(156d) Structural Optimization and Modeling of Carbon Capture through Adsorption

The CO₂ emissions associated with human economic activity are known to cause undesired changes to the earth's climate. An essential step in mitigating these emissions is their separation from flue gas mixtures from point sources, e.g., power and industry plants, or from air. Thus, Carbon Capture and Sequestration (CCS) is one of the most promising technologies developed to alleviate trends in global warming and detrimental effects of CO₂ on human ecosystems. Furthermore, industrial stakeholders and policy makers are particularly interested in developing these technologies on a larger scale to achieve sustainability goals and agendas.

In this work, we focus on developing novel computational tools and reactor designs to model and scale-up the adsorption process, mainly known for its effectiveness in treating dilute mixtures. More precisely, we target a process called Direct Air Capture (DAC) which uses adsorption for removing CO₂ directly from air. In greater detail, we will develop novel, optimal reactor designs for the Pressure Swing Adsorption process (PSA) and Temperature Swing Adsorption (TSA) in CO₂ capture through a powerful, versatile, and flexible mathematical framework called Topology Optimization. Moreover, we wish to leverage the detailed modelling and simulations to gain insights regarding the scale-up of the device.

In the past, some useful insights into optimizing and scaling-up microfluidic reactors for first-order kinetics coupled with mass and momentum transport have been developed [1]. However, these studies have not been applied to more complicated kinetics e.g. coupled reaction-diffusion for adsorption process. Another challenge in deriving optimal structures for adsorption is the inherent dynamic nature of the process and the not well understood mass transfer between solid material and fluid. To model the mass transfer, we get inspiration from work done for PSA and TSA process optimization using trust region methods [2]. In these models, the mass transfer has been treated as a linear driving force coupled to the other governing and constitutive equations.

To achieve these goals, we set the coupled partial differential equations (PDEs) problem in structural optimization format and expand the computational framework developed for optimizing the first order reactor, to include kinetics from the literature pertaining to state-of-the-art materials for DAC e.g. [3]. The pressure drop along the PSA or TSA device is the natural objective function to minimize. An iterative approach is applied, where we solve the coupled PDEs by the finite elements method and in each iteration the algorithm generates a computationally updated design. After the system converges, the potential scalability of the system is evaluated. The results from the topology optimization of catalytic reactors will be a steppingstone for large-scale carbon capture through adsorption.

References

[1] F. Okkels and H. Bruus, “Scaling behavior of optimally structured catalytic microfluidic reactors,” Physiscal Review E, 2007.

[2] J. Uebbing, L. Biegler, L. Rihko-Struckmann and S. Sager, “Optimization of pressure swing adsorption via a trust-region filter algorithm and equilibrium theory,” Computers and Chemical Engineering, 2021.

[3] R. Hughes, G. Kotamreddy, A. Ostace, D. Bhattacharyya, R. L. Siegelman, S. T. Parker, S. A. Didas, J. R. Long, B. Omell and M. Matuszewski, “Isotherm, Kinetic, Process Modeling, and Techno-Economic Analysis of a Diamine-Appended Metal–Organic Framework for CO2 Capture Using Fixed Bed Contactors,” Energy Fuels, vol. 35 , no. (7), p. 6040–6055. , 2021.

*This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.