Experimental Study on Mass Transfer in a Packed Distillation Column

This study experimentally investigates a comprehensive mass transfer model for a packed column distillation process. The experimental data for the local analysis of distillation mass transfer were obtained by observing the vertical distribution of the temperature of the liquid using thermocouples embedded in the packing sections. To analyze the vapor- and liquid-phase film coefficients and/or the height of the transfer unit, a simultaneous equation method for calculating film coefficients was primarily considered by applying the film resistance equation based on the two-film theory at two vertically adjacent positions. The results showed that although this method can provide an appropriate solution in the middle-bed region of the column, the simultaneous equations in the near-top and near-bottom regions become inconsistent, owing to the almost constant slope of the equilibrium curve. Therefore, to overcome this difficulty as well as to simplify model construction, another countermeasure was considered based on the assumption that a set of the tangential vector of the equilibrium curve and the tie-line vector defined at the crossing point is pairwise orthogonal at the "vapor-liquid" interface at each theoretical stage. As a result, the local analysis of the film resistances and/or volumetric mass transfer coefficients was sufficiently improved in these regions. The experimental mass transfer knowledge acquired using the proposed model could contribute to the construction of an engineering database, which would not only be useful for the development of novel or highly efficient packings, but also for improving the design of the practical columns, resulting in process intensification.