Publication – Development of a Validated Rate-Based Model

Abstract

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 𝑚𝑜𝑙𝐶𝑂2/𝑚𝑜𝑙𝐴𝑀𝑃+𝑚𝑜𝑙𝑃𝑍. 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.

Authors: Diego Morlando, Ying Zhang,  Shu Wang, Hanna K. Knuutila.