Liquid air energy storage liquefaction automatic control system

Abstract

The utility model discloses a kind of liquid air energy storage liquefaction automatic control systems, including the heat storage module for recovering air compression heat, the liquefied energy storage module for liquefying and storing air and control module, heat storage module is connected with liquefied energy storage module and provides heat stream to liquefied energy storage module, heat storage module, liquefied energy storage module is electrically connected with control module respectively;The utility model cooperates through heat storage module, liquefied energy storage module, control module, realizes the automatic control of liquid air energy storage liquefaction, solves the problem that liquefied energy storage system variable is multiple and exists coupling between variable, leading to liquefied system frequent start-stop, guarantees the safe and efficient operation of liquefied system.

Description

Technical Field

[0001] This utility model relates to the technical field of liquefied energy storage systems, specifically to an automatic control system for liquid air energy storage liquefaction. Background Technology

[0002] Against the backdrop of a "dual carbon" environment, my country's installed capacity of new energy sources, primarily photovoltaic and wind power, has surpassed that of thermal power. The intermittent and unstable nature of new energy sources also increases the pressure on large-scale grid connection and safe, stable operation, significantly limiting the large-scale application of renewable energy. To achieve widespread utilization of renewable energy, address its transient and unstable nature, and resolve the mismatch between energy supply and demand, energy storage technology plays a crucial role. Large-scale energy storage technology is an important strategic area for technological innovation worldwide and a major direction for achieving technological leadership.

[0003] Among various energy storage technologies, pumped hydro storage, large-capacity battery energy storage, and compressed air energy storage are the main ones that can be applied on a large scale. Pumped hydro storage depends on specific terrain, while compressed air energy storage requires underground salt caverns or gas storage caverns, limiting its applicable scenarios. Large-capacity battery energy storage deployment suffers from high costs, short cycle life, safety hazards, and environmental recycling challenges. Liquid air energy storage, as one of the compressed air energy storage technology routes, is a new type of large-scale grid energy storage technology with outstanding advantages such as high energy density, no geographical restrictions on site selection, high safety, and long life. It can be widely used in renewable energy consumption, grid peak shaving and frequency regulation, black start, distributed energy, and integrated energy services. The density of liquid air is much greater than that of compressed air, and its energy density (power generation per unit volume) is 15-20 times that of compressed air energy storage. It does not require special geographical conditions (salt caverns, artificial chambers, abandoned mines) or a large number of high-pressure containers, and the system has no safety issues. Based on its significant advantages, liquid air energy storage is expected to become one of the most promising new energy storage technologies.

[0004] Liquid air energy storage consists of a liquefaction system and a power generation system. The liquefaction system operates during the energy storage phase, while the power generation system operates during the energy release phase. The liquefaction system involves numerous process devices and control variables, which are coupled together. The system is time-varying and nonlinear, with significant inertia, making automatic operation difficult. Drastic changes in any parameter can lead to deviations in operating conditions, resulting in frequent start-ups and shutdowns of the liquid air energy storage liquefaction system. This places high pressure and workload on personnel, increases the risk of operational errors, and hinders the safe and efficient operation of the liquefaction system. Utility Model Content

[0005] The technical problem to be solved by this utility model is to provide an automatic control system for liquid air energy storage liquefaction, which can realize the automatic operation and regulation of the liquid air energy storage liquefaction system, reduce the workload of personnel and reduce the risk of misoperation under high-intensity work, and ensure the safe and efficient operation of the liquefaction system.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by this utility model is as follows.

[0007] An automatic control system for liquid air energy storage and liquefaction includes a heat storage module for recovering the heat of air compression, a liquefaction energy storage module for liquefying and storing air, and a control module. The heat storage module is connected to the liquefaction energy storage module and provides a heat flow stream to the liquefaction energy storage module. The heat storage module and the liquefaction energy storage module are electrically connected to the control module. The heat storage module includes, in sequence, an air compressor, an air compressor cooler, a molecular sieve, a booster compressor, a booster compressor cooler, a booster turbine expander booster, and a booster cooler. The air compressor cooler, booster compressor cooler, and booster are also connected in sequence. The cooling water inlet of the cooler is connected to the outlet of the cold water storage tank, and the cooling water outlet of the air compressor cooler, the booster cooler, and the booster cooler is connected to the inlet of the hot water storage tank. The liquefied energy storage module includes a cold box heat exchanger, which is connected to the hot flow inlet of the booster turbine expander, the hot flow inlet of the throttle valve, the cold flow outlet of the cold storage tank, and the cold flow outlet of the gas-liquid separator. The cold flow outlet of the booster turbine expander and the cold flow outlet of the throttle valve are connected to the inlet of the gas-liquid separator, and the gas-liquid separator is connected to the liquid-air storage tank.

[0008] In the aforementioned liquid air energy storage liquefaction automatic control system, the air compressor cooler is equipped with, in sequence, an air compressor cooling water flow regulating valve, an air compressor cooling water inlet thermometer, and an air compressor cooling water inlet pressure gauge at the cooling water inlet end; the air compressor cooler is equipped with an air compressor cooling water outlet thermometer at the cooling water outlet end; and the air compressor cooler is equipped with, in sequence, an air compressor cooling temperature gauge, an air compressor cooling pressure gauge, an air compressor flow meter, and an air compressor outlet vent regulating valve to maintain stable air compressor cooling pressure at the hot end outlet.

[0009] In the aforementioned liquid air energy storage liquefaction automatic control system, the cooling water inlet end of the booster cooler is sequentially equipped with a booster cool water flow regulating valve, a booster cool water inlet thermometer, and a booster cool water inlet pressure gauge; the cooling water outlet end of the booster cooler is equipped with a booster cool water outlet thermometer; and the hot end outlet of the booster cooler is sequentially equipped with a booster cool-down thermometer, a booster cool-down pressure gauge, a booster flow meter, and a booster outlet vent regulating valve to maintain stable booster cool-down pressure.

[0010] In the aforementioned liquid air energy storage liquefaction automatic control system, the inlet end of the turbocharger cooler is sequentially equipped with a turbocharger cooling water flow regulating valve, a turbocharger cooling water inlet thermometer, and a turbocharger cooling water inlet pressure gauge; the outlet end of the turbocharger cooler is equipped with a turbocharger cooling water outlet thermometer for detecting the outlet water temperature of the turbocharger cooler; and the hot end outlet of the turbocharger cooler is sequentially equipped with a turbocharger cooling temperature gauge and a turbocharger cooling pressure gauge.

[0011] In the aforementioned liquid air energy storage liquefaction automatic control system, the inlet end of the turbo expander is sequentially equipped with a turbo expander inlet pressure gauge, a turbo expander inlet thermometer, and a turbo expander inlet flow meter; the outlet end of the turbo expander is equipped with a turbo expander outlet thermometer.

[0012] In the aforementioned liquid air energy storage liquefaction automatic control system, a booster return pipeline is also provided between the outlet end and the inlet end of the booster of the booster turbine expander, and a booster return regulating valve for adjusting the speed of the booster turbine expander is provided on the booster return pipeline.

[0013] In the aforementioned liquid air energy storage liquefaction automatic control system, the cold storage tank provides circulating cooling capacity for the cold box heat exchanger to deliver a cold storage stream. The outlet end of the cold storage stream is connected to a circulating fan, and the outlet end of the circulating fan is connected to the inlet of the cold storage tank.

[0014] In the aforementioned liquid air energy storage liquefaction automatic control system, the cold flow outlet end of the gas-liquid separator is sequentially equipped with a gas-liquid separator return gas pressure gauge and a gas-liquid separator return gas temperature gauge; the outlet end of the gas-liquid separator return gas stream in the cold box heat exchanger is connected to the booster compressor through a cold box return gas pipeline, and the cold box return gas pipeline is sequentially equipped with a cold box return gas temperature gauge, a cold box return gas pressure gauge, a cold box return gas flow meter, and a cold box return gas regulating valve for maintaining stable gas-liquid separator return gas pressure.

[0015] The technological advancements achieved by this utility model are as follows, due to the adoption of the above technical solutions.

[0016] This invention provides an automatic control system for liquid air energy storage liquefaction. Through the coordinated operation of a heat storage module, a liquefaction energy storage module, and a control module, it achieves automatic control of liquid air energy storage liquefaction, solving the problem of frequent start-stop of the liquefaction system due to the large number of variables and the coupling between these variables, thus ensuring the safe and efficient operation of the liquefaction system. In the heat storage module, the coordinated operation of the chilled water delivery pump, the air compressor cooling water flow regulating valve, the booster compressor cooling water flow regulating valve, and the booster compressor cooling water flow regulating valve ensures that the pressure of the chilled water delivery pump reaches the desired set value, reducing the influence of pressure and flow coupling between the three coolers in the heat storage module. This not only achieves cooling of the compressed air but also ensures the heat storage efficiency of the heat storage module, realizing dual-objective control of the coolers. Furthermore, by improving the operation of the cold box heat exchanger, the air liquefaction rate is kept at a high level, ensuring the stable operation of the liquefaction system. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the specific structure of the present utility model; Figure 2 This is a schematic diagram of the specific structure of the heat exchange of the heat storage module described in this utility model.

[0018] The components include: 1. Air compressor, 2. Air compressor outlet thermometer, 3. Air compressor cooling water outlet thermometer, 4. Air compressor cooler, 5. Air compressor cooling water inlet thermometer, 6. Air compressor cooling water inlet pressure gauge, 7. Air compressor cooling water flow regulating valve, 8. Air compressor after cooling thermometer, 9. Air compressor after cooling pressure gauge, 10. Air compressor flow meter, 11. Air compressor outlet vent regulating valve, 12. Molecular sieve, 13. Booster compressor, 14. Booster compressor outlet thermometer, 15. Booster compressor cooling water outlet thermometer, 16. Booster compressor cooling water inlet thermometer, 17. Booster compressor cooling water inlet pressure gauge, 18. Booster compressor cooling water flow regulating valve, 19. Booster compressor after cooling thermometer, 20. Booster compressor 21. Aftercooling pressure gauge; 22. Booster compressor flow meter; 23. Booster compressor cooler; 24. Booster compressor outlet vent regulating valve; 25. Booster compressor reflux regulating valve; 26. Booster compressor inlet flow meter; 27. Booster compressor inlet thermometer; 28. Booster compressor inlet pressure gauge; 29. ​​Booster compressor turbine expander booster; 30. Booster compressor turbine expander expander; 31. Booster compressor cooling water outlet thermometer; 32. Booster compressor outlet thermometer; 33. Booster compressor turbine expander tachometer; 34. Booster compressor cooling water inlet pressure gauge. 35. Turbocharger cooling water inlet thermometer; 36. Turbocharger post-cooling pressure gauge; 37. Turbocharger post-cooling temperature gauge; 38. Turbocharger cooler; 39. Turbocharger cooling water flow regulating valve; 40. Expansioner inlet nozzle; 41. Expansioner inlet flow meter; 42. Expansioner inlet pressure gauge; 43. Expansioner inlet temperature gauge; 44. Expansioner outlet temperature gauge; 45. Expansioner outlet pressure gauge; 46. Thermometer before throttle valve; 47. Thermometer before throttle valve; 48. Throttle valve; 49. Gas-liquid separator return gas pressure gauge; 50. Gas-liquid separator return gas temperature gauge; 51. Cold box return gas temperature gauge; 52. Cold box return gas pressure gauge; 53. Cold box return gas flow meter; 54. Cold box return gas regulating valve; 55. Gas-liquid separator. 55. Liquid air storage tank, 56. Cold storage tank, 57. Gas-liquid separator level gauge, 58. Liquid air storage tank level gauge, 59. Self-regulating pressure regulating valve, 60. Circulating fan, 61. Circulating fan inlet pressure gauge, 62. Circulating fan inlet thermometer, 63. Circulating fan outlet flow meter, 64. Circulating fan outlet pressure gauge, 65. Circulating fan outlet thermometer, 66. Cold box heat exchanger, 67. Liquid air transfer regulating valve, 68. Cold water storage tank, 69. Hot water storage tank, 70. Cold water transfer pump, 71. Cold water transfer pump outlet pressure gauge, 72. Cold water transfer pump outlet thermometer, S1. Hot flow stream, S2. Gas-liquid separator return flow stream, S3. Cold storage stream, S4. Expansion liquefaction stream, S5. Throttling liquefaction stream. Detailed Implementation

[0019] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0020] An automatic control system for liquid air energy storage liquefaction, such as Figures 1 to 2 As shown, it includes a heat storage module, a liquefaction energy storage module and a control module. The heat storage module and the liquefaction energy storage module are electrically connected to the control module. The heat storage module is used to recover the heat of air compression and provide a heat flow stream S1 to the liquefaction energy storage module. The liquefaction energy storage module is used to liquefy and store the air.

[0021] The heat storage module includes an air compressor 1, an air compressor cooler 4, a molecular sieve 12, a booster compressor 13, a booster compressor cooler 22, a booster turbine expander booster 28, and a booster cooler 37 connected in sequence. The cooling water inlets of the air compressor cooler 4, the booster compressor cooler 22, and the booster cooler 37 are respectively connected to the outlet of a cold water storage tank 68. The cooling water outlets of the air compressor cooler 4, the booster compressor cooler 22, and the booster cooler 37 are respectively connected to the inlet of a hot water storage tank 69. A cold water delivery pump 70 is installed at the outlet of the cold water storage tank 68. A cold water delivery pump outlet pressure gauge 71 and a cold water delivery pump outlet thermometer 72 are sequentially installed at the outlet of the cold water delivery pump 70.

[0022] Air compressor 1 is used to compress raw material air. During the compression process, mechanical energy is converted into gas internal energy, which causes the air temperature to rise. An air compressor outlet thermometer 2 is installed at the outlet of air compressor 1 to detect the outlet temperature of the air compressor.

[0023] The air compressor cooler 4 is equipped with an air compressor cooling water flow regulating valve 7, an air compressor cooling water inlet thermometer 5, and an air compressor cooling water inlet pressure gauge 6 at its cooling water inlet end. The air compressor cooler 4 is equipped with an air compressor cooling water outlet thermometer 3 at its cooling water outlet end. The air compressor cooling water flow regulating valve 7 is used to regulate the water flow into the air compressor cooler. The air compressor cooling water inlet thermometer 5 and the air compressor cooling water inlet pressure gauge 6 are used to detect the water inlet temperature and water inlet pressure of the air compressor cooler, respectively. The air compressor cooling water outlet thermometer 3 is used to detect the water outlet temperature of the air compressor cooler.

[0024] The hot end outlet of the air compressor cooler 4 is sequentially equipped with an air compressor cooling thermometer 8, an air compressor cooling pressure gauge 9, an air compressor flow meter 10, and an air compressor outlet venting regulating valve 11. The air compressor cooling thermometer 8, air compressor cooling pressure gauge 9, and air compressor flow meter 10 are used to detect the temperature, pressure, and flow rate of the air after it has been cooled by the air compressor cooler.

[0025] The air compressor outlet venting regulating valve 11 can adjust the air compressor cooling pressure according to the pressure value measured by the air compressor cooling pressure gauge 9, so as to maintain the stability of the air compressor cooling pressure.

[0026] Specifically, when the air compressor's pressure increases after cooling, the opening of the air compressor outlet venting regulating valve 11 is increased; conversely, when the air compressor's pressure decreases after cooling, the opening of the air compressor outlet venting regulating valve 11 is decreased.

[0027] A booster outlet thermometer 14 is installed at the outlet end of the booster 13 to detect the outlet temperature of the booster 13.

[0028] The inlet end of the turbocharger cooler 22 is equipped with a turbocharger cooling water flow regulating valve 18, a turbocharger cooling water inlet thermometer 16, and a turbocharger cooling water inlet pressure gauge 17. The outlet end of the turbocharger cooler 22 is equipped with a turbocharger cooling water outlet thermometer 15. The turbocharger cooling water flow regulating valve 18 is used to regulate the inlet water flow of the turbocharger cooler. The turbocharger cooling water inlet thermometer 16 and the turbocharger cooling water inlet pressure gauge 17 are used to detect the inlet water temperature and inlet water pressure of the turbocharger cooler, respectively. The turbocharger cooling water outlet thermometer 15 is used to detect the outlet water temperature of the turbocharger cooler.

[0029] The hot end outlet of the booster cooler 22 is sequentially equipped with a booster cooling thermometer 19, a booster cooling pressure gauge 20, a booster flow meter 21, and a booster outlet venting regulating valve 23. The booster cooling thermometer 19, the booster cooling pressure gauge 20, and the booster flow meter 21 are used to detect the temperature, pressure, and flow rate of the air cooled by the booster cooler, respectively.

[0030] The booster outlet venting regulating valve 23 can adjust the booster cooling pressure according to the pressure value measured by the booster cooling pressure gauge 20, so as to maintain the stability of the booster cooling pressure.

[0031] Specifically, when the pressure of the booster increases after cooling, the opening of the booster outlet venting regulating valve 23 is increased; conversely, when the pressure of the booster decreases after cooling, the opening of the booster outlet venting regulating valve 23 is decreased.

[0032] In this embodiment, the air compressor outlet venting regulating valve 11 and the booster compressor outlet venting regulating valve 23 respectively adopt the proportional-integral-derivative (PID) control algorithm.

[0033] The inlet end of the turbocharger 28 is equipped with a turbocharger inlet pressure gauge 27, a turbocharger inlet thermometer 26, and a turbocharger inlet flow meter 25, which are used to detect the air pressure, temperature, and flow rate at the inlet of the turbocharger 28. The outlet end of the turbocharger 28 is equipped with a turbocharger outlet thermometer 31, which is used to detect the air temperature at the outlet of the turbocharger 28.

[0034] The turbocharger cooler 37 is equipped with a turbocharger cooling water flow regulating valve 38, a turbocharger cooling water inlet thermometer 34, and a turbocharger cooling water inlet pressure gauge 33 at its cooling water inlet end. The turbocharger cooling water flow regulating valve 38 is used to regulate the inlet water flow of the turbocharger cooler 37, and the turbocharger cooling water inlet thermometer 34 and the turbocharger cooling water inlet pressure gauge 33 are used to detect the inlet water temperature and inlet water pressure of the turbocharger cooler 37.

[0035] A turbocharger cooling water outlet thermometer 30 is installed at the cooling water outlet end of the turbocharger cooler 37 to detect the outlet water temperature of the turbocharger cooler 37.

[0036] A turbocharger cooling thermometer 36 and a turbocharger cooling pressure gauge 35 are sequentially installed at the hot end outlet of the turbocharger cooler 37 to detect the temperature and pressure of the air after being cooled by the turbocharger cooler 37.

[0037] The heat storage module primarily cools compressed air and collects the heat of compression in a hot water storage tank. The module contains three coolers, a cold water delivery pump, a cold water storage tank, and a hot water storage tank. Therefore, the heat storage module operates with two objectives: cooling and heat storage. This differs significantly from typical heat exchangers, which only require maintaining either the hot or cold end outlet temperature—a single-objective control. In this embodiment, the heat storage module operates with dual objectives: cooling the compressed air while ensuring high-quality heat storage. These two objectives are contradictory. Each cooler has a regulating valve at its cooling water inlet; any valve action affects the cooling water flow to the other two coolers and the cooling water pump outlet pressure. The pressure and flow rates in the cooling water pipelines within the heat storage module are strongly coupled and mutually influential, posing a challenge to the module's automated operation.

[0038] To address the aforementioned issues, this embodiment improves the automatic operation method of the thermal storage module. This algorithm only functions in automatic mode. The frequency of the chilled water delivery pump 70 employs a proportional-integral-derivative (PID) control algorithm to ensure the chilled water delivery pump outlet pressure reaches the desired value. The improved automatic operation method of the thermal storage module is as follows: Taking the air compressor cooling water flow regulating valve 7 and the cold water delivery pump 70 as examples, in order to achieve dual-target control of the cooler temperature, the heat storage module automatically runs an algorithm to detect the cold end temperature difference T2-T1 and the hot end temperature difference T4-T3.

[0039] When the cold end temperature difference T2-T1 is greater than deadband1, and after pausetime1 the cold end temperature difference is still greater than deadband1, and the opening of the air compressor cooling water flow regulating valve 7 has not reached the upper limit of 70%, then the cold water delivery pump 70 is put into automatic mode to maintain a constant pump outlet pressure and avoid the subsequent operation of the air compressor cooling water flow regulating valve 7 from affecting the other two cooling water regulating valves; then the regulating valve is opened larger according to step1, and the system response time worktime2 is waited. If the cold end temperature difference T2-T1 is still greater than deadband1, the above steps are repeated until the opening of the regulating valve is greater than or equal to 70%.

[0040] In this embodiment, the regulating valve basically loses its regulating function when the valve opening is greater than 70%. In other embodiments, the valve opening value at which it loses its function can be set according to the valve's own conditions.

[0041] To prevent the cooling water flow regulating valve from losing its regulating function due to excessive opening, if the cold end temperature difference T2-T1 is greater than deadband1 and the opening of the regulating valve is greater than or equal to 70%, and the above conditions are still met after pausetime1, then the cold water delivery pump 70 will be put into automatic mode.

[0042] If the pump frequency is less than 50Hz, the pump pressure setting value is increased step by step 3. If the pump frequency increases to a certain value and the opening of the air compressor cooling water flow regulating valve 7 is less than 70% or the pump frequency has reached 50Hz, the cold water delivery pump 70 is put into manual mode to avoid the cooling water pump being constantly put into automatic mode and causing disturbance to the heat storage module.

[0043] When the hot end temperature difference T4-T3 is greater than deadband2, and after pausetime1 the hot end temperature difference is still greater than deadband2, then the cold water delivery pump 70 is put into automatic mode, and then the regulating valve is opened in small increments according to step2.

[0044] If the cold end temperature difference T2-T1 and the hot end temperature difference T4-T3 of the air compressor cooler are both within an acceptable range, the cold water delivery pump 70 will exit automatic mode, and the heat storage module will be in a relatively ideal working state.

[0045] The control algorithms for the booster cool water flow regulating valve 18 and the booster cool water flow regulating valve 38 are the same as those for the air compressor cool water flow regulating valve 7.

[0046] The above-mentioned automatic operation method of the heat storage module realizes the dual-target control of the cooler and reduces the coupling and mutual influence of pressure and flow between the heat storage module and the cooler. In order to reduce energy consumption, the pump frequency is only increased when the cold end temperature difference is large enough. When the cooler is in a relatively ideal working state, the cold water delivery pump and the cooling water flow regulating valve do not operate, so as to avoid excessive control causing disturbance to the heat storage module.

[0047] The liquefaction energy storage module includes a cold box heat exchanger 66, which is connected to the hot flow inlet of the turbo expander 29, the hot flow inlet of the throttle valve 47, the cold flow outlet of the cold storage tank 56, and the cold flow outlet of the gas-liquid separator 54. The cold flow outlets of the turbo expander 29 and the throttle valve 47 are connected to the inlet of the gas-liquid separator 54, which is connected to the liquid air storage tank 55 to facilitate the storage of liquid air during the liquefaction process.

[0048] A liquid air conveying regulating valve 67 is also installed on the conveying pipeline between the gas-liquid separator 54 and the liquid air storage tank 55 to regulate the flow rate and speed of the conveyed liquid air.

[0049] A liquid level gauge 58 is installed on the liquid air storage tank 55 to detect the liquid level inside the liquid air storage tank 55.

[0050] The liquid air storage tank 55 is also equipped with a self-regulating pressure regulating valve 59, which is used to maintain the pressure balance inside and outside the liquid air storage tank 55.

[0051] Specifically, the hot flow S1 entering the cold box heat exchanger 66 is divided into two streams: an expansion liquefaction stream S4 and a throttling liquefaction stream S5. The expansion liquefaction stream S4 enters the expander 29 of the booster turbine expander for expansion, cooling and liquefaction, while the throttling liquefaction stream S5 enters the throttling valve 47 for throttling and liquefaction.

[0052] The liquefied gas-liquid mixture enters the gas-liquid separator 54 for gas-liquid separation. The separated gas-liquid separator return flow S2 enters the cold box heat exchanger 66 for reuse, while the separated liquid air is sent to the liquid air storage tank 55 for storage.

[0053] The cold storage tank 56 provides circulating cooling capacity to the cold box heat exchanger 66 by supplying the cold storage stream S3. The outlet end of the cold storage stream S3 is connected to the circulating fan 60, and the outlet end of the circulating fan 60 is connected to the inlet of the cold storage tank 56.

[0054] The outlet end of the cold storage tank 56 is equipped with a circulating fan outlet thermometer 65, a circulating fan outlet pressure gauge 64, and a circulating fan outlet flow meter 63, which are used to detect the temperature, pressure, and flow rate of the cold storage stream S3 before it enters the cold box heat exchanger 66.

[0055] The inlet end of the circulating fan 60 is equipped with a circulating fan inlet pressure gauge 61 and a circulating fan inlet temperature gauge 62, which are used to detect the pressure and temperature of the cold storage stream S3 before entering the circulating fan.

[0056] The inlet end of the turbo expander expander 29 is equipped with an expander inlet thermometer 42, an expander inlet pressure gauge 41, and an expander inlet flow meter 40, which are used to detect the temperature, pressure, and flow rate of the expanding liquefied stream S4 before entering the turbo expander expander 29.

[0057] The inlet end of the turbo expander expander 29 is also provided with an expander inlet nozzle 39, which is used to regulate the flow rate of the expansion liquefaction stream S4 entering the turbo expander expander 29.

[0058] The outlet end of the turbo expander 29 is equipped with an expander outlet thermometer 43 and an expander outlet pressure gauge 44, which are used to detect the temperature and pressure of the liquefied gas-liquid mixture.

[0059] A thermometer 45 and a pressure gauge 46 are sequentially installed at the inlet end of the throttle valve 47 to detect the temperature and pressure of the liquefied stream S5 that is throttled before entering the throttle valve 47.

[0060] The cold flow outlet end of the gas-liquid separator 54 is equipped with a gas-liquid separator return gas pressure gauge 48 and a gas-liquid separator return gas temperature gauge 49, which are used to detect the pressure and temperature of the gas-liquid separator return gas stream S2 that flows back into the cold box heat exchanger 66.

[0061] The gas-liquid separator 54 is also equipped with a gas-liquid separator level gauge 57, which is used to detect the liquid level inside the gas-liquid separator 54.

[0062] The outlet end of the return gas stream S2 of the gas-liquid separator inside the cold box heat exchanger 66 is connected to the booster 13 through the cold box return gas pipeline. The cold box return gas pipeline is equipped with a cold box return gas thermometer 50, a cold box return gas pressure gauge 51, a cold box return gas flow meter 52, and a cold box return gas regulating valve 53 in sequence. The cold box return gas thermometer 50, cold box return gas pressure gauge 51, and cold box return gas flow meter 52 are used to detect the temperature, pressure, and flow rate of the cold box return gas.

[0063] The cold box return gas regulating valve 53 is used to regulate the flow rate of the cold box return gas entering the booster 13, thereby maintaining the stability of the gas-liquid separator return gas pressure. When the gas-liquid separator return gas pressure gauge 48 detects an increase in the gas-liquid separator return gas pressure, it increases the opening of the cold box return gas regulating valve 53; conversely, it decreases the opening of the cold box return gas regulating valve 53.

[0064] Because the PID algorithm used in the cold box return gas regulating valve 53 will cause the cold box return gas regulating valve 53 to operate frequently, the frequent operation of the cold box return gas regulating valve 53 will cause the air compressor outlet vent regulating valve 11 to operate frequently, resulting in unstable system pressure. Therefore, the proportional-integral-derivative (PID) control algorithm should not be used for the cold box return gas regulating valve 53.

[0065] This embodiment improves the operation method of the cold box return gas regulating valve 53 from the perspective of system pressure stability. Specifically, the automatic operation method of the cold box return gas regulating valve 53 is as follows: The control algorithm of the cold box return gas regulating valve 53 only works in automatic mode. This algorithm sets a deadband, a filtration pause time, and a waiting time work time to avoid measurement errors causing frequent operation of the cold box return gas regulating valve 53. Each adjustment is only a fine-tuning, and after the fine-tuning, a period of time is waited for the pressure to take effect, and the return gas pressure of the gas-liquid separator is slowly adjusted to avoid pressure oscillation, thereby maintaining the pressure stability of the liquid air energy storage liquefaction system.

[0066] In addition, the pausetime, worktime, and deadband parameters can be adjusted according to actual operating needs to change the response speed of the cold box return gas regulating valve 53.

[0067] Specifically, in automatic mode, the pressure value Pressure48 measured by the gas-liquid separator return gas pressure gauge 48 is continuously monitored. If the pressure value continuously exceeds the sum of the set value Pressure48.SP and the dead zone, the opening of the cold box return gas regulating valve 53 is increased by a small step (e.g., 0.5%) after the filtration waiting time pausetime. Conversely, if the pressure value continuously falls below the difference between the set value and the dead zone, the opening is decreased by the same step after the filtration waiting time.

[0068] After each adjustment, the system waits for a preset stabilization time (worktime) to allow the pipeline pressure to fully respond to the adjustment, thereby avoiding pressure oscillations and maintaining the overall pressure stability of the liquid air energy storage liquefaction system.

[0069] The turbo expander 29 is equipped with a turbo expander tachometer 32, which is used to detect the rotational speed of the turbo expander 29. The turbo expander 29 and the turbo expander turbo booster 28 share a rotor through a coupling.

[0070] A turbocharger return pipeline is also provided between the outlet end and the inlet end of the turbocharger 28 of the turbocharger expander, and a turbocharger return regulating valve 24 is provided on the turbocharger return pipeline.

[0071] In this embodiment, the air liquefaction efficiency is mainly determined by the cold box heat exchanger 66 in the liquefaction energy storage module. This embodiment improves the automatic operation method of the cold box heat exchanger 66 to achieve a higher air liquefaction rate.

[0072] In this embodiment, the automatic operation method of the cold box heat exchanger 66 and its auxiliary equipment only works in automatic mode. The automatic operation method of the cold box heat exchanger 66 is as follows: To ensure air liquefaction efficiency, the speed ST1 of the turbo expander 29 should first be kept near the rated speed ST1_SP. When the speed ST1 of the turbo expander is low, the opening of the expander inlet nozzle 39 should be increased. When the expander inlet nozzle 39 is opened to 70%, the nozzle loses its regulating function. If the speed ST1 of the turbo expander is still low at this time, the opening of the turbo expander return regulating valve 24 should be reduced. If the speed is still low after the turbo expander return regulating valve 24 is closed, the opening of the throttle valve 47 should be reduced.

[0073] When the speed ST1 of the turbo expander is high, the turbo expander return regulating valve 24 should be opened first. If the speed ST1 of the turbo expander is still high, the opening of the expander inlet nozzle 39 should be reduced to ensure that the cooling capacity of the return airflow stream S2 in the gas-liquid separator in the cold box heat exchanger 66 is sufficient to ensure basic air liquefaction efficiency.

[0074] If the temperature of the throttling liquefied stream S5 measured by the thermometer 45 before entering the throttling valve 47 is too high, the throttling valve 47 should be closed slightly; conversely, the throttling valve 47 should be opened wider. This will ensure that the flow rate of the throttling liquefied stream S5 is within a suitable range, at which point the liquefaction efficiency will be at a high level.

[0075] In addition, the cold storage stream S3 of the cold box heat exchanger 66 comes from the cold storage tank 56. If the cold storage stream S3 is too large, it will cause waste of cold energy and also cause excessive power consumption of the circulating fan 60.

[0076] To achieve automatic operation of the circulating fan 60, a perturbation optimization method was adopted for the circulating fan 60, which can ensure high air liquefaction efficiency and reduce energy consumption and save cooling capacity.

[0077] Specifically, a small disturbance step9 is applied to the frequency of the circulating fan 60 in each cycle. If the opening of the air compressor outlet venting regulating valve 11 changes significantly after the disturbance, that is, it has a significant impact on the liquefaction efficiency, then the frequency of the circulating fan 60 should be increased to improve the air liquefaction efficiency.

[0078] If the opening of the air compressor outlet venting regulating valve 11 does not change significantly after a small disturbance is applied to the frequency of the circulating fan 60 in step 9, it proves that the frequency of the circulating fan 60 is too high. Its frequency should be reduced to save the cooling capacity of the fan and the cooling capacity of the cold storage tank 56, and at the same time reduce the energy consumption of the circulating fan 60.

[0079] If the inlet temperature of the circulating fan (62°C) is too low, it indicates that the flow rate of the cold storage stream (S3) is too high. The frequency of the circulating fan (60°C) should be reduced directly until the inlet temperature of the circulating fan is appropriate.

[0080] Because the cold box heat exchanger 66 and its auxiliary equipment operate under complex conditions and have many devices, and the controlled object has large inertia and nonlinearity, the automatic operation method of the cold box heat exchanger 66 and its auxiliary equipment adopts small step adjustment and allows sufficient reaction time for the controlled object to ensure the stability of the system.

[0081] This invention provides an automatic control system for liquid air energy storage liquefaction. Through the coordinated operation of a heat storage module, a liquefaction energy storage module, and a control module, it achieves automatic control of liquid air energy storage liquefaction, solving the problem of frequent start-stop of the liquefaction system due to the large number of variables and the coupling between these variables, thus ensuring the safe and efficient operation of the liquefaction system. In the heat storage module, the coordinated operation of the chilled water delivery pump, the air compressor cooling water flow regulating valve, the booster compressor cooling water flow regulating valve, and the booster compressor cooling water flow regulating valve ensures that the pressure of the chilled water delivery pump reaches the desired set value, reducing the influence of pressure and flow coupling between the three coolers in the heat storage module. This not only achieves cooling of the compressed air but also ensures the heat storage efficiency of the heat storage module, realizing dual-objective control of the coolers. Furthermore, by improving the operation of the cold box heat exchanger, the air liquefaction rate is kept at a high level, ensuring the stable operation of the liquefaction system.

Claims

1. An automatic control system for liquid air energy storage liquefaction, characterized in that: The system includes a heat storage module for recovering the heat of air compression, a liquefaction energy storage module for liquefying and storing air, and a control module. The heat storage module is connected to the liquefaction energy storage module and provides a heat flow stream (S1) to the liquefaction energy storage module. The heat storage module and the liquefaction energy storage module are electrically connected to the control module. The heat storage module includes an air compressor (1), an air compressor cooler (4), a molecular sieve (12), a booster compressor (13), a booster compressor cooler (22), a booster turbine expander booster (28), and a booster cooler (37) connected in sequence. The cooling water inlets of the air compressor cooler (4), the booster compressor cooler (22), and the booster cooler (37) are respectively connected to a cold water storage tank (68). The outlet of the air compressor cooler (4), the cooler (22), and the cooler (37) are connected to the inlet of the hot water storage tank (69), respectively. The liquefied energy storage module includes a cold box heat exchanger (66), which is connected to the hot flow inlet of the turbo expander expander (29), the hot flow inlet of the throttle valve (47), the cold flow outlet of the cold storage tank (56), and the cold flow outlet of the gas-liquid separator (54), respectively. The cold flow outlet of the turbo expander expander (29) and the cold flow outlet of the throttle valve (47) are connected to the inlet of the gas-liquid separator (54), respectively. The gas-liquid separator (54) is connected to the liquid air storage tank (55).

2. The liquid air energy storage liquefaction automatic control system according to claim 1, characterized in that: The air compressor cooler (4) is provided with an air compressor cooling water flow regulating valve (7), an air compressor cooling water inlet thermometer (5), and an air compressor cooling water inlet pressure gauge (6) in sequence at the cooling water inlet end; the air compressor cooler (4) is provided with an air compressor cooling water outlet thermometer (3) at the cooling water outlet end; the air compressor cooler (4) is provided with an air compressor cooling after thermometer (8), an air compressor cooling after pressure gauge (9), an air compressor flow meter (10), and an air compressor outlet vent regulating valve (11) to maintain stable air compressor cooling after pressure in sequence at the hot end outlet.

3. The liquid air energy storage liquefaction automatic control system according to claim 1, characterized in that: The inlet end of the compressor cooler (22) is provided with a compressor cooling water flow regulating valve (18), a compressor cooling water inlet thermometer (16), and a compressor cooling water inlet pressure gauge (17). The outlet end of the compressor cooler (22) is provided with a compressor cooling water outlet thermometer (15). The hot end outlet of the compressor cooler (22) is provided with a compressor cooling water outlet thermometer (19), a compressor cooling water outlet pressure gauge (20), a compressor flow meter (21), and a compressor outlet vent regulating valve (23) to maintain stable compressor cooling water pressure.

4. The liquid air energy storage liquefaction automatic control system according to claim 1, characterized in that: The inlet end of the turbocharger cooler (37) is provided with a turbocharger cooling water flow regulating valve (38), a turbocharger cooling water inlet thermometer (34), and a turbocharger cooling water inlet pressure gauge (33); the outlet end of the turbocharger cooler (37) is provided with a turbocharger cooling water outlet thermometer (30) for detecting the outlet water temperature of the turbocharger cooler (37); the hot end outlet of the turbocharger cooler (37) is provided with a turbocharger cooling after thermometer (36) and a turbocharger cooling after pressure gauge (35).

5. The liquid air energy storage liquefaction automatic control system according to claim 1, characterized in that: The inlet end of the turbocharger (28) is provided with a turbocharger inlet pressure gauge (27), a turbocharger inlet thermometer (26), and a turbocharger inlet flow meter (25); the outlet end of the turbocharger (28) is provided with a turbocharger outlet thermometer (31).

6. The liquid air energy storage liquefaction automatic control system according to claim 1, characterized in that: A turbocharger return pipeline is also provided between the outlet end and the inlet end of the turbocharger (28) of the turbocharger expander, and a turbocharger return regulating valve (24) for adjusting the speed of the turbocharger expander (29) is provided on the turbocharger return pipeline.

7. The liquid air energy storage liquefaction automatic control system according to claim 1, characterized in that: The cold storage tank (56) provides circulating cooling capacity for the cold box heat exchanger (66) to deliver the cold storage stream (S3). The outlet end of the cold storage stream (S3) is connected to the circulating fan (60), and the outlet end of the circulating fan (60) is connected to the inlet of the cold storage tank (56).

8. The liquid air energy storage liquefaction automatic control system according to claim 1, characterized in that: The gas-liquid separator (54) is provided with a gas-liquid separator return gas pressure gauge (48) and a gas-liquid separator return gas temperature gauge (49) in sequence at the cold flow outlet end; the outlet end of the gas-liquid separator return gas stream (S2) in the cold box heat exchanger (66) is connected to the booster (13) through the cold box return gas pipeline, and the cold box return gas pipeline is provided with a cold box return gas temperature gauge (50), a cold box return gas pressure gauge (51), a cold box return gas flow meter (52), and a cold box return gas regulating valve (53) to maintain the stable pressure of the gas-liquid separator return gas in sequence.

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