CO2 capture using monoethanolamine solutions : development and validation of a process model based on the SAFT-VR equation of state

The development of a predictive model for an absorber-desorber process for the separation of carbon dioxide (CO2) from a gas stream using an aqueous alkanolamine solution as a solvent is presented. Post-combustion carbon dioxide capture by absorption with aqueous amine solvents is likely to play an important role in climate change mitigation, by helping to reduce a significant fraction of CO2 emissions from fossil fuel power plants. There are, however, a number of concerns with the large scale deployment of this technology, including energy requirements, solvent degradation and the environmental and health impact resulting from a potential loss of solvent and solvent degradation products. Modelling studies can play an invaluable and complementary role in addressing some of these issues, including the choice of solvent and operating conditions that yield optimal performance. The model presented here incorporates state-of-the-art SAFT-VR thermodynamics into a rate-based process model. A characteristic of the proposed approach is that all the reactions are treated within a thermodynamic description, assuming chemical equilibrium throughout. This greatly reduces the amount of experimental data required to model the behaviour of the absorber. Furthermore, in contrast with many treatments of reactive systems of this type, no enhancement factor is used in the process model. The absorber-desorber process model is implemented in the gPROMS software platform and validated using published pilot plant experimental data for the removal of CO2 from an air and CO2 stream using monoethanolamine (MEA) solutions. A scaling of the diffusivity in the liquid phase, that is found to be transferable to different operating conditions, is proposed. Reliable predictions are obtained for the temperature and composition profiles in the gas and liquid phases, including a good description of the temperature bulge which sometimes appears along the height of the absorber column. The same transferable model is used to describe both the absorber and the desorber columns. The influence of key parameters of the model for different operating conditions is assessed through a sensitivity analysis. The model developed in this study is applied to simulate a complete amine-based carbon capture absorber-desorber process. Given the relatively simple modelling of the solvent/CO2 interactions, in which the reactions are treated implicitly through a physical approach, the proposed model lends itself well to the investigation of other solvents.Open Acces