Numerical simulation of gas–solid flow behavior and heat transfer characteristics for suspension magnetization roasting: Effect of air inlet velocity

The main furnace is an essential part of a suspension magnetization system, and its performance directly determines the quality of roasting products. In this study, a Computational Fluid Dynamics-Discrete Phase Model (CFD-DPM) was established for a main furnace. The gas–solid flow behavior and heat transfer characteristics of the main furnace were studied with air inlet velocities of 1.5 m/s, 1.8 m/s, 2.1 m/s, and 2.4 m/s, respectively. The simulation results show that as the air inlet velocity increases, the gas-phase velocity gradually decreases, and the particle-phase velocity tends to stabilize after reaching the minimum value. With the increasing air inlet velocity from 1.5 m/s to 2.4 m/s, the particle residence time was significantly reduced from 1.67 s to 1.16 s. In addition, the increases in air inlet velocity led to the dilution of the particle phase concentration in the furnace, without improving in the particle backmixing phenomenon. Furthermore, both the gas-phase and particle-phase temperatures in the furnace decrease with the increase in air inlet velocity. These can provide guidance for the operation of the suspension magnetization roaster.