FLUIDIZATION OF A BED OF SOLID PARTICLES IN A TWO DIMENSIONAL VERTICAL BOX

Simulation of fluidization of a bed of solid particles in a two-dimensional box is performed using molecular dynamics methods by assuming that superposition of buoyant, gravitational, viscous, collision force will make the particle to move in two dimensions. Two different fluid type is used in this simulation, i.e., gas and liquid fluid. By increasing the fluid velocity from small to high, then minimum fluidization condition reached. As a result, fluidization of alumina particle with liquid fluid has a minimum fluidization velocity lower than gas fluid.

Study of Defluidization Region of Large Particles in Fluidized Bed Using the Gaussian Spectral Pressure Distribution

The present work aimed to identify the defluidization region of a gas-solid fluidized bed system composed by Geldart group D particles using the Gaussian spectral pressure distribution technique, which is based on pressure fluctuation measurements in the plenum. In experiments, the defluidization condition of glass beads with apparent density of 2,450 kg/m3 was induced in a plexiglas column of 0.11 m in inner diameter and 1.0 m in height. The gas-solid behavior close to the incipient fluidization condition was assessed for two fixed bed heights (0.10 and 0.20 m) and two mean sizes of particles (1.55 and 2.18 mm in diameter). The bed was fluidized with air at environment temperature. The experimental equipment was instrumented with a pressure transmitter connected to a data acquisition system in order to record the pressure fluctuations of the gas-solid flow. The results showed that the defluidization region can be detected efficiently by using the Gaussian spectral pressure distribution technique, which contributes for a better control of fluidized bed processes.

ASYMPTOTIC POWER SPECTRUM ANALYSIS OF CHAOTIC BEHAVIOR IN FLUIDIZED BEDS

The nonlinear behavior of fluidized beds is analyzed quantitatively using an asymptotic power spectrum method. A model based on kinetic theory is used to compute the voidage signals in a two-dimensional bubbling fluidized bed with a fluidization condition of U/Umf=4, where U is the fluidizing velocity and Umf is the minimum fluidizing velocity. The data for power versus frequency in the asymptotic frequency regime are shown to obey a power-law falloff. This means that the bubbling fluidization under such a fluidization condition cannot be a low-dimensional strange attractor. Pressure fluctuation data, obtained from a three-dimensional bubbling fluidized bed, are also analyzed and clearly show the power-law falloff. This is consistent with previous findings in that the correlation dimension for these data cannot be small (i.e., 2 or 3). The differences between our findings and others are discussed.