Phase Behavior Modeling for Carbon Dioxide/Brine Mixtures

  • Author / Creator
    Sun, Ziting
  • Accurately predicting CO2 solubility in saline aquifers is very important for CO2 capture and storage. A reliable and accurate thermodynamic model is needed to accurately predict the phase behavior of the CO2+brine systems over a wide range of temperature, pressure, and molality. This study aims at developing a cubic-equation-of-state-based thermodynamic model that can accurately describe the phase behavior of the CO2+brine systems. Peng-Robinson equation of state (PR EOS) (Peng & Robinson, 1976) and the Huron-Vidal (HV) mixing rule (Huron and Vidal, 1979) are utilized to model the phase equilibria of CO2+brine systems containing salt species including NaCl, KCl, CaCl2, and MgCl2. Binary interaction parameters as functions of temperature and salt molality are established for specific CO2+single-salt+H2O systems. The model is extended to account for the effects of different salt species on CO2 solubility in aqueous phase solutions, which can cover the typical geological conditions (273-550K, 0-800 bar, 0-6 mol/kg). We employ the PR EOS together with the proposed BIP strategy in the HV mixing rule to reproduce the mutual solubility of CO2 and H2O in vapor-liquid equilibria (VLE). The collected experimental data are used to determine the optimal BIP model. The validation of the model calculations against the available experimental data indicates that the average absolute percentage error (%AAD) in reproducing the CO2 concentration in the mixed-salt brine is 12.63%. Compared to the calculation results provided by the state-of-the-art models in the literature (Søreide & Whitson, 1992; Sun et al., 2021), the PR EOS together with the proposed BIP strategies in the HV mixing rule can more accurately predict the VLE of CO2+brine systems over large ranges of temperature, pressure, and molality.

  • Subjects / Keywords
  • Graduation date
    Fall 2021
  • Type of Item
  • Degree
    Master of Science
  • DOI
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.