A Mechanism of As₂O₃/Sb₂O₃ Accretion Formation in a Cu/Fe/S/O Solid Matrix in an Electrostatic Precipitator

Accretion formation within the electrostatic precipitator (ESP) of the Copper Concentrate Roasting Plant at CODELCO’s Ministro Hales Mine is studied, focusing on the accumulation of arsenic (As₂O₃) and antimony (Sb₂O₃) oxides. The accretions, found on electrodes, collector plates and walls, reduce ESP efficiency and cause mechanical failures; resistivity measurements showed that high-resistivity accretions can hinder ESP performance by causing charge retention, back corona, and component insulation. Mineralogical and chemical analyses revealed concentrations of copper, iron, sulfates, and arsenicantimony oxides in both fine entrained calcine and accretions. While Sb₂O₃ condenses at operating temperatures, As₂O₃ unexpectedly forms accretions despite its high vapor pressure under these conditions, driven by interactions with sulfates and oxides. The study identified Sb₂O₃ as a nucleation site for As₂O₃, facilitating the formation of crystalline oxide networks. Sulfation reactions involving copper and iron were also found to contribute to the bonding of particles in accretions. These results suggest that increasing the operating temperature of the ESP could mitigate accretion formation. Further studies are recommended to explore the gas–solid equilibrium of As₂O₃/Sb₂O₃ and its implications for improving ESP operation.