CO2 absorption in biphasic solvents with enhanced low temperature solvent regeneration

Reductions of capital cost and energy consumption are the key challenges for the development of amine-based CO2 capture technology from flue gases. Lipophilic amine solvents exhibit a thermomorphic phase transition upon heating, leading to auto extractive behaviour, which intensifies desorption at temperatures well below the boiling point of the aqueous solutions. Solvent screening experiments in a 100 mL bubble column with CO2 absorption at a partial pressure of 19.4 kPa and desorption with N2 gas stripping or magnetic agitation demonstrate that those solvents have a regeneration temperature of less than 80 °C combined with a high net loading capacity of 3.34 mol−CO2/L. This permits the use of low value and even waste heat for desorption purposes and can thus improves the process economics for CO2 capture in industrial complexes. The new biphasic solvent system was evaluated in a newly constructed benchmark unit, which is comprised of an absorber column (2.5 cm in diameter and 145 cm in height) filled with high efficiency structured packing and a 500 mL stirred-tank as regenerator. In order to observe the phase transition phenomenon, the absorber and regenerator were made of glass. Three solvent formulations were tested at various regeneration temperatures ranging from 50 to 95 °C. A maximum 100% recovery was attained with certain solvent formulations at a regeneration temperature around 90 °C with total gas flow rate of 300 NL/hr (85% N2 and 15% CO2).