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.