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Kinetic and thermodynamic analysis of high-pressure co2 capture using ethylenediamine: Experimental study and modeling

Abstract:

One of the alternatives to reduce CO<inf>2</inf> emissions from industrial sources (mainly the oil and gas industry) is CO<inf>2</inf> capture. Absorption with chemical solvents (alkanolamines in aqueous solutions) is the most widely used conventional technology for CO<inf>2</inf> capture. Despite the competitive advantages of chemical solvents, the technological challenge in improving the absorption process is to apply alternative solvents, reducing energy demand and increasing the CO<inf>2</inf> captured per unit of solvent mass. This work presents an experimental study related to the kinetic and thermodynamic analysis of high-pressure CO<inf>2</inf> capture using ethylenediamine (EDA) as a chemical solvent. EDA has two amine groups that can increase the CO<inf>2</inf> capture capacity per unit of solvent. A non-stirred experimental setup was installed and commissioned for CO<inf>2</inf> capture testing. Tests of the solubility of CO<inf>2</inf> in water were carried out to validate the experimental setup. CO<inf>2</inf> capture testing was accomplished using EDA in aqueous solutions (0, 5, 10, and 20 wt.% in amine). Finally, a kinetic model involving two steps was proposed, including a rapid absorption step and a slow diffusion step. EDA accelerated the CO<inf>2</inf> capture performance. Sudden temperature increases were observed during the initial minutes. The CO<inf>2</inf> capture was triggered after the absorption of a minimal amount of CO<inf>2</inf> (~10 mmol) into the liquid solutions, and could correspond to the “lean amine acid gas loading” in a typical sweetening process using alkanolamines. At equilibrium, there was a linear relationship between the CO<inf>2</inf> loading and the EDA concentration. The CO<inf>2</inf> capture behavior obtained adapts accurately (AAD < 1%) to the kinetic mechanism.