Abstract
According to the coexistence theory of slag structure, a calculation model for the activity of FeO in the quaternary system SiO2-CaO-Al2O3-FeO of depleted copper slag was established. The model was used to calculate and analyze the effects of temperature (T), basicity (B), and Al2O3 content on the activity of FeO (NFeO). The results show that temperature has little impact on NFeO. With increased basicity, NFeO first increased slightly, then increased sharply, and finally decreased. It is easier for CaO to combine with SiO2 than FeO to form calcium silicate, which replaces FeO in 2FeO·SiO2 and increases NFeO. However, when basicity is higher than 2.0, CaO not only reacts with SiO2, but also combines with FeO to form calcium ferrate compounds to decrease NFeO. In addition, the activity of FeO decreases with increased Al2O3 content because of the reaction between CaO and Al2O3. The results can be used as a theoretical basis to guide the carbothermal reduction process of copper slag.
Highlights
In the last 50 years, copper consumption has tripled because of rapid industrial development [1].The production of refined copper was 23.33 Mt in 2016, and the quantity of copper increases year by year [1]
The results can be used as a theoretical basis to guide the carbothermal reduction process of copper slag
According to a prediction by the International Copper Study Group (ICSG), the global supply of refined copper slightly increased by 0.9% in 2017, far below the average growth rate of 3% in the previous 10 years, due to the fact that the depletion of global mines is more and more serious, and the grade of newly discovered mines is low
Summary
In the last 50 years, copper consumption has tripled because of rapid industrial development [1]. There are several main processes of recycling copper and iron in copper slag, such as beneficiation, oxidation-magnetic separation, smelting reduction, and carbothermal reduction at high temperature. Zhang [16] utilized the coexistence theory of slag structure to calculate the activity of FeO in the ternary slag system SiO2 -CaO-FeO, and compared with other studies [17], the results are similar. SiO2 -CaO-FeO to calculate the activity of FeO with different basicity in order to recovery iron in copper slag. SiO2 -CaO-Al2 O3 -FeO is established according to the coexistence theory of slag structure, in order to analyze the variation of FeO activity with the effect of temperature (T), basicity (B), and Al2 O3 content and provide a theoretical basis to guide the carbothermal reduction process of copper slag
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