The reactor residence time required for a sCO2 combustor is comparatively higher than an equal power, airdiluted conventional combustor. Therefore, the strategies to reduce the reactor residence time are very important in the design of sCO2 combustors. The current work recommends a method to reduce the residence time requirement in the sCO2 combustion chamber. Here, the combustor is modelled by coupling the perfectly-stirred-reactor (PSR) and plug-flow-reactor (PFR) models along with the detailed Aramco 2.0 combustion chemical kinetic mechanism. The real gas effects are considered by using the Soave-Redlich-Kwong (SRK) equation of state incorporated in CHMEKIN-RG. Though, the CO emission level at the exit of the primary zone of the sCO2 combustor is lower or in some cases equal to the conventional combustor, the further decline of CO in the dilution zone is identified as very poor. Therefore, very high CO levels can be expected at the exit of the sCO2 combustor compared to conventional combustors. CO from the sCO2 combustor exhaust can be eliminated by lean operation of the combustor and the excess O2 retained in the re-cycled CO2 stream due to lean operation can be mixed with primary methane before entering the primary combustion zone. This strategy is shown to reduce the primary zone residence time requirement of sCO2 combustion. However, the minimum level of O2 in the re-cycled CO2 stream is approximately 5000 ppm and the minimum required residence time in this pre-mixing chamber is around 4 ms. Also, it is observed that the primary zone residence time requirement decreases linearly with respect to the O2 level in the re-cycled CO2 stream.
- International Gas Turbine Institute
A Strategy of Mixture Preparation for Methane Direct-Fired sCO2 Combustors
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Manikantachari, KRV, Martin, S, Vesely, L, Bobren-Diaz, JO, Vasu, S, & Kapat, J. "A Strategy of Mixture Preparation for Methane Direct-Fired sCO2 Combustors." Proceedings of the ASME Turbo Expo 2018: Turbomachinery Technical Conference and Exposition. Volume 9: Oil and Gas Applications; Supercritical CO2 Power Cycles; Wind Energy. Oslo, Norway. June 11–15, 2018. V009T38A009. ASME. https://doi.org/10.1115/GT2018-75557
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