The p-ρ-T behaviors of four lean synthetic natural gas mixtures were measured along isotherms of 250 K, 350 K, and 450 K with pressures to 37 MPa with a two-sinker, magnetic-suspension densimeter. The gravimetrically prepared mixtures have seven to nine components (methane to pentane). They are all nominally 0.90 mole fraction methane, and they differ primarily in the amount of pentane and isopentane and the presence or absence of nitrogen and carbon dioxide. The expanded (k = 2) uncertainty in density is (32 10 6 ρ + 0.0014 kg⋅m 3) at near-ambient conditions, increasing to (84 10 6 ρ + 0.0014 kg⋅m 3) at 450 K and 37 MPa. The uncertainties in temperature and pressure are 0.004 K and (52 10 6 p + 0.4 kPa), respectively. The expanded uncertainty in the composition is equivalent to a density uncertainty of 158 10 6 ρ to 174 10 6 ρ. The analysis for density accounts for the force transmission error in the magnetic suspension coupling of the densimeter and the magnetic effects of the fluid. These data are compared to the GERG 2004 and AGA-8 models for natural gas mixtures. The densities calculated by both the models are generally very good (deviations less than 0.10 %) at the higher temperatures and lower pressures. But at higher pressures and lower temperatures, the deviations are substantially larger. Additional data on these same mixtures were measured by Texas A&M University and are reported in companion papers.
Citation: Journal of Chemical and Engineering Data
Pub Type: Journals
natural gas, density, measurements, mixture, experimental uncertainty, mixture models