Carbon dioxide concentration detection device based on optical fiber sensing and sealing monitoring system

Abstract

According to the carbon dioxide concentration detection device based on optical fiber sensing and the storage monitoring system provided by the invention, the first optical fiber sensing unit with a modular structure is designed, so that the contact part of the sensitive coating and the optical fiber Bragg grating can be independently maintained and replaced, and the optical fiber reflection wavelength drift caused by the CO2 concentration change in the environment can be accurately detected. Meanwhile, a fiber bragg grating which is not covered with a CO2 sensitive coating is arranged as a reference, and wavelength drift mainly generated by environmental interference factors is detected. The influence of environmental interference factors on the wavelength drift of the CO2 optical fiber sensor can be eliminated by calculating the wavelength drift distance of the two fiber bragg gratings and combining the mathematical model of the wavelength drift distance and the CO2 concentration, and then the accurate CO2 concentration value is obtained. According to the invention, high-efficiency real-time monitoring of CO2 concentration in the geological storage process of CO2 is realized, and data accuracy and reliability are ensured. Moreover, the modular design facilitates the regular inspection and replacement of the sensor, prolongs the service life, reduces the maintenance cost, and is high in sensitivity, strong in stability, and good in maintainability.

Description

Technical Field

[0001] The present invention relates to the technical field of geological storage, and particularly to a carbon dioxide concentration detection device and a storage monitoring system based on optical fiber sensing. Background Art

[0002] At present, with the continuous development of CO2 geological storage technology, the real-time monitoring of CO2 concentration has become increasingly important. In the prior art, the main methods for CO2 concentration monitoring include chemical sensors, electrochemical sensors, infrared absorption method, and optical fiber sensing-based technologies, etc.

[0003] Among them, chemical sensors and electrochemical sensors are widely used in CO2 monitoring. These sensors usually detect the change of CO2 concentration through electrochemical reaction or chemical reaction. However, such sensors generally have the disadvantages of slow response speed, poor selectivity, easy aging, and complex maintenance. The infrared absorption method calculates the CO2 concentration by measuring the absorption intensity of CO2 gas on infrared light with a specific wavelength. Although this method has good sensitivity, it requires a specific light source and a high-precision optical detector, resulting in a high system cost and requiring a strong light-free interference and relatively stable temperature and humidity in the use environment, otherwise it will affect the measurement accuracy.

[0004] Optical fiber sensing technology, especially the sensing technology based on fiber Bragg grating or long-period grating, has been widely used in recent years. Optical fiber sensors have the advantages of good anti-electromagnetic interference ability, strong environmental resistance, high sensitivity, fast response speed, etc., so they have great application potential in CO2 concentration monitoring. Although optical fiber sensing technology has certain advantages in CO2 monitoring, the prior art still faces problems such as aging and maintenance of the sensitive coating, lack of modular design, and insufficient temperature stability. Although optical fiber sensing technology has shown high potential in CO2 concentration detection, due to the imperfect combination method of fiber Bragg grating or fiber grating and CO2 sensitive coating, and the lack of modular structure in the existing design, it is difficult to meet the long-term, stable, and efficient monitoring requirements. Summary of the Invention

[0005] In view of the above-mentioned disadvantages of the prior art, the purpose of the present invention is to provide a carbon dioxide concentration detection device and a storage monitoring system based on optical fiber sensing, which are used to solve the technical problems such as slow response speed, poor selectivity, easy aging, complex maintenance, high cost, poor environmental adaptability, lack of modular design, and insufficient temperature stability in the prior art for CO2 concentration monitoring.

[0006] To achieve the above and other related objectives, the present invention provides a carbon dioxide concentration detection device based on fiber optic sensing. The device includes: a first fiber optic sensing unit, a second fiber optic sensing unit, a light source unit, a data acquisition unit, and a data processing unit. Among them, the first fiber optic sensing unit adopts a modular design and includes: a fiber Bragg grating and a CO2 sensitive coating module. The CO2 sensitive coating module is installed on the fiber Bragg grating so that the CO2 sensitive coating inside it covers the fiber Bragg grating. The first fiber optic sensing unit is used to generate wavelength drift through the fiber Bragg grating covered with the CO2 sensitive coating and reflect the corresponding optical signal. The second fiber optic sensing unit includes: a fiber Bragg grating not covered with the CO2 sensitive coating, arranged around the fiber Bragg grating of the first fiber optic sensing unit. The second fiber optic sensing unit is used to generate wavelength drift through the fiber Bragg grating inside it that is not covered with the CO2 sensitive coating and reflect the corresponding optical signal. The light source unit is used to provide a stable excitation optical signal to the first fiber optic sensing unit and the second fiber optic sensing unit. The data acquisition unit is used to receive the optical signals reflected by the fiber Bragg gratings in the first fiber optic sensing unit and the second fiber optic sensing unit respectively, and extract the wavelength drift information corresponding to the optical signals reflected by the first fiber optic sensing unit and the second fiber optic sensing unit. The data processing unit is used to calculate the wavelength drift amount respectively according to the extracted wavelength drift information corresponding to the optical signals reflected by the first fiber optic sensing unit and the second fiber optic sensing unit, and obtain the corresponding CO2 concentration based on the established mathematical model of the wavelength drift amount and the CO2 concentration.

[0007] In an embodiment of the present invention, the CO2 sensitive coating module is provided with a CO2 sensitive coating, a substrate for supporting the CO2 sensitive coating, and a protective housing. Among them, the surface of the substrate is coated with the CO2 sensitive coating, and allows CO2 gas to penetrate to the CO2 sensitive coating. The protective housing is used to prevent the external environment from damaging the first fiber optic sensing unit. By installing the CO2 sensitive coating module on the fiber Bragg grating of the first fiber optic sensing unit and making the surface of the substrate coated with the CO2 sensitive coating in close contact with the corresponding fiber surface, when CO2 gas penetrates to the CO2 sensitive coating, it reacts with the CO2 sensitive coating, resulting in changes in the physical properties of the CO2 sensitive coating, and further causing the reflection wavelength of the fiber Bragg grating to drift.

[0008] In an embodiment of the present invention, the protective housing is provided with a fixing structure for detachably installing the CO2 sensitive coating module on the fiber Bragg grating. Among them, the fixing structure includes: one or more of a mechanical interlocking structure, an elastic clamping mechanism, and a magnetic coupling structure.

[0009] In an embodiment of the present invention, the light source unit includes: a light source for providing a stable excitation optical signal through a broadband spontaneous emission light source or a supercontinuum light source; a temperature control system connected to the light source for real-time monitoring of the temperature of the light source and automatically adjusting the temperature through a thermoelectric cooler to provide a stable excitation optical signal.

[0010] In an embodiment of the present invention, the data acquisition unit includes: a signal receiving module for receiving, through a spectrometer or an optical detector, the optical signals respectively reflected by the fiber Bragg gratings in the first fiber sensing unit and the second fiber sensing unit, and respectively converting them into electrical signals; a signal processing module connected to the signal receiving module for amplifying the electrical signals converted from the optical signals reflected by the fiber Bragg gratings in the first fiber sensing unit and the second fiber sensing unit through a low-noise amplifier, and performing filtering and demodulation processing on the amplified electrical signals to extract the wavelength drift information corresponding to the optical signals reflected by the first fiber sensing unit and the second fiber sensing unit; a storage module connected to the signal processing module for storing the wavelength drift information extracted by the signal processing module; a position determination module connected to the signal receiving module for identifying the light source position from which the received optical signal comes.

[0011] In an embodiment of the present invention, the data processing unit includes: a wavelength drift amount acquisition module for obtaining the central wavelength of the corresponding reflection spectrum according to the wavelength drift information of the optical signals reflected by the first fiber sensing unit and the second fiber sensing unit by using high-speed sampling and frequency analysis algorithms, and calculating the wavelength drift amounts of the first fiber sensing unit and the second fiber sensing unit; a CO2 concentration calculation module connected to the wavelength drift amount acquisition module for obtaining the corresponding CO2 concentration based on the mathematical model constructed between the wavelength drift amount and the CO2 concentration according to the wavelength drift amounts of the first fiber sensing unit and the second fiber sensing unit.

[0012] In an embodiment of the present invention, the construction method of the mathematical model between the wavelength drift amount and the CO2 concentration includes: receiving the optical signals reflected by the fiber Bragg gratings of the first fiber sensing unit and the second fiber sensing unit in a standard gas environment with different CO2 concentrations, and calculating the wavelength drift amounts of the first fiber sensing unit and the second fiber sensing unit corresponding to different CO2 concentrations; training to obtain the mathematical model between the wavelength drift amount and the CO2 concentration based on the wavelength drift amounts of the first fiber sensing unit and the second fiber sensing unit corresponding to each CO2 concentration.

[0013] In an embodiment of the present invention, the mathematical model of the wavelength drift amount and the CO2 concentration includes: a decoupling module, configured to separate the influences of temperature and pressure on the wavelength drift of the fiber Bragg grating in the first fiber sensing unit according to the input wavelength drift amount corresponding to the second fiber sensing unit, so as to extract the wavelength drift amount mainly related to the CO2 concentration from the wavelength drift amount corresponding to the first fiber sensing unit; a CO2 concentration detection module, connected to the decoupling module, configured to calculate the corresponding CO2 concentration based on the calibration curve constructed between the wavelength drift and the CO2 concentration according to the wavelength drift amount mainly related to the CO2 concentration.

[0014] In an embodiment of the present invention, the data processing unit further includes: an automatic calibration module, configured to regularly calibrate the mathematical model of the wavelength drift amount and the CO2 concentration with data of standard gases with different CO2 concentrations; a remote data transmission module, configured to upload the obtained CO2 concentration to a remote monitoring platform; an anomaly detection module, configured to perform anomaly analysis on the wavelength drift data, automatically identify possible fault states, and trigger an alarm signal; a visualization display module, configured to real-time display the CO2 concentration change curve through a graphical interface and provide historical data query and analysis functions.

[0015] To achieve the above object and other related objects, the present invention provides a carbon dioxide geological sequestration monitoring system, and the system includes: the carbon dioxide concentration detection device based on fiber sensing as described above.

[0016] As described above, the present invention is a carbon dioxide concentration detection device and a sequestration monitoring system based on fiber sensing, and has the following beneficial effects: The present invention designs a first fiber sensing unit with a modular structure, so that the contact part between the sensitive coating and the fiber Bragg grating can be independently maintained and replaced, and can accurately detect the wavelength drift of the fiber reflection caused by the change of CO2 concentration in the environment. At the same time, the present invention sets a fiber Bragg grating without a CO2 sensitive coating as a reference to detect the wavelength drift mainly generated by environmental interference factors. By calculating the wavelength drift amounts of the two fiber Bragg gratings and combining the mathematical model of the wavelength drift amount and the CO2 concentration, the influence of environmental interference factors on the wavelength drift of the CO2 fiber sensor can be eliminated, and then an accurate CO2 concentration value can be obtained. The present invention realizes the efficient real-time monitoring of the CO2 concentration during the carbon dioxide geological sequestration process, ensuring accurate and reliable data. And the modular design facilitates the regular inspection and replacement of the sensor, extends the service life, reduces the maintenance cost, and has high sensitivity, strong stability and good maintainability. Description of the Drawings

[0017] Figure 1 It shows a schematic structural diagram of the carbon dioxide concentration detection device based on fiber sensing in an embodiment of the present invention.

[0018] Figure 2 It shows a schematic structural diagram of the first optical fiber sensing unit in an embodiment of the present invention.

[0019] Figure 3 It shows a schematic structural diagram of a carbon dioxide concentration detection device based on optical fiber sensing in an embodiment of the present invention.

[0020] Figure 4 It shows a schematic structural diagram of a CO2 geological storage monitoring system in an embodiment of the present invention. Detailed implementation manners

[0021] The following uses specific specific examples to illustrate the implementation manners of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation manners. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0022] It should be noted that in the following description, reference is made to the accompanying drawings, which describe several embodiments of the present invention. It should be understood that other embodiments can also be used, and mechanical composition, structure, electrical, and operational changes can be made without departing from the spirit and scope of the present invention. The following detailed description should not be considered restrictive, and the scope of the embodiments of the present invention is only defined by the claims of the published patent. The terms used here are only for describing specific embodiments and are not intended to limit the present invention. Spatially related terms, such as "upper", "lower", "left", "right", "below", "beneath", "lower part", "above", "upper part", etc., can be used in the text to facilitate the description of the relationship between one element or feature shown in the figure and another element or feature.

[0023] Throughout the specification, when it is said that a certain part is "connected" to another part, this includes not only the case of "direct connection", but also the case of "indirect connection" with other elements placed in between. In addition, when it is said that a certain part "includes" a certain component, unless there is a particularly contrary record, it does not mean excluding other components, but means that other components can also be included.

[0024] The first, second, third, etc. terms mentioned herein are used to illustrate various parts, components, regions, layers, and / or segments, but are not limited thereto. These terms are only used to distinguish a part, component, region, layer, or segment from other parts, components, regions, layers, or segments. Therefore, the first part, component, region, layer, or segment described below may refer to the second part, component, region, layer, or segment without exceeding the scope of the present invention.

[0025] Furthermore, as used herein, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It should be further understood that the terms "comprising", "including" indicate the presence of the stated features, operations, elements, components, items, kinds, and / or groups, but do not preclude the presence, occurrence, or addition of one or more other features, operations, elements, components, items, kinds, and / or groups. The terms "or" and "and / or" used herein are interpreted as inclusive, or meaning any one or any combination. Thus, "A, B, or C" or "A, B, and / or C" means "any one of the following: A; B; C; A and B; A and C; B and C; A, B, and C". An exception to this definition occurs only when the combination of elements, functions, or operations is inherently mutually exclusive in some way.

[0026] The present invention provides a carbon dioxide concentration detection device based on fiber optic sensing. A first fiber optic sensing unit with a modular structure is designed, enabling the contact part between the sensitive coating and the fiber Bragg grating to be independently maintained and replaced, and capable of accurately detecting the wavelength drift of the fiber reflection caused by changes in the CO2 concentration in the environment. At the same time, the present invention sets a fiber Bragg grating without a CO2 sensitive coating as a reference to detect the wavelength drift mainly generated by environmental interference factors. By calculating the wavelength drift amounts of the two fiber Bragg gratings and combining the mathematical model of the wavelength drift amount and the CO2 concentration, the influence of environmental interference factors on the wavelength drift of the CO2 fiber sensor can be eliminated, and then an accurate CO2 concentration value can be obtained. The present invention realizes the efficient real-time monitoring of the CO2 concentration during the CO2 geological sequestration process, ensuring accurate and reliable data. And the modular design facilitates the regular inspection and replacement of the sensor, extends the service life, reduces the maintenance cost, and has high sensitivity, strong stability, and good maintainability.

[0027] The following will be described in detail with reference to the accompanying drawings for the embodiments of the present invention, so that those skilled in the technical field of the present invention can easily implement it. The present invention can be embodied in many different forms and is not limited to the embodiments described herein.

[0028] As Figure 1 shows a schematic structural diagram of a carbon dioxide concentration detection device based on fiber optic sensing in an embodiment of the present invention.

[0029] The system includes: a first fiber optic sensing unit 1, a second fiber optic sensing unit 2, a light source unit 3, a data acquisition unit 4, and a data processing unit 5; The first fiber optic sensing unit 1 is designed specifically for detecting changes in CO2 concentration in the environment. Its core component is a fiber Bragg grating (FBG) covered with a CO2-sensitive coating. This unit reflects the change in CO2 concentration through the wavelength drift generated by the FBG and reflects the corresponding optical signal for subsequent analysis. Among them, in order to improve the maintainability of the sensor and extend its service life, the first fiber optic sensing unit 1 is designed as a modular structure. This design mainly includes two key parts: FBG is a technology that realizes sensing by introducing periodic refractive index changes in the optical fiber. Its working principle is based on the reflection of light with a specific wavelength by the grating. When light passes through the FBG, only light with a specific wavelength will be reflected back.

[0030] The CO2-sensitive coating module is a structure specifically designed to cooperate with the FBG sensing area. The module contains a CO2-sensitive coating inside. After being installed on the FBG, the coating will cover the surface of the FBG. When the CO2 concentration in the environment changes, the sensitive coating will respond to CO2, resulting in changes in the refractive index or volume of the coating.

[0031] When the CO2 concentration changes, the change in the refractive index or volume of the sensitive coating will directly affect the reflection characteristics of the FBG. This change is manifested as the drift of the FBG reflection wavelength, that is, the wavelength of the reflected light will move with the change in CO2 concentration. By monitoring the amount of drift of the reflection wavelength, the CO2 concentration in the environment can be calculated.

[0032] Since the wavelength drift information of the optical fiber is extremely susceptible to interference from temperature and pressure at the same time, this will seriously affect the accuracy of CO2 concentration detection. To solve this problem, the second fiber optic sensing unit 2 is set. The second fiber optic sensing unit contains a fiber Bragg grating that is not covered with a CO2-sensitive coating. This FBG is arranged around the fiber Bragg grating of the first fiber optic sensing unit. The second fiber optic sensing unit uses the fiber Bragg grating inside it that is not covered with a CO2-sensitive coating to generate wavelength drift and reflects the corresponding optical signal. Since this grating is not covered with a CO2-sensitive coating, it is insensitive to changes in CO2 concentration in the environment, but will respond to changes in temperature and pressure, resulting in a drift of the reflection wavelength. Taking the second fiber optic sensing unit as a reference sensing unit, it is not affected by the CO2 concentration, but will be affected by the same temperature and pressure changes as the first fiber optic sensing unit 1. In this way, the amount of FBG wavelength drift of the second fiber optic sensing unit mainly reflects the changes in temperature and pressure.

[0033] The light source unit 3 is used to provide a stable excitation light signal to the first fiber optic sensing unit 1 and the second fiber optic sensing unit 2, so as to ensure that the two fiber optic sensing units can accurately monitor the wavelength drift.

[0034] The data acquisition unit 4 is used to receive the optical signals respectively reflected by the fiber Bragg gratings in the first fiber optic sensing unit 1 and the second fiber optic sensing unit 2, and extract the wavelength drift information corresponding to the optical signals reflected by the first fiber optic sensing unit and the second fiber optic sensing unit; The data processing unit 5 is used to calculate the wavelength drift amount respectively according to the extracted wavelength drift information corresponding to the optical signals reflected by the first fiber optic sensing unit 1 and the second fiber optic sensing unit 2, and obtain the corresponding CO2 concentration based on the constructed mathematical model of the wavelength drift amount and the CO2 concentration.

[0035] In this solution, by simultaneously collecting the wavelength drift data of the first fiber optic sensing unit 1 (for detecting CO2 concentration) and the second fiber optic sensing unit 2 (for monitoring temperature and pressure), and deeply analyzing and processing these data, the influence of temperature and pressure on the wavelength drift of the CO2 fiber optic sensor can be accurately separated. This makes the finally detected CO2 concentration result more accurate and reliable. This effectively improves the anti-interference ability and measurement accuracy of the CO2 concentration monitoring system.

[0036] In one embodiment, the CO2 sensitive coating module includes: a substrate, a CO2 sensitive coating, and a protective shell; Among them, the substrate provides stable support for the CO2 sensitive coating and at the same time allows CO2 gas to penetrate into the coating. The material of the substrate is a flexible and highly breathable polymer, such as polydimethylsiloxane (PDMS), polyimide, or microporous structure material. These materials not only have good support performance, but also ensure that CO2 gas can quickly penetrate into the sensitive coating, improving the detection response speed.

[0037] The CO2 sensitive coating is uniformly coated on the surface of the substrate. The coating method can adopt methods such as spraying, spin coating or dip coating to ensure that the thickness of the coating is uniform. The CO2 sensitive coating uses highly selective CO2-responsive materials, such as metal-organic frameworks, functionalized polymers or nanocomposites. These materials will undergo volume expansion or refractive index changes during the CO2 adsorption or desorption process, thus affecting the spectral response of the fiber Bragg grating. The coating thickness is optimized to ensure a balance between sensitivity and response time. When CO2 gas penetrates into the coating, it reacts with the coating, causing changes in the physical properties (such as volume, refractive index) of the coating, and then causing the reflection wavelength of the fiber Bragg grating to drift.

[0038] The protective housing 103 prevents the external environment from damaging the first fiber optic sensing unit 1. The housing made of breathable material can not only protect the sensor unit but also allow CO2 gas to penetrate to the sensitive coating without affecting the normal operation of the sensor.

[0039] In a preferred embodiment, as Figure 2 , a cylindrical accommodation space is formed in the middle of the CO2 sensitive coating module for placing the optical fiber 100.

[0040] The substrate 101 adopts two connected semi-circular structures. The cross-section of each semi-circular substrate is approximately semi-circular. When these two semi-circular structures are combined at both ends, they jointly enclose a hollow cylindrical space. This space is specifically designed for accommodating the optical fiber, reflecting the precision and efficiency of the structural design. The inner diameter of the substrate is precisely designed according to the diameter of the optical fiber used, usually slightly larger than the optical fiber diameter by 0.1 - 0.3 mm. Such a dimension design aims to ensure that the optical fiber 100 can be easily placed in it while leaving a certain amount of movement space to avoid weakening the close contact between the CO2 sensitive coating 102 and the optical fiber 100 due to too large a gap.

[0041] The protective housing 103 as a whole presents a hollow cylindrical structure and is closely connected to the substrate. The formed cylindrical inner surface matches the inner surface of the substrate 101. It should be noted that the protective housing 103 is not integrally formed but consists of two structures. This split design has significant advantages as it greatly facilitates the installation and disassembly process of the sensor. One side of the protective housing 103 is connected by a specific connecting component, which can be a flexible plastic sheet, an elastic rubber strip, or a hinge structure with a certain strength, etc. The other side of the protective housing 103 is carefully designed with a fixing structure, and common forms of the fixing structure include snap fasteners, magnetic attraction devices, etc. This fixing structure design enables convenient and quick operation of the protective housing 103 when installing and disassembling the sensor, thus significantly improving the work efficiency.

[0042] During the installation process, first place the optical fiber 100 into the accommodation space of the substrate 101. After the optical fiber 100 is placed in place, combine the two semi-circular substrates and firmly fix them together using the fixing structure on the protective housing 103. At this time, the internal CO2 sensitive coating 102 will tightly wrap the surface of the optical fiber, thus constructing a stable and reliable detection environment. When disassembling, just operate the fixing structure on the other side of the protective housing 103 to separate the two structures of the protective housing 103. As the two structures of the protective housing 103 are separated, the substrate 101 originally wrapped by the housing is also exposed, and then the two semi-circular substrates can be separated to take out the optical fiber 100 from the accommodation space.

[0043] In one embodiment, a fixing structure is provided on the protective housing 103 for detachably mounting the CO2 sensitive coating module on the fiber Bragg grating, which facilitates maintenance and replacement. The fixing structure can be one or more of a mechanical interlocking structure, an elastic clamping mechanism, or a magnetic coupling structure. There are various mechanical interlocking structures, such as snap-fit and slot, cam locking, wedge block interlocking, tongue and groove interlocking, etc. The elastic clamping mechanism includes spring clip type and rubber elastic clamping type. The magnetic coupling structure includes magnet and iron sheet adsorption type, magnetic ring coupling type, magnetic snap type, magnetic slide rail type, etc. For example, the snap structure shown in Figure 2, the snap 104 on one side of the protective housing can firmly fix the CO2 sensitive coating module on the fiber Bragg grating.

[0044] In one embodiment, each CO2 sensitive coating module corresponds to a type of CO2 sensitive coating. In practical applications, to meet the precise measurement requirements under different environmental conditions, the CO2 sensitive coating modules with different CO2 sensitive coating types can be flexibly replaced in the first fiber optic sensing unit. Specifically, there are various types of CO2 sensitive coatings to adapt to diverse detection scenarios: High-sensitivity coating: It is used in the micro-detection scenario of low-concentration CO2. It has extremely high sensitivity and can accurately capture the changes of extremely low-concentration CO2 in the environment, providing reliable data support for application scenarios with extremely high requirements for CO2 concentration accuracy, such as laboratory precision research, environmental micro-pollution monitoring, etc.

[0045] High-temperature resistant coating: Considering the special requirements of high-temperature environment for CO2 concentration detection, the high-temperature resistant coating is used in high-temperature environments. It can maintain stable chemical and physical properties under high-temperature conditions, ensuring accurate measurement of CO2 concentration in high-temperature environments, and is suitable for gas monitoring in high-temperature environments such as industrial high-temperature furnaces and aerospace.

[0046] Fast-response coating: When it is necessary to quickly understand the gas concentration change, the fast-response coating is used. It responds quickly and can feedback the fluctuation of CO2 concentration in the first time.

[0047] In one embodiment, as Figure 3 , the light source unit 3 includes: A light source for providing a stable excitation optical signal through a broadband spontaneous emission light source (ASE) or a supercontinuum light source (SCS). Specifically, the ASE light source is based on the stimulated emission and spontaneous emission processes of doped optical fibers (such as erbium-doped optical fibers). Using an ASE light source can provide a broadband, low-noise optical signal with high spectral flatness, ensuring that the fiber Bragg grating can be uniformly excited within its operating range. For higher-sensitivity applications, an SCS light source can be used. The SCS light source is typically obtained by injecting a high-power pulsed laser into a nonlinear optical fiber and using the nonlinear effect of the fiber to broaden the input narrowband pulsed laser into an ultra-broadband continuous spectrum. The spectrum of the SCS light source can cover multiple bands from visible light to near-infrared and even mid-infrared, far exceeding the spectral range of the ASE light source. The SCS light source has a high optical power density and can maintain a high signal intensity over a long transmission distance, making it suitable for long-distance fiber optic sensing systems.

[0048] Since the wavelength stability of the light source is greatly affected by temperature, to ensure the stability and consistency of the light source signal, the light source unit 3 is equipped with a high-precision temperature control system. The temperature control system is connected to the light source and is used to monitor the temperature of the light source in real time using a high-precision temperature sensor and automatically adjust the temperature through a thermoelectric cooler to provide a stable excitation optical signal. This system avoids the influence of ambient temperature changes on the output wavelength and power of the light source, thereby maintaining the stability of the optical signal and ensuring the reliability of the signal during long-term monitoring.

[0049] In one embodiment, as Figure 3 , the data acquisition unit 4 includes: A signal receiving module, which is mainly responsible for receiving the optical signals reflected by the fiber Bragg gratings in the first fiber optic sensing unit 1 and the second fiber optic sensing unit 2 through a spectrometer or an optical detector and converting them into electrical signals. Specifically, when the optical signal arrives, since it is an analog signal, a spectrometer or an optical detector is needed to complete the conversion process from the optical signal to an electrical signal (such as a voltage or current signal).

[0050] A signal processing module, connected to the signal receiving module, mainly undertakes the task of processing the electrical signal. It first amplifies the electrical signals converted from the optical signals reflected by the fiber Bragg gratings in the first fiber optic sensing unit 1 and the second fiber optic sensing unit 2 using a low-noise amplifier. This amplification process is crucial, especially when the signal intensity is low, to ensure the accurate extraction of wavelength information. Subsequently, the module performs filtering and demodulation processing on the amplified electrical signal. Specifically, digital filtering techniques such as Kalman filtering and adaptive noise suppression algorithms are used to remove environmental noise, thereby improving the signal quality and accurately extracting the wavelength drift information corresponding to the reflected optical signals of the first fiber optic sensing unit and the second fiber optic sensing unit.

[0051] A storage module, connected to the signal processing module, whose main function is to locally store the wavelength drift information extracted by the signal processing module. This stored information provides a basis for subsequent data analysis and monitoring.

[0052] A position judgment module, connected to the signal receiving module, whose core function is to judge the position of the light source corresponding to the received optical signal, that is, to identify which distance the optical signal is transmitted from. Through this function, the source of the optical signal can be accurately determined, and then accurate spatial positioning information can be provided for subsequent monitoring and analysis, which helps to better understand the distribution of CO2 concentration changes at different positions.

[0053] In one embodiment, as Figure 3 , the data processing unit 5 includes: A wavelength drift amount acquisition module, configured to use high-speed sampling and frequency analysis algorithms to obtain the central wavelength of the corresponding reflected spectrum according to the wavelength drift information of the optical signals reflected by the corresponding first optical fiber sensing unit 1 and the second optical fiber sensing unit 2, and calculate the wavelength drift amounts of the corresponding first optical fiber sensing unit and the second optical fiber sensing unit; specifically, in an optical fiber sensing system, the optical signal reflected by the FBG is a continuously changing analog signal. Through high-speed sampling, discrete point data of the signal in time can be obtained. By performing Fourier transform or matched filtering on the sampled digital signal, the central wavelength of the reflected spectrum can be accurately obtained, and thus the wavelength drift amount can be calculated; for the Fourier transform method, performing Fourier transform on the sampled digital signal can convert the signal from the time domain to the frequency domain to obtain the frequency spectrum distribution of the signal. In the frequency spectrum, the central wavelength of the FBG reflected light corresponds to a specific frequency peak. By detecting the position of this peak, the central position of the reflected wavelength can be accurately extracted. For the matched filtering method, by passing the sampled digital signal through a matched filtering algorithm, the position with the highest matching degree with the reference signal can be found, thereby determining the central position of the reflected wavelength. Among them, in the optical fiber sensing system, the theoretical waveform of the FBG reflected light can be known in advance and used as the reference signal. After obtaining the central position of the FBG reflected wavelength, comparing it with the initial central wavelength can calculate the corresponding wavelength drift amount.

[0054] A CO2 concentration calculation module, connected to the wavelength drift amount acquisition module, is configured to obtain the corresponding CO2 concentration based on the mathematical model of the wavelength drift amount and the CO2 concentration constructed by regression analysis or machine learning algorithms according to the wavelength drift amounts of the corresponding first optical fiber sensing unit and the second optical fiber sensing unit.

[0055] In one embodiment, the construction method of the mathematical model of the wavelength drift amount and the CO2 concentration includes: Mix CO2 at different concentrations with other gases (such as nitrogen or air) to prepare a series of standard gases with different CO2 concentrations. This step is the basis for ensuring the accuracy and reliability of experimental data, because the concentration accuracy of the standard gas directly affects the accuracy of the subsequent relationship between the wavelength drift and the CO2 concentration. Precisely regulate the flow rates of various gases through a flow controller to achieve accurate control of the CO2 concentration.

[0056] The light emitted by the light source is transmitted through an optical fiber to the fiber Bragg gratings of the first fiber sensing unit 1 and the second fiber sensing unit 2. The FBG will reflect light of a specific wavelength. Calculate the wavelength drift amounts corresponding to the first fiber sensing unit 1 and the second fiber sensing unit 2 at different CO2 concentrations using the reflected optical signals of the FBG. The specific calculation method is similar to the wavelength drift amount calculation method described in the above embodiments and will not be elaborated here.

[0057] Take the wavelength drift amounts of the two units corresponding to different carbon dioxide concentrations as data samples, and fit the relationship between them through an algorithm, so that the model can accurately calculate the carbon dioxide concentration based on the drift amount.

[0058] Specifically, establish the relationship between temperature, pressure and wavelength drift amount based on the wavelength drift amounts corresponding to the first fiber sensing unit 1 and the second fiber sensing unit 2 at different CO2 concentrations to construct a decoupling module. Based on this decoupling module, the effective drift amount mainly related to the CO2 concentration can be extracted according to the input wavelength drift amounts of the first fiber sensing unit 1 and the second fiber sensing unit 2. Pair the wavelength drift amount mainly related to the CO2 concentration output by the decoupling module with the standard CO2 concentration data and use it as a sample. Use regression analysis or machine learning algorithms to fit the sample data to generate a calibration curve that can accurately reflect the corresponding relationship between the two, and construct a CO2 concentration detection module, so that the module can quickly calculate the corresponding CO2 concentration value according to the input wavelength drift amount mainly related to the CO2 concentration.

[0059] After constructing the mathematical model, it is necessary to verify and optimize the model. An independent test data set can be used to verify the model, calculate the prediction error of the model, and evaluate the accuracy and reliability of the model. If the prediction error of the model is large, the model needs to be adjusted and optimized, such as changing the form of the mathematical model, increasing the complexity of the model, etc., until the prediction error of the model meets the requirements.

[0060] In one embodiment, the mathematical model of the wavelength drift amount and the CO2 concentration includes: A decoupling module, configured to separate the effects of temperature and pressure on the wavelength drift of the fiber Bragg grating in the first fiber sensing unit according to the input wavelength drift amount corresponding to the second fiber sensing unit, so as to extract the wavelength drift amount mainly related to the CO2 concentration from the wavelength drift amount corresponding to the first fiber sensing unit; A CO2 concentration detection module, connected to the decoupling module, configured to calculate the corresponding CO2 concentration based on the wavelength drift amount mainly related to the CO2 concentration according to the calibration curve established between the wavelength drift and the CO2 concentration.

[0061] In one embodiment, as Figure 3 , the data processing unit further includes: An automatic calibration module, which has an automatic regular calibration function and will calibrate the mathematical model of the wavelength drift amount and the CO2 concentration using the standard gas data of different CO2 concentrations at a preset time interval or specific trigger condition. In practical applications, the detection device may age due to long-term use, and at the same time, changes in environmental conditions (such as fluctuations in factors such as temperature, humidity, and pressure) may also affect the performance of the detection device, resulting in measurement errors. The automatic calibration module can effectively eliminate the errors caused by these factors and ensure the accuracy and stability of the model by introducing standard gas data and dynamically adjusting the mathematical model.

[0062] A remote data transmission module, which is responsible for uploading the CO2 concentration data obtained by the data processing unit to a remote monitoring platform. It supports multiple communication protocols and network connection methods, such as Ethernet, Wi-Fi, 4G / 5G, etc., to ensure that the data can be stably and reliably transmitted to the remote end. Through remote data transmission, users can obtain the CO2 concentration data in real time anywhere with a network connection, realizing remote management of the detection system. The remote monitoring platform not only has a real-time data reception function but also provides powerful data storage and management capabilities. The platform will classify and store the uploaded CO2 concentration data and establish a corresponding database. Users can query, statistically analyze, and analyze the historical data as needed to provide data support for decision-making in fields such as environmental monitoring and industrial production. At the same time, the platform also has data backup and recovery functions to ensure the security and integrity of the data.

[0063] Anomaly detection module, which is used to monitor and analyze wavelength drift data in real time. It adopts a variety of anomaly detection algorithms, such as the threshold judgment method based on statistics and the pattern recognition method based on machine learning, to deeply study the distribution law, change trend, etc. of wavelength drift data. When it detects that the wavelength drift data exceeds the normal range or shows abnormal fluctuations, the module will automatically identify the possible fault status. Once the fault status is identified, the anomaly detection module will immediately trigger an alarm signal. The alarm signal can be sent to relevant personnel in various ways, such as text messages, emails, audible and visual alarms, etc., to ensure that users can timely understand the abnormal situation of the system. At the same time, the module will also record information such as the time, location, and type of the anomaly, providing a basis for fault troubleshooting and repair.

[0064] Visual display module, which real-time displays the CO2 concentration change curve through a graphical interface. Users can intuitively see the change of CO2 concentration over time and understand the dynamic of carbon dioxide concentration in the environment. The interface design is simple and clear, and the operation is convenient. Users can adjust the displayed time range, data accuracy, etc. according to their needs. In addition to the real-time display function, this module also provides historical data query and analysis functions. Users can query historical CO2 concentration data by inputting specific time ranges, locations, etc. At the same time, the module also supports statistical analysis of historical data, such as calculating the average value, maximum value, minimum value, etc., and generating corresponding reports and charts to provide users with more in-depth data analysis results.

[0065] Such as Figure 4 Show the structural schematic diagram of a carbon dioxide geological storage monitoring system in an embodiment of the present invention.

[0066] The carbon dioxide geological storage monitoring system includes: the carbon dioxide concentration detection device based on optical fiber sensing described in the above embodiment, so it will not be elaborated here. The carbon dioxide concentration detection device based on optical fiber sensing is applicable to the monitoring of CO2 geological storage sites and can operate stably in extreme environments such as high pressure, high humidity, and corrosiveness. With the multi-point distributed sensing technology, it can realize the real-time and all-round monitoring of the CO2 concentration in the storage area. Other environmental monitoring devices, such as temperature, pressure, and seismic monitoring devices, can also be set in the system. By collecting and comprehensively analyzing various detection data, this not only effectively improves the reliability and accuracy of the data, but also can accurately evaluate the safety of the storage environment.

[0067] The present invention has the following advantages compared with the prior art: 1. High sensitivity and accuracy By combining a fiber Bragg grating with a CO2-sensitive coating, the present invention can accurately monitor the wavelength drift caused by changes in CO2 concentration in the environment. When the CO2 concentration changes, the sensitive coating produces significant refractive index or volume changes. Combining with the high sensitivity of the fiber Bragg grating, stable and accurate monitoring signals can be obtained under small concentration changes, greatly improving the detection accuracy and reliability.

[0068] 2. Modular design for easy maintenance The first fiber optic sensing unit of the present invention adopts a modular structure design, enabling the contact part between the sensitive coating and the optical fiber to be independently maintained and replaced, facilitating regular inspection and replacement of the sensor, extending the service life of the sensor, and reducing the maintenance cost.

[0069] 3. Temperature control system to ensure light source stability The light source unit of the present invention adopts a high-precision temperature control system to monitor and adjust the temperature of the light source in real time, avoiding the influence of environmental temperature changes on the output wavelength and power of the light source, ensuring the stability and consistency of the light source, and thus ensuring the reliability of the signal during long-term monitoring of the system.

[0070] 4. Real-time data acquisition and analysis The data acquisition unit of the present invention can obtain the changes in the reflection spectrum in the fiber optic sensing unit in real time, and accurately obtain the wavelength drift information through high-speed sampling and precise frequency analysis algorithms. The data acquisition unit also has noise filtering and calibration functions to ensure data stability and accuracy during long-term operation.

[0071] 5. Efficient data processing and precise calculation The data processing unit of the present invention adopts advanced signal processing technologies, such as high-pass filtering, low-pass filtering, and Kalman filtering, to remove noise and ensure the quality of the input signal. Through linear or nonlinear regression models, combined with calibration data for quantitative analysis, the accurate CO2 concentration value is finally calculated. The regular system calibration function ensures that the device can continuously maintain high precision and avoid errors caused by environmental changes or sensor aging.

[0072] In summary, for the carbon dioxide concentration detection device and the storage monitoring system based on fiber optic sensing of the present invention, a first fiber optic sensing unit with a modular structure is designed, enabling the contact part between the sensitive coating and the fiber Bragg grating to be independently maintained and replaced, and capable of accurately detecting the wavelength drift of the fiber reflection caused by the change in the CO2 concentration in the environment. At the same time, the present invention sets a fiber Bragg grating not covered with the CO2 sensitive coating as a reference to detect the wavelength drift mainly generated by environmental interference factors. By calculating the wavelength drift amounts of the two fiber Bragg gratings and combining the mathematical model of the wavelength drift amount and the CO2 concentration, the influence of environmental interference factors on the wavelength drift of the CO2 fiber sensor can be eliminated, and then an accurate CO2 concentration value can be obtained. The present invention realizes the efficient and real-time monitoring of the CO2 concentration during the CO2 geological storage process, ensuring accurate and reliable data. Moreover, the modular design facilitates the regular inspection and replacement of the sensor, extends the service life, reduces the maintenance cost, and has high sensitivity, strong stability, and good maintainability. Therefore, the present invention effectively overcomes various drawbacks in the prior art and has high industrial utilization value.

[0073] The above embodiments are only used to exemplarily illustrate the principles and effects of the present invention, rather than to limit the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes completed by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. A carbon dioxide concentration detection device based on optical fiber sensing, characterized in that, The device includes: a first fiber optic sensing unit, a second fiber optic sensing unit, a light source unit, a data acquisition unit, and a data processing unit; wherein, The first fiber optic sensing unit adopts a modular design and includes: an optical fiber Bragg grating and a CO2-sensitive coating module; the CO2-sensitive coating module is installed on the optical fiber Bragg grating so that the CO2-sensitive coating inside it covers the optical fiber Bragg grating; the first fiber optic sensing unit is used to generate a wavelength shift through the optical fiber Bragg grating covered with the CO2-sensitive coating and reflect the corresponding optical signal; The second fiber optic sensing unit includes: an optical fiber Bragg grating not covered with a CO2-sensitive coating, arranged around the optical fiber Bragg grating of the first fiber optic sensing unit; the second fiber optic sensing unit is used to generate a wavelength shift through the optical fiber Bragg grating inside it that is not covered with a CO2-sensitive coating and reflect the corresponding optical signal; The light source unit is used to provide a stable excitation optical signal to the first fiber optic sensing unit and the second fiber optic sensing unit; The data acquisition unit is used to receive the optical signals reflected by the optical fiber Bragg gratings in the first fiber optic sensing unit and the second fiber optic sensing unit respectively, and extract the wavelength shift information corresponding to the optical signals reflected by the first fiber optic sensing unit and the second fiber optic sensing unit; The data processing unit is used to calculate the wavelength shift amount respectively according to the extracted wavelength shift information corresponding to the optical signals reflected by the first fiber optic sensing unit and the second fiber optic sensing unit, and obtain the corresponding CO2 concentration based on the constructed mathematical model of the wavelength shift amount and the CO2 concentration.

2. The carbon dioxide concentration detection device based on optical fiber sensing according to claim 1, characterized in that, The CO2-sensitive coating module is provided with a CO2-sensitive coating, a substrate for supporting the CO2-sensitive coating, and a protective housing; Wherein, the surface of the substrate is coated with a CO2-sensitive coating and allows CO2 gas to penetrate to the CO2-sensitive coating; the protective housing is used to prevent the external environment from damaging the first fiber optic sensing unit; By installing the CO2-sensitive coating module on the optical fiber Bragg grating of the first fiber optic sensing unit and making the surface of the substrate coated with the CO2-sensitive coating in close contact with the corresponding fiber surface, when CO2 gas penetrates to the CO2-sensitive coating, it reacts with the CO2-sensitive coating, resulting in a change in the physical properties of the CO2-sensitive coating, and further causing a reflection wavelength shift of the optical fiber Bragg grating.

3. The carbon dioxide concentration detection device based on optical fiber sensing according to claim 2, characterized in that, The protective housing is provided with a fixing structure for detachably installing the CO2-sensitive coating module on the optical fiber Bragg grating; wherein, the fixing structure includes: one or more of a mechanical interlock structure, an elastic clamping mechanism, and a magnetic coupling structure.

4. The carbon dioxide concentration detection device based on fiber optic sensing according to claim 1, wherein The light source unit includes: A light source for providing a stable excitation optical signal through a broadband spontaneous emission light source or a supercontinuum light source; A temperature control system connected to the light source, used to monitor the temperature of the light source in real time and automatically adjust the temperature through a semiconductor refrigeration chip so that the light source provides a stable excitation optical signal.

5. The carbon dioxide concentration detection device based on optical fiber sensing according to claim 1, characterized in that, The data acquisition unit includes: A signal receiving module, configured to receive, through a spectrometer or an optical detector, the optical signals respectively reflected by the fiber Bragg gratings in the first fiber sensing unit and the second fiber sensing unit, and convert them into electrical signals respectively; A signal processing module, connected to the signal receiving module, configured to amplify the electrical signals converted from the optical signals reflected by the fiber Bragg gratings in the first fiber sensing unit and the second fiber sensing unit through a low-noise amplifier, and perform filtering and demodulation processing on the amplified electrical signals to extract the wavelength drift information corresponding to the optical signals reflected by the first fiber sensing unit and the second fiber sensing unit; A storage module, connected to the signal processing module, configured to store the wavelength drift information extracted by the signal processing module; A position determination module, connected to the signal receiving module, configured to identify the light source position from which the received optical signal comes.

6. The carbon dioxide concentration detection device based on fiber optic sensing according to claim 1, wherein, The data processing unit includes: A wavelength drift amount acquisition module, configured to obtain the central wavelength of the corresponding reflection spectrum according to the wavelength drift information of the optical signals reflected by the first fiber sensing unit and the second fiber sensing unit respectively by using a high-speed sampling and frequency analysis algorithm, and calculate the wavelength drift amounts of the first fiber sensing unit and the second fiber sensing unit respectively; A CO2 concentration calculation module, connected to the wavelength drift amount acquisition module, configured to obtain the corresponding CO2 concentration according to the wavelength drift amounts of the first fiber sensing unit and the second fiber sensing unit respectively based on the constructed mathematical model of the wavelength drift amount and the CO2 concentration.

7. The carbon dioxide concentration detection device based on fiber optic sensing according to claim 6, wherein, The construction method of the mathematical model of the wavelength drift amount and the CO2 concentration includes: Receiving the optical signals reflected by the fiber Bragg gratings of the first fiber sensing unit and the second fiber sensing unit in a standard gas environment with different CO2 concentrations, and calculating the wavelength drift amounts of the first fiber sensing unit and the second fiber sensing unit corresponding to different CO2 concentrations; Training based on the wavelength drift amounts of the first fiber sensing unit and the second fiber sensing unit corresponding to each CO2 concentration to obtain the mathematical model of the wavelength drift amount and the CO2 concentration.

8. The carbon dioxide concentration detection device based on optical fiber sensing according to claim 7, characterized in that, The mathematical model of the wavelength drift amount and the CO2 concentration includes: A decoupling module, configured to separate the influence of temperature and pressure on the wavelength drift of the fiber Bragg grating in the first fiber sensing unit according to the input wavelength drift amount of the second fiber sensing unit, so as to extract the wavelength drift amount mainly related to the CO2 concentration from the wavelength drift amount of the first fiber sensing unit; A CO2 concentration detection module, connected to the decoupling module, configured to calculate the corresponding CO2 concentration based on the calibrated curve constructed between the wavelength drift and the CO2 concentration according to the wavelength drift amount mainly related to the CO2 concentration.

9. The carbon dioxide concentration detection device based on optical fiber sensing according to claim 6, characterized in that, The data processing unit further includes: An automatic calibration module, configured to regularly calibrate the mathematical model of the wavelength drift amount and the CO2 concentration by using the data of standard gases with different CO2 concentrations; A remote data transmission module, configured to upload the obtained CO2 concentration to a remote monitoring platform; An anomaly detection module, configured to perform anomaly analysis on the wavelength drift data, automatically identify possible fault states, and trigger an alarm signal; A visualization display module, which is used to display the CO2 concentration change curve in real time through a graphical interface and provide functions for querying and analyzing historical data.

10. A carbon dioxide geological storage monitoring system, characterized in that, The system includes: a carbon dioxide concentration detection device based on optical fiber sensing as described in any one of claims 1 to 9.

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