A major ongoing effort of the Fluid Science and Resources Laboratory is measuring the thermodynamic properties of fluid mixtures at industrially relevant conditions, in particular those relevant to the liquefied natural gas (LNG) industry. Using a suite of precision measurement tools, we provide reference-quality data for vapour-liquid equilibria, solid-liquid equilibria, density, viscosity, thermal conductivity, heat capacity, surface tension, and dew point.
This reference-quality data is used to underpin computer simulations that are employed in the design and optimisation of gas processing plants. For example, a key process in a LNG production plant is the scrub column, which is used to remove heavy components from the product stream that are of value (liquefied petroleum gases (LPGs)) or may solidify (C5+) in subsequent processes, such as the main cryogenic heat exchanger (MCHE). The modeling of the scrub column in simulation packages is challenging because it requires numerous calculations of vapour-liquid equilibrium (VLE) for multi-component mixtures at high pressures (4000 to 6500 kPa) over a wide range of temperatures (243 to 323 K). However, there is a scarcity of high quality VLE data relevant to scrub column conditions. Furthermore, the accurate measurement of density (by dual sinker and vibrating tube densimetry) and heat capacity (by differential scanning calorimetry) of scrub column and natural gas liquids is needed to simulate and determine the volumetric flows within the column and the scrub column temperature profile respectively. Since the equations of state (EOS) used in these simulations can only be as accurate as the data to which they are anchored, the Fluid Sciences and Resources Laboratory is focusing on the measurement of binary and multicomponent natural gas mixture properties at scrub column conditions.
The Fluid Science and Resources Laboratory is also working on the development of modifications to cubic equations of state to improve their performance. Complex multi-parameter EOS such as GERG-2008 can be used in the simulation of scrub columns, but to solve the iterative material and energy balances cubic EOS such as Peng-Robinson EOS are more computationally efficient and are still the standard used by industry. However, cubic EOS are particularly deficient at the conditions where scrub column condenser’s operate. We are developing specialized EOS that are both computationally efficient and accurate for the descriptions of multi-component mixture phase behavior in LNG scrub columns.