Investigation On Material Property Degradation And Failure Consequence Of The High-pressure Natural Gas/Hydrogen Blends Pipeline

The development of wind and solar energy is limited for intermittence and remote location,thus wind and solar curtailment is a frequent occurrence.Using the excessive wind and/or photovoltaic power to produce hydrogen by water electrolysis,then hydrogen is blended into natural gas to make up hydrogen and compressed natural gas(HCNG)and eventually HCNG is transported by the natural gas pipeline,which is considered as a feasible measure.However,the presence of hydrogen always enhanced the risk.Recently,the safety of natural gas/hydrogen blends(HCNG and coal based synthetic natural gas(SNG))pipeline has attracted broad attention around the world.The safety of high-pressure natural gas/hydrogen blends pipeline is investigated in this paper,which includes material property degradation and failure consequence.The main contents are shown as follows:(1)Study on property degradation of pipeline steel in natural gas/hydrogen blends environment.Based on the established material compatibility test methods,the mechanical properties of X70 and X80 pipeline steels are obtained.Moreover,the fracture morphologies are analyzed by scanning electron microscope(SEM).The degraded effect of added hydrogen on tensile and fatigue properties is studied from macro-and micro-perspective.(2)Fatigue life evaluation and fracture safety assessment of high-pressure natural gas/hydrogen blends pipeline.Based on the mechanical properties of the pipeline steel,fatigue life evaluation and fracture safety assessment are carried out for a representative high-pressure natural gas/hydrogen blends pipeline in accordance with ASME VIII-3 KD-10 and BS 7910,respectively.The effect of material property degradation from added hydrogen on fatigue life,tolerable size of internal surface and embedded flaws is analyzed quantitatively.(3)Study on failure consequence of natural gas/hydrogen blends pipeline.For the probable under-expanded jet fire caused by the failure of a high-pressure natural gas/hydrogen blends pipeline,a suitable natural gas/hydrogen blends under-expanded jet fire simulation model is developed by a CFD tool.On the basis of the simulation model above,the effects of hydrogen content,pipeline pressure and jet size on axial temperature distribution and flame length are investigated to find out the mechanism.The results can offer technical support to design,manufacture,safety evaluation and standard establishment of high-pressure natural gas/hydrogen blends pipeline in China.Additionally,they can contribute to the pipeline inspection and examination,proper hydrogen content determination,pipeline layout,and risk management about high-pressure natural gas/hydrogen blends pipeline.