An LNG power generation system with integrated liquid nitrogen energy storage system

Abstract

The present invention provides an LNG power generation system integrated with a liquid nitrogen energy storage system, comprising an LNG combustion system, a power generation system and an energy storage system; the LNG combustion system comprises an LNG gasification and compression branch; the energy storage system comprises a nitrogen energy storage branch and a liquid nitrogen energy release branch; the power generation system comprises a gas power generation branch; the outlet of the LNG gasification and compression branch is connected to the inlet of the gas power generation branch; the LNG gasification and compression branch comprises an LNG storage tank, a first heat exchanger and an NG compressor connected in sequence; the outlet of the nitrogen energy storage branch is connected to the inlet of the liquid nitrogen energy release branch, the nitrogen energy storage branch comprises an air separation device, a nitrogen compressor and a second heat exchanger connected in sequence, the second heat exchanger is connected to the first heat exchanger, and the liquid nitrogen energy release branch comprises a liquid nitrogen storage tank, a liquid nitrogen pump, a cold accumulator, a third heat exchanger, a nitrogen expander and a heat accumulator connected to the third heat exchanger connected in sequence.

Description

Technical Field

[0001] The present technology belongs to the field of energy-saving technology, and in particular provides an LNG power generation system with an integrated liquid nitrogen energy storage system. Background Art

[0002] With the frequent changes in the supply and demand relationship of the power market, the peak and valley load differences of the power grid have increased. However, more than 70% of China's power load comes from coal-fired power generation units. In order to help achieve the goal of energy conservation and emission reduction, the energy structure transformation of the power industry has become more urgent. Compared with coal-fired power generation, LNG power generation has the characteristics of high efficiency, low pollution and strong flexibility, and is an important driving force for power transformation and upgrading. LNG contains a large amount of high-grade cold energy and needs to be gasified before combustion. The current gasification treatment mainly includes the use of waste heat resources for reheating, or the use of carbon dioxide for cold energy exchange and liquefaction of carbon dioxide. The former does not utilize LNG cold energy. In the latter utilization method, due to the low liquefaction temperature of carbon dioxide, only a low-grade cold source is required to provide cold energy. Therefore, in the direct exchange process between LNG and carbon dioxide gas, the high-grade cold energy of LNG is transferred to liquid carbon dioxide, that is, the high-grade cold energy is transferred and low-grade cold energy is formed. Therefore, the current utilization method has the problem of unreasonable utilization of LNG cold energy. Furthermore, in the current LNG power generation system, oxygen-enriched combustion is usually adopted to improve combustion efficiency and increase the power generation capacity of combustion flue gas, and combustion power generation is continuously operated. In this case, oxygen is produced by the air separation unit (ASU) to achieve oxygen-enriched combustion, but the large amount of high-purity nitrogen produced by the ASU at the same time is not used. The continuous operation of LNG power generation results in low power peak-shaving capacity, causing serious waste of resources and energy.

[0003] Therefore, how to efficiently and reasonably utilize LNG cold energy and make full use of ASU equipment to further enhance LNG flexible power generation and peak load regulation capabilities is the key to improving LNG power generation efficiency and balancing the power grid. It is necessary to provide an effective way and system to solve the above problems. Summary of the invention

[0004] A brief overview of the present disclosure will be given below in order to provide a basic understanding of certain aspects of the present disclosure. It should be understood that this overview is not an exhaustive overview of the present disclosure. It is not intended to identify key or important parts of the present disclosure, nor is it intended to limit the scope of the present disclosure. Its purpose is simply to give certain concepts in a simplified form as a prelude to a more detailed description discussed later.

[0005] The purpose of the present invention is to provide a new LNG power generation system with an integrated liquid nitrogen energy storage system to address the problems of unreasonable LNG cold energy utilization, lack of flexible peak-shaving capability, insufficient ASU equipment utilization, and low system efficiency in existing LNG power generation systems.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0007] The present invention provides an LNG power generation system integrated with a liquid nitrogen energy storage system, which is characterized by comprising an LNG combustion system, a power generation system and an energy storage system;

[0008] Wherein, the LNG combustion system includes an LNG gasification and compression branch; the energy storage system includes a nitrogen energy storage branch and a liquid nitrogen energy release branch; the power generation system includes a gas power generation branch;

[0009] The outlet of the LNG gasification and compression branch is connected to the inlet of the gas power generation branch;

[0010] The LNG gasification and compression branch includes an LNG storage tank, a first heat exchanger, and an NG compressor connected in sequence;

[0011] The outlet of the nitrogen energy storage branch is connected to the inlet of the liquid nitrogen energy release branch. The nitrogen energy storage branch includes an air separation device, a nitrogen compressor and a second heat exchanger connected in sequence. The second heat exchanger is connected to the first heat exchanger. The liquid nitrogen energy release branch includes a liquid nitrogen storage tank, a liquid nitrogen pump, a cold accumulator, a third heat exchanger, a nitrogen expander, and a heat accumulator connected to the third heat exchanger.

[0012] Furthermore, the LNG combustion system also includes an oxygen compression branch; the power generation system also includes a circulating carbon dioxide compression branch, a carbon dioxide capture branch and a steam power generation circulating branch; the outlets of the oxygen compression branch and the circulating carbon dioxide compression branch are respectively connected to the inlet of the gas power generation branch; the outlet of the gas power generation branch is respectively connected to the inlet of the circulating carbon dioxide compression branch and the carbon dioxide capture branch; the circulating carbon dioxide compression branch is connected in parallel with the carbon dioxide capture branch.

[0013] Furthermore, the oxygen compression branch includes the air separation equipment and the oxygen compressor connected in sequence; the gas power generation branch includes a burner, a gas generator, a fourth heat exchanger, a first water cooler, a gas-liquid separator and a carbon dioxide splitter connected in sequence; the circulating carbon dioxide compression branch includes a circulating carbon dioxide compressor; the carbon dioxide capture branch includes a captured carbon dioxide compressor, a second water cooler, the cold storage device and a liquid carbon dioxide storage tank connected in sequence; the steam power generation circulation branch includes the fourth heat exchanger, the steam generator, the third water cooler and the water pump connected in sequence, and a coaxial generator connected to the steam generator.

[0014] Furthermore, the NG compressor outlet is connected to the burner inlet; the oxygen compressor outlet is connected to the burner inlet; and the circulating carbon dioxide compressor outlet is connected to the burner inlet.

[0015] Furthermore, the flow from the LNG storage tank is a low-temperature, normal-pressure LNG flow; the nitrogen flow from the air separation equipment enters the nitrogen compressor and is pressurized into a high-temperature, high-pressure nitrogen flow, and the high-temperature, high-pressure nitrogen flow becomes a normal-temperature, high-pressure nitrogen flow after heat exchange in the second heat exchanger; the first heat exchanger connects the low-temperature, normal-pressure LNG flow, the normal-temperature, normal-pressure NG flow, the normal-temperature, high-pressure nitrogen flow and the liquid nitrogen flow, and the low-temperature, normal-pressure LNG flow is heated to a normal-temperature, normal-pressure NG flow in the first heat exchanger after heat exchange with the normal-temperature, high-pressure nitrogen flow, and enters the NG compressor, where it is compressed to form a high-temperature, high-pressure NG flow and then enters the burner.

[0016] Furthermore, the second heat exchanger is connected to the ambient air inlet flow stream, the ambient air outlet flow stream, the high-temperature and high-pressure nitrogen flow stream and the normal temperature and high-pressure nitrogen flow stream, the high-temperature and high-pressure nitrogen flow stream enters the second heat exchanger, and after the high-temperature and high-pressure nitrogen flow stream and the ambient air inlet flow stream exchange heat, the high-temperature and high-pressure nitrogen flow stream is cooled to form the normal temperature and high-pressure nitrogen flow stream and enters the first heat exchanger, and the normal temperature and high-pressure nitrogen flow stream is liquefied into the liquid nitrogen flow stream and enters the liquid nitrogen storage tank; the ambient air inlet flow stream is heated to become the ambient air outlet flow stream and enters the heat accumulator.

[0017] Furthermore, the second heat exchanger is connected to the second heat exchanger ambient air inlet flow stream, the second heat exchanger ambient air outlet flow stream, the high-temperature and high-pressure nitrogen flow stream and the normal temperature and high-pressure nitrogen flow stream, the high-temperature and high-pressure nitrogen flow stream enters the second heat exchanger, and after the high-temperature and high-pressure nitrogen flow stream and the second heat exchanger ambient air inlet flow stream exchange heat, the high-temperature and high-pressure nitrogen flow stream is cooled to form the normal temperature and high-pressure nitrogen flow stream and enters the first heat exchanger, and the normal temperature and high-pressure nitrogen flow stream is liquefied into the liquid nitrogen flow stream and enters the liquid nitrogen storage tank; the second heat exchanger ambient air inlet flow stream is heated to the second heat exchanger ambient air outlet flow stream and enters the heat accumulator.

[0018] Furthermore, the heat accumulator is connected to a cold flow stream at the heat accumulator environment inlet, a hot flow stream at the heat accumulator environment outlet, an air outlet flow stream at the second heat exchanger environment, and a cold flow stream at the heat accumulator outlet; after the air outlet flow stream at the second heat exchanger environment exchanges heat with the heat storage medium in the heat accumulator, it is cooled to become the cold flow stream at the heat accumulator outlet and discharged into the environment; the cold flow stream at the heat accumulator environment inlet exchanges heat with the heat storage medium in the heat accumulator, is heated to become the hot flow stream at the heat accumulator environment outlet, and enters the third heat exchanger.

[0019] Furthermore, the flow from the liquid nitrogen storage tank is a liquid nitrogen flow; the cold accumulator is connected to the liquid nitrogen flow, the nitrogen flow, the normal temperature high pressure carbon dioxide flow and the liquid carbon dioxide flow; the third heat exchanger is connected to the nitrogen flow, the hot flow at the outlet of the third heat exchanger, the hot flow at the outlet of the heat accumulator environment and the cold flow at the outlet of the third heat exchanger; the liquid nitrogen flow passes through the cold accumulator, exchanges heat with the cold storage medium in the cold accumulator, and is heated to become the nitrogen flow, and the normal temperature high pressure carbon dioxide flow passes through the cold accumulator, exchanges heat with the cold storage medium in the cold accumulator, is cooled to become the liquid carbon dioxide flow, and enters the liquid carbon dioxide storage tank.

[0020] Furthermore, the burner outlet is connected to the gas generator; the high-temperature and high-pressure flue gas from the burner enters the gas generator to expand and generate electricity, becoming a medium-temperature and low-pressure flue gas flow stream; the fourth heat exchanger is connected to a normal-temperature and high-pressure water flow stream, a high-temperature and high-pressure steam flow stream, the medium-temperature and low-pressure flue gas flow stream, and a medium-low-temperature and low-pressure flue gas flow stream; the medium-temperature and low-pressure flue gas flow stream enters the fourth heat exchanger, forms the medium-low-temperature and low-pressure flue gas flow stream after cooling, and then enters the first water cooler to form a gas-liquid two-phase flow stream; the gas-liquid two-phase flow stream enters the gas-liquid separator, and is separated into a water flow stream and a carbon dioxide flow stream; the carbon dioxide flow stream enters the carbon dioxide diverter, and is separated into a circulating carbon dioxide flow stream and a captured carbon dioxide flow stream.

[0021] Furthermore, the circulating carbon dioxide stream enters the circulating carbon dioxide compressor to form the high-temperature and high-pressure carbon dioxide stream, and then enters the burner; the captured carbon dioxide stream enters the captured carbon dioxide compressor to form the high-temperature and high-pressure carbon dioxide stream, and then enters the second water cooler, and after cooling, forms the normal-temperature and high-pressure carbon dioxide stream and enters the cold storage device.

[0022] Compared with the existing LNG power generation system, the beneficial effects of the present invention are:

[0023] 1. Based on the efficient utilization of LNG cold energy and the matching of LNG and nitrogen liquefaction temperatures, the present invention proposes a heat exchange process between LNG at normal pressure and low temperature and nitrogen at high pressure and normal temperature, and effectively utilizes the high-purity nitrogen produced by ASU as a low-temperature energy storage medium. It proposes an LNG power generation system integrated with a liquid nitrogen energy storage system. The system realizes the efficient utilization of LNG cold energy and ASU equipment, and greatly improves the efficiency of resource utilization.

[0024] 2. The cold energy released by the intermittent liquid nitrogen energy release process is stored in the cold storage device of the energy storage system, which enables continuous liquefaction of carbon dioxide to achieve carbon capture and further saves energy.

[0025] 3. Use the heat accumulator of the energy storage system to store the heat of the high-temperature nitrogen after compression, and use it to preheat the nitrogen during the liquid nitrogen energy release process to further increase the power generation of liquid nitrogen energy storage.

[0026] 4. The present invention effectively combines the LNG power generation system with the liquid nitrogen energy storage system. The LNG power generation system operates continuously, and the liquid nitrogen energy storage system operates intermittently to release energy for power generation. This improves the power peak-shaving capacity of the LNG power generation system. Against the background of peak-valley electricity price differences, the power generation efficiency of the LNG system is improved, making the system as a whole have higher economic value. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The specific contents of the present disclosure are described below with reference to the accompanying drawings, which will help to more easily understand the above and other purposes, features and advantages of the present disclosure. The accompanying drawings are only for illustrating the principles of the present disclosure. The sizes and relative positions of the units in the accompanying drawings need not be drawn to scale.

[0028] Figure 1 It is a structural schematic diagram of the LNG power generation system integrated with the liquid nitrogen energy storage system of the present invention. DETAILED DESCRIPTION

[0029] Exemplary disclosures of the present disclosure are described below in conjunction with the accompanying drawings. For the sake of clarity and conciseness, not all features of implementing the present disclosure are described in the specification. However, it should be understood that many decisions specific to the present disclosure may be made in the process of developing any such implementation of the present disclosure in order to achieve the developer's specific goals, and these decisions may vary from one disclosure to another.

[0030] It should also be noted here that in order to avoid obscuring the contents of the present disclosure due to unnecessary details, only the pipe network structure closely related to the scheme according to the contents of the present disclosure is shown in the accompanying drawings, while other details that are not closely related to the contents of the present disclosure are omitted.

[0031] It should be understood that the present disclosure is not limited to the described implementation forms due to the following description with reference to the accompanying drawings. Herein, where feasible, features between different embodiments may be replaced or borrowed, and one or more features may be omitted in one embodiment.

[0032] Based on the fact that the liquefaction temperatures of nitrogen and natural gas are relatively close, the present invention considers using the nitrogen produced by ASU equipment as a low-temperature energy storage medium and using the high-grade cold energy of LNG as a cold resource, and provides an LNG power generation system with an integrated liquid nitrogen energy storage system. While improving the utilization rate of resources and energy, the peak-shaving capacity of the LNG power generation system is further improved, and the economic benefits of the system are improved through the peak-valley electricity price difference.

[0033] In order to avoid the temperature crossing caused by different liquefaction temperatures during the heat exchange between LNG and nitrogen, the present invention exchanges heat between LNG at normal pressure and low temperature, such as 0.1Mpa and -170°C, and nitrogen at high pressure and normal temperature, such as 3.0Mpa and 30°C. In addition, in order to ensure the continuous and stable operation of the carbon dioxide capture process in the LNG power generation system, the cold energy released by the intermittent nitrogen energy release process is stored in the cold storage device and provided to the carbon dioxide liquefaction process. Since the cold energy contained in LNG is of high quality and large cold energy, the cold energy released by the nitrogen energy release process can meet the needs of the carbon dioxide capture process in the process.

[0034] Figure 1 The structure of the LNG power generation system of the integrated liquid nitrogen energy storage system of the present invention is shown, including an LNG combustion system, a power generation system and an energy storage system. The LNG combustion system includes an LNG gasification and compression branch 100, an oxygen compression branch 200, an energy storage system includes a nitrogen energy storage branch 300 and a liquid nitrogen energy release branch 400, and the power generation system includes a gas power generation branch 500, a circulating carbon dioxide compression branch 600, a carbon dioxide capture branch 700, and a steam power generation circulation branch 800. The outlet of the LNG gasification and compression branch 100 is connected to the inlet of the gas power generation branch 500, and the outlets of the oxygen compression branch 200 and the circulating carbon dioxide compression branch 600 are also connected to the inlet of the gas power generation branch 500. The outlet of the nitrogen energy storage branch 300 is connected to the inlet of the liquid nitrogen energy release branch 400. The outlet of the gas power generation branch 500 is connected to the inlet of the circulating carbon dioxide compression branch 600 and the carbon dioxide capture branch 700 respectively. The circulating carbon dioxide compression branch 600 is connected in parallel with the carbon dioxide capture branch 700.

[0035] Among them, the LNG gasification and compression branch 100 includes an LNG storage tank 0, a first heat exchanger 1 and an NG compressor 2. Specifically, the LNG storage tank 0, the first heat exchanger 1 and the NG compressor 2 are connected in sequence, and the outlet of the NG compressor 2 is connected to the inlet of the burner 4 of the gas power generation branch 500; the oxygen compression branch 200 includes an air separation device 5 and an oxygen compressor 7 connected in sequence, and the outlet of the oxygen compressor 7 is connected to the inlet of the burner 4 of the gas power generation branch 500; the nitrogen energy storage branch 300 includes an air separation device 5, a nitrogen compressor 10 and a second heat exchanger 11 connected in sequence, and the second heat exchanger 11 is connected to the first heat exchanger 1; the liquid nitrogen energy release branch 400 includes a liquid nitrogen storage tank 12, a liquid nitrogen pump 37, a cold storage device 13, a third heat exchanger 14, a nitrogen expander 15, and The third heat exchanger 14 is connected to the heat accumulator 17; the gas power generation branch 500 includes a burner 4, a gas generator 20, a fourth heat exchanger 21, a first water cooler 22, a gas-liquid separator 24 and a carbon dioxide diverter 25 connected in sequence; the circulating carbon dioxide compression branch 600 includes a circulating carbon dioxide compressor 29, and the outlet of the circulating carbon dioxide compressor 29 is connected to the inlet of the burner 4 of the gas power generation branch 500; the carbon dioxide capture branch 700 includes a captured carbon dioxide compressor 26, a second water cooler 28, a cold accumulator 13 and a liquid carbon dioxide storage tank 18 connected in sequence; the steam power generation circulation branch 800 includes a fourth heat exchanger 21, a steam generator 31, a third water cooler 34 and a water pump 36 connected in sequence, and a coaxial generator 32 connected to the steam generator 31.

[0036] The working principle of the LNG power generation system of the present invention is as follows: in the LNG gasification and compression branch 100, one end of the first heat exchanger 1 is respectively connected to the NG compressor 2 and the second heat exchanger 11, and the other end is respectively connected to the liquid nitrogen storage tank 12 and the LNG storage tank 0. Specifically, the first heat exchanger 1 is connected to the low-temperature and atmospheric pressure LNG stream 1-1, the normal temperature and atmospheric pressure NG stream 1-2, the normal temperature and high pressure nitrogen stream 1-3 and the liquid nitrogen stream 1-4. The low-temperature and atmospheric pressure LNG stream 1-1 from the LNG storage tank 0 is fully heat exchanged with the normal temperature and high pressure nitrogen stream 1-3 from the second heat exchanger 11 in the first heat exchanger 1. The low-temperature and atmospheric pressure LNG stream 1-1 is heated to the normal temperature and atmospheric pressure NG stream 1-2, enters the NG compressor 2, is compressed to form the high temperature and high pressure NG stream 3, and then enters the burner 4.

[0037] In the oxygen compression branch 200 , the oxygen stream 6 in the air separation device 5 enters the oxygen compressor 7 , is pressurized into a high-temperature and high-pressure oxygen stream 8 and enters the combustor 4 .

[0038] In the nitrogen energy storage branch 300, the nitrogen stream 9 in the air separation device 5 enters the nitrogen compressor 10, is pressurized into a high-temperature and high-pressure nitrogen stream 11-1 and enters the second heat exchanger 11. The second heat exchanger 11 is connected to the second heat exchanger ambient air inlet stream 11-3, the second heat exchanger ambient air outlet stream 11-4, the high-temperature and high-pressure nitrogen stream 11-1 and the normal temperature and high-pressure nitrogen stream 1-3. After the high-temperature and high-pressure nitrogen stream 11-1 and the second heat exchanger ambient air inlet stream 11-3 exchange heat, the high-temperature and high-pressure nitrogen stream 11-1 is cooled to form a normal temperature and high-pressure nitrogen stream 1-3 and enters the first heat exchanger 1. The normal temperature and high-pressure nitrogen stream 1-3 is liquefied into a liquid nitrogen stream 1-4 and enters the liquid nitrogen storage tank 12, completing the nitrogen energy storage process. In this way, the cold energy of LNG and the surplus high-purity nitrogen provided by ASU production can be fully utilized. Further combined with the cold energy stored in the regenerator during the energy release process, the continuous operation of LNG oxygen-enriched combustion power generation and the intermittent operation of liquid nitrogen energy release power generation can be achieved, thereby improving the power peak-shaving capacity of the LNG power generation system.

[0039] In the liquid nitrogen energy release branch 400, the second heat exchanger ambient air inlet flow stream 11-3 of the second heat exchanger 11 is heated to become the second heat exchanger ambient air outlet flow stream 11-4 and enters the heat accumulator 17. The heat accumulator 17 connects the heat accumulator ambient inlet cold flow stream 17-2, the heat accumulator ambient outlet hot flow stream 17-3, the second heat exchanger ambient air outlet flow stream 11-4 and the heat accumulator outlet cold flow stream 17-1. After the second heat exchanger ambient air outlet stream 11-4 exchanges heat with the heat storage medium filled in the heat accumulator 17, the heat generated by the continuously running energy storage system is stored in the heat accumulator 17. The second heat exchanger ambient air outlet stream 11-4 is cooled to the heat accumulator outlet cold stream 17-1 and discharged into the environment. After the heat accumulator ambient inlet cold stream 17-2 exchanges heat with the heat storage medium filled in the heat accumulator 17, it is heated to the heat accumulator ambient outlet hot stream 17-3. After entering the third heat exchanger 14 and exchanging heat with the nitrogen stream 13-2, it is cooled to the third heat exchanger outlet cold stream 14-1 and discharged into the environment. The heat accumulator 17 of the energy storage system is used to store the heat generated by the continuously running nitrogen energy storage system to realize the preheating of liquid nitrogen before the intermittent operation of liquid nitrogen energy release power generation. Compared with preheating with air, it not only makes rational use of resources, but also increases the power generation of energy release power generation.

[0040] The cold storage device 13 is connected with a liquid nitrogen stream 13-1, a nitrogen stream 13-2, a normal temperature high pressure carbon dioxide stream 13-3 and a liquid carbon dioxide stream 13-4. The third heat exchanger 14 is connected with a nitrogen stream 13-2, a third heat exchanger outlet hot stream 14-2, a heat storage device environment outlet hot stream 17-3 and a third heat exchanger outlet cold stream 14-1. The liquid nitrogen stream 13-1 from the liquid nitrogen storage tank 12 is controlled by starting and stopping the liquid nitrogen pump 37, so that the liquid nitrogen stream 13-1 passes through the cold storage device 13, and fully exchanges heat with the cold storage medium in the cold storage device 13, and the cold energy released by the intermittent liquid nitrogen energy release power generation process is stored in the cold storage device 13, and the liquid nitrogen stream 13-1 is heated into a nitrogen stream 13-2, and the normal temperature high-pressure carbon dioxide stream 13-3 fully exchanges heat with the cold storage medium in the cold storage device 13, and is cooled into a liquid carbon dioxide stream 13-4, and enters the liquid carbon dioxide storage tank 18. The cold storage device 13 of the energy storage system is used to store the cold energy released by the intermittent liquid nitrogen energy release power generation process, to achieve continuous liquefaction of carbon dioxide, complete carbon capture, and further save energy. After being preheated by the third heat exchanger 14, the nitrogen gas stream 13-2 enters the nitrogen expansion generator 15 to generate electricity. The intermittent operation of the power generation process is controlled by the start and stop of the nitrogen expander 15, that is, it only operates during the peak period of electricity consumption, thereby improving the power peak-shaving capacity of the LNG power generation system. Subsequently, the normal temperature and pressure stream 16 is discharged into the environment, and the liquid nitrogen energy release power generation process can be controlled by the start and stop of the liquid nitrogen pump 37 and the start and stop of the nitrogen expander 15 to achieve intermittent operation of the power generation process. Specifically, the LNG combustion power generation process is a 24-hour continuous production. Therefore, the LNG gasification and compression branch 100, the oxygen compression branch 200, the nitrogen energy storage branch 300, the gas power generation branch 500, the circulating carbon dioxide compression branch 600, the carbon dioxide capture branch 700, and the steam power generation circulation branch 800 are all in continuous operation, and only the liquid nitrogen energy release branch 400 is in operation during the peak period of electricity demand, which is intermittent operation. In order to ensure the continuous operation of the carbon dioxide capture branch 700, the cold energy of the energy release process is stored by the cold storage device 13, so that continuous liquefaction of carbon dioxide is realized to achieve carbon capture, which further saves energy. The second heat exchanger 11 and the heat storage device 17 are used to store the heat of the high-temperature nitrogen after compression in the nitrogen energy storage branch 300, and it is used to preheat the nitrogen during the liquid nitrogen energy release and power generation process, which further increases the power generation of liquid nitrogen energy release and further improves the peak-shaving capacity of the LNG power generation system.

[0041] In the gas power generation branch 500, the inlet of the burner 4 is connected to the NG compressor 2, the oxygen compressor 7 and the circulating carbon dioxide compressor 29. The outlet of the burner 4 is connected to the gas generator 20. The high-temperature and high-pressure oxygen stream 8, the high-temperature and high-pressure NG stream 3 and the high-temperature and high-pressure carbon dioxide stream 30 enter the burner 4 and form high-temperature and high-pressure flue gas 19 after full combustion. The high-temperature and high-pressure flue gas 19 enters the gas generator 20 to expand and generate electricity. The fourth heat exchanger 21 has two ends connected to the gas generator 20 and the first water cooler 22 respectively, and the other two ends of the fourth heat exchanger 21 are connected to the water pump 36 and the steam generator 31 respectively. The fourth heat exchanger 21 is connected to the normal temperature and high-pressure water stream 21-3, the high-temperature and high-pressure steam stream 21-4, the medium temperature and low pressure flue gas stream 21-1 and the medium and low temperature and low pressure flue gas stream 21-2. The medium-temperature low-pressure flue gas stream 21-1 after power generation enters the fourth heat exchanger 21, and forms a medium-temperature low-pressure flue gas stream 21-2 after cooling, and then enters the first water cooler 22 to form a gas-liquid two-phase flow stream 23. The gas-liquid two-phase flow stream 23 enters the gas-liquid separator 24 and is separated into two streams, namely, a water stream 24-2 and a carbon dioxide stream 24-1. Preferably, the separator 24 uses a bottom separation of the water stream 24-2 and an upper separation of the carbon dioxide stream 24-1. The carbon dioxide stream 24-1 enters the carbon dioxide splitter 25 and is separated into a circulating carbon dioxide stream 25-1 and a captured carbon dioxide stream 25-2.

[0042] In the circulating carbon dioxide compression branch 600 , the circulating carbon dioxide stream 25 - 1 from the carbon dioxide splitter 25 enters the circulating carbon dioxide compressor 29 , is compressed to form a high-temperature and high-pressure carbon dioxide stream 30 , and then enters the combustor 4 .

[0043] In the carbon dioxide capture branch 700 , the captured carbon dioxide stream 25 - 2 enters the captured carbon dioxide compressor 26 , is compressed to form a high-temperature and high-pressure carbon dioxide stream 27 , and then enters the second water cooler 28 , is cooled to form a normal-temperature and high-pressure carbon dioxide stream 13 - 3 , and enters the cold storage device 13 .

[0044] In the steam power generation circulation branch 800, the normal temperature and high pressure water stream 21-3 from the water pump 36 enters the fourth heat exchanger 21, is heated to form a high temperature and high pressure steam stream 21-4, and then enters the steam generator 31 to drive the coaxial generator 32 to generate electricity. The medium and low temperature and low pressure steam stream 33 at the outlet of the steam generator 31 enters the third water cooler 34, is cooled to form a normal temperature and low pressure water stream 35, enters the water pump 36 to be pressurized to become a normal temperature and high pressure water stream 21-3, enters the fourth heat exchanger 21 to circulate again, and completes the cycle steam power generation.

[0045] Preferably, the first heat exchanger 1, the second heat exchanger 11, the third heat exchanger 14, the fourth heat exchanger 21, the cold accumulator 13 and the heat accumulator 17 of the present invention can all adopt a countercurrent type, or other forms, which are not specifically limited here.

[0046] A specific application example is given below to further describe the specific implementation mode of the present invention in detail.

[0047] LNG gasification and compression branch 100 includes LNG storage tank 0 storing LNG at a pressure of 0.1MPa, a temperature of -170°C, and a mass flow rate of 1kg / s. The ambient air pressure is 0.1MPa and the temperature is 25°C. The inter-section water cooler of LNG compressor 2 ensures that the outlet temperature is 40°C. In addition, the pressure and temperature of oxygen and nitrogen at the outlet of air separation equipment 5 are 0.1MPa and 35°C, respectively. The pressurization pressure of oxygen, nitrogen, NG, circulating carbon dioxide and captured carbon dioxide are all 3.0MPa, and the mass flow rates are 3.92kg / s, 2.86kg / s, 1kg / s, 25.18kg / s and 2.79kg / s, respectively. The mass flow rate of circulating water is 6.54kg / s, and the pressurization pressure of the water pump is 12MPa. The outlet pressures of gas generator 20 and steam generator 31 are 0.1MPa and 0.2MPa, respectively.

[0048] It is assumed that the isentropic efficiency and mechanical efficiency of the compressor are 0.85 and 0.88 respectively, the isentropic efficiency and mechanical efficiency of the nitrogen expander 15 are 0.88 and 0.98 respectively, and the efficiency of the generator is 0.9. Based on this assumption, the total power consumption of nitrogen compression is 1505.90kW, and in the energy release power generation process, the power generation of nitrogen expansion is 2722.82kW. The nitrogen energy storage process runs continuously for 24 hours, while the liquid nitrogen energy release power generation process only runs during the peak power period, assuming 8 hours, and the operation of the power generation process is controlled by starting and stopping the liquid nitrogen pump 37 and the nitrogen expander 15. Therefore, the liquid nitrogen energy release power generation process reduces the net power demand by 766.92kW.

[0049] Assuming that the daily off-peak, normal and peak hours are all 8 hours, and the corresponding electricity prices are 0.30 yuan / kWh, 0.60 yuan / kWh and 1.03 yuan / kWh respectively. Under this assumption, the daily additional expenditure caused by the electricity consumption of the nitrogen energy storage process is 18,570.87 yuan, and the daily benefit corresponding to the power output of the nitrogen energy release power generation process is 22,389.40 yuan, with a daily net benefit of 3,818.53 yuan.

[0050] The present invention makes full use of the cold energy of LNG and the surplus high-purity nitrogen provided in the production of ASU. By combining the cryogenic liquid nitrogen energy storage system and the LNG power generation system, the cold energy of the energy release process is stored in the cold storage device of the cryogenic liquid nitrogen energy storage system, thereby realizing the continuous operation of LNG oxygen-enriched combustion power generation and the indirect operation of liquid nitrogen energy release power generation. The LNG cold energy is utilized efficiently and reasonably, the ASU equipment is utilized to the maximum extent, the peak-shaving capacity of the LNG power generation system is improved, and energy conservation and emission reduction and energy waste are effectively achieved.

[0051] The above specific implementation methods are only for illustrating the technical concept and structural features of the present invention, and the purpose is to enable relevant persons familiar with this technology to implement it. However, the above content does not limit the protection scope of the present invention. Any equivalent changes or modifications made based on the technical features of the present invention should fall within the protection scope of the present invention.

[0052] The present disclosure is described above in conjunction with specific implementation schemes, but it should be clear to those skilled in the art that these descriptions are exemplary and are not intended to limit the scope of protection of the present disclosure. Those skilled in the art can make various modifications and variations to the present disclosure based on the spirit and principles of the present disclosure, and these modifications and variations are also within the scope of the present disclosure.

Claims

1. An LNG power generation system integrated with a liquid nitrogen energy storage system, characterized in that: Including LNG combustion system, power generation system and energy storage system; Wherein, the LNG combustion system includes an LNG gasification and compression branch; the energy storage system includes a nitrogen energy storage branch and a liquid nitrogen energy release branch; the power generation system includes a gas power generation branch; The outlet of the LNG gasification and compression branch is connected to the inlet of the gas power generation branch; The LNG gasification and compression branch includes an LNG storage tank, a first heat exchanger, and an NG compressor connected in sequence; The outlet of the nitrogen energy storage branch is connected to the inlet of the liquid nitrogen energy release branch, the nitrogen energy storage branch includes an air separation device, a nitrogen compressor and a second heat exchanger connected in sequence, the second heat exchanger is connected to the first heat exchanger, and the liquid nitrogen energy release branch includes a liquid nitrogen storage tank, a liquid nitrogen pump, a cold accumulator, a third heat exchanger, a nitrogen expander, and a heat accumulator connected to the third heat exchanger connected in sequence; The LNG combustion system also includes an oxygen compression branch; The power generation system also includes a circulating carbon dioxide compression branch, a carbon dioxide capture branch and a steam power generation circulating branch; The outlets of the oxygen compression branch and the circulating carbon dioxide compression branch are respectively connected to the inlet of the gas power generation branch; The oxygen compression branch includes the air separation equipment and the oxygen compressor connected in sequence; The gas power generation branch includes a burner, a gas generator, a fourth heat exchanger, a first water cooler, a gas-liquid separator and a carbon dioxide splitter connected in sequence; The NG compressor outlet is connected to the burner inlet; The oxygen compressor outlet is connected to the burner inlet; The stream from the LNG storage tank is a low-temperature, normal-pressure LNG stream; The nitrogen gas stream from the air separation device enters the nitrogen compressor and is pressurized into a high-temperature and high-pressure nitrogen gas stream, and the high-temperature and high-pressure nitrogen gas stream is heat exchanged in the second heat exchanger to become a normal-temperature and high-pressure nitrogen gas stream; The first heat exchanger is connected to the low-temperature, normal-pressure LNG stream, the normal-temperature, normal-pressure NG stream, the normal-temperature, high-pressure nitrogen stream and the liquid nitrogen stream. After the low-temperature, normal-pressure LNG stream exchanges heat with the normal-temperature, high-pressure nitrogen stream in the first heat exchanger, the low-temperature, normal-pressure LNG stream is heated to become a normal-temperature, normal-pressure NG stream and enters the NG compressor. After being compressed, it forms a high-temperature, high-pressure NG stream and then enters the burner.

2. The LNG power generation system according to claim 1, characterized in that: The outlet of the gas power generation branch is respectively connected to the inlet of the circulating carbon dioxide compression branch and the carbon dioxide capture branch; the circulating carbon dioxide compression branch is connected in parallel with the carbon dioxide capture branch.

3. The LNG power generation system according to claim 2, characterized in that: The circulating carbon dioxide compression branch includes a circulating carbon dioxide compressor; The carbon dioxide capture branch comprises a carbon dioxide capture compressor, a second water cooler, the cold storage device and a liquid carbon dioxide storage tank connected in sequence; The steam power generation cycle branch includes the fourth heat exchanger, the steam generator, the third water cooler and the water pump connected in sequence, and a coaxial generator connected to the steam generator.

4. The LNG power generation system according to claim 3, characterized in that: The circulating carbon dioxide compressor outlet is connected to the burner inlet.

5. The LNG power generation system according to claim 4, characterized in that: The second heat exchanger is connected to the second heat exchanger ambient air inlet stream, the second heat exchanger ambient air outlet stream, the high-temperature and high-pressure nitrogen stream and the normal-temperature and high-pressure nitrogen stream. The high-temperature and high-pressure nitrogen stream enters the second heat exchanger. After the high-temperature and high-pressure nitrogen stream exchanges heat with the second heat exchanger ambient air inlet stream, the high-temperature and high-pressure nitrogen stream is cooled to form the normal-temperature and high-pressure nitrogen stream and enters the first heat exchanger. The normal-temperature and high-pressure nitrogen stream is liquefied into the liquid nitrogen stream and enters the liquid nitrogen storage tank. The second heat exchanger ambient air inlet stream is heated as the second heat exchanger ambient air outlet stream enters the heat accumulator.

6. The LNG power generation system according to claim 5, characterized in that: The heat accumulator is connected to the heat accumulator environment inlet cold flow stream, the heat accumulator environment outlet hot flow stream, the second heat exchanger environment air outlet flow stream and the heat accumulator outlet cold flow stream. After the second heat exchanger environment air outlet flow stream exchanges heat with the heat storage medium in the heat accumulator, it is cooled to become the heat accumulator outlet cold flow stream and discharged into the environment. The heat accumulator environment inlet cold flow stream exchanges heat with the heat storage medium in the heat accumulator, is heated to become the heat accumulator environment outlet hot flow stream, and enters the third heat exchanger.

7. The LNG power generation system according to claim 6, characterized in that: The stream from the liquid nitrogen storage tank is a liquid nitrogen stream; The cold storage device is connected to the liquid nitrogen stream, the nitrogen gas stream, the normal temperature high pressure carbon dioxide stream and the liquid carbon dioxide stream; The third heat exchanger connects the nitrogen gas stream, the hot stream at the outlet of the third heat exchanger, the hot stream at the outlet of the heat accumulator environment, and the cold stream at the outlet of the third heat exchanger; The liquid nitrogen stream passes through the cold accumulator, exchanges heat with the cold storage medium in the cold accumulator, and is heated to become the nitrogen stream. The normal temperature and high pressure carbon dioxide stream passes through the cold accumulator, exchanges heat with the cold storage medium in the cold accumulator, and is cooled to become the liquid carbon dioxide stream and enters the liquid carbon dioxide storage tank.

8. The LNG power generation system according to claim 7, characterized in that: The burner outlet is connected to the gas generator; The high-temperature and high-pressure flue gas from the burner enters the gas generator to expand and generate electricity, becoming a medium-temperature and low-pressure flue gas stream; The fourth heat exchanger is connected to the normal temperature high pressure water flow stream, the high temperature high pressure steam flow stream, the medium temperature low pressure flue gas flow stream and the medium temperature low pressure flue gas flow stream; The medium-temperature low-pressure flue gas stream enters the fourth heat exchanger, is cooled to form the medium-temperature low-pressure flue gas stream, and then enters the first water cooler to form a gas-liquid two-phase stream; The gas-liquid two-phase flow stream enters the gas-liquid separator and is separated into a water flow stream and a carbon dioxide flow stream; The carbon dioxide stream enters the carbon dioxide splitter and is separated into a circulating carbon dioxide stream and a captured carbon dioxide stream.

9. The LNG power generation system according to claim 8, characterized in that: The circulating carbon dioxide stream enters the circulating carbon dioxide compressor to form a high-temperature and high-pressure carbon dioxide stream, which enters the combustor; The captured carbon dioxide stream enters the captured carbon dioxide compressor to form a high-temperature and high-pressure carbon dioxide stream, and then enters the second water cooler to be cooled to form the normal-temperature and high-pressure carbon dioxide stream that enters the cold storage device.

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