Modeling of a Packed Column Contactor

A 5.5 cm diameter and 125 cm long glass column, packed with 10 mm glass Raschig rings was used as a liquid-liquid contactor. The contactor performance was investigated by the system acetic acid-toluene-water at 25 °C. The data obtained have been compared with previous works using mixer-settler contactors with the same test system. A new modeling approach is used to simulate extraction in packed columns. This approach is based on dividing the packing section into a number of strips simulating the stages in tray contactors. A nonequilibrium stage model is developed in which equilibration of the phases is not necessarily attained. Material balance relationships have to be only strictly observed. The model results are in excellent agreement with the experimental data. An extraction efficiency parameter similar to the vaporization efficiency developed by Holland is introduced. This parameter is given by the ratio of the actual composition of the extract to that of the raffinate phases obtained from the contactor divided by the equilibrium ratios. The extraction efficiency is in effect the fractional equilibrium achieved in an actual situation. Using the nonequilibrium stage model may result in better simulation of the actual performance of the commercial contactors and in the design of this equipment.