Numerical study of transient thermochemical states inside an ironmaking blast furnace: Impacts of blast temperature drop and recovery

Ironmaking blast furnace (BF) is an energy-intensive chemical process, and its in-furnace phenomena are relatively steady under stable operating conditions. However, it cannot be avoided when the operating conditions are changed including undesired blast temperature (BT) drop and subsequent countermeasures. Thus, it is necessary to comprehend the time-related BF behaviors after the operating conditions are changed. In the study, for the first time, the in-furnace dynamic behaviors of several scenarios related to BT decrease are investigated by using a state-of-the-art transient-state BF model. It is found that the responses of different BF regions to the BT change are different. In short, the regions near BF gas inlet can respond more promptly and significantly than other regions. In Scenario I, when the BT is decreased by 200 K without any remedial actions deployed, the cohesive zone inside the BF moves downwards consistently. In Scenario II, the flame temperature is approximately maintained by cutting down pulverized coal injection and by increasing coke rate, side-effects of low BT on blast enthalpy inflow can be offset largely. In Scenario III, by adopting a high BT and a high coke rate, the in-furnace thermochemical states can be quickly recovered in less than 10 h after a low BT operation. This work provides a cost-effective tool to study time-related behaviors across the whole BF domain when BT changes take place towards stable and low-cost BF operation.