A simulation-based evaluation of a direct air capture system with coupled electrochemical and thermochemical processes

As the climate change has become more pronounced, the limitations around mitigation strategies such as renewable energy deployment and energy efficiency improvements are becoming more visible. While these approaches are indispensable, they are unlikely to achieve the full-scale decarbonization required to meet global climate targets alone. Consequently, technologies that actively remove carbon dioxide from the atmosphere, known as Negative Emission Technologies (NETs), are gaining recognition as essential components of a comprehensive and across-the-board climate strategy. This study focuses on Direct Air Capture (DAC) technology, one of the NETs. A novel system for CO2 capture from the atmosphere that integrates electrochemical and thermochemical processes is studied. The system captures CO2 using an aqueous NaOH solution, regenerates the sorbent electrochemically via Na2CO3 electrolysis, and releases CO2 through the thermochemical decomposition of NaHCO3. The process offers three key advantages: it produces valuable by-products such as hydrogen and oxygen; it relies primarily on electricity, facilitating integration with renewable energy sources; and it requires only low-temperature heat, enabling effective coupling with waste heat recovery solutions. The system was modeled using Aspen Plus and designed to support a CO2 methanation process for synthetic natural gas (SNG) production, taking advantage of the combined CO2 and H2 production. The simulation aimed to assess the energy demand of the process and identify key operational and design parameters. A preliminary techno-economic evaluation was conducted to estimate the CO2 capture cost of the process and assess the economic viability of the system. The analysis explored the influence of economic parameters and components cost, with particular attention to the benefits of hydrogen co-production. The findings contribute to a broader understanding of how integrated DAC technologies can support scalable and cost-effective carbon removal, especially in applications where both CO2 and H2 are valuable inputs.