Hydrogen direct reduction ironmaking process for zero CO2 emission: A study on the effect of particle properties changes during the multiple non-catalytic gas-solid reactions

Abstract

Direct hydrogen reduction (H-DR) is one of the most attractive technologies for decarbonization in the iron and steelmaking industries. Improvements in process efficiency depend on a multi-scale evaluation since the industrial performance is significantly affected by transient non-catalytic gas–solid reactions at the pellet scale. This study investigated the effect of temperature-dependent morphological changes in industrially produced pellets during isothermal reduction temperatures from 600 to 900 °C. A 2D axisymmetric pellet grain model using the finite element method and considering the three reduction reactions and the mass and heat transfer phenomena was developed to evaluate the evolution of the solid transformations along the pellet radius during the reduction time. Based on the experimental results, structural properties of the pellets, such as grain size, tortuosity, and transient porosity, were incorporated into the proposed pellet model. The simulation results under different conditions show good agreement with experimental data when changes in the pellet tortuosity are considered, particularly at higher temperatures. Furthermore, predictions of solid and gas concentration and temperature profiles over the pellet radius during the reduction process evidenced the transient behavior of the process. The findings represent an important contribution to the degree of knowledge on the H-DR process application by providing information on the effect of structural parameters of the pellets for the current status of mathematical models of the process.