Thermodynamic Mechanism Analysis of Calcification Roasting Process of Bastnaesite Concentrates

A novel calcification roasting decomposition method for bastnaesite concentrates has been proposed previously. In this work, the thermodynamic mechanism was investigated via simultaneous measurements of thermogravimetry and differential thermal analyses, combined with X-ray diffraction analyses. Rare earth oxides and calcium fluorides were generated after bastnaesite and calcium hydroxide broke down, respectively. The generation and decomposition of calcium carbonate occurred at the same time. Considering the difficulties in obtaining pure substances, theoretical calculations were applied to determine the standard enthalpy of formation (Delta(f) H (298)), Gibbs free energies of formation (Delta(f) G (298)), and heat capacities at constant pressure (C (p)) of some rare earth minerals (CeFCO3 and CeOF). Based on these results, the standard Gibbs energy of reaction at different temperatures (Delta(r) G (T)) was ascertained, and the major reactions were verified to be thermodynamically reasonable.