The structure and metallurgical properties of HBI obtained in Midrex and HYL reactors are studied. It is revealed that HBI obtained using the HYL-III technology differs significantly in the Fe3C content from Midrex briquettes. Carbon-containing phases (pearlite, cementite) are formed in smaller quantities in the HYL-III process than in the Midrex process and are distributed unevenly throughout the pellets, forming clusters in the form of flakes. From the point of view of pellet carburization, the limiting process is carbon diffusion into the iron crystal lattice. If an interphase boundary of oxide nature (wustite, gangue) is encountered on the path of diffusing atoms, diffusion is inhibited and carbon accumulates with the formation of its own phases pearlite and cementite. An increase in the mass fraction of carbon in HBI is possible due to: an increase in the surface area of the gas-metal reaction; minimization of the number and extent of oxide inclusions. The duration of the carburization process and the increase in process temperature. The specific pore surface area of the initial (oxidized) pellet ranges from 9.5 to 35.3 cm2/g.
Bersenev et al. (Mon,) studied this question.