Density Measurements of Methane + Propane Mixtures at Temperatures between (256 and 422) K and Pressures from (24 to 35) MPa

Abstract

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 standard 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.

Measurements of helium adsorption on natural clinoptilolite at temperatures from (123.15 to 423.15) K and pressures up to 35 MPa

“…The gravimetric helium adsorption measurements were performed at temperatures in the range (253.15 -423.15) K and pressures up to 35 MPa on an IsoSORP commercial magneticsuspension balance (Rubotherm, Bochum, Germany). The Rubotherm microbalance was a Mettler WXS series with a weighing range of 20 g and resolution of 1 μg 17 . The resolution of this microbalance is 10 times better than that of the Belsorp instrument (10 μg) used in our previous studies of helium adsorption on Escott zeolite (Arami-Niya, et al 10 ), and the maximum operating pressure is also 10 times larger.…”

“…The last term in Equation 5 was determined at various experimental temperatures and pressures using argon as a calibration gas using the method explained by Karimi et al; 17 the results are presented in Table 3S. The volume of adsorbed phase (Vads) was assumed to be negligible compared to the basket and solid volume (Vb + Vs) because the absolute volume of helium adsorbed is very small.…”

The Full Pressure–Temperature Phase Envelope of a Mixture in 1000 Microfluidic Chambers

“…use a polar piston fluid for a nonpolar test mixture), 2) have strong wall‐wetting properties, 3) remain liquid at all test pressures and temperatures, 4) have a low vapor pressure, 5) have a low viscosity and 6) provide sharp visual contrast with the test fluid. Here, to contain our test fluid—an 80.0 % propane + 20.0 % methane mixture (mole fraction, Praxair Canada, Inc.) representative of thermogenic natural gas,—we used ethylene glycol (99.99 % purity, Shell Chemical, LP. ), which readily satisfies these criteria and has been deployed successfully in related applications in industry .…”

High-Pressure Thermal Conductivity Measurements of a (Methane + Propane) Mixture with a Transient Hot-Wire Apparatus

“…The apparatus was commissioned with the measurements of pure argon, methane, and propane, and then a binary system (0.9514 methane + 0.0486 propane) was investigated for the purpose of improving the data situation for mixtures. The density and viscosity , of this binary mixture had been investigated previously at similar conditions via measurements conducted by our group. Only a few experimental thermal conductivity data can be found in the literature , for this binary system, and most of them were measured at atmosphere pressure.…”