Investigation of the characteristics and mechanisms of the layer inversion in binary liquid–solid fluidized beds with coarse particles

This paper adopts an optimized Euler–Lagrange method proposed in our previous work to study the characteristics and formation mechanisms of layer inversion in binary liquid–solid fluidized beds (LSFBs) with coarse particles. The LSFBs are formed in a cylindrical pipe with a diameter of 50 mm and a length of 0.6 m and consist of two species of coarse particles with different sizes: 6 mm glass spheres (species 1) and 10 mm glass spheres (species 2) with the particle density of 2600 kg/m3. First, the characteristics of the layer inversion of LSFBs with coarse particles are qualitatively analyzed. The positions of species 1 and species 2 are converted during layer inversion. Second, the changes in the trajectory and volume fraction of two species of particles are quantitatively investigated. Finally, the formation mechanisms of layer inversion with coarse particles are analyzed. The results show that the relative magnitude of the fluid–solid interaction force and the gravity is the main reason for determining the layer inversion of binary coarse particles of different sizes. The collision force is to balance the net force of the particle–fluid interaction force and the net gravity, so that the fluidized bed is in relative equilibrium. In addition, through the analysis of the evolution of the network of contact forces, the constraint of the wall on coarse particles is discussed during the layer inversion.