Reduction Kinetics of Cold-Bonded Briquette Prepared from Return Fines of Sinter with Carbon Monoxide and Coke

The reduction kinetics of cold-bonded briquette prepared from return fines of sinter is studied. The results reveal that cold-bonded briquettes with coke (CBBC) have a higher reduction velocity index (RVI) value than cold-bonded briquettes without coke (CBB). Interfacial chemical reaction controls the early stages of the CBB reduction process at 900 and 950 °C, followed by both interfacial chemical reaction and internal diffusion. At 1000, 1050, and 1100 °C, the early and final stages of the CBB reduction process are controlled by interfacial chemical reaction and internal diffusion, respectively, while both interfacial chemical reaction and internal diffusion control middle stage. The apparent activation energies of the different stages are 46.20, 56.74, 38.24, and 40.74 kJ mol^?1, respectively. The gasification of carbon reaction controls the reduction process of CBBC, and the apparent activation energy is 32.42 kJ mol^?1. According to the Friedman method, the apparent activation energy of CBB and CBBC is reasonable. Coke promotes the phase transformation in CBBC. Scanning electron microscopy results show that the CBBC sample is more fully reduced than the CBB sample and that it has smoother corners and edges of the iron-bearing phase or the metallic iron phase than the CBB sample.