CFD-Based Evaluation of a Serial Air-Supply Strategy in a Continuous Annular Cooler for Uniform Sinter Discharge Temperature

Non-uniform discharge temperature during sinter cooling is a practical issue in ironmaking, as local overheating may increase the thermal load on downstream conveying equipment. To mitigate insufficient cooling in the upper sinter bed under the conventional bottom-blowing mode, this study developed a three-dimensional transient CFD model for an industrial continuous annular cooler and optimized the air-supply strategy in Zones IV and V. Under the conventional condition, ambient air is supplied independently to Zones IV and V from the bottom wind boxes. In the novel air-supply strategy, while keeping the total fresh cooling-air flow rate in the final cooling region unchanged, ambient air is introduced from the upper side of Zone V and discharged from its bottom; the outlet gas from Zone V is then supplied to the bottom of Zone IV, forming a serial air-supply path. The results show that the novel arrangement improves the spatial matching between the cooling gas and the sinter bed during final cooling and suppresses the local high-temperature region near the discharge end. The maximum discharge temperature decreases from 459 K to 410 K, below the process limit of 423 K, while the average discharge temperature decreases from 377 K to 364 K. Based on the enthalpy-flow difference calculation, the predicted recoverable waste heat also increases under the novel condition. These findings suggest that redesigning the gas-flow route in the final cooling region can effectively enhance the uniformity of the discharge temperature in industrial annular coolers.