Dynamic study of direct CO2 capture from indoor air using poly(ethylenimine)-impregnated fiber sorbents

Abstract

Supported amine adsorbents are promising materials for direct air capture (DAC) of CO₂ due to their high CO₂ capacity and relatively low energy requirement for regeneration. For a DAC process, it is essential to properly define operating parameters to achieve high sorbent productivity (amount of CO₂ captured per unit quantity of sorbent material over unit time). It is furthermore essential to understand the kinetic behavior of the process under the influence of various operating conditions such as the inlet air velocity, sorbent composition, and humidity to select an effective range of operating conditions to maximize sorbent productivity. Here, the dynamic behavior of a DAC process is probed using a fixed fiber sorbent contactor containing poly(ethylenimine) (PEI)-impregnated composite silica/cellulose acetate (CA) fibers. Experiments are conducted using both simulated air (398 ppm CO₂ balanced by N₂) and real indoor air (∼400–500 ppm CO₂). The experimental behavior of the fibers using simulated air and indoor air is compared, and the influence of the inlet air velocity on the breakthrough behavior is assessed. By changing operating conditions, the impact on the fiber sorbent productivity (mmol CO₂ g_fiber⁻¹ h⁻¹) is quantified to identify conditions that could favor high rates of CO₂ removal. The kinetics of steam-assisted CO₂ desorption are studied, identifying achievable desorption times. Productivities of 1.2 mmol CO₂ g_fiber⁻¹ h⁻¹ are obtained using an inlet air velocity of 1.1 m s⁻¹. Performance trends show that further increasing the inlet air velocity will likely lead to even higher productivities.