Cold electricity comprehensive utilization system based on energy coupling

Abstract

The invention relates to a cold power and gas comprehensive utilization system based on energy coupling, which comprises an LNG receiving station, LNG is gasified into natural gas after cold energy utilization by a cold energy power generation and cold exchange system, a liquid air energy storage system, a cold energy air separation system and a light hydrocarbon separation system, and the natural gas respectively enters a natural gas pipe network, a gas power generation system and a natural gas hydrogen production system; the cold energy power generation and cold exchange system utilizes cold energy to generate electric energy for self-generation and self-use in a factory area, residual electricity is transmitted to a power grid, and meanwhile frozen products are generated. The liquid air energy storage system utilizes cold energy to generate electric energy for self-generation and self-use in a factory area, and residual electricity is transmitted to a power grid. The cold energy air separation system generates liquid oxygen, liquid nitrogen and liquid helium through cold energy. The light hydrocarbon separation system generates ethane and LPG (Liquefied Petroleum Gas) products by utilizing cold energy; the gas power generation system directly transmits electric energy generated by natural gas to a power grid; the natural gas hydrogen production system utilizes natural gas to produce hydrogen. The system can be widely applied to the technical field of LNG cold energy utilization.

Description

Technical Field

[0001] The invention relates to the technical field of LNG (liquefied natural gas) cold energy utilization, in particular to a cold electricity comprehensive utilization system based on energy coupling. Background Art

[0002] Freezing natural gas to about -162℃ under normal pressure can turn it into liquid. Liquefied natural gas is formed by purifying natural gas and then using the process of compression, throttling, expansion and external cooling source refrigeration.

[0003] LNG contains a large amount of low-temperature energy. Before it is used as fuel or chemical raw materials, it needs to be gasified into room-temperature gas through heat exchange. During the LNG gasification process, the cold energy released can be used directly or indirectly. Direct use includes: power generation, low-temperature air separation, refrigerated warehouses, production of liquefied carbon dioxide, seawater desalination, air conditioning, low-temperature breeding, cultivation, etc.; indirect use includes: using liquid nitrogen, liquid oxygen, and liquid argon after air separation for low-temperature crushing, freeze drying, low-temperature drying, water and pollutant treatment, and frozen food, etc.

[0004] In the LNG gasification process, the total amount of cold that can be recovered in various application sites is certain, but the useful work obtained at different recovery temperatures is different, that is, the exergy utilization efficiency of the cold contained in LNG is different. From the principle of refrigeration, it can be seen that the lower the required process temperature, the more energy is consumed by the conventional refrigeration method. When reaching a certain low temperature zone, the energy consumption will increase by 10% for every 1K decrease in the evaporation temperature. At this time, the energy saving effect of using LNG cold energy is more obvious, and the utilization rate of cold energy is also high. Therefore, cold energy should be used at the lowest possible temperature. When the temperature of the cold energy utilization site is high, a large amount of cold energy that cannot be utilized in the heat transfer process is lost in vain. When LNG cold energy is used in air separation units, because the process temperature (90~100K) is lower than the LNG temperature (111K), compared with refrigeration and freezing (253K), low-temperature power generation (233K), dry ice production (193K), low-temperature crushing (133K) and other occasions, the cold energy of LNG is utilized to the greatest extent, which is the most technically reasonable way at present. Summary of the invention

[0005] In view of the above problems, the purpose of the present invention is to provide a cold-electricity comprehensive utilization system based on energy coupling, which is suitable for LNG receiving stations. By carrying out the cascade utilization of LNG cold energy, the cold energy utilization rate of the LNG receiving station is improved, and at the same time, the natural gas resources of the LNG receiving station are fully utilized, thereby fully supplying electricity and additionally producing other industrial products.

[0006] To achieve the above object, the present invention adopts the following technical solutions: A cold electricity comprehensive utilization system based on energy coupling, comprising: LNG receiving station, cold energy power generation and refrigeration system, liquid air energy storage system, cold energy air separation system, light hydrocarbon separation system, gas power generation system and natural gas hydrogen production system; The LNG in the LNG receiving station is gasified into natural gas after being utilized for cold energy by the cold energy power generation and cold exchange system, the liquid air energy storage system, the cold energy air separation system and the light hydrocarbon separation system. The natural gas enters the natural gas pipeline network, the gas power generation system and the natural gas hydrogen production system respectively; The cold energy power generation and cold exchange system uses the cold energy of LNG to generate electricity for self-use within the plant area, and transmits the surplus electricity to the power grid, while producing frozen products; The liquid air energy storage system uses the cold energy of LNG to generate electricity for self-use within the factory, and the surplus electricity is transmitted to the power grid; The cold energy air separation system utilizes the cold energy of LNG to produce liquid oxygen, liquid nitrogen and liquid helium; The light hydrocarbon separation system utilizes the cold energy of LNG to produce ethane and LPG products; The gas-fired power generation system utilizes natural gas to generate electricity which is directly transmitted to the power grid; The natural gas hydrogen production system utilizes natural gas to produce hydrogen.

[0007] Further, the cold energy power generation and cold exchange system comprises a cold energy power generation device and a cold exchange station; The cold energy power generation device includes an LNG-intermediate medium heat exchanger, an intermediate medium pump, a refrigerant-intermediate medium heat exchanger and an expansion power generation device; The LNG-intermediate medium heat exchanger exchanges heat with the LNG of the LNG receiving station through the intermediate medium to release high-grade cold energy of the LNG. The LNG sent out by the LNG-intermediate medium heat exchanger then releases low-grade cold energy through the cold exchange station and is converted into natural gas, which is returned to the LNG receiving station and transported to the natural gas pipeline network. The intermediate medium pump is used to pressurize the intermediate medium, heat the refrigerant in the refrigerant-intermediate medium heat exchanger, and then gasify it, send it to the expansion power generation equipment to generate electricity, and finally return it to the LNG-intermediate medium heat exchanger; The refrigerant in the cold exchange station is cooled by the refrigerant-intermediate medium heat exchanger, cooled by the LNG in the cold exchange station, and then supplied to downstream cold users.

[0008] Furthermore, the intermediate medium is propane or a mixed refrigerant.

[0009] Furthermore, the expander in the expansion power generation device is a single-stage or multi-stage expander.

[0010] Furthermore, the liquid air energy storage system uses liquid air energy storage or liquid carbon dioxide energy storage to realize the cold energy utilization of LNG.

[0011] Further, when the liquid air energy storage system adopts liquid air energy storage, it includes a multi-stage compression unit, a liquefaction unit, a purification unit, a liquid air storage tank, a gasification unit, a multi-stage expansion unit, a heat storage tank and a cryogenic storage tank; The purification unit is used to purify the air and send the purified air to the multi-stage compression unit; the multi-stage compression unit is used to perform multi-stage compression on the purified air and send the released heat energy to the heat storage tank, and at the same time send the compressed air to the liquefaction unit; the liquefaction unit uses the LNG transported by the LNG receiving station to pre-cool the air and then sends it to the liquid air storage tank for storage, completing the energy storage process; The liquid air in the liquid air storage tank is pressurized by a cryogenic pump, flows through the vaporization unit for vaporization, and is then sent to the expansion unit, while the cold is sent to the cryogenic storage tank for storage; the vaporized low-temperature and high-pressure air is heated by the heat storage tank and then expanded in multiple stages by the expansion unit, generating high-pressure, room-temperature gas to drive the air turbine generator to generate electricity, thereby completing the energy release process.

[0012] Furthermore, the cold energy air separation system includes a filtration system, a compression system, air compressor coolers at various stages, a purification system, an air separation cold box, an ethylene glycol system, an LNG cold box and a cryogenic liquid storage system; The filtering system, compression system, air compressor coolers at various levels and purification system filter, compress, cool and purify the air in sequence; The air separation cold box is used to distill the purified air and send the distilled liquid oxygen, liquid nitrogen and liquid argon products to the cryogenic liquid storage system for low-temperature storage; The LNG cold box utilizes the LNG delivered by the LNG receiving station to exchange heat with the nitrogen cycle, and the nitrogen cycle provides cold energy to the air separation cold box. The remaining cold energy after the heat exchange between the LNG and nitrogen cycles is absorbed by the ethylene glycol system, and the ethylene glycol system is used to cool the coolers of each stage of the air compressor.

[0013] Further, the light hydrocarbon separation system includes a primary heat exchanger, a secondary heat exchanger, a flash tower, a demethanizer and a deethanizer; The LNG from the LNG receiving station is subjected to heat exchange in the primary heat exchanger and the secondary heat exchanger, and then enters the flash tower for flash evaporation. The liquid phase separated from the flash tower is then pressurized and enters the demethanizer. The flash gas and methane gas separated from the flash tower and the demethanizer are respectively heat exchanged with the secondary heat exchanger and the primary heat exchanger without compression to condense the liquid methane product, and the cold energy of LNG is used for liquefaction of the liquid methane product; The liquid phase separated from the demethanizer is passed through a deethanizer to separate light hydrocarbons to obtain ethane products and propane products.

[0014] Furthermore, the gas-fired power generation system adopts a gas-steam combined cycle, with natural gas as the high-temperature working fluid and steam as the low-temperature working fluid, and uses the exhaust gas of the gas turbine as a heating source for the steam turbine device cycle to generate electricity and supply it to the power grid.

[0015] Furthermore, in the natural gas hydrogen production system, natural gas generates hydrogen after being sequentially subjected to natural gas desulfurization, natural gas steam reforming, CO2 water vapor shift and pressure swing adsorption processes.

[0016] The present invention adopts the above technical solution, which has the following advantages: The present invention utilizes cold energy of LNG receiving station in various ways, greatly improving the utilization rate of cold energy of LNG receiving station. Through the cascade utilization of cold energy, the exergy efficiency of LNG cold energy utilization is improved, and the energy consumption of seawater pumps in the receiving station is saved. By adopting various forms of natural gas utilization, the location advantage of LNG receiving station is fully utilized, multiple structured additional products are formed, and the industrial chain of LNG receiving station is expanded. Through various forms of power supply, the LNG receiving station plant area can generate power for self-use, and the power supply to the power grid enhances the regional power supply capacity.

[0017] In summary, the present invention has excellent use effect and high use and promotion value. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. Throughout the accompanying drawings, the same reference numerals are used to represent the same components. In the accompanying drawings: Figure 1 It is a flow chart of a cold and electricity comprehensive utilization system based on energy coupling provided in an embodiment of the present invention; Figure 2 It is a schematic diagram of a cold energy power generation and cold exchange station of a cold electricity comprehensive utilization system based on energy coupling provided in an embodiment of the present invention; Figure 3 It is a schematic diagram of liquid air energy storage in a cold-electricity comprehensive utilization system based on energy coupling provided in an embodiment of the present invention; Figure 4 It is a schematic diagram of cold energy and air separation of a cold electricity comprehensive utilization system based on energy coupling provided in an embodiment of the present invention; Figure 5 It is a schematic diagram of light hydrocarbon separation in a cold electricity comprehensive utilization system based on energy coupling provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solution and advantages of the embodiment of the present invention clearer, the technical solution of the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings of the embodiment of the present invention. Obviously, the described embodiment is a part of the embodiment of the present invention, not all of the embodiments. Based on the described embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field belong to the scope of protection of the present invention.

[0020] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0021] In some embodiments of the present invention, a cold electricity comprehensive utilization system based on energy coupling is provided, including an LNG receiving station, a cold energy power generation and cold exchange station, liquid air energy storage, cold energy air separation, light hydrocarbon separation, gas power generation and natural gas hydrogen production, the cold energy power generation and cold exchange station includes an LNG-intermediate medium heat exchanger, an intermediate medium pump, a refrigerant-intermediate medium heat exchanger, an expansion power generation equipment and a cold exchange station, the liquid air energy storage includes multi-stage compression, liquefaction, purification, liquid air storage tanks, gasification, multi-stage expansion, heat storage tanks and deep cold storage tanks, the cold energy air separation includes a filtration system, a compressor system, air compressor coolers at various stages, a purification system, an air separation cold box, an ethylene glycol system, an LNG cold box, a low-temperature liquid storage system, and the light hydrocarbon separation includes a heat exchanger, a flash tower, a demethanizer, and a deethanizer.

[0022] The present invention designs a cold-electricity comprehensive utilization system based on energy coupling, comprehensively utilizes the cold energy and natural gas resources of the LNG receiving station and performs regional power supply, thus giving full play to the location advantage of the LNG receiving station.

[0023] Example 1 like Figure 1As shown, the present invention provides a cold electricity comprehensive utilization system based on energy coupling, including: LNG receiving station, cold energy power generation and refrigeration system, liquid air energy storage system, cold energy air separation system, light hydrocarbon separation system, gas power generation system and natural gas hydrogen production system. Among them, the LNG in the LNG receiving station is gasified into natural gas after cold energy utilization by the cold energy power generation and refrigeration system, liquid air energy storage system, cold energy air separation system and light hydrocarbon separation system, and the natural gas enters the natural gas pipeline network, gas power generation system and natural gas hydrogen production system respectively; the cold energy power generation and refrigeration system uses the cold energy of LNG to generate electricity for self-generation and self-use in the factory area, and the surplus electricity is transmitted to the power grid, and frozen products are produced at the same time; the liquid air energy storage system uses the cold energy of LNG to generate electricity for self-generation and self-use in the factory area, and the surplus electricity is transmitted to the power grid; the cold energy air separation system uses the cold energy of LNG to generate liquid oxygen, liquid nitrogen and liquid helium; the light hydrocarbon separation system uses the cold energy of LNG to generate ethane and LPG; the gas power generation system uses natural gas to generate electricity and directly transmits it to the power grid, and the natural gas hydrogen production system uses natural gas to produce hydrogen.

[0024] Preferably, Figure 2 As shown, the cold energy power generation and cooling system includes a cold energy power generation device and a cooling station, wherein the cold energy power generation device is based on an intermediate medium vaporizer (IFV) split device, adopts a low-temperature Rankine cycle system, takes the cooling station refrigerant as a heat source, and the intermediate medium as a working medium, forming a closed low-temperature steam power cycle, and utilizes the high-quality low-temperature cold energy of LNG and the low-grade energy of the cooling station refrigerant to generate electricity.

[0025] Specifically, the cold energy power generation device includes an LNG-intermediate medium heat exchanger, an intermediate medium pump, a refrigerant-intermediate medium heat exchanger, an expansion power generation device, and a cold exchange station. Among them, the LNG-intermediate medium heat exchanger exchanges heat with the LNG at the LNG receiving station through the intermediate medium to release the high-grade cold of the LNG. The LNG sent out by the LNG-intermediate medium heat exchanger then releases the low-grade cold through the cold exchange station and is converted into natural gas and returned to the receiving station to be transported to the natural gas pipeline network; the intermediate medium in the LNG-intermediate medium heat exchanger is pressurized by the intermediate medium pump, and the refrigerant in the refrigerant-intermediate medium heat exchanger is heated and then gasified, and sent to the expansion power generation device to generate electricity, and finally returns to the LNG-intermediate medium heat exchanger. At the same time, the refrigerant in the cold exchange station is cooled by the refrigerant-intermediate medium heat exchanger, and then cooled by the LNG of the cold exchange station and supplied to downstream cold users.

[0026] Preferably, the cold energy power generation device may also adopt a direct expansion method.

[0027] Preferably, the intermediate medium of the Rankine cycle system may be propane or a mixed refrigerant, etc., and the expander in the expansion power generation equipment may be a single-stage or multi-stage expander.

[0028] Preferably, the cold exchange station cascade utilizes the low-temperature cold energy of NG. LNG is gasified in the cold energy power generation device to become NG, and NG still contains a large amount of low-temperature (such as below -50°C) cold energy, which is taken away by the refrigerant of the cold exchange station for low-temperature cold storage, frozen seafood, freeze-dried fruits and vegetables, cooling of large data centers, etc. Its refrigerant can be selected from ammonia, carbon dioxide or environmentally friendly Freon, etc.

[0029] Preferably, Figure 3 As shown, the liquid air energy storage system includes a multi-stage compression unit, a liquefaction unit, a purification unit, a liquid air storage tank, a gasification unit, a multi-stage expansion unit, a thermal storage tank and a cryogenic storage tank. Among them, the liquid air energy storage system can be divided into an energy storage process and an energy release process.

[0030] During the energy storage process: the purification unit is used to purify the air and send the purified air to the multi-stage compression unit; the multi-stage compression unit is used to perform multi-stage compression on the purified air and send the released heat energy to the heat storage tank, and at the same time send the compressed high-pressure air to the liquefaction unit; the liquefaction unit is used to pre-cool the high-pressure air with LNG transported by the LNG receiving station, and then send it to the liquid air storage tank for storage.

[0031] During the energy release process: the liquid air in the liquid air storage tank is pressurized by a cryogenic pump, flows through the vaporization unit for vaporization, and is then sent to the expansion unit. At the same time, the cold is sent to a cryogenic storage tank for storage; the vaporized low-temperature and high-pressure air is heated by a heat storage tank and then expanded in multiple stages by an expansion unit to generate high-pressure, room-temperature gas that drives an air turbine generator to generate electricity.

[0032] Preferably, the liquid air energy storage system can use liquid air energy storage or liquid carbon dioxide energy storage, and can use the over-service life storage tanks of the LNG receiving station to adopt a closed cycle or use a traditional closed cycle. The present invention does not impose any restrictions on this.

[0033] Preferably, Figure 4 As shown, the cold energy air separation system is a process that combines the LNG gasification system with the air separation system to fully utilize the huge amount of cold released during LNG gasification to produce air separation liquid products such as liquid nitrogen and liquid oxygen.

[0034] Specifically, the cold energy air separation system includes a filtration system, a compression system, air compressor coolers at various levels, a purification system, an air separation cold box, an ethylene glycol system, an LNG cold box, and a cryogenic liquid storage system. Among them, the filtration system, the compression system, air compressor coolers at various levels, and the purification system filter, compress, cool, and purify the air in turn; the air separation cold box is used to distill the purified air, and send the distilled liquid oxygen, liquid nitrogen, and liquid argon products to the cryogenic liquid storage system for low-temperature storage; the LNG cold box uses the LNG transported by the LNG receiving station to exchange heat with the nitrogen cycle, and the nitrogen cycle provides cold energy to the air separation cold box. After the heat exchange between the LNG and nitrogen cycles, the remaining cold energy is absorbed by the ethylene glycol system, and the ethylene glycol system cools the air compressor coolers at various levels.

[0035] In this embodiment, the refrigeration liquefaction system in the cold energy air separation process directly utilizes the cold energy of LNG for refrigeration and liquefaction through the nitrogen liquefier heat exchanger, and the air cooling fully utilizes the low-temperature NG cooling after passing through the refrigeration liquefaction system through the ethylene glycol cooling system. The cold energy air separation system uses cold energy in a cascade manner. The low-temperature LNG at the LNG receiving station first releases high-grade cold energy through the nitrogen cycle, and then releases low-grade cold energy through the ethylene glycol system. Compared with the usual air separation process, it replaces the expansion mechanism refrigeration, eliminates the air cooling tower, and greatly reduces the power consumption and water consumption.

[0036] Preferably, Figure 5 As shown, the light hydrocarbon separation system includes a primary heat exchanger, a secondary heat exchanger, a flash tower, a demethanizer and a deethanizer. Among them, the LNG from the LNG receiving station enters the flash tower for flash evaporation after heat exchange in the primary heat exchanger and the secondary heat exchanger, and the liquid phase separated from the flash tower is pressurized and enters the demethanizer; the flash gas and methane gas separated from the flash tower and the demethanizer are heat exchanged with the secondary heat exchanger and the primary heat exchanger respectively without compression to condense the liquid methane product, and the cold energy of LNG is used for liquefaction of the liquid methane product; the liquid phase separated from the demethanizer is separated from the light hydrocarbons by the deethanizer to obtain ethane products and propane products.

[0037] In particular, the preheating of raw materials in the light hydrocarbon separation can also adopt the LNG multi-stage pressure-boosting flash process, the LNG single-stage pressure-boosting flash full compression process, the LNG two-stage pressure-boosting and one-stage flash partial compression process, and the LNG two-stage pressure-boosting and one-stage flash non-compression process; the light hydrocarbon separation process can adopt single-tower and double-tower processes or high, medium and low pressure processes.

[0038] Preferably, the gas-fired power generation system adopts a gas-steam combined cycle, with gas as the high-temperature working fluid and steam as the low-temperature working fluid. The exhaust gas of the gas turbine is used as the heating source for the steam turbine device cycle, and the generated electricity is supplied to the power grid.

[0039] Preferably, the natural gas hydrogen production system includes several main processes including natural gas desulfurization, natural gas steam reforming, CO2 steam shift and pressure swing adsorption (PSA). Hydrogen is mainly produced by natural gas reforming, and the steam generation system recovers heat from high-temperature flue gas for natural gas reforming.

[0040] The specific working process of the embodiment of the present invention is introduced below: like Figure 1 The figure shows a flow chart of the cold and electricity comprehensive utilization system based on energy coupling. The LNG from the LNG receiving station passes through the cold energy power generation and cold exchange station, cold energy air separation system at the same time during the day, and passes through the liquid air energy storage system and cold energy air separation system at night. When there are more light hydrocarbons in the LNG receiving station, it passes through the light hydrocarbon separation system. After passing through the above facilities, the LNG cold energy is released and converted into natural gas. The natural gas is simultaneously transported to the natural gas pipeline network, gas-fired power generation and natural gas hydrogen production system for natural gas utilization. Among them, the cold energy is cascaded in the cold energy power generation and cold exchange station. The low-temperature LNG first passes through the cold energy power generation to release high-grade cold energy, and then passes through the cold exchange station to release low-grade cold energy. The electricity generated by cold energy power generation and liquid air energy storage is transmitted to the power grid during the day, and the gas-fired power generation is transmitted to the power grid for peak load supply throughout the day.

[0041] like Figure 2 The figure shows the flow chart of cold energy power generation and cold exchange station of cold electricity comprehensive utilization system based on energy coupling. LNG from LNG receiving station passes through LNG-intermediate medium heat exchanger and intermediate medium for heat exchange to release high-grade cold of LNG, and then passes through cold exchange station to release low-grade cold, which is converted into natural gas and returned to receiving station for external transmission. After the intermediate medium absorbs cold energy through LNG-intermediate medium heat exchanger, it undergoes Rankine cycle, is pressurized by intermediate medium pump, is heated by refrigerant in refrigerant-intermediate medium heat exchanger, is gasified and expanded, and then returns to LNG-intermediate medium heat exchanger to generate electricity. The refrigerant of cold exchange station is cooled by refrigerant-intermediate medium heat exchanger, cooled by LNG of cold exchange station, and then supplied to downstream cold users.

[0042] like Figure 3 The figure shows the flow chart of liquid air energy storage in the cold and electricity comprehensive utilization system based on energy coupling. In the energy storage stage of liquid air energy storage, the air is purified and then subjected to multi-stage compressors for LNG pre-cooling and liquefaction, and the liquefied air is stored in liquid air storage tanks; in the energy release stage, the liquid air is gasified and then subjected to multi-stage expansion to generate electricity and be transmitted to the power grid. The compression heat generated by multi-stage compression is stored in the heat storage tank and then released to the expander stage, and the coldness of the liquid air is stored in the cryogenic storage tank and then released to the liquefied cold box.

[0043] like Figure 4The figure shows the cold energy air separation flow chart of the cold electricity comprehensive utilization system based on energy coupling. After the air is filtered, it enters the compression system and then the purification system for purification. After purification, it enters the air separation cold box to distill liquid oxygen, liquid nitrogen, and liquid argon products and store them in low-temperature liquid state. LNG is introduced from the LNG receiving station into the LNG cold box and heat exchanged with the nitrogen cycle. The nitrogen cycle provides cold energy to the air separation cold box. After the heat exchange between LNG and the nitrogen cycle, the ethylene glycol system absorbs the remaining cold energy, and then the ethylene glycol system cools the coolers of each level of the air compressor. The cold energy air separation uses cold energy in a cascaded manner. The low-temperature LNG first releases high-grade cold energy through the nitrogen cycle, and then releases low-grade cold energy through the ethylene glycol system.

[0044] like Figure 5 The figure shows a flow chart of light hydrocarbon separation based on the cold electricity comprehensive utilization system of energy coupling. After two-stage heat exchange, LNG is flashed in the flash tower, then in the demethanizer to remove methane, and then enters the deethanizer to remove ethane and propane products. The natural gas produced in the demethanizer and flash tower is cooled by LNG cold energy and liquefied and returned to the LNG receiving station.

[0045] The innovation of the system of the present invention is that the LNG receiving station uses LNG cold energy in a cascaded manner. In the cold energy power generation and cold exchange station, LNG first releases high-grade cold energy through cold energy power generation, and then releases low-grade cold energy through the cold exchange station. In the cold energy air separation, LNG first releases high-grade cold energy through nitrogen circulation, and then releases low-grade cold energy through ethylene glycol circulation, which improves the utilization rate of LNG cold energy and reduces the overall energy exergy loss. By giving full play to the location advantages of the LNG receiving station, the cold energy and natural gas resources of the LNG receiving station are comprehensively utilized and a stable power supply is provided to the region.

[0046] The above embodiments are preferred implementation modes of the present invention and are only used to facilitate the description of the present invention. They are not intended to limit the present invention in any form. Any person with ordinary knowledge in the relevant technical field, if they do not depart from the scope of the technical features of the present invention, can make equivalent embodiments by partial changes or modifications to the technical contents disclosed in the present invention, and they still fall within the scope of the technical features of the present invention without departing from the technical features of the present invention.

[0047] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A cold electricity comprehensive utilization system based on energy coupling, characterized in that: include: LNG receiving station, cold energy power generation and refrigeration system, liquid air energy storage system, cold energy air separation system, light hydrocarbon separation system, gas power generation system and natural gas hydrogen production system; The LNG in the LNG receiving station is gasified into natural gas after being utilized for cold energy by the cold energy power generation and cold exchange system, the liquid air energy storage system, the cold energy air separation system and the light hydrocarbon separation system. The natural gas enters the natural gas pipeline network, the gas power generation system and the natural gas hydrogen production system respectively; The cold energy power generation and cold exchange system uses the cold energy of LNG to generate electricity for self-use within the plant area, and transmits the surplus electricity to the power grid, while producing frozen products; The liquid air energy storage system uses the cold energy of LNG to generate electricity for self-use within the factory, and the surplus electricity is transmitted to the power grid; The cold energy air separation system utilizes the cold energy of LNG to produce liquid oxygen, liquid nitrogen and liquid helium; The light hydrocarbon separation system utilizes the cold energy of LNG to produce ethane and LPG products; The gas-fired power generation system utilizes natural gas to generate electricity which is directly transmitted to the power grid; The natural gas hydrogen production system utilizes natural gas to produce hydrogen.

2. The cold electricity comprehensive utilization system based on energy coupling according to claim 1, characterized in that: The cold energy power generation and cooling system comprises a cold energy power generation device and a cooling station; The cold energy power generation device includes an LNG-intermediate medium heat exchanger, an intermediate medium pump, a refrigerant-intermediate medium heat exchanger and an expansion power generation device; The LNG-intermediate medium heat exchanger exchanges heat with the LNG of the LNG receiving station through the intermediate medium to release high-grade cold energy of the LNG. The LNG sent out by the LNG-intermediate medium heat exchanger then releases low-grade cold energy through the cold exchange station and is converted into natural gas, which is returned to the LNG receiving station and transported to the natural gas pipeline network. The intermediate medium pump is used to pressurize the intermediate medium, heat the refrigerant in the refrigerant-intermediate medium heat exchanger, and then gasify it, send it to the expansion power generation equipment to generate electricity, and finally return it to the LNG-intermediate medium heat exchanger; The refrigerant in the cold exchange station is cooled by the refrigerant-intermediate medium heat exchanger, cooled by the LNG in the cold exchange station, and then supplied to downstream cold users.

3. The cold electricity comprehensive utilization system based on energy coupling as claimed in claim 2, characterized in that: The intermediate medium is propane or a mixed refrigerant.

4. The cold electricity comprehensive utilization system based on energy coupling as claimed in claim 2, characterized in that: The expander in the expansion power generation equipment is a single-stage or multi-stage expander.

5. The cold electricity comprehensive utilization system based on energy coupling according to claim 1, characterized in that: The liquid air energy storage system uses liquid air energy storage or liquid carbon dioxide energy storage to realize the cold energy utilization of LNG.

6. The cold electricity comprehensive utilization system based on energy coupling as claimed in claim 5, characterized in that: When the liquid air energy storage system adopts liquid air energy storage, it includes a multi-stage compression unit, a liquefaction unit, a purification unit, a liquid air storage tank, a gasification unit, a multi-stage expansion unit, a heat storage tank and a cryogenic storage tank; The purification unit is used to purify the air and send the purified air to the multi-stage compression unit; The multi-stage compression unit is used to perform multi-stage compression on the purified air, and send the released heat energy to the heat storage tank, and at the same time send the compressed air to the liquefaction unit; the liquefaction unit uses the LNG delivered by the LNG receiving station to pre-cool the air, and then sends it to the liquid air storage tank for storage, completing the energy storage process; The liquid air in the liquid air storage tank is pressurized by a cryogenic pump, flows through the vaporization unit for vaporization, and is then sent to the expansion unit, while the cold is sent to the cryogenic storage tank for storage; the vaporized low-temperature and high-pressure air is heated by the heat storage tank and then expanded in multiple stages by the expansion unit, generating high-pressure, room-temperature gas to drive the air turbine generator to generate electricity, thereby completing the energy release process.

7. The cold electricity comprehensive utilization system based on energy coupling according to claim 1, characterized in that: The cold energy air separation system includes a filtration system, a compression system, air compressor coolers at various stages, a purification system, an air separation cold box, an ethylene glycol system, an LNG cold box and a cryogenic liquid storage system; The filtering system, compression system, air compressor coolers at various levels and purification system filter, compress, cool and purify the air in sequence; The air separation cold box is used to distill the purified air and send the distilled liquid oxygen, liquid nitrogen and liquid argon products to the cryogenic liquid storage system for low-temperature storage; The LNG cold box utilizes the LNG delivered by the LNG receiving station to exchange heat with the nitrogen cycle, and the nitrogen cycle provides cold energy to the air separation cold box. The remaining cold energy after the heat exchange between the LNG and nitrogen cycles is absorbed by the ethylene glycol system, and the ethylene glycol system is used to cool the coolers of each stage of the air compressor.

8. The cold electricity comprehensive utilization system based on energy coupling according to claim 1, characterized in that: The light hydrocarbon separation system includes a primary heat exchanger, a secondary heat exchanger, a flash tower, a demethanizer and a deethanizer; The LNG from the LNG receiving station is subjected to heat exchange in the primary heat exchanger and the secondary heat exchanger, and then enters the flash tower for flash evaporation. The liquid phase separated from the flash tower is then pressurized and enters the demethanizer. The flash gas and methane gas separated from the flash tower and the demethanizer are respectively heat exchanged with the secondary heat exchanger and the primary heat exchanger without compression to condense the liquid methane product, and the cold energy of LNG is used for liquefaction of the liquid methane product; The liquid phase separated from the demethanizer is passed through a deethanizer to separate light hydrocarbons to obtain ethane products and propane products.

9. The cold electricity comprehensive utilization system based on energy coupling according to claim 1, characterized in that: The gas-fired power generation system adopts a gas-steam combined cycle, with natural gas as a high-temperature working fluid and steam as a low-temperature working fluid, and uses the exhaust gas of the gas turbine as a heating source for the steam turbine device cycle to generate electricity and supply it to the power grid.

10. The cold electricity comprehensive utilization system based on energy coupling according to claim 1, characterized in that: In the natural gas hydrogen production system, natural gas is sequentially subjected to natural gas desulfurization, natural gas steam reforming, CO water vapor shift and pressure swing adsorption processes to generate hydrogen.

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