Numerical Investigation of Liquid-Solid Flow Dynamics in an Oscillatory Baffled Reactor

The oscillatory baffled reactor (OBR) is widely used in the chemical and biochemical industry to perform solid-catalyzed reactions such as fermentation, leaching, polymerization, etc., and is a good reactor intensification strategy. The overall performance of these reactors depends on the dynamics of the spatial distribution of micron-scale catalyst particles. The spatial distribution of the particles is not only a function of the physical properties of the solid and liquid phase but also a function of baffle geometry and oscillatory conditions [i.e., frequency and amplitude], which substantially influences the hydrodynamics of OBR. To the best of the author's knowledge, the hydrodynamics of OBR, in the presence of particles is not investigated. In view of the above, we investigate the hydrodynamics of OBR, in the presence of particles, with the aid of a 3D two-fluid Eulerian-Eulerian approach combined with the kinetic theory of granular flow (EE-KTGF). Before using the simulations to investigate the hydrodynamics for a wide range of conditions, the predictions of EE-KTGF were validated with aid of measurements in terms of mixing/settling time as a function of solid properties. The validated model is further used to understand the role of particle size (10 to 100 µm), density (1100 to 2200 kg/m3), and (0.833 to 1.583 Hz) on the local liquid-solid hydrodynamics. The predictions demonstrate that, at a high, small particle size and density, recirculatory vortices are formed, aiding uniform radial mixing. However, at low, large particle sizes, and densities, local dead zones start appearing leading to the sedimentation of particles. The presented hydrodynamics predictions provide a useful basis for further intensification of liquid-solid OBRs.