(598u) Steady State and Dynamic Modeling and Simulation of Post-Combustion CO2 Capture Technologies

Qiang Zhang, Debangsu Bhattacharyya, and Richard Turton
Department of Chemical Engineering, West Virginia University,
Morgantown WV, 26506, USA

The process of CO2 capture and storage has proven to be a promising and effective
way to control the emission of CO2 from large-scale, stationary sources such as
conventional, pulverized-coal, power plants. In this work, a liquid MEA-based, post-
combustion CO2 capture and compression system, was simulated in Aspen Plus
and Aspen Plus Dynamics. The process was also integrated with the steam system
of a 550 MWe coal-fired power plant. The steady state simulation was carried out
in Aspen Plus using rate-based separation processes for the absorber and stripper
columns. Under the constraint of 90% capture efficiency, the effect of column
height, flue gas temperature, lean-solvent temperature, stripper pressure, MEA wt%,
and lean-solvent loading of CO2 were investigated in order to reduce the energy
requirement for rich-solvent regeneration. With the optimized parameters of lean CO 2
loading of 0.208, a 30 wt.% MEA solution, 24 m of packed height in the absorber
and a stripper operating pressure of 2.1 bar, the thermal energy requirement for CO2
recovery was 3.075 GJ/ton CO2 and the net power efficiency was 29.2%, which was
more efficient than the values reported in the base case study of 4.048 GJ/ton CO2 and
26.55%, respectively.
The steady state model developed in Aspen Plus was converted to a dynamic model in
Aspen Plus Dynamics with appropriate modifications in the plant configuration for a
pressure-driven dynamic simulation and by providing the required dynamic data such
as equipment sizes, equipment heat transfer options, etc. The CO2 capture process
should satisfy the overall target of CO2 capture in the face of typical disturbances such
as changes in the flue gas flowrate and composition. However, for post-combustion
CO2 capture in typical power plants, a number of CO2 capture trains are coupled
together. Due to the pressure-flow dynamics, a precise distribution of the flue gas
between the trains is a challenge for this highly interactive system. In addition, the
control of liquid inventory and the regulation of the stripper efficiency pose further
challenges. The presentation will include results from a number of innovative control
strategies, both model-free and model-based, for maintaining the desired CO2 capture
in the face of typical disturbances for this highly interactive process. .