7TH EUROPEAN COKE AND IRONMAKING CONGRESS - ECIC 2016

Reduction disintegration of sinter at low temperature is one of important factors to maintain the stable operation of the blast furnace. The main factor of the disintegration is volumetric expansion of the iron oxide phase due to the reduction from hematite to magnetite at the temperature from 673 to 873 K. Furthermore, it is reported that the disintegration of sinter by CO reduction is caused by hematite reduction at temperatures from 773 to 873 K and by calcium ferrite reduction at temperatures from 923 to 1073 K. In this study, disintegration mechanism of calcium ferrite in sinter was studied at the temperature from 773 to 973 K. The reduction of acicular calcium ferrite proceeds at 773 K for 5.4 ks, while columnar calcium ferrite is not reduced. At higher temperature, reduction of acicular calcium ferrite begins for a shorter time and accelerate disintegration of sinter. At the same time, fine acicular particles with sizes of a dozen micrometers form, but the direct effect of this powder formation on the RDI value is small. However, cracks form due to the connection of pores caused by this falling, and the sinter becomes weak. At 973 K, on the other hand, disintegration is inhibited because the volume expansion of skeletal hematite becomes small and the cracks formed in the sinter seem to be mended.