Removal of carbon dioxide from flue gases with aqueous MEA solution containing ethanol

Adding ethanol to an aqueous amine solution offers several advantages for post-combustion CO2 capture. The equilibrium isotherms at higher temperatures shift towards lower loadings, leading to an easier desorption. At constant temperature in the desorber bottom, the desorber pressure is increased, leading to energy savings in the CO2 compression. Alternatively, at constant desorber pressure, the temperature in the desorber bottom is decreased, leading to a smaller efficiency drop of the power plant. Furthermore, the absorption rate of CO2 is enhanced by adding ethanol. In the present work, the potential of using ethanol as a co-solvent for a 0.3 g/g aqueous monoethanolamine (MEA) solution is assessed based on simulations with an equilibrium stage model. A major drawback is the volatility of ethanol. The recovery of ethanol can be achieved using a water scrubber and subsequent stripping. The recovered ethanol vapor is sent directly to the desorber for heat integration. The process with ethanol recovery results in an increased complexity of the capture plant, difficulties in controlling the water balance and higher investment costs and offers, if any, only a moderate energetic advantage. The process concept could, however, be used for other co-solvents with similar properties as ethanol but lower vapor pressures.