Mass transfer behaviour of a flow-by fixed bed electrochemical reactor under different hydrodynamic conditions

Abstract

Mass transfer behaviour of a flow-by electrode made of a fixed bed of Raschig rings and cylinders supported by a vertical plate feeder electrode was studied. The rate of mass transfer of the bed–plate assembly was determined under single phase, gas sparging and two phase flow-by measuring the limiting current of the cathodic deposition of copper from acidified copper sulphate solutions. Variables studied were: particle diameter, height of bed–plate assembly, physical properties of the solution, superficial gas velocity, superficial solution velocity. The data under different conditions were correlated by dimensionless equations. Although the mass transfer coefficient of the bed electrode is less than that of the plate electrode, it was found that the volumetric mass transfer coefficient of the bed electrode and hence its productivity is higher than that of the plate electrode by a factor which ranges from 2.8 to 9.6 depending on the operating conditions. Power consumption calculation has shown that for a given set of conditions, bed electrodes consume less electrical energy in kWh/kg than the plate electrode under different flow conditions.