Decoupling air separation-LNG (Liquefied Natural Gas) cold energy power generation system and control method
By designing a decoupled air separation-LNG cold energy power generation system and a real-time control method, the problems of system operation flexibility and unstable cold energy supply were solved, achieving efficient energy recovery and stable operation.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-09
- Publication Date
- 2026-03-13
AI Technical Summary
In existing LNG cold energy utilization systems, there are mutual constraints among the various units, resulting in poor operational flexibility and unstable cold energy supply, which affects equipment lifespan and economic benefits.
Design a decoupled air separation-LNG cold energy power generation system. By setting a bypass and bypass regulating valve in the cold energy power generation unit to regulate the circulating working fluid flow path, the air separation unit, cold energy power generation unit and LNG gasification unit can be decoupled and operated. In addition, an LNG gasification load prediction model is established by combining multi-dimensional data to regulate the system status in real time.
It improves the flexibility and stability of system operation, enhances energy recovery efficiency, adapts to LNG gasification load fluctuations, and maintains the system's high-efficiency operation.
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Figure CN121654494A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of LNG cold energy utilization technology, specifically to a decoupled air separation-LNG cold energy power generation system and its control method. Background Technology
[0002] LNG (Liquefied Natural Gas) cold energy is the low-temperature energy released during the gasification process of liquefied natural gas. Due to its enormous cold energy content, it is typically recovered and utilized through various technologies. Currently, the utilization of LNG cold energy usually involves tightly coupling air separation units, cold energy power generation units, and LNG gasification units to achieve comprehensive energy utilization. For example, the waste heat from compressed air generated by the air separation unit can be used to heat the working fluid in the cold energy power generation unit, while the LNG gasification unit provides the cold source required for cold energy power generation.
[0003] However, LNG cold energy utilization systems formed through coupling suffer from inter-unit constraints and poor operational flexibility. Furthermore, in actual operation, the outbound load of the LNG receiving terminal is primarily affected by the gas demand of downstream users, which is often volatile and can even lead to significant reductions or interruptions in the outbound load. Due to the fluctuations in LNG regasification load, the supply of LNG cooling capacity exhibits significant instability, directly causing the coupled air separation unit to struggle to maintain continuous and stable operation, thus impacting equipment lifespan and the overall system's economic efficiency.
[0004] To address the issue of unstable cooling supply, existing technologies typically employ external cold boxes for liquid nitrogen storage, allowing for replenishment when cooling energy is insufficient. However, while this method maintains operation to some extent, it leads to a significant increase in unit energy consumption, reducing the system's energy efficiency. Summary of the Invention
[0005] To address the above problems, this invention provides a decoupled air separation-LNG cold energy power generation system and control method, which enables the various units of the system to operate decoupled under fluctuating LNG gasification load, thereby improving the flexibility and stability of the system operation.
[0006] The first aspect of this invention provides a decoupled air separation-LNG cold energy power generation system, comprising: an air separation unit for pressurizing and purifying ambient air; a cold energy power generation unit having a circulating working fluid inside, the circulating working fluid circulating within the cold energy power generation unit to generate electricity, the cold energy power generation unit including a working fluid heater, the circulating working fluid in the working fluid heater directly or indirectly cooling and exchanging heat with the compressed air formed in the air separation unit; an LNG vaporization unit, LNG entering the LNG vaporization unit cooling and exchanging heat with the circulating working fluid in the cold energy power generation unit; the cold energy power generation unit further includes a first air heat exchanger and a bypass; the circulating working fluid outlet of the first air heat exchanger is connected to the circulating working fluid inlet of the working fluid heater; the bypass is arranged in parallel with the first air heat exchanger, the circulating working fluid outlet of the bypass is connected to the circulating working fluid inlet of the working fluid heater, and a bypass regulating valve is provided on the bypass.
[0007] Optionally, the cold energy power generation unit also includes a turbine generator set and an LNG heat exchanger, wherein the circulating working fluid inlet of the turbine generator set is connected to the circulating working fluid outlet of the working fluid heater; the circulating working fluid inlet of the LNG heat exchanger is connected to the circulating working fluid outlet of the turbine generator set, and the circulating working fluid outlet of the LNG heat exchanger is connected to the circulating working fluid inlet of the first air heat exchanger.
[0008] Optionally, the cold energy power generation unit further includes: a working fluid gas tank, located between the turbine generator set and the LNG heat exchanger; and a working fluid liquid tank, located between the LNG heat exchanger and the first air heat exchanger.
[0009] Optionally, the cold energy power generation unit further includes: a first working fluid pump, disposed between the LNG heat exchanger and the working fluid tank; and a second working fluid pump, disposed between the working fluid tank and the first air heat exchanger.
[0010] Optionally, the air separation unit includes: an air compressor, an air cooler, and an air liquefaction and distillation unit, wherein the air outlet of the air compressor is connected to the air inlet of the air cooler; and the air outlet of the air cooler is connected to the air inlet of the air liquefaction and distillation unit.
[0011] Optionally, a coolant circulation unit is provided between the air cooling device and the working fluid heater; the coolant in the coolant circulation unit absorbs heat in the air cooling device and releases heat in the working fluid heater.
[0012] Optionally, the LNG vaporization unit includes: a second air heat exchanger and an intermediate medium vaporizer, wherein the second air heat exchanger and the intermediate medium vaporizer are arranged in parallel, and the LNG inlets of the second air heat exchanger and the intermediate medium vaporizer are both connected to the LNG outlet of the LNG heat exchanger; a first valve is provided between the second air heat exchanger and the LNG heat exchanger, and a second valve is provided between the intermediate medium vaporizer and the LNG heat exchanger.
[0013] A second aspect of the present invention provides a control method applied to the aforementioned decoupled air separation-LNG cold energy power generation system, comprising the following steps: an LNG gasification load prediction step, which establishes an LNG gasification load prediction model based on multidimensional data to predict the LNG gasification load in real time; a unit linkage control step, which regulates the operating status of the air separation unit, the cold energy power generation unit, and the LNG gasification unit according to the prediction results of the LNG gasification load prediction step; and an energy peak shaving step, which regulates the flow rates of the first working fluid pump and the second working fluid pump respectively according to the prediction results of the LNG gasification load prediction step and the waste heat status in the air separation unit.
[0014] Optionally, the unit linkage control steps include the following sub-steps: based on the control steps of predicting an increase in LNG vaporization load, instructing the air separation unit to increase operating power to increase heat energy supply, closing the bypass regulating valve opening, increasing the flow rate of the first working fluid pump delivering the circulating working fluid in advance, and delaying the increase in the flow rate of the second working fluid pump delivering the circulating working fluid; based on the control steps of predicting a decrease in LNG vaporization load, instructing the air separation unit to reduce operating power to reduce heat energy supply, opening the bypass regulating valve opening, decreasing the flow rate of the first working fluid pump delivering the circulating working fluid in advance, and delaying the decrease in the flow rate of the second working fluid pump delivering the circulating working fluid.
[0015] Optionally, the energy peak shaving step includes the following sub-steps: a gas storage step, reducing the flow rate of the circulating working fluid delivered by the first working fluid pump and / or increasing the flow rate of the circulating working fluid delivered by the second working fluid pump; and a liquid storage step, increasing the flow rate of the circulating working fluid delivered by the first working fluid pump and / or decreasing the flow rate of the circulating working fluid delivered by the second working fluid pump.
[0016] The decoupled air separation-LNG cold energy power generation system provided by this invention can adjust the flow rate of the circulating working fluid entering the first air heat exchanger by using parallel bypass and bypass regulating valves when the heat provided by the air separation unit and the cold energy provided by the LNG gasification unit are mismatched. This allows for flexible adjustment of the heat exchange capacity of the cold energy power generation unit, achieving decoupled operation between the air separation unit, the cold energy power generation unit, and the LNG gasification unit. This improves the overall operational flexibility of the system and enables it to maintain high energy recovery efficiency and operational stability when adapting to fluctuations in LNG gasification load. Attached Figure Description
[0017] Figure 1 This is a schematic diagram of a decoupled air separation-LNG cold energy power generation system provided in the first embodiment of the present invention.
[0018] Figure 2 The flowchart illustrates a control method for a decoupled air separation-LNG cold power generation system provided in the second embodiment of the present invention.
[0019] Reference numerals: 100-Decoupled air separation-LNG cold energy power generation system, 1-Cold energy power generation unit, 11-Working fluid heater, 12-First air heat exchanger, 13-Bypass, 131-Bypass regulating valve, 14-Turbine generator set, 15-LNG heat exchanger, 16-Working fluid gas tank, 17-Working fluid liquid tank, 18-First working fluid pump, 19-Second working fluid pump, 2-Air separation unit, 21-Air compression device, 22-Air cooling device, 23-Air liquefaction distillation device, 24-Coolant circulation unit, 3-LNG vaporization unit, 31-Second air heat exchanger, 32-First valve, 33-Intermediate medium vaporizer, 34-Second valve. Detailed Implementation
[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0021] <First Implementation Method> This embodiment provides a decoupled air separation-LNG cold energy power generation system 100. The system includes an air separation unit 2, which pressurizes and purifies ambient air; a cold energy power generation unit 1, which has a circulating working fluid that circulates within the cold energy power generation unit to generate electricity; the cold energy power generation unit 1 includes a working fluid heater 11; the circulating working fluid in the working fluid heater 11 directly or indirectly cools and exchanges heat with the compressed air formed in the air separation unit 2; an LNG vaporization unit 3, in which LNG entering the LNG vaporization unit 3 cools and exchanges heat with the circulating working fluid in the cold energy power generation unit 1; the cold energy power generation unit 1 also includes a first air heat exchanger 12, the circulating working fluid outlet of the first air heat exchanger 12 being connected to the circulating working fluid inlet of the working fluid heater 11; and a bypass 13, which is arranged in parallel with the first air heat exchanger 12, the circulating working fluid outlet of the bypass 13 being connected to the circulating working fluid inlet of the working fluid heater 11, and a bypass regulating valve 131 is provided on the bypass 13.
[0022] The cooling energy supplied to air separation unit 2 is typically provided by LNG supplied from the receiving terminal. However, the LNG supply from some receiving terminals fluctuates frequently due to downstream gas consumption, making traditional LNG-cooled power generation systems coupled with air separation units prone to unstable operation and low energy utilization efficiency due to fluctuations in cooling energy input. Therefore, this embodiment provides a decoupled air separation-LNG cooling power generation system 100. By setting a bypass 13 and a bypass regulating valve 131 in the cooling power generation unit 1, and adjusting the flow path of the circulating working fluid according to load changes, decoupled operation of each unit in the system can be achieved. This allows for a balanced matching of the heat and cooling energy provided by air separation unit 2 and LNG vaporization unit 3, improving the overall flexibility of system operation. The process of achieving decoupled system operation by adjusting the bypass regulating valve 131 is as follows: When the load of heat provided by air separation unit 2 remains unchanged, and the load of cooling provided by LNG vaporization unit 3 increases, the cold energy power generation unit 1 needs to consume more cooling energy under the same heat conditions. At this time, the opening of the bypass regulating valve 131 is reduced to increase the amount of circulating working fluid entering the first air heat exchanger 12 for heat exchange, so that the power generation of cold energy power generation unit 1 increases while consuming more LNG cooling energy.
[0023] When the load of heat provided by air separation unit 2 increases while the load of cooling provided by LNG vaporization unit 3 remains unchanged, cold energy power generation unit 1 needs to consume more heat under the same cooling conditions. At this time, the opening of bypass regulating valve 131 is increased to reduce the amount of circulating working fluid entering the first air heat exchanger 12 for heat exchange, thereby increasing the amount of heat absorbed by the circulating working fluid for air separation unit 2.
[0024] When the loads of air separation unit 2 and LNG vaporization unit 3 increase or decrease in the same direction, the load of cold energy power generation unit 1 also increases or decreases in the same direction as the overall system. When the load change of air separation unit 2 is greater than that of LNG vaporization unit 3, the opening of bypass regulating valve 131 is increased; conversely, the opening of bypass regulating valve 131 is decreased.
[0025] In this embodiment, the air separation unit 2 includes an air compressor 21, an air cooler 22, and an air liquefaction and distillation unit 23. The air outlet of the air compressor 21 is connected to the air inlet of the air cooler 22; the air outlet of the air cooler 22 is connected to the air inlet of the air liquefaction and distillation unit 23. The air compressor 21 pressurizes ambient air, the air cooler 22 cools the compressed air, and the air liquefaction and distillation unit 23 purifies and separates the cooled air into products such as liquid nitrogen and liquid oxygen. A coolant circulation unit 24 is provided between the air cooler 22 and the working fluid heater 11 of the cold energy power generation unit 1. The coolant in the coolant circulation unit 24 circulates between the air cooler 22 and the working fluid heater 11 to facilitate energy transfer between the air separation unit 2 and the cold energy power generation unit 1. More specifically, when the low-temperature coolant in the coolant circulation unit 24 enters the air cooler 22, it absorbs the heat generated when the air compressor 21 compresses the air. After absorbing heat, the high-temperature coolant will continue to flow to the working fluid heater 11, releasing heat to the circulating working fluid entering the working fluid heater 11. The low-temperature coolant, after releasing heat in the working fluid heater 11, will re-enter the air cooling device 22 to absorb heat and cool the compressed air. By utilizing the coolant circulation unit 24 to exchange heat between the thermal energy in the air cooling device 22 and the cold energy in the working fluid heater 11, not only can the waste heat of the air separation unit 2 be recovered and utilized for power generation in the cold energy power generation unit 1, but the cold energy of LNG can also be used to cool the compressed air, thereby improving the air separation and purification efficiency. In other embodiments, the thermal energy in the air separation unit 2 and the cold energy in the cold energy power generation unit 1 can also directly exchange heat between the circulating working fluid in the working fluid heater 11 and the compressed air in the air compressor 21 without passing through the coolant circulation unit 24; no specific limitations are imposed here.
[0026] In this embodiment, the working fluid in the cold power generation unit 1 operates under low-temperature conditions, such as using a Rankine cycle. The working fluid can be hydrofluorocarbons, hydrofluorocarbons, hydrocarbons, or carbon dioxide, etc. In other embodiments, other types of working fluids may be selected based on the actual operating environment and power generation requirements; no specific limitations are imposed here. (Reference) Figure 1The cold energy power generation unit 1 includes a working fluid heater 11, a turbine generator set 14, an LNG heat exchanger 15, a first air heat exchanger 12, a bypass 13, a bypass regulating valve 131, a working fluid gas tank 16, a working fluid liquid tank 17, a first working fluid pump 18, and a second working fluid pump 19. The circulating working fluid inlet of the turbine generator set 14 is connected to the circulating working fluid outlet of the working fluid heater 11; the circulating working fluid inlet of the LNG heat exchanger 15 is connected to the circulating working fluid outlet of the turbine generator set 14, and the circulating working fluid outlet of the LNG heat exchanger 15 is connected to the circulating working fluid inlet of the first air heat exchanger 12; the working fluid gas tank 16 is located between the turbine generator set 14 and the LNG heat exchanger 15; the working fluid liquid tank 17 is located between the LNG heat exchanger 15 and the first air heat exchanger 12; the first working fluid pump 18 is located between the LNG heat exchanger 15 and the working fluid liquid tank 17; and the second working fluid pump 19 is located between the working fluid liquid tank 17 and the first air heat exchanger 12.
[0027] More specifically, the operation process of the cold energy power generation unit 1 is as follows: The circulating working fluid in the working fluid heater 11 is heated by the heat provided by the coolant circulation unit 24. The resulting gaseous circulating working fluid, with higher temperature and pressure, enters the turbine generator set 14 to expand and perform work, thereby driving the generator to generate electricity. The gaseous working fluid, with reduced temperature and pressure after performing work, enters the working fluid gas tank 16 for storage. The gaseous circulating working fluid in the working fluid gas tank 16 then enters the LNG heat exchanger 15, where it exchanges heat with the LNG provided by the LNG vaporization unit 3, which has a lower temperature and higher cold energy. The gaseous circulating working fluid is cooled into a liquid circulating working fluid. Subsequently, the liquid circulating working fluid is transported to the working fluid liquid tank 17 for storage via the first working fluid pump 18. The liquid circulating working fluid in the working fluid liquid tank 17 is then pressurized by the second working fluid pump 19 and enters the first air heat exchanger 12 for preheating and heat exchange with the ambient air, before returning to the working fluid heater 11 to complete the cycle.
[0028] In this embodiment, the first air heat exchanger 12 and the bypass 13 are arranged in parallel. The bypass 13 is equipped with a bypass regulating valve 131 to regulate the flow rate of the circulating working fluid passing through the first air heat exchanger 12. When the bypass regulating valve 131 is open, a portion of the circulating working fluid discharged from the working fluid tank 17 bypasses the first air heat exchanger 12 and directly enters the working fluid heater 11, thereby recovering as much waste heat as possible from the air separation unit 2. When the bypass regulating valve 131 is closed, all the circulating working fluid discharged from the working fluid tank 17 flows through the first air heat exchanger 12. By setting the above-described parallel structure formed by the first air heat exchanger 12 and the bypass 13, the cold energy power generation unit 1 can flexibly adjust the circulating working fluid flow path according to the actual heating and cooling needs of the overall system, thus achieving decoupled operation between the various units. For example, when the LNG vaporization load increases, opening the bypass regulating valve 131 slightly can increase the heat exchange between the working fluid and the air, consuming more LNG cooling energy; when the load of the air separation unit 2 increases, opening the bypass regulating valve 131 more can reduce the heat exchange between the working fluid and the air, utilizing more heat generated by the air separation unit 2.
[0029] In this embodiment, when the air separation unit 2 or the LNG vaporization unit 3 is not in operation, or when the heat energy released by the air separation unit 2 and the cold energy released by the LNG vaporization unit 3 are not matched during operation, the working gas tank 16 and the working liquid tank 17 can be used as energy storage devices to store or release the gaseous or liquid circulating working fluid, thereby further realizing the decoupled operation of each unit in the system. For example, when air separation unit 2 is not operating but LNG vaporization unit 3 is operating normally, the gaseous circulating working fluid in working fluid tank 16 is converted into liquid circulating working fluid through LNG heat exchanger 15 and stored in working fluid liquid tank 17 via first working fluid pump 18, thereby temporarily storing excess cold energy provided by LNG vaporization unit 3. When air separation unit 2 is operating normally but LNG vaporization unit 3 is not operating, the liquid circulating working fluid in working fluid liquid tank 17 is sequentially pumped into first air heat exchanger 12, working fluid heater 11, and turbine generator set 14 via second working fluid pump 19, and converted into gaseous circulating working fluid stored in working fluid tank 16, thereby temporarily storing excess heat energy provided by air separation unit 2. In this embodiment, the flow rates of the circulating working fluid delivered by first working fluid pump 18 and second working fluid pump 19 are adjustable, thereby further realizing energy peak shaving.
[0030] In this embodiment, due to the limited heat exchange area of the first air heat exchanger 12, when there is a large difference between the thermal energy provided by the air separation unit 2 and the cold energy provided by the LNG vaporization unit 3, it is difficult to achieve heat exchange balance between thermal and cold energy using only the bypass regulating valve 131. Therefore, it is necessary to use the working fluid gas tank 16 and the working fluid liquid tank 17 to store and adjust the thermal or cold energy. The specific process is as follows: When the heat output of air separation unit 2 cannot be increased due to maintenance or other reasons, and the bypass regulating valve 131 is fully closed, while the cooling capacity of LNG vaporization unit 3 continues to increase, the flow rate of liquid circulating working fluid delivered by the first working fluid pump 18 can be increased, while maintaining or decreasing the flow rate of liquid circulating working fluid delivered by the second working fluid pump 19. By increasing the amount of liquid circulating working fluid stored in the working fluid tank 17 and decreasing the amount of gaseous circulating working fluid stored in the working fluid tank 16, the increased cooling energy is consumed.
[0031] When the cooling capacity of the LNG vaporization unit 3 cannot be increased due to maintenance or other reasons, and the bypass regulating valve 131 is fully open, and the heat of the air separation unit 2 continues to increase, the flow rate of the liquid circulating working fluid delivered by the second working fluid pump 19 can be increased, while maintaining or reducing the flow rate of the liquid circulating working fluid delivered by the first working fluid pump 18. By reducing the amount of liquid circulating working fluid stored in the working fluid tank 17 and increasing the amount of gaseous circulating working fluid stored in the working fluid tank 16, the increased heat energy is consumed, while simultaneously increasing power generation.
[0032] In this embodiment, the LNG vaporization unit 3 includes a second air heat exchanger 31 and an intermediate medium vaporizer 33. The second air heat exchanger 31 and the intermediate medium vaporizer 33 are connected in parallel. The LNG inlets of both the second air heat exchanger 31 and the intermediate medium vaporizer 33 are connected to the LNG outlet of the LNG heat exchanger 15. A first valve 32 is provided between the second air heat exchanger 31 and the LNG heat exchanger 15, and a second valve 34 is provided between the intermediate medium vaporizer 33 and the LNG heat exchanger 15. When the system is operating normally, the second air heat exchanger 31 is used preferentially, while the intermediate medium vaporizer 33 serves as a backup, thereby ensuring uninterrupted vaporization and further enhancing the stability of the system operation. The specific operation process is as follows: LNG supplied by the receiving terminal first enters the LNG heat exchanger in the cold power generation unit 1, where it exchanges heat with the gaseous circulating working fluid that has completed power generation, releasing the cold energy of the LNG into the cold power generation unit 1. The LNG then further exchanges heat with the air separation unit 2, ultimately achieving energy conversion and air separation and purification. Subsequently, the heated LNG enters the second air heat exchanger 31 through the first valve 32, exchanging heat with ambient air to convert it into ambient temperature NG (Natural Gas), which is then output for use. When the second air heat exchanger 31 malfunctions or is under maintenance, the first valve 32 is closed and the second valve 34 is opened, allowing the LNG discharged from the LNG heat exchanger to enter the intermediate medium vaporizer 33, where it exchanges heat with the intermediate medium to convert it into ambient temperature NG.
[0033] <Second Implementation Method> refer to Figure 2, this embodiment provides a control method applied to the above-mentioned decoupled air separation-LNG cold energy power generation system 100. The method includes the following steps: LNG gasification load prediction step S1, unit linkage regulation step S2, and energy peak shaving step S3.
[0034] The steps in this control method will be described below.
[0035] <LNG gasification load prediction step S1> Based on multi-dimensional data, an LNG gasification load prediction model is established to predict the LNG gasification load in real time. Among them, the multi-dimensional data includes historical data related to factors such as user demand, environmental conditions, system self-state, and market policies. The corresponding relationship between each factor and the LNG gasification load is mined through machine learning methods, and a prediction model is constructed to realize the real-time prediction of the LNG gasification load.
[0036] Specifically, this prediction step includes: mining the corresponding relationship between user demand and LNG gasification load from the historical data of downstream user agreements, gas company dispatching systems, and tanker reservation platforms; mining the corresponding relationship between environmental conditions and LNG gasification load from the data of meteorological monitoring stations, meteorological warning platforms, and historical climate databases; mining the corresponding relationship between the system itself and LNG gasification load from the data of the receiving terminal DCS system, equipment management ledgers, and storage tank monitoring systems; mining the corresponding relationship between market policies and LNG gasification load from the data of energy trading platforms, environmental protection department documents, and power grid dispatching centers.
[0037] <Unit linkage regulation step S2> According to the prediction result of the LNG gasification load in the LNG gasification load prediction step, the operating states of the air separation unit 2, the cold energy power generation unit 1, and the LNG gasification unit 3 are regulated; The unit linkage regulation step includes the following sub-steps: The regulation step S21 based on the predicted increase in LNG gasification load, and the specific operation process is as follows: Because the load increase of air separation unit 2 has a significant lag, when the LNG vaporization load prediction step S1 predicts a substantial increase in LNG vaporization load, on the one hand, the system control unit (not shown in the figure) issues a load increase command to air separation unit 2 in advance, thereby increasing the operating power of air separation unit 2 in a timely manner to provide more heat energy to cold energy power generation unit 1, thus ensuring that when the cold energy provided by LNG vaporization unit 3 increases, it can still be synchronously matched with the heat energy provided by air separation unit 2; on the other hand, the opening of bypass regulating valve 131 can be reduced in advance or completely closed, thereby increasing the heat exchange between the circulating working fluid and air. In some embodiments, if the load of air separation unit 2 has reached 105% or even higher, and if bypass regulating valve 131 is already fully closed, the flow rate of the first working fluid pump 18 delivering liquid circulating working fluid can be increased in advance, and the flow rate of the second working fluid pump 19 delivering liquid circulating working fluid can be increased with a delay according to the load of air separation unit 2. By increasing the storage capacity of the liquid circulating working fluid, excess cold energy provided by LNG vaporization unit 3 is temporarily stored and then stably consumed when the LNG vaporization load decreases.
[0038] Based on the predicted decrease in LNG regasification load, the specific operation procedure for the regulation step S22 is as follows: Because the load reduction of air separation unit 2 has a significant lag, when the LNG vaporization load prediction step S1 predicts a substantial decrease in LNG vaporization load, on the one hand, the system control unit issues a load reduction command to air separation unit 2 in advance, thereby reducing the operating power of air separation unit 2 in a timely manner to reduce the heat energy supply to cold energy power generation unit 1, thus ensuring that when the cold energy provided by LNG vaporization unit 3 decreases, it can still be synchronized with the heat energy provided by air separation unit 2; on the other hand, the opening of bypass regulating valve 131 can be increased in advance or fully opened, thereby reducing the heat exchange between the circulating working fluid and air. In some embodiments, if the load of air separation unit 2 has reached 75% or even lower, and if bypass regulating valve 131 is already fully open, the flow rate of liquid circulating working fluid delivered by the first working fluid pump 18 can be reduced in advance, and the flow rate of liquid circulating working fluid delivered by the second working fluid pump 19 can be reduced with a delay based on the load of air separation unit 2. By reducing the amount of liquid circulating working fluid stored, the limited cooling energy provided by LNG vaporization unit 3 is supplemented, and the amount of liquid circulating working fluid stored is gradually restored when the LNG vaporization load increases in the future.
[0039] <Energy Peak Shaving Step S3> Based on the LNG vaporization load prediction results from the LNG vaporization load prediction step and the residual heat status in the air separation unit 2, the flow rates of the first working fluid pump 18 and the second working fluid pump 19 for delivering the circulating working fluid are adjusted respectively.
[0040] Energy peaking step S3 includes the following sub-steps: In the gas storage step S31, when the LNG vaporization load prediction step predicts a low LNG vaporization load (i.e., insufficient cold energy) and the air separation unit 2 supplies excess heat energy, the flow rate of the liquid circulating working fluid delivered by the first working fluid pump 18 can be reduced, while simultaneously or individually increasing the flow rate of the liquid circulating working fluid delivered by the second working fluid pump 19. This gradually increases the amount of gaseous circulating working fluid in the working fluid gas tank 16 and gradually decreases the amount of liquid working fluid in the working fluid liquid tank 17. Through these operations, the cold energy in the liquid circulating working fluid stored in the working fluid liquid tank 17 can be fully matched with the heat energy supplied by the air separation unit 2.
[0041] In the liquid storage step S32, when the LNG vaporization load prediction step predicts a high LNG vaporization load (i.e., sufficient cold energy) and the heat energy supplied by the air separation unit 2 is insufficient, the flow rate of the liquid circulating working fluid delivered by the second working fluid pump 19 can be reduced, while simultaneously or individually increasing the flow rate of the liquid circulating working fluid delivered by the first working fluid pump 18. This gradually reduces the gaseous circulating working fluid in the working fluid gas tank 16 and gradually increases the liquid working fluid in the working fluid liquid tank 17. Through the above operations, the excess cold energy provided during LNG vaporization can be stored in the working fluid liquid tank 17 as liquid circulating working fluid for later use.
[0042] In this embodiment, the energy peak shaving step S3 can also be matched with grid price operation: When the grid electricity price is low, the load of air separation unit 2 is increased while the load of LNG vaporization unit 3 remains unchanged. The flow rate of liquid circulating working fluid delivered by the first working fluid pump 18 is maintained, and the flow rate of liquid circulating working fluid delivered by the second working fluid pump 19 is increased. This reduces the amount of liquid working fluid in working fluid tank 17 and increases the amount of gaseous circulating working fluid in working fluid tank 16, thereby increasing the power generation of cold energy power generation unit 1. When the electricity price is low, the output of air separation unit 2 is increased, thereby reducing the unit product electricity consumption cost of air separation unit 2.
[0043] When the grid electricity price is high, the load of air separation unit 2 is reduced, while the load of LNG vaporization unit 3 remains unchanged. The flow rate of liquid circulating working fluid delivered by the first working fluid pump 18 is maintained, while the flow rate of liquid circulating working fluid delivered by the second working fluid pump 19 is reduced. This increases the liquid working fluid storage in working fluid tank 17 and decreases the gaseous circulating working fluid storage in working fluid tank 16, thus reducing the power generation of cold energy power generation unit 1. When the electricity price is high, the output of air separation unit 2 is reduced, thereby lowering the unit product electricity consumption cost of air separation unit 2.
[0044] The control method provided in this embodiment improves the decoupling capability and operational flexibility of the decoupled air separation-LNG cold energy power generation system 100 to adapt to LNG gasification load fluctuations. On one hand, this control method effectively enhances the utilization efficiency of thermal and cold energy within the system. Specifically, when the system is in a state where air separation unit 2 does not generate waste heat or the waste cooling provided by LNG gasification unit 3 is discarded, the utilization rate of thermal energy provided by air separation unit 2 increases to over 90%, and the utilization rate of cold energy provided by LNG gasification unit 3 increases to over 90%. On the other hand, by introducing the LNG gasification load prediction step S1 to optimize the system's energy storage and power generation strategies, this control method effectively increases the system's power generation. Specifically, the annual average power generation of cold energy power generation unit 1 increases by over 20%, thereby improving project revenue and the overall return on investment of the system.
[0045] In this embodiment, the control method can be used for some typical application scenarios faced by the decoupled air separation-LNG cold energy power generation system 100.
[0046] <Winter Cold Wave Scene> When a weather warning indicates that the temperature will drop sharply by 10°C in the next 24 hours, the prediction model provided by the LNG vaporization load prediction step S1 will predict in advance that the LNG vaporization load will increase by 10% using the "temperature-load" correlation coefficient trained on historical cold wave data. Based on the above load prediction, the system control unit will issue a load increase command to the air separation unit 2 in advance, and at the same time increase the operating power of the first working fluid pump 18 and the second working fluid pump 19 as needed, and close the bypass regulating valve 131, so as to ensure the smooth operation of the overall system.
[0047] <Industrial User Maintenance Scenarios> When a large gas turbine power plant announces a 3-day shutdown for maintenance, the prediction model provided by the LNG vaporization load prediction step S1, combined with the user's historical gas consumption ratio (10%), predicts that the LNG vaporization load will decrease by 10%. Based on the above load prediction, the system control unit issues a load reduction command to the air separation unit 2 in advance, and at the same time, reduces the operating power of the first working fluid pump 18 and the second working fluid pump 19 as needed, and opens the bypass regulating valve 131. Meanwhile, the working fluid tank 16 is used to store the excess heat energy provided by the air separation unit 2 to avoid heat energy waste, ultimately ensuring the stable operation of the overall system.
[0048] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A decoupled air separation-LNG cold energy power generation system, characterized in that, include: The air separation unit pressurizes and purifies ambient air. The cold energy power generation unit has a circulating working fluid inside, which circulates within the unit to generate electricity. The cold energy power generation unit includes a working fluid heater. The circulating working fluid in the working fluid heater directly or indirectly cools and exchanges heat with the compressed air generated in the air separation unit. The LNG vaporization unit uses LNG entering the LNG vaporization unit to cool and exchange heat with the circulating working fluid in the cold energy power generation unit; The cold energy power generation unit also includes: A first air heat exchanger, wherein the circulating working fluid outlet of the first air heat exchanger is connected to the circulating working fluid inlet of the working fluid heater; A bypass is provided in parallel with the first air heat exchanger. The circulating working fluid outlet of the bypass is connected to the circulating working fluid inlet of the working fluid heater, and a bypass regulating valve is provided on the bypass.
2. The decoupled air separation-LNG cold energy power generation system as described in claim 1, characterized in that, The cold energy power generation unit also includes: A turbine generator set, wherein the circulating working fluid inlet of the turbine generator set is connected to the circulating working fluid outlet of the working fluid heater. An LNG heat exchanger, wherein the inlet of the LNG heat exchanger is connected to the outlet of the turbine generator set, and the outlet of the LNG heat exchanger is connected to the inlet of the first air heat exchanger.
3. The decoupled air separation-LNG cold energy power generation system as described in claim 2, characterized in that, The cold energy power generation unit also includes: A working gas tank is located between the turbine generator set and the LNG heat exchanger; A working fluid tank is located between the LNG heat exchanger and the first air heat exchanger.
4. The decoupled air separation-LNG cold energy power generation system as described in claim 3, characterized in that, The cold energy power generation unit also includes: A first working fluid pump is installed between the LNG heat exchanger and the working fluid tank; The second working fluid pump is located between the working fluid tank and the first air heat exchanger.
5. The decoupled air separation-LNG cold energy power generation system as described in claim 1, characterized in that, The space separation unit includes: Air compression device, An air cooling device, wherein the air outlet of the air compressor is connected to the air inlet of the air cooling device; An air liquefaction distillation apparatus, wherein the air outlet of the air cooling device is connected to the air inlet of the air liquefaction distillation apparatus.
6. The decoupled air separation-LNG cold energy power generation system as described in claim 5, characterized in that, A coolant circulation unit is provided between the air cooling device and the working fluid heater; the coolant in the coolant circulation unit absorbs heat in the air cooling device and releases heat in the working fluid heater.
7. The decoupled air separation-LNG cold energy power generation system as described in claim 1, characterized in that, The LNG vaporization unit includes: Second air heat exchanger, An intermediate medium vaporizer is provided, wherein the second air heat exchanger and the intermediate medium vaporizer are arranged in parallel, and the LNG inlets of both the second air heat exchanger and the intermediate medium vaporizer are connected to the LNG outlet of the LNG heat exchanger. A first valve is provided between the second air heat exchanger and the LNG heat exchanger, and a second valve is provided between the intermediate medium vaporizer and the LNG heat exchanger.
8. A control method applied to a decoupled air separation-LNG cold energy power generation system as described in any one of claims 1-7, characterized in that, Includes the following steps: The LNG vaporization load prediction process involves establishing an LNG vaporization load prediction model based on multidimensional data to predict the LNG vaporization load in real time. The unit linkage control step adjusts the operating status of the air separation unit, the cold energy power generation unit, and the LNG gasification unit based on the LNG gasification load prediction result of the LNG gasification load prediction step. In the energy peak shaving step, based on the LNG vaporization load prediction results from the LNG vaporization load prediction step and the waste heat status within the air separation unit, the flow rates of the first and second working fluid pumps delivering the circulating working fluid are adjusted respectively.
9. The control method as described in claim 8, characterized in that, The unit linkage control step includes the following sub-steps: Based on the control steps for predicting the increase in LNG vaporization load, the air separation unit is instructed to increase its operating power to increase heat energy supply, the opening of the bypass regulating valve is reduced, the flow rate of the first working fluid pump delivering the circulating working fluid is increased in advance, and the increase in the flow rate of the second working fluid pump delivering the circulating working fluid is delayed. Based on the control steps of predicting the decrease in LNG vaporization load, the air separation unit is instructed to reduce its operating power to reduce heat supply, the opening of the bypass regulating valve is increased, the flow rate of the circulating working fluid delivered by the first working fluid pump is reduced in advance, and the flow rate of the circulating working fluid delivered by the second working fluid pump is reduced in a delayed manner.
10. The control method as described in claim 8, characterized in that, The energy peak-shaving step includes the following sub-steps: In the gas storage step, the flow rate of the circulating working fluid delivered by the first working fluid pump is reduced and / or the flow rate of the circulating working fluid delivered by the second working fluid pump is increased. In the liquid storage step, the flow rate of the circulating working fluid delivered by the first working fluid pump is increased and / or the flow rate of the circulating working fluid delivered by the second working fluid pump is decreased.