Exchange between the stagnant and flowing zone in gas-flowing solids-fixed bed contactors

In countercurrent gas - flowing solids - fixed bed contactors, a fraction of the flowing solids is in motion (dynamic holdup), while the other fraction is resting on the fixed bed elements. In this study it was experimentally proved that the stagnant zone should not be considered as a dead part of the column, but that there is a dynamic exchange between these two portions of flowing solids particles. Combining a mathematical model with tracer experiments, the rate of exchange was determined and it was shown that only a small part (ca. 20 %) of the stagnant region should be considered as a dead one.

Dynamic holdup in a countercurrent gas - flowing solids - packed bed contactors

Equations for the prediction of the holdup of dynamic solids in countercurrent gas ? flowing solids ? packed bed contactors are presented in this paper. The correlations do not require the use of parameters that need to be determined by experimental measurements in the actual system of interest. They could be used for a wide range of operational conditions different packing types and a variety of flowing solids materials. The equations are compared with all available experimental data from the literature.