Structure design of fiber sorbents for maximizing direct air capture efficiency

Abstract

As carbon dioxide ($CO_2$) emissions have increased rapidly since the industrial revolution, the concentration of carbon dioxide in the atmosphere has risen to 416 ppm in 2021, which has caused the average surface temperature of the earth to rise by 1.2 degrees compared to 1920. As a result, technologies for reducing the concentration of carbon dioxide in the atmosphere have been developed. In the past, carbon capture and storage technologies have been integrated into fossil fuels, steel and cement manufacturing facilities to stop the emission of $CO_2$. Recently, direct air capture (DAC) technology, which lowers the concentration of carbon dioxide in the atmosphere by directly removing carbon dioxide from air has been in the spotlight. One of the main benefits of DAC technology is that the location of the DAC plant is not constrained due to the ubiquitous nature of carbon dioxide. However, DAC technology has an extremely high process cost when compared to other carbon dioxide removal technologies. Therefore, for an effective DAC process, the absorption and adsorption system have a strong $CO_2$ affinity in an a very low $CO_2$ partial pressure of about 400 ppm. DAC process handles a huge amount of air, so the mass transfer of the air within the system should be excellent, and the pressure drop must be kept to a minimum, which is possible to lower the fan cost of the system. Given that the adsorbent used in DACs has a significant affinity to carbon dioxide, the regeneration process must be carried out as an energy-efficient swing process, and the source of energy for regeneration should be taken into accounts. Additionally, the process cost of the DAC can be significantly decreased when the system for it can be mass-produced affordably. The significance of carbon dioxide removal technology was discussed in Chapter 1, and the fiber sorbent employed in this study, the fabrication process, and structural benefits were introduced in Chapter 2. In Chapter 3, we concentrated on high $CO_2$ adsorption capacity and airflow optimization in the system under DAC conditions. a metal-organic framework, one of the best solid adsorbents for $CO_2$ adsorption at DAC conditions, was impregnated into a porous polymer support with the goal of creating high-performance fiber sorbent and optimizing air flow in the contact system. In Chapter 4, the electric-vacuum swing adsorption method was taken into consideration for effective solid sorbent regeneration in DAC conditions. A novel electrified fiber sorbent that was suitable for use with the swing process and capable of Joule heating was created by dip coating process of metal on surface of the fiber. The metal with exceptional conductivity such as silver (Ag) was used to maximize the Joule heating effect while requiring less energy. The issue with the supply of regeneration energy for DAC will finally be resolved thanks to the electrified fiber sorbent’s low-power regeneration drive, which raises the prospect of utilizing renewable energy sources like solar or wind power. In this study, to reduce the cost of the DAC process, the various fiber sorbents with a novel structure has been developed and the resulting high-performance fiber sorbents will introduce a new paradigm in the field of DAC technology.