Thermodynamics Research Center / ThermoML | Journal of Chemical Thermodynamics

ABSTRACT

A special densimeter has been developed for accurate density measurements of liquid mixtures at cryogenic temperatures, e.g., liquefied natural gas (LNG). It covers the density range from (10 to 1000) kg m 3, thus enabling density measurements in the supercritical region, in the homogeneous liquid region, along the saturated liquid line as well as in the homogeneous gas region. The apparatus is designed for measurements over a temperature range from (90 to 300) K at pressures up to 12 MPa. The densimeter is based on the Archimedes (buoyancy) principle and is a single-sinker system incorporating a magnetic suspension coupling. The density can be obtained directly without the need for calibration fluids. The relative combined expanded uncertainty (k = 2) for density measurements in the homogeneous liquid region (including the contribution resulting from the uncertainty of the sample gas analysis) was estimated to be 0.044%. First results for a synthetic five-component LNG mixture were obtained at the temperatures T = (105, 115, 120, 125, and 135) K with pressures up to 8.1 MPa. The results were compared to the GERG-2008 reference equation of state for natural gases, which represents the experimental values within 0.06%.