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

Abstract

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.