Non-isothermal Carbothermic Reduction Kinetics of Calcium Ferrite

摘要

Calcium ferrite is recognized as the ideal bonding phase with superior strength and reducibility in the iron ore sintering process. In present study, the reduction behavior of CaO ? Fe_2O_3 with graphite was studied by a non-isothermal method using thermo-gravimetric analysis coupled with mass spectrometry. The Flynn-Wall-Ozawa method and the Skvara-Sestak method were adopted to analyze the 'kinetics triplet' (activation energy, pre-exponential factor, and model function). Results indicated that the reduction process did not start until 1090 K, and the reactions shifted toward a higher temperature with an increase of heating rate. The maximum reduction degree of CaO ? Fe_2O_3 could reach 0.93 at 1473 K. X-ray diffraction measurements indicated that CaO ? Fe_2O_3 was reduced to CaO and Fe with four steps (CF→ CWF → CW_3F→ C_2F→ Fe). The apparent activation energy of CaO ? Fe_2O_3 varied from 543.33 to 753.10 kJ/mol. The reduction in CaO ? Fe_2O_3 can be described by 2-D diffusion model with an integral form of G(α) = [1 - (1 - α)~(1/2)]~2.