Supercritical CO2 compressor unloading shutdown system and operation method thereof

Abstract

The invention discloses a supercritical CO2 compressor unloading shutdown system and an operation method thereof. According to a compressor unit, supercharging route sections are arranged in a graded mode to be a transcritical supercharging stage route, a sub-high-pressure supercharging stage route and a highest-pressure supercharging stage route. A bypass system comprising a first bypass pipeline, a second bypass pipeline, a third bypass pipeline, a first bypass valve, a second bypass valve and a third bypass valve is correspondingly arranged, an inlet automatic shut-off valve is arranged at an inlet of the compressor, and an outlet automatic shut-off valve and an outlet check valve are arranged at an outlet of the compressor. An automatic emptying valve is arranged at an emptying port of a compressor and at the downstream of an outlet of a highest pressure boosting stage route, opening and closing of all the valves are intelligently controlled through a central control system in communication connection, unloading shutdown operation of a compressor unit is automatically carried out, stable pressure reduction emptying of high-pressure CO2 with the exhaust pressure ranging from 40 MPa to 50 MPa is achieved, and the pressure of CO2 is reduced. And pipeline freezing and blocking caused by liquefaction and dry ice formation in the supercritical CO2 depressurization process are prevented, and safety and stability in the unloading shutdown process are ensured.

Description

Technical Field

[0001] This invention relates to the field of CCUS engineering technology. More specifically, this invention relates to a supercritical CO2 compressor unloading and shutdown system and its operation method. Background Technology

[0002] China's carbon capture, utilization, and storage (CCUS) technology is rapidly developing as a safety net for large-scale carbon emission reduction. By injecting captured CO2, after pressurization, into oil reservoirs, the volume and viscosity of the crude oil are increased, and the interfacial tension between oil and water is reduced, effectively improving oil recovery. This process also permanently stores CO2 underground, making it an energy-saving, emission-reducing, and highly efficient production technology. The key equipment for CO2 pressurization and injection is a supercritical CO2 compressor. The injection pressure after pressurization reaches 40-50 MPa, and since CO2 is an asphyxiating gas, extremely high requirements are placed on the safety and reliability of the compressor.

[0003] Traditional compressor unloading methods involve opening the bypass regulating valve with the compressor's inlet and outlet valves open, allowing high-pressure gas to be directly depressurized and returned to the inlet from the compressor outlet. After unloading to a certain pressure, the bypass shut-off valve is opened, completely connecting the outlet and inlet, and finally, the compressor is vented and depressurized to stop. CO2 has high critical parameters (critical temperature Tc = 31.1℃, critical pressure Pc = 7.38MPa), making it easily liquefied and forming dry ice. The conventional compressor unloading method has the following problems: First, the pressure regulating valve has limited pressure regulating capacity. When the bypass regulating valve is opened to unload backflow, the inlet pressure rises, posing a risk of overpressure. Secondly, the temperature drops during the decompression process of supercritical CO2, making it extremely easy to liquefy or even form dry ice, causing ice blockage in the pipeline; Third, the unloading process requires manual operation, and CO2 decompression and cooling can easily cause frostbite to personnel, and high-pressure operation poses safety risks. Summary of the Invention

[0004] One object of the present invention is to solve at least the above-mentioned problems and to provide at least the advantages that will be described later.

[0005] Another objective of this invention is to provide a supercritical CO2 compressor unloading and shutdown system and its operation method, so as to solve the technical problem that the unloading of CO2 compressors can easily cause overpressure and thus lead to high safety risks.

[0006] To achieve these objectives and other advantages according to the present invention, in one aspect, the present invention provides a supercritical CO2 compressor unloading and shutdown system, comprising: An automatic shut-off valve is installed at the compressor inlet; The outlet automatic shut-off valve and the outlet check valve are sequentially installed at the compressor outlet along the gas outlet direction. The bypass system corresponds to the multi-stage boosting system of the compressor. The multi-stage boosting system of the compressor includes a transcritical boosting stage route, a secondary high-pressure boosting stage route, and a maximum pressure boosting stage route arranged in sequence for increasing pressure. The bypass system includes a first bypass line, a first bypass valve, a second bypass line, a second bypass valve, a third bypass line, and a third bypass valve. The first bypass line connects the outlet of the transcritical boosting stage route to the compressor inlet, and the first bypass valve is installed on the first bypass line. The second bypass line connects the outlet of the secondary high-pressure boosting stage route to the compressor inlet, and the second bypass valve is installed on the second bypass line. The third bypass line connects the outlet of the maximum pressure boosting stage route to the compressor inlet, and the third bypass valve is installed on the third bypass line. An automatic vent valve is installed at the compressor's vent port and is located downstream of the outlet of the highest pressure boosting stage route; The central control system includes a central controller and a pressure sensor group that are interconnected. The central controller is interconnected with the inlet automatic shut-off valve, the outlet automatic shut-off valve, the outlet check valve, the automatic venting valve, the first bypass valve, the second bypass valve, and the third bypass valve, respectively, and is used to receive shutdown signals and control the opening and closing of the corresponding valves. The pressure sensor group is used to monitor the inlet and outlet pressures of the compressor unit, as well as the inlet and outlet pressures of the transcritical booster stage route, the secondary high-pressure booster stage route, and the highest-pressure booster stage route.

[0007] Preferably, each stage of the compressor's boosting route includes an intake scrubbing tank, an intake buffer tank, a booster compressor, and an exhaust buffer tank connected in sequence. The inlet end of each stage bypass line is connected to the outlet end of the exhaust buffer tank, and the outlet end of each stage bypass line is connected to the inlet end of the intake scrubbing tank.

[0008] Preferably, a temperature control system of corresponding stage number is set between the pressurization routes of adjacent stages. The temperature control system is equipped with a motor for cooling. The motor is communicatively connected to the central control system, and the motor speed is controlled by the central control system.

[0009] Preferably, the multi-stage boosting system of the compressor is configured as a four-stage boosting system, wherein the first-stage boosting route and the second-stage boosting route together constitute the transcritical boosting stage route, the first bypass pipeline connects the inlet of the first-stage boosting route and the outlet of the second-stage boosting route, the third-stage boosting route is the sub-high pressure boosting stage route, and the fourth-stage boosting route is the highest pressure boosting stage route.

[0010] Preferably, the bypass valve is a flow regulating valve.

[0011] On the other hand, the present invention also provides an operation method for a supercritical CO2 compressor unloading and shutdown system, comprising the following steps: S1. Determine the number of boosting stages of the CO2 compressor and the route segment corresponding to each boosting stage, determine the target set value for each boosting stage, configure the unloading shutdown system, receive pressure data and shutdown signals monitored by the pressure sensor group through the central control system, set the first unloading pressure target value, the second unloading pressure target value and the minimum set speed of the motor in the central control system, the first unloading pressure target value is not lower than the target set value of the boosting stage route of the secondary high pressure boosting stage, the second unloading pressure target value is not lower than the target set value of the boosting stage route of the transcritical boosting stage, before shutdown, the inlet automatic shut-off valve, the outlet automatic shut-off valve, the outlet check valve, the automatic vent valve, the first bypass valve, the second bypass valve and the third bypass valve are all in the closed state; S2. Send a shutdown command to the central control system, and the central control system will prioritize opening the automatic vent valve; S3. Open the third bypass valve, reduce the motor speed to the lowest set speed, and close the outlet shut-off valve. S4. When the central control system receives the monitored inlet and outlet pressures of the highest pressure boosting stage route, which tend to stabilize and drop to the first unloading pressure target value, the second bypass valve is opened. S5. When the central control system receives the monitored inlet and outlet pressures of the secondary high-pressure booster stage route, which tend to stabilize and drop to the unloading second pressure target value, the first bypass valve is opened. S6. When the third bypass valve, the second bypass valve, and the first bypass valve are fully opened, the compressor unit is unloaded. At this time, continue to vent. When the internal pressure of the compressor unit is equal to the intake pressure, the motor stops and the inlet shut-off valve is closed. S7. After the entire compressor unit system is continuously vented to atmospheric pressure, the automatic vent valve closes, and the compressor unit stops.

[0012] Preferably, the maximum pressure boosting target value of the multi-stage boosting system of the compressor is set to 50 MPa, the first unloading pressure target value is set in the range of 16-37 MPa, and the second unloading pressure target value is set in the range of 8-12 MPa.

[0013] Preferably, the initial boost pressure of the multi-stage boosting system of the compressor is 2.6 MPa. The pressure is increased from 2.6 MPa to 50 MPa through four boosting stages: the first stage boosts to 4.8 MPa, the second stage boosts to 9.5 MPa, the third stage boosts to 22.1 MPa, and the fourth stage boosts to 50 MPa. The first unloading pressure target value is set to 22.1 MPa, and the second unloading pressure target value is set to 9.5 MPa.

[0014] Preferably, the method also includes a control method for dynamically adjusting the unloading rate of the first bypass valve, second bypass valve, and third bypass valve under pressure and temperature parameters. First, monitoring parameters are set, including the compressor unit's inlet temperature, outlet temperature, real-time discharge pressure, real-time discharge temperature T, a safe upper limit for discharge temperature T0, and a discharge temperature intervention threshold T. c The current pressure unloading rate is V, when T c If T < T0, then the adjustment factor is... Control the current pressure unloading rate V t =V*f t The pressure unloading rate is controlled by changing the opening size of the first bypass valve, the second bypass valve, and the third bypass valve.

[0015] The present invention includes at least the following beneficial effects: The supercritical CO2 compressor unloading and shutdown system and its operation method of the present invention, corresponding to the compressor group, are set up with the booster route segments as transcritical booster stage route, secondary high pressure booster stage route, and highest pressure booster stage route, and respectively set up a bypass system including a first bypass pipeline, a second bypass pipeline, a third bypass pipeline and corresponding first bypass valve, second bypass valve and third bypass valve. An inlet automatic shut-off valve is set at the compressor inlet, and an outlet automatic shut-off valve and an outlet check valve are set at the compressor outlet. An automatic vent valve is set at the compressor vent port and downstream of the outlet of the highest pressure booster stage route. The opening and closing of each valve is intelligently controlled by a central control system connected by communication, and the compressor group is automatically unloaded and shut down, so as to achieve stable pressure reduction and venting of high pressure CO2 with an exhaust pressure of 40~50MPa, prevent liquefaction and dry ice formation during the supercritical CO2 depressurization process, which would cause pipeline freezing and blockage, and ensure the safety and stability of the unloading and shutdown process.

[0016] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0017] Fig. 1 This is a schematic flowchart of the operation method of the supercritical CO2 compressor unloading and shutdown system of the present invention; Fig. 2 This is a schematic diagram of the supercritical CO2 compressor unloading and shutdown system of the present invention.

[0018] The following are the reference numerals in the instruction manual: 1. Inlet automatic shut-off valve, 2. First bypass valve, 3. Second bypass valve, 4. Third bypass valve, 5. Automatic vent valve, 6. Slow-down throttling device, 7. Outlet automatic shut-off valve, 8. Outlet check valve. Detailed Implementation

[0019] The present invention will now be described in further detail with reference to the accompanying drawings, so that those skilled in the art can implement it based on the description.

[0020] It should be noted that, unless otherwise specified, the experimental methods described in the following embodiments are all conventional methods, and the reagents and materials described are all commercially available unless otherwise specified. In the description of this invention, the terms "lateral", "longitudinal", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0021] First, such as Figs. 1-2 As shown, the present invention provides a supercritical CO2 compressor unloading and shutdown system, comprising: Automatic shut-off valve 1 is installed at the compressor inlet; The outlet automatic shut-off valve 7 and the outlet check valve 8 are sequentially installed at the compressor outlet along the gas outlet direction. The bypass system corresponds to the multi-stage boosting system of the compressor. The multi-stage boosting system of the compressor includes a transcritical boosting stage route, a secondary high-pressure boosting stage route, and a maximum pressure boosting stage route arranged in sequence for increasing pressure. The bypass system includes a first bypass line, a first bypass valve 2, a second bypass line, a second bypass valve 3, a third bypass line, and a third bypass valve 4. The first bypass line connects the outlet of the transcritical boosting stage route to the compressor inlet. The first bypass valve 2 is installed on the first bypass line. The second bypass line connects the outlet of the secondary high-pressure boosting stage route to the compressor inlet. The second bypass valve 3 is installed on the second bypass line. The third bypass line connects the outlet of the maximum pressure boosting stage route to the compressor inlet. The third bypass valve 4 is installed on the third bypass line. Automatic vent valve 5 is installed at the vent port of the compressor and is located downstream of the outlet of the highest pressure boosting stage route; The central control system includes a central controller and a pressure sensor group that are interconnected. The central controller is interconnected with the inlet automatic shut-off valve 1, the outlet automatic shut-off valve 7, the outlet check valve 8, the automatic vent valve 5, the first bypass valve 2, the second bypass valve 3, and the third bypass valve 4, respectively, and is used to receive shutdown signals and control the opening and closing of the corresponding valves. The pressure sensor group is used to monitor the inlet and outlet pressures of the compressor unit, as well as the inlet and outlet pressures of the transcritical booster stage route, the secondary high-pressure booster stage route, and the highest-pressure booster stage route.

[0022] Taking a four-stage booster system as an example, the compressor unit has a first bypass line for the transcritical booster stage, a second bypass line for the sub-high pressure booster stage, and a third bypass line for the highest pressure booster stage. First, the automatic vent valve 5 is opened, and the other valves are closed. Then, the third bypass valve 4 is opened. The third bypass line is used to circulate the pressure reduction and venting operations within the highest pressure range, reducing the pressure difference between the compressor unit's inlet and outlet, lowering the motor speed to the lowest set speed, and finally closing the outlet shut-off valve. Pressure reduction is achieved through the vent line. During the unloading and shutdown operation, when the inlet and outlet pressures of the highest pressure boosting stage route steadily drop to the set value (usually not lower than the third-stage exhaust pressure), the second bypass valve 3 is opened to continue depressurizing and unloading. When the inlet and outlet pressures of the secondary high-pressure boosting stage route steadily drop to the set value (usually not lower than the second-stage exhaust pressure), and all bypass valves are fully open, the unit unloading is complete. At this time, the system continues to ventilate. When the internal pressure of the unit is equal to the inlet pressure, the motor stops and the inlet shut-off valve closes. After the entire system continues to ventilate to atmospheric pressure, the automatic vent valve 5 closes, and the unit shutdown is complete.

[0023] By configuring an outlet check valve 8 downstream of the compressor outlet automatic shut-off valve 7, backflow of the downstream high-pressure medium is prevented during pressure reduction in the unloading process. A slow-descent throttling device 6 is configured downstream of the automatic vent valve 5, and a multi-stage slow-descent pressure reduction and venting bypass system is established to achieve stable pressure reduction and venting of high-pressure CO2 at an exhaust pressure of 40-50 MPa, preventing liquefaction and dry ice formation during the supercritical CO2 pressure reduction process, which could cause pipeline freezing and blockage. Through these specific implementation methods, this invention successfully and safely unloads and shuts down a 40-50 MPa high-pressure supercritical CO2 compressor. The use of a reliable, programmable, automated control method ensures a safe and stable unloading and shutdown process.

[0024] In another technical solution, such as Figs. 1-2 As shown, each stage of the compressor's boosting path includes an intake scrubber tank, an intake buffer tank, a booster compressor, and an exhaust buffer tank, connected sequentially. The inlet end of each stage bypass line is connected to the outlet end of the exhaust buffer tank, and the outlet end of each stage bypass line is connected to the inlet end of the intake scrubber tank. A pressure sensor is also installed at the booster compressor to detect the pressure.

[0025] In another technical solution, such as Figs. 1-2 As shown, temperature control systems of corresponding stages are set between adjacent booster circuits. Each temperature control system contains a cooling motor, which is communicatively connected to the central control system, which controls the motor speed. By controlling the motor rotation, the cooling efficiency is dynamically changed, and in conjunction with the pressure reduction rate adjustment, the pressure reduction process is better balanced, maintaining stable pressure reduction and safe unit operation.

[0026] In another technical solution, such as Figs. 1-2As shown, the multi-stage boosting system of the compressor is configured as a four-stage boosting system. The first-stage boosting route and the second-stage boosting route together constitute the transcritical boosting stage route. The first bypass pipeline connects the inlet of the first-stage boosting route and the outlet of the second-stage boosting route. The third-stage boosting route is the sub-high pressure boosting stage route, and the fourth-stage boosting route is the highest pressure boosting stage route, corresponding to the stage boosting target value and the pressure reduction control target value.

[0027] In another technical solution, such as Figs. 1-2 As shown, the bypass valve is a flow regulating valve, which facilitates the adjustment of the flow rate.

[0028] This invention also provides an operation method for a supercritical CO2 compressor unloading and shutdown system, combined with Figs. 1-2 As shown, it includes the following steps: S1. Determine the number of boosting stages of the CO2 compressor and the route segment corresponding to each boosting stage, determine the target set value for each boosting stage, configure the unloading shutdown system, receive pressure data and shutdown signals monitored by the pressure sensor group through the central control system, set the first unloading pressure target value, the second unloading pressure target value and the minimum set speed of the motor in the central control system, the first unloading pressure target value is not lower than the target set value of the boosting stage route of the secondary high pressure boosting stage, the second unloading pressure target value is not lower than the target set value of the boosting stage route of the transcritical boosting stage, before shutdown, the inlet automatic shut-off valve 1, the outlet automatic shut-off valve 7, the outlet check valve 8, the automatic vent valve 5, the first bypass valve 2, the second bypass valve 3, and the third bypass valve 4 are all in the closed state; S2. Send a shutdown command to the central control system, and the central control system will prioritize opening the automatic vent valve 5; S3. Open the third bypass valve 4, reduce the motor speed to the lowest set speed, and close the outlet shut-off valve. S4. When the central control system receives the monitored inlet and outlet pressures of the highest pressure boosting stage route, which tend to stabilize and drop to the unloading first pressure target value, the second bypass valve 3 is opened. S5. When the central control system receives the monitored inlet and outlet pressures of the secondary high-pressure booster stage route, which tend to stabilize and drop to the unloading second pressure target value, the first bypass valve 2 is opened. S6. When the third bypass valve 4, the second bypass valve 3, and the first bypass valve 2 are fully opened, the compressor unit is unloaded. At this time, continue to vent. When the internal pressure of the compressor unit is equal to the intake pressure, the motor stops and the inlet shut-off valve is closed. S7. After the entire compressor unit system is continuously vented to atmospheric pressure, the automatic vent valve 5 closes, and the compressor unit stops.

[0029] This invention employs a tiered and regional reflux method to smoothly unload the unit, preventing liquefaction and dry ice formation during the supercritical CO2 depressurization unloading process, which could cause pipeline freezing and blockage, preventing unloading and shutdown. It also solves the problem of excessive pressure differential during unloading and reflux, which could easily lead to inlet overpressure.

[0030] In another technical solution, such as Figs. 1-2 As shown, the maximum pressure target setting of the multi-stage boosting system of the compressor is 50 MPa, the first unloading pressure target setting ranges from 16 to 37 MPa, and the second unloading pressure target setting ranges from 8 to 12 MPa. Preferably, the initial boosting pressure of the multi-stage boosting system of the compressor is 2.6 MPa, and the pressure is increased from 2.6 MPa to 50 MPa through four boosting routes: the first boosting route increases the pressure to 4.8 MPa, the second boosting route increases the pressure to 9.5 MPa, the third boosting route increases the pressure to 22.1 MPa, and the fourth boosting route increases the pressure to 50 MPa. The first unloading pressure target is set to 22.1 MPa, and the second unloading pressure target is set to 9.5 MPa. Through the above specific implementation method, the unloading process is automated, and the 40~50 MPa high-pressure supercritical CO2 compressor is safely and smoothly unloaded and shut down, ensuring the safety and stability of the unloading and shutdown process.

[0031] In another technical solution, such as Figs. 1-2 As shown, it also includes a control method for dynamically adjusting the first bypass valve, second bypass valve, and third bypass valve to control the unloading rate under pressure and temperature parameters. First, monitoring parameters are set, including the compressor unit's inlet temperature, outlet temperature, real-time discharge pressure, real-time discharge temperature T, setting a safe upper limit for discharge temperature T0, and setting a discharge temperature intervention threshold T. c The current pressure unloading rate is V, when T c If T < T0, then the adjustment factor is... Control the current pressure unloading rate V t =V*f t The pressure unloading rate is controlled by changing the opening size of the first bypass valve, the second bypass valve, and the third bypass valve.

[0032] Higher exhaust temperatures require a reduced unloading rate to prevent thermal stress shock. Adjusting the unloading speed based on temperature factors can further improve the stability and safety of unloading.

[0033] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A supercritical CO2 compressor unloading and shutdown system, characterized in that, include: An automatic shut-off valve is installed at the compressor inlet; The outlet automatic shut-off valve and the outlet check valve are sequentially installed at the compressor outlet along the gas outlet direction. The bypass system corresponds to the multi-stage boosting system of the compressor. The multi-stage boosting system of the compressor includes a transcritical boosting stage route, a secondary high-pressure boosting stage route, and a maximum pressure boosting stage route arranged in sequence for increasing pressure. The bypass system includes a first bypass line, a first bypass valve, a second bypass line, a second bypass valve, a third bypass line, and a third bypass valve. The first bypass line connects the outlet of the transcritical boosting stage route to the compressor inlet, and the first bypass valve is installed on the first bypass line. The second bypass line connects the outlet of the secondary high-pressure boosting stage route to the compressor inlet, and the second bypass valve is installed on the second bypass line. The third bypass line connects the outlet of the maximum pressure boosting stage route to the compressor inlet, and the third bypass valve is installed on the third bypass line. An automatic vent valve is installed at the compressor's vent port and is located downstream of the outlet of the highest pressure boosting stage route; The central control system includes a central controller and a pressure sensor group that are interconnected. The central controller is interconnected with the inlet automatic shut-off valve, the outlet automatic shut-off valve, the outlet check valve, the automatic venting valve, the first bypass valve, the second bypass valve, and the third bypass valve, respectively, and is used to receive shutdown signals and control the opening and closing of the corresponding valves. The pressure sensor group is used to monitor the inlet and outlet pressures of the compressor unit, as well as the inlet and outlet pressures of the transcritical booster stage route, the secondary high-pressure booster stage route, and the highest-pressure booster stage route.

2. The supercritical CO2 compressor unloading and shutdown system as described in claim 1, characterized in that, Each stage of the compressor's boosting path includes an intake scrubber tank, an intake buffer tank, a booster compressor, and an exhaust buffer tank, which are connected in sequence. The inlet end of each stage bypass line is connected to the outlet end of the exhaust buffer tank, and the outlet end of each stage bypass line is connected to the inlet end of the intake scrubber tank.

3. The supercritical CO2 compressor unloading and shutdown system as described in claim 1, characterized in that, A temperature control system corresponding to the number of stages is set between the booster routes of adjacent stages. The temperature control system is equipped with a motor for cooling. The motor is communicatively connected to the central control system, and the motor speed is controlled by the central control system.

4. The supercritical CO2 compressor unloading and shutdown system as described in claim 1, characterized in that, The compressor's multi-stage boosting system is configured as a four-stage boosting system, wherein the first-stage boosting route and the second-stage boosting route together constitute the transcritical boosting stage route, the first bypass pipeline connects the inlet of the first-stage boosting route and the outlet of the second-stage boosting route, the third-stage boosting route is the sub-high pressure boosting stage route, and the fourth-stage boosting route is the highest pressure boosting stage route.

5. The supercritical CO2 compressor unloading and shutdown system as described in claim 1, characterized in that, The bypass valve is a flow regulating valve.

6. The operation method of the supercritical CO2 compressor unloading and shutdown system as described in claim 3, characterized in that, Includes the following steps: S1. Determine the number of boosting stages of the CO2 compressor and the route segment corresponding to each boosting stage, determine the target set value for each boosting stage, configure the unloading shutdown system, receive pressure data and shutdown signals monitored by the pressure sensor group through the central control system, set the first unloading pressure target value, the second unloading pressure target value and the minimum set speed of the motor in the central control system, the first unloading pressure target value is not lower than the target set value of the boosting stage route of the secondary high pressure boosting stage, the second unloading pressure target value is not lower than the target set value of the boosting stage route of the transcritical boosting stage, before shutdown, the inlet automatic shut-off valve, the outlet automatic shut-off valve, the outlet check valve, the automatic venting valve, the first bypass valve, the second bypass valve and the third bypass valve are all in the closed state; S2. Send a shutdown command to the central control system, and the central control system will prioritize opening the automatic vent valve; S3. Open the third bypass valve, reduce the motor speed to the lowest set speed, and close the outlet shut-off valve. S4. When the central control system receives the monitored inlet and outlet pressures of the highest pressure boosting stage route, which tend to stabilize and drop to the first unloading pressure target value, the second bypass valve is opened. S5. When the central control system receives the monitored inlet and outlet pressures of the secondary high-pressure booster stage route, which tend to stabilize and drop to the unloading second pressure target value, the first bypass valve is opened. S6. When the third bypass valve, the second bypass valve, and the first bypass valve are fully opened, the compressor unit is unloaded. At this time, continue to vent. When the internal pressure of the compressor unit is equal to the intake pressure, the motor stops and the inlet shut-off valve is closed. S7. After the entire compressor unit system is continuously vented to atmospheric pressure, the automatic vent valve closes, and the compressor unit stops.

7. The operation method of the supercritical CO2 compressor unloading and shutdown system as described in claim 6, characterized in that, The maximum pressure boosting target value of the multi-stage boosting system of the compressor is set to 50 MPa, the first unloading pressure target value is set in the range of 16-37 MPa, and the second unloading pressure target value is set in the range of 8-12 MPa.

8. The operation method of the supercritical CO2 compressor unloading and shutdown system as described in claim 7, characterized in that, The compressor's multi-stage boosting system starts at a boosting pressure of 2.6 MPa. The boosting pressure increases from 2.6 MPa to 50 MPa through four boosting routes: the first boosting route increases the pressure to 4.8 MPa, the second boosting route increases the pressure to 9.5 MPa, the third boosting route increases the pressure to 22.1 MPa, and the fourth boosting route increases the pressure to 50 MPa.

9. The first unloading pressure target value is set to 22.1 MPa, and the second unloading pressure target value is set to 9.5 MPa.

10. The operation method of the supercritical CO2 compressor unloading and shutdown system as described in claim 7, characterized in that, It also includes a control method that dynamically adjusts the first, second, and third bypass valves to control the unloading rate under pressure and temperature parameters. First, monitoring parameters are set, including the compressor unit's inlet temperature, outlet temperature, real-time discharge pressure, and real-time discharge temperature T. An upper limit for discharge temperature T0 is set, and an intervention threshold for discharge temperature T is also set. c The current pressure unloading rate is V, when T c If T < T0, then the adjustment factor is... Control the current pressure unloading rate V t =V*f t The pressure unloading rate is controlled by changing the opening size of the first bypass valve, the second bypass valve, and the third bypass valve.

Images