A combined supply system based on tank BOG and a control method thereof

Abstract

The application discloses a kind of based on storage tank BOG's combined supply system, including storage tank, first heat exchanger, second heat exchanger, buffer tank and fuel cell, LNG is stored in storage tank, BOG formed by LNG evaporation in storage tank is entered into buffer tank as the fuel of fuel cell by pressurizing pump through the primary side of first heat exchanger, the electric energy generated by fuel cell is transported to power supply bus, the cooling water import and export of fuel cell are connected to the secondary side of second heat exchanger and form first heat exchange circulation loop, the primary side of second heat exchanger is connected with the secondary side of first heat exchanger and forms second heat exchange circulation loop, working medium pump and expander are installed on second heat exchange circulation loop, the output shaft of expander is connected with generator, and the electric energy generated by generator is transported to power supply bus.The application can recover the cold energy of BOG to generate electricity and use BOG as the fuel of fuel cell, form combined supply system based on BOG cold energy power generation and fuel cell, improve the comprehensive efficiency of fuel cell and the adaptability of combined supply system.

Description

Technical Field

[0001] This invention relates to the field of energy utilization technology, and more specifically, to a combined heat and power system based on a tank-based BOG and its control method. Background Technology

[0002] When liquefied natural gas (LNG) storage tanks are in a static state or during unloading or loading, causing disturbance to the LNG inside, the stored LNG will absorb heat and produce boil-off gas (BOG). There are two existing BOG handling processes at LNG receiving terminals: one is direct compression and transportation of BOG; the other is re-condensation and return of BOG to the storage tank. The direct compression method involves sending BOG discharged from the LNG storage tank to a compressor room for pressurization before being supplied to downstream city gas users via natural gas pipelines. In this case, the cold energy of the BOG is not recovered, and pressurizing a large amount of BOG also consumes a significant amount of energy.

[0003] A fuel cell is an electrochemical device that directly converts chemical energy into electrical energy. Unlike conventional batteries, fuel cells generate electricity continuously as long as there is a continuous supply of fuel. Unlike internal combustion engines and gas turbines that use fuel combustion to drive a power unit, fuel cells generate electricity through electrochemical reactions. This makes the entire process very quiet and pollution-free, with power generation efficiency 2-3 times higher than traditional methods, achieving true zero emissions. Solid oxide fuel cells (SOFCs) are currently the most efficient power generation technology in the world, operating at temperatures ranging from 800°C to 1000°C without emitting NO. X SO X And solid particulate matter, which will help accelerate the strategic energy transition.

[0004] Therefore, how to rationally utilize BOG in conjunction with fuel cells has become a technical problem that urgently needs to be solved and a key research focus for those skilled in the art. Summary of the Invention

[0005] The purpose of this invention is to provide a combined heat and power system based on BOG (Boiled Gas Tank) and its control method, which can recover the cold energy of BOG for power generation and use BOG as fuel for fuel cells, forming a combined heat and power system based on BOG cold energy power generation and fuel cells, thereby improving the overall efficiency of fuel cells and the adaptability of the combined heat and power system.

[0006] To achieve the aforementioned technical objectives, this invention discloses a combined heat and power system based on tank-based BOG (Booster Gas), comprising a tank, a first heat exchanger, a second heat exchanger, a buffer tank, and a fuel cell. The tank stores LNG. BOG formed by the evaporation of LNG in the tank is pumped through a pressurization pump into the buffer tank via the primary side of the first heat exchanger. The BOG in the buffer tank serves as fuel for the fuel cell. The electrical energy generated by the fuel cell is transmitted to the power supply bus via a first busbar. The cooling water inlet and outlet of the fuel cell are connected to the secondary side of the second heat exchanger, forming a first heat exchange loop via a water pump. The primary side of the second heat exchanger is connected to the secondary side of the first heat exchanger, forming a second heat exchange loop. A working fluid pump is installed on the pipeline between the secondary side outlet of the first heat exchanger and the primary side inlet of the second heat exchanger. An expander is installed on the pipeline between the secondary side inlet of the first heat exchanger and the primary side outlet of the second heat exchanger. The output shaft of the expander is connected to a generator, and the electrical energy generated by the generator is transmitted to the power supply bus via the second busbar.

[0007] Furthermore, the present invention provides a combined heat and power system based on a tank BOG, which also includes an absorption chiller unit. The inlet of the absorption chiller unit is connected to the outlet of the fuel cell cooling water, and the outlet of the absorption chiller unit is connected to the secondary side inlet of the second heat exchanger. The absorption chiller unit is also provided with a cold water circulation interface.

[0008] Furthermore, the present invention provides a combined heat and power system based on a tank-fired gasifier (BOG), which further includes a submerged combustion gasifier. The primary side inlet of the submerged combustion gasifier is connected to the cooling water outlet of the fuel cell, the primary side outlet of the submerged combustion gasifier is connected to the secondary side inlet of the second heat exchanger, LNG is introduced into the secondary side inlet of the submerged combustion gasifier, and the secondary side outlet of the submerged combustion gasifier is connected to the city gas pipeline. The submerged combustion gasifier is also equipped with a hot water circulation interface.

[0009] Furthermore, the present invention provides a combined heat and power system based on a storage tank BOG, wherein the water pump is installed on the pipeline between the secondary side outlet of the second heat exchanger and the cooling water inlet of the fuel cell, and a first switching valve and a second switching valve are installed sequentially on the pipeline between the secondary side inlet of the second heat exchanger and the cooling water outlet of the fuel cell in the direction of water flow.

[0010] Furthermore, the present invention provides a combined heat and power system based on a tank-based BOG, wherein a third switching valve is installed on the pipeline between the cooling water outlet of the fuel cell and the inlet of the absorption chiller, and a fourth switching valve is installed on the pipeline between the outlet of the absorption chiller and the secondary side inlet of the second heat exchanger. One end of the fourth switching valve is connected to the outlet of the absorption chiller, and the other end of the fourth switching valve is connected to the pipeline between the first switching valve and the second switching valve.

[0011] Furthermore, the present invention provides a combined heat and power system based on a tank-based BOG, wherein a fifth switching valve is installed on the pipeline between the primary side inlet of the submerged combustion gasifier and the cooling water outlet of the fuel cell, and a sixth switching valve is installed on the pipeline between the primary side outlet of the submerged combustion gasifier and the secondary side inlet of the second heat exchanger, and the outlet of the sixth switching valve is connected to the pipeline between the second switching valve and the secondary side inlet of the second heat exchanger.

[0012] Furthermore, the present invention provides a combined gas supply system based on a storage tank BOG, wherein a gas supply pump is installed on the pipeline between the buffer tank and the city gas pipeline, and the outlet of the gas supply pump and the secondary gas outlet of the submerged combustion gasifier are connected to the city gas pipeline.

[0013] Furthermore, the present invention provides a combined supply system based on a storage tank BOG, wherein a gas supply pipeline is connected between the buffer tank and the submerged combustion gasifier, and a gas supply switch valve is installed on the gas supply pipeline.

[0014] This invention also provides a control method for a combined heat and power (CHP) system based on a tank BOG, comprising the following steps:

[0015] Shut down the absorption chiller, submerged combustion gasifier, third switch valve, fourth switch valve, fifth switch valve and sixth switch valve;

[0016] Start the pressurization pump so that the BOG evaporated in the storage tank absorbs heat on the primary side of the first heat exchanger and is stored in the buffer tank. Then, part of the BOG in the buffer tank is supplied to the fuel cell and the other part is supplied to the city gas pipeline.

[0017] The working fluid pump is started, which converts the low-temperature, low-pressure liquid working fluid in the second heat exchange cycle into a high-pressure, low-temperature liquid working fluid. The high-pressure, low-temperature liquid working fluid is then converted into a high-pressure, high-temperature gaseous working fluid through the primary side of the second heat exchanger. The high-pressure, high-temperature gaseous working fluid is then converted into a low-pressure, high-temperature liquid working fluid through the work done by the expander. The low-pressure, high-temperature gaseous working fluid is then converted into a low-pressure, low-temperature liquid working fluid through the secondary side of the first heat exchanger and returned to the working fluid pump, forming a working fluid cycle. When the expander does work, the output shaft drives the generator to rotate.

[0018] Start the water pump and open the first and second switch valves, so that the cooling water flows from the water pump outlet through the cooling water inlet of the fuel cell, the cooling water outlet of the fuel cell, the first switch valve, the second switch valve, the secondary side inlet of the second heat exchanger and the secondary side outlet of the second heat exchanger, and then returns to the water pump inlet, forming a cooling water circulation.

[0019] The electrical energy generated by the generator is transported to the power supply bus via the first busbar, and the electrical energy generated by the fuel cell is transported to the power supply bus via the second busbar, forming a combined power supply system.

[0020] Furthermore, the present invention provides a control method for a combined heat and power system based on a tank BOG, which further includes the following steps:

[0021] 1. Under summer operating conditions, open the second, third, and fourth switch valves, and close the first, fifth, and sixth switch valves; start the absorption chiller unit, so that the cooling water from the fuel cell cooling water outlet flows through the absorption chiller unit. The absorption chiller unit absorbs part of the heat from the cooling water and produces cold water, which is then supplied to the cooling equipment through the cold water circulation interface. The secondary side of the second heat exchanger uses the remaining heat from the cooling water to exchange heat with its own primary side, providing heat for the working fluid circulation.

[0022] 2. Under winter operating conditions, open the fifth and sixth switch valves, and close the first, second, third, and fourth switch valves; start the submerged combustion gasifier and shut down the absorption chiller; allow the cooling water from the fuel cell cooling water outlet to flow through the submerged combustion gasifier, using the submerged combustion gasifier to absorb part of the heat from the cooling water to gasify LNG, and supply it to the heating equipment through the hot water circulation interface; allow the secondary side of the second heat exchanger to exchange heat with its own primary side using the remaining heat from the cooling water to provide heat for the working fluid circulation; when the heat required for LNG gasification is insufficient, open the make-up gas switch valve, allowing the BOG in the buffer tank to enter the submerged combustion gasifier through the make-up gas pipeline for combustion and heat supplementation.

[0023] This invention discloses a combined heat and power (CHP) system based on BOG (Boiled Air Gathering) from a storage tank and its control method. Compared with existing technologies, this system has the following advantages: The system includes core components such as a storage tank, a first heat exchanger, a second heat exchanger, a buffer tank, and a fuel cell. Through a series of heat exchange and energy conversion processes, it achieves the recovery and utilization of BOG cold energy, improving the overall efficiency of the fuel cell and the adaptability of the CHP system. The storage tank is the starting point of the system and stores LNG. In the storage tank, some LNG evaporates to form BOG. ​​This BOG is pressurized by a pressurization pump and then passes through the primary side of the first heat exchanger before entering the buffer tank. During this process, the cold energy of the BOG is effectively utilized, providing cooling energy for the system. Simultaneously, the pressurized BOG is fed into the fuel cell as fuel, realizing its reuse as an energy source. The fuel cell converts the chemical energy in the BOG into electrical energy through a chemical reaction. The generated electrical energy is directly transmitted to the power supply bus. Furthermore, the heat generated by the fuel cell during operation is dissipated through cooling water. The inlet and outlet of the cooling water are connected to the secondary side of the second heat exchanger, forming a first heat exchange circulation loop. Through this loop, the heat generated by the fuel cell is transferred and dissipated using the cold energy of the BOG (Boiler Energy Collector), ensuring the stable operation of the fuel cell. The primary side of the second heat exchanger is connected to the secondary side of the first heat exchanger, forming a second heat exchange loop. In this loop, the working fluid pump drives the circulating working fluid to flow through the loop, while the expander uses the pressure and heat energy of the working fluid to generate electricity. The output shaft of the expander is connected to a generator, which converts the mechanical energy output by the expander into electrical energy, which is then transmitted back to the power supply bus. The innovation of this invention lies in combining the cold energy recovery of the BOG with power generation and fuel cell energy utilization, forming a highly efficient cogeneration system. Through this system, not only is the effective utilization of the BOG and the efficient recovery of energy achieved through a series of heat exchange and energy conversion processes, improving the overall efficiency of the fuel cell, but the adaptability and reliability of the cogeneration system are also enhanced. In addition, this system also has the advantages of simple structure, convenient operation, and low maintenance cost. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of a combined heat and power system based on a storage tank BOG according to the present invention. Detailed Implementation

[0025] The following description, in conjunction with the accompanying drawings, provides a detailed explanation and illustration of a combined heat and power system based on a tank BOG and its control method according to the present invention.

[0026] like Figure 1As shown, this embodiment of the invention discloses a combined heat and power system based on BOG (Boiled Gas from Tank 1), including a tank 1, a first heat exchanger 2, a second heat exchanger 3, a buffer tank 4, and a fuel cell 5. The tank 1 stores LNG. BOG formed by the evaporation of LNG in the tank 1 is pumped by a pressurization pump 6 through the primary side of the first heat exchanger 2 into the buffer tank 4. The BOG in the buffer tank 4 serves as fuel for the fuel cell 5, and the electrical energy generated by the fuel cell 5 is transmitted to the power supply bus 8 via a first conductive busbar 7. The cooling water inlet and outlet of the fuel cell 5 are connected to the secondary side of the second heat exchanger 3, forming a first heat exchange circulation loop via a water pump 9, used to cool the interior of the fuel cell 5. The primary side of the second heat exchanger 3 is connected to the secondary side of the first heat exchanger 2 to form a second heat exchange loop, which is used to generate electricity using the cold energy of the BOG. ​​More specifically, a working fluid pump 10 is installed on the pipeline between the secondary side outlet of the first heat exchanger 2 and the primary side inlet of the second heat exchanger 3, and an expander 11 is installed on the pipeline between the secondary side inlet of the first heat exchanger 2 and the primary side outlet of the second heat exchanger 3. The output shaft of the expander 11 is connected to a generator 12, and the electrical energy generated by the generator 12 is transmitted to the power supply bus 8 through the second conductive bus 13.

[0027] In practical use, storage tank 1 serves as the starting point of the combined heat and power system, storing LNG. Fuel cell 5 is a solid oxide fuel cell (SOFC). In storage tank 1, some LNG evaporates to form BOG (Boiled Air Gaseous). This BOG is pressurized by pressurization pump 6, passes through the primary side of the first heat exchanger 2, and further enters buffer tank 4. During this process, the cold energy of the BOG can be effectively utilized by the first heat exchanger 2 to provide cooling energy for the second heat exchange cycle. Simultaneously, the pressurized BOG is fed into fuel cell 5 as fuel, realizing its reuse as an energy source. Fuel cell 5 converts the chemical energy in the BOG into electrical energy through a chemical reaction, and the generated electrical energy is directly transmitted to the power supply bus 8. Furthermore, the heat generated by fuel cell 5 during operation is dissipated through cooling water. The inlet and outlet of the cooling water for fuel cell 5 are connected to the secondary side of the second heat exchanger 3, forming the first heat exchange cycle. Through this cycle, the heat generated by fuel cell 5 is transferred and dissipated using the cold energy of the BOG, ensuring the stable operation of fuel cell 5. The primary side of the second heat exchanger 3 is connected to the secondary side of the first heat exchanger 2, forming a second heat exchange loop. In this loop, the working fluid pump 10 drives the circulating working fluid to flow in the loop, while the expander 11 uses the pressure energy and thermal energy of the working fluid to generate electricity. The output shaft of the expander 11 is connected to a generator 12, which converts the mechanical energy output by the expander 11 into electrical energy, which is then transmitted to the power supply bus 8. This ensures that the electrical energy generated by the fuel cell 5 and the generator 12 is transmitted to the power supply bus 8, forming a multi-mode combined power supply system. The electrical energy generated by the generator 12 and the fuel cell 5 can be adjusted by a transformer and then connected to the user's internal power grid. Excess electrical energy can be adjusted by another transformer and then connected to the public power grid. More specifically, in the second heat exchange cycle, after the working fluid pump 10 is started, the low-temperature, low-pressure liquid working fluid in the second heat exchange cycle is converted into a high-pressure, low-temperature liquid working fluid under the action of the working fluid pump 10. The high-pressure, low-pressure liquid working fluid absorbs heat from the cooling water in the secondary side of the second heat exchanger 3 after passing through the primary side of the second heat exchanger 3, and is converted into a high-pressure, high-temperature gaseous working fluid. After the high-pressure, high-temperature gaseous working fluid is supplied to the expander 11, the expander 11 performs work to convert the high-pressure, high-temperature gaseous working fluid into a low-pressure, high-temperature liquid-gas working fluid. The low-pressure, high-temperature liquid-gas working fluid absorbs the cold energy of the BOG in the primary side of the first heat exchanger 2 after passing through the secondary side of the first heat exchanger 2, and is converted back into a low-pressure, low-temperature liquid working fluid and returned to the working fluid pump 10, forming a working fluid cycle. During this process, when the expander 11 performs work, the output shaft drives the generator 12 to rotate and generate electricity. In summary, the innovation of this system lies in combining the cold energy recovery of the BOG with power generation and the energy utilization of the fuel cell 5, forming a highly efficient combined heat and power system. This system not only achieves efficient utilization of BOG and efficient energy recovery through a series of heat exchange and energy conversion processes, thus improving the overall efficiency of fuel cell 5, but also enhances the adaptability and reliability of the combined heat and power system.In addition, the system has the advantages of simple structure, convenient operation and low maintenance cost.

[0028] In one embodiment of the present invention, based on the above embodiment, an absorption chiller 14 and a submerged combustion gasifier 15 are further included. The inlet of the absorption chiller 14 is connected to the outlet of the cooling water of the fuel cell 5, and the outlet of the absorption chiller 14 is connected to the secondary side inlet of the second heat exchanger 3. The absorption chiller 14 is also provided with a cold water circulation interface 24. More specifically, the inlet of the absorption chiller 14 is actually the hot water inlet of the generator in the absorption chiller 14. Through this connection structure, the hot water flowing out of the cooling water outlet of the fuel cell 5 flows back into the generator inside the absorption chiller 14 through the inlet to provide the required heat. However, the generator cannot absorb all the heat of the cold water. The cooling water flowing out of the generator will flow into the secondary side of the second heat exchanger 3, and the second heat exchanger 3 will perform secondary heat recovery on the cooling water. This step not only helps to increase the temperature of the working fluid in the first heat exchange cycle, but also allows most of the heat to be recovered. The cooling water, after secondary heat recovery, flows back to the fuel cell 5 via the secondary outlet of the second heat exchanger 3 and the water pump 9, continuing to cool the fuel cell 5. The water pump 9 ensures a continuous supply of hot water to the absorption chiller 14, allowing it to continuously generate chilled water from its internal evaporator. This chilled water can then be used by external cooling equipment through the chilled water circulation interface 24. This configuration fully utilizes the heat energy generated by the fuel cell 5, effectively reducing energy waste. This heat recovery method not only improves energy efficiency but also helps reduce environmental pollution and achieve green and sustainable development. The primary-side inlet of the submerged combustion gasifier 15 is connected to the cooling water outlet of the fuel cell 5, and the primary-side outlet of the submerged combustion gasifier 15 is connected to the secondary-side inlet of the second heat exchanger 3. LNG is introduced into the secondary-side air inlet of the submerged combustion gasifier 15, and the secondary-side air outlet of the submerged combustion gasifier 15 is connected to the city gas pipeline. The submerged combustion gasifier 15 is also equipped with a hot water circulation interface 25. Through this connection structure, the cooling water from the cooling water outlet of the fuel cell 5 flows through the submerged combustion gasifier 15. The submerged combustion gasifier 15 absorbs part of the heat from the cooling water for LNG gasification and supplies it to the heating equipment through the hot water circulation interface 25 for heating. The remaining heat of the cooling water is exchanged between the secondary side of the second heat exchanger 3 and its own primary side. This step not only helps to increase the temperature of the working fluid in the first heat exchange loop but also allows most of the heat to be recovered. In this way, the thermal energy generated by the fuel cell 5 is fully utilized, thereby effectively reducing energy waste. This configuration allows for the effective use of the thermal energy generated by the fuel cell 5, achieving efficient energy utilization and reducing waste.

[0029] In one embodiment of the present invention, a water pump 9 is installed on the pipeline between the secondary side outlet of the second heat exchanger 3 and the cooling water inlet of the fuel cell 5 to provide power for fluid circulation in the first heat exchange loop. A first switching valve 16 and a second switching valve 17 are sequentially installed on the pipeline between the secondary side inlet of the second heat exchanger 3 and the cooling water outlet of the fuel cell 5 in the direction of water flow. A third switching valve 18 is installed on the pipeline between the cooling water outlet of the fuel cell 5 and the inlet of the absorption chiller unit 14. A fourth switching valve 19 is installed on the pipeline between the outlet of the absorption chiller unit 14 and the secondary side inlet of the second heat exchanger 3. One end of the fourth switching valve 19 is connected to the outlet of the absorption chiller unit 14, and the other end of the fourth switching valve 19 is connected to the pipeline between the first switching valve 16 and the second switching valve 17. A fifth switching valve 20 is installed on the pipeline between the primary side inlet of the submerged combustion gasifier 15 and the cooling water outlet of the fuel cell 5. A sixth switching valve 21 is installed on the pipeline between the primary side outlet of the submerged combustion gasifier 15 and the secondary side inlet of the second heat exchanger 3. The outlet of the sixth switching valve 21 is connected to the pipeline between the second switching valve 17 and the secondary side inlet of the second heat exchanger 3. With this arrangement, three parallel pipelines can be formed between the cooling water outlet of the fuel cell 5 and the secondary side inlet of the second heat exchanger. More specifically, the first pipeline is the pipeline where the first switching valve 16 is located; the second pipeline is the pipeline where the third switching valve 18, the absorption chiller 14, and the fourth switching valve 19 are located; and the opening and closing of the first and second pipelines is controlled by the second switching valve 17; the third pipeline is the pipeline where the fifth switching valve 20, the submerged combustion gasifier 15, and the sixth switching valve 21 are located. This not only increases the system's flexibility but also provides operators with more options, enabling them to precisely control the cooling water circuit according to different operating states and external environmental conditions. In other words, by controlling the on / off states of relevant valves, operators can flexibly select which pipeline participates in the first heat exchange cycle to adapt to different operating needs and environmental conditions. This setup not only improves the system's adaptability but also makes the cooling process more precise and efficient.

[0030] In one embodiment of the present invention, a gas supply pump 22 is installed on the pipeline between the buffer tank 4 and the city gas pipeline. The outlet of the gas supply pump 22 and the secondary gas outlet of the submerged combustion gasifier 15 are connected to the city gas pipeline, thereby absorbing excess BOG and avoiding resource waste. A make-up gas pipeline is connected between the buffer tank 4 and the submerged combustion gasifier 15. A make-up gas switch valve 23 is installed on the make-up gas pipeline. When the gasifier 15 is not hot enough, the make-up gas switch valve 23 can be quickly opened to supply fuel to the gasifier 15, thereby increasing the heat and meeting its operating requirements. This setting improves the economics of the BOG recycling project and reduces the energy consumption for processing BOG.

[0031] Based on a unified concept, this invention provides a control method for a combined heat and power (CHP) system based on a storage tank 1BOG, comprising the following steps:

[0032] Shut down the absorption chiller 14, the submerged combustion gasifier 15, the third switch valve 18, the fourth switch valve 19, the fifth switch valve 20 and the sixth switch valve 21;

[0033] Start the pressurization pump 6 so that the BOG evaporated in the storage tank 1 absorbs heat on the primary side of the first heat exchanger 2 and is stored in the buffer tank 4. Then, part of the BOG in the buffer tank 4 is supplied to the fuel cell 5 and the other part is supplied to the city gas pipeline.

[0034] The working fluid pump 10 is started, which converts the low-temperature, low-pressure liquid working fluid in the second heat exchange cycle into a high-pressure, low-temperature liquid working fluid. The high-pressure, low-temperature liquid working fluid is then converted into a high-pressure, high-temperature gaseous working fluid through the primary side of the second heat exchanger 3. The high-pressure, high-temperature gaseous working fluid is then converted into a low-pressure, high-temperature liquid working fluid through the work done by the expander 11. The low-pressure, high-temperature gaseous working fluid is then converted into a low-pressure, low-temperature liquid working fluid through the secondary side of the first heat exchanger 2 and returned to the working fluid pump 10, forming a working fluid cycle. When the expander 11 is working, the output shaft drives the generator 12 to rotate.

[0035] Start the water pump 9 and open the first switch valve 16 and the second switch valve 17, so that the cooling water flows from the outlet of the water pump 9 through the cooling water inlet of the fuel cell 5, the cooling water outlet of the fuel cell 5, the first switch valve 16, the second switch valve 17, the secondary side inlet of the second heat exchanger 3 and the secondary side outlet of the second heat exchanger, and then returns to the inlet of the water pump 9, forming a cooling water circulation.

[0036] The electrical energy generated by the generator 12 is transmitted to the power supply bus 8 via the first busbar 7, and the electrical energy generated by the fuel cell 5 is transmitted to the power supply bus 8 via the second busbar 13, forming a combined power supply system.

[0037] In addition to the above embodiments, the following steps are also included:

[0038] 1. Under summer operating conditions, open the second switch valve 17, the third switch valve 18 and the fourth switch valve 19, and close the first switch valve 16, the fifth switch valve 20 and the sixth switch valve 21; start the absorption chiller unit 14, so that the cooling water from the cooling water outlet of the fuel cell 5 flows through the absorption chiller unit 14. After the absorption chiller unit 14 absorbs part of the heat of the cooling water, it generates cold water, which is supplied to the cooling equipment through the cold water circulation interface 24. The secondary side of the second heat exchanger 3 uses the remaining heat of the cooling water to exchange heat with its own primary side, providing heat for the working fluid circulation.

[0039] 2. Under winter operating conditions, open the fifth switch valve 20 and the sixth switch valve 21, and close the first switch valve 16, the second switch valve 17, the third switch valve 18 and the fourth switch valve 19; start the submerged combustion gasifier 15 and shut down the absorption chiller unit 14; allow the cooling water from the cooling water outlet of the fuel cell 5 to flow through the submerged combustion gasifier 15, utilize the submerged combustion gasifier 15 to absorb part of the heat from the cooling water to gasify LNG, and supply it to the heating equipment through the hot water circulation interface 25; allow the secondary side of the second heat exchanger 3 to exchange heat with its own primary side using the remaining heat from the cooling water to provide heat for the working fluid circulation; when the heat required for LNG gasification is insufficient, open the gas replenishment switch valve 23, allowing the BOG in the buffer tank 4 to enter the submerged combustion gasifier 15 through the gas replenishment pipeline for combustion and heat replenishment.

[0040] In this embodiment, the control method not only allows for flexible adjustment of the system's operating mode according to seasonal and operational changes, improving energy efficiency, but also ensures system stability and reliability. Furthermore, this method exhibits strong adaptability and scalability, not only improving energy efficiency and reducing operating costs, but also making a positive contribution to environmental protection and sustainable development.

[0041] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0042] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0043] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0044] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and simple improvements made on the substantive content of the present invention should be included within the protection scope of the present invention.

Claims

1. A combined heat and power system based on tank BOG, characterized in that: The system includes a storage tank, a first heat exchanger, a second heat exchanger, a buffer tank, and a fuel cell. The storage tank stores LNG. Boiled gas (BOG) formed by the evaporation of LNG in the storage tank enters the buffer tank via a pressurized pump through the primary side of the first heat exchanger. The BOG in the buffer tank serves as fuel for the fuel cell. The electrical energy generated by the fuel cell is transmitted to the power supply bus via a first busbar. The cooling water inlet and outlet of the fuel cell are connected to the secondary side of the second heat exchanger, forming a first heat exchange loop via a water pump. The primary side of the second heat exchanger is connected to the secondary side of the first heat exchanger, forming a second heat exchange loop. A working fluid pump is installed on the pipeline between the secondary side outlet of the first heat exchanger and the primary side inlet of the second heat exchanger. An expander is installed on the pipeline between the secondary side inlet of the first heat exchanger and the primary side outlet of the second heat exchanger. The output shaft of the expander is connected to a generator, and the electrical energy generated by the generator is transmitted to the power supply bus via the second busbar.

2. The combined heat and power system based on tank BOG according to claim 1, characterized in that: It also includes an absorption chiller unit, the inlet of which is connected to the outlet of the fuel cell cooling water, and the outlet of which is connected to the secondary side inlet of the second heat exchanger. The absorption chiller unit is also equipped with a cold water circulation interface.

3. A combined heat and power system based on a tank BOG according to claim 2, characterized in that: It also includes a submerged combustion gasifier, wherein the primary side inlet of the submerged combustion gasifier is connected to the cooling water outlet of the fuel cell, the primary side outlet of the submerged combustion gasifier is connected to the secondary side inlet of the second heat exchanger, LNG is introduced into the secondary side inlet of the submerged combustion gasifier, the secondary side outlet of the submerged combustion gasifier is connected to the city gas pipeline, and the submerged combustion gasifier is also equipped with a hot water circulation interface.

4. A combined heat and power system based on a tank BOG as described in claim 3, characterized in that: The water pump is installed on the pipeline between the secondary side outlet of the second heat exchanger and the cooling water inlet of the fuel cell. A first switching valve and a second switching valve are installed sequentially on the pipeline between the secondary side inlet of the second heat exchanger and the cooling water outlet of the fuel cell in the direction of water flow.

5. A combined heat and power system based on a tank BOG according to claim 4, characterized in that: A third switching valve is installed on the pipeline between the cooling water outlet of the fuel cell and the inlet of the absorption chiller. A fourth switching valve is installed on the pipeline between the outlet of the absorption chiller and the secondary side inlet of the second heat exchanger. One end of the fourth switching valve is connected to the outlet of the absorption chiller, and the other end of the fourth switching valve is connected to the pipeline between the first and second switching valves.

6. A combined heat and power system based on a tank BOG according to claim 5, characterized in that: A fifth switching valve is installed on the pipeline between the primary side inlet of the submerged combustion gasifier and the cooling water outlet of the fuel cell. A sixth switching valve is installed on the pipeline between the primary side outlet of the submerged combustion gasifier and the secondary side inlet of the second heat exchanger. The outlet of the sixth switching valve is connected to the pipeline between the second switching valve and the secondary side inlet of the second heat exchanger.

7. A combined heat and power system based on a tank BOG according to claim 6, characterized in that: A gas supply pump is installed on the pipeline between the buffer tank and the city gas pipeline. The outlet of the gas supply pump and the secondary gas outlet of the submerged combustion gasifier are both connected to the city gas pipeline.

8. A combined heat and power system based on a tank BOG according to claim 7, characterized in that: A gas supply line is connected between the buffer tank and the submerged combustion gasifier, and a gas supply switch valve is installed on the gas supply line.

9. A control method for a combined heat and power system based on a tank BOG as described in claim 8, characterized in that: Includes the following steps: Shut down the absorption chiller, submerged combustion gasifier, third switch valve, fourth switch valve, fifth switch valve and sixth switch valve; Start the pressurization pump so that the BOG evaporated in the storage tank absorbs heat on the primary side of the first heat exchanger and is stored in the buffer tank. Then, part of the BOG in the buffer tank is supplied to the fuel cell and the other part is supplied to the city gas pipeline. The working fluid pump is started, which converts the low-temperature, low-pressure liquid working fluid in the second heat exchange cycle into a high-pressure, low-temperature liquid working fluid. The high-pressure, low-temperature liquid working fluid is then converted into a high-pressure, high-temperature gaseous working fluid through the primary side of the second heat exchanger. The high-pressure, high-temperature gaseous working fluid is then converted into a low-pressure, high-temperature liquid working fluid through the work done by the expander. The low-pressure, high-temperature gaseous working fluid is then converted into a low-pressure, low-temperature liquid working fluid through the secondary side of the first heat exchanger and returned to the working fluid pump, forming a working fluid cycle. When the expander does work, the output shaft drives the generator to rotate. Start the water pump and open the first and second switch valves, so that the cooling water flows from the outlet of the water pump through the cooling water inlet of the fuel cell, the cooling water outlet of the fuel cell, the first switch valve, the second switch valve, the secondary side inlet of the second heat exchanger and the secondary side outlet of the second heat exchanger, and then returns to the inlet of the water pump, forming a cooling water circulation. The electrical energy generated by the generator is transported to the power supply bus via the first busbar, and the electrical energy generated by the fuel cell is transported to the power supply bus via the second busbar, forming a combined power supply system.

10. The control method for a combined heat and power system based on a tank BOG according to claim 9, characterized in that: It also includes the following steps:

1. Under summer operating conditions, open the second, third, and fourth switch valves, and close the first, fifth, and sixth switch valves; Start the absorption chiller unit so that the cooling water from the fuel cell cooling water outlet flows through the absorption chiller unit. The absorption chiller unit absorbs part of the heat from the cooling water and produces cold water, which is then supplied to the cooling equipment through the cold water circulation interface. The secondary side of the second heat exchanger uses the remaining heat from the cooling water to exchange heat with its own primary side, providing heat for the working fluid circulation.

2. Under winter operating conditions, open the fifth and sixth switch valves, and close the first, second, third, and fourth switch valves; start the submerged combustion gasifier and shut down the absorption chiller; allow the cooling water from the fuel cell cooling water outlet to flow through the submerged combustion gasifier, using the submerged combustion gasifier to absorb part of the heat from the cooling water to gasify LNG, and supply it to the heating equipment through the hot water circulation interface; allow the secondary side of the second heat exchanger to exchange heat with its own primary side using the remaining heat from the cooling water to provide heat for the working fluid circulation; when the heat required for LNG gasification is insufficient, open the make-up gas switch valve, allowing the BOG in the buffer tank to enter the submerged combustion gasifier through the make-up gas pipeline for combustion and heat supplementation.

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