Phase change, micro-structure and reaction mechanism during high temperature roasting of high grade rare earth concentrate

Abstract

The deposit of Bayan Obo in Inner Mongolia is the world's largest rare earth element (abbreviated as REE) resource. The exploration of the theory of mineral formation of Bayan Obo is an important foundation for mineralogical research, and is the scientific basis for mining, industrial beneficiation, smelting and extraction, and processing and utilization. With the rapid development of science and technology, the demand for the utilization of rare earth elements is increasing, and the separation process between rare earth elements needs to be developed. The purpose of this paper is to provide high temperature experimental information for the formation and application of rare earth minerals. To this end, the mineral evolution of high-grade rare earth concentrates with increasing temperature and the migration of rare earths at different stages and their reaction mechanisms were studied. According to thermogravimetric analysis and differential scanning calorimetry (TG-DSC), calcination was carried out at different temperature ranges, and the calcined products were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope and energy dispersive spectrometer (SEM-EDS) and other analytical techniques. The results are shown in this process, the rare earth phase is first converted into rare earth oxide and rare earth oxyfluoride. As the temperature increases, Ca5(PO4)3F and a large number of self-shaped spherical Ca-RE-OF and Ca-RE-PO4 particles are formed, and the separation of La and Ce elements is discovered. According to the phase diagram analysis, the production of Ca5(PO4)3F is due to the reaction of monazite and fluorite, and the phases CeF2 and CeF3 are formed during the reaction. When it reaches 1500 °C, barium ferrite is produced and a new substance containing Ba2+ is formed.