Control Relevant Model of Amine Scrubbing for CO₂ Capture from Power Plants

A low-order amine scrubbing model was developed for an intercooled absorber and advanced flash stripper configuration with piperazine solvent. The low-order lumped parameter model uses semi-empirical thermodynamics and rate-based mass transfer and embeds reaction kinetics in a constant overall transfer coefficient. The predicted off-design steady state of this model is compared to a high-order Aspen Plus simulation for 100–85% power plant load. The difference in CO₂ removal rate between the two models is less than 1% when power plant load is greater than 94%. The removal rate is systematically overpredicted in the low-order model because a constant CO₂ mass transfer coefficient in the absorber leads to an overprediction of absorber performance at part-load operation. Compared to pilot plant data, the low-order model captures the dynamic response of a step change in the stripper pressure control valve. The characteristic time of the total CO₂ inventory is found to be 77 min, compared to a total liquid residence time of 48 min. The low-order model sufficiently represents process behavior and will be used in future work to screen regulatory process control strategies.