WALL-TO-BED MASS TRANSFER IN AN ELECTROCHEMICAL CELL WITH COAXIALLY ROTATING COMPOSITE PROMOTER IN THE PRESENCE OF FLUIDIZING SOLIDS

Abstract

Limiting current data have been obtained at point electrodes fixed flush with the inner surface of the outer cylinder of an annular electrochemical cell. A central rod with tape rigidly fixed at varying pitches served as composite promoter. It was coaxially placed in the test section and rotated by a transmission gear mechanism in a bed of fluidizing solids. The metered electrolyte through a rotameter was recirculated through the test section. The data were obtained at different flow rates and rotational speeds in the absence and presence of fluidizing solids. The effect of presence of solids and ϵ were analyzed using two different particle sizes. It was found that the rotation of the central rod enhanced the coefficients significantly, while the presence of solids had marginal improvements. The rotation in general was found to change the fixed bed status to expanded bed even for superficial velocities below 0.06 m/s. The data on mass transfer were correlated using an equation of j_D-Re format, incorporating pertinent dynamic variables, modified Reynolds and Froude groups, and solids holdup.

Keywords:

• Composite promoter
• Electrochemical cell
• Fluidized bed
• Ionic mass transfer
• Rotation
• Wall-to-bed mass transfer