Absorption of carbon dioxide into novel single and blended amine solvents

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Over the last few decades, the increasing concentration of carbon dioxide (CO2) in the atmosphere has contributed adversely to the environment and has been a subject of worldwide attention. The capture of CO2, which is one of the main greenhouse gas (GHG), currently represents an essential step in the performance of electric power stations, petroleum refineries, chemical fertilizer plants, coal gasifiers, cement factories, and the steel industries. In the recent days, gas scrubbing using activated aqueous alkanolamine solutions is the most reliable retrofit option for post combustion CO2 capture. The present study investigates a novel activator, bis(3-aminopropyl)amine (APA), which can be an effective mode of eliminating CO2 from flue gas. The kinetics of CO2 absorption into chosen aqueous solution of APA was carried out at 303, 308, 313 and 323 K over a concentration range of 0.1-0.5 kmol m-3 and at different CO2 partial pressure. A wetted-wall column absorber was used for the kinetics measurement. The reaction mechanism of CO2 with primary and secondary amines (zwitterionic mechanism) is described and accordingly the experimentally obtained kinetic data are interpreted. A qualitative nuclear magnetic resonance [NMR (1D and 2D)] spectroscopy method has been applied to develop the reaction scheme for novel aqueous APA with CO2. The kinetic rate parameters were investigated according to the pseudo-first-order condition for CO2 absorption at each experimental condition. The values of second-order rate constant, k2-APA and reaction rate with CO2 reported in this study were higher than many existing amine activators like ethylenediamine (EDA), N-(2-aminoethyl ethanolamine (AEEA), piperazine (PZ), 2-(1-piperazinl)-ethylamine (PZEA), etc. Two blended solvents such as aqueous blend of APA with N-Methyldiethanolamine (MDEA) and 2-Amino-2-methyl-1-propanol (AMP) were considered for potential use in CO2 capture. It was observed that the enhancement factor increases significantly in comparison to single amine (aqueous MDEA) solutions when the APA concentrations increased in the blends with MDEA.
Supervisor: Bishnupada Mandal