This paper is focused
on the development and validation of a dynamic
model for a monoethanolamine-based CO2 capture unit. Starting
with a rigorous steady-state process model, the dynamic model is developed
in Aspen Plus Dynamics using a modified Murphree efficiency approach
and is validated using dynamic data collected from the National Carbon
Capture Center in Wilsonville, Alabama. The dynamic test runs were
designed with due consideration of process excitation and process
nonlinearities constrained by the available time to conduct the test
runs and implement the experimental designs in the plant control system.
The experimental data include solvent composition and loading. Because
the experimental data were found to violate mass and energy balances,
filtering algorithms coupled with dynamic data reconciliation techniques
were used. Without adjusting any model parameters, the dynamic model
satisfactorily predicted the dynamic response of CO2 capture
due to step changes in the solvent flow rate, flue gas flow rate,
and steam flow rates. Transient studies show that the process gain
and time constants can considerably change depending on the direction
of the disturbance or manipulated variables, indicating process nonlinearities.
Because of a storage tank between the absorber and stripper, the time
constant of the full plant can be considerably longer than the time
constants of the absorber or stripper individually. Furthermore, impact
of the control system on the process efficiency while following an
optimal CO2 capture schedule was also studied.