oa Atomistic Molecular Dynamics Simulations Of Transport Properties Of Co2 - H2o - Nacl Mixture At Conditions Relevant To Ccs Processes

Emissions of long-lived greenhouse gases (GHGs) are believed to be a major driver of climate change. Carbon dioxide (CO2) is the most important greenhouse gas, according to latest available studies and one of the most prominent strategies to lower its emissions is carbon capture and sequestration (CCS). CO2 can be stored in geological repositories, such as hydrocarbon reservoirs in which sodium chloride (NaCl) is the most common dissolved salt. For the optimum design of any CCS process, accurate experimental data and computational models are necessary that can provide reliable prediction of primary and derivative thermodynamic properties as well as transport properties. Despite the increasing importance of CCS processes, the lack of reliable physical property data cause significant uncertainties and create barriers toward the optimum design of the process. This study focuses on generating and validating molecular-based models and methodologies to allow for reliable prediction of the thermodynamic and transport properties of CO2-brine mixtures over a broad range of temperatures and pressures relevant for geological storage. Atomistic Molecular Dynamics simulations were employed for the calculation of diffusion and viscosity coefficients in the CO2 - H2O and H2O - NaCl mixture. Various combinations of existing force fields for H2O (SPC, SPC/E, SPC/E-flexible, TIP4P/2005 and Exponential-6), CO2 (EPM2, TraPPE, Zhang, Merker and Exponentian-6) and NaCl (Joung-Cheatham, Smith-Dang and Tosi-Fumi) were tested over a wide range of temperatures (283.15 K < T < 623.15 K), pressures (0.1 MPa < P < 100.0 MPa) and molalities (0-4). The MD results were compared with the respective experimental studies and useful comparisons about the models precision were drawn. Our group takes advantage of recent developments of efficiently parallelized codes that allow significant reduction of computer time compared to serial executions and for this reason we use highly optimized open-source codes such as LAMMPS and GROMACS. Acknowledgments This study was made possible by NPRP grant number 6-1157-2-471 form the Qatar National Research Fund (a member of Qatar Foundation). The statements made herein are solely the responsibility of the authors [1] Metz B, Intergovernmental Panel on Climate Change. Working Group III. Cambridge; New York: Cambridge University Press (2007). [2] International Energy Agency, A Policy Strategy for Carbon Capture and Storage (2012). [3] Berendsen, H. J. C.; Grigera, J. R.; Straatsma, T. P. J. Phys. Chem. 1987, 91, 6269. [4] Abascal, J. L. F.; Vega, C. J. Chem. Phys. 2005, 123, 234505. [5] Harris, J.G. and Yung, K.H. J. Phys. Chem. 1995 , 99 (31), 12021. [6] Potoff, J.J. and Siepmann, J.I. AlChE J. 2001, 47(7), 1676. [7] I. Joung and T. Cheatham, J. Phys. Chem. B 2008, 112, 9020. [8] D. E. Smith and L. X. Dang, J. Chem. Phys. 1994, 100, 3757. [9] F. Fumi and M. Tosi, J. Phys. Chem. Solids 1964, 25, 31. [9] Cadogan, S. P.; Maitland, G. C.; Trusler, J. P. M. J. Chem. Eng. Data 2014, 59, 519. [10] Moultos, O. A.; Tsimpanogiannis, I. N.; Panagiotopoulos, A. Z.; Economou, I. G. J. Phys. Chem. B 2014, 118, 5532. [11] See: http://lammps.sandia.gov/ and http://www.gromacs.org/