High Current Density Operation at Toyo Tank House

Toyo Smelter & Refinery, Sumitomo Metal Mining Co., Ltd. produces 450,000 tons of high grade copper per year in three tank houses. Conventional starting sheet technology has been used at Toyo tank house #1 and Niihama tank house. The Niihama tank house commenced operations in 1919. The current density at the Niihama tank house and the Toyo tank house #1 has reached 320 A/m² with approximately 100 years of operational experience and technological advancements. To achieve high current efficiency under condition of 320 A/m² operation, both tank houses have undertaken measures to optimize the adjustment of the cathode assembly machine and the anode pressing machine in order to improve the verticality of cathodes and anodes and to maintain uniform distances between cathodes and anodes. Additionally, the concentration of the electrolyte was meticulously controlled to prevent anode passivation, and the adjustment of the processing raw materials to regulate the impurity concentration in the electrolyte was also improved to maintain stable high current density operations. As a result, a current efficiency close to 98% was achieved at a current density of 320 A/m². This report outlines the improvements that have been implemented to date.