Experimental results versus model predictions for dense gas extraction using a hollow fiber membrane contactor

Hollow fiber membrane contactors offer a number of advantages over dispersed phase contactors for extraction of aqueous feeds. In addition, dense gases provide benefits that traditional extraction solvents do not. In a previous paper we described the development of a mathematical model of a membrane contactor, and showed that model predictions were reasonably close to experimental data obtained in our laboratory for the extraction of isopropanol or acetone from water into dense CO2. s paper, results obtained by others upon extraction of various solutes from aqueous solution into dense CO2 or propane were also compared to model predictions. Solutes studied ranged from low mA (i.e., partition coefficient) compounds like caffeine, ethanol, and dimethylformamide, to high mA ones such as 1,2-dichloroethane and ethyl acetate. Again the predicted mass transfer coefficients and yields were reasonably close to the actual ones, except for the data obtained using a membrane module that was particularly susceptible to flow maldistribution. igher mA solutes, most of the mass transfer resistance was in the aqueous phase boundary layer. On the other hand, some of the resistance encountered with lower mA compounds shifted to the solvent-filled pore and the solvent phase boundary layer, although the aqueous resistance was still significant in most cases. In general, mass transfer coefficients and yields were higher for solutes with higher partition coefficients, and aqueous boundary layer penetration was more rapid. sults presented in this and in our previous paper validate the ability of the model to predict hollow fiber membrane contactor performance in dense gas extraction. This validation confirms the utility of the model for screening potential applications of the technology, with considerable reduction in the required amount of expensive laboratory experimentation.