Influence of CaO on thermal decomposition of REFCO3 was studied. The results showed that CaO did not affect significantly the decomposition ratio of REFCO3. The XRD experiment showed that there was a great deal of CaF2 in the roasting production, the gas chromatographic analysis on the gas of REFCO3 decomposed, and the 70% content of fluorine in the gas of REFCO3 added 15% CaO was reduced. CaO could absorb the fluorine from the decomposition of REFCO3, and the environmental pollution of the fluorine was greatly alleviated.
The decomposed process of bastnaesite, monazite and mixed rare earth concentrate in CaO-CaCl-CaCl2 was studied by means of TG-DTA method. The relationship among decomposition ratio, roasting temperature, and CaO-NaCl addition was studied by the quadratic regression orthogonal analysis, and then the regression equation was obtained. Through analysis, the optimum process conditions of mixed rare earth concentrate decomposed by CaO-CaCl-CaCl2 were obtained as follows: roasting temperature: 700 ℃, CaO addition: 15%, NaCl-CaCl2 addition: 10%, roasting time: 60 min, the decomposition ratio: 91.3%.
