Dynamic study of direct CO ₂ capture from indoor air using poly(ethylenimine)-impregnated fiber sorbents

Abstract

Fiber sorbents made from commercial materials are tested in a variety of conditions to optimize direct air capture performance.

Abstract

Supported amine adsorbents are promising materials for direct air capture (DAC) of CO ₂ due to their high CO ₂ 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 CO ₂ 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 CO ₂ balanced by N ₂) and real indoor air (∼400–500 ppm CO ₂). 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 CO ₂ g _fiber ⁻¹ h ⁻¹) is quantified to identify conditions that could favor high rates of CO ₂ removal. The kinetics of steam-assisted CO ₂ desorption are studied, identifying achievable desorption times. Productivities of 1.2 mmol CO ₂ 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.