Calcination parameters on phosphogypsum waste recycling

Abstract The calcination at low temperatures transforms phosphogypsum (PG) waste in a material with binder properties. This study evaluated two parameters of PG calcination: kiln residence time (1 h, 2 h, and 5 h) and temperature (120 °C, 150 °C, and 200 °C). The main objective was to find adequate calcination conditions considering PG transformation into β-hemihydrate gypsum, with minimum energy spent. Physical properties, thermal analysis, chemical and mineralogical compositions, and microstructure were analysed. The increase in residence time and temperature showed to result in higher β-hemihydrate content; however, there is an increase in energy spent. A temperature of 150 °C with residence times on the kiln of 1 h and 2 h were found as adequate parameters to obtain considerable β-hemihydrate content with lower energy consumption.