A supercritical carbon dioxide cycle generator set working fluid recovery system and control method

Abstract

A supercritical carbon dioxide circulating power generation unit working medium recovery system and control method, including a liquid storage tank, CO2 working medium from the liquid storage tank is pressurized by a low-temperature piston booster pump A and enters an evaporator, and a circulating water pump is configured on the water side of the evaporator; CO2 working medium is heated and gasified by the evaporator and enters a buffer tank and a pressure regulating tank in sequence, the output end of the pressure regulating tank is connected to a high-pressure storage tank, the outlet of the high-pressure storage tank is connected to an electric oil heater, the output end of the electric oil heater is connected to the compressor through a compressor dry gas sealing pipeline, and is connected to the turbine through a turbine dry gas sealing pipeline, the compressor is connected to a recovery tank A through a compressor exhaust pipeline, the turbine is connected to a recovery tank B through a turbine exhaust pipeline, and the output ends of the recovery tanks A and B are connected to a liquid storage tank after merging. The present invention can achieve near-zero emissions during the startup and operation of the S-CO2 circulating power generation unit, reduce the economic losses caused by CO2 gas emissions, and effectively prevent safety risks in on-site operations.

Description

Technical Field

[0001] The invention relates to the technical field of supercritical carbon dioxide cycle power generation sets, and in particular to a working medium recovery system and a control method for a supercritical carbon dioxide cycle power generation set. Background Art

[0002] The supercritical carbon dioxide (S-CO2) cycle was proposed in the 1950s and 1960s. In the past 10 years, many countries have invested a lot of manpower and material resources in the research of the S-CO2 cycle, making it a hot spot in the industry. On the one hand, this development trend is related to the efficient and flexible use of various energy sources and the reduction of environmental pollution by humans. On the other hand, the development of the Rankine cycle with water vapor as the working fluid has entered a bottleneck period due to factors such as metal materials. CO2 is a non-toxic, colorless, odorless, non-flammable and easily obtained working fluid in nature, and is highly favored.

[0003] Different from conventional thermal power units, S-CO2 cycle power generation units are equipped with complete liquefied storage tanks, booster pumps, evaporators, buffer tanks, pressure-stabilizing tanks, high-pressure storage tanks and auxiliary equipment using CO2 as the working fluid. This series of equipment constitutes the entire CO2 working fluid storage, charging, exhausting and monitoring system, providing the S-CO2 cycle power generation unit with stable, reliable CO2 working fluid that meets the parameters required by the process system. However, CO2 working fluid recovery devices are rarely seen in the existing literature on S-CO2 cycle power generation units.

[0004] The core equipment of the S-CO2 cycle generator set includes the main compressor, high and low pressure turbines and their auxiliary equipment. Unlike conventional thermal power units, the main compressor shaft end seal uses CO2 gas as the sealing gas, and the high and low pressure turbine shaft end seals also use CO2 gas as the sealing gas, which is similar to the turbine shaft seal steam of the thermal power unit. Before the compressor or turbine is started, CO2 gas with a specific temperature and pressure needs to be filled first, which is called dry gas sealing gas. In order to quickly meet the temperature of the dry gas sealing gas at the initial start-up, in addition to setting up a dry gas sealing electric oil heating device, in actual operation, it is necessary to discharge a large amount of dry gas sealing gas through the compressor cylinder and pipeline to increase the temperature, resulting in a large amount of CO2 gas waste. In addition, when various storage tanks filled with CO2 gas are overhauled or the system pressure exceeds the limit, a large amount of CO2 needs to be discharged, which aggravates the waste of system working fluid. On the one hand, the discharge of a large amount of CO2 gas directly causes objective economic losses, and on the other hand, the accumulation of CO2 gas in a small space will cause great safety risks and greenhouse gas pollution to the environment. Summary of the invention

[0005] In order to overcome the deficiencies of the above-mentioned prior art, the purpose of the present invention is to provide a supercritical carbon dioxide cycle power generation unit working fluid recovery system and control method, which integrates a CO2 working fluid recovery system on the basis of CO2 working fluid storage, charging and monitoring, forming a complete process. The new CO2 working fluid recovery system includes different functional units such as collection, pressurization, cooling liquefaction, sewage discharge, and transportation, which can achieve near-zero emissions of the S-CO2 cycle power generation unit during startup and operation, significantly reducing the economic losses caused by CO2 gas emissions, and effectively preventing safety risks in on-site operations.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] A supercritical carbon dioxide circulating power generation unit working medium recovery system comprises a liquid storage tank 1, wherein the CO2 working medium from the liquid storage tank 1 is pressurized by a low-temperature piston booster pump A2 and then enters an evaporator 3, wherein a circulating water pump 4 is arranged on the water side of the evaporator 3; wherein the CO2 working medium is heated and gasified by the evaporator 3 and then enters a buffer tank 5 and a pressure stabilizing tank 6 in sequence, wherein a branch is drawn out from the pressure stabilizing tank 6 and connected to a high-pressure storage tank 7, wherein the outlet of the high-pressure storage tank 7 is connected to an electric oil heater H, wherein the output end of the electric oil heater H is connected to a compressor 8 through a compressor dry gas sealing pipeline I, and is connected to a turbine 9 through a turbine air supply pipeline II, wherein the compressor 8 is connected to a recovery tank A10 through a compressor exhaust pipeline I III, wherein the turbine 9 is connected to a recovery tank B11 through a turbine exhaust pipeline II IV, and wherein the output ends of the recovery tanks A10 and B11 are joined and then connected to the liquid storage tank 1.

[0008] The cylinder exhaust, pipeline exhaust, and dry gas seal leakage of the compressor 8 are collected in the compressor exhaust pipeline III.

[0009] The carbon ring protection gas, cylinder exhaust, and dry gas seal leakage of the turbine 9 are collected in the turbine exhaust pipeline II IV.

[0010] The input end of the turbine exhaust pipeline II IV is connected to the exhaust pipeline III V, on which a pneumatic shut-off valve I 31 and a check valve VI 27 are provided. The exhaust pipeline III V is connected to gas from a system venting pipeline and exhaust from maintenance of each storage tank.

[0011] A normally closed pneumatic shut-off valve 6 37 for isolation is arranged between the exhaust pipeline 1 III and the exhaust pipeline 2 IV.

[0012] The recovery tank A10 has the same structure as the recovery tank B11. The recovery tank A10 is provided with a vacuum pump 16 and a matching pneumatic shut-off valve 232, which are used to evacuate the tank body before the working medium is recovered; the recovery tank A10 is provided with a working medium compression device and a compression motor 20. A working medium cooling device 18 is provided on the side of the recovery tank A. The recovery tank A10 is provided with a sewage tank 14, and the switch is controlled by a pneumatic shut-off valve 4 34 at the bottom.

[0013] The recovery tank A10 and the working fluid recovery inlet pipeline are sequentially provided with a check valve 22 and a regulating valve 28 for controlling the gas parameters entering the recovery tank A.

[0014] The bottom of the recovery tank A10 is connected to the delivery pump B42, and the pressurized liquefied working medium is re-sent into the liquid storage tank 1 through the check valve three 24 and the regulating valve three 30.

[0015] The outlet of the delivery pump B42 is provided with a pipeline in parallel, which is directly connected to the inlet of the evaporator 3 through the regulating valve four 36 and the check valve five 26. When the gas pressure and temperature in the recovery tank A10 meet the evaporator intake requirements, it is directly fed in without entering the liquid storage tank 1.

[0016] A control method for a working medium recovery system of a supercritical carbon dioxide cycle power generation unit comprises the following steps:

[0017] Working fluid recovery control on the exhaust side of compressor 8:

[0018] The working medium recovery on the exhaust side of the compressor 8 is mainly carried out at the initial start-up and after the compressor 8 is shut down. At the initial start-up of the compressor 8, the CO2 working medium in the high-pressure storage tank 7 needs to be introduced into an electric oil heater H for heating. The heated CO2 working medium enters the compressor dry gas sealing station from the gas supply pipeline I, and a large amount of cold CO2 working medium that cannot be heated in the gas supply pipeline I is introduced into the compressor 8, and discharged through the compressor cylinder exhaust valve 39 and the outlet pipeline vent valve 38. This part of the discharged gas is collected in the compressor exhaust pipeline-III, and enters the recovery tank A through the check valve-22 and the regulating valve-28;

[0019] After the compressor 8 is shut down, according to the normal shutdown protection logic, the compressor outlet pipeline vent valve 38 is interlocked and opened, and a large amount of high-temperature and high-pressure CO2 working fluid enters the exhaust pipeline III and finally enters the recovery tank A10;

[0020] Working fluid recovery control on the exhaust side of turbine 9:

[0021] The working medium recovery on the exhaust side of the turbine 9 is also carried out at the initial stage of turbine startup and after shutdown. The CO2 working medium in the high-pressure storage tank 7 is introduced into the electric oil heater H for heating. The heated CO2 working medium enters the turbine dry gas sealing plate station through the gas supply pipeline II. A large amount of low-temperature CO2 working medium that cannot be heated in the gas supply pipeline II is introduced into the turbine 9 and discharged through the turbine carbonization protection discharge valve 40 and the cylinder vent valve 41. The discharged gas is collected in the turbine exhaust pipeline II IV and enters the recovery tank B11 through the check valve II 23 and the regulating valve II 29.

[0022] The gas from the system venting pipeline and the exhaust gas from each tank maintenance are collected in the exhaust pipeline 3V, and are controlled by the pneumatic valve 31 and the check valve 6 27. They can enter the pressure stabilizing tank A or the pressure stabilizing tank B, and the discharge is selected according to the actual situation of the system;

[0023] Control of recovery tank A10:

[0024] Before the recovery tank A10 is used for the recovery of the working fluid, the pneumatic shut-off valve 2 32 is first opened, and the vacuum pump 16 is started to evacuate the recovery tank A10. When the pressure gauge P in the recovery tank A10 is a When the display is above -80kPa, it indicates that the vacuuming is completed, the pneumatic shut-off valve 232 is automatically closed, the vacuum pump 16 is interlocked and stopped, and the vacuuming of the recovery tank A10 is completed. At this time, the air inlet regulating valve of the recovery tank A10 is opened to introduce the gas in the exhaust pipeline 1III into the recovery tank A10, and the pressure P in the tank is monitored in real time. a , when P a After the pressure reaches 4.5MPa, the compressor motor 20 of the recovery tank A10 is started to compress the recovered working medium, and at the same time, the cooling device 18 of the recovery tank A10 is put into use to cool the compressed working medium to below 8°C (the liquidus point of CO2 corresponding to 4.5MPa is 9.9°C). The temperature sensor monitors the temperature of the working medium in real time. The working medium becomes liquid after compression and cooling. At this time, the delivery pump B42 is started to deliver the liquefied CO2 working medium to the liquid storage tank 1, completing the recovery of the entire working medium;

[0025] Before the recovery tank A10 is started for the first time, the recovery tank A10 is purged with the introduced CO2 working medium and purged into the sewage tank A14 through the pneumatic valve 34. The discharge valve at the bottom of the recovery tank is opened for 1 minute every 8 hours to drain the bottom. When the liquid storage tank 1 fails or the pressure at the outlet of the delivery pump B42 does not match the pressure of the liquid storage tank 1, the liquid working medium in the recovery tank A10 is directly sent to the evaporator 3 through the regulating valve 4 36;

[0026] The control method of the recovery tank B11 is similar to that of the recovery tank A10. By opening the pneumatic shut-off valve 6 37, the compressor exhaust pipeline 1 III and the turbine exhaust pipeline 2 IV are combined and sent to different recovery tanks according to actual needs. In actual use, when one of the tanks fails, the air intake is cut off through the inlet regulating valve, and the other tank is started to recover the working medium.

[0027] A pneumatic shut-off valve 6 37 is provided between the compressor exhaust pipeline 1 III and the turbine exhaust pipeline 2 IV. The valve is a normally closed valve used to isolate the exhaust of the pipeline.

[0028] Beneficial effects of the present invention:

[0029] 1) Based on the working fluid storage, charging, exhausting and monitoring of the conventional S-CO2 cycle power generation system, a CO2 working fluid recovery system is integrated to form the entire complete process.

[0030] 2) The CO2 working fluid recovery system includes different functional units such as collection, pressurization, cooling liquefaction, sewage discharge and transportation, which can achieve near-zero emissions during the startup and operation of the S-CO2 cycle power generation unit, significantly reducing the economic losses caused by CO2 gas emissions, effectively preventing safety risks in on-site operations, and reducing greenhouse gas pollution.

[0031] 3) The recovery system has two rows of recovery tanks in parallel, which not only increases the amount of recovered working fluid, but also makes it more flexible in use. It has the characteristics of fault removal, interactive operation, and real-time monitoring of operating parameters.

[0032] 4) The vacuum pump configured in the recovery tank can draw a vacuum of more than -80kPa from the tank body before the working fluid is recovered. When the vacuum reaches the set value, the vacuum pump is interlocked and shut down, and the inlet pneumatic door is interlocked and closed, thus ensuring the purity of the recovered carbon dioxide.

[0033] 5) The recovery tank is equipped with a bottom sewage pool, which can not only be used to purge the tank body during the first recovery, but also can be used to relieve the pressure, drain water and air of the tank body at any time during use.

[0034] 6) Automatic sewage discharge: Open the discharge valve at the bottom of the recovery tank for 1 minute every 8 hours to drain water and air from the bottom.

[0035] 7) After the purity in the recovery tank is qualified, compression and cooling will begin. If the purity is unqualified, discharge will be given priority.

[0036] 8) The temperature, pressure and purity monitoring devices installed on the recovery tank can realize real-time display during the entire recovery process and serve as the basis for equipment control. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1It is a schematic diagram of the process of the present invention.

[0038] In the figure: 1, liquid storage tank; 2, booster pump; 3, evaporator; 4, water pump; 5, buffer tank; 6, pressure stabilizing tank; 7, high-pressure storage tank; 8, compressor; 9, turbine; 10, recovery tank A; 11, recovery tank B; 12, low-temperature delivery pump B; 13, low-temperature delivery pump C; 14, sewage tank 1; 15, sewage tank 2; 16, vacuum pump 1; 17, vacuum pump 2; 18, cooling device 1; 19, cooling device 2; 20, recovery tank compression motor 1; 21, recovery tank compression motor 2; 22, check valve 1; 23, check valve 2; 24, check valve 3; 25, check valve 4; 26, check valve 5; 27, check valve 6; 28, regulating valve 1; 29, regulating valve 2; 30, regulating valve Throttle valve three; 36, regulating valve four; 31, pneumatic shut-off valve one; 32, pneumatic shut-off valve two; 33, pneumatic shut-off valve three; 34, pneumatic shut-off valve four; 35, pneumatic shut-off valve five; 37, pneumatic shut-off valve six; 38, compressor outlet pipeline vent valve; 39, compressor cylinder discharge valve; 40, turbine carbon ring protection discharge valve; 41, turbine cylinder discharge valve; 42, inlet manual valve of delivery pump B; 43, inlet manual valve of delivery pump C.

[0039] I is the first gas supply pipeline; II is the second gas supply pipeline; III is the first exhaust pipeline; IV is the second exhaust pipeline; V is the third pipeline; H is the electric oil heater; P is the first exhaust pipeline; a is the pressure measuring point of the working fluid in the pressure-surge tank A, T a is the temperature measurement point of the working fluid in the pressure-surge tank A, S a is the purity measurement point of the working fluid in the pressure-surge tank A, P b is the pressure measuring point of the working fluid in the pressure-surge tank B, T b is the temperature measurement point of the working fluid in the surge tank B, S b is the purity measurement point of the working fluid in the pressure-stabilizing tank B, P1 is the pressure of the liquid storage tank, and P2 is the evaporator inlet pressure. DETAILED DESCRIPTION

[0040] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0041] like Figure 1As shown, in a conventional S-CO2 cycle generator set, the CO2 working medium from the liquid storage tank 1 is pressurized by a low-temperature piston booster pump A and enters the evaporator 3, and is heated and vaporized by a water bath electric heater in the evaporator 3. A circulating water pump 4 is configured on the water side of the evaporator 3; the CO2 working medium after heating and vaporization enters the buffer tank 5 and the pressure stabilizing tank 6 in turn. The pressure stabilizing tank 6 is used as the intake circulation unit of the S-CO2 cycle generator set and needs to maintain a stable intake pressure. A branch is drawn from the pressure stabilizing tank 6 to connect to the high-pressure storage tank 7, which is connected to the electric oil heater H, and the gas temperature entering the compressor and turbine supply dry gas seal can be set through H. When the unit is started and shut down, the gas in the high-pressure storage tank 7 is heated to the set temperature by the electric oil heater H and then supplied to the compressor 8 and turbine 9 through the compressor dry gas sealing pipeline I and the turbine gas supply pipeline II. A part of the dry gas sealing gas entering the compressor 8 is discharged through the leakage pipeline, and the other part is directly discharged from the cylinder exhaust and outlet pipeline of the compressor 8 to meet the requirements of the gas temperature entering the compressor, and then directly discharged to the atmosphere. The process of entering the turbine 9 is similar. In addition, during the operation of the unit, the gas from the system venting pipeline and the exhaust gas from the maintenance of each tank are also directly discharged to the atmosphere.

[0042] In the present invention, the vent line III of the compressor 8, the vent line IV of the turbine, the gas from the system vent pipeline, and the main vent line V from each tank maintenance exhaust are combined together to form a total vent line, which are respectively introduced into the recovery tank A10 and the recovery tank B. The recovered working fluid is pressurized, cooled and liquefied in the recovery tank A / B, and then recovered into the liquid storage tank 1 through the delivery pump 12 / 13, the check valve three 24 / 25, and the regulating valve three 30, and the other part enters the evaporator inlet through the regulating valve four 36 and the check valve five 26, completing the recovery of the entire working fluid.

[0043] Taking the recovery tank A10 as an example, the complete recovery device includes a vacuum pump 16 and a control valve 32, a tank compressor 20, a sewage tank 14 and a control valve 34, a recovery tank cooling device 18, a delivery pump B for reflux of the working fluid after pressurization and liquefaction, and a temperature measuring point T for real-time monitoring of the recovery tank parameters. a , Pressure measuring point P a and purity measurement point S a , a check valve 22 and an inlet regulating valve 28 for controlling the recovery of the working fluid.

[0044] Recovery tank B has the same structure.

[0045] The cylinder exhaust (controlled by the pneumatic valve 39), the outlet pipe exhaust (controlled by the pneumatic valve 38), and the dry gas seal leakage of the compressor 8 are collected in the compressor exhaust pipeline III.

[0046] The carbon ring protection gas (controlled by the pneumatic valve 40), cylinder exhaust (controlled by the pneumatic valve 41), and dry gas seal leakage of the turbine 9 are collected in the turbine exhaust pipeline II IV.

[0047] The gas from the system venting pipeline and the exhaust from the maintenance of each storage tank are gathered into the exhaust pipeline three V.

[0048] A normally closed isolation valve 37 is provided between the exhaust pipeline 1 III and the exhaust pipeline 2 IV for isolation.

[0049] The exhaust pipeline three V is merged into the exhaust pipeline two IV through the pneumatic shut-off valve one 31 and the check valve six 27.

[0050] The recovery tank A is provided with a vacuum pump 16 and a matching pneumatic shut-off valve 32, which are used to evacuate the tank body before the working medium is recovered.

[0051] The recovery tank A is provided with a working fluid compression device and is equipped with a compression motor 20, which starts compression when the tank pressure reaches a certain static pressure.

[0052] The recovery tank A is provided with a working fluid cooling device 18, which can reduce the temperature of the working fluid during the compression process, thereby compressing, cooling and liquefying the working fluid.

[0053] The recovery tank A is provided with a sewage tank 14, which is switched by a pneumatic shut-off valve 4 34 at the bottom to discharge sewage from the system before the recovery tank is pressurized.

[0054] The bottom of the recovery tank A is connected to the delivery pump B, and the pressurized liquefied working medium is re-sent into the liquid storage tank 1 through the check valve 3 24 and the regulating valve 3 30.

[0055] The outlet of the delivery pump B is provided with a pipeline in parallel, which is directly connected to the inlet of the evaporator 3 through the regulating valve 4 36 and the check valve 5 26. When the gas pressure and temperature in the recovery tank A meet the air intake requirements of the evaporator 3, it is directly delivered to the evaporator 3 without entering the liquid storage tank 1.

[0056] A check valve 22 and a regulating valve 28 are sequentially arranged on the recovery tank A and the working medium recovery inlet pipeline to control the gas parameters entering the recovery tank A.

[0057] The recovery tank A is provided with a pressure measuring point P for monitoring the parameters of the recovery medium. a , Temperature measurement point T a , Purity measurement point S a , used to control the liquid storage tank measuring point P1 and the evaporator inlet measuring point P2.

[0058] The control method and system configuration of the recovery tank B are consistent with those of the recovery tank A, and the protection range is also consistent.

[0059] (1) Recovery control of dry gas and seal gas entering compressor 8:

[0060] The low-temperature CO2 working medium from the high-pressure storage tank 7 is first sent to the electric oil heater H, and the temperature of the heater outlet gas is set to 85~95°C. In order to increase the temperature of the low-temperature CO2 working medium and the gas already existing in the discharge pipeline, the gas at the outlet of the heater H is passed into the compressor chamber through the dry gas seal gas supply pipeline I, and the compressor cylinder exhaust valve 39 and the compressor outlet pipeline discharge valve 38 are opened at the same time, and all the gas introduced into the compressor 8 is discharged into the exhaust pipeline-III, and finally enters the recovery tank A through the check valve-22 and the regulating valve-28.

[0061] (2) Recovery control of dry gas seal gas entering turbine 9:

[0062] The low-temperature CO2 working fluid from the high-pressure storage tank 7 is sent to the electric oil heater H, and the temperature of the heater outlet gas is set to 120~135℃. It should be noted that the compressor dry gas seal gas and the turbine dry gas seal gas will not be put into operation at the same time, so the temperature of the outlet gas can be set separately. In order to increase the temperature of the low-temperature CO2 working fluid and the gas already existing in the discharge pipeline, the gas at the outlet of the heater H is passed into the turbine chamber through the dry gas seal gas supply pipeline II, and the turbine carbon ring protection exhaust valve 40 and the turbine cylinder exhaust valve 41 are opened at the same time, and all the gas introduced into the turbine 9 is discharged into the exhaust pipeline II IV, and finally enters the recovery tank B through the check valve II 23 and the regulating valve II 29.

[0063] (3) Recovery control of the three Vs of the exhaust pipeline:

[0064] When the unit is shut down, when the filter is replaced or the equipment is overhauled (including the overhaul of each storage tank), all the working fluids in the system need to be vented. First, the system venting gas and the exhaust gas from the overhaul of each storage tank are introduced into the exhaust pipeline III V, and merged into the recovery tank B inlet check valve II 23 through the pneumatic shut-off valve I 31 and the check valve VI 27, and controlled by the inlet regulating valve II 29 of the recovery tank B, and enter the recovery tank B. When the recovery tank B is abnormal and cannot be recovered, open the pneumatic shut-off valve VI 37, merge the gas in the exhaust pipeline III V into the exhaust pipeline III, and finally recover it to the recovery tank A.

[0065] (4) Control of vacuum pump 16 in recovery tank A:

[0066] Before the working fluid is recovered, close the inlet regulating valve 28, close the tank pneumatic shut-off valve 34, close the inlet manual valve 42 of the delivery pump B, open the vacuum pump inlet shut-off valve 32, and start the vacuum pump 16. After the vacuum pump starts normally, closely monitor the pressure P of the recovery tank A. a , when P aWhen < -80kPa, the vacuum pump inlet shut-off valve 32 is interlocked and the vacuum pump 16 is shut down.

[0067] (5) Control of the motor 20 of the compression device in the recovery tank A:

[0068] When the recovery tank A is evacuated to a vacuum level above -80 kPa, the vacuum pump 16 stops operating and the shut-off valve 32 closes. The manual valve 42 at the inlet of the delivery pump B remains closed, the pneumatic shut-off valve 434 remains closed, and the pressure of the inlet regulating valve 28 of the recovery tank A is set to be automatic, tracking the tank pressure point P a , set the pressure constant to 4.5MPa. a When the pressure reaches 4.5 MPa, the motor 20 of the compression device starts to compress the recovered working fluid in the recovery tank A. After the motor 20 of the compression device starts, the cooling device 18 is interlocked to start, and finally the working fluid recovered in the recovery tank is compressed, cooled and liquefied. a >When P1+0.5, the compression device motor 20 is shut down.

[0069] (6) Control of the drain valve of recovery tank A:

[0070] Before the recovery tank is started for the first time, the recovery tank is purged with the introduced CO2 working medium and purged into the sewage pool A through the pneumatic valve 34. The discharge valve 34 also has the functions of emergency pressure relief and tank body water and gas drainage. In order to prevent the recycled circulating working medium from carrying impurities such as water vapor, the automatic sewage discharge function of the recovery tank is added, that is, the discharge valve 34 at the bottom of the recovery tank is opened every 8 hours and kept for 1 minute to drain water and gas from the bottom.

[0071] (7) Control of the delivery pump B of the recovery tank A:

[0072] When the working fluid pressure P in the recovery tank A a >P1+0.5, the motor 20 of the compression device stops running. Open the manual valve 42 at the inlet of the delivery pump B, open the inlet regulating valve 30 of the liquid storage tank 1, keep the opening degree at 10~50%, which is manually adjustable, and start the delivery pump at this time to recover the liquid CO2 working medium in the recovery tank to the storage tank 1.

[0073] When the liquid storage tank 1 fails or the pressure does not match, and P a >P2+0.5, the recovered working fluid at the outlet of the delivery pump B can be directly delivered to the inlet of the evaporator through the regulating valve four 36 and the check valve five 26.

[0074] (8) The control of recovery tank B and its supporting equipment is similar to the control of recovery tank A in (4) to (6) above.

Claims

1. A supercritical carbon dioxide cycle power generation unit working fluid recovery system, characterized in that: The invention comprises a liquid storage tank (1), wherein the CO2 working medium in the liquid storage tank (1) is pressurized by a low-temperature piston booster pump A (2) and then enters an evaporator (3), and a circulating water pump (4) is arranged on the water side of the evaporator (3); the CO2 working medium is heated and gasified by the evaporator (3) and then enters a buffer tank (5) and a pressure stabilizing tank (6) in sequence, a branch is led out from the pressure stabilizing tank (6) and connected to a high-pressure storage tank (7), the outlet of the high-pressure storage tank (7) is connected to an electric oil heater (H), the output end of the electric oil heater (H) is connected to a compressor (8) through an air supply pipeline 1 (I), and is connected to a turbine (9) through an air supply pipeline 2 (II) for a turbine, the compressor (8) is connected to a recovery tank A (10) through a compressor exhaust pipeline 1 (III), the turbine (9) is connected to a recovery tank B (11) through a turbine exhaust pipeline 2 (IV), and the output ends of the recovery tanks A (10) and B (11) are connected to the liquid storage tank (1) after merging; The cylinder exhaust, pipeline exhaust, and dry gas seal leakage of the compressor (8) are collected in a compressor exhaust pipeline 1 (III); The carbon ring protection gas, cylinder exhaust gas and dry gas seal leakage of the turbine (9) are collected in the turbine exhaust pipeline II (IV); The input end of the turbine exhaust pipeline II (IV) is connected to the pipeline III (V), and the pipeline III (V) is provided with a pneumatic shut-off valve I (31) and a check valve VI (27). The pipeline III (V) is connected to gas from the system venting pipeline and exhaust gas from each storage tank during maintenance; The recovery tank A (10) has the same structure as the recovery tank B (11). The recovery tank A (10) is provided with a vacuum pump (16) and a matching pneumatic shut-off valve (32) for vacuumizing the tank body before the working medium is recovered. The recovery tank A (10) is provided with a working medium compression device and a compression motor (20). The side of the recovery tank A (10) is provided with a working medium cooling device (18). The recovery tank A (10) is provided with a sewage tank (14), and the switch is controlled by a pneumatic shut-off valve (34). A check valve 1 (22) and a regulating valve 1 (28) are sequentially arranged on the recovery tank A (10) and the working fluid recovery inlet pipeline to control the gas parameters entering the recovery tank A (10); The bottom of the recovery tank A (10) is connected to a delivery pump B (42) to deliver the pressurized liquefied working fluid back into the liquid storage tank (1) through a check valve three (24) and a regulating valve three (30).

2. A supercritical carbon dioxide cycle power generation unit working medium recovery system according to claim 1, characterized in that: A pipeline is arranged in parallel with the outlet of the delivery pump B (42), which is directly connected to the inlet of the evaporator (3) through the regulating valve four (36) and the check valve five (26). When the gas pressure and temperature in the recovery tank A (10) meet the evaporator intake requirements, the gas is directly fed into the recovery tank A (10) without entering the liquid storage tank (1).

3. A control method for a working medium recovery system of a supercritical carbon dioxide cycle power generation unit according to any one of claims 1 or 2, characterized in that: The following steps are involved: Working fluid recovery control on the exhaust side of the compressor (8): The working medium recovery on the exhaust side of the compressor (8) is mainly carried out at the initial start-up of the compressor (8) and after shutdown. At the initial start-up of the compressor (8), the CO2 working medium in the high-pressure storage tank (7) needs to be introduced into an electric oil heater (H) for heating. The heated CO2 working medium enters the compressor dry gas sealing station through the gas supply pipeline (I). A large amount of cold CO2 working medium that cannot be heated in the gas supply pipeline (I) is introduced into the compressor (8) and discharged through the compressor cylinder exhaust valve (39) and the outlet pipeline vent valve (38). The discharged gas is collected in the compressor exhaust pipeline (III) and enters the recovery tank A (10) through the check valve (22) and the regulating valve (28). After the compressor (8) is shut down, according to the normal shutdown protection logic, the compressor outlet pipeline vent valve (38) is interlocked and opened, and a large amount of high-temperature and high-pressure CO2 working fluid enters the exhaust pipeline 1 (III) and finally enters the recovery tank A (10); Working fluid recovery control on the exhaust side of the turbine (9): The working medium recovery on the exhaust side of the turbine (9) is also carried out at the initial stage of turbine startup and after shutdown. The CO2 working medium in the high-pressure storage tank (7) is introduced into the electric oil heater (H) for heating. The heated CO2 working medium enters the turbine dry gas sealing station through the gas supply pipeline II (II). The large amount of low-temperature CO2 working medium that cannot be heated in the gas supply pipeline II (II) is introduced into the turbine (9) and discharged through the turbine carbonization protection discharge valve (40) and the cylinder vent valve (41). The discharged gas is collected in the turbine exhaust pipeline II (IV) and enters the recovery tank B (11) through the check valve II (23) and the regulating valve II (29); The gas from the system venting pipeline and the exhaust gas from each tank maintenance are collected in the exhaust pipeline three (V), and are controlled by the pneumatic shut-off valve one (31) and the check valve six (27). They can enter either the recovery tank A or the recovery tank B, and the discharge is selected according to the actual situation of the system; Control of recovery tank A (10): Before the recovery tank A (10) is used to recover the working fluid, the pneumatic shut-off valve 2 (32) is first opened, and the vacuum pump 1 (16) is started to evacuate the recovery tank A (10). When the pressure gauge P in the recovery tank A (10) is a When the display is above -80 kPa, it indicates that the vacuuming is completed, and the pneumatic shut-off valve 2 (32) is automatically closed, the vacuum pump 1 (16) is interlocked and stopped, and the vacuuming of the recovery tank A (10) is completed. At this time, the air inlet regulating valve of the recovery tank A (10) is opened, and the gas in the exhaust pipeline 1 (III) is introduced into the recovery tank A (10), and the pressure P in the tank is monitored in real time. a , when P a After the pressure reaches 4.5 MPa, the compression motor 1 (20) of the recovery tank A (10) is started to compress the recovered working fluid, and at the same time, the cooling device 1 (18) of the recovery tank A (10) is put into use to cool the compressed working fluid to below 8°C. The temperature sensor monitors the temperature of the working fluid in real time. The working fluid becomes liquid after being compressed and cooled. At this time, the delivery pump B (42) is started to deliver the liquefied CO2 working fluid to the liquid storage tank (1), completing the recovery of the entire working fluid. Before the recovery tank A (10) is started for the first time, the recovery tank A (10) is purged with the introduced CO2 working medium and purged into the sewage tank 1 (14) through the pneumatic shut-off valve 4 (34). The discharge valve at the bottom of the recovery tank is opened for 1 minute every 8 hours to drain the bottom. When the liquid storage tank (1) fails or the pressure at the outlet of the delivery pump B (42) does not match the pressure of the liquid storage tank (1), the liquid working medium in the recovery tank A (10) is directly delivered to the evaporator (3) through the regulating valve 4 (36); The control method of the recovery tank B (11) is similar to the control method of the recovery tank A (10) described above. By opening the pneumatic shut-off valve six (37), the compressor exhaust pipeline one (III) and the turbine exhaust pipeline two (IV) are combined together and sent to different recovery tanks according to actual needs. When one of the tanks fails in actual use, the air intake is cut off through the inlet regulating valve, and the other tank is started to recover the working medium.

4. The control method of a supercritical carbon dioxide cycle power generation unit working medium recovery system according to claim 3 is characterized in that: A pneumatic shut-off valve six (37) is provided between the compressor exhaust pipeline one (III) and the exhaust pipeline two (IV). The valve is a normally closed valve and is used to isolate the exhaust of the pipeline.

Images