The study on the reconstruction and evolution pathway of free lime by hot stage mixing molten ironmaking and steelmaking slags in a laboratory

Abstract

Decreasing the content of the phase of free lime (f-CaO) in the basic oxygen furnace slag (BOFS) effectively is the key and prerequisite for making use of them further. Herein, for the purpose of reducing the f-CaO in original BOFS, both of the original BOFS and blast furnace slag were mixed at hot stage. In consequence for this disposal process, the f-CaO in the original BOFS is able to be stabilized evidently, and its content in reconstructed and modified slag (R&MS) can be as low as 0.52% with the elimination rate for 92.51% under the setting reaction conditions. The mineralogical findings exhibited the diffraction peaks with respect to f-CaO disappearing and there is no obvious f-CaO phase detected in R&MS samples. After reconstruction, the main mineral phases such as akermanite, merwinite and wuestite exist in R&MS. According to the analyses from ternary phase diagrams and FT-IR, the evolution of f-CaO goes through two pathways in the final formation of silicates, and the oxygen anions from the f-CaO are captured by the silicate networks.