Evaluation of a modified hydrocyclone as electrochemical reactor for processing of two-phase (gas-liquid) systems

Abstract

A standardised hydrocyclone is examined as analternative reactor for the electrochemical processing of two-phase systems.Experimental measurements and computational predictions of residence timedistributions demonstrate an appropriate hydrodynamics of the equipment. A mainpeak near the mean residence time was detected revealing that a fluid by-pass ordead regions are absent and the Peclet number, obtained by correlation of theexperimental data, was higher than 9. Mass-transfer measurements made by usinga segmented, or a grooved or a smooth cathode corroborate the good performanceof the cylindrical body of the hydrocyclone. The presence of the gas phase has littleinfluence on the residence time distribution as well as on the mass-transferbehaviour of this device. Sulphurdioxide reduction to colloidal sulphur was used as a test reaction to check theperformance of the reactor. The best results were obtained at a cathodicpotential of -0.5 V, against a saturated calomelelectrode, where hydrogen evolution is not possible as a cathodic side reaction.Thus, a 56% current efficiency with a specific energy consumption of 20.4 kWh kg-1 and a space time yield of 10.4 kg m-3 h-1 were attainedunder a two-phase flow of 5% SO2 in nitrogen. The sulphur particles obtainedfrom the spigot present an average size of 6.7 ìm being those carried by theoverflow stream smaller, both of them of high purity.