Liquid oxygen pressurization vaporization and cold energy recovery system

Abstract

The application discloses a liquid oxygen pressurization vaporization and cold energy recovery system. The system comprises a liquid oxygen storage tank for storing low-temperature liquid oxygen; a variable frequency driven plunger pump, the inlet of which is connected with the outlet of the liquid oxygen storage tank, for dynamically pressurizing the liquid oxygen; a partition type electric heater, the inlet of which is connected with the outlet of the plunger pump, for vaporizing the pressurized high-pressure liquid oxygen into high-pressure gaseous oxygen; an oxygen high-pressure storage device, the inlet of which is connected with the outlet of the partition type electric heater, for storing the high-pressure gaseous oxygen; a cold energy recovery channel, the cold energy input end of which is connected with the cold energy release part of the plunger pump, and the cold energy output end of which is connected with the liquid oxygen storage tank, for recovering the cold energy released in the plunger pump pressurization process to the liquid oxygen storage tank; and a variable frequency control system, electrically connected with the plunger pump, for adjusting the operation frequency of the plunger pump in real time according to the downstream gas load. The application effectively reduces the system energy consumption and reduces the cold energy waste.

Description

Technical Field

[0001] This invention relates to the field of cryogenic liquid processing and gas supply technology, and more specifically, to a liquid oxygen pressurization and vaporization and cold energy recovery system. Background Technology

[0002] Liquid oxygen (LOX) is a widely used cryogenic liquid, typically stored in insulated tanks at around -183°C. Before use, liquid oxygen needs to be pressurized and vaporized into high-pressure gaseous oxygen. Traditional liquid oxygen supply systems usually employ a process of "plunger pump pressurization + electric heating or ambient vaporizer".

[0003] However, existing technologies have the following prominent problems: 1. High energy consumption: Plunger pumps mostly operate at a constant frequency and cannot be dynamically adjusted according to the actual gas load, resulting in a large amount of "waste" of electrical energy.

[0004] 2. Significant waste of cooling capacity: Liquid oxygen absorbs a large amount of heat during pressurization and vaporization. At the same time, the cooling capacity released during the mechanical compression process of the plunger pump is usually directly discharged into the environment without any utilization.

[0005] 3. Unstable output: Under variable load conditions, traditional systems are prone to pressure fluctuations and temperature drift, which can affect the safe operation of downstream equipment.

[0006] 4. Low system integration: Each functional module operates independently, lacks coordinated control, and has a low overall energy efficiency ratio.

[0007] Therefore, developing a system that can simultaneously achieve efficient pressurization, stable vaporization, and recovery of cold energy of liquid oxygen is of significant engineering importance and economic value. Summary of the Invention

[0008] This invention provides a liquid oxygen pressurization vaporization and cold energy recovery system to solve the problems of high energy consumption, cold energy waste, and unstable output in the existing liquid oxygen pressurization vaporization process.

[0009] To achieve the above objectives, the present invention provides a method for evaluating the performance of a generator unit. The method includes: a liquid oxygen storage tank for storing cryogenic liquid oxygen; a variable frequency drive plunger pump, the inlet of which is connected to the outlet of the liquid oxygen storage tank for dynamically pressurizing the liquid oxygen; a partition wall electric heater, the inlet of which is connected to the outlet of the plunger pump for vaporizing the pressurized high-pressure liquid oxygen into high-pressure gaseous oxygen; a high-pressure oxygen storage tank, the inlet of which is connected to the outlet of the partition wall electric heater for storing high-pressure gaseous oxygen; a cold energy recovery channel, the cold energy input end of which is connected to the cold energy release section of the plunger pump, and the cold energy output end of which is connected to the liquid oxygen storage tank, for recovering the cold energy released during the pressurization process of the plunger pump back to the liquid oxygen storage tank; and a variable frequency control system electrically connected to the plunger pump for adjusting the operating frequency of the plunger pump in real time according to the downstream gas load.

[0010] Optionally, the frequency conversion control system includes: a frequency converter electrically connected to the drive motor of the plunger pump; a PLC controller communicatively connected to the frequency converter; a pressure sensor installed in the oxygen high-pressure storage tank or downstream gas supply pipeline, with its signal output terminal connected to the PLC controller; and a flow sensor installed in the downstream gas supply pipeline, with its signal output terminal connected to the PLC controller. The PLC controller outputs a frequency setpoint to the frequency converter based on the feedback signals from the pressure sensor and the flow sensor through PID calculation.

[0011] Optionally, the cold energy recovery channel includes a low-temperature control valve, installed on the pipeline of the cold energy recovery channel, for adjusting the flow rate of the recovered cold energy.

[0012] Optionally, the indirect-wall electric heater has a shell-and-tube structure, wherein: the tube side is used for the flow of high-pressure liquid oxygen, and the tube side material is low-temperature resistant stainless steel; the shell side is equipped with an electric heating element, and the shell side material is carbon steel; the tube side and the shell side exchange heat indirectly through the metal wall; a temperature sensor is provided at the outlet of the electric heater, and its signal is fed back to the frequency conversion control system to adjust the heating power.

[0013] Optionally, a closed-loop monitoring module for end-to-end parameters is also included. This module includes: multiple temperature sensors, respectively installed in the liquid oxygen storage tank, the plunger pump outlet, the indirect-contact electric heater outlet, and the cold energy recovery channel; and multiple pressure sensors, respectively installed in the plunger pump outlet, the indirect-contact electric heater outlet, and the high-pressure oxygen storage tank. The signals from the temperature and pressure sensors are all connected to the frequency converter control system, which performs overpressure shutdown, overtemperature power cut-off, or valve adjustment protection actions according to preset safety thresholds.

[0014] Optionally, the inlet end of the plunger pump is equipped with a pressure maintaining valve, which is linked to the outlet of the cold energy recovery channel through a pipeline to maintain the subcooling of the liquid oxygen at the inlet of the plunger pump by recovering cold energy, thereby preventing cavitation inside the pump.

[0015] Optionally, the system adopts a modular structure, including: a pressurization module that can be independently disassembled and assembled, which includes at least a plunger pump and a frequency converter; a vaporization module that can be independently disassembled and assembled, which includes at least a partition electric heater; and a cold energy recovery module that can be independently disassembled and assembled, which includes at least a cold energy recovery channel and a cryogenic control valve; the modules are connected to each other through standard cryogenic flanges or vacuum insulated joints.

[0016] The beneficial effects of this invention are: This invention provides a liquid oxygen pressurization and vaporization system with cold energy recovery. The system uses a variable frequency driven plunger pump to dynamically adjust the frequency of pressurization according to the downstream load, vaporizes the oxygen at a controllable temperature via a partition electric heater, and establishes a cold energy recovery channel to return the cold energy released during the pressurization process to the liquid oxygen storage tank. This effectively solves the technical problems in existing technologies, such as high energy consumption due to the constant frequency operation of the plunger pump, energy waste caused by the direct discharge of a large amount of cold energy during pressurization and vaporization, and unstable output pressure and temperature. It achieves a comprehensive effect: variable frequency control matches the pump power with the actual gas load in real time to avoid no-load and overload energy consumption; recovers the cold energy directly lost in the traditional process to maintain the low temperature state of the storage tank and the subcooling of the plunger pump inlet to reduce natural evaporation losses in the storage tank and suppress cavitation within the pump; and ensures stable output oxygen pressure and temperature through closed-loop control throughout the entire process. This results in substantial progress in reducing operating costs, improving energy utilization, and ensuring gas supply quality. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of a liquid oxygen pressurization vaporization and cold energy recovery system provided in an embodiment of the present invention.

[0018] Symbol explanation: Liquid oxygen storage tank-1, plunger pump-2, indirect electric heater-3, high-pressure oxygen storage tank-4, cold energy recovery channel-5, frequency conversion control system-6. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0020] Figure 1 This is a schematic diagram of a liquid oxygen pressurization vaporization and cold energy recovery system provided in an embodiment of the present invention; as shown below. Figure 1 As shown, the system includes: 1. Liquid oxygen storage tank 1, used for storing cryogenic liquid oxygen; Specifically, it adopts a high-vacuum multi-layer insulation structure with a volume of 50m³. 3 Designed with a pressure of 1.0 MPa and an operating temperature of -183℃, this tank is used for storing cryogenic liquid oxygen. The tank body is made of austenitic stainless steel S30408, with perlite filling between the inner and outer cylinders and a vacuum of ≤0.001 Pa to ensure a daily evaporation rate of ≤0.3%. The tank top is equipped with a safety valve, pressure gauge, and level gauge, while the bottom has a drain port and a sludge drain port.

[0021] 2. A variable frequency driven plunger pump 2, the inlet of which is connected to the outlet of the liquid oxygen storage tank 1, is used to dynamically pressurize the liquid oxygen; Specifically, a cryogenic reciprocating plunger pump 2, model BPO-2000 / 35, is selected, with a rated flow rate of 2000 L / h and a maximum output pressure of 35 MPa. The pump head and plunger seals are made of cryogenic 316L stainless steel and polytetrafluoroethylene composite material. The inlet of the plunger pump 2 is connected to the outlet flange of the liquid oxygen storage tank 1 via a DN40 cryogenic insulated pipe for dynamic pressurization of the liquid oxygen. A cold energy collection jacket is provided on the outside of the pump body as a cold energy release point.

[0022] 3. A partition wall electric heater 3, the inlet of which is connected to the outlet of the plunger pump 2, is used to vaporize the pressurized high-pressure liquid oxygen into high-pressure gaseous oxygen. Specifically, its inlet is connected to the outlet of the plunger pump 2 via a DN25 high-pressure cryogenic pipeline, used to vaporize the pressurized high-pressure liquid oxygen into high-pressure gaseous oxygen. In this embodiment, the heater is designed to operate at a pressure of 40 MPa, with an outlet oxygen temperature adjustment range of -50°C to +60°C and a rated heating power of 150 kW.

[0023] 4. High-pressure oxygen storage device 4, the inlet of which is connected to the outlet of the partition electric heater 3, for storing high-pressure gaseous oxygen; Specifically, its inlet is connected to the outlet of the indirect-contact electric heater 3 via a DN25 high-pressure stainless steel pipe for storing high-pressure gaseous oxygen. The storage tank has a volume of 10m³. 3 It is designed for a pressure of 35MPa, made of 35CrMoA forged steel, with standard elliptical heads at both ends, and equipped with a safety relief device and a pressure gauge interface.

[0024] 5. Cold energy recovery channel 5, whose cold energy input end is connected to the cold energy release part of the plunger pump 2, and whose cold energy output end is connected to the liquid oxygen storage tank 1, is used to recover the cold energy released during the pressurization process of the plunger pump 2 to the liquid oxygen storage tank 1. Specifically, its cold energy input end is connected to the cold energy release part of the plunger pump 2 (i.e., the cold energy collection jacket outside the pump body), and its cold energy output end is connected to the upper gas phase inlet or lower liquid phase inlet of the liquid oxygen storage tank 1 through a DN20 cryogenic pipeline, for recovering the cold energy released during the pressurization process of the plunger pump 2 back to the liquid oxygen storage tank 1. This channel adopts a vacuum-insulated double-layer tube structure, with the inner tube being 316L stainless steel and the outer tube being 304 stainless steel, and the pressure of the intermediate vacuum layer being ≤0.01Pa.

[0025] 6. Variable frequency control system 6, which is electrically connected to the plunger pump 2, is used to adjust the operating frequency of the plunger pump 2 in real time according to the downstream gas load.

[0026] Specifically, the frequency converter control system 6 is electrically connected to the drive motor of the plunger pump 2, and is used to adjust the operating frequency of the plunger pump 2 in real time according to the downstream gas load. The frequency converter control system 6 is installed in an explosion-proof control cabinet, has local / remote switching function, and communicates with the central control room via a Profibus DP bus.

[0027] In an optional implementation, the frequency conversion control system 6 includes: The frequency converter is electrically connected to the drive motor of the plunger pump 2; The PLC controller communicates with the frequency converter. The pressure sensor is installed in the oxygen high-pressure storage tank 4 or the downstream gas supply line, and its signal output terminal is connected to the PLC controller. A flow sensor is installed in the downstream gas supply pipeline, and its signal output terminal is connected to a PLC controller. The PLC controller outputs a frequency setpoint to the frequency converter through PID calculation based on the feedback signals from the pressure sensor and the flow sensor.

[0028] Specifically, the frequency converter is an ABB ACS880-01-09A4-3 model with a rated power of 22kW, which is electrically connected to the drive motor of plunger pump 2 (a three-phase asynchronous motor, 380V / 50Hz, 18.5kW). The frequency converter has a built-in EMC filter and a brake chopper, supports V / F control and vector control modes, and has a control accuracy of ±0.1Hz.

[0029] The PLC controller uses a Siemens S7-1200 series CPU 1214C DC / DC / DC converter, which connects to the frequency converter via an RS485 communication interface using the Modbus RTU communication protocol. The PLC controller has an embedded PID calculation function block with a scan cycle of 100ms.

[0030] The pressure sensor is installed on the downstream gas supply line of the oxygen high-pressure storage tank outlet 4. It has a range of 0~40MPa, an output signal of 4-20mA, and an accuracy class of 0.5. Its signal output terminal is connected to the analog input module (SM1231 AI 8×13bit) of the PLC controller via a shielded cable.

[0031] The flow sensor is installed downstream of the pressure sensor in the gas supply pipeline. A thermal mass flow meter with a range of 0~1000 Nm is selected. 3 The output signal is 4-20mA with an accuracy of ±1.5%FS. Its signal output terminal is also connected to the analog input module of the PLC controller.

[0032] During operation, the PLC controller reads the feedback signals from the pressure and flow sensors in real time. When the downstream gas consumption increases, causing a drop in pipeline pressure, the PID calculation block inside the PLC controller automatically increases the frequency setpoint based on the deviation between the pressure setpoint (e.g., 25 MPa) and the actual pressure value; conversely, it decreases the frequency setpoint. This frequency setpoint is written to the frequency converter via Modbus communication, and the frequency converter adjusts the output frequency accordingly, thereby changing the speed and output flow of the plunger pump 2. The PID parameters, after on-site tuning, are determined as follows: proportional coefficient Kp = 0.8, integral time Ti = 2.0 s, derivative time Td = 0.2 s, response time less than 1.5 seconds, and overshoot ≤ 5%.

[0033] In an optional implementation, the cold energy recovery channel 5 includes: The cryogenic control valve is installed on the pipeline of the cold energy recovery channel 5 and is used to regulate the flow rate of the recovered cold energy.

[0034] Specifically, the cryogenic control valve is installed on the pipeline of the cold energy recovery channel 5, specifically in the middle section of the cold energy recovery channel 5, approximately 1.5m from the cold energy input end. This valve is a pneumatic bellows-sealed gate valve, model DJ61Y-320P, with a nominal diameter of DN20, applicable medium temperature of -196℃ to +80℃, valve body material of CF8M (equivalent to 316L stainless steel), bellows material of Inconel 625, and Stellite alloy overlay on the sealing surface. The valve is equipped with a pneumatic actuator (double-acting, air source pressure 0.4~0.6MPa) and an electric positioner (4-20mA input) to regulate the flow rate of recovered cold energy, with an opening adjustment range of 0~100% and a control accuracy of ±1.5%.

[0035] In this embodiment, the cold energy recovery channel 5 also includes auxiliary components: a cryogenic insulated pipeline (double-layer vacuum insulation, heat leakage rate ≤2W / m), a cold energy collection jacket (welded to the outer wall of the outlet section of the plunger pump 2, filled with thermally conductive silicone grease), and a return liquid distributor (installed inside the liquid oxygen storage tank 1, with a ring-shaped spray pipe structure, evenly distributed). A 2mm orifice ensures that the recovered cold energy is evenly distributed on the surface of the liquid oxygen inside the tank. The opening of the cryogenic control valve is automatically adjusted by the frequency conversion control system 6 according to the current operating frequency of the plunger pump 2: when the frequency increases (high load), the valve opening increases, and the amount of cold energy recovered increases; when the frequency decreases (low load), the valve opening decreases to avoid overcooling of the storage tank.

[0036] In an optional embodiment, the indirect-contact electric heater 3 has a shell-and-tube structure, comprising: a tube side and a shell side; wherein: The tube side is used to flow high-pressure liquid oxygen, and the tube side material is low-temperature resistant stainless steel. The shell side is equipped with an electric heating element, and the shell side material is carbon steel; Heat exchange occurs indirectly between the tube side and the shell side through the metal wall. A temperature sensor is installed at the outlet of the electric heater, and its signal is fed back to the frequency conversion control system 6 to adjust the heating power.

[0037] Specifically, the tube side is used to flow high-pressure liquid oxygen. The tube side consists of 19 tubes. It consists of 12 × 1.5mm U-shaped tubes, made of low-temperature resistant 316L stainless steel (chemical composition conforming to ASTM A213 standard), with a tube length of 2500mm and a heat exchange area of ​​3.2m². 2 The design pressure of the pipe is 35 MPa, the test pressure is 52.5 MPa, and the liquid oxygen flow rate inside the pipe is controlled within the range of 1.5~2.5 m / s.

[0038] Heating elements are installed inside the shell side. The shell-side cylinder is... The seamless steel pipe measures 273×8mm and is made of Q345R carbon steel. Nine U-shaped electric heating elements are installed inside the shell, each with a power of 16.7kW, for a total rated power of 150kW. The heating elements are made of Incoloy 840, and the surface heat load is ≤3.5W / cm². 2 The heating elements are arranged in a triangular pattern, interspersed with the U-shaped tubes in the tube side, to enhance convective heat transfer.

[0039] Heat exchange occurs indirectly between the tube side and the shell side via the metal wall. When the heating element is energized, it generates heat, which is transferred through the shell-side medium (air or nitrogen) to the inner wall of the U-shaped tube, and then conducted through the tube wall to the liquid oxygen in the tube side, causing it to vaporize and heat up. There is no direct contact between the tube side and the shell side; heat exchange is entirely achieved through the metal wall, ensuring the oxygen purity remains uncontaminated.

[0040] A PT100 platinum resistance temperature sensor is installed at the outlet of the electric heater. The probe is inserted to the center of the pipe, with a temperature measurement range of -200℃ to +200℃ and an accuracy of Class A. The signal from this temperature sensor is fed back to the frequency conversion control system 6 (specifically, the analog input module of the PLC controller) via a 4-20mA transmitter. The PLC controller compares the measured outlet temperature with the set value (e.g., 20℃) and outputs a 4-20mA signal through PID calculation to control the thyristor power regulator of the heating element, thereby adjusting the heating power and stabilizing the outlet oxygen temperature within the target value ±3℃ range.

[0041] In addition, the electric heater is equipped with the following auxiliary components: shell-side over-temperature protection switch (operating temperature 150℃), tube-side safety valve (set pressure 38MPa), and grounding terminal (grounding resistance ≤4Ω).

[0042] In an optional implementation, the system further includes a full-link parameter closed-loop monitoring module, which includes: Multiple temperature sensors are respectively installed in the liquid oxygen storage tank 1, the outlet of the plunger pump 2, the outlet of the indirect electric heater 3, and the cold energy recovery channel 5; Multiple pressure sensors are respectively installed at the outlet of the plunger pump 2, the outlet of the indirect electric heater 3, and the oxygen high-pressure storage tank 4; The signals from the temperature sensor and the pressure sensor are both connected to the frequency converter control system 6. The frequency converter control system 6 performs overpressure shutdown, overtemperature power cut-off, or valve adjustment protection actions according to the preset safety threshold.

[0043] Specifically, the arrangement of multiple temperature sensors: First temperature sensor: installed inside liquid oxygen storage tank 1, specifically in the liquid phase zone in the middle of the tank, used to monitor the temperature of liquid oxygen inside the tank, with a range of -200℃ to +50℃.

[0044] The second temperature sensor is located on the outlet pipe of the plunger pump 2, 0.3m away from the pump outlet flange. It is used to monitor the temperature of the liquid oxygen after pressurization, with a range of -200℃ to +50℃.

[0045] The third temperature sensor is installed on the outlet pipe of the partition electric heater 3 and is used to monitor the temperature of the vaporized oxygen, with a range of -50℃ to +100℃.

[0046] The fourth temperature sensor is located in the cold energy recovery channel 5, 0.2m upstream of the low-temperature control valve. It is used to monitor the temperature of the medium recovering cold energy, with a range of -200℃ to +50℃.

[0047] Arrangement of multiple pressure sensors: First pressure sensor: installed on the outlet pipe of plunger pump 2, in the same pipe section as the second temperature sensor, with a range of 0~40MPa.

[0048] The second pressure sensor is installed on the outlet pipe of the partition electric heater 3, in the same pipe section as the third temperature sensor, with a range of 0~40MPa.

[0049] The third pressure sensor is located at the top gas phase port of the high-pressure oxygen storage tank 4 and is used to monitor the pressure inside the storage tank, with a range of 0~40MPa.

[0050] Signal access and protection actions: All signals from temperature and pressure sensors (4-20mA or PT100 resistance signals) are connected to the frequency converter control system 6 (the analog input module of the PLC controller) via shielded cables. The PLC controller has a preset safety threshold table, as follows:

[0051] When any parameter exceeds the protection threshold, the PLC controller executes the corresponding action according to preset logic: for overpressure, it automatically reduces the inverter frequency or opens the pressure relief valve; for overtemperature, it cuts off the electric heater power supply; for abnormal cold energy recovery, it closes the low-temperature control valve and switches to direct discharge mode. All protection actions are completed within 50ms to ensure system safety. Simultaneously, the PLC controller uploads alarm information to the central control room touchscreen and records it in the historical data storage area.

[0052] In an optional embodiment, the inlet end of the plunger pump 2 is provided with a pressure maintaining valve, which is linked to the outlet of the cold energy recovery channel 5 through a pipeline to maintain the subcooling of the liquid oxygen at the inlet of the plunger pump 2 by recovering cold energy, thereby preventing cavitation inside the pump.

[0053] Specifically, the pressure maintaining valve is installed on the inlet pipe of plunger pump 2, 0.2m away from the pump inlet flange. This valve is a self-operated back pressure valve, model KAP-3M, with a nominal diameter of DN40, a set pressure of 0.6MPa (adjustable range 0.3~1.0MPa), a valve body material of CF8M, and a valve core material of Stellite alloy. When the inlet pressure is lower than the set value, the valve automatically closes to increase the back pressure; when the inlet pressure is higher than the set value, the valve automatically opens to reduce the back pressure.

[0054] A DN15 branch pipe extends from the outlet of cold energy recovery channel 5 (located after the cryogenic control valve) and connects to the pilot port of the pressure maintaining valve. This branch pipe also employs a vacuum-insulated structure to guide a portion of the recovered cold energy to the vicinity of the temperature sensing element of the pressure maintaining valve.

[0055] The working principle is as follows: When plunger pump 2 is operating, its inlet requires sufficient net positive suction head (NPSH) and a certain degree of subcooling to prevent liquid oxygen from vaporizing and causing cavitation within the pump chamber. When the cold energy recovery channel 5 returns the cold energy released during the pressurization process of plunger pump 2 to liquid oxygen storage tank 1, the temperature of the liquid oxygen in the storage tank is maintained or even further reduced (the subcooling increases). When this portion of cryogenic liquid oxygen enters the inlet pipe of plunger pump 2 through the outlet of liquid oxygen storage tank 1, its temperature is significantly lower than the saturation temperature under normal operating conditions.

[0056] The linkage pipeline directs some of the cooling energy from the cooling energy recovery channel 5 to the pilot port of the pressure maintaining valve, causing the temperature sensing element of the pressure maintaining valve to detect a lower temperature. This slightly adjusts the valve's opening characteristics—specifically, at the same inlet pressure, the valve opening is slightly smaller than when there is no cooling energy recovery, resulting in a slight increase in the actual back pressure at the pump inlet. This increased back pressure, combined with the increased subcooling, significantly reduces the risk of liquid oxygen vaporization within the pump chamber.

[0057] Actual measurements show that in a traditional system without cold energy recovery, when the inlet liquid oxygen temperature of the plunger pump 2 is -183℃ (saturated state), the inlet pressure needs to be maintained above 0.65MPa to prevent cavitation. However, in this embodiment, by subcooling the inlet liquid oxygen to -188℃ through the cold energy recovery channel 5, the inlet pressure only needs to be 0.50MPa to meet the anti-cavitation requirements. This not only reduces the pump inlet head requirement but also reduces the self-pressurization energy consumption of the liquid oxygen storage tank 1, while extending the lifespan of the seals and plunger of the plunger pump 2.

[0058] In an optional implementation, the system employs a modular structure, including: The independently detachable booster module includes at least a plunger pump 2 and a frequency converter; The vaporization module, which can be detached and installed independently, includes at least a partition-type electric heater 3; The independently detachable cold energy recovery module includes at least a cold energy recovery channel 5 and a low-temperature control valve; The modules are connected by standard cryogenic flanges or vacuum insulated joints.

[0059] Specifically, the booster module includes at least a plunger pump 2 and a frequency converter. Specifically, this module includes the plunger pump 2, the frequency converter, some I / O modules in the frequency conversion control system 6, an inlet filter (50μm accuracy), an outlet check valve, and a DN40 cryogenic flange for connecting the pump body to the pipeline. The booster module is mounted on a common base (1.2m × 0.8m, welded channel steel), with adjustable vibration damping pads at the four corners. All interfaces between the module and external pipelines use standard cryogenic flanges (HG / T20592-2009), and electrical interfaces use aviation plugs (IP67 protection rating). This module can be disassembled, transported, and replaced individually without welding.

[0060] Vaporization Module: Includes at least a partitioned electric heater 3. Specifically, this module includes the electric heater body, a thyristor power regulator, an outlet temperature sensor, and DN25 high-pressure pipe fittings at the inlet and outlet. The vaporization module is mounted on an independent bracket (1.0m × 0.6m), with a grounding terminal on the side of the bracket. The vaporization module is connected to the booster module via a vacuum-insulated connector (DN25, with a metal sealing gasket), and to the oxygen high-pressure storage tank 4 via a high-pressure hose (1.5m long, 40MPa pressure rating). The vaporization module can be completely removed and replaced within 30 minutes.

[0061] The cold energy recovery module includes at least a cold energy recovery channel 5 and cryogenic control valves. Specifically, this module includes a cold energy collection jacket (welded to the outlet section of plunger pump 2, but the jacket itself is removable), a vacuum-insulated double-layer pipe (length 3~15m, customizable according to site requirements), cryogenic control valves and pneumatic actuators, an electric positioner, and a return port distributor (installed inside the storage tank, but the modular interface is at the external flange of the storage tank). The module's interface is a DN20 cryogenic flange and a 4-20mA control signal aviation connector. The cold energy recovery module can be repaired or replaced independently of the pressurization module and the vaporization module.

[0062] Inter-module connection methods: The process piping connections between modules use standard cryogenic flanges (PN40, DN20 / DN25 / DN40, with RJ ring connection face for sealing), equipped with 304 stainless steel spiral wound gaskets and 35CrMoA double-ended studs.

[0063] For parts that require quick disassembly and assembly (such as between the vaporization module and the booster module), a vacuum insulated connector (VCR type, 1 / 2 inch) is used. The connector has a metal gasket inside, which can be disassembled and assembled within 10 minutes without the need for adhesive.

[0064] The electrical signal lines are connected using aviation plugs, with plug type M12 (4-pin, A code) and a waterproof and dustproof rating of IP67.

[0065] In this embodiment, the technical effects brought about by the modular structure include: Easy to transport and install: Each module weighs no more than 300kg and can be moved by forklift or handcart. On-site, it can be put into use simply by connecting flanges and aviation plugs.

[0066] Easy to maintain and replace: If any module fails, the entire module can be replaced with a spare module without stopping the system (or with a short-term shutdown). The faulty module can be returned to the factory for repair, and the system availability rate reaches over 99.5%.

[0067] Easy to expand: In continuous industrial gas supply scenarios, a second set of booster module and a second set of vaporization module can be added in parallel, sharing the original liquid oxygen storage tank 1 and cold energy recovery module (or expanding the cold energy recovery channel 5), and the gas supply capacity can be increased to 200%.

[0068] The following example, a complete startup-run-shutdown process, further illustrates the specific implementation of the present invention.

[0069] Preparations before startup: 1. Confirm that the liquid oxygen content in liquid oxygen storage tank 1 is ≥20% (as shown by the level gauge) and the pressure inside the tank is 0.3~0.5MPa.

[0070] 2. Check that all flange connection bolts are tight and that electrical aviation plugs are in place.

[0071] 3. Power on the frequency converter control system 6. The PLC controller passes the self-test, and the touch screen displays the initial values ​​of each sensor.

[0072] 4. Set target parameters: downstream gas supply pressure 25MPa, outlet oxygen temperature 20℃.

[0073] 5. Open the low-temperature control valve of cold energy recovery channel 5 to 30% opening (pre-cooling stage).

[0074] Start-up phase: 1. The operator presses the "System Start" button on the touchscreen.

[0075] 2. The PLC controller first starts the frequency converter of plunger pump 2, running it at the lowest frequency of 15Hz for 30 seconds, so that liquid oxygen slowly fills the pump chamber and pipeline, avoiding liquid slugging.

[0076] 3. After 30 seconds, the PLC controller will increase the frequency to 25Hz (initial operating frequency), and the plunger pump 2 will start to pressurize normally, with the outlet pressure gradually increasing.

[0077] 4. When the outlet pressure of the plunger pump 2 reaches 20MPa, the PLC controller starts the partition electric heater 3 with an initial heating power of 30kW, and the outlet temperature of the electric heater begins to rise.

[0078] 5. Once the pressure in the high-pressure oxygen storage tank 4 reaches 22MPa and the outlet temperature of the electric heater reaches 15℃, the system automatically opens the downstream gas supply valve and begins to supply gas downstream.

[0079] Steady-state operation phase: 1. The variable frequency control system 6 reads the signals from the downstream pressure sensor and flow sensor in real time, and dynamically adjusts the operating frequency of the plunger pump 2 (which varies between 25 and 50 Hz) through PID calculation, so that the downstream pressure is stabilized at 25 MPa ± 0.5 MPa.

[0080] 2. The opening of the low-temperature control valve of the cold energy recovery channel 5 is automatically adjusted according to the frequency of the plunger pump 2: when the frequency is below 30Hz, the valve opening is 20%~30%; when the frequency is 30~40Hz, the valve opening is 40%~60%; when the frequency is above 40Hz, the valve opening is 70%~90%.

[0081] 3. The recovered cold energy is returned to the liquid oxygen storage tank 1 through the cold energy recovery channel 5 to maintain the liquid oxygen temperature in the tank between -185℃ and -190℃ (supercooled state).

[0082] 4. The pressure maintaining valve is linked to the outlet of the cold energy recovery channel 5, and automatically adjusts the back pressure according to the inlet liquid oxygen temperature to ensure that the net positive suction head at the inlet of the plunger pump 2 always meets the anti-cavitation requirements.

[0083] 5. The full-link parameter closed-loop monitoring module continuously monitors all temperature and pressure points, refreshing every 100ms. If any parameter exceeds the limit, a protection action is immediately triggered.

[0084] Shutdown phase: 1. The operator presses the "System Stop" button on the touchscreen.

[0085] 2. The PLC controller first shuts off the downstream gas supply valve.

[0086] 3. Gradually reduce the frequency of the plunger pump 2 inverter (reducing by 5Hz every 5 seconds) until it reaches 5Hz, while gradually reducing the power of the electric heater.

[0087] 4. When the outlet pressure of plunger pump 2 drops below 5MPa, stop plunger pump 2 and electric heater.

[0088] 5. Continue running the cold energy recovery channel 5 for 10 minutes to recover all residual cold energy, and then close the low temperature control valve.

[0089] 6. The system enters standby mode, and the liquid oxygen storage tank 1 and the high-pressure oxygen storage device 4 remain pressurized and ready for use.

[0090] To ensure the safety and durability of the system in liquid oxygen (strong oxidizing agent, ultra-low temperature) conditions, this embodiment proposes the following material and process requirements for all components in contact with liquid oxygen: 1. Degreasing and Cleaning: All pipes, valves, pump heads, and heater tubing must undergo rigorous degreasing before assembly. Carbon tetrachloride or trichloroethylene is used as the degreasing agent. After degreasing, inspect with a UV lamp (no fluorescence) or wipe with clean filter paper (no oil spots). Residual grease content ≤125mg / m³. 2 After degreasing, the parts should be sealed and packaged immediately to prevent secondary contamination.

[0091] 2. Passivation treatment: Stainless steel parts (316L, 304) need to be pickled and passivated after degreasing. The pickling solution is 15% nitric acid + 3% hydrofluoric acid. Soak at room temperature for 30 minutes, then rinse with deionized water until the pH is neutral. The passivation film thickness should be ≥50nm.

[0092] 3. Welding Process: All low-temperature, high-pressure pipeline welds are welded using argon arc welding (GTAW) with welding wire grade ER316L or ER308L. Post-weld, 100% radiographic testing (RT) is performed, achieving Level II qualification. Welds undergo deep cryogenic treatment with liquid nitrogen (immersion at -196℃ for 2 hours) followed by re-inspection; no cracks are found.

[0093] 4. Seal selection: All static seals use stainless steel spiral wound gaskets (with inner and outer rings) or metal O-rings (silver plated); dynamic seals (plunger pump 2) use PTFE + carbon fiber composite packing and are equipped with leakage detection ports.

[0094] 5. Electrical explosion protection: The frequency converter, PLC control cabinet and sensor junction box all meet the Ex db ⅡB T4 explosion protection level. The cables are flame-retardant armored cables and are laid in conduits.

[0095] The beneficial effects of this invention are: This invention provides a liquid oxygen pressurization and vaporization system with cold energy recovery. The system uses a variable frequency driven plunger pump 2 to dynamically adjust the frequency of pressurization according to the downstream load, vaporizes the oxygen at a controllable temperature via a partition electric heater 3, and includes a cold energy recovery channel 5 to return the cold energy released during the pressurization process of the plunger pump 2 to the liquid oxygen storage tank 1. This effectively solves the technical problems in the prior art, such as high energy consumption due to the constant frequency operation of the plunger pump 2, energy waste caused by the direct discharge of a large amount of cold energy during pressurization and vaporization, and unstable output pressure and temperature. It achieves a comprehensive effect: variable frequency control matches the pump power with the actual gas load in real time to avoid no-load and overload energy consumption; recovers the cold energy directly lost in the traditional process to maintain the low temperature state of the storage tank and the subcooling of the plunger pump 2 inlet to reduce natural evaporation loss in the storage tank and suppress cavitation within the pump; and ensures stable output oxygen pressure and temperature through closed-loop control throughout the entire process. This results in substantial progress in reducing operating costs, improving energy utilization, and ensuring gas supply quality.

[0096] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A liquid oxygen pressurization vaporization and cold energy recovery system, characterized in that, include: Liquid oxygen storage tanks are used to store cryogenic liquid oxygen. A variable frequency driven plunger pump, the inlet of which is connected to the outlet of the liquid oxygen storage tank, is used to dynamically pressurize the liquid oxygen. A partition wall electric heater, the inlet of which is connected to the outlet of the plunger pump, is used to vaporize the pressurized high-pressure liquid oxygen into high-pressure gaseous oxygen. An oxygen high-pressure storage device, the inlet of which is connected to the outlet of the indirect-contact electric heater, is used to store high-pressure gaseous oxygen; The cold energy recovery channel has its cold energy input end connected to the cold energy release part of the plunger pump and its cold energy output end connected to the liquid oxygen storage tank, which is used to recover the cold energy released during the pressurization process of the plunger pump to the liquid oxygen storage tank. The variable frequency control system is electrically connected to the plunger pump and is used to adjust the operating frequency of the plunger pump in real time according to the downstream gas load.

2. The system according to claim 1, characterized in that, The frequency conversion control system includes: The frequency converter is electrically connected to the drive motor of the plunger pump; The PLC controller communicates with the frequency converter. The pressure sensor is installed in the high-pressure oxygen storage tank or downstream gas supply line, and its signal output terminal is connected to the PLC controller. A flow sensor is installed in the downstream gas supply pipeline, and its signal output terminal is connected to a PLC controller. The PLC controller outputs a frequency setpoint to the frequency converter through PID calculation based on the feedback signals from the pressure sensor and the flow sensor.

3. The system according to claim 1, characterized in that, The cold energy recovery channel includes: The cryogenic control valve is installed on the pipeline of the cold energy recovery channel to regulate the flow rate of recovered cold energy.

4. The system according to claim 1, characterized in that, The indirect-contact electric heater has a shell-and-tube structure, wherein: The tube side is used to flow high-pressure liquid oxygen, and the tube side material is low-temperature resistant stainless steel. The shell side is equipped with an electric heating element, and the shell side material is carbon steel; Heat exchange occurs indirectly between the tube side and the shell side through the metal wall. A temperature sensor is installed at the outlet of the electric heater, and its signal is fed back to the frequency conversion control system to adjust the heating power.

5. The system according to claim 1, characterized in that, It also includes a full-link parameter closed-loop monitoring module, which includes: Multiple temperature sensors are respectively installed in the liquid oxygen storage tank, the plunger pump outlet, the indirect electric heater outlet, and the cold energy recovery channel; Multiple pressure sensors are respectively installed at the outlet of the plunger pump, the outlet of the indirect electric heater, and the oxygen high-pressure storage tank; The signals from the temperature and pressure sensors are both connected to the frequency converter control system. The frequency converter control system performs overpressure shutdown, overtemperature power cut-off, or valve adjustment protection actions according to the preset safety threshold.

6. The system according to claim 1, characterized in that: The plunger pump is equipped with a pressure maintaining valve at its inlet end. This pressure maintaining valve is linked to the outlet of the cold energy recovery channel through a pipeline. The recovered cold energy is used to maintain the subcooling of the liquid oxygen at the inlet of the plunger pump and prevent cavitation inside the pump.

7. The system according to claim 1, characterized in that, The system adopts a modular structure, including: The booster module, which can be detached and installed independently, includes at least a plunger pump and a frequency converter; The vaporization module, which can be detached and installed independently, includes at least a partition-type electric heater; The independently detachable cold energy recovery module includes at least a cold energy recovery channel and a low-temperature control valve; The modules are connected by standard cryogenic flanges or vacuum insulated joints.

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