(194g) Enhancement of Fluidization of Fine Powders

Gas-solid fluidization is one of the most broadly used techniques in the industry, where homogenous mixing and vigorous interphase contact are of the primary interest. Fine powders (from nanos to a few microns) of a large surface area are typically good candidates for catalytic materials, but their fluidization is problematic, very hard to achieve. At this scale, interparticle forces, such as capillary force and van der Waals force, play a significant role, making the powders cohesive. As a result, an assembly of fine powders tends to agglomerate and creates gas channels when fluidized at a steady flow, leading to rather poor contacts with the supplied gas [1]. Mitigating agglomeration and breaking up gas channels are, obviously, the key steps to improve their fluidization performance.

Introducing additional degrees of freedom provides flexibility to manipulate fluidization behavior. In the last decade, many works demonstrated the successful uses of external actuators, across different force types and energy sources, to enhance fluidization behavior [2, 3], as shown in Fig. 1. In this work, we experimentally investigate industrially relevant assistance methods that are prevalent, such as vibration, pulsation and stirrer mixing. X-ray computational tomography and pressure probes are used to visualize and characterize the hydrodynamics with particular interests to monitor the effects on agglomeration and gas channels. By pinpointing the degree-of-enhancement induced and uncovering the underlying mechanism, the results will allow us to optimize existing reactors, and design a new class of efficient production process accordingly.

[1] J.R. van Ommen, J. Nijenhuis, M.-O. Coppens, Reshaping the structure of fluidized beds, CEP (2009) 49-57.

[2] V. Francia, K. Wu, M.-O. Coppens, Dynamically structured fluidization: Oscillating the gas flow and other opportunities to intensify gas-solid fluidized bed operation, Chem. Eng. Process. 159 (2021) 108143.

[3] J.R. van Ommen, J.M. Valverde, R. Pfeffer, Fluidization of nanopowders: a review, J. Nanopart. Res. 14 (2012) 737.