Thermodiffusion of CO2 in Water by Nonequilibrium Molecular Dynamics Simulations

Author(s)

Coelho, Felipe M. ; Franco, Luis F. M. ; Firoozabadi, Abbas

• Document type: Journal article
• Source: Journal of Physical Chemistry B; v. 127, n. 12, p. 12-pg., 2023-03-17.

Abstract

The components of a fluid mixture may segregate due to the Soret effect, a coupling phenomenon in which mass flux can be induced by a thermal gradient. In this work, we evaluate systematically the thermodiffusion of the CO2-H2O mixture, and the influence of the geothermal gradient on CO2 segregation in deep saline aquifers in CO2 storage. The eHeX method, a nonequilibrium molecular dynamics simulation approach, is judiciously selected to simulate the phenomenon. At 350 K, 400 bar, and CO2 mole fraction of 0.02 (aquifer conditions), CO2 accumulates on the cold side, and the thermal diffusion factor is close to 1 in a number of force fields. The lower the temperature, the higher is the separation and the thermal diffusion factor. In colder regions, water self-association is stronger, whereas the CO2-H2O cross-association and the CO2-CO2 interactions enhance at higher temperatures. Thermodiffusion and gravitational segregation have opposite effects on CO2 segregation. At typical subsurface conditions, the Soret effect is more pronounced than gravity segregation, and CO2 concentrates in the top (colder region). Our work sets the stage to model the effect of electrolytes on CO2 segregation in subsurface aquifers and other areas of interest. (AU)

• FAPESP's process: 18/02713-8 - Molecular dynamics of confined fluids: equilibrium and transport properties
• Grantee: Luís Fernando Mercier Franco
• Support Opportunities: Research Grants - Young Investigators Grants
• FAPESP's process: 20/13300-6 - Molecular dynamics simulations for studying equilibrium properties of confined mixtures
• Grantee: Felipe Mourão Coelho
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)
• FAPESP's process: 21/13068-9 - Thermodiffusion of CO2 in water: the Impact of the geothermal gradient in the carbon sequestration within deep saline aquifers via molecular simulation
• Grantee: Felipe Mourão Coelho
• Support Opportunities: Scholarships abroad - Research Internship - Doctorate (Direct)