(2jv) Optimised Integrated Processes for Carbon Capture: From Direct Air Capture to Concentrated Point Sources

The achievement of net-zero transition by 2050 requires a complete transformation of how energy is produced, consumed and transported, all over the world. One of the key actions proposed by the International Energy Agency is carbon capture, utilization and storage (CCUS).

CO₂ emissions are generated by a number of sources, especially from fuel combustion for power generation, industrial processes, residential applications and transportation. In order to reduce the emissions, two fundamental strategies can be implemented and integrated: (i) technology advancement to improve energy efficiency and to generate more power via renewable energies; (ii) implementation of carbon capture, utilization and storage (CCUS).

This second strategy is particularly important for the industrial sector: while in the power sector a transition towards renewables is expected in the short-to-medium term, in the industrial sector decarbonization without carbon capture is very difficult or even impossible in some cases such as the cement industry ¹.

In addition, negative emission technologies such as direct air capture are needed to compensate for “hard-to-abate” emissions.

Therefore, a detailed analysis and techno-economic optimization of capture processes for different CO₂ sources and for direct air capture is key to facilitate net-zero transition.

Currently, a thorough selection of technology and materials for capture process is missing. In fact, only a single technology is typically considered (i.e., state-of-art absorption process with monoethanolamine (MEA)) and, within CCUS chains, the cost of capture is fixed (around 50 $/ton for post-combustion capture) ². Only a few studies performed a comparison of capture technologies, including adsorption or membrane processes ^3,4. However, these works did not take into account the recent developments of high-performance membrane and sorbent materials, which are making such processes very promising even with low-concentration CO₂ sources. The inclusion of novel capture processes would significantly reduce the cost for capture (around 50% reduction, since capture cost can go down to 20-30 $/ton for post-combustion capture ⁵), which typically covers the highest share of the total cost of CCUS chains.

As a group leader, I aim at proposing economically-feasible integrated capture processes for different applications corresponding to a wide range of CO₂ concentration. The objective of my research will be to develop a modelling framework that will design and optimize feasible combinations of capture technologies, including novel, advanced technologies that are not commercially available yet. Although some of these technologies are still in a preliminary development stage, we expect significant improvements, especially in the scale-up direction that will make these technologies available at the large scale in the short to medium term. Therefore, our analysis looking at the large-scale implementation is particularly important at this moment, as it can provide information about the technical and economic feasibility of such technologies and can give indications about how to improve them in terms of either material performances or process design to make them more competitive.

The optimization framework will find configurations that minimize total capture penalty and environmental impact indicators, while fulfilling the requirements for captured CO₂ recovery and purity. Importantly, the most performing configuration and operating conditions for the different cases will be assessed based on both techno-economic analysis and life cycle assessment via suitable algorithms, such as Bayesian optimization algorithm.

In particular, I intend to investigate novel combinations of membrane and adsorption processes (see Figure), to exploit the strengths of the two technologies: membranes are suitable to bulk separations, whereas adsorption can deal with very low CO₂ concentration and, at the same time, can produce almost pure CO₂ streams. The integration of such processes is highly promising for different applications, from direct air capture to concentrated point sources where high CO₂ purity is requested by the CO₂ sink. In the first case, adsorption process would increase the CO₂ concentration up to a moderate purity that will constitute the inlet purity for membrane process. In the second case, membranes would be responsible for most of the separation up to 70-80% CO₂ purity, while adsorption would increase the purity up to ~ 100%.

The proposed research will have high scientific relevance and practical impact, as it will give useful tools to identify the best strategies for different carbon capture applications. A successful demonstration of the techno-economic feasibility of integrated capture processes based on high-capacity sorption materials and highly permeable membranes will interest a broad community, from theoreticians to industrial stakeholders.

Current state of personal research

During my career, I have worked extensively on the development and implementation of models for the design, techno-economic assessment and optimization of various processes: clean energy technologies (reverse electrodialysis), thermal-based water desalination processes (e.g., multi-effect distillation), membrane-based water desalination processes (e.g., nanofiltration) and membrane-based gas separation processes. Therefore, I acquired a set of skills related to process modelling, multi-stage process design, process integration and profitability analysis. In addition, all the technologies and the systems I have investigated were applied to improve the sustainability of the industrial and energy sector, mainly by treating the liquid and gaseous effluents. Thus, I have acquired significant experience in devising sustainable integrated strategies to reduce the environmental impact of some challenging sectors.

During my Ph.D. at the Institute of Energy System Analysis at the German Aerospace Center, I implemented detailed techno-economic models of pre-treatment and desalination processes for highly-polluted liquid effluents, and then I integrated them into a simulation platform to test different treatment chains for industrial wastewater. The developed method was designed to be flexible and able to simulate treatment chains for different effluents.

During my Postdoc at the Laboratory of Advanced Separations at EPFL, I built a highly flexible modelling tool for gas separation processes, able to simulate multi-stage membrane processes with different configurations. I designed multi-stage membrane systems based on the performance parameters of the innovative ultra-thin graphene-based membranes manufactured in our lab. In particular, we performed for the first time the techno-economic assessment of a multi-stage membrane process based on ultra-thin nanoporous single-layer graphene membranes for post-combustion carbon capture ⁵. We optimized the system layout and the operating conditions to minimize the capture penalty: we found minimum values of 31.8 $/ton for final CO₂ purity of 90% and 34.4 $/ton for final CO₂ purity of 95%. These values are very competitive with those estimated for state-of-art absorption and polymeric membrane-based processes and significantly lower than those used in the CCUS supply chain optimization for the calculation of capture cost (50 $/ton). These results already show the big potentiality of novel capture technologies in making the CCUS supply chains much more economically attractive and energy efficient.

In addition, in collaboration with the Laboratory of Functional Inorganic Materials led by Prof. Queen at EPFL, I have developed a mathematical model for adsorption process for direct air capture based on the high-performance sorbent materials generated in the lab. Preliminary results already show the advantages of implementing hybrid strategies in terms of energy and costs reduction, as the total cost for direct air capture can go down to around 200 $/ton (much lower than the cost currently reported in the literature, between 600 and 1000 $/ton ⁶).

Teaching interest

I have a strong interest in teaching, and I believe that the modeling approaches, I am an expert of, are a crucial skill for future engineers. These methods provide innovators the means to root creative leaps and novel solutions within a techno-economic framework and real- world context. Therefore, I would be keen on teaching courses relevant to chemical process design, as well as on mathematical models and numerical methods applied to chemical engineering processes.

Finally, as I am convinced of the importance of showing the impact of theoretical knowledge in solving real-world problems, I would like to teach courses that connects basic science, as transport phenomena, with specific application, as membrane processes. Within these courses, the final objective would be to build step by step a model to design a large-scale process based on the transport phenomena principles.

Bibliography

1. d’Amore, F., Romano, M. C. & Bezzo, F. Carbon capture and storage from energy and industrial emission sources: A Europe-wide supply chain optimisation. J. Clean. Prod. 290, 125202 (2021).
2. Becattini, V. et al. Carbon dioxide capture, transport and storage supply chains: Optimal economic and environmental performance of infrastructure rollout. Int. J. Greenh. Gas Control 117, 103635 (2022).
3. Hasan, M. M. F., Baliban, R. C., Elia, J. A. & Floudas, C. A. Modeling, simulation, and optimization of postcombustion CO2 capture for variable feed concentration and flow rate. 2. Pressure Swing Adsorption and Vacuum Swing Adsorption Processes. Ind. Eng. Chem. Res. 51, 15665–15682 (2012).
4. Zanco, S. E. et al. Postcombustion CO 2 Capture: A Comparative Techno-Economic Assessment of Three Technologies Using a Solvent, an Adsorbent, and a Membrane . ACS Eng. Au 1, 50–72 (2021).
5. Micari, M., Dakhchoune, M. & Agrawal, K. V. Techno-economic assessment of postcombustion carbon capture using high-performance nanoporous single-layer graphene membranes. J. Memb. Sci. 624, 119103 (2021).
6. Sabatino, F. et al. A comparative energy and costs assessment and optimization for direct air capture technologies. Joule 1–30 (2021) doi:10.1016/j.joule.2021.05.023.