The Inspiration Leaching Plant

This paper describes the design, construction, and operating performance of the Inspiration Consolidated Copper Company’s large-scale leaching plant at Inspiration, Arizona, built to treat up to 9000 tons of ore per day. The leaching process relies on dissolving oxidized copper with sulfuric acid and chalcocite-type sulfide copper with ferric sulfate, the latter regenerated electrolytically from ferrous sulfate. After initial operation, it was found that certain ores produced excessive colloidal slimes that hindered percolation, leading to the installation of a washing plant and the systematic removal and separate treatment of primary slimes. The plant layout, including coarse and fine crushing, screening, dust collection, and classification with Dorr bowl classifiers, is described, along with measures to control moisture and particle size for optimal leaching. Metallurgical data over five years show that slime removal and process refinements improved and stabilized oxide copper extraction at about 96% and sulfide copper extraction at about 81%, giving higher overall copper recovery than originally estimated. The paper also discusses practical operational details such as tank design, lead linings, roll performance, dust handling, and water-use constraints imposed by subsequent flotation treatment of slimes.