Verification of the Importance of Introducing Particle Size Distributions to Bubbling Fluidized Bed Simulations

Fluidized beds are widely used in industrial operations due to their ability to give good mixing and a high contact area between the phases. The excellent controlling ability of temperature allows good operating conditions for solid catalyzed gas phase reactions and also the ease of the design. Powders used in industrial ‡uidized beds have a particle size distribution, and the particle size distribution in‡uence signi…cantly on the ‡ow behaviour. In modelling of ‡uidized beds a mean particle diameter is often used, and important information about ‡ow behaviour can therefore be lost. The objective of this work is to study the in‡uence of including particle size distribution in the simulation of a 2-D bubbling ‡uidized bed. Related to this work a series of simulations are performed using the commercial CFD software FLUENT 6.3. The simulations are run with one, two, three and four particle phases. The particle size distribution is accounted for by including multiple particle phases. The computational results are compared to results from experiments performed by Mr. W.J. Wu at Telemark University College, Norway. The computational results are compared with each other with respect to the bubble appearance, bubble distribution, bubble velocity, bed expansion and particle segregation. The comparison shows that the results vary signi…cantly depending on the number of particle phases used. Computational results of bubble velocity, bubble distribution, bed expansion and particle segregation are compared to the experimental data. The results from the simulations with three and four particle phases agree well with the experimental results according to bed expansion and bubble behaviour. The simulations show the importance of accounting for the particle size distribution in the computational model. By using one particle size, important information of the ‡ow behaviour is lost, and the results deviate signi…cantly from the experiments.