(227f) The Challenges Associated with Amine-Containing 3D Printed Sorbents and Their Impacts on the Cost of CO2 Capture By Temperature Swing Adsorption (TSA) Process.

Adsorption technology using solid sorbents is one of the alternatives to amine-based processes for CO₂ capture. Although the energy needs of solid sorbent-based processes are low, the main challenge with the implementation of a CO₂ capture process is the footprint. To lower the footprint, fast cycling and high feed flow rates are required. Traditionally, adsorption processes employ packed beds which contain the adsorbent in the form of pellets. At high flow rates, pellets suffer from high pressure drop issues and with repeated cycling, attrition issues arise. To overcome these challenges, processes having structured adsorbents like laminates, monoliths, etc. are needed owing to their lower pressure drop, low attrition, and better mass transfer characteristics¹. In recent times, 3D printing of structured adsorbents has been gaining significant attention for producing structured sorbents. The advantage of 3D printing is the flexibility with respect to channel sizes and geometry of the channels in the adsorbent². However, large uncertainty exists with respect to the cost of these sorbents, as it depends not only on the precursor paste but also on the printing method as well.

Sorbents containing amine groups are touted as alternatives to zeolites and MOFs owing to their strong CO₂ adsorption and tolerance to moisture³. Recent studies from our laboratory evaluated 3D printed sorbents containing amine groups towards post-combustion CO₂ capture by vacuum swing adsorption processes^4-6. The 3D-printed sorbent contained multi-walled carbon nanotubes (MWCNT) and polyethylene imine. The sorbent was printed on a kg scale with good reproducibility in printing achieved. Further, rigorous process optimization showed that the sorbent was able to achieve 95% purity and 90% recovery targets for capturing CO₂ from a 15% CO₂ stream available at 90°C. Despite the promise shown from simulations, laboratory tests revealed that these sorbents suffered from stability issues^5-6. This was evident from the significant capacity loss over time as well as the differences in the capacity between the precursor paste and the printed structure. This can have a significant impact on the overall cost of the process.

The current study is undertaken to understand the effect of the sorbent lifetime and the cost of the 3D printing process on the levelized cost of electricity (LCOE) and the specific primary energy consumption for CO₂ avoided (SPECCA) for CO₂ capture from a representative natural gas combustion cycle process with exhaust gas recirculation (NGCC-EGR). EGR offers advantages of higher CO₂ concentration and low oxygen content⁷. The feed was available at 40°C and 1 atmosphere and contained 7.6% CO₂. For this study a 5-step TSA process consisting of adsorption heavy reflux, heating, light reflux and cooling shown in Figure 1 is selected. Rigorous process optimization was performed to identify the minimum SPECCA and LCOE for 95% purity and 90% recovery targets. The performance of the 3D-printed sorbent was benchmarked against reference-packed bed systems containing a similar sorbent.

References

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3. Gelles et al., Adsorption, 2020 26 5-50
4. Krishnamurthy et al., Frontiers in climate, 2021,
5. Krishnamurthy, Chem Eng Sci,2022,253, 117585
6. Krishnamurthy et al., Int J Greenhgas con, 2024, 132, 104069
7. Alcarez-calderon et al., J Energy Inst, 2019, 92 370-381.