Screening tests of new hybrid solvents for the post-combustion CO2 capture processby chemical absorption

Abstract

This study focused on the screening of new hybrid solvents (mixture of a chemical (usually an amine) and a physical (ether, alcohol, etc.) solvent) for the post-combustion CO2 capture process by chemical absorption. Such scrubbing solutions aim at combining the advantages of the two components, namely: a low regeneration energy and a high absorption capacity of the physical solvent at intermediate CO2 partial pressures, a better absorption performances of the chemical solvent at low CO2 partial pressures and also high absorption kinetics due to chemical reactions with CO2. The innovative aspect of our approach was based on the use of acetals as physical components of the hybrid solvent. The purpose of our study was to characterize and compare these new hybrid solvents in terms of absorption and regeneration performances using two types of screening tests. Different blended solutions (composed of a conventional amine such as monoethanolamine (MEA), diethanolamine (DEA), 2-amino-2-methyl-1-propanol (AMP)) and an acetal compound such as 2,5,7,10-tetraoxaundecane (TOU) were tested. Regarding the absorption performances, a double stirred cell reactor was used to compare the absorption efficiencies of the solvents at 298 K. It was observed that the addition of the acetal compound improves significantly the absorption efficiencies, especially at the beginning of the batch absorption test, namely at low CO2 loadings of the solution. Meanwhile, regeneration tests were performed using a regeneration cell allowing to compare the regeneration efficiency of the solvents at fixed heating power (600 W). The higher cyclic capacities and better regeneration efficiencies with acetals base solvents were also highlighted. Globally, this work confirms through this first step that new hybrid solvents, composed of amine(s) and acetal, could be a very promising alternative to classical solvents. NomenclatureA [%] CO2 absorption ratio of the scrubbing solution CCO2 [mol m -3 ] CO2 concentration of the scrubbing solution GCO2,in [m³ s -1 ] CO2 gas flow rate at the inlet of the gas-liquid contactor GCO2,out [m³ s -1 ] CO2 gas flow rate at the outlet of the gas-liquid contactor IC [kg m -3 ] inorganic carbon content of the scrubbing solution t [s] time yCO2,in [vol.%] CO2 volume fraction of the gas phase at the inlet of the gas-liquid contactor yCO2,out [vol.%] CO2 volume fraction of the gas phase at the outlet of the gas-liquid contactor ηregen [%] regeneration efficiency of the scrubbing solution