Gas-Phase Mass-Transfer Characteristics of Mellapak 250Y Structured Packing Under Distillation Conditions

The packing efficiency is usually presented in the form of the dependence of HETP on the load. As an integral quantity, HETP cannot be recalculated to another conditions, namely to other systems. This disadvantage is overcome when rate-based approach is applied instead, but the knowledge of the mass-transfer coefficients is inevitable.   

This contribution summarizes results of the measurement of the gas phase volumetric mass-transfer coefficient (k_Ga) for Mellapak 250Y structured packing under distillation conditions. The k_Ga has been determined using “profile method” out of the molar fraction profiles along the column packing under the total reflux and atmospheric pressure for several alcohol systems and cyclohexane-heptane standard test system.  

The results demonstrate the agreement of k_Ga prediction of several dedicated mass-transfer models (Billet-Schultes, Rocha-Bravo-Fair, Delft model) with the experimental data. Revealed k_Ga dependence on the gas flow is also discussed. The different distribution of the mass-transfer resistance between the phases for alcohol and organic systems is demonstrated.

Combination of the results with the extrapolation of the absorption derived Sh_G correlation enabled estimation of the distillation effective interfacial area, perhaps the most obscured mass-transfer parameter.