Abstract
To recover iron from water-quenched nickel slags, CaO was added. Thermodynamic analysis showed that CaO promotes the reaction between fayalite (Fe2SiO4) and O2. Phase diagrams of the FeO-SiO2-MgO-CaO slag with various CaO contents in an air atmosphere drawn by FactSage 7.1 showed that the phase components can be significantly affected by the CaO contents. With increasing CaO content, the fusion characteristic temperatures decreased rapidly to a minimum and subsequently increased slightly. The oxidization of Fe2SiO4 in nickel slags was accelerated significantly by the addition of CaO, which led to an increase of FeO activity and decrease of Fe2O3 activity to promote the formation of MgFe2O4. Excess addition of CaO led to the formation of more silicates. In addition, the crystallization temperature was also reduced with increasing CaO content, causing less spinel to crystalize. With increasing CaO content, the iron recovery and yield of concentrate first increased and subsequently decreased, while the total iron (TFe) content was almost not influenced and maintained a relatively stable value.
Highlights
More than 1.6 million tons of nickel slags are produced annually by Jinchuan Nonferrous MetalsCompany (JNMC), the 4th largest nickel manufacturer in the world, most of which are landfilled.This iron-rich slag contains appropriately 40 wt.% iron, as well as high-value metals such as Ni, Co and Cu
The results showed that iron recycling by both methods can be significantly improved by the appropriate addition of Calcium oxide (CaO), suggesting that the addition of CaO is beneficial for iron recycling from iron-rich nickel slags
The effects of CaO on the iron recycling from nickel slags by oxidization-magnetic separation were investigated in this study
Summary
More than 1.6 million tons of nickel slags are produced annually by Jinchuan Nonferrous Metals. FeO-CaO-SiO2 slag, Semykina et al [11] found that the products consisted of Fe2 O3 , Fe3 O4 , and CaSiO3 at 1773 K, while Ca2 Fe2 O5 was formed during oxidation at 1673 K. The oxidation kinetics of the liquid FeO-MnO-CaO-SiO2 slag in air were investigated by Semykina [12], who found that the products were MnFe2 O4 , Fe3 O4 , CaSiO3 , and Ca3 Si2 O7. FactSage 6.3 was used by Heo et al [14] to investigate the influence of CaO addition on the mass fraction of solid phases, results showed that the solid phase cannot be precipitated only at. The effects of CaO addition on the fusion characteristic, oxidation, crystallization, and magnetic separation were investigated in the present work
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