Abstract:
The power sector needs to be decarbonised by 2050 to meet the global target
for greenhouse gas emission reduction and prevent climate change. With fossil
fuels expected to play a vital role in the future energy portfolio and high
efficiency penalties related to mature CO2 capture technologies, this research
aimed at evaluating the efficiency improvements and alternate operating modes
of the coal-fired power plants (CFPP) retrofitted with post-combustion CO2
capture. To meet this aim, process models of the CFPPs, chilled ammonia
process (CAP) and calcium looping (CaL) were developed in Aspen Plus® and
benchmarked against data available in the literature. Also, the process model of
chemical solvent scrubbing using monoethanolamine (MEA) was adapted from
previous studies. Base-load analysis of the 580 MWel CFPP retrofits revealed
that if novel CAP retrofit configurations were employed, in which a new auxiliary
steam turbine was coupled with the boiler feedwater pump for extracted steam
pressure control, the net efficiency penalty was 8.7–8.8% points. This was close
to the 9.5% points in the MEA retrofit scenario. Conversely, CaL retrofit resulted
in a net efficiency penalty of 6.7–7.9% points, depending on the fuel used in
the calciner. Importantly, when the optimised supercritical CO2 cycle was used
instead of the steam cycle for heat recovery, this figure was reduced to 5.8%
points. Considering part-load operation of the 660 MWel CFPP and uncertainty
in the process model inputs, the most probable net efficiency penalties of
the CaL and MEA retrofits were 9.5% and 11.5% points, respectively.
Importantly, in the CaL retrofit scenarios, the net power output was found to be
around 40% higher than that of the CFPP without CO2 capture and double than
that for the MEA retrofit scenario. Such performance of the CaL retrofit scenario
led to higher profit than that of the 660 MWel CFPP without CO2 capture,
especially if its inherent energy storage capability was utilised. Hence, this study
revealed that CaL has the potential to significantly reduce the efficiency and
economic penalties associated with mature CO2 capture technologies.
