Liquid nitrogen recycling system and method applicable to gas cylinder inspection stations

Abstract

This invention discloses a liquid nitrogen recycling system and method suitable for gas cylinder inspection stations. The system includes a liquid nitrogen supply module, a static evaporation rate testing module, a liquid nitrogen recovery control module, a liquid nitrogen storage tank, a nitrogen buffer tank, an airtightness testing module, and a central control module. Through the coordinated operation of these modules, the system achieves effective recovery and reuse of used liquid nitrogen. The liquid portion of the liquid nitrogen is recovered to the liquid nitrogen storage tank for subsequent use, while the gaseous portion is introduced into the nitrogen buffer tank for replacement operations on non-liquid nitrogen medium gas cylinders. This achieves integrated optimization of liquid nitrogen resource recycling and testing processes. Employing a two-stage replacement method and pulse replacement, the system can be customized for different gas cylinders. Through artificial neural network models and dynamic priority allocation, the system's adaptability and predictive capabilities are enhanced. This creates a closed-loop process and resource system, improving the operational efficiency and resource utilization of gas cylinder inspection stations while reducing costs.

Description

Technical Field

[0001] This invention relates to the field of cryogenic insulated gas cylinder testing technology, and in particular to a liquid nitrogen recycling system and method suitable for gas cylinder inspection stations. Background Technology

[0002] In the testing of cryogenic insulated gas cylinders, liquid nitrogen is used as the testing medium for cryogenic performance, primarily to evaluate the static evaporation rate of cryogenic insulated gas cylinders (such as liquid oxygen and liquid argon cylinders). This test is a key means of verifying the cylinder's insulation performance and product safety performance. It typically involves filling the cylinder with liquid nitrogen and recording the rate of liquid nitrogen loss at a constant external temperature. However, in the current testing system, the liquid nitrogen used in this test is supplied only once, and the liquid nitrogen evaporates and is discharged after the test, failing to form a systematic closed-loop energy utilization system.

[0003] In addition, gas cylinder inspection stations typically also inspect cylinders containing other cryogenic media (such as liquid oxygen and liquefied natural gas) during routine operations. These cylinders require gas purging, or inertization, during the pre-inspection treatment stage to eliminate oxidizing or flammable residues and avoid the risk of explosion. Traditional methods use high-pressure nitrogen or liquid nitrogen vaporization for purging, which suffers from complex cylinder supply scheduling and high costs.

[0004] The current related technologies have the following problems:

[0005] (1) Low recovery rate of liquid nitrogen residue: Only part of the liquid nitrogen is vaporized after the test is completed, and a large amount of cryogenic liquid is directly released into the air, which cannot be effectively reused, resulting in a waste of resources;

[0006] (2) The detection system modules are scattered: liquid nitrogen is used for static evaporation rate testing, while the airtightness testing relies on an external nitrogen system. The process is fragmented and does not form a closed resource loop.

[0007] (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 will be released in vain, and the overall energy efficiency of the system will be low.

[0008] (4) Weakened safety and environmental protection indicators: The large amount of liquid nitrogen evaporates and releases cold energy and nitrogen gas, which may cause local hypoxia, frost or frostbite to personnel, and there is a lack of targeted safety recycling control. Summary of the Invention

[0009] This invention aims to solve at least one of the technical problems existing in the prior art. To this end, this invention proposes a liquid nitrogen recycling system and method suitable for gas cylinder inspection stations, which can form a closed-loop process and resource system, improving the operational efficiency and resource utilization of gas cylinder inspection stations, and achieving cost reduction and efficiency improvement.

[0010] On one hand, embodiments of the present invention provide a liquid nitrogen recycling system suitable for gas cylinder inspection stations, comprising:

[0011] A liquid nitrogen supply module is used to supply liquid nitrogen to the gas cylinder under test for static evaporation rate testing.

[0012] A static evaporation rate testing module is provided, which is equipped with a multi-channel temperature sensor and a flow data acquisition unit to monitor the evaporation rate of liquid nitrogen in the gas cylinder in real time and evaluate the insulation performance.

[0013] The liquid nitrogen recovery control module includes a 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 cylinder with the pressure in the recovery pipeline. The flow meter and the pressure feedback controller work together to adjust the ratio of liquid nitrogen to gaseous nitrogen to precisely control the flow.

[0014] A liquid nitrogen storage tank 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. The inner wall of the liquid nitrogen storage tank is coated with a nano-aerogel composite insulation layer to extend the liquid nitrogen storage period.

[0015] A nitrogen buffer tank is connected to the liquid nitrogen recovery control module. The nitrogen buffer tank is equipped with a multi-stage pressure regulating valve and a multi-channel output interface. The multi-channel output interface includes 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 cylinders and dynamically balance the pressure inside the nitrogen buffer tank.

[0016] An airtightness testing module is provided, which is connected to the nitrogen buffer tank and uses gaseous nitrogen in the nitrogen buffer tank for inertization treatment and airtightness testing.

[0017] The central control module integrates an Internet of Things (IoT) communication unit 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.

[0018] The embodiments of the present invention have at least the following beneficial effects:

[0019] This invention provides a liquid nitrogen recycling system for gas cylinder inspection stations, comprising a micro-arc oxidation device and a control terminal. Through modular integration, intelligent control, and the application of novel materials, the self-pressurizing component dynamically matches the residual liquid nitrogen pressure in the gas cylinder with the pressure in the recovery pipeline. A flow meter and pressure feedback controller collaboratively adjust the flow ratio of liquid nitrogen to gaseous nitrogen for precise control. This allows the residual liquid and nitrogen gas after static testing to be separately introduced into a liquid nitrogen storage tank and a gas buffer tank, serving as a reused testing medium and a replacement gas source, respectively. The inner wall of the liquid nitrogen storage tank is coated with a nano-aerogel composite insulation layer to enhance liquid nitrogen storage performance. This forms a closed-loop process and resource system, significantly improving the operational efficiency and resource utilization of the inspection station. It achieves efficient liquid nitrogen recovery, multi-scenario reuse of nitrogen gas, and system energy efficiency optimization, solving resource waste and safety hazards, improving the operational efficiency and resource utilization of gas cylinder inspection stations, and achieving cost reduction and efficiency improvement.

[0020] According to 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, wherein the response time of the main valve is ≤0.5 seconds, and the standby valve automatically switches when the main valve is detected to be faulty.

[0021] According to some embodiments of the present invention, the flow meter is a Coriolis flow meter with a flow error rate ≤1.5%.

[0022] According to some embodiments of the present invention, the outer wall of the liquid nitrogen storage tank is provided with a phase change material coating, and the nano-aerogel composite insulation layer includes multiple layers of SiO2 aerogel and a vacuum interlayer, with a thermal conductivity ≤0.015 W / (m·K).

[0023] According to some embodiments of the present invention, the multi-stage pressure regulating valve is a pilot-operated proportional valve with an output pressure range of 0.1-2.5 MPa and a built-in self-cleaning function to prevent valve port blockage caused by low-temperature nitrogen freezing.

[0024] On the other hand, embodiments of the present invention provide a method for recycling liquid nitrogen, including:

[0025] Liquid nitrogen is injected into the gas cylinder under test through the liquid nitrogen supply module, the static evaporation rate test module is started, and the liquid nitrogen evaporation rate in the gas cylinder is collected by the multi-channel temperature sensor and flow data acquisition unit to generate a thermal insulation performance evaluation report.

[0026] The residual liquid nitrogen is pressurized to 0.8~1.2 MPa using a gas cylinder self-pressurization component, and the flow rates of liquid and gaseous nitrogen are monitored in real time using a flow meter;

[0027] According to the instructions of the pressure feedback controller, an adaptive algorithm is used 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.

[0028] The gaseous nitrogen in the nitrogen buffer tank is called up, and the replacement interface is automatically matched according to the type of non-liquid nitrogen cylinder. The nitrogen pressure is adjusted to the target value through a multi-stage pressure regulating valve to perform inertization treatment and airtightness test.

[0029] The central control module monitors the liquid nitrogen storage tank level in real time. When the level is lower than the set threshold, it prioritizes the recovery of liquid nitrogen for the next round of static evaporation rate testing. It also uses an artificial neural network model to predict the amount of external liquid nitrogen replenishment, thus forming a closed-loop resource cycle.

[0030] The operating data is uploaded to the backend server for remote fault diagnosis and energy efficiency optimization.

[0031] 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, the pressure is increased to 0.5 MPa at a rate of 0.2 MPa / s, and in the second stage, the pressure is increased to the target pressure at a rate of 0.1 MPa / s to avoid uncontrolled leakage caused by violent vaporization of liquid nitrogen.

[0032] According to some embodiments of the present invention, the inertization process includes:

[0033] A two-stage replacement method was used for liquid oxygen cylinders. First, nitrogen was injected at a flow rate of 50 L / min for 5 minutes to replace the oxygen, and then the flow rate was switched to 20 L / min and maintained for 10 minutes to reduce the oxygen concentration in the cylinder to below 1%.

[0034] The LNG cylinders are replaced using a pulse-type replacement method, which breaks up residual methane gas clusters by intermittent high-pressure nitrogen injection, improving the replacement efficiency by more than 40%.

[0035] According to some embodiments of the present invention, the method of using an adaptive algorithm to optimize liquid nitrogen recovery efficiency and nitrogen distribution strategy includes:

[0036] An artificial neural network model trained based on historical data is used to predict peak liquid nitrogen demand and initiate external liquid nitrogen replenishment in advance.

[0037] A dynamic priority allocation strategy is adopted, which automatically adjusts the resource allocation weight based on the urgency of gas cylinder testing and nitrogen reserves.

[0038] According to some embodiments of the present invention, the step of sending operational data to a backend server and performing remote fault diagnosis and energy efficiency optimization includes:

[0039] By analyzing historical data through machine learning, system maintenance warnings and optimization instructions are generated;

[0040] The optimization instructions are sent to the central control module for execution.

[0041] The liquid nitrogen recycling method according to embodiments of the present invention has at least the following beneficial effects:

[0042] This liquid nitrogen recycling system achieves effective recovery and reuse of used liquid nitrogen through the coordinated operation of its various modules. The liquid portion is recovered to a liquid nitrogen storage tank for subsequent use, while the gaseous portion is introduced into a nitrogen buffer tank for purging non-liquid nitrogen cylinders. This integrates and optimizes the recycling and detection processes of liquid nitrogen resources. Employing a two-stage purging method and pulse-type purging, it allows for customized processes for different cylinders. Artificial neural network models and dynamic priority allocation enhance the system's adaptability and predictive capabilities. It boasts advantages such as high recovery rate, high versatility, and energy efficiency, improving the overall utilization rate of liquid nitrogen and reducing external purchases; optimizing energy efficiency and improving the overall system energy efficiency ratio; reducing failure rate and enhancing safety through pressure feedback control and redundant valve group design; and employing intelligent management to achieve remote diagnostics and process optimization, reducing operation and maintenance costs.

[0043] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0044] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0045] Figure 1 This is a block diagram of a liquid nitrogen recycling system applicable to a gas cylinder inspection station according to an embodiment of the present invention;

[0046] Figure 2 One of the flowcharts for the liquid nitrogen recycling method according to an embodiment of the present invention;

[0047] Figure 3 This is a schematic diagram of the scene layout of a gas cylinder inspection station according to an embodiment of the present invention;

[0048] Figure 4 This is the second flowchart of the liquid nitrogen recycling method according to an embodiment of the present invention.

[0049] Figure label:

[0050] 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, and central control module 700. Detailed Implementation

[0051] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein 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 and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0052] In the description of this invention, it should be understood that the orientation descriptions, such as up, down, front, back, left, right, etc., are based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0053] In the description of this invention, "several" means one or more, "multiple" means two or more, "greater than," "less than," "exceeding," etc. are understood to exclude the stated number, and "above," "below," "within," etc. are understood to include the stated number. If "first," "second," etc. are used in the description, they are only for the purpose of distinguishing technical features and should not be construed as indicating or implying relative importance or implicitly indicating the number of indicated technical features or the order of the indicated technical features.

[0054] In the description of this invention, unless otherwise explicitly defined, the terms "setting", "installing", "connecting" and "linking" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this invention in conjunction with the specific content of the technical solution.

[0055] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0056] Please refer to Figures 1 to 3This embodiment discloses a liquid nitrogen recycling system suitable for gas cylinder inspection stations, including a liquid nitrogen supply module 100, a static evaporation rate testing module 200, a liquid nitrogen recovery control module 300, a liquid nitrogen storage tank 400, a nitrogen buffer tank 500, an airtightness testing module 600, and a central control module 700. The liquid nitrogen supply module 100 supplies liquid nitrogen to the gas cylinders under inspection for static evaporation rate testing. The static evaporation rate testing module 200 is equipped with a multi-channel temperature sensor and a flow data acquisition unit for real-time monitoring of the liquid nitrogen evaporation rate within the gas cylinder and for evaluating its 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 work together to adjust the ratio of liquid nitrogen to gas nitrogen flow for precise flow control. Liquid nitrogen storage tank 400 is connected to liquid nitrogen recovery control module 300. Liquid nitrogen storage tank 400 is equipped with a liquid level sensor and a temperature sensor. The inner wall of liquid nitrogen storage tank 400 is coated with a nano-aerogel composite insulation layer to extend the liquid nitrogen storage period. Nitrogen buffer tank 500 is connected to liquid nitrogen recovery control module 300. Nitrogen buffer tank 500 is equipped with multi-stage pressure regulating valves and multi-channel output interfaces, including liquid oxygen cylinder replacement interfaces, LNG cylinder replacement interfaces, and airtightness test interfaces, to adapt to the replacement flow requirements of different cylinders and dynamically balance the internal pressure of nitrogen buffer tank 500. Airtightness test module 600 is connected to nitrogen buffer tank 500 and uses gaseous nitrogen in nitrogen buffer tank 500 for inertization treatment and airtightness testing. Central control module 700 integrates an IoT communication unit for real-time acquisition of system operating data and adjustment of the opening degree of cryogenic solenoid valve group, forming a closed-loop resource circulation network.

[0057] It should be noted that the central control module 700 also includes a monitoring terminal and a back-end server. The IoT communication unit includes equipment status monitors (such as vibration sensors and current detection modules), a communication gateway, an Ethernet switch, and wireless communication. Vibration sensors are used to monitor abnormal vibrations of the cryogenic solenoid valve assembly, with a frequency range of 10Hz-1kHz; the current detection module is used to acquire the operating current waveform of the cryogenic solenoid valve assembly. The flow data acquisition unit collects data through a flow meter and can be integrated into a static evaporation rate tester.

[0058] 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 the main valve is detected to be faulty.

[0059] In some embodiments of the present invention, the flow meter is a Coriolis flow meter, which can monitor the flow rate in real time in conjunction with a PID control loop, with a flow error rate of ≤1.5%. The self-pressurizing component is equipped with an evaporation coil, which pressurizes the liquid nitrogen in the bottle through the internal evaporation coil, thereby facilitating the discharge of the liquid.

[0060] In some embodiments of the present invention, the outer wall of the liquid nitrogen storage tank 400 is coated with a phase change material, and the nano-aerogel composite insulation layer includes multiple layers of SiO2 aerogel and a vacuum interlayer, with a thermal conductivity ≤0.015 W / (m·K). Temperature sensors and humidity sensors are arranged around the liquid nitrogen storage tank 400.

[0061] In some embodiments of the present invention, the multi-stage pressure regulating valve is a pilot-operated proportional valve with an output pressure range of 0.1-2.5 MPa and a built-in self-cleaning function to prevent valve port blockage caused by low-temperature nitrogen freezing.

[0062] Please see Figure 2 This embodiment also provides a method for recycling liquid nitrogen based on the above-described liquid nitrogen recycling system, mainly including steps S101~S106:

[0063] S101. Liquid nitrogen is injected into the gas cylinder to be tested through the liquid nitrogen supply module 100, the static evaporation rate test module 200 is started, and the liquid nitrogen evaporation rate in the gas cylinder is collected using a multi-channel temperature sensor and flow data acquisition unit to generate an insulation performance evaluation report.

[0064] S102. The residual liquid nitrogen is pressurized to 0.8~1.2 MPa through the gas cylinder self-pressurization component, and the flow rate of liquid and gaseous nitrogen is monitored in real time using a flow meter.

[0065] S103. According to the instructions of the pressure feedback controller, the adaptive algorithm is used 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 400 and the gaseous nitrogen into the nitrogen buffer tank 500.

[0066] S104. Call up the gaseous nitrogen in the nitrogen buffer tank 500, automatically match the replacement interface according to the type of non-liquid nitrogen cylinder, and adjust the nitrogen pressure to the target value through the multi-stage pressure regulating valve to perform inertization treatment and airtightness test.

[0067] S105 and the central control module 700 monitor the liquid nitrogen storage tank 400 in real time. When the storage level is lower than the set threshold, the recovered liquid nitrogen is prioritized for use in the next round of static evaporation rate test. The external liquid nitrogen replenishment amount is predicted through an artificial neural network model to form a closed-loop resource cycle.

[0068] S106. Upload the operating data to the backend server and perform remote fault diagnosis and energy efficiency optimization.

[0069] The pressurization process of the gas cylinder self-pressurization component in step S102 above adopts a segmented pressurization strategy. In the first stage, the pressure is increased to 0.5 MPa at a rate of 0.2 MPa / s, and in the second stage, the pressure is increased to the target pressure at a rate of 0.1 MPa / s to avoid uncontrolled leakage caused by violent vaporization of liquid nitrogen. The flow meter is installed at the liquid phase inlet. When there is no flow from the flow meter, gas phase recovery is performed.

[0070] The inertization process in step S104 above includes:

[0071] A two-stage replacement method was used for the liquid oxygen cylinder. First, nitrogen was injected at a flow rate of 50 L / min for 5 minutes to replace the oxygen, and then the flow rate was switched to 20 L / min and maintained for 10 minutes to reduce the oxygen concentration in the liquid oxygen cylinder to below 1%.

[0072] The LNG cylinders are replaced using a pulse-type replacement method, which breaks up residual methane gas clusters by intermittent high-pressure nitrogen injection to improve replacement efficiency.

[0073] The adaptive algorithm used in step S105 above to optimize liquid nitrogen recovery efficiency and nitrogen distribution strategy includes:

[0074] An artificial neural network model trained based on historical data is used to predict peak liquid nitrogen demand and initiate external liquid nitrogen replenishment in advance.

[0075] A dynamic priority allocation strategy is adopted, which automatically adjusts the resource allocation weight based on the urgency of gas cylinder detection and the amount of nitrogen.

[0076] The input layer data of the artificial neural network model trained based on historical data includes: real-time liquid nitrogen inventory (liquid level sensor), historical liquid nitrogen consumption rate (time series data), ambient temperature / humidity (temperature and humidity sensors), and the number and type of gas cylinders to be inspected. The output layer decisions include: the amount of purchased liquid nitrogen to be replenished and the optimal replenishment time, liquid nitrogen allocation priority scoring (0-1 weight values), and fault risk warning level (high / medium / low). LSTM (Long Short-Term Memory) 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:

[0077] Collect 6 months of historical operational data (including seasonal changes, peak testing periods, etc.);

[0078] Data preprocessing: normalize liquid nitrogen consumption and label abnormal events (such as valve failure);

[0079] Loss function: Mean squared error (MSE) optimizes prediction accuracy;

[0080] Evidence set test: Prediction accuracy ≥ 92%.

[0081] This involves employing a dynamic priority allocation strategy, which monitors resource consumption in real time, calculates priority weights, and triggers neural network retraining. The priority weight calculation formula is as follows:

[0082] Weight W = α·urgency coefficient + β·resource matching degree + γ·security risk

[0083] In the formula, α (emergency coefficient weight) refers to the priority of order delivery timeliness, β (resource matching degree weight) refers to the suitability of liquid nitrogen / nitrogen supply capacity, and γ (safety risk weight) refers to the concentration of residual flammable gas in the gas cylinder.

[0084] Urgency factor: Countdown to order delivery deadline (factor = 1.0 if less than 24 hours);

[0085] Resource matching degree: The ratio of current liquid nitrogen inventory to demand (matching degree = 0 when the ratio is <0.5);

[0086] Safety risk: Concentration of residual flammable gas in the gas cylinder (risk = 1.0 when concentration > 5%).

[0087] The default values ​​for the coefficients are: 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 cylinders.

[0088] The resource allocation rules are as follows:

[0089] (1) Liquid nitrogen distribution

[0090] For gas cylinders with a weight ≥ 0.8: Liquid nitrogen from liquid nitrogen storage tank 400 should be used first for recovery;

[0091] Gas cylinders with a weight of <0.5: Delay detection or use purchased liquid nitrogen.

[0092] (2) Nitrogen distribution

[0093] Liquid oxygen cylinder replacement: When the weight is ≥0.7, start the two-stage replacement method (50 L / min→20 L / min);

[0094] LNG cylinder pulse replacement: High-pressure injection mode (1.8 MPa, 2 Hz) is activated when the weight is ≥0.6.

[0095] The step S106 above, which involves uploading operational data to the backend server and performing remote fault diagnosis and energy efficiency optimization, includes:

[0096] By analyzing historical data through machine learning, system maintenance warnings and optimization instructions are generated;

[0097] The optimization instructions are sent to the central control module 700 for execution.

[0098] For example, equipment failure prediction uses an LSTM-Attention model, with input features being the number of valve actions over the past 30 days and pressure fluctuation curves, and the output being the failure probability for the next 7 days. Insulation layer performance degradation analysis uses a random forest model, with input features being liquid nitrogen vaporization rate, ambient temperature and humidity, and tank usage time, and the output being a prediction of remaining service life. Process parameter optimization uses a Bayesian network model, with input features being the historical best evaporation rate test parameters and the current cylinder type, and the output being the recommended liquid nitrogen injection volume (liters) and test duration (hours). Training and validation are performed using a 70% training set, a 20% validation set, and a 10% real-time online test set.

[0099] Please see Figure 3 This embodiment demonstrates its applicability to multi-module collaborative scenarios in gas cylinder inspection stations, including: liquid nitrogen cylinder inspection area, liquid oxygen cylinder inspection area, LNG cylinder inspection area, tank truck pressure testing area, etc., showcasing the system integration effect through pipeline and modular structural layout. The unified nitrogen supply and nitrogen replacement main pipeline enables the joint operation of multiple cylinder inspection areas. Specifically, the liquid nitrogen supply main station connects to an external liquid nitrogen supply port and is equipped with a liquid nitrogen supply module 100; the static evaporation rate inspection area is used for testing the cryogenic insulation performance of cryogenic insulated cylinders; the liquid oxygen cylinder inspection area achieves pre-test inertization through nitrogen replacement; the LNG cylinder inspection area also ensures test safety through nitrogen replacement; the airtightness testing area is used for leak testing of containers such as tank trucks and containers; the control center and monitoring system unify the scheduling, recovery, distribution, and switching logic; the nitrogen replacement main pipeline provides inert nitrogen to multiple inspection areas; the nitrogen buffer and discharge device connects the replacement residual gas to the system's end-of-pipe treatment; the liquid nitrogen storage tank 400 and the recovery pipeline network are the core energy storage and reuse units of the entire liquid nitrogen circulation system. By using closed-loop resource recycling, the problems of diversion control, multi-scenario nitrogen reuse and intelligent regulation are solved, achieving a comprehensive utilization rate of liquid nitrogen of ≥85%, reducing the amount of purchased liquid nitrogen replenishment by 40%, and improving the overall energy efficiency ratio of the system by 25%.

[0100] Please see Figure 4 The overall process flow of the liquid nitrogen recycling method in this embodiment is as follows:

[0101] The liquid nitrogen supply module 100 is connected to an external nitrogen supply interface to supply liquid nitrogen to the gas cylinder under test for static evaporation rate testing.

[0102] The static evaporation rate test module 200 evaluates the cold insulation performance of cryogenic insulated gas cylinders.

[0103] 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 gas states, realizing a closed loop of system recovery.

[0104] The liquid portion is introduced into the liquid nitrogen storage tank 400 through the liquid nitrogen recovery pipeline.

[0105] The vaporized nitrogen is introduced into the nitrogen buffer tank 500 through the nitrogen recovery pipeline.

[0106] Liquid nitrogen storage tank 400 and recovery pipeline network store and recover liquid nitrogen for reuse in subsequent tests.

[0107] A nitrogen buffer tank of 500 stores and recovers nitrogen.

[0108] The recirculation detection liquid supply module returns the liquid nitrogen in the liquid nitrogen storage tank 400 to the static evaporation rate test module 200 for a new round of testing.

[0109] The non-liquid nitrogen cylinder replacement module uses nitrogen from the nitrogen buffer tank 500 to inertly replace LNG, liquid oxygen, and other gas cylinders.

[0110] The airtightness test module uses nitrogen from nitrogen buffer tank 500 as the test medium for leak detection.

[0111] The liquid oxygen cylinder detection and replacement adopts 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 as 0.8% / day. The residual liquid nitrogen is recovered, 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 used to replace the liquid oxygen cylinder at a flow rate of 50 L / min for 5 minutes, and then switched to 20 L / min and maintained for 10 minutes, reducing the oxygen concentration in the cylinder to 0.5%. The central control module 700 predicts the next round of detection needs and uses the liquid nitrogen in the liquid nitrogen storage tank 400 to complete the cycle.

[0112] LNG cylinder replacement employs a pulse-type replacement method. For example, during LNG cylinder replacement, a pulsed high-pressure nitrogen injection is used at a pressure of 1.8 MPa and a frequency of 2 Hz to break up residual methane gas clouds; the replacement efficiency is increased by 45% compared to traditional methods, and the time is shortened to 8 minutes; the system energy efficiency ratio is improved by 28%, and the amount of liquid nitrogen purchased externally is reduced by 52%.

[0113] This liquid nitrogen recycling system comprises a liquid nitrogen supply module 100, a static evaporation rate testing module 200, a liquid nitrogen recovery control module 300, a liquid nitrogen storage tank 400, a nitrogen buffer tank 500, an airtightness testing module 600, and a central control module 700. It integrates resource closed-loop management, precise control, and intelligent optimization into a liquid nitrogen recycling system. During operation, the system achieves effective recovery and reuse of used liquid nitrogen through the coordinated action of its various modules. The liquid portion of the liquid nitrogen is recovered to the liquid nitrogen storage tank 400 for subsequent use, while the gaseous portion is introduced into the nitrogen buffer tank 500 for the replacement of non-liquid nitrogen medium cylinders. This achieves integrated optimization of liquid nitrogen resource recycling and testing processes. Employing a two-stage replacement method and pulse replacement, it can customize processes for different cylinders. Through an artificial neural network model and dynamic priority allocation, the system's adaptability and predictive capabilities are enhanced. It boasts advantages such as high recovery rate, high versatility, and green energy saving, improving the comprehensive utilization rate of liquid nitrogen and reducing external purchases; optimizing energy efficiency and improving the overall energy efficiency ratio of the system; reducing failure rate and enhancing safety through pressure feedback control and redundant valve group design; and adopting intelligent management to achieve remote diagnosis and process optimization, reducing operation and maintenance costs. It improves the operational efficiency and resource utilization of gas cylinder inspection stations, achieving cost reduction and efficiency improvement.

[0114] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A liquid nitrogen recycling system suitable for gas cylinder inspection stations, characterized in that, include: A liquid nitrogen supply module is used to supply liquid nitrogen to the gas cylinder under test for static evaporation rate testing. A static evaporation rate testing module is provided, which is equipped with a multi-channel temperature sensor and a flow data acquisition unit to monitor the evaporation rate of liquid nitrogen in the gas cylinder in real time and evaluate the insulation performance. The liquid nitrogen recovery control module includes a 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 cylinder with the pressure in the recovery pipeline. The flow meter and the pressure feedback controller work together to adjust the ratio of liquid nitrogen to gaseous nitrogen to precisely control the flow. A liquid nitrogen storage tank 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. The inner wall of the liquid nitrogen storage tank is coated with a nano-aerogel composite insulation layer to extend the liquid nitrogen storage period. A nitrogen buffer tank is connected to the liquid nitrogen recovery control module. The nitrogen buffer tank is equipped with a multi-stage pressure regulating valve and a multi-channel output interface. The multi-channel output interface includes 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 cylinders and dynamically balance the pressure inside the nitrogen buffer tank. An airtightness testing module is provided, which is connected to the nitrogen buffer tank and uses gaseous nitrogen in the nitrogen buffer tank for inertization treatment and airtightness testing. The central control module integrates an Internet of Things (IoT) communication unit for real-time acquisition of system operation data and adjustment of the opening degree of the cryogenic solenoid valve group to form a closed-loop resource circulation network. The central control module also integrates an artificial neural network model for predicting liquid nitrogen demand and dynamically adjusting resource allocation.

2. The liquid nitrogen recycling system for gas cylinder inspection stations according to claim 1, characterized in that, The cryogenic solenoid valve assembly adopts a redundant design, including a main valve and a backup valve arranged in parallel. The response time of the main valve is ≤0.5 seconds, and the backup valve automatically switches when the main valve is detected to be faulty.

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

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

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

6. A method for recycling liquid nitrogen, characterized in that, The liquid nitrogen recycling system for gas cylinder inspection stations as described in any one of claims 1 to 5 includes: Liquid nitrogen is injected into the gas cylinder under test through the liquid nitrogen supply module, the static evaporation rate test module is started, and the liquid nitrogen evaporation rate in the gas cylinder is collected by the multi-channel temperature sensor and flow data acquisition unit to generate a thermal insulation performance evaluation report. The residual liquid nitrogen is pressurized to 0.8~1.2 MPa using a gas cylinder self-pressurization component, and the flow rates of liquid and gaseous nitrogen are monitored in real time using a flow meter; According to the instructions of the pressure feedback controller, an adaptive algorithm is used 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. The gaseous nitrogen in the nitrogen buffer tank is called up, and the replacement interface is automatically matched according to the type of non-liquid nitrogen cylinder. The nitrogen pressure is adjusted to the target value through a multi-stage pressure regulating valve to perform inertization treatment and airtightness test. The central control module monitors the liquid nitrogen storage tank level in real time. When the level is lower than the set threshold, it prioritizes the recovery of liquid nitrogen for the next round of static evaporation rate testing. It also uses an artificial neural network model to predict the amount of external liquid nitrogen replenishment, thus forming a closed-loop resource cycle. The operating data is uploaded to the backend server for remote fault diagnosis and energy efficiency optimization.

7. The method for recycling liquid nitrogen according to claim 6, characterized in that, The pressurization process of the gas cylinder self-pressurization component adopts a segmented pressurization strategy. In the first stage, the pressure is increased to 0.5 MPa at a rate of 0.2 MPa / s, and in the second stage, the pressure is increased to the target pressure at a rate of 0.1 MPa / s to avoid uncontrolled leakage caused by violent vaporization of liquid nitrogen.

8. The method for recycling liquid nitrogen according to claim 6, characterized in that, The inertization process includes: A two-stage replacement method was used for the liquid oxygen cylinder. First, nitrogen was injected at a flow rate of 50 L / min for 5 minutes to replace the oxygen, and then the flow rate was switched to 20 L / min and maintained for 10 minutes to reduce the oxygen concentration in the liquid oxygen cylinder to below 1%. The LNG cylinders are replaced using a pulse-type replacement method, which breaks up residual methane gas clusters by intermittent high-pressure nitrogen injection to improve replacement efficiency.

9. The method for recycling liquid nitrogen according to claim 6, characterized in that, The method of optimizing liquid nitrogen recovery efficiency and nitrogen distribution strategy using an adaptive algorithm includes: An artificial neural network model trained based on historical data is used to predict peak liquid nitrogen demand and initiate external liquid nitrogen replenishment in advance. A dynamic priority allocation strategy is adopted, which automatically adjusts the resource allocation weight based on the urgency of gas cylinder testing and nitrogen reserves.

10. The method for recycling liquid nitrogen according to claim 6, characterized in that, The process of uploading operational data to a backend server and performing remote fault diagnosis and energy efficiency optimization includes: By analyzing historical data through machine learning, system maintenance warnings and optimization instructions are generated; The optimization instructions are sent to the central control module for execution.

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