Gas analyzer and gas analysis method

Abstract

It accurately measures gas concentration even when disturbances such as vibrations are present. [Solution] The gas analyzer 1 according to the present disclosure comprises a laser light source 11 that irradiates a gas to be measured 20 with laser light, a first light receiving unit 14 that receives laser light that has passed through the gas to be measured 20, a second light receiving unit 15 that receives laser light that does not pass through the gas to be measured 20, and a calculation unit 16 that corrects the first light quantity, which is the amount of laser light received by the first light receiving unit 14, based on a second light quantity, which is the amount of laser light received by the second light receiving unit 15 when the first light receiving unit 14 is receiving the laser light.

Description

Technical Field

[0007] ,

[0001] The present disclosure relates to a gas analyzer and a gas analysis method.

Background Art

[0002] A method for measuring the concentration of a gas by laser gas absorption spectroscopy is known. Laser gas absorption spectroscopy utilizes the property that gas molecules absorb light of a specific wavelength. Laser gas absorption spectroscopy is an analytical technique that irradiates a measurement target gas with laser light adjusted to the wavelength of the gas type, calculates the absorbance from the ratio between the signal obtained by receiving the laser light that has passed through the gas and the irradiated laser light, and measures the concentration of the gas.

[0003] For example, Patent Document 1 discloses a gas analyzer that branches a part of the measurement light irradiated from a light emitting unit as reference light and accurately calculates the concentration of a gas using the reference light.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] When measuring the concentration of a measurement target gas, if disturbances such as vibrations are applied to the gas analyzer, it is difficult to perform accurate measurement due to a decrease in the amount of measurement light caused by an optical axis deviation.

[0006] Therefore, an object of the present disclosure is to provide a gas analyzer and a gas analysis method capable of accurately measuring the concentration of a gas even when disturbances such as vibrations are applied.

Means for Solving the Problems

[0007] [1] A laser light source that irradiates the gas to be measured with laser light, A first light-receiving unit that receives the laser light that has passed through the gas to be measured, A second light-receiving unit that receives the laser light that does not pass through the gas to be measured, A calculation unit that corrects the first light quantity, which is the amount of light from the laser beam received by the first light receiving unit, based on the second light quantity, which is the amount of light from the laser beam received by the second light receiving unit when the first light receiving unit is receiving the laser beam, A gas analyzer equipped with the following features. With this type of gas analyzer, even if disturbances such as vibrations reduce the amount of light being measured, it is possible to accurately measure the gas concentration by correcting the first light intensity.

[0008] [2] In the gas analyzer described in [1] above, The calculation unit may calculate the concentration of the gas to be measured based on the corrected first light intensity. This allows for the accurate calculation of the concentration of the target gas.

[0009] [3] In the gas analyzer described in [1] or [2] above, The system further comprises a first optical component disposed between the laser light source and the gas to be measured. The first optical component may irradiate the gas to be measured with the laser light emitted from the laser light source in parallel. This allows the laser light emitted from the laser light source to be directed parallel to the gas being measured.

[0010] [4] In the gas analyzer described in any one of the above items [1] to [3], The first light receiving unit receives the laser light that has passed through the first optical component and the gas to be measured, The second light-receiving unit may receive the laser light that does not pass through the first optical component and the gas to be measured. This allows the second light-receiving unit to receive stray light that does not pass through the first optical component and the gas being measured.

[0011] [5] In the gas analyzer described in any one of the above items [1] to [4], The first optical component may be a collimator. This allows the laser light emitted by the laser light source to be made parallel by the collimator.

[0012] [6] In the gas analyzer described in any one of the above items [1] to [5], The calculation unit may correct the first light quantity based on the following formula (1). Pm = P1 - N × (P2 - P0) (1) However, in equation (1), Pm is the corrected light intensity, P1 is the first light intensity, P2 is the second light intensity, P0 is the light intensity measured in advance by the second light receiving unit in the absence of disturbances, and N is a parameter that indicates the amplification factor for equalizing the difference in intensity between the second and first light intensity. This allows for accurate correction of the first light intensity.

[0013] [7] The step of irradiating the gas to be measured with laser light, The first light receiving unit receives the laser light that has passed through the gas to be measured, The second light-receiving unit receives the laser light that does not pass through the gas to be measured, The steps include correcting the first light intensity, which is the amount of laser light received by the first light receiving unit, based on the second light intensity, which is the amount of laser light received by the second light receiving unit when the first light receiving unit is receiving the laser light, Gas analysis methods, including those mentioned above. This type of gas analysis method makes it possible to accurately measure gas concentrations even when disturbances such as vibrations are present.

[0014] [8] In the gas analysis method described in [7] above, The process may further include the step of calculating the concentration of the gas to be measured based on the corrected first light intensity. As a result, the concentration of the gas to be measured can be accurately calculated.

Advantages of the Invention

[0015] According to the present disclosure, it is possible to provide a gas analyzer and a gas analysis method capable of accurately measuring the concentration of a gas even when disturbances such as vibrations are applied and the amount of light of the measurement light decreases.

Brief Description of the Drawings

[0016] [Figure 1] It is a diagram showing a schematic configuration of a gas analyzer according to an embodiment. [Figure 2] It is a diagram showing an example of the current of a laser light source and the amount of light of a second light receiving unit. [Figure 3] It is a diagram showing a state where the laser light source is vibrating. [Figure 4] It is a diagram showing an example of the vibration of a laser light source and the amount of light of a second light receiving unit when there is vibration. [Figure 5] It is a diagram showing an example of the amount of light of a first light receiving unit when there is no vibration. [Figure 6] It is a diagram showing an example of the amount of light of a first light receiving unit when there is vibration. [Figure 7] It is a flowchart showing an example of the operation of a gas analyzer according to an embodiment.

Modes for Carrying Out the Invention

[0017] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0018] FIG. 1 is a diagram showing a schematic configuration of a gas analyzer 1 according to an embodiment. The gas analyzer 1 includes a laser light source 11, a first optical component 12, a second optical component 13, a first light receiving unit 14, a second light receiving unit 15, and an arithmetic unit 16.

[0019] The gas analyzer 1 can measure the concentration of the target gas 20 by laser gas absorption spectroscopy. The gas analyzer 1 can measure the concentration of the target gas 20 by positioning the target gas 20 between the first optical component 12 and the second optical component 13.

[0020] The laser light source 11 emits laser light. The laser light source 11 can irradiate the gas to be measured 20 with laser light via the first optical component 12. The laser light source 11 may be any laser light source capable of sweeping the wavelength of the laser light by adjusting the current flowing through the laser light source 11. The laser light source 11 irradiates the gas to be measured 20 with laser light so as to sweep the wavelength around the wavelength absorbed by the gas to be measured 20.

[0021] The first optical component 12 is positioned between the laser light source 11 and the gas to be measured 20. The first optical component 12 directs the laser beam emitted from the laser light source 11 parallel to the gas to be measured 20. The first optical component 12 may be any optical component capable of directing the laser beam emitted from the laser light source 11 parallel. The first optical component 12 may be, for example, a collimator.

[0022] The laser light source 11 emits laser light at a predetermined irradiation angle, but of the laser light emitted by the laser light source 11, some of the laser light passes through the first optical component 12, and some of the laser light does not pass through the first optical component 12.

[0023] Of the laser light emitted by the laser light source 11, the laser light that passes through the first optical component 12 is irradiated onto the gas to be measured 20. Of the laser light emitted by the laser light source 11, a portion of the laser light that does not pass through the first optical component 12 reaches the second light receiving unit 15 as leaked light.

[0024] The second optical component 13 is positioned between the gas to be measured 20 and the first light-receiving unit 14. The second optical component 13 focuses the laser light that has passed through the gas to be measured 20. The laser light focused by the second optical component 13 is received by the first light-receiving unit 14. The second optical component 13 may be any optical component capable of focusing the laser light that has passed through the gas to be measured 20.

[0025] The first light-receiving unit 14 receives laser light that has passed through the gas 20 to be measured via the second optical component 13. The first light-receiving unit 14 may have any photodetector capable of detecting laser light. For example, the first light-receiving unit 14 may have a photodiode. The first light-receiving unit 14 outputs an electrical signal corresponding to the amount of light of the received laser light.

[0026] The second light-receiving unit 15 receives laser light that does not pass through the gas 20 to be measured. The second light-receiving unit 15 is positioned to receive laser light from the laser light source 11 that does not pass through the first optical component 12. This allows the second light-receiving unit 15 to receive laser light that does not pass through the gas 20 to be measured. The second light-receiving unit 15 may have any photodetector capable of detecting laser light. For example, the second light-receiving unit 15 may have a photodiode. The second light-receiving unit 15 outputs an electrical signal corresponding to the amount of light of the received laser light.

[0027] The arithmetic unit 16 includes at least one processor, at least one dedicated circuit, or a combination thereof. The processor is a general-purpose processor such as a CPU (Central Processing Unit) or GPU (Graphics Processing Unit), or a dedicated processor specialized for a specific process. The dedicated circuit is, for example, an FPGA (Field-Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit). The arithmetic unit 16 controls each part of the gas analyzer 1 and executes processes related to the operation of the gas analyzer 1.

[0028] The calculation unit 16 corrects the amount of laser light received by the first light receiving unit 14 based on the amount of laser light received by the second light receiving unit 15 when the first light receiving unit 14 is receiving the laser light. Details of the processing performed by the calculation unit 16 will be described later.

[0029] Next, we will explain the operation of the gas analyzer 1.

[0030] The gas analyzer 1 sweeps the wavelength of the laser light emitted by the laser light source 11 by sweeping the current flowing through the laser light source 11. The upper graph of Figure 2 shows how the current flowing through the laser light source 11 is swept. In the example shown in Figure 2, the current flowing through the laser light source 11 is swept so that the current increases monotonically from time ts to time te. Since the wavelength of the laser light emitted by the laser light source 11 depends on the current, the laser light source 11 can sweep the wavelength of the emitted laser light in this way.

[0031] The lower graph in Figure 2 shows the amount of light received by the second light-receiving unit 15 when the current flowing through the laser light source 11 is swept. As shown in Figure 2, as the current flowing through the laser light source 11 increases, the amount of light received by the second light-receiving unit 15 also increases accordingly.

[0032] Figure 3 shows the vibration of the laser light source 11 as a disturbance to the gas analyzer 1. In this embodiment, as an example of a disturbance to the gas analyzer 1, we will explain the case in which a disturbance such as vibration of the laser light source 11 is applied to the gas analyzer 1.

[0033] The upper graph in Figure 4 shows the oscillation of the laser light source 11 when it oscillates once while the wavelength of the laser light is swept from time ts to time te. In the example shown in the upper graph of Figure 4, the laser light source 11 is stationary at the position indicated by the dashed line in Figure 3 from time ts to time t1. Then, between time t1 and time t2, the laser light source 11 moves to the position indicated by the solid line in Figure 3, and then returns to the position indicated by the dashed line. Then, between time t2 and time te, the laser light source 11 is stationary at the position indicated by the dashed line in Figure 3.

[0034] The lower graph in Figure 4 shows the amount of laser light received by the second light receiving unit 15 when the laser light source 11 vibrates as shown in the upper graph in Figure 4. Hereafter, the "amount of laser light received by the second light receiving unit 15" may be simply referred to as the "second light quantity."

[0035] The second light-receiving unit 15 directly receives the stray laser light emitted by the laser light source 11. Therefore, the second light quantity received by the second light-receiving unit 15 changes depending on the vibration of the laser light source 11. The lower graph of Figure 4 shows how the second light quantity changes in response to the vibration of the laser light source 11 between time t1 and time t2. Here, "stray light" refers to the laser light emitted by the laser light source 11 that reaches the second light-receiving unit 15 directly without passing through the first optical component 12 and the gas to be measured 20.

[0036] Figure 5 shows an example of the amount of light received by the first light receiving unit 14 when the laser light source 11 is not vibrating. Hereafter, the "amount of laser light received by the first light receiving unit 14" may be simply referred to as the "first light quantity."

[0037] In the example shown in Figure 5, there is a portion just before time t2 in which the first light intensity received by the first light receiving unit 14 decreases. This means that just before time t2, the target gas 20 is absorbing a large amount of laser light at the wavelength of the laser light emitted by the laser light source 11.

[0038] Figure 6 shows an example of the amount of light received by the first light receiving unit 14 when the laser light source 11 is vibrating. Figure 6 shows the first amount of light received by the first light receiving unit 14 when the laser light source 11 is vibrating as shown in the upper graph of Figure 4.

[0039] In Figure 6, the "Before Correction" graph shows the first light intensity received by the first light receiving unit 14. The "After Correction" graph shows the first light intensity received by the first light receiving unit 14 corrected based on the second light intensity received by the second light receiving unit 15.

[0040] As mentioned above, the uncorrected graph shown in Figure 6 represents the first light intensity itself received by the first light receiving unit 14. Looking at the uncorrected graph, there is a portion between time t1 and time t2 where the first light intensity decreases. This decrease in the first light intensity is the result of two overlapping effects: the absorption of laser light by the gas being measured 20 and the vibration of the laser light source 11. Therefore, in order to measure only the portion of laser light absorbed by the gas being measured 20, it is necessary to correct the graph to remove the effect of the vibration of the laser light source 11.

[0041] The calculation unit 16 corrects the first light quantity received by the first light receiving unit 14 based on the second light quantity received by the second light receiving unit 15 when the first light receiving unit 14 is receiving laser light. The calculation unit 16 corrects the first light quantity based, for example, on the following equation (1). Pm = P1 - N × (P2 - P0) (1) However, in equation (1), Pm is the corrected light intensity, P1 is the first light intensity, P2 is the second light intensity, P0 is the light intensity measured in advance by the second light receiving unit 15 in the absence of disturbances, and N is a parameter.

[0042] Let's explain equation (1) above in more detail.

[0043] In equation (1) above, P0 is the amount of light received by the second light receiving unit 15 when the wavelength of the laser light is swept in a state free from disturbances such as vibrations. P0 is, for example, the data shown in the lower graph of Figure 2. The calculation unit 16 may store the P0 data. Alternatively, the calculation unit 16 may read the P0 data stored in an external memory or the like.

[0044] In equation (1) above, P2 is the amount of light received by the second light receiving unit 15 when the wavelength of the laser light is swept. If the laser light source 11 vibrates while the wavelength of the laser light is being swept, P2 will be, for example, the data shown in the lower graph of Figure 4.

[0045] In equation (1) above, the calculation unit 16 can calculate the contribution of the vibration of the laser light source 11 by subtracting P0 from P2.

[0046] In equation (1) above, parameter N is determined by the ratio of the amount of laser light emitted by the laser light source 11 to the amount of laser light emitted to the second light receiving unit 15 as stray light. In other words, parameter N is a parameter that indicates the amplification factor for equalizing the difference in intensity between the second and first light quantities. Since the amount of laser light emitted to the second light receiving unit 15 as stray light can be small compared to the amount of laser light emitted to the first optical component 12, parameter N will be a larger value. For example, parameter N may be around 10 to 100.

[0047] As shown in equation (1) above, the calculation unit 16 can calculate the corrected light intensity Pm, which subtracts the effect of vibration of the laser light source 11, by subtracting P0 from P2 and multiplying the result by N from P1. The corrected light intensity Pm will be the data shown as "corrected" in the lower graph of Figure 6, for example. By performing such a correction, the corrected light intensity Pm will be equivalent to the data of the first light intensity when there is no vibration, as shown in Figure 5.

[0048] The calculation unit 16 acquires an electrical signal corresponding to the first light intensity from the first light receiving unit 14 and an electrical signal corresponding to the second light intensity from the second light receiving unit 15. Based on the electrical signal corresponding to the first light intensity and the electrical signal corresponding to the second light intensity, the calculation unit 16 may perform the calculation shown in equation (1) above.

[0049] The calculation unit 16 calculates the corrected light intensity Pm, then calculates the absorption spectrum based on the corrected light intensity Pm, and can calculate the concentration of the target gas 20. The calculation unit 16 can calculate the concentration of the target gas 20 by, for example, a conventionally known laser gas absorption spectroscopy method.

[0050] As described above, the gas analyzer 1 according to this embodiment corrects the first light quantity received by the first light receiving unit 14 based on the second light quantity received by the second light receiving unit 15 at the same timing as when the first light receiving unit 14 receives the laser light that has passed through the gas 20 to be measured. As a result, even if disturbances such as vibrations occur while the laser light source 11 is sweeping the laser light, causing fluctuations in the first light quantity received by the first light receiving unit 14, the concentration of the gas 20 to be measured can be measured with high accuracy.

[0051] For example, it is conceivable to correct the amount of light received by the first light receiving unit 14 based on the amount of stray light measured by the second light receiving unit 15 at a different timing before the measurement by the first light receiving unit 14 is performed. In this case, for example, if the disturbance is periodic and continues for a long time, it may be possible to appropriately correct the disturbance. However, for disturbances such as instantaneous mechanical vibrations, the method of correcting based on stray light measured at a different timing cannot appropriately correct the amount of light received by the first light receiving unit 14. In contrast, the gas analyzer 1 according to this embodiment corrects the first amount of light received by the first light receiving unit 14 based on the second amount of light received by the second light receiving unit 15 at the same timing as when the first light receiving unit 14 is receiving the laser light that has passed through the gas 20 to be measured. Therefore, even when mechanical vibrations occur instantaneously, the concentration of the gas 20 to be measured can be measured with high accuracy.

[0052] The operation of the gas analyzer 1 will be explained with reference to the flowchart shown in Figure 7.

[0053] Step S101: The first light receiving unit 14 receives the laser light that has passed through the gas 20 to be measured. At this time, the wavelength of the laser light emitted by the laser light source 11 is swept.

[0054] Step S102: The second light-receiving unit 15 receives laser light that does not pass through the gas 20 to be measured. The timing at which the second light-receiving unit 15 receives laser light that does not pass through the gas 20 to be measured in step S102 is the same timing at which the first light-receiving unit 14 receives laser light that has passed through the gas 20 to be measured in step S101.

[0055] Step S103: The calculation unit 16 corrects the first light quantity received by the first light receiving unit 14 based on the second light quantity received by the second light receiving unit 15 when the first light receiving unit 14 is receiving laser light. The calculation unit 16 may correct the first light quantity based on, for example, equation (1) described above. This allows the calculation unit 16 to correct disturbances such as vibrations of the laser light source 11.

[0056] Step S104: The calculation unit 16 calculates the concentration of the target gas 20 based on the corrected first light intensity. As a result, the gas concentration of the target gas 20 calculated by the calculation unit 16 is the gas concentration corrected for the effect of concentration errors caused by disturbances such as vibrations of the laser light source 11.

[0057] According to the gas analyzer 1 of the above embodiment, the concentration of the target gas 20 can be measured accurately even when disturbances such as vibrations are applied. More specifically, the gas analyzer 1 includes a laser light source 11 that irradiates the target gas 20 with laser light, a first light receiving unit 14 that receives the laser light that has passed through the target gas 20, a second light receiving unit 15 that receives the laser light that has not passed through the target gas 20, and a calculation unit 16 that corrects the first light quantity received by the first light receiving unit 14 based on the second light quantity received by the second light receiving unit 15 when the first light receiving unit 14 is receiving the laser light. Thus, in order to correct the first light quantity received by the first light receiving unit 14 based on the second light quantity received by the second light receiving unit 15 at the same timing as when the first light receiving unit 14 is receiving the laser light, the gas analyzer 1 according to one embodiment can correct the effect of disturbances such as vibrations when the first light receiving unit 14 is receiving the laser light. Therefore, the gas analyzer 1 according to one embodiment can accurately measure the concentration of the target gas 20 even when disturbances such as vibrations are present.

[0058] It will be apparent to those skilled in the art that this disclosure can be implemented in other predetermined forms besides the embodiments described above without deviating from its spirit or essential features. Therefore, the prior description is illustrative and not limiting. The scope of the disclosure is defined not by the prior description but by the added claims. Any modifications within their equivalent scope are incorporated therein.

[0059] For example, the arrangement and number of each component described above are not limited to those shown in the above description and drawings. The arrangement and number of each component may be configured arbitrarily, as long as it can achieve its function.

[0060] For example, in the embodiment described above, the case in which the laser light source 11 vibrates was used as an example, but this is just one example, and the gas analyzer 1 according to this embodiment can correct the first light quantity received by the first light receiving unit 14 even when components other than the laser light source 11 vibrate.

[0061] For example, in the embodiment described above, the wavelength band of the laser light emitted by the laser light source 11 and the type of gas to be measured 20 are not specified, but the gas analyzer 1 according to this embodiment can accurately correct the first light quantity received by the first light receiving unit 14 regardless of the wavelength band of the laser light and the type of gas to be measured 20. [Explanation of symbols]

[0062] 1. Gas analyzer 11 Laser light source 12. First optical component 13. Second optical component 14 1st light receiving section 15 2nd light receiving section 16 Arithmetic section 20. Gases to be measured

Claims

1. A laser light source that irradiates the gas to be measured with laser light, A first light receiving unit that receives the laser light that has passed through the gas to be measured, A second light-receiving unit that receives the laser light that does not pass through the gas to be measured, A calculation unit that corrects the first light quantity, which is the amount of light from the laser beam received by the first light receiving unit, based on the second light quantity, which is the amount of light from the laser beam received by the second light receiving unit when the first light receiving unit is receiving the laser beam, A gas analyzer equipped with the following features.

2. In the gas analyzer according to claim 1, The calculation unit calculates the concentration of the target gas based on the corrected first light intensity, and is a gas analyzer.

3. In the gas analyzer according to claim 1, The system further comprises a first optical component positioned between the laser light source and the gas to be measured. The first optical component is a gas analyzer that irradiates the target gas with the laser light emitted by the laser light source in parallel.

4. In the gas analyzer described in claim 3, The first light receiving unit receives the laser light that has passed through the first optical component and the gas to be measured, The second light-receiving unit receives the laser light that does not pass through the first optical component and the gas to be measured, in a gas analyzer.

5. In the gas analyzer described in claim 3, The first optical component is a collimator, in a gas analyzer.

6. In the gas analyzer according to claim 1, The calculation unit corrects the first light intensity based on the following formula (1) in the gas analyzer. Pm=P1-N×(P2-P0) (1) However, in equation (1), Pm is the corrected light intensity, P1 is the first light intensity, P2 is the second light intensity, P0 is the light intensity measured in advance by the second light receiving unit in the absence of disturbances, and N is a parameter that indicates the amplification factor for equalizing the difference in intensity between the second light intensity and the first light intensity.

7. The steps include irradiating the gas to be measured with laser light, The first light receiving unit receives the laser light that has passed through the gas to be measured, The second light-receiving unit receives the laser light that does not pass through the gas to be measured, The first light receiving unit corrects the first light receiving unit's light intensity based on the second light intensity, which is the light intensity of the laser light received by the second light receiving unit when the first light receiving unit is receiving the laser light. Gas analysis methods, including those mentioned above.

8. In the gas analysis method described in claim 7, A gas analysis method further comprising the step of calculating the concentration of the gas to be measured based on the corrected first light intensity.

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