Particulate Matter Formation in Post-combustion CO_2 Capture Columns: Insights from Molecular Dynamics Simulations

摘要

The recent socio-political and climate changes have sparked tremendous interest in developing effective CO2 capture processes. Conventional post-combustion CO2 capture (PCCC) processes employ aqueous monoethanolamine (MEA) as a solvent; however, one of the major problems in the PCCC columns is the loss of a significant amount of the solvent in the form of particulate matter (PM). In spite of its importance, the formation of PM in a PCCC column has been overlooked, until recently. We herein analyze the process of the PM formation at a molecular level by underlining interactions between the participating components. Molecular dynamics (MD) simulations were performed on different systems consisting of CO2 and MEA, and also in the presence of other components and conditions that are typically present in a PCCC column. The simulation revealed the evolution of molecular clusters, which are in a separate phase than the gas present around, comprising all the gaseous MEA, SO2, and most of the CO2 and water vapor. We found the nucleation rate of the formed PM to be in the order of 10(30) cm(-3) s(-1) for the studied systems. The presence of water vapor enhanced the growth of the clusters, although the structure remained largely unchanged. On the other hand, although SO2 was all absorbed in the cluster, it did not alter the growth rate or the structure of the formed cluster. Interestingly, the results also showed formation of large molecular clusters even at a low degree of supersaturation because of strong CO2-water interactions. Taken together, the results are the first of the efforts to understand PM formation in a typical PCCC column based on molecular simulations, and the findings led to certain practical suggestions to reduce PM formation.