Abstract
Densities of two methane-rich binary mixtures were measured in the homogeneous liquid and the supercritical region at temperatures between (100 and 160) K using a low-temperature single-sinker magnetic-suspension densimeter. For each mixture, four isotherms were studied over the pressure range from (0.3 to 10.8) MPa. Molar compositions of the gravimetrically prepared methane-rich binary mixtures were approximately 0.01 butane and 0.02 isopentane, respectively, with the balance being methane. The relative expanded combined uncertainty (k = 2) of the experimental densities was estimated to be in the range of (0.02 to 0.06) %. 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 liquefied mixture. Based on the supercritical liquefaction procedure, a new time-saving measurement procedure was developed and applied. Moreover, saturated-liquid densities were determined by extrapolation of the experimental single-phase liquid densities to the vapor pressure calculated with an equation of state (EOS); here, the relative expanded combined uncertainty (k = 2) is less than 0.05 % in most cases. The new experimental results were compared with the GERG-2008 equation of state, the EOS-LNG and the enhanced revised Klosek and McKinley (ERKM) method.
Highlights
The anthropogenic climate change driven by emissions of greenhouse gases (GHG) increases risks for natural and human systems [1, 2]
In our previous paper [5], we presented density data for seven binary methane-rich mixtures, including and mixtures that were used for the development of a new fundamental equation of state for liquefied natural gases (EOS-LNG) by Thol et al [6] in 2019
The density measurements reported in this paper were carried out with a precision densimeter, which was deliberately designed for accurate density measurements of cryogenic liquid mixtures such as LNG; it covers a temperature range from (90 to 300) K at pressures up to 12 MPa
Summary
The anthropogenic climate change driven by emissions of greenhouse gases (GHG) increases risks for natural and human systems [1, 2]. The process efficiency improves significantly with the availability of accurate thermodynamic properties of LNG. Against this background, a series of Joint Research Projects as part of the European Metrology Research Programme (EMRP) and the European Metrology Programme for Innovation and Research (EMPIR) focusing on metrology for LNG, i.e., achieving smaller uncertainties for the quantities to be measured in custody transfer, were carried out. In our previous paper [5], we presented density data for seven binary methane-rich mixtures, including (methane + isobutane) and (methane + pentane) mixtures that were used for the development of a new fundamental equation of state for liquefied natural gases (EOS-LNG) by Thol et al [6] in 2019. The apparatus utilized for density measurements is a special single-sinker densimeter for cryogenic liquid mixtures [9,10,11]
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