Combined Cycle Power Plants with Chemical Looping Combustion

Abstract

The objective of this work is to study the dynamics
of process configurations of combined cycle power plants with chemical looping combustion
for CO₂ capture. The focus of this presentation is on plants that
operate within uncertain/variable market power demand, which is the source of many
challenges in the everyday operation of power plants. The fluctuation in power
demand is the result of a number of external factors related to the time of
day, the time of the year, the power plant location with regards to the
surrounding use of competitive renewable energy sources and the overall market.
Nonetheless, the real-time power demand in the United States is forecasted on a
minute to minute basis by the Federal Energy Regulatory Commission (FERC), as
shown for a given day in New England in Figure
1. Therefore, an opportunity exists for modern power plants to take
advantage of model-based approaches for optimization and system design, within environmental
constraints. In order to remain competitive in the future, power plants need to
operate dynamically while capturing CO₂ at a minimal cost and energy
penalty. The methodology proposed herein uses dynamic models of natural
gas-fired, combined cycle power plants and chemical-looping for the combustion
of the fuel with inexpensive CO₂ capture.

Figure 1: Forecasted Power Demand for a
Given Day in New England from FERC

The increasing rate of CO₂ emissions from
fossil fuel combustion draws urgency to the development of alternative and
sustainable sources of energy [1,2]. While the
implementation of alternative energy sources is ongoing, the slow rate of
adoption leaves fossil fuels to remain the world leader in energy production
for some time. The most practical solution to reduce anthropogenic CO₂
emissions in the short term is to deploy Carbon Capture and Storage (CCS)
strategies [3]. Chemical-looping combustion (CLC) has emerged as one of the
most promising, low-cost CCS technologies, [4-6] with the potential to reduce
the cost of CO₂ capture by 50% [7]. Chemical looping is a two-step technology
for the oxidation of fossil fuels in the absence of nitrogen, which results in a
stream of CO₂ ready for sequestration. The two steps of chemical
looping comprise the cyclic reduction and oxidation of a metallic oxygen
carrier.

Figure 2 shows the structure of the
integrated CLC combined-cycle power plant examined in this work. The CLC
oxidizer replaces the traditional gas turbine combustion chamber of a
conventional Brayton cycle, while the heat released during the CLC reduction
step is used for heat recuperation within the plant. The exhaust heat of the
gas turbine is used in a reheat Rankine cycle downstream to improve the overall
efficiency of the plant. The power plant shown in Figure 2 was simulated in Dymola [8], using the Modelica [9] language.
Several scenarios of varying fuel loads were simulated and the performance of
the integrated plant was explored.

Figure 2: Combined cycle power plant with
chemical-looping combustion

In summary, a combined cycle power plant with
integrated for CO₂ capture using was simulated for various scenarios
of variable market power demand. A proof of concept analysis of the dynamic
model adjusting the fuel load based on predicted power demand will be
presented. The overall efficiency of the plant was estimated under various
scenarios. An analysis of the cost of capturing CO₂ in natural gas
fired power plants will be presented and discussed. An outlook of the use of
model-based approaches in modern power plants will be discussed.

Acknowledgements: This material is based upon work
supported by the National Science Foundation under Grant No. 1054718.

References:

[1]       
IPCC. IPCC - Intergovernmental Panel on Climate Change.
(2007).

[2]        Archer, D. Fate of fossil fuel CO2 in
geologic time. Journal of Geophysical Research C: Oceans 110, 1?6 (2005).

[3]        Spigarelli,
B. P. & Kawatra, S. K. Opportunities and
challenges in carbon dioxide capture. J. CO₂ Util. 1, 69?87 (2013).

[4]        Boot-Handford,
M. E. et al. Carbon capture and storage update. Energy Environ. Sci. 7, 130 (2014).

[5]        Adanez, J.,
Abad, A., Garcia-Labiano, F., Gayan,
P. & De Diego, L. F. Progress in chemical-looping combustion and reforming
technologies. Prog. Energy Combust. Sci. 38, 215?282 (2012).

[6]        Hossain, M. M. & de Lasa, H. I.
Chemical-looping combustion (CLC) for inherent separations?a review. Chem. Eng. Sci. 63, 4433?4451 (2008).

[7]        DC, T. & SM., B. Carbon dioxide
capture for storage in deep geologic formationse-results
from the CO₂ capture project, Vol 1-2. (Elsevier,
2005).

[8]        H.
Elmqvist, D. Brück, M. Otter, Dymola User's Manual, (1996).

[9]        Modelica-Association,
?Modelica Language Specification, Version 3.3,? (2012).