Impact of Non-Ideality Revealed in Numerical Simulations of Mixing of Hydrocarbons and Supercritical Water

Upgrading heavy crude oil using near-critical or supercritical water (NCW/SCW) shows advantages such as high yielding of light oils, less coke formation, removal of sulfur content and heavy metals, etc. We study the thermodynamic and mixing process of crude oil and NCW/SCW, using representative hydrocarbons, e.g., n-C10, n-C30, benzene, naphthalene, and 1-decylnaphthalene. GCA-EoS, the first equation of state that takes into account association using a SAFT-like group contribution term, is used to predict the thermodynamic properties and phase equilibrium compositions. Chung et al. correlation method is used to estimate the viscosity and thermal conductivity of the supercritical mixture, and the Tracer Liu-Silva-Macedo equation is used to calculate the binary diffusion coefficients. The mixing process of a hydrocarbon droplet (D=0.5mm) in a bulk of NCW/SCW at 24 MPa is simulated for different components and at different temperations. Our results reveal the importance of the non-ideal diffusion in this mixing process of supercritical fluids: Above the upper critical solution temperature, the diffusion of water into hydrocarbons is significantly delayed. The characteristics of alkanes and aromatics when mixing with NCW/SCW are summarized based on our numerical study.