Postcombustion CO2 Capture from Wet Flue Gas by Temperature Swing Adsorption

We present an analysis of a novel temperature swing adsorption (TSA) process with condensers capable of treating wet flue gas reaching 90% CO2 recovery and 95% purity (on a dry basis). In the first part, the characterization of the binary CO2/water vapor adsorption equilibrium on zeolite 13X is presented, quantifying residual CO2 adsorption at different levels of water adsorption. On this basis, we propose an empirical and analytical isotherm model able to capture the competition between CO2 and water vapor. In the second part, the isotherm model is used in a process simulator to assess the performance of the proposed TSA process in detail. The strict specifications on the CO2 product could be reached by employing a layered bed configuration, where a portion of the zeolite 13X bed is replaced by activated alumina. Further, the process is optimized by parametric analysis with respect to productivity and energy consumption while using the specifications as constraints. It is shown that reasonable performance can be obtained, comparable to the scenario where a drying step precedes the cyclic adsorption process but achieving this in a single process step. Moreover, the critical effect of the significant mass transfer resistance of water vapor on zeolite 13X is quantified. Due to a spread of reported mass transfer coefficients of water vapor on zeolite 13X, the process is assessed for three representative values, showing that comparable performance can be obtained for all cases considered by varying the length of the guard layer. The robustness of the process is further underlined by the reasonable performance for varying concentrations of water vapor in the feed.