The Effect of a Conical Inner Electrode on the Mass-transfer Behavior in a Cylindrical Electrochemical Reactor under Single-Phase and Two-Phase (Gas-Liquid) Swirling Flow

Abstract

The influence of a continuous change in the cross-section area on mass-transfer performance is analyzed in an electrochemical reactor under swirling flow. Thus, a conical frustum is used as an inner electrode in a cylindrical arrangement. A convergent flow is obtained by placing the conical frustum with its smaller base at the bottom of the reactor, or conversely, it produces a divergent flow. Experimental local mass-transfer coefficients along the electrode length are reported using the reduction of ferricyanide as a test reaction. The mass-transfer distribution as well as the global mass-transfer coefficient are both discussed in three geometric arrangements, i.e. constant interelectrode gap, convergent and divergent cases under single-phase and two-phase (gas-liquid) flow. The highest global mass-transfer coefficients are obtained for the convergent arrangement in the middle range of volumetric flow rates, giving out values 7.6% higher than those for the constant interelectrode gap case. Divergent geometry presents, as its main asset, the most uniform mass-transfer distribution in comparison with the other two configurations. The presence of the gas phase also has little influence on the mass-transfer performance of the reactor. Computational fluid dynamics calculations are in good agreement with experimental measurements.