论文部分内容阅读
Staged reduction kinetics and characteristics of iron oxide direct reduction by carbon were studied in this work. The characteristics were investigated by simultaneous thermogravimetric analysis, X-ray diffraction(XRD), and quadrupole mass spectrometry. The kinetics parameters of the reduction stages were obtained by isoconversional(model-free) methods. Three stages in the reduction are Fe_2O_3→Fe_3O_4, Fe_3O_4→Fe O, and Fe O→Fe, which start at 912 K, 1255 K, and 1397 K, respectively. The CO content in the evolved gas is lower than the CO_2 content in the Fe_2O_3→Fe_3O_4 stage but is substantially greater than the CO2 contents in the Fe_3O_4→Fe O and Fe O→Fe stages, where gasification starts at approximately 1205 K. The activation energy(E) of the three stages are 126–309 k J/mol, 628 k J/mol, and 648 k J/mol, respectively. The restrictive step of the total reduction is Fe O→Fe. If the rate of the total reduction is to be improved, the rate of the Fe O→Fe reduction should be improved first. The activation energy of the first stage is much lower than those of the latter two stages because of carbon gasification. Carbon gasification and FexOy reduction by CO, which are the restrictive step in the last two stages, require further study.
Staged reduction kinetics and characteristics of iron oxide direct reduction by carbon were studied in this work. The characteristics were investigated by simultaneous thermogravimetric analysis, X-ray diffraction (XRD), and quadrupole mass spectrometry. The kinetics parameters of the reduction stages were obtained by Three stages in the reduction are Fe_2O_3 → Fe_3O_4, Fe_3O_4 → FeO, and FeO → Fe, which start at 912 K, 1255 K, and 1397 K, respectively. The CO content in the evolved gas is lower than the CO_2 content in the Fe_2O_3 → Fe_3O_4 stage but is substantially greater than the CO_2 contents in the Fe_3O_4 → FeO and FeO → Fe stages where gasification starts at at 1205 K. The activation energy (E) of the Three stages are 126-309 kJ / mol, 628 kJ / mol, and 648 kJ / mol, respectively. The restrictive step of the total reduction is Fe 0 → Fe. If the rate of the total reduction is to be improved , the rate of the Fe O → Fe reduction sh ould be improved first. The activation energy of the first stage is much lower than those of the latter two stages because of carbon gasification. Carbon gasification and FexOy reduction by CO, which are the restrictive step in the last two stages, require further study.