Wall-to-bed mass transfer in a three-phase fluidized bed with coaxially placed string of spheres internal

Abstract

Turbulent promoters are generally used to realize enhancement in heat and mass transfer rates. With a view to exploit this advantage for the favor of obtaining magnitudes of improvements in mass transfer rates in electrochemical processes, in the present study experiments were conducted in three phase fluidized bed electrochemical cells in the presence of coaxially placed string of spheres. Diffusion controlled electrode reactions were employed to obtain limiting current densities, and hence, mass transfer coefficients. An equimolar potassium ferrocyanide and potassium ferricyanide solution in the presence of sodium hydroxide supporting electrolyte was used as the liquid phase. Glass spheres of different sizes were employed as fluidizing solids and nitrogen was used as the inert gas phase. In three phase fluidized bed, mass transfer coefficient increased with increasing sphere diameter and particle diameter. The parametric effect of gas and liquid velocities on mass transfer coefficient was found to be marginal. The mass transfer coefficient was found to decrease with increase in pitch. A correlation to predict mass transfer coefficient has been developed by using least squares regression analysis.