Laboratory-to-pilot evaluation of CO2 absorption by aqueous KOH in packed columns

Electrochemical regeneration techniques have renewed interest in aqueous potassium hydroxide (KOH) solution as a potential absorbent for post-combustion CO 2 capture. However, absorber performance at different scales and its sensitivity to the loading of the regenerated solvent remain underexplored, primarily due to the traditional reliance on thermal regeneration methods which are not kinetically favorable to KOH. This study evaluates the CO 2 capture behavior for aqueous KOH solutions and performance in terms of achieved CO 2 capture efficiencies and rich (CO 2 ) loading of the solvent. Absorption experiments were conducted using both laboratory-scale (4.2 Nm 3 /h gas flow capacity) and pilot scale packed absorbers (40 Nm 3 /h), with three lean loading levels (0, 0.25 and 0.6 mol CO 2 /mol K + ) to establish baseline performance. The absorbers were operated to pinpoint conditions allowing for 100% CO 2 capture efficiency from simulated flue gas. Higher CO 2 capture efficiency was obtained at higher ratios of solvent flow rate to gas flow rate, corresponding to higher gas residence time. Regardless of K + molality and lean loading (0.25–0.6), the obtained rich loading (up to 0.85) is closely related to n ̇ CO2 / n ̇ OH - ratio, following a logarithmic trend. The results from the pilot-scale absorber were in excellent agreement with those from the laboratory-scale, reaching comparable rich loading at full capture. The consistency across scales underscores the potential for commercial-scale application and viability of KOH as a solvent for post-combustion CO 2 capture. These findings provide a comprehensive understanding of the CO 2 absorption process using KOH solution, which is crucial for advancing electrochemical CO 2 absorption technology and designing carbon capture plants.