Numerical study of the particles segregation phenomenon in the fluidized beds

Abstract

Purpose The purpose of this paper is to present a computational fluid dynamic simulation for the investigation of the particles segregation phenomenon in the gas–solid fluidized beds. Design/methodology/approach These particles have the same size and different densities. The k–ε model and multiphase particle-in-cell method have been utilized for modeling the turbulent fluid flow and solid particles behaviors, respectively. The coupled equations of the velocity and pressure have been solved by using a combination of SIMPLE and PISO algorithms. After validating the simulation, different mixing indices, with different calculation bases, have been investigated, and it has been found that the Lacey mixing index, which was defined based on statistical concepts, is suitable to investigate the segregation/mixing phenomena of this bed in different conditions. Finally, the effects of parameters such as velocity, particle density ratio, jetsam concentration, and initial arrangement on the segregation/mixing behaviors of the bed have been studied. Findings The results show that the increase in the superficial gas velocity decreases the mixing index to a minimum value and then increases this index in the beds with mixed initial condition, unlike the beds with separated initial condition. Moreover, an increase in the particle density ratio increases the minimum fluidization velocity of the bed, and also the amount of segregation, and increase in the jetsam concentration increases the value of the mixing index. Originality/value A computational fluid dynamics simulation has been presented for the particles segregation phenomenon in the gas–solid fluidized beds.

Three-dimensional CFD simulation and experimental validation of particle segregation in CFB riser

“…Nowadays, with higher computer facilities and simulation techniques, the computational fluid dynamics (CFD) modeling becoming an alternate way to investigate the gas-particle hydrodynamics inside the CFB riser (Bandara et al, 2019;Xie et al, 2018). Although, the selection and reactivity of fluidized bed reactors are closely depends on the poly-disperse flow and solid back mixing inside the riser section, however, most of the numerical research studies were based on the mono-disperse assumption (Karami and Goharrizi, 2020). In most of previous CFD modeling and simulations work, both common models, Eulerian-Eulerian two fluid model (Gidaspow et al, 2004) and Eulerian-Lagrangian discrete element model (Zhu et al, 2007) have been used for investigating the gas-particle hydrodynamics of fluidized bed system.…”