A carbon dioxide isotope detection device

Abstract

The present invention provides a carbon dioxide isotope detection device, including: a mid-infrared laser, a direct-type absorption cell, a mid-infrared detection device and a gas path module for generating negative pressure; the absorption cell is provided with a first transparent window and a second transparent window at both ends in the length direction; the absorption cell is provided with a closed cavity; the mid-infrared laser is arranged outside the first transparent window, for emitting mid-infrared light that passes through the first transparent window and the second transparent window in sequence; the mid-infrared detection device is arranged outside the second transparent window, for receiving mid-infrared light that passes through the second transparent window. The carbon isotope detection device provided by the embodiment of the present invention can reduce the required optical path, so that the direct-type absorption cell can also meet the demand, and the size of the absorption cell can be reduced; there is no standard tool interference when the mid-infrared light passes through the absorption cell, and the low-pressure state can avoid cross-interference of absorption lines, thereby improving the measurement accuracy and having high stability.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon dioxide gas isotope detection, and in particular to a carbon dioxide isotope detection device. Background Art

[0002] At present, the existing carbon dioxide gas isotope abundance detection usually adopts NDIR (Non-Dispersive InfraRed) technology and IRMS (Isotope Ratio Mass Spectrometry) technology.

[0003] The basic principle of IRMS technology for measuring isotopes is to distinguish isotope molecules based on the different bending paths in the magnetic field caused by different molecular mass-to-charge ratios. This method cannot distinguish isomers with the same molecular mass. In addition, IRMS technology detection requires pretreatment and vacuum environment, and the instrument system is large, complex to operate and expensive. It can only be used for laboratory analysis, which has certain limitations and is especially not suitable for real-time online measurement.

[0004] The principle of NDIR technology is based on the Lambert-Beer law, that is, to select narrowband interference filters according to the specific absorption peak of each isotope gas, so that the infrared light source and the specific wavelength light with the same absorption peak can pass through, and the light passing through the air mass in the absorption cell is received by the detector, and the attenuation of the detected light signal is used to quantify the concentration of the gas to be measured, so as to calculate the concentration of each CO2 carbon isotope gas, and then calculate the abundance. Among them, the light needs to have a long enough optical path to meet the detection accuracy requirements, which leads to a longer absorption cell size; the White cell uses multiple reentry methods to achieve the required optical path, but because the narrowband filter has a large bandwidth, there is cross-interference between different isotope gases, and there will also be interference between the multiple reentry lights, which affects the measurement accuracy and has poor stability. Summary of the invention

[0005] In order to solve the problem of poor measurement accuracy of traditional detection equipment, an embodiment of the present invention aims to provide a carbon dioxide isotope detection device.

[0006] The embodiment of the present invention provides a carbon dioxide isotope detection device, comprising: a laser module, a gas path module and a detector module; the laser module comprises a mid-infrared laser, the gas path module comprises a direct-type absorption cell, and the detector module comprises a mid-infrared detection device;

[0007] The absorption cell is provided with a first transparent window and a second transparent window at both ends in the length direction; between the first transparent window and the second transparent window, the absorption cell is provided with a closed cavity for placing the gas to be measured;

[0008] The mid-infrared laser is arranged outside the first transparent window, and is used to emit mid-infrared light that passes through the first transparent window and the second transparent window in sequence;

[0009] The mid-infrared detection device is arranged outside the second transparent window, and is used for receiving the mid-infrared light passing through the second transparent window.

[0010] In the solution provided in the embodiment of the present invention, a mid-infrared laser is used as a light source, and mid-infrared light is used for detection, which can reduce the required optical path, so that a direct-type absorption cell can also meet the needs, and the size of the absorption cell can be reduced; and there is no need to set multiple return components in the absorption cell, and there is no standard tool interference when the mid-infrared light passes through the absorption cell, thereby improving the measurement accuracy and having high stability. Using this mid-infrared light, multiple carbon dioxide isotopes have strong absorption, and there is no interference from the water absorption peak, so multiple carbon dioxide isotopes can be accurately detected at the same time.

[0011] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0013] Figure 1 A first structural schematic diagram of a carbon dioxide isotope detection device provided in an embodiment of the present invention is shown;

[0014] Figure 2 shows the absorption intensity spectrum line near 2.0 μm in an embodiment of the present invention;

[0015] Figure 3 shows the absorption intensity spectrum line near 4.3 μm in an embodiment of the present invention;

[0016] Figure 4 A second structural schematic diagram of a carbon dioxide isotope detection device provided in an embodiment of the present invention is shown;

[0017] Figure 5 A first structural schematic diagram of a gas pipeline of a carbon dioxide isotope detection device provided in an embodiment of the present invention is shown;

[0018] Figure 6A second structural schematic diagram of the gas pipeline of the carbon dioxide isotope detection device provided in an embodiment of the present invention is shown;

[0019] Figure 7 A schematic structural diagram of an extended component in a gas pipeline of a carbon dioxide isotope detection device provided in an embodiment of the present invention is shown;

[0020] Figure 8 The cross-sectional structure diagram of the absorption cell in the carbon dioxide isotope detection device provided in the embodiment of the present invention is shown;

[0021] Fig. 9 An axonometric diagram of an absorption cell in the carbon dioxide isotope detection device provided in an embodiment of the present invention is shown.

[0022] Icons: 1-laser module, 2-gas path module, 3-detector module, 4-main control module, 5-sealed housing, 11-mid-infrared laser, 12-laser current drive unit, 13-laser temperature control unit, 21-absorption cell, 211-first transparent window, 212-second transparent window, 213-sealed cavity, 214-inlet pipeline, 215-outlet pipeline, 216-first slot, 217-second slot, 22-inlet unit, 221-carbon dioxide filter, 222- Sampling assembly, 2221-sampling port, 223-water vapor filter, 224-extension assembly, 2241-extended sample inlet, 23-pressure sensor, 24-cylinder, 25-exhaust processor, 261-housing, 262-insulation layer, 263-heating film, 264-insulation bracket, 31-mid-infrared detection device, 32-signal processing unit, 33-refrigeration control unit, SV1-air outlet control valve, SV2-air inlet control valve, SV3-sampling control valve, SV4-extension control valve. DETAILED DESCRIPTION

[0023] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0024] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0025] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0026] In the process of completing the invention, the inventors found that the reason why traditional absorption cells (such as White cells, etc.) need to adopt a multi-side return method is that the detection laser is usually near-infrared light, and its absorption line strength is lower than that of mid-infrared light; the carbon dioxide isotope detection device provided by the embodiment of the present invention is based on mid-infrared light to achieve detection. The absorption line strength of mid-infrared light is 1 to 3 orders of magnitude higher than that of near-infrared light. The absorption line strength is relatively high, and a certain absorption depth can be achieved without too long an optical path or precise cavity operation, which can effectively reduce the optical path. See Figure 1 As shown, the detection device includes: a laser module 1, a gas path module 2 and a detector module 3; wherein the laser module 1 includes a mid-infrared laser 11, the gas path module 2 includes a direct absorption cell 21, and the detector module 3 includes a mid-infrared detection device 31. The direct absorption cell 21 means that the absorption cell 21 allows light to pass directly through. Specifically, the absorption cell 21 is provided with a first transparent window 211 and a second transparent window 212 at both ends in the length direction; between the first transparent window 211 and the second transparent window 212, the absorption cell 21 is provided with a closed cavity 213 for placing the gas to be measured.

[0027] In this embodiment, the mid-infrared laser 11 is arranged outside the first transparent window 211. Figure 1 The left side is used to emit mid-infrared light that passes through the first transparent window 211 and the second transparent window 212 in sequence; the mid-infrared detection device 31 is arranged outside the second transparent window 212, such as Figure 1 The right side is used to receive the mid-infrared light passing through the second transparent window 212.

[0028] In the embodiment of the present invention, the laser used to generate the detection laser is a mid-infrared laser 11, which can emit mid-infrared light. In the present embodiment, "mid-infrared" corresponds to a wavelength range between 2.5 microns and 25 microns (μm), and the corresponding wavelength of the mid-infrared light is also within this wavelength range; the wavelength range can specifically be 4 to 5 μm. Using mid-infrared light as the detection light can reduce the optical path of the detection light, thereby reducing the volume of the absorption cell 21 (especially reducing its length), or the absorption cell 21 does not need to adopt a multiple return structure similar to the White cell. The absorption cell 21 in the present embodiment is a direct absorption cell, that is, the detection light can be directly emitted from one side of the absorption cell 21 to the other side, and the light does not need to be returned. Figure 1 As shown, the absorption pool 21 is provided with a first transparent window 211 and a second transparent window 212 at both ends in the length direction, and a cavity capable of placing the gas to be measured, namely a closed cavity 213 ( Figure 1 (not shown in the figure), so that the mid-infrared light emitted by the mid-infrared laser 11 can pass through the first transparent window 211, the closed cavity 213, and the second transparent window 212 in sequence, and can undergo absorption reaction with the gas to be measured (such as carbon dioxide, etc.) in the closed cavity 213, so that the mid-infrared detection device 31 outside the second transparent window 212 can receive the mid-infrared light emitted from the absorption cell 21, and then can extract the absorption spectrum of the gas to be measured for analysis.

[0029] Among them, the mid-infrared detection device 31 can specifically be a mid-infrared photoelectric sensor, such as an indium arsenic antimony mid-infrared photoelectric sensor, which can convert the spectral signal corresponding to the mid-infrared light into an electrical signal to facilitate subsequent analysis and processing. Both transparent windows (i.e., the first transparent window and the second transparent window) have a high light transmittance (such as a light transmittance higher than 80%), while allowing laser and other light to pass through, they can also seal the two ends of the closed cavity 213 to prevent leakage of the gas to be measured. The transparent window is a window made of transparent material, which can specifically be a white sapphire lens.

[0030] In addition, in order to improve the analysis effect, the band used in this embodiment is determined based on the absorption peak spectrum of the mid-infrared band. Specifically, the carbon dioxide isotope analysis is mainly concentrated in the absorption bands of 2.0μm, 2.7μm, and 4.3μm; in addition, carbon dioxide isotopes include 16 O 12 C 18 O(16O12C18O), 13 C 16 O2(16O13C16O), 12 C 16 O2(16O12C16O), etc. Figure 2The absorption intensity spectrum near 2.0 μm is shown; 12 C 16 O2 has a strong absorption line, but 13 C 16 The O2 spectral line is weaker and two orders of magnitude lower (10 -23 ),and 13 C 16 O2 concentration is relatively low, so a long absorption optical path is required for accurate detection, which means that the two can no longer be accurately measured in the same absorption cell. Two sets of gas chambers and lasers are required, which is complex and costly. The 2.7μm band meets the basic requirements, but the 2.7μm band has strong water absorption peak interference, which requires a complex water removal device. The absorption intensity spectrum near 4.3μm can be seen in Figure 3 As shown, 12 C 16 O2 and 13 C 16 O2 wavelength spacing is within 1-2nm, with strong absorption, including 13 C 16 O2 is greater than 12 C 16 The absorption peak of O2 absorption intensity can be completed in a very short absorption light path. 13 C can be detected with high precision, so the size of the absorption cell 21 can be smaller; in addition, 16 O 12 C 18 The absorption intensity of O is also strong, which can achieve high-precision detection of three components at 1-2nm, and there is no interference from the water absorption peak in the middle, which increases 18 O detection function, so that the device can simultaneously measure 12 C. 13 C. 18 Therefore, the mid-infrared band corresponding to 4.3-4.35 μm is used in this embodiment, that is, the wavelength of the mid-infrared light is 4.3-4.35 μm, such as 4.33 μm.

[0031] In this embodiment, the closed cavity 213 of the absorption cell 21 is a strip structure to ensure that the mid-infrared light can directly pass through the closed cavity 213. And as mentioned above, the present embodiment uses mid-infrared light as the detection light, which can reduce the size of the absorption cell 21. Specifically, the length of the closed cavity 31 is 10-100mm, the optical path is short, and the cross-sectional size of the closed cavity 213 is 3-6mm, and the cross-sectional size can specifically be length, width or diameter. For example, the closed cavity 213 is a cylindrical structure with a length of 50mm and a cross-sectional diameter of 4mm, then the volume of gas that can pass into it is only 0.628ml, so that the small volume of the absorption cell 21 can also be suitable for the carbon dioxide isotope detection equipment, which can reduce the volume of the detection equipment.

[0032] A carbon dioxide isotope detection device provided by an embodiment of the present invention uses a mid-infrared laser 11 as a light source and uses mid-infrared light for detection, which can reduce the required optical path, so that a direct-type absorption cell 21 can also meet the needs, and the size of the absorption cell 21 can also be reduced; and there is no need to set multiple return components in the absorption cell, and there is no standard tool interference when the mid-infrared light passes through the absorption cell 21, thereby improving the measurement accuracy and having high stability. Using this mid-infrared light, multiple carbon dioxide isotopes have strong absorption, and there is no interference from the water absorption peak, so that multiple carbon dioxide isotopes can be accurately detected at the same time, for example, the carbon dioxide isotope abundance can be detected.

[0033] Based on the above embodiments, see Figure 4 As shown, the laser module 1 further includes: a laser current driving unit 12, a laser cooling plate, a first temperature sensor and a laser temperature control unit 13. The laser current driving unit 12 is connected to the mid-infrared laser 11, and is used to convert the laser driving waveform into a current driving signal to drive the mid-infrared laser 11 to emit mid-infrared light with wavelength modulation.

[0034] The first temperature sensor is arranged at the mid-infrared laser 11, and is used to measure the first temperature signal of the mid-infrared laser 11, and send the first temperature signal to the laser temperature control unit 13; the laser temperature control unit 13 is used to control the current size and / or current direction of the laser cooling plate according to the first temperature signal; the laser cooling plate is arranged at the mid-infrared laser 11, and is used to control the temperature of the mid-infrared laser 11.

[0035] In the embodiment of the present invention, a first temperature sensor is provided inside the mid-infrared laser 11, and the first temperature sensor can be a thermistor, which is used to collect the temperature of the mid-infrared laser 11, and then generate a corresponding temperature signal, i.e., a first temperature signal. The first temperature sensor is connected to the laser temperature control unit 13, and can send the first temperature signal to the laser temperature control unit 13, so that the laser temperature control unit 13 can control the current size and / or current direction of the laser cooling plate. Among them, the laser cooling plate can be a TEC (Thermo Electric Cooler, semiconductor refrigerator) cooling plate, which is arranged inside the mid-infrared laser 11; the laser temperature control unit 13 can control the current size and current direction of the laser cooling plate based on a control method such as PID (Proportion Integral Differential, proportional integral differential), thereby realizing precise control of the core temperature of the mid-infrared laser 11, and the accuracy can reach ±0.01°C, which is conducive to achieving laser frequency stabilization. In addition, the specific wavelength emitted by the mid-infrared laser 11 is determined by the laser temperature and the laser current drive, so the wavelength output by the mid-infrared laser 11 can be roughly adjusted by adjusting the constant temperature control point of the laser.

[0036] When the operating temperature of the mid-infrared laser 11 is stable, the laser current driving unit 12 can digitally synthesize the laser driving waveform and convert it into a current driving signal, which can be applied to the current input terminal of the mid-infrared laser 11 to achieve the current tuning process of the mid-infrared laser 11. Specifically, the laser driving waveform may include a low-frequency (such as 5Hz) triangular wave and a high-frequency (such as 5KHz) sine wave. The low-frequency triangular wave is the tuning signal, and the high-frequency sine wave is the modulation signal. The use of a high-frequency modulation signal can greatly reduce background noise. In this embodiment, "low frequency" and "high frequency" are relative concepts, that is, the frequency of the sine wave is higher than the frequency of the triangular wave. Figure 4 As shown, the laser driving waveform can be specifically generated by the main control module 4. In this embodiment, the scanning based on the low-frequency triangle wave can achieve fine adjustment of the output wavelength of the mid-infrared laser 11, so as to output the required mid-infrared light, and the mid-infrared light is wavelength-modulated.

[0037] Alternatively, see Figure 4As shown, the carbon dioxide isotope detection device also includes a main control module 4; and the detector module 3 also includes: a signal processing unit 32. Specifically, the signal processing unit 32 is connected to the mid-infrared detection device 31, and is used to receive the electrical signal corresponding to the mid-infrared light collected by the mid-infrared detection device 31, and to process the electrical signal accordingly. The main control module 4 is connected to the signal processing unit 32, and is used to receive the processed electrical signal, and perform carbon dioxide isotope detection processing according to the processed electrical signal to determine the carbon dioxide isotope parameters of the gas to be tested.

[0038] In an embodiment of the present invention, the mid-infrared laser 11 emits mid-infrared light of a specific wavelength, which is absorbed by the absorption cell 21 to form a corresponding spectral signal. The mid-infrared detection device 31 can convert the spectral signal into a weak electrical signal (a current signal). At this time, the electrical signal needs to be amplified and processed based on the signal processing unit 32. Optionally, the signal processing unit 32 may include a preamplifier circuit, a main amplifier circuit, a frequency divider circuit, and a single-turn differential amplifier circuit connected in series. Among them, the preamplifier circuit is used to convert the weak current signal into a voltage signal, and a current amplifier with low bias current and low offset voltage can be used. The main amplifier circuit is used to amplify the voltage signal of the preamplifier stage, such as amplifying to 2-3V, etc., which can be implemented by one or more stages of operational amplifiers. The frequency divider circuit is used to separate the modulation signal and the tuning signal through a filter, and further amplify the modulation signal. For example, a 5Hz triangle wave and a 5KHz sine wave signal are separated by a high-pass filter and a low-pass filter, and the sine wave signal is further amplified to 3-4V. The single-turn differential amplifier circuit is used to convert the signal output by the frequency division circuit into a differential signal, and then the differential signal can be converted into an analog-to-digital signal, and finally input into the main control module 4, so that the main control module 4 can perform carbon dioxide isotope detection processing, and then determine the carbon dioxide isotope parameters of the gas to be tested, wherein the carbon dioxide isotope parameters can specifically be the concentration and abundance of carbon dioxide isotopes. Among them, after determining the signal that can represent the spectral signal, the processing process of carbon dioxide isotope detection processing is an existing mature technology, which will not be described in detail here.

[0039] Optionally, the detector module 3 further includes: a sensor cooling plate, a second temperature sensor and a cooling control unit 33. The second temperature sensor is arranged at the mid-infrared detection device 31, and is used to measure a second temperature signal of the mid-infrared detection device 31, and send the second temperature signal to the cooling control unit 33; the cooling control unit 33 is used to control the current magnitude and / or current direction of the sensor cooling plate according to the second temperature signal; the sensor cooling plate is arranged at the mid-infrared detection device 31, and is used to absorb heat from the mid-infrared detection device 31.

[0040] In the embodiment of the present invention, similar to the principle of temperature-controlled cooling of the mid-infrared laser 11, the second temperature sensor can be set in the mid-infrared detection device 31 to accurately detect the temperature of the mid-infrared detection device 31 and generate a corresponding second temperature signal; then, the refrigeration control unit 33 connected to the second temperature sensor can control the sensor refrigeration plate to absorb heat based on the second temperature signal, thereby achieving refrigeration. Among them, the sensor refrigeration plate can also be a TEC refrigeration plate, and the mid-infrared detection device 31 can be effectively cooled by superimposing sensor refrigeration plates in multiple stages (such as two stages). The refrigeration control unit 33 can control the current size and current direction of the sensor refrigeration plate based on control methods such as PID.

[0041] Based on the above embodiments, see Figure 4 As shown, the absorption pool 21 is provided with an air inlet pipeline 214 and an air outlet pipeline 215 connected to the closed cavity 213, and the air outlet pipeline 215 is connected to the cylinder 24. The air path module 2 is operated by the air cylinder 24 to suck the gas to be tested into the absorption pool 21 through the air inlet pipeline 214 and the air outlet pipeline 215. Figure 5 As shown, the gas circuit module 2 also includes: an air intake unit 22, a pressure sensor 23, an air outlet control valve SV1, a cylinder 24 and an exhaust processor 25. The pressure sensor 23 can be arranged in the air intake pipeline 214, the air outlet pipeline 215 or the closed cavity 213; and see Figure 4 and Figure 5 As shown, the air intake unit 22 is connected to the air intake pipeline 214; the first end of the air outlet control valve SV1 is connected to the air outlet pipeline 215, the second end of the air outlet control valve SV1 is connected to the exhaust processor 25, and the common end of the air outlet control valve SV1 is connected to the cylinder 24. When the first end of the air outlet control valve SV1 is connected to the common end and the air intake unit 22 is connected, the cylinder 24 pumps air from the absorption pool 21 to complete the sampling; when the second end of the air outlet control valve SV1 is connected to the common end, the cylinder 24 is back-pressurized, so that the gas in the cylinder 24 can be discharged to the exhaust processor 25 to remove the gas in the cylinder 24. When the first end of the air outlet control valve SV1 is connected to the common end and the air intake unit 22 is cut off, the cylinder 24 pumps air from the absorption pool 21 until the pressure value detected by the pressure sensor 23 meets the preset conditions.

[0042] In the embodiment of the present invention, the air intake unit 22 is connected to the air intake pipeline 214, so that the gas to be tested can be filled into the absorption tank 21. The air outlet control valve SV1 is a three-way valve, which is provided with a common end, a first end and a second end, and has two conduction states: the common end is connected to the first end, and the common end is connected to the second end; the air outlet control valve SV1 can be specifically a three-way solenoid valve, and the conduction state of the air outlet control valve SV1 can be controlled by the main control module 4. In the embodiment of the present invention, when the first end of the air outlet control valve SV1 is connected to the common end and the air intake unit 22 is connected, the cylinder 24, the absorption tank 21, and the air intake unit 22 are connected. At this time, the cylinder 22 is evacuated, so that the gas to be tested at the air intake unit 22 can be drawn into the absorption tank 21 to achieve sampling. When the first end of the gas outlet control valve SV1 is connected to the common end and the air intake unit 22 is cut off, the cylinder 24 is connected to the gas outlet pipeline 215, that is, the cylinder 24 can be connected to the absorption tank 21, and the cylinder 24 pumps air so that the absorption tank 21 is in a negative pressure state, which is convenient for accurate detection of the gas to be tested; the pressure can also be maintained when the cylinder 24 stops pumping air. Among them, a pressure sensor 23 is provided in the air intake pipeline 214, the air outlet pipeline 215 or the closed cavity 213, and based on the pressure sensor 23, it can be determined whether the pressure in the absorption tank 21 meets the requirements. When the second end of the gas outlet control valve SV1 is connected to the common end, the cylinder 24 is connected to the exhaust processor 25. At this time, the back pressure of the cylinder 24 can discharge the gas in the cylinder 24 into the exhaust processor 25 for processing; after the exhaust is completed, the gas absorption tank can also be cleaned.

[0043] In the embodiment of the present invention, the gas circuit module 2 realizes a negative pressure environment through pressure monitoring, valve control, and air extraction, etc. The detection device may be provided with a main control module 4, which is connected to a pressure sensor 23; based on the pressure value detected by the pressure sensor 23, the main control module controls the on-off of the valve, the working state of the cylinder 24 (open, stop, cylinder running speed setting, etc.); the cylinder 24 realizes negative pressure extraction under the action of a stepping motor.

[0044] Specifically, the working process of the detection device is as follows: connect the first end of the gas outlet control valve SV1 to the common end, and connect the air intake unit 22, for example, open the air intake control valve SV2, at this time, the cylinder 24 performs a vacuum operation, so that the gas to be tested at the air intake unit 22 can be drawn into the absorption pool 21 to achieve gas sampling. After the gas sampling is completed, the main control module 4 switches the gas outlet control valve SV1, that is, controls the second end of the gas outlet control valve SV1 to be connected to the common end, at this time, the cylinder 24 is connected to the exhaust processor 25, and the back pressure of the cylinder 24 can discharge the gas in the cylinder 24 into the exhaust processor 25, so that the cylinder 24 is restored to the initial state, so as to facilitate the next vacuum operation. Among them, the exhaust processor 25 can be specifically an exhaust interface for discharging the gas in the cylinder 24; optionally, the exhaust processor 25 can also have a filtering function, which is used to filter the gas discharged from the cylinder 24, and then discharge it into the atmosphere to avoid the toxic gas in the sample gas from being discharged at will.

[0045] At the same time, the air intake unit 22 is turned off so that the air intake unit 22 is cut off. For example, the air intake control valve SV2 of the air intake unit 22 can be turned off. After that, the main control module 4 can control the first end of the air outlet control valve SV1 to be connected to the common end, and the main control module 4 sets the parameters of the stepper motor, controls the cylinder 24 to perform the air extraction operation through the stepper motor, and detects the pressure in the absorption tank 21 in real time through the pressure sensor 23. When the pressure value in the absorption tank 21 meets the preset condition, the air extraction operation is stopped. Among them, the preset condition can be specifically a pressure value range of 10-25Kpa, that is, when the pressure of the absorption tank 21 meets the 10-25Kpa, the air extraction operation can be stopped. At this time, the stepper motor can be stopped, or the air outlet control valve SV1 can be closed, for example, the second end of the air outlet control valve SV1 is controlled to be connected to the common end. At this time, detection can be performed. After the detection is completed, the main control module 4 can control the cylinder 24 to be connected to the exhaust processor 25, that is, the second end of the air outlet control valve SV1 is controlled to be connected to the common end, so that the exhaust back pressure operation can be performed.

[0046] In an embodiment of the present invention, the gas path module 2 can evacuate the gas in the absorption cell 21 to a low pressure state, such as a low pressure state of 10-25Kpa. Since the linearity of the absorption signal is greatly affected by pressure, under low pressure conditions, the molecular absorption line broadening is reduced, and the molecular line width under this condition, the lower the pressure, the narrower the line width. Although the lower the pressure, the smaller the line width, and the more independent they are from each other, at a certain temperature, since the pressure is inversely proportional to the number of molecules, too low pressure will cause the number of molecules in the gas absorption cell to decrease, affecting the measurement accuracy. In this embodiment, the pressure is limited to 10-25Kpa, and the absorption signals can be separated from each other, and the pressure is not too low, which reduces the cross interference of the absorption lines between gases. Therefore, using the low pressure state as the detection environment can effectively avoid cross interference of absorption lines and improve detection accuracy.

[0047] Alternatively, if Figure 5 As shown, the air intake unit 22 includes a carbon dioxide filter 221, a sampling assembly 222, a water vapor filter 223 and an air intake control valve SV2; wherein the sampling assembly 222 includes a sampling port 2221 and a sampling control valve SV3. In this embodiment, the sampling port 2221 is connected to the first end of the sampling control valve SV3, and the carbon dioxide filter 221 is connected to the second end of the sampling control valve SV3; one end of the water vapor filter 223 is connected to the common end of the sampling control valve SV3, and the other end of the water vapor filter 223 is connected to the air intake end of the air intake control valve SV2, and the air outlet end of the air intake control valve SV2 is connected to the air intake pipeline 214.

[0048] In the embodiment of the present invention, air can be introduced into the input end of the carbon dioxide filter 221, which can filter out carbon dioxide and the like in the air to prevent the carbon dioxide gas in the air from affecting the detection results. The water vapor filter 223 is used to filter out water vapor in the gas to prevent water vapor from condensing into the gas pipeline or cylinder. The sampling component 222 is used to sample the gas to be tested, and deliver the gas to be tested into the absorption tank 21 after passing through the sampling control valve SV3, the water vapor filter 223, and the air intake control valve SV2. Among them, the sampling component 222 can be multiple, and can be divided into multiple types; in this embodiment, the sampling port 2221 can specifically have at least three types: an injection sampling port, a real-time sampling port, and an extended sampling port. See Figure 6 As shown, when there are multiple sampling assemblies 222, the sampling control valves SV3 of the multiple sampling assemblies 222 are connected in series.

[0049] In the embodiment of the present invention, the gas to be tested is mainly divided into three categories: sample gas, real-time sampled gas and gas collected by extended mode. Accordingly, the three types of gas can be respectively charged into the absorption pool 21 based on the sampling port, the real-time sampling port and the extended sampling port; in order to avoid mutual interference between different sampling ports 2221, multiple sampling components 222 are connected in series, that is, the sampling control valves SV3 of multiple sampling components 222 are connected in series. Figure 6 Taking the structure shown as an example, the carbon dioxide isotope detection device includes two sample injection sampling ports (i.e., injection port A1 and injection port A2), one real-time sampling port (i.e., real-time port T), and four extended sampling ports (i.e., extended port B, extended port C, extended port D, and extended port E). The sampling control valves corresponding to the multiple sampling ports are SV3a1, SV3a2, SV3t, SV3b, SV3c, SV3d, and SV3e. The working process of the carbon dioxide isotope detection device can be as follows:

[0050] First, the cleaning process is performed. The cleaning process is specifically as follows: when all sampling control valves SV3 remain in a closed state (i.e., the second end of the sampling control valve is connected to the common end), the air intake control valve SV2 is opened, and the first end and the common end of the air outlet control valve SV1 are connected (in this embodiment, this state is referred to as the air outlet control valve SV1 is in an open state), at which time air is introduced from the carbon dioxide filter 221, and the cylinder 24 is used for air extraction; after being filtered by the carbon dioxide filter 221 and the water vapor filter 223, the air passes through the absorption tank 21 and is sucked into the cylinder 24, thereby achieving cleaning of the absorption tank 21 and the cylinder 24. After that, the passage of the air outlet control valve SV1 is switched, i.e., the second end of the air outlet control valve SV2 is connected to the common end, so that the back pressure of the cylinder 24 discharges the gas in the cylinder 24 into the exhaust processor for processing.

[0051] Afterwards, the exhaled air at 0 minutes of exhaled sampling is sampled through the sampling port A1, and the sampling control valve SV3a1, the air intake control valve SV2 and the air outlet control valve SV1 are opened at this time; after the sampling is completed, the air intake control valve SV2 is closed, and the main control module 4 controls the cylinder 24 to pump negative pressure to the absorption pool 21. When the required pressure is reached, the pressure is maintained for a certain time (such as 100s, etc.). During the pressure maintenance period, the mid-infrared detection device 31 collects data, which is processed by the signal processing unit 32, and the main control module 4 performs isotope abundance calculation. After the detection is completed, the above-mentioned cleaning process can be performed again.

[0052] The exhaled air during the 30-minute exhaled sampling is sampled through the sampling port A2, and the sampling control valve SV3a2, the air intake control valve SV2 and the air outlet control valve SV1 are opened at this time; after the sampling is completed, the air intake control valve SV2 is closed, and then the main control module 4 controls the cylinder 24 to pump negative pressure to the absorption pool 21, and when the required pressure (such as 10-25KPa) is reached, the pressure is maintained for a certain time (such as 100s, etc.), and detection is performed based on the incident mid-infrared light; specifically, during the pressure maintenance period, the mid-infrared detection device 31 collects data, which is processed by the signal processing unit 32, and the main control module 4 performs isotope abundance calculation. After the detection is completed, the above-mentioned cleaning process can be performed again.

[0053] The real-time sampling port can be used to inject reagents (such as 13 The detection principle is similar to the above process, except that the sampling control valve SV3t needs to be opened. Optionally, the sampling component 222 corresponding to the real-time sampling port SV3t may also be provided with a sampling pump, and air intake may be achieved based on the sampling pump.

[0054] The extended sampling port is used to expand the sampling port so that one detection device can be connected to more sampling ports. In the embodiment of the present invention, when the sampling port 2221 of the sampling component 222 can be an extended sampling port, the air intake unit 22 further includes: a plurality of extended components 224 connected to the extended sampling ports. Figure 7 As shown, the expansion component 224 includes an expansion injection port 2241 and an expansion control valve SV4. The first end of the expansion control valve SV4 is connected to the expansion injection port 2241, the second end of the expansion control valve SV4 is used to access air, and the common end of the expansion control valve SV4 is used to be connected to the expansion sampling port; the expansion control valves SV4 of multiple expansion components 224 are connected in series.

[0055] In the embodiment of the present invention, the principle of the expansion component 224 is substantially similar to that of the sampling component 222, and the expansion component 224 may also include multiple, Figure 7 In the example, four expansion components 224 are included; correspondingly, the expansion control valves SV4 of the multiple expansion components are also connected in series. In the present embodiment, the final output ends of the multiple expansion components 224 are connected to the expansion sampling port, so that the injection gas of the expansion injection port 2241 can also be input to the expansion sampling port, and then input into the absorption cell 21. In the present embodiment, the number of sampling ports can be greatly increased based on the expansion component 224. For example, if the number of the expansion sampling ports is 4, each expansion sampling port can be connected to a structure including 10 expansion components 224, and a total of 40 sampling ports can be expanded. In addition, the on-off of the expansion injection port 2241 can be controlled by the sampling expansion controller, which can be specifically achieved by controlling the on-off state of the expansion control valve SV4.

[0056] On the basis of the above embodiment, since the gas absorption coefficient is affected by the temperature of the gas when it is calculated based on the laser infrared spectrum, the absorption cell 21 in this embodiment has a constant temperature function. Figure 8 As shown, the gas path module 2 further includes a shell 261, a heat preservation layer 262, a third temperature sensor and a heating film 263. The third temperature sensor is arranged in the absorption pool 21, and is used to absorb the temperature in the absorption pool 21; the heating film 263 is arranged outside the absorption pool 21, and is used to heat the absorption pool 21; the heat preservation layer 262 is arranged to cover the outside of the absorption pool 21, and the shell 261 is arranged to cover the outside of the heat preservation layer 262; at the position corresponding to the first transparent window 211 or the second transparent window 212, the heat preservation layer 262 and the shell 261 are both provided with openings.

[0057] In the embodiment of the present invention, a heating film 263 is provided on the outside of the absorption cell 21, and the absorption cell 21 can be heated by the heating film 263 to prevent the low temperature of the gas to be measured in the absorption cell 21 from affecting the measurement; the material of the absorption cell 21 can be a heat-conducting material, such as aluminum alloy and other materials, which is convenient for quickly conducting the heat of the heating film 263 to the entire absorption cell 21. At the same time, a thermal insulation layer 262 is provided on the outside of the absorption cell 21, and a shell 261 is provided on the outside of the thermal insulation layer 262, thereby forming a hierarchical structure of the absorption cell 21, the thermal insulation layer 262, and the shell 261 from the inside to the outside, and the thermal insulation layer 262 and the shell 261 can realize double-layer insulation of the absorption cell 21. The thermal insulation layer 262 and the shell 261 are sequentially arranged on the outside of the absorption cell 21 to realize double-layer insulation, which is conducive to temperature control and ensures that the temperature in the closed cavity 213 is constant.

[0058] like Figure 8 As shown, the heating film 263 can be arranged on the outside of the bottom of the absorption tank 21 (such as attached to the bottom of the absorption tank 21), and arranged between the absorption tank 21 and the thermal insulation layer 262, so that the heating film 263 can heat the entire absorption tank 21 from bottom to top, and the thermal insulation layer 262 surrounds the heating film 263, which can play a thermal insulation effect. Optionally, the thermal insulation layer 262 is specifically arranged around the absorption tank 21; generally, the absorption tank 21 as a whole has a structure with six faces (similar to a rectangular parallelepiped structure), and six thermal insulation layers 262 can be set at this time, and they are respectively arranged on one side of the absorption tank 21 to provide a layer of thermal protection; the outermost shell 261 can be composed of two shells, such as two left and right shells, etc., Figure 8 The corresponding cross section is the gap between the two shells; Fig. 9 The structure diagram after removing one of the shells is shown. Fig. 9 The shell body on the side close to the observer is not shown; the two shell bodies can be fixedly connected via two fixing screw holes at the top and the bottom (four fixing screw holes in total).

[0059] In addition, in this embodiment, a plurality of third temperature sensors are distributed in the absorption tank 21, so that the temperature of different components can be measured to achieve multi-point temperature measurement. Figure 8 As shown, a first slot 216 and a second slot 217 are provided in the absorption pool 21. The first slot 216 is provided on the outside of the absorption pool 21, and the first slot 216 is used to set a third temperature sensor. Under the action of the external insulation layer 262, the temperature measured by the third temperature sensor is the temperature of the absorption pool 21 itself.

[0060] A second slot 217 is disposed in the absorption pool 21, and the second slot 217 is communicated with the closed cavity 213, so that the gas to be measured can enter the second slot 217; another third temperature sensor is disposed at the second slot 217, so that the third temperature sensor can directly contact the gas to be measured and can accurately measure the temperature of the gas to be measured.

[0061] The working process of the absorption cell 21 is as follows: the gas to be measured (such as carbon dioxide, etc.) is filled into the closed cavity 213, and then heated by the heating film 263, and the temperature of the absorption cell 21 and the temperature of the gas to be measured are detected based on multiple third temperature sensors. When the temperature meets the detection requirements (such as the temperature of the absorption cell body 30 and the temperature of the gas to be measured reach the preset value), the mid-infrared light can be injected into the closed cavity 213 through the first transparent window 211, and then pass through the closed cavity 213 and then be emitted from the second transparent window 212, so that the mid-infrared detection device 31 at the second transparent window 212 can collect the corresponding absorption spectrum for further analysis.

[0062] Based on the above embodiments, Figure 8 and Fig. 9 As shown, the absorption pool 21 is provided with an air inlet pipeline 214 and an air outlet pipeline 215 connected to the closed cavity 213. Among them, at the position corresponding to the air inlet pipeline 214 or the air outlet pipeline 215, the thermal insulation layer 262 and the shell 261 are both provided with openings. In this embodiment, the thermal insulation layer 262 and the shell 261 are both provided with openings to prevent the thermal insulation layer 262 and the shell 261 from affecting the air inlet or air outlet. The air inlet pipeline 214 and the air outlet pipeline 215 are sealed to prevent the gas to be tested from leaking. In this embodiment, when it is necessary to fill the gas to be tested into the closed cavity 213, the gas to be tested can be filled into the closed cavity 213 through the air inlet pipeline 214; after the detection is completed, the gas to be tested in the closed cavity 213 can be extracted through the air outlet pipeline 215. The absorption pool provided in this embodiment has the characteristics of small size and compact structure, so that the gas in the absorption pool can be quickly kept at a constant temperature and conveniently achieve precise temperature control.

[0063] Optionally, the absorption pool 21 further includes a heat-insulating bracket 264; the heat-insulating bracket 264 is disposed at the bottom of the shell 261 and is used to support the shell 261. In this embodiment, the heat-insulating bracket 264 is made of a heat-insulating material and can isolate heat from the bottom as a whole; wherein the shell 261 can be fixed to the heat-insulating bracket 264 in a vertical direction.

[0064] On the basis of the above embodiment, the absorption pool further includes a thermistor, which is arranged at the heating film 263; the main control module 4 can control the heating film 263 to heat to a preset temperature, such as 40°C. In this embodiment, the main control module can simply and quickly control the heating film 263 to heat, and if the temperature of the absorption pool 21 exceeds the threshold, the heating can be stopped to achieve cooling.

[0065] Optionally, the mid-infrared laser 11, the absorption cell 21 and the mid-infrared detection device 31 are arranged in the sealed housing 5. In this embodiment, the sealed housing 5 is made of opaque material, which can seal all light paths to prevent the external ambient light from affecting the detection.

[0066] The carbon dioxide isotope detection device provided by the embodiment of the present invention adopts a mid-infrared laser 11 as a light source and uses mid-infrared light for detection, which can reduce the required optical path, so that the direct absorption cell 21 can also meet the needs, and the size of the absorption cell 21 can also be reduced; and there is no need to set multiple return components in the absorption cell, and there is no standard tool interference when the mid-infrared light passes through the absorption cell 21, thereby improving the measurement accuracy and high stability. Using this mid-infrared light, a variety of carbon dioxide isotopes have strong absorption, and there is no interference from the water absorption peak, so that a variety of carbon dioxide isotopes can be accurately detected at the same time. The gas path module 2 can evacuate the gas in the absorption cell 21 to a low pressure state, thereby effectively avoiding cross-interference of absorption lines and improving the detection accuracy. The detection equipment has low cost, good accuracy and stability, and can facilitate real-time rapid measurement of carbon dioxide isotopes.

[0067] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any technical solution that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A carbon dioxide isotope detection device, characterized in that: include: A laser module, a gas path module and a detector module; the laser module includes a mid-infrared laser, the gas path module includes a direct absorption cell, and the detector module includes a mid-infrared detection device; The absorption cell is provided with a first transparent window and a second transparent window at both ends in the length direction; between the first transparent window and the second transparent window, the absorption cell is provided with a closed cavity for placing the gas to be measured; The mid-infrared laser is arranged outside the first transparent window, and is used to emit mid-infrared light that passes through the first transparent window and the second transparent window in sequence; The mid-infrared detection device is arranged outside the second transparent window, and is used to receive the mid-infrared light passing through the second transparent window; The detector module also includes: a sensor cooling plate, a second temperature sensor and a cooling control unit; The second temperature sensor is arranged at the mid-infrared detection device, and is used to measure a second temperature signal of the mid-infrared detection device, and send the second temperature signal to the refrigeration control unit; The refrigeration control unit is used to control the current size and / or current direction of the sensor refrigeration plate according to the second temperature signal; the sensor refrigeration plate is arranged at the mid-infrared detection device to absorb heat from the mid-infrared detection device.

2. The carbon dioxide isotope detection device according to claim 1, characterized in that: The laser module further comprises: a laser current driving unit, a laser cooling plate, a first temperature sensor and a laser temperature control unit; The laser current driving unit is connected to the mid-infrared laser and is used to convert the laser driving waveform into a current driving signal to drive the mid-infrared laser to emit the mid-infrared light with wavelength modulation; The first temperature sensor is arranged at the mid-infrared laser, and is used to measure a first temperature signal of the mid-infrared laser, and send the first temperature signal to the laser temperature control unit; The laser temperature control unit is used to control the current size and / or current direction of the laser cooling plate according to the first temperature signal; the laser cooling plate is arranged at the mid-infrared laser to control the temperature of the mid-infrared laser.

3. The carbon dioxide isotope detection device according to claim 1, characterized in that: The gas circuit module further includes: an air intake unit, a pressure sensor, an air outlet control valve, a cylinder and an exhaust processor; the absorption tank is provided with an air intake pipeline and an air outlet pipeline connected to the closed cavity; The air intake unit is connected to the air intake pipeline; The pressure sensor is arranged in the air inlet pipeline, the air outlet pipeline or the closed cavity; The first end of the gas outlet control valve is connected to the gas outlet pipeline, the second end of the gas outlet control valve is connected to the exhaust processor, and the common end of the gas outlet control valve is connected to the cylinder; When the first end of the gas outlet control valve is connected to the common end and the gas inlet unit is connected, the gas cylinder evacuates the absorption pool to complete sampling; When the second end of the gas outlet control valve is connected to the common end, the cylinder is back-pressurized to discharge the gas in the cylinder into the exhaust processor; When the first end of the gas outlet control valve is connected to the common end and the gas inlet unit is cut off, the gas cylinder evacuates the absorption tank until the pressure value detected by the pressure sensor meets the preset condition.

4. The carbon dioxide isotope detection device according to claim 3, characterized in that: The air intake unit includes a carbon dioxide filter, a sampling assembly, a water vapor filter and an air intake control valve, and the sampling assembly includes a sampling port and a sampling control valve; The sampling port is connected to the first end of the sampling control valve, and the carbon dioxide filter is connected to the second end of the sampling control valve; One end of the water vapor filter is connected to the common end of the sampling control valve, the other end of the water vapor filter is connected to the air inlet end of the air intake control valve, and the air outlet end of the air intake control valve is connected to the air intake pipeline.

5. The carbon dioxide isotope detection device according to claim 4, characterized in that: There are multiple sampling components, and the sampling control valves of the multiple sampling components are connected in series; The sampling port is an injection sampling port, a real-time sampling port or an extended sampling port.

6. The carbon dioxide isotope detection device according to claim 5, characterized in that: When the sampling port of the sampling component is an extended sampling port, the air intake unit further comprises: a plurality of extended components; the extended components comprise an extended sampling port and an extended control valve; The first end of the extended control valve is connected to the extended injection port, the second end of the extended control valve is used to access air, and the common end of the extended control valve is used to be connected to the extended sampling port; A plurality of expansion control valves of the expansion assembly are connected in series.

7. The carbon dioxide isotope detection device according to claim 1, characterized in that: It also includes a main control module, and the detector module also includes: a signal processing unit; The signal processing unit is connected to the mid-infrared detection device, and is used to receive the electrical signal corresponding to the mid-infrared light collected by the mid-infrared detection device, and process the electrical signal; The main control module is connected to the signal processing unit, and is used to receive the processed electrical signal, and perform carbon isotope detection processing according to the processed electrical signal to determine the carbon isotope parameters of the gas to be tested.

8. The carbon dioxide isotope detection device according to claim 1, characterized in that: The gas path module also includes a shell, a heat-insulating layer, a third temperature sensor and a heating film; The third temperature sensor is disposed in the absorption tank and is used to measure the temperature in the absorption tank; The heating film is arranged outside the absorption cell and is used to heat the absorption cell; The heat-insulating layer is disposed on the outside of the absorption tank, and the outer shell is disposed on the outside of the heat-insulating layer; the heat-insulating layer and the outer shell are both provided with openings at positions corresponding to the first transparent window or the second transparent window.

9. The carbon dioxide isotope detection device according to claim 1, characterized in that: The mid-infrared laser, the absorption cell and the mid-infrared detection device are arranged in a sealed housing.

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