Influence of anions and cations on the phase behavior of ternary salt solutions studied by high pressure differential scanning calorimetry

• The phase behavior of ternary hydrothermal salt solutions was studied using DSC.
• The ternary systems comprised the ions Na+, K+, Mg2+, SO42−, HPO42−, and CO32−.
• A stable liquid immiscibility region was found in some systems.
• The influence of the individual ions on the phase behavior is reported.

The knowledge of the phase behavior of salt solutions at elevated temperatures and pressures is important for processes using hot compressed water as the process medium, such as supercritical water gasification (SCWG) and supercritical water oxidation (SCWO). Furthermore hydrothermal salt solutions play an important role in geochemical processes in the Earth's crust. We studied ternary solutions related to biomass for obtaining relevant data for the conversion of wet biomass to synthetic natural gas (SNG) in a SCWG process. The experiments were conducted using isochoric high-pressure differential scanning calorimetry (HP-DSC) at a fixed average fluid density of 300 kg/m3, a fixed concentration of 0.1 mol/kg(H2O) and molar ratios between the two salts of 100:1–1:100. We investigated salts with Na+, K+ and Mg2+ as cations and SO42−, HPO42− and CO32− as anions.

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