Heat and Mass Transfer Study during the Reduction of Iron Ore Pellets in a Fixed-Bed Reactor

As the pressure of the "dual carbon" target in the steel industry intensifies, the hydrogen-based direct reduction (H₂-DR) process has become a key path for green and low-carbon ironmaking due to its significant emission reduction potential. However, the existing process lacks intelligent perception and control capabilities, and cannot accurately grasp the gas-solid heat and mass transfer state in the fixed bed reactor, which limits the reduction efficiency and energy consumption optimization level. To this end, this paper combines computational fluid dynamics (CFD) technology with reaction kinetics modeling methods to construct a numerical model of heat transfer-mass transfer-reaction coupling in the hydrogen reduction pellet process, and conducts high-precision simulation analysis of key parameters such as gas composition (H₂/CO/N₂), temperature, flow rate, and pellet stacking structure. This paper simulates three typical hydrogen concentration conditions (H₂ 100%, 80%, 60%) through a two-dimensional axisymmetric model, couples the RNG k-ε turbulence model with the Fe₂O₃→Fe reduction path, and combines the porous medium model to calculate the heat and mass transfer of the stacked pellet bed. The changes in the temperature field, velocity field and mole fraction distribution of the gas in the reactor are comprehensively analyzed, and the heat transfer efficiency, gas dissipation path and rate control link of the reduction zone are accurately identified. The results show that under the operating temperature of 950°C and the H₂ concentration of 82%, the temperature drop of the gas in the pellet bed reaches 80K, the H₂ mole fraction decreases by about 17%, and the reaction rate increases to 0.0524 kmol/m³•s, which is much higher than 0.0021 kmol/m³•s under CO conditions.