Effect of liquid-phase properties on separation efficiency in a randomly packed distillation column

The effects of the liquid properties on packing efficiency were investigated experimentally. Tests were performed in a column packed with ceramic Intalox((R)) saddles, 7mm in diameter. The distillation column was operated under total reflux and at atmospheric pressure (94kPa). Surface tension positive (methanol/water, n-heptane/toluene), surface tension negative (benzene/n-heptane), and surface tension neutral (methanol/isopropanol and cyclohexane/n-heptane) systems were selected to examine the wide range liquid property effects on the height of equivalent to a theoretical tray (HETP). The surface tension gradient was found to be the dominant factor affecting HETP in surface tension positive systems, but had no effect for the surface tension negative system. For the surface tension neutral system, it was found that the liquid diffusivities and viscosities had the greatest effect on HETP. The measured HETP data was also compared with tray results obtained from literature, to determine if packing and tray efficiencies are affected in a similar manner by the liquid properties. It was concluded that the surface tension gradient, liquid diffusivities, and viscosity have similar effects on the efficiency of packed and tray columns.