Effect of electrostatic charges on single bubble in gas-solid fluidized beds

Electrostatic charges are well known to influence the hydrodynamics of gas-solid fluidized beds, but no detailed description is currently available showing how they can influence bubble properties such as shape and velocity. This study simulates the injection of single bubbles into a fluidized bed of charged particles. The effect of electrostatic charge is modeled by the Two Fluid Model (TFM) implemented in MFIX code, solving the governing momentum, continuity and electrical equations. This model is initially evaluated for an uncharged system by comparing the numerical predictions with the bubble shape measured by Gidaspow D., Seo, Y., Ettehadieh, B. [1983. Hydrodynamics of fluidization: Experimental and theoretical bubble sizes in a two dimensional bed with jet. Chem. Eng. Commun. 22, 253-272] and particle pressures measured by Rahman, K., Campbell, C. [2002. Particle pressures generated around bubbles in gas fluidized beds. J. Fluid Mech. 455, 103-127]. The effect of charged particles on bubble behavior is then simulated. The simulations show bubble elongation in the flow direction. As a result, bubbles rise more quickly than for the uncharged case. Analysis is performed on the magnitude of charge density and the choice of frictional model. The bubble deformation is explained based on forces on particles at the bubble periphery. (C) 2012 Elsevier Ltd. All rights reserved.