Characterization of axial liquid dispersion in gas–liquid and gas–liquid–solid reactors

Abstract

Axial liquid mixing was studied in gas–liquid systems (bubble columns) and two types of gas–liquid–solid system (the turbulent and inverse turbulent beds) for different types of gas sparger (membrane and perforated plate). In the turbulent and inverse turbulent beds, solids, larger and lighter than water and of large diameter (3–4 mm) are fluidized only by an upward gas flow. In two-phase systems, the type of gas sparger has a strong effect on the gas flow regime and consequently on the axial liquid mixing. A general diagram with co-ordinates Pe versus Fr (1/3) has been established in order to explain all the results. It allows the hydrodynamic characteristics to be predicted by a simple measurement of the axial liquid dispersion coefficient E zl . In the gas–liquid–solid reactors tested, the effect of the gas sparger on axial liquid mixing can be pronounced. A flow regime diagram is proposed, which shows a heterogeneous flow behaviour independent of the gas sparger when the solid content of the column is sufficiently high.