Abstract: Hydrodynamic characteristics of VST with different cap configurations were studied in a 500 × 370mm rectangular column and a circular column of φ1.2m with air-water system. The influences of various geometrical parameters and hydrodynamic conditions upon the pressure drops of trays, the upper and lower limits of allowable gas velocities and the amounts of the lifted liquid were examined. By discussing and analyzing the experimental results on the hydrodynamic view, we presented empirical correlations used for the hydro-dynamic design of the VST column. In order to minimize the pressure drop of the VST, a modified VST with the nozzle-type vapour riser was used. The experimental results showed that the pressure drops of the modified VST are 40% less than those of conventional VST operating under the same conditions.