A computational fluid dynamics study of gas-solid distribution of Geldart Group B particles in a swirling fluidized bed

The study's main goal, as reported in this research paper, was to investigate the gas-solid flow behaviors in a twin cyclonic fluidized-bed combustor (T-FBC) in swirling mode under a range of operating conditions. Silica sand in three size ranges, 300-500 mu m, 500-710 mu m, and 710-1000 mu m, with 1700 kg/m(3) solid density was used as the bed material in the study's experimental tests and its computer simulations. The Eulerian-Eulerian approach for two-phase fluid flows was selected to investigate the cold hydrodynamic characteristics of gas-solid particles, at a constant ambient temperature, in the fluidized-bed combustor. The three different turbulence models; the standard k-epsilon model, the renormalization group (RNG) k-epsilon model, and the Reynolds Stress Models (RSM) were studied in order to select the most appropriate model. Finally, the RNG k-epsilon turbulence model was applied in all simulations for both phases of our work. The computational simulations were performed using the same parameters and operating conditions as in the experimental tests, with the validity of the computational simulations thus experimentally verified. In the simulation results, it was shown that the increasing size of the bed particles, the solid hold-up tended to decrease, the time duration for initializing full-bed fluidization increased, and the bed fluctuation frequency decreased. When increasing excess air (EA), the simulation results showed the opposite trend. The secondary to total air ratio (S/T) had substantial effects on time duration to initialize bed fluidization and the bed fluctuation frequency in the swirling fluidized bed; however, it had slightly effects on the radial solid hold-up and radial solid velocity in the dense bed region. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

The main aim of this study was to investigate gas-solid flow behaviors in a twin cyclonic fluidized-bed combustor in swirling mode. Three different turbulence models were studied to select the most appropriate one for computational simulations. The results showed that the size of bed particles, excess air, and secondary to total air ratio all had significant effects on fluidization behavior in the swirling fluidized bed.