Numerical simulation of homogeneous fluidization behaviour of Geldart Group A particles in gas tapered fluidized beds

Abstract

A two-dimensional gas-solid tapered fluidized bed at laboratory-scale in a homogenous fluidization regime is simulated using the computational fluid dynamics (CFD) software COMSOL 5.4. The Eulerian-Eulerian (EE) hydrodynamic model is used to predict the minimum fluidization velocity, minimum bubbling velocity, bed height, and solid volume fraction of alumina particles (in Geldart Group A) in the bed with different tapered angles.The effects of static bed heights on the minimum fluidization velocity of tapered beds are investigated. The highest minimum fluidization velocity is 6 mm/s with a static height of 11 mm and a tapered angle of 12 . The bed height is increased with increasing superficial air velocity. At a given air velocity, the minimum bed height is obtained at a 12 tapered angle. A decrease in solid volume fraction is also observed upon an increase in the superficial air velocity. The CFD results show an almost uniform solid concentration over the bed height. The homogenous or non-bubbling regime appears in a wider range of critical velocity at a 12 tapered angle. In the case of a 0 tapered angle, the results of this study and the discrete element method computational fluid dynamics (DEM-CFD) simulation exhibit a good match. In the case of 6 and 12 tapered angles, the proposed model leads to good predictions based on the theory of homogenous fluidization of Geldart Group A. This research introduces a rapid and cost-effective approach for the better design and operation of a tapered fluidized bed in large scales.

Gas Bubble Diameter and Rise Velocities in Tapered Fluidized Beds: Experiment and Computational Fluid Dynamics Simulation

“…In tapered beds, an additional stress exerted by the slanted walls is included in eq 4 as a new term. Thus, two new solid phase source terms are introduced as follows: 34 , , , , ) c g s s g g g (23) where k a represents the pressure drop ratio in a tapered fluidized bed to that of a columnar bed. In this work, the value of k c was set to 1 for simplicity.…”

“…Kia Lashaki et al 23 studied the hydrodynamic behavior of Geldart A particles in tapered fluidized beds. Minimum fluidization velocity, minimum bubbling velocity, bed height, and solid volume fraction for various apex angles were predicted using CFD simulations.…”

Optimization of simulation model adaptability and CFD of particles of Geldart‐B in a gas–solid fluidized bed for silicone monomer synthesis

“…[6] Previous studies have optimized the gas distributor porosity and the arrangement of the pores, [7,8] and obtained that the gas-solid phase distribution is more uniform when the porosity is 0.53% and when it is arranged in a circular shape, which makes the flow more beneficial to the gas-solid phase mixing. To better investigate the uniform fluidization state of the gas-solid phase, Mansureh K. L. et al [9] investigated the flow characteristics of Geldart A particles in a conical fluidized bed at different taper degrees and suggested that a smaller time step should be used to simulate a three-dimensional conical fluidized bed. The above works have explored the fluidized bed structure only in terms of its investigation on the flow characteristics, but the effects of different models on the simulation results are not negligible, hence it is necessary to study the model sensitivity and applicability.…”

Experimental Investigation and CFD–DEM Simulation of Solids Mixing in Tapered Fluidized Beds

“…Their findings showed the highest level of agreement with the model proposed by Raste et al, as compared to other recently developed models. Kia Lashaki et al employed the Eulerian–Eulerian hydrodynamic model to forecast fundamental characteristics such as the minimum fluidization velocity, minimum bubbling velocity, bed height, and solid volume fraction of Geldart A particles within a 2D gas–solid tapered fluidized bed featuring various apex angles. The Eulerian–Eulerian (EE) or two-fluid model (TFM) treats both the gas and solid phases as interpenetrating continuous media, without limitations on particle count and without the need to individually track discrete particles.…”