Modeling of Rapid Temperature Swing Adsorption Using Hollow Fiber Sorbents

The use of novel polymeric hollow fiber contactors loaded with CO₂ sorbents has been recently demonstrated experimentally as a new and scalable process configuration for post-combustion CO₂ capture. The hollow fiber contactor allows coupling of efficient heat transfer and gas contacting, potentially yielding lower parasitic loads on host power plants compared to traditional contacting strategies using solid sorbents. In this study, a two dimensional mathematical model of a rapid temperature swing adsorption (RTSA) process is developed for the first time to predict polymer-supported amine hollow fiber sorbent performance during post-combustion CO₂ capture from flue gas. In particular, this work is focused on developing a single fiber model to simulate a four-step RTSA system accounting for adsorption, heating/desorption, heating/sweeping and cooling steps. The model is validated with experimental breakthrough data obtained from our RTSA system. The sensitivity of the model to parameter values such as gas and water velocity and initial temperatures are evaluated accordingly by considering the effect of these parameters on CO₂ concentration and temperature profiles. Furthermore, the CO₂ adsorption isotherms obtained experimentally were fitted with the Toth model. In addition, our model was validated against experimental breakthrough profiles. A good agreement was found between experimental and numerical data indicating that our proposed model can describe experimental observation very well. The numerical results obtained from RTSA cycle modeling indicate that under operating conditions considered here, it is possible to achieve high purity and recovery within a cycle time of shorter than 3 min. It was also found that there is a trade-off in cycle time, shorter for lower capital cost and longer to enable heat recovery for lower utility costs.