Carbon dioxide energy storage and efficiency improvement system coupled with gas turbine and working method of carbon dioxide energy storage and efficiency improvement system

Abstract

The invention belongs to the field of carbon dioxide energy storage of gas turbines, particularly discloses a carbon dioxide energy storage efficiency improving system coupled with a gas turbine and a working method of the carbon dioxide energy storage efficiency improving system, and aims at overcoming the defects that a conventional compressed carbon dioxide heat storage system is large in loss, and the electricity-electricity efficiency of the compressed carbon dioxide energy storage system is greatly reduced. In the energy storage process of the compressed carbon dioxide energy storage system, high-temperature flue gas of the gas turbine is used for refrigeration through the lithium bromide unit, cold energy is provided for carbon dioxide liquefaction in the energy storage process, an original electric refrigeration unit is replaced, and the economical efficiency of the system is improved; heat provided by a heat storage system in a conventional compressed carbon dioxide energy storage system is supplemented through heat of high-temperature flue gas of a gas turbine, the initial temperature of carbon dioxide gas entering the turbine is increased, the system circulation efficiency is improved, and therefore the electricity-electricity conversion efficiency of the compressed carbon dioxide energy storage system is improved.

Description

Technical Field

[0001] This invention belongs to the field of carbon dioxide energy storage for gas turbines, and specifically relates to a carbon dioxide energy storage efficiency improvement system coupled to a gas turbine and its working method. Background Technology

[0002] Gas turbine exhaust gas temperatures are high, and there are generally two ways to utilize them. One is for large gas turbines with large exhaust flow rates, where waste heat boilers are used to evaporate and superheat water, producing a large amount of high-temperature, high-pressure steam to drive the turbine for power generation again, i.e., gas-steam combined cycle. The other is for micro gas turbines with small exhaust flow rates, where high-temperature flue gas is used to exchange heat with water using waste heat boilers or flue gas heat exchangers for direct heating or to meet other process heat requirements, or it can enter lithium bromide units for cooling.

[0003] With the development of energy storage technology, compressed carbon dioxide (CCCO) energy storage technology is gradually being widely used due to its high safety, long system life, and easy expansion capabilities. One of the key factors limiting the electro-electric efficiency of CCCO energy storage is the thermal storage system. When the system stores energy, carbon dioxide gas is compressed into a high-temperature, high-pressure gas. The heat is then exchanged with water through the thermal storage system and stored in a hot water tank. When the system releases energy, the heat stored in the thermal storage system is transferred back to the carbon dioxide, which then enters the turbine expander to generate electricity. If the charging and discharging interval is long, the heat loss in the thermal storage system gradually increases, thus reducing the electro-electric efficiency of the CCCO energy storage system. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a carbon dioxide energy storage efficiency improvement system coupled with a gas turbine and its operating method. The aim is to solve the problem of large losses in conventional compressed carbon dioxide thermal storage systems and significantly reduce the electrical-electric efficiency of compressed carbon dioxide energy storage systems.

[0005] To achieve the objectives of this invention, the following technical solution is adopted: A carbon dioxide energy storage efficiency improvement system coupled with a gas turbine includes an energy storage structure of a compressed carbon dioxide energy storage system and an energy release structure of a compressed carbon dioxide energy storage system. The energy storage structure includes a carbon dioxide gas chamber 1, a compressor low-pressure cylinder 2, a compressor high-pressure cylinder 3, an electric motor 4, a medium-pressure water system I 12, a medium-pressure water system II 13, a medium-pressure water system III 14, a compressor interstage cooler 15, a compressor aftercooler 16, a condenser 17, a liquid tank 18, a medium-pressure water system IV 19, a medium-pressure water system V 20, a gas turbine 22, a flue gas type lithium bromide unit 23, a flue gas type lithium bromide unit inlet flue gas pipe 26, a flue gas type lithium bromide unit outlet flue gas pipe 27, a cooling water return pipe 28, a cooling water supply pipe 29, a switch valve I 32, a switch valve II 33, a gaseous carbon dioxide pipe II 35, and a generator II 36. The energy release structure includes a carbon dioxide gas chamber 1, a generator I 5, a turbine low-pressure cylinder 6, a turbine high-pressure cylinder 7, a reheater 8, a flue gas heat exchanger 9, a superheater 10, an evaporator 11, a medium-pressure water system I 12, a medium-pressure water system II 13, a medium-pressure water system III 14, a liquid tank 18, a medium-pressure water system IV 19, a medium-pressure water system V 20, a liquid pump 21, a gas turbine 22, a liquid carbon dioxide pipeline I 24, a saturated gaseous carbon dioxide pipeline 25, a flue gas pipeline, a flue gas heat exchanger inlet pipeline 30, a flue gas heat exchanger outlet pipeline 31, a switch valve I 32, a switch valve II 33, a gaseous carbon dioxide pipeline 34, and a generator II 36.

[0006] The working method of the carbon dioxide energy storage efficiency improvement system coupled with a gas turbine provided by this invention: During energy storage operation, the compressor in the compressed carbon dioxide energy storage system compresses the room-temperature gaseous carbon dioxide gas in the carbon dioxide chamber to obtain high-temperature and high-pressure carbon dioxide gas, which exchanges heat with the cold water in the thermal storage system. The medium-temperature water obtained after the heat exchange is stored in the thermal storage system. At the same time, the high-temperature flue gas from the gas turbine directly enters the flue gas type lithium bromide unit. The high-temperature flue gas provides a heat source for the flue gas type lithium bromide unit to achieve cooling, and the carbon dioxide gas after heat exchange is cooled a second time, finally obtaining room-temperature and high-pressure liquid carbon dioxide, which is stored and will be utilized again during the energy release process. During the energy release operation, the medium-temperature water in the thermal storage system heats the room-temperature, high-pressure liquid carbon dioxide to high-temperature, high-pressure carbon dioxide gas. At the same time, the high-temperature flue gas from the gas turbine no longer enters the lithium bromide unit, but directly enters the compressed carbon dioxide energy storage system, further heating the high-temperature, high-pressure gaseous carbon dioxide to an even higher temperature. It then passes through the turbine expander to generate electricity. The exhaust carbon dioxide gas after power generation enters the carbon dioxide gas chamber, realizing the cycle of energy storage and release in the entire compressed carbon dioxide energy storage system.

[0007] Furthermore, the more specific working methods of the carbon dioxide energy storage efficiency improvement system coupled with gas turbines include: 1. Energy storage of compressed carbon dioxide energy storage systems: (1) The ambient temperature gaseous carbon dioxide in the carbon dioxide chamber 1 enters the low-pressure cylinder 2 of the compressor for compression, driven by the electric motor 4, to obtain high temperature and high pressure gaseous carbon dioxide and enter the compressor interstage cooler 15. (2) The low-temperature medium-pressure water in the medium-pressure water system Ⅳ19 also enters the compressor interstage cooler 15 to exchange heat with high-temperature and high-pressure gaseous carbon dioxide; (3) Low-temperature medium-pressure water is heat exchanged to obtain high-temperature medium-pressure water, which is stored in the hot water tanks of medium-pressure water system II13 and medium-pressure water system III14 for use when energy is released; (4) High-temperature and high-pressure gaseous carbon dioxide is exchanged to obtain low-temperature and high-pressure gaseous carbon dioxide; (5) Low-temperature high-pressure gaseous carbon dioxide enters the high-pressure cylinder 3 of the compressor for further compression, driven by the electric motor 4, to obtain high-temperature high-pressure gaseous carbon dioxide with higher pressure and enters the compressor stage aftercooler 16. (6) The low-temperature medium-pressure water in medium-pressure water system V20 also enters the compressor stage aftercooler 16 to exchange heat with high-temperature and high-pressure gaseous carbon dioxide; (7) Low-temperature medium-pressure water is heat exchanged to obtain high-temperature medium-pressure water, which is stored in the hot water tank of medium-pressure water system I12 and is ready for use when energy is released; (8) High-temperature and high-pressure gaseous carbon dioxide is exchanged to obtain low-temperature and high-pressure gaseous carbon dioxide; (9) Low-temperature high-pressure gaseous carbon dioxide enters the condenser 17 through the gaseous carbon dioxide pipeline II 35 for cooling to obtain low-temperature high-pressure liquid carbon dioxide, which is stored in the liquid tank 18 and is ready for use when energy is released; (10) Switch valve I 32 is closed and switch valve II 33 is opened. Gas turbine 22 supplies power to generator II 36 by burning fuel and generating electricity. The high-temperature flue gas generated enters the flue gas inlet pipe 26 of flue gas type lithium bromide unit. (11) Driven by high-temperature flue gas, the flue gas type lithium bromide unit 23 begins to cool and obtain cooling water; (12) Cooling water enters the condenser 17 from the cooling water supply pipe 29. After cooling the carbon dioxide, it returns to the flue gas type lithium bromide unit 23 from the cooling water return pipe 28. The carbon dioxide compression energy storage system completes the entire energy storage process.

[0008] 2. Energy release from compressed carbon dioxide energy storage systems: (1) The liquid carbon dioxide in the liquid tank 18 enters the evaporator 11 through the liquid carbon dioxide pipeline I 24 via the liquid pump 21; (2) The high-temperature medium-pressure water in the medium-pressure water system Ⅲ14 simultaneously enters the evaporator 11 and exchanges heat with liquid carbon dioxide; (3) The high-temperature medium-pressure water is heat exchanged to obtain low-temperature medium-pressure water, which is then stored in the cold water tank of the medium-pressure water system Ⅳ19 for use during energy storage. (4) Liquid carbon dioxide is converted into saturated gaseous carbon dioxide through heat exchange; (5) Saturated gaseous carbon dioxide enters superheater 10; (6) The high-temperature medium-pressure water in the medium-pressure water system II13 also enters the superheater 10 to exchange heat with saturated gaseous carbon dioxide; (7) The high-temperature medium-pressure water is heat exchanged to obtain low-temperature medium-pressure water, which is then stored in the cold water tank in the medium-pressure water system Ⅳ19 for use during energy storage. (8) Saturated gaseous carbon dioxide is converted into superheated gaseous carbon dioxide through heat exchange; (9) Superheated gaseous carbon dioxide enters the flue gas heat exchanger 9 for secondary heating; (10) Switch valve II 33 is closed and switch valve I 32 is opened. The high-temperature flue gas generated by the gas turbine 22 at this time enters the flue gas heat exchanger inlet pipe 30. (11) The high-temperature flue gas is heated a second time in the flue gas heat exchanger 9 to obtain high-temperature and high-pressure gaseous carbon dioxide, which then enters the turbine high-pressure cylinder 7 to generate electricity. (12) The exhaust gas after power generation enters the reheater 8; (13) The high-temperature medium-pressure water in the medium-pressure water system I12 simultaneously enters the reheater 8 to exchange heat with the exhaust gas; (14) The high-temperature medium-pressure water is heat exchanged to obtain low-temperature medium-pressure water, which is then stored in the cold water tank in the medium-pressure water system V20 for use during energy storage. (15) The exhaust gas is heated to obtain high-temperature and high-pressure gaseous carbon dioxide; (16) High-temperature and high-pressure gaseous carbon dioxide enters the turbine low-pressure cylinder 6 to do work and supply energy to the generator I5 to generate electricity. The exhaust gas after power generation enters the carbon dioxide gas chamber 1 through the gaseous carbon dioxide pipeline 34 and compresses the carbon dioxide energy storage system to complete the entire energy release process.

[0009] 3. Calculation of total power generation and electro-electric conversion efficiency of the carbon dioxide energy storage efficiency improvement system: (1) Let the power generation of the gas turbine be E1, the exhaust gas temperature be T1, the flow rate be q1, and the specific heat capacity of the flue gas be C. f The temperature of the flue gas after passing through the flue gas heat exchanger is T2; The heat Q1 provided by the flue gas in the flue gas heat exchanger is calculated as follows: Q1 = C f q1(T1-T2); (2) Under energy storage conditions, let COP be the energy efficiency ratio of the flue gas type lithium bromide unit, η1 be the heat exchange efficiency of the flue gas type lithium bromide unit, T3 be the supply water temperature of the flue gas type lithium bromide unit, T4 be the return water temperature, q2 be the flow rate, and C be the specific heat capacity of water. w ; The cooling capacity Q2 of the flue gas type lithium bromide unit is calculated as follows: Q2 = η1 × Q1 × COP; (3) Let the inlet temperature of the carbon dioxide in the condenser be T5, the outlet temperature be T6, and the flow rate be q3. The specific heat capacity of carbon dioxide in this state is C. CO2 The condenser heat exchange efficiency is η1'; The heat exchange capacity of the condenser, Q3, is calculated as follows: Q3 = C w ×q2×(T4-T3; Since the cooling capacity of the flue gas type lithium bromide unit is the same as the heat exchange capacity of the condenser, Q2=Q3; We obtain Q3×η1'=C CO2 ×q3×(T5-T6; By adjusting the gas turbine load to change the cooling capacity Q2 of the flue gas-type lithium bromide unit, it is made to match the cooling capacity required for carbon dioxide cooling, i.e., satisfying Q3×η1'=Q2×η1=C. CO2 ×q3×(T5-T6; (4) During the energy release operation, the carbon dioxide gas in the conventional compressed carbon dioxide energy storage system is heated by the superheater. At this time, the temperature at the inlet of the turbine high-pressure cylinder is T7, the flow rate is q4, the pressure is P1, and the enthalpy value corresponding to this state is H1; the exhaust pressure of the turbine high-pressure cylinder is P2, the exhaust temperature is T8, and the enthalpy value corresponding to this state is H2; the mechanical loss is W, and the motor efficiency is η2. The calculated power output of the motor connected to the high-pressure cylinder of the turbine in a conventional compressed carbon dioxide energy storage system is: E2 = ((H1-H2)×q4-W)×η2; (5) Let the power output of the motor connected to the low-pressure cylinder of the conventional compressed carbon dioxide energy storage system be E3, and the sum of the power of the low-pressure cylinder and the high-pressure cylinder of the compressor be P; The total power generation of a conventional compressed carbon dioxide energy storage system is calculated as: E = E2 + E3; Therefore, the electro-electric conversion efficiency of a conventional compressed carbon dioxide energy storage system is η3 = E ÷ P × 100%; (6) Assume that after the efficiency improvement, the carbon dioxide gas in the system is heated by the superheater and no longer directly enters the turbine high-pressure cylinder, but instead enters the flue gas heat exchanger. The heat exchange efficiency of the flue gas heat exchanger is η4, and the specific heat capacity of the carbon dioxide gas under this condition is C. CO2 '; The temperature of carbon dioxide after heating by the flue gas heat exchanger is calculated as T9 = Q. f ×η4÷q4÷C CO2'+T7 (7) At this time, the temperature of the carbon dioxide gas entering the turbine high-pressure cylinder is T9, the flow rate is q4, the pressure is P1, and the corresponding enthalpy value under this state is H3. The calculated power output of the motor connected to the high-pressure cylinder of the compressed carbon dioxide energy storage system after efficiency improvement is: E4 = ((H3-H2)×q4-W)×η2; At this point, the total power generation of the improved compressed carbon dioxide energy storage system is: E' = E3 + E4; The improved electro-to-electric conversion efficiency of the compressed carbon dioxide energy storage system is η5 = E' ÷ P × 100%.

[0010] The above technical solution has the following beneficial effects: 1. The technical solution provided by this invention is to improve the efficiency of a carbon dioxide energy storage system by utilizing the waste heat from the exhaust gas of a gas turbine. For scenarios with high flexibility in electricity demand, the high-temperature flue gas after the gas turbine generates electricity is used to compress the carbon dioxide energy storage system for energy storage or release. The flue gas directly heats the carbon dioxide a second time or enters the flue gas type lithium bromide unit for cooling to provide cooling for the carbon dioxide liquefaction process in the energy storage process, thus realizing the flexible application of waste heat resources.

[0011] 2. In the energy storage process of the compressed carbon dioxide energy storage system, the present invention utilizes the high-temperature flue gas of the gas turbine to be cooled by a lithium bromide unit, providing cold energy for the liquefaction of carbon dioxide in the energy storage process, replacing the original electric refrigeration unit and improving the system's economy.

[0012] 3. In the energy release process of the compressed carbon dioxide energy storage system, the present invention utilizes the heat of the high-temperature flue gas from the gas turbine to supplement the heat provided by the thermal storage system in the conventional compressed carbon dioxide energy storage system, thereby increasing the initial temperature of the carbon dioxide gas entering the turbine, improving the system circulation efficiency, and thus improving the electro-electric conversion efficiency of the compressed carbon dioxide energy storage system.

[0013] 4. The carbon dioxide energy storage efficiency improvement system and its working method for coupled gas turbine provided by the present invention can be applied to large-scale energy storage power stations, integrated energy utilization systems, urban and rural distributed energy systems and other fields to improve efficiency. It has wide applicability and high economic benefits. Attached Figure Description

[0014] Figure 1 A schematic diagram of a carbon dioxide energy storage efficiency improvement system for coupled gas turbines provided by the present invention; In the diagram: 1-Carbon dioxide gas chamber, 2-Compressor low-pressure cylinder, 3-Compressor high-pressure cylinder, 4-Electric motor, 5-Generator I, 6-Turbine low-pressure cylinder, 7-Turbine high-pressure cylinder, 8-Reheater, 9-Flue gas heat exchanger, 10-Superheater, 11-Evaporator, 12-Medium-pressure water system I, 13-Medium-pressure water system II, 14-Medium-pressure water system III, 15-Compressor interstage cooler, 16-Compressor aftercooler, 17-Condenser, 18-Liquid tank, 19-Medium-pressure water system IV, 20-Medium-pressure water system V, 21-Liquid pump. 22-Gas turbine, 23-Lithium bromide flue gas generator unit, 24-Liquid carbon dioxide pipeline I, 25-Saturated gaseous carbon dioxide pipeline, 26-Inlet flue gas pipeline of lithium bromide flue gas generator unit, 27-Outlet flue gas pipeline of lithium bromide flue gas generator unit, 28-Cooling water return pipeline, 29-Cooling water supply pipeline, 30-Inlet pipeline of flue gas heat exchanger, 31-Outlet pipeline of flue gas heat exchanger, 32-Switch valve I, 33-Switch valve II, 34-Gaseous carbon dioxide pipeline, 35-Gaseous carbon dioxide pipeline II, 36-Generator II. Detailed Implementation

[0015] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0016] Example 1 A carbon dioxide energy storage efficiency improvement system coupled with a gas turbine includes an energy storage structure of a compressed carbon dioxide energy storage system and an energy release structure of a compressed carbon dioxide energy storage system. The energy storage structure includes a carbon dioxide gas chamber 1, a compressor low-pressure cylinder 2, a compressor high-pressure cylinder 3, an electric motor 4, a medium-pressure water system I 12, a medium-pressure water system II 13, a medium-pressure water system III 14, a compressor interstage cooler 15, a compressor aftercooler 16, a condenser 17, a liquid tank 18, a medium-pressure water system IV 19, a medium-pressure water system V 20, a gas turbine 22, a flue gas type lithium bromide unit 23, a flue gas type lithium bromide unit inlet flue gas pipe 26, a flue gas type lithium bromide unit outlet 27, a cooling water return pipe 28, a cooling water supply pipe 29, a switch valve I 32, a switch valve II 33, a gaseous carbon dioxide pipe II 35, and a generator II 36. The energy release structure includes a carbon dioxide gas chamber 1, a generator I 5, a turbine low-pressure cylinder 6, a turbine high-pressure cylinder 7, a reheater 8, a flue gas heat exchanger 9, a superheater 10, an evaporator 11, a medium-pressure water system I 12, a medium-pressure water system II 13, a medium-pressure water system III 14, a liquid tank 18, a medium-pressure water system IV 19, a medium-pressure water system V 20, a liquid pump 21, a gas turbine 22, a liquid carbon dioxide pipeline I 24, a saturated gaseous carbon dioxide pipeline 25, a flue gas pipeline, a flue gas heat exchanger inlet pipeline 30, a flue gas heat exchanger outlet pipeline 31, a switch valve I 32, a switch valve II 33, a gaseous carbon dioxide pipeline 34, and a generator II 36.

[0017] Example 2 The working method of the carbon dioxide energy storage efficiency improvement system coupled with a gas turbine provided by the present invention includes the following steps for energy storage in the compressed carbon dioxide energy storage system: (1) The ambient temperature gaseous carbon dioxide in the carbon dioxide chamber 1 enters the low-pressure cylinder 2 of the compressor for compression, driven by the electric motor 4, to obtain high temperature and high pressure gaseous carbon dioxide and enter the compressor interstage cooler 15. (2) The low-temperature medium-pressure water in the medium-pressure water system Ⅳ19 also enters the compressor interstage cooler 15 to exchange heat with high-temperature and high-pressure gaseous carbon dioxide; (3) Low-temperature medium-pressure water is heat exchanged to obtain high-temperature medium-pressure water, which is stored in the hot water tanks of medium-pressure water system II13 and medium-pressure water system III14 for use when energy is released; (4) High-temperature and high-pressure gaseous carbon dioxide is exchanged to obtain low-temperature and high-pressure gaseous carbon dioxide; (5) Low-temperature high-pressure gaseous carbon dioxide enters the high-pressure cylinder 3 of the compressor for further compression, driven by the electric motor 4, to obtain high-temperature high-pressure gaseous carbon dioxide with higher pressure and enters the compressor stage aftercooler 16. (6) The low-temperature medium-pressure water in medium-pressure water system V20 also enters the compressor stage aftercooler 16 to exchange heat with high-temperature and high-pressure gaseous carbon dioxide; (7) Low-temperature medium-pressure water is heat exchanged to obtain high-temperature medium-pressure water, which is stored in the hot water tank of medium-pressure water system I12 and is ready for use when energy is released; (8) High-temperature and high-pressure gaseous carbon dioxide is exchanged to obtain low-temperature and high-pressure gaseous carbon dioxide; (9) Low-temperature high-pressure gaseous carbon dioxide enters the condenser 17 through the gaseous carbon dioxide pipeline II 35 for cooling to obtain low-temperature high-pressure liquid carbon dioxide, which is stored in the liquid tank 18 and is ready for use when energy is released; (10) Switch valve I 32 is closed and switch valve II 33 is opened. Gas turbine 22 supplies power to generator II 36 by burning fuel and generating electricity. The high-temperature flue gas generated enters the flue gas inlet pipe 26 of flue gas type lithium bromide unit. (11) Driven by high-temperature flue gas, the flue gas type lithium bromide unit 23 begins to cool and obtain cooling water; (12) Cooling water enters the condenser 17 from the cooling water supply pipe 29. After cooling the carbon dioxide, it returns to the flue gas type lithium bromide unit 23 from the cooling water return pipe 28. The carbon dioxide compression energy storage system completes the entire energy storage process.

[0018] Example 3 The working method of the carbon dioxide energy storage efficiency improvement system coupled with a gas turbine provided by the present invention includes the following steps for releasing energy from the compressed carbon dioxide energy storage system: (1) The liquid carbon dioxide in the liquid tank 18 enters the evaporator 11 through the liquid carbon dioxide pipeline I 24 via the liquid pump 21; (2) The high-temperature medium-pressure water in the medium-pressure water system Ⅲ14 simultaneously enters the evaporator 11 and exchanges heat with liquid carbon dioxide; (3) The high-temperature medium-pressure water is heat exchanged to obtain low-temperature medium-pressure water, which is then stored in the cold water tank of the medium-pressure water system Ⅳ19 for use during energy storage. (4) Liquid carbon dioxide is converted into saturated gaseous carbon dioxide through heat exchange; (5) Saturated gaseous carbon dioxide enters superheater 10; (6) The high-temperature medium-pressure water in the medium-pressure water system II13 also enters the superheater 10 to exchange heat with saturated gaseous carbon dioxide; (7) The high-temperature medium-pressure water is heat exchanged to obtain low-temperature medium-pressure water, which is then stored in the cold water tank in the medium-pressure water system Ⅳ19 for use during energy storage. (8) Saturated gaseous carbon dioxide is converted into superheated gaseous carbon dioxide through heat exchange; (9) Superheated gaseous carbon dioxide enters the flue gas heat exchanger 9 for secondary heating; (10) Switch valve II 33 is closed and switch valve I 32 is opened. The high-temperature flue gas generated by the gas turbine 22 at this time enters the flue gas heat exchanger inlet pipe 30. (11) The high-temperature flue gas is heated a second time in the flue gas heat exchanger 9 to obtain high-temperature and high-pressure gaseous carbon dioxide, which then enters the turbine high-pressure cylinder 7 to generate electricity. (12) The exhaust gas after power generation enters the reheater 8; (13) The high-temperature medium-pressure water in the medium-pressure water system I12 simultaneously enters the reheater 8 to exchange heat with the exhaust gas; (14) The high-temperature medium-pressure water is heat exchanged to obtain low-temperature medium-pressure water, which is then stored in the cold water tank in the medium-pressure water system V20 for use during energy storage. (15) The exhaust gas is heated to obtain high-temperature and high-pressure gaseous carbon dioxide; (16) High-temperature and high-pressure gaseous carbon dioxide enters the turbine low-pressure cylinder 6 to do work and supply energy to the generator I5 to generate electricity. The exhaust gas after power generation enters the carbon dioxide gas chamber 1 through the gaseous carbon dioxide pipeline 34 and compresses the carbon dioxide energy storage system to complete the entire energy release process.

[0019] Example 4 The working method of the carbon dioxide energy storage efficiency improvement system coupled with a gas turbine provided by the present invention, taking a certain compressed carbon dioxide energy storage system as an example, is calculated using the formula provided by the present invention as follows: The gas turbine is a 15MW-class gas turbine with a rated power of 14240kW, a flue gas temperature of 482.5℃, a flue gas flow rate of 198000kg / h, and a flue gas temperature of 150℃ after heat exchange in the flue gas heat exchanger.

[0020] When operating under energy storage conditions, if the gas turbine is running at its rated load, the cooling capacity of the lithium bromide unit is slightly greater than the required cooling capacity. Therefore, the gas turbine needs to reduce its power. At this time, the cooling capacity of the flue gas type lithium bromide unit is about 15673kW, the supply water temperature is 7℃, the return water temperature is 12℃, and the flow rate is 683.7kg / s, which can meet the cooling requirements. Compared with conventional process cooling water systems, the cooling effect is better, the required water volume is less, and the complexity of the system is greatly reduced.

[0021] During the energy release operation, the temperature of the carbon dioxide gas in the pre-efficiency compressed carbon dioxide energy storage system after being heated by the superheater (i.e. entering the turbine high-pressure cylinder inlet) is 181℃, the flow rate is 402.2kg / s, the pressure is 6.27MPa, the exhaust pressure of the turbine high-pressure cylinder is 1.02MPa, and the exhaust temperature is 51.96℃.

[0022] The carbon dioxide gas, after being heated by the reheater (i.e., at the inlet of the turbine low-pressure cylinder), has a temperature of 180℃, a flow rate of 402.2 kg / s, and a pressure of 0.93 MPa. The exhaust pressure of the turbine low-pressure cylinder is 0.092 MPa, and the exhaust temperature is 32.42℃.

[0023] After deducting mechanical losses and motor losses, the electrical power of the compressed carbon dioxide energy storage system before the efficiency improvement was approximately 93,022 kW.

[0024] After the efficiency improvement, the temperature of the carbon dioxide gas in the compressed carbon dioxide energy storage system after being heated by the superheater (i.e. entering the turbine high-pressure cylinder inlet) is 220℃, the flow rate is 402.2kg / s, and the pressure is 6.27MPa. The exhaust pressure of the turbine high-pressure cylinder is 1.02MPa, and the exhaust temperature is 85.43℃. The inlet and outlet parameters of the turbine low-pressure cylinder are the same as before the efficiency improvement.

[0025] After deducting mechanical losses and motor losses, the electrical power of the compressed carbon dioxide energy storage system before the efficiency improvement was approximately 97,695 kW.

[0026] The compressor power was 152245kW before and after the efficiency improvement. Before the efficiency improvement, the electro-to-electric conversion efficiency of the compressed carbon dioxide energy storage system was 61.1%; after the efficiency improvement, the electro-to-electric conversion efficiency of the compressed carbon dioxide energy storage system was 64.2%.

[0027] As can be seen from this embodiment, the working method of the carbon dioxide energy storage efficiency improvement system coupled with gas turbine provided by the present invention can improve the electro-electric conversion efficiency of the compressed carbon dioxide energy storage system by about 3.1%, and has very good economic benefits while improving the system cycle efficiency.

[0028] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A carbon dioxide energy storage efficiency improvement system coupled with a gas turbine, characterized in that: This includes the energy storage structure of a compressed carbon dioxide energy storage system and the energy release structure of a compressed carbon dioxide energy storage system. The energy storage structure of the compressed carbon dioxide energy storage system includes a carbon dioxide gas chamber (1), a compressor low-pressure cylinder (2), a compressor high-pressure cylinder (3), an electric motor (4), a medium-pressure water system I (12), a medium-pressure water system II (13), a medium-pressure water system III (14), a compressor interstage cooler (15), a compressor stage aftercooler (16), a condenser (17), a liquid tank (18), a medium-pressure water system IV (19), a medium-pressure water system V (20), a gas turbine (22), a flue gas type lithium bromide unit (23), a flue gas type lithium bromide unit inlet flue gas pipe (26), a flue gas type lithium bromide unit outlet flue gas pipe (27), a cooling water return pipe (28), a cooling water supply pipe (29), a switch valve I (32), a switch valve II (33), a gaseous carbon dioxide pipe II (35), and a generator II (36). The energy release structure of the compressed carbon dioxide energy storage system includes a carbon dioxide gas chamber (1), generator I (5), turbine low-pressure cylinder (6), turbine high-pressure cylinder (7), reheater (8), flue gas heat exchanger (9), superheater (10), evaporator (11), medium-pressure water system I (12), medium-pressure water system II (13), medium-pressure water system III (14), liquid tank (18), medium-pressure water system IV (19), medium-pressure water system V (20), liquid pump (21), gas turbine (22), liquid carbon dioxide pipeline I (24), saturated gaseous carbon dioxide pipeline (25), flue gas pipeline, flue gas heat exchanger inlet pipeline (30), flue gas heat exchanger outlet pipeline (31), switch valve I (32), switch valve II (33), gaseous carbon dioxide pipeline (34), and generator II (36).

2. A method for operating a carbon dioxide energy storage efficiency improvement system coupled with a gas turbine as described in claim 1, characterized in that, The steps include: (1) In the energy storage condition, the compressor in the compressed carbon dioxide energy storage system compresses the room temperature gaseous carbon dioxide gas in the carbon dioxide gas chamber to obtain high temperature and high pressure carbon dioxide gas, which exchanges heat with the cold water in the heat storage system. The medium temperature water obtained after the cold water heat exchange is stored in the heat storage system. At the same time, the high temperature flue gas of the gas turbine directly enters the flue gas type lithium bromide unit. The high temperature flue gas provides a heat source for the flue gas type lithium bromide unit to achieve cooling. The carbon dioxide gas after heat exchange is cooled a second time, and finally room temperature and high pressure liquid carbon dioxide is obtained and stored for use in the energy release process. (2) In the energy release condition, the medium temperature water in the heat storage system heats the room temperature and high pressure liquid carbon dioxide to high temperature and high pressure carbon dioxide gas. At the same time, the high temperature flue gas of the gas turbine no longer enters the lithium bromide unit, but directly enters the compressed carbon dioxide energy storage system to further heat the high temperature and high pressure gaseous carbon dioxide to a higher temperature. Then, it is used for power generation through the turbine expander. The carbon dioxide exhaust gas after power generation enters the carbon dioxide gas chamber, realizing the cycle of energy storage and energy release of the entire compressed carbon dioxide energy storage system.

3. The working method of the carbon dioxide energy storage efficiency improvement system coupled with a gas turbine according to claim 2, characterized in that, The energy storage operating condition includes the following steps: (1) The ambient temperature gaseous carbon dioxide in the carbon dioxide chamber enters the low-pressure cylinder of the compressor for compression, driven by the electric motor, to obtain high temperature and high pressure gaseous carbon dioxide and enter the compressor interstage cooler. (2) The low-temperature medium-pressure water in the medium-pressure water system IV also enters the compressor interstage cooler to exchange heat with high-temperature and high-pressure gaseous carbon dioxide; (3) Low-temperature medium-pressure water is heat exchanged to obtain high-temperature medium-pressure water, which is stored in the hot water tanks of medium-pressure water system II and medium-pressure water system III for use when energy is released; (4) High-temperature and high-pressure gaseous carbon dioxide is exchanged to obtain low-temperature and high-pressure gaseous carbon dioxide; (5) Low-temperature high-pressure gaseous carbon dioxide enters the high-pressure cylinder of the compressor for further compression, driven by an electric motor, to obtain high-temperature high-pressure gaseous carbon dioxide at higher pressure and enter the compressor stage aftercooler. (6) The low-temperature medium-pressure water in medium-pressure water system V also enters the compressor stage aftercooler to exchange heat with high-temperature and high-pressure gaseous carbon dioxide; (7) Low-temperature medium-pressure water is heat exchanged to obtain high-temperature medium-pressure water, which is stored in the hot water tank of medium-pressure water system I and is ready for use when energy is released; (8) High-temperature and high-pressure gaseous carbon dioxide is exchanged to obtain low-temperature and high-pressure gaseous carbon dioxide; (9) Low-temperature high-pressure gaseous carbon dioxide enters the condenser through gaseous carbon dioxide pipeline II for cooling to obtain low-temperature high-pressure liquid carbon dioxide, which is stored in a liquid tank and is ready for use when energy is released; (10) Switch valve I is closed and switch valve II is open. The gas turbine supplies power to generator II by burning fuel and generates electricity. The high-temperature flue gas generated enters the flue gas inlet pipe of the flue gas type lithium bromide unit. (11) Driven by high-temperature flue gas, the flue gas type lithium bromide unit begins to cool and obtain cooling water; (12) Cooling water enters the condenser from the cooling water supply pipe, and after cooling the carbon dioxide, it returns to the flue gas type lithium bromide unit from the cooling water return pipe. The compressed carbon dioxide energy storage system completes the entire energy storage process.

4. The working method of the carbon dioxide energy storage efficiency improvement system coupled with a gas turbine according to claim 2, characterized in that, The energy release condition includes the following steps: (1) The liquid carbon dioxide in the liquid tank enters the evaporator through the liquid carbon dioxide pipeline I via the liquid pump; (2) The high-temperature medium-pressure water in medium-pressure water system III simultaneously enters the evaporator and exchanges heat with liquid carbon dioxide; (3) The high-temperature medium-pressure water is heat exchanged to obtain low-temperature medium-pressure water, which is then stored in the cold water tank of the medium-pressure water system IV for use during energy storage. (4) Liquid carbon dioxide is converted into saturated gaseous carbon dioxide through heat exchange; (5) Saturated gaseous carbon dioxide enters the superheater; (6) The high-temperature medium-pressure water in medium-pressure water system II also enters the superheater to exchange heat with saturated gaseous carbon dioxide; (7) The high-temperature medium-pressure water is heat exchanged to obtain low-temperature medium-pressure water, which is then stored in the cold water tank in the medium-pressure water system IV for use during energy storage. (8) Saturated gaseous carbon dioxide is converted into superheated gaseous carbon dioxide through heat exchange; (9) Superheated gaseous carbon dioxide enters the flue gas heat exchanger for secondary heating; (10) Switch valve II is closed and switch valve I is open. The high-temperature flue gas generated by the gas turbine at this time enters the inlet pipe of the flue gas heat exchanger. (11) The high-temperature flue gas is heated a second time in the flue gas heat exchanger to obtain high-temperature and high-pressure gaseous carbon dioxide, which then enters the turbine high-pressure cylinder for power generation. (12) The exhaust gas after power generation enters the reheater; (13) The high-temperature medium-pressure water in medium-pressure water system I simultaneously enters the reheater to exchange heat with the exhaust gas; (14) The high-temperature medium-pressure water is heat exchanged to obtain low-temperature medium-pressure water, which is then stored in the cold water tank in the medium-pressure water system V for use during energy storage. (15) The exhaust gas is heated to obtain high-temperature and high-pressure gaseous carbon dioxide; (16) High-temperature and high-pressure gaseous carbon dioxide enters the turbine low-pressure cylinder to do work and supply energy to generator I to generate electricity. The exhaust gas after power generation enters the carbon dioxide gas chamber through the gaseous carbon dioxide pipeline and compresses the carbon dioxide energy storage system to complete the entire energy release process.

5. The working method of the carbon dioxide energy storage efficiency improvement system coupled with a gas turbine according to claim 2, characterized in that: Calculation of the total power generation and electro-electric conversion efficiency of the carbon dioxide energy storage efficiency improvement system: (1) Let the power generation of the gas turbine be E1, the exhaust gas temperature be T1, the flow rate be q1, and the specific heat capacity of the flue gas be C. f The temperature of the flue gas after passing through the flue gas heat exchanger is T2; The heat Q1 provided by the flue gas in the flue gas heat exchanger is calculated as follows: Q1 = C f q1(T1-T2); (2) Under energy storage conditions, let COP be the energy efficiency ratio of the flue gas type lithium bromide unit, η1 be the heat exchange efficiency of the flue gas type lithium bromide unit, T3 be the supply water temperature of the flue gas type lithium bromide unit, T4 be the return water temperature, q2 be the flow rate, and C be the specific heat capacity of water. w ; The cooling capacity Q2 of the flue gas type lithium bromide unit is calculated as follows: Q2 = η1 × Q1 × COP; (3) Let the inlet temperature of the carbon dioxide in the condenser be T5, the outlet temperature be T6, and the flow rate be q3. The specific heat capacity of carbon dioxide in this state is C. CO2 The condenser heat exchange efficiency is η1'; The heat exchange capacity of the condenser, Q3, is calculated as follows: Q3 = C w ×q2×(T4-T3; Since the cooling capacity of the flue gas type lithium bromide unit is the same as the heat exchange capacity of the condenser, Q2=Q3; We obtain Q3×η1'=C CO2 ×q3×(T5-T6; By adjusting the gas turbine load to change the cooling capacity Q2 of the flue gas-type lithium bromide unit, it is made to match the cooling capacity required for carbon dioxide cooling, i.e., satisfying Q3×η1'=Q2×η1=C. CO2 ×q3×(T5-T6; (4) During the energy release operation, the carbon dioxide gas in the conventional compressed carbon dioxide energy storage system is heated by the superheater. At this time, the temperature at the inlet of the turbine high-pressure cylinder is T7, the flow rate is q4, the pressure is P1, and the enthalpy value corresponding to this state is H1; the exhaust pressure of the turbine high-pressure cylinder is P2, the exhaust temperature is T8, and the enthalpy value corresponding to this state is H2; the mechanical loss is W, and the motor efficiency is η2. The calculated power output of the motor connected to the high-pressure cylinder of the turbine in a conventional compressed carbon dioxide energy storage system is: E2 = ((H1-H2)×q4-W)×η2; (5) Let the power output of the motor connected to the low-pressure cylinder of the conventional compressed carbon dioxide energy storage system be E3, and the sum of the power of the low-pressure cylinder and the high-pressure cylinder of the compressor be P; The total power generation of a conventional compressed carbon dioxide energy storage system is calculated as: E = E2 + E3; Therefore, the electro-electric conversion efficiency of a conventional compressed carbon dioxide energy storage system is η3 = E ÷ P × 100%; (6) Assume that after the efficiency improvement, the carbon dioxide gas in the system is heated by the superheater and no longer directly enters the turbine high-pressure cylinder, but instead enters the flue gas heat exchanger. The heat exchange efficiency of the flue gas heat exchanger is η4, and the specific heat capacity of the carbon dioxide gas under this condition is C. CO2 '; The temperature of carbon dioxide after heating by the flue gas heat exchanger is calculated as T9 = Q. f ×η4÷q4÷C CO2 '+T7 (7) At this time, the temperature of the carbon dioxide gas entering the turbine high-pressure cylinder is T9, the flow rate is q4, the pressure is P1, and the corresponding enthalpy value under this state is H3. The calculated power output of the motor connected to the high-pressure cylinder of the compressed carbon dioxide energy storage system after efficiency improvement is: E4=((H3-H2)×q4-W)×η2; At this point, the total power generation of the improved compressed carbon dioxide energy storage system is: E' = E3 + E4; The improved electro-to-electric conversion efficiency of the compressed carbon dioxide energy storage system is η5 = E' ÷ P × 100%.

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