Analysis of CO2 separation and simulation of a partially wetted hollow fiber membrane contactor.

A steady state model was developed for a microporous hollow fiber membrane contactor operated under partially wetted conditions accompanied by chemical reactions, to analyze CO2 absorption into the aqueous solution of diethanolamine (DEA). The proposed diffusion-reaction model contains reversible chemical reactions in the liquid bulk as well as wetted parts of the membrane pores. A numerical scheme was employed to solve the simultaneous nonlinear mathematical expressions, and the results were validated with experimental data in the literature. The gas phase concentration and velocity profile in axial direction inside the shell, liquid concentration profile in axial and radial directions inside the fibers, and also those within the wetted parts of the pores were predicted by using the model. The results of the model and proposed numerical scheme show that membrane wetting, even in very low fractions, can decrease the absorption flux significantly. The wetting fraction of membrane was predicted both with and without consideration of chemical reactions inside the wetted pores. The results indicate that the chemical reactions inside the wetted pores, which have been disregarded in the literature, have considerable effects on the prediction of membrane wetting fraction.

Theoretical study of liquid droplet dispersion in a venturi scrubber.

The droplet concentration distribution in an atomizing scrubber was calculated based on droplet eddy diffusion by a three-dimensional dispersion model. This model is also capable of predicting the liquid flowing on the wall. The theoretical distribution of droplet concentration agrees well with experimental data given by Viswanathan et al. for droplet concentration distribution in a venturi-type scrubber. The results obtained by the model show a non-uniform distribution of drops over the cross section of the scrubber, as noted by the experimental data. While the maximum of droplet concentration distribution may depend on many operating parameters of the scrubber, the results of this study show that the highest uniformity of drop distribution will be reached when penetration length is approximately equal to one-fourth of the depth of the scrubber. The results of this study can be applied to evaluate the removal efficiency of a venturi scrubber.