Experimental and numerical investigations on the electrostatics generation and transport in the downer reactor of a triple-bed combined circulating fluidized bed

Abstract

Electrostatics is an inevitable phenomenon in fluidization processes and granular flow systems where collisions between particulates and walls with different materials occur. In this study, the electrostatic performance in the downer reactor of a triple-bed combined circulating fluidized bed was investigated through both experiments and numerical simulations. In numerical simulation the Discrete Element Method (DEM) was adopted to simulate the electrostatic charge generation and transfer occurring in the downer. Both experimental and numerical results showed that the averaged induced currents caused by electrostatics increased with increasing solids mass flux in the downer, and the electrostatics was the strongest near the entrance of the downer because of the highest frequency of collisions between particles and the wall caused by the largest solids holdup at that location. Numerical studies also revealed that the averaged induced currents increased with increasing initial particle velocity and particle size, and the averaged induced current caused by the charge transfer was much larger than those by charge generation through tribocharging. These results may help us better understand the mechanism of electrostatic phenomena, and better cope with challenges and problems caused by electrostatics. © 2012 American Chemical Society.