Visual measurements of solid-fluid equilibria in hydrocarbon mixtures for enhanced LNG production

Around 25 % of the world energy demand is met through natural gas production, with a significant proportion traded globally and delivered as Liquefied Natural Gas (LNG) which has been cryogenically "shrunk" from gas to liquid through sophisticated high-pressure cooling processes. There are two main challenges associated with those processes: (1) over-engineered equipment due to the lack of understanding upon the thermophyscial properties of LNG mixtures, and (2) unscheduled LNG plant shutdowns due to the blockages caused by the freeze-out of impurities such as heavy hydrocarbons (HHC), mainly BTEX compounds (benzene, toluene, ethylbenzene, xylene). Central to the identification and prediction of the HHC concentration limits above which solids will form are thermodynamic models anchored to reliable and relevant solid−fluid equilibrium (SFE) data, which are sparse.
The overarching objective of this PhD project is to generate accurate and reliable experimental data using a novel experimental system, named the CryoSolid apparatus, designed and constructed to measure SFE and melting (liquidus) temperatures in hydrocarbon mixtures at different temperatures, pressures, and compositions. The CryoSolid apparatus consists of two major parts: (1) a high pressure sapphire equilibrium cell equipped with a Peltier-driven copper post which can be sub-cooled relative to the bulk liquid mixture to control the location of the solid formed within the cell, and (2) a cooling environmental chamber including an air-bath to study heavy hydrocarbons with high-boiling points, a cryogenic thermostat fitted with periscopes for measurements down to 150 K, and a cryogenic chamber for measurements down to 85 K.