A Rigorous Integrated Approach to Model Electrochemical Regeneration of Alkaline CO₂ Capture Solvents

This work develops a rigorous model for electrochemical regeneration in Aspen Custom Modeler (ACM), designed to seamlessly integrate into ASPEN Plus, allowing to model complete carbon dioxide (CO₂) capture – electrochemical regeneration cycles on a single modelling platform. The modelling of CO₂ electrochemical cells has gained significant attention in CO₂ capture and utilization processes. This emphasizes the importance of modelling in driving the progress of CO₂ electrochemical cells which combines absorption by alkaline solvents and electrochemical solvent regeneration. In such process, potassium hydroxide (KOH, or other metal hydroxides) is used as a solvent for CO₂ capture. This process involves a series of chemical reactions that result in the formation of potassium carbonate (K₂CO₃) and potassium bicarbonate (KHCO₃). After CO₂ is captured through absorption, the K₂CO₃/KHCO₃ solution is directed towards the regeneration cell where an electrochemically driven pH swing takes place facilitating the desorption of CO₂. The cell’s primary objective is to lower the pH of the solution by generating protons at the anode, thereby moving its chemical equilibrium towards carbonic acid. Given the limited solubility of CO₂ in water, it desorbs once it reaches saturation. The residual solution can be reclaimed in the cathode compartment and recycled. Electrochemistry models are currently unavailable in popular simulation software like ASPEN Plus, thus making the development of integrated process models, in this case for CO₂ capture, more challenging. Here, we introduced a rigorous model to be applied in ACM/ASPEN Plus software to simulate the CO₂ regeneration process. The model’s validity was assessed against experimental measurements. Following this validation, the model was subsequently employed to design pilot plant campaigns for the Horizon 2020 project ConsenCUS.