which the infrared rays pass and a sample gas containing a first gas that absorbs the infrared rays in a first wavelength band of the infrared rays;
a second chamber disposed on the optical path and filled with a second gas through which infrared rays pass and which absorbs infrared rays in a second wavelength band that partially overlaps with the first wavelength band;
a received light amount detection unit that receives infrared rays that have passed through the first chamber and the second chamber in order, and detects the amount of the received light;
a pressure detection unit that detects the pressure of gas existing in the second chamber;
a calculation unit that calculates the concentration of the first gas in the sample gas based on the amount of received light;
a first calibration curve showing the relationship between the pressure of the gas existing in the second chamber and the concentration of the second gas contained in the sample gas in the first chamber; A relationship between the concentration of the gas and the concentration correction value (R) of the actual measured concentration of the first gas in the first chamber calculated by the calculation unit based on the amount of received light detected by the amount of received light detection unit is shown. comprising a storage unit that stores the second calibration curve;
The calculation unit calculates the concentration of the second gas in the first chamber based on the pressure value of the gas existing in the second chamber detected by the pressure detection unit and the first calibration curve, and further , a concentration correction value (R) of the first gas is determined from the determined concentration of the second gas in the first chamber and the second calibration curve, and based on the amount of received light detected by the amount of received light detection section. A gas detection device characterized in that the concentration of the first gas is calculated by correcting the measured value of the concentration of the first gas in the sample gas to be calculated using the determined concentration correction value (R). The second chamber has a partition portion that partitions the inside of the second chamber into two spaces, and a communication portion that communicates the two spaces,
The gas detection device according to claim 1, wherein infrared rays pass through one of the two spaces, and the pressure detection section is arranged in the other space. The gas detection device according to claim 1, wherein the length along the optical path in the second chamber is 5 mm or more and 50 mm or less. The gas detection device according to any one of claims 1 to 3, wherein the concentration of the second gas in the second chamber is 20 g/Nm ³ or more and 700 g/Nm ³ or less. The gas detection device according to claim 1, wherein the pressure detection section includes a piezoelectric conversion section that electrically detects changes in the pressure. The gas detection device according to claim 1, further comprising an adjustment section that adjusts the concentration of the second gas in the second chamber. The storage unit stores a plurality of first calibration curves and second calibration curves depending on the concentration of the second gas in the second chamber, and stores a plurality of first calibration curves and second calibration curves in accordance with the concentration of the second gas in the second chamber. The gas detection device according to any one of claims 1 to 6, wherein the calibration curves are used for different purposes. The gas detection device according to claim 1, wherein the first gas is sulfur dioxide gas and the second gas is methane gas.

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