Gas analyzer

Abstract

A gas analysis device (100) is provided with a measurement cell (1), a light source (3), a separation member (5), a first sensor unit (7, 7', 7''), a second sensor unit (9, 9', 9''), and a calculation unit (111). A sample gas (Gs) is introduced into the measurement cell (1). The light source (3) radiates measurement light (Lm) inside the measurement cell (1). The separation member (5) splits the measurement light (Lm) having passed through the measurement cell (1) into first component light (CL1) that includes a component in a first wavelength range and third component light (CL3) that includes at least second component light including a component in a second wavelength range. The calculation unit (111) calculates information relating to a component gas in a low concentration range, on the basis of the intensity of the first component light (CL1) measured by the first sensor unit (7, 7', 7''). In addition, the calculation unit (111) calculates information relating to the component gas in a high concentration range, on the basis of the intensity of the second component light (CL2) measured by the second sensor unit (9, 9', 9'').

Description

Technical Field

[0001] The present invention relates to a gas analyzer for analyzing component gases contained in a sample gas.

Background Art

[0002] Conventionally, as a gas analyzer for analyzing a predetermined component gas (for example, sulfur oxides (SO x ), nitrogen oxides (NO x ), carbon dioxide (CO2), carbon monoxide (CO)) contained in a sample gas sampled from a predetermined location (for example, a flue), those using the light absorption characteristics of the component gas are known (see, for example, Patent Document 1).

[0003] This gas analyzer includes a measurement cell into which a sample gas is introduced, a light source that emits measurement light toward the measurement cell, and a sensor that measures the intensity of the measurement light that has passed through the measurement cell.

[0004] In the above gas analyzer, measurement light is emitted toward the measurement cell with the sample gas introduced into the measurement cell, the intensity of the measurement light after passing through the sample gas in the measurement cell is measured by the sensor, and analysis of the component gas (calculation of information regarding the component gas) is performed based on the intensity of the measurement light measured by the sensor.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In the gas analyzer described above, the analysis of component gases is performed on the premise that the relationship between the intensity of the measurement light after passing through the sample gas and the information regarding the concentration of the component gases does not change from a predetermined relationship. However, when analyzing component gases over a wide concentration range, the relationship between the intensity of the measurement light measured by the sensor and the information regarding the concentration of the component gases may change from a predetermined relationship. For example, the change in the intensity of the measurement light in response to a change in the concentration of the component gas when the concentration of the component gas is high may be smaller than the change in the intensity of the measurement light when the concentration of the component gas is low.

[0007] When analyzing component gases under the assumption that the relationship between the intensity of the measured light measured by the sensor and the information regarding the concentration of the component gases remains unchanged, if that relationship changes within a certain concentration range, errors will occur in the analysis results.

[0008] It is conceivable to correct changes in the relationship between the intensity of the measured light, as measured by the sensor, and the information regarding the concentration of the component gas, using electrical or predetermined calculations. However, if the above relationship changes drastically, it may not be possible to fully correct this change even by electrical or calculation methods.

[0009] Alternatively, the above problems could be solved by providing separate devices: one for low-concentration analysis with a longer optical path length for the light passing through the component gas, and another for high-concentration analysis with a shorter optical path length for the light passing through the component gas. However, in this case, since two separate devices would be required, problems such as the analytical device becoming larger, more expensive, and consuming more power would arise.

[0010] The objective of the present invention is to provide an analytical device that analyzes component gases using the optical absorption characteristics of the component gases, and to enable accurate analysis of component gases over a wide concentration range. [Means for solving the problem]

[0011] Several embodiments for solving the problem are described below. These embodiments can be combined as needed. The gas analyzer according to the present invention is a device for analyzing component gases contained in a sample gas. The gas analyzer comprises a measuring cell, a light source, a separation member, a first sensor unit, a second sensor unit, and a calculation unit. A sample gas is introduced into the measurement cell. The light source emits measurement light into the measurement cell. The separation member separates the measurement light that has passed through the measurement cell into a first component light and a third component light that includes at least a second component light. The first component light includes components in a first wavelength range. The first wavelength range includes the wavelength range that is most absorbed by the component gas within a specific wavelength range absorbed by the component gas, and is narrower than the specific wavelength range. The second component light includes components in a second wavelength range that are included in the specific wavelength range but not in the first wavelength range. The first sensor unit measures the intensity of the first component light. The second sensor unit measures the intensity of the second component light. The calculation unit calculates information about component gases in the low-concentration range based on the intensity of the first component light measured by the first sensor unit. The calculation unit also calculates information about component gases in the high-concentration range based on the intensity of the second component light measured by the second sensor unit.

[0012] As a result, the relationship between the intensity of component light measured by the sensor and information such as the concentration of component gases does not change from a predetermined relationship over a wide concentration range, allowing for accurate analysis of component gases across a wide concentration range contained in the sample gas.

[0013] The gas analyzer described above may further include a gas switching unit. The gas switching unit switches between introducing a sample gas and a reference gas into the measurement cell. The reference gas is a gas that does not contain component gases. Since the reference gas does not contain component gases, the intensity of the measurement light when the reference gas is introduced into the measurement cell becomes background relative to the intensity of the measurement light when the sample gas is introduced into the measurement cell. Therefore, for example, when calculating information about component gases, the intensity of the measurement light when the reference gas is introduced into the measurement cell can be taken into consideration to calculate information about component gases more accurately.

[0014] The separation member may be a bandpass filter that transmits the first component light and reflects the third component light. This ensures reliable separation of the first component light, which includes components within the first wavelength range, and the third component light, which includes components outside the first wavelength range.

[0015] The first sensor unit may include a first pneumatic detector capable of measuring the intensity of light in a specific wavelength range. This allows for selective measurement of the intensity of first component light containing components in a specific wavelength range.

[0016] The first sensor unit may include a first transmission filter that transmits light in a specific wavelength range, and a thermal solid-state sensor or semiconductor sensor that measures the intensity of the light that has passed through the first transmission filter. This allows for selective measurement of the intensity of first component light containing components in a specific wavelength range, even if the sensor itself does not have selectivity for wavelength.

[0017] The second sensor unit may include a second pneumatic detector capable of measuring the intensity of light in a specific wavelength range. This allows for selective measurement of the intensity of the second component light, which includes components in a specific wavelength range, from among the third component light.

[0018] The second sensor unit may be provided between the separation member and the second pneumatic detector, and may include a second transmission filter that transmits light in a specific wavelength range. Thereby, only the second component light including the component in the specific wavelength range among the third component lights can be incident on the second pneumatic detector, so that the selectivity of the second sensor unit for the second component light can be further enhanced.

[0019] The second sensor unit may include a third transmission filter that transmits light in a specific wavelength range, and a thermal solid-state sensor or a semiconductor sensor that measures the intensity of the light that has passed through the third transmission filter. Thereby, only the second component light including the component in the specific wavelength range among the third component lights can be incident on the sensor, so that even when the sensor itself has no selectivity for wavelength, the intensity of the second component light can be selectively measured.

[0020] The above gas analyzer may further include a fourth transmission filter. The fourth transmission filter is provided between the measurement cell and the separation member and transmits light in a specific wavelength range. Thereby, only the light including the component in the specific wavelength range among the measurement lights can be incident on the separation member. As a result, the separation member can separate the first component light and the component light (i.e., the second component light) including the component in the specific wavelength range among the third component lights.

[0021] When the gas analyzer includes the fourth transmission filter, the first sensor unit and the second sensor unit may be a thermal solid-state sensor or a semiconductor sensor that measures the intensity of light in a specific wavelength range. Thereby, it is not necessary to provide a transmission filter for each of the first sensor unit and the second sensor unit, so that the first sensor unit and the second sensor unit can be configured at a low cost.

Advantages of the Invention

[0022] In the above analyzer, the relationship between the intensity of the component light measured by the sensor unit and the information regarding the concentration of the component gas does not change from a predetermined relationship over a wide concentration range, so that component gases in a wide concentration range contained in the sample gas can be accurately analyzed.

Brief Description of the Drawings

[0023] [Figure 1] Figure showing the configuration of the analysis device. [Figure 2] Figure showing an example of the transmission spectrum and reflection spectrum of the separation member. [Figure 3] Figure showing the intensity spectrum of each component light. [Figure 4] Figure showing the configuration of the control unit. [Figure 5] Flowchart showing the analysis operation of the component gas. [Figure 6] Figure showing the configuration of the gas analyzer of Modification 1. [Figure 7] Figure showing the configuration of the gas analyzer of Modification 2. [Figure 8] Figure showing the connection relationship between the sampling unit and the analysis device.

Mode for Carrying Out the Invention

[0024] 1. First Embodiment (1) Configuration of the Gas Analyzer Hereinafter, the configuration of the gas analyzer 100 will be described with reference to FIG. 1. FIG. 1 is a figure showing the configuration of the gas analyzer. The gas analyzer 100 is, for example, an apparatus that analyzes the component gases contained in a sample gas Gs such as air, exhaust gas flowing through a flue, process gas generated in various processes, exhaust gas generated by combustion of waste, exhaust gas generated by combustion of a boiler, and gas filled in a gas cylinder, using the light absorption characteristics of the component gases. Specifically, the gas analyzer 100 emits measurement light Lm into a space filled alternately with the sample gas Gs and the reference gas Gr, measures the intensity of the measurement light Lm after passing through the sample gas Gs and the reference gas Gr, respectively, and calculates information (for example, concentration) regarding the component gases contained in the sample gas Gs based on the difference between the intensity of the measurement light Lm measured when the sample gas Gs is filled and the intensity of the measurement light Lm measured when the reference gas Gr is filled. The reference gas Gr is a gas that does not contain component gases. The reference gas Gr is, for example, nitrogen gas (N2), purified air (from which component gases etc. have been removed), etc.

[0025] Since the reference gas Gr does not contain any component gases, the intensity of the measurement light Lm that passes through the space filled with the reference gas Gr becomes background relative to the intensity of the measurement light Lm that passes through the space filled with the sample gas Gs. Therefore, by calculating information about the component gases contained in the sample gas Gs based on the difference between the intensity of the measurement light Lm that passes through the space filled with the sample gas Gs and the intensity of the measurement light Lm that passes through the space filled with the reference gas Gr, it is possible to calculate information about the component gases more accurately.

[0026] Examples of component gases that can be analyzed by the gas analyzer 100 include carbon dioxide (CO2), carbon monoxide (CO), sulfur dioxide (SO2), and nitrogen oxides (NO2). x These include gases (e.g., nitric oxide (NO), nitrogen dioxide (NO2), nitrous oxide (N2O), etc.) and hydrocarbon gases (e.g., methane (CH4), propane (C3H8), etc.).

[0027] The specific configuration of the gas analyzer 100 will be described below. In the gas analyzer 100 described below, the component gas will be carbon dioxide (CO2). Even when other gases listed above are used as component gases, the gas analyzer 100 will have almost the same configuration as described below. As shown in Figure 1, the analyzer mainly comprises a measurement cell 1, a gas switching unit 2, a light source 3, a separation member 5, a first sensor unit 7, a second sensor unit 9, and a control unit 11.

[0028] The measurement cell 1 is a hollow member into which a sample gas Gs or reference gas Gr can be introduced. The measurement cell 1 has an inlet 1a for introducing the sample gas Gs or reference gas Gr into the interior, and an outlet 1b for discharging the gas introduced into the interior to the outside. Infrared transmission windows (e.g., calcium fluoride crystal windows) are fitted at both ends in the longitudinal direction of the measurement cell 1, forming a sealing structure. The space inside the hollow member into which the sample gas Gs or reference gas Gr is introduced is called the measurement space Sp.

[0029] In the measurement cell 1 described above, for example, the sample gas Gs or reference gas Gr can be introduced into the measurement space Sp via the inlet 1a by drawing in the measurement space Sp using a pump (not shown) connected to the outlet 1b. Alternatively, the sample gas Gs or reference gas Gr can also be introduced into the measurement space Sp by pressurizing it. In this case, drawing in the gas from the outlet 1b is not particularly necessary.

[0030] The optical path length of the measurement light Lm within the measurement space Sp of the measurement cell 1 is preferably such that the measurement light Lm passing through the measurement space Sp is sufficiently absorbed by the component gas, even if the concentration of the component gas contained in the sample gas Gs is low. Therefore, the measurement cell 1 has a certain length.

[0031] If the length of the measurement cell 1 cannot be sufficiently secured, for example, multiple mirrors may be provided in the measurement space Sp to cause multiple reflections of the measurement light Lm, and the measurement light Lm may be made to circulate multiple times within the measurement space Sp.

[0032] The gas switching unit 2 introduces the sample gas Gs and the reference gas Gr into the measurement space Sp of the measurement cell 1 by switching them alternately at a fixed time period. The gas switching unit 2 is, for example, a solenoid valve that can alternately switch between allowing gas flow between the gas line supplied with the sample gas Gs and the inlet 1a, and allowing gas flow between the gas line supplied with the reference gas Gr and the inlet 1a.

[0033] Light source 3 is provided at one end of the measurement cell 1 in the longitudinal direction. Light source 3 emits measurement light Lm containing at least components within the wavelength range that the component gas can absorb into the measurement space Sp of the measurement cell 1. In this embodiment, since the component gas is carbon dioxide, the measurement light Lm in this embodiment is infrared light. Any light source capable of emitting infrared light can be used as light source 3. The wavelength range of measurement light Lm can be appropriately changed depending on the type of component gas. Furthermore, any light source can be used as light source 3 depending on the wavelength range that measurement light Lm should have.

[0034] The separation member 5 separates the measurement light Lm that has passed through the measurement space Sp of the measurement cell 1 into a first component light CL1 used for analyzing component gases in the low concentration range, and a third component light CL3 which includes at least a second component light CL2 used for analyzing component gases in the high concentration range. In this embodiment, the separation member 5 is a bandpass filter having a transmission spectrum and a reflection spectrum as shown in Figure 2. Figure 2 is a diagram showing an example of the transmission spectrum and reflection spectrum of the separation member.

[0035] Specifically, if the wavelength range of a particular absorption spectrum (absorbance) among the absorption spectra (absorbance) absorbed by the component gas (referred to as the specific wavelength range) is set to be between λ1 and λ2, and the peak of that absorption spectrum is located within the wavelength range of λ3 (λ1 < λ3 < λ2) and λ4 (λ1 < λ4 < λ2), then the separation member 5 transmits light in the wavelength range of λ3 and λ4. In this way, the separation member 5 transmits component light that includes the wavelength range most absorbed by the component gas within the specific wavelength range, and also includes components in a first wavelength range that is narrower than the specific wavelength range. The "wavelength range most absorbed by the component gas" includes the peak position of a particular absorption spectrum (absorbance) of the component gas.

[0036] The component light described above, which contains components in the first wavelength range that are most absorbed by the component gas, is sufficiently absorbed even when the concentration of component gas in the sample gas Gs is low, and therefore exhibits high sensitivity even to component gases in the low concentration range. Furthermore, when the concentration of component gas is low, the relationship between the concentration information of the component gas and the intensity of the component light measured by the sensor remains constant. Therefore, in this embodiment, the component light transmitted by the separation member 5 is used as the first component light CL1 for the analysis of component gases in the low concentration range. Specifically, as shown in Figure 3, the first component light CL1 has intensity within the wavelength range of λ3 or more and λ4 or less (i.e., the first wavelength range). Figure 3 is a diagram showing the intensity spectra of each component light.

[0037] On the other hand, the reflection spectrum of the separation member 5 has characteristics opposite to those of the transmission spectrum described above. That is, the separation member 5 reflects the component light (referred to as the third component light CL3) of the measurement light Lm that has passed through the measurement space Sp of the measurement cell 1, excluding the first component light CL1 which contains components in the first wavelength range. Specifically, as shown in Figure 3, the third component light CL3 includes component light with wavelengths less than λ3 and component light with wavelengths greater than λ4 of the measurement light Lm. In other words, the first component light CL1 is not included in the third component light CL3.

[0038] As shown in Figure 2, the reflection spectrum of the separation member 5 includes some components in a specific wavelength range. That is, the third component light CL3 reflected by the separation member 5 includes component light that is not included in the first wavelength range but is included in the specific wavelength range. This component light is absorbed by the component gas because it is included in the specific wavelength range, but its sensitivity to the component gas is low. This is because this component light is component light in the wavelength range at the "edge" of the specific wavelength range, and its absorption by the component gas is smaller compared to the first component light CL1.

[0039] However, this component light is sufficiently absorbed if the concentration of the component gas is high. Furthermore, even if the concentration of the component gas is high, the relationship between the information regarding the concentration of the component gas and the intensity of the component light measured by the sensor remains constant. Therefore, in this embodiment, the component light from the third component light CL3 that is not included in the first wavelength range but is included in a specific wavelength range is used as the second component light CL2 for the analysis of component gases in the high-concentration range. Specifically, as shown in Figure 3, the second component light CL2 has a significant intensity in the wavelength range of λ1 or more and λ3 or less, and in the wavelength range of λ4 or more and λ2 or less (the second wavelength range).

[0040] Thus, the separation member 5, which is a bandpass filter, can reliably separate the first component light CL1 containing components in the first wavelength range from the third component light CL3 containing components outside the first wavelength range. When the component gas is carbon dioxide and the measurement light Lm is infrared light, a bandpass filter having the above characteristics can be used, for example, a bandpass filter having a multilayer structure in which thin films of germanium (Ge) and thin films of silicon monoxide (SiO) are alternately deposited on a silicon (Si) substrate.

[0041] The configuration of the bandpass filter can be appropriately changed depending on the wavelength range of the measurement light Lm, the type of component gas, etc. Also, the separation member 5 only needs to be able to separate the measurement light Lm into the first component light CL1 and the third component light CL3 (second component light CL2), and may be a member other than a bandpass filter.

[0042] The first sensor unit 7 measures the intensity of the first component light CL1 transmitted through the separation member 5. In this embodiment, the first sensor unit 7 is a first pneumatic detector 7a having a sealed cell 7b containing a component gas (carbon dioxide in this embodiment) and capable of measuring the intensity of light in the above-mentioned specific wavelength range. By making the first sensor unit 7 a first pneumatic detector 7a, the intensity of the first component light CL1 included in the specific wavelength range can be selectively measured. The above-mentioned "selective" (or "selectivity") means that the measurement sensitivity to the intensity of light in a specific wavelength range is high, while the measurement sensitivity to the intensity of light in other wavelength ranges is low.

[0043] The second sensor unit 9 measures the intensity of the second component light CL2 contained in the third component light CL3 reflected by the separation member 5. In this embodiment, the second sensor unit 9 is a second pneumatic detector 9a having an enclosed cell 9b containing a component gas (carbon dioxide in this embodiment) and capable of measuring the intensity of light in the above-mentioned specific wavelength range. By using the second pneumatic detector 9a for the second sensor unit 9, the intensity of the second component light CL2 containing components in the specific wavelength range from the third component light CL3 can be selectively measured.

[0044] As shown in Figure 1, the second sensor unit 9 may have a second transmission filter 9c. The second transmission filter 9c is provided between the separation member 5 and the second pneumatic detector 9a and transmits light in a specific wavelength range. By providing the second transmission filter 9c in the second sensor unit 9, only the second component light CL2, which includes components in a specific wavelength range from the third component light CL3 reflected by the separation member 5, can be incident on the second pneumatic detector 9a. As a result, the selectivity of the second sensor unit 9 for the second component light CL2 can be further enhanced.

[0045] The second transmission filter 9c is, for example, a bandpass filter having a configuration similar to that of the separation member 5. However, the second transmission filter 9c is configured to transmit light in a wider wavelength range than the first wavelength range transmitted by the separation member 5, in order to cause the second component light CL2 to be incident on the second pneumatic detector 9a.

[0046] Furthermore, if the second pneumatic detector 9a has high selectivity for the second component light CL2, the second transmission filter 9c is not particularly necessary.

[0047] The control unit 11 is a computer system composed of a CPU, memory (RAM, ROM, etc.), various interfaces (e.g., D / A converter, A / D converter, etc.), a display, etc. The control unit 11 controls the gas analyzer 100 and performs various information processing. Some or all of the control and information processing performed by the control unit 11 may be implemented by a program stored in the memory of the computer system that constitutes the control unit 11. The control unit 11 may implement some or all of the control and information processing of the gas analyzer 100 in hardware. Furthermore, the control unit 11 may be a System on Chip (SoC) in which the CPU, memory, various interfaces, etc. are formed on a single chip.

[0048] As shown in Figure 4, the control unit 11 includes a calculation unit 111, a storage unit 113, and a display unit 115. Figure 4 is a diagram showing the configuration of the control unit.

[0049] The calculation unit 111 processes the electrical signal relating to the intensity of the first component light CL1 measured by the first sensor unit 7 and the electrical signal relating to the intensity of the second component light CL2 measured by the second sensor unit 9, and calculates the amount of absorption of the first component light CL1 and the second component light CL2 by the component gas. Based on this absorption amount, the calculation unit 111 calculates information regarding the concentration of the component gas contained in the sample gas Gs.

[0050] In this embodiment, the calculation unit 111 calculates information regarding the concentration of component gases in the low-concentration range based on the intensity of the first component light CL1 measured by the first sensor unit 7, and calculates information regarding the concentration of component gases in the high-concentration range based on the intensity of the second component light CL2 measured by the second sensor unit 9. Specifically, the calculation unit 111 can calculate information regarding component gases in the low-concentration range using a first calibration curve C1 that represents the relationship between information regarding the concentration of component gases and the intensity of the first component light CL1, and the intensity of the first component light CL1 measured by the first sensor unit 7. On the other hand, the calculation unit 111 can calculate information regarding component gases in the high-concentration range using a second calibration curve C2 that represents the relationship between information regarding the concentration of component gases and the intensity of the second component light CL2, and the intensity of the second component light CL2 measured by the second sensor unit 9.

[0051] As described above, the intensity of the first component light CL1 is measured by the first sensor unit 7, and the intensity of the second component light CL2 is measured by the second sensor unit 9. In other words, the intensities of the first component light CL1 and the second component light CL2 are measured by different sensors. Furthermore, the first component light CL1 and the second component light CL2 have different sensitivities to the component gas. Therefore, the first calibration curve C1 and the second calibration curve C2 are created separately.

[0052] The memory unit 113 is all or part of the memory area of ​​the memory device that constitutes the control unit 11, and stores setting values, various parameters, etc. used in the gas analyzer 100. Specifically, the memory unit 113 stores the first calibration curve C1 and the second calibration curve C2.

[0053] The display unit 115 is a display (for example, a liquid crystal display, an organic EL display, etc.) that constitutes the control unit 11. The display unit 115 displays various information related to the gas analyzer 100, such as the analysis results of component gases.

[0054] (2) Analysis of component gases using a gas analyzer The following describes the analysis operation of component gases using the gas analyzer 100 having the above configuration, with reference to Figure 5. Figure 5 is a flowchart of the analysis operation of component gases. First, the sample gas Gs or the reference gas Gr is alternately introduced into the measurement space Sp of the measurement cell 1. Then, in step S1, the light source 3 emits measurement light Lm toward the measurement cell 1.

[0055] The measurement light Lm emitted from the light source 3 passes through the measurement space Sp into which the sample gas Gs or reference gas Gr is introduced. When the sample gas Gs is introduced into the measurement space Sp, the measurement light Lm passes through the measurement space Sp while being absorbed by the component gases contained in the sample gas Gs. On the other hand, when the reference gas Gr is introduced into the measurement space Sp, the measurement light Lm passes through the measurement space Sp without being absorbed. This is because the reference gas Gr does not contain any component gases.

[0056] The measurement light Lm, which has passed through the measurement cell 1 in which sample gas Gs and reference gas Gr are alternately introduced, is incident on the separation member 5. The separation member 5 separates (transmits) the first component light CL1 from the incident measurement light Lm and causes it to enter the first sensor unit 7. The separation member 5 also separates (reflects) the third component light CL3 (second component light CL2) from the measurement light Lm and causes it to enter the second sensor unit 9.

[0057] Next, in step S2, the first pneumatic detector 7a of the first sensor unit 7 detects the first component light CL1. The first pneumatic detector 7a outputs a signal corresponding to the difference between the intensity of the first component light CL1 that has passed through the measurement space Sp filled with sample gas Gs and the intensity of the first component light CL1 that has passed through the measurement space Sp filled with reference gas Gr.

[0058] Furthermore, the second pneumatic detector 9a of the second sensor unit 9 detects the second component light CL2 contained in the third component light CL3. The second pneumatic detector 9a outputs a signal corresponding to the difference between the intensity of the second component light CL2 that has passed through the measurement space Sp filled with sample gas Gs and the intensity of the second component light CL2 that has passed through the measurement space Sp filled with reference gas Gr.

[0059] The calculation unit 111 receives a signal corresponding to the difference between the intensity of the first component light CL1 detected by the first pneumatic detector 7a after passing through the measurement space Sp filled with sample gas Gs, the intensity of the first component light CL1 after passing through the measurement space Sp filled with reference gas Gr, and the intensity of the sample gas Gs and reference gas Gr as they pass through the measurement cell.

[0060] Furthermore, the calculation unit 111 receives a signal corresponding to the intensity difference between the second component light CL2 detected by the second pneumatic detector 9a when it passes through the measurement cell between the sample gas Gs and the reference gas Gr. The second component light CL2 is output by the second pneumatic detector 9a, which has passed through the measurement space Sp filled with the sample gas Gs, and the second component light CL2 is passed through the measurement space Sp filled with the reference gas Gr. Based on the input signal, the calculation unit 111 analyzes the component gases.

[0061] In analyzing the component gases, the calculation unit 111 determines in step S3 whether the concentration of the component gases contained in the sample gas Gs is estimated to be above a predetermined concentration. The "predetermined concentration" used as the criterion for this determination can be appropriately determined by considering, for example, the concentration range in which the first calibration curve C1 and the second calibration curve C2 are constant (or can be considered constant with small changes), and the concentration range in which significant measurement results can be obtained by the second sensor unit 9.

[0062] Whether or not the concentration of the component gas is presumed to be above a predetermined concentration can be determined, for example, by actually calculating the concentration of the component gas from the signal corresponding to the intensity of the first component light CL1 and / or the signal corresponding to the intensity of the second component light CL2, and then determining whether or not the calculated concentration is above a predetermined concentration.

[0063] In addition, for example, it is possible to determine whether the concentration of the component gas contained in the sample gas Gs is estimated to be above a predetermined concentration by checking whether the signal corresponding to the intensity of the first component light CL1 and / or the signal corresponding to the intensity of the second component light CL2 is above (or below) a predetermined threshold.

[0064] If, as a result of the above determination, it is estimated that the concentration of the component gas is not above a predetermined concentration (No in step S3), the calculation unit 111 calculates information regarding the concentration of the component gas in step S4 based on the signal corresponding to the intensity of the first component light CL1 output from the first pneumatic detector 7a and the first calibration curve C1. For example, the calculation unit 111 can calculate the concentration of component gases in the low concentration range below the predetermined concentration by substituting the signal value corresponding to the intensity of the first component light CL1 output from the first pneumatic detector 7a into the first calibration curve C1, which represents the relationship between the intensity of the first component light CL1 and the concentration of the component gas.

[0065] On the other hand, if it is estimated that the concentration of the component gas is above a predetermined concentration (Yes in step S3), the calculation unit 111 calculates information regarding the concentration of the component gas in step S5 based on the signal corresponding to the intensity of the second component light CL2 output from the second pneumatic detector 9a and the second calibration curve C2. For example, the calculation unit 111 can calculate the concentration of component gases in the high-concentration range above a predetermined concentration by substituting the signal value corresponding to the intensity of the second component light CL2 output from the second pneumatic detector 9a into the second calibration curve C2, which represents the relationship between the intensity of the second component light CL2 and the concentration of the component gas.

[0066] As described above, the first component light CL1 contains components in the first wavelength range that are most absorbed by the component gas, and therefore exhibits high sensitivity even to low concentrations of component gas. In other words, by using the first component light CL1, significant measurement results can be obtained by the first sensor unit 7 even when the concentration of the component gas is low. Furthermore, when the concentration of the component gas is low, the relationship between the intensity of the first component light CL1 measured by the first sensor unit 7 and the information regarding the concentration of the component gas coincides with the first calibration curve C1. Therefore, by calculating information regarding the concentration of component gas in the low concentration range based on the intensity of the first component light CL1 measured by the first sensor unit 7, component gas can be analyzed accurately in the low concentration range.

[0067] On the other hand, the second component light CL2 includes components in a second wavelength range that includes a specific wavelength range absorbed by the component gas but does not include the first wavelength range. Therefore, the sensitivity of the second component light CL2 to the component gas is lower than that of the first component light CL1. However, the second component light CL2 shows significant sensitivity to the component gas when the concentration of the component gas is high. In other words, when the concentration of the component gas is high, significant measurement results can be obtained by the second sensor unit 9 using the second component light CL2. Furthermore, in the range of high component gas concentration, the relationship between the intensity of the second component light CL2 measured by the second sensor unit 9 and the information regarding the concentration of the component gas is consistent with the second calibration curve C2. Therefore, by calculating information regarding the concentration of the component gas in the high-concentration range based on the intensity of the second component light CL2 measured by the second sensor unit 9, the component gas can be analyzed accurately in the high-concentration range.

[0068] As described above, in the gas analyzer 100, the relationship between the intensity of component light measured by the sensor unit and the information regarding the concentration of component gases matches the first calibration curve C1 and the second calibration curve C2 over a wide range of component gas concentrations. In other words, the relationship between the intensity of component light measured by the sensor unit and the information regarding the concentration of component gases does not change from a predetermined relationship over a wide range of concentrations. As a result, the gas analyzer 100 can accurately analyze component gases over a wide concentration range contained in the sample gas Gs.

[0069] (3) Variation 1 In the first embodiment described above, the first sensor unit 7 was configured as a first pneumatic detector 7a and the second sensor unit 9 as a second pneumatic detector 9a in order to provide selectivity for light in a specific wavelength range absorbed by the component gas. However, the first sensor unit 7 and the second sensor unit 9 can be realized with other configurations as long as they have selectivity for light in a specific wavelength range.

[0070] For example, as shown in Figure 6, the first sensor unit 7' of the gas analyzer 100 of Modified Example 1 includes a first transmission filter 7a' and a first sensor element 7b'. Figure 6 is a diagram showing the configuration of the gas analyzer of Modified Example 1.

[0071] The first transmission filter 7a' is placed between the separation member 5 and the first sensor element 7b' and transmits light in a specific wavelength range. The first transmission filter 7a' is, for example, a bandpass filter having a configuration similar to that of the separation member 5. Preferably, the first transmission filter 7a' has the property of transmitting light in a wavelength range wider than the first wavelength range transmitted by the separation member 5.

[0072] The first sensor element 7b' measures the intensity of light that has passed through the first transmission filter 7a'. Since the first transmission filter 7a' transmits only light in a specific wavelength range, the first sensor element 7b' itself does not necessarily need to have any particular selectivity for light in a specific wavelength range. The first sensor element 7b' is, for example, a thermal solid-state sensor, a semiconductor sensor, or a quantum semiconductor sensor.

[0073] Furthermore, the second sensor unit 9' includes a third transmission filter 9a' and a second sensor element 9b'. The third transmission filter 9a' is positioned between the separating member 5 and the second sensor element 9b' and transmits light in a specific wavelength range. The third transmission filter 9a' is a bandpass filter having similar properties to the first transmission filter 7a' described above.

[0074] The second sensor element 9b' measures the intensity of light that has passed through the third transmission filter 9a'. Since the third transmission filter 9a' transmits only light in a specific wavelength range, the second sensor element 9b' itself does not necessarily need to have any particular selectivity for light in a specific wavelength range. The second sensor element 9b' is, for example, a thermal solid-state sensor, a semiconductor sensor, or a quantum semiconductor sensor.

[0075] In the modified example 1, even if the first sensor element 7b' and the second sensor element 9b' themselves do not have selectivity for a specific wavelength range, the intensities of the first component light CL1 and the second component light CL2, which include components in a specific wavelength range, can be selectively measured.

[0076] Alternatively, either the first sensor section 7, 7' or the second sensor section 9, 9' may be composed of the above-mentioned transmission filter and sensor element, while the other is a pneumatic detector that measures the intensity of light in a specific wavelength range.

[0077] (4) Modification example 2 Furthermore, as another modified example 2, as shown in Figure 7, the gas analyzer 100 may further include a fourth permeation filter 13, the first sensor section 7'' may be configured with a third sensor element 7a'', and the second sensor section 9'' may be configured with a fourth sensor element 9a''. Figure 7 is a diagram showing the configuration of the gas analyzer according to modified example 2.

[0078] The fourth transmission filter 13 is provided between the measurement cell 1 and the separation member 5 and transmits light in a specific wavelength range. The fourth transmission filter 13 is, for example, a bandpass filter having a configuration similar to that of the separation member 5 described above. Preferably, the fourth transmission filter 13 has the property of transmitting light in a wavelength range wider than the first wavelength range transmitted by the separation member 5.

[0079] By providing a fourth transmission filter 13 between the measurement cell 1 and the separation member 5, light containing only components within a specific wavelength range of the measurement light Lm can be incident on the separation member 5. As a result, the separation member 5 can reliably separate the first component light CL1 from the component light (i.e., the second component light CL2) of the third component light CL3 that contains components within a specific wavelength range.

[0080] The third sensor element 7a'' measures the intensity of the light (i.e., the first component light CL1) that has passed through the fourth transmission filter 13 and been transmitted by the separation member 5. Since the fourth transmission filter 13 transmits only light in a specific wavelength range, the third sensor element 7a'' itself does not necessarily have to have any particular selectivity for light in a specific wavelength range. The third sensor element 7a'' is, for example, a thermal solid-state sensor, a semiconductor sensor, or a quantum semiconductor sensor.

[0081] The fourth sensor element 9a'' measures the intensity of the light (i.e., the second component light CL2) that has passed through the fourth transmission filter 13 and been reflected by the separation member 5. Since the fourth transmission filter 13 transmits only light in a specific wavelength range, the fourth sensor element 9a'' itself does not necessarily have to have any particular selectivity for light in a specific wavelength range. The fourth sensor element 9a'' is, for example, a thermal solid-state sensor, a semiconductor sensor, or a quantum semiconductor sensor.

[0082] The third sensor element 7a'' and the fourth sensor element 9a'' may be of the same type or different types. Furthermore, one or both of the third sensor element 7a'' and the fourth sensor element 9a'' may be pneumatic detectors with selectivity for a specific wavelength range.

[0083] In the modified example 2, since it is not necessary to provide a transmission filter that transmits light in a specific wavelength range in each of the first and second sensor units, the first and second sensor units can be constructed at a low cost.

[0084] 2. Other Embodiments Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications are possible without departing from the spirit of the invention. In particular, the multiple embodiments and modifications described herein can be arbitrarily combined as needed. (A) The gas analyzer 100 (inlet 1a) may be connected to a sampling unit 101 that samples a gas containing the sample gas Gs from a flue or pipe and introduces it into the measurement space Sp (i.e., measurement cell 1) of the gas analyzer 100, as shown in Figure 8. Figure 8 is a diagram showing the connection relationship between the sampling unit and the analyzer.

[0085] The sampling unit 101 consists of, for example, a probe 1011 for sampling gas flowing through a flue or pipe, a collection filter 1013 for collecting dust and other particles contained in the sampled gas, and a pretreatment device 1015 for pre-treating the sampled gas (for example, comprising an electric cooler, a drain separator, a tube pump, and a mist catcher for removing sulfuric acid mist, salt, etc.).

[0086] (B) The gas analyzer 100 may include a comparison cell and an optical interruption mechanism. The comparison cell is a cell filled with a gas that does not absorb the measurement light Lm. The optical interruption mechanism is a mechanism that switches whether or not to simultaneously introduce the measurement light Lm into the measurement cell 1 and the comparison cell. Examples of such optical interruption mechanisms include a mechanism that combines a light source for the measurement cell 1, a light source for the comparison cell, and a chopper, and a mechanism that combines a flashing light source for the measurement cell 1 and a flashing light source for the comparison cell. The above light sources may be a single light source that can simultaneously introduce the measurement light Lm into the measurement cell 1 and the comparison cell. Alternatively, the optical interruption mechanism may be a mechanism that alternately introduces the measurement light Lm into the measurement cell 1 and the comparison cell.

[0087] In this case, the calculation unit 111 analyzes the component gases based on the difference between the intensity of the measurement light Lm (i.e., the first component light CL1 and the second component light CL2) that has passed through the measurement cell 1 and the intensity of the measurement light Lm that has passed through the comparison cell. This allows for more accurate analysis of the analytical gas by subtracting the background components included in the measurement result of the measurement light Lm after passing through the measurement cell 1. As a result, a reference gas Gr is not required. In addition, a gas switching unit 2, which alternately switches and introduces the sample gas Gs and the reference gas Gr into a single measurement cell 1, is not required.

[0088] (C) The information regarding component gases calculated based on the first component light CL1 and the second component light CL2 is not limited to information regarding the concentration of component gases. For example, the information regarding component gases may be a signal indicating that the component gases contained in the sample gas are outside a predetermined concentration range.

[0089] In this case, a signal indicating that the concentration of the component gas has fallen below a predetermined concentration range can be calculated based on the intensity of the first component light CL1 measured by the first sensor unit 7. On the other hand, a signal indicating that the concentration of the component gas has risen above a predetermined concentration range is calculated based on the intensity of the second component light CL2 measured by the second sensor unit 9.

[0090] (D) If the sample gas Gs is, for example, exhaust gas discharged from various combustion plants, the information regarding the component gases may be a control signal for controlling combustion in the combustion plant. In this case, the calculation unit 111 communicates with the control system (control panel) of the combustion plant and outputs the calculated information regarding the component gases to the control system.

[0091] In this case, the control signal required when the component gas concentration becomes low can be calculated based on the intensity of the first component light CL1 measured by the first sensor unit 7. On the other hand, the control signal required when the component gas concentration becomes high is calculated based on the intensity of the second component light CL2 measured by the second sensor unit 9.

[0092] Furthermore, information regarding the component gases (control signals for controlling combustion in the combustion plant) may be calculated based on the intensity of the first component light CL1 measured by the first sensor unit 7 and the intensity of the second component light CL2 measured by the second sensor unit 9. For example, the calculation unit 111 may calculate information regarding the component gases using the formula f(X) + g(Y) (f(X): a function of the intensity of the first component light CL1 measured by the first sensor unit 7, g(Y): a function of the intensity of the second component light CL2 measured by the second sensor unit 9). [Industrial applicability]

[0093] This invention can be widely applied to gas analyzers that analyze component gases contained in a sample gas. [Explanation of Symbols]

[0094] 100 Gas analyzer 1 Measurement cell Sp measurement space 1a Inlet 1b Outlet 2. Gas switching section 3 light source 5 Separation member 7, 7', 7'' First sensor section 7a First pneumatic detector 7b Enclosed Cell 7a' First transmission filter 7b' First sensor element 7a'' Third sensor element 9, 9', 9'' Second sensor section 9a Second pneumatic detector 9b Enclosed Cell 9a' Third transmission filter 9b' Second sensor element 9a'' Fourth sensor element 9c Second transmission filter 11 Control Unit 111 Arithmetic section 113 Storage section 115 Display section C1 First Calibration Curve C2 Second Calibration Curve 13. Fourth transmission filter 101 Sampling Unit 1011 Probe 1013 Collection filter 1015 Preprocessing device Lm measurement light CL1 First component light CL2 2nd component light CL3 Third component light Gs sample gas Gr reference gas

Claims

1. An apparatus for analyzing component gases contained in a sample gas, A measuring cell into which the sample gas is introduced, A light source that emits measurement light is placed inside the measurement cell, A separating member separates the measurement light that has passed through the measurement cell into: first component light, which includes a wavelength range that is most absorbed by the component gas within a specific wavelength range absorbed by the component gas, and which includes components in a first wavelength range that is narrower than the specific wavelength range; and third component light, which includes at least second component light, which includes components in a second wavelength range that is included in the specific wavelength range but not in the first wavelength range. A first sensor unit for measuring the intensity of the first component light, A second sensor unit for measuring the intensity of the second component light, A calculation unit calculates information about component gases in a low concentration range based on the intensity of the first component light measured by the first sensor unit, and calculates information about component gases in a high concentration range based on the intensity of the second component light measured by the second sensor unit. A gas analyzer equipped with the following features.

2. The gas analyzer according to claim 1, further comprising a gas switching unit inside the measuring cell for switching between introducing the sample gas and a reference gas that does not contain the component gas.

3. The gas analyzer according to claim 1, wherein the separating member is a bandpass filter that transmits the first component light and reflects the third component light.

4. The gas analyzer according to claim 1, wherein the first sensor unit includes a first pneumatic detector capable of measuring the intensity of light in the specific wavelength range.

5. The gas analyzer according to claim 1, wherein the first sensor unit includes a first transmission filter that transmits light in the specific wavelength range, and a thermal solid-state sensor or semiconductor sensor that measures the intensity of light that has passed through the first transmission filter.

6. The gas analyzer according to claim 1, wherein the second sensor unit includes a second pneumatic detector capable of measuring the intensity of light in the specific wavelength range.

7. The gas analyzer according to claim 6, wherein the second sensor unit is provided between the separation member and the second pneumatic detector and includes a second transmission filter that transmits light in the specific wavelength range.

8. The gas analyzer according to claim 1, wherein the second sensor unit includes a third transmission filter that transmits light in the specific wavelength range, and a thermal solid-state sensor or semiconductor sensor that measures the intensity of light that has passed through the third transmission filter.

9. The gas analyzer according to claim 1, further comprising a fourth transmission filter provided between the measuring cell and the separating member, which transmits light in the specific wavelength range.

10. The gas analyzer according to claim 9, wherein the first sensor unit and the second sensor unit are thermal solid-state sensors or semiconductor sensors that measure the intensity of light in the specific wavelength range.

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