Advancing promoter enhanced KOH-based carbon capture with electrochemical regeneration

Abstract

This thesis investigates a novel CO2 capture technology utilizing an alkaline solvent (KOH) for chemical absorption with electrochemical regeneration. A key challenge in this technology is the slow CO2 absorption kinetics of KOH-based solvents. To address this, a systematic screening methodology was developed to identify potential promoters capable of enhancing CO2 absorption rates. Promising candidates, including piperazine (PZ), glycinate, carbonic anhydrase (CA), and [Bmim][Ac], were evaluated based on their kinetic enhancement potential, electrochemical compatibility, and oxidative stability. The oxidative degradation behavior of PZ and glycinate in KOH-based blends was investigated to assess their long-term stability. The study revealed that both promoters undergo severe oxidative degradation, with glycinate exhibiting higher degradation rates than PZ. The presence of CO2 was found to inhibit degradation by reducing the concentration of hydroxyl ions. Comprehensive process modeling and techno-economic analysis were performed for the benchmark CESAR1 and the novel ConsenCUS carbon capture technologies. The results highlighted the potential of the ConsenCUS technology, particularly with the integration of CA as a promoter. The integration of CA demonstrated significant improvements, including a 6.5% reduction in solvent usage, a 50% decrease in absorber height, a 6.40% reduction in regeneration energy requirements, an 11% decrease in total capital requirement, a 4.4% decrease in operating cost, and a 10.7% decrease in the cost of CO2 avoided. Despite requiring 25% less capital investment than CESAR1, the ConsenCUS technology with CA shows mixed economic performance due to competing cost factors. The primary economic trade-off centers on capital costs versus operational costs: while ConsenCUS benefits from lower capital requirements and reduced thermal energy needs, it incurs 30% higher annual operational costs primarily due to electricity requirements for electrochemical regeneration. The economic comparison reveals minimal differences in key metrics, with CESAR1 showing slight advantages: 23 €/tonne lower capture costs, 3.8 €/tonne lower avoided costs, and 6 €/tonne lower steam costs compared to the consenCUS case. These marginal variations suggest that the economic viability of ConsenCUS technology is primarily controlled by electricity costs and the efficiency of the electrochemical regeneration process. The technology demonstrates economic competitiveness when paired with effective promoters like CA, and its commercial viability can be enhanced through future innovations targeting electrochemical process optimization and electricity cost reduction.