Experimental study of CO₂ capture from air via steam-assisted temperature-vacuum swing adsorption with a compact kg-scale pilot unit

CO2 from air is one of the few sustainable carbon sources. Technologies to capture and concentrate this CO2 are being demonstrated on an increasingly large scale. Adsorption using supported-amine sorbent via a temperature-vacuum swing adsorption process is such technology. This work provides a detailed description of this technology and identifies options for process optimization based on experimental results. For this, a novel kg-scale pilot unit was designed and constructed with four parallel fixed bed reactors. Reproducible results were obtained during the complete experimental campaign of several weeks. The base case scenario led to a productivity of 1.3 kgCO2 per day or 0.27 kgCO2 kgs^-1 per day with an energy consumption of 14.5 MJ kgCO2^-1. The sensible heat of sorbent and inert material was the major contributor to the energy duty, while gas-solid contacting only accounted for a minor part. Various optimization options were identified based on the experimental results. Including these options, this potentially reduces the energy consumption of this direct air capture process to 5.1 MJ kgCO2^-1.