Thermophysical properties data presently available are insufficient to confidently design gas gathering and processing equipment at pressures near system critical points and cricondenbars. Poor understanding of supercritical fluid transport and physical properties at these pressures lead to over-design and higher operating and capital costs, where current uncertainties in fluid property predictions typically lead to equipment over designs of 15% or more. In this work, we present a wide range of experimental measurements made for different binary and ternary mixtures relevant to LNG processing. For this purpose, specialized state of art apparatuses were designed and validated over the temperature range (200 to 423) K at pressures above the mixture critical points, up to 35 MPa. The mixtures studied include (CH4 + C3H8), (CH4 + C3H8 + CO2) and (CH4 + C3H8 + C7H16); in the last of these the heptane contents was up to 15 mol %. Properties studied include density, viscosity, thermal conductivity, phase equilibrium, heat capacity, SLE and surface tension. The extensive experimental data gathered in this work were compared with a variety of different advanced engineering models frequently used for predicting thermophysical properties of mixtures relevant to LNG processing. In many cases the discrepancies between the predictions of different engineering models for these mixtures was large, and the high quality data allowed erroneous but often widely-used models to be identified. The data enabled the development of new and improved models, to be implemented in process simulation software, so that the fluid properties needed for equipment and process design can be predicted reliably which is essential for LNG industry. This in turn minimized environmental impacts and enabled reduced capital and operational expenditure by the LNG industry.
Keywords LNG, modelling, thermophysical properties