MINERALS & METALLURGICAL PROCESSING Vol. 27 No. 3 • August 2010 141 Copper losses in sulfide concentrate smelting slag are dependent on slag composition Ž. Živkovic Professor, University of Belgrade, Technical faculty in Bor, Bor, Serbia N. Mitevska Research engineer, Mining and Metallurgy Institute, Bor, Serbia I. Mihajlovic Professor, University of Belgrade, Technical faculty in Bor, Bor, Serbia; E-mail: imihajlovic@tf.bor.ac.rs Ð. Nikolic Professor, University of Belgrade, Technical faculty in Bor, Bor, Serbia Abstract The silicate slag and copper matte that are the byproducts of smelting copper in a reverberatory furnace contain SiO 2 , FeO, Fe 3 O 4 , CaO and Al 2 O 3 , and Cu, Fe and S, respectively. These components infuence the oxide (Cu ox ), sulfde (Cu sul ) and total (Cu total ) copper content lost in the waste slag. This paper uses multiple linear regression analysis (MLRA) to determine the degree of infuence. The results of calculations obtained using MLRA were compared to actual measured results and found to have a large degree of correspondence, with the coeffcient of determination R 2 = 0.975. These results indicate that slag composition and copper content in the matte infuence the copper losses in the waste slag with a probability of above 97%. It was determined that, of the total copper content of the slag, 74% is in sulfde and 26% in oxide form, and that this ratio is not dependent on the slag or matte composition. Paper number MMP-09-047. Original manuscript submitted October 2009. Revised manuscript accepted for publication March 2010. Discussion of this peer-reviewed and approved paper is invited and must be submitted to SME Publications Dept. prior to February 28, 2011. Copyright 2010, Society for Mining, Metallurgy, and Exploration, Inc. Introduction During pyrometallurgical copper extraction, smelt- ing follows the oxidative roasting of the concentrates. In the modern pyrometallurgical processes of copper extraction, both operations are performed in the same unit, resulting in the development of two main prod- ucts: silicate slag and copper matte. These products are differentiated along the melting zone length by gravitational settling, according to their specifc gravities. Partially dissolved copper and unsettled copper matte droplets present in the waste slag result in copper losses (Biswas and Davenport, 2003). With stationary smelting processes, such as smelting in a reverberatory furnace, this loss is about 0.5% Cu and is permanent, because such slag is disposed of in the waste yard. With dynamic smelting processes such as Flash, INCO, etc., the copper content in the silicate slag can reach 2%, an amount that demands further processing of the slag. Processing of such copper-rich slag is facilitated using fotation or electroprecipitation of remaining sulfdes, resulting in about 0.5% Cu in the remaining waste slag (Živković and Savović, 1996; Sarraf et al., 2003; Habashi, 2007). Global annual slag production resulting from copper smelting operations is above 25 tons (Gorai and Jana, 2003). Thus, copper loss to waste slag strongly infuences the worldwide rise of the copper extraction process (Maweja et al., 2009). Numerous investigations have revealed that slag composi- tion has a dominant infuence on its copper content (Matousek, 1991; Imriš et al., 1997; Jalkanen et al., 2003; Goni and Sanchez, 2009). The slag is a silicate solution, with SiO 2 and FeO as dominant constituents. Accordingly, the prevailing compound in the slag is fayalite (2FeO . SiO 2 ). Copper losses in silicate smelting slag depend on a large number of factors, ranging from objective ones, such as the composition of the input materials or the overall physicochemical structure of the smelting products, to subjective factors, such as those depending on the management of the process (Jalkanen et al., 2003). In recent investigations it was determined that there is a connec- tion between individual components of the slag composition, copper content in the matte and the copper content in the slag (Živković et al., 2009). A relationship between the copper in Key words: Smelting, Slag, Copper/ copper ores, Copper losses, Multiple linear regression analysis ´ ´ ´