Medium-temperature pressure leaching of copper concentrates - Part III: Commercial demonstration at Baghdad, Arizona

Parts I and II in this series of papers presented the chemistry of medium-temperature pressure leaching of copper sulfide concentrates and reviewed the metallurgical development of a process to effectively recover copper using medium-temperature pressure leaching and direct electrowinning (DEW). Key features of the process were the use of superfine grinding of the concentrate (to a P-98 of 12 to 15 pm and P-80 of 6 to 7 pm), pressure leaching at 160 degrees C and 1,380 kPa (200 psi) oxygen overpressure, DEW to produce LME Grade A cathode, recycling of the lean electrolyte to the pressure leaching step and treatment of a lean electrolyte bleed by solution extraction (SX). Recycling of the lean electrolyte provided all of the acid required to effectively dissolve copper and convert approximately 65% to 70% of the sulfide sulfur to elemental sulfur, resulting in an "acid-autogenous" process referred to as the "MT-DEW-SX" process. This paper (Part III) discusses the steps taken to develop and complete a large-scale demonstration of the process at Bagdad, Arizona, in 2005.