Procedure to determine the phase region of high-pressure, high-temperature binary salt-water mixtures

Abstract A decision tree to determine the phase region of high-pressure, high-temperature binary salt-water mixtures was developed. Based on the temperature, pressure and feed concentration of binary salt-water mixtures, the phase regions of either a type I or II salt were identified for a selected condition range. The Anderko and Pitzer equation of state (AP EoS) was used to calculate the equilibrium concentrations of the respective salt-water mixtures under high-pressure (P > 220 bar) and high-temperature (T > 300 oC) conditions. The EoS was adapted to calculate the thermodynamic properties of KCl-H2O and Na2SO4-H2O mixtures, in addition to the properties of NaCl-H2O. The developed decision tree was able to accurately identify the phase regions and indicate the transition from one phase to another for different feed concentrations. The developed decision tree can be useful in determining operating conditions and preventing solid deposition for processes operating under the supercritical conditions of water.