Effect of solid holdup on radial gas holdup profiles and transition to slug flow within annular section in a double-tube slurry bubble column

The local gas holdup of a poly (vinylchloride) (PVC) slurry-air system within an annular section in a double-tube bubble column is measured by an electrical probe technique. The local gas holdup decreases with increasing PVC holdup for a given superficial gas velocity. The empirical equation developed for water-air system to estimate the maximum gas holdup in the annular section is modified taking account of the PVC holdup term. Comparing with the experimental results,it is demonstrated that the modified correlation is appliable to a PVC slurry-air system for estimating the radial gas holdup profile. Further, a critical condition in which the behavior shifts from bubble flow to slug flow is found from analysis of the bubble-contact time passing through the probe.