Chemical absorption of CO2 into an aqueous piperazine (PZ) solution: development and validation of a rigorous dynamic rate-based model

Abstract

Carbon dioxide (CO₂) chemical absorption into reactive solvents, is regarded as a proven technology to mitigate global warming aversive effects. Reliable design, modeling and simulation of the regenerative amine-based chemical absorption/desorption units, are essential in CO₂ capture from the flue gas of fossil-fuel fired power plants. For this purpose, non-equilibrium rate-based stage models (NEQ), are recognized as a state-of-the-art approach compared to traditional equilibrium ones (EQ). In this paper, a modified non-equilibrium dynamic rate-based stage model, was developed to model CO₂ chemical absorption into an aqueous solution of piperazine (PZ: C₄H₁₀N₂), a highly reactive cyclic secondary diamine. In the developed rigorous model, the effect of non-ideal flow hydrodynamics, i.e. deviation from ideal plug flow regime, was taken into account via incorporation of the liquid phase axial dispersion/mixing in the absorber packed column. Due to the important role of the kinetics and CO₂ mass transfer rate correlations in the prediction ability of the ultimate rat-based model, our newly developed correlations for CO₂–PZ–H₂O reactive system (Norouzbahari et al., 2015a) were employed, avoiding a non-exact enhancement factor (E) method with a pseudo-first-order (P.F.O) simplifying assumption. The thermodynamic non-idealities in both the liquid and gas phases, were considered via applying a proper (γ − φ) approach coupled with our proposed model in our recent contribution (Norouzbahari et al., 2015b), as well. The developed model, was successfully evaluated against the experimental data and a close agreement between the simulated results and experimental values, justifies its validity.