Efficient hydrogen doping system and hydrogen doping method for natural gas pigging station

Abstract

The invention discloses an efficient hydrogen doping system and method for a natural gas pigging station, and belongs to the technical field of natural gas hydrogen doping. The system comprises an intelligent natural gas flow dividing and mixing system and a pigging device protection system; part of natural gas is introduced to be premixed with hydrogen, the uniformly premixed hydrogen-doped natural gas is mixed into a natural gas main line, and efficient mixing of hydrogen and part of natural gas and mixing of hydrogen and main line natural gas are achieved in stages; the pipe cleaning device protection system is used for intermittently introducing uniformly premixed hydrogen-doped natural gas to disturb a dead gas area near the barrier strip tee joint in normal operation. According to the efficient hydrogen doping system and method for natural gas pigging station transformation, the natural gas hydrogen doping technology and process are optimized, the investment of hydrogen doping facilities is reduced, and the safety of the hydrogen doping process is guaranteed.

Description

Technical Field

[0001] The present invention belongs to the technical field of natural gas hydrogen blending, and in particular relates to a high-efficiency hydrogen blending system and a hydrogen blending method for a natural gas pigging station. Background Art

[0002] Hydrogen-blended natural gas, created by adding a certain percentage of hydrogen to natural gas, can be used directly as a mixed fuel or transported downstream through existing natural gas pipelines for hydrogen separation. Therefore, hydrogen-blended natural gas is currently recognized within the industry as a highly promising method for efficiently utilizing hydrogen energy.

[0003] Natural gas hydrogenation can be achieved by coordinating and controlling the amount of hydrogen injected, and by installing a static mixer to improve the mixing efficiency of natural gas and hydrogen. Currently, the transportation of hydrogenated natural gas through medium- and high-pressure pipelines has not been substantially advanced. Demonstrations of hydrogenated natural gas have primarily been conducted through low-pressure gas pipelines, and their operational scenarios differ significantly from those of hydrogenated natural gas through high-pressure pipelines. Furthermore, hydrogenated natural gas through high-pressure pipelines has the potential to address the large-scale absorption of hydrogen energy. Technical advancement of hydrogenated natural gas pipelines should be deepened based on engineering needs, optimization, and simplification.

[0004] Natural gas pipelines require pigging stations at the mainline's origin or at intermediate stations to deploy pigs for cleaning impurities and conducting internal inspections. Natural gas hydrogen blending stations can be integrated with these stations to save space and investment. However, the addition of hydrogen blending equipment to natural gas pigging stations can raise concerns about potential hydrogen damage to pigging facilities, static mixer maintenance, and the accidental detachment of static mixer internals into downstream pipelines. Therefore, it is necessary to fully identify risks and explore mitigation strategies.

[0005] However, there is currently little public information on the setup of hydrogen blending systems for natural gas pigging stations, and there is also limited information on hydrogen blending systems for high-pressure natural gas pipelines. Therefore, in order to comprehensively implement efficient hydrogen blending in natural gas pigging stations, it is necessary to conduct relevant research, optimize natural gas hydrogen blending processes, and establish efficient, economical, and reliable hydrogen blending systems and methods to support technological development in this field. Summary of the Invention

[0006] The purpose of the present invention is to overcome the shortcomings of the existing technology and provide a high-efficiency hydrogen blending system and method for natural gas pigging stations. Based on existing natural gas pigging stations and combining the basic principles of natural gas hydrogen blending, the present invention provides a natural gas intelligent diversion and blending system, a static mixer maintenance and support system, and a pigging device protection system to collaboratively ensure the safe and efficient operation of natural gas pigging stations after they are modified to add natural gas hydrogen blending capabilities.

[0007] The object of the present invention is achieved through the following technical solutions:

[0008] A high-efficiency hydrogen blending system for a natural gas pigging station includes a conventional natural gas station pigging system, the conventional natural gas station pigging system including a natural gas trunk line, a downstream trunk line, a first pigging shutoff valve, a second pigging shutoff valve, a third pigging shutoff valve, a tee bar, and a pigging ball launcher, one end of each of the first pigging shutoff valve, the second pigging shutoff valve, and the third pigging shutoff valve being connected to an outlet of the tee bar, respectively; the other end of the first pigging shutoff valve being connected to the natural gas trunk line, the other end of the second pigging shutoff valve being connected to the downstream trunk line, and the other end of the third pigging shutoff valve being connected to the pigging ball launcher; a manual trunk shutoff valve is further provided near the upstream of the natural gas trunk line; the hydrogen blending system further includes:

[0009] A natural gas intelligent diversion and blending system is used to introduce natural gas from a natural gas trunk line, mix it with hydrogen, and then inject the resulting uniformly mixed medium into the natural gas trunk line for a second time;

[0010] The pigging device protection system is used to intermittently introduce the uniformly mixed medium to control the hydrogen concentration of the baffle tee during normal operation, and provide the uniformly mixed medium as the isolation gas between the front end and the rear end of the pigging ball barrel.

[0011] Furthermore, the natural gas intelligent diversion and blending system includes a static mixer, which introduces natural gas upstream of the main manual shut-off valve through a first mixing branch line and mixes it with hydrogen introduced through a second mixing branch line, and then introduces the mixed gas downstream of the main manual shut-off valve through a third mixing branch line.

[0012] Furthermore, the pipe cleaning device protection system includes a pipe cleaning ball-serving branch and a ball-serving barrel pressure balancing branch. The pipe cleaning ball-serving branch is connected to the front end of the pipe cleaning ball-serving barrel, and the pipe cleaning ball-serving branch is provided with a pipe cleaning ball-serving branch shut-off valve and a pipe cleaning device ball-pushing regulating valve in sequence. The ball-serving barrel pressure balancing branch is connected to the pipe cleaning ball-serving branch and the rear end of the pipe cleaning ball-serving barrel, and the ball-serving barrel pressure balancing branch is provided with a ball-serving barrel pressure balancing regulating valve.

[0013] Furthermore, the pigging device protection system also includes a blind-end purge branch, the starting end of the blind-end purge branch is arranged on the upstream natural gas trunk line of the first pigging shut-off valve, the terminal end of the blind-end purge branch is arranged on the pipeline between the baffle tee and the third pigging shut-off valve, and the blind-end purge branch is provided with a purge branch regulating valve and a purge branch flow transmitter.

[0014] Furthermore, the first mixing branch line is provided with a natural gas branch regulating valve and a natural gas branch flow transmitter; the second mixing branch line is provided with a hydrogen injection pipeline shut-off valve, a hydrogen injection pipeline regulating valve and a hydrogen injection pipeline flow transmitter; the third mixing branch line is provided with a mixing branch shut-off valve connected to the downstream of the main line manual shut-off valve.

[0015] Furthermore, the hydrogen doping system further comprises:

[0016] A static mixer maintenance and support system includes a filter separator and a downstream bypass shutoff valve provided on the third mixing branch line, and an upstream bypass shutoff valve provided on the first mixing branch line.

[0017] On the other hand, the present invention also provides a method for efficient hydrogen blending at a natural gas pigging station, the method being implemented based on any of the aforementioned efficient hydrogen blending systems for a natural gas pigging station, the method comprising:

[0018] Open the trunk manual shutoff valve, the first pigging shutoff valve, and the second pigging shutoff valve, keep all other valves closed, and start natural gas transmission. Introduce part of the natural gas in the natural gas trunk line into the natural gas intelligent diversion and blending system for mixing;

[0019] When the pigging operation is ready to begin, the blind plate of the pig launching barrel is opened, the pig is placed in, and the blind plate is closed. The operation continues for a preset period of time. Then, the pig launching barrel is filled with natural gas and the pressure is gradually increased to the operating pressure of the natural gas trunk line. Then, the pig is pushed into the downstream trunk line to complete the pig launching operation.

[0020] Furthermore, the gas flow rate of the natural gas intelligent diversion and blending system is determined as follows:

[0021] The maximum allowable hydrogen blending ratio is fed back based on the hydrogen damage analysis results of the natural gas trunk line material as the maximum hydrogen blending ratio for the natural gas introduced into the natural gas intelligent diversion and blending system;

[0022] The natural gas volume flow rate introduced into the natural gas intelligent diversion and blending system is converted based on the maximum hydrogen blending ratio and the set hydrogen blending flow rate of the natural gas trunk line;

[0023] According to the natural gas volume flow rate and the known maximum flow rate index, the diameter of the pipe that can be introduced into the natural gas intelligent diversion and blending system is converted.

[0024] Furthermore, the method sets a safety margin ratio of the maximum hydrogen blending ratio, and uses the maximum hydrogen blending ratio*safety margin ratio as the actual maximum hydrogen blending ratio.

[0025] Furthermore, the method further comprises:

[0026] The differential pressure of the third mixing branch line is continuously monitored, and when the differential pressure is greater than a preset differential pressure threshold, maintenance is performed on the third mixing branch line.

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

[0028] (1) The present invention fully considers the application background and application scenarios of hydrogen-blended natural gas, based on the functions and scenarios of natural gas pigging stations, with the transformation of natural gas pigging stations into hydrogen-blended natural gas pigging stations as the specific background, comprehensively considering specific issues and industry pain points such as efficient hydrogen blending, optimized hydrogen blending, static mixer maintenance, and hydrogen damage protection of pigging systems, and specifically sets up a natural gas intelligent diversion and blending system, a static mixer maintenance and guarantee system, and a pigging device protection system, etc., and proposes a method for determining the pre-hydrogen blending concentration of natural gas, which achieves an efficient balance in terms of static mixer size optimization and hydrogen blending safety, and specifically limits and overcomes the impact of hydrogen-blended natural gas pigging on pigging facilities faced in actual production.

[0029] (2) The present invention proposes setting up a pre-blending system based on the maximum allowable hydrogen concentration of the pipe material performance, which greatly optimizes the size of the static mixer and significantly reduces costs. At the same time, it provides operational safety protection measures for the branch static mixer. On the one hand, it prevents the internal components of the static mixer from accidentally falling off and entering the natural gas trunk line, affecting production operations. On the other hand, it prevents the maintenance of the static mixer from affecting the normal operation of the natural gas trunk line. The potential economic benefits are significant. Furthermore, the present invention provides a pigging device protection system, which plays an essential role in protecting the expensive natural gas internal detector (or pig). BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The present invention provides a schematic diagram of a high-efficiency hydrogen blending system for a natural gas pigging station.

[0031] Figures: 1-natural gas trunk line, 2-natural gas trunk line flow transmitter, 3-trunk manual shut-off valve, 4-pigging first shut-off valve, 5-blocking bar tee, 6-downstream trunk line, 7-pigging second shut-off valve, 8-pigging third shut-off valve, 9-pigging ball launcher, 10-pigging ball launcher temperature transmitter, 11-pigging ball launcher first pressure transmitter, 12-pigging ball launcher second pressure transmitter, 21-natural gas blending branch pipe, 22-natural gas branch pipe regulating valve, 23-natural gas branch pipe flow transmitter, 24-static mixer , 25-hydrogen injection pipeline shut-off valve, 26-hydrogen injection pipeline regulating valve, 27-hydrogen injection pipeline flow transmitter, 28-mixing branch shut-off valve, 31-filter separator, 32-upstream bypass shut-off valve, 33-downstream bypass shut-off valve, 41-pig launching branch, 42-pig launching branch shut-off valve, 43-pig pusher regulating valve, 44-launching cylinder pressure balancing regulating valve, 45-launching cylinder pressure balancing branch, 46-blind end purge branch, 47-purge branch regulating valve, 48-purge branch flow transmitter. DETAILED DESCRIPTION

[0032] The following describes the embodiments of the present invention through specific examples. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments. The details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the following embodiments and features in the embodiments can be combined with each other unless they conflict.

[0033] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative work shall fall within the scope of protection of the present invention.

[0034] By adding natural gas hydrogen blending equipment to the natural gas pigging station, there may be problems such as potential damage to the hydrogen in the pigging facilities, operation and maintenance of the static mixer, and accidental detachment of the internal components of the static mixer and entry into the downstream pipeline. Therefore, it is necessary to fully identify risks and explore response strategies.

[0035] However, there is currently little public information on the setup of hydrogen blending systems for natural gas pigging stations, and there is also limited information on hydrogen blending systems for high-pressure natural gas pipelines. Therefore, in order to comprehensively implement efficient hydrogen blending in natural gas pigging stations, it is necessary to conduct relevant research, optimize natural gas hydrogen blending processes, and establish efficient, economical, and reliable hydrogen blending systems and methods to support technological development in this field.

[0036] In order to solve the above technical problems, the present invention proposes the following embodiments of a high-efficiency hydrogen blending system and method for a natural gas pigging station.

[0037] Example 1

[0038] Reference Figure 1 ,like Figure 1 The figure shows a schematic diagram of a high-efficiency hydrogen blending system for a natural gas pigging station, as provided in this embodiment. This system includes an intelligent natural gas diversion and blending system, a static mixer maintenance and support system, and a pigging device protection system. It should be noted that this embodiment is based on the basic setup of a conventional natural gas pigging station, but this aspect does not constitute its innovative content.

[0039] The conventional natural gas station pigging system is a conventional configuration, including a natural gas trunk line 1, a natural gas trunk line flow transmitter 2, a trunk line manual shutoff valve 3, a first pigging shutoff valve 4, a retaining bar tee 5, a downstream trunk line 6, a second pigging shutoff valve 7, a third pigging shutoff valve 8, a pigging launcher 9, a pigging launcher temperature transmitter 10, a first pigging launcher pressure transmitter 11, and a second pigging launcher pressure transmitter 12. It is used to pig the downstream natural gas trunk line and provide a natural gas flow channel through the station. It should be noted that the natural gas trunk line flow transmitter 2 and the trunk line manual shutoff valve 3 are unconventional pigging station settings and are installed in the conventional natural gas station pigging system in this embodiment.

[0040] Among them, the natural gas blending branch pipe 21, the natural gas branch pipe regulating valve 22, the natural gas branch pipe flow transmitter 23, the static mixer 24, the hydrogen injection pipeline shut-off valve 25, the hydrogen injection pipeline regulating valve 26, the hydrogen injection pipeline flow transmitter 27, the blending branch pipe shut-off valve 28, etc. constitute a natural gas intelligent diversion and blending system, which is used to introduce a portion of natural gas from the natural gas trunk line, efficiently mix it with hydrogen, and then the formed uniform blending medium is blended into the natural gas trunk line for a second time, avoiding the concentration distribution problem caused by directly injecting hydrogen into the trunk line, and also effectively reducing the size of the static mixer and avoiding the potential risk of detachment of the internal components of the static mixer affecting the downstream trunk line.

[0041] The natural gas intelligent diversion and blending system includes a natural gas blending branch pipe 21, a natural gas branch pipe regulating valve 22, a natural gas branch pipe flow transmitter 23, a static mixer 24, a hydrogen injection pipeline shut-off valve 25, a hydrogen injection pipeline regulating valve 26, a hydrogen injection pipeline flow transmitter 27, a blending branch pipe shut-off valve 28, etc., which is used to introduce a portion of natural gas from the natural gas trunk line, efficiently mix it with hydrogen, and then mix the formed uniform blending medium into the natural gas trunk line for a second time, avoiding the concentration distribution problem caused by directly injecting hydrogen into the trunk line, and also effectively reducing the size of the static mixer and avoiding the potential risk of detachment of the internal components of the static mixer and the impact on the downstream trunk line.

[0042] The natural gas blending branch pipe 21 is a bypass pipe for the main manual shut-off valve 3, preferably made of low-grade carbon steel (L360 steel grade and below), and is used to divert a portion of natural gas from the natural gas main line 1 as a carrier for the natural gas and hydrogen premix. The natural gas branch pipe regulating valve 22 is an electric regulating valve made of carbon steel, which is used to control the flow of natural gas drawn from the natural gas blending branch pipe 21. Furthermore, the flow rate regulated by the natural gas branch pipe regulating valve 22 is determined based on the maximum allowable blending concentration entering the natural gas main line 1 and the hydrogen injection amount. The natural gas branch pipe flow transmitter 23 is located downstream of the natural gas branch pipe regulating valve 22 and is used to measure the volume flow of natural gas introduced into the natural gas blending branch pipe 21 in real time. In combination with the set introduction set value, it supports the adjustment of the opening of the natural gas branch pipe regulating valve 22. The static mixer 24 is a natural gas and hydrogen static mixer made of carbon steel, preferably a conventional SV type static mixer, which is used to efficiently mix the introduced natural gas and the injected hydrogen, and the unevenness after mixing is less than 1%; the hydrogen injection pipeline shut-off valve 25 is arranged on the hydrogen injection pipeline, made of carbon steel, and is an electric ball valve for controlling the opening or shutoff of the hydrogen injection pipeline; the hydrogen injection pipeline regulating valve 26 is arranged downstream of the hydrogen injection pipeline shut-off valve 25, and is an electric regulating valve made of carbon steel for controlling the hydrogen injection volume flow rate; the hydrogen injection pipeline flow transmitter 27 is arranged downstream of the hydrogen injection pipeline regulating valve 26, and is used to perform real-time measurement of the hydrogen volume flow rate of the hydrogen injection pipeline, and support the adjustment of the opening of the hydrogen injection pipeline regulating valve 26 in combination with the set mixing ratio.

[0043] The static mixer maintenance and protection system includes a filter separator 31, an upstream bypass shut-off valve 32, a downstream bypass shut-off valve 33, etc., which are used to actively protect the static mixer from the risk of internal components detaching, and also provide a spare bypass interface for the static mixer for online replacement of the static mixer.

[0044] The filter separator 31 is arranged downstream of the static mixer 24, and is preferably a filter-type filter separator, which is used to remove dust and filter the premixed natural gas and hydrogen mixed gas. It can also be used as a blocking element for accidental detachment of internal components of the static mixer 24, to prevent the detached internal components from accidentally entering the downstream natural gas trunk line; further, the filter separator 31 is provided with a differential pressure transmitter for indicating the pressure difference between the inlet and outlet, and characterizing the passability of the filter separator 31; the upstream bypass shut-off valve 32 and the downstream bypass shut-off valve 33 are both manual carbon steel ball valves, which are normally closed and are distributed upstream of the static mixer 24 and downstream of the filter separator 31, and are used to provide a spare bypass interface for the static mixer, supporting online replacement of the static mixer.

[0045] The pigging device protection system includes a pigging ball launching branch 41, a pigging ball launching branch shut-off valve 42, a pigging ball pushing regulating valve 43, a launching barrel pressure balancing regulating valve 44, a launching barrel pressure balancing branch 45, a blind-end purge branch 46, a purge branch regulating valve 47, a purge branch flow transmitter 48, etc., which are used to intermittently introduce premixed and uniformly hydrogen-blended natural gas to disturb the "dead gas" area near the baffle tee during normal operation to prevent the accumulation of hydrogen-blended natural gas with excessively high hydrogen concentration. At the same time, during the pigging process, premixed and uniformly hydrogen-blended natural gas is provided as isolation gas between the front and rear ends of the pig. Furthermore, by adjusting the hydrogen injection amount, the isolation gas between the front and rear ends of the pig can be temporarily adjusted to pure natural gas to ensure the structural and functional safety of the pig and its internal components.

[0046] The cleaning ball launching branch 41 is made of carbon steel and is led out from the natural gas mixing branch 21. It is used to provide the cleaning ball launching cylinder with balancing gas, isolation gas and initial pushing gas during the cleaning process; the cleaning ball launching branch shut-off valve 42 is set at the inlet position of the cleaning ball launching branch 41. It is a carbon steel manual ball valve, which is normally closed and opened only during the launching operation; the cleaning ball pushing regulating valve 43 is set on the branch at the large cylinder end of the cleaning ball launching cylinder 9. It is a manual regulating valve used to adjust the air intake during the cleaning ball launching stage and provide the driving force for the cleaning ball; the launching cylinder pressure balance regulating valve 44 is a manual regulating valve made of carbon steel. It is set on the launching cylinder pressure balance branch 45 and is used to provide a pressure between the front end of the cleaning ball and the third cleaning shut-off valve 8. The pipe section provides pressurized gas to establish back pressure; the pressure balance branch 45 of the launching cylinder is a carbon steel pipe, connecting the large cylinder and the small cylinder of the pig launching cylinder 9; the blind-end purge branch 46 connects the upstream of the first pigging shut-off valve 4 and the downstream of the third pigging shut-off valve 8, made of carbon steel, and is used to introduce a small flow of hydrogen-blended natural gas from the natural gas trunk line 1 to the downstream of the third pigging shut-off valve 8 (close to the third pigging shut-off valve 8) to avoid the formation of a dead gas zone in the pipeline between the third pigging shut-off valve 8 and the baffle tee 5, causing potential high-concentration hydrogen accumulation risk; the purge branch regulating valve 47, the purge branch flow transmitter 48, etc. are arranged on the blind-end purge branch 46, and are distributed to control the introduced gas flow and gas flow measurement.

[0047] The working principle of this embodiment is as follows:

[0048] This embodiment is based on the background that a natural gas pigging station is used for hydrogen blending and is transformed into a pigging station with hydrogen blending function. In combination with the basic principles of natural gas hydrogen blending, a natural gas intelligent diversion and blending system, a static mixer maintenance and guarantee system, and a pigging device protection system are provided to collaboratively ensure the safe and efficient operation of the natural gas pigging station after it is transformed to add the natural gas hydrogen blending function.

[0049] Hydrogen blending in natural gas pipelines poses the risk of hydrogen damage to the mainline materials, necessitating a reasonable maximum hydrogen blending ratio. Furthermore, the hydrogen blending ratio for hydrogen-blended natural gas pipelines is influenced by the natural gas throughput and the actual volume of hydrogen to be blended. In other words, the hydrogen blending ratio is influenced by the hydrogen source's supply capacity and downstream demand. The hydrogen tolerance of pipeline materials is often greater than the actual required hydrogen blending concentration, which provides the conditions for the development of this embodiment.

[0050] Furthermore, currently, hydrogen blending in medium- and low-pressure gas pipelines uses static mixers to achieve efficient mixing of natural gas and hydrogen. However, for medium- and high-pressure natural gas trunk lines, directly adding a static mixer to the natural gas trunk line faces problems such as high equipment investment and damage to downstream pipelines caused by detachment of static mixer internal components. Considering the aforementioned background conditions for hydrogen blending ratios, this embodiment achieves mixing of the premixed hydrogen-blended natural gas with the remaining trunk line natural gas by drawing a portion of natural gas from the natural gas trunk line, premixing it with hydrogen, and then reinjecting the premixed hydrogen-blended natural gas into the natural gas trunk line. This significantly reduces the volume of the static mixer and also prevents static mixer internal components from detaching and entering the downstream natural gas trunk line by installing a small filtration system. Furthermore, because the hydrogen concentration ratio of the premixed hydrogen-blended natural gas is insufficient to damage the natural gas trunk line, the premixed hydrogen-blended natural gas is blended with the remaining trunk line natural gas through natural flow mixing, fully utilizing the flow characteristics of the medium and overcoming the problems of adding a new trunk line static mixer.

[0051] In terms of the pigging system, this embodiment provides several considerations for pigging equipment protection. First, for expensive in-pipe detectors, this embodiment can be used to provide drainage pipes during the pigging process, adjusting the gas at the front and rear ends of the detector to natural gas, thereby preventing damage to the detector by hydrogen components and providing operating conditions for temporarily reducing the hydrogen blending ratio. Second, for the pipe section between the shut-off valve downstream of the pigging launcher and the retaining bar tee, since there may be a "dead gas zone" there, this embodiment provides a drainage pipe to continuously supply a small flow of gas to this area, keeping the medium in this area in a flowing state and avoiding the problem of high hydrogen concentration and hydrogen accumulation after the local gas is left to stand.

[0052] Example 2

[0053] This embodiment is based on the working principle of the efficient hydrogen blending system for a natural gas pigging station provided in the previous embodiment, and proposes a method for efficient hydrogen blending for a natural gas pigging station.

[0054] Step 1: Connect and modify the existing natural gas pigging station transmission system. Specifically, close the first and second pigging block valves 4 and 7, as well as the upstream inlet block valve of the natural gas pigging station, and vent and replace the natural gas pipeline medium at the natural gas pigging station. Then, modify the natural gas pigging station by installing a natural gas intelligent diversion and blending system, a static mixer maintenance and support system, and a pigging device protection system.

[0055] Step 2: Hydrogen blending is performed on the normally transported natural gas. Specifically, the main line manual shutoff valve 3, the first pigging shutoff valve 4, and the second pigging shutoff valve 7 are opened, while all other valves are closed, and natural gas delivery begins. The natural gas branch regulating valve 22 and the blending branch shutoff valve 28 are opened to introduce some of the natural gas from the natural gas main line 1 into the natural gas blending branch 21. The flow rate is controlled by adjusting the natural gas branch regulating valve 22. The natural gas flow rate introduced into the natural gas blending branch 21 is determined according to the following principles:

[0056] (1) Based on the hydrogen damage analysis results of the natural gas trunk material, the maximum allowable hydrogen blending ratio M is fed back as the maximum hydrogen blending ratio in the natural gas blending branch pipe 21. With an 80% safety margin, the maximum hydrogen blending ratio V1 in the natural gas blending branch pipe 21 can be obtained, which is expressed as:

[0057] V1=0.8M

[0058] Where,

[0059] V1——the maximum hydrogen blending ratio allowed in the natural gas blending branch pipe 21, %

[0060] M——The maximum hydrogen content allowed in hydrogen damage analysis of natural gas trunk line materials, %

[0061] The purpose is to ensure that even if the hydrogen-blended natural gas blended by the natural gas blending branch pipe 21 enters the trunk pipeline unevenly, the hydrogen content ratio after premixing will not cause hydrogen damage to the trunk pipeline material;

[0062] (2) Based on the determined maximum hydrogen blending ratio V1 of the natural gas blending branch 21, combined with the set hydrogen blending flow rate Q of the natural gas trunk line H , convert the natural gas volume flow introduced into the natural gas blending branch pipe 21, recorded as Q N1 :

[0063] Q N1 =Q H V1-Q H

[0064] Where,

[0065] QH——Hydrogen blending volume flow rate set in natural gas trunk line, m 3 / d(standard condition);

[0066] Q N1 ——Volume flow of natural gas that can be introduced into the natural gas blending branch pipe 21, m 3 / d(standard condition);

[0067] Thus, the volume flow of natural gas that can be introduced into the natural gas blending branch pipe 21 is obtained, and the diameter of the natural gas blending branch pipe 21 can be converted based on the volume flow and the maximum flow rate of 20 m / s.

[0068] Subsequently, the hydrogen injection pipeline shutoff valve 25 and hydrogen injection pipeline regulating valve 26 are gradually opened. Based on the target hydrogen blending ratio and the detection results of the natural gas trunk line flow transmitter 2, the opening of the hydrogen injection pipeline regulating valve 26 is dynamically adjusted to ensure that the hydrogen blending ratio of the natural gas entering the natural gas trunk line 1 meets the target hydrogen blending ratio. Furthermore, as the flow rate of the natural gas trunk line 1 fluctuates, the opening of the hydrogen injection pipeline regulating valve 26 is adjusted according to the target hydrogen blending ratio, and the opening of the natural gas branch pipe regulating valve 22 is adjusted according to the maximum allowable blending ratio.

[0069] Step 3: Continuously monitor the differential pressure of the filter separator 31 downstream of the static mixer. When the differential pressure is greater than 0.1 MPa, it indicates that there is a certain amount of blockage inside the static mixer. Then, connect the spare static mixer to the upstream bypass shut-off valve 32 and the downstream bypass shut-off valve 33, depressurize and replace the filter separator 31 and the static mixer 24, clean the filter structure of the filter separator 31, and check the integrity of the internal components of the static mixer 24. Similarly, it is preferred to check the integrity of the internal components of the static mixer 24 at a frequency of 2 months to avoid blowing off its internal structure and affecting the mixing efficiency.

[0070] Step 4: When preparing to start the pigging operation, open the blind plate of the pig launching barrel 9, put in the pig, and close the blind plate; preferably suspend hydrogen injection, that is, close the hydrogen injection pipeline shut-off valve 25 and the hydrogen injection pipeline regulating valve 26, and continue to run for 2 minutes; then open the pig launching branch shut-off valve 42, the pig pushing ball regulating valve 43, and the launching barrel pressure balance regulating valve 44, and fill the pig launching barrel 9 (the front and back parts of the pig) with natural gas, and gradually increase the pressure to the operating pressure of the natural gas trunk line 1; then close the launching barrel pressure balance regulating valve 44, open the third pigging shut-off valve 8, increase the opening of the pig pushing ball regulating valve 43, and gradually push the pig into the downstream trunk line 6, then close the pig launching branch shut-off valve 42 and the pig pushing ball regulating valve 43 to complete the pig ball launching operation. It should be noted that the above steps are based on the consideration of complete protection of the pig. When the pig can withstand a certain hydrogen concentration, it is possible not to cut off the hydrogen injection. Instead, the first pig shut-off valve 4 is opened to introduce all the mixed hydrogen-blended natural gas into the pig launching barrel 9 through the pig launching branch 41, and the pig is pushed.

[0071] Step 4: During normal hydrogen blending operation, it is preferred to open the purge branch regulating valve 47 to introduce part of the blended hydrogen-blended natural gas into the downstream pipeline near the third pigging shut-off valve 8 to avoid the formation of a dead air zone between the third pigging shut-off valve 8 and the baffle tee 5, which would cause local high-concentration accumulation of unmixed hydrogen-blended natural gas.

[0072] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A natural gas pigging station efficient hydrogen blending system, comprising a conventional natural gas station pigging system, the conventional natural gas station pigging system comprising a natural gas trunk line, a downstream trunk line, a first pigging shut-off valve, a second pigging shut-off valve, a third pigging shut-off valve, a retaining bar tee and a pigging ball launcher, wherein one end of the first pigging shut-off valve, the second pigging shut-off valve and the third pigging shut-off valve are respectively connected to an outlet of the retaining bar tee, the other end of the first pigging shut-off valve is connected to the natural gas trunk line, the other end of the second pigging shut-off valve is connected to the downstream trunk line, and the other end of the third pigging shut-off valve is connected to the pigging ball launcher, characterized in that: The natural gas trunk line is also provided with a trunk manual shut-off valve near the upstream, and the hydrogen blending system further comprises: A natural gas intelligent diversion and blending system is used to introduce natural gas from a natural gas trunk line, mix it with hydrogen, and then inject the resulting uniformly mixed medium into the natural gas trunk line for a second time; The pigging device protection system is used to intermittently introduce the uniformly mixed medium to control the hydrogen concentration of the baffle tee during normal operation, and provide the uniformly mixed medium as the isolation gas between the front end and the rear end of the pigging ball barrel.

2. The efficient hydrogen blending system for a natural gas pigging station according to claim 1, characterized in that: The natural gas intelligent diversion and blending system includes a static mixer, which introduces natural gas upstream of the main manual shut-off valve through a first mixing branch line and mixes it with hydrogen introduced through a second mixing branch line, and then introduces the mixed gas downstream of the main manual shut-off valve through a third mixing branch line.

3. The efficient hydrogen blending system for a natural gas pigging station according to claim 2, characterized in that: The pipe cleaning device protection system includes a pipe cleaning ball-serving branch and a ball-serving barrel pressure balancing branch. The pipe cleaning ball-serving branch is connected to the front end of the pipe cleaning ball-serving barrel, and the pipe cleaning ball-serving branch is provided with a pipe cleaning ball-serving branch shut-off valve and a pipe cleaning device ball-pushing regulating valve in sequence. The ball-serving barrel pressure balancing branch is connected to the pipe cleaning ball-serving branch and the rear end of the pipe cleaning ball-serving barrel, and the ball-serving barrel pressure balancing branch is provided with a ball-serving barrel pressure balancing regulating valve.

4. The high-efficiency hydrogen blending system for a natural gas pigging station according to claim 3, characterized in that: The pigging device protection system also includes a blind-end purge branch pipe, the starting end of which is arranged at the upstream natural gas trunk line of the first pigging shut-off valve, and the terminal end of which is arranged at the pipeline between the baffle tee and the third pigging shut-off valve, and the blind-end purge branch pipe is provided with a purge branch pipe regulating valve and a purge branch pipe flow transmitter.

5. The efficient hydrogen blending system for a natural gas pigging station according to claim 2, characterized in that: The first mixing branch line is provided with a natural gas branch regulating valve and a natural gas branch flow transmitter; the second mixing branch line is provided with a hydrogen injection pipeline shut-off valve, a hydrogen injection pipeline regulating valve and a hydrogen injection pipeline flow transmitter; the third mixing branch line is provided with a mixing branch shut-off valve connected to the downstream of the main line manual shut-off valve.

6. The efficient hydrogen blending system for a natural gas pigging station according to claim 2, characterized in that: The hydrogen doping system further comprises: A static mixer maintenance and support system includes a filter separator and a downstream bypass shutoff valve provided on the third mixing branch line, and an upstream bypass shutoff valve provided on the first mixing branch line.

7. A method for efficiently adding hydrogen to a natural gas pigging station, the method being implemented based on the efficient hydrogen adding system for a natural gas pigging station according to any one of claims 1 to 6, the method comprising: Open the trunk manual shutoff valve, the first pigging shutoff valve, and the second pigging shutoff valve, keep all other valves closed, and start natural gas transmission. Introduce part of the natural gas in the natural gas trunk line into the natural gas intelligent diversion and blending system for mixing; When the pigging operation is ready to begin, the blind plate of the pig launching barrel is opened, the pig is placed in, and the blind plate is closed. The operation continues for a preset period of time. Then, the pig launching barrel is filled with natural gas and the pressure is gradually increased to the operating pressure of the natural gas trunk line. Then, the pig is pushed into the downstream trunk line to complete the pig launching operation.

8. The efficient hydrogen blending method for a natural gas pigging station according to claim 7, characterized in that: The gas flow rate introduced into the natural gas intelligent diversion and blending system is determined as follows: The maximum allowable hydrogen blending ratio is fed back based on the hydrogen damage analysis results of the natural gas trunk line material as the maximum hydrogen blending ratio for the natural gas introduced into the natural gas intelligent diversion and blending system; The natural gas volume flow rate introduced into the natural gas intelligent diversion and blending system is converted based on the maximum hydrogen blending ratio and the set hydrogen blending flow rate of the natural gas trunk line; According to the natural gas volume flow rate and the known maximum flow rate index, the diameter of the pipe that can be introduced into the natural gas intelligent diversion and blending system is converted.

9. The efficient hydrogen blending method for a natural gas pigging station according to claim 8, characterized in that: The method sets a safety margin ratio for the maximum hydrogen blending ratio, and uses the maximum hydrogen blending ratio*safety margin ratio as the actual maximum hydrogen blending ratio.

10. The method for efficient hydrogen blending in a natural gas pigging station according to claim 7, characterized in that: The method further comprises: The differential pressure of the third mixing branch line is continuously monitored, and when the differential pressure is greater than a preset differential pressure threshold, maintenance is performed on the third mixing branch line.

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