Molecular to Process Scale: A Review of Holistic Direct Air Capture Contactor Design

Abstract

Air-sorbent contactors are an essential part of direct air capture processes. Their design can have a great influence on the process energy demand and efficiency. Three aspects of this design have been identified and differentiated by length scale. On a molecular scale, the adsorption sites are defined by the chemisorbent-containing molecules, generally amines. The support of these amines defines the second length scale and plays an important role in mass and heat transfer. These two length scales have been studied in detail in academic literature and a short overview is given. The third length scale is the process scale, or contactor module scale. Together with the first two length scales, it is necessary to characterize the third to perform adequate process optimization. Research on this third length scale is scarce in academic literature, though it has been researched in industry. The direction of research tends towards structured sorbents due to their ability to process large volumes of air and academic research in this area should be expanded.