Model validation and simulation issues for carbon dioxide reactive absorption with mixed amines

Abstract

Capture of CO2 form point emission sources is a dramatically urgent task to limit the current impact of the power generation sector and of industrial fields classified as “hard to abate”. Many challenges are still present from the design point of view to define correctly the properties (chemical, physical, rheological) of the used solvents. These affect the sizing and rating of absorption devices and the regeneration systems. In turn, this jeopardises the prediction of feasibility of capture plants and the relative economics.In this work, the modeling steps commonly applied to calculate the CO2 absorption into a mixed amine-water solvent have been exemplified starting from ground data. First, several open datasets of equilibrium and rheological quantities have been reviewed. This allowed the selection of the thermodynamic parameters that give the best compromise between physical and chemical equilibria. Then an adsorption tower was dimensioned, checking the impact that different tunable parameters have on the calculation outcome. Furthermore, two absorber-stripper tandem columns have been simulated in order to reproduce available plant data. The performed rate-based simulations find a convergence point only for proper liquid/gas ratios, and are significantly slowed-down as the number of kinetic reactions increases respect to instantaneous equilibrium ones.Results demonstrate that the CO2 loading into a solvent depends crucially on the partial pressures of all the species and on setting the mixture at fixed volume or pressure. This data collection and validation was exemplified following the whole procedure, as a guidance for technicians in the field. An example of gas flowrate up to 160 kg/h, with CO2 content 15 – 20 vol% and for CO2 capture efficiencies up to 90%.