2016/07/11 by Armand Karimi, Thomas J. Hughes, Markus Richter +1 · 1 citation
Chemical Engineering · Chemistry · Engineering · #Analytical Chemistry (journal) #Chemical Thermodynamics and Molecular Structure #Chemistry #Environmental chemistry #Materials science #Methane #Organic chemistry #Phase Equilibria and Thermodynamics #Physics #Propane #Thermodynamic properties of mixtures #Thermodynamics
paper · doi:10.1021/acs.jced.6b00131
openalex publication_date 2016/07/11 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
High-accuracy equations of state (EOS) are crucial to industrial applications such as natural gas custody transfer and the development of gas processing facilities. The GERG-2008 EOS, which is the ISO standard for calculating the equilibrium properties of natural gas mixtures, has a stated relative uncertainty in density of 0.1% over the temperature range from (250 to 450) K at pressures up to 35 MPa. However, for the crucial (methane + propane) binary system, most of the density data sets used in the development of the GERG EOS that extend to pressures above 20 MPa have root-mean-square relative density deviations of (0.4 to 0.8)% and maximum relative deviations of up to approximately 3%. In this work, a single-sinker magnetic-suspension densimeter adapted from a commercial sorption apparatus was used to measure the density of two (methane + propane) mixtures along four isotherms at T = (256, 310, 366, and 422) K over the pressure range from (24 to 35) MPa. The binary mixtures were prepared gravimetrically with methane mole fractions of 0.9472 and 0.8924, respectively. The titanium sinker’s volume ( V ≈ 3.17 cm 3 ) was determined at each temperature as a function of pressure using pure methane and the reference equation of state for this pure fluid, which has a relative expanded uncertainty of 0.03%. The relative combined expanded uncertainty ( k = 2) in mixture density measurements ranged from (0.11 to 0.24)%, including the uncertainty in composition. The measured binary mixture densities had relative deviations from those calculated with the GERG-2008 EOS of less than 0.14%. When considered together with other recently measured high-accuracy density data for this binary system, these results help prioritize the nature of future improvements needed for the EOS.