Phase Equilibrium Studies of Iron Silicate Slag Under Direct to Blister Copper-Making Condition
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pper making from sulfide concentrates consists of two major steps: smelting and converting. In comparison, for the iron-lean concentrates rich in bornite and chalcocite or upgraded concentrates, the direct to blister (DTB) process combines the smelting and converting into one integrated step.[1–3] Therefore, it has particular advantages, such as a single stable off-gas with high SO2 strength, and low volume will be produced, which will markedly reduce the fugitive emission and the operating cost of the acid plant. Through the DTB process, the primary Cu-Fe-S phase will be oxidized to blister (Cu) phase via a series of oxidation reactions. In the final stage, the blister phase will be in equilibrium with the liquid slag, SO2-rich gas, and solid phase. For currently commercialized processes, iron silicate slags (main components ‘‘FeO’’ and SiO2) account for a very basic system.[2,3] However, the phase equilibria of this system under accurately
YONGQI SUN, MAO CHEN, and BAOJUN ZHAO are with the School of Chemical Engineering, The University of Queensland, Brisbane 4072, Australia. Contact e-mail: [email protected] ZHIXIANG CUI is with the Dongying Fangyuan Nonferrous Metals, Dongying, 257000, P.R. China. LEONEL CONTRERAS is with the National Copper Corporation of Chile, Huefanos 1270, Santiago, Chile. Manuscript submitted September 17, 2019.
METALLURGICAL AND MATERIALS TRANSACTIONS B
controlled P(SO2) and P(O2) conditions were rarely investigated. Regarding the modern DTB process, the compositions of DTB slags are usually located in the spinel primary phase field, where less SiO2 is fluxed. However, as for thermodynamic aspects of DTB slags, limited study has been reported in the spinel-saturation system. Therefore, the present study was motivated to fill this gap. The present study used the advanced equilibrium techniques that slags and blister were equilibrated on the spinel substrate to identify the equilibrium in the liquid/ spinel/blister/gas system, which accounted for one main innovation here. On the other hand, for the DTB process, previous studies only controlled the partial pressure of oxygen P(O2), without taking into account the effects of SO2.[4–6] Henao et al.[4] investigated the liquidus of FeO-CaO-SiO2 and Fe3O4-CaO-SiO2 slags in the SO2-free atmosphere with the P(O2) of 10 4 to 10 1 Pa. In the studies reported by Nikolic et al.,[5,6] the liquidus temperatures in different slag systems at metallic copper saturation were determined without the existence of SO2 in the atmosphere. In this study, both P(O2) and P(SO2) were accurately controlled, namely, 10 5 and 0.4 atm, which are the common conditions for the DTB process.[2,3] In addition to experiments, FactSage 7.3[7] was used to calculate the equilibrium state to assist the experimental design and to compare the differences. The databases of ‘‘FactPS,’’ ‘‘FToxide,’’ and ‘‘FTmisc’’ were selected and the solution species of ‘‘FTmisc-CuLQ,’’ ‘‘FToxide-SLAGA,’’ and ‘‘FToxide-SPINA’’ were used for blister, liquid slags, and spinel, respectively. In addition, negli
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