Reduction Behaviors of Silicon–Ferrite from Calcium and Aluminum in a Hydrogen-Rich Blast Furnace

Silicon–ferrite from calcium and aluminum (SFCA) is one of the primary binding phases in sinter. To better investigate the reduction process of SFCA under hydrogen-rich conditions in a blast furnace, isothermal reduction experiments were designed using three different hydrogen volume fractions (6%, 10%, and 14%) at temperatures within the blast furnace’s lump zone range (1073 K, 1173 K, and 1273 K). The experimental results revealed that the reduction of SFCA proceeds in two stages: in the first stage, SFCA is initially reduced to Fe3O4; in the second stage, Fe3O4 is further reduced to FeO, with the equilibrium phases being FeO, Ca2Al2SiO7, and Ca2SiO4. The fastest reduction rate was observed at 1273 K. When the hydrogen volume fraction was 6% and the temperatures were 1073 K, 1173 K, and 1273 K, the reaction mechanism followed the 3D diffusion model (G-B), with an apparent activation energy of 32.087 kJ·mol−1 and a pre-exponential factor of 0.1419. In comparison, at hydrogen volume fractions of 10% and 14%, the reaction mechanism shifted to the Shrinking core model (n = 3). The findings of this study can provide guidance for actual production and optimization of blast furnace parameters aimed at achieving low-carbon emissions in the steel-making process.