(21b) Process Intensification By Miniaturization of Fluidized Beds

Chemical micro-process technologies are relatively new concepts that offer much promise in terms of achieving process intensification by taking advantage of excellent mass and heat transfer characteristics of micro-structured devices. Recently there is a trend of miniaturization of fluidized bed systems to utilize further enhancement in mixing, heat and mass transfer provided by fluidized particles. However, there are some fundamental differences with classical macro-scale counterparts beds which need to be taken into account when designing these kinds of devices. The two major differences are the unavoidable wall effects due to small bed sizes and more importantly surface forces which start to be comparable or even dominate over gravitational force. These can be used to define the boundary between micro and macro-scale fluidization at 1 cm with a stricter limit at 1 mm in line with general microfluidics.
In terms of applications, the micro-fluidized bed holds promise in the already mentioned micro-process and micro-fluidic context. Besides fundamental studies on mixing and mass transfer enhancement, the current applications are mainly in high-throughput screening and testing of catalysts. The miniaturized fluidized bed also enables fast and reliable measurements of solid catalyzed reaction kinetics. Some more specific applications are in a low-cost device for detection of infectious bacteria, granulation screening of pharmaceutical tablet fillers, photocatalytic reactors and compact carbon dioxide HVAC units.

Acknowledgment

The authors acknowledge the support of the European Commission under the HORIZON 2020 Programme, for EU Project 680565 – ‘Intensified by Design’ (IbD).