ZHENG Huandong, DING Yingui, CHEN Shichao, YOU Shaowei, HAN Zhibiao, ZHANG Shengen, HAN Fenglan
To address the technical bottlenecks of both high consumption of materials and energy and low recovery efficiency in traditional pyrometallurgical recycling of high-value copper-bearing solid wastes such as waste printed circuit boards, the slag phase regulation mechanism in cooperative smelting of multi-source copper-bearing solid waste was investigated. An analysis of the quaternary phase diagram of CaO-SiO2-Al2O3-FeO system reveals that when the mass ratio of FeO to SiO2 ranges from 1/9 to 1/1 and mass fraction of CaO is within the range of 10%－40%, the primary crystal phase regions of molten slag are primarily distributed in the areas of clinopyroxene, wollastonite and spinel, and a theoretical melting point is lower than 1300 ℃. A prediction model for physicochemical properties of slag demonstrates that the fluidity of the molten slag can be significantly improved by increasing FeO/SiO2 ratio from 0.5 to 1.0, and the optimal fluidity is achieved with FeO and SiO2 at a mass ratio of 1.0, which can meet the requirements of industrial smelting. An experiment was performed with the optimized conditions, including FeO and SiO2 at a mass ratio of 0.8, CaO and SiO2 at a mass ratio of 0.4, smelting at a constant-temperature of 1350 ℃ for 1 h, resulting in the obtained slag with the residual copper content therein reduced to 0.18% and copper recovery up to 99.39%. The produced crude copper alloy mainly contained Cu, C, S, Pb, Fe, Sn and other elements. It is concluded that increasing the FeO/SiO2 ratio can contribute to improving metal recovery, but it can also increase separation difficulty in the subsequent electrolytic refining process.
