Phase equilibrium measurements and advanced modelling for optimising liquefied natural gas production

High-Pressure Melting Temperature Measurements in Mixtures Relevant to Liquefied Natural Gas Production and Comparisons with Model Predictions

“…At the composition measured here, Multiflash model underpredicts the SLE temperature by +9.4 K, while ThermoFAST exhibits a difference of only +2.7 K. The deviation in Multiflash is much larger than that seen in previous mixtures and is likely attributable to the very different physical and chemical properties of the aromatic benzene solute relative to the lighter aliphatic hydrocarbons (C 1 to C 4 ) comprising the solvent. For ThermoFAST, the smaller deviation likely reflects the tuning of the model’s binary interaction parameter of benzene to the literature data , and is consistent with the results obtained recently by May and co-authors using a variety of experimental techniques. − …”

“…Figure shows that Multiflash underpredicts the SLE temperatures reported in this work and literature. ThermoFAST, on the other hand, matches the literature data (which were included in its development) very well and more closely predicts the SLE temperatures in this work. , Both models capture the observed trends of the combined data sets and suggest a slight flattening of the phase boundary from 0.84 ≤ x 1 ≤ 0.96. Additional data points would be needed to confirm this predicted flattening of the SLE curve.…”

“…However, the T melt measured in this work correspond to solid–liquid equilibria (SLE), which has a small dependence on pressure. Comparisons are made for all mixtures with the predictions of the EOS-based solid–fluid equilibrium (SFE) implemented in the software packages Multiflash version 4.4 and ThermoFAST 1.2. ,, Both models use the equation attributed to Hildebrand and Scott among others , to calculate the fugacity of the pure solid phase in equilibrium with the fluid mixture, as detailed in eq . where for component i , f i S , φ pure, i L , Δ H f, i , T m, i , Δ c p, i L→S , and p m are the solid fugacity, liquid phase fugacity coefficient, enthalpy of fusion, melting temperature, specific heat difference between the liquid and solid phase, and the melting pressure, respectively. As discussed by Baker et al, this model assumes the solid phase consists of a pure substance even though multiple pure solid phases can simultaneously exist.…”