Temperature optimal control and entropy–enthalpy compensation phenomenon in the CO2 capture with DEA/PEG200 as absorbent

Abstract

The traditional chemical absorption method using alkanolamine aqueous solution for carbon dioxide (CO₂) capture suffers from high volatility and high energy consumption for regeneration. In the present work, a mixed absorbent comprising diethanolamine (DEA) and polyethylene glycol 200 (PEG200) with high thermal stability and low specific heat capacity was designed for CO₂ absorption. Absorption capacity was measured at different temperatures and pressures; the first-order kinetic and bimolecular reaction thermodynamic models were also developed, and relative parameters were obtained. An optimal simulation of the absorption process was carried out. Based on the optimal control (OC) theory and kinetic parameters, the optimal absorption temperature of the absorption process at a certain fixed time was obtained, which decreases with the increase of time. Moreover, the optimal absorption temperature curve can further enhance the absorption capacity. Furthermore, an entropy–enthalpy compensation phenomenon was found for the capture of CO₂ with different absorbents.