Intensification of the Rate of Diffusion-controlled Electrochemical and Catalytic Reactions at a Helical Coil by a Fixed Bed Turbulence Promoter

Intensifications of the rate of diffusion-controlled electrochemical and catalytic reactions taking place at the outer surface of a helical coil imbedded in an inert fixed bed of cylinders acting as turbulence promoters was studied using the electrochemical technique. The technique involved measuring the limiting current of the cathodic reduction of [K.sub.3]Fe[(CN).sub.6] in a large excess of NaOH as a supporting electrolyte. The variables studied were solution velocity, packing cylinder diameter, helical coil tube diameter, and physical properties of the solution. The rate of mass transfer at the outer surface of the coil was found to increase with increasing solution velocity and decreasing packing cylinder diameter, helical coil tube diameter was found to have a little effect on the rate of mass transfer. The data were correlated with the dimensionless equation Sh = 7.14 x [10.sup.-4] [Sc.sup.0.33] [Re.sup.0.52] [([d.sub.p]/d).sup.-2.32] Implication of the above equation for the design and operation of the present reactor was pointed out. The potential importance of using the inner surface of the coil as a built-in heat transfer facility for conducting exothermic electrochemical and catalytic reactions requiring rapid cooling was highlighted. The possibility of using multiple imbedded coaxial helical coils of different coil diameter in practical catalytic reactors to increase their rate of production was noted. Keywords: mass transfer, heat transfer, helical coils, fixed beds, turbulence promoters