Investigation of the phase composition of accretions formed into WHB under flash smelting of copper concentrate

The phase composition of the depositions formed in the radiation section of the waste heat boiler utilizer (RS of WHB) after injecting sulphatizing flow in the volume of the off-gases from the uptake of flash smelting furnace for copper sulphide concentrate smelting was studied. With the help of X-ray diffraction (XRD), Reflected-light microscopy and Electron probe microanalysis (EPMA) of samples from the accretions, it was established that the main crystalline phases in the accretions were spinel, delafossite, cuprite and tenorite. The results from EPMA have shown that the spinel phase is with variable composition from cuprospinel to solid solution into the system Fe₃O₄-CuFe₂O₄-ZnFe₂O₄ (magnetite-cuprospinel-franklinite). Calculated on the basis of XRD and EPMA approximate formulae for the phases, identified in the samples from the accretions were the following: of the cuprospinel-(Cu_0.85²⁺Zn_0.09²⁺Fe_0.06²⁺)(Fe_1.87³⁺Al_0.10³⁺Si_0.03⁴⁺)O₄; of the spinel solid solution—(Cu_0.32²⁺Zn_0.36²⁺Fe_0.32²⁺)(Fe_1.81³⁺Al_0.19³⁺)O₄; Delafossite—Cu_1.07Fe_0.93O₂; cuprite—Cu_1.99Fe_0.02Si_0.01O and tenorite—Cu_0.993Fe_0.008O. The influence of the temperature on the sulphate formation processes of copper and iron oxides in the dust-gas flow was evaluated, based on experimental data and thermodynamic analysis of phase equilibriums in the systems Cu-S-O and Fe-S-O for the conditions, typical of the radiation section of the waste heat boiler (RS of WHB).