Water recovery from stripping gas overhead CO2 desorber through air cooling enhanced by transport membrane condensation

At the CO2 regeneration stage in a CO2 chemical absorption process, the stripping gas (i.e., H2O(g)/CO2) leaving the CO2 desorber is cooled down to return the condensate into the desorber. Mostly the circulating cooling-water is used to provide this cooling duty. In this study, the air-cooling technology enhanced by transport membrane condensation was investigated with the aim of reducing the additional cooling-water duty of the chemical absorption process. A tubular hydrophilic ceramic membrane with the mean pore size of the inner separation layer of 4 nm and the length of 400 mm was used for water recovery from H2O(g)/CO2 using N-2 as the sweeping gas. Results showed that the cooling performance of the N-2-cooling ceramic membrane condenser is about 4-7 times higher than that of the N-2-cooling stainless steel condenser with the same dimensions. For the water recovery from H2O(g)/CO2 using the N-2-cooling ceramic membrane condenser, increasing the flow rate and pressure of inlet H2O(g)/CO2 can bring about the increase of the water transfer flux. The water transfer flux can increase with the H2O(g) molar fraction in H2O(g)/CO2 as well. Additionally, the increase of N-2 flow rate in addition to the reduction of inlet N-2 pressure can enhance the water transfer performance. Moreover, the temperatures of H2O(g)/CO2 and N-2 have little impacts on the water transfer flux. Finally, an empirical correlation for predicting the water transfer flux as a function of the key operation variables was proposed for the N-2-cooling ceramic membrane condenser. Most of the calculated water transfer flux data are in good agreement with the experimental results with an average absolute deviation of 12.5%.