CN111878708A - Dense-phase carbon dioxide pipeline safety discharge system and method - Google Patents
Dense-phase carbon dioxide pipeline safety discharge system and method Download PDFInfo
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- CN111878708A CN111878708A CN202010755342.XA CN202010755342A CN111878708A CN 111878708 A CN111878708 A CN 111878708A CN 202010755342 A CN202010755342 A CN 202010755342A CN 111878708 A CN111878708 A CN 111878708A
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
- F17D—PIPE-LINE SYSTEMS; PIPE-LINES
- F17D1/00—Pipe-line systems
- F17D1/005—Pipe-line systems for a two-phase gas-liquid flow
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
- F17D—PIPE-LINE SYSTEMS; PIPE-LINES
- F17D3/00—Arrangements for supervising or controlling working operations
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Abstract
The invention discloses a dense-phase carbon dioxide pipeline safety relief system and a dense-phase carbon dioxide pipeline safety relief method. The dense-phase carbon dioxide pipeline emptying system is based on the characteristics of a dense-phase carbon dioxide pipeline operation process, combines a conventional oil pipeline maintenance and discharge scheme, considers the characteristics of dense-phase carbon dioxide low-temperature solidification, and effectively avoids the risk of formation of dry ice in the dense-phase carbon dioxide pipeline emptying system, effectively guarantees the material safety of the main pipeline discharge pipeline and realizes the safe discharge of the dense-phase carbon dioxide pipeline by arranging units such as a two-stage discharge system, an interstage heat exchange system, a main pipeline temperature detection system, a control system and the like.
Description
Technical Field
The invention belongs to the technical field of carbon dioxide discharge, and particularly relates to a dense-phase carbon dioxide pipeline safety discharge system and method.
Background
With the increasing of energy conservation and emission reduction and environmental protection requirements in the energy and chemical industry and the improvement of carbon dioxide oil displacement and yield increasing technologies, the long-distance carbon dioxide transportation through pipelines becomes an important way for promoting and realizing the efficient capture, storage and utilization of carbon dioxide. The critical temperature of carbon dioxide is about 31.1 ℃, the critical pressure is about 7.38MPa.g, and when the carbon dioxide is transported by a long distance pipeline, a dense phase transportation mode with the pressure higher than the critical pressure is generally adopted to improve the economical efficiency of transportation. In addition, the carbon dioxide has the characteristic of solid stating at low temperature, and the triple point of the pure carbon dioxide is-56.6 ℃ and 0.518MPa.g, which is a remarkable characteristic that the carbon dioxide is different from the conventional hydrocarbon medium.
Similar to conventional hydrocarbon pipelines, carbon dioxide pipelines need to be provided with a block valve chamber along the way and provide a relief function before pipeline maintenance, so that efficient maintenance of a pipeline section with potential safety hazards is guaranteed, and the total medium discharge volume is reduced. For conventional hydrocarbons, when the pipeline is drained, the problem of low temperature caused by vaporization of the medium after drainage needs to be considered, and the safety of the emptying process is ensured by selecting proper materials. In contrast, for a dense-phase-conveyed carbon dioxide pipeline, when pressure relief is directly performed on the carbon dioxide pipeline, and the emptying medium is discharged to the atmosphere, the temperature of the discharged medium is close to-90 ℃ possibly caused by the adiabatic expansion process of the dense-phase-state medium, and in addition, the emptying back pressure exists in the emptying pipeline, so that the temperature and the pressure of the emptying medium easily enter a solid phase forming area, the formation risk of dry ice is caused, the blockage of the emptying pipeline or a pipe fitting is caused, the normal emptying operation is influenced, and even potential safety hazards are caused. Therefore, reasonable measures should be taken for the dense-phase carbon dioxide pipeline emptying system, and the safety problem caused by dry ice is avoided.
At present, related documents report more carbon dioxide pipeline conveying technology, mainly focus on the problems of pipeline routing selection, conveying phase state control, pipeline material selection and the like, pay attention to the problem of low-temperature dry ice during emptying, but the problems are reported by research results of a solution and have no configuration requirement of a safe emptying system.
Disclosure of Invention
The invention aims to: aiming at the existing problems, in order to further promote the development of dense-phase carbon dioxide pipeline conveying technology and guarantee the operation safety, an economical and reasonable mode is provided for safely discharging carbon dioxide, and the problem of channel blockage caused by dry ice due to low temperature of a medium in the discharging process is avoided, so that the industry technology development and progress are promoted.
The main technical idea of the invention is based on the operation process characteristics of the dense-phase carbon dioxide pipeline, combines the conventional oil pipeline maintenance and discharge scheme, considers the characteristics of dense-phase carbon dioxide low-temperature solidification (forming dry ice), and not only effectively avoids the risk of the dense-phase carbon dioxide pipeline emptying system formed by the dry ice by arranging units such as a two-stage discharge system, an interstage heat exchange system, a main line temperature detection system, a control system and the like, but also effectively ensures the material safety of the main line discharge pipeline and realizes the safe discharge of the dense-phase carbon dioxide pipeline. Furthermore, by arranging the movable module, the efficient reuse of the carbon dioxide relief device in a plurality of trunk valve chambers is realized, and the construction cost is reduced.
The technical scheme adopted by the invention is as follows: a dense phase carbon dioxide pipeline safety relief system which characterized in that: the system comprises a dense-phase carbon dioxide pipeline conveying and intercepting system, a valve chamber bypass system, a two-stage relief system and a pipeline temperature and pressure detection system;
the dense-phase carbon dioxide pipeline conveying and cutting system comprises an upstream trunk, a trunk cutting valve and a downstream trunk which are sequentially connected, wherein the upstream trunk and the downstream trunk are used for connecting the upstream and downstream pipelines and forming a dense-phase carbon dioxide conveying channel, and the trunk cutting valve is used for controlling the communication or cutting between the upstream trunk and the downstream trunk;
the valve chamber bypass system comprises a valve chamber bypass and a bypass block valve group arranged on the valve chamber bypass, wherein a pipeline of the valve chamber bypass is connected out of an upstream trunk line of a trunk line block valve and is connected in by a downstream trunk line of the trunk line block valve to form a trunk line bypass, and the valve chamber bypass system is used for providing a maintenance emptying bypass of the upstream trunk line and the downstream trunk line after the trunk line is blocked and providing a communication bypass when the upstream trunk line or the downstream trunk line is ready to be restarted;
the two-stage discharge system is used for carrying out stage pressure relief on dense-phase carbon dioxide, an interstage heat exchange system is arranged in the two-stage discharge system, and the interstage heat exchange system is used for carrying out temperature regulation on a medium discharged from the previous stage.
The dense-phase carbon dioxide pipeline safety relief system is characterized in that a bypass cut-off valve group arranged on a bypass of the valve chamber consists of a bypass front-section cut-off valve and a bypass rear-section cut-off valve, and the bypass front-section cut-off valve and the bypass rear-section cut-off valve are respectively used for controlling relief channels of an upstream trunk line and a downstream trunk line.
According to the dense-phase carbon dioxide pipeline safety discharge system, the bypass pipeline between the upstream trunk line and the bypass front-section block valve is a bypass front-section pipeline, the bypass pipeline between the bypass front-section block valve and the bypass rear-section block valve is a bypass middle-section pipeline, and the bypass pipeline between the bypass rear-section block valve and the downstream trunk line is a bypass rear-section pipeline.
The dense-phase carbon dioxide pipeline safety relief system comprises a first-stage relief valve, a second-stage relief valve, a relief liquid tank and a relief vertical pipe, wherein the inlet end of the first-stage relief valve is connected with a bypass middle-section pipeline through a relief branch pipeline, the outlet end of the first-stage relief valve is connected with the inlet end of the second-stage relief valve through a first-stage relief pipeline, the outlet end of the second-stage relief valve is connected with the relief vertical pipe through a second-stage relief pipeline, the interstage heat exchange system is arranged on the first-stage relief pipeline between the first-stage relief valve and the second-stage relief valve, and the relief liquid tank is arranged on the second-stage relief pipeline between the second-stage relief valve and the relief vertical pipe.
The dense-phase carbon dioxide pipeline safety discharge system comprises an inlet pipeline, a heating vaporizer and an outlet pipeline, wherein the heating vaporizer is used for exchanging medium and ambient heat for low-temperature carbon dioxide discharged at a first stage, the inlet pipeline is connected with the front section of the first-stage discharge pipeline, and the outlet pipeline is connected with the rear section of the downstream first-stage discharge pipeline.
According to the dense-phase carbon dioxide pipeline safety discharge system, the heating vaporizer selects the air-temperature vaporizer or the electric heating water bath vaporizer according to the environmental conditions, namely, if the temperature of the operation environment is higher than 0 ℃, the heating vaporizer adopts the air-temperature vaporizer, and if the temperature of the operation environment is lower than 0 ℃, the heating vaporizer adopts the electric heating water bath vaporizer.
The dense-phase carbon dioxide pipeline safety relief system is characterized in that an air injection valve is arranged between the bypass front section block valve and the primary relief valve.
The invention relates to a dense-phase carbon dioxide pipeline safety discharge system, which comprises a bypass front-section temperature transmitter and a bypass front-section pressure transmitter which are arranged on a bypass front-section pipeline, a bypass rear-section temperature transmitter and a bypass rear-section pressure transmitter which are arranged on a bypass rear-section pipeline, a discharge branch pressure transmitter which is arranged on a discharge branch pipeline, a primary discharge branch pressure transmitter and a primary discharge branch temperature transmitter which are arranged on a primary discharge pipeline front-section pipeline, and a secondary discharge branch temperature transmitter which is arranged on a primary discharge pipeline rear-section pipeline.
According to the dense-phase carbon dioxide pipeline safety discharge system, the two-stage discharge system and the interstage heat exchange system are in a skid-mounted mode.
A dense phase carbon dioxide pipeline safety discharge method is characterized in that: the method comprises the following steps:
the method comprises the following steps: the dense-phase carbon dioxide pipeline safety relief system is arranged on a pipeline trunk line for conveying dense-phase carbon dioxide and comprises a dense-phase carbon dioxide pipeline conveying and intercepting system, a valve chamber bypass system, a two-stage relief system, an interstage heat exchange system and a pipeline temperature and pressure detection system;
step two: when the pipeline conveying system needs to stop conveying and maintenance in an upstream main line, a starting-point external conveying pump of the pipeline conveying system, a main line cut-off valve of the station, a main line cut-off valve of an adjacent upstream valve chamber and a downstream tail end cut-off valve are closed, and when a movable two-stage relief system and an interstage heat exchange system are adopted, the two-stage relief system and the interstage heat exchange system are pryingly conveyed to the valve chamber and are connected to a valve chamber bypass system after maintenance and shutdown;
step three: keeping a bypass front-section block valve, a bypass rear-section block valve, a first-stage discharge valve and a second-stage discharge valve closed, injecting nitrogen into a pipe section between the bypass front-section block valve and the first-stage discharge valve, wherein the pressure is the same as the stop pressure of a main pipeline, injecting nitrogen into the pipe section between the first-stage discharge valve and the second-stage discharge valve, and controlling the pressure to be 2-2.2 MPa.g;
step four: configuring the type of a vaporizer according to the ambient temperature, and selecting an air-temperature vaporizer if the air temperature of the operating environment is higher than 0 ℃ to ensure that the temperature of the heated medium is higher than-5 ℃; if the ambient temperature is lower than 0 ℃, an electric heating water bath vaporizer is selected, and the temperature of the heated medium is ensured to be higher than-5 ℃;
step five: firstly, opening a bypass cut-off valve group and a primary pressure release valve, starting a heating vaporizer, slowly opening a secondary pressure release valve, and discharging a release medium into the atmosphere from an emptying vertical pipe after the release medium is vaporized;
specifically, the pressure in the primary discharge pipeline is controlled to be stabilized at 2-2.2MPa.g, the temperature of a medium at the outlet of the heating vaporizer is controlled to be higher than-5 ℃, the temperature of a medium in the main pipeline is controlled to be higher than-20 ℃, when the upstream main line pressure is reduced to 2MPa.g, the pressure in the primary discharge pipeline is controlled to be stabilized at 1-1.2MPa.g, the temperature of the medium at the outlet of the heating vaporizer is controlled to be higher than-5 ℃, the temperature of the medium in the main pipeline is controlled to be higher than-20 ℃, when the upstream main line pressure is reduced to 1MPa.g, the discharge valve is completely opened, and the secondary discharge valve is utilized to complete the subsequent discharge operation;
step six: when the pressure of the main pipeline is reduced to 0.1MPa.g, dry air is injected from the upstream block valve chamber to replace carbon dioxide still in the pipeline and is discharged from the emptying system of the local valve chamber.
Compared with the prior art, the invention has the beneficial effects that:
the dense-phase carbon dioxide pipeline emptying system is based on the characteristics of a dense-phase carbon dioxide pipeline operation process, combines a conventional oil pipeline maintenance and discharge scheme, considers the characteristics of dense-phase carbon dioxide low-temperature solidification, and effectively avoids the risk of formation of dry ice in the dense-phase carbon dioxide pipeline emptying system, effectively guarantees the material safety of the main pipeline discharge pipeline and realizes the safe discharge of the dense-phase carbon dioxide pipeline by arranging units such as a two-stage discharge system, an interstage heat exchange system, a main pipeline temperature detection system, a control system and the like. Further, through setting up portable module, realize that carbon dioxide bleeder's high efficiency is multiplexing.
The concrete expression is as follows:
(1) science of setup
The system focuses on the requirements of dense-phase carbon dioxide pipeline maintenance and discharge, and focuses on the problem that dense-phase carbon dioxide generates large temperature drop after pressure reduction and forms dry ice. Because the temperature change has little influence on adiabatic discharge when dense-phase carbon dioxide is in a dense-phase state, the temperature after discharge cannot be effectively improved by conventional discharge after heating. Therefore, on the arrangement concept of a conventional hydrocarbon pipeline emptying system, the number of discharge stages is increased, the method of combining graded pressure discharge with interstage heat exchange is utilized, the carbon dioxide (gas phase and liquid phase) subjected to primary pressure discharge is fully heated by means of the external environment, the temperature of the medium after secondary pressure reduction is always higher than the formation temperature of dry ice, and therefore safe discharge is guaranteed.
(2) Is economical and reasonable
The valve chamber relief system is prefabricated in a skid-mounted mode, so that reuse of a plurality of emptying systems similar to the valve chambers can be realized, and the economy of the system is embodied. Meanwhile, the form of the vaporizer is selected according to the ambient temperature, and the air-temperature vaporizer is preferably selected, so that the carbon dioxide heat exchange without energy consumption is basically realized. In addition, the problem of dense-phase carbon dioxide emptying can be solved by adopting low-temperature carbon steel by utilizing a mode of combining two-stage discharge with interstage heat exchange, and the arrangement concept of a stainless steel emptying system in conventional arrangement is avoided.
(3) Promote the development of technology
In view of the fact that the dense-phase carbon dioxide pipeline is still in a starting stage in the development of China, the method is beneficial to further development of medium discharge safety processing technology of the dense-phase carbon dioxide pipeline and also beneficial to the idea popularization of a movable discharge system in a special medium pipeline conveying engineering valve chamber.
Drawings
The invention will be described by way of specific embodiments and with reference to the accompanying drawings, in which
FIG. 1 is a schematic diagram of the system of the present invention.
The labels in the figure are: 1 is the upper reaches trunk, 2 is the trunk shutoff valve, 3 is the low reaches trunk, 4 is bypass anterior segment temperature transmitter, 5 is bypass anterior segment pressure transmitter, 6 is bypass back end temperature transmitter, 7 is bypass back end pressure transmitter, 8 is bypass anterior segment shutoff valve, 9 is bypass back end shutoff valve, 10 is the gas injection valve, 11 is bypass anterior segment pipeline, 12 is bypass middle segment pipeline, 13 is bypass back end pipeline, 21 is the relief branch pipeline, 22 is the one-level relief pipeline, 23 is the second grade relief pipeline, 24 is the one-level relief valve, 25 is the second grade relief valve, 26 is the vaporizer that heats, 27 is the unloading knockout drum, 28 is the unloading riser, 29 is the branch pressure transmitter of bleeding, 30 is the one-level relief branch pressure transmitter, 31 is the one-level relief branch temperature transmitter, 32 is the branch temperature transmitter of bleeding of second grade.
Detailed Description
All of the features disclosed in this specification, or all of the steps in any method or process so disclosed, may be combined in any combination, except combinations of features and/or steps that are mutually exclusive.
Any feature disclosed in this specification (including any accompanying claims, abstract) may be replaced by alternative features serving equivalent or similar purposes, unless expressly stated otherwise. That is, unless expressly stated otherwise, each feature is only an example of a generic series of equivalent or similar features.
As shown in fig. 1, a dense phase carbon dioxide pipeline safety relief system comprises a dense phase carbon dioxide pipeline conveying and intercepting system, a valve chamber bypass system, a two-stage relief system and a pipeline temperature and pressure detection system.
Specifically, the dense-phase carbon dioxide pipeline conveying and intercepting system comprises an upstream trunk line 1, a trunk line intercepting valve 2 and a downstream trunk line 3 which are connected in sequence, wherein the upstream trunk line 1 and the downstream trunk line 3 are used for connecting the upstream and downstream pipelines and forming a dense-phase carbon dioxide conveying channel, and the trunk line intercepting valve 2 is used for controlling the communication or the interception between the upstream trunk line 1 and the downstream trunk line 3. In the embodiment, the upstream trunk line 1 is buried underground, and the pipeline is made of carbon steel; the trunk line block valve 2 is a full-diameter block valve with an automatic block function, is made of carbon steel and is installed in a buried manner; the downstream trunk line 3 is buried underground, the material of the pipeline is carbon steel, and the opening is arranged on the upstream pipeline and the downstream pipeline close to the trunk line block valve 2 and connected with the valve chamber bypass pipeline.
Specifically, the valve chamber bypass system comprises a valve chamber bypass and a bypass block valve set arranged on the valve chamber bypass, wherein the pipeline of the valve chamber bypass is connected out of an upstream trunk line 1 of a trunk block valve 2 and is connected in by a downstream trunk line 3 of the trunk block valve 2 to form a trunk line bypass and play a role of communicating the upstream trunk line and the downstream trunk line, the valve chamber bypass system is used for providing a service emptying bypass of the upstream trunk line 1 and the downstream trunk line 3 after the trunk line is blocked and providing a communication bypass when the upstream trunk line 1 or the downstream trunk line 2 is ready to be restarted.
The bypass block valve set arranged on the valve chamber bypass line consists of a bypass front-section block valve 8 and a bypass rear-section block valve 9, the bypass front-section block valve and the bypass rear-section block valve are manual ball valves and are normally closed, and the bypass front-section block valve and the bypass rear-section block valve are made of carbon steel and are consistent in size with a valve chamber bypass pipeline and used for communicating an upstream trunk line, a valve chamber bypass line, a downstream trunk line and an emptying system; the bypass pipeline between the upstream main line 1 and the bypass front-section block valve 8 is a bypass front-section pipeline 11, the bypass pipeline between the bypass front-section block valve 8 and the bypass rear-section block valve 9 is a bypass middle-section pipeline 12, the bypass pipeline between the bypass rear-section block valve 9 and the downstream main line 3 is a bypass rear-section pipeline 13, the bypass front-section pipeline, the bypass middle-section pipeline and the bypass rear-section pipeline are all made of carbon steel, the pipe diameter is preferably DN100, the bypass front-section block valve 8 and the bypass rear-section block valve 9 are installed in a exposed mode, the design pressure is consistent with that of the main line pipeline, and the bypass front-section block valve 8 and the bypass rear-section block valve 9 are respectively used for controlling the discharge channels.
Specifically, the two-stage discharge system is used for emptying an upstream main line or a downstream main line to be overhauled and performing graded pressure relief on dense-phase carbon dioxide, an interstage heat exchange system is arranged between at least two adjacent stages of pressure relief in the two-stage discharge system and is used for adjusting the temperature of a medium discharged by the previous stage, the temperature of the carbon dioxide is properly increased, dry ice generated after subsequent two-stage discharge is avoided, the requirement on material selection of a pipeline is further reduced, and the two-stage discharge system and the interstage heat exchange system adopt a skid-mounted mode. In this embodiment, a two-stage discharge mode is adopted, and the interstage heat exchange system is arranged between two-stage discharge, namely external heat input is provided after the first-stage pressure discharge, the medium temperature is moderately raised, and then the medium enters the second-stage pressure discharge, so that dry ice is prevented from being formed in the medium in the pressure discharge process.
Wherein, the two-stage discharge system comprises a one-stage discharge valve 24, a two-stage discharge valve 25, a discharge liquid tank 27 and a discharge vertical pipe 28, the inlet end of the one-stage discharge valve 24 is connected with the bypass middle-stage pipeline 12 through a discharge branch pipeline 21, the outlet end of the one-stage discharge valve 24 is connected with the inlet end of the two-stage discharge valve 25 through a one-stage discharge pipeline 22, the one-stage discharge valve is used for performing one-stage discharge to discharge dense-phase medium to gas-liquid two-phase, an air injection valve 10 is arranged between the bypass front-stage block valve 8 and the one-stage discharge valve 24, the air injection valve is a manual ball valve and made of carbon steel, has the size of DN50, is provided with a short section and a normally closed valve, and is used for injecting gas into the pipeline to regulate pressure during discharge, the outlet end of the two-stage discharge valve 25 is connected with the discharge vertical pipe 28 through a two-stage discharge pipeline 23, the, the interstage heat exchange system is arranged on a first-stage discharge pipeline 22 between a first-stage discharge valve 24 and a second-stage discharge valve 25, the air discharge liquid tank 27 is arranged on a second-stage discharge pipeline 23 between the second-stage discharge valve 25 and an air discharge vertical pipe 28, the air discharge liquid tank is used for buffering a discharge medium and temporarily separating, storing and regasifying a possibly entrained liquid phase, and the air discharge vertical pipe is used for safely discharging carbon dioxide decompressed to normal pressure (or slight positive pressure) to the atmosphere.
In this embodiment, the relief branch pipeline is made of carbon steel, the design pressure is the same as that of the bypass middle-stage pipeline, and the relief branch pipeline is used for providing a channel communicated with the primary relief valve when the main pipeline is relieved, the primary relief pipeline is made of carbon steel, the design pressure is 3mpa.g, and the primary relief pipeline is used for providing a carbon dioxide flow channel after primary relief; the first-stage discharge pipeline is divided into a front section and a rear section and is connected with the interstage heat exchange system. The secondary discharge pipeline is made of low-temperature carbon steel, the lowest design temperature is-45 ℃, the design pressure is 1.2MPa.g, the secondary discharge pipeline is used for providing a carbon dioxide flow channel after secondary discharge, the middle part is connected with a discharge space liquid tank, and the tail end is connected with a discharge vertical pipe. The first-stage discharge valve is an electric regulating valve made of carbon steel and is normally closed, the control is carried out through a logic control system, and the opening degree is regulated after the feedback. The second-stage discharge valve is an electric regulating valve, is made of low-temperature carbon steel, is normally closed, is controlled by a logic control system, and is used for regulating the opening after feedback. The first-stage discharge valve and the second-stage discharge valve work cooperatively, and the temperature control requirement of an upstream trunk or a downstream trunk, the temperature control requirement of a first-stage discharge pipeline and the temperature control requirement of a second-stage discharge pipeline are met by controlling the discharge amount of carbon dioxide. The discharge air separation liquid tank is made of low-temperature carbon steel, and the horizontal separator is provided with an electric tracing system and is used for receiving liquid-phase media possibly carried in the discharge media and providing re-vaporization treatment. The emptying vertical pipe is made of low-temperature carbon steel, the height is not less than 20m, and the terminal medium Mach number is not less than 0.3.
The interstage heat exchange system comprises an inlet pipeline, a heating vaporizer 26 and an outlet pipeline, wherein the inlet pipeline and the outlet pipeline are both made of low-temperature carbon steel, the heating vaporizer 26 is used for exchanging heat of a medium and the environment for low-temperature carbon dioxide discharged at a first stage, the inlet pipeline is connected with the front section of the first-stage discharge pipeline 22, the outlet pipeline is connected with the rear section of the downstream first-stage discharge pipeline 22, the heating vaporizer 26 selects an air-temperature vaporizer or an electric heating water bath vaporizer according to environmental conditions, namely if the temperature of an operation environment is higher than 0 ℃, the heating vaporizer 26 adopts the air-temperature vaporizer, and if the temperature of the operation environment is lower than 0 ℃, the heating vaporizer 26 adopts the electric heating water bath vaporizer, so that moderate temperature rise is guaranteed without completely vaporizing the medium.
In the present embodiment, it is preferred that,
specifically, the pipeline temperature and pressure detection system comprises a bypass front-section temperature transmitter 4 and a bypass front-section pressure transmitter 5 which are arranged on a bypass front-section pipeline 11, a bypass rear-section temperature transmitter 6 and a bypass rear-section pressure transmitter 7 which are arranged on a bypass rear-section pipeline 13, and a discharge branch pressure transmitter 29 which is arranged on a discharge branch pipeline 21, a first-stage discharge branch pressure transmitter 30 and a first-stage discharge branch temperature transmitter 31 which are arranged on a first-stage discharge pipeline 22 front-section pipeline, and a second-stage discharge branch temperature transmitter 32 which is arranged on a first-stage discharge pipeline 22 rear-section pipeline, and is used for monitoring the working states of pipelines and equipment in real time and uploading data.
The bypass front-section temperature transmitter and the bypass rear-section temperature transmitter are mainly used for monitoring the medium temperature in the main pipeline in the discharge process and ensuring that the medium temperature is higher than the lowest allowable use temperature (-20 ℃) of a main pipeline material; the pressure transmitter of the release branch is arranged on the release branch pipeline and used for indicating the inner leakage condition of the bypass front-section block valve and the bypass rear-section block valve under the normal pipeline operation and indicating the stamping pressure of the release branch pipeline before release. The primary discharge branch temperature transmitter is arranged on a discharge pipeline at the upstream of the interstage heat exchange system and used for detecting the lowest medium temperature of the primary discharge pipeline in real time, and alarming and sending a low-temperature signal when the temperature is lower than-15 ℃. The first-stage discharge branch pressure transmitter is arranged on a section of discharge pipeline at the upstream of the interstage heat exchange system and used for detecting the highest pressure of the first-stage discharge pipeline in real time. The secondary discharge branch temperature transmitter is arranged at the downstream of the secondary discharge valve and used for detecting the lowest medium temperature of the secondary discharge pipeline in real time, and alarming and sending a low-temperature signal when the temperature is lower than minus 40 ℃.
The system comprises a logic control system, a pressure transmitter, a temperature transmitter, a regulating valve, a vaporizer load and a control system, wherein the logic control system is used for controlling the opening of the regulating valve and the load of the vaporizer to control the temperature transmitter and the vaporizer load.
The working principle and the working process of the invention are as follows:
(1) when a section of the dense-phase carbon dioxide pipeline needs to be shut down for maintenance, the upstream block valve and the downstream block valve of the section of the trunk line are closed. In this embodiment, the upstream trunk requires a shutdown for service, requiring the adjacent trunk block valve to be closed.
(2) In the trunk discharging, the problems that dense-phase carbon dioxide in the trunk is depressurized and cooled and carbon dioxide is likely to form dry ice due to low temperature in an emptying system exist, so the safety discharging system provided by the invention is required to be arranged to ensure the safety of the discharging process.
(3) The system is provided with a secondary regulating valve and an interstage heat exchange system of a discharge system to replace the conventional primary discharge, and aims to control the medium pressure to be near 2MPa.g after primary pressure reduction to form a gas-liquid two-phase, and the temperature after discharge is near-10 ℃; the interstage heat exchange system can be used for providing enough heat supplement for the two-phase carbon dioxide (the interstage heat exchange system can adopt an air-temperature type vaporizer or an electric heating water bath type vaporizer and a combination thereof), the temperature of the medium is increased, and after the secondary discharge, the temperature of the medium is controlled to be higher than minus 45 ℃. The arrangement avoids the medium from forming dry ice, and the material of the secondary discharge system can be optimized from stainless steel (dense phase carbon dioxide is directly discharged to normal pressure, and the temperature is reduced to-90 ℃) to low-temperature carbon steel. Further, when the dense-phase carbon dioxide to be discharged is heated in the conventional first-stage discharge, the temperature of the medium subjected to pressure discharge cannot be improved, so that the second-stage discharge is considered, and the temperature of the interstage two-phase medium is increased to meet the temperature requirement after the discharge.
(4) In the system, a plurality of temperature monitoring instruments are arranged to mainly track the temperature of a main pipeline in the main pipeline discharge process and the temperature of a medium in a secondary discharge system, and under the condition of overlarge temperature reduction, the temperature is timely fed back to a discharge valve, the discharge speed is controlled, and the safety of the main pipeline and the safety of the discharge system are guaranteed.
(5) Furthermore, the secondary discharge system and the interstage heat exchange system can adopt a skid-mounted mode and are transported to corresponding valve chambers before planned maintenance, and the overall construction investment of dense-phase carbon dioxide pipelines can be reduced.
A dense phase carbon dioxide pipeline safety discharge method, comprising the following steps:
the method comprises the following steps: the dense-phase carbon dioxide pipeline safety relief system is arranged on a pipeline trunk line for conveying dense-phase carbon dioxide and comprises a dense-phase carbon dioxide pipeline conveying and intercepting system, a valve chamber bypass system, a two-stage relief system, an interstage heat exchange system and a pipeline temperature and pressure detection system;
step two: when the pipeline conveying system needs to stop conveying and maintenance in an upstream main line, a starting-point external conveying pump of the pipeline conveying system, a main line cut-off valve of the station, a main line cut-off valve of an adjacent upstream valve chamber and a downstream tail end cut-off valve are closed, and when a movable two-stage relief system and an interstage heat exchange system are adopted, the two-stage relief system and the interstage heat exchange system are pryingly conveyed to the valve chamber and are connected to a valve chamber bypass system after maintenance and shutdown;
step three: keeping a bypass front-section block valve, a bypass rear-section block valve, a first-stage discharge valve and a second-stage discharge valve closed, injecting nitrogen into a pipe section between the bypass front-section block valve and the first-stage discharge valve, wherein the pressure is the same as the stop pressure of a main pipeline, injecting nitrogen into the pipe section between the first-stage discharge valve and the second-stage discharge valve, and controlling the pressure to be 2 MPa.g;
step four: configuring the type of a vaporizer according to the ambient temperature, and selecting an air-temperature vaporizer if the air temperature of the operating environment is higher than 0 ℃ to ensure that the temperature of the heated medium is higher than-5 ℃; if the ambient temperature is lower than 0 ℃, an electric heating water bath vaporizer is selected, and the temperature of the heated medium is ensured to be higher than-5 ℃;
step five: firstly, opening a bypass cut-off valve group and a primary pressure release valve, starting a heating vaporizer, slowly opening a secondary pressure release valve, and discharging a release medium into the atmosphere from an emptying vertical pipe after the release medium is vaporized;
specifically, the pressure in the primary discharge pipeline is controlled to be stabilized at 2MPa.g, the temperature of a medium at the outlet of the heating vaporizer is controlled to be higher than-5 ℃, the temperature of a medium in the main pipeline is controlled to be higher than-20 ℃, when the upstream main line pressure is reduced to 2MPa.g, the pressure in the primary discharge pipeline is controlled to be stabilized at 1MPa.g, the temperature of the medium at the outlet of the heating vaporizer is controlled to be higher than-5 ℃, the temperature of the medium in the main pipeline is controlled to be higher than-20 ℃, when the upstream main line pressure is reduced to 1MPa.g, the discharge valve is completely opened, and the secondary discharge valve is utilized to complete the subsequent discharge operation;
step six: when the pressure of the main pipeline is reduced to 0.1MPa.g, dry air is injected from the upstream block valve chamber to replace carbon dioxide still in the pipeline and is discharged from the emptying system of the local valve chamber. .
The invention is not limited to the foregoing embodiments. The invention extends to any novel feature or any novel combination of features disclosed in this specification and any novel method or process steps or any novel combination of features disclosed.
Claims (10)
1. A dense phase carbon dioxide pipeline safety relief system which characterized in that: the system comprises a dense-phase carbon dioxide pipeline conveying and intercepting system, a valve chamber bypass system, a two-stage relief system and a pipeline temperature and pressure detection system;
the dense-phase carbon dioxide pipeline conveying and cutting system comprises an upstream trunk (1), a trunk cutting valve (2) and a downstream trunk (3) which are sequentially connected, wherein the upstream trunk (1) and the downstream trunk (3) are used for connecting upstream and downstream pipelines and forming a dense-phase carbon dioxide conveying channel, and the trunk cutting valve (2) is used for controlling the communication or cutting between the upstream trunk (1) and the downstream trunk (3);
the valve chamber bypass system comprises a valve chamber bypass and a bypass block valve group arranged on the valve chamber bypass, wherein a pipeline of the valve chamber bypass is connected out of an upstream trunk line (1) of a trunk line block valve (2) and is connected in by a downstream trunk line (3) of the trunk line block valve (2) to form a trunk line bypass, and the valve chamber bypass system is used for providing a maintenance emptying bypass of the upstream trunk line (1) and the downstream trunk line (3) after the trunk line is blocked and providing a communication bypass when the upstream trunk line (1) or the downstream trunk line (2) is ready to be restarted;
the two-stage discharge system is used for carrying out stage pressure relief on dense-phase carbon dioxide, an interstage heat exchange system is arranged in the two-stage discharge system, and the interstage heat exchange system is used for carrying out temperature regulation on a medium discharged from the previous stage.
2. The dense phase carbon dioxide pipeline safety relief system of claim 1, wherein: the bypass block valve set arranged on the valve chamber bypass line is composed of a bypass front-section block valve (8) and a bypass rear-section block valve (9), and the bypass front-section block valve (8) and the bypass rear-section block valve (9) are respectively used for controlling the discharge channels of the upstream trunk line (1) and the downstream trunk line (3).
3. The dense phase carbon dioxide pipeline safety relief system of claim 2, wherein: the bypass pipeline between the upstream main line (1) and the bypass front-section block valve (8) is a bypass front-section pipeline (11), the bypass pipeline between the bypass front-section block valve (8) and the bypass rear-section block valve (9) is a bypass middle-section pipeline (12), and the bypass pipeline between the bypass rear-section block valve (9) and the downstream main line (3) is a bypass rear-section pipeline (13).
4. The dense phase carbon dioxide pipeline safety relief system of claim 3, wherein: the two-stage discharge system comprises a one-stage discharge valve (24), a two-stage discharge valve (25), a discharge separating tank (27) and a discharge vertical pipe (28), wherein the inlet end of the one-stage discharge valve (24) is connected with a bypass middle-section pipeline (12) through a discharge branch pipeline (21), the outlet end of the one-stage discharge valve (24) is connected with the inlet end of the two-stage discharge valve (25) through a one-stage discharge pipeline (22), the outlet end of the two-stage discharge valve (25) is connected with the discharge vertical pipe (28) through a two-stage discharge pipeline (23), the interstage heat exchange system is arranged on the one-stage discharge pipeline (22) between the one-stage discharge valve (24) and the two-stage discharge valve (25), and the discharge liquid tank (27) is arranged on the two-stage discharge pipeline (23) between the two-stage discharge valve (25) and the discharge vertical pipe (28.
5. The dense phase carbon dioxide pipeline safety relief system of claim 4, wherein: the interstage heat exchange system comprises an inlet pipeline, a warming vaporizer (26) and an outlet pipeline, wherein the warming vaporizer (26) is used for exchanging medium and ambient heat of low-temperature carbon dioxide subjected to primary discharging, the inlet pipeline is connected with the front section of the primary discharging pipeline (22), and the outlet pipeline is connected with the rear section of the downstream primary discharging pipeline (22).
6. The dense phase carbon dioxide pipeline safety relief system of claim 5, wherein: the heating vaporizer (26) selects an air-temperature vaporizer or an electric heating water bath vaporizer according to environmental conditions, namely, if the temperature of the operation environment is higher than 0 ℃, the heating vaporizer (26) adopts the air-temperature vaporizer, and if the temperature of the operation environment is lower than 0 ℃, the heating vaporizer (26) adopts the electric heating water bath vaporizer.
7. The dense phase carbon dioxide pipeline safety relief system of claim 4, wherein: an air injection valve (10) is arranged between the bypass front-section block valve (8) and the primary release valve (24).
8. The dense phase carbon dioxide pipeline safety relief system of claim 4, wherein: pipeline temperature pressure detecting system is including setting up bypass anterior segment temperature transmitter (4) and bypass anterior segment pressure transmitter (5) on bypass anterior segment pipeline (11), setting up bypass back end temperature transmitter (6) and bypass back end pressure transmitter (7) on bypass back end pipeline (13) and setting up branch road pressure transmitter (29) of releasing on branch road pipeline (21), setting up one-level branch road pressure transmitter (30) and one-level branch road temperature transmitter (31) of releasing on one-level pipeline (22) anterior segment part pipeline and setting up second grade branch road temperature transmitter (32) of releasing on one-level pipeline (22) back end part pipeline, pipeline temperature pressure detecting system is used for the operating temperature state of real-time supervision pipeline, equipment to upload data.
9. The dense phase carbon dioxide pipeline safety relief system according to any one of claims 1 to 8, wherein: and the two-stage discharge system and the interstage heat exchange system adopt a skid-mounted mode.
10. A dense phase carbon dioxide pipeline safety discharge method is characterized in that: the method comprises the following steps:
the method comprises the following steps: the dense-phase carbon dioxide pipeline safety relief system is arranged on a pipeline trunk line for conveying dense-phase carbon dioxide and comprises a dense-phase carbon dioxide pipeline conveying and intercepting system, a valve chamber bypass system, a two-stage relief system, an interstage heat exchange system and a pipeline temperature and pressure detection system;
step two: when the pipeline conveying system needs to stop conveying and maintenance in an upstream main line, a starting-point external conveying pump of the pipeline conveying system, a main line cut-off valve of the station, a main line cut-off valve of an adjacent upstream valve chamber and a downstream tail end cut-off valve are closed, and when a movable two-stage relief system and an interstage heat exchange system are adopted, the two-stage relief system and the interstage heat exchange system are pryingly conveyed to the valve chamber and are connected to a valve chamber bypass system after maintenance and shutdown;
step three: keeping a bypass front-section block valve, a bypass rear-section block valve, a first-stage discharge valve and a second-stage discharge valve closed, injecting nitrogen into a pipe section between the bypass front-section block valve and the first-stage discharge valve, wherein the pressure is the same as the stop pressure of a main pipeline, injecting nitrogen into the pipe section between the first-stage discharge valve and the second-stage discharge valve, and controlling the pressure to be 2-2.2 MPa.g;
step four: configuring the type of a vaporizer according to the ambient temperature, and selecting an air-temperature vaporizer if the air temperature of the operating environment is higher than 0 ℃ to ensure that the temperature of the heated medium is higher than-5 ℃; if the ambient temperature is lower than 0 ℃, an electric heating water bath vaporizer is selected, and the temperature of the heated medium is ensured to be higher than-5 ℃;
step five: firstly, opening a bypass cut-off valve group and a primary pressure release valve, starting a heating vaporizer, slowly opening a secondary pressure release valve, and discharging a release medium into the atmosphere from an emptying vertical pipe after the release medium is vaporized;
specifically, the pressure in the primary discharge pipeline is controlled to be stabilized at 2-2.2MPa.g, the temperature of a medium at the outlet of the heating vaporizer is controlled to be higher than-5 ℃, the temperature of a medium in the main pipeline is controlled to be higher than-20 ℃, when the upstream main line pressure is reduced to 2MPa.g, the pressure in the primary discharge pipeline is controlled to be stabilized at 1-1.2MPa.g, the temperature of the medium at the outlet of the heating vaporizer is controlled to be higher than-5 ℃, the temperature of the medium in the main pipeline is controlled to be higher than-20 ℃, when the upstream main line pressure is reduced to 1MPa.g, the discharge valve is completely opened, and the secondary discharge valve is utilized to complete the subsequent discharge operation;
step six: when the pressure of the main pipeline is reduced to 0.1MPa.g, dry air is injected from the upstream block valve chamber to replace carbon dioxide still in the pipeline and is discharged from the emptying system of the local valve chamber.
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| CN116105071A (en) * | 2023-02-15 | 2023-05-12 | 新疆敦华绿碳技术股份有限公司 | Supercritical carbon dioxide pipeline safety relief system and control method |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN116105071A (en) * | 2023-02-15 | 2023-05-12 | 新疆敦华绿碳技术股份有限公司 | Supercritical carbon dioxide pipeline safety relief system and control method |
| CN116105071B (en) * | 2023-02-15 | 2024-05-24 | 新疆敦华绿碳技术股份有限公司 | Supercritical carbon dioxide pipeline safety relief system and control method |
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