How does structured adsorbent channel heterogeneity influence the efficiency of adsorptive CO2 capture?

• Monoliths allow a higher productivity and a lower energy demand than a fixed bed. • Process performance becomes less dependent of gas velocity with a monolith. • Defects in monolith channels decrease CO 2 capture performance. Adsorbent monoliths are increasingly studied for carbon capture applications. These monoliths often contain a distribution of channels, due to defects in the die or inhomogeneous drying. The effect of such heterogeneities on CO2 capture process performance is not well investigated. In this work, the performance of a fixed bed, an ideal monolith and monoliths containing a wall size distribution are compared in a vacuum swing adsorption (VSA) cycle using a modelling approach. Using a monolith allows for a higher productivity (0.78 mmol/kgs) compared to a fixed bed (0.68 mmol/kgs) and a lower energy demand (190 kWh /tonne CO2 versus 320 kWh/tonne CO2). When the monolith contains a distribution of wall sizes, the process performance decreases. The recovery drops from 81 % to 68 %, the throughput drops from 0.78 mmol/kgs to 0.65 mmol/kgs and the energy demand increases from 190 kWh/tonne CO2 to 251 kWh/tonne CO2 for the widest distribution. Defects can severely impact performance.