A supercritical carbon dioxide delivery pigging system and method

Abstract

The present invention discloses a supercritical carbon dioxide transmission and pigging system, comprising a relay pressurizing system, a charging and discharging piping system, and an instrument detection system connected to the pigging system. The relay pressurizing system is connected to the pigging system's in-station trunk line and the pigging barrel via pipelines. Before the pigging system pigs, the relay pressurizing system is used to displace the medium in the pigging barrel and to control the supercritical carbon dioxide relay pressure. After the pigging system pigs, the relay pressurizing system is used to control the relay temperature of the discharged medium in the pigging barrel. The charging and discharging piping system is connected to the pigging barrel of the pigging system. Based on the characteristics of the supercritical carbon dioxide medium and the process requirements for pipeline pigging, the present invention simplifies the piping configuration of the pigging barrel by providing a movable relay pressurizing system, a pigging system, a charging and discharging piping system, and an instrument detection system, thereby achieving safe operation and economic configuration of the entire supercritical carbon dioxide pipeline pigging process.

Description

Technical Field

[0001] The present invention belongs to the technical field of pipeline transportation, and in particular relates to a system and method for supercritical carbon dioxide transportation pigging. 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 path to effectively reduce carbon emissions. Long-distance pipeline transportation is key to supporting carbon dioxide capture and utilization. Carbon dioxide has a critical temperature of approximately 31.1°C and a critical pressure of approximately 7.38 MPa. Long-distance pipeline transportation typically utilizes a dense phase or supercritical transport mode with pressures above the critical pressure to improve transportation economics. Furthermore, carbon dioxide 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.

[0003] Pipeline pigging is a crucial component of pipeline system integrity management and the primary means of clearing internal impurities and improving pipeline transportation efficiency. Pipeline pigging is largely performed using pig launchers. For conventional oil and gas pipelines, during planned pigging, the launcher draws medium directly from the mainline for charging. When the pressure after charging approaches the mainline transmission pressure, the mainline medium is introduced into the pig launcher area, the pig is ejected, and the pig launch is completed. In contrast, when supercritical carbon dioxide is directly charged into a pig launcher at atmospheric pressure, the medium adiabatically expands from the supercritical phase to atmospheric pressure, resulting in ultra-low temperatures approaching -90°C. This creates the potential for dry ice blockage, posing significant challenges to pig material selection and pipeline flow safety. It also hinders the proper temperature control of the charging medium, potentially allowing low-temperature medium to enter the downstream pipeline system and cause flow fluctuations.

[0004] However, there is currently no public literature that comprehensively and thoroughly reports on the aforementioned issues in supercritical CO2 pipeline transportation, and the safe pigging methods for conventional oil and gas pipelines lack sufficient reference value. Therefore, it is necessary to conduct relevant research to explore and optimize pigging methods for supercritical CO2 pipeline systems, promote the development of related technologies, and ensure pigging safety. Summary of the Invention

[0005] The purpose of the present invention is to provide a system and method for safely and efficiently implementing supercritical carbon dioxide pipeline pigging operations in order to solve the above-mentioned problems.

[0006] Based on the phase characteristics of carbon dioxide and the requirements of pigging and launching operations, the present invention addresses safety issues such as low temperature and blockage caused by direct introduction of supercritical carbon dioxide into the pigging and launching barrel, and from the perspective of efficient replacement and safe pressure increase, respectively provides a movable relay charging system, a launching system, a filling and discharge pipeline system, and an instrument detection system. Among them, the movable relay charging system is set in the launching area, and serves multiple functions such as providing a replacement gas source for the launching system, supercritical carbon dioxide relay pressure stabilization control, and pigging and launching barrel venting medium relay temperature control; the launching system is set in the trunk bypass, and is used to provide the installation and push-out of the pig during trunk pigging; the filling and discharge pipeline system is set in the launching system, and is used to provide the necessary flow channels during replacement, filling, and discharge; the instrument detection system includes the necessary pressure and temperature detection instruments set in the aforementioned system, which are used to provide temperature and pressure detection values at key points. In this way, the function of safe pigging of supercritical carbon dioxide pipelines is achieved.

[0007] The technical solution adopted by the present invention is: a supercritical carbon dioxide transportation pigging and ball launching system, characterized by comprising a relay pressurizing system connected to the ball launching system, a filling and discharging pipeline system and an instrument detection system;

[0008] The relay pressure charging system is connected to the station trunk line and the pigging barrel of the ball-charging system through pipelines. Before the ball-charging system is used for pigging, the relay pressure charging system is used for replacing the medium in the pigging barrel and controlling the supercritical carbon dioxide relay pressure. After the ball-charging system is used for pigging, the relay pressure charging system is used for controlling the relay temperature of the vented medium in the pigging barrel.

[0009] The filling and discharging piping system is connected to the pigging and ball-discharging barrel of the ball-discharging system, and is used to provide a flow channel when the pigging and ball-discharging barrel is replaced, filled and discharged;

[0010] The instrument detection system is used for real-time detection of temperature and pressure in the ball-serving system and the relay pressurizing system.

[0011] The supercritical carbon dioxide transportation pigging and ball-launching system of the present invention has a relay pressurizing system including a storage tank, which is respectively connected to an in-station trunk line and a pigging and ball-launching barrel of the ball-launching system through a pipeline provided with a valve group. The in-station trunk line and the pigging and ball-launching barrel are connected via a bypass connected in parallel with the storage tank. The storage tank is provided with a discharge pipeline for discharging the medium in the pigging and ball-launching barrel, and the storage tank is provided with a tank safety valve for controlling the maximum pressure of the medium in the storage tank.

[0012] The supercritical carbon dioxide transportation pigging and ball launching system of the present invention comprises a storage tank connected to a trunk bypass third ball valve provided on a trunk line within a station via a pipeline provided with a first storage tank ball valve and a first storage tank regulating valve; the storage tank is connected to a pigging and ball launching barrel via a pipeline provided with a second storage tank ball valve and a second storage tank regulating valve; the first storage tank regulating valve and the second storage tank regulating valve are connected via a bypass provided with a third storage tank regulating valve.

[0013] The supercritical carbon dioxide conveying pigging and ball-launching system described in the present invention has a filling and discharge pipeline system including a first replacement discharge valve and a second replacement discharge valve, which are used to provide medium replacement, filling and discharge interfaces for the pigging and ball-launching barrel during the entire pigging process; the first replacement discharge valve is arranged on a branch pipe at the large barrel end of the pigging and ball-launching barrel, and the second replacement discharge valve is arranged on a branch pipe at the small barrel end of the pigging and ball-launching barrel.

[0014] The supercritical carbon dioxide transportation pigging and ball-launching system of the present invention comprises an instrument detection system comprising a first ball-launching cylinder pressure transmitter, a ball-launching cylinder temperature transmitter, a second ball-launching cylinder pressure transmitter, a storage tank pressure transmitter, and a storage tank temperature transmitter;

[0015] The first pressure transmitter of the ball launching cylinder is arranged on the large cylinder of the pig launching cylinder and is used to provide the pressure detection value in the large cylinder;

[0016] The ball-serving barrel temperature transmitter is placed on the small barrel of the pigging ball-serving barrel, and is used to provide a temperature detection value in the small barrel. The ball-serving barrel second pressure transmitter is placed on the small barrel of the pigging ball-serving barrel, and is used to provide a pressure detection value in the small barrel.

[0017] The storage tank pressure transmitter and the storage tank temperature transmitter are respectively arranged on the storage tank.

[0018] A supercritical carbon dioxide transportation pigging method, characterized by comprising the following steps:

[0019] Step 1: In accordance with the requirements of pipeline transportation technology and operation management, a pigging and launching system is installed at the process station where the supercritical carbon dioxide pipeline requires pigging and launching. During normal operation, the pigging and launching system is kept in a zero-pressure state, and all valves connecting the pigging and launching system to the trunk system are closed;

[0020] Step 2: When implementing a planned pigging operation on a pipeline, first replace the pig barrel with the pipeline to discharge the non-CO2 gas inside it, ensuring that the medium in the downstream pipeline can maintain a stable phase under the operating conditions during the pigging process;

[0021] Specifically, the mobile relay pressure charging system is transported to the vicinity of the pigging barrel, the mobile storage tank of the relay pressure charging system is pre-filled with gaseous carbon dioxide at a certain pressure, and the mobile storage tank is respectively connected to the third ball valve of the trunk bypass of the station trunk line and the first displacement relief valve of the pigging barrel. The carbon dioxide gas in the mobile storage tank slowly enters the pigging barrel, and the displaced gas is discharged from the second displacement relief valve.

[0022] Step 3: Implement the tank pressure boosting operation, introduce the carbon dioxide in the station trunk line into the tank in multiple batches, and gradually increase the pressure in the tank to the predetermined value;

[0023] Step 4: Implement the pig launcher pressure-increasing operation, injecting the carbon dioxide in the storage tank into the pig launcher until the pressure in the pig launcher exceeds 2.0 MPa. Then, disconnect the storage tank from the pig launcher and directly draw carbon dioxide from the station trunk line to fill the pig launcher until the pressure in the pig launcher rises to within 0.5 MPa below the trunk line operating pressure.

[0024] Step 5: Implement the ball launching operation, using the main line medium in the station to push the pig out of the pig launching barrel and send it into the external transmission main line;

[0025] Step 6: Implement the residual medium discharge operation in the pigging cylinder, discharge the residual carbon dioxide in the pigging cylinder into the storage tank, and discharge the medium in the pigging cylinder and the storage tank through the storage tank to complete the safe pigging operation of the supercritical carbon dioxide transmission system.

[0026] In the supercritical carbon dioxide transportation pigging and ball-serving method of the present invention, in step 2, the internal pressure of the movable storage tank is 2.5-2.8 MPa, the third ball valve of the trunk bypass is connected to the first regulating valve of the storage tank, and the first displacement relief valve is connected to the second regulating valve of the storage tank to complete the assembly;

[0027] Load the pig into the pig launching barrel, open the barrel connecting valve, the first displacement relief valve, the second displacement relief valve, open the second ball valve of the storage tank, and the second regulating valve of the storage tank. The carbon dioxide gas in the movable storage tank slowly enters the pig launching barrel, and the displaced gas is discharged from the second displacement relief valve and connected to the venting system. After continuous purging for several minutes, stop the displacement, control the pressure in the tank to above 1.8MPa, close the second displacement relief valve, the second ball valve of the storage tank and the second regulating valve of the storage tank, and complete the replacement of the medium in the pig launching barrel.

[0028] The supercritical carbon dioxide transportation pigging and ball-feeding method of the present invention comprises the following steps: in step 3, opening the third ball valve of the trunk bypass, the first ball valve of the storage tank, and the first regulating valve of the storage tank, introducing a portion of supercritical carbon dioxide from the station trunk line into the movable storage tank; closing the first regulating valve of the storage tank after the storage tank pressure rises by 0.2 MPa each time; and increasing the pressure after the carbon dioxide in the storage tank exchanges heat with the surrounding environment; and when the temperature stabilizes to the ambient temperature, opening the first regulating valve of the storage tank again, and introducing carbon dioxide from the station trunk line again, and increasing the tank pressure, until the tank pressure rises to a predetermined value at the ambient temperature;

[0029] In this step, the tank venting shut-off valve is kept open. When the pressure in the tank exceeds 3.0 MPa, the tank safety valve intervenes to implement overpressure protection. After the tank pressure is increased, the third ball valve of the main bypass, the first ball valve of the tank, and the first regulating valve of the tank are closed to complete the tank pressure increase.

[0030] The supercritical carbon dioxide transportation pigging and ball-charging method of the present invention comprises the following steps: in step 4, opening the first displacement relief valve, the second ball valve of the storage tank and the second regulating valve of the storage tank, injecting the carbon dioxide in the movable storage tank into the pigging and ball-charging cylinder, and when the pressure transmitter on the pigging and ball-charging cylinder indicates that the pressure is lower than 2.0 MPa, when the pressure in the storage tank is insufficient to continue to increase the pressure of the pig launching cylinder, close the first displacement relief valve, the second ball valve of the storage tank, and the second regulating valve of the storage tank, and repeat step three to continue to replenish the pressure of the storage tank; when the pressure transmitter on the pig launching cylinder indicates that the pressure is higher than 2.0MPa, close the second ball valve of the storage tank, open the third ball valve of the storage tank, the third ball valve of the trunk bypass and the first regulating valve of the storage tank, and directly introduce carbon dioxide from the station trunk to fill the pig launching cylinder until the pressure in the pig launching cylinder rises to within 0.5MPa below the operating pressure of the station trunk; close the third ball valve of the storage tank, the third ball valve of the trunk bypass, the first regulating valve of the storage tank and the first displacement relief valve, open the first ball valve of the trunk bypass and the second ball valve of the trunk bypass to keep the pressure in the trunk and the pig launching cylinder consistent. At this point, the pressure increase of the pig launching cylinder is completed.

[0031] The supercritical carbon dioxide transportation pigging and ball-launching method described in the present invention, in the step six, close the main line bypass first ball valve and the main line bypass second ball valve, slowly open the first displacement relief valve, the second regulating valve of the storage tank and the second ball valve of the storage tank, and discharge carbon dioxide from the pigging and ball-launching cylinder into the storage tank. After the pressure of the storage tank rises to 2.8 MPa, close the second regulating valve of the storage tank. After the carbon dioxide in the storage tank exchanges heat with the surrounding environment, the pressure increases. When the pressure exceeds 3.0 MPa, the safety valve of the storage tank trips to discharge the overpressure medium; when the temperature stabilizes to the ambient temperature, open the storage tank relief valve to reduce the storage tank pressure to 1.8 MPa; if the pressure in the pigging and ball-launching cylinder is higher than 2.8 MPa at this time, the above-mentioned operation of step six is cyclically implemented; if the pressure in the pigging and ball-launching cylinder is lower than 2.8 MPa, directly open the storage tank relief valve to directly discharge the pigging and ball-launching cylinder and the storage tank medium.

[0032] Compared with the existing technology, the positive effects of the present invention are: based on the medium characteristics of supercritical carbon dioxide and the process requirements of pipeline pigging, a supercritical carbon dioxide transmission pigging and launching system and method are proposed; by setting a movable relay pressurizing system, a launching system, a filling and discharge pipeline system and an instrument detection system, the pipeline configuration of the pigging and launching barrel is simplified, and the safe operation and economic configuration of the entire supercritical carbon dioxide pipeline pigging process are achieved.

[0033] Specifically:

[0034] (1) Setting up science

[0035] Based on the phase characteristics of carbon dioxide and the operational requirements of pigging and launching, this invention addresses safety issues such as low temperatures and blockages caused by direct introduction of supercritical carbon dioxide into a pigging and launching barrel. From the perspectives of efficient replacement and safe pressure increase, it incorporates a removable relay charging system, a launching system, a charging and discharge piping system, and an instrumentation detection system. The removable relay charging system utilizes a stepped pressure and temperature control scheme to match the planned nature of pipeline pigging. It utilizes a removable storage tank to relay the required charging pressure for the pigging and launching barrel, eliminating the need for a low-temperature vaporizer for low-temperature carbon dioxide temperature regulation. It also integrates functions such as supplying replacement gas to the pigging and launching barrel, relaying the pressure-filling medium for the pigging and launching barrel, and relaying the pressure-releasing medium for the pigging and launching barrel. Compared to conventional oil and gas pipeline pigging and launching systems, the launching system is more streamlined, relocating a portion of the pipeline to the removable relay charging system, reducing daily maintenance workload. Furthermore, this system eliminates the need for cryogenic materials for the supercritical carbon dioxide pigging unit and piping, ensuring operational safety.

[0036] (2) Good economic performance

[0037] In view of the operating characteristics of the supercritical carbon dioxide pipeline pigging and launching system, the present invention sets up a movable pressure relay system, which can be used as a reuse device for pigging and launching at multiple stations; by extending the operation time, under the premise of meeting the planned implementation characteristics of the pigging operation, it replaces the vaporizer or mobile pressurized gas source used for adjusting the temperature after the supercritical carbon dioxide is depressurized, and is also suitable for the pressure relay of the discharge medium after the pigging is completed. The material of the pigging and launching system is consistent with the pipeline transportation system, avoiding the use of low-temperature materials.

[0038] (3) Advanced concepts

[0039] my country has not yet carried out large-scale construction and operation of supercritical carbon dioxide pipelines. The present invention focuses on the medium properties of supercritical carbon dioxide and the objective needs of pigging and launching operations. The proposed operation mode with pressure relay as the core overcomes the problems of low medium temperature and dry ice formation during the pressure filling and pressure release of pigging and launching barrels. It can provide important reference and reference for subsequent similar projects and promote the development of supercritical carbon dioxide pipeline transportation technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The present invention will be described by way of specific embodiments with reference to the accompanying drawings, in which

[0041] Figure 1 It is a structural schematic diagram of the present invention.

[0042] Markings in the figure: 1 is the main line in the station, 2 is the external transmission main line, 3 is the first shut-off valve of the main line, 4 is the external transmission shut-off valve, 5 is the first ball valve of the main line bypass, 6 is the second ball valve of the main line bypass, 7 is the third ball valve of the main line bypass, 11 is the pigging cylinder, 12 is the pigging main line, 13 is the first shut-off valve downstream of the cylinder, 14 is the second shut-off valve downstream of the cylinder, 15 is the cylinder connecting pipeline, 16 is the cylinder connecting valve, 21 is the storage tank, 22 is the first regulating valve of the storage tank, 23 is the second regulating valve of the storage tank, 24 is the first ball valve of the storage tank, 25 is the second ball valve of the storage tank, 26 is the third ball valve of the storage tank, 27 is the tank discharge shut-off valve, 28 is the tank safety valve, 29 is the tank discharge valve, 31 is the first pressure transmitter of the ball cylinder, 32 is the temperature transmitter of the ball cylinder, 33 is the second pressure transmitter of the ball cylinder, 34 is the tank pressure transmitter, 35 is the tank temperature transmitter, 41 is the first displacement relief valve, and 42 is the second displacement relief valve. DETAILED DESCRIPTION

[0043] 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.

[0044] 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 claimed invention, 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 inventive effort are within the scope of protection of the present invention. It should be noted that the embodiments of the present invention and the features therein may be combined with each other unless there is a conflict.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] like Figure 1 As shown, a supercritical carbon dioxide transportation pigging and launching system includes a relay charging system connected to the launching system, a charging and discharging pipeline system and an instrument detection system.

[0049] Among them, the ball launching system includes the station trunk line 1, the external transmission trunk line 2, the first trunk block valve 3, the external transmission block valve 4, the first trunk bypass ball valve 5, the second trunk bypass ball valve 6, the third trunk bypass ball valve 7, the pipe cleaning ball launching barrel 11, the pipe cleaning trunk line 12, the first block valve 13 downstream of the ball launching barrel, the second block valve 14 downstream of the ball launching barrel, the ball barrel connecting pipeline 15 and the ball barrel connecting valve 16. The ball launching system is mainly responsible for providing functions such as pipe cleaning device installation and pipe cleaning device launching.

[0050] Specifically, in the system shown, the station trunk line 1 connects the upstream supercritical carbon dioxide station system and the downstream external transmission trunk line 2, which is made of carbon steel and provides a medium flow channel during normal operation, that is, under non-pigging conditions; the external transmission trunk line 2 is an external transmission pipeline for supercritical carbon dioxide; the first trunk line shut-off valve 3 is arranged at the end of the station trunk line 1, an electric ball valve, normally open, closed under pigging conditions, and made of carbon steel; the external transmission shut-off valve 4 is arranged at the head end of the downstream external transmission trunk line 2, normally open, made of carbon steel, and closed when the downstream external transmission trunk line 2 is under maintenance or an accident occurs; the first trunk line bypass ball valve 5 and the second trunk line bypass ball valve 6 are arranged on the same branch pipe of the station trunk line 1, normally closed, and both are made of carbon steel. The first trunk line bypass ball valve 5 is an electric ball valve, and the second trunk line bypass ball valve 6 is a manual ball valve, and is also provided to serve as a connection between the trunk line and the pigging launch cylinder 11 The function of double isolation is to open it under pigging conditions; the third ball valve 7 of the trunk bypass is set on another branch of the trunk line 1 in the station, a manual ball valve, normally closed, made of carbon steel, with a blind plate at the other end, connected to a movable relay pressurizing system before pigging, and opened when the pig launching cylinder 11 is pressurized; the pig launching cylinder 11 is the main facility for pipeline pigging and launching, made of carbon steel, divided into a large cylinder and a small cylinder, connected by a transition between large and small heads, one end of the pig launching cylinder 11 is a quick-opening blind plate, and the other end is connected to the pigging trunk line 12; the pigging trunk line 12 is a channel connected to the external transmission trunk line 2 after the pig is launched, made of carbon steel; the first shut-off valve 13 downstream of the launching cylinder A second shut-off valve 14 downstream of the ball-launching cylinder is sequentially arranged on the cleaning trunk line 12, preferably an electric ball valve, both of which are made of carbon steel, normally closed, and opened when the pipeline is cleaning; a ball-cylinder connecting pipeline 15 is arranged on the cleaning ball-launching cylinder 11, and connects the large cylinder and the small cylinder, and is used to provide a replacement and pressurizing channel connecting the large cylinder and the small cylinder after the cleaning ball is installed in place; a ball-cylinder connecting valve 16 is arranged on the ball-cylinder connecting pipeline 15, normally closed, made of carbon steel, and opened when the ball cylinder is replaced, pressurized and discharged.

[0051] The relay pressurization system is connected to the station trunk line 1 and the pig launching barrel 11 of the launching system via pipelines. Before the launching system launches and pigs the pipe, the relay pressurization system is used to replace the medium in the pig launching barrel 11 and to control the supercritical carbon dioxide relay pressure. After the launching system launches and pigs the pipe, the relay pressurization system is used to control the relay temperature of the discharged medium in the pig launching barrel 11, ensuring the stability of the medium input and output status under the pig launching barrel pressurization and discharge conditions, and preventing the generation of dry ice and low-temperature carbon dioxide from damaging pipelines and equipment. Furthermore, the relay pressurization system is a movable connection structure. The movable relay pressurization system is transported to the pig launching area before the planned pigging operation and is connected to the pipeline.

[0052] Specifically, the relay charging system includes a storage tank 21, a first storage tank regulating valve 22, a second storage tank regulating valve 23, a first storage tank ball valve 24, a second storage tank ball valve 25, a third storage tank ball valve 26, a storage tank discharge shut-off valve 27, a storage tank safety valve 28 and a storage tank discharge valve 29.In the system shown, the movable storage tank 21 is a small vertical pressurized storage tank made of carbon steel. It is pre-filled with gaseous carbon dioxide. The pre-filling pressure is preferably 2.5-2.8 MPa. The actual pressure is determined according to the ambient temperature. The principle is that after the carbon dioxide at the ambient temperature and the tank pressure enters the ball barrel, the temperature after adiabatic expansion is higher than -15 ° C. The minimum working pressure is preferably 1.8 MPa. First, it is used to provide gaseous carbon dioxide as a replacement medium when the pigging ball barrel is replaced. Second, it is used to relay the temperature and pressure of the supercritical carbon dioxide drawn out of the trunk when the pigging ball barrel is pressurized. Third, it is used to intermediate the supercritical carbon dioxide discharged when the pigging ball barrel is discharged. Continuing with temperature and pressure regulation; further, the movable storage tank 21 is preferably provided with fins on the outer surface to improve the heat exchange capacity with the atmosphere; the first regulating valve 22 of the storage tank is connected to the third ball valve 7 of the trunk bypass, which is provided on the first branch pipe of the storage tank 21, is normally closed and manually adjusted to control the flow of the medium introduced from the station trunk line 1 to the movable storage tank 21; the second regulating valve 23 of the storage tank is provided on the second branch pipe of the storage tank, is normally closed and manually adjusted to control the flow of the medium introduced from the movable storage tank 21 to the pig launching barrel 11, and also reversely controls the flow of the medium introduced from the pig launching barrel 11 to the movable storage tank 21 when the pig launching barrel 11 discharges the medium; the first ball valve 24 of the storage tank is provided on the first branch pipe of the storage tank 21, installed downstream of the first regulating valve 22 of the storage tank, is normally closed, a manual ball valve, and is opened when the medium is introduced from the station trunk line 1 to the movable storage tank 21; the second ball valve 25 of the storage tank It is arranged on the second branch pipe of the storage tank 21, installed upstream of the second regulating valve 23 of the storage tank, and is normally closed. It is a manual ball valve and is opened when the medium is transferred between the movable storage tank 21 and the pig launching barrel 11; the third ball valve 26 of the storage tank is arranged on the bypass branch pipe connecting the first regulating valve 22 of the storage tank and the second regulating valve 23 of the storage tank, and is opened when the main line 1 in the station directly pressurizes the pig launching barrel 11, that is, when the pressure in the pig launching barrel 11 rises to more than 2.0MPa, carbon dioxide can be directly introduced from the main line 1 in the station to the pig launching barrel 11 without having to be relayed through the storage tank 21; the storage tank 21 is provided with a discharge pipeline for discharging the medium in the pig launching barrel 11, and the discharge pipeline It includes a tank discharge shut-off valve 27 and a tank discharge valve 29. The tank discharge shut-off valve 27 is arranged on the discharge branch of the movable tank 21, is normally closed, and is made of carbon steel. It is opened when the movable tank 21 performs pressure relay; the tank discharge valve 29 is a manual regulating valve, which is arranged downstream of the tank discharge shut-off valve 27, is normally closed, and is made of carbon steel. It is opened when the movable tank 21 performs pressure relay. By adjusting the opening, the medium pressure in the tank 21 is controlled not to exceed the set value; the tank 21 is provided with a tank safety valve 28 for controlling the maximum pressure of the medium in the tank 21. The tank safety valve 28 is arranged on the bypass of the tank discharge valve 29 to serve as a backup safety guarantee.

[0053] The filling and discharging pipeline system is connected to the pigging and launching barrel 11 of the launching system, and is used to provide a flow channel when the pigging and launching barrel 11 is replaced, filled and discharged.

[0054] Specifically, the filling and discharge pipeline system includes a first replacement discharge valve 41 and a second replacement discharge valve 42, which are used to provide medium replacement, filling and discharge interfaces for the pigging ball barrel during the entire pigging process; in the shown system, the first replacement discharge valve 41 is arranged on the branch pipe at the large barrel end of the pigging ball barrel 11, close to the quick-opening blind plate, normally closed, made of carbon steel, a manual ball valve, and a blind flange is provided at the other end of the ball valve, and the ball valve is only opened during replacement, pressurization and discharge; the second replacement discharge valve 42 is arranged on the branch pipe at the small barrel end of the pigging ball barrel 11, close to the external transmission trunk line 2, normally closed, made of carbon steel, a manual ball valve, and the other end of the ball valve is connected to the discharge pipeline and is only opened during replacement.

[0055] The instrument detection system is used for real-time detection of temperature and pressure in the ball-serving system and the relay pressurizing system, and includes a first pressure transmitter 31 of the ball-serving cylinder, a temperature transmitter 32 of the ball-serving cylinder, a second pressure transmitter 33 of the ball-serving cylinder, a pressure transmitter 34 of the storage tank, and a temperature transmitter 35 of the storage tank.

[0056] Specifically, in the system shown, the first pressure transmitter 31 of the serving cylinder is arranged on the large cylinder of the cleaning serving cylinder 11, and is used to provide the pressure detection value in the large cylinder; the temperature transmitter 32 of the serving cylinder is placed on the small cylinder of the cleaning serving cylinder 11, and is used to provide the temperature detection value in the small cylinder; the second pressure transmitter 33 of the serving cylinder is arranged on the small cylinder of the cleaning serving cylinder 11, and is used to provide the pressure detection value in the small cylinder, and compare it with the detection value of the first pressure transmitter 31 of the serving cylinder, indicating whether pressure blockage occurs between the large cylinder and the small cylinder; the storage tank pressure transmitter 34 and the storage tank temperature transmitter 35 are respectively arranged on the movable storage tank 21, indicating the temperature and pressure status of the medium in the storage tank, and guiding the operation of the corresponding regulating valve during the replacement, charging and discharge processes.

[0057] The working principle of the present invention is:

[0058] (1) Pipe cleaning is required during supercritical carbon dioxide pipeline transportation to improve pipeline transportation efficiency and provide internal detection parameters required for pipeline integrity operation. Pipeline cleaning is implemented by using pipeline medium to push the pipe cleaner, and the pipeline medium is introduced into the pipe cleaning ball barrel during pipe cleaning. Due to the high operating pressure of supercritical carbon dioxide, when it is adiabatically expanded (depressurized) to normal pressure, it can form a temperature environment as low as -90°C. At the same time, there is a risk of generating dry ice, which will have a serious impact on the material selection of the pipe cleaning ball barrel and the safe operation of the pipe cleaning operation. For this reason, the structural design of the supercritical carbon dioxide transportation pipe cleaning ball barrel system is proposed.

[0059] (2) This system is equipped with a movable relay pressure charging system, which is reserved in the warehouse during daily operation and does not occupy the production area. It is transported to the cleaning area during planned cleaning. The core of the movable relay pressure charging system is a movable storage tank, which is pre-filled with gaseous carbon dioxide at a certain pressure. It serves as the medium for the cleaning ball cylinder to replace and also as the cushion gas of the storage tank. By providing back pressure, after receiving the supercritical carbon dioxide introduced from the trunk line, the temperature in the storage tank is prevented from falling below -20°C. The temperature and pressure of the carbon dioxide in the storage tank are reasonably increased by heat exchange with the atmosphere. When the pressure in the storage tank meets the requirements, the medium in the storage tank is introduced into the cleaning ball cylinder, and the pressure of the cleaning ball cylinder is gradually increased. The pressure relay is used to ensure that the temperature of the carbon dioxide in the cleaning ball cylinder is higher than the design allowable lower limit temperature of the carbon steel material. Since pipeline cleaning is a planned working condition, its time limit requirement is not high, and the cleaning ball cylinder is small in size, the filling medium demand is small, and the demand for other large flow and continuous heat exchange facilities such as air bath vaporizer is low. Furthermore, a stepped pressure relay utilizes atmospheric heat exchange to naturally increase the pressure of the medium within the tank, reducing the probability and amount of overpressure caused by the medium's temperature rise. When the pressure in the pig launcher increases to approximately 2MPa or above, supercritical carbon dioxide is introduced directly from the station's main line into the pig launcher via a charging bypass within the mobile relay pressure charging system, ensuring that the medium temperature within the pig launcher meets material safety requirements.

[0060] (3) After the cleaning operation is completed, the movable relay pressure charging system is used as a pressure relay again. After the discharge medium is fully heated in the storage tank, it is discharged into the release system to ensure the safety of the materials in the release system.

[0061] The present invention also discloses a supercritical carbon dioxide transportation pigging and balling method, which includes the following main steps:

[0062] Step 1: Install a pigging system at the process station where supercritical carbon dioxide pipelines require pigging, in accordance with pipeline transportation technology and operation management requirements. During normal operation, the pigging system maintains a zero-pressure state, and all valves connecting the pigging system to the mainline system are closed.

[0063] Step 2: When implementing a planned pipeline pigging operation, first replace the pig barrel with the pipeline to discharge the non-CO2 gas inside it, ensuring that the medium in the downstream pipeline can maintain a stable phase under the operating conditions during the pigging process.

[0064] Specifically, the mobile relay pressurization system is transported to the vicinity of the pigging launcher, with the internal pressure of its mobile storage tank 21 at 2.5-2.8 MPa (the actual pressure is determined by the ambient temperature; the principle is that after the carbon dioxide at ambient temperature and tank pressure enters the launcher, the temperature after adiabatically expanding is above -15°C). The mainline bypass third ball valve 7 is connected to the first regulating valve 22 of the storage tank, and the first displacement relief valve 41 is connected to the second regulating valve 23 of the storage tank to complete the assembly. A pig is then loaded into the pigging launcher 11. The ball tank connecting valve 16, the first displacement relief valve 41, and the second displacement relief valve 42 are opened. The second ball valve 25 and the second regulating valve 23 of the storage tank are opened. The carbon dioxide gas in the mobile storage tank 21 slowly enters the pigging launcher 11, and the displaced gas is discharged through the second displacement relief valve 42 and connected to the venting system. After 5 minutes of continuous purge, displacement is stopped, and the internal tank pressure is controlled above 1.8 MPa. The second displacement relief valve 42 , the second storage tank ball valve 25 and the second storage tank regulating valve 23 are closed.

[0065] Step 3: Implement the tank pressure boosting operation, specifically: open the third ball valve 7 of the trunk bypass, the first ball valve 24 of the storage tank and the first regulating valve 22 of the storage tank, and introduce part of the supercritical carbon dioxide from the station trunk line 1 to the movable storage tank 21; after the tank pressure rises by 0.2MPa each time, close the first regulating valve 22 of the storage tank, and the carbon dioxide in the storage tank exchanges heat with the surrounding environment, and the pressure increases. When the temperature stabilizes to the ambient temperature, open the first regulating valve 22 of the storage tank again, and introduce carbon dioxide again and increase the tank pressure; until the tank pressure rises to the predetermined value (about 2.8MPa) at the ambient temperature.

[0066] During this step, the tank vent shutoff valve remains open. When the pressure in the tank exceeds 3.0 MPa, the tank safety valve 28 intervenes to provide overpressure protection. After the tank pressure is increased, the mainline bypass third ball valve 7, the tank first ball valve 24, and the tank first regulating valve 22 are closed.

[0067] Step 4: Implement the pressure-increasing operation of the pigging cylinder 11, specifically: open the first displacement relief valve 41, the second ball valve 25 of the storage tank and the second regulating valve 23 of the storage tank, and inject the carbon dioxide in the movable storage tank 21 into the pigging cylinder. When the pressure transmitter on the pigging cylinder indicates that the pressure is lower than 2.0 MPa and the pressure in the tank is insufficient to continue to increase the pressure of the pigging cylinder, close the first displacement relief valve 41, the second ball valve 25 of the storage tank and the second regulating valve 23 of the storage tank, and repeat step 3 to continue to add pressure to the tank; when the pressure transmitter on the pigging cylinder indicates that the pressure is lower than 2.0 MPa, the pressure in the tank is insufficient to continue to increase the pressure of the pigging cylinder. When the pressure exceeds 2.0 MPa, close the second tank ball valve 25, open the third tank ball valve 26, the trunk bypass third ball valve 7, and the first tank regulating valve 22, and introduce carbon dioxide directly from the station trunk line 1 to fill the pig launch cylinder until the pressure in the pig launch cylinder rises to within 0.5 MPa below the trunk operating pressure. Close the third tank ball valve 26, the trunk bypass third ball valve 7, the first tank regulating valve 22, and the first displacement relief valve 41, open the trunk bypass first ball valve 5 and the trunk bypass second ball valve 6, and maintain the trunk pressure and the pig launch cylinder pressure at the same level. This completes the pig launch cylinder pressure increase step.

[0068] Step 5: Execute the pigging operation, specifically: slowly close the first mainline block valve 3, slowly open the first mainline bypass ball valve 5, the second mainline bypass ball valve 6, the first downstream block valve 13 of the pigging barrel, and the second downstream block valve 14 of the pigging barrel. The mainline medium pushes the pig out of the pigging barrel and into the external transmission mainline 2. After the pigging is completed, first slowly open the first mainline block valve 3, then slowly close the first downstream block valve 13 of the mainline pigging barrel and the second downstream block valve 14 of the pigging barrel. Before proceeding to Step 6, to prevent the medium in the pigging barrel 11 from forming a seal, keep the first mainline bypass ball valve 5 and the second mainline bypass ball valve 6 open.

[0069] Step 6: Release the residual medium in the pig launcher. Specifically, close the mainline bypass first ball valve 5 and the mainline bypass second ball valve 6, slowly open the first displacement relief valve 41, the tank second regulating valve 23, and the tank second ball valve 25, and discharge carbon dioxide from the pig launcher into the tank. After the tank pressure rises to 2.8 MPa, close the tank second regulating valve 23. The carbon dioxide in the tank exchanges heat with the surrounding environment, causing the pressure to rise. When the pressure exceeds 3.0 MPa, the tank safety valve 28 trips, discharging the overpressure medium. When the temperature stabilizes to ambient temperature, open the tank relief valve 29 to reduce the tank pressure to 1.8 MPa. If the pig launcher pressure is higher than 2.8 MPa at this point, repeat the above steps in step 6. If the pig launcher pressure is lower than 2.8 MPa, directly open the tank relief valve 29 to directly discharge the pig launcher and tank medium. This completes the safe pigging of the supercritical carbon dioxide delivery system.

[0070] 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 supercritical carbon dioxide transportation pigging and ball delivery system, characterized by: It includes a relay charging system connected to the ball launching system, a charging and discharging piping system and an instrument detection system; The relay pressure-charging system is connected to the station trunk line (1) and the pigging and launching barrel (11) of the ball launching system through pipelines. Before the ball launching system launches and pigs the pipe, the relay pressure-charging system is used to replace the medium in the pigging and launching barrel (11) and to control the supercritical carbon dioxide relay pressure stabilization. After the ball launching system launches and pigs the pipe, the relay pressure-charging system is used to control the relay temperature of the vented medium in the pigging and launching barrel (11). The filling and discharging pipeline system is connected to the pigging and ball-discharging barrel (11) of the ball-discharging system, and is used to provide a flow channel when the pigging and ball-discharging barrel (11) is replaced, filled and discharged; The instrument detection system is used for real-time detection of temperature and pressure in the ball-serving system and the relay pressurizing system.

2. The supercritical carbon dioxide transportation pigging and ball delivery system according to claim 1, characterized in that: The relay pressure charging system comprises a storage tank (21), wherein the storage tank (21) is respectively connected to a station trunk line (1) and a pigging and launching barrel (11) of a launching system via a pipeline provided with a valve group, wherein the station trunk line (1) and the pigging and launching barrel (11) are connected via a bypass connected in parallel with the storage tank (21), wherein the storage tank (21) is provided with a discharge pipeline for discharging the medium in the pigging and launching barrel (11), and wherein the storage tank (21) is provided with a tank safety valve (28) for controlling the maximum pressure of the medium in the storage tank (21).

3. The supercritical carbon dioxide transportation pigging and ball delivery system according to claim 2, characterized in that: The storage tank (21) is connected to a trunk bypass third ball valve (7) provided on a trunk line (1) within the station via a pipeline provided with a first storage tank ball valve (24) and a first storage tank regulating valve (22); the storage tank (21) is connected to a pigging ball barrel (11) via a pipeline provided with a second storage tank ball valve (25) and a second storage tank regulating valve (23); the first storage tank regulating valve (22) and the second storage tank regulating valve (23) are connected via a bypass provided with a third storage tank regulating valve (26).

4. The supercritical carbon dioxide transportation pigging and ball delivery system according to claim 1, characterized in that: The filling and discharge pipeline system comprises a first replacement discharge valve (41) and a second replacement discharge valve (42), which are used to provide a medium replacement, filling and discharge interface for the pigging ball barrel (11) during the entire pigging process; the first replacement discharge valve (41) is arranged on a branch pipe at the large barrel end of the pigging ball barrel (11), and the second replacement discharge valve (42) is arranged on a branch pipe at the small barrel end of the pigging ball barrel (11).

5. The supercritical carbon dioxide transportation pigging and ball delivery system according to claim 1, characterized in that: The instrument detection system includes a first pressure transmitter (31) of the ball-serving cylinder, a temperature transmitter (32) of the ball-serving cylinder, a second pressure transmitter (33) of the ball-serving cylinder, a pressure transmitter (34) of the storage tank, and a temperature transmitter (35) of the storage tank; The first pressure transmitter (31) of the ball launching cylinder is arranged on the large cylinder of the pig launching cylinder (11) and is used to provide a pressure detection value in the large cylinder; The ball-serving cylinder temperature transmitter (32) is placed on the small cylinder of the pigging ball-serving cylinder (11) and is used to provide a temperature detection value in the small cylinder. The ball-serving cylinder second pressure transmitter (33) is placed on the small cylinder of the pigging ball-serving cylinder (11) and is used to provide a pressure detection value in the small cylinder. The storage tank pressure transmitter (34) and the storage tank temperature transmitter (35) are respectively arranged on the storage tank (21).

6. A method for pigging and serving supercritical carbon dioxide, characterized by: The steps include: Step 1: In accordance with the requirements of pipeline transportation technology and operation management, a pigging and launching system is installed at the process station where the supercritical carbon dioxide pipeline requires pigging and launching. During normal operation, the pigging and launching system is kept in a zero-pressure state, and all valves connecting the pigging and launching system to the trunk system are closed; Step 2: When implementing a planned pigging operation on a pipeline, first replace the pig barrel with the pipeline to discharge the non-CO2 gas inside it, ensuring that the medium in the downstream pipeline can maintain a stable phase under the operating conditions during the pigging process; Specifically, the mobile relay pressure charging system is transported to the vicinity of the pigging barrel, and the mobile storage tank of the relay pressure charging system is pre-filled with gaseous carbon dioxide at a certain pressure. The mobile storage tank is connected to the third ball valve of the trunk bypass of the station trunk line and the first displacement relief valve of the pigging barrel, respectively. The carbon dioxide gas in the mobile storage tank slowly enters the pigging barrel, and the displaced gas is discharged from the second displacement relief valve. Step 3: Implement the tank pressure boosting operation, introduce the carbon dioxide in the station trunk line into the tank in multiple batches, and gradually increase the pressure in the tank to the predetermined value; Step 4: Implement the pig launcher pressure-increasing operation, injecting the carbon dioxide in the storage tank into the pig launcher until the pressure in the pig launcher exceeds 2.0 MPa. Then, disconnect the storage tank from the pig launcher and directly draw carbon dioxide from the station trunk line to fill the pig launcher until the pressure in the pig launcher rises to within 0.5 MPa below the trunk line operating pressure. Step 5: Implement the ball launching operation, using the main line medium in the station to push the pig out of the pig launching barrel and send it into the external transmission main line; Step 6: Implement the residual medium discharge operation in the pigging cylinder, discharge the residual carbon dioxide in the pigging cylinder into the storage tank, and discharge the medium in the pigging cylinder and the storage tank through the storage tank to complete the safe pigging operation of the supercritical carbon dioxide transmission system.

7. The supercritical carbon dioxide transportation pigging and balling method according to claim 6, characterized in that: In step 2, the internal pressure of the movable storage tank is 2.5-2.8 MPa, the third ball valve of the trunk bypass is connected to the first regulating valve of the storage tank, and the first displacement relief valve is connected to the second regulating valve of the storage tank to complete the assembly; Load the pig into the pig launching barrel, open the barrel connecting valve, the first displacement relief valve, the second displacement relief valve, open the second ball valve of the storage tank, and the second regulating valve of the storage tank. The carbon dioxide gas in the movable storage tank slowly enters the pig launching barrel, and the displaced gas is discharged from the second displacement relief valve and connected to the venting system. After continuous purging for several minutes, stop the displacement, control the pressure in the tank to above 1.8MPa, close the second displacement relief valve, the second ball valve of the storage tank and the second regulating valve of the storage tank, and complete the replacement of the medium in the pig launching barrel.

8. The supercritical carbon dioxide transportation pigging and balling method according to claim 6, characterized in that: In the step three, the third ball valve of the trunk bypass, the first ball valve of the storage tank, and the first regulating valve of the storage tank are opened, and some supercritical carbon dioxide is introduced from the trunk line within the station into the movable storage tank. After the pressure of the storage tank rises by 0.2 MPa each time, the first regulating valve of the storage tank is closed. After the carbon dioxide in the storage tank exchanges heat with the surrounding environment, the pressure increases. When the temperature stabilizes to the ambient temperature, the first regulating valve of the storage tank is opened again, and carbon dioxide in the trunk line within the station is introduced again and the tank pressure is increased until the tank pressure rises to a predetermined value at the ambient temperature. In this step, the tank venting shut-off valve is kept open. When the pressure in the tank exceeds 3.0 MPa, the tank safety valve intervenes to implement overpressure protection. After the tank pressure is increased, the third ball valve of the main bypass, the first ball valve of the tank, and the first regulating valve of the tank are closed to complete the tank pressure increase.

9. The supercritical carbon dioxide transportation pigging and balling method according to claim 6, characterized in that: In the step 4, the first displacement relief valve, the second ball valve of the storage tank and the second regulating valve of the storage tank are opened to inject the carbon dioxide in the movable storage tank into the pig launching cylinder. When the pressure transmitter on the pig launching cylinder indicates that the pressure is lower than 2.0 MPa and the pressure in the storage tank is insufficient to continue to increase the pressure of the pig launching cylinder, the first displacement relief valve, the second ball valve of the storage tank and the second regulating valve of the storage tank are closed, and step 3 is repeated to continue to supplement the pressure of the storage tank. When the pressure transmitter on the pig launching cylinder indicates that the pressure is higher than 2.0 MPa, the pressure transmitter is closed. Close the second ball valve of the storage tank, open the third ball valve of the storage tank, the third ball valve of the trunk bypass and the first regulating valve of the storage tank, and directly introduce carbon dioxide from the trunk line in the station to fill the pig launching cylinder until the pressure in the pig launching cylinder rises to within 0.5MPa below the operating pressure of the trunk line in the station; close the third ball valve of the storage tank, the third ball valve of the trunk bypass, the first regulating valve of the storage tank and the first displacement relief valve, open the first ball valve of the trunk bypass and the second ball valve of the trunk bypass, and keep the pressure in the trunk and the pig launching cylinder consistent. At this point, the pressure increase of the pig launching cylinder is completed.

10. The supercritical carbon dioxide transportation pigging and balling method according to claim 6, characterized in that: In step six, the first ball valve and the second ball valve of the trunk bypass are closed, and the first displacement relief valve, the second regulating valve of the storage tank, and the second ball valve of the storage tank are slowly opened to discharge carbon dioxide from the pig launch cylinder into the storage tank. After the pressure of the storage tank rises to 2.8 MPa, the second regulating valve of the storage tank is closed. After the carbon dioxide in the storage tank exchanges heat with the surrounding environment, the pressure increases. When the pressure exceeds 3.0 MPa, the safety valve of the storage tank is tripped to discharge the overpressure medium; when the temperature stabilizes to the ambient temperature, the tank relief valve is opened to reduce the pressure of the storage tank to 1.8 MPa; If the pressure in the pig launcher is higher than 2.8 MPa at this time, the above-mentioned operation of step 6 is repeated; if the pressure in the pig launcher is lower than 2.8 MPa, the tank discharge valve is directly opened to directly discharge the pig launcher and the tank medium.

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