(29e) Assessing the Influence of the Particle Size Distribution on Fluidized Bed Hydrodynamics Using High-Throughput Experimentation

An important process in gas-solid fluidized beds is the transport from gas in the dilute phase (voids or bubbles) to the particles in the dense phase. It is a well-known fact in fluidization technology that the addition of fines improves the fluidization behaviour and leads to a better mass transfer, but the importance of fines has never been completely explained. The current practice, however, is that fluidized bed particles (carriers for catalytic material) are mainly optimised on the scale of a single particle. Most attention is given to their pore size distribution so that a high surface area is achieved and that the active sites are easily accessible by the gaseous components.

We aim at improving the conversion and selectivity of gas-solid fluidized bed reactors by designing mixtures of particles with optimal properties (size distribution, density, shape, elasticity), aided by high-throughput experimentation, a novel approach for hydrodynamics research. The automated set-up we use allows access to quantitative information from large numbers of particle mixtures. Catalyst carrier materials such as silica and alumina are used as particles. Experiments are carried out in two industrially relevant fluidization regimes: bubbling fluidization and turbulent fluidization. In the experiments, pressure measurements, optical probes, and video analysis are used to assess the hydrodynamics.

The results for Geldart A particles show that broadening the particle size leads to up to 60% reduction in the bubble size. The addition of fines to a given particle size distribution also decreases the bubble size, whereas the addition of coarse particles hardly influence the bubble size.