Abstract:The utilization of chloride solutions is advantageous due to the aggressiveness in leaching and the stability of the cuprous ion. However, the electrowinning of copper from chloride solutions promotes dendroid copper deposits, making operations somewhat complicated in an electrolytic diaphragm cell. To overcome this drawback, a novel process has been developed, in which cuprous oxide is precipitated with sodium hydroxide from the purified pregnant leach solution. Sodium hydroxide is regenerated in a chlor-alkali cell. The other products of the electrolyser are also recirculated, chlorine gas to concentrate leaching and hydrogen gas to the reduction of cuprous oxide to metallic copper.This paper discusses the new technology for copper production and the experimental work on Outokumpu HydroCopper. To verify the technology Outokumpu has designed and constructed a demonstration plant in Pori, Finland. Operation started in March 2003.