The effect of MgO on the phase equilibria between matte and tridymite-saturated FeO x −SiO 2 −MgO slag was investigatedusing high-temperature equilibration and microanalysis technique. The results showed that at 1300 °C and p (SO 2 ) of 10 kPa, the presence of MgO reduced the FeO activity of the slag, leading to the decrease in the oxygen partial pressure ( p (O 2 )) over the slag and the Cu solubility in the slag. Due to the lower FeO activity, FeS was oxidized from matte into slag, increasing the Cu concentration of the matte. In high-SiO 2 concentrationslags, excessive MgO in the liquid slag recrystallized as solid olivine (Mg 2 SiO 4 −Fe 2 SiO 4 ), increasing the slag viscosity and copper losses in the slag. The maximum MgO solubility in the FeO x −SiO 2 −MgO slag increased from 3 wt.% to 8 wt.% when the temperature raised from 1200 to 1300 °C under p (O 2 ) of 10 −6 kPa. At higher MgO content, the slag composition could be optimized by increasing temperature and adding SiO 2 flux to maintain a fully molten slag or avoid high proportions of solids.
Settling time, system temperature and reductant amount play an important role in the recovery of matte from copper slag. This study investigated the settling behavior of matte particles in copper slag and the effects of the settling time, system temperature, and reductant amount on the macrostructure of slag, microstructure of matte particles, and copper loss. The results showed that the settling behavior of matte particles in slag at the experimental temperature was a process of aggregation and growth. With an increase in settling time and temperature, as well as the addition of an appropriate amount of anthracite, the foaming slag layer of the slowly cooled slag gradually disappeared, while the recovery of matte increased. However, when the amount of anthracite was too high, Fe–Cu alloy formed at the experimental temperature, which resulted in worsened fluidity of the matte in the molten slag and copper loss increased. At the experimental temperature, the settling environment of matte particles in the liquid phase layer was superior to that of the foaming slag layer. The novel idea of using rubber seed oil instead of a traditional fossil reductant to clean the copper slag was put forward. At the temperature of 1250 °C, 4 mL of rubber seed oil was injected, resulting in a settling time of ≥90 min, after which the copper content in the upper part of the slowly cooled slag was less than 0.57 wt.%, reaching the acceptable level of discardable slag in industry.
Kun WANG,Yan LIU,Jun HAO,Zhi-he DOU,Guo-zhi LV,Ting-an ZHANG
To recover copper from copper slag, a novel slag cleaning method was proposed. The thermodynamics and binary phase diagram of FeO–SiO 2 were calculated first. Then, the effects of experimental parameters on the reduction of Fe 3 O 4 , recovery of copper, and slag cleaning mechanism were investigated. The results showed that the addition of SiO 2 significantly reduced the initial reduction temperature of magnetite and pyrite. The contents of Fe 3 O 4 and copper decreased to 2.45 wt.% and 0.39 wt.%, respectively, with copper recovery of 92.52% under the optimum conditions. More than 94% silver and 99% gold subsided into the copper matte after slag cleaning. Approximately 72% of zinc and 75% of lead volatilized in the flue gas. The viscosity of the copper slag decreased from 0.68 to 0.12 Pa·s due to the reduction of magnetite. The sedimentation of copper matte droplets could be enhanced by mechanical stirring.
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