Supercritical co2 pipeline venting system and method based on bilateral bleed

Abstract

The application discloses a supercritical CO2 pipeline venting system and method based on bilateral venting, which comprises a valve chamber cutoff system, a valve chamber venting system, a medium introduction and heating system and a low point temporary temperature detection system. In the early stage of venting, the two valve chambers are used for rapid venting. In the middle and late stages of venting, the single-side introduction of the upstream or downstream trunk pipe is used for pressure regulation and heating to promote the vaporization of the liquid accumulation. The low point temperature detection system is arranged, the venting rate of the cutoff pipeline is effectively improved, and the problem of extremely low temperature caused by the vaporization of the liquid phase accumulation in the low point area of the cutoff pipeline is overcome. The application can realize efficient and safe operation of the planned venting of the supercritical CO2 pipeline.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of carbon dioxide pipeline transportation, and particularly relates to a supercritical CO2 pipeline emptying system and method based on bilateral release. BACKGROUND

[0002] Compared with conventional natural gas pipelines, supercritical CO2 pipelines have the characteristics of large unit volume density and phase change during the release process of the pipeline medium, which puts specific requirements on the control of the release time and the control of the temperature change caused by medium vaporization during the release process.

[0003] For example, when supercritical CO2 medium is released between two cut-off valves, the release rate is not only affected by the medium pressure, but also related to the phase state of the medium. The supercritical CO2 will experience three typical phase states, i.e., supercritical phase (dense phase), gas-liquid two-phase and gas phase, during the release process.

[0004] During the phase transition, the medium in the pipeline will experience different degrees of relatively significant temperature drop. During the release process, due to the influence of the pipeline undulation, the incompletely vaporized CO2 will tend to gather at the low point of the pipeline due to the influence of density, which will cause the pipeline section near the low point to experience more serious temperature drop, which may cause monitoring blind spots in the dispersed temperature detection and misjudgment in the temperature control during the release. In addition, due to the high pipeline pressure and large pipeline medium, the release time of supercritical CO2 will be much longer than that of conventional natural gas pipelines. The existing technology lacks a corresponding solution to solve the above problems. SUMMARY

[0005] The present application aims to overcome the defects of the prior art and provide a supercritical CO2 pipeline emptying system and method based on bilateral release, which greatly improves the safe release rate, improves the operating temperature of the trunk pipeline during the release process, and realizes efficient and safe operation of the planned emptying of the supercritical CO2 pipeline.

[0006] The present application achieves the above-mentioned purpose by the following technical solutions:

[0007] A supercritical CO2 pipeline emptying system based on bilateral release, which is arranged in a trunk pipeline of a CO2 pipeline, and comprises:

[0008] A valve chamber cut-off system, which comprises a first valve chamber cut-off subsystem arranged upstream of the trunk pipeline and a second valve chamber cut-off subsystem arranged downstream of the trunk pipeline, and is used for cutting off the trunk pipeline, and the first valve chamber cut-off subsystem and the second valve chamber cut-off subsystem comprise a bypass pipeline interface, which is used for connecting a valve chamber emptying system and a medium introduction and heating system;

[0009] A valve chamber venting system, which comprises a first valve chamber venting subsystem in communication with the first valve chamber blocking subsystem and a second valve chamber venting subsystem in communication with the second valve chamber blocking subsystem, for pressure regulating and releasing supercritical CO2 in the pipeline after the pipeline is shut down;

[0010] A medium introduction and heating system, which is used for temperature regulating liquid-phase medium accumulated in the blocked pipeline by injecting high-temperature medium into the blocked pipeline;

[0011] A low-point temporary temperature detection system, which is arranged at the maximum liquid accumulation position of the pipeline determined according to the release simulation.

[0012] Further, the first valve chamber blocking subsystem and the second valve chamber blocking subsystem each comprise a blocking valve arranged in the trunk line, a trunk line bypass in parallel with the trunk line, and a bypass regulating valve, the trunk line bypass is in communication with the trunk line of the pipeline at both ends of the blocking valve, the bypass regulating valve divides the trunk line bypass into a first trunk line bypass and a second trunk line bypass, the first trunk line bypass is in communication with the trunk line pipeline at the input end of the blocking valve, the second trunk line bypass is in communication with the trunk line pipeline at the output end of the blocking valve, the first trunk line bypass and the second trunk line bypass are respectively provided with bypass blocking valves, and temperature monitoring equipment and pressure monitoring equipment are arranged between the bypass blocking valves and the trunk line of the pipeline.

[0013] Further, the bypass pipeline interface comprises a first bypass pipeline interface arranged between the bypass blocking valve of the first trunk line bypass and the bypass regulating valve, a second bypass pipeline interface arranged between the bypass regulating valve and the bypass blocking valve of the second trunk line bypass, and a third bypass pipeline interface arranged between the second bypass pipeline interface and the bypass blocking valve of the second trunk line bypass.

[0014] The medium introduction and heating system is in communication with the valve chamber blocking system through the first bypass pipeline interface and the second bypass pipeline interface.

[0015] The valve chamber venting system is in communication with the valve chamber blocking system through the third bypass pipeline interface.

[0016] Further, the medium introduction and heating system comprises a flow regulating valve, a vaporizer and a heater connected in series, the input end of the flow regulating valve is in communication with the first bypass pipeline interface through a branch line inlet blocking valve, and the output end of the heater is in communication with the second bypass pipeline interface through a branch line outlet regulating valve.

[0017] Further, the valve chamber venting system comprises a venting regulating valve and a bypass venting regulating valve connected in parallel, the input ends of the venting regulating valve and the bypass venting regulating valve are connected to the third bypass pipeline through the venting cut-off valve, and the output ends of the venting regulating valve and the bypass venting regulating valve are connected to the heat exchanger and the venting vertical pipe in sequence.

[0018] Further, the low point temporary temperature detection system comprises a trunk branch first cut-off valve and a trunk branch second cut-off valve connected in sequence, the input end of the trunk branch first cut-off valve is connected to the pipeline maximum liquid accumulation position of the trunk, and the output end of the trunk branch second cut-off valve is further provided with a connection port for connecting a temperature transmitter.

[0019] In another aspect, the application also provides a supercritical CO2 pipeline venting method based on double-sided venting, which is realized based on any one of the venting systems described above, and the method comprises the following steps:

[0020] In normal transportation, the valve chamber cut-off system and the low point temporary temperature detection system are not connected to the trunk of the pipeline, and the maximum liquid accumulation position of the cut-off pipeline in the venting process is determined as the setting position of the low point temporary temperature detection system;

[0021] Before the pipeline is planned to be maintained, the pipeline transportation capacity is reduced, the temperature and pressure at each position along the pipeline are monitored, the difference between the pipeline pressure and the saturated steam pressure of the medium at the corresponding minimum temperature is kept as a preset pressure value, the medium storage amount in the pipeline during the planned venting is reduced by reducing the medium density, the valve chamber cut-off system is opened to realize pipeline shutdown;

[0022] The trunk of the pipeline is connected to the valve chamber cut-off system, the trunk pipeline is vented from the supercritical state to the gas-liquid two-phase state according to the maximum allowable venting amount of the first valve chamber cut-off subsystem and the second valve chamber cut-off subsystem, the temperature and pressure at each preset position are continuously monitored, the venting amount of the valve chamber venting system is reduced when the temperature is lower than the preset temperature threshold, and the venting of the valve chamber venting system is stopped when the pressure is lower than the preset threshold;

[0023] The valve chamber cut-off subsystem is connected to the medium introduction and heating system, the valve chamber venting subsystem corresponding to the valve chamber cut-off subsystem where the medium introduction and heating system is located is closed, the other valve chamber venting subsystem is kept in the connected state, the medium introduction and heating system is opened, the amount of introduced CO2 and discharged CO2 on the upstream and downstream of the trunk is kept consistent, and the introduced CO2 reaches the preset temperature to enter the trunk of the pipeline, when the temperature of the low point temperature transmitter continuously rises to the preset temperature, the inlet of the medium introduction and heating system is closed, and the valve chamber venting subsystem without the medium introduction and heating system is used to vent the medium in the trunk of the pipeline.

[0024] Further, the medium introduction and heating system is connected to the valve chamber cut-off subsystem closer to the maximum liquid accumulation position, and the valve chamber venting system is opened.

[0025] Further, the method further comprises:

[0026] During the venting process, the medium temperature at the low point of the pipeline is continuously monitored, and when the temperature is lower than a preset threshold, the medium introduction and heating system is started again until the trunk medium of the pipeline is completely discharged.

[0027] The beneficial effects of the present application are:

[0028] (1) Based on the basic physical properties, phase change rules and planned venting characteristics of the supercritical CO2, and in view of the characteristics of the supercritical CO2 pipeline, such as large pipe volume between the cut-off valves (at least 8 km of pipe length), high medium storage, and uneven liquid accumulation in the ups and downs of the pipeline, from the aspects of efficient discharge, promoting liquid vaporization, and safe operation, the valve chamber cut-off system, the valve chamber venting system, the upstream and downstream medium introduction and heating system, and the low point temporary temperature detection system are set up, which can greatly improve the safe discharge rate and the operating temperature of the trunk pipeline during the discharge process, and realize efficient and safe operation of the planned venting of the supercritical CO2 pipeline, thereby realizing efficient, economic and safe planned venting of the supercritical CO2 pipeline.

[0029] (2) The present application innovatively adopts the medium introduction scheme of the upstream (or downstream) trunk pipe, which avoids the number of openings in the non-cut-off valve area of the pipeline, reduces the pipeline leakage probability and operation and maintenance burden; at the same time, the double-side discharge can effectively share the discharge load of the single valve chamber, reduce the influence range of medium diffusion after discharge, and greatly eliminate the low-temperature problem caused by the pressure reduction of the pipeline during the discharge process, which provides support for the rapid production of the pipeline. More importantly, by identifying the low-point liquid accumulation and the low-temperature problem caused thereby, the discharge idea is innovated, which essentially guarantees the safety of the material.

[0030] (3) The valve chamber venting system and the medium introduction and heating system of the present application are detachably connected with the valve chamber cut-off system, which greatly reduces the investment of setting a fixed discharge system and the upstream and downstream medium introduction and heating system. The present application proposes a mode of reducing the operating pressure of the pipeline before planned shutdown, which can reduce the discharge amount of the pipeline planned venting, and also supports the rapid production to some extent. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 is a structural block diagram of the supercritical CO2 pipeline venting system based on double-side discharge according to an embodiment of the present application. DETAILED DESCRIPTION

[0032] Following, the embodiments of the present application are illustrated by specific examples, and other advantages and effects of the present application can be easily understood by those skilled in the art from the disclosure of this specification. The present application can also be implemented or applied by other different specific embodiments, and each detail in the specification can be modified or changed based on different views and applications without departing from the spirit of the present application. It should be noted that the following examples and features in the examples can be combined with each other without conflict.

[0033] All other embodiments obtained by those skilled in the art based on the embodiments of the present application without creative labor are within the scope of protection of the present application.

[0034] During the phase transition, the medium in the pipeline will experience different degrees of considerable temperature drop. During the release process, due to the influence of the pipeline undulation, the incompletely vaporized CO2 will tend to gather at the low point of the pipeline due to the influence of density, so that the pipeline section near the low point will experience more serious temperature drop, which may cause monitoring blind area of the distributed temperature detection and misjudgment of the temperature control in the release. In addition, due to the high pipeline pressure and large amount of medium in the pipeline, the release time of supercritical CO2 will be much longer than that of conventional natural gas pipelines. The prior art lacks a corresponding solution to solve the above problems.

[0035] In order to solve the above technical problems, the following embodiments of the supercritical CO2 pipeline emptying system and method based on double-side release of the present application are proposed.

[0036] Embodiment 1

[0037] The embodiment is based on the basic physical characteristics, phase change law and pipeline planned venting characteristics of supercritical CO2. In view of the characteristics of large pipe capacity (at least 8 km pipe length), high medium storage and uneven liquid accumulation in the ups and downs of the pipeline between the supercritical CO2 pipeline shut-off valves, from the aspects of safe diffusion, efficient venting and safe operation, the valve chamber shut-off system, the valve chamber venting system, the upstream and downstream medium introduction and heating system and the low point temporary temperature detection system are respectively set to realize the efficient and safe operation of the planned venting of the supercritical CO2 pipeline. The valve chamber shut-off system is arranged in the pipeline valve chamber and mainly includes the trunk shut-off valve, the bypass pipeline and the bypass instrument for shutting off the pipeline during the planned shutdown of the pipeline and supporting the segmented release. The valve chamber venting system includes the venting valve arranged in the valve chamber and the movable venting system to support the planned venting. The upstream and downstream medium introduction and heating system includes the bypass regulating valve arranged in the valve chamber and the movable water bath vaporizer to take the high-pressure CO2 from the pipeline upstream and downstream of the shut-off pipeline and heat it, continuously purge the shut-off pipeline, realize the medium temperature compensation of the shut-off pipeline and promote the gasification of the liquid phase in the low point gas-liquid two-phase state of the shut-off pipeline. The low point temporary temperature detection system includes the valve well temporarily arranged in the low point pipe section with serious liquid accumulation to add the temperature transmitter before the planned release for real-time monitoring of the medium temperature of the low point of the pipeline in the later stage of the planned release. Thus, the efficient, economical and safe planned venting of the supercritical CO2 pipeline is realized.

[0038] Reference Figure 1 As Figure 1 shown is a structure block diagram of the supercritical CO2 pipeline venting system based on the bilateral release of the embodiment.

[0039] The valve chamber shut-off system includes the shut-off valve arranged in the trunk. In the embodiment, it includes the trunk upstream shut-off valve 1, the trunk downstream shut-off valve 9, the bypass first shut-off valve 2, the bypass regulating valve 3, the bypass second shut-off valve 4, the bypass first temperature transmitter 5, the bypass first pressure transmitter 6, the bypass second temperature transmitter 7, the bypass second pressure transmitter 8 and the like. It is mainly used for shutting off the trunk of the pipeline before the planned maintenance or after the pipeline leakage to reduce the pipeline release amount. The bypass pipeline interface of the shut-off valve chamber is connected with the valve chamber venting system, the upstream and downstream medium introduction and heating system and the like to realize the efficient release of the shut-off pipeline by the valve chamber. At the same time, the bypass instrument is used for pressure and temperature detection at the point. In addition, the bypass regulating valve is used for safe medium charging of the pipeline after the maintenance. The valve chamber of the trunk downstream shut-off valve 9 is consistent with the valve chamber of the trunk upstream shut-off valve 1, so it is not described in detail in the embodiment.

[0040] The valve chamber venting system includes a venting cut-off valve 11, a venting regulating valve 12, a bypass venting regulating valve 13, an air bath heat exchanger 14, a venting vertical pipe 15 and the like arranged downstream of the valve chamber interface, for pressure regulating and releasing of supercritical CO2 in the pipeline after pipeline shutdown. It should be noted that the downstream of the venting cut-off valve 11 is a blind flange, which is connected with the movable venting system before venting; the movable venting system includes the venting regulating valve 12, the bypass venting regulating valve 13, the air bath heat exchanger 14, the venting vertical pipe 15 and the like arranged in a sled, and further includes temperature transmitters, flow transmitters and the like installed on the pipeline, which are pulled by a car. Similar interfaces are arranged in the downstream cut-off valve chamber, which have the same functions as the upstream cut-off valve chamber.

[0041] The venting cut-off valve 11 is arranged on the valve chamber bypass pipeline, which is a carbon steel manual ball valve, and is only opened when the trunk pipeline is vented, and the downstream end thereof is connected with a blind flange (which is replaced and connected with the movable venting system during venting); the venting regulating valve 12, the bypass venting regulating valve 13, the air bath heat exchanger 14, the venting vertical pipe 15 and the like form the movable venting system; the venting regulating valve 12 and the bypass venting regulating valve 13 are manually controlled regulating valves, which are made of stainless steel, the venting regulating valve 12 is a priority opening regulating valve, which is opened in the initial stage of venting (from supercritical state to a pressure interval close to 3 MPa); the bypass venting regulating valve 13 is opened in the late stage of venting (from 1.5 MPa to atmospheric pressure interval), which is used for coordinated operation, and under the premise that the temperature of the medium in the trunk is not lower than -15℃, the venting rate is as high as possible; the air bath heat exchanger 14 is made of stainless steel, which uses air as the heat exchange medium to increase the temperature of the vented CO2; the venting vertical pipe 15 is made of carbon steel, which is used to lift the vented CO2 to a safe venting height (preferably more than 15 m).

[0042] The upstream and downstream medium introduction and heating system includes a branch inlet cut-off valve 21, a branch outlet regulating valve 22, a flow regulating valve 23, an air bath vaporizer 24, a heater 25 and the like arranged downstream of the valve chamber interface, which is used to regulate the temperature of the liquid phase medium accumulated in the cut-off pipeline in the middle and late stages of venting of the cut-off pipeline, promote the temperature rise and vaporization of the liquid phase medium, overcome the low temperature problem caused by the pressure reduction and vaporization of the liquid phase medium, and improve the venting efficiency of the cut-off pipeline. Further, the flow regulating valve 23, the air bath vaporizer 24, the heater 25 and the like are arranged in a sled, and are pulled by a car.

[0043] Branch line inlet cutoff valve 21 and branch line outlet regulating valve 22 are arranged on the valve chamber bypass pipeline (upstream and downstream of bypass regulating valve 3 respectively), normally closed, carbon steel material, only opened when high-temperature medium needs to be introduced into the vent pipeline; flow regulating valve 23 is an automatic regulating valve, stainless steel material, used for pressure regulating and flow control of high-pressure CO2; air bath vaporizer 24 is stainless steel, using air as heat exchange medium to raise the temperature of the regulated CO2 by one stage; heater 25 is carbon steel, using hot medium (water) as heat exchange medium to raise the temperature of the regulated CO2 by the second stage, and the target temperature is preferably set to 70°C. Flow regulating valve 23, air bath vaporizer 24, heater 25, etc. are implemented in a pry, pulled by a car, and the introduced and heated medium is continuously sent into the cutoff pipeline to forcibly exchange heat with the accumulated liquid phase in the cutoff pipeline, stimulate vaporization, and avoid over-low temperature caused by pressure reduction vaporization of the accumulated liquid phase.

[0044] Low point temporary temperature detection system is arranged near the pipeline maximum liquid accumulation position determined according to the relief simulation, including first cutoff valve 31 and second cutoff valve 32 of the main branch, and a temporarily accessible temperature transmitter is configured to detect the medium temperature at the pipeline low point in real time when the cutoff pipeline is relieved, guiding the regulation of the vent rate.

[0045] The working principle of the supercritical CO2 pipeline venting system based on bilateral relief provided by the embodiment is as follows:

[0046] (1) In normal operating conditions, supercritical phase state is used to transport CO2 to improve the transportation efficiency as much as possible. Under this transportation condition, the density of CO2 can reach more than 850 kg / m3. Before the pipeline is planned to stop transportation, a method of reducing the transportation pressure is proposed to reduce the mass of the accumulated medium in the pipeline, but the transportation phase state is still stable. Further, in order to improve the accuracy of low point liquid accumulation and low point temperature detection, the embodiment proposes to use relief simulation analysis software to simulate the relief of the cutoff pipeline to determine the most serious liquid accumulation pipeline section and provide guidance for selecting the valve chamber of the upstream and downstream medium introduction and heating system.

[0047] (2) Because the long-distance pipeline is laid along the terrain, there is an elevation problem. For a conventional natural gas pipeline, after planned shutdown, the target pipe section (the pipe section between the block valves) is discharged in the block valve chamber, and the discharge time is generally 6-8 hours. For supercritical CO2 medium, there are problems such as phase change (supercritical phase, gas-liquid two-phase, gas phase) during the discharge process, temperature reduction of the medium in the pipeline caused by phase change, and gas-liquid two-phase medium separation caused by terrain undulation, especially the gas-liquid two-phase separation caused by terrain undulation, which will cause the medium temperature in the low terrain section of the pipeline to be significantly lower than that in the high terrain section of the same pipeline, so the discharge rate should be identified and controlled. Further, in the front section of the discharge, because the medium pressure in the main line is always high, it will not cause the temperature of the main line to be too low, so the discharge rate can be increased in the front section of the discharge, so this embodiment recommends bilateral discharge, which reduces the load of unilateral discharge on one hand, and bilateral discharge at the same time helps to improve the discharge efficiency. On the problem of pipeline liquid accumulation, by setting the upstream and downstream medium introduction and heating system, CO2 is introduced from the upstream or downstream main line and heated at high temperature to heat and vaporize the low-pressure liquid in the pipeline to be discharged, which greatly improves the vaporization rate (compared with natural heat exchange with the environment).

[0048] (3) For the discharge system, this embodiment proposes to use a movable discharge system mode, which aims to set a more flexible movable discharge system that can minimize construction investment, and the part of the system can radiate multiple pipe sections at the same time.

[0049] (4) In order to ensure the safety of the pipeline, this embodiment proposes to monitor the temperature of the medium in the pipeline during the discharge process to avoid the temperature of the medium in the pipeline being lower than -15℃; in order to improve the low-temperature identification rate, this embodiment proposes to set a temperature transmitter at the low point of the pipeline.

[0050] Based on the above emptying system, this embodiment provides a supercritical CO2 pipeline planned emptying method based on bilateral discharge, which specifically includes the following steps:

[0051] Step 1: During normal transportation, keep the upstream block valve 1 and the downstream block valve 9 of the main line open, and the main line normally transports supercritical CO2; close each branch valve. The valve chamber emptying system, the upstream and downstream medium introduction and heating system, and the low point temporary temperature detection system are not connected to the main line system. By using a flow simulation software, the maximum liquid accumulation position of the blocked pipeline during the discharge process is determined, so as to determine the setting position of the low point temporary temperature detection system of the pipeline, and the valve chamber position where the upstream and downstream medium introduction and heating system is installed (the upstream and downstream medium introduction and heating system should be selected to be closer to the valve chamber with the maximum liquid accumulation position).

[0052] Step two: Before the scheduled maintenance of the pipeline, reduce the pipeline throughput, monitor the temperature transmitter and pressure transmitter parameters at various points along the line, keep the pipeline pressure only 0.5 MPa higher than the corresponding minimum temperature of the medium saturated steam pressure, reduce the medium inventory in the pipeline during the scheduled release by reducing the medium density. Then, slowly close the upstream shutoff valve 1 and the downstream shutoff valve 9 of the main line to achieve pipeline shutdown.

[0053] Step three: Connect the valve chamber venting system at both ends of the cutoff pipeline to the venting shutoff valve of the valve chamber cutoff system. Open the venting regulating valve 12, bypass venting regulating valve 13, air bath heat exchanger 14, venting vertical pipe 15, etc., and according to the maximum allowable venting amount of the single-sided valve chamber (determined by CO2 diffusion analysis after release, the venting amount is monitored by the flow transmitter of the venting system), the main line pipeline is vented from supercritical state to gas-liquid two-phase state (the venting pressure range is from the initial pressure to about 3 MPa); continuously monitor the temperature transmitter and pressure transmitter values at each low-altitude point, when the temperature transmitter temperature is lower than -15℃, immediately reduce the release amount by adjusting the venting regulating valve 12 and bypass venting regulating valve 13, when the low point pressure approaches about 3 MPa, close the bypass venting regulating valve 13. In this step, the upstream valve chamber and the downstream valve chamber are released cooperatively, and the values of the temperature transmitters of the two valve chambers and the low point temperature transmitters need to be monitored simultaneously.

[0054] Step four: According to the valve chamber selected in step one for installing the upstream and downstream medium introduction and heating system (in this example, the valve chamber where the upstream shutoff valve 1 of the main line is located is selected as the valve chamber for installing the upstream and downstream medium introduction and heating system, and the valve chamber where the downstream shutoff valve 9 of the main line is located is selected as the valve chamber for subsequent release), connect the upstream and downstream medium introduction and heating system downstream of the branch line inlet shutoff valve 21, close the venting shutoff valve 11, but still keep the movable venting system of the downstream valve chamber connected. Open the branch line inlet shutoff valve 21, branch line outlet regulating valve 22, flow regulating valve 23, air bath vaporizer 24, heater 25, etc. in an orderly manner, maintain the consistency of the upstream introduced CO2 amount and the downstream discharged CO2, and maintain the upstream introduced CO2 at about 70℃ after multi-stage warming. When the low point temperature transmitter temperature continuously rises to 20℃, temporarily close the branch line inlet shutoff valve 21, and use the venting system of the downstream valve chamber to vent the medium in the cutoff pipeline. During the venting process, continue to monitor the temperature of the low point temperature transmitter, and when the temperature is lower than -20℃, open the branch line inlet shutoff valve 21 and the heating system again; repeat the operation until the medium in the cutoff pipeline is completely released.

[0055] In this way, efficient scheduled venting of supercritical CO2 pipeline is achieved.

[0056] The embodiment is based on the basic physical characteristics, phase change law and planned venting characteristics of the supercritical CO2, and in view of the characteristics of the large pipe volume (at least 8 km of pipe length) between the supercritical CO2 pipe cut-off valves, high medium storage, and uneven liquid accumulation in the undulating pipe, from the aspects of efficient discharge, promoting liquid accumulation vaporization, safe operation and the like, the valve chamber cut-off system, the valve chamber venting system, the upstream and downstream medium introduction and heating system, and the low point temporary temperature detection system are respectively set, compared with the conventional means, the safe discharge rate can be greatly improved, the operating temperature of the trunk pipeline during the discharge process is improved, the efficient and safe operation of the supercritical CO2 pipeline planned venting is realized, and thus the efficient, economic and safe supercritical CO2 pipeline planned venting is realized.

[0057] The upstream (or downstream) trunk pipe medium introduction scheme is innovatively adopted in the embodiment, the number of openings in the pipeline non-cut-off valve area is avoided, and the pipeline leakage probability and operation and maintenance burden are reduced; meanwhile, the double-side discharge can effectively share the discharge load of the single valve chamber, reduce the influence range of medium diffusion after discharge, and greatly eliminate the low-temperature problem caused by the pressure reduction of the pipeline medium during the discharge process, and support the rapid production of the pipeline. More importantly, by identifying the low point liquid accumulation and the low temperature problem caused thereby, the discharge idea is innovated, and the material safety is essentially guaranteed.

[0058] The valve chamber venting system and the medium introduction and heating system of the embodiment are detachably connected with the valve chamber cut-off system, and the investment of the fixed discharge system and the upstream and downstream medium introduction and heating system is greatly reduced. The embodiment proposes a mode of reducing the pipeline operating pressure before the planned shutdown, so that the discharge amount of the pipeline planned venting can be reduced, and the rapid production is also supported to some extent.

[0059] The above only describes the preferred embodiments of the present application and is not used to limit the present application, and any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A supercritical CO2 pipeline venting system based on double-sided discharge, the pipeline venting system is arranged on the main line of the CO2 pipeline, characterized in that: The pipeline venting system includes: A valve chamber shutoff system, comprising a first valve chamber shutoff subsystem disposed upstream of the main line and a second valve chamber shutoff subsystem disposed downstream of the main line, the valve chamber shutoff system being used to shut off the main line of the pipeline, the first valve chamber shutoff subsystem and the second valve chamber shutoff subsystem comprising bypass pipe interfaces, the bypass pipe interfaces being used to connect the valve chamber venting system and the medium introduction and heating system; A valve chamber venting system, comprising a first valve chamber venting subsystem in communication with the first valve chamber shutoff subsystem and a second valve chamber venting subsystem in communication with the second valve chamber shutoff subsystem, for regulating the pressure and releasing supercritical CO2 in the pipeline after pipeline transportation is stopped; a medium introduction and heating system for regulating the temperature of the liquid phase medium accumulated in the cut-off pipeline by injecting a high-temperature medium into the cut-off pipeline; A low-point temporary temperature detection system, the low-point temporary temperature detection system being set at a maximum liquid accumulation position in the pipeline determined according to the discharge simulation; The low point temporary temperature detection system includes a first shut-off valve of the main branch and a second shut-off valve of the main branch connected in series in sequence. The input end of the first shut-off valve of the main branch is connected to the maximum liquid accumulation position of the main line of the pipeline, and the output end of the second shut-off valve of the main branch is also provided with a connection port for connecting a temperature transmitter.

2. The supercritical CO2 pipeline venting system based on double-sided discharge according to claim 1 is characterized in that: The first valve chamber shut-off subsystem and the second valve chamber shut-off subsystem both include a shut-off valve arranged on the main line, a main line bypass connected in parallel with the main line, and a bypass regulating valve. The two ends of the main line bypass are respectively connected to the main line of the pipeline at both ends of the shut-off valve. The bypass regulating valve divides the main line bypass into a first main line bypass and a second main line bypass. The first main line bypass is connected to the main line pipeline where the input end of the shut-off valve is located, and the second main line bypass is connected to the main line pipeline where the output end of the shut-off valve is located. The first main line bypass and the second main line bypass are respectively provided with bypass shut-off valves. Temperature monitoring equipment and pressure monitoring equipment are also provided between the bypass shut-off valve and the main line of the pipeline.

3. The supercritical CO2 pipeline venting system based on double-sided discharge according to claim 2 is characterized in that: The bypass pipeline interface includes a first bypass pipeline interface provided between the bypass cut-off valve of the first trunk bypass and the bypass regulating valve, a second bypass pipeline interface provided between the bypass regulating valve and the bypass cut-off valve of the second trunk bypass, and a third bypass pipeline interface provided between the second bypass pipeline interface and the bypass cut-off valve of the second trunk bypass; The medium introduction and heating system is connected to the valve chamber shutoff system through a first bypass pipe interface and a second bypass pipe interface; The valve chamber venting system is communicated with the valve chamber shutoff system through a third bypass pipeline interface.

4. The supercritical CO2 pipeline venting system based on double-sided discharge according to claim 3 is characterized in that: The medium introduction and heating system includes a drainage regulating valve, a vaporizer and a heater connected in series in sequence. The input end of the drainage regulating valve is connected to the first bypass pipe interface through a branch inlet shut-off valve, and the output end of the heater is connected to the second bypass pipe interface through a branch outlet regulating valve.

5. The supercritical CO2 pipeline venting system based on double-sided discharge according to claim 3 is characterized in that: The valve chamber venting system includes a vent regulating valve and a bypass vent regulating valve connected in parallel. The input ends of the vent regulating valve and the bypass vent regulating valve are connected to the third bypass pipeline interface through a vent shut-off valve. The output ends of the vent regulating valve and the bypass vent regulating valve are connected in series with a heat exchanger and a vent riser in sequence.

6. The supercritical CO2 pipeline venting system based on double-sided discharge according to claim 1 is characterized in that: The valve chamber venting system and the valve chamber shutoff system are detachably connected; the medium introduction and heating system and the valve chamber shutoff system are detachably connected.

7. A supercritical CO2 pipeline venting method based on double-sided discharge, characterized in that: The method is performed based on the pipeline venting system according to any one of claims 1 to 6, and the method comprises: During normal transportation, the valve chamber shutoff system and the low-point temporary temperature detection system are not connected to the pipeline main line. The maximum liquid accumulation position in the shutoff pipeline during the emptying process is determined as the setting position of the low-point temporary temperature detection system; Before a planned pipeline maintenance, reduce the pipeline flow rate, monitor the temperature and pressure at various points along the pipeline, and maintain the difference between the pipeline pressure and the saturated vapor pressure of the medium at the corresponding lowest temperature at the preset pressure value. Reduce the medium inventory in the pipeline during planned discharge by reducing the medium density, and open the valve chamber to cut off the system to stop the pipeline flow; The main line and valve chamber shutoff system of the pipeline are connected, and the main line pipeline is vented from a supercritical state to a gas-liquid two-phase state according to the maximum allowable venting volume of the first valve chamber shutoff subsystem and the second valve chamber shutoff subsystem. The temperature and pressure of each preset point are continuously monitored. When the temperature is lower than the preset temperature threshold, the discharge volume of the valve chamber venting system is reduced. When the pressure is lower than the preset pressure threshold, the venting of the valve chamber venting system is stopped. Select the valve chamber cut-off subsystem to access the medium introduction and heating system, close the valve chamber venting subsystem corresponding to the valve chamber cut-off subsystem where the medium introduction and heating system is located, keep the other valve chamber venting subsystem in a connected state, open the medium introduction and heating system, maintain the consistency of the amount of CO2 introduced and discharged upstream and downstream of the trunk line, and make the amount of CO2 introduced reach the first preset temperature to enter the trunk line of the pipeline. When the temperature of the temperature transmitter of the low point temporary temperature detection system continues to rise to the second preset temperature, close the entrance of the medium introduction and heating system, and use the valve chamber venting subsystem without a medium introduction and heating system to vent the medium in the trunk line of the pipeline.

8. The supercritical CO2 pipeline venting method based on double-sided discharge according to claim 7, characterized in that: The medium introduction is connected to the heating system and the valve chamber cutoff subsystem closer to the maximum liquid accumulation position, and the valve chamber venting system is opened.

9. The supercritical CO2 pipeline venting method based on double-sided discharge according to claim 7, characterized in that: The method further comprises: During the venting process, the temperature of the temperature transmitter of the low point temporary temperature detection system is continuously monitored. When the temperature is lower than the third preset temperature, the medium introduction and heating system are turned on again until all the main line medium of the pipeline is discharged.

Images