A Two-Phase CFD Modeling Approach to Investigate the Flow Characteristics in Radial Flow Moving-Bed Reactors

Abstract

Based on a complete CFD Eulerian-Eulerian two-fluid approach, a comprehensive three-dimensional (3D) two-phase reactor model was suggested to describe the flow behavior in radial flow moving-bed reactors (RFMBRs). A porous media model was incorporated into the reactor model in order to describe the flow resistance provided by the porous walls of the center and annular pipes. Compared with these previous reactor models, the reactor model considers the solid-phase movement instead of immobilization, which benefits for predicting the formation of cavity practically. The simulation results are agreement with the published experimental data. By employing the verified model, the flow field parameters in the reactors such as pressure drop and flow velocity were obtained. Besides, the simulations were then carried out to investigate the effect of the bed voidage on the flow behavior and to understand the phenomenon of cavity in the RFMBRs. The simulation results showed that both the centripetal and the centrifugal flow configurations have the inhomogeneous flow distribution and the phenomenon of cavity. Furthermore, the inhomogeneous distribution increases with the increase of the bed voidage, whereas the phenomenon of cavity is more obvious with the increase of gas inlet velocity. As a whole, this work provided a realistic modeling and a useful approach for the understanding of RFMBRs.

Gas Axial Dispersion Behavior and Gas Residence Time in the Radial Flow Bed

“…Three different mesh sizes (5 mm, 10 mm, and 15 mm) were tested according to similar simulation cases. ,,, The corresponding total numbers of the mesh cells are 1 782 336, 372 738, and 94 677, respectively. The maximum equisize skew is approximately 0.84, 0.79, and 0.77, while the maximum aspect ratio is 3.8, 3.3, and 4.0.…”

“…In recent years, the flow pattern in the radial flow bed is investigated by many researchers, including some undesirable phenomena (e.g., cavity, ,− pinning, ,− air lock, , gas nonuniformity distribution ,− ), the simulation methods (e.g., single phase, ,,, Eulerian–Eulerian, ,, Eulerian–Lagrangian methods), the structural optimization (e.g., trapezoidal/conical bed, , baffles/Johnson-net/louvers ,, ), and the reaction process simulation (the flow pattern is usually assumed to be plug flow).…”