A study of options to enhance the operation of a H2 direct reduction shaft furnace using a two-dimensional model

With the intent to explore techno-economically feasible options for improving the performance of the hydrogen (H2) -operated direct reduction shaft furnace for iron ores, a two-dimensional computational fluid dynamics model was applied to assess the potential of a new top gas recycling system featuring dual-row injection. A special numerical routine was developed to bridge data communication during the iterative calculation, where the composition of the gas injected in the upper (tuyere) row varies with the conditions. The results showed that a poor gas utilization is inevitable for a (conventional) single-row recycling system since it cannot properly address the strong heat demand of the process. For dual-row top gas recycling with a reduced lower-row feed rate, the in-furnace thermochemical state is inappropriate if the upper-row feed rate is low, but is gradually improved as the upper-row feed rate increases, since more thermal energy is supplied to the part of the furnace where it is needed. With an appropriate configuration of the upper- and lower-row feed rates, the overall furnace performance can be substantially improved particularly with respect to gas utilization degree. The findings of this work are expected to aid the future design of more efficient operation of H2-based direct reduction of iron ores.