Kinetic and Thermodynamic Analysis of High-Pressure CO2 Capture Using Ethylenediamine: Experimental Study and Modeling

Josselyne A Villarroel,Alex Palma-Cando,Marvin Ricaurte,Alfredo Viloria

doi:10.3390/en14206822

Abstract

One of the alternatives to reduce CO2 emissions from industrial sources (mainly the oil and gas industry) is CO2 capture. Absorption with chemical solvents (alkanolamines in aqueous solutions) is the most widely used conventional technology for CO2 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 CO2 captured per unit of solvent mass. This work presents an experimental study related to the kinetic and thermodynamic analysis of high-pressure CO2 capture using ethylenediamine (EDA) as a chemical solvent. EDA has two amine groups that can increase the CO2 capture capacity per unit of solvent. A non-stirred experimental setup was installed and commissioned for CO2 capture testing. Tests of the solubility of CO2 in water were carried out to validate the experimental setup. CO2 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 CO2 capture performance. Sudden temperature increases were observed during the initial minutes. The CO2 capture was triggered after the absorption of a minimal amount of CO2 (~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 CO2 loading and the EDA concentration. The CO2 capture behavior obtained adapts accurately (AAD < 1%) to the kinetic mechanism.

Highlights

CO2 is a greenhouse gas that has a high impact on atmospheric pollution
EDA has two amino groups that promote affinity and reactivity towards CO2; this trend is not consistent with the results reported by Gomes et al [61], where DEA and MEA achieved greater absorption capacity compared to EDA, possibly because the equilibrium conditions were not reached under their experimental setup
Initial testing of the solubility of CO2 in water allowed the validation of the experimental setup and the proposed methodology, demonstrating that it was possible to reach equilibrium conditions in short times (

Summary

Introduction

CO2 is a greenhouse gas that has a high impact on atmospheric pollution. In 2020, the global CO2 emissions were estimated at 30.6 Gt [1], and sustained growth (approximately 0.43 Gt/y) is expected until 2040 [2]. CO2 capture using chemical solvents under high-pressure conditions is a typical process in the oil and gas industry—in natural gas processing operations—to meet quality specifications or reduce operational problems due to the presence of CO2 in pipelines and equipment [33]. Many studies of CO2 capture at the laboratory scale are carried out to improve and identify new solvents; many of them are performed in low-pressure experimental systems, and their results could differ significantly from those obtained in high-pressure systems. To the best of our knowledge, an integrated study focused on the kinetics and thermodynamics of CO2 capture using EDA in aqueous solutions has not been reported using high-pressure systems. An experimental study is presented that aims to delve into the kinetic and thermodynamic analysis of the high-pressure CO2 capture process using EDA. A kinetic model that allows for the determination of the CO2 loading vs. time and the apparent absorption rate performance was proposed

Materials

Experimental Setup

Data Processing

CO2 Solubility Testing

CO2 Capture Using EDA

Summary and Outlook