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

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 N-2) and real indoor air (& SIM;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.