Abstract
The desulfurization waste slag from hot metal pretreatment process is a typical solid waste generated in the integrated steel company. About 7- to 9-kg waste slag is produced per ton hot metal treated in the Kanbara Reactor (KR) desulfurization process, and the waste slag contains approximately 40–60 % CaO and large amounts of iron. Therefore, effectively valorization of these waste slags is significant for resources reutilization and environmental protection. A novel valorization process of KR desulfurization waste slag into iron-containing substances and desulfurization agent for hot metal pretreatment was investigated. Magnetic separation method was conducted to recovery iron-containing substances from the KR waste slag. Various techniques such as XRD, TG-DSC, SEM–EDS were used to characterize the non-magnetic (NM) waste slag. The pyrometallurgical recycling experiments of NM waste slag were performed in a tube furnace after considering various parameters, such as reaction temperature, ratio of slag volume and slag composition. The results show that ~56 wt% of the KR slag can potentially be recycled as an iron-bearing raw material for steelmaking process. The major components of NM KR waste slag are calcium, silicon and iron oxides, and ~70 vol% of NM waste slag particles are <100 μm. The major crystalline phases present in NM waste slag are C, Ca (OH)2, CaSO4, CaF2, CaCO3, CaS and Ca2SiO4. A mass loss of ~20 wt% from room temperature to 1573 K is possibly due to the vaporization of moisture, water of crystallization and fluoride, decomposition of carbonates and CaSO4. The desulfurization ratio in pig iron increases with reaction time, which indicates that the NM waste slag still has desulfurization ability. Moreover, the desulfurization ratio increases with temperature and ratio of slag volume. It is also found that the apparent desulfurization rate constants are in the range between 0.007 and 0.016 min−1.
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