The role of impurities in CCS from pilot capture plants to sequestration sites—A review

Abstract

We investigate the presence and effects of impurities in the carbon capture, transportation and sequestration (CCS) technology chain. We start from the composition of flue gases and investigate the subsequent treatment methods, the technical and operating characteristics of solvent-based CO₂ capture pilot plants, the compositions of the absorber and desorber outlet streams and the CO₂ stream specifications for downstream compression, transportation and storage processes. We present public data from 40 campaigns in large capture pilot plants and 20 sets of specifications for CO₂ transportation and underground storage from national agencies, companies and projects worldwide. We identify and categorize the impurities depending on the flue gas source and the solvent type. The most commonly identified emissions in the treated gas are ammonia (NH₃) and the solvent used in each plant. Monoethanolamine (MEA) emissions are higher compared to those of the other amine solvents. Sulfur and nitrogen oxides (SO_x, NO_x) are the most investigated impurities, whereas oxalate and formate are the most reported degradation products. Regardless of the solvent used, NO_x, NH₃ and aldehydes are reported in the CO₂ gas product stream of most campaigns. The specifications for transportation and sequestration have similarities, with those of Northern Lights being stricter.