THERMAL DECOMPOSITION BEHAVIOUR OF NATURAL BASTNASITE CRYSTAL IN CALCINATION
(Department of Nonferrous Metals Metallurgy; Northeastern University; Shenyang 110006)
Abstract: The thermal decomposition behaviour of natural bastnasite crystal, mined from Mianning,Sichuan province, in calcination in air was studied by DTA, TG, XRD and chemical analysis methods.The decomposition procedure can be separated into two steps. At first,(Ce, La)CO3F is oxidized and decomposed into (Ce, La)O1＋xF1－x at lower temperature. When calcination temperature and time increase, (Ce, La)O1＋xF1－x is farther oxidzed and decomposed. The final products are CeO2 and other rare earth compounds. Part of F is lost during the calcination procedure,but not for Si. The total weight lost is 17.095%. The activation energy E of the calcination reaction is 49. 325 kJ/mol and the reaction order n is 1.123 by thermal dynamic calculation.
Key words: bastnasite calcination thermal dynamic calculation