Performance improvement of the H ₂ shaft furnace: A numerical study on hot-charge operation

This work proposes a retrofitted gas feed system for increasing thermal energy supply when the hydrogen-operated direct reduction shaft furnace adopts hot-charge operation. The potential of the new feed system is assessed further using a two-dimensional computational fluid dynamics model. The results show that the ascending gas is heated up quickly by the descending hot solid within a narrow uppermost zone when employing the conventional gas feed system, so the opportunities to obtain better furnace performance are limited since the thermal energy of the hot solid leaves the furnace in the form of high-temperature off-gas. Under a scenario adopting the hot-charge operation in conjunction with the new feed system, a high temperature favoring the endothermic reactions is maintained within almost the entire upper part of the furnace. Using an appropriate upper-row gas feed rate, the overall furnace performance can be substantially improved particularly with respect to final solid reduction degree.