Hydrodynamics and gas mixing in a carbon nanotube agglomerate fluidized bed

A typical nanoscale fiber material, carbon nanotubes (CNTs), was fluidized in a 280 mm inner diameter (ID) nano-agglomerate fluidized bed (NAFB). The solids distribution and gas mixing were measured by a self-developed conductance method and the hydrogen tracer technique. Typical nano-agglomerate fluidization characteristics, such as high bed expansion ratio and multi-staged agglomerate structure, were observed. Fluidization experiments over a wide gas velocity range showed that the CNT agglomerates have agglomerate-bubbling-fluidization (ABF) characteristics. Particulate fluidization can also be achieved in the range 0.017 similar to 0.038 m/s, showing they also have Geldart-A particle characteristics. A systematic comparison of the transition velocities, solids distributions, and gas mixing between the fluidizations of CNT agglomerates and Geldart-A particles was carried out. CNT NAFBs have more non-uniform solids concentration profiles near the wall, but more homogenous micro-flow structures than Geldart-A particles, which leads to good gas mixing. These unique hydrodynamics behaviors are attributed to the difference in the microstructure between the nano-agglomerates and ordinary particles. (c) 2006 American Institute of Chemical Engineers.