Water environment dissolved gas concentration detection system

Abstract

The invention discloses a water environment dissolved gas concentration detection system, which comprises a light source, a lens group, a hollow-core anti-resonance optical fiber, an optical fiber gas sensor, a spectrometer and a processor, and is characterized in that light emitted by the light source is converged to the hollow-core anti-resonance optical fiber through the lens group; the optical fiber gas sensor comprises a water-gas separation device, a to-be-detected gas bin and a negative pressure bin, the to-be-detected gas bin and the negative pressure bin are connected with an opening of the hollow-core anti-resonance optical fiber, and emergent light of the hollow-core anti-resonance optical fiber enters the spectrograph; and the processor is used for calculating the gas concentration according to a spectrum detection result of the spectrograph. The embodiment of the invention can improve gas detection precision, reduce power consumption and volume, and can be widely applied to the technical field of gas detection.

Description

Technical Field

[0001] The present invention relates to the technical field of gas detection, and in particular to a dissolved gas concentration detection system in a water environment. Background Art

[0002] Gas concentration detection technology in water environment is used as an important tool for monitoring greenhouse gas content such as CO2 and CH4 in the ocean. Currently, it mainly includes the following methods, such as electrochemical method, Raman spectroscopy and infrared absorption spectroscopy. At present, there are the following problems in gas concentration detection in water environment: based on indirect sample measurement, it is easily affected by the environment, there is the possibility of gas escape, the detection accuracy is relatively low, the power consumption is high, and the volume is large. Summary of the invention

[0003] In view of this, in order to solve one of the above problems, an embodiment of the present invention aims to provide a dissolved gas concentration detection system in a water environment, which can improve gas detection accuracy and reduce power consumption and volume.

[0004] An embodiment of the present invention provides a system for detecting dissolved gas concentration in a water environment, comprising a light source, a lens group, a hollow-core anti-resonant optical fiber, a fiber optic gas sensor, a spectrometer and a processor, wherein light emitted by the light source is converged to the hollow-core anti-resonant optical fiber through the lens group, the fiber optic gas sensor comprises a water-gas separation device, a gas chamber to be tested and a negative pressure chamber, the gas chamber to be tested and the negative pressure chamber are connected to an opening of the hollow-core anti-resonant optical fiber, the outgoing light of the hollow-core anti-resonant optical fiber enters the spectrometer, and the processor calculates the gas concentration according to the spectral detection result of the spectrometer.

[0005] Optionally, the light source includes a near-infrared laser and a mid-infrared laser.

[0006] Optionally, the hollow-core antiresonant optical fiber comprises a capillary and a cladding, the inner wall of the cladding is provided with several layers of the capillary, and the center of the cladding is an air core.

[0007] Optionally, the dissolved gas concentration detection system in the water environment also includes a ventilation device, the opening of the hollow-core anti-resonant optical fiber includes an air inlet and an air outlet, the gas chamber to be tested is connected to the air inlet of the hollow-core anti-resonant optical fiber through the ventilation device, and the negative pressure chamber is connected to the air outlet of the hollow-core anti-resonant optical fiber through the ventilation device.

[0008] Optionally, the distance between the air inlet and the air outlet is in the range of 1 to 5 meters.

[0009] Optionally, the number of the air inlet holes or the air outlet holes is 2-6.

[0010] Optionally, the diameter of the opening of the hollow-core antiresonant optical fiber is less than 2 μm.

[0011] Optionally, the water-gas separation device includes a water treatment unit, a gas separation unit and a recovery unit.

[0012] Optionally, the processor calculates the gas concentration according to the following method:

[0013] The spectrum detection result of the spectrometer is obtained, and the spectrum detection result is input into a relational model for calculation to obtain the gas concentration; the relational model is determined according to sample data, and the sample data includes a spectrum detection sample and a sample gas concentration.

[0014] Optionally, during the test, the optical fiber gas sensor is placed in a water environment.

[0015] The implementation of the embodiment of the present invention includes the following beneficial effects: in this embodiment, the dissolved gas concentration detection system in the water environment includes a light source, a lens group, a hollow core anti-resonant optical fiber, an optical fiber gas sensor, a spectrometer and a processor. The light emitted by the light source is converged to the hollow core anti-resonant optical fiber through the lens group. The optical fiber gas sensor includes a water-gas separation device, a gas chamber to be tested and a negative pressure chamber. The gas chamber to be tested and the negative pressure chamber are connected to the opening of the hollow core anti-resonant optical fiber. The output light of the hollow core anti-resonant optical fiber enters the spectrometer. The processor calculates the gas concentration according to the spectral detection result of the spectrometer, directly separates the water vapor of the aqueous solution containing the dissolved gas, and performs concentration detection on the separated gas to be tested, thereby reducing the environmental impact and the possibility of escape of the gas to be tested, thereby improving the gas detection accuracy. In addition, the energy consumption of the detection system includes the light source and the spectrometer, and no other high-power devices are required, thereby reducing power consumption. The gas to be tested forms a resonant cavity in the hollow core anti-resonant optical fiber, reducing the length of the chamber where the gas to be tested interacts with the incident light, thereby reducing the volume of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a structural block diagram of a dissolved gas concentration detection system in a water environment provided by an embodiment of the present invention;

[0017] Figure 2 is a structural block diagram of an optical fiber gas sensor provided by an embodiment of the present invention;

[0018] Figure 3 is a stereoscopic diagram of a hollow-core antiresonant optical fiber provided by an embodiment of the present invention;

[0019] Figure 4 is a cross-sectional view of a hollow-core antiresonant optical fiber provided by an embodiment of the present invention;

[0020] Figure 5 It is a cross-sectional view of another hollow-core antiresonant optical fiber provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0021] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. The step numbers in the following embodiments are only provided for the convenience of explanation and description, and the order between the steps is not limited in any way. The execution order of each step in the embodiment can be adaptively adjusted according to the understanding of those skilled in the art.

[0022] like Figure 1 As shown, an embodiment of the present invention provides a system for detecting dissolved gas concentration in a water environment, comprising a light source (202), a lens group (203), a hollow core anti-resonance optical fiber (204), an optical fiber gas sensor (208), a spectrometer (205) and a processor (206). Light emitted by the light source (202) is converged to the hollow core anti-resonance optical fiber (204) through the lens group (203). The optical fiber gas sensor (205) comprises a water-gas separation device, a gas chamber to be tested and a negative pressure chamber. The gas chamber to be tested and the negative pressure chamber are connected to the opening of the hollow core anti-resonance optical fiber (204). The output light of the hollow core anti-resonance optical fiber (204) enters the spectrometer (205). The processor (206) calculates the gas concentration according to the spectrum detection result of the spectrometer (205).

[0023] Optionally, during the test, the optical fiber gas sensor is placed in a water environment. The optical fiber gas sensor (208) is placed in an underwater environment (207) during the detection process, and other components of the gas concentration detection system (light source (202), lens group (203), spectrometer (205) and processor (206)) are placed on a water platform or on land (201).

[0024] It should be noted that the lens group includes a "condenser lens" or a "focusing lens", which can be a combination lens formed by a spherical lens or an aspherical lens, etc. The lens group is used to focus the incident light to meet the transmission conditions of the incident light in the optical fiber and reduce the loss of light.

[0025] Hollow-core anti-resonant optical fiber can achieve low-loss, high-bandwidth transmission in the mid-infrared region. The water-gas separation device is used to separate the gas dissolved in the water environment. The gas separated by the water-gas separation device is gathered in the gas chamber to be tested. The gas chamber to be tested and the negative pressure chamber are connected by hollow-core anti-resonant optical fiber. The negative pressure chamber forms a negative pressure state, allowing the gas to flow in the hollow-core anti-resonant optical fiber, thereby fully interacting with the incident light.

[0026] Optionally, the gas concentration detection system also includes a ventilation device, the opening of the hollow-core anti-resonant optical fiber includes an air inlet and an air outlet, the gas chamber to be tested is connected to the air inlet of the hollow-core anti-resonant optical fiber through the ventilation device, and the negative pressure chamber is connected to the air outlet of the hollow-core anti-resonant optical fiber through the ventilation device.

[0027] The ventilation device is used to input the gas separated from the water environment into the hollow-core anti-resonant optical fiber, and the ventilation needs to ensure the airtightness of the connection. A chamber for gas circulation is formed between the air inlet and the air outlet of the hollow-core anti-resonant optical fiber. The ventilation device is determined according to the actual application, and this embodiment does not make specific restrictions. For example, the ventilation device is a gas guide port.

[0028] See also Figure 2 The optical fiber gas sensor (205) includes a water-gas separation device (101), a gas chamber to be tested (102) and a negative pressure chamber (103). The gas to be tested in the gas chamber to be tested (102) is connected to the air inlet (105) of the hollow core anti-resonant optical fiber (204) through the air guide port (104), and the negative pressure chamber (103) is also connected to the air outlet of the hollow core anti-resonant optical fiber through the air guide port, forming a resonant cavity (106) between the air inlet and the air outlet of the hollow core anti-resonant optical fiber (204). The negative pressure chamber can generate a negative pressure environment to accelerate the circulation of the gas to be tested (107) in the optical fiber sensing chamber. The air guide port connects the air inlet chamber and the opening of the anti-resonant optical fiber, and has airtightness.

[0029] Optionally, the light source comprises a near infrared laser or a mid infrared laser.

[0030] The wavelength of the laser light source is determined according to the characteristic absorption peak of the gas to be measured, and this embodiment does not impose any specific restrictions. For example, methane gas (CH4) has an absorption peak in the infrared region at a wavelength of 3.3 μm, and carbon dioxide gas (CO2) has an absorption peak in the infrared region at 4.26 μm. The light source includes but is not limited to a near-infrared laser or a mid-infrared laser.

[0031] Optionally, the hollow-core antiresonant optical fiber includes a capillary and a cladding, the inner wall of the cladding is provided with a plurality of layers of capillaries, and the center of the cladding is an air core.

[0032] See also Figures 3 to 5 , Figure 3 A three-dimensional diagram showing a hollow-core antiresonant fiber. Figure 4 A cross-sectional diagram showing a hollow-core antiresonant fiber. Figure 5 Another cross-sectional view of a hollow-core antiresonant fiber. The core of a hollow-core antiresonant fiber is an air hole, and one or more layers of quartz capillaries are introduced into the cladding. The capillaries are equivalent to resonant cavities. When the light transmitted in the fiber meets the resonance conditions, it will leak out from the cladding; otherwise, the light of the antiresonant wavelength will be confined to the core for transmission.

[0033] Optionally, the distance between the air inlet and the air outlet ranges from 1 to 5 meters.

[0034] In order to make the incident light contact and react more fully with the gas, the optical fiber length between the air inlet and the air outlet is designed to be 1-5 meters in the embodiment of the present invention. The actual length can be adjusted according to the reaction time and sensitivity, and this embodiment does not impose any specific restrictions.

[0035] Optionally, the number of the air inlet holes or the air outlet holes is 2-6.

[0036] Optionally, the diameter of the opening of the hollow-core antiresonant optical fiber is less than 2 μm.

[0037] It should be noted that the diameter, number and position of the openings of the hollow-core anti-resonant optical fiber can be determined by optical mode field simulation software to ensure that the intensity of the optical fiber and the transmittance of light are not affected. The design of the position and size of the openings of the hollow-core anti-resonant optical fiber needs to have little effect on the transmission of light inside the optical fiber. The embodiment of the present invention uses multi-physics field simulation software to simulate the light transmission characteristics after opening a hole in the hollow-core anti-resonant optical fiber, and uses a femtosecond laser to perform hole processing to obtain a hollow-core optical fiber with a vent.

[0038] Optionally, the water-gas separation device includes a water treatment unit, a gas separation unit and a recovery unit.

[0039] The water-gas separation device can capture and recover gases such as CH4 and CO2 dissolved in seawater. The water-gas separation device includes a seawater treatment unit, a gas separation unit and a recovery unit. After the seawater is filtered by the treatment unit, it is degassed by a membrane in the gas separation unit to obtain the gas dissolved in the seawater and flow into the air inlet of the recovery unit. The biological fouling and impurities in the seawater are removed by the seawater treatment unit to improve the sensitivity and accuracy of the detection.

[0040] Optionally, the processor calculates the gas concentration according to the following method:

[0041] The spectrum detection result of the spectrometer is obtained, and the spectrum detection result is input into the relational model for calculation to obtain the gas concentration; the relational model is determined according to the sample data, and the sample data includes the spectrum detection sample and the sample gas concentration.

[0042] Specifically, a relationship model is first constructed by spectral detection samples and sample gas concentrations in the sample data, and then the gas concentration is obtained according to the real-time spectral detection results and the determined relationship model. It should be noted that the specific form of the relationship model is determined according to the actual application, and this embodiment does not make any specific restrictions.

[0043] In a specific embodiment, a spectrum analysis algorithm is used to analyze the spectrum, and the corresponding relationship between the spectrum intensity and the gas concentration is obtained as follows:

[0044] C=ω(A′(λ,I))+b

[0045] Among them, C represents the gas concentration, ω represents the relationship model, A′(λ,I) represents the spectrum detection result of the spectrometer, and b represents the offset.

[0046] The detection process of the gas concentration detection system is described below with two specific embodiments.

[0047] Embodiment 1

[0048] The dissolved gas concentration detection system in the water environment is used for the in-situ detection of CH4 gas dissolved in the ocean. The gas concentration detection system includes an above-water part and an underwater part. The above-water part can be set on a ship or on land, and the underwater part can be seawater or other underwater environments. Since CH4 gas has an absorption peak in the infrared region with a wavelength of about 3.3μm, the spectrum range of the infrared light source is 1-5μm, and the power range is within 10W. The lens group is a lens system dedicated to infrared light, which can focus the infrared beam to the entrance of the hollow-core anti-resonant optical fiber to ensure that the light can be effectively transmitted to the hollow-core anti-resonant optical fiber. Since the CH4 gas in the optical fiber gas chamber has an absorption effect in the infrared region of 3.3μm, the infrared light passing through the optical fiber will be absorbed by the gas at a wavelength of 3.3μm, and finally received by the infrared spectrometer and converted into a corresponding relationship between wavelength and light intensity. Finally, the in-situ detection device of CH4 gas dissolved in the ocean is realized by simulating the relationship model ω1 between the spectral intensity I and the gas concentration C1.

[0049] C1=ω1(A1(λ,I))+b1

[0050] Among them, C1 represents the methane gas concentration, ω1 represents the relationship model between the CH4 gas concentration and the spectral intensity received by the spectrometer, A1(λ,I) represents the spectral detection result output by the spectrometer after gas absorption, and b1 represents the offset of the CH4 gas concentration detection model.

[0051] Embodiment 2

[0052] The dissolved gas concentration detection system in the water environment is used for the in-situ detection of dissolved CO2 gas in the marine environment. The detection of CO2 concentration in the marine environment is of great significance for greenhouse effect monitoring, marine biological research and global carbon cycle research. Since CO2 gas has a strong absorption peak in the 4.26μm infrared region, the hollow-core anti-resonant optical fiber is simulated and processed according to the characteristic absorption spectrum of CO2 so that its optical transmission range can cover the characteristic absorption spectrum of CO2, such as the spectral transmission range of 3.5-5μm. In addition, in view of the characteristic absorption spectrum of CO2, this embodiment needs to establish a spectral analysis algorithm model ω2 for CO2 gas concentration, that is:

[0053] C2=ω2(A2(λ,I))+b2

[0054] Among them, C2 represents the concentration of CO2 gas, ω2 represents the relationship model between CO2 gas concentration and the spectral intensity received by the spectrometer, A2(λ,I) represents the spectral detection result output by the spectrometer after gas absorption, and b2 represents the offset of the CO2 gas concentration detection model.

[0055] The implementation of the embodiment of the present invention includes the following beneficial effects: in this embodiment, the dissolved gas concentration detection system in the water environment includes a light source, a lens group, a hollow core anti-resonant optical fiber, an optical fiber gas sensor, a spectrometer and a processor. The light emitted by the light source is converged to the hollow core anti-resonant optical fiber through the lens group. The optical fiber gas sensor includes a water-gas separation device, a gas chamber to be tested and a negative pressure chamber. The gas chamber to be tested and the negative pressure chamber are connected to the opening of the hollow core anti-resonant optical fiber. The output light of the hollow core anti-resonant optical fiber enters the spectrometer. The processor calculates the gas concentration according to the spectral detection result of the spectrometer, directly separates the water vapor of the aqueous solution containing the dissolved gas, and performs concentration detection on the separated gas to be tested, thereby reducing the environmental impact and the possibility of escape of the gas to be tested, thereby improving the gas detection accuracy. In addition, the energy consumption of the detection system includes the light source and the spectrometer, and no other high-power devices are required, thereby reducing power consumption. The gas to be tested forms a resonant cavity in the hollow core anti-resonant optical fiber, reducing the length of the chamber where the gas to be tested interacts with the incident light, thereby reducing the volume of the system.

[0056] The above is a specific description of the preferred implementation of the present invention, but the invention is not limited to the embodiments. Those skilled in the art may make various equivalent modifications or substitutions without violating the spirit of the present invention. These equivalent modifications or substitutions are all included in the scope defined by the claims of this application.

Claims

1. A dissolved gas concentration detection system in a water environment, characterized in that: The optical fiber gas sensor comprises a light source, a lens group, a hollow-core anti-resonant optical fiber, a fiber optic gas sensor, a spectrometer and a processor. The light emitted by the light source is converged to the hollow-core anti-resonant optical fiber through the lens group. The fiber optic gas sensor comprises a water-gas separation device, a gas chamber to be tested and a negative pressure chamber. The gas chamber to be tested and the negative pressure chamber are connected to the opening of the hollow-core anti-resonant optical fiber. The outgoing light of the hollow-core anti-resonant optical fiber enters the spectrometer. The processor calculates the gas concentration according to the spectral detection result of the spectrometer.

2. The dissolved gas concentration detection system in water environment according to claim 1, characterized in that: The light source includes a near-infrared laser or a mid-infrared laser.

3. The dissolved gas concentration detection system in water environment according to claim 1, characterized in that: The hollow core anti-resonance optical fiber comprises a capillary and a cladding, the inner wall of the cladding is provided with several layers of the capillary, and the center of the cladding is an air core.

4. The dissolved gas concentration detection system in water environment according to claim 1, characterized in that: The dissolved gas concentration detection system in the water environment also includes a ventilation device, the opening of the hollow-core anti-resonance optical fiber includes an air inlet and an air outlet, the gas chamber to be tested is connected to the air inlet of the hollow-core anti-resonance optical fiber through the ventilation device, and the negative pressure chamber is connected to the air outlet of the hollow-core anti-resonance optical fiber through the ventilation device.

5. The dissolved gas concentration detection system in water environment according to claim 4, characterized in that: The distance between the air inlet and the air outlet is in the range of 1 to 5 meters.

6. The dissolved gas concentration detection system in water environment according to claim 4, characterized in that: The number of the air inlet holes or the air outlet holes is 2-6.

7. The dissolved gas concentration detection system in water environment according to claim 1, characterized in that: The diameter of the opening of the hollow-core anti-resonance optical fiber is less than 2 μm.

8. The dissolved gas concentration detection system in water environment according to claim 1, characterized in that: The water-gas separation device comprises a water treatment unit, a gas separation unit and a recovery unit.

9. The dissolved gas concentration detection system in water environment according to claim 1, characterized in that: The processor calculates the gas concentration according to the following method: The spectrum detection result of the spectrometer is obtained, and the spectrum detection result is input into a relational model for calculation to obtain the gas concentration; the relational model is determined according to sample data, and the sample data includes a spectrum detection sample and a sample gas concentration.

10. The dissolved gas concentration detection system in water environment according to claim 1, characterized in that: During the test, the optical fiber gas sensor was placed in a water environment.

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