Reaction kinetics of hydrogen reduction of iron oxides with different particle sizes

The reaction kinetic process of hydrogen reducing iron oxides was investigated based on the fundamental reduction reaction of iron oxides by hydrogen at high temperatures, and the advantages of hydrogen as a reducing agent in the production of metallic iron were explored. Iron oxide reduction experiments were conducted under hydrogen atmosphere at different temperatures, and the effects of particle size and hydrogen volume fraction on the kinetic parameters of the reduction reaction were studied. The experimental results indicate that the reduction rate during different stages of iron oxide reduction is influenced by hydrogen volume fraction, oxide particle size and temperature. For iron oxide with particle sizes of 5 p,m and 30 jjim within the temperature range of 500-900 C, the reduction process can be divided into three stages based on the degree of reduction. In the first stage, the reduction of Fe203 to Fe304 follows the chemical reaction control model. The activation energy decreases gradually with increasing hydrogen volume fraction. In the second stage, the reduction of Fe304 to FeO conforms to the random nucleation and subsequent growth model. For iron oxide with a particle size of 30 p.m, the activation energy increases sharply with decreasing hydrogen volume fraction. In the third stage, the reduction of FeO to Fe follows the gas-phase three-dimensional diffusion model, and the activation energy generally decreases with increasing hydrogen volume fraction. Compared to iron oxide with a particle size of 30 |xm, the 5 |xm particle size exhibits faster reduction rate and lower activation energy when the hydrogen volume fraction exceeds 50% .