Development of a Validated Rate-Based Model for CO₂ Absorption in Aqueous 2-Amino-2-methyl-1-propanol and Piperazine Blends Using Aspen Plus

In this work, we developed a new e-NRTL thermodynamic framework for CO₂ absorption in aqueous mixtures of 2-amino-2-methyl-1-propanol (AMP) and piperazine (PZ) in Aspen Plus. The e-NRTL AMP/PZ/H₂O/CO₂ model was fitted on experimental data covering a range of AMP concentration from 12 to 48 mass % and PZ concentration from 2 to 26 mass %, temperature from 20 to 160 °C and CO₂ loading from 0 to 1.03 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mfrac><mml:mrow><mml:mi>m</mml:mi> <mml:mi>o</mml:mi> <mml:msub><mml:mrow><mml:mi>l</mml:mi></mml:mrow> <mml:mrow><mml:mi>C</mml:mi> <mml:msub><mml:mrow><mml:mi>O</mml:mi></mml:mrow> <mml:mrow><mml:mn>2</mml:mn></mml:mrow> </mml:msub> </mml:mrow> </mml:msub> </mml:mrow> <mml:mrow><mml:mi>m</mml:mi> <mml:mi>o</mml:mi> <mml:msub><mml:mrow><mml:mi>l</mml:mi></mml:mrow> <mml:mrow><mml:mi>A</mml:mi> <mml:mi>M</mml:mi> <mml:mi>P</mml:mi></mml:mrow> </mml:msub> <mml:mo>+</mml:mo> <mml:mi>m</mml:mi> <mml:mi>o</mml:mi> <mml:msub><mml:mrow><mml:mi>l</mml:mi></mml:mrow> <mml:mrow><mml:mi>P</mml:mi> <mml:mi>Z</mml:mi></mml:mrow> </mml:msub> </mml:mrow> </mml:mfrac> </mml:math> . The model predicts the CO₂ solubility, as partial pressure of CO₂, over aqueous AMP/PZ solutions within an absolute average relative deviation (AARD) of 26.3%, the total pressure of the system with an AARD value of 7.0%, the heat of absorption of CO₂ with an AARD value of 10.2%, and the estimated free CO₂ concentration with an AARD value of 13.1%. The model gives a good representation of liquid speciation as a function of the CO₂ loading and amine concentration. The model shows good predictions of the CO₂ solubility over aqueous AMP/PZ solutions at relevant absorber, stripper and water wash amine concentrations and temperatures. The developed e-NRTL model, in combination with mass transfer and CO₂ absorption kinetics modeling, is validated with two pilot campaigns: one at the University of Kaiserslautern and one at the Technology Centre of Mongstad. The developed rate-based model predicts the CO₂ capture, rich loading, and specific reboiler duty within 5% absolute average relative deviation.