1990, Ke Mingke (Cominco) Process Engineering Services Limited proposed a technique called the CESL (CESL the company name abbreviation full) ^[1], use of two leaching, including processed mineral brass low pyrite And chalcopyrite - bronze ore mixed mine. The first level is 150 °C The lower leaching solution is diluted with dilute sulfuric acid and a small amount of hydrochloric acid, and the leaching solution contains a chloride ion concentration of about 12g /L , 15~ 20g /LCu ²⁺ , Cu ²⁺ is a direct oxidant. The amount of acid added is controlled so that the final pH is 2.3 to 3.5 and copper is converted to basic copper sulfate. Second stage atmospheric leaching, leaching temperature 40 ° C Maintain a pH of 1.5~2 to dissolve the basic copper sulfate and minimize the entry of iron into the solution. Since the reaction is exothermic, no heating is required for both reactions. The leaching time of both sections is about 1 h . In the first stage of leaching, iron is converted to hematite, 90% of the sulfur is converted to elemental sulfur, and a small amount is sulfate. After extracting and evaporating a section of leachate, returning to a section of leaching, extracting copper by two-stage leaching solution, and electrowinning after stripping. The process is shown below. The recovery rate of copper in the whole process is about 99% . Extraction 1 and extraction 2 were combined with the extract 3 organic phase and washed together for stripping.

The CESL process is constantly evolving to accommodate different materials, and the flow chart has changed many times. It is estimated that investment in plant CESL process of production capacity of 200,000 t to $ 225 million, with half-scale fire plant. Production costs are estimated at 176~286 USD /t electrolytic copper.
References :
1.Cominco, Copper Hydrometallurgy Forum, 1998, Australia

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