Hydrodynamics of three-phase draft tubed spouted and spout-fluid beds

In this study, the hydrodynamics of Three Phase Draft-tubed Spouted/Spout-fluid beds (TPDS) are investigated with the intent of designing a three phase contacting reactor useful for many applications in the industry. In the system investigated, solid particles are circulated using an aqueous phase, in a systematic manner, between the central draft tube region and the external annular region of the reactor. In this annular region, the solid particles in downflow are contacted with upflow of gas distributed through spargers and liquid, both introduced in the annular region.;The effect of extrinsic factors such as system geometry and gas and liquid flowrates on intrinsic design parameters such as particle circulation and liquid distribution between the draft tube and the three phase annular regions in TPDS beds are studied, and hydrodynamic models for these two regions are proposed. Particle circulation and liquid distribution are measured by trapping the draft tube outflow and weighing. Bubble size, rise velocity and gas holdup are determined using novel dual electrical resistance probes. All measurements including pressures and gas flowrates, are made using on-line data acquisition and control. The hydrodynamics of the entire system is modeled by separately modeling the draft tube and annular regions using one-dimensional mass and momentum conservation equations with simplified phasic interaction parameters and combining the two models for closure. The results show that gas holdup and solid-fluid contacting characteristics of TPDS beds are superior to those of their industrial three phase fluidized/packed counterparts, with a new and potentially useful regime in the three phase annular region for enhanced heat and mass transfer.