Discrete Element Modeling and Validation of Fluidized Bed With Multiple Jets

Fluidized beds with multiple jets have widespread industrial applications. They are used to aid in proper mixing of coal or biomass in the bed, which in turn increases the combustion and heat transfer. The objective of this paper is to investigate the jet interactions and hydrodynamics of a fluidized bed with multiple jets. Discrete Element Modeling coupled with a CFD code GenIDLEST has been used to numerically simulate 9 jets. The results are compared with published experiments. Mono dispersed particles of size 550 microns are used with 1.4 times the minimum fluidization for the particles. Two dimensional computations have been performed. The solid fraction at different heights from the jetting bed is compared with the experiments along with the solid circulation at the grid zone or the jetting zone. Average solid fraction across the cross-section of the bed is plotted along the height and compared with the experiments to estimate the bed expansion due to fluidization. Comparison of time averaged jet heights with the experiments is also shown. Discrepancies between the experiments and simulations are discussed in the context of the dimensionality of the simulations. The time averaged solid fraction at different heights from the distributor plate match well with the experimental results except near the walls. A slight over prediction of solid fraction values is obtained near the walls from the simulations. The average solid fraction along the height of the bed is in good agreement with the experiments, showing similar trends in bed expansion for both the experiments and simulations. The results obtained from DEM computations serve as validation for the experiments and help us understand the complex jet interaction and solid circulation patterns in a multiple jet fluidized bed system.