The slag flotation process has become a common option to recover Cu from slags obtained in theclassical pyrometallurgical route for primary copper production from sulphide concentrates. It iswell known and accepted that the slag cooling rate is a key parameter for the performance of theflotation process, the slower the cooling rate, the higher the copper recovery, given an appropriategrinding fineness. The general understanding is that the slow cooling helps to promote thenucleation and growth of the copper sulphide particles so they are suitable to be recovered in theflotation plant. The available scientific and technical information do not provide quantifiable dataof those phenomena and neither a relation between the slag cooling rate, the size of the particlesprecipitated and the performance of this material in standard flotation tests. The work presentedaims to propose an analysis of these variables using a quantitative experimental approach usingslags from Chagres Smelter operation in Chile.Two types of slags were used to study the size distribution of copper sulphides particles obtainedin slags cooled at different controlled cooling rates at laboratory scale. Those results were correlatedwith a flotation standard test allowing to propose a relation on the expected recovery based on thecooling rate of the slag. The flotation tests were done with 1 kg of slag that was cooled under verystrict control of temperature and atmosphere. A discussion is presented on the possibility tooptimize copper recovery based on the physical chemistry description of the multicomponent slagsystem under smelting and solidification conditions.
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