(538a) A Novel Power Cycle Integrated With Post Combustion CO2 Capture Process Using LNG Cryogenic Exergy

Lee, U., Seoul National Univ.
Han, C., Seoul National University
Park, K., Seoul National University

climate change and related disasters have attracted worldwide attention and
brought efforts to reduce greenhouse gases especially for CO2. Among
the various sources of the CO2 emission, power plants combusting
fossil fuel such as coal, oil and gas contribute to the CO2 emission
the most 1.
Several techniques to remove CO2 from the power plant flue gas have
been proposed, and amine based CO2 absorbing systems are considered
the one of the most suitable options because it has been demonstrated as the
most mature and less expensive technology 2.
However, the large energy consumption and corresponding electricity cost increment
have been pointed out as the obstacle of the commercialization. The estimated cost
of CO2 capture increases the cost of electricity production by 40–85%
for a supercritical pulverized coal power plant. 3
In this study, a novel pulverized coal (PC) power plant integrated with CO2
Rankine cycle utilizing Liquefied Natural Gas (LNG) cryogenic exergy has been
proposed. By utilizing the latent heat of low quality steam which originally
wasted in the steam condenser, this process is able to extract additional power
from the CO2 Rankine cycle.

1 Process Flow Diagram of Novel Power Generation Cycle

1 gives a principal process scheme of the novel power generating process
proposed in this study. The four main parts of the process are the steam cycle,
CO2 capture process, gas conditioning process and CO2
Rankine cycle integrated with LNG gasification process. Flue gas pathway is
similar to the conventional power plant with post combustion CO2
capture process. The CO2 generated from the PC power plant is delivered
to the Rankine cycle through CO2 capture and gas conditioning
process. Steam pathway is, however, somewhat different from the conventional
cycle. Both the steam condensate and low pressure steam are utilized for the CO2
Rankine cycle superheating. The steam condensate (C-1) from the Feed Water
Heater (FWH) (23) is directed to preheater and the low pressure steam (S-1) id introduced
to CO2 super heater (41) in CO2 Rankine cycle. In this
process, Cryogenic Exergy of LNG is utilized for CO2 condensation
integrating it with LNG gasification process. In addition, the steam from the
low pressure turbine, in contrast to the conventional steam cycle, is condensed
in the CO2 super heater in the CO2 Rankine cycle. In this
manner, the latent heat of the steam which is originally wasted in conventional
steam cycle can be utilized for CO2 super heating and the amount of
power generation of entire plant is eventually increased. Total Energy production of the steam
cycle and CO2 Rankine cycle without integration is turns out to be
70.75 MWe. On the other hand, total energy generation in the novel
process is increased to 80MWe by utilizing the wasted low pressure
steam. It is about 20 % increment of the total power production. The exergy
efficiency of the CO2 Rankine cycle increases from 0.34% to 40% by
integrating steam cycle with CO2 Rankine cycle. Using the integrated
power cycle, the fuel cost for the power production can be lowered to only 61%
of the conventional steam cycle from 12.8 Euro/MW to 7.81 Euro/MW.

This research was supported by a grant
from the LNG Plant R&D Center funded by the Ministry of Land,
Transportation and Maritime Affairs (MLTM) of the Korean government.

1.         Abu-Zahra,
M. R.; Schneiders, L. H.; Niederer, J. P.; Feron, P. H.; Versteeg, G. F., CO2
capture from power plants: Part I. A parametric study of the technical
performance based on monoethanolamine. International Journal of Greenhouse
Gas Control
2007, 1 (1), 37-46.

2.         Rao,
A. B.; Rubin, E. S., A technical, economic, and environmental assessment of
amine-based CO2 capture technology for power plant greenhouse gas
control. Environmental Science & Technology 2002, 36
(20), 4467-4475.

3.         Abu-Zahra, M. R.;
Niederer, J. P.; Feron, P. H.; Versteeg, G. F., CO2 capture from
power plants: Part II. A parametric study of the economical performance based
on mono-ethanolamine. International journal of greenhouse gas control 2007,
1 (2), 135-142.