Discussion on the process safety issues of hydrogen and hydrogen-blended natural gas pipelines based on the law of thermodynamics
Injecting hydrogen into natural gas pipelines for transportation or pure hydrogen transportation is an effective way to promote large-scale utilization of hydrogen energy.Since the physical properties of hydrogen and natural gas are quite different,the operational safety of hydrogen pipelines or hydrogen-blended natural gas pipelines is an unavoidable issue.In recent years,preliminary theoretical research on hydrogen-blended transportation via natural gas pipelines,analysis of the impact of transportation processes,receiving terminal adaptability and low-pressure pilot tests have been carried out at home and abroad.Some representative hydrogen pipelines have also been built,but the impact of hydrogen physical properties on process safety issues has not yet been fully studied.Hence,the process safety issues of hydrogen pipelines and hydrogen-blended natural gas pipelines deserve further discussion.Based on the design and operation scenarios of natural gas pipelines,starting from the impact of thermodynamics on the physical properties of hydrogen and hydrogen-blended natural gas,the key issues faced in the design of hydrogen and hydrogen-blended natural gas pipeline projects were sorted out.Through theoretical analysis and simulation study,the impact of thermodynamics on process safety in pipeline design was discussed.The process safety assurance requirements put forward the relevant key considerations and directions in engineering design.The research shows that under the same pressure,a lower operating temperature will increase the adiabatic coefficient of hydrogen and hydrogen-blended natural gas,resulting in an increase in the leakage mass flow rate.Under the same leakage scenario,a lower operating temperature will have a positive impact on the thermal radiation after leakage,horizontal diffusion and explosion.The potential radius of influence method proposed by the existing codes and standards does not fully consider the influence of temperature,which should be accounted for in the refined evaluation of actual projects.Under emergency release,equipment containing hydrogen will experience lower medium temperature.The research results provide reference for subsequent hydrogen-related pipeline projects.
HydrogenHydrogen-blended natural gasImpact of the law of thermodynamicsProcess safetyDiscussion
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