Long distance supercritical carbon dioxide pipeline commissioning system and method

Abstract

The application provides a long-distance supercritical carbon dioxide pipeline commissioning system and method, a gas source charging system, which comprises three charging branches for charging different phase state carbon dioxide, the downstream of the three charging branches is connected to a trunk line at a first station, a branch cutoff valve is arranged on each charging branch, a trunk line cutoff valve is arranged on the trunk line at the first station; an intermediate valve chamber system is connected to the downstream of the trunk line cutoff valve and comprises a plurality of sequentially connected intermediate valve chambers, a valve chamber cutoff valve is arranged between any two adjacent intermediate valve chambers; a terminal trunk line is connected to the downstream of the intermediate valve chamber system and is provided with a terminal cutoff valve; and a venting system is used for venting carbon dioxide in the pipeline. The carbon dioxide of different phase states is charged in stages and boosted in sections, the change of the phase state of the carbon dioxide in the pipeline is fully considered, the carbon dioxide commissioning efficiency is improved, and the phase state of the carbon dioxide in the pipeline is not controlled, and the commissioning failure is avoided.

Description

Technical Field

[0001] This invention belongs to the field of carbon dioxide pipeline transportation technology, and particularly relates to a long-distance supercritical carbon dioxide pipeline commissioning system and method. Background Technology

[0002] Currently, CCUS (Carbon Capture, Utilization, and Storage) technology is highly valued. Through CCUS, carbon dioxide emissions can be effectively reduced and converted into valuable resources or safely stored. This not only helps alleviate the challenges posed by climate change but also promotes sustainable development and improves resource utilization efficiency. Carbon dioxide transportation is a crucial link in the CCUS industry chain, making the construction of long-distance carbon dioxide pipeline infrastructure imperative.

[0003] The current three-stage development path for carbon dioxide pipelines involves: deploying demonstration projects for supercritical carbon dioxide transmission with a capacity of one million tons; building a regional carbon dioxide pipeline transportation network with a capacity of ten million tons centered on the basin; and constructing inter-regional trunk pipelines to achieve a transportation scale of 10×10 8 t class, total mileage approximately 6×10 4 A carbon dioxide pipeline network spanning km. Therefore, the development prospects of carbon dioxide pipeline networks are broad.

[0004] Carbon dioxide exists in five phases: solid, gas, liquid, dense, and supercritical. In its supercritical state, carbon dioxide's macroscopic state is similar to that of a gas; its density is close to that of a liquid, its diffusion coefficient is higher than that of a liquid, and its viscosity is close to that of a gas, exhibiting characteristics of low viscosity and high density. Liquid-phase carbon dioxide transportation requires careful attention to pipeline insulation and the establishment of refrigeration stations along the route, making implementation difficult. Gas-phase carbon dioxide transportation, to prevent phase change, generally uses lower transportation pressures, making it less economical compared to supercritical carbon dioxide transportation.

[0005] Long-distance, large-scale supercritical carbon dioxide pipeline transportation is currently recognized internationally as the safest and most economical method. However, there is a lack of experience in commissioning supercritical carbon dioxide pipelines, and supercritical carbon dioxide commissioning technology is scarce. Regarding patents, only Chinese patent CN117307968A proposes a commissioning system for branch supercritical carbon dioxide pipelines. However, the proposed commissioning steps are extremely similar to existing and technologically mature natural gas pipeline commissioning methods, and it targets the commissioning of supercritical carbon dioxide branch pipelines, not trunk pipelines. Furthermore, the charging medium required for branch pipeline commissioning is sourced from the trunk pipeline, failing to fully consider the complexity of gas source organization required for trunk pipeline commissioning and the phase transition process of carbon dioxide during pressurization and replacement commissioning, thus significantly limiting the charging efficiency. Summary of the Invention

[0006] The main objective of this invention is to propose a long-distance supercritical carbon dioxide pipeline commissioning system and method, aiming to solve the technical problems of high implementation difficulty and low transmission efficiency in the prior art.

[0007] To achieve the above objectives, the present invention provides a long-distance supercritical carbon dioxide pipeline commissioning system, comprising: a gas source charging system, including three charging branches for charging carbon dioxide of different phases, the downstream of the three charging branches converging at the main line of the first station; each charging branch is equipped with a branch shut-off valve, and the main line of the first station is equipped with a main line shut-off valve; an intermediate valve chamber system, connected downstream of the main line shut-off valve and including multiple intermediate valve chambers connected in sequence, with a valve chamber shut-off valve between any two adjacent intermediate valve chambers; and a terminal main line. The pipeline is connected downstream of the intermediate valve chamber system and a terminal shut-off valve is installed on the terminal trunk line; a venting system is used to vent carbon dioxide in the pipeline, and the multiple venting systems are a first-station venting system, an intermediate venting system, and a terminal venting system. The upstream and downstream of the trunk shut-off valve are connected to a first-station venting system through two venting branches, the upstream and downstream of the valve chamber shut-off valve are connected to an intermediate venting system through two venting branches, and the upstream of the terminal shut-off valve is connected to a terminal venting system through a venting branch. A first throttling shut-off venting valve is installed on the venting branch.

[0008] In this embodiment of the invention, the long-distance supercritical carbon dioxide pipeline commissioning system further includes a pig sending system and a pig receiving system. The pig sending system is connected to the first station trunk line and located downstream of the trunk line shut-off valve. The intermediate valve chamber system is connected between the pig sending system and the pig receiving system. The last station trunk line is connected downstream of the pig receiving system. The pig sending system is used to cooperate with the pig receiving system to replace the fluid in the pipeline through a pig isolator.

[0009] In this embodiment of the invention, the pig delivery system includes a first pig delivery branch, a pig delivery tube, and a second pig delivery branch. The first and second pig delivery branches are connected in parallel between the main line of the first station and the intermediate valve chamber system. A first delivery shut-off valve is provided on the first pig delivery branch. The pig delivery tube is located on the second pig delivery branch. Second delivery shut-off valves are provided upstream and downstream of the pig delivery tube.

[0010] In this embodiment of the invention, the pig receiving system is connected downstream of the intermediate valve chamber system and includes a third pig branch, a pig collecting cylinder, and a fourth pig branch. The third and fourth pig branches are connected in parallel between the intermediate valve chamber system and the terminal station trunk line. A first receiving shut-off valve is provided on the third pig branch, and the pig collecting cylinder is located on the fourth pig branch. Second receiving shut-off valves are provided upstream and downstream of the pig collecting cylinder.

[0011] In this embodiment of the invention, the venting system includes a multi-stage pressure regulating pipeline and a multi-stage pressure regulating assembly, a second throttling venting valve, a buffer tank, and a venting riser, which are sequentially arranged along the carbon dioxide flow direction on the multi-stage pressure regulating pipeline. The multi-stage pressure regulating assembly is used to perform multi-stage pressure regulation on the carbon dioxide in the multi-stage pressure regulating pipeline.

[0012] In this embodiment of the invention, the multi-stage pressure regulating assembly includes regulating valves and heat exchangers, and the number of regulating valves and heat exchangers is at least two, with one heat exchanger disposed between any two adjacent regulating valves.

[0013] This invention also proposes a method for commissioning a long-distance supercritical carbon dioxide pipeline, applied to the long-distance supercritical carbon dioxide pipeline commissioning system described above. The three charging branches are a gas phase charging branch, a liquid phase charging branch, and a two-phase charging branch. The method for commissioning the long-distance supercritical carbon dioxide pipeline includes:

[0014] Close the terminal shut-off valve, open the main line shut-off valve, valve chamber shut-off valve and terminal venting system, and inject inert gas into the intermediate valve chamber and terminal main line through the gas phase charging branch.

[0015] The air in the entire pipeline of the long-distance supercritical carbon dioxide pipeline commissioning system is replaced by the terminal venting system until the air in the entire pipeline is completely replaced by inert gas.

[0016] Shut down the terminal venting system and continue to inject inert gas until the fluid pressure in the entire pipeline is higher than the first preset value;

[0017] Open the terminal venting system and inject gaseous carbon dioxide into the intermediate valve chamber and the terminal main line through the gas phase charging branch until the inert gas in the entire pipeline is replaced by gaseous carbon dioxide. Then close the terminal venting system.

[0018] Close the valve chamber shut-off valve and continue to charge gaseous carbon dioxide until the fluid pressure in the pipeline between the gas source charging system and the valve chamber shut-off valve is higher than the second preset value;

[0019] Close the gas phase charging branch and charge liquid carbon dioxide into the pipeline through the liquid phase charging branch. The charged liquid carbon dioxide exerts a pressure-blocking effect on the gas phase carbon dioxide in the gas source charging system and valve chamber cutoff valve pipeline until the fluid pressure in the pipeline is higher than the third preset value.

[0020] By sequentially opening the shut-off valves of the control valve chambers, the pressure of multiple intermediate valve chambers is increased in stages until the liquid carbon dioxide in all intermediate valve chambers is converted into dense carbon dioxide.

[0021] Close the liquid phase charging branch, charge supercritical carbon dioxide through the two-phase charging branch, and open the terminal shut-off valve to allow the supercritical carbon dioxide to push the dense phase carbon dioxide toward the pipeline outlet until the fluid pressure of the entire pipeline is higher than the fourth preset value.

[0022] In this embodiment of the invention, the method for commissioning a long-distance supercritical carbon dioxide pipeline further includes:

[0023] If the pressure in the filling branch is found to be overpressure, start the first station venting system to vent and depressurize the filling branch;

[0024] If the upstream and downstream pressures of the valve chamber shut-off valve are found to be excessive, open the intermediate venting system to vent and depressurize the intermediate valve chamber.

[0025] If the pressure on the main line at the terminal station is found to be overpressured, the terminal station venting system is activated to vent and depressurize the main line at the terminal station.

[0026] In this embodiment of the invention, the method for commissioning a long-distance supercritical carbon dioxide pipeline further includes:

[0027] To determine if a leak has occurred in the long-distance supercritical carbon dioxide pipeline system, the leak point is determined based on the fluid pressure in the pipeline.

[0028] Close the shut-off valves located upstream and downstream of the leak point and obtain the venting distance between the leak point and each venting system;

[0029] Select the nearest venting system based on the venting distance;

[0030] Activate the latest air venting system.

[0031] In this embodiment of the invention, the long-distance supercritical carbon dioxide pipeline commissioning system further includes a pig sending system and a pig receiving system. The pig sending system is connected to the first station trunk line and located downstream of the trunk line shut-off valve. The intermediate valve chamber system is connected between the pig sending system and the pig receiving system. The last station trunk line is connected downstream of the pig receiving system. The pig sending system cooperates with the pig receiving system to displace the fluid in the pipeline through a pig isolator, open the last station venting system, and inject gaseous carbon dioxide into the intermediate valve chamber and the last station trunk line through a gas phase charging branch until the inert gas in the entire pipeline is replaced by gaseous carbon dioxide.

[0032] While charging with gaseous carbon dioxide, the pig isolator is sent to the pig receiving system through the pig sending system;

[0033] Once it is confirmed that the pig receiving system has received the pig isolator and the carbon dioxide concentration at the terminal shut-off valve is greater than the preset concentration, and the inert gas has been completely replaced by gaseous carbon dioxide, the terminal venting system is shut down.

[0034] Through the above technical solution, the long-distance supercritical carbon dioxide pipeline commissioning system provided by the embodiments of the present invention has the following beneficial effects:

[0035] The long-distance supercritical carbon dioxide pipeline commissioning system uses the section between the gas source injection system and the downstream intermediate valve chamber as a back-pressure section. The valve chamber shut-off valve is closed, and gaseous and liquid carbon dioxide are sequentially injected into the back-pressure section until the pressure in all back-pressure sections reaches the required level. Then, liquid carbon dioxide is injected into the entire line. Once the overall pressure reaches above the critical pressure of carbon dioxide (7.38 MPa), the carbon dioxide transforms from a liquid phase to a dense phase. Supercritical carbon dioxide is then injected into the entire line. When the supercritical carbon dioxide completes the replacement of the dense phase carbon dioxide, commissioning is complete. This system fully considers the phase transition process of carbon dioxide during the pressurization and replacement commissioning process. This invention, through staged injection of carbon dioxide in different phases and segmented pressurization, fully considers the changes in the carbon dioxide phase within the pipeline, improving carbon dioxide commissioning efficiency and avoiding uncontrolled carbon dioxide phase changes within the pipeline. This reduces the difficulty of carbon dioxide commissioning and prevents commissioning failures.

[0036] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0037] The accompanying drawings are provided to illustrate the invention and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation thereof. In the drawings:

[0038] Figure 1This is a schematic diagram of a long-distance supercritical carbon dioxide pipeline commissioning system according to an embodiment of the present invention;

[0039] Figure 2 This is a schematic diagram of the structure of a long-distance supercritical carbon dioxide pipeline commissioning system according to another embodiment of the present invention;

[0040] Figure 3 This is a schematic diagram of the venting system structure of a long-distance supercritical carbon dioxide pipeline commissioning system according to an embodiment of the present invention.

[0041] Explanation of reference numerals in the attached figures

[0042] Label Name Label Name

[0043] 1. Gas source charging system; 52. Heat exchanger

[0044] 11. Filling branch 53. Second throttling shut-off vent valve

[0045] 11a Vapor phase charging branch 54 Buffer tank

[0046] 11b Liquid phase charging branch 55 Vent riser

[0047] 11c Two-phase charging branch 6 Pig delivery system

[0048] 111 Flowmeter 61 Pipeline cleaning first branch

[0049] 112 Branch shut-off valve 62 First sending shut-off valve

[0050] 12 First Station Main Line 63 Pipeline Cleaning Launching Cylinder

[0051] 13 Main line shut-off valve; 64 Pipeline pigging second branch.

[0052] 2. Intermediate Trunk Line 65. Second Sending Cut-off Valve

[0053] 21 Valve chamber shut-off valve 7 Pig receiving system

[0054] 3. Terminal Main Line 71, Cleaning and Management Third Branch Road

[0055] 31 Terminal shut-off valve; 72 First receiving shut-off valve

[0056] 32 Gas chromatography-mass spectrometry (GC-MS) analyzer; 73 Pig collection tube.

[0057] 4. Empty branch road 74. Clean and manage the fourth branch road.

[0058] 41 First throttling shut-off valve; 75 Second receiving shut-off valve

[0059] 5 Venting system 8 Microcontroller

[0060] 51 Control valve Detailed Implementation

[0061] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0062] The following description, with reference to the accompanying drawings, describes a long-distance supercritical carbon dioxide pipeline commissioning system according to the present invention.

[0063] like Figures 1 to 3 As shown in the embodiment of the present invention, the long-distance supercritical carbon dioxide pipeline commissioning system includes a gas source charging system 1, an intermediate valve chamber system, a terminal main line 3, and a venting system 5. The gas source charging system 1 includes three charging branches 11 for charging carbon dioxide of different phases, and the downstream of the three charging branches 11 converges into the terminal main line 12. Each charging branch 11 is equipped with a branch shut-off valve 112, and the terminal main line 12 is equipped with a main line shut-off valve 13. The intermediate valve chamber system is connected downstream of the main line shut-off valve 13 and includes multiple intermediate valve chambers connected in sequence. A valve chamber shut-off is provided between any two adjacent intermediate valve chambers. Valve 21; the terminal trunk line 3 is connected downstream of the intermediate valve chamber system and a terminal shut-off valve 31 is installed on the terminal trunk line 3; the venting system 5 is used to vent carbon dioxide in the pipeline. The multiple venting systems 5 are the first station venting system, the intermediate venting system and the terminal venting system. The upstream and downstream of the trunk line shut-off valve 13 are connected to a first station venting system through two venting branches 4, the upstream and downstream of the valve chamber shut-off valve 21 are connected to an intermediate venting system through two venting branches 4, and the upstream of the terminal shut-off valve 31 is connected to a terminal venting system through a venting branch 4. A first throttling shut-off venting valve 41 is installed on the venting branch 4.

[0064] like Figure 1 As shown, the gas source filling system 1, intermediate valve chamber system, terminal trunk line 3, and venting system 5 are arranged sequentially from the beginning to the end, with the carbon dioxide being transported from the beginning to the end. Any two adjacent valve chamber shut-off valves 21 are connected by the intermediate trunk line 2. Solid lines in the diagram represent pipeline connections, while dashed lines represent circuit connections. Multiple microcontrollers 8 can transmit signals to each other and can also remotely transmit signals to the station control room and control center.

[0065] When using the long-distance supercritical carbon dioxide pipeline commissioning system in this embodiment for carbon dioxide commissioning, the terminal shut-off valve 31 can be closed, the main shut-off valve 13, the valve chamber shut-off valve 21, and the terminal venting system can be opened, and inert gas can be injected into the intermediate valve chamber and the terminal main line 3 through the gas phase injection branch 11a; the air in the entire pipeline of the long-distance supercritical carbon dioxide pipeline commissioning system can be replaced by the terminal venting system until the air in the entire pipeline is completely replaced by inert gas; the terminal venting system can be closed and inert gas can be injected until the fluid pressure in the entire pipeline is higher than the first preset value; the terminal venting system can be opened, and gaseous carbon dioxide can be injected into the intermediate valve chamber and the terminal main line 3 through the gas phase injection branch 11a until the inert gas in the entire pipeline is replaced by gaseous carbon dioxide, and the terminal venting system can be closed; the valve chamber shut-off valve 21 can be closed and gas phase can be injected. Carbon dioxide is injected until the fluid pressure in the pipeline between the gas source charging system 1 and the valve chamber shut-off valve 21 exceeds the second preset value; the gas phase charging branch 11a is closed and liquid phase carbon dioxide is injected into the pipeline through the liquid phase charging branch 11b, so that the injected liquid phase carbon dioxide exerts a pressure-blocking effect on the gas phase carbon dioxide in the pipeline between the gas source charging system 1 and the valve chamber shut-off valve 21 until the fluid pressure in the pipeline exceeds the third preset value; the valve chamber shut-off valve 21 is opened sequentially to increase the pressure in multiple intermediate valve chambers in stages until the liquid phase carbon dioxide in all intermediate valve chambers is converted into dense phase carbon dioxide; the liquid phase charging branch 11b is closed, supercritical carbon dioxide is injected through the two-phase charging branch 11c, and the terminal shut-off valve 31 is opened, so that the supercritical carbon dioxide pushes the dense phase carbon dioxide to move towards the pipeline outlet until the fluid pressure in the entire pipeline exceeds the fourth preset value.

[0066] In this embodiment, the long-distance supercritical carbon dioxide pipeline commissioning system uses the section between the gas source charging system 1 and the downstream intermediate valve chamber as a back-pressure section. The valve chamber shut-off valve 21 is closed, and gaseous and liquid carbon dioxide are sequentially charged into the back-pressure section until the pressure in all back-pressure sections reaches the required level. Liquid carbon dioxide is then charged into the entire line. Once the pressure reaches the critical pressure of carbon dioxide (7.38 MPa) or higher, the carbon dioxide changes from a liquid phase to a dense phase. Supercritical carbon dioxide is then charged into the entire line. When the supercritical carbon dioxide completes the replacement of the dense phase carbon dioxide, commissioning is complete. This system fully considers the phase transition process of carbon dioxide during the pressurization and replacement commissioning process. This embodiment, by charging carbon dioxide in stages with different phases and increasing the pressure in stages, fully considers the changes in the phase state of carbon dioxide within the pipeline, improving the efficiency of carbon dioxide commissioning. Furthermore, it avoids uncontrolled carbon dioxide phase changes within the pipeline, reducing the difficulty of carbon dioxide commissioning and preventing commissioning failures.

[0067] Specifically, the long-distance supercritical carbon dioxide pipeline commissioning system also includes a pig sending system 6 and a pig receiving system 7. The pig sending system 6 is connected to the first station trunk line 12 and located downstream of the trunk line shut-off valve 13. An intermediate valve chamber system is connected between the pig sending system 6 and the pig receiving system 7. The last station trunk line 3 is connected downstream of the pig receiving system 7. The pig sending system 6 works in conjunction with the pig receiving system 7 to replace the fluid in the pipeline through a pig isolator. When replacing carbon dioxide with inert gas, the pig sending system 6 and the pig receiving system 7 work together to replace the fluid in the pipeline through the pig isolator. The pig isolator completely isolates the carbon dioxide and inert gas, preventing mixing and ensuring the purity of the carbon dioxide during commissioning.

[0068] In another embodiment, the pig delivery system 6 includes a first pig delivery branch 61, a pig delivery tube 63, and a second pig delivery branch 64. The first pig delivery branch 61 and the second pig delivery branch 64 are connected in parallel between the main line 12 of the first station and the intermediate valve chamber system. A first delivery shut-off valve 62 is provided on the first pig delivery branch 61. The pig delivery tube 63 is located on the second pig delivery branch 64. A second delivery shut-off valve 65 is provided upstream and downstream of the pig delivery tube 63.

[0069] In this embodiment, the pig delivery system 6 is located downstream of the main line shut-off valve 13. When no pig delivery operation is being performed, the second delivery shut-off valve 65 is closed, and the fluid flows downstream through the first pig delivery branch 61. When a pig delivery operation is being performed, the first delivery shut-off valve 62 is closed, and the fluid flows downstream through the pig delivery cylinder 63 and the second pig delivery branch 64. The pig delivery cylinder 63 is equipped with second delivery shut-off valves 65 both upstream and downstream to prevent fluid from flowing into the second pig delivery branch 64 when no pig delivery operation is being performed, ensuring the accuracy of pig delivery and delivery by the pig delivery system 6. The first pig delivery branch 61 and the second pig delivery branch 64 are connected in parallel, and the pig delivery cylinder 63 is equipped with second delivery shut-off valves 65 both upstream and downstream, facilitating pipeline switching between pig delivery and non-pipe delivery operations.

[0070] Specifically, the pig receiving system 7 is connected downstream of the intermediate valve chamber system and includes a third pigging branch 71, a pigging ball receiving cylinder 73, and a fourth pigging branch 74. The third pigging branch 71 and the fourth pigging branch 74 are connected in parallel between the intermediate valve chamber system and the terminal main line 3. A first receiving shut-off valve 72 is provided on the third pigging branch 71, and the pigging ball receiving cylinder 73 is located on the fourth pigging branch 74. A second receiving shut-off valve 75 is provided upstream and downstream of the pigging ball receiving cylinder 73.

[0071] In this embodiment, the pig receiving system 7 is located at the entrance of the terminal main line 3. When the pig receiving system 7 is not in operation, the second receiving shut-off valve 75 is closed, and the fluid flows downstream through the third branch 71 of the pig. When the pig is in operation, the first receiving shut-off valve 72 is closed, and the fluid flows downstream through the pig receiving cylinder 73 and the fourth branch 74 of the pig. In this embodiment, the fourth branch 74 of the pig and the third branch 71 of the pig are connected in parallel, and the pig receiving cylinder 73 is equipped with a second receiving shut-off valve 75 both upstream and downstream, which facilitates the switching between pig operation and non-pipe operation.

[0072] In one embodiment, the venting system 5 includes a multi-stage pressure regulating pipeline and a multi-stage pressure regulating assembly, a second throttling venting valve 53, a buffer tank 54, and a venting riser 55 arranged sequentially along the carbon dioxide flow direction on the multi-stage pressure regulating pipeline. The multi-stage pressure regulating assembly is used to perform multi-stage pressure regulation on the carbon dioxide in the multi-stage pressure regulating pipeline.

[0073] like Figure 2 As shown, the two venting branches 4 of the first station venting system are led out from the upstream and downstream ends of the main line shut-off valve 13 on the first station main line 12, respectively, and both venting branches 4 are equipped with shut-off valves. The other ends of the two venting branches 4 converge at the multi-stage pressure regulating assembly. The station venting system 5 can realize the release of fluid medium in the pipeline upstream or downstream of the main line shut-off valve 13 from the first station venting system after multi-stage pressure regulation and heat exchange.

[0074] The terminal venting system is basically the same as the initial venting system, except for a venting branch 4 extending upstream from the terminal shut-off valve 31. The medium in the pipeline upstream of the terminal shut-off valve 31 can be released from the terminal venting system after multi-stage pressure regulation and heat exchange. The initial venting system, intermediate venting system, and terminal venting system can all be controlled by a microcontroller 8. Pressure sensors PT and TT installed on the long-distance supercritical carbon dioxide pipeline commissioning system, and multiple pressure sensors PT and temperature sensors TT installed on the venting pipeline, detect the pressure and temperature within the pipeline at corresponding locations and transmit the signals to the microcontroller 8. The microcontroller 8 can control the opening degree of the three-stage regulating valve 51 and the second throttling shut-off venting valve 53 in the multi-stage pressure regulation assembly, as well as the heating power of the two-stage heat exchangers 52 in the multi-stage pressure regulation assembly, ensuring that the pipeline temperature does not fall below the pipe material's withstand temperature and preventing ice blockage within the pipeline of the long-distance supercritical carbon dioxide pipeline commissioning system, thereby automatically and efficiently achieving pipeline venting operations.

[0075] like Figure 3As shown, the multi-stage pressure regulating assembly includes a regulating valve 51 and a heat exchanger 52. There are at least two regulating valves 51 and heat exchangers 52, with one heat exchanger 52 positioned between any two adjacent regulating valves 51. The specific type of heat exchanger 52 can be selected based on the ambient temperature. If the ambient temperature of the operating environment of the heat exchanger 52 is above 0°C, an air-cooled vaporizer is selected; if the ambient temperature of the operating environment of the heat exchanger 52 is below 0°C, an electrically heated water bath vaporizer is selected. The heat exchanger 52 can reheat the carbon dioxide after throttling and cooling. A gas composition analyzer 32 is installed upstream of the terminal shut-off valve 31 to detect gas composition components such as air, nitrogen, and multiphase carbon dioxide at the terminal main line 3 inlet, identifying the gas type entering the terminal and providing a basis for gas replacement work.

[0076] In one embodiment, the multi-stage pressure regulating assembly includes three regulating valves 51 and two heat exchangers 52. The three-stage regulation and two-stage heat exchange work together to achieve three-stage pressure regulation. If the fluid pressure inside the pipeline differs significantly from the external atmospheric pressure, and the fluid is directly vented to the atmosphere, dry ice will form and block the venting pipeline due to the Joule-Thomson effect of carbon dioxide during the carbon dioxide venting process, potentially leading to a dangerous accident. In this embodiment, three-stage pressure regulation can prevent large pressure differential venting. Furthermore, rapid pressure reduction in the main pipeline may cause rapid expansion or evaporation of the fluid, resulting in a drastic drop in temperature inside the pipe. Low temperatures may damage the pipe materials and instruments on the pipeline. The buffer tank 54 can buffer the released medium and separate and re-vaporize the liquid phase components of the carbon dioxide gas-liquid mixture.

[0077] A pressure sensor PT and a temperature sensor TT are installed downstream of the first regulating valve 51 in the initial venting system to obtain the temperature, pressure, and phase state of the fluid after the first throttling. A temperature sensor TT is installed downstream of the first heat exchanger 52 to obtain the temperature of the fluid after the first heating. A pressure sensor PT and a temperature sensor TT are installed downstream of the second regulating valve 51 to obtain the temperature, pressure, and phase state of the fluid after the second throttling. A temperature sensor TT is installed downstream of the second heat exchanger 52 to obtain the temperature of the fluid after the second heating. A pressure sensor PT and a temperature sensor TT are installed downstream of the third regulating valve 51 to obtain the temperature, pressure, and phase state of the fluid after the third throttling. The settings and functions of the pressure sensors PT and TT in the intermediate venting system are the same as those in the initial venting system. The settings and functions of the pressure sensors PT and TT in the final venting system are the same as those in the initial venting system. A pressure sensor PT and a temperature sensor TT are installed on the pipeline between the downstream of each regulating valve 51 and the upstream of each heat exchanger 52. Each pressure sensor PT and temperature sensor TT is connected to the microcontroller 8, transmitting pressure and temperature signals to it, facilitating automatic venting settings of the venting system 5. The first, second, and third regulating valves 51 are arranged sequentially from beginning to end, as are the first and second heat exchangers 52. Multiple intermediate valve chambers are arranged sequentially from beginning to end, with the first intermediate valve chamber located at the beginning; all other components closest to the beginning are designated as the first.

[0078] In one embodiment, the long-distance supercritical carbon dioxide pipeline commissioning system also includes a carbon dioxide concentration sensor. This sensor can be installed near the above-ground pipelines of the first station trunk line 12, intermediate valve chambers, and the last station trunk line 3 to monitor atmospheric carbon dioxide concentration. When the concentration is abnormal, it can trigger a timely alarm. The carbon dioxide concentration sensor, temperature sensor TT, pressure sensor PT, flow meter 111, and gas chromatography-mass spectrometry analyzer 32 can all remotely transmit the detection data to the station control room or control center, facilitating remote data monitoring of the long-distance supercritical carbon dioxide pipeline commissioning system.

[0079] In one embodiment, each of the charging branches 11 is equipped with a flow meter 111 and a detection component for measuring temperature and pressure. The detection component is located upstream of the branch shut-off valve 112, and the flow meter 111 is located downstream of the branch shut-off valve 112. The three charging branches 11 are a gas phase charging branch 11a, a liquid phase charging branch 11b, and a two-phase charging branch 11c. The gas phase charging branch 11a includes a gas phase charging pipe, a branch shut-off valve 112, and a flow meter 111, which can be an ultrasonic flow meter 111. The liquid phase charging branch 11b includes a liquid phase charging pipe, a branch shut-off valve 112, and a flow meter 111, which can be a turbine flow meter 111. The two-phase charging branch 11c includes a supercritical / dense phase charging pipe, a branch shut-off valve 112, and a flow meter 111, which can be a turbine flow meter 111. The supercritical / dense phase charging pipe can be used to charge supercritical phase carbon dioxide or dense phase carbon dioxide. The downstream of the three charging branches 11 converges at the main line 12 of the first station. Pressure sensors PT, temperature sensors TT, and flow meters 111 are installed in the gas phase charging branch 11a, liquid phase charging branch 11b, and two-phase charging branch 11c to facilitate the acquisition of the temperature, pressure, flow rate, and phase of the charging fluid. Pressure sensors PT and temperature sensors TT are installed upstream and downstream of the main line shut-off valve 13 to facilitate obtaining the temperature, pressure, and phase state of the fluid at the inlet and outlet of the gas source charging system 1. Pressure sensors PT and temperature sensors TT are also installed upstream and downstream of the valve chamber shut-off valve 21 to facilitate obtaining the temperature, pressure, and phase state upstream and downstream of the valve chamber shut-off valve 21.

[0080] This invention also proposes a method for commissioning a long-distance supercritical carbon dioxide pipeline, applied to the aforementioned long-distance supercritical carbon dioxide pipeline commissioning system. The three charging branches 11 are a gas phase charging branch 11a, a liquid phase charging branch 11b, and a two-phase charging branch 11c. The long-distance supercritical carbon dioxide pipeline commissioning method includes:

[0081] Close the terminal shut-off valve 31, open the main line shut-off valve 13, the valve chamber shut-off valve 21 and the terminal venting system, and inject inert gas into the intermediate valve chamber and the terminal main line 3 through the gas phase charging branch 11a.

[0082] The air in the entire pipeline of the long-distance supercritical carbon dioxide pipeline commissioning system is replaced by the terminal venting system until the air in the entire pipeline is completely replaced by inert gas.

[0083] Shut down the terminal venting system and continue to inject inert gas until the fluid pressure in the entire pipeline is higher than the first preset value;

[0084] Open the terminal venting system and inject gaseous carbon dioxide into the intermediate valve chamber and the terminal trunk line 3 through the gas phase charging branch 11a until the inert gas in the entire pipeline is replaced by gaseous carbon dioxide. Then close the terminal venting system.

[0085] Close the valve chamber shut-off valve 21 and continue to charge gaseous carbon dioxide until the fluid pressure in the pipeline between the gas source charging system 1 and the valve chamber shut-off valve 21 is higher than the second preset value;

[0086] Close the gas phase charging branch 11a and charge the pipeline with liquid phase carbon dioxide through the liquid phase charging branch 11b. The charged liquid phase carbon dioxide exerts a pressure-blocking effect on the gas phase carbon dioxide in the pipeline between the gas source charging system 1 and the valve chamber shut-off valve 21 until the fluid pressure in the pipeline is higher than the third preset value.

[0087] By sequentially opening the control valve chamber shut-off valve 21, the pressure of multiple intermediate valve chambers is increased in stages until the liquid carbon dioxide in all intermediate valve chambers is converted into dense carbon dioxide.

[0088] Close the liquid phase charging branch 11b, and charge supercritical carbon dioxide through the two-phase charging branch 11c. Open the terminal shut-off valve 31 to allow the supercritical carbon dioxide to push the dense phase carbon dioxide towards the pipeline outlet until the fluid pressure of the entire pipeline exceeds the fourth preset value. Nitrogen can be used as the inert gas.

[0089] In this embodiment, the first preset value can be 0.05 MPa, the second preset value can be 3.7 MPa, the third preset value can be 6 MPa, and the fourth preset value can be 8.1 MPa. In other embodiments, the first, second, third, and fourth preset values ​​can be preset according to actual usage requirements.

[0090] In this embodiment, nitrogen is first injected and sealed, then carbon dioxide is used to replace the nitrogen, followed by segmental pressurization of the entire pipeline, and finally supercritical carbon dioxide injection. This avoids the problem of excessively high temperatures at the pipeline end during liquid carbon dioxide injection, which could cause the inner coating to fail. It also avoids the influence of initial back pressure, the mass flow rate of each phase of injected carbon dioxide, and ambient temperature on the replacement time, carbon dioxide usage, the heating and pressurization process, liquid holdup, and phase transformation process. Compared with existing technologies, this invention fully considers the phase transformation process of carbon dioxide during pressurization and replacement commissioning, using segmented valve chambers for pressurization and replacement, and timely injection of the appropriate phase of carbon dioxide.

[0091] To address the issue of potentially excessively high temperatures at the pipeline end during liquid carbon dioxide filling, which could lead to inner coating failure, this invention effectively prevents such hazards by controlling the filling branch 11 and adjusting the filling rate of each phase of carbon dioxide. It can efficiently enable the commissioning of long-distance supercritical carbon dioxide pipelines, demonstrating strong practicality and widespread application value.

[0092] In one embodiment, the method for commissioning a long-distance supercritical carbon dioxide pipeline further includes:

[0093] If the pressure in the filling branch 11 is found to be overpressured, start the first station venting system to vent and depressurize the filling branch 11;

[0094] If the upstream and downstream pressures of the valve chamber shut-off valve 21 are found to be overpressured, open the intermediate venting system to vent and depressurize the intermediate valve chamber.

[0095] If the pressure of the terminal main line 3 is found to be overpressure, the terminal venting system is activated to vent and depressurize the terminal main line 3.

[0096] Emergency overpressure relief operations during pipeline commissioning; real-time monitoring of carbon dioxide concentration in the first station, intermediate valve chambers, and terminal station above-ground pipelines using carbon dioxide concentration monitoring devices reduces the risk of personnel asphyxiation due to accidental carbon dioxide leaks or improper venting operations. This invention provides an effective commissioning system and method for the safe commissioning of supercritical carbon dioxide pipelines, demonstrating significant practicality and broad application prospects.

[0097] In another embodiment, the method for commissioning long-distance supercritical carbon dioxide pipelines further includes:

[0098] To determine if a leak has occurred in the long-distance supercritical carbon dioxide pipeline system, the leak point is determined based on the fluid pressure in the pipeline.

[0099] Close the shut-off valves located upstream and downstream of the leak point and obtain the venting distance between the leak point and each venting system 5.

[0100] Select the nearest venting system 5 based on the venting distance;

[0101] Activate the latest air venting system 5.

[0102] In one embodiment, the specific steps for the carbon dioxide overpressure relief operation of the main pipeline are as follows:

[0103] The microcontroller 8 of the terminal venting system detects that the pipeline pressure exceeds the overpressure relief pressure (13MPa) through the pressure sensor PT on the terminal trunk line 3, and opens the first throttling stop venting valve 41 and the second throttling stop venting valve 53 of the terminal venting system to start the terminal venting operation.

[0104] Adjust the opening of the first regulating valve 51 of the terminal venting system, start the first heat exchanger 52 of the terminal venting system, slowly adjust the opening of the second regulating valve 51 of the terminal venting system, start the second heat exchanger 52 of the terminal venting system, slowly adjust the opening of the third regulating valve 51 of the terminal venting system, and the vaporized carbon dioxide is released through the buffer tank 54 and the station venting riser 55.

[0105] Throughout the venting process, the main line temperature remains above -20℃ to prevent damage to the pipeline materials from low temperatures. The main line temperature is monitored by temperature sensor TT on the terminal main line 3. The opening of each stage of regulating valve 51 is adjusted to control the first-stage throttling outlet pressure to 4.0 MPa, the second-stage throttling outlet pressure to 2.2 MPa, and the third-stage throttling outlet pressure to 1.2 MPa. The outlet pressures of each stage of regulating valve 51 are monitored by the first, second, and third pressure sensors PT of the terminal venting system.

[0106] The heating power of heat exchanger 52 is dynamically adjusted to ensure that the outlet temperature of the first heat exchanger 52 and the second heat exchanger 52 is higher than -5℃. The temperature before and after the two-stage heat exchanger 52 is detected by the first temperature sensor TT, the second temperature sensor TT, the third temperature sensor TT, and the fourth temperature sensor TT of the terminal venting system.

[0107] When the pressure sensor PT on the terminal main line 3 detects that the main line pressure is lower than 4.0MPa, the first regulating valve 51 of the terminal venting system is fully opened, the first heat exchanger 52 does not work, and the venting operation is continued by using only the second regulating valve 51, the second heat exchanger 52, and the third regulating valve 51.

[0108] When the pressure sensor PT on the terminal main line 3 detects that the main line pressure is lower than 2.2MPa, the second regulating valve 51 of the terminal venting system is fully opened, the second heat exchanger 52 does not work, and the subsequent venting operation is completed only by using the third regulating valve 51 of the terminal venting system.

[0109] In one embodiment, the long-distance supercritical carbon dioxide pipeline commissioning system further includes a pig sending system 6 and a pig receiving system 7. The pig sending system 6 is connected to the first station trunk line 12 and located downstream of the trunk line shut-off valve 13. An intermediate valve chamber system is connected between the pig sending system 6 and the pig receiving system 7. The last station trunk line 3 is connected downstream of the pig receiving system 7. The pig sending system 6 is used in conjunction with the pig receiving system 7 to replace the fluid in the pipeline through a pig isolator, open the last station venting system, and inject gaseous carbon dioxide into the intermediate valve chamber and the last station trunk line 3 through the gas phase charging branch 11a until the inert gas in the entire pipeline is replaced by gaseous carbon dioxide.

[0110] While charging with gaseous carbon dioxide, the pig isolator is sent from the pig sending system 6 to the pig receiving system 7.

[0111] Once it is confirmed that the pig receiving system 7 has received the pig isolator and the carbon dioxide concentration at the terminal shut-off valve 31 is greater than the preset concentration, and the inert gas has been completely replaced by gaseous carbon dioxide, the terminal venting system is shut down.

[0112] After sealing the pipeline with nitrogen, the pig sending system 6 and the pig receiving system 7 work together to isolate the gas and inject gaseous carbon dioxide into the pipeline. The isolation effect of the pig isolator allows the gaseous carbon dioxide to replace the nitrogen. However, the existing technology suffers from insufficient carbon dioxide concentration monitoring, failing to effectively prevent the risk of personnel asphyxiation due to accidental carbon dioxide leakage or improper venting operations.

[0113] In one embodiment, the method for commissioning a long-distance supercritical carbon dioxide pipeline includes:

[0114] (1) Nitrogen injection and sealing stage:

[0115] After the pipeline has completed pressure testing and drying, the terminal venting system is activated.

[0116] Close the terminal shut-off valve 31, and open the first receiving shut-off valve 72, the valve chamber shut-off valve 21, the first transmitting shut-off valve 62, and the main line shut-off valve 13;

[0117] Nitrogen is injected into the pipeline from the gas phase charging branch 11a. When the gas composition analyzer 32 identifies that the nitrogen concentration at the entrance of the terminal main line 3 is 100%, it is determined that the entire pipeline is filled with nitrogen.

[0118] The terminal venting system was shut down, and nitrogen was continued to be injected into the pipeline until the pressure inside the pipeline rose to 0.05 MPa. The pressure sensors PT on the first station trunk line 12, the intermediate valve chamber, and the terminal station trunk line 3 all detected a pressure of 0.05 MPa.

[0119] Close the main line shut-off valve 13 and seal the nitrogen in the pipeline;

[0120] (2) Stage of nitrogen replacement by gaseous carbon dioxide:

[0121] Open the terminal venting system, open the main line shut-off valve 13, keep the terminal shut-off valve 31 in the closed state, inject gaseous carbon dioxide at a temperature of 2°C into the pipeline from the gas phase charging branch 11a, and control the pig sending system 6 to send the pig isolator to the pig receiving system 7.

[0122] Once the pig receiving system 7 receives the pig isolator and the gas composition analyzer 32 identifies that the carbon dioxide concentration at the entrance of the terminal main line 3 is 100%, it is determined that the entire pipeline is filled with gaseous carbon dioxide; at this time, the terminal venting system is shut down.

[0123] (3) Pipeline segmented pressurization stage:

[0124] Close the valve chamber shut-off valve 21 of the first intermediate valve chamber and continue to inject gaseous carbon dioxide into the pipeline until the gas pressure of the gas source filling system 1 to the pipeline of the first intermediate valve chamber rises to 3.7 MPa. The carbon dioxide pressure and temperature operating point are close to the gas-liquid balance line, and it is determined that the gaseous carbon dioxide is about to liquefy.

[0125] Close the gas phase charging branch 11a, and inject liquid carbon dioxide at a temperature of 2°C into the pipeline through the liquid phase charging branch 11b at a certain flow rate. The injected liquid carbon dioxide pressurizes the gas phase carbon dioxide in the pipeline from the gas source charging system 1 to the first intermediate valve chamber, causing the gas phase carbon dioxide to be converted into liquid phase.

[0126] During the stage of injecting liquid carbon dioxide into the pipeline, gaseous carbon dioxide is pushed out, and under the pressure-locking effect, the pressure and temperature of gaseous carbon dioxide also increase.

[0127] When the temperature sensor TT on the first intermediate valve chamber pipeline shows that the temperature reaches 50°C, reduce the liquid phase injection flow rate of the liquid phase charging branch 11b.

[0128] Once the pressure in the pipeline between the gas source charging system 1 and the first intermediate valve chamber reaches 6 MPa, the valve chamber shut-off valve 21 of the first intermediate valve chamber is opened. The fluid flows through the valve chamber shut-off valve 21 of the first intermediate valve chamber and goes downstream. At this time, the valve chamber shut-off valve 21 of the second intermediate valve chamber is closed. Liquid carbon dioxide continues to be charged into the pipeline at a certain flow rate.

[0129] Once the pressure in the pipeline between the gas source filling system 1 and the second intermediate valve chamber reaches 6 MPa, open the valve chamber shut-off valve 21 of the second intermediate valve chamber, and so on, until the pressure in the entire pipeline reaches 6 MPa, so that the gaseous carbon dioxide in the entire pipeline is completely converted into liquid carbon dioxide.

[0130] (4) Pipeline pressurization phase:

[0131] Liquid carbon dioxide is injected into the pipeline at a certain flow rate. When the pressure of the liquid carbon dioxide in the pipeline is determined to be higher than the critical pressure of 7.38 MPa, the liquid carbon dioxide in the pipeline is transformed into dense carbon dioxide.

[0132] Once the pressure of the medium inside the pipe reaches 7.38 MPa, dense phase carbon dioxide is injected into the pipe at a certain flow rate through the two-phase charging branch 11c. Once the pressure of the medium inside the pipe reaches 13 MPa, the pressurization of the entire pipeline is completed.

[0133] During the stage of injecting liquid phase and dense phase carbon dioxide into the pipeline, when the temperature sensor TT on the terminal station trunk line 3 is determined to reach 50°C, the carbon dioxide medium injection flow rate of the liquid phase filling branch 11b and the two-phase filling branch 11c is reduced.

[0134] (5) Supercritical phase carbon dioxide injection stage:

[0135] Once the pressure of the medium in the pipeline reaches 13MPa, supercritical carbon dioxide at a temperature of 50℃ and a pressure of 13MPa is injected through the two-phase injection branch 11c at a certain flow rate. The terminal shut-off valve 31 is then opened. The supercritical carbon dioxide injected into the pipeline pushes the dense phase carbon dioxide toward the pipeline outlet, thereby replacing the dense phase carbon dioxide with the supercritical carbon dioxide.

[0136] Dense-phase carbon dioxide can be injected into the formation via a downstream plunger pump to enhance crude oil extraction.

[0137] (6) Commissioning completed:

[0138] During the axial migration of supercritical carbon dioxide in the pipeline, the temperature continuously decreases. It is confirmed that the fluid temperature at the end of the pipeline is below 31°C, and the pressure and temperature of the entire pipeline reach a stable state. The pressure of the entire pipeline reaches above 8.1 MPa, and the temperature of the upstream section of the pipeline reaches above 31°C. It can be confirmed that the supercritical carbon dioxide pipeline has been successfully put into operation.

[0139] If an overpressure is detected in the gas source filling system 1, the first station venting system can be opened immediately to release pressure through the first station venting system;

[0140] During the phased pressurization stage of pipeline commissioning and replacement, if it is determined that the pressure upstream and downstream of valve chamber shut-off valve 21 is too high, the intermediate venting system can be opened immediately to vent and depressurize.

[0141] During the liquid phase carbon dioxide injection stage, gaseous carbon dioxide is continuously pushed to the end of the pipeline. Under the pressure buildup, the thermal motion of gaseous carbon dioxide molecules intensifies, leading to a simultaneous increase in pressure and temperature. When overpressure is detected at the inlet of the terminal station's main line 3, the terminal station's venting system can be opened immediately to release the pressure.

[0142] When a leak occurs in the main pipeline of a long-distance supercritical carbon dioxide pipeline system and maintenance is required, the shut-off valves at both ends of the pipeline section near the leak point can be closed, and the nearest station or valve chamber venting system 5 can be opened to release the carbon dioxide in the pipeline.

[0143] In one embodiment, the method for commissioning a long-distance supercritical carbon dioxide pipeline includes:

[0144] S1: Open the branch shut-off valve 112 on the gas phase charging branch 11a, start the normal delivery process at the first station, open the main line shut-off valve 13 and the first sending shut-off valve 62, open the valve chamber shut-off valve 21, start the venting process at the end station, open the first receiving shut-off valve 72, the first throttling shut-off venting valve 41 of the venting system at the end station, fully open the three regulating valves 51 of the venting system at the end station, and the second throttling shut-off venting valve 53 at the tail of the venting system at the end station, and close the remaining valves;

[0145] S2: Inject nitrogen at 2℃ into gas phase charging branch 11a at a flow rate of 5m / s. When the gas composition analyzer 32 detects that the nitrogen content is 100%, close the terminal venting process, keep the terminal shut-off valve 31 closed, and continue to charge nitrogen into the pipeline. When the pressure sensor PT on the terminal trunk 3 shows 0.05MPa (gauge pressure), close the branch shut-off valve 112 on gas phase charging branch 11a, stop injecting nitrogen into the pipeline, and at the same time close the terminal venting system to seal the entire pipeline with nitrogen.

[0146] S3: When the entire pipeline is sealed with nitrogen and the commissioning operation is confirmed, place the pigging isolator in the pigging launcher 63, close the first sending cut-off valve 62, then open the first station second sending cut-off valve 65, close the first receiving cut-off valve 72, open the second receiving cut-off valve 75, start the terminal venting process, open the branch cut-off valve 112 on the gas phase charging branch 11a, inject gas phase carbon dioxide at a temperature of 2℃ into the gas phase charging branch 11a at a flow rate of 5m / s, use the pigging isolator to isolate the newly injected gas phase carbon dioxide from the nitrogen in the pipeline, the newly injected gas phase carbon dioxide pushes the nitrogen downstream, and the nitrogen at the end of the pipeline is vented through the venting riser 55 of the terminal venting system;

[0147] S4: After the pigging isolator is successfully launched from the first station launching tube, switch the pigging isolator launching process of the first station to the normal delivery process, open the first launching cut-off valve 62, and close the second launching cut-off valve 65.

[0148] S5: When the pigging isolator reaches the pigging receiver 73 at the downstream terminal station, switch the receiving process of the terminal pigging isolator to the normal conveying process, open the first receiving cut-off valve 72, and close the second receiving cut-off valve 75.

[0149] S6: The gas composition analyzer 32 continuously samples and detects the composition of the medium in the pipeline. When the sampling index meets the requirement that the carbon dioxide concentration is 100%, it is confirmed that the gas phase carbon dioxide replacement nitrogen operation has been successfully completed. The first throttling stop vent valve 41 and the regulating valve 51 of the terminal vent system are closed, the second throttling stop vent valve 53 of the terminal vent system are closed, the terminal vent process is closed, and the long-distance supercritical carbon dioxide pipeline commissioning system enters the staged pressurization, and the gas phase carbon dioxide is converted into liquid phase carbon dioxide.

[0150] S6: Close the valve chamber shut-off valve 21 of the first intermediate valve chamber, and continue to inject gaseous carbon dioxide at a temperature of 2℃ into the gas phase charging branch 11a at a flow rate of 5m / s, so that the gaseous carbon dioxide in the pipeline between the gas source charging system 1 and the first intermediate valve chamber is pressurized to 3.7MPa.

[0151] S7: When the pressure sensor PT on the first intermediate valve chamber displays 3.7MPa, close the branch shut-off valve 112 on the gas phase charging branch 11a and open the branch shut-off valve 112 on the liquid phase charging branch 11b. Inject liquid carbon dioxide at a temperature of 2℃ into the liquid phase charging branch 11b at a flow rate of 0.5m / s, thereby increasing the pressure of the medium in the pipeline between the gas source charging system 1 and the first intermediate valve chamber to 6MPa.

[0152] During this stage, due to the increase in pressure, the gaseous carbon dioxide in the pipe gradually transforms into liquid carbon dioxide. During the stage of filling the pipe with liquid carbon dioxide, the gaseous carbon dioxide is continuously pushed out. Under the pressure-locking effect, the thermal motion of the gaseous carbon dioxide molecules intensifies, resulting in an increase in temperature at the same time as the pressure increases. If the temperature sensor TT of the main line of the first intermediate valve chamber shows that the temperature reaches 50°C, the liquid phase filling flow rate of the liquid phase filling branch 11b is reduced.

[0153] S8: When the main line pressure sensor PT of the first intermediate valve chamber displays 6MPa, open the valve chamber shut-off valve 21 of the first intermediate valve chamber and continue to inject liquid carbon dioxide into the pipeline at a flow rate of 0.5m / s. When the pressure between the gas source charging system 1 and the second intermediate valve chamber rises to 6MPa, open the valve chamber shut-off valve 21 of the second intermediate valve chamber, and so on, until the pressure of the entire line rises to 6MPa;

[0154] S9: When the pressure sensor PT on the terminal main line 3 displays 6MPa, continue injecting liquid carbon dioxide into the pipeline at a flow rate of 0.5m / s. Confirm that the pressure of the liquid carbon dioxide in the pipeline is higher than the critical pressure of 7.38MPa, and the liquid carbon dioxide in the pipeline transforms into a dense phase. Close the branch shut-off valve 112 of the liquid phase charging branch 11b, open the branch shut-off valve 112 of the two-phase charging branch 11c, and inject dense carbon dioxide at a flow rate of 2m / s. When the medium pressure in the pipeline reaches 13MPa, the pressurization stage of the entire pipeline is completed.

[0155] During the dense phase carbon dioxide injection stage into the pipeline, the gaseous carbon dioxide that was not liquefied during the liquid phase carbon dioxide injection stage at the end of the pipeline is continuously pushed out. Under the pressure-locking effect, the thermal motion of the gaseous carbon dioxide molecules intensifies, resulting in an increase in both pressure and temperature. It is determined that the temperature sensor TT on the terminal main line 3 shows that the temperature has reached 50°C, so the dense phase injection flow rate of the two-phase charging branch 11c is reduced.

[0156] S10: Determine that the pressure sensor PT on the terminal trunk line 3 shows 13MPa. Inject supercritical carbon dioxide at a temperature of 50℃ and a pressure of 13MPa through the two-phase injection branch 11c at a flow rate of 2m / s. At the same time, open the terminal shut-off valve 31. The supercritical carbon dioxide injected into the pipeline pushes the dense phase carbon dioxide to move towards the pipeline outlet, so that the supercritical carbon dioxide in the pipeline replaces the dense phase carbon dioxide.

[0157] S11: After a period of time, the pressure sensor PT on the first station trunk line 12, the pressure sensor PT on the intermediate valve chamber trunk line, and the pressure sensor PT on the last station trunk line 3 all showed that the pressure was above 8.1MPa. The temperature sensor TT on the first station trunk line 12 showed that the temperature reached above 31℃. It can be confirmed that the supercritical carbon dioxide pipeline has been successfully put into operation.

[0158] In the description of this invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0159] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0160] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0161] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for commissioning a long-distance supercritical carbon dioxide pipeline, characterized in that, An application to long-distance supercritical carbon dioxide pipeline commissioning systems, wherein the long-distance supercritical carbon dioxide pipeline commissioning system includes: The gas source filling system (1) includes three filling branches (11) for filling carbon dioxide of different phases. The downstream of the three filling branches (11) converges into the first station trunk line (12). Each filling branch (11) is equipped with a branch shut-off valve (112), and the first station trunk line (12) is equipped with a trunk line shut-off valve (13). The intermediate valve chamber system is connected downstream of the main line shut-off valve (13) and includes multiple intermediate valve chambers connected in sequence, with a valve chamber shut-off valve (21) provided between any two adjacent intermediate valve chambers. The terminal trunk line (3) is connected to the downstream of the intermediate valve chamber system and the terminal trunk line (3) is equipped with a terminal shut-off valve (31). Venting system (5) is used to vent carbon dioxide in the pipeline. The multiple venting systems (5) are respectively the first station venting system, the intermediate venting system and the last station venting system. The upstream and downstream of the main line shut-off valve (13) are connected to the first station venting system through two venting branches (4). The upstream and downstream of the valve chamber shut-off valve (21) are connected to the intermediate venting system through two venting branches (4). The upstream of the last station shut-off valve (31) is connected to the last station venting system through a venting branch (4). The venting branch (4) is equipped with a first throttling shut-off venting valve (41). The three charging branches (11) are a gas phase charging branch (11a), a liquid phase charging branch (11b), and a two-phase charging branch (11c). The commissioning method for the long-distance supercritical carbon dioxide pipeline includes: Close the terminal shut-off valve (31), open the main line shut-off valve (13), valve chamber shut-off valve (21) and terminal venting system, and inject inert gas into the intermediate valve chamber and terminal main line (3) through the gas phase charging branch (11a); The air in the entire pipeline of the long-distance supercritical carbon dioxide pipeline commissioning system is replaced by the terminal venting system until the air in the entire pipeline is completely replaced by inert gas. Shut down the terminal venting system and continue to inject inert gas until the fluid pressure in the entire pipeline is higher than the first preset value; Open the terminal venting system and inject gaseous carbon dioxide into the intermediate valve chamber and the terminal main line (3) through the gas phase injection branch (11a) until the inert gas in the entire pipeline is replaced by gaseous carbon dioxide. Then close the terminal venting system. Close the valve chamber shut-off valve (21) and continue to charge gaseous carbon dioxide until the fluid pressure in the pipeline between the gas source charging system (1) and the valve chamber shut-off valve (21) is higher than the second preset value; Close the gas phase charging branch (11a) and charge liquid phase carbon dioxide into the pipeline through the liquid phase charging branch (11b), so that the charged liquid phase carbon dioxide exerts a pressure-blocking effect on the gas phase carbon dioxide in the pipeline between the gas source charging system (1) and the valve chamber shut-off valve (21) until the fluid pressure in the pipeline is higher than the third preset value. By controlling the valve chamber shut-off valve (21) to open sequentially, the pressure of multiple intermediate valve chambers is increased in stages until the liquid phase carbon dioxide in all intermediate valve chambers is converted into dense phase carbon dioxide. Close the liquid phase charging branch (11b), charge supercritical carbon dioxide through the two-phase charging branch (11c), and open the terminal shut-off valve (31) to allow the supercritical carbon dioxide to push the dense phase carbon dioxide toward the pipeline outlet until the fluid pressure of the entire pipeline is higher than the fourth preset value.

2. The method for commissioning a long-distance supercritical carbon dioxide pipeline according to claim 1, characterized in that, The long-distance supercritical carbon dioxide pipeline commissioning system also includes a pig sending system (6) and a pig receiving system (7). The pig sending system (6) is connected to the first station trunk line (12) and located downstream of the trunk line shut-off valve (13). The intermediate valve chamber system is connected between the pig sending system (6) and the pig receiving system (7). The last station trunk line (3) is connected downstream of the pig receiving system (7). The pig sending system (6) is used to cooperate with the pig receiving system (7) to replace the fluid in the pipeline through the pig isolator.

3. The method for commissioning a long-distance supercritical carbon dioxide pipeline according to claim 2, characterized in that, The pig delivery system (6) includes a first branch (61), a pig delivery tube (63), and a second branch (64). The first branch (61) and the second branch (64) are connected in parallel between the main line (12) of the first station and the intermediate valve chamber system. A first delivery shut-off valve (62) is provided on the first branch (61). The pig delivery tube (63) is located on the second branch (64). A second delivery shut-off valve (65) is provided upstream and downstream of the pig delivery tube (63).

4. The method for commissioning a long-distance supercritical carbon dioxide pipeline according to claim 2, characterized in that, The pig receiving system (7) is connected downstream of the intermediate valve chamber system and includes a third branch (71), a pig receiving cylinder (73), and a fourth branch (74). The third branch (71) and the fourth branch (74) are connected in parallel between the intermediate valve chamber system and the terminal main line (3). A first receiving shut-off valve (72) is provided on the third branch (71). The pig receiving cylinder (73) is located on the fourth branch (74). A second receiving shut-off valve (75) is provided upstream and downstream of the pig receiving cylinder (73).

5. The method for commissioning a long-distance supercritical carbon dioxide pipeline according to any one of claims 1 to 4, characterized in that, The venting system (5) includes a multi-stage pressure regulating pipeline and a multi-stage pressure regulating component, a second throttling venting valve (53), a buffer tank (54), and a venting riser (55) arranged sequentially along the carbon dioxide flow direction on the multi-stage pressure regulating pipeline. The multi-stage pressure regulating component is used to perform multi-stage pressure regulation on the carbon dioxide in the multi-stage pressure regulating pipeline.

6. The method for commissioning a long-distance supercritical carbon dioxide pipeline according to claim 5, characterized in that, The multi-stage pressure regulating assembly includes a regulating valve (51) and a heat exchanger (52). The number of regulating valves (51) and heat exchangers (52) is at least two, and a heat exchanger (52) is provided between any two adjacent regulating valves (51).

7. The method for commissioning a long-distance supercritical carbon dioxide pipeline according to claim 1, characterized in that, The method for commissioning long-distance supercritical carbon dioxide pipelines also includes: If the pressure of the filling branch (11) is found to be overpressure, the first station venting system is started to vent and depressurize the filling branch (11); If the upstream and downstream pressures of the valve chamber shut-off valve (21) are found to be overpressured, the intermediate venting system is opened to vent and depressurize the intermediate valve chamber. If the pressure of the terminal main line (3) is found to be overpressured, the terminal venting system is activated to vent and depressurize the terminal main line (3).

8. The method for commissioning a long-distance supercritical carbon dioxide pipeline according to claim 1, characterized in that, The method for commissioning long-distance supercritical carbon dioxide pipelines also includes: To determine if a leak has occurred in the long-distance supercritical carbon dioxide pipeline system, the leak point is determined based on the fluid pressure in the pipeline. Close the shut-off valves located upstream and downstream of the leak point and obtain the venting distance between the leak point and each venting system (5); Select the nearest venting system based on the venting distance (5); Activate the latest air venting system (5).

9. The method for commissioning a long-distance supercritical carbon dioxide pipeline according to claim 1, characterized in that, The long-distance supercritical carbon dioxide pipeline commissioning system also includes a pig sending system (6) and a pig receiving system (7). The pig sending system (6) is connected to the first station trunk line (12) and located downstream of the trunk line shut-off valve (13). The intermediate valve chamber system is connected between the pig sending system (6) and the pig receiving system (7). The last station trunk line (3) is connected downstream of the pig receiving system (7). The pig sending system (6) is used to cooperate with the pig receiving system (7) to replace the fluid in the pipeline through the pig isolator, open the last station venting system, and inject gaseous carbon dioxide into the intermediate valve chamber and the last station trunk line (3) through the gas phase charging branch (11a) until the inert gas in the entire pipeline is replaced by gaseous carbon dioxide. While charging with gaseous carbon dioxide, a pig isolator is sent to the pig receiving system (7) through the pig sending system (6); Once it is confirmed that the pig receiving system (7) has received the pig isolator and the carbon dioxide concentration at the terminal shut-off valve (31) is greater than the preset concentration, and the inert gas has been completely replaced by gaseous carbon dioxide, the terminal venting system is shut down.

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