Efficient cycles for carbon capture CLC power plants based on thermally balanced redox reactors
Name
Ghoniem_Efficient cycles.pdf
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Author(s)
Iloeje, Chukwunwike Ogbonnia
Zhao, Zhenlong
Ghoniem, Ahmed F
Date Issued
August 2015
Journal
International Journal of Greenhouse Gas Control
Publisher
Elsevier
Citation
Iloeje, Chukwunwike et al. “Efficient Cycles for Carbon Capture CLC Power Plants Based on Thermally Balanced Redox Reactors.” International Journal of Greenhouse Gas Control 41 (October 2015): 302–315 © 2015 Elsevier Ltd
Version
Author's final manuscript
Abstract
The rotary reactor differs from most alternative chemical looping combustion (CLC) reactor designs because it maintains near-thermal equilibrium between the two stages of the redox process by thermally coupling channels undergoing oxidation and reduction. An earlier study showed that this thermal coupling between the oxidation and reduction reactors increases the efficiency by up to 2% points when implemented in a regenerative Brayton cycle. The present study extends this analysis to alternative CLC cycles with the objective of identifying optimal configurations and design tradeoffs. Results show that the increased efficiency from reactor thermal coupling applies only to cycles that are capable of exploiting the increased availability in the reduction reactor exhaust. Thus, in addition to the regenerative cycle, the combined CLC cycle and the combined-regenerative CLC cycle are suitable for integration with the rotary reactor. Parametric studies are used to compare the sensitivity of the different cycle efficiencies to parameters like pressure ratio, turbine inlet temperature, carrier-gas fraction and purge steam generation. One of the key conclusions from this analysis is that while the optimal efficiency for regenerative CLC cycle was the highest of the three (56% at 3 bars, 1200 °C), the combined-regenerative cycle offers a trade-off that combines a reasonably high efficiency (about 54% at 12 bars, 1200 °C) with much lower gas volumetric flow rate and consequently, smaller reactor size. Unlike the other two cycles, the optimal compressor pressure ratio for the regenerative cycle is weakly dependent on the design turbine inlet temperature. For the regenerative and combined regenerative cycles, steam production in the regenerator below 2× fuel flow rate improves exhaust recovery and consequently, the overall system efficiency. Also, given that the fuel side regenerator flow is unbalanced, it is more efficient to generate steam from the fuel side regenerator than from the air side regenerator.
MIT Department
Massachusetts Institute of Technology. Department of Mechanical Engineering
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Creative Commons Attribution-NonCommercial-NoDerivs License
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DOI of Published Version
https://doi.org/10.1016/j.ijggc.2015.07.023
