Abstract:ffect of aluminum chloride on fluorine escape during roasting of Bayan Obo rare earth concentrate was deeply studied. The addition of aluminum chloride during roasting achieved a good fluorine fixation effect. Firstly, changes of weight and thermal effect during thermal decomposition of rare earth concentrate, aluminum chloride and rare earth concentrate aluminum chloride mixture were analyzed by synchronous thermal analyzer. Thermal decomposition reaction of rare earth concentrate and crystalline aluminum chloride mixture occurs at 100-508 ℃. Secondly, effects of roasting temperature, ratio of ore to aluminum, and roasting time on fluorine fixation efficiency were studied. The results show that fluorine fixation efficiency is 66.9% and escape of fluorine drops from 22.71% to 7.51% under the conditions including ratio of ore to aluminum of 1︰1, roasting temperature of 510 ℃, and roasting time of 2 h. Finally, phase analysis of rare earth concentrate, roasting products of rare earth concentrate and mixed roasting products of rare earth concentrate and aluminum chloride were carried out by X-ray diffraction analyzer, the results show that fluorine in concentrate is fixed in roasting products in form of AlF3.