Enrichment enhanced photoacoustic spectrometry gas detection device

Abstract

The enrichment-enhanced photoacoustic spectrometry gas detection device comprises a signal generator, the signal output end of the signal generator is connected with the signal input end of a tunable laser light source, and the signal output end of the signal generator is connected with the signal input end of a lock-in amplifier; a light source emitted by the tunable laser light source penetrates through first glass of the photoacoustic cell to enter the photoacoustic cell, the gas inlet end and the gas outlet end of the photoacoustic cell are communicated with the enrichment enhancement gas circuit, and the signal output end of a microphone of the photoacoustic cell is connected with the signal input end of the lock-in amplifier. The signal output end of the lock-in amplifier is connected with the signal input end of the processor; through the signal enhancement module formed by the enrichment enhancement gas circuit and the photoacoustic cell, the local concentration of the sample gas entering the photoacoustic cell is increased, and the absorption of the detected gas to the laser is enhanced, so that the detection sensitivity is improved, the response time is shorter, the dynamic range is wider, and the concentration calibration linearity of gas sensing is better.

Description

Technical Field

[0001] This utility model relates to the field of trace gas detection technology, and in particular to an enrichment-enhanced photoacoustic spectroscopy gas detection device. Background Technology

[0002] The application of photoacoustic spectroscopy in gas detection is based on Beer-Lambert's law for gases. When a gas absorbs incident light, it excites an acoustic resonance signal. The amplitude of this signal is proportional to the gas concentration, and its frequency changes in accordance with the frequency of the incident light. The generated resonance signal is detected using an acoustic detector. By analyzing the spectral lines and intensity of the signal, the gas species can be identified and its concentration can be quantitatively determined. This technology features high selectivity, continuous sampling, and simultaneous measurement of multiple gases, making it highly favored in gas detection research. In the process of gas detection using photoacoustic spectroscopy, improving detection sensitivity is crucial for optimizing the accuracy of the detection results.

[0003] Currently, the main methods commonly used to improve the sensitivity of gas detection are as follows:

[0004] First, one approach utilizes the direct proportionality between photoacoustic signal intensity and optical power. For example, by using high-power lasers or fiber amplifiers to increase optical power, a stronger photoacoustic signal can be generated, achieving higher detection sensitivity at the same gas concentration. However, high-power lasers are expensive, and fiber amplifiers are bulky, resulting in high economic costs. Second, based on the exponential relationship between absorbed signal intensity and optical path length in Beer-Lambert's law for gases, different photoacoustic cell structures can be designed to increase the number of laser reflections, thereby increasing the absorbed signal intensity and ultimately improving sensitivity. However, this method requires a sophisticated optical system with a complex structure and high precision in the optical path incident position. Third, more efficient acoustic conversion devices can be used, such as custom tuning forks, cantilever beams, and fiber optic microphones, but this also involves high manufacturing costs.

[0005] Patent application CN118758873A discloses a gas detection system based on acousto-optic dual resonance, which enhances the amplification capability of the photoacoustic cell to improve the photoacoustic signal detected by the sensor, thereby achieving a higher detection limit and a larger dynamic range; however, its optical cavity is composed of optical lenses, which has high requirements for beam coupling and accuracy, and the optical path adjustment is relatively complex.

[0006] Patent application CN118758920A discloses a Raman spectroscopy gas detection device with long optical path and high-convergence excitation. A parabolic mirror is placed in the gas chamber to achieve multiple reflections of the incident light, and a dichroic mirror is used to reflect the Raman scattered light, ultimately achieving efficient excitation and collection of the Raman signal. Raman spectroscopy has a low detection limit and low linearity of the concentration curve, which is not conducive to quantitative analysis. Furthermore, its practical application involves adjustments to the incident position of the excitation source, the optical path within the gas chamber, and the convergence of the emitted light, making it challenging and complex. Summary of the Invention

[0007] To overcome the shortcomings of the prior art, the present invention aims to provide an enrichment-enhanced photoacoustic spectroscopy gas detection device. By setting up a signal enhancement module composed of an enrichment-enhanced gas path and a photoacoustic cell, the local concentration of the sample gas entering the photoacoustic cell is increased, thereby enhancing the absorption of laser light by the gas being measured, thus improving the detection sensitivity, having a faster response time and a wider dynamic range, better linearity of gas sensing concentration calibration, and stronger anti-interference ability.

[0008] To achieve the above objectives, the technical solution adopted by this utility model is as follows:

[0009] An enrichment-enhanced photoacoustic spectroscopy gas detection device includes a signal generator 1. The signal output terminal of the signal generator 1 is connected to the signal input terminal of a tunable laser light source 2. The signal output terminal of the signal generator 1 is also connected to the signal input terminal of a lock-in amplifier 5. The tunable laser light source 2 emits light that passes through the first glass 302 of the photoacoustic cell 3 and enters the photoacoustic cell 3. The inlet and outlet of the photoacoustic cell 3 are respectively connected to an enrichment-enhanced gas path 4. The signal output terminal of the microphone 311 of the photoacoustic cell 3 is connected to the signal input terminal of the lock-in amplifier 5. The signal output terminal of the lock-in amplifier 5 is connected to the signal input terminal of a processor 6.

[0010] Further, the enrichment-enhancing gas path 4 includes a first main pipe 401, on which a first needle valve 402, a first tee 403, an adsorption tube 404, a buffer tube 405, and a second needle valve 406 are sequentially arranged; the first main pipe 401 is connected to a first branch pipe 407 through the first tee 403, and the end of the first main pipe 401 near the second needle valve 406 is connected to a second branch pipe 408; the first branch pipe 407 is connected to the second main pipe 409; the second main pipe 409 is sequentially arranged with... The third needle valve 410, the four-way valve 411, the second three-way valve 412, and the fourth needle valve 413 are connected. The second main pipe 409 is connected to the second branch pipe 408 through the four-way valve 411, and the second main pipe 409 is connected to the third branch pipe 414 through the second three-way valve 412. The second branch pipe 408 is connected to the fourth branch pipe 418 through the four-way valve 411. The fourth branch pipe 418 is equipped with a fifth needle valve 415. The fourth branch pipe 418 is connected to the air inlet of the photoacoustic cell 3, and the third branch pipe 414 is connected to the air outlet of the photoacoustic cell 3.

[0011] Furthermore, a resistance heating band 416 is provided around the outer surface of the adsorption tube 404, a molecular sieve is provided inside the adsorption tube 404, and a thermistor probe 417 is provided between the adsorption tube 404 and the resistance heating band 416.

[0012] Furthermore, the photoacoustic cell 3 includes a first glass 302 and a second glass 303 vertically opposite to the first glass 302. The first glass 302 and the second glass 303 are respectively disposed on both sides of the base 301, and a shell 304 opposite to the base 301 is disposed between the first glass 302 and the second glass 303. The base 301, the first glass 302, the second glass 303, and the shell 304 enclose and form a first buffer cavity 305, an absorption cavity 306, and a resonant cavity 30 that are interconnected with each other. 7 and the second buffer cavity 308, the first buffer cavity 305 and the second buffer cavity 308 are located on both sides of the absorption cavity 306, the central axis of the resonant cavity 307 is perpendicular to the central axis of the absorption cavity 306; an air inlet 309 is provided on the housing 304 of the first buffer cavity 305 on the side away from the base 301, an air outlet 310 is provided on the housing 304 of the second buffer cavity 308 on the side away from the base 301, and a microphone 311 is embedded in the housing 304 of the resonant cavity 307 on the side away from the absorption cavity 306.

[0013] Furthermore, the adsorption tube 404 is made of stainless steel.

[0014] Furthermore, the surface of the resistance heating band 416 is covered with a polyimide film (PI film), and the material of the resistance heating band 416 is rubber.

[0015] Furthermore, the buffer tube 405 has a hollow cylindrical structure and is made of stainless steel.

[0016] Furthermore, the first glass 302 and the second glass 303 are made of calcium fluoride.

[0017] Furthermore, the first buffer cavity 305, the absorption cavity 306, the resonant cavity 307, and the second buffer cavity 308 are all hollow cylindrical structures.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1. This utility model improves detection sensitivity by using gas path enrichment method. The tunable laser source 2 is directly incident into the photoacoustic cell 3 through the first glass 302 without involving light path reflection. It has low requirements for beam coupling accuracy and low light loss, which greatly reduces the impact of power attenuation caused by optical path lengthening on the detection results.

[0020] 2. This utility model, by setting up a signal enhancement module composed of enrichment enhancement gas path 4 and photoacoustic cell 3, increases the local concentration of sample gas entering the photoacoustic cell, thereby enhancing the absorption of laser by the gas being measured, thus improving the detection sensitivity, having a faster response time and a wider dynamic range, better linearity of gas sensing concentration calibration, and stronger anti-interference ability.

[0021] In summary, by employing an enrichment-enhanced photoacoustic spectroscopy detection system and multi-component gas demodulation anti-interference technology, it is possible to achieve high-sensitivity gas detection and determination of background gas interference factors. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the enrichment-enhanced photoacoustic spectroscopy gas detection device of this utility model.

[0023] Figure 2 This is a schematic diagram of the structure of the photoacoustic cell 3 and the enrichment and enhancement gas path 4 of this utility model.

[0024] Figure 3 This is a schematic diagram of the dynamic enrichment and adsorption of gas according to this invention.

[0025] Figure 4 This is a schematic diagram of the static heating and desorption of gas according to the present invention.

[0026] Figure 5 This is a schematic diagram of the gas exchange process during desorption in this invention.

[0027] Figure 6 This is a comparison of the second harmonic spectra of 2.5 ppm NO gas before and after enrichment according to this invention.

[0028] Figure 7 This is a calibration curve of the photoacoustic signal response with concentration before and after NO enrichment according to this invention.

[0029] In the diagram: 1. Signal generator; 2. Tunable laser source; 3. Photoacoustic cell; 301. Base; 302. First glass; 303. Second glass; 304. Housing; 305. First buffer cavity; 306. Absorption cavity; 307. Resonant cavity; 308. Second buffer cavity; 309. Air inlet; 310. Air outlet; 311. Microphone; 4. Enrichment and enhancement gas path; 401. First main pipe; 402. First needle valve; 403. First... 404. T-connector; 405. Adsorption tube; 406. Buffer tube; 407. Second needle valve; 408. First branch tube; 409. Second main tube; 410. Third needle valve; 411. Four-way connector; 412. Second tee connector; 413. Fourth needle valve; 414. Third branch tube; 415. Fifth needle valve; 416. Resistance heating band; 417. Thermistor probe; 418. Fourth branch tube; 5. Lock-in amplifier; 6. Processor. Detailed Implementation

[0030] The present invention will now be described in further detail with reference to the accompanying drawings.

[0031] See Figure 1-5 An enrichment-enhanced photoacoustic spectroscopy gas detection device includes a signal generator 1. The signal output terminal of the signal generator 1 is connected to the signal input terminal of a tunable laser light source 2. The signal output terminal of the signal generator 1 is also connected to the signal input terminal of a lock-in amplifier 5. The tunable laser light source 2 emits light that passes through the first glass 302 of the photoacoustic cell 3 and enters the photoacoustic cell 3. The inlet and outlet of the photoacoustic cell 3 are respectively connected to an enrichment-enhanced gas path 4. The signal output terminal of the microphone 311 of the photoacoustic cell 3 is connected to the signal input terminal of the lock-in amplifier 5. The signal output terminal of the lock-in amplifier 5 is connected to the signal input terminal of a processor 6.

[0032] In this embodiment, the signal generator 1 sends signals to the tunable laser source 2 and the lock-in amplifier 5 respectively. The tunable laser source 2 generates incident light that passes through the first glass 302 of the photoacoustic cell 3 and irradiates the interior of the photoacoustic cell 3. The enrichment enhancement gas path 4 fills the photoacoustic cell 3 with enriched gas. The moderate enrichment of the short adsorption period makes the gas detection limit within the sampling period reach the ppb level. The microphone 311 of the photoacoustic cell 3 outputs a photoacoustic signal and transmits it to the lock-in amplifier 5. The lock-in amplifier 5 filters, demodulates and amplifies the voltage signal according to the reference signal input by the signal generator 1. The processor 6 processes the filtered, demodulated and amplified voltage signal to complete the gas detection.

[0033] Among them: signal generator 1 is based on AFG3021C from Tektronix, Inc., USA; tunable laser source 2 is based on HPQCL-Q from Ningbo Haierxin Optoelectronics Technology Co., Ltd.; lock-in amplifier 5 is based on SR850 from Stanford Research Systems, Inc., USA; processor 6 is based on the computer's built-in USB port and a LabVIEW host computer operating system.

[0034] like Figure 2-5 As shown, the enrichment enhancement gas path 4 includes a first main pipe 401, on which a first needle valve 402, a first tee 403, an adsorption tube 404, a buffer tube 405, and a second needle valve 406 are sequentially arranged; the first main pipe 401 is connected to a first branch pipe 407 through the first tee 403, and the end of the first main pipe 401 near the second needle valve 406 is connected to a second branch pipe 408; the first branch pipe 407 is connected to the second main pipe 409; the second main pipe 409 is sequentially arranged with a first needle valve 402, a first tee 403, an adsorption tube 404, a buffer tube 405, and a second needle valve 406. The system includes a three-needle valve 410, a four-way valve 411, a second three-way valve 412, and a fourth needle valve 413. The second main pipe 409 is connected to the second branch pipe 408 via the four-way valve 411, and the second main pipe 409 is connected to the third branch pipe 414 via the second three-way valve 412. The second branch pipe 408 is connected to the fourth branch pipe 418 via the four-way valve 411. The fourth branch pipe 418 is equipped with a fifth needle valve 415. The fourth branch pipe 418 is connected to the air inlet of the photoacoustic cell 3, and the third branch pipe 414 is connected to the air outlet of the photoacoustic cell 3.

[0035] By controlling the opening and closing modes of the first needle valve 402, the second needle valve 406, the third needle valve 410, the fourth needle valve 413, and the fifth needle valve 415, the flow path of the gas is changed, thereby achieving the purpose of gas adsorption and desorption.

[0036] like Figure 2 and Figure 4 As shown, a resistance heating band 416 is provided around the outer surface of the adsorption tube 404, and a molecular sieve is disposed inside the adsorption tube 404. A thermistor probe 417 is disposed between the adsorption tube 404 and the resistance heating band 416. The resistance heating band 416 is used to control the temperature of the molecular sieve, and the actual temperature of the molecular sieve is monitored in real time by the thermistor probe 417.

[0037] The functionality of this embodiment mainly includes three aspects: sample adsorption, desorption, and spectral measurement. The input gas is first collected on a molecular sieve, then the adsorption cell is heated and desorbed using a PI membrane, and finally, photoacoustic spectroscopy is used to detect gas information from the enriched sample.

[0038] like Figure 2-5As shown, the photoacoustic cell 3 includes a first glass 302 and a second glass 303 vertically opposite to the first glass 302. The first glass 302 and the second glass 303 are respectively disposed on both sides of the base 301. A shell 304 opposite to the base 301 is disposed between the first glass 302 and the second glass 303. The base 301, the first glass 302, the second glass 303 and the shell 304 enclose and form a first buffer cavity 305, an absorption cavity 306 and a resonant cavity 307 that are interconnected with each other. The first buffer cavity 305 and the second buffer cavity 308 are located on both sides of the absorption cavity 306. The central axis of the resonant cavity 307 is perpendicular to the central axis of the absorption cavity 306. An air inlet 309 is provided on the housing 304 of the first buffer cavity 305 on the side away from the base 301. An air outlet 310 is provided on the housing 304 of the second buffer cavity 308 on the side away from the base 301. A microphone 311 is embedded in the housing 304 of the resonant cavity 307 on the side away from the absorption cavity 306.

[0039] In this embodiment, the light source generated by the tunable laser source 2 passes through the first glass 302 and the second glass 303. The enriched gas is introduced into the photoacoustic cell 3 through the enrichment enhancement gas path 4. The incident light, modulated by the signal generator 1, passes through the first buffer cavity 305 and the absorption cavity 306 before finally reaching the second buffer cavity 308. During this process, the gas to be measured in the incident light path is fully absorbed at the absorption cavity 306, generating a periodically modulated local heat source, which then diffuses to other surrounding gas molecules, thereby exciting a sound wave signal of the same frequency in the resonant cavity 307. The microphone 311 collects the sound wave signal and transmits it to the lock-in amplifier 5. Finally, by utilizing the moderate enrichment of the short adsorption period, the gas detection limit within the sampling period reaches the ppb level.

[0040] The adsorption tube 404 is made of stainless steel.

[0041] The surface of the resistance heating band 416 is covered with a polyimide film (PI film), and the material of the resistance heating band 416 is rubber.

[0042] The buffer tube 405 is a hollow cylindrical structure made of stainless steel. The buffer tube 405 ensures sufficient gas volume to transfer the desorbed gas to the entire adsorption tube 404 and the photoacoustic cell 3.

[0043] The first glass 302 and the second glass 303 are made of calcium fluoride.

[0044] The first buffer cavity 305, the absorption cavity 306, the resonant cavity 307, and the second buffer cavity 308 are all hollow cylindrical structures.

[0045] The working principle of this utility model is as follows:

[0046] The working principle of this invention is explained in detail by taking the enrichment of NO by Cu-ZSM-5 molecular sieve as an example, using the unique strong adsorption capacity of Cu-ZSM-5 molecular sieve for NO.

[0047] like Figure 1 As shown, during operation, signal generator 1 generates a modulation signal to modulate the tunable laser source 2. Simultaneously, this modulation signal serves as a reference signal input to lock-in amplifier 5. The modulated light is incident on photoacoustic cell 3. A gas sample enriched by enrichment enhancement gas path 4 is injected into photoacoustic cell 3. At this point, gas molecules in photoacoustic cell 3 are excited by the light, undergoing non-radiative transitions, generating a temperature gradient that excites the photoacoustic signal. Microphone 311 transmits the acquired photoacoustic signal to lock-in amplifier 5 for filtering and demodulation. Finally, the signal is transmitted to processor 6 for recording and calculation.

[0048] like Figure 2 As shown, after the sample gas is input, it flows directly through adsorption tube 404, which contains approximately 3 grams of Cu-ZSM-5 molecular sieve and has a volume of 24 mL. Thanks to the strong adsorption capacity of Cu-ZSM-5 molecular sieve for NO, good results are achieved even at relatively low flow volumes, with short adsorption times. Furthermore, this ensures effective desorption of NO even at higher temperatures, thus shortening the duration of the entire measurement cycle. A voltage-controlled electromagnetic needle valve allows for switching the gas flow path through the molecular sieve and photoacoustic cell 3. To control the temperature of the molecular sieve, a rubber resistance heating strip 416 wrapped with a PI film is coiled around the stainless steel adsorption tube 404, and the heating temperature is monitored by a thermistor probe 417 inserted around the periphery of the adsorption tube. In addition to heating, the flow rate on the molecular sieve surface also aids in NO desorption. To ensure sufficient gas volume for transferring the desorbed gas throughout the adsorption tube 404 and photoacoustic cell 3, a stainless steel buffer tube 405 with the same additional volume is installed after the adsorption tube 404. Forward flow is used during the adsorption stage, while reverse flow is used during desorption and rinsing of the molecular sieve. At this time, the lock-in amplifier 5 filters, demodulates, and amplifies the voltage signal detected by the microphone 311 of the photoacoustic cell 3 based on the reference signal input from the signal generator 1, and the processor 6 processes the voltage signal to complete the detection of the gas.

[0049] like Figure 3 As shown, the first needle valve 402, the second needle valve 406, and the fourth needle valve 413 are opened, while the third needle valve 410 and the fifth needle valve 415 are closed. The mixed sample gas flows through the adsorption tube 404 containing the Cu-ZSM-5 molecular sieve and then along... Figure 3The gas is discharged directly in the direction indicated by the dashed line, and the entire photoacoustic cell 3 does not participate in the enrichment process. At this time, the gas molecules of the sample, which are positively correlated with the concentration, are adsorbed on the surface of the molecular sieve material. This stage requires continuous gas filling for about 40 seconds. This ensures that the sample gas is in full contact with the surface of the molecular sieve, removes residual gas, and ensures adsorption efficiency and measurement accuracy.

[0050] like Figure 4 As shown, during the sample gas desorption stage, the first needle valve 402 is closed to prevent sample gas from flowing in, separating the adsorption tube 404 from the photoacoustic cell 3. The first needle valve 402, the second needle valve 406, the third needle valve 410, and the fifth needle valve 415 are closed, and the fourth needle valve 413 is opened. The rubber resistance heating strip 416 wrapped with PI film around the adsorption tube 404 begins to work, and the heating temperature is monitored by the thermistor probe 417 until it reaches 150°C, then pauses for several minutes. While the adsorption tube 404 is heating, a vacuum pump is used at the gas outlet 310 of the photoacoustic cell 3 to evacuate the cell to a pressure of 150 mbar.

[0051] like Figure 5 As shown, the system performs gas exchange during desorption, with the spectral measurement and enrichment rinsing stages starting simultaneously. Heating is stopped, and the adsorption tube 404 is connected to the inlet 309 of the photoacoustic cell 3, allowing the gas to flow counterclockwise along the dotted line in the figure. The third needle valve 410 and the fifth needle valve 415 are opened, while the first needle valve 402, the second needle valve 406, and the fourth needle valve 413 are closed, initiating cooling of the adsorption tube 404. Due to pressure, the enriched sample gas desorbed from the adsorption tube 404 expands into the evacuated photoacoustic cell 3. During this stage, the pressure inside the photoacoustic cell 3 rapidly rises to approximately 680 mbar. The buffer tube 405 assists in desorption from the molecular sieve surface during this stage and ensures that no new gas flows through the molecular sieve from the input end during the transfer process. Conversely, the gas enriched in the adsorption tube 404 is passively transferred to the photoacoustic spectral measurement section, where the enriched sample in the photoacoustic cell 3 is spectrally measured, acquiring photoacoustic signals and second harmonic spectral lines. After the spectral measurement is completed, gas flow is stopped, and the sample gas concentration is calculated.

[0052] After one measurement cycle, the adsorption tube 404 and the photoacoustic cell 3 are rinsed with pure N2 for 60 seconds. At this time, the temperature of the adsorption tube 404 is still relatively high, which can effectively remove any residual NO in the molecular sieve. After rinsing, the gas flow direction is switched to... Figure 3The forward flow shown restarts the adsorption phase, initiating the next enrichment measurement cycle. The measurement system continuously monitors the molecular sieve temperature and the flow rate of the sample gas at inlet 309, as these factors affect the retention of NO and H2O in the molecular sieve. In experimental measurements based on this invention, no significant changes in these parameters were observed, demonstrating excellent repeatability without the need for any algorithmic correction. If the ambient temperature varies considerably, it may be necessary to heat the photoacoustic cell 3 and calibrate the enrichment enhancement effect using a formula relating temperature and mass flow rate.

[0053] The relationship between the second harmonic spectrum of NO and current is obtained through processor 6 as follows: Figure 6 As shown, the photoacoustic signal amplitude rapidly increases to around 1.07 mV and fluctuates, while the noise level remains almost unchanged during static measurement. Therefore, the enrichment-enhanced photoacoustic spectroscopy gas detection device can improve the signal-to-noise ratio of NO by 3.3 times, thereby significantly improving the sensitivity of the photoacoustic spectroscopy gas detection system with the assistance of the molecular sieve enrichment method. Calculations show that the signal-to-noise ratio of the 2.5 ppm NO spectral signal is 1389.61, indicating that the lowest detection limit (1σ) after NO enrichment enhancement is 1.8 ppb, corresponding to a normalized noise equivalent absorption coefficient of 3.23 × 10⁻⁶. -9 cm -1 W Hz -1 / 2 The concentration response of NO gas before and after enrichment was calibrated, and the results are as follows: Figure 7 As shown, the photoacoustic signal amplitude after enrichment has a good linear relationship with the sample gas concentration. The photoacoustic signal amplitude at the same sample gas concentration after enrichment is greater than that before enrichment.

[0054] The above embodiments are merely detailed descriptions of the present utility model, but the present utility model is not limited to the above embodiments. Any modifications, substitutions, and changes made to the present utility model within the spirit and scope of the claims are within the scope of protection of the present utility model.

Claims

1. A photoacoustic spectroscopy gas detection device with enrichment enhancement, comprising a signal generator (1), wherein the signal output terminal of the signal generator (1) is connected to the signal input terminal of a tunable laser source (2), and the signal output terminal of the signal generator (1) is connected to the signal input terminal of a lock-in amplifier (5), characterized in that: The tunable laser light source (2) emits light through the first glass (302) of the photoacoustic pool (3) and enters the photoacoustic pool (3). The air inlet and outlet of the photoacoustic pool (3) are respectively connected to the enrichment enhancement air path (4). The signal output terminal of the microphone (311) of the photoacoustic pool (3) is connected to the signal input terminal of the lock-in amplifier (5). The signal output terminal of the lock-in amplifier (5) is connected to the signal input terminal of the processor (6).

2. The enrichment-enhanced photoacoustic spectroscopy gas detection device according to claim 1, characterized in that: The enrichment enhancement gas path (4) includes a first main pipe (401), on which a first needle valve (402), a first tee (403), an adsorption tube (404), a buffer tube (405), and a second needle valve (406) are sequentially arranged; the first main pipe (401) is connected to a first branch pipe (407) through the first tee (403), the end of the first main pipe (401) near the second needle valve (406) is connected to a second branch pipe (408), and the first branch pipe (407) is connected to the second main pipe (409); a third needle valve is sequentially arranged on the second main pipe (409). 410), four-way (411), second three-way (412) and fourth needle valve (413), the second main pipe (409) is connected to the second branch pipe (408) through the four-way (411), the second main pipe (409) is connected to the third branch pipe (414) through the second three-way (412); the second branch pipe (408) is connected to the fourth branch pipe (418) through the four-way (411), the fourth branch pipe (418) is equipped with a fifth needle valve (415), the fourth branch pipe (418) is connected to the air inlet of the photoacoustic cell (3), and the third branch pipe (414) is connected to the air outlet of the photoacoustic cell (3).

3. The enrichment-enhanced photoacoustic spectroscopy gas detection device according to claim 2, characterized in that: The outer surface of the adsorption tube (404) is provided with a resistance heating band (416), a molecular sieve is provided inside the adsorption tube (404), and a thermistor probe (417) is provided between the adsorption tube (404) and the resistance heating band (416).

4. The enrichment-enhanced photoacoustic spectroscopy gas detection device according to claim 1, characterized in that: The photoacoustic cell (3) includes a first glass (302) and a second glass (303) vertically opposite to the first glass (302). The first glass (302) and the second glass (303) are respectively disposed on both sides of the base (301). A shell (304) opposite to the base (301) is disposed between the first glass (302) and the second glass (303). The base (301), the first glass (302), the second glass (303), and the shell (304) enclose and form a first buffer cavity (305), an absorption cavity (306), a resonant cavity (307), and a resonant cavity that are interconnected with each other. The second buffer cavity (308), the first buffer cavity (305) and the second buffer cavity (308) are located on both sides of the absorption cavity (306), and the central axis of the resonant cavity (307) is perpendicular to the central axis of the absorption cavity (306); an air inlet (309) is provided on the housing (304) of the first buffer cavity (305) away from the base (301), an air outlet (310) is provided on the housing (304) of the second buffer cavity (308) away from the base (301), and a microphone (311) is embedded in the housing (304) of the resonant cavity (307) away from the absorption cavity (306).

5. The enrichment-enhanced photoacoustic spectroscopy gas detection device according to claim 2 or 3, characterized in that: The adsorption tube (404) is made of stainless steel.

6. The enrichment-enhanced photoacoustic spectroscopy gas detection device according to claim 3, characterized in that: The surface of the resistance heating band (416) is covered with a polyimide film, and the material of the resistance heating band (416) is rubber.

7. The enrichment-enhanced photoacoustic spectroscopy gas detection device according to claim 2, characterized in that: The buffer tube (405) has a hollow cylindrical structure and is made of stainless steel.

8. The enrichment-enhanced photoacoustic spectroscopy gas detection device according to claim 4, characterized in that: The first glass (302) and the second glass (303) are made of calcium fluoride.

9. The enrichment-enhanced photoacoustic spectroscopy gas detection device according to claim 4, characterized in that: The first buffer cavity (305), the absorption cavity (306), the resonant cavity (307), and the second buffer cavity (308) are all hollow cylindrical structures.

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