Numerical simulation of 3-phase fluidized bed particle segregation

• CFD simulation of density-based coal beneficiation.
• Experimentally validation of 2D and 3D, 3-phase simulation model.
• Modification of Syamlal-O’Brien drag model and solid–solid restitution coefficients.
• Comparison of 3-phase, 2D versus 3D simulation model performance.

Air dense medium fluidized bed technique has been proposed as a viable technique for dry coal beneficiation with acceptable separation efficiency. In the current work, CFD simulation has been used to provide deeper understanding of the bed hydrodynamics in this system. The simulation results have been compared with the experimental data from sedimentation or flotation of 3.675 mm coal particles in a bed of Geldart group B silica sand particles (390 μm, 2600 kg/m3). The superficial velocity has been adjusted (between minimum fluidization and minimum bubbling) to keep the bed in the particulate regime. The results of several 2D and 3D Eulerian multiphase CFD models have been evaluated and compared with the experimental data of bed expansion, bubble pattern and frequency, and coal particles density classes. It was found that the modification of the coefficients of Syamlal-O’Brien drag model to 0.52 and 5.30369 and solid–solid restitution coefficient of 0.9 would enhance model predictions for both sand fluidized bed and coal segregation compared to the experimental data. Comparison of the simulation results with experiments showed that 3D simulation model performed 29.1% better than similar 2D models.