Electrolyte Circulation in Copper Refinery

Abstract

The importance of natural convection accompanied with electrochemical reactions along vertical electrodes has been recognized in the field of industrial electrochemical engineering as well as electrodeposition. Brenner applied a freezing method to analyze the concentration distribution[1]. Wagner demonstrated that the limiting current density distribution along the vertical cathode was governed by natural convection, based on the boundary layer theory [2, 3]. Wilke, Eisenberg and Tobias described a similarity between the natural convection caused by electrodeposition and by heat transfer [4]. Ibl and Muller examined the ionic mass transfer rate by the interferometry technique [5]. Since then, numerous studies have been carried out on the ionic mass transfer rate associated with natural convection caused by the electrochemical deposition and dissolution of copper in unstirred CuSO4-H2SO4aqueous electrolyte solutions [6-15]. However, most studies have focused on the steady state phenomena along a relatively short electrode at most 15 cm high confined in semi-infinite electrolyte media and have neglected the effects caused by the existence of the counter electrode. In industrial scale of copper refinery, vertical impure casted anode and starting sheet of electrolytic copper cathode are installed in the tank. Significant electrolyte stratification may frequently cause various troubles to induce poor cathode quality. Each refinery designs their own electrolyte circulation system with their confidence. Additive control technique is a key technology. Sometime a slightly different circulation system is introduced even in one refinery in the same company. It is simply because the principle of electrolyte circulation has been never discussed from the fundamental electrochemical engineering point. It may be a starting point for this problem in such a modernized computational technology.