(515f) Improving Fluidized-Bed Performance by Optimizing the Particle Size Distribution

Authors: 
van Ommen, J. R., Delft University of Technology
Beetstra, R., Delft University of Technology
Ellis, N., The University of British Columbia
Nijenhuis, J., Delft University of Technology


Manipulating the structure of multiphase reactors introduces extra degrees of freedom allowing decoupling of conflicting design objectives, such as high mass transfer versus low pressure drop (packed bed) and high gas flow rate versus small bubble size (fluidized bed). In this way, structuring facilitates reaching goals such as process intensification and more sustainable operation. At Delft University of Technology, much effort has been put over the past years in the research and development of structured reactors, such as structured fixed bed reactors, structured slurry bubble columns, and structured gas solid-fluidized beds. In this paper, we will focus on the latter category.

In a gas-solid fluidized bed, structuring can be imposed either (1) via the gas phase or (2) via the particles. Moreover, we can modify a) the geometry or b) the dynamic behaviour of each of the two phases. This gives in total four possible combinations. In this paper, we will discuss the effect of Approach (2).a): changing the geometry of the particles. Our goal is to design mixtures of particles with optimal fluidization properties. Using high-throughput experimentation, the relevant hydrodynamic data can be obtained in a limited period of time. This approach is demonstrated by assessing the influence of the particle size distribution on fluidized bed hydrodynamics of Geldart A powders. By manipulating the width of the particle size distribution of alumina powder the bubble diameter is reduced up to 40%. The addition of fines to a given particle size distribution also decreases the bubble diameter up to 40%, whereas the addition of coarse particles hardly influence the bubble size. At low gas velocities the bubble size was found to increase with fines addition. We will show that this approach can equip chemical engineers with practical tools to improve the operation of fluidized bed reactors.