Influence mechanism of particle density in a gas−solid fluidized bed

This paper presents a comprehensive analysis of gas−solid fluidized beds with different particle densities using a coupled computational fluid dynamics−discrete element method. The accuracy of the numerical method is experimentally verified, and the characterization parameters of the gas−solid fluidized bed are evaluated, including velocity distribution, bubble equivalent diameter, dead zone angle, particle force, bed pressure, and mixing index. The effects of five particle densities on the gas−solid fluidized bed were analyzed in detail while contact and drag models were fixed. The predicted results show that an increase in particle density will reduce the distribution of translational and rotational velocities, which will have an inhibitory effect on the bubbles in the bed, with a positive correlation with the angle of the dead zone. It is explained that the main forces on particles during fluidization are contact force, drag force, and pressure gradient force, and the normal contact force is two orders of magnitude larger than the drag force and the pressure gradient force. The phenomenon that the normal contact force is much larger than the tangential contact force is explained. The increase in particle density has an increasing effect on the bed pressure, takes more time to reach a good degree of mixing, and reduces the mixing performance. The study of the effect of particle density on gas−solid fluidized beds can provide theoretical guidance for the structural design as well as theoretical development of subsequent fluidized beds.