Density Measurements of (0.99 Methane + 0.01 Butane) and (0.98 Methane + 0.02 Isopentane) over the Temperature Range from (100 to 160) K at Pressures up to 10.8 MPa (original) (raw)
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The Journal of Chemical Thermodynamics, 2019
Densities of seven methane-rich binary mixtures were measured in the homogeneous liquid and supercritical regions at temperatures between (100 and 180) K using a low-temperature single-sinker magnetic-suspension densimeter. For each mixture, four to six isotherms were measured, and seven values were taken along each isotherm in the pressure range from (0.19 to 9.7) MPa. Molar compositions of the gravimetrically-prepared methane-rich binary mixtures were 0.25 ethane, 0.12 propane, 0.030 isobutane, 0.010 n-pentane as well as (0.30, 0.030 and 0.010) nitrogen with the balance being methane. The relative expanded combined uncertainty (k = 2) of the experimental densities was less than 0.020% in most cases. Due to a supercritical liquefaction procedure and the integration of a special VLE-cell, it was possible to measure densities in the homogeneous liquid phase without changing the composition of the mixture. Moreover, saturated-liquid densities were determined by extrapolation of the isothermal densities to the vapour pressure; their uncertainty is less than 0.05% in most cases. The new experimental results were compared with the GERG-2008 equation of state and two correlation methods. The results were already used as a reliable basis for the development of a new fundamental equation of state for liquefied natural gases (LNG).
International Journal of Thermophysics, 2021
Densities of two synthetic biomethane-like mixtures were measured in the homogeneous liquid phase and the supercritical region using a low-temperature single-sinker magnetic-suspension densimeter. Both mixtures consist of methane, nitrogen, hydrogen and oxygen, whereas the second mixture additionally contains carbon dioxide. For the first mixture, four isotherms from (100 to 160) K were studied over the pressure range from (1.5 to 6.6) MPa. The second mixture was investigated along three isotherms from (140 to 180) K at pressures of (2.6 to 9.0) MPa, where only the densities at 180 K are usable due to solidification of the carbon dioxide at the lower temperatures. The relative expanded combined uncertainty (k = 2) of the experimental densities was estimated to be in the range of (0.022 to 0.027) % for the first mixture and (0.046 to 0.054) % for the second mixture, respectively. Due to a supercritical liquefaction procedure and the integration of a special VLE-cell, densities in t...
Journal of Chemical & Engineering Data, 2011
Work reported in this paper is the continuation of a previous work (Atilhan et al. J. Chem. Eng. Data 2011, 56, 212À221) and reports measurements of density and phase envelope characteristics of three synthetic natural gas-like mixtures. These mixtures consist of primarily 0.9000 methane in mole fraction and variable amounts of ethane, propane, 2-methylpropane, butane, 2-methylbutane, and pentane as well as the presence or absence of nitrogen and carbon dioxide. A high-pressure singlesinker magnetic suspension densimeter was used to measure the density of the mixtures along three isotherms at (250, 350, and 450) K with pressures up to 150 MPa. Density measurements are compared to the GERG04 and AGA-8 equations of state, which are the two leading models used for natural gas density predictions. Predictions from both equations have a similar agreement with the data, yet it is observed that GERG04 model shows better performance in predictions with deviations less than around 0.2 % at different temperatures (T = 350 K and T = 450 K) and pressures (p > 20 MPa). An isochoric apparatus was used for phase envelope experiments, and the data are compared to several cubic biparametric, cubic triparametric, and molecular-based equation of states. Equation-of-state predictions for the mixtures and comparison with the experimental data are shown. Equation-of-state predictions show substantial deviations around the entire phase envelope for the third mixture, in which the nitrogen and carbon dioxide have not been included.
Viscosity and density of mixtures of methane and n-decane from 298 to 393 K and up to 75 MPa
Fluid Phase Equilibria, 2004
Experimental results of viscosity and density of mixtures of methane and n-decane are reported at temperatures from 303 to 393 K and pressures up to 75 MPa, at five compositions. This binary mixture is considered as a model for gas-condensate fluids since it presents dew-point and bubble point lines extending up to 35 MPa at room temperature. Viscosity and density were measured simultaneously using a vibrating-wire sensor, in an apparatus specifically built to study gas-liquid mixtures. The present results for both properties are compared with values from the literature when possible and present overall uncertainties of ±0.2% for density and ±3% for viscosity. Precisions are of about one third of the uncertainties for both properties. The excess volume of the mixture reaches −20 cm 3 mol −1 at 393 K and 40 MPa. Viscosity has a marked non linear behaviour with composition, that is nonetheless well represented by a predictive scheme based on the theory of transport properties of the hard-sphere fluid.
Proceedings of the 1st Annual Gas Processing Symposium, 2009
High-accuracy density measurement data are necessary to validate equations of state (EOS) used in natural gas transport. The American Gas Association (AGA) AGA8-DC92 EOS, currently the industry standard, has been validated against a databank of gas mixtures with compositions containing up to 0.2 mole percent of the C 6+ fraction and should predict densities of natural gas mixtures containing higher mole percentages of the C 6+ fraction with the same accuracy. Several attempts have been made to develop a new EOS that can serve the gas industry because the reliabilibity of AGA8-DC92 has been criticized over the past years. One of the biggest reasons that academia seeks opportunities to develop new EOS is the need to express the PρT behaviour of natural gas mixtures that contain heavy components in larger fractions than AGA8-DC92 can handle. Production of natural gas streams containing higher percentages of the C 6+ fraction has begun recently in North America. High-accuracy, density data for such natural gas mixtures are necessary to check the ability of AGA8-DC92 to cover the entire range of pressure, temperature and compositions encountered in custody transfer. Therefore, this work reveals the ability of the AGA8-DC92 to predict the densities of such mixtures. A state-of-the-art, high pressure, high temperature, compact singlesinker magnetic suspension densimeter has been used to collect densities of simulated natural gas mixtures having several different methane compositions after validating the densimeters operation by measuring densities of pure argon, nitrogen and methane in the range 270 to 340 K and 3.5 to 35 MPa. Based upon the measurements, temperatures were within ±3.8 mK, pressures had an uncertainty of 0.002 %, the weighing balance readings for the true mass of the sinker in vacuum had an uncertainty of 0.01 mg and the weighing balance readings for the apparent mass sinker under pressure had an uncertainty of 0.02 mg. The measured data indicate the advisability of performing an extensive study of AGA8-DC92 for natural gas mixtures.
Journal of Chemical & Engineering Data, 2011
This paper presents experimental liquid densities for n-pentane, n-octane, and n-nonane and their binary mixtures from (273.15 to 363.15) K over the entire composition range (for the mixtures) at atmospheric pressure. The experimental apparatus is a vibrating-tube densimeter. It is possible to compare the results to a generalized correlation for liquid densities of n-alkanes and to molecular dynamics simulations. The average absolute percentage deviation is (0.06 and 0.8) % using the equation and the simulation results.
The Journal of Chemical Thermodynamics, 2015
New isothermal pTxy data are reported for methane + benzene and methane + methylbenzene (toluene) at pressures up to 13 MPa over the temperature range (188 to 313) K using a custom-built vapor-liquid equilibrium (VLE) apparatus. The aim of this work was to investigate literature data inconsistencies and to extend the measurements to lower temperatures. For methane (1) + benzene (2), measurements were made along six isotherms from (233 to 348) K at pressures to 9.6 MPa. At temperatures below 279 K there was evidence of a solid phase, and thus only vapor phase samples were analyzed at these temperatures. For the methane (1) + methylbenzene (3) system, measurements were made along seven isotherms from (188 to 313) K at pressures up to 13 MPa. Along the 198 K isotherms, a significant change in the data's p,x slope was observed indicating liquid-liquid equilibria at higher pressures. The data were compared with literature data and with calculations made using the Peng-Robinson (PR) equation of state (EOS). For both binary systems our data agree with much of the literature data that also deviate from the EOS in a similar manner. However, the data
The Journal of Chemical Physics, 1997
The vapor pressure isotope effect of samples of isotopically substituted methane and their mixtures was measured as a function of temperature and mixture composition: The differential vapor pressure between CH i D 4Ϫi ͑with iϭ0 or 4͒ and CH j D 4Ϫ j ͑with jϭ1, 2, or 3͒, the differential vapor pressure between mixtures of (CH i D 4Ϫi ϩCH j D 4Ϫ j ) and CH 4 ͑if iϭ4͒ or CH j D 4Ϫ j ͑if iϭ0͒ and the absolute vapor pressure of CH 4 ͑if iϭ4͒ or CH j D 4Ϫ j ͑if iϭ0͒, were measured simultaneously between 96 and 121 K for mixtures of nominal composition 0.25, 0.50, and 0.75 mole fraction in the reference methane species. The p(x,T) data were used to calculate the excess molar Gibbs energy function, G E (x,T) and the excess molar enthalpy H E (x), assuming that this last function is independent of temperature in the experimental range. The deviations from ideal behavior are very small, G E being only some tenths of J/mol for equimolar mixtures. The experimental G E values compare well with estimated results based on a modified version of the statistical theory of isotope effects in condensed phases. Comparisons with reported values of the liquid-vapor isotope fractionation factor for the CD 3 H-CH 4 system are also made.
Viscosity and Density of Methane + Methylcyclohexane from (323 to 423) K and Pressures to 140 MPa
Journal of Chemical & Engineering Data, 2001
A new apparatus is described for measuring phase behavior and flow properties of water and/or hydrocarbon systems from ambient conditions to pressures of 140 MPa and temperatures to 474 K. Viscosity and density measurements have been made on pentane and decane and compared to the literature data. The measurements on pentane and decane have been made to 140 MPa and 423 K. Viscosity and density are reported for methane + methylcyclohexane at 25, 50, and 75 mass % methane, and at three temperatures, (323, 373, and 423) K, from saturation pressure to 140 MPa. Figure 1. Schematic diagram of the experimental facility.