Assessment of the flue gas recycle strategies on oxy-coal power
plants using an exergy-based methodology
Hayato Hagia,b, Maroun Nemera, Yann Le Moullecb, Chakib Boualloua,*
a
b
MINES ParisTech,, CEP - Center for Energy and Processes, 60 Bd St Michel, 75272 Paris Cedex 06, France
EDF R&D, Fluid Dynamics Power Generation and Environment Department, 6 quai Watier, 78401 Chatou, France
A decade ago, post-combustion and oxy-combustion carbon dioxide (CO2) capture technologies exhibited
equivalent energy penalty around 400 kWh/tO2 while higher improvement potentials were expected for the latter.
However, research has not been carried at the same pace since then, and post-combustion technologies can now
achieve up to 290 kWh/tCO2 total equivalent work and exhibits a higher technological maturity. Thus, significant
efficiency improvement is needed for oxy-combustion to be competitive with post-combustion and process
integration is needed to assess its energy savings potential. This work focuses on the exergetic-based assessment
of various flue gas recirculation schemes as well as the heat integration possibilities offered by the oxycombustion process.
A 1000 MWe gross oxy-fired power plant operating at base-load and steady-state is modeled and simulated
using Aspen Plus. A state-of-the-art supercritical steam cycle is considered as well as a flue gas depollution train
composed of electrostatic precipitator, wet flue gas desulfurization unit (FGD) and direct contact polishing
scrubber (DCCPS). The air separation unit and the gas purification unit are conventional cryogenic processes.
Alternative depollution devices allowing new flue gas recycle arrangements and integration schemes are
investigated with respect to their operating limitations. In this study, an exergetic approach is used for the
identification of the optimal design since it gives access to the true efficiency at system level by assessing the
entropy creation in each apparatus in a given configuration.
Several promising flue gas recirculation schemes featuring alternative technological options such as
condensing heat exchangers, high temperature desulfurization and integrated sour compression process have
been studied. Among them, the warm recycle scheme is particularly promising for low-sulfur coals since it
allows the downsizing of the depollution devices and improves the overall plant efficiency. Oxy-combustion
offers unique opportunities in terms of process configuration and their study is the way to go for significant
energy penalty decrease.
* Corresponding author. Tel.: +33 1 69 19 17 00; fax: +33 1 69 19 45 01.
E-mail address: chakib.bouallou@mines-paristech.fr (C. Bouallou)