Solvent absorption processes involve the selective transfer of carbon dioxide from a gas stream to a liquid stream, such as an amine, in an absorption column. The CO2 loaded liquid is then pumped to a regenerator where the temperature is increase of the pressure reduced to liberate the concentrated CO2 stream, and the lean solvent returned to the absorber. The liberated CO2 may be subsequently dried, compressed and stored in a storage reservoir.
Whilst this method has many advantages, the primary limitations are: the high energy requirements for the regeneration of the solvent and the compression of the CO2 which is approximately a 30% parasitic load, the impurities in the gas stream, namely SOx and NOx which may preferentially react with the solvent, reducing its capacity for CO2 or irreversibly causing the poisoning of the solvent.
Currently research is focused on addressing these issues, specifically developing solvents with a lower energy requirement, high CO2 capacities and high chemical stabilities.