(596d) Dynamic Modeling and Analysis of a Post-Combustion Carbon Dioxide Capture System

While there is a desire for the use of sustainable/renewable energy to reduce net carbon dioxide emissions, fossil fuels will continue to serve as the dominant energy source in the near future, because of their availability and high energy density. To reduce carbon dioxide emissions from hydrocarbon energy sources, many carbon capture methods are being explored; post-combustion carbon dioxide chemical absorption technology is the most feasible near-term solution. Since MEA absorption or chilled ammonia based carbon dioxide capture processes are energy-intensive and expensive to construct and operate, model-based design and operation of the carbon capture process is useful to reduce capital cost and energy consumption.

In this work a rate-based steady-state model of an integrated MEA-based carbon dioxide capture system, consisting of an absorber and stripper, is developed using the widely-accepted commercial platform-Aspen Plus. The rate-based model has better predictive capability than the equilibrium-based model, and agrees well with experimental data from the pilot plant at the University of Texas at Austin (Zhang et al, 2009). Based on this steady-state model, comprehensive flowsheet parametric studies have been done to investigate the integrated system characteristics.

The steady-state model is converted into a dynamic model in Aspen Dynamics; because of software limitations, the equilibrium reactions in Aspen Dynamics must be converted into kinetic expressions with the equivalent equilibrium behavior. The resulting dynamic model is used to analyze the dynamic characteristics of the carbon dioxide capture process. Model-based control and optimization is shown to be a valuable tool to improve overall energy efficiency and therefore reduce the operational cost of clean coal-fired power generation system with carbon capture.

Literature Cited

Zhang, Y., H. Chen, C.-C. Chen, J.M. Plaza, R. Dugas and G.T. Rochelle “Rate-based process modeling study of CO2 capture with aqueous monoethanolamine solutions,” Industrial & Engineering Chemistry Research, 48(20), 9233-9246 (2009).