Experimental Campaign with a 1 Kg/Day Fixed Bed Dac Unit Using Solid Amines

Abstract

Direct air capture is an important technology to enable net zero CO2 emission technologies. It provides a sustainable carbon source, namely CO2 from air, to use as feedstock for various CO2 utilization technologies, such as cultivation of microalgae. A direct air capture pilot unit is designed and constructed at the University of Twente with a targeted capacity of 1 kgCO2/day. It utilized adsorption with supported-amine sorbents in four parallel fixed bed reactors. This study evaluates the performance of the pilot unit during continuous operation at a microalgae cultivation facility where the captured CO2 is used as feedstock for microalgae cultivation. In the reported campaign, 49 consecutive adsorption-regeneration cycles were performed with a total operation time of more than one week. On average, the CO2 production capacity matched the targeted capacity at 1.0 kgCO2/day with a CO2 working capacity of 0.57 molCO2/kgs. The energy duty was estimated at 19 MJ/kgCO2, with sensible heat for the regeneration at increased temperature is the major contributor. A clear day-night difference was observed. The productivity increased during the night when the temperature is low and relative humidity is high. Algae cultivation was carried out in a 300-litre tubular photobioreactor with pH control via injection of CO2. During the entire experimental campaign, the pH was regulated successfully using the CO2 harvested from air. Overall, we conclude that providing concentrated CO2 by locally using direct air capture as sustainable carbon source for the cultivation of microalgae is demonstrated successfully and is ready for further upscaling and implementation.