Deposit build-up and corrosion in a copper flash smelting heat recovery boiler

The aim of the work was to improve the understanding of deposit formation and corrosion in a copper flash smelting plant, focusing on the effects of process gas temperature (400–900 °C) and heat-transfer surface temperature (160–320 °C) on deposit formation and corrosion rate. The rate of build-up increased as a function of process gas temperature, which was explained by a larger extent of sintering at higher temperatures, resulting in slagging and thus, in better adhesion of particles hitting the surface. The corrosion rate increased as a function of process gas temperature. Iron sulphate (FeSO₄ or Fe₂(SO₄)₃) was found at the interface between the deposit and the corroded metal surface, suggesting that corrosion was induced by sulphuric acid (H₂SO₄) from the reaction between SO₃ (originating from SO₂ in the process gas) and water vapour.