Influences of Hydrogen Blending on the Joule-Thomson Coefficient of Natural Gas

Blending hydrogen into the natural gas pipeline is considered as a feasible way for large-scale and long-distance delivery of hydrogen. However, the blended hydrogen can exert major impacts on the Joule-Thomson (J-T) coefficient of natural gas, which is a significant parameter for liquefaction of natural gas and formation of natural gas hydrate in engineering. In this study, the J-T coefficient of natural gas at different hydrogen blending ratios is numerically investigated. First, the theoretical formulas for calculating the J-T coefficient of the natural gas-hydrogen mixture using the Soave-Redlich-Kwong (SRK) equation of state (EOS), Peng-Robinson EOS (PR-EOS), and Benedict-Webb-Rubin-Starling EOS (BWRS-EOS) are, respectively, derived, and the calculation accuracy is verified by experimental data. Then, the J-T coefficients of natural gas at six different hydrogen blending ratios and thermodynamic conditions are calculated and analyzed using the derived theoretical formulas and a widely used empirical formula. Results indicate that the J-T coefficient of the natural gas-hydrogen mixture decreases approximately linearly with the increase of the hydrogen blending ratio. When the hydrogen blending ratio reaches 30% (mole fraction), the J-T coefficient of the natural gas-hydrogen mixture decreases by 40-50% compared with that of natural gas. This work also provides a J-T coefficient database of a methane-hydrogen mixture with a hydrogen blending ratio of 5-30% at a pressure of 0.5-20 MPa and temperatures of 275, 300, and 350 K as a reference and a benchmark for interested readers.