PEPT study of particle motion for different riser exit geometries

Laboratory and industrial risers are equipped with exits of many different layouts, and numerous publications discuss the influence of riser exit geometry on local and overall solids hydrodynamics in the riser. The present paper reviews literature findings—mostly based upon indirect experimental techniques and often somewhat contradictory. Direct measurement of particle velocity and particle occupancy near and in the riser exit provide a better indication of the effect of riser exit geometry. Positron Emission Particle Tracking (PEPT) was used in this work for the first time to investigate the exit region of the riser. An abrupt or sharp exit causes particles to be knocked out of the gas flow, so forming a recirculation or reflux region in the upper part of the riser. This is much less pronounced with a curved or gradual exit.

Positron Emission Particle Tracking technique (PEPT) was used for the first time to investigate the exit region of a fluidized bed riser. A sharp exit results in particle recirculation and a high density region in the upper part of the riser, in contrast to the situation with curved exit geometries. Particle trajectories in the exit are observed directly.Figure optionsDownload as PowerPoint slide