Application of equations of state to predict methane solubility under hydrate-liquid water two-phase equilibrium

• Methane solubility in water under H-Lw two-phase equilibrium was predicted.
• Three equations of state were tested to calculate methane fugacity in water.
• The binary interaction parameters in non-density-dependent mixing rules was modified.
• The vdW-P theory with improved VPT EoS was recommended.

Gas solubility in water under hydrate-liquid water (H-Lw) two-phase equilibrium is the foundation of gas hydrate kinetic study. It is significant for the simulation of multiphase pipeline flow, the stability and amount evaluation of natural gas hydrate resources in deep water as well as gas storage and separation. In the current work, thermodynamic models were established by combining van der Waals-Platteeuw theory with PR, VPT and TB equations of state separately, named as Model VPR, VVPT and VTB, to predict methane solubility in water under H-Lw equilibrium. The Henry’s law was also included for comparison. Available experimental data in literature were collected to test the applicability of these equations of state. In order to improve the predicting accuracy, binary interaction parameters in the asymmetric contribution term of non-density-dependent (NDD) mixing rules were modified. Good agreements between predicted and experimental data were obtained by Model VVPT with the modified NDD mixing rules.