Faith, hope and clarity

摘要

In SX/EW metals production the basic elements in process design are the Pregnant leach solution (PLS) available, the solvent extraction reagent to used, the mixing and settling technology and the electrowinning system, But process variables almost invariably create problems so that subsidiary treatment of solutions is necessary to ensure the electrolyte quality required for high-grade cathode production. Like your average Tetrapaked fruit juice, the pregnant leach solution is often prepared from concentrate but must be supplied to the SX circuit clear - not cloudy, no bits. Usually, quite simple techniques, such as sand filtration and counter-current decantation, remove suspended solids from the arriving PLS and more sophisticated techniques purify the electrolyte solution leaving the solvent extraction process. For example, at Codelco's Radomiro Tomic plant where WME started this series of articles on SW/EW technology, the heap leach PLS passes through desliming ponds before entering the SX trains, while the copper electrolyte is not only deslimed but also purified by a combination of coagulation, column flotation and electrolyte filtration. Process engineers working for operators like Codelco, who developed the coagulation and filtration systems for Radomiro Tomic, and manufacturers such as Canadian Process Technologies, whose column flotation cells are used there, have paid a great deal of attention to the purification step and applied a range of technical solutions. But process developers in Australia and Africa have also focussed on avoiding process disturbance by more effective removal of solids from the PLS.