A Safety Assurance System and Method for Hydrogen-Enriched Natural Gas Based on Blind End Accumulation Control

Abstract

The present invention discloses a safety guarantee system and method for hydrogen - doped natural gas based on blind - end accumulation control. The system includes a forced flow - disturbing system and an instrument monitoring system connected to the blind - end side of the pig - launching tee of an existing pig - launching and receiving system. The forced flow - disturbing system is used to connect the flow path on the blind - end side of the pig - launching tee of the existing pig - launching and receiving system with the flow path of the pig - bypass of the existing pig - launching and receiving system, and is used to disturb the gas stagnant area on the blind - end side of the pig - launching tee. The instrument monitoring system is used to monitor the medium flow conditions in the forced flow - disturbing system and the secondary guarantee system. Based on the long - term stratification trend of hydrogen - doped natural gas after standing still and combined with the actual situation of pipeline transportation, the present invention implements control countermeasures in the pig - launching tee area where gas blind - end standing still and accumulation are most likely to occur, and sets up a forced flow - disturbing system, a secondary guarantee system and an instrument monitoring system, effectively solving the relatively hidden but extremely harmful problem of blind - end gas stratification.

Description

Technical Field

[0001] The present invention belongs to the technical field of natural gas transportation, and particularly relates to a safety guarantee system and method for hydrogen-blended natural gas based on blind-end accumulation control. Background Art

[0002] As one of the important development directions of new energy, compared with traditional fossil fuels, hydrogen has significant advantages such as high calorific value, non-polluting combustion products, wide sources, and renewability. It is called the future clean energy and will become a new way for humanity to solve the increasingly severe energy and environmental problems in the future. At present, injecting hydrogen into the existing natural gas pipeline transportation system is recognized as an effective way for large-scale hydrogen energy utilization. It can not only effectively reduce the investment in the newly built hydrogen pipeline system but also make full use of the advantages of the existing natural gas pipeline network to achieve flexible resource allocation and efficient utilization.

[0003] Although hydrogen is easy to leak and has a wide explosion limit (4% - 75%); at the same time, hydrogen is very likely to cause spontaneous combustion (burning) after leakage. The combustion mechanism mainly includes diffusion spontaneous combustion, friction spontaneous combustion, and ignition combustion, and it is extremely easy to develop into deflagration or explosion inside the pipeline. However, the proportion of hydrogen injection in natural gas pipeline transportation is generally controlled within a relatively low range. Under normal transportation conditions, the explosion limit range and combustion characteristics of the mixed medium are relatively close to those of natural gas. At the same time, the current relevant research on hydrogen-blended natural gas mainly focuses on the combustion and explosion safety issues of hydrogen-blended natural gas mixtures, and the relevant problems have been revealed relatively deeply.

[0004] During the operation of the pipeline, there are blind ends near the three-way pipe of the pipeline pig launcher and receiver. That is, in this part of the position, due to the closure of the branch, the gas flow and disturbance are not smooth, and the so-called "dead gas area" of the gas will appear. The range of this area is mainly related to the flow velocity and flow field of the medium inside the nearby pipeline. The greater the flow velocity of the medium, the greater the disturbance range in the blind-end area, and the relatively smaller the range of the dead gas area; when the direction of the medium flow deviates from the dead gas area, the range of the dead gas area is more obvious. In particular, there is a relatively stagnant flow blind area (near the pigging three-way pipe) downstream of the pig launcher in the hydrogen injection station, and the mixed gas will stagnate for a long time, and relative stratification of hydrogen and natural gas may occur due to the density difference; if the hydrogen-blended natural gas that has not been fully mixed enters this area, the concentration stratification will be further accelerated. All of these will cause a significant increase in the hydrogen concentration at some positions (the top) in this area, significantly increasing the risk of hydrogen damage to the high-grade pipeline system and exceeding the material evaluation range of hydrogen-blended natural gas (evaluated according to the uniform hydrogen concentration), posing a great potential safety hazard. However, the current public literature and research have not covered such problems, and the relevant reports are still in the blank stage. Therefore, it is necessary to conduct in-depth research on the identification and control of the "dead gas area" in the hydrogen-blended natural gas system, and propose a safety guarantee system for hydrogen-blended natural gas based on blind-end accumulation control to fill the blank of the existing technical reports and promote the technological progress in this field. Summary of the Invention

[0005] The object of the present invention is to provide a hydrogen - doped natural gas safety guarantee system and method based on blind - end accumulation control, which can eliminate and suppress the accumulation at the blind end of the hydrogen - doped natural gas pipeline, thereby ensuring the safe operation of the system in view of the above - mentioned existing problems.

[0006] The main technical idea of the present invention for a natural gas hydrogen - doping station is to set a forced flow - disturbing system at the blind end of the pigging tee of the existing natural gas pipeline to interfere with and remove potential gas stagnation areas, avoiding gas stratification and hydrogen accumulation locally. Further, a secondary guarantee system is set near the pigging launcher to perform blow - off compensation when the forced flow - disturbing system is blocked or the flow is obstructed. At the same time, a supporting instrument monitoring system is set to monitor key parameters in real - time, and finally, the accumulation at the blind end of the hydrogen - doped natural gas pipeline is eliminated and suppressed, effectively guaranteeing the safe operation of the hydrogen - doped natural gas pipeline station.

[0007] The technical solution adopted by the present invention is: a hydrogen - doped natural gas safety guarantee system based on blind - end accumulation control, characterized in that it includes a forced flow - disturbing system and an instrument monitoring system connected to the blind - end side of the pigging tee of the existing pigging system.

[0008] The forced flow - disturbing system is used to connect the flow path of the blind - end side of the pigging tee of the existing pigging system with the flow path of the pigging bypass of the existing pigging system, and is used to disturb the gas stagnation area on the blind - end side of the pigging tee.

[0009] The instrument monitoring system is used to monitor the medium flow conditions in the forced flow - disturbing system and the secondary guarantee system.

[0010] In the hydrogen - doped natural gas safety guarantee system based on blind - end accumulation control of the present invention, the forced flow - disturbing system includes a blind - end disturbing branch pipe, and a disturbing branch pipe cut - off valve, a disturbing branch pipe end cut - off valve and a disturbing branch pipe blow - off valve arranged on the blind - end disturbing branch pipe. The blind - end disturbing branch pipe is arranged downstream of the first pigging cut - off valve of the existing pigging system. The disturbing branch pipe cut - off valve is arranged at the head end of the blind - end disturbing branch pipe. The disturbing branch pipe end cut - off valve is arranged at the tail end of the blind - end disturbing branch pipe. The disturbing branch pipe blow - off valve is arranged on the middle branch pipe of the blind - end disturbing branch pipe.

[0011] In the hydrogen - doped natural gas safety guarantee system based on blind - end accumulation control of the present invention, the blind - end disturbing branch pipe straddles and enters the end of the existing pigging system, and the distance from the first pigging cut - off valve is less than 300 mm.

[0012] The hydrogen - blended natural gas safety guarantee system based on blind - end accumulation control described in the present invention further includes a secondary guarantee system. The secondary guarantee system is connected to the flow channel on the blind - end side of the pigging tee, and is used to connect the main pipeline of the existing pigging launching system and the venting system, providing safety redundancy for the forced turbulence system.

[0013] In the hydrogen - blended natural gas safety guarantee system based on blind - end accumulation control described in the present invention, the secondary guarantee system includes a secondary guarantee vent pipe, a secondary guarantee vent valve and a choke orifice plate arranged on the secondary guarantee vent pipe. The secondary guarantee vent pipe is arranged downstream of the first pigging shut - off valve, and the choke orifice plate is arranged downstream of the secondary guarantee vent valve.

[0014] In the hydrogen - blended natural gas safety guarantee system based on blind - end accumulation control described in the present invention, the secondary guarantee vent pipe is connected across the head end of the existing venting system, and the distance between the secondary guarantee vent pipe and the first pigging shut - off valve is less than 600 mm.

[0015] In the hydrogen - blended natural gas safety guarantee system based on blind - end accumulation control described in the present invention, the instrument monitoring system includes a first flow transmitter and a second flow transmitter. The first flow transmitter is arranged on the blind - end disturbance branch pipe of the forced turbulence system and is used to monitor the medium flow condition in the blind - end disturbance branch pipe. The second flow transmitter is arranged on the secondary guarantee vent pipe of the secondary guarantee system and is used to monitor the medium flow condition in the secondary guarantee vent pipe.

[0016] A hydrogen - blended natural gas safety guarantee method based on blind - end accumulation control is characterized by the following steps:

[0017] Step 1: Set up a forced turbulence system, a secondary guarantee system and an instrument monitoring system on the blind - end side of the pigging tee of the existing pigging launching system;

[0018] Step 2: Before pipeline operation, start the forced turbulence system. Specifically, open the disturbance branch pipe shut - off valve and the disturbance branch pipe end shut - off valve to connect the blind - end of the pigging tee and the in - station main pipeline, and keep the first pigging shut - off valve and the second pigging shut - off valve of the existing pigging launching system closed. Two medium flow directions including a pigging bypass flow channel and a blind - end flow channel are formed in the station, and at the same time, the functions of large - scale medium transportation and blind - end area disturbance are realized.

[0019] The hydrogen-blended natural gas safety assurance method based on blind-end accumulation control of the present invention is that when the pipeline is in operation, if the flow rate of the blind-end disturbance branch pipe decreases, the secondary assurance system is immediately opened, specifically, the secondary assurance vent valve is opened, the secondary assurance vent pipe is connected with the vent system, and the continuous disturbance in the blind-end area is maintained; at the same time, the replacement of the existing pigging and launching system is immediately implemented, that is, the second pigging shut-off valve of the existing pigging and launching system is opened, and the overall nitrogen replacement is implemented from the downstream of the first pigging shut-off valve to the launching barrel area, and the back pressure control valve of the pigging and launching barrel is opened to introduce the hydrogen-blended natural gas from the trunk pipeline to the pigging and launching barrel. Hydrogen natural gas, at this time, open the vent regulating valve and vent pipe shut-off valve of the launching cylinder, and maintain the operation of large-scale charging and small-scale discharge at the same time; after being pressurized to the operating pressure, close the vent regulating valve, vent pipe shut-off valve and back pressure control valve of the cleaning launching cylinder, open the first cleaning shut-off valve and the third cleaning shut-off valve, close the secondary security system, and the system is switched to simultaneous production of the main flow channel and the cleaning flow channel, and immediately inspect and repair the forced disturbance system; after the forced disturbance system is repaired, close the first cleaning shut-off valve, the second cleaning shut-off valve and the third cleaning shut-off valve, and return to the production mode of step two.

[0020] The hydrogen-blended natural gas safety assurance method based on blind-end accumulation control of the present invention performs numerical analysis on the closed area between the cleaning tee and the first cleaning shut-off valve before setting the forced disturbance system on the blind-end side of the cleaning tee of the built cleaning ball system, performs self-disturbance area simulation and minimum self-disturbance flow simulation under the designed output through full-scale numerical simulation, obtains the maximum disturbance length and the minimum self-disturbance pipeline flow, and sets the hydrogen-blended natural gas safety assurance system when the maximum disturbance length is less than the closed section length or the actual output is lower than a certain times the minimum self-disturbance flow.

[0021] Compared with the prior art, the present invention has the following positive effects: based on the stratification trend of hydrogen-blended natural gas after long-term standing, combined with the actual situation of pipeline transportation, control measures are implemented in the cleaning tee area where gas blind end standing and accumulation are very likely to occur, and a forced turbulence system, a secondary protection system and an instrument monitoring system are set up. Together with the existing cleaning and launching system, a hydrogen-blended natural gas safety protection system based on blind end accumulation control is formed, which effectively solves the relatively hidden but extremely harmful blind end gas stratification problem.

[0022] The specific manifestations are:

[0023] (1) Scientific setting

[0024] Based on the basic principle of the aggregation and stratification of hydrogen-doped natural gas, and combined with the actual problem of the existence of a blind end on one side of the pigging tee in the pig launcher area of the long-distance pipeline, the present invention first reveals the existence problem of the aggregation and stratification of hydrogen-doped natural gas in this area. In view of this problem, considering aspects such as safety and economy, a forced flow disturbance system, a secondary guarantee system, and an instrument monitoring system are set up to forcibly flow the system with the risk of aggregation and stratification at the blind end, so as to maintain the flow state of the medium in the blind end for a long time. At the same time, a secondary guarantee system is equipped to further improve the system safety redundancy, and the control effect of the stratification problem of hydrogen-doped natural gas at the blind end is achieved collaboratively.

[0025] (2) Good economy

[0026] By revealing the operation risks and setting up a safety guarantee system, the present invention essentially avoids the risk of hydrogen damage to the materials in the blind end area after the hydrogen-doped transportation of the existing natural gas system, and has good implicit economic benefits. By setting up a double-flow channel, on the one hand, the local fluidity of the blind end is guaranteed, and on the other hand, the realization of a similar function by means of blind end venting is avoided, which has good economy.

[0027] (3) Advanced concept

[0028] In view of the fact that this type of medium contains hydrogen, there must be a risk of medium residence and stratification in the blind end area. The ideas and methods proposed by the present invention will provide important reference for the safe operation and management of hydrogen-doped natural gas pipelines. Brief description of the drawings

[0029] The present invention will be described by way of specific embodiments with reference to the drawings, where

[0030] Figure 1 is the structural schematic diagram of the present invention.

[0031] Markings in the figure: 1 is the main pipeline, 2 is the main pipeline block valve, 3 is the pigging bypass, 4 is the pigging tee, 5 is the first pigging block valve, 6 is the second pigging block valve, 7 is the bypass block valve, 8 is the pressure regulating valve, 9 is the pig launcher, 10 is the third pigging block valve, 11 is the pigging tool vent pipe, 12 is the vent regulating valve, 13 is the vent pipe block valve, 21 is the blind end disturbance branch pipe, 22 is the disturbance branch pipe block valve, 23 is the disturbance branch pipe end block valve, 24 is the disturbance branch pipe relief valve, 31 is the secondary guarantee vent pipe, 32 is the secondary guarantee vent valve, 33 is the orifice plate, 41 is the first flow transmitter, 42 is the second flow transmitter. Specific implementation mode

[0032] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of them. Usually, the components of the embodiments of the present invention described and illustrated in the accompanying drawings here can be arranged and designed in various different configurations.

[0033] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed present invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0034] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0035] It should be noted that like reference numerals and letters denote like items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0036] In the description of the embodiments of the present invention, it should be noted that the orientation or positional relationship indicated is based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of the invention is usually placed during use, or the orientation or positional relationship commonly understood by those skilled in the art, or the orientation or positional relationship in which the product of the invention is usually placed during use. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. In addition, the terms "first" and "second" are only used for descriptive distinction and should not be construed as indicating or implying relative importance.

[0037] In the description of the embodiments of the present invention, it should also be noted that unless otherwise clearly specified and limited, the terms "set" and "connect" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection or an indirect connection through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances; the accompanying drawings in the embodiments are used to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of them. Usually, the components of the embodiments of the present invention described and illustrated in the accompanying drawings here can be arranged and designed in various different configurations.

[0038] Such as Figure 1As shown in the figure, a safety guarantee system for hydrogen - doped natural gas based on blind - end accumulation control includes a forced flow - disturbance system, a secondary guarantee system, and an instrument monitoring system, which are connected to the blind - end side of the pig - launching and receiving tee 4 of the existing pig - launching and receiving system. By setting up this system, special control is carried out on the problems of gas accumulation and stratification in the blind - end of the pig - launching and receiving tee of the hydrogen - doped natural gas pipeline, avoiding material damage caused by high - concentration hydrogen accumulation in the blind - end area. This not only effectively improves the operation safety of the system, but also is of great significance for safe operation in cases such as low throughput and poor mixing degree in the initial stage of hydrogen mixing during production operation. Moreover, it provides important promotion and support for the technological development in the field of hydrogen - doped natural gas transportation technology.

[0039] Among them, the existing pig - launching and receiving system includes a main pipeline 1, a main - line block valve 2, a pig - bypass 3, a pig - launching and receiving tee 4, a first pig - block valve 5, a second pig - block valve 6, a bypass block valve 7, a pressure - guiding regulating valve 8, a pig - launching barrel 9, a third pig - block valve 10, a pig - cleaner vent pipe 11, a vent regulating valve 12, and a vent - pipe block valve 13. The existing pig - launching and receiving system is used to provide the functions of normal operation of the pipeline terminal and pig - launching operation, and after introducing the system of the present invention, it cooperates to support the functions of the present invention system.

[0040] Among them, the forced flow - disturbance system includes a blind - end disturbance branch pipe 21, and a disturbance - branch - pipe block valve 22, a disturbance - branch - pipe end block valve 23, and a disturbance - branch - pipe vent valve 24 arranged on the blind - end disturbance branch pipe 21. The forced flow - disturbance system is used to connect the flow path on the blind - end side of the pig - launching and receiving tee 4 of the existing pig - launching and receiving system with the flow path of the pig - bypass 3 of the existing pig - launching and receiving system, and is used to disturb the potentially stagnant gas area on the blind - end side of the pig - launching and receiving tee 4 to avoid gas stratification locally.

[0041] Specifically, the blind - end disturbance branch pipe 21 is arranged downstream of the first pig - block valve 5 of the existing pig - launching and receiving system, and the distance from the first pig - block valve 5 is less than 300 mm. The diameter of the blind - end disturbance branch pipe is preferably DN50, made of carbon steel. The blind - end disturbance branch pipe 21 straddles into the end of the existing pig - launching and receiving system, that is, near the end of the pig - launching barrel. Preferably, through hydraulic simulation analysis, it is ensured that the flow distribution of the disturbance branch pipe is not less than 3%. The disturbance - branch - pipe block valve 22 is arranged at the head of the blind - end disturbance branch pipe 21, made of carbon steel, a full - bore ball valve, manually controlled, and is used to open when it is predicted that blind - end gas stagnation and stratification may occur. The disturbance - branch - pipe end block valve 23 is arranged at the end of the blind - end disturbance branch pipe 21, made of carbon steel, a full - bore ball valve, manually controlled, and is used to open when it is predicted that blind - end gas stagnation and stratification may occur. The disturbance - branch - pipe vent valve 24 is arranged on the middle branch of the blind - end disturbance branch pipe 21, normally closed, and is opened when the blind - end disturbance branch pipe is emptied.

[0042] Among them, the secondary protection system includes a secondary protection vent pipe 31, a secondary protection vent valve 32 and a choke orifice plate 33 arranged on the secondary protection vent pipe 31. The secondary protection system is connected to the flow channel on the blind end side of the pigging tee 4, providing safety redundancy for the forced turbulence system. In the case where the effect of the forced turbulence system is not good, it is used to connect the main pipeline 1 of the existing pigging launching system and the venting system, from the main pipeline to the venting system flow channel, further avoiding gas stillness and stratification in the downstream of the pigging tee and within the pigging system.

[0043] Specifically, the secondary protection vent pipe 31 is arranged downstream of the first pigging cut-off valve 5, and the distance from the first pigging cut-off valve 5 is less than 600 mm. The diameter of the secondary protection vent pipe is preferably DN50, made of carbon steel; the secondary protection vent pipe 31 is connected across the head end of the existing venting system; the material of the secondary protection vent valve is selected as carbon steel, full-bore ball valve, manually controlled. Preferably, two cut-off valves are installed on the secondary protection vent pipe; the choke orifice plate 33 is arranged downstream of the secondary protection vent valve 32, made of carbon steel, and plays a role in controlling the discharge flow during the venting process. Through hydraulic simulation analysis, it is ensured that the flow distribution of the turbulence branch pipe is not less than 10%.

[0044] Among them, the instrument monitoring system includes a first flow transmitter 41 and a second flow transmitter 42, which are used to monitor the medium flow conditions in the forced turbulence system and the secondary protection system.

[0045] Specifically, the first flow transmitter 41 is arranged on the blind end disturbance branch pipe 21 of the forced turbulence system, used to monitor the medium flow conditions in the blind end disturbance branch pipe 21. If the flow monitoring value is lower than the set minimum disturbance value, it indicates that the blind end disturbance branch pipe is blocked or the blind end area is blocked, and the secondary protection system is immediately instructed to open; the second flow transmitter 42 is arranged on the secondary protection vent pipe 31 of the secondary protection system, used to monitor the medium flow conditions in the secondary protection vent pipe 31. If the flow monitoring value is lower than the set minimum disturbance value, it indicates that the blind end area is blocked, and the system operation should be immediately suspended.

[0046] The working principle of the present invention is as follows:

[0047] After hydrogen is blended into natural gas for transportation, it appears to be in a uniform transportation state on the surface, with the medium being fully mixed. Material evaluation is carried out according to the blending concentration and hydrogen partial pressure. At the head end of the pipeline system downstream of the hydrogen blending station, a pigging and launching system is usually set up. Usually, the gas flows downstream through the pigging bypass, while the pipeline leading to the pigging launcher is in a closed state, and the flow direction switching function is achieved through a pigging tee. However, in the area of the pigging tee and the pigging channel, there is a blind area where the gas does not flow. There are gas vortices in this area, but the influence length is limited. Further, downstream of the hydrogen blending point, there is a possibility that the hydrogen blending is not yet uniform, which will further increase the probability of gas stratification in the nearby dead ends. In order to avoid the problem of gas stratification in the remaining dead ends caused by the excessive length of the dead ends (the distance between the pigging tee and the first pigging block valve) in the existing facilities or the shortening of the gas vortex length under low throughput (gas stratification will lead to local hydrogen accumulation and an increase in hydrogen partial pressure), relevant measures need to be taken to control it, so this system is set up.

[0048] This system is equipped with a forced flow disturbance system, a secondary guarantee system, and an instrument monitoring system to force the flow in the areas at risk of dead end accumulation and stratification, so as to maintain the flow state of the medium in the dead ends in the long term. At the same time, a secondary guarantee system is equipped to further improve the system safety redundancy and jointly achieve the control effect of the problem of hydrogen blended natural gas stratification in the dead ends.

[0049] The present invention also provides a safety guarantee method for hydrogen blended natural gas based on dead end accumulation control, including the following steps:

[0050] Step 1: Set up a forced flow disturbance system, a secondary guarantee system, and an instrument monitoring system on the dead end side of the pigging tee of the existing pigging and launching system.

[0051] Step 2: Before the pipeline operation, turn on the forced flow disturbance system. Specifically, open the disturbance branch block valve and the disturbance branch end block valve to connect the dead end of the pigging tee with the main pipeline in the station, keep the first pigging block valve and the second pigging block valve of the existing pigging and launching system closed, and form two-way medium flow directions including the pigging bypass flow channel and the dead end flow channel in the station, while realizing the functions of large-scale medium transportation and disturbance in the dead end area.

[0052] Among them, when the pipeline is in operation, if the flow rate of the blind-end disturbing branch pipe decreases (or decreases to almost zero), it indicates that there may be a blockage in the disturbing flow branch or the blind end. Immediately activate the secondary protection system. Specifically, open the secondary protection vent valve to connect the secondary protection vent pipe with the vent system and maintain continuous disturbance in the blind-end area. At the same time, to reduce the discharge of hydrogen-blended natural gas, immediately implement the replacement of the existing pigging and launching system, that is, open the second pigging cut-off valve of the existing pigging and launching system, conduct overall nitrogen replacement from downstream of the first pigging cut-off valve to the launching barrel area, and open the back pressure control valve of the pigging and launching barrel to introduce hydrogen-blended natural gas from the main pipeline into the pigging and launching barrel. At this time, open the vent regulating valve and the vent pipe cut-off valve of the launching barrel, and maintain the operation of charging a large amount while discharging a small amount, aiming to keep gas flow still existing inside the pigging and launching barrel. After charging to the operating pressure, close the vent regulating valve, the vent pipe cut-off valve, and the back pressure control valve of the pigging and launching barrel, open the first pigging cut-off valve and the third pigging cut-off valve, close the secondary protection system, and the system switches to simultaneous production of the main pipeline flow path and the pigging flow path. And immediately repair the forced disturbing flow system. After the forced disturbing flow system is repaired, close the first pigging cut-off valve, the second pigging cut-off valve, and the third pigging cut-off valve, and re-switch to the production mode of step two.

[0053] When the natural gas pipeline transportation system is prepared to be converted into a hydrogen-blended natural gas transportation pipeline system, in order to avoid forming the described enclosed and gas-stratified area, before setting the forced disturbing flow system on the blind-end side of the pigging tee in the existing pigging and launching system, conduct a numerical analysis on the enclosed area between the pigging tee and the first pigging cut-off valve. Specifically, since the internal flow velocity of the pipeline is relatively fast at a higher throughput, if the gas in the enclosed area between the pigging tee and the first pigging cut-off valve is prone to generate internal eddies in the entire area, self-disturbance can be implemented to avoid gas stratification. If due to the enclosed area between the pigging tee and the first pigging cut-off valve, the internal eddy area cannot cover the entire enclosed area, there is a possibility of stratification in the second half of the enclosed area. Further, if the throughput decreases, the range of the stratified area expands. Therefore, preferably, through full-scale numerical simulation, simulate the self-disturbance area and the minimum self-disturbance flow rate at the designed throughput to obtain the maximum disturbance length (at the designed throughput) and the minimum self-disturbance pipeline flow rate. When the maximum disturbance length is less than the length of the enclosed section or the actual throughput (in various situations during the entire life cycle) is lower than 1.4 times (considering the design margin) of the minimum self-disturbance flow rate, set up the hydrogen-blended natural gas safety protection system, that is, transform the pipeline system of the pigging tee (launching barrel end), and add the forced disturbing flow system, the secondary protection system, and instrument monitoring of the present invention.

[0054] The present invention is not limited to the foregoing specific embodiments. The present invention extends to any new feature or any new combination disclosed in this specification, as well as any new method or process step or any new combination disclosed.

Claims

1. A hydrogen-doped natural gas safety guarantee system based on blind end accumulation control, characterized in that: It includes a forced flow disturbance system and an instrument monitoring system connected to the blind end side of the pigging tee (4) of the existing pigging and launching system; The forced flow disturbance system is used to connect the flow channel on the blind end side of the pigging tee (4) of the existing pigging and launching system to the flow channel of the pigging bypass (3) of the existing pigging and launching system, and is used to disturb the gas stagnation area on the blind end side of the pigging tee (4); The forced flow disturbance system includes a blind end disturbance branch pipe (21), a disturbance branch pipe cut-off valve (22), a disturbance branch pipe end cut-off valve (23), and a disturbance branch pipe vent valve (24) arranged on the blind end disturbance branch pipe (21). The blind end disturbance branch pipe (21) is arranged downstream of the first pigging cut-off valve (5) of the existing pigging and launching system. The disturbance branch pipe cut-off valve (22) is arranged at the head end of the blind end disturbance branch pipe (21). The disturbance branch pipe end cut-off valve (23) is arranged at the tail end of the blind end disturbance branch pipe (21). The disturbance branch pipe vent valve (24) is arranged on the middle branch pipe of the blind end disturbance branch pipe (21); The instrument monitoring system is used to monitor the medium flow conditions in the forced flow disturbance system and the secondary guarantee system; The secondary guarantee system is connected to the flow channel on the blind end side of the pigging tee (4), and is used to connect the main pipeline (1) of the existing pigging and launching system to the venting system, providing safety redundancy for the forced flow disturbance system. The secondary guarantee system includes a secondary guarantee vent pipe (31), a secondary guarantee vent valve (32), and a flow limiting orifice plate (33) arranged on the secondary guarantee vent pipe (31). The secondary guarantee vent pipe (31) is arranged downstream of the first pigging cut-off valve (5). The flow limiting orifice plate (33) is arranged downstream of the secondary guarantee vent valve (32); The instrument monitoring system includes a first flow transmitter (41) and a second flow transmitter (42). The first flow transmitter (41) is arranged on the blind end disturbance branch pipe (21) of the forced flow disturbance system, and is used to monitor the medium flow conditions in the blind end disturbance branch pipe (21). The second flow transmitter (42) is arranged on the secondary guarantee vent pipe (31) of the secondary guarantee system, and is used to monitor the medium flow conditions in the secondary guarantee vent pipe (31).

2. The hydrogen-doped natural gas safety guarantee system based on blind end accumulation control according to claim 1, wherein: The blind end disturbance branch pipe (21) straddles and enters the end of the existing pigging and launching system, and the distance from the first pigging cut-off valve (5) is less than 300 mm.

3. The hydrogen-doped natural gas safety guarantee system based on blind end accumulation control according to claim 1, wherein: The secondary guarantee vent pipe (31) straddles and enters the head end of the existing venting system, and the distance from the first pigging cut-off valve (5) is less than 600 mm.

4. A safeguard method for a hydrogen-doped natural gas safety safeguard system based on blind-end accumulation control according to claim 1, characterized in that: It includes the following steps: Step 1: Set up a forced flow disturbance system, a secondary guarantee system, and an instrument monitoring system on the blind end side of the pigging tee of the existing pigging and launching system; Step 2: Before the pipeline is put into operation, the forced disturbance flow system is turned on. Specifically, the disturbance branch pipe shut-off valve and the disturbance branch pipe end shut-off valve are opened to connect the blind end of the pigging tee with the trunk pipeline in the station. The first pigging shut-off valve and the second pigging shut-off valve of the established pigging launching system are kept closed. Two medium flow directions, including a pigging bypass flow channel and a blind end flow channel, are formed in the station, and the functions of large-scale medium transportation and blind end area disturbance are realized at the same time.

5. The safeguard method according to claim 4, characterized in that: During pipeline operation, if the flow rate of the blind-end disturbance branch pipe decreases, immediately open the secondary protection system, specifically, open the secondary protection vent valve, connect the secondary protection vent pipe with the vent system, and maintain continuous disturbance in the blind-end area; at the same time, immediately implement the replacement of the existing pigging and launching system, that is, open the second pigging shut-off valve of the existing pigging and launching system, implement overall nitrogen replacement from the downstream of the first pigging shut-off valve to the launching barrel area, and open the back pressure control valve of the pigging and launching barrel, introduce hydrogen-blended natural gas from the trunk pipeline to the pigging and launching barrel, and then open the vent valve of the launching barrel. The air regulating valve and the vent pipe shut-off valve maintain the operation of large-scale charging and small-scale discharge at the same time; after being pressurized to the operating pressure, close the vent regulating valve, vent pipe shut-off valve and back pressure control valve of the cleaning tube launching barrel, open the first cleaning tube shut-off valve and the third cleaning tube shut-off valve, close the secondary security system, and the system switches to simultaneous production of the main flow channel and the cleaning flow channel, and immediately inspect and repair the forced disturbance system; after the forced disturbance system is repaired, close the first cleaning tube shut-off valve, the second cleaning tube shut-off valve and the third cleaning tube shut-off valve, and return to the production mode of step two.

6. The safeguard method according to claim 4, characterized in that: Before setting up the forced disturbance system on the blind end side of the cleaning tee of the built cleaning ball system, a numerical analysis is carried out on the closed area between the cleaning tee and the first cleaning shut-off valve, and the self-disturbance area simulation and the minimum self-disturbance flow simulation are carried out under the designed output through full-scale numerical simulation to obtain the maximum disturbance length and the minimum self-disturbance pipeline flow. When the maximum disturbance length is less than the closed section length or the actual output is lower than a certain times the minimum self-disturbance flow, a hydrogen-blended natural gas safety assurance system is set.

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