Gas measurement system with long optical path and low detection limit
By setting the laser beam in the gas measurement system to reflect through the multi-reverse gas tank and increasing the optical path limit, the problem of uncontrollable optical path in the prior art is solved, and accurate measurement of the long-range optical path of gas in industrial production is achieved.
Patent Information
- Application Number
- CN202421627183.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-07-08
- Publication Date
- 2025-05-09
- Estimated Expiration
- 2034-07-08
AI Technical Summary
In the application of existing TDLAS technology in industrial production sites, the optical path is affected by the diameter of the gas pipeline and the optical path length cannot be controlled, resulting in inaccurate measurement of low-concentration gases.
A gas measurement system with a long optical path and low detection limit is designed, and a laser beam is sequentially reflected through the first reflector, a multi-reflection cell, and a second reflector to the photoelectric conversion module, so as to realize multiple reflections to increase the optical path limit.
It realizes accurate and effective measurement of process gases generated in industrial production processes with long optical paths, significantly improving the signal-to-noise ratio of the gas measurement system.
Smart Images
Figure CN222850509U_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the technical field of laser gas analysis, and in particular to a gas measurement system with a long optical path and a low detection limit. Background Art
[0002] In modern industrial production, process gas monitoring can effectively reflect industrial production efficiency and improve industrial production safety. Therefore, high-precision gas analysis equipment is of great significance. According to the Beer-Lamber law, a specific gas can absorb a laser of a specific wavelength, and the absorption intensity is proportional to the interaction distance between the laser and the target gas (hereinafter referred to as the optical path). TDLAS (Tunable Diode Laser Absorption Spectroscopy) is a spectral technology based on the Beer-Lamber law, which mainly includes laser light sources, photodetectors, gas cells and data processing systems. According to the Beer-Lamber law, the detection limit of TDLAS technology is directly affected by the optical path.
[0003] The most direct application method of TDLAS technology in industrial production sites is in-situ installation, that is, opening holes on both sides of the process gas exhaust pipeline, and installing the laser light source and the detector opposite each other to directly measure. However, the optical path of this installation method is affected by the diameter of the gas pipeline, and the optical path length cannot be controlled. In addition, some low-concentration gases are affected by the optical path, which ultimately makes it impossible to accurately and effectively measure the process gas. Utility Model Content
[0004] In order to solve or partially solve the problems existing in the above-mentioned related technologies, the present application provides a gas measurement system with a long optical path and a low detection limit, which can realize accurate and effective long optical path measurement of process gases generated in industrial production processes.
[0005] In a first aspect, the embodiments of the present application provide a gas measurement system with a long optical path and a low detection limit, which adopts the following technical solutions:
[0006] A gas measurement system with a long optical path and a low detection limit comprises: a laser, a first reflector, a multi-gas reflector, a second reflector, a photoelectric conversion module, a signal processing module and a display module, wherein the photoelectric conversion module is electrically connected to the signal processing module, the signal processing module is electrically connected to the display module, and the multi-gas reflector is used to reflect the laser beam multiple times; wherein the laser is used to emit the laser beam to the first reflector, the laser beam is reflected by the first reflector, the multi-gas reflector and the second reflector in sequence to the photoelectric conversion module for conversion into an electrical signal, and the converted electrical signal is transmitted to the signal processing module for analysis and processing to obtain target data, and then the target data is sent to the display module for display.
[0007] By adopting the above technical solution, the laser beam is arranged to be reflected by the first reflector, the multi-gas pool, and the second reflector in sequence to the photoelectric conversion module for conversion into an electrical signal, thereby increasing the optical path limit of the laser beam by multiple reflections through multiple reflectors, so as to realize accurate and effective measurement of the long optical path of the process gas generated in the industrial production process.
[0008] Optionally, the multi-reflection cell includes a window plate, a third reflector and a fourth reflector, the third reflector and the fourth reflector are arranged relative to each other, and the window plate is located above the third reflector for the incident and emitted laser beam; wherein the laser beam first passes through the window plate into between the third reflector and the fourth reflector to be reflected, and then is transmitted through the window plate to the second reflector.
[0009] By adopting the above technical solution, the third reflector and the fourth reflector are arranged relative to each other, so that the laser beam can be reflected multiple times between the two, thereby increasing the optical path of the laser beam; and both the incident and the outgoing are through the window piece, and the window piece is located above the third reflector, that is, on the same side, which can facilitate the miniaturization integration of the gas measurement system.
[0010] Optionally, the distance between the third reflector and the fourth reflector is 0.25 m.
[0011] By adopting the above technical solution and setting the distance between the third reflector and the fourth reflector to 0.25 m, the laser beam can be reflected back and forth 52 times between the third reflector and the fourth reflector, increasing the optical path from 0.25 m to 13 m, greatly increasing the optical path and improving the signal-to-noise ratio of the gas measurement system.
[0012] Optionally, the long optical path and low detection limit gas measurement system further includes: a laser driving module electrically connected to the laser and used to control the output wavelength of the laser based on the driving temperature and the driving current.
[0013] By adopting the above technical solution, the laser driving module can drive the laser to emit a laser beam, and at the same time can change the output wavelength of the laser based on the driving temperature and the driving current.
[0014] Optionally, the first reflector, the second reflector, the third reflector and the fourth reflector are all plated with a gold film, and the thickness of the gold film is 100 um.
[0015] By adopting the above technical solution, a gold film is plated on the reflector, and the gold film is 100 um, which can increase the reflectivity of the reflector to infrared lasers, so as to reduce the energy loss of laser reflection as much as possible.
[0016] Optionally, the third reflector and the fourth reflector are both coated with a SiO2 protective film.
[0017] By adopting the above technical solution and coating the SiO2 protective film, it is possible to avoid damage to the reflector surface caused by corrosive gases during the gas testing process of the system, thus greatly saving costs.
[0018] Optionally, an anti-reflection film is coated on the window piece.
[0019] By adopting the above technical solution, the coating of the anti-reflection film can reduce the energy loss generated when the laser passes through the window piece.
[0020] Optionally, the optical surfaces on both sides of the window sheet have a wedge angle of 0.5°.
[0021] By adopting the above technical solution, a wedge angle of 0.5° can reduce the interference noise generated by the laser between the optical surfaces on both sides of the window.
[0022] In summary, the present application includes at least one of the following beneficial technical effects:
[0023] 1. The laser beam is sequentially reflected by the first reflector, the multi-gas reflector, and the second reflector to the photoelectric conversion module for conversion of electrical signals. Multiple reflections by multiple reflectors can increase the optical path limit of the laser beam, so as to achieve accurate and effective measurement of the process gas generated in the industrial production process over a long optical path;
[0024] 2. The third reflector and the fourth reflector are arranged relative to each other, so that the laser beam can be reflected multiple times between the two, thereby increasing the optical path of the laser beam; and both the incident and the outgoing are through the window piece, and the window piece is located above the third reflector, that is, on the same side, which can facilitate the miniaturization integration of the gas measurement system.
[0025] 3. Setting the distance between the third reflector and the fourth reflector to 0.25 m allows the laser beam to reflect back and forth 52 times between the third reflector and the fourth reflector, increasing the optical path from 0.25 m to 13 m, greatly increasing the optical path and improving the signal-to-noise ratio of the gas measurement system. BRIEF DESCRIPTION OF THE DRAWINGS
[0026] Figure 1 A schematic diagram of the structure of a gas measurement system with a long optical path and a low detection limit disclosed in an embodiment of the present application;
[0027] Figure 2 is a schematic diagram of a state where the light spot is located at the outer circle of the third reflector and the fourth reflector;
[0028] Figure 3 Schematic diagram of the comparison of the signal intensity of 40 ppm H2S in a multi-reverse gas cell and the signal intensity of 750 ppm H2S in a normal gas cell.
[0029] Description of reference numerals:
[0030] 10. Laser driving module; 20. Laser; 30. First reflector; 40. Multi-reflector pool; 41. Window; 42. Third reflector; 43. Fourth reflector; 50. Second reflector; 60. Photoelectric conversion module; 70. Signal processing module; 80. Display module. DETAILED DESCRIPTION
[0031] The terms used in the following embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to be used as limitations to the present application. As used in the specification and appended claims of the present application, the singular expressions "one", "a kind of", "above", "the" and "this" are intended to also include plural expressions, unless there is an explicit contrary indication in the context. It should also be understood that the term "and / or" used in the present application refers to and includes any or all possible combinations of one or more listed items.
[0032] In the following, the terms "first" and "second" are used for descriptive purposes only and are not to be understood as suggesting or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features, and in the description of the embodiments of the present application, unless otherwise specified, "plurality" means two or more.
[0033] The technical solution of the embodiments of the present application is described in detail below with reference to the accompanying drawings.
[0034] See also Figure 1, which is a long optical path and low detection limit gas measurement system disclosed in an embodiment of the present application, including: a laser driving module 10, a laser 20, a first reflector 30, a multi-reflector pool 40, a second reflector 50, a photoelectric conversion module 60, a signal processing module 70 and a display module 80.
[0035] The laser driving module 10 can control the laser 20 to emit a laser wavelength within the range of, for example, 1574.6±1 nm based on temperature and current, which can cover the absorption peak of H2S, thereby enabling measurement of H2S gas. It is noted that in the embodiment of the present application, the "low detection limit" is the lower limit of the detected gas concentration.
[0036] The laser 20 is, for example, a TO-packaged narrow-linewidth semiconductor laser with a central wavelength of 1574.6 nm. The laser 20 has the advantage of a narrow spectral linewidth and can suppress the influence of laser intensity noise on the gas measurement system.
[0037] The first reflector 30 and the second reflector 50 are both light reflectors for reflecting laser light.
[0038] The multi-reflection pool 40 is a multi-reflection space composed of multiple reflectors, for example, two reflectors. When the laser beam enters the multi-reflection pool 40, multiple reflections will occur. It is explained here that the optical path length is related to the number of reflections. The more reflections there are, the longer the optical path length is.
[0039] Among them, the multi-reflection cell 40 includes a window piece 41, a third reflector 42 and a fourth reflector 43. The window piece 41 is located above the third reflector 42 and is used for the incident and emitted laser beam. The third reflector 42 and the fourth reflector 43 are arranged opposite to each other, and the window piece 41 is located above the third reflector 42.
[0040] It is worth mentioning that in another embodiment, the window piece 41 and the third reflector 42 can be integrated, such as digging out the window piece 41 at the upper end of the third reflector 42 , or directly setting the window piece 41 at the upper end of the third reflector 42 .
[0041] During measurement, the laser beam reflected by the first reflector 30 first passes through the window 41 and enters between the third reflector 42 and the fourth reflector 43 for multiple reflections, and then reflects to the second reflector 50 through the window 41. Therefore, the laser beam is reflected multiple times between the third reflector 42 and the fourth reflector 43, which can increase the optical path of the laser beam. In addition, the incident and emitted laser beams are both through the window 41, and the window 41 is located above the third reflector 42, that is, on the same side, which can facilitate the miniaturization integration of the gas measurement system, reduce the investment in devices, and reduce costs.
[0042] For example, the distance between the third reflector 42 and the fourth reflector 43 is set to 0.25 m, and the corresponding laser beam can be reflected back and forth 52 times between the third reflector and the fourth reflector ( Figure 2 The number of reflections shown in the figure is only for reference), which increases the optical path from 0.25 m to 13 m, greatly increasing the optical path and improving the signal-to-noise ratio of the gas measurement system.
[0043] It is explained here that the third reflector 42 and the fourth reflector 43 are also light reflectors, and during reflection, the laser spot is located at the outer ring of the third reflector 42 and the fourth reflector 43 (see Figure 2 ), and ensure that there is no intersection between the light spots, thereby avoiding interference noise generated when the laser beam is reflected between the third reflector 42 and the fourth reflector 43.
[0044] The photoelectric conversion module 60 is electrically connected to the signal processing module 70, and is used to convert the optical signal of the laser beam into an electrical signal and transmit it to the signal processing module 70. The signal processing module 70 is electrically connected to the display module 80, and is used to perform data analysis on the electrical signal and then transmit the analyzed data to the display module 80 such as a host computer for display.
[0045] In this embodiment, during measurement, the overall optical path is that the laser beam emitted by the laser 20 is reflected by the first reflector 30, the multi-gas pool 40, and the second reflector 50 in sequence to the photoelectric conversion module 60 for conversion of electrical signals, and the converted electrical signals are transmitted to the signal processing module 70 for analysis and processing to obtain target data, and then the target data is sent to the display module 80 for display. In this way, the optical path of the laser beam is increased by multiple reflections through multiple reflectors, thereby achieving accurate and effective measurement of process gases generated in industrial production processes over long optical paths.
[0046] Furthermore, a gold film is plated on the first reflector 30 , the second reflector 50 , the third reflector 42 and the fourth reflector 43 .
[0047] Among them, the thickness of the gold film is 100 um, and the reflectivity of the gold film to infrared laser can reach more than 98%, which can reduce the energy loss of laser reflection as much as possible.
[0048] Furthermore, the third reflector 42 and the fourth reflector 43 are also coated with a SiO2 protective film, which can prevent the corrosive gas from damaging the surface of the third reflector 42 and the fourth reflector 43 during the gas test process of the system, thereby greatly saving costs. It is noted that the coating of the SiO2 protective film can be performed after the gold film is plated, and the first reflector 30 and the second reflector 50 are also applicable.
[0049] In addition, in order to increase the light transmittance of the window plate 41 and reduce the energy loss generated when the laser passes through the window plate 41 , an anti-reflection film is plated on the window plate 41 .
[0050] It is explained here that the coating of the anti-reflection film is more suitable for the 1050-1700 nm laser band, and the laser transmittance in this band can reach more than 99.5%, so as to further reduce the energy loss generated when the laser passes through the window plate 41.
[0051] In addition, it is worth mentioning that the optical surfaces on both sides of the window piece 41, namely the incident surface and the exit surface, have a wedge angle of 0.5°, namely the window piece has a wedge structure of 0.5°, thereby reducing the interference noise generated by the laser between the optical surfaces on both sides of the window piece 41.
[0052] For example, see Figure 3 , which is a comparison diagram of the signal intensity of 40 ppm H2S in the multi-retrogas cell 40 (optical path of 13 m) and the signal intensity of 750 ppm H2S in the ordinary gas cell (optical path of 0.7 m). It can be seen from the figure that the signal intensity of 40 ppm H2S gas in the multi-retrogas cell 40 is close to the signal intensity of 750 ppm H2S gas in the ordinary gas cell. This shows that the setting of the multi-retrogas cell 40 significantly improves the detection limit of the gas measurement system.
[0053] In summary, the embodiment of the present application discloses a gas measurement system with a long optical path and a low detection limit, in which a laser beam is reflected sequentially through a first reflector 30, a multi-gas reflector 40, and a second reflector 50 to a photoelectric conversion module 60 for conversion into an electrical signal, thereby increasing the optical path limit of the laser beam by multiple reflections through multiple reflectors, so as to achieve accurate and effective long optical path measurement of process gases generated in industrial production processes; the third reflector 42 and the fourth reflector 43 are arranged relative to each other, so that the laser beam can be reflected multiple times between the two, thereby increasing the optical path of the laser beam; and both the incident and the outgoing are through the window piece 41, and the window piece 41 is located above the third reflector 42, that is, on the same side, which can facilitate the miniaturization integration of the gas measurement system.
[0054] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application.
Claims
1. A gas measurement system with long optical path and low detection limit, characterized in that: include: A laser (20), a first reflector (30), a multi-reflector gas pool (40), a second reflector (50), a photoelectric conversion module (60), a signal processing module (70) and a display module (80), wherein the photoelectric conversion module (60) is electrically connected to the signal processing module (70), the signal processing module (70) is electrically connected to the display module (80), and the multi-reflector gas pool (40) is used to reflect the laser beam multiple times; The laser (20) is used to emit the laser beam toward the first reflector (30), and the laser beam is reflected by the first reflector (30), the multi-reflector (40), and the second reflector (50) in sequence to the photoelectric conversion module (60) for conversion into an electrical signal, and the converted electrical signal is transmitted to the signal processing module (70) for analysis and processing to obtain target data, and the target data is then sent to the display module (80) for display.
2. The long optical path and low detection limit gas measurement system according to claim 1, characterized in that: The multi-reflection gas cell (40) comprises a window sheet (41), a third reflector (42) and a fourth reflector (43), the third reflector (42) and the fourth reflector (43) being arranged opposite to each other, the window sheet (41) being located above the third reflector (42) and being used for the laser beam to be incident and emitted; The laser beam first passes through the window sheet (41) to enter between the third reflector (42) and the fourth reflector (43) for reflection, and then passes through the window sheet (41) to be reflected to the second reflector (50).
3. The long optical path and low detection limit gas measurement system according to claim 2, characterized in that: The distance between the third reflector (42) and the fourth reflector (43) is 0.25 m.
4. The long optical path and low detection limit gas measurement system according to claim 1, characterized in that: Also includes: A laser driving module (10) is electrically connected to the laser (20) and is used to control the output wavelength of the laser beam based on a driving temperature and a driving current.
5. The long optical path and low detection limit gas measurement system according to claim 2, characterized in that: The first reflector (30), the second reflector (50), the third reflector (42) and the fourth reflector (43) are all plated with a gold film, and the thickness of the gold film is 100 um.
6. The long optical path and low detection limit gas measurement system according to claim 2, characterized in that: The third reflector (42) and the fourth reflector (43) are both plated with a SiO2 protective film.
7. The long optical path and low detection limit gas measurement system according to claim 2, characterized in that: The window plate (41) is plated with an anti-reflection film.
8. The long optical path and low detection limit gas measurement system according to claim 2, characterized in that: The optical surfaces on both sides of the window plate (41) have a wedge angle of 0.5°.