Experimental and computational study on the bubble behavior in a 3-D fluidized bed

Abstract

a b s t r a c tThe results from a two fluid Eulerian Eulerian three dimensional (3 D) simulation of a cylindrical bed, filled with Geldart B particles and fluidized with air in the bubbling regime, are compared with experimental data obtained from pressure and optical probe measurements in a real bed of similar dimensions and operative conditions. The main objectives of this comparison are to test the validity of the simulation results and to characterize the bubble behavior and bed dynamics. The fluidized bed is 0.193 m internal diameter and 0.8 m height, and it is filled with silica sand particles, reaching a settle height of 0.22 m. A frequency domain analysis of absolute and differential pressure signals in both the measured and the simulated cases shows that the same principal phenomena are reproduced with similar distributions of peak frequencies in the power spectral density (PSD) and width of the spectrum. The local dynamic behavior is also studied in the present work by means of the PSD of the simulated particle fraction and the PSD of the measured optical signal, which reveals as well good agreement between both the spectra. This work also presents, for the first time, comparative results of the measured and the simulated bubble size and velocity in a fully 3 D bed configuration. The values of bubble pierced length and velocity retrieved from the experimental optical signals and from the simulated particle fraction compare fairly well in different radial and axial positions. Very similar values are obtained when these bubble parameters are deduced from either simulated pressure signals or simulated particle volume fraction. In addition, applying the maximum entropy method technique, bubble size probability density functions are also calculated. All these results indicate that the two fluid model is able to reproduce the essential dynamics and interaction between bubbles and dense phase in the 3 D bed studied.

Three-dimensional computational fluid dynamics (CFD) study of the gas–particle circulation pattern within a fluidized bed granulator: By full factorial design of fluidization velocity and particle size

“…However, because of the computational limitations of the Eulerian-Lagrange model which is normally limited to a relatively small number of particles, the Eulerian-Eulerian model is the preferred choice for simulating the gas-particle hydrodynamics of a fluidized bed. The effectiveness of the Eulerian-Eulerian model of CFD has been extensively validated by the experiments [30,37,38,44].…”

“…In literature, CFD has been widely applied for modeling multiphase flow of wet granulation process to reduce 6 the design time and cost [26][27][28][29][30][31][32][33][34][35]. In general, two different approaches of CFD modelling are used to model a gas-solid fluizied bed: the Eulerian-Eulerian approach, in which all phases are considered as interpenetrating continua and the Eulerian-Lagrangian approach in which at least one phase is considered as a discrete phase interacting with the other phases [30,[36][37][38][39][40][41][42][43]. To date, several models built upon the Eulerian-Lagrange framework have been developed such as the computational fluid dynamics-discrete element method (CFD-DEM), dense discrete phase model (DDPM) and multi-phase-particle-in-cell (MP-PIC) method.…”

A novel methodology for simulating vibrated fluidized beds using two-fluid models

“…(T3.5). This code resorts to a finite volume formulation with an implicit time advance algorithm to solve these transient govern ing equations, the coupling between the gas and particle phases being done by a modified SIMPLE algorithm (Phase coupled SIM PLE), which has given satisfactory results in the prediction of the pressure and bubble behavior of conventional fluidized beds [17]. Since the transformed governing equations to be solved are ex pressed in a moving system of coordinates, vibration of the bed vessel was incorporated in the simulation through the equivalent vector of mass force, Eq.…”

Estimation and experimental validation of the circulation time in a 2D gas–solid fluidized beds

“…Kunii and Levenspiel [8] used pressure and optical probes to measure the fluidized bed dynamics (bubble size and bubble velocity) in a 3 D (three dimensional) bubbling fluidized bed. Their experimental results were compared with the results from a two fluid Eulerian Eulerian 3 D simulation of a cylindrical bed, filled with Geldart B particles and fluidized with air in the bubbling regime.…”