Improved thermochemical data for computation of phase and chemical equilibria in flue-gas/water systems

A thermodynamic model for the computation of phase and chemical equilibrium in aqueous systems based on minimization of the Gibbs energy is developed using new thermochemical data and Pitzerʹs activity coefficient model. New data for the thermodynamic standard properties ΔfG0, ΔfH0and Cp0, are determined from our experimental results, which are based on the spectrometric in situ analysis of both the vapor and the liquid phase. The studies have been made in the concentration range pertinent to flue gas purification processes: pSO2between 0.01 and 1 kPa, cHCl up to 1 mol dm−3, cH2SO4 and cCaCl2up to 0.5 mol dm−3. The temperature varies from 298 to 333 K. In comparison with earlier data, a better correlation of important flue-gas/water subsystems like SO2+water is achieved and a formerly proposed complexation of sulfur dioxide in the SO2+HCl+H2O system is confirmed. In particular, it is shown that on this basis the phase equilibria of SO2+CaCl2+H2O and SO2+HCl+H2SO4+H2O can be predicted without further adjustment of parameters.