(203y) Dynamic Simulation and Model Validation of a Pre-Combustion CO2 Capture Unit for IGCC Power Plants

Pre-combustion CO₂ capture applied to integrated gasification combined cycle (IGCC) power plants is a promising technical solution to mitigate CO₂ emissions and therefore the effect of climate change. The integration of the CO₂ removal unit with the very complex gasification process and combined cycle power plant leads to challenges especially regarding dynamic operation. Nowadays, dynamic performance of fossil-fuelled power plants becomes increasingly important as the share of electricity produced by renewable energy sources which is inherently unsteady is steadily growing. Therefore, the capture process has to be able to follow frequent and fast load changes without restraining the performance of the IGCC power plant. In order to study the transient performance of the pre-combustion CO₂ capture unit during load variations a unique, fully instrumented CO₂-capture pilot plant has been realized at the Buggenum IGCC power station in the Netherlands by the utility company Vattenfall. Dynamic models of the entire system and models of the subsystems have thus been developed. The carbon monoxide present in the syngas entering the CO₂ capture unit is converted into hydrogen and carbon dioxide via a three-stage, sweet, high-temperature water-gas shift process. Subsequently, the carbon dioxide is removed from the syngas by means of physical absorption resulting in a H₂-rich syngas, which is fed to the gas turbine of the combined cycle power plant.

The models are developed following a state-of-the-art, object-oriented, lumped-parameter modeling approach, using the open-source Modelica language, implemented in a commercial software tool. The thermophysical properties of the highly non-ideal mixtures involved in the capture process are calculated with the PC-SAFT Equation of State (EoS). This EoS has been implemented, together with fast and robust algorithms, into an in-house property package which is interfaced with the dynamic modeling tool. The subsystem models and the entire system model are validated by comparison with experimental data obtained from the pilot plant. Various open-loop and closed-loop transient tests have been performed, monitoring the response to step-wise changes of different operational parameters, such as syngas load, syngas composition and solvent mass flow rate. Finally, the validated models have been used to  identify operational limitations of the capture unit if integrated with the IGCC power plant. The validated models will also be used to design control strategies aiming at the improvement of the dynamic operation of the highly complex power plant.

References:

K. Damen, R. Gnutek, J. Kaptein, N.R. Nannan, B. Oyarzun, C. Trapp, P. Colonna E. van Dijk, J.

Gross, A. Bardow, “Developments in the pre-combustion CO2 capture pilot plant at the Buggenum IGCC”, Energy Procedia 4 (2011) 1214-1221

D. Bhattacharyya, R. Turton, S.E. Zitney, “Dynamic Simulation and Load-Following Control of an IGCC Power Plant with CO2 Capture”, 2012 AIChE Annual Meeting, Conference Proceedings