Redlich–Kwong equation of state for modelling the solubility of methane in water over a wide range of pressures and temperatures

• Redlich–Kwong equation of state for modelling of methane-water phase equilibrium.
• Modelling experimental data over a large range of temperature and pressure.
• Estimation of the binary interaction coefficient by data regression.
• Verifying the consistency of the experimental data.
• Quantifying the relation between temperature and binary interaction coefficient.

A thorough approach to the environmental and technological issues regarding natural gas extraction from underground and underwater reserves requires a very good understanding of the phase equilibrium between hydrocarbon gas and water. In this work we present an accessible way to predict methane-water phase equilibrium. For this purpose we selected from the literature experimental data for the solubility of methane in water, covering a large range of temperature (274.35 K–627.15 K) and pressure (0.57 MPa–197.26 MPa). Mathematical modelling was performed using the online available modelling tool Phase Equilibria, 2000 (PE2000) and applying the Redlich–Kwong equation of state. To best fit the calculated solubility to the experimental values, we estimated the binary interaction coefficient by data regression, and we used the results to verify the consistency of the experimental data. The binary interaction coefficient is dependent of temperature, and this connection can be quantified and further used to estimate the phase equilibrium at the needed conditions.

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