Effect of Cooling Rate and Slag Modification on the Copper Matte in Smelting Slag
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Effect of Cooling Rate and Slag Modification on the Copper Matte in Smelting Slag Xiang Gao 1
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Zhuo Chen 1
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Junjie Shi 2,3
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Pekka Taskinen 2
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Ari Jokilaakso 2
Received: 11 February 2020 / Accepted: 16 July 2020 # The Author(s) 2020
Abstract The amount of copper flash smelting slag has increased during the recent years along with an increasing slag-to-metal ratio. During slag tapping, some copper sulfide is mechanically entrained. As a result, it is necessary to recover copper matte from the slag by suitable methods. At present, the most common way is slow, controlled cooling in a transfer ladle. However, research on the detailed effects of slow cooling and the function of slag modification is rare. This paper described experiments that were performed at different cooling rates (0.5, 1.5, 3, and 7 °C/min), with and without additive. A detailed characterization of the copper-rich phase and its particle size was subsequently made using SEM-EDS micrographs and image analysis software. With a decrease in cooling rate, the particle size of the copper-rich matte phase became larger. The addition of gypsum and carbon as a slag modifier affected the size of the copper-rich phase slightly, and its chemical composition was modified compared with the experiments without additive. Keywords Slag cleaning . Ladle cooling . Copper matte . Image analysis
1 Introduction Flash smelting technology has been widely applied in the smelting of copper sulfide concentrate because of its numerous merits, such as environmental friendliness, for example high SO2 fixing, and its low demand for external fossil fuels [1]. However, some copper matte is dispersed mechanically and entrained during slag tapping, and some copper dissolves in molten slag as cuprous oxide, resulting in a waste of resources [2]. It has been estimated that 2.2–3.0 metric tons of slag is produced for each ton of metal [3]; about 46 million tons of slag Clarification The designation of corresponding author is correct. Ari Jokilaakso is the corresponding author, even though this paper was submitted by first author Xiang Gao. * Ari Jokilaakso [email protected] 1
School of Energy Science and Engineering, Central South University, Changsha, Hunan Province, People’s Republic of China
2
Department of Chemical and Metallurgical Engineering, School of Chemical Engineering, Aalto University, Espoo, Finland
3
Key Laboratory for Ecological Metallurgy of Multimetallic Mineral (Ministry of Education), Northeastern University, Shenyang 110819, China
are produced annually in the copper industry [4]. Although the concentration of copper in the discarded slag is not large, typically about 0.8–1 wt%, the total amount contained in slags is significant [5, 6]. As a result, it is necessary to recover the copper in the slags by suitable methods in a separate slag cleaning step. In the past few years, methods like flotation [7, 8], leaching [9, 10], and bioleaching [11] have been proposed. Milling and froth flotation methods are quite common when dealing with slow-coole
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