Slurry Cooling Towers Implementation at Cobre Las Cruces Hydrometallurgical Plant

C. Frias, E. Delgado, L. Lerin, L. Pastor

Since 2009, Cobre las Cruces (CLC) is operating successfully an integrated mine and hydrometallurgical plant near Seville, Spain. The CLC hydro plant deals with chalcocite ores through direct atmospheric leaching process followed by solvent extraction and electrowinning. CLC is producing about 72,000 t/y Cu cathodes, Grade A, 99.999 % Cu. To achieve an efficient and smooth operation is necessary to control properly the heat balance and the water balance in CLC hydro plant. That way, installed cooling towers play a crucial role; on one side, cooling towers allow to dissipate heat and to cool required streams; on the other side, cooling towers evaporate significant amount of water and help to keep in balance the whole circuit. Two liquid cooling towers have been running along last years at CLC to cool PLS stream from 90 ºC to 35 ºC, approximately, and it is remarkable that gypsum scaling was a relevant issue. Now, CLC has implemented two new slurry cooling towers to cool, first, the leach pulp leaving reactors cascade from 90 ºC to 45 ºC, and then, such a cooled pulp is fed to the leach thickener; next, overflow PLS is cooled in existing liquid cooling towers from 45 ºC to 25 ºC while underflow pulp at 45 ºC is sent to filtration and washing. Now, gypsum scaling has been minimised. The new slurry cooling towers combined with existing liquid cooling towers provides a more effective process configuration to CLC hydro plant, presenting the next advantages: (i) evaporated water has been substantially increased; (ii) crystalized gypsum is mostly incorporated to the leach pulp and produced PLS contains low gypsum, and in consequence, gypsum deportment to SX and gypsum scaling has been notoriously reduced; (iii) leached pulp is now filtered at 45 ºC instead of 90 ºC (in the past), and so as, used press filters will have less corrosion and longer life. This paper refers to a major technological advance in copper hydrometallurgy developed and implemented by CLC, demonstrating that a heat and acidic leached pulp is easily cooled through slurry cooling towers application.