Imposing dynamic structures on fluidised beds

Structuring fluidised beds can increase the conversion and selectivity, and facilitate control and scale-up. Two methods for introducing a dynamic structure into gas–solid fluidised beds are compared based on their overall hydrodynamics: electric field enhanced fluidisation and distributed secondary gas injection by a fractal injector. It is shown that, under various conditions, these systems lead to significant decreases in bubble size and bubble hold-up and to an increase in the number of bubbles. It was found that the electric field enhancement can lead to homogeneous fluidisation at lower flow rates, and the distributed secondary flow leads to smaller bubbles at higher flow rates.