Carbon dioxide removal using carbon monolith as electric swing adsorption to improve indoor air quality

This study explores the feasibility of excess CO2 removal from living spaces. Electric-swing adsorption (ESA) splits ambient air into two portions: waste gas for removal and recovery air for recycling back into the living space. Ambient air holds dilute but unacceptable concentrations of CO2 (selected as 3000 ppm in this study), while the waste gas contains higher concentrations. The concentration in the recovered air is below ambient levels. Carbon monolith functions as an adsorbent and direct heating resistance material. Cooling is accomplished by the convective flow of ambient air. The computational model and preliminary tests establish ways to quantify the separation characteristics and thermal response of the monolith. Based on the ESA steps identified with the single monolith, a prototype of a two-bed device is built to demonstrate the cyclical operation of multiple beds with phase shift. The electrical energy requirement for treating air containing 3000 ppm CO2 is in the range of 57.8 kJ/(m3 air) under the selected temperature swing of 20 °C. This requirement indicates that further refinement is essential for practical application. However, the overall findings are in agreement with the well-established fact that the concentration of CO2 is the most important factor affecting energy consumption, especially when the mole fraction of CO2 is less than 0.15.