Optimization of Heat Transfer Process in a Walking Beam Reheat Furnace Using Computational Fluid Dynamics

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In the steelmaking process, reheating furnaces are used to reheat steel slabs to a target rolling temperature. The bottom intermediate zone inside the reheating furnace plays a decisive role in controlling the slab temperature distribution before slabs enter the soaking zone. Efforts to maintain a uniform slab surface temperature and thus enhance product quality require a good understanding of the furnace’s operation. However, traditional physical experiments are costly and have high risks as well. In this study, a three-dimensional steady-state computational fluid dynamics (CFD) model was developed to investigate the flow field in the bottom intermediate zone of a full-scale reheating furnace. The commercial software ANSYS Fluent® was used to solve the transport equations to predict the flame length, heat transfer, and gas temperature near the slab. Total input mass flow rate, preheated air temperature, and air/fuel ratio were selected to investigate the comprehensive influence of the furnace’s performance, which can be evaluated from the flame length, flame angle, and average gas temperature near the slab. Importantly, an orthogonal experimental design was conducted to optimize the evaluation factors by considering the multi influencing factors simultaneously. The simulation results indicate that a higher mass flow rate produces a lower upwards flame angle, which can prevent the hot spot detected on the slab surface. A higher preheated air temperature leads to a higher average gas temperature in this furnace; meanwhile, the flame becomes shorter by enhancing the air-fuel ratio.