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The volumic solid-liquid mass transfer coefficients in downward and upward two-phase flow through packed beds were determined by dissolution of benzoic acid cylinders; several liquid phases were tested. The coefficients were compared with those obtained by other authors and correlations were proposed. In addition, the solid-liquid mass transfer area was determined by a chemical method (dissolution of phthalic anhydride cylinders In buffer solutions); the area increased on increasing both the gas and the liquid flow rate and total wetting of the particles was reached for some operative conditions. The ratio between the solid-liquid area and the particle geometrical area was found to be a function of the actual average liquid velocity, i.e., taking into account the liquid holdup.

In a previous paper hydrodynamic conditions, interfacial areas and mass transfer coefficients in a packed tower with concurrent downward flows were measured. In this work a packed column with concurrent upward flow has been examined.The results show greater area and liquid mass transfer coefficient values than with downward flow. In concurrent upward flow the increase of power consumption was less than proportional to the mass transfer increase.The experimental data show some factors which affect the increase of area and of the liquid mass transfer coefficient.Energy correlations of mass transfer parameters were proposed.