Computational analysis of hydrogen reduction of iron oxide pellets in a shaft furnace process

To gain a better understanding of the performance characteristics of a shaft furnace for hydrogen reduction of iron oxide pellets under operation with top gas recycling (TGR), a kinetic model was applied to investigate the coupled phenomena of gas-solid countercurrent reactive flow and heat transfer. The effects of operating parameters were studied for scenarios where the furnace is equipped with a single-row injection TGR system. The potential of a new TGR system featuring dual-row injection was also assessed preliminarily. The results showed that the productivity of the shaft furnace is much higher than in a syngas-based shaft furnace provided that a high mass flow of feed gas can be ensured to introduce adequate sensible heat. Hot charging of the pellets yielded an increase in the total energy consumption so the scope to reduce the gas mass flow by this method was found to be limited due to the poor heat utilization. By contrast, using a dual-row gas injection system was found to improve the performance, especially with respect to gas utilization and total energy consumption. This is chiefly attributed to a clear improvement in the thermochemical state of the furnace, which leads to a better utilization of the furnace volume.