Dynamic Modeling and Validation of a Precombustion CO2 Capture Plant for Control Design

Abstract

In view of the increasing share of electricity produced by renewable energy sources, transient operation of decarbonized power plants is gaining more relevance. This is due to the inherent fluctuating operation of wind or solar plants. Accurate physically based dynamic models are important tools to study the interaction between power plant and CO2 capture unit during dynamic operation. Moreover, such models are indispensable to design appropriate control systems aimed at improvement of dynamic performance. This paper documents the development of dynamic components as well as system models of a precombustion CO2 capture unit applied to integrated gasification combined cycle (IGCC) systems following an object-oriented modeling approach. The models have been implemented by means of the Modelica language into an open source software library. The fluid properties are computed with accurate thermodynamic models implemented within an in-house property package which is interfaced with the Modelica process models. Comprehensive model validation has been performed at component, subsystem, and system level by comparison against experimental measurements obtained from various open- and closed-loop transient tests at the CO2 capture pilot plant situated at the Buggenum IGCC power station. Results are in satisfactory agreement, considering the main process mass flow and temperature variables. To demonstrate the use of validated, dynamic process models, a control design study is presented whereby a control strategy based on feed-forward, feed-back, and cascade control has been implemented and tested with the aim to improve dynamic performance of the capture unit. It can be concluded that prompt syngas load variation is a feasible operating mode for precombustion CO2 capture units featuring sophisticated control systems. The software library containing the validated component and system models serves as a reliable foundation for the development of large-scale precombustion capture unit models.