Speaker
Description
Metallurgical slags and oxidic side streams from steel and non-ferrous metals production are potential sources for recovering valuable metals. Due to large volumes of slags and side streams, it is of economic interest to develop methods to recover the valuable metals from these streams. In copper and nickel smelting, valuable metals such as Cu, Ni and Co, may be either entrained as metal alloy or matte in the slag or as chemically dissolved. Slags can be reduced by various reductants to recover the metals. We have studied how different reductants, such as hydrogen and different biochars, affect the reduction efficiency of nickel smelting slag, copper smelting slag, and iron-rich residue from zinc production. Experiments were performed in lab scale vertical tube furnaces at 1200-1400 °C, and the samples were quenched after experiments and analysed using SEM/EDXA and EPMA. For experiments with biochar, the formation of CO/CO2 was also measured during the experiments. In addition, molten oxide electrolysis was utilized to reduce Fe and Cr from slags at 1600 °C.
Experiments showed that the biochars and hydrogen are efficient in reducing the levels of valuable metals in the slags, and the biochars were more efficient compared to metallurgical cokes, possibly due to higher reactivity. Molten oxide electrolysis was also a potential method to clean the slags, but however, there are several challenges associated to that approach, such as material stability issues.
Overall, the use of non-fossil reductants in pyrometallurgical processing of side streams and slags is a promising way to recover more metals and produce clean slags that can be used as different products.
References
Avarmaa, K., Taskinen, P., Klemettinen, L., O'Brien, H., Lindberg, D. Ni_Fe-Co alloy - magnesia-iron-silicate slag equilibria and the behavior of minor elements Cu and P in nickel slag cleaning. Journal of Materials Research and Technology Volume 15, November–December 2021, Pages 719-730
| Keywords | Pyrometallurgical processing, non-fossil reductants, hydrogen |
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