(20b) Challenges and State of Art of Multiphase Flow Modeling in F-T Synthesis

Modeling the gas-liquid-solid flow is critical for the scale-up and optimization of slurry bubble column reactors in Fischer-Tropsch (F-T) Synthesis. This is, however, a challenging task for CFD modelers due to inadequate understanding of the complex mesoscale flow structure and the complex coupling of multiphase flow, interfacial mass and heat transfer as well as reaction kinetics. This talk gives a state of art review in literature and the challenging issues of multiphase flow modeling in F-T synthesis. The challenges in physical models involve the phase interaction (drag) and multiphase turbulence modeling, and bubble breakage and coalescence modeling. The challenges in reactor modeling involve the simulation of complex geometry of a large number of internal cooling tubes, the effects of gas contraction due to reaction on fluid dynamics and the models for catalyst particle attrition. A mesoscale modeling approach for modeling multiphase reactors is then developed based on the Energy-Minimization Multiscale (EMMS) methods, and a stability-constrained multi-fluid model is established to provide closure models for CFD modeling.