Natural gas station to hydrogen station service pressure optimization method

Abstract

The invention discloses a natural gas station-to-hydrogen station service pressure optimization method, and belongs to the technical field of hydrogen station design. According to the method, a thermal radiation evaluation model of a hydrogen / natural gas station at the same aperture and different pressure scales is established, and hydrogen and natural gas leakage consequence influence ranges are compared based on leakage consequence comparison results; and establishing an in-service natural gas pipeline-to-hydrogen service operation pressure correction model with equal influence and consequences, and actively optimizing the highest operation pressure after conversion in combination with the actual transmission and distribution situation to ensure that the fireproof spacing meets the lower gear standard of the natural gas station.

Description

Technical Field

[0001] This invention belongs to the field of hydrogen station design technology, and in particular relates to a method for optimizing the service pressure of a natural gas station when converting it to a hydrogen station. Background Technology

[0002] With the development of clean energy alternatives, using existing natural gas pipelines to transport hydrogen will become one of the future trends for large-scale hydrogen storage, transportation, and application. Its significant advantage lies in avoiding the duplication of pipeline transportation systems, and the efficient use of natural gas pipelines for hydrogen transportation through reasonable modifications. Its main components include the transportation pipeline and the transportation stations. In fact, the processes of hydrogen pipeline transportation and natural gas pipeline transportation are similar. Since both are single-phase gas transportation, the main functions of pipeline transportation stations are dust removal, metering, pipeline cleaning, distribution, and pressure regulation.

[0003] Compared to natural gas (which mainly contains methane), hydrogen has a wider explosive range, lower ignition energy, and higher thermal energy per unit mass. However, hydrogen also exhibits certain hydrogen-damaging properties towards high-strength steel pipes. Furthermore, experience in constructing hydrogen pipelines is significantly less than that in natural gas pipelines. Therefore, when converting existing natural gas pipelines to hydrogen service, safety assurance must be given high priority.

[0004] To ensure the safety of the surrounding environment of pipeline transportation stations, current designs for these stations must consider external fire separation distances. However, if natural gas stations are converted to hydrogen service and fire separation distances are applied based on equivalent pressure levels, it could lead to excessively large demolition areas in the surrounding area. Generally, the operating pressure of hydrogen pipelines is much lower than that of natural gas pipelines. For example, due to factors such as transmission distance, flow rate, and terminal consumption, the transmission pressure of hydrogen pipelines is typically 3–5 MPa, far lower than that of conventional natural gas pipelines. If natural gas stations are classified according to a 4 MPa fire separation distance, most natural gas stations, after renovation or expansion, would have to adhere to a standard greater than 4 MPa, significantly increasing external fire separation distances. Since hydrogen pipelines operate at relatively lower pressures, classifying them according to the fire separation distance standards applied to converted natural gas pipeline stations could result in significant space waste. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method for optimizing the service pressure of natural gas stations after they are converted to hydrogen stations. This method fully considers the external fire protection distance problem after the conversion of in-service natural gas pipelines to hydrogen stations, optimizes the evaluation criteria, and forms a method for evaluating the fire protection distance of natural gas stations after they are converted to hydrogen stations, so as to quantitatively support the optimization and control of the fire protection distance of in-service natural gas pipeline stations after they are converted to hydrogen stations.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] A method for optimizing the service pressure of a natural gas station converted to a hydrogen station, the method comprising:

[0008] Obtain the distribution of pipeline design coefficients and regional classification information during the renovation of natural gas stations, and calculate the maximum allowable operating pressure of the target natural gas station when it is converted into a hydrogen station as the initial recommended operating pressure for the hydrogen station;

[0009] Obtain the pressure parameters of the natural gas station under comparative operating conditions, and calculate the thermal radiation influence distance ratio of hydrogen and natural gas based on the pressure parameters of the natural gas station under the comparative operating conditions and the recommended operating pressure of the initial hydrogen station.

[0010] The operating pressure of the hydrogen station is determined based on the aforementioned thermal radiation influence distance ratio, specifically including:

[0011] When the thermal radiation influence distance ratio does not exceed the preset distance ratio threshold, the recommended operating pressure for the hydrogen station is the optimal operating pressure.

[0012] When the thermal radiation influence distance ratio exceeds a preset distance ratio threshold, the recommended operating pressure of the hydrogen station is reduced, and the thermal radiation influence distance ratio of hydrogen and natural gas is recalculated until the thermal radiation influence distance ratio of hydrogen and natural gas does not exceed the preset threshold. At this time, the recommended operating pressure of the hydrogen station is the optimal operating pressure.

[0013] Furthermore, the pressure parameter of the natural gas station under the comparative operating condition is 4 MPa.

[0014] Furthermore, the calculation of the thermal radiation influence distance ratio between hydrogen and natural gas based on the natural gas station pressure parameters under the comparative operating conditions and the initial recommended operating pressure of the hydrogen station specifically includes:

[0015] Calculate the critical expansion coefficients of hydrogen and natural gas;

[0016] Calculate the leakage mass flow rate of hydrogen and natural gas under different leakage orifice diameters;

[0017] The thermal radiation influence distances of hydrogen and natural gas are calculated based on the leakage mass flow rates of hydrogen and natural gas under different leakage orifice diameters and the critical expansion coefficients of hydrogen and natural gas. The ratio of the thermal radiation influence distance of hydrogen to that of natural gas is called the ratio of the thermal radiation influence distances of hydrogen and natural gas.

[0018] Furthermore, the design factors include the pipe outer diameter, pipe wall thickness, and pipe minimum yield strength.

[0019] Furthermore, the preset distance ratio threshold is 0.95.

[0020] Furthermore, the leakage orifice diameter includes 50 mm and 100 mm.

[0021] Furthermore, the distance affected by hydrogen thermal radiation and the distance affected by natural gas thermal radiation are calculated using the horizontal direction as the direction.

[0022] The beneficial effects of this invention are as follows:

[0023] Based on the physical properties of hydrogen and natural gas and the regional classification information of the pipeline, this invention proposes a method for adjusting the maximum operating pressure of a pipeline system after a natural gas pipeline is converted to a hydrogen pipeline, in order to fundamentally ensure pipeline safety. Given that the conversion of a natural gas pipeline system to hydrogen operation falls under the category of existing station renovation, and considering the operating pressure characteristics of hydrogen pipelines, to effectively overcome the problem of a significant increase in external firebreak distances after the conversion, this invention proposes using the maximum allowable operating pressure of the hydrogen station as a variable, and the pressure parameters of the natural gas station under comparative operating conditions as a quantitative comparison basis. Furthermore, it compares the thermal radiation influence range of hydrogen and natural gas stations under the same aperture to further optimize the maximum allowable operating pressure of the hydrogen station and avoid a significant increase in external firebreak distances after the conversion. Attached Figure Description

[0024] Figure 1 This is a flowchart of a method for optimizing the service pressure of a natural gas station converted to a hydrogen station according to an embodiment of the present invention. Detailed Implementation

[0025] The following specific examples illustrate the implementation of the present invention. 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, and various 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, unless otherwise specified, the following embodiments and features described therein can be combined with each other.

[0026] Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] After some natural gas stations are converted to hydrogen service, applying the same fire separation distances as natural gas stations based on equivalent pressure levels could lead to excessive demolition and relocation of surrounding areas. Generally, hydrogen pipelines operate at much lower pressures than natural gas pipelines. For example, due to factors such as transmission distance, flow rate, and end-point consumption, hydrogen pipelines typically operate at pressures of 3–5 MPa, significantly lower than conventional natural gas pipelines. If natural gas stations are classified according to 4 MPa fire separation distances, most stations, after renovation or expansion, would have to adhere to standards exceeding 4 MPa, resulting in a substantial increase in external fire separation distances. However, hydrogen pipelines operate at relatively lower pressures; therefore, applying the same fire separation distance standards as converted natural gas stations could lead to significant space waste.

[0028] To address the aforementioned technical problems, the following embodiments of a method for optimizing the service pressure of a natural gas station converted to a hydrogen station according to the present invention are proposed.

[0029] Reference Figure 1 The figure shows a flowchart of a method for optimizing the service pressure of a natural gas station converted to a hydrogen station according to this embodiment. The method specifically includes the following steps:

[0030] Step 1: Obtain the distribution of pipeline design coefficients and regional classification information during the renovation of the natural gas station, and calculate the maximum allowable operating pressure of the target natural gas station when it is converted into a hydrogen station as the initial recommended operating pressure for the hydrogen station.

[0031] Specifically, this embodiment collects the original natural gas pipeline design coefficient distribution and regional grade information during the renovation, and selects the pipeline section with the highest design coefficient (smallest wall thickness) and the largest change in regional grade as the target for operating pressure adjustment, so as to determine the maximum allowable operating pressure P1 of the entire converted pipeline.

[0032] Design factors include:

[0033] (1) Pipe outer diameter D;

[0034] (2) Pipeline wall thickness t;

[0035] (3) Minimum yield strength SMYS of the pipe material;

[0036] Wherein, "pipeline region level m" represents the pipeline region classification as stipulated in GB 50251 "Code for Design of Gas Transmission Pipelines," and its purpose is to determine the pipeline region level at the time of service transition. The specific method is as follows:

[0037] 1) Based on the regional grade change survey, the pipeline professionals will provide the maximum allowable operating pressure P1 after comprehensively considering the regional grade and design coefficient of the entire pipeline;

[0038] 2) If the maximum allowable operating pressure based on the change in regional classification cannot be obtained, the design factor f2 should be adjusted according to the original lowest regional classification of the pipeline as the updated design factor. The preferred value for f2 is 0.5. The maximum allowable operating pressure P1 should be calculated using the following formula:

[0039]

[0040] In the formula,

[0041] P1—Maximum allowable operating pressure of the pipeline, MPa

[0042] t1—Pipe service wall thickness, mm; preferably the minimum pipe wall thickness in the target pipe section.

[0043] D—Outer diameter of the pipe, mm;

[0044] f1 — Material hydrogen service correction factor, dimensionless. For X52 and below steel grades, f1 is 1; for X60 steel grade, f1 is 0.87; X70 steel grade and above are not considered in this embodiment.

[0045] f2—Regional level design coefficient, dimensionless; if the smallest wall thickness pipe in the target pipeline is located in a level 4 region, then select 0.4, otherwise 0.5 is preferred.

[0046] Thus, the maximum permissible operating pressure P1 under the condition that the entire target pipeline is converted to hydrogen service was obtained.

[0047] Step 2: Obtain the pressure parameters of the natural gas station under the comparative operating conditions, and calculate the thermal radiation influence distance ratio of hydrogen and natural gas based on the pressure parameters of the natural gas station under the comparative operating conditions and the initial recommended operating pressure of the hydrogen station.

[0048] In this embodiment, P1 will be used as the initial maximum operating pressure value of the hydrogen station for thermal radiation comparison, and the maximum operating pressure value P2 of the hydrogen station will be optimized and adjusted.

[0049] In this embodiment, the comparison pressure for natural gas pipeline stations is considered to be 4 MPa. 4 MPa is chosen as the comparison value for the highest operating pressure of natural gas stations because, in the past, natural gas stations did not have external firebreak distances defined according to operating pressure. Future firebreak requirements for natural gas stations may consider 4 MPa as the dividing standard; natural gas stations with pressures below 4 MPa require smaller external firebreak distances, while those above 4 MPa require larger ones. To avoid significant changes in the distance between the station and the outside environment after the conversion from natural gas to hydrogen transmission, a 4 MPa natural gas station and its external firebreak distance are preferred as the comparison index. Considering the scale of hydrogen transmission, gas source characteristics, and user consumption, and based on the distribution of the highest operating pressures of existing hydrogen pipelines both domestically and internationally, approximately 4 MPa is considered the main pressure range for hydrogen pipeline transmission. Therefore, this embodiment compares the leakage consequences of a natural gas station at 4 MPa with the leakage consequences of a station at the highest permissible operating pressure for hydrogen, and determines the recommended operating pressure for hydrogen stations based on the constraint of consistent external firebreak distances. In this invention, methane is used to represent natural gas.

[0050] In addition, the following parameters need to be collected for calculating the thermal radiation influence distance ratio:

[0051] (1) Hydrogen specific heat ratio γ H2 Methane specific heat ratio γ C1 ;

[0052] (2) Calorific value of hydrogen combustion H H2 The calorific value of methane (H) C1 ;

[0053] (3) Molar mass of hydrogen M H2 Methane molar mass M C1 ;

[0054] (4) Hydrogen compressibility factor Z H2 Methane compressibility factor Z C1 ;

[0055] (5) Hydrogen density ρ under operating conditions H2 Natural gas density ρ under operating conditions C1

[0056] (6) Hydrogen thermal emissivity F H2 Methane thermal emissivity F C1 ;

[0057] (7) Atmospheric thermal radiation transfer efficiency τ of hydrogen H2 The atmospheric thermal radiation transfer efficiency τ of methane C1 .

[0058] The above parameters are to support subsequent calculations of leakage flow rate and the impact range of leakage fire, in order to quantify and differentiate the consequences of hydrogen and natural gas leaks.

[0059] Since neither natural gas pipeline stations nor hydrogen pipeline stations contain gas storage tanks, only pipeline leakage scenarios are considered. Based on experience with the pipe diameter distribution of natural gas pipeline leakage risk, medium-sized and large-sized leaks are recommended as preferred comparison leakage orifice diameters, i.e., d=50mm and d=100mm. Complete rupture is not recommended because its probability of occurrence is low (although the probability of leakage in a 100mm large-sized orifice is also low, the d=100mm condition is also compared to further ensure the comparison effect). Both hydrogen and natural gas pipeline stations are equipped with complete intrinsic protection and station maintenance functions, and the purpose of this embodiment is to compare the leakage consequences under the same orifice diameter.

[0060] Generally, the direction of the jet fire caused by a leak includes both vertical and horizontal directions. When the jet fire is horizontal, it has a greater impact on people and buildings near the ground; therefore, the horizontal direction is chosen as the direction for analyzing the impact of the jet fire. Furthermore, to fully characterize the impact of the leak, the effect of pipe closure on the total discharge is not considered. The specific calculation method is as follows:

[0061] (1) Calculate the critical expansion coefficients of hydrogen and natural gas:

[0062]

[0063] In the formula,

[0064] γ — Specific heat ratio of hydrogen or methane, dimensionless;

[0065] z—compressibility factor for hydrogen or methane, dimensionless;

[0066] Y—critical expansion coefficient of hydrogen or methane, dimensionless;

[0067] In this formula, the specific heat ratio and compressibility factor of hydrogen and methane under leakage conditions are input respectively, and the corresponding critical expansion coefficient is calculated.

[0068] (2) Calculate the leakage mass flow rates of hydrogen and natural gas to provide key input for thermal radiation calculations. The calculation formulas are as follows:

[0069]

[0070] In the formula,

[0071] P i —Initial leakage pressure of hydrogen or methane, Pa; where the hydrogen pressure is selected as pressure P2, and the initial natural gas pressure is selected as 4MPa (4000000Pa);

[0072] T1—Initial leakage temperature of hydrogen or methane, K;

[0073] d—the leakage orifice diameter of hydrogen or methane, in meters; calculate the operating conditions for 50 mm and 100 mm respectively;

[0074] W—Leakage mass flow rate of hydrogen or methane, kg / s;

[0075] M—Molecular weight of hydrogen or methane;

[0076] Rg—gas constant;

[0077] (3) Calculate the thermal radiation range

[0078]

[0079] In the formula,

[0080] τ—Atmospheric thermal radiation transfer efficiency of hydrogen or methane, dimensionless; preferably 1 for both hydrogen and methane;

[0081] F – thermal emissivity of hydrogen or methane, dimensionless; preferably 0.17 for hydrogen and 0.23 for methane;

[0082] L – Range of thermal radiation influence of hydrogen or methane, in meters.

[0083] H – Higher heating value of hydrogen or natural gas, kJ / kg.

[0084] Therefore, the comprehensive thermal radiation range L of hydrogen can be obtained separately. H2-50 L H2-100 The combined thermal radiation influence range of natural gas L C1-50 L C1-100 Among them, L H2-50 This indicates the range of thermal radiation impact from a horizontal hydrogen leak at a 50 mm orifice diameter (considering a thermal radiation intensity of 4.73 kW / m²). 2 );L C1-50 This indicates the range of thermal radiation impact from a horizontal leak of natural gas with a 50mm leak orifice diameter (considering a thermal radiation intensity of 4.73 kW / m²). 2 ).

[0085] Step 3: Determine the operating pressure of the hydrogen station based on the thermal radiation influence distance ratio, specifically including:

[0086] When the thermal radiation influence distance ratio does not exceed the preset distance ratio threshold, the recommended operating pressure for the hydrogen station is the optimal operating pressure; the thermal radiation influence distance ratio R is calculated as follows:

[0087]

[0088]

[0089] R = min[R] 50 ,R 100 ]

[0090] In the formula,

[0091] R 50 —The ratio of the thermal radiation effects of hydrogen and methane leaks over a 50 mm orifice;

[0092] R 100 — The ratio of the thermal radiation effects of hydrogen and methane leaking through a 100mm orifice at different distances.

[0093] R—the minimum ratio of the thermal radiation influence distance between hydrogen and methane at a leakage orifice diameter of 50 mm or 100 mm, which is used as the thermal radiation influence distance ratio.

[0094] When the thermal radiation influence distance ratio R exceeds the preset distance ratio threshold (0.95), the recommended operating pressure of the hydrogen station is reduced, and the thermal radiation influence distance ratio of hydrogen and natural gas is recalculated until the thermal radiation influence distance ratio of hydrogen and natural gas does not exceed the preset threshold. At this time, the recommended operating pressure of the hydrogen station is the optimal operating pressure.

[0095] This embodiment calculates the thermal radiation distance ratio (hydrogen thermal radiation distance / natural gas thermal radiation distance) based on the thermal radiation impact distance of hydrogen leaks and natural gas leaks under comparative operating conditions. When the thermal radiation distance ratio is less than 0.95, the external fire prevention distance of the hydrogen pipeline station shall be implemented (adjusted) in accordance with the relevant specifications of the 4MPa pressure level of the natural gas pipeline station. When the thermal radiation distance ratio is greater than 0.95, it is necessary to reduce the thermal radiation distance by reducing the operating pressure P2 of the hydrogen station. That is, after adjusting the operating pressure of the hydrogen station, steps two and three are repeated until the thermal radiation distance ratio is less than 0.95.

[0096] The principle of this embodiment is as follows:

[0097] (1) With the development of clean energy substitution, using existing natural gas pipelines to transport hydrogen will become one of the future trends for large-scale hydrogen storage, transportation, and application. Its significant advantage lies in avoiding redundant construction of pipeline systems, and the efficient use of natural gas pipelines for hydrogen pipeline transportation through reasonable modifications. Its main components include the pipeline and the transportation station. In fact, the processes of hydrogen pipeline transportation and natural gas pipeline transportation are similar. Since both are single-phase gas transportation, the main functions of the pipeline transportation station are dust removal, metering, pipeline cleaning, distribution, and pressure regulation. Compared to natural gas, hydrogen has a significantly lower minimum ignition energy, a lower explosive limit, and a lower density, making it easier to ignite after a leak. The distance between the station and the surrounding environment is generally determined based on fire safety distances. After a natural gas pipeline station is converted to hydrogen service, the issue essentially involves pipeline modification. With the upgrading of natural gas pipeline fire protection standards, a 4MPa pressure level has emerged. When the maximum operating pressure is below 4MPa, the requirements for modifying the original station's fire separation distance are relatively small; however, when the operating pressure is above 4MPa (regardless of the maximum pressure limit), the requirements for modifying the original station's fire separation distance increase significantly. Hydrogen pipelines, due to factors such as transmission distance, flow rate, and end-point consumption, generally have a transmission pressure of 3-5MPa, far lower than conventional natural gas pipelines. If natural gas stations are classified according to the 4MPa fire separation distance level, most natural gas stations, after modification and expansion, must adhere to a standard greater than 4MPa, significantly increasing external fire separation distances. However, hydrogen pipelines operate at relatively low pressures; if classified according to the fire separation distance levels of the converted natural gas pipeline stations, it could result in significant space waste.

[0098] (2) Fire separation distances are proposed based on the station size and transmission pressure, taking into full account the consequences of fire and the frequency of accidents. Natural gas pipeline stations and hydrogen pipeline stations have similar accident consequences. It is advisable to compare the accident consequences of natural gas pipeline stations and hydrogen pipeline stations with the same pipe diameter and functional configuration. Using the external fire separation distance of a 4MPa natural gas pipeline station as a basis, compare the fire impact range of a hydrogen pipeline station after leakage at the preset maximum operating pressure. When the ratio of the fire impact range of a hydrogen pipeline station after leakage to the fire impact range of a 4MPa natural gas pipeline station after leakage is greater than 0.95, the maximum operating pressure of the hydrogen pipeline station is optimized.

[0099] (3) In order to fully consider the safety of hydrogen pipeline stations, firstly, by investigating the regional distribution and design coefficients of the in-service natural gas pipeline system, and combining the updated regional levels, the maximum allowable operating pressure after the natural gas pipeline is converted into a hydrogen pipeline as determined by the pipeline engineering is used as the basis, or when the basic data is not complete, the maximum allowable operating pressure is calculated by using an updated design coefficient of 0.4; furthermore, the thermal radiation impact range of horizontal leakage is compared with the maximum allowable operating pressure of hydrogen stations and the maximum allowable operating pressure of natural gas stations at 4MPa, and the leakage orifice diameters of 50mm and 100mm, and a critical impact distance ratio of 0.95 is set to provide a calculation margin to improve the safety of the comparison; finally, the maximum allowable operating pressure value of hydrogen pipeline stations that meets the conversion service requirements can be obtained, and it is ensured that after the in-service natural gas pipeline is converted into hydrogen service, the external fire protection distance of the pipeline station is slightly adjusted according to the external fire protection distance index of natural gas stations at 4MPa, and the external fire protection distance index of natural gas stations at greater than 4MPa is avoided.

[0100] This embodiment proposes a method for adjusting the maximum operating pressure of a pipeline system after a natural gas pipeline is converted to a hydrogen pipeline, based on the physical properties of hydrogen and natural gas and the regional classification information of the pipeline, to fundamentally ensure pipeline safety. Given that the conversion of a natural gas pipeline system to hydrogen operation falls under the category of existing station renovation, and considering the operating pressure characteristics of hydrogen pipelines, to effectively overcome the problem of a significant increase in external firebreak distances after the conversion, this embodiment proposes using the maximum allowable operating pressure of the hydrogen station as a variable and the pressure parameters of the natural gas station under comparative operating conditions as a quantitative comparison basis. Furthermore, it compares the thermal radiation influence range of hydrogen and natural gas stations under the same aperture to further optimize the maximum allowable operating pressure of the hydrogen station and avoid a significant increase in external firebreak distances after the conversion.

[0101] The above description is only a preferred embodiment of the present invention and is 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 within the protection scope of the present invention.

Claims

1. A method for optimizing the service pressure of a natural gas station converted to a hydrogen station, characterized in that, The method includes: Obtain the distribution of pipeline design coefficients and regional classification information during the renovation of natural gas stations, and calculate the maximum allowable operating pressure of the target natural gas station when it is converted into a hydrogen station as the initial recommended operating pressure for the hydrogen station; Obtain the pressure parameters of the natural gas station under comparative operating conditions, and calculate the thermal radiation influence distance ratio of hydrogen and natural gas based on the pressure parameters of the natural gas station under the comparative operating conditions and the recommended operating pressure of the initial hydrogen station. The operating pressure of the hydrogen station is determined based on the aforementioned thermal radiation influence distance ratio, specifically including: When the thermal radiation influence distance ratio does not exceed the preset distance ratio threshold, the recommended operating pressure for the hydrogen station is the optimal operating pressure. When the thermal radiation influence distance ratio exceeds a preset distance ratio threshold, the recommended operating pressure of the hydrogen station is reduced, and the thermal radiation influence distance ratio of hydrogen and natural gas is recalculated until the thermal radiation influence distance ratio of hydrogen and natural gas does not exceed the preset threshold. At this time, the recommended operating pressure of the hydrogen station is the optimal operating pressure.

2. The method for optimizing the service pressure of a natural gas station converted to a hydrogen station as described in claim 1, characterized in that, The pressure parameter of the natural gas station under the comparative operating condition is 4 MPa.

3. The method for optimizing the service pressure of a natural gas station converted to a hydrogen station as described in claim 1, characterized in that, The calculation of the thermal radiation influence distance ratio between hydrogen and natural gas based on the natural gas station pressure parameters under the comparative operating conditions and the initial recommended operating pressure of the hydrogen station specifically includes: Calculate the critical expansion coefficients of hydrogen and natural gas; Calculate the leakage mass flow rate of hydrogen and natural gas under different leakage orifice diameters; The thermal radiation influence distances of hydrogen and natural gas are calculated based on the leakage mass flow rates of hydrogen and natural gas under different leakage orifice diameters and the critical expansion coefficients of hydrogen and natural gas. The ratio of the thermal radiation influence distance of hydrogen to that of natural gas is called the ratio of the thermal radiation influence distances of hydrogen and natural gas.

4. The method for optimizing the service pressure of a natural gas station converted to a hydrogen station as described in claim 1, characterized in that, The design factors include the pipe outer diameter, pipe wall thickness, and minimum yield strength of the pipe.

5. The method for optimizing the service pressure of a natural gas station converted to a hydrogen station as described in claim 1, characterized in that, The preset distance ratio threshold is 0.

95.

6. The method for optimizing the service pressure of a natural gas station converted to a hydrogen station as described in claim 3, characterized in that, The leakage orifice diameters include 50 mm and 100 mm.

7. The method for optimizing the service pressure of a natural gas station converted to a hydrogen station as described in claim 3, characterized in that, The distance affected by hydrogen thermal radiation and the distance affected by natural gas thermal radiation are calculated using the horizontal direction.

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