A branch supercritical carbon dioxide pipeline commissioning system and method

Abstract

The present invention discloses a branch supercritical carbon dioxide pipeline commissioning system and method, the system comprising a mainline medium introduction system, a commissioning and discharge control system, a terminal discharge system, and an instrument detection system. The mainline medium introduction system is connected to an upstream supercritical carbon dioxide mainline pipeline, and the mainline medium introduction system is provided with a branch commissioning process pressure regulating bypass; the commissioning and discharge control system is connected to the pressure regulating bypass of the mainline medium introduction system, the terminal discharge system is provided at the branch terminal station, and the instrument detection system comprises a plurality of pressure transmitters and temperature transmitters. The present invention addresses the issues of medium flow control, temperature control, and pressure filling before the commissioning of branch supercritical carbon dioxide pipeline transportation, and from the perspectives of mainline flow stability, safe replacement, and stepped pressure filling, achieves safe and efficient replacement and pressure filling of the branch pipeline while providing a stable trunk line download volume.

Description

Technical Field

[0001] The present invention belongs to the technical field of carbon dioxide pipeline transportation, and in particular relates to a branch supercritical carbon dioxide pipeline commissioning system and method. Background Art

[0002] Against the backdrop of growing demands for energy conservation, emission reduction, and environmental protection in the energy and chemical industry, large-scale capture and utilization of carbon dioxide is the preferred way to effectively reduce carbon emissions. Among them, long-distance pipeline transportation is a key way to support carbon dioxide capture and utilization. The critical temperature of carbon dioxide is approximately 31.1°C, and the critical pressure is approximately 7.38MPa. When transporting carbon dioxide through long-distance pipelines, it is generally recognized that a supercritical transport phase mode with a pressure higher than the critical pressure is used to improve the economic efficiency of transportation. Similar to conventional pipeline systems, with the development of carbon capture, carbon storage, or carbon utilization technologies, the construction trend of supercritical carbon dioxide pipelines will inevitably develop towards a "trunk pipeline + branch pipeline" pipeline network model, in order to form a complete integrated network system and improve the utilization or storage efficiency of carbon sources.

[0003] Carbon dioxide's properties indicate that it solidifies at low temperatures. The triple point of pure carbon dioxide is -56.6°C and 0.518 MPa, a significant characteristic that distinguishes it from conventional hydrocarbon media. For conventional liquid-phase pipelines, water is often used as the initial filling medium during commissioning, with oil-to-water replacement during operation. Unlike conventional liquid-phase pipelines, dense-phase carbon dioxide is highly corrosive in aqueous environments, requiring high pipeline drying requirements. Therefore, using water to establish backpressure before commissioning is unsuitable. Furthermore, due to the high drying requirements for supercritical carbon dioxide pipelines, pre-drying with nitrogen or dry air is preferred prior to commissioning. It is important to note that for long-distance branch pipelines that unload product from a supercritical carbon dioxide trunk pipeline, the commissioning process must fully comply with the trunk line's transportation plan. This means that the branch pipeline commissioning process must be characterized by a relatively high unloading rate relative to the rated capacity. Failure to do so will significantly impact the stability of the trunk line's long-distance transportation.

[0004] At the same time, under the low-temperature conditions (-20°C) of carbon steel pipeline service, the pressure at which carbon dioxide forms a liquid phase is approximately 2 MPa. This means that below this pressure or temperature, carbon dioxide is in the gas phase or both. Therefore, during commissioning, full consideration should be given to establishing, controlling, and maintaining backpressure.

[0005] At present, there are few public documents reporting on the commissioning process of branch supercritical carbon dioxide pipelines with stable flow control of the trunk line, and there are very few relevant reference practices and experiences. Therefore, it is necessary to study and optimize the relevant pre-commissioning flow control, low-temperature control and filling processes to ensure the safety of the pipeline system and provide reference and reference for subsequent large-scale carbon dioxide pipeline transportation projects. Summary of the Invention

[0006] The purpose of the present invention is to provide a branch supercritical carbon dioxide pipeline commissioning system and method that can safely and efficiently implement branch supercritical carbon dioxide pipeline transportation in response to the above-mentioned problems.

[0007] Based on the phase characteristics of carbon dioxide and the objective constraints and requirements of the branch pipeline commissioning, the present invention aims to solve the problems of medium flow control, temperature control, pressure filling, etc. before the branch supercritical carbon dioxide pipeline transportation is put into production. From the perspectives of main line flow stability, safe replacement, and stepped pressure filling, the main line medium introduction system, commissioning and discharge control system, terminal discharge system, instrument detection system, etc. are respectively set up.

[0008] Among them, the main line medium introduction system is set at the first station of the branch line, mainly including the introduction branch line, supporting valves, pipe cleaning and launching barrels, etc., which are used to introduce the main line medium into the branch system, provide a pressure regulation bypass during the branch line commissioning process, and provide medium discharge facilities in emergency situations during the branch line commissioning process. The commissioning and discharge control system is set at the first station of the branch line, mainly including a flow regulating valve, a pressure regulating valve, a two-stage multi-row air bath heat exchanger, stainless steel pipelines, etc., which are used to control the flow and pressure of the commissioning medium downloaded from the main line, and at the same time perform temperature compensation on the initial low-temperature medium after pressure regulation to meet the minimum temperature requirement for filling into the downstream branch line. In addition, the flow rate of different commissioning stages is controlled separately. The terminal discharge system is set at the end of the branch line pipeline, which is used to empty the nitrogen accumulated in the pipeline during the initial commissioning process, and to monitor the gas composition at the end of the pipeline for a long time, indicate the replacement situation, and determine the starting time of pressurization. The instrument detection system includes pressure transmitters and temperature transmitters set in each system of the present invention, which are used to monitor the temperature and pressure at key points in the commissioning process and feedback to the production system. As a result, the branch supercritical carbon dioxide pipeline can be put into operation efficiently and safely.

[0009] The technical solution adopted by the present invention is: a branch supercritical carbon dioxide pipeline production system, characterized by: comprising a trunk medium introduction system, a production and discharge control system, a terminal discharge system and an instrument detection system;

[0010] The main line medium introduction system is connected to the upstream supercritical carbon dioxide main line pipeline and is used to introduce the main line medium into the branch line system. The main line medium introduction system is provided with a pressure regulating bypass during the branch line production process;

[0011] The production and discharge control system is connected to the pressure regulating bypass of the main line medium introduction system, and is used to control the flow rate and pressure of the production medium downloaded from the main line, and at the same time perform temperature compensation for the initial low-temperature medium after pressure regulation, and discharge the medium downloaded from the main line under emergency conditions;

[0012] The terminal discharge system is set up at the terminal station of the branch line, and is used to empty the nitrogen accumulated in the pipeline during the initial production process and monitor the gas composition at the end of the pipeline;

[0013] The instrument detection system includes multiple pressure transmitters and temperature transmitters, which are used to monitor the temperature and pressure of key points during the production process.

[0014] The branch supercritical carbon dioxide pipeline production system of the present invention, wherein the main line medium introduction system includes a carbon dioxide branch line access pipeline, a branch line first bypass and a branch line second bypass;

[0015] The carbon dioxide branch line access pipeline is connected to the upstream supercritical carbon dioxide trunk pipeline, and a branch line inlet shut-off valve, a branch line regulating valve and a branch line second shut-off valve are sequentially arranged on the carbon dioxide branch line access pipeline along the medium flow direction;

[0016] The branch line first bypass is arranged downstream of the branch line inlet shut-off valve, and is used to provide an inlet channel connecting the production and discharge control systems. The branch line first bypass is provided with a branch line first bypass shut-off valve;

[0017] The branch line second bypass is arranged downstream of the branch line second shut-off valve, and is used to provide an outlet channel connecting the production and discharge control system. The branch line second bypass is provided with a branch line second shut-off valve.

[0018] The branch line supercritical carbon dioxide pipeline commissioning system described in the present invention is provided with a branch line inlet flow transmitter downstream of the branch line inlet shut-off valve, which is used to detect the carbon dioxide flow introduced into the branch line in real time; and a branch line pressure transmitter is provided downstream of the branch line second shut-off valve, which is used to detect the pressure of the branch line after pressure adjustment in real time.

[0019] The branch line supercritical carbon dioxide pipeline commissioning system described in the present invention is provided with a pigging assembly downstream of the branch line second shut-off valve. The pigging assembly includes a pigging ball barrel, a first pigging shut-off valve, a branch line pigging shut-off valve and a second pigging shut-off valve. The first pigging shut-off valve is connected to the large end of the pigging ball barrel, and the branch line pigging shut-off valve is connected to the outlet end of the pigging ball barrel. The first pigging shut-off valve and the second pigging shut-off valve are opened only under the branch line first station replacement and pigging conditions, and are closed immediately after the pig is sent out. The branch line pigging shut-off valve is closed only under the branch line first station replacement and pigging conditions, and is opened immediately after the pig is sent out.

[0020] The branch supercritical carbon dioxide pipeline commissioning system described in the present invention comprises a commissioning and discharge control system comprising a first-stage regulating valve rear pipeline, a second-stage regulating valve rear pipeline, and a venting assembly. The first-stage regulating valve rear pipeline is connected to the branch first bypass shut-off valve via the first-stage regulating valve, and the second-stage regulating valve rear pipeline is connected to the branch second bypass shut-off valve. Between the first-stage regulating valve rear pipeline and the second-stage regulating valve rear pipeline, a first-stage air bath heat exchanger, a second-stage regulating valve, a filter, and a second-stage air bath heat exchanger are sequentially arranged along the medium flow direction. The venting assembly is connected downstream of the second-stage regulating valve.

[0021] The branch supercritical carbon dioxide pipeline production system of the present invention comprises a venting assembly including a venting pipeline and a venting riser. The venting pipeline is connected to a secondary regulating valve and the venting riser, and a venting flow regulating valve is provided on the venting pipeline.

[0022] The branch supercritical carbon dioxide pipeline production system described in the present invention has a terminal discharge system comprising a discharge branch pipe and a discharge riser, on which a discharge shutoff valve, a discharge regulating valve and a sampling valve are sequentially arranged.

[0023] The branch supercritical carbon dioxide pipeline commissioning system described in the present invention, wherein the instrument detection system includes a first-level pressure regulation pressure transmitter, a first-level pressure regulation temperature transmitter, a first-level heat exchange temperature transmitter, a second-level pressure regulation pressure transmitter, a second-level pressure regulation temperature transmitter and a second-level heat exchange temperature transmitter, wherein the first-level pressure regulation pressure transmitter and the first-level pressure regulation temperature transmitter are arranged downstream of the first-level regulating valve, the first-level heat exchange temperature transmitter is arranged downstream of the first-level air bath heat exchanger, the second-level pressure regulation pressure transmitter and the second-level pressure regulation temperature transmitter are arranged downstream of the filter, and the second-level heat exchange temperature transmitter is arranged downstream of the second-level air bath heat exchanger.

[0024] A method for commissioning a branch supercritical carbon dioxide pipeline system, characterized in that it specifically comprises the following steps:

[0025] Step 1: Before the branch supercritical carbon dioxide pipeline is put into operation, maintain normal transportation of the main pipeline, keep the branch inlet block valve closed, and keep the branch regulating valve and branch second block valve closed;

[0026] Step 2: Introduce supercritical carbon dioxide from the main line to replace the nitrogen pre-filled in the branch line before production. Specifically, first inject pressurized carbon dioxide downstream of the branch line inlet shut-off valve to establish back pressure, open the branch line inlet shut-off valve, connect the upstream main line with the branch line inlet section, then open the branch line first bypass shut-off valve, the first-level regulating valve, the second-level regulating valve, and the branch line second bypass shut-off valve in sequence to open the main line medium introduction channel, and introduce the main line medium into the downstream external transmission branch line through the pipeline of the production and discharge control system. At the same time, open the downstream discharge shut-off valve and discharge regulating valve to open the replacement system;

[0027] Step 3: After the replacement is completed, the branch pipeline enters the pressurization stage. The main line download volume is adjusted to the pressurization output. By adjusting the control valve and heat exchanger parameters in the production and discharge control system, the main line download volume is kept at the pressurization output and the branch line introduction flow is kept stable. When the pressure of the downstream branch line reaches above 3MPa, the production and discharge control system can be directly closed and the main line medium can be directly introduced through the branch line regulating valve.

[0028] Step 4: After the pipeline is filled, immediately open the terminal shut-off valve and the terminal regulating valve, and the pipeline system is tested according to the filling flow, thereby completing the medium replacement and pressure filling process for commissioning, and realizing full commissioning of the system by controlling the rated branch line flow.

[0029] Compared with the existing technology, the positive effects of the present invention are: based on the phase characteristics of carbon dioxide and the objective constraints and requirements of the branch pipeline commissioning, the present invention aims at the problems of medium flow control, temperature control, pressure filling and other issues before the branch supercritical carbon dioxide pipeline transportation is put into production. From the perspectives of main line flow stability, safe replacement, and step-by-step pressure filling, the main line medium introduction system, commissioning and discharge control system, terminal discharge system, instrument detection system, etc. are respectively set up. While providing stable trunk line download volume, the safe and efficient replacement and pressure filling of the branch pipeline are realized, providing a reference and reference for the commissioning and operation of the branch supercritical carbon dioxide pipeline.

[0030] Specifically:

[0031] (1) Scientific setting

[0032] The present invention is based on the operating characteristics of the supercritical carbon dioxide trunk pipeline and the characteristics of the supercritical carbon dioxide medium. It takes the control of the main line's transportation stability during the commissioning of the branch line as the basic principle, and sets up a main line medium introduction system, a commissioning and discharge control system, a terminal discharge system, an instrument detection system, etc. On the one hand, the flow control is strictly carried out according to the set introduction flow value. On the other hand, the introduced supercritical carbon dioxide is safely pressure-regulated and temperature-regulated to avoid low temperature after pressure regulation causing system blockage and pipeline system material risks. Furthermore, a multi-stage flow control system is set to achieve controllable flow rate in the replacement process and ensure efficient and rapid pressurization process. In addition, in order to avoid the impact of branch line replacement, pressurization, etc. on the main line transportation in an emergency, a temporary discharge system is set at the first station of the branch line. The medium that cannot be absorbed in the branch line in an emergency is discharged through the emergency discharge system to avoid affecting the stable transportation of the main line. Therefore, by setting up this system, safe and efficient replacement and pressure filling of the branch line pipeline are achieved.

[0033] (2) Good economic efficiency

[0034] During the replacement process, this system utilizes pigs for isolated replacement, significantly reducing branch line replacement time and improving replacement efficiency. In the commissioning and release control system, the installation of multi-stage regulating valves and a two-stage, multi-row air-bath heat exchanger avoids the risk of dry ice blockage in the commissioning system, improving replacement and commissioning efficiency. Furthermore, after temperature regulation, the temperature of the medium entering the downstream branch pipeline is higher than the permissible operating temperature of carbon steel, ensuring material safety and avoiding the use of cryogenic materials in the launch tube, first-station pipeline, and first-station valves. This overall improves the economic efficiency of system construction and operation. Furthermore, the air-bath heat exchanger in the commissioning and release control system is only a temporary facility, detachable and reusable, improving equipment utilization efficiency.

[0035] (3) Promoting technological development

[0036] The solution proposed by this system plays an important role in engineering guidance and reference. The proposed key process system configurations and methods such as trunk flow stability, safe and efficient replacement, and efficient pressurization can take into account the reliability and safety of commissioning and subsequent operation, and promote technological progress in this field. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The present invention will be described by way of specific embodiments with reference to the accompanying drawings, in which

[0038] Figure 1 It is a structural schematic diagram of the present invention.

[0039] Markings in the figure: 1 is the carbon dioxide branch line access pipeline, 2 is the branch line inlet shut-off valve, 3 is the branch line regulating valve, 4 is the branch line second shut-off valve, 5 is the branch line pressure transmitter, 6 is the branch line inlet flow transmitter, 7 is the first pigging shut-off valve, 8 is the branch line pigging shut-off valve, 9 is the second pigging shut-off valve, 10 is the first branch line bypass, 11 is the first branch line bypass shut-off valve, 12 is the second branch line bypass shut-off valve, 13 is the second branch line bypass, 14 is the pigging ball barrel, 21 is the first-level regulating valve, 22 is the pipeline after the first-level regulating valve, 23 is the first-level air bath heat exchanger, 24 is Secondary regulating valve, 25 is the filter, 26 is the secondary air bath heat exchanger, 27 is the pipeline after the secondary regulating valve, 28 is the vent pipeline, 29 is the vent flow regulating valve, 30 is the vent riser, 31 is the pressure transmitter after the first-level pressure regulation, 32 is the temperature transmitter after the first-level pressure regulation, 33 is the temperature transmitter after the first-level heat exchange, 34 is the pressure transmitter after the second-level pressure regulation, 35 is the temperature transmitter after the second-level pressure regulation, 36 is the temperature transmitter after the second-level heat exchange, 41 is the discharge shut-off valve, 42 is the discharge regulating valve, 43 is the sampling valve, 44 is the discharge riser, and 45 is the discharge branch pipe. DETAILED DESCRIPTION

[0040] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0041] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort shall fall within the scope of protection of the present invention.

[0042] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0043] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0044] In the description of the embodiments of the present invention, it should be noted that the indicated orientations or positional relationships are based on the orientations or positional relationships shown in the accompanying drawings, or the orientations or positional relationships in which the inventive product is typically placed when in use, or the orientations or positional relationships commonly understood by those skilled in the art, or the orientations or positional relationships in which the inventive product is typically placed when in use. These are merely for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore should not be understood as limiting the present invention. In addition, the terms "first" and "second" are used only to distinguish descriptions and should not be understood as indicating or implying relative importance.

[0045] In describing the embodiments of the present invention, it should be noted that, unless otherwise specified or limited, the terms "disposed" and "connected" should be understood broadly. For example, they may refer to fixed connections, detachable connections, or integral connections; they may refer to direct connections or indirect connections through an intermediary. Those skilled in the art will understand the specific meanings of these terms in the present invention based on the specific circumstances.

[0046] like Figure 1 The figure shows a branch supercritical CO2 pipeline commissioning system, including a mainline medium introduction system, a commissioning and release control system, a terminal release system, and an instrumentation detection system. This system supports the efficient and safe commissioning of branch supercritical CO2 pipelines extending from the main transmission line.

[0047] Among them, the trunk medium introduction system is connected to the upstream supercritical carbon dioxide trunk pipeline, and is used to introduce the trunk medium into the branch system. The trunk medium introduction system is provided with a pressure regulating bypass during the branch commissioning process, and provides functions such as medium discharge facilities in emergency situations during the branch commissioning process; it should be pointed out that the trunk medium introduction system also provides a conventional branch pipeline cleaning system, but it does not belong to the unique technical requirements of the present invention, and is only described to ensure functional integrity.

[0048] Specifically, the trunk medium introduction system includes a carbon dioxide branch access pipeline 1, a branch first bypass 10 and a branch second bypass 13. The carbon dioxide branch access pipeline 1 is made of carbon steel and is connected to the upstream supercritical carbon dioxide trunk pipeline to provide a branch download access function; on the carbon dioxide branch access pipeline 1, a branch inlet shut-off valve 2, a branch regulating valve 3 and a branch second shut-off valve 4 are sequentially arranged along the medium flow direction. The branch inlet shut-off valve 2 is made of carbon steel, a full-bore electric ball valve, normally open, and is used to control the start and close of the branch pipeline; the branch regulating valve 3 is made of carbon steel, an electric A dynamic regulating valve is normally open (closed before commissioning) and is used to control the medium flow of the branch line and adjust the pressure after introduction; the second branch line shut-off valve 4 is made of carbon steel and is a full-bore electric ball valve, which is closed before commissioning; a branch line pressure transmitter 5 is provided downstream of the second branch line shut-off valve 4 for real-time detection of the pressure after branch line pressure adjustment; a branch line inlet flow transmitter 6 is provided downstream of the branch line inlet shut-off valve 2 for real-time detection of the carbon dioxide flow introduced into the branch line, preferably a Coriolis flowmeter; a pigging assembly is provided downstream of the second branch line shut-off valve 4, the pigging assembly comprising a pigging ball barrel 14, a pigging first shut-off valve Valve 7, branch line pigging shut-off valve 8 and pigging second shut-off valve 9, the first pigging shut-off valve 7 is connected to the large end of the pigging ball cylinder 14, the branch line pigging shut-off valve 8 is connected to the outlet end of the pigging ball cylinder 14, the first pigging shut-off valve 7 and the second pigging shut-off valve 9 are electric ball valves, made of carbon steel, which are opened only when the branch line first station is replaced and the pigging is in operation, and are closed immediately after the pig is sent out; the branch line pigging shut-off valve 8 is an electric ball valve, made of carbon steel, which is closed only when the branch line first station is replaced and the pigging is in operation, and are opened immediately after the pig is sent out; the first branch bypass 10 is arranged downstream of the branch line inlet shut-off valve 2, made of carbon steel, and is used In order to provide an inlet channel connecting the commissioning and discharge control system, a branch line first bypass shut-off valve 11 is provided on the branch line first bypass 10. The branch line first bypass shut-off valve 11 is a manual ball valve made of carbon steel and is opened only when the commissioning and discharge control system is activated; the branch line second bypass 13 is provided downstream of the branch line second shut-off valve 4 and is made of carbon steel. It is used to provide an outlet channel connecting the commissioning and discharge control system. A branch line second bypass shut-off valve 12 is provided on the branch line second bypass 13. The branch line second bypass shut-off valve 12 is a manual ball valve made of carbon steel and is opened only when the commissioning and discharge control system is activated.

[0049] Among them, the production and discharge control system is connected to the pressure regulating bypass of the main line medium introduction system, which is used to control the flow and pressure of the production medium downloaded from the main line, and at the same time perform temperature compensation on the initial low-temperature medium after pressure regulation to meet the minimum temperature requirement for filling into the downstream branch line. In addition, the flow rate in different production stages is controlled separately, and in emergency conditions, the medium downloaded from the main line is emptied to give priority to ensuring the stable operation of the main line.

[0050] Specifically, the production and discharge control system includes a first-stage regulating valve rear pipeline 22, a second-stage regulating valve rear pipeline 27 and a venting component. The first-stage regulating valve rear pipeline 22 is connected to the branch line first bypass shut-off valve 11 through the first-stage regulating valve 21, that is, the first-stage regulating valve 21 is arranged downstream of the branch line first bypass shut-off valve 11. The electric regulating valve is made of carbon steel and is used for the first pressure regulation and flow control of the supercritical carbon dioxide introduced into the trunk line during the production phase. After the pressure regulation, the pressure is stabilized at above 3 MPa; The secondary regulating valve rear pipeline 27 is connected to the branch line second bypass shut-off valve 12. Between the primary regulating valve rear pipeline 22 and the secondary regulating valve rear pipeline 27, a primary air bath heat exchanger 23, a secondary regulating valve 24, a filter 25 and a secondary air bath heat exchanger 26 are sequentially arranged along the medium flow direction, that is, the primary regulating valve rear pipeline 22 connects the primary regulating valve 21 and the primary air bath heat exchanger 23, which are made of low-temperature carbon steel; the primary air bath heat exchanger 23 is arranged downstream of the primary regulating valve 21, and the low-temperature carbon steel is provided. Made of steel, it is a multi-tube air bath heat exchanger used to regulate the temperature of the low-temperature carbon dioxide after the first-level pressure regulation, increase the medium temperature before the downstream second-level pressure regulation, and avoid freezing and blockage of the medium after the downstream second-level pressure regulation; the second-level regulating valve 24 is arranged downstream of the first-level air bath heat exchanger 23, and is an electric regulating valve used to perform secondary pressure regulation on the medium to meet the pressure requirements of downstream pipeline replacement and pressurization; the filter 25 is made of low-temperature carbon steel and is used to perform secondary filtration of solid impurities on the supercritical carbon dioxide introduced from the upstream to avoid erosion of downstream branch pipelines and valves due to the high medium flow rate during the initial replacement; the second-level air bath heat exchanger 26 is arranged downstream of the filter 25, and is made of low-temperature carbon steel and is a multi-tube air bath heat exchanger used to regulate the temperature of the low-temperature carbon dioxide after the second-level pressure regulation, increase the medium temperature entering the downstream branch pipeline, and ensure the material safety of the long-distance branch pipeline system; the pipeline 27 after the second-level regulating valve connects the second-level air bath heat exchanger 26 and the branch second bypass shut-off valve 12, and is made of carbon steel.

[0051] Specifically, the vent assembly is connected downstream of the secondary regulating valve 24 and includes a vent pipe 28 and a vent riser 30. The vent pipe 28, made of low-temperature carbon steel, connects the secondary regulating valve 24 and the vent riser 30 and is used to divert some carbon dioxide to the vent riser for treatment in an emergency, reducing the impact on the flow stability of the upstream mainline. A vent flow control valve 29 is installed on the vent pipe 28. This vent flow control valve is an electric regulating valve made of low-temperature carbon steel and is used to control the flow of medium discharged to the vent riser in an emergency. The vent riser 30 is located downstream of the vent flow control valve 29 at a height of no less than 20 meters and is used to release the emergency released medium into the air. Furthermore, an initial carbon dioxide injection valve is installed on the pipeline 22 after the primary regulating valve to inject pressurized carbon dioxide into the production and venting control system before commissioning. The injection pressure is no less than 2.0 MPa to prevent the system temperature from falling below -40°C during the initial stage of multi-stage pressure regulation.

[0052] Among them, the terminal discharge system is set up at the terminal station of the branch line, which is used to empty the nitrogen accumulated in the pipeline during the initial production process, and to monitor the gas components at the end of the pipeline for a long time, indicate the replacement situation, and determine the starting time point of the upstream branch line pressurization.

[0053] Specifically, the terminal discharge system includes a discharge branch pipe 45 and a discharge riser 44, on which a discharge shutoff valve 41, a discharge regulating valve 42, and a sampling valve 43 are sequentially arranged. The discharge shutoff valve 41 is made of carbon steel and is a manual ball valve. It is installed on the discharge branch pipe before the terminal entrance and is opened during the commissioning and replacement phase. The discharge regulating valve 42 is an electric regulating valve. Its opening control is interlocked with the first-level regulating valve 21 and the second-level regulating valve 24. It is used to control the system discharge flow and provide a back pressure control function for the branch line during the replacement process. The control pressure is 0.1-0.2MPa. The sampling valve 43 is installed downstream of the discharge regulating valve 42 for sampling and testing the discharged medium during the commissioning and replacement process. The discharge riser 44 is installed downstream of the discharge regulating valve 42 to safely discharge the medium, such as nitrogen and carbon dioxide, during the commissioning and replacement process.

[0054] Among them, the instrument detection system includes multiple pressure transmitters and temperature transmitters, which are used to monitor the temperature and pressure of key points during the production process and feed back to the production system.

[0055] Specifically, the instrument detection system includes a first-level pressure transmitter 31 after pressure regulation, a first-level temperature transmitter 32 after pressure regulation, a first-level temperature transmitter 33 after heat exchange, a second-level pressure transmitter 34 after pressure regulation, a second-level temperature transmitter 35 after pressure regulation, and a second-level temperature transmitter 36 after heat exchange. The first-level pressure transmitter 31 after pressure regulation and the first-level temperature transmitter 32 after pressure regulation are arranged downstream of the first-level regulating valve 21, the first-level temperature transmitter 33 after heat exchange is arranged downstream of the first-level air bath heat exchanger 23, the second-level pressure transmitter 34 after pressure regulation and the second-level temperature transmitter 35 after pressure regulation are arranged downstream of the filter 25, and the second-level temperature transmitter 36 after heat exchange is arranged downstream of the second-level air bath heat exchanger 26.

[0056] The working principle of the present invention is:

[0057] (1) General principle. The transmission pressure of supercritical carbon dioxide pipeline is relatively high (exceeding the critical pressure, the critical pressure of carbon dioxide is generally 7.3MPa). Before the pipeline is put into production, nitrogen is generally used for drying. Therefore, the gas accumulated in the branch pipeline is dry nitrogen, which must be replaced before the branch is put into production. In order to replace it safely and efficiently, the supercritical carbon dioxide introduced from the main line is used for displacement, and at the same time, the nitrogen-pig-carbon dioxide isolation is carried out with the help of the branch pigging system. The replacement process is controlled and detected by the terminal discharge system to ensure the replacement effect. After the replacement is completed, the branch line is pressure-filled with carbon dioxide continuously introduced from the main line, and the branch line pressure is continuously increased until all the media are converted to a supercritical state and the production conditions are met.

[0058] (2) Replacement process. Specifically, during the replacement process, when the supercritical carbon dioxide in the upstream trunk line is directly adjusted to normal pressure, a low temperature of about -90°C will be generated, which will not only easily generate solid dry ice and block the pipeline system, but also cause serious damage to the carbon steel material of the branch system. Therefore, a commissioning and discharge control system is set up, taking into account the two-stage pressure regulation and the two-stage air bath heat exchange. The first stage pressure regulation is used to adjust the introduced carbon dioxide into the gas-liquid two-phase region, and then the first stage air bath heat exchange is used to further increase the carbon dioxide temperature to avoid reaching the dry ice production conditions after the second stage pressure regulation. Then, the second stage pressure regulation is used to reduce the pressure to normal pressure (or gradually increase the pressure during the pressurization process), and the second stage heat exchange is continued to make the outlet medium temperature reach the safe service temperature of carbon steel; it is particularly important that since the trunk pipeline continuously and stably transports supercritical carbon dioxide, the commissioning process of the branch pipeline should not affect the stability of the trunk transmission. Therefore, a venting system is set up so that in an emergency situation such as insufficient heat exchange temperature, the excess carbon dioxide can be vented in time to reduce the heat exchange load and avoid taking the conventional method of controlling the introduced flow, which will cause a large fluctuation in the trunk flow.

[0059] (3) Pressurization process. Specifically, after the replacement is completed, the outlet of the branch terminal needs to be closed, and the pipeline is continuously filled with the introduced medium. With the help of the production and discharge control system, the stability of the introduced flow is prioritized, and the opening of the regulating valve is adjusted in real time to cope with the continuous increase in pressure in the pipeline and the stable flow input. When the pressure in the downstream branch pipeline reaches above 3MPa, due to the reduction of the pressure difference between the main line and the branch line and the reduction of the throttling temperature drop, it can be directly introduced into the branch regulating system, and carbon dioxide can be filled into the branch line through the branch regulating valve, and finally the pressure in the branch line is increased to slightly equal to the main line pressure to meet the production conditions. Similar to the replacement process, in an emergency, the carbon dioxide that is downloaded from the main line but cannot be absorbed by the branch line in time is still sent to the venting system for discharge to avoid interfering with the stability of the main line flow.

[0060] (4) Commissioning process. Specifically, by simultaneously opening the terminal shutoff valve and regulating valve, gradually adjusting the branch regulating valve, and coordinating with the main line flow rate adjustment, the branch pipeline gradually reaches the hydraulic conditions of stable flow, completing the commissioning operation.

[0061] The present invention also relates to a production method using the branch supercritical carbon dioxide pipeline production system, which specifically comprises the following steps:

[0062] Step 1: Before the branch supercritical CO2 pipeline is put into operation, maintain normal flow through the main pipeline and close the branch inlet block valve, as well as the branch regulating valve and branch secondary block valve. When the branch supercritical CO2 pipeline is ready for commissioning, plan two types of branch line downflow ramps: replacement output and pressure charging output.

[0063] The displacement output is set based on the principle that the gas flow rate during pigging of the branch pipeline does not exceed 5 m / s (at the displacement pressure). This is the displacement output removed from the main line, and the removal time is determined accordingly. The pressure charging output is considered to be two to three times the displacement output. Furthermore, based on the set values for the displacement and pressure charging outputs, the parameters of the primary regulating valve, primary air-bath heat exchanger, secondary regulating valve, and secondary air-bath heat exchanger in the commissioning and relief control system are determined to ensure stable flow from the main line during commissioning and that the temperature of the main line medium after pressure regulation meets the minimum safe temperature limit requirements of the branch pipeline.

[0064] Step 2: Introduce supercritical carbon dioxide from the main line to replace the nitrogen pre-filled in the branch line before production, specifically: first inject pressurized carbon dioxide downstream of the branch line inlet shut-off valve to establish back pressure, that is, inject carbon dioxide with a pressure of about 2.0-2.3MPa from the injection port between the branch line inlet shut-off valve and the branch line regulating valve to avoid the upstream main line supercritical carbon dioxide from falling below -20°C due to pressure differential throttling after the branch line inlet shut-off valve is opened, thereby ensuring the material safety of this section of the pipeline; open the branch line inlet shut-off valve to connect the upstream main line and the branch line inlet section to stabilize the pressure, and then open the first bypass shut-off valve, the first-level regulating valve, the second-level regulating valve, and the second bypass shut-off valve of the branch line in sequence to open the main line medium introduction channel, and introduce the main line medium into the downstream external transmission branch line through the pipeline of the production and discharge control system. Next, open the primary and secondary air-bath heat exchangers. Through these operations, control the branch line CO2 flow rate to meet the replacement output set in step one. The temperature downstream of the primary regulating valve is maintained above -40°C (to prevent dry ice formation), and the medium temperature downstream of the secondary air-bath heat exchanger is maintained above -15°C, ensuring material safety in the branch pipeline. Simultaneously, open the downstream bleed block valve and bleed regulating valve to open the replacement system. Maintain the branch pigging block valve open for 10 minutes. Place a pig in the pigging launcher, close the branch pigging block valve, and open the primary and secondary pigging block valves. Use the pig to isolate the introduced CO2 from the CO2 / nitrogen mixture in the branch pipeline, enhancing replacement efficiency through isolation. After the pig is deployed, reopen the branch pigging block valve and close the primary and secondary pigging block valves. After the pig reaches the pig ball collection drum at the downstream terminal, the sampling valve is opened and continuous sampling is performed to test the CO2 content. When the sampling indicators meet the branch line transmission requirements, the replacement is complete, and the bleed block valve, bleed regulating valve, sampling valve, and bleed riser are closed, and the branch line pressure charging phase begins. Furthermore, during this step, if the medium temperature downstream of the secondary air-bath heat exchanger deviates from the set warning value, the bleed flow regulating valve is immediately opened to directly release some of the CO2 to be introduced into the branch line through the bleed riser to avoid disrupting normal transmission in the main pipeline.

[0065] Step 3: After the replacement is complete, the branch pipeline enters the pressurization phase. The mainline discharge rate is adjusted to the pressurized output. Specifically, the parameters of the first-stage regulating valve, the first-stage air-bath heat exchanger, the second-stage regulating valve, and the second-stage air-bath heat exchanger are adjusted to maintain the mainline discharge rate at the pressurized output. The temperature downstream of the first-stage regulating valve is above -40°C (to prevent dry ice formation), and the medium temperature downstream of the second-stage air-bath heat exchanger is always above -15°C. As the downstream pressure increases, the openings of the first-stage and second-stage regulating valves are dynamically increased to maintain a stable branch line flow rate. During this step, if the medium temperature downstream of the second-stage air-bath heat exchanger deviates from the set warning value, the vent flow regulating valve is immediately opened to directly release some of the CO2 to be introduced into the branch line through the vent riser to avoid disrupting normal flow in the main pipeline. When the pressure in the downstream branch line reaches above 3 MPa, the pressure-regulated medium temperature, caused by the pressure differential between the main and branch lines, exceeds -10°C. Therefore, the commissioning and discharge control system can be directly shut down, and the mainline medium is directly introduced through branch line regulating valve 3.

[0066] Step 4: After the pipeline is filled, immediately open the terminal shut-off valve and terminal regulating valve, and the pipeline system is tested according to the filling flow, thereby completing the medium replacement and pressure filling process for commissioning, and further controlling the rated branch line flow to achieve full commissioning of the system.

[0067] The present invention is not limited to the foregoing specific embodiments, and the present invention extends to any new features or any new combination disclosed in this specification, as well as any new method or process steps or any new combination disclosed.

Claims

1. A branch supercritical carbon dioxide pipeline production system, characterized by: Including mainline medium introduction system, production and discharge control system, terminal discharge system and instrument detection system; The main line medium introduction system is connected to the upstream supercritical carbon dioxide main line pipeline and is used to introduce the main line medium into the branch line system. The main line medium introduction system is provided with a pressure regulating bypass during the branch line production process; The trunk medium introduction system comprises a carbon dioxide branch line access pipeline (1), a branch line first bypass (10) and a branch line second bypass (13); the carbon dioxide branch line access pipeline (1) is connected to the upstream supercritical carbon dioxide trunk pipeline, and a branch line inlet shut-off valve (2), a branch line regulating valve (3) and a branch line second shut-off valve (4) are sequentially arranged on the carbon dioxide branch line access pipeline (1) along the medium flow direction; the branch line first bypass (10) is arranged downstream of the branch line inlet shut-off valve (2) for providing an inlet channel connecting the production and discharge control system, and a branch line first bypass shut-off valve (11) is arranged on the branch line first bypass (10); the branch line second bypass (13) is arranged downstream of the branch line second shut-off valve (4) for providing an outlet channel connecting the production and discharge control system, and a branch line second bypass shut-off valve (12) is arranged on the branch line second bypass (13); A pigging assembly is provided downstream of the second branch line shut-off valve (4), the pigging assembly comprising a pigging ball barrel (14), a first pigging shut-off valve (7), a branch line pigging shut-off valve (8) and a second pigging shut-off valve (9), the first pigging shut-off valve (7) being connected to the large end of the pigging ball barrel (14), the branch line pigging shut-off valve (8) being connected to the outlet end of the pigging ball barrel (14), the first pigging shut-off valve (7) and the second pigging shut-off valve (9) being opened only under the branch line first station replacement and pigging conditions, and being closed immediately after the pig is dispatched, the branch line pigging shut-off valve (8) being closed only under the branch line first station replacement and pigging conditions, and being opened immediately after the pig is dispatched; The production and discharge control system is connected to the pressure regulating bypass of the main line medium introduction system, and is used to control the flow rate and pressure of the production medium downloaded from the main line, and at the same time perform temperature compensation for the initial low-temperature medium after pressure regulation, and discharge the medium downloaded from the main line under emergency conditions; The production and discharge control system comprises a first-stage regulating valve rear pipeline (22), a second-stage regulating valve rear pipeline (27) and a venting assembly, wherein the first-stage regulating valve rear pipeline (22) is connected to the branch line first bypass shut-off valve (11) through the first-stage regulating valve (21), and the second-stage regulating valve rear pipeline (27) is connected to the branch line second bypass shut-off valve (12). Between the first-stage regulating valve rear pipeline (22) and the second-stage regulating valve rear pipeline (27), a first-stage air-bath heat exchanger (23), a second-stage regulating valve (24), a filter (25) and a second-stage air-bath heat exchanger (26) are sequentially arranged along the medium flow direction, and the venting assembly is connected downstream of the second-stage regulating valve (24); The terminal discharge system is set up at the terminal station of the branch line, and is used to empty the nitrogen accumulated in the pipeline during the initial production process and monitor the gas composition at the end of the pipeline; The instrument detection system includes multiple pressure transmitters and temperature transmitters, which are used to monitor the temperature and pressure of key points during the production process.

2. The branch supercritical carbon dioxide pipeline production system according to claim 1, characterized in that: A branch line inlet flow transmitter (6) is provided downstream of the branch line inlet shut-off valve (2) for real-time detection of the carbon dioxide flow introduced into the branch line; and a branch line pressure transmitter (5) is provided downstream of the branch line second shut-off valve (4) for real-time detection of the pressure of the branch line after pressure adjustment.

3. The branch supercritical carbon dioxide pipeline production system according to claim 1, characterized in that: The vent assembly comprises a vent pipe (28) and a vent standpipe (30). The vent pipe (28) is connected to the secondary regulating valve (24) and the vent standpipe (30). A vent flow regulating valve (29) is provided on the vent pipe (28).

4. The branch supercritical carbon dioxide pipeline production system according to claim 1, characterized in that: The terminal discharge system comprises a discharge branch pipe (45) and a discharge riser (44), and a discharge shutoff valve (41), a discharge regulating valve (42) and a sampling valve (43) are sequentially arranged on the discharge branch pipe (45).

5. The branch supercritical carbon dioxide pipeline production system according to claim 1, characterized in that: The instrument detection system includes a first-stage pressure-regulated pressure transmitter (31), a first-stage pressure-regulated temperature transmitter (32), a first-stage heat-exchange temperature transmitter (33), a second-stage pressure-regulated pressure transmitter (34), a second-stage pressure-regulated temperature transmitter (35), and a second-stage heat-exchange temperature transmitter (36). The first-stage pressure-regulated pressure transmitter (31) and the first-stage pressure-regulated temperature transmitter (32) are arranged downstream of the first-stage regulating valve (21), the first-stage heat-exchange temperature transmitter (33) is arranged downstream of the first-stage air-bath heat exchanger (23), the second-stage pressure-regulated pressure transmitter (34) and the second-stage pressure-regulated temperature transmitter (35) are arranged downstream of the filter (25), and the second-stage heat-exchange temperature transmitter (36) is arranged downstream of the second-stage air-bath heat exchanger (26).

6. A method for commissioning a branch supercritical carbon dioxide pipeline system according to any one of claims 1 to 5, characterized in that: The specific steps include: Step 1: Before the branch supercritical carbon dioxide pipeline is put into operation, maintain normal transportation of the main pipeline, keep the branch inlet block valve closed, and keep the branch regulating valve and branch second block valve closed; Step 2: Introduce supercritical carbon dioxide from the main line to replace the nitrogen pre-filled in the branch line before production. Specifically, first inject pressurized carbon dioxide downstream of the branch line inlet shut-off valve to establish back pressure, open the branch line inlet shut-off valve, connect the upstream main line with the branch line inlet section, then open the branch line first bypass shut-off valve, the first-level regulating valve, the second-level regulating valve, and the branch line second bypass shut-off valve in sequence to open the main line medium introduction channel, and introduce the main line medium into the downstream external transmission branch line through the pipeline of the production and discharge control system. At the same time, open the downstream discharge shut-off valve and discharge regulating valve to open the replacement system; Step 3: After the replacement is completed, the branch pipeline enters the pressurization stage. The main line download volume is adjusted to the pressurization output. By adjusting the control valve and heat exchanger parameters in the production and discharge control system, the main line download volume is kept at the pressurization output and the branch line introduction flow is kept stable. When the pressure of the downstream branch line reaches above 3MPa, the production and discharge control system can be directly closed and the main line medium can be directly introduced through the branch line regulating valve. Step 4: After the pipeline is filled, immediately open the terminal shut-off valve and the terminal regulating valve, and the pipeline system is tested according to the filling flow, thereby completing the medium replacement and pressure filling process for commissioning, and realizing full commissioning of the system by controlling the rated branch line flow.

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