Coupling an equation of state and Henry's Law to model the phase equilibria of gases and brines: Examples in the N 2–H 2O–NaCl system

Abstract

We propose a thermodynamic model for the mixing of gases in aqueous sodium chloride solutions valid to high pressures, high temperatures, and high ionic strength solutions. Our model couples Henry's Law with any equation of state to reproduce experimental data in the aqueous-rich liquid and gas-rich vapor region. In our model, the chemical potential of the solute in the brine is related to the chemical potential of the solute in pure water through salting-out coefficients. The model reproduces all crucial phenomena of binary (gas–water) and pseudo-binary (gas–water–salt) vapor–liquid mixtures below their critical point. We applied the model to reproduce the phase behavior of nitrogen in water and NaCl brines. Results and discussions are shown.