(403a) Supercritical Water Hydrocarbon Mixing in Complex 3-D Mixer Geometry Under Partially-Miscible Conditions

Authors: 
Raghavan, A., Massachusetts Institute of Technology
He, P., Massachusetts Institute of Technology
Ghoniem, A. F., Massachusetts Institute of Technology

In this study, the mixing of supercritical water (SCW) and model hydrocarbons in a 3-D mixer geometry under partially-miscible conditions is investigated using 3-D multiphase CFD simulations. This mixing process is of considerable significance in the process of supercritical water upgrading and desulfurization of crude oil. A Volume of Fluid (VoF) method is applied to track the water-hydrocarbon interface followed by phase equilibrium computations to determine the concentrations of the water and oil-rich phases on either side of the interface. The species and energy fluxes across the interface are also computed using consistent modeling procedures. The near-critical thermodynamics of the water-hydrocarbon mixture is modeled using a cubic Peng-Robinson equation of state. The numerical method is validated against previously reported 1-D simulation results of a spherically symmetric case of a hydrocarbon (n-decane and toluene) droplet in SCW. Thereafter, the mixing of SCW and two model hydrocarbons (n-decane and toluene, with a significant difference in upper critical sloution temperature (UCST) in water) in a 3-D cylindrical tee mixer is studied. The impact of the persistence of the water-hydrocarbon phase interface on the retardation of the rate of mixing is quantified. The impact of the water inlet temeprature (far below, close to and far above the UCST) on the rate of mixing is also investigated