Photoacoustic spectrometry fumigation gas concentration analysis system

Abstract

The invention discloses a photoacoustic spectrometry fumigation gas concentration analysis system, and relates to the technical field of fumigation operation. The system comprises a system cabinet, a fumigation gas concentration analysis module which is arranged in the system cabinet and detects the concentration of methyl bromide gas based on a photoacoustic spectrum principle, and an environmental parameter detection module which is arranged in the system cabinet. According to the invention, based on a photoacoustic spectrum principle, an active temperature control and real-time humidity digital compensation mechanism is combined, so that the defects that a traditional sensor is easily influenced by environmental temperature and humidity and has cross interference and drift are fundamentally overcome, and the accuracy and stability of data in a full range are ensured; the equipment cabinet with the IP54 protection level guarantees long-term stable operation of internal elements in a severe industrial environment, the unique multi-step triggering process of calibration, temperature control, humidity judgment and detection ensures that measurement is automatically carried out under the optimal condition, and personal errors are reduced.

Description

Technical Field

[0001] This application relates to the field of fumigation operation technology, and in particular to a photoacoustic spectroscopy fumigation gas concentration analysis system. Background Technology

[0002] Fumigation is a key means of ensuring that harmful organisms are not spread with goods. Methyl bromide is widely used due to its highly effective insecticidal and bactericidal effects. However, as a potent ozone-depleting substance and a highly toxic chemical, the use of methyl bromide must be strictly regulated, with the key being the accurate and continuous monitoring of its concentration in the space.

[0003] Traditional fumigation gas concentration detection technologies, such as gas chromatography, while highly accurate, have inherent drawbacks, including long analysis cycles, the need to carry high-pressure gas cylinders, complex operation, and difficulty in achieving real-time continuous on-site monitoring. These limitations fail to meet the stringent requirements of fumigation operations that need to continue for hours or even days and require real-time monitoring of concentration dynamics to assess the cumulative dose of CT value (concentration × time). While some portable detectors based on semiconductor, electrochemical, or PID (photoionization) principles can achieve real-time monitoring, they often suffer from poor selectivity, susceptibility to cross-interference from other gases in the fumigation environment (such as moisture and carbon dioxide), sensor poisoning or drift, and insufficient measurement range. These issues significantly reduce measurement reliability in complex, high-humidity environments, making it difficult to guarantee the accuracy of fumigation effect assessment and regulatory compliance. Photoacoustic spectroscopy, as a highly sensitive light absorption detection technology, is considered an ideal way to solve the above-mentioned pain points. However, successfully applying photoacoustic spectroscopy to the specific industrial scenario of methyl bromide fumigation still faces many challenges, including how to design a robust system to withstand the harsh environment (corrosive gases, dust, and drastic temperature and humidity changes), how to achieve precise temperature control of key components (such as the photoacoustic cell) to suppress baseline drift, and how to effectively overcome the serious interference caused by the high humidity environment on the detection signal. Summary of the Invention

[0004] To address the aforementioned issues, this application provides a photoacoustic spectroscopy system for analyzing the concentration of fumigation gases.

[0005] The photoacoustic spectroscopy fumigation gas concentration analysis system provided in this application adopts the following technical solution: The photoacoustic spectroscopy fumigation gas concentration analysis system includes: System cabinet; A fumigation gas concentration analysis module is installed in the system cabinet. The fumigation gas concentration analysis module detects the concentration of methyl bromide gas based on the photoacoustic spectroscopy principle. An environmental parameter detection module is installed inside the system cabinet. The environmental parameter detection module is used to detect the temperature and humidity inside the system cabinet in real time. The environmental parameter detection module includes a heating unit, a temperature sensing unit, and a humidity detection unit. A control and processing module is installed in the system cabinet and is connected to the fumigation gas concentration analysis module and the environmental parameter detection module.

[0006] As a preferred technical solution of this application, the control and processing module is configured as follows: First, control the fumigation gas concentration analysis module to complete zero-point calibration, and generate a first trigger signal after calibration confirmation. Then, in response to the first trigger signal, start the heating unit to heat the detection area of ​​the fumigation gas concentration analysis module to a preset temperature, and maintain temperature stability based on the feedback of the temperature sensing unit. After confirming temperature stability, generate a second trigger signal. Then, in response to the second trigger signal, start the humidity detection unit to acquire current humidity data, and determine whether the current humidity data is lower than a preset threshold. If it is lower, generate a third trigger signal. Finally, in response to the third trigger signal, control the fumigation gas concentration analysis module to perform methyl bromide concentration detection, and simultaneously use the current humidity data to perform real-time digital compensation on the detected photoacoustic signal to eliminate humidity interference.

[0007] As a preferred technical solution of this application, the heating unit is a heating film wrapped around the outer wall of the photoacoustic cell of the fumigation gas concentration analysis module, and the temperature sensing unit is a platinum resistance temperature sensor attached to the outer wall of the photoacoustic cell. The heating film and the platinum resistance temperature sensor, together with the control and processing module, are used to control the gas temperature fluctuation in the photoacoustic cell within the range of ±0.2℃.

[0008] As a preferred technical solution of this application, the control and processing module is configured to: while using the current humidity data for real-time digital compensation, also shield interference from non-target gases by identifying the unique photoacoustic signal frequency and amplitude characteristics of methyl bromide gas.

[0009] As a preferred technical solution of this application, the system cabinet is equipped with a data acquisition and storage module. The data acquisition and storage module is configured to synchronously acquire and associate the methyl bromide concentration data finally output by the fumigation gas concentration analysis module, the temperature data measured by the temperature sensing unit, and the humidity data measured by the humidity detection unit, and to stamp each data record with a unified timestamp.

[0010] As a preferred technical solution of this application, the output end of the data acquisition and storage module is communicatively connected to an intelligent evaluation system. The intelligent evaluation system is configured to read the data associated with the data acquisition and storage module, and automatically generate a fumigation process effect analysis report based on the trend of methyl bromide concentration over time, combined with the corresponding historical temperature and humidity data.

[0011] As a preferred technical solution of this application, the preset temperature ranges from 30°C to 40°C.

[0012] As a preferred technical solution of this application, the fumigation gas concentration analysis module has a detection range of 0-250 g / m³ for methyl bromide and a resolution of ≤0.01 g / m³.

[0013] In summary, this application includes at least the following beneficial technical effects of the photoacoustic spectroscopy fumigation gas concentration analysis system: This application, based on the photoacoustic spectroscopy principle and combined with active temperature control and real-time humidity digital compensation mechanisms, fundamentally overcomes the shortcomings of traditional sensors, such as susceptibility to environmental temperature and humidity, cross-interference, and drift. It ensures the accuracy and stability of data across the entire measurement range. The IP54-rated cabinet guarantees the long-term stable operation of internal components in harsh industrial environments. The unique multi-step triggering process of "calibration-temperature control-humidity judgment-detection" ensures that measurements are automatically performed under optimal conditions, reducing human error. The synchronous acquisition and timestamped storage of concentration, temperature, and humidity data, along with seamless integration with the backend intelligent evaluation system, not only achieves full traceability of the fumigation process but also automatically generates effect analysis reports. This frees operators from tedious data recording, elevating them to process managers. Ultimately, it provides strong data support and decision-making basis for optimizing fumigation processes, ensuring treatment effects, and meeting environmental regulations. Attached Figure Description

[0014] Figure 1 This is the architecture diagram of the photoacoustic spectroscopy fumigation gas concentration analysis system of this application. Detailed Implementation

[0015] The following is in conjunction with the appendix Figure 1 This application will be described in further detail.

[0016] See Figure 1 A photoacoustic spectroscopy fumigation gas concentration analysis system, including: System cabinet; Server racks are typically made of cold-rolled steel plates with a thickness of no less than 1.5 mm, and the surface is powder-coated or galvanized to resist corrosive gases that may be present in the fumigation environment. The protection level of the server rack is at least IP54, which can effectively prevent dust intrusion and water splashes from all directions, ensuring the long-term stable operation of the internal precision electronic components in harsh industrial environments. Structurally, the cabinet is equipped with multiple mounting plates or rails fixed by welding or bolts. The photoacoustic cell and circuit unit of the fumigation gas concentration analysis module, the controller of the environmental parameter detection module, the main control unit of the control and processing module, and the industrial control computer of the data acquisition and storage module are installed in an orderly and partitioned manner. This not only ensures structural stability but also optimizes the layout space of gas lines and cables, reducing mutual interference. The front of the cabinet has a sealed door with a tempered glass observation window and system status indicator lights (such as power, operation, and alarm) to facilitate on-site personnel to quickly understand the system status. In addition, the side or bottom of the cabinet has reserved cable entry holes protected by waterproof connectors for connecting sampling gas pipelines and 220V AC power lines. All interfaces are sealed to maintain a clean and stable microenvironment inside the cabinet.

[0017] The fumigation gas concentration analysis module is located in the system cabinet. It detects the concentration of methyl bromide gas based on the photoacoustic spectroscopy principle. The detection range of the fumigation gas concentration analysis module for methyl bromide is 0-250 g / m³, and the resolution is ≤0.01 g / m³. The fumigation gas concentration analysis module is based on the photoacoustic spectroscopy principle and realizes highly sensitive and selective quantitative detection of methyl bromide gas. The core component of the module is a cylindrical photoacoustic cell made of stainless steel. The inner wall of the cell is polished with high gloss to reduce light energy loss. Infrared transmission windows (such as zinc selenide or calcium fluoride crystals) are installed at both ends. The cell wall has an air inlet, an air outlet, and a precision interface for installing a microphone. During operation, infrared light emitted from a broadband infrared light source optimized by filters, with its wavelength precisely tuned to the strong absorption peak of bromomethane molecules (e.g., the characteristic absorption line near approximately 3.4 micrometers), is modulated at a specific frequency (typically tens to hundreds of hertz) by a modulator before passing through a photoacoustic cell. Bromomethane gas molecules within the cell selectively absorb the light energy of this specific wavelength, transitioning from the ground state to the excited state. Subsequently, through intermolecular collisions, the absorbed light energy is converted into heat energy via non-radiative relaxation. This periodic thermal expansion and contraction generates sound pressure fluctuations of the same frequency within the sealed photoacoustic cell, i.e., a photoacoustic signal. This weak pressure signal is then detected by a highly sensitive capacitive microphone and converted into a weak electrical signal. This electrical signal is then sent to a preamplifier for initial amplification, followed by narrowband filtering and secondary amplification via a lock-in amplifier. The reference frequency of the lock-in amplifier is strictly synchronized with the modulation frequency of the light source, thereby greatly suppressing environmental noise interference. Ultimately, a robust photoacoustic signal proportional to the concentration of bromomethane gas is extracted.

[0018] The fumigation gas concentration analysis module can achieve a wide linear detection range of 0 to 250 g / m³ and ensure a resolution better than 0.01 g / m³, thereby meeting the precise concentration monitoring requirements of the entire process from initial dosing to long-term gas dissipation in fumigation operations.

[0019] An environmental parameter detection module is installed inside the system cabinet. The environmental parameter detection module is used to detect the temperature and humidity inside the system cabinet in real time. The environmental parameter detection module includes a heating unit, a temperature sensing unit, and a humidity detection unit. The environmental parameter detection module obtains accurate concentration readings by real-time monitoring and controlling the temperature and humidity conditions around the photoacoustic cell. This module consists of a heating unit, a temperature sensing unit, and a humidity detection unit. The heating unit is specifically a flexible silicone rubber heating film, which is tightly wrapped around most of the outer wall of the photoacoustic cell. Its power is calculated and selected to ensure that it can provide uniform and controllable heat. The temperature sensing unit uses a platinum resistance temperature sensor with extremely high accuracy and long-term stability. Its platinum resistance element is firmly attached to a precision-machined groove or plane on the outer wall of the photoacoustic cell and filled with high thermal conductivity adhesive to ensure good thermal contact, so as to directly sense the real-time temperature of the cell. The humidity detection unit uses a humidity sensor based on the principle of capacitive polymer film. It is installed in the air intake passage of the photoacoustic cell or in the air chamber very close to the cell body to directly measure the relative humidity of the gas flowing through or present in the cell.

[0020] All three units are connected to the control and processing module via cables, receiving its instructions and uploading data. The collaborative work of the environmental parameter detection module ensures that the gas temperature in the photoacoustic cell can be actively controlled within the optimal operating range and provides the accurate data necessary for humidity interference compensation.

[0021] The control and processing module is located in the system cabinet and is connected to the fumigation gas concentration analysis module and the environmental parameter detection module.

[0022] The control and processing module is configured as follows: First, it controls the fumigation gas concentration analysis module to complete zero-point calibration and generates a first trigger signal after calibration confirmation. Then, in response to the first trigger signal, it starts the heating unit to heat the detection area of ​​the fumigation gas concentration analysis module to a preset temperature and maintains temperature stability based on feedback from the temperature sensing unit. After confirming temperature stability, it generates a second trigger signal. Then, in response to the second trigger signal, it starts the humidity detection unit to acquire the current humidity data and determines whether the current humidity data is lower than a preset threshold. If it is lower, it generates a third trigger signal. Finally, in response to the third trigger signal, it controls the fumigation gas concentration analysis module to detect methyl bromide concentration and simultaneously uses the current humidity data to perform real-time digital compensation on the detected photoacoustic signal to eliminate humidity interference. The preset temperature range is 30℃ to 40℃.

[0023] After the control and processing module is powered on, its built-in firmware program first performs an initialization self-test, and then enters a strict multi-step control sequence: The first step is to send a command to the fumigation gas concentration analysis module to introduce high-purity nitrogen or filtered clean air to perform zero-point calibration to eliminate system baseline drift. After confirming that the signal is stable at zero, the first trigger signal is generated in the internal logic. The second step involves the module activating the heating unit (heating film) in response to the first trigger signal. Simultaneously, it begins high-speed acquisition of the voltage signal fed back from the temperature sensing unit (platinum resistance thermometer). Through a built-in PID control algorithm, the power output to the heating film is adjusted in real time (typically using pulse width modulation), forming a closed-loop control circuit. The goal is to rapidly and stably raise and maintain the gas temperature within the photoacoustic cell at a preset constant value (e.g., 35°C) between 30°C and 40°C. When the system determines that the temperature fluctuation range has been successfully controlled within ±0.2°C for a continuous period, it considers the temperature stable and then generates a second trigger signal. Third, in response to the second trigger signal, the module activates the humidity detection unit to obtain the current relative humidity reading of the gas in the photoacoustic cell and compare it with the preset humidity threshold (e.g., 80%RH, designed to prevent condensation). If the humidity is lower than the threshold, a critical third trigger signal is generated. Finally, in response to the third trigger signal, the module officially starts the bromomethane concentration detection process. While collecting photoacoustic signals, it simultaneously calls the humidity-signal correction coefficient lookup table or compensation algorithm model stored in memory, and uses the real-time acquired humidity data to perform real-time digital compensation on the original photoacoustic signal, thereby effectively eliminating the interference of water vapor on bromomethane detection. In addition, the module runs an advanced signal recognition algorithm. By continuously monitoring the frequency purity and amplitude stability of the photoacoustic signal generated at the characteristic absorption wavelength of methyl bromide, it can effectively distinguish the target signal from non-specific signals that may be caused by other gases or mechanical vibrations, thereby significantly enhancing the system's ability to resist cross-interference.

[0024] The heating unit is a heating film wrapped around the outer wall of the photoacoustic cell of the fumigation gas concentration analysis module, and the temperature sensing unit is a platinum resistance temperature sensor attached to the outer wall of the photoacoustic cell. The heating film and the platinum resistance temperature sensor, together with the control and processing module, are used to control the gas temperature fluctuation in the photoacoustic cell within the range of ±0.2℃.

[0025] The control and processing module is configured to perform real-time digital compensation using current humidity data, while also shielding against interference from non-target gases by identifying the unique photoacoustic signal frequency and amplitude characteristics of methyl bromide gas.

[0026] The system cabinet is equipped with a data acquisition and storage module. The data acquisition and storage module is configured to synchronously acquire and associate the methyl bromide concentration data finally output by the fumigation gas concentration analysis module, the temperature data measured by the temperature sensing unit, and the humidity data measured by the humidity detection unit, and to add a uniform timestamp to each data record.

[0027] The data acquisition and storage module is a multi-functional data acquisition card integrated into the industrial control computer. The data acquisition and storage module triggers three data channels simultaneously at fixed time intervals (configurable, such as once per second)—reading the final processed methyl bromide concentration value from the control and processing module, the temperature value converted by the transmitter from the platinum resistance temperature sensor, and the relative humidity value read from the humidity sensor.

[0028] The module's internal high-precision real-time clock assigns a unified and unalterable timestamp to the three sets of data collected simultaneously. Subsequently, these "timestamp-concentration-temperature-humidity" data packets are sequentially written in a structured format (such as CSV or a custom binary format) to the module's high-capacity, industrial-grade non-volatile memory, such as a solid-state drive or eMMC storage chip. This ensures that even in the event of an unexpected power outage, the stored data will not be lost. All data records are indexed, supporting fast querying and export by time range. This meticulous data management mechanism lays a solid foundation for the digitalization and traceability of the entire fumigation process.

[0029] The output of the data acquisition and storage module is connected to an intelligent evaluation system. The intelligent evaluation system is configured to read the data associated with the data acquisition and storage module, and based on the trend of methyl bromide concentration over time, combined with the corresponding historical temperature and humidity data, automatically generate a fumigation process effect analysis report.

[0030] Connecting to the data acquisition and storage module via standard communication interfaces (such as Ethernet, RS485, or USB), the intelligent evaluation system periodically (e.g., hourly) or on demand reads the complete dataset with time-series markers stored within. The system integrates a series of data analysis algorithms: First, it plots the curve of methyl bromide concentration changing over time throughout the entire fumigation cycle and identifies key nodes through algorithms, such as the time when the concentration reaches a preset peak value (CT value) and the cumulative duration (CT value integral) at or above the effective concentration (e.g., ≥20 g / m³). Second, it comprehensively analyzes historical temperature and humidity data on the same time axis to assess the impact of environmental conditions on concentration maintenance, such as temperature fluctuations. Whether it caused abnormal concentration readings or whether the system's compensation mechanism was triggered during periods of high humidity; based on these multi-dimensional analyses, the system can automatically generate a structured fumigation process effect analysis report. This report not only includes a visual chart of the concentration curve, but also provides qualitative or quantitative conclusions such as "evaluation of the uniformity of fumigant distribution", "achievement of the set concentration target", "whether there are possible leak points (judged by abnormal concentration drop)" and "overall evaluation of the fumigation effect (e.g., excellent, good, qualified, unqualified)". This greatly improves the intelligence level of fumigation operations, helps operators transform from simple data recorders into process managers, optimizes fumigation strategies, and ensures treatment effectiveness.

[0031] This application, based on the photoacoustic spectroscopy principle and combined with active temperature control and real-time humidity digital compensation mechanisms, fundamentally overcomes the shortcomings of traditional sensors, such as susceptibility to environmental temperature and humidity, cross-interference, and drift. It ensures the accuracy and stability of data across the entire measurement range. The IP54-rated cabinet guarantees the long-term stable operation of internal components in harsh industrial environments. The unique multi-step triggering process of "calibration-temperature control-humidity judgment-detection" ensures that measurements are automatically performed under optimal conditions, reducing human error. The synchronous acquisition and timestamped storage of concentration, temperature, and humidity data, along with seamless integration with the backend intelligent evaluation system, not only achieves full traceability of the fumigation process but also automatically generates effect analysis reports. This frees operators from tedious data recording, elevating them to process managers. Ultimately, it provides strong data support and decision-making basis for optimizing fumigation processes, ensuring treatment effects, and meeting environmental regulations.

[0032] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A photoacoustic spectroscopy fumigation gas concentration analysis system, characterized in that, include: System cabinet; A fumigation gas concentration analysis module is installed in the system cabinet. The fumigation gas concentration analysis module detects the concentration of methyl bromide gas based on the photoacoustic spectroscopy principle. An environmental parameter detection module is installed inside the system cabinet. The environmental parameter detection module is used to detect the temperature and humidity inside the system cabinet in real time. The environmental parameter detection module includes a heating unit, a temperature sensing unit, and a humidity detection unit. A control and processing module is installed in the system cabinet and is connected to the fumigation gas concentration analysis module and the environmental parameter detection module.

2. The photoacoustic spectroscopy fumigation gas concentration analysis system according to claim 1, characterized in that, The control and processing module is configured to: first, control the fumigation gas concentration analysis module to complete zero-point calibration, and generate a first trigger signal after calibration confirmation; then, in response to the first trigger signal, start the heating unit to heat the detection area of ​​the fumigation gas concentration analysis module to a preset temperature, and maintain temperature stability based on feedback from the temperature sensing unit; after confirming temperature stability, generate a second trigger signal; then, in response to the second trigger signal, start the humidity detection unit to acquire current humidity data, and determine whether the current humidity data is lower than a preset threshold; if it is lower, generate a third trigger signal; finally, in response to the third trigger signal, control the fumigation gas concentration analysis module to perform methyl bromide concentration detection, and simultaneously use the current humidity data to perform real-time digital compensation on the detected photoacoustic signal to eliminate humidity interference.

3. The photoacoustic spectroscopy fumigation gas concentration analysis system according to claim 1, characterized in that, The heating unit is a heating film wrapped around the outer wall of the photoacoustic cell of the fumigation gas concentration analysis module, and the temperature sensing unit is a platinum resistance temperature sensor attached to the outer wall of the photoacoustic cell. The heating film and the platinum resistance temperature sensor, together with the control and processing module, are used to control the gas temperature fluctuation in the photoacoustic cell within the range of ±0.2℃.

4. The photoacoustic spectroscopy fumigation gas concentration analysis system according to claim 2, characterized in that, The control and processing module is configured to perform real-time digital compensation using the current humidity data, while also shielding against interference from non-target gases by identifying the unique photoacoustic signal frequency and amplitude characteristics of methyl bromide gas.

5. The photoacoustic spectroscopy fumigation gas concentration analysis system according to claim 1, characterized in that, The system cabinet is equipped with a data acquisition and storage module. The data acquisition and storage module is configured to synchronously acquire and associate the methyl bromide concentration data finally output by the fumigation gas concentration analysis module, the temperature data measured by the temperature sensing unit, and the humidity data measured by the humidity detection unit, and to add a uniform timestamp to each data record.

6. The photoacoustic spectroscopy fumigation gas concentration analysis system according to claim 5, characterized in that, The output of the data acquisition and storage module is connected to an intelligent evaluation system. The intelligent evaluation system is configured to read the data associated with the data acquisition and storage module, and based on the trend of methyl bromide concentration over time, combined with the corresponding historical temperature and humidity data, automatically generate a fumigation process effect analysis report.

7. The photoacoustic spectroscopy fumigation gas concentration analysis system according to claim 2, characterized in that, The preset temperature ranges from 30°C to 40°C.

8. The photoacoustic spectroscopy fumigation gas concentration analysis system according to claim 1, characterized in that, The fumigation gas concentration analysis module has a detection range of 0-250 g / m³ for methyl bromide and a resolution of ≤0.01 g / m³.

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