Accurate p–ρ–T Data for a Synthetic Residual Natural Gas Mixture (0.95 CH4 + 0.04 C2H6 + 0.01 C3H8) at Temperatures between (135 and 500) K at Pressures to 200 MPa

Abstract

This paper reports p–ρ–T (pressure, mass density, temperature) data measured for a mixture with molar composition (0.95039 methane + 0.03961 ethane + 0.01000 propane) using a high-pressure, single-sinker, magnetic-suspension densimeter (MSD) and high- and low-pressure automated isochoric apparatus at temperatures from (135 to 500) K and pressures to 200 MPa. The composition is representative of a residual natural gas in pipelines, but the range of conditions covers conditions possibly encountered in production and processing. The k = 2 relative uncertainty for the density measurements using the MSD is 5 × 10–4·ρ based upon an uncertainty analysis for the instrument. The isothermal densities measured in the MSD in combination with the low- and high-pressure isochoric data determine additional density data with essentially the same estimated relative uncertainty as the MSD in the high temperature range (above 300 K) and a relative uncertainty of 3 × 10–3·ρ at lower temperatures. The measured densities range...