Molecular Dynamics Investigations of Hydrogen-Enriched Natural Gas Permeation in Polyethylene

It is the trend of future energy development to blend a certain proportion of hydrogen into natural gas for utilization due to the zero carbon emissions characteristic of hydrogen after combustion. The hydrogen embrittlement and other hydrogen damages caused by metal pipelines can be effectively avoided by using non-metallic pipelines to transport hydrogen-enriched natural gas (HENG). However, due to the material characteristics, the degree of gas permeation of non-metal pipelines is greater than that of metal pipelines. In the study, the molecular dynamics combined with Giant Canonical Monte Carlo method is used to investigate the dissolution, diffusion and permeation characteristics of HENG with different hydrogen blending ratios (HBR, 5–20%) in amorphous polyethylene at temperatures of 270–310 K and pressures of 0.1–0.7 MPa. Results show that the solubility coefficient of hydrogen increases with increasing temperature and HBR, while the solubility coefficient of methane presents the opposite trend. The diffusion coefficients of hydrogen and methane increase with the rise of temperature and pressure but decrease with the increase of HBR. The permeability coefficients of hydrogen and methane increase with the increase of temperature. In addition, with the increase of HBR, the permeability coefficient of hydrogen increases, while that of methane decreases.