1992 Volume 78 Issue 4 Pages 536-543
In order to clarify the thermal decomposition behavior of fine iron ore which is injected into the raceway of a blast furnace, thermal analyses of fine iron ore have been made under various atmospheric conditions (N2, CO2, air, O2 and N2+O2 with different oxygen concentrations from 1% to 25%), particle size (average dia.: 55, 155 and 325 μm) and heating rate (0.033, 0.167 and 0.33 K/s). A kinetic analysis of the reaction (3Fe2O3=2Fe3O4+1/2O2) has been made based on measured thermalgravimetric curves by the Coats' method. Its results show that the reaction rate could be described by a second order reaction rate equation with relation to unreacted degree.
dα/dt=k(1-α)2
k=exp(A-E/RT)
Furthermore it was found that the starting temperature (TD1) and the kinetic behavior of the reaction were independent of the particle size in the range from 55 to 325 μm. However, they were strongly affected by the oxygen potential of the gas atmosphere. Empirical equations to estimate TD1, E and A were obtained as a function of PO2 in the gas atmosphere as follows:
TD1=75560/{44.56-ln[PO2/(1.013*105)]}
E=20730/{6.543-ln[PO2/(1.013*105)]}
A={14.43+ln[PO2/(1.013*105)]}/102/6.9306
Using these equations, the thermal decomposition processes of iron ore were analyzed under various conditions and the results coincided well with our experimental results. Under heating conditions simulating raceway in a blast furnace, it was predicted that the injected fine iron ore could be almost decomposed from Fe2O3 to Fe3O4 in the raceway.
