The effect of impurities in captured CO2 on the distribution of liquefaction and purification costs

Carbon Capture, Utilisation, and Storage is an unavoidable tool in reducing greenhouse gas emissions from energy and industrial sectors. Shared transport infrastructures are necessary to implement the technology on large-scale at acceptable costs. The CO₂ quality varies with different emitters, and if these should use a common infrastructure, it is important to understand the economic effects of the impurities throughout the Carbon Capture value chain. The captured CO₂ is typically purified and liquefied using a conditioning system prior to transportation. This study performs an exergoeconomic analysis of a conditioning process considering four different feed gas compositions. The system was modelled using a chemical process modelling tool, and energy and economic analyses were performed. Exergy was used as a basis for distributing the costs associated with reaching the liquid state and the correct quality, respectively. It was found, that the various feed gas compositions did not significantly affect the costs directly associated with liquefaction, which remained at 18 EUR/(t CO₂) to 21 EUR/(t CO₂). Removal of the incondensable gases accounted for between 0.1 EUR/(t CO₂) to 18.7 EUR/(t CO₂) and depended on the feed gas composition. Higher costs associated with water removal through cooling and higher losses during the distillation process were observed when more impurities were present in the feed gas. This resulted in increased purification costs. The results show that quality requirements from off-takers and transport operators can impose economic drawbacks for emitters. It emphasises the relevance of considering which CO₂ sources are best suitable for different off-takers when impurity constraints are imposed.