Reactive absorption of CO2 into enzyme accelerated solvents: From laboratory to pilot scale

CO2 capture could contribute to a reduction of CO2 emissions by decreasing CO2 concentrations in flue gas streams of fossil fuelled power plants. State of the art technology for CO2 capture is reactive absorption using monoethanolamine (MEA) as a solvent, which requires a high energy demand for solvent regeneration in a continuous process. This study investigated the ability of the biocatalyst carbonic anhydrase, to significantly increase the absorption rate when combined with reactive solvents. Based on laboratory scale experiments the proof of chemical capability was evaluated for different solvents. CO2 absorption rates of 30 wt.% MEA, 30 wt.% N-methyldiethanolamine (MDEA), 30 wt.% diethylethanolamine (DEEA) and 10 wt.% potassium carbonate (K2CO3) were measured with the addition of carbonic anhydrase (0.2 wt.%). Aqueous solutions of 30 wt.% MDEA as well as 30 wt.% K2CO3 were identified as promising solvents whose CO2 absorption rate was accelerated by the enzyme, as the addition of 0.2 wt.% carbonic anhydrase led to an increase of the absorbed mole flow by a factor > 4. Next, the technical feasibility of the enzyme-solvent concept was tested in packed columns to check for transferability of laboratory scale performance to pilot scale (diameter: 56 mm, height: 2.3 m, Sulzer BX gauze packing). The increase of the absorbed mole flow in pilot scale in the presence of biocatalyst was in good accordance with the laboratory scale experiments. No undesired effects such as foaming or aggregation were observed. Subsequently, mass transfer parameter determination was performed for enzyme-solvent combinations in a wetted wall column. Together, the data presented in this study enables for the first time, the application of rigorous models for conceptual process design for biocatalyst-accelerated CO2 capture.