Liquid nitrogen recycling system and method suitable for gas cylinder inspection station

Abstract

The invention discloses a liquid nitrogen recycling system and method suitable for a gas cylinder inspection station. The preparation system comprises a liquid nitrogen supply module, a static evaporation rate test module, a liquid nitrogen recovery control module, a liquid nitrogen storage tank, a nitrogen buffer tank, an air tightness test module and a central control module. Through the synergistic effect of all the modules, effective recovery and reutilization of used liquid nitrogen are achieved, the liquid-state part of the liquid nitrogen can be recovered to the liquid nitrogen storage tank for subsequent use, the gaseous-state part of the liquid nitrogen can be guided into the nitrogen buffer tank for replacement operation of a non-liquid-nitrogen medium gas cylinder, and recycling of liquid nitrogen resources and integrated optimization of the detection technology are achieved. A two-stage replacement method and pulse type replacement are adopted, so that customization processes can be carried out aiming at different gas cylinders; through an artificial neural network model and dynamic priority distribution, the adaptability and prediction capability of the system are enhanced; a process closed loop and a resource closed loop can be formed, the operation efficiency and the resource utilization rate of the gas cylinder inspection station are improved, and the cost is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of cryogenic insulated gas cylinder detection, and particularly to a liquid nitrogen recycling system and method applicable to a gas cylinder inspection station. Background Art

[0002] In the inspection of cryogenic insulated gas cylinders, liquid nitrogen is used as a cryogenic performance test medium, mainly for evaluating the static evaporation rate of cryogenic insulated gas cylinders (such as liquid oxygen cylinders, liquid argon cylinders). This test is a key means to inspect the thermal insulation performance and product safety performance of the cylinder body. Usually, liquid nitrogen is filled into the cylinder, and the liquid nitrogen loss rate is recorded at a constant external temperature. However, in the current detection system, the liquid nitrogen used in this test link is supplied once, and the liquid nitrogen evaporates and is discharged after the test, without forming a systematic energy utilization closed loop.

[0003] In addition, the gas cylinder inspection station usually involves the detection of other cryogenic medium (such as liquid oxygen, liquefied natural gas) cylinders in its daily operation. These cylinders need to be gas replaced, that is, inerted, in the pre-test pretreatment stage to exclude oxidizing or combustible residues and avoid explosion risks. The traditional method uses high-pressure nitrogen or liquid nitrogen vaporization for replacement, which has problems of complex supply cylinder scheduling and high cost.

[0004] The current related technologies have the following problems: (1) Low recovery rate of liquid nitrogen residue: Only part of the liquid nitrogen after detection is vaporized, and a large amount of cryogenic liquid is directly emptied, which cannot be effectively reused, resulting in waste of resources; (2) Dispersed detection system modules: Liquid nitrogen is used for static evaporation rate testing, while the airtightness testing link relies on an external nitrogen system, and the process is fragmented without forming a resource closed loop; (3) Low energy utilization efficiency: Liquid nitrogen itself has a high unit energy density. If the vaporized nitrogen cannot be fully utilized, the calorific value is released in vain, and the comprehensive energy efficiency of the system is low; (4) Weakening of safety and environmental protection indicators: The large evaporation of liquid nitrogen releases cold energy and nitrogen, which may cause problems such as local hypoxia, frosting or personnel frostbite, and lack of targeted safety recovery control. Summary of the Invention

[0005] The present invention aims to solve at least one of the technical problems existing in the prior art. For this purpose, the present invention provides a liquid nitrogen recycling system and method applicable to a gas cylinder inspection station, which can form a process closed loop and a resource closed loop, improve the operation efficiency and resource utilization rate of the gas cylinder inspection station, and achieve cost reduction and efficiency increase.

[0006] On the one hand, an embodiment of the present invention provides a liquid nitrogen recycling system applicable to a gas cylinder inspection station, including: Liquid nitrogen supply module, which is used to supply liquid nitrogen to the gas cylinders to be inspected for static evaporation rate testing; Static evaporation rate testing module, which is provided with multi-channel temperature sensors and a flow data acquisition unit, and is used to monitor the evaporation rate of liquid nitrogen in the gas cylinder in real time and evaluate the adiabatic performance; Liquid nitrogen recovery control module, which includes a gas cylinder self-pressurization component, a cryogenic solenoid valve group, a flow meter and a pressure feedback controller. The self-pressurization component dynamically matches the residual liquid nitrogen pressure in the gas cylinder with the pressure in the recovery pipeline. The flow meter and the pressure feedback controller cooperate to adjust the diversion ratio of liquid nitrogen and gaseous nitrogen to accurately control the diversion; Liquid nitrogen storage tank, which is connected to the liquid nitrogen recovery control module. The liquid nitrogen storage tank is equipped with a liquid level sensor and a temperature sensor, and the inner wall of the liquid nitrogen storage tank is coated with a nano-aerogel composite thermal insulation layer to extend the liquid nitrogen storage period; Nitrogen buffer tank, which is connected to the liquid nitrogen recovery control module. The nitrogen buffer tank is provided with multi-stage pressure regulating valves and multi-channel output interfaces. The multi-channel output interfaces include liquid oxygen cylinder replacement interfaces, LNG cylinder replacement interfaces and airtightness test interfaces to adapt to the replacement flow requirements of different gas cylinders and dynamically balance the pressure in the nitrogen buffer tank; Airtightness test module, which is connected to the nitrogen buffer tank and uses the gaseous nitrogen in the nitrogen buffer tank for inerting and airtightness testing; Central control module, which integrates an Internet of Things communication unit, is used to collect system operation data in real time, adjust the opening degree of the cryogenic solenoid valve group, and form a closed-loop resource circulation network.

[0007] The embodiments of the present invention have at least the following beneficial effects: The liquid nitrogen recycling system applicable to gas cylinder inspection stations provided by the present invention includes a micro-arc oxidation device and a control terminal. Through modular integration, intelligent control and the application of new materials, the self-pressurization component dynamically matches the residual liquid nitrogen pressure in the gas cylinder with the pressure in the recovery pipeline. The flow meter and the pressure feedback controller cooperate to adjust the diversion ratio of liquid nitrogen and gaseous nitrogen to accurately control the diversion, and can respectively introduce the residual liquid and nitrogen after the static test of liquid nitrogen into the liquid nitrogen storage tank and the gas buffer tank, which are used as detection reuse media and replacement gas sources respectively; the inner wall of the liquid nitrogen storage tank is coated with a nano-aerogel composite thermal insulation layer to improve the liquid nitrogen storage performance. Thus, a process closed-loop and a resource closed-loop are formed, significantly improving the operation efficiency and resource utilization rate of the inspection station; realizing efficient liquid nitrogen recovery, multi-scenario reuse of nitrogen and system energy efficiency optimization, solving the problems of resource waste and safety hazards, improving the operation efficiency and resource utilization rate of the gas cylinder inspection station, and achieving cost reduction and efficiency increase.

[0008] According to some embodiments of the present invention, the low-temperature solenoid valve group adopts a redundant design, including a main valve and a standby valve arranged in parallel. The response time of the main valve is ≤0.5 seconds, and the standby valve automatically switches when detecting a failure of the main valve.

[0009] According to some embodiments of the present invention, the flowmeter is a Coriolis flowmeter, and the flow error rate is ≤1.5%.

[0010] According to some embodiments of the present invention, a phase change material coating is provided on the outer wall of the liquid nitrogen storage tank. The nano-aerogel composite thermal insulation layer includes multiple layers of SiO2 aerogel and a vacuum interlayer, and the thermal conductivity is ≤0.015 W / (m·K).

[0011] According to some embodiments of the present invention, the multi-stage pressure regulating valve is a pilot-operated proportional valve, the output pressure range is 0.1 - 2.5 MPa, and it has a built-in self-cleaning function to prevent the valve port from being blocked caused by the freezing of low-temperature nitrogen.

[0012] On the other hand, embodiments of the present invention provide a method for recycling liquid nitrogen, including: Inject liquid nitrogen into the gas cylinder to be inspected through the liquid nitrogen supply module, start the static evaporation rate test module, collect the liquid nitrogen evaporation rate in the gas cylinder by using a multi-channel temperature sensor and a flow data acquisition unit, and generate an adiabatic performance evaluation report; Pressurize the residual liquid nitrogen to 0.8 - 1.2 MPa through the gas cylinder self-pressurization component, and use a flowmeter to monitor the flow rates of liquid and gaseous nitrogen in real time; According to the instructions of the pressure feedback controller, optimize the liquid nitrogen recovery efficiency and nitrogen distribution strategy by using an adaptive algorithm, adjust the opening degree of the low-temperature solenoid valve group, and introduce the pressurized liquid nitrogen into the liquid nitrogen storage tank and the gaseous nitrogen into the nitrogen buffer tank; Call the gaseous nitrogen in the nitrogen buffer tank, automatically match the replacement interface according to the type of non-liquid nitrogen gas cylinder, and adjust the nitrogen pressure to the target value through the multi-stage pressure regulating valve for inerting treatment and airtightness test; The central control module monitors the liquid nitrogen storage volume in the liquid nitrogen storage tank in real time. When the storage volume is lower than the set threshold, it preferentially calls the recycled liquid nitrogen for the next round of static evaporation rate test, and predicts the external liquid nitrogen supplement amount through an artificial neural network model to form a closed-loop resource cycle; Upload the operation data to the background server for remote fault diagnosis and energy efficiency optimization.

[0013] According to some embodiments of the present invention, the pressurization process of the gas cylinder self-pressurization component adopts a segmented pressurization strategy. In the first stage, it is pressurized to 0.5 MPa at a rate of 0.2 MPa / s, and in the second stage, it is switched to a rate of 0.1 MPa / s to pressurize to the target pressure, avoiding the loss of control caused by the violent vaporization of liquid nitrogen.

[0014] According to some embodiments of the present invention, the inerting treatment includes: Adopt a two-stage replacement method for the liquid oxygen cylinder. First, inject nitrogen at a flow rate of 50 L / min for 5 minutes, and then switch to a flow rate of 20 L / min and maintain it for 10 minutes to reduce the oxygen concentration in the cylinder to less than 1%. Adopt a pulsed replacement for the LNG cylinder. Break up the residual methane gas mass through intermittent high-pressure nitrogen injection, and the replacement efficiency is increased by more than 40%.

[0015] According to some embodiments of the present invention, the adoption of an adaptive algorithm to optimize the liquid nitrogen recovery efficiency and nitrogen distribution strategy includes: Based on an artificial neural network model trained with historical data, predict the peak demand for liquid nitrogen and start external liquid nitrogen supplementation in advance. Adopt a dynamic priority allocation strategy to automatically adjust the resource allocation weight according to the urgency of cylinder detection and the nitrogen reserve.

[0016] According to some embodiments of the present invention, the operation data is sent to the background server for remote fault diagnosis and energy efficiency optimization, including: Analyze historical data through machine learning to generate system maintenance warnings and optimization instructions. Send the optimization instructions to the central control module for execution.

[0017] The liquid nitrogen recycling method according to the embodiments of the present invention has at least the following beneficial effects: Through the collaborative action of each module of the liquid nitrogen recycling system, the effective recovery and reuse of used liquid nitrogen are realized. The liquid part of the liquid nitrogen can be recovered to the liquid nitrogen storage tank for subsequent use, and the gaseous part is introduced into the nitrogen buffer tank for the replacement operation of non-liquid nitrogen medium cylinders, realizing the recycling of liquid nitrogen resources and the integrated optimization of the detection process. The two-stage replacement method and the pulsed replacement can be used for customized processes for different cylinders; through the artificial neural network model and the dynamic priority allocation, the self-adaptability and prediction ability of the system are strengthened. It has the advantages of high recovery rate, high versatility, green energy saving, etc., improves the comprehensive utilization rate of liquid nitrogen, reduces the external purchase volume; optimizes energy efficiency and improves the overall energy efficiency ratio of the system; through pressure feedback control and redundant valve group design, reduces the failure rate and enhances safety; adopts intelligent management to realize remote diagnosis and process optimization, and reduces the operation and maintenance cost.

[0018] The additional aspects and advantages of the present invention will be partially given in the following description, partially become obvious from the following description, or be understood through the practice of the present invention. Description of the Drawings

[0019] The above and / or additional aspects and advantages of the present invention will become obvious and easy to understand from the description of the embodiments in conjunction with the following drawings, where: Figure 1 It is a module diagram of the liquid nitrogen recycling system applicable to a gas cylinder inspection station according to an embodiment of the present invention; Figure 2 One of the flowcharts of the liquid nitrogen recycling method according to an embodiment of the present invention; Figure 3 It is a schematic diagram of the scene layout of the gas cylinder inspection station according to an embodiment of the present invention; Figure 4 It is the second flowchart of the liquid nitrogen recycling method according to an embodiment of the present invention.

[0020] Reference numerals: Liquid nitrogen supply module 100, static evaporation rate test module 200, liquid nitrogen recovery control module 300, liquid nitrogen storage tank 400, nitrogen buffer tank 500, airtightness test module 600, central control module 700. Detailed implementation manners

[0021] The embodiments of the present invention will be described in detail below. Examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary only for explaining the present invention and should not be construed as limiting the present invention.

[0022] In the description of the present invention, it should be understood that for the orientation description, such as up, down, front, back, left, right, etc., the orientation or positional relationship indicated is based on the orientation or positional relationship shown in the accompanying drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as limiting the present invention.

[0023] In the description of the present invention, "several" means one or more, "multiple" means two or more, greater than, less than, exceeding, etc. are understood not to include the present number, and "above", "below", "within", etc. are understood to include the present number. If there is a description of "first", "second", etc., it is only for the purpose of distinguishing technical features and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features or the sequence relationship of the indicated technical features.

[0024] In the description of the present invention, unless otherwise clearly defined, words such as "set", "installed", "connected" and "linked" should be understood in a broad sense, and those skilled in the art can reasonably determine the specific meanings of the above words in the present invention in combination with the specific content of the technical solution.

[0025] The technical solutions of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0026] Please refer to Figures 1 to 3 In this embodiment, a liquid nitrogen recycling system applicable to a gas cylinder inspection station is disclosed, which includes a liquid nitrogen supply module 100, a static evaporation rate test module 200, a liquid nitrogen recovery control module 300, a liquid nitrogen storage tank 400, a nitrogen buffer tank 500, a airtightness test module 600, and a central control module 700. The liquid nitrogen supply module 100 is used to provide liquid nitrogen to the gas cylinders to be inspected for static evaporation rate testing. The static evaporation rate test module 200 is provided with multi-channel temperature sensors and a flow data acquisition unit, which is used to monitor the evaporation rate of liquid nitrogen in the gas cylinders in real time and evaluate the heat insulation performance. The liquid nitrogen recovery control module 300 includes a gas cylinder self-pressurization component, a cryogenic solenoid valve group, a flow meter, and a pressure feedback controller. The self-pressurization component dynamically matches the residual liquid nitrogen pressure in the gas cylinder with the pressure in the recovery pipeline. The flow meter and the pressure feedback controller cooperate to adjust the diversion ratio of liquid nitrogen and gaseous nitrogen to accurately control the diversion. The liquid nitrogen storage tank 400 is connected to the liquid nitrogen recovery control module 300. The liquid nitrogen storage tank 400 is equipped with a liquid level sensor and a temperature sensor, and the inner wall of the liquid nitrogen storage tank 400 is coated with a nano-aerogel composite heat insulation layer to extend the liquid nitrogen storage period. The nitrogen buffer tank 500 is connected to the liquid nitrogen recovery control module 300. The nitrogen buffer tank 500 is provided with a multi-stage pressure regulating valve and multi-channel output interfaces. The multi-channel output interfaces include a liquid oxygen cylinder replacement interface, an LNG cylinder replacement interface, and an airtightness test interface to adapt to the replacement flow requirements of different gas cylinders and dynamically balance the pressure in the nitrogen buffer tank 500. The airtightness test module 600 is connected to the nitrogen buffer tank 500 and uses the gaseous nitrogen in the nitrogen buffer tank 500 for inerting treatment and airtightness test. The central control module 700 is integrated with an Internet of Things communication unit, which is used to collect system operation data in real time, adjust the opening degree of the cryogenic solenoid valve group, and form a closed-loop resource recycling network.

[0027] It should be noted that the central control module 700 also includes a monitoring terminal and a background server. The Internet of Things communication unit includes a device status monitor (such as a vibration sensor, a current detection module), a communication gateway, an Ethernet switch, and a wireless communication. The vibration sensor is used to monitor the abnormal vibration of the cryogenic solenoid valve group, with a frequency range of 10 Hz - 1 kHz; the current detection module is used to collect the action current waveform of the cryogenic solenoid valve group. The flow data acquisition unit collects data through a flow meter and can be integrated into a static evaporation rate tester.

[0028] In some embodiments of the present invention, the cryogenic solenoid valve group adopts a redundant design, including a main valve and a standby valve arranged in parallel. The response time of the main valve is ≤ 0.5 seconds, and the standby valve automatically switches when it detects a failure of the main valve.

[0029] In some embodiments of the present invention, the flowmeter is a Coriolis flowmeter, which can monitor the flow situation in real time in combination with a PID control loop, and the flow error rate is ≤1.5%. The self-pressurizing component is equipped with an evaporation coil, and the liquid nitrogen in the bottle is pressurized through the internal evaporation coil to promote the discharge of the liquid.

[0030] In some embodiments of the present invention, the outer wall of the liquid nitrogen storage tank 400 is provided with a phase change material coating. The nano-aerogel composite insulation layer includes multiple layers of SiO2 aerogel and a vacuum interlayer, and the thermal conductivity is ≤0.015 W / (m·K). Temperature sensors and humidity sensors are arranged in the surrounding environment of the liquid nitrogen storage tank 400.

[0031] In some embodiments of the present invention, the multi-stage pressure regulating valve is a pilot-operated proportional valve, the output pressure range is 0.1 - 2.5 MPa, and it has a built-in self-cleaning function to prevent the valve port from being blocked caused by the freezing of low-temperature nitrogen.

[0032] Please refer to Figure 2 , this embodiment also provides a method for recycling liquid nitrogen based on the above liquid nitrogen recycling system, which mainly includes steps S101~S106: S101. Inject liquid nitrogen into the gas cylinder to be inspected through the liquid nitrogen supply module 100, start the static evaporation rate test module 200, and use the multi-channel temperature sensor and the flow data acquisition unit to collect the evaporation rate of liquid nitrogen in the gas cylinder to generate an adiabatic performance evaluation report.

[0033] S102. Pressurize the residual liquid nitrogen to 0.8 - 1.2 MPa through the gas cylinder self-pressurizing component, and use a flowmeter to monitor the flow of liquid and gaseous nitrogen in real time.

[0034] S103. According to the instructions of the pressure feedback controller, use an adaptive algorithm to optimize the liquid nitrogen recovery efficiency and the nitrogen distribution strategy, adjust the opening degree of the cryogenic solenoid valve group, and introduce the pressurized liquid nitrogen into the liquid nitrogen storage tank 400, and the gaseous nitrogen into the nitrogen buffer tank 500.

[0035] S104. Call the gaseous nitrogen in the nitrogen buffer tank 500, automatically match the replacement interface according to the type of non-liquid nitrogen gas cylinder, and adjust the nitrogen pressure to the target value through the multi-stage pressure regulating valve for inerting treatment and airtightness test.

[0036] S105. The central control module 700 monitors the inventory of the liquid nitrogen storage tank 400 in real time. When the inventory is lower than the set threshold, it preferentially calls the recycled liquid nitrogen for the next round of static evaporation rate test, and predicts the external liquid nitrogen supplement amount through an artificial neural network model to form a closed-loop resource cycle.

[0037] S106. Upload the operation data to the background server for remote fault diagnosis and energy efficiency optimization.

[0038] The pressurization process of the gas cylinder self-pressurization component in step S102 adopts a segmented pressurization strategy. In the first stage, it is pressurized to 0.5 MPa at a rate of 0.2 MPa / s, and in the second stage, the rate is switched to 0.1 MPa / s for pressurization to the target pressure to avoid loss of control caused by violent vaporization of liquid nitrogen. The flowmeter is installed at the liquid phase port, and when there is no flow in the flowmeter, gas phase recovery is carried out.

[0039] The inerting treatment in step S104 includes: For the liquid oxygen cylinder, a two-stage replacement method is adopted. First, nitrogen is injected at a flow rate of 50 L / min for 5 minutes for replacement, and then the flow rate is switched to 20 L / min and maintained for 10 minutes to reduce the oxygen concentration in the liquid oxygen cylinder to less than 1%; For the LNG cylinder, pulsed replacement is adopted, and the residual methane gas mass is broken by intermittent high-pressure nitrogen injection to improve the replacement efficiency.

[0040] The adoption of an adaptive algorithm to optimize the liquid nitrogen recovery efficiency and nitrogen distribution strategy in step S105 includes: Based on an artificial neural network model trained with historical data, predict the peak demand for liquid nitrogen and initiate external liquid nitrogen supplementation in advance; Adopt a dynamic priority allocation strategy to automatically adjust the resource allocation weight according to the urgency of cylinder detection and the amount of nitrogen.

[0041] Among them, the input layer data of the artificial neural network model trained with historical data includes: real-time liquid nitrogen inventory (liquid level sensor), historical liquid nitrogen consumption rate (time series data), ambient temperature / humidity (temperature sensor and humidity sensor), the number and type of cylinders to be inspected; the output layer decisions include: the amount of purchased liquid nitrogen supplementation and the best supplementation time point, the liquid nitrogen distribution priority score (0-1 weight value), and the failure risk warning level (high / medium / low). LSTM (Long Short-Term Memory Network) is used to process time series data (such as liquid nitrogen consumption fluctuations); CNN (Convolutional Neural Network) is used to analyze spatial distribution data (such as the inventory status of multiple storage tanks). The training process is as follows: Collect 6 months of historical operation data (including scenarios such as seasonal changes and detection peaks); Data preprocessing: Normalize the liquid nitrogen consumption and label abnormal events (such as valve failures); Loss function: Mean Square Error (MSE) to optimize the prediction accuracy; Verification set test: Prediction accuracy ≥ 92%.

[0042] Among them, the dynamic priority allocation strategy is adopted to monitor the resource consumption in real time, calculate the priority weight, and trigger the retraining of the neural network. The priority weight calculation formula is: Weight W = α·Emergency coefficient + β·Resource matching degree + γ·Safety risk In the formula, α (urgency coefficient weight) refers to the priority of order delivery timeliness, β (resource matching degree weight) refers to the adaptability of liquid nitrogen / nitrogen supply capacity, and γ (safety risk weight) refers to the concentration of combustible gas remaining in the gas cylinder.

[0043] Urgency coefficient: countdown of order delivery deadline (<24 hours, then the coefficient = 1.0); Resource matching degree: ratio of current liquid nitrogen stock to demand (when the ratio <0.5, the matching degree = 0); Safety risk: concentration of combustible gas remaining in the gas cylinder (when the concentration >5%, the risk = 1.0).

[0044] Default value of coefficient setting: α = 0.5, β = 0.3, γ = 0.2. When a sudden drop in liquid nitrogen recovery rate is detected, such as a diversion failure, the safety risk coefficient γ is automatically increased to 0.5 to prioritize the handling of high-risk gas cylinders.

[0045] The resource allocation rules are as follows: (1) Liquid nitrogen allocation Gas cylinders with a weight ≥0.8: preferentially call the liquid nitrogen storage tank 400 to recover liquid nitrogen; Gas cylinders with a weight <0.5: delay detection or use purchased liquid nitrogen.

[0046] (2) Nitrogen allocation Oxygen-liquid gas cylinder replacement: start the two-stage replacement method (50 L / min → 20 L / min) when the weight ≥0.7; LNG gas cylinder pulse replacement: activate the high-pressure injection mode (1.8 MPa, 2 Hz) when the weight ≥0.6.

[0047] Uploading the operation data to the background server and performing remote fault diagnosis and energy efficiency optimization in the above S106 step includes: Analyzing historical data through machine learning to generate system maintenance warnings and optimization instructions; Issuing the optimization instructions to the central control module 700 for execution.

[0048] For example, the LSTM-Attention model is used for equipment fault prediction, the input features are the number of valve actions in the past 30 days + the pressure fluctuation curve, and the output result is the fault probability in the next 7 days. The random forest model is used for the analysis of the degradation of the thermal insulation layer performance, the input features are the liquid nitrogen vaporization rate + ambient temperature and humidity + storage tank usage duration, and the output result is the prediction of the remaining service life. The Bayesian network model is used for process parameter optimization, the input features are the historical optimal evaporation rate test parameters + the current gas cylinder type, and the output result is the recommended liquid nitrogen injection volume (liters) and test duration (hours). 70% training set, 20% validation set, and 10% real-time online test set are used for training and validation.

[0049] Please refer to Figure 3 , which shows the collaborative scenario of multiple detection modules applicable to gas cylinder inspection stations, including: liquid nitrogen gas cylinder detection area, liquid oxygen gas cylinder detection area, LNG gas cylinder detection area, tanker pressure test area, etc. The system integration effect is demonstrated through pipelines and modular structure layout. Through the unified nitrogen supply and the main pipe for nitrogen gas replacement, the joint operation of multiple gas cylinder detection areas is realized. Among them, the main liquid nitrogen supply station is connected to the external liquid nitrogen supply port and is provided with a liquid nitrogen supply module 100; the static evaporation rate detection area is used for detecting the cryogenic insulation performance of cryogenic insulated gas cylinders; the liquid oxygen gas cylinder detection area is inerted before detection through nitrogen replacement; the LNG gas cylinder detection area also ensures test safety through nitrogen replacement; the airtight test area is used for leakage testing of containers such as tankers and container bottles; the control center and the monitoring system uniformly dispatch the recycling, distribution, and switching logic; the nitrogen replacement main pipe provides inert nitrogen for multiple detection areas; the nitrogen buffer and discharge device is connected to the replaced residual gas and the end-of-system treatment; the liquid nitrogen storage tank 400 and the recovery pipeline network are the core energy storage and reuse units in the entire liquid nitrogen circulation system. Through the closed-loop resource recycling, the problems of shunt control, nitrogen reuse in multiple scenarios, and intelligent regulation are solved, achieving a liquid nitrogen comprehensive utilization rate of ≥85%, a 40% reduction in the supplementary amount of externally purchased liquid nitrogen, and a 25% increase in the overall energy efficiency ratio of the system.

[0050] Please refer to Figure 4 , the overall process flow of the liquid nitrogen recycling method in this embodiment is as follows: The liquid nitrogen supply module 100 is connected to the external nitrogen supply interface and supplies liquid nitrogen to the gas cylinders to be inspected for static evaporation rate testing.

[0051] The static evaporation rate testing module 200 evaluates the cold insulation performance of cryogenic insulated gas cylinders.

[0052] After the static evaporation rate test is completed, the liquid nitrogen recovery control module 300 pressurizes and recovers the residual liquid through the gas cylinder self-pressurization component, and the residual liquid nitrogen is exported separately in liquid and gaseous states to achieve a closed-loop system recovery.

[0053] Through the liquid nitrogen recovery pipeline, the liquid part is introduced into the liquid nitrogen storage tank 400.

[0054] Through the nitrogen recovery pipeline, the gasified nitrogen is introduced into the nitrogen buffer tank 500.

[0055] The liquid nitrogen storage tank 400 and the recovery pipeline network store the recovered liquid nitrogen and supply it for subsequent tests to be reused.

[0056] The nitrogen buffer tank 500 stores the recovered nitrogen.

[0057] The recirculation detection liquid supply module returns the liquid nitrogen in the liquid nitrogen storage tank 400 to the static evaporation rate testing module 200 for a new round of testing.

[0058] The non-liquid nitrogen cylinder replacement module uses the nitrogen in the nitrogen buffer tank 500 to inertially replace cylinders such as LNG and liquid oxygen cylinders.

[0059] The airtightness test module uses the nitrogen in the nitrogen buffer tank 500 as a test medium for leak detection.

[0060] Among them, the detection and replacement of liquid oxygen cylinders adopt a two-stage replacement method. For example, liquid nitrogen is injected into the liquid oxygen cylinder, and the static evaporation rate test module 200 monitors the evaporation rate to be 0.8% / day; the remaining liquid nitrogen is recovered, self-pressurized to 1.0 MPa, and the liquid nitrogen (accounting for 70%) is diverted to the liquid nitrogen storage tank 400, and the gaseous nitrogen (accounting for 30%) is diverted to the nitrogen buffer tank 500; the nitrogen in the nitrogen buffer tank 500 is called, and the liquid oxygen cylinder is replaced at a flow rate of 50 L / min for 5 minutes, and then switched to 20 L / min to maintain for 10 minutes, and the oxygen concentration in the cylinder is reduced to 0.5%; the central control module 700 predicts the next round of detection requirements, and calls the liquid nitrogen in the liquid nitrogen storage tank 400 to complete the cycle.

[0061] The replacement of LNG cylinders adopts pulsed replacement. For example, when replacing LNG cylinders, pulsed high-pressure nitrogen injection is used, with a pressure of 1.8 MPa and a frequency of 2 Hz to break up the residual methane gas mass; the replacement efficiency is increased by 45% compared with the traditional method, and the time-consuming is shortened to 8 minutes; the system energy efficiency ratio is increased by 28%, and the external purchase volume of liquid nitrogen is reduced by 52%.

[0062] The liquid nitrogen recycling system includes a liquid nitrogen supply module 100, a static evaporation rate test module 200, a liquid nitrogen recovery control module 300, a liquid nitrogen storage tank 400, a nitrogen buffer tank 500, an airtightness test module 600, and a central control module 700, integrating a liquid nitrogen circulation system with closed-loop resources, precise control, and intelligent optimization. During the use of the system, through the coordinated action of each module, the effective recovery and reuse of the used liquid nitrogen are realized. The liquid part of the liquid nitrogen can be recovered to the liquid nitrogen storage tank 400 for subsequent use, and the gaseous part is introduced into the nitrogen buffer tank 500 for the replacement operation of non-liquid nitrogen medium cylinders, realizing the circular use of liquid nitrogen resources and the integrated optimization of the detection process. Adopting the two-stage replacement method and pulsed replacement can achieve customized processes for different cylinders; through the artificial neural network model and dynamic priority allocation, the self-adaptability and prediction ability of the system are enhanced. It has the advantages of high recovery rate, high versatility, green energy conservation, etc., improves the comprehensive utilization rate of liquid nitrogen, reduces the external purchase volume; optimizes energy efficiency and improves the overall energy efficiency ratio of the system; through pressure feedback control and redundant valve group design, the failure rate is reduced and the safety is enhanced; intelligent management is adopted to realize remote diagnosis and process optimization, reducing the operation and maintenance cost. It improves the operation efficiency and resource utilization rate of the cylinder inspection station, realizing cost reduction and efficiency increase.

[0063] The embodiments of the present invention have been described in detail above in conjunction with the accompanying drawings. However, the present invention is not limited to the above embodiments, and various changes can be made without departing from the spirit of the present invention within the scope of knowledge possessed by those of ordinary skill in the art.

Claims

1. A liquid nitrogen recycling system applicable to a gas cylinder inspection station, characterized in that, Comprising: A liquid nitrogen supply module for supplying liquid nitrogen to the gas cylinders to be inspected for static evaporation rate testing; A static evaporation rate testing module equipped with multi-channel temperature sensors and a flow data acquisition unit for real-time monitoring of the liquid nitrogen evaporation rate in the gas cylinders and evaluation of the adiabatic performance; A liquid nitrogen recovery control module including a gas cylinder self-pressurizing assembly, a cryogenic solenoid valve group, a flowmeter, and a pressure feedback controller. The self-pressurizing assembly dynamically matches the residual liquid nitrogen pressure in the gas cylinder with the pressure in the recovery pipeline, and the flowmeter and the pressure feedback controller cooperate to adjust the diversion ratio of liquid nitrogen and gaseous nitrogen to precisely control the diversion; A liquid nitrogen storage tank connected to the liquid nitrogen recovery control module. The liquid nitrogen storage tank is equipped with a liquid level sensor and a temperature sensor, and the inner wall of the liquid nitrogen storage tank is coated with a nano-aerogel composite thermal insulation layer to extend the liquid nitrogen storage cycle; A nitrogen buffer tank connected to the liquid nitrogen recovery control module. The nitrogen buffer tank is provided with a multi-stage pressure regulating valve and multi-channel output interfaces, including a liquid oxygen cylinder replacement interface, an LNG cylinder replacement interface, and an airtightness test interface, to adapt to the replacement flow requirements of different gas cylinders and dynamically balance the pressure in the nitrogen buffer tank; An airtightness test module connected to the nitrogen buffer tank for inerting and airtightness testing using the gaseous nitrogen in the nitrogen buffer tank; A central control module integrated with an Internet of Things communication unit for real-time collection of system operation data, adjustment of the opening degree of the cryogenic solenoid valve group, and formation of a closed-loop resource recycling network.

2. The liquid nitrogen recycling system applicable to a gas cylinder inspection station according to claim 1, wherein The cryogenic solenoid valve group adopts a redundant design, including a main valve and a standby valve arranged in parallel. The response time of the main valve is ≤0.5 seconds, and the standby valve automatically switches when detecting a failure of the main valve.

3. The liquid nitrogen recycling system applicable to a gas cylinder inspection station according to claim 2, characterized in that, The flowmeter is a Coriolis flowmeter with a flow error rate ≤1.5%.

4. The liquid nitrogen recycling system applicable to a gas cylinder inspection station according to claim 1, characterized in that, The outer wall of the liquid nitrogen storage tank is provided with a phase change material coating. The nano-aerogel composite thermal insulation layer includes multiple layers of SiO2 aerogel and a vacuum interlayer with a thermal conductivity ≤0.015 W / (m·K).

5. The nitrogen liquid recycling system applicable to a gas cylinder inspection station according to claim 1, wherein, The multi-stage pressure regulating valve is a pilot-operated proportional valve with an output pressure range of 0.1 - 2.5 MPa and an in-built self-cleaning function to prevent blockage of the valve port caused by freezing of low-temperature nitrogen.

6. A method for recycling liquid nitrogen, characterized in that, Based on the liquid nitrogen recycling system for a gas cylinder inspection station according to any one of claims 1 to 5, comprising: Inject liquid nitrogen into the gas cylinders to be inspected through the liquid nitrogen supply module, start the static evaporation rate testing module, use the multi-channel temperature sensors and the flow data acquisition unit to collect the liquid nitrogen evaporation rate in the gas cylinders, and generate an adiabatic performance evaluation report; Pressurize the residual liquid nitrogen to 0.8 - 1.2 MPa through the gas cylinder self-pressurizing assembly, and use the flowmeter to real-time monitor the flow rates of liquid and gaseous nitrogen; According to the instructions of the pressure feedback controller, adopt an adaptive algorithm to optimize the liquid nitrogen recovery efficiency and nitrogen distribution strategy, adjust the opening degree of the cryogenic solenoid valve group, and introduce the pressurized liquid nitrogen into the liquid nitrogen storage tank and the gaseous nitrogen into the nitrogen buffer tank; Call the gaseous nitrogen in the nitrogen buffer tank, automatically match the replacement interface according to the type of non-liquid nitrogen cylinder, and adjust the nitrogen pressure to the target value through a multi-stage pressure regulating valve for inerting treatment and airtightness test; The central control module monitors the inventory of the liquid nitrogen storage tank in real time. When the inventory is lower than the set threshold, it preferentially calls the recycled liquid nitrogen for the next round of static evaporation rate tests, and predicts the external liquid nitrogen supplement amount through an artificial neural network model to form a closed-loop resource cycle; Upload the operation data to the background server for remote fault diagnosis and energy efficiency optimization.

7. The method for recycling liquid nitrogen according to claim 6, wherein The pressurization process of the cylinder self-pressurization component adopts a segmented pressurization strategy. In the first stage, it is pressurized to 0.5 MPa at a rate of 0.2 MPa / s, and in the second stage, it is switched to a rate of 0.1 MPa / s to pressurize to the target pressure to avoid loss of control caused by violent vaporization of liquid nitrogen.

8. The method for recycling liquid nitrogen according to claim 6, characterized in that The inerting treatment includes: Adopt a two-stage replacement method for the liquid oxygen cylinder. First, inject nitrogen at a flow rate of 50 L / min for 5 minutes for replacement, and then switch to a flow rate of 20 L / min to maintain for 10 minutes to reduce the oxygen concentration in the liquid oxygen cylinder to less than 1%; Adopt pulsed replacement for the LNG cylinder, and break the residual methane gas mass through intermittent high-pressure nitrogen injection to improve the replacement efficiency.

9. The method for recycling liquid nitrogen according to claim 6, wherein The adaptive algorithm is used to optimize the liquid nitrogen recovery efficiency and nitrogen distribution strategy, including: Based on the artificial neural network model trained with historical data, predict the peak demand for liquid nitrogen and start the external liquid nitrogen supplement in advance; Adopt a dynamic priority allocation strategy to automatically adjust the resource allocation weight according to the urgency of cylinder detection and the nitrogen storage.

10. The method for recycling liquid nitrogen according to claim 6, characterized in that, The uploading of the operation data to the background server for remote fault diagnosis and energy efficiency optimization includes: Analyze the historical data through machine learning to generate system maintenance warnings and optimization instructions; Send the optimization instructions to the central control module for execution.

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