Numerical Simulation Of Fluid Dynamics In Circulating Fluidized Bed

Though fluidized bed technology has been widely used in energy source, chemical engineering and other industrial fields, the understanding of fluidized bed is in a laggard place because of the complex mechanism and interaction among hydrodynamic, heat transfer and combustion. Based on the Euerian two-fluid models, hydrodynamic in fluidized bed is numerical simulated by means of FLUENT CFD software.In the Euerian two-fluid models, solid phase is handled as a continuum media. Thus, the gas and solid phase can be treated similarly. In this way, satisfactory result can be gained form a less computation cost.FLUENT is selected for the numerical simulation of hydrodynamic in fluidized bed because of the advantage of compute method and stabilization, astringency of computation of this software. Grid in computation zone is drawn by preprocessing software GAMBIT, quadrangular grid is adopted in planar zone, the control equations of computational model is dispersed using the finite volume method (FVM) and pressure-velocity couple is solved by Phase Coupled SIMPLE method. Simulation employs the unsteady segregated solver, progressed with a small time step size till convergence.The simulation to the dense zone of fluidized bed clearly shows the dynamical process of formation, movement upward, grown and eruption of bubbles, and the curve of bubble raise velocity vs. bubble area computed accords well with Kuipers' experiment results.Investigation on the solid phase concentration distribution in the radial and axial direction shows a core- annulus frame where solid phase is more denser in annulus zone than core zone exists in the fluidized bed, and particle cluster behavior such as congregate, disassembly, upward and downward is observed.Particle velocity in fluidized bed is researched in this thesis and result grained shows particle movement has two manners, one is upward movement in the core zone and down in the annulus zone, the other is movement from core zone to wall, which is according well with experiment result.Research on the pressure drop in fluidized bed indicates pressure drop relates with two factors: fluidized air velocity and circulating quantity of solids. In a fixed fluidized air velocity, pressure drop increases with circulating quantity of solids; in a invariable circulating quantity of solids, pressure drop decreases account for the enhance of air velocity, but the alter of circulating quantity of solids plays a more important role.