Solvent effects on design with operability considerations in post-combustion CO2 capture plants

This work presents an evaluation of the operation of alternative solvents for post-combustion CO2 capture under varying process conditions. The proposed methodology is part of a generalized design and operability framework and relies on the determination of the processes' steady-state controllability as an inherent system feature, independent of the control structure selection. Assessment of such characteristics can shed light on the effect different capture solvents, process configurations and control structures have on the achieved dynamic responses and further associate them to the physico-chemical properties of the solvents. Three amine based solvents, namely monoethanolamine (MEA), diethanolamine (DEA) and 3-amino-1-propanol (MPA) are introduced to an advanced CO2 capture flowsheet previously designed for optimal steady-state operation. The dynamic characteristics of the investigated solvent-process systems under the influence of disturbances emulating real-time industrial conditions are then assessed and rank-ordered using an index that measures the departure of the process variables from the region of desired operation. As such, for a given disturbance, the drift from the acceptable steady-state operating point and the response of dynamic closed-loop simulations determine the suitability and applicability of each solvent in the employed CO2 capture process configuration. Results reveal the superiority of the dynamic behavior of MPA in terms of economic performance as well as expected process operability for variations in the inlet flue gas flowrate, greatly surpassing the performance of the benchmark solvent, MEA.