(200e) Analogy of Mass Transfer in Absorption and Distillation Columns: Wetted Wall Column Study Distillation

Rate-base modeling of packed distillation columns represents an advanced approach to design these devices. Compared to the traditional stage-wise approach the rate-based modeling offers more information about the conditions inside the column and enables to the column designer to simulate the behavior of the column if the operation conditions are changed. The possibilities of the rate-based approach are limited by the reliability of mass-transfer parameters, the mass-transfer coefficients. Unlike the absorption conditions, the measurement of the individual mass-transfer coefficients under distillation conditions in the industrial scale columns has never been mastered. Therefore, the values of those parameters for distillation conditions are usually recalculated out of the results of standardized absorption experiments. The possibility of such recalculation, i.e. the analogy of the mass-transfer in absorption and distillation columns, is tacitly assumed. This work is focused on the study of this analogy and the possibility of the recalculation of the mass-transfer coefficients between absorption and distillation conditions in the wetted wall column. The correlations for absorption gas- and liquid-side mass transfer coefficients (k_G and k_L, respectively), measured under conditions close to the distillation ones, were presented on this conference last year. These correlations have been used for the HETP prediction for the atmospheric distillation of methanol-propanol and ethanol-propanol systems in the same wetted wall. In this paper we bring the comparison of the predicted and experimental values of distillation separation efficiency in terms of HETP and individual mass-transfer coefficients evaluated using the profile method. The difference of 10 – 30 % in the experimental and predicted HETP values was determined.  The distillation k_G values have been found to be 10 – 20 % and the k_L values even 20 – 60 % lower than predicted out of the results of absorption experiments. The influences of the heat-transfer and the uncertainty of the physical properties on the results are discussed.