Online monitoring system for gas purity of alkaline electrolytic cell

Abstract

The invention discloses an online monitoring system for gas purity of an alkaline electrolytic cell, and aims to solve the problems of response lag, insufficient detection precision and adaptability and the like in the prior art. Through modular integrated design, a gas sampling module, a pretreatment module, a gas chromatographic analysis module and a control alarm module are integrated in an analysis cabinet, and the analysis cabinet is arranged at an outlet of a separator nearby for on-site sampling and detection; sampling points are accurately arranged in a stable flow field area at the downstream of the separator; the pretreatment module adopts a multi-stage purification link to ensure that the gas is clean and dry and the temperature is constant; the gas chromatograph is provided with a mixed chromatographic column and a micro thermal conductivity detector, so that second-level accurate detection of oxygen in hydrogen and hydrogen in oxygen is realized, and closed-loop protection is formed in cooperation with a safety interlocking mechanism. The spectrum detection module constructs a chromatography-spectrum dual-detection collaborative architecture which is complementary with gas chromatography accurate calibration. The system remarkably improves the detection response speed and low-load adaptability, guarantees safe and stable operation of the electrolytic cell, and is suitable for various alkaline water electrolysis hydrogen production scenes.

Description

Technical Field

[0001] This invention relates to the field of alkaline water electrolysis for hydrogen production technology, specifically to an online monitoring system for the purity of gas in an alkaline electrolyzer. Background Technology

[0002] As a core piece of equipment for large-scale hydrogen production, the purity monitoring of hydrogen and oxygen during the operation of alkaline electrolyzers directly affects production safety and efficiency. Current technologies often employ a "remote sampling + centralized analysis" model for gas purity monitoring. This involves transmitting gas samples from the separator outlet to a central analytical laboratory via long-distance pipelines, where they are analyzed using equipment such as gas chromatographs. This model has significant drawbacks: Firstly, long-distance transmission leads to prolonged residence time of gas samples within the pipeline, resulting in response delays of up to several minutes. This makes it impossible to promptly capture rapid fluctuations in gas purity under low-load conditions—at low loads, the electrolyzer produces less gas, shortens the residence time of gas in the separator, reduces separation efficiency, and allows the oxygen content in hydrogen and the hydrogen content in oxygen to rise sharply, forming an explosive mixture. The delayed detection results can lead to missing the optimal treatment window. Secondly, the sampling pipeline is susceptible to environmental temperature and humidity, and alkaline droplets easily adhere to and scale on the pipe walls, causing distortion of sample composition. Furthermore, traditional pretreatment devices often rely on spray washing and adsorbent purification, resulting in high water consumption and frequent adsorbent replacement, increasing maintenance costs and downtime risks. Furthermore, a single detection method cannot simultaneously achieve both response speed and detection accuracy. While traditional gas chromatographs can provide precise quantification, their detection cycles are relatively long, making them unsuitable for real-time monitoring under fluctuating operating conditions. On the other hand, some rapid detection technologies are susceptible to interference from alkaline mist and water vapor, resulting in insufficient detection stability. These shortcomings collectively lead to the existing monitoring systems failing to meet the actual needs of large-scale, highly stable operation of alkaline electrolyzers in terms of safety, adaptability, and economy.

[0003] For the reasons mentioned above, it is necessary to propose an online monitoring system for the purity of gases in alkaline electrolyzers to solve the aforementioned problems. Summary of the Invention

[0004] The purpose of this invention is to overcome the defects in the prior art and provide an online monitoring system for the purity of gas in an alkaline electrolyzer.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows: An online monitoring system for the purity of gas in an alkaline electrolyzer is provided, which modularly integrates the online monitoring system into an analysis cabinet located near the separator outlet. The analysis cabinet integrates a gas sampling module, a pretreatment module, an analysis module, and a control and alarm module. The sampling end of the gas sampling module is connected to the hydrogen outlet pipe and the oxygen outlet pipe of the alkaline electrolyzer to form a sampling at the nearest point. The pretreatment module is located after the gas sampling module and performs gas-liquid separation, adsorption, and isothermal cooling on the sampled gas. The analysis module includes a gas chromatograph, which is used to perform quantitative analysis of the components of the pretreated gas and detect the hydrogen and oxygen components in the gas. The control and alarm module is electrically connected to the analysis module. It transmits the detection data to the remote control terminal in real time, compares the monitoring data with the preset safety threshold, and alarms and automatically cuts off the power supply to the electrolytic cell when the threshold is exceeded.

[0006] Furthermore, the gas chromatograph is equipped with a micro thermal conductivity detector (μ-TCD), a mixed chromatographic column, and a carrier gas supply unit. The mixed chromatographic column consists of a molecular sieve 5A column and a Porapak Q column, wherein the molecular sieve 5A column is used to separate O2 and H2, and the Porapak Q column is used to separate hydrocarbon impurities.

[0007] Furthermore, the mixed chromatographic columns are connected in series, with the inlet end of the molecular sieve 5A chromatographic column connected to the sampling end of the gas outlet pipe of the electrolytic cell, and the outlet end of the PorapakQ chromatographic column connected to the inlet of the micro thermal conductivity detector (μ-TCD). The carrier gas supplied by the carrier gas supply unit is high-purity nitrogen, and the purity of the high-purity nitrogen is ≥99.999%. The carrier gas flow rate of the main body of the gas chromatograph is set to 30 mL / min, and the detection cycle is ≤30 seconds; The gas chromatograph has a detection limit of ≤0.2% for oxygen in hydrogen and a detection limit of ≤2.0% for hydrogen in oxygen.

[0008] Furthermore, the sampling probe of the gas sampling module is made of Hastelloy C-276; the sampling point is located 20D downstream of the electrolytic cell separator.

[0009] Furthermore, the pretreatment module includes a gas-liquid separator, an adsorption device, and a cooling device arranged in sequence; the gas-liquid separator is a cyclone demister, the adsorption device is filled with a solid desiccant and a catalyst, and the cooling device is a spiral tube heat exchanger or a shell-and-tube heat exchanger to reduce the gas temperature to 25±2℃.

[0010] Furthermore, the analysis module is a chromatographic-spectral dual detection collaborative design, including a gas chromatography module and a spectral detection module. The gas chromatography module is for precise detection, while the spectral detection module is for rapid detection through near-infrared spectroscopy, forming a collaborative detection system with rapid response and precise calibration.

[0011] Furthermore, the spectral detection module includes a detection channel, which includes a laser source that emits specific laser light to match the O2 / H2 absorption peaks, and a photodetector that captures the laser absorption signal; The laser source wavelength is designed as follows: a characteristic absorption peak of 1.58 μm is set for H2, which is the exclusive wavelength for the vibrational transition of H2 molecules; a characteristic absorption peak of 760 nm is set for O2, which is the exclusive wavelength for the electronic transition of O2 molecules. The photodetector is an indium gallium arsenide (InGaAs) high-speed detector; The detection point of the spectral detection module is set in the same manner as the sampling end of the gas sampling module. It is installed "20D downstream of the electrolytic cell separator" (D is the pipe diameter) and arranged side by side with the original gas chromatograph sampling probe (spacing ≥10cm). This ensures the consistency of the collected gas samples, facilitates data calibration of the dual detection channels, and avoids interference areas: it is far away from pipe bends, valves, welds, and other locations that are prone to eddy currents, avoiding detection deviations caused by uneven local gas concentrations. Mounting bases are set on both sides of the pipe, and the laser light source and photodetector are respectively mounted on the mounting bases on both sides, so that the laser beam penetrates the pipe cross section perpendicular to the pipe axis and irradiates the photodetector.

[0012] Furthermore, the spectral detection module also includes a reference channel for real-time correction of light intensity attenuation caused by alkaline mist and water vapor. The reference channel and the detection channel are integrated in the same optical housing to form a dual-optical-path parallel structure. The reference light source of the reference channel emits laser light without O2 / H2 absorption peaks as a reference reference. It also includes a reference detector, which is installed on the other side of the pipeline along with the detector of the detection channel.

[0013] Furthermore, the alarm signals include audible and visual alarm signals, as well as a shutdown control signal for cutting off the power supply to the electrolytic cell; the alarm logic is integrated into the DCS system, and a shutdown command and valve shut-off control command are triggered simultaneously when the threshold is exceeded. (This forms a safety closed loop of "detection-alarm-interlock," and the response time of the audible and visual alarm is ≤5 seconds.) Furthermore, the following monitoring methods are included: S1: Gas samples are collected from the hydrogen and oxygen outlets of the alkaline electrolyzer using the gas sampling module. S2: The sample is sequentially processed by the pretreatment module for gas-liquid separation, adsorption and isothermal cooling, and then transported to the gas chromatograph. S3: The gas chromatograph uses a micro thermal conductivity detector (μ-TCD) and a mixed chromatographic column to detect the oxygen content in hydrogen and the hydrogen content in oxygen, and obtains real-time detection values; S4: Compare the real-time detection value with the preset threshold. If the value exceeds the limit, an alarm will be triggered through the alarm module, and a control signal will be output to the electrolytic cell control system.

[0014] The advantages and beneficial effects of this invention are as follows: First, the response speed is extremely fast: by installing independent gas monitoring systems near the hydrogen and oxygen outlet pipelines of the electrolyzer, the delay of long-distance sampling pipelines is eliminated. Combined with a high-response gas chromatograph, the lag time of gas purity analysis is shortened from several minutes to seconds, realizing true real-time monitoring.

[0015] Secondly, it offers high safety assurance: the system can quickly and accurately detect situations where the oxygen content in hydrogen or the hydrogen content in oxygen exceeds the standard due to changes in operating conditions such as low load, and immediately issue an alarm through the control and alarm module, giving operators valuable time to adjust the operating conditions or take safety measures in a timely manner, and effectively preventing the accumulation of explosive gases.

[0016] Third, it is highly targeted and reliable: It is designed specifically for the outlet gas of the electrolytic cell. The pretreatment module effectively solves the interference and damage to precision analytical instruments caused by problems such as alkali, humidity and high temperature, ensuring the long-term stable operation of the gas chromatograph and improving the reliability of the detection data.

[0017] Fourth, the system is compact and easy to implement: it can be integrated into the analysis cabinet, and the installation is flexible. It is suitable for both new electrolytic cell projects and for retrofitting existing electrolytic cells. Attached Figure Description

[0018] Figure 1 This is a control flowchart of Embodiment 1 of the present invention; Figure 2 This is a control flowchart of Embodiment 2 of the present invention; Figure 3 This is a schematic diagram showing the arrangement of the line monitoring device in this invention; Figure 4 This is a schematic diagram of the structure of an online monitoring device for the purity of gas in an alkaline electrolyzer according to the present invention; In the diagram: 1. Electrolytic cell body; 2. Hydrogen gas-liquid separator; 3. Oxygen gas-liquid separator; 4. Separator outlet pipe; 5. Analytical cabinet; 6. T-junction flange; 7. Gas-liquid separator; 8. Adsorption device; 9. Constant temperature cooling device; 10. Analytical module; 11. Sampling pipeline; 12. Separation cylinder; 13. Gas pipeline; 14. Baffle plate; 15. Gas outlet pipe; 16. Inlet pipe; 17. Spiral guide vane; 18. Liquid drop gap; 19. Drain pipe; 20. Diaphragm; 21. Inlet chamber; 22. Adsorption chamber; 23. Outlet chamber; 24. Adsorption inlet pipe; 25. Adsorption outlet pipe; 26. Horizontal diaphragm; 27. Grid chamber; 30. Spray washing device; 31. Washing chamber; 32. Washing outlet; 33. Circulation pump; 34. Spray head. Detailed Implementation

[0019] The specific embodiments of the present invention will be further described below with reference to examples. These examples are only used to more clearly illustrate the technical solutions of the present invention and should not be construed as limiting the scope of protection of the present invention.

[0020] Example 1: This invention discloses an online gas purity monitoring system for an alkaline electrolyzer, designed with the core principles of "local integration, precision and efficiency, and safety and reliability." Through modular integration and key technology optimization, it specifically addresses the pain points of traditional monitoring solutions, such as slow response and insufficient low-load adaptability, providing comprehensive protection for electrolyzer operation. The system integrates a gas sampling module, a pretreatment module, an analysis module 10, and a control and alarm module within a single analysis cabinet 5, located near the separator outlet. This integrated design allows the sampling end to be directly connected to the hydrogen and oxygen outlet pipes of the alkaline electrolyzer, achieving "on-site sampling and on-site detection." This overcomes the shortcomings of traditional solutions involving long-distance sample transmission, effectively preventing changes in gas composition during transmission and significantly shortening the detection response time. It can promptly capture rapid fluctuations in gas purity, fundamentally solving the problem of "excessive response time from sampling in the separation system to the central analyzer," making the detection data more timely and valuable. Specifically, it integrates a gas sampling module, a pretreatment module, an analysis module 10, and a control and alarm module.

[0021] As the "first line of defense" for sample acquisition in the system, the design of the gas sampling module directly determines the accuracy of subsequent detection. The sampling probe is made of Hastelloy C-276, a material that not only possesses excellent resistance to alkali corrosion, resisting long-term erosion from KOH alkaline mist entrained in the electrolyzer outlet gas, but also exhibits outstanding resistance to hydrogen embrittlement. It can operate stably in high-concentration hydrogen environments, avoiding problems such as breakage and sealing failure caused by hydrogen embrittlement in ordinary metal probes, significantly extending the probe's lifespan and reducing maintenance costs. Furthermore, the sampling point is precisely calculated and set approximately 20D (D is the pipe diameter) downstream of the electrolyzer separator. The actual distance can be flexibly adjusted according to the pipe layout. This location avoids the eddy current area near the separator outlet, preventing uneven local gas concentration caused by eddies from affecting sample representativeness, while ensuring that the collected gas has undergone preliminary gas-liquid separation by the separator, reducing the direct impact of large amounts of liquid alkali on the sampling probe. This allows the collected sample to accurately reflect the overall purity of the gas within the pipe.

[0022] The pretreatment module is a "pre-purification system" that ensures the accurate operation of the analysis module 10. It constructs a complete gas purification chain through the sequential connection of "gas-liquid separator 7 → adsorption device 8 → cooling device". The gas-liquid separator 7 uses a cyclone demister with a separation efficiency of over 99%, effectively removing droplets larger than 5μm from the gas. Centrifugal force separates and discharges most of the alkaline droplets and liquid water, greatly reducing the processing pressure on subsequent devices. The adsorption device 8 is filled with a solid desiccant and catalyst specifically designed to remove certain impurities, effectively removing residual alkaline droplets while balancing the alkalinity removal effect with water consumption. The cooling device uses a spiral tube heat exchanger or a shell-and-tube heat exchanger, precisely reducing the gas temperature to 25±2℃. This temperature closely matches the optimal operating temperature of the gas chromatograph in the subsequent analysis module 10, effectively avoiding the impact of temperature fluctuations on column separation efficiency and detector sensitivity. The device also features an automatic drainage structure to promptly discharge condensate generated during cooling, ensuring that the gas entering the analysis module 10 is clean, dry, and at a constant temperature. Furthermore, the pretreatment module and the analysis module 10 are connected by an insulated pipe, which further maintains the stability of the gas temperature and provides a good foundation for accurate detection. Alternatively, a spray washing device 30 can be added. This device is positioned at the front end of the cyclone demister and uses deionized water to spray and clean the sampled gas at a flow rate of 100-200 L / h to remove residual alkaline droplets, balancing the dealkali removal effect with water consumption.

[0023] The analysis module 10, as the core detection unit of the system, employs a high-performance gas chromatograph. Its miniature thermal conductivity detector (μ-TCD) consumes ≤5W, making it ideal for on-site installation without requiring additional high-power power supply equipment, thus adapting to the complex environments of industrial sites. The chromatographic column adopts a hybrid column design of "Molecular Sieve 5A + PorapakQ," with clear division of labor and efficient collaboration: the molecular sieve 5A column is specifically responsible for the separation of O2 and H2, utilizing the difference in adsorption-desorption capabilities of different gas molecules to achieve precise separation of the two core components; the PorapakQ column focuses on separating hydrocarbon impurities, avoiding interference from impurities in the detection results of the core components and ensuring the accuracy of quantitative analysis. High-purity nitrogen with a purity of ≥99.999% was selected as the carrier gas, and the carrier gas flow rate was set to 30 mL / min. This parameter was repeatedly optimized to ensure the separation efficiency of the chromatographic column and to compress the detection cycle to 15 seconds, with a maximum of no more than 30 seconds. This enabled the second-level rapid detection of oxygen in hydrogen and hydrogen in oxygen, with a detection limit of ≤0.2% for oxygen in hydrogen and ≤2.0% for hydrogen in oxygen, which can accurately capture subtle changes in gas purity.

[0024] The control and alarm module is the "decision and execution center" for ensuring the safe operation of the electrolyzer. Electrically connected to the analysis module 10, it receives detection data in real time and remotely transmits the data and alarm information to the central control system via a data communication interface. This enables remote monitoring, storage, and traceability of the data, allowing staff to monitor the electrolyzer's operating status in real time. Furthermore, the system has preset safety thresholds: oxygen content in hydrogen > 0.2% vol and hydrogen content in oxygen > 2.0% vol. The controller continuously compares real-time detection values ​​with these preset thresholds. Once a value exceeds the threshold, the system immediately triggers multiple responses: first, it issues an audible and visual alarm signal with a response time of ≤ 5 seconds, promptly alerting on-site operators with a sharp alarm sound and flashing lights; simultaneously, it outputs a shutdown control signal to cut off the electrolyzer's power supply and triggers a valve shut-off command. The alarm logic is deeply integrated into the DCS system, forming a complete safety closed loop of "detection-alarm-interlock," effectively preventing the accumulation of excessive gases and the formation of explosive mixtures, thus maximizing the safety of the electrolyzer and on-site personnel. In addition, the control signals output by the system can also be used to adjust the current load of the electrolyzer, the pressure of the separator, or the opening of the gas discharge valve. Under non-extreme conditions, it attempts to restore the oxygen content in hydrogen and the hydrogen content in oxygen to a safe range, thus balancing safety and production continuity.

[0025] Specifically: such as Figure 1 As shown, this embodiment is for 1000 Nm 3 This / h-scale alkaline electrolyzer (rated current 15kA, rated pressure 3.0MPa) is designed to adapt to the fluctuating operating conditions of wind-solar hybrid hydrogen production projects, enabling real-time and accurate monitoring of hydrogen and oxygen purity. The specific implementation details are as follows: The gas sampling module, pretreatment module, analysis module 10, and control and alarm module are integrated into a mobile analysis cabinet 5 (dimensions 1.2m × 0.8m × 1.5m). The analysis cabinet 5 is fixedly installed within 3m of the outlet of the hydrogen and oxygen separators in the electrolyzer, connected to the outlet pipe via a quick-connect pipe interface, reducing the length of the sampling pipeline 11 and achieving "on-site sampling and on-site testing." The sampling probe is made of Hastelloy C-276 material, with a probe length of 150mm and a sampling hole diameter of 3mm. The surface is treated with anti-scaling to prevent alkaline droplet adhesion. One sampling probe is installed on each of the hydrogen and oxygen outlet pipes, with the sampling point set 20D downstream of the separator (pipe diameter D = 150mm, therefore the sampling point is 3m from the separator outlet).

[0026] The pretreatment module adopts a series structure of "spray washing device 30 → cyclone demister → adsorption device 8 → spiral tube heat exchanger". Each unit is connected by a flange quick-connect interface for easy disassembly and maintenance. The spray washing device 30 is located at the front end of the cyclone demister. It uses an ultrasonic atomizer to atomize deionized water into a fine mist of 5-10μm, which comes into countercurrent contact with the sampling gas. The washing flow rate is set to 150L / h, and the conductivity of the deionized water is ≤0.1μS / cm. The water level in the tank is monitored in real time by a liquid level sensor, and water is automatically replenished when the water level is low. The cyclone demister is made of titanium alloy and has a separation efficiency of ≥99.5%. It can remove droplets with a particle size >5μm. The bottom conical liquid accumulation tank is equipped with a pneumatic drain valve, which automatically opens and discharges when the liquid level reaches 5mm. The drain pipe 19 is connected to the alkali recovery system of the electrolytic cell. The adsorption device 8 is filled with a composite adsorbent of activated carbon and molecular sieves (particle size 3-5mm), with a filling volume of 5L and an adsorbent layer height of 300mm. The gas residence time is ≥0.8 seconds, effectively removing residual alkaline mist, hydrocarbon impurities, and trace amounts of moisture. The spiral tube heat exchanger is made of 316L stainless steel, with a heat exchange area of ​​0.5m². 2 Temperature is controlled by industrial cooling water at a flow rate of 10 L / min, precisely reducing the gas temperature to 25 ± 2℃. An automatic drain valve is installed at the heat exchanger outlet to promptly drain condensate and prevent water accumulation from affecting gas transmission. The connecting pipe between the pretreatment module and the analysis module 10 uses insulated tubing, maintaining the internal temperature at 25 ± 3℃ to ensure stable gas temperature.

[0027] The core of the analysis module 10 is a miniature gas chromatograph equipped with a miniature thermal conductivity detector (μ-TCD), consuming 4.5W and achieving a detection accuracy of ±0.01%. The mixed chromatographic columns are arranged in series. The front end of a molecular sieve 5A column (1.5m long, 3mm inner diameter) is connected to the pretreatment module outlet, and the rear end is connected in series with a PorapakQ column (1.0m long, 3mm inner diameter). The outlet of the PorapakQ column is connected to the μ-TCD detector inlet. High-purity nitrogen (99.9995%) is used as the carrier gas, supplied in two 40L cylinders (primary + backup). The pressure is stabilized at 0.4MPa via a pressure reducing valve, and the carrier gas flow rate is precisely controlled at 30mL / min by a mass flow controller, with flow fluctuations ≤±1%. The gas chromatograph is set to a detection cycle of 15 seconds per test, including 1 second for sample injection, 10 seconds for separation, and 4 seconds for detection. The detection limits for oxygen in hydrogen are 0.15% and for hydrogen in oxygen are 1.8%. Detection data is transmitted to the control module in real time via an RS485 interface. The instrument has a built-in automatic calibration function, which automatically starts the calibration program at midnight on the 1st of each month, using standard gases (0.2% oxygen in hydrogen and 2.0% hydrogen in oxygen) to correct the detection accuracy. The calibration time is ≤10 minutes and does not affect the normal operation of the system.

[0028] The control and alarm module is centered around a PLC controller and equipped with a touch screen display, which can display hydrogen and oxygen purity test values, equipment operating status, and alarm information in real time. The PLC controller communicates with the central control system via an Ethernet interface, transmitting data once per second, and supports data storage and historical data retrieval. The system has preset safety thresholds: oxygen content in hydrogen > 0.2% vol and hydrogen content in oxygen > 2.0% vol. When the detected value exceeds the threshold, the controller immediately triggers multiple responses: an audible and visual alarm emits a flashing red light at a frequency of 2 Hz and an alarm sound of 85 dB, with a response time of ≤ 3 seconds; simultaneously, a DO signal is output to the electrolyzer control cabinet, triggering shutdown control (cutting off the electrolyzer power supply) and valve shut-off commands (closing the main outlet valves of hydrogen and oxygen). The alarm logic is deeply integrated with the DCS system, forming a safety closed loop of "detection-alarm-interlock". In addition, the controller outputs analog control signals (4-20mA) to adjust the electrolyzer current load (adjustment range ±5% of rated value), separator pressure (adjustment range ±0.05MPa), and gas discharge valve opening (adjustment range ±10%). When the detected value approaches the threshold (0.18% oxygen in hydrogen, 1.9% hydrogen in oxygen), it automatically starts regulation to attempt to restore the gas purity to a safe range.

[0029] The alkaline electrolyzer gas purity online monitoring device used in this embodiment is, specifically, as follows: Figure 3 , 4 As shown, the system includes an analysis cabinet 5 located near the separator outlet. The analysis cabinet 5 integrates a gas sampling module, a pretreatment module, and an analysis module 10. The sampling probe of the gas sampling module is mounted on a three-way flange 6 of the separator outlet pipe 4. The sampling probe is connected to the pretreatment module via a sampling pipeline 11. The pretreatment module includes a gas-liquid separator 7, an adsorption device 8, and a constant temperature cooling device 9 arranged in sequence. The outlet end of the pretreatment module is connected to the analysis module 10, which includes a gas chromatograph.

[0030] Furthermore, the sampling probe is sealed to the tee flange 6 via a probe flange. The sampling probe is made of Hastelloy C-276 material. The front end of the sampling probe has a built-in metal filter screen, which can intercept impurities with a particle size of not less than 10µm. This initial interception of large-particle impurities extends the service life of subsequent processing modules.

[0031] Furthermore, the sampling pipeline 11 is made of stainless steel with a diameter of 8mm, the length of the sampling pipeline 11 is ≤5m, and the sampling pipeline 11 is wrapped with an insulation layer to avoid the influence of ambient temperature on the gas composition.

[0032] Furthermore, the gas-liquid separator 7 includes a separation cylinder 12, with a gas pipe 13 coaxially arranged inside the separation cylinder 12. The upper end of the gas pipe 13 is fixedly connected to the top of the separation cylinder 12, and the lower end of the gas pipe 13 extends to the lower part of the separation cylinder 12, with a distance from the lower baffle plate 14 not less than the radius of the gas pipe 13. A gas outlet pipe 15 is connected to the upper side of the gas pipe 13, and the gas outlet pipe 15 extends out of the separation cylinder 12. An inlet pipe 16 is tangentially arranged along the inner wall of the upper part of the separation cylinder 12. A spiral guide vane 17 is coiled around the outside of the gas pipe 13. The inlet pipe 16 is positioned directly opposite the upper starting point of the spiral guide vane 17. A liquid drop gap 18 is provided between the outer peripheral edge of the spiral guide vane 17 and the inner wall of the separation cylinder 12. A solution tank is formed at the lower part of the baffle plate 14, and a drain pipe 19 is provided at the bottom of the solution tank.

[0033] Furthermore, the adsorption device 8 includes a housing, inside which a sealed chamber is formed. Two longitudinal diaphragms 20 are vertically arranged inside the housing, dividing the sealed chamber into an inlet chamber 21, an adsorption chamber 22, and an outlet chamber 23. The outlet chamber is connected to an adsorption inlet pipe 24, and the outlet chamber 23 is connected to an adsorption outlet pipe 25. Multiple transverse diaphragms 26 are arranged parallel to each other in the adsorption chamber 22, dividing the adsorption chamber 22 into multiple transverse grid chambers 27. Each grid chamber 27 is filled with adsorbent. The longitudinal diaphragms 20 are provided with through holes corresponding to each grid chamber 27. The adsorption inlet pipe 24 is connected to the gas outlet pipe 15 of the gas-liquid separator 7, and the adsorption outlet pipe 25 is connected to the inlet of the constant temperature cooling device 9.

[0034] Furthermore, the constant temperature cooling device 9 includes a spiral tube heat exchanger or a shell-and-tube heat exchanger to control the outlet gas temperature at 25±2℃.

[0035] Furthermore, the pretreatment module also includes a spray washing device 30, which is located upstream of the gas-liquid separator 7. The washing device includes a washing chamber 31, which is placed vertically. The sampling pipeline 11 is connected to the bottom of the washing chamber 31, and a washing outlet 32 ​​is provided at the top of the washing chamber 31. The washing outlet 32 ​​is connected to the gas-liquid separator 7. The spray washing device 30 is also equipped with a circulation pump 33. The inlet of the circulation pump 33 is connected to the bottom of the washing chamber 31 below the liquid surface, and the outlet is connected to the spray head 34 at the top of the washing chamber 31. The circulation pump 33 establishes a circulating spray in the washing chamber 31. In order to form a better gas-liquid contact effect, packing material can be filled in the middle of the washing chamber 31. The packing material can be Pall ring packing.

[0036] Example 2: To further improve the system's detection response speed and adaptability, such as Figure 2As shown, this embodiment adds a spectral detection module based on the previous embodiment, enabling the analysis module 10 to form a chromatographic-spectral dual detection collaborative design. While retaining the precise quantitative advantages of the gas chromatography module, a new near-infrared spectral detection module is added as a rapid response channel. The detection point of the spectral detection module and the sampling end of the gas sampling module are located at the same source, approximately 20D downstream of the electrolytic cell separator, arranged side by side with the gas chromatograph sampling probe with a distance ≥10cm. This ensures the consistency of the samples collected by both, facilitates data calibration of the dual detection channels, and keeps the module away from pipe bends, valves, welds, and other locations prone to eddy currents, avoiding detection deviations caused by uneven local gas concentrations. The laser source of the spectral detection module uses a distributed feedback (DFB) laser diode, with a characteristic absorption peak of 1.58 μm for H2 (a wavelength specific to molecular vibrational transitions) and a characteristic absorption peak of 760 nm for O2 (a wavelength specific to molecular electronic transitions). Wavelength stability is as high as ±0.01 nm, ensuring detection specificity and effectively avoiding cross-interference. The photodetector in the detection channel uses a high-speed indium gallium arsenide (InGaAs) detector with a response time ≤1 ms, enabling millisecond-level signal capture and immediate detection of sudden increases in gas purity under low-load conditions. To cope with interference from complex on-site conditions, the spectral detection module also integrates a reference channel, forming a dual-optical-path parallel structure. The reference light source emits laser light without O2 / H2 absorption peaks as the detection benchmark. The reference detector is installed on the other side of the pipeline along with the detector in the detection channel, synchronously acquiring the light intensity signal of the reference laser. By comparing the light intensity changes of the reference channel and the detection channel, errors caused by non-specific interference such as alkaline mist scattering, water vapor absorption, and optical window contamination are corrected in real time, ensuring high accuracy of spectral detection even in high humidity and high alkaline mist environments. This collaborative mode of "rapid spectral capture + precise chromatographic calibration" not only leverages the advantage of fast response in spectral detection but also compensates for the susceptibility of spectral detection to interference by utilizing the high precision of gas chromatography. It is particularly suitable for scenarios where gas purity fluctuates rapidly under low-load conditions. Furthermore, when any channel fails, the system can automatically switch to another channel to work independently, forming fault redundancy and ensuring uninterrupted detection.

[0037] Specifically, based on Example 1, the control unit and optical drive module of the spectral detection module are integrated. The internal layout of the analysis cabinet 5 is optimized to "sampling module → preprocessing module → analysis module 10 (gas chromatograph + spectral detection control unit) → control and alarm module". The optical transmitter and receiver of the spectral detection are installed at the sampling points of the hydrogen and oxygen outlet pipes via flange bases, arranged side by side with the gas chromatography sampling probe of Example 1 (15cm apart) to ensure sampling from the same source. A fiber optic interface and signal adapter board are added to the analysis cabinet 5 to realize the electrical connection between the spectral detection module and the control and alarm module. Its data transmission is synchronously uploaded to the central control system along with the gas chromatograph data.

[0038] The laser source uses a distributed feedback (DFB) laser diode dual-wavelength integrated module (model: DFB-1580 / 760), which integrates two emission channels: 1.58μm (H2 detection) and 760nm (O2 detection), as well as a 1.3μm (reference channel) emission unit. It achieves wavelength stability of ±0.01nm, output power of 10mW, and power consumption ≤2W. Both the optical transmitter and receiver use Hastelloy C-276 mounting bases, which are fixedly connected to the pipe flange (316L stainless steel). The base incorporates a single-crystal sapphire optical window (5mm thick, transmittance ≥98%), with an alkali-repellent nano-coating (contact angle ≥110°) to prevent alkaline droplet adhesion and corrosion.

[0039] The transmitter and receiver are symmetrically installed on both sides of the pipeline. The laser beam penetrates laterally perpendicular to the pipeline axis, with a path length equal to the pipeline's inner diameter (150mm) and a spot diameter of 50mm (covering 1 / 3 of the core flow area of ​​the pipeline cross-section). A complete spectral detection optical unit is installed in each of the hydrogen and oxygen outlet pipelines, positioned identically to the sampling probe in Example 1 (approximately 20D downstream of the separator, 3m from the separator outlet), away from pipe bends, valves, and other eddy current areas to ensure representativeness of the test samples.

[0040] The photodetector in the detection channel is an InGaAs high-speed detector (model: InGaAs-2000), with a response time ≤1ms, dark current ≤1nA, and a detection efficiency ≥90% for wavelengths of 1.58μm and 760nm. The reference channel detector uses the same InGaAs detector, specifically designed to receive 1.3μm reference laser signals. The weak current signal output by the detector is transmitted via shielded cable to the signal processing unit in analysis cabinet 5. This unit integrates a low-noise operational amplifier (1000x gain) and a lock-in amplifier to eliminate electromagnetic interference and environmental noise, converting the signal into a digital quantity before transmitting it to the control module.

[0041] The signal processing unit incorporates a platinum resistance temperature sensor (PT1000, accuracy ±0.1℃) to synchronously acquire the ambient temperature near the optical window, used to correct for the influence of temperature on laser intensity. The entire spectral detection module consumes ≤8W of power. When working in conjunction with the gas chromatograph (4.5W) in Example 1, the total power consumption of analysis cabinet 5 remains ≤50W, eliminating the need for power supply system upgrades.

[0042] A new spectral data acquisition module was added to the PLC controller in Example 1, expanding the communication interface to achieve synchronous acquisition and time-series alignment of spectral detection data (one set per second) and gas chromatography data (one set every 15 seconds) (timestamp deviation ≤ 10ms). The control software added a "dual-detection collaborative algorithm" module, with built-in data fusion, drift correction, and fault switching logic, capable of processing two detection data streams in real time and outputting the final results. A new real-time display area for spectral detection values ​​was added to the touchscreen display, distinguishing between "rapid detection values ​​(spectral)" and "precise calibration values ​​(chromatographic)" for easy and intuitive viewing by staff.

[0043] The pretreatment module in Example 1 serves only the gas chromatograph, while the spectral detection module directly performs in-situ detection of the gas in the pipeline without requiring a pretreatment process, thus avoiding response delays caused by pretreatment. To ensure that the spectral detection environment is consistent with the gas chromatograph sampling environment, the insulation layer of the sampling pipeline 11 in Example 1 extends to the spectral detection mounting base to maintain a stable pipeline surface temperature and reduce the impact of temperature fluctuations on optical detection.

[0044] In this implementation, the spectral detection module outputs one set of rapid H2 / O2 concentration values ​​per second, while the gas chromatograph outputs one set of precise calibration values ​​every 15 seconds. The PLC controller compares the rapid spectral values ​​with the most recent chromatographic calibration values, corrects the systematic errors of the spectral values ​​through a linear interpolation algorithm, and outputs the "calibrated rapid value" (updated once per second). This approach retains both the spectral response speed and the chromatographic detection accuracy, achieving synchronous data acquisition and fusion.

[0045] Every 15 seconds, after the gas chromatograph completes one accurate detection, the system automatically updates the "spectrum-chromatogram" mapping model parameters, correcting drift errors caused by environmental changes (such as alkali mist concentration and temperature fluctuations). Under low-load conditions (current ≤3kA, i.e., 20% of the rated value), the system automatically compresses the gas chromatography detection cycle to 10 seconds, increasing the calibration frequency by 50%, ensuring the long-term stability of rapid spectral values, and forming dynamic calibration.

[0046] The entire system's monitoring process is clear, orderly, and tightly integrated: First, gas samples are collected from the hydrogen and oxygen outlets of the alkaline electrolyzer via the gas sampling module. Then, the samples enter the pretreatment module, undergoing gas-liquid separation, adsorption, and constant-temperature cooling to become clean, dry, and temperature-controlled gases. Next, the treated gas is transported to the analysis module 10, where a gas chromatograph performs precise detection using a micro thermal conductivity detector (μ-TCD) and a mixed column. Simultaneously, a spectral detection module performs rapid detection and corrects for interference, with both detection channels collaboratively outputting real-time detection values. Finally, the control and alarm module compares the real-time detection values ​​with preset thresholds, triggering corresponding alarms, interlocks, or adjustments based on the comparison results. This process not only ensures rapid and accurate detection but also enables proactive risk management, making it particularly suitable for low-load operation of the alkaline electrolyzer. Even when the current drops below 20% of the rated value, the precise pretreatment and dual-detection collaborative design maintain stable detection accuracy and response speed, completely solving the monitoring challenges caused by reduced gas production and decreased separation efficiency under low-load conditions.

[0047] Overall, through a series of innovative designs such as modular integration, precise sampling, full-process preprocessing, dual-detection collaboration, and safety interlocking closed loop, the system possesses core advantages such as fast response speed, high detection accuracy, and strong safety assurance. It also features compact structure, flexible installation, and convenient maintenance. It is suitable for the overall support of new electrolyzer projects and can be easily retrofitted to existing electrolyzers, providing reliable technical support for the safe and efficient operation of the alkaline water electrolysis hydrogen production industry.

[0048] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An online monitoring system for the purity of gas in an alkaline electrolyzer, characterized in that, The online monitoring system is modularly integrated into the analysis cabinet, which is located near the separator outlet. The analysis cabinet integrates a gas sampling module, a pretreatment module, an analysis module, and a control and alarm module. The sampling ends of the gas sampling module are connected to the hydrogen outlet pipe and the oxygen outlet pipe of the alkaline electrolyzer to form a nearby sampling. The pretreatment module is located after the gas sampling module and performs gas-liquid separation, adsorption, and isothermal cooling on the sampled gas. The analysis module includes a gas chromatograph, which is used to perform quantitative analysis of the components of the pretreated gas and detect the hydrogen and oxygen components in the gas. The control and alarm module is electrically connected to the analysis module. It transmits the detection data to the remote control terminal in real time, compares the monitoring data with the preset safety threshold, and alarms and automatically cuts off the power supply to the electrolytic cell when the threshold is exceeded.

2. The online monitoring system for the purity of gas in an alkaline electrolyzer according to claim 1, characterized in that, The gas chromatograph is equipped with a micro thermal conductivity detector (μ-TCD), a mixed chromatographic column, and a carrier gas supply unit. The mixed chromatographic column consists of a molecular sieve 5A column and a Porapak Q column, wherein the molecular sieve 5A column is used to separate O2 and H2, and the Porapak Q column is used to separate hydrocarbon impurities.

3. The online monitoring system for the purity of gas in an alkaline electrolyzer according to claim 2, characterized in that, The mixed chromatographic columns are connected in series. The inlet end of the molecular sieve 5A chromatographic column is connected to the sampling end of the gas outlet pipe of the electrolyzer, and the outlet end of the PorapakQ chromatographic column is connected to the inlet of the micro thermal conductivity detector (μ-TCD). The carrier gas supplied by the carrier gas supply unit is high-purity nitrogen, and the purity of the high-purity nitrogen is ≥99.999%. The carrier gas flow rate of the main body of the gas chromatograph is set to 30 mL / min, and the detection cycle is ≤30 seconds; The gas chromatograph has a detection limit of ≤0.2% for oxygen in hydrogen and a detection limit of ≤2.0% for hydrogen in oxygen.

4. The online monitoring system for the purity of gas in an alkaline electrolyzer according to claim 1, characterized in that, The gas sampling module's sampling probe is made of Hastelloy C-276; the sampling point is located 20D downstream of the electrolytic cell separator.

5. The online monitoring system for the purity of gas in an alkaline electrolyzer according to claim 1, characterized in that, The pretreatment module includes a gas-liquid separator, an adsorption device, and a cooling device arranged in sequence. The gas-liquid separator is a cyclone demister. The adsorption device is filled with a solid desiccant and a catalyst. The cooling device is a spiral tube heat exchanger or a shell-and-tube heat exchanger to reduce the gas temperature to 25±2℃.

6. The online monitoring system for the purity of gas in an alkaline electrolyzer according to claim 1, characterized in that, The analysis module is a chromatographic-spectral dual detection collaborative design, including a gas chromatography module and a spectral detection module. The gas chromatography module is for precise detection, while the spectral detection module is for rapid detection through near-infrared spectroscopy, forming a collaborative detection system with rapid response and precise calibration.

7. The online monitoring system for the purity of gas in an alkaline electrolyzer according to claim 6, characterized in that, The spectral detection module includes a detection channel, which includes a laser source that emits specific laser light to match the O2 / H2 absorption peaks, and a photodetector that captures the laser absorption signal. The laser wavelength of the laser source is designed as follows: a characteristic absorption peak of 1.58 μm is set for H2, and a characteristic absorption peak of 760 nm is set for O2. The photodetector is an indium gallium arsenide (InGaAs) high-speed detector; The detection point of the spectral detection module is set at the same source as the sampling end of the gas sampling module; mounting bases are set on both sides of the pipeline, and the laser source and photodetector are respectively mounted on the mounting bases on both sides, so that the laser beam penetrates the pipeline cross section perpendicular to the pipeline axis and irradiates the photodetector.

8. The online monitoring system for the purity of gas in an alkaline electrolyzer according to claim 7, characterized in that, The spectral detection module also includes a reference channel for real-time correction of light intensity attenuation caused by alkaline mist and water vapor. The reference channel and the detection channel are integrated in the same optical housing to form a dual-optical-path parallel structure. The reference light source of the reference channel emits laser light without O2 / H2 absorption peaks as a reference standard. It also includes a reference detector, which is installed on the other side of the pipeline along with the detector of the detection channel.

9. The online monitoring system for the purity of gas in an alkaline electrolyzer according to claim 1, characterized in that, The alarm signals include audible and visual alarm signals, as well as shutdown control signals for cutting off the power supply to the electrolytic cell; the alarm logic is integrated into the DCS system, and when the threshold is exceeded, a shutdown command and a valve shut-off control command are triggered simultaneously.

10. The online monitoring system for the purity of gas in an alkaline electrolyzer according to claim 1, characterized in that, The following monitoring methods are included: S1: Gas samples are collected from the hydrogen and oxygen outlets of the alkaline electrolyzer using the gas sampling module. S2: The sample is sequentially processed by the pretreatment module for gas-liquid separation, adsorption and isothermal cooling, and then transported to the gas chromatograph. S3: The gas chromatograph uses a micro thermal conductivity detector (μ-TCD) and a mixed chromatographic column to detect the oxygen content in hydrogen and the hydrogen content in oxygen, and obtains real-time detection values; S4: Compare the real-time detection value with the preset threshold. If the value exceeds the limit, an alarm will be triggered through the alarm module, and a control signal will be output to the electrolytic cell control system.

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