Density Data and Calculation Methods for Hydrogen-Blended Natural Gas Containing Neopentane

Blending hydrogen into mature natural gas pipelines for mixed transportation is a relatively fast way to achieve large-scale and low-cost hydrogen energy transportation. The density of hydrogen-blended natural gas has a significant impact on process optimization, metrological calibration, and pipeline design. Our previous work involved experimental density measurements for hydrogen-blended natural gas mixtures representative of a Chinese pipeline gas (without neopentane). This study, as the second part of our investigation, aims to determine the density of hydrogen blended with a typical Chinese natural gas containing neopentane using the same high-accuracy single-sinker densimeter. The data cover a range of mole fractions of H2 (3–20%), and temperatures (253.15–350.15 K), with pressures up to 10 MPa. The relatively high neopentane concentration leads to degradation in the predictive performance of the GERG-2008 and AGA8-DC92 equations of state for the studied hydrogen-blended natural gas, with the maximum relative deviation reaching approximately 0.5%. Based on GERG-2008, a systematic evaluation of the neopentane assignment rule was conducted, and a calculation method suitable for relatively high neopentane concentrations (up to 0.1%) is proposed.