Intensification of interfacial mass, heat & momentum transfer in high-G fluidized beds in vortex chambers : experimental & theoretical study of potential applications

Eliaers, Philippe [UCL]

Vortex chambers can be used for the generation of rotating fluidized beds. High-G operation allows eliminating many of the limitations faced in conventional fluidized beds. In particular, interfacial transfer of mass, heat and momentum can be significantly intensified. This opens perspectives for increasing the efficiency of some existing fluidized bed processes, but also for developing novel processing routes. Two processes were studied in this context: 1. Biomass drying is frequently carried out in a conventional fluidized bed. An experimental comparison between the performances of such a conventional fluidized bed and of a vortex chamber at varying operating conditions demonstrated the about one-order magnitude process intensification factor that can be achieved in vortex chambers. The intensification of interfacial momentum transfer and its influence on the particle bed density and uniformity was shown to contribute significantly to the process intensification, next to the intensification of interfacial mass and heat transfer. To study scale-up, a detailed simulation model was developed and validated. The scale-up study focused on the air utilization and product uniformity and demonstrated the potential of multi-zone operation. 2. The low-temperature wet coating of cohesive particles cannot be carried out in a conventional fluidized bed. High-G operation intensifies interfacial momentum transfer, reducing the effects of the van der Waals forces and opening the way to the fluidization and coating of cohesive particles. The influence of the operating conditions and the quality of the produced coated particles were experimentally studied. It was shown that agglomeration can be controlled by means of the gas flow rate. The flexibility of vortex chambers with respect to the latter is interesting in this respect. Finally, through a first experimental study, vortex chamber spray drying was demonstrated. An outlook on this application is given at the end of this work.