Bed collapse behavior of pulsed fluidized beds of nano-powder

•Collapse of fluidized bed subject to 0.1 Hz frequency square wave was investigated.•Nano-powder that shows strong agglomeration behavior was used as bed material.•Both pressure as well as velocity transients were recorded.•Agglomerate size was relatively insensitive to fluidization velocities.•Flow pulsation helps to substantially reduce the agglomerate diameter.

An important class of assisted fluidization techniques, which are neither energy-intensive nor suffer from post-processing issues, is based on pulsation of inlet gas flow to the fluidized bed. Collapse experiments have been carried out in a pulsed-flow fluidized bed containing a widely used nano-powder that shows strong agglomeration behavior. Pulsation in the inlet air flow was introduced using 0.1 Hz frequency square wave that controlled opening and closing of a solenoid valve. Transients of the total pressure-drop across the bed were carefully recorded using fast-response pressure transducers connected to a data acquisition system. Flow transients were also monitored during the bed collapse. Average size of nanoparticle agglomerates was computed using a mathematical model reported in the literature. Flow pulsation was found to substantially reduce the average agglomerate size of the nano-powder.

Graphical abstractBoth pressure and velocity transients were recorded during the collapse of a low frequency pulsed fluidized bed containing a nano-powder that shows strong agglomeration behavior. Though the effect of the fluidization velocities on the agglomerate size was found to be negligible, yet the flow pulsation helps to significantly reduce the agglomerate size.Figure optionsDownload full-size imageDownload as PowerPoint slide