Abstract
The low prices and its relatively low carbon intensity of natural gas have encouraged the coal replacement with natural gas power generation. Such a replacement reduces greenhouse gases and other emissions. To address the significant energy penalty of carbon dioxide (CO2) sequestration in gas turbine systems, a novel high efficiency concept is proposed and analyzed, which integrates a flame-assisted fuel cell (FFC) with a supercritical CO2 (sCO2) Brayton cycle air separation. The air separation enables the exhaust from the system to be CO2 sequestration-ready. The FFC provides the heat required for the sCO2 cycle. Heat rejected from the sCO2 cycle provides the heat required for adsorption-desorption pumping to isolate oxygen via air separation. The maximum electrical efficiency of the FFC sCO2 turbine hybrid (FFCTH) without being CO2 sequestration-ready is 60%, with the maximum penalty being 0.68% at a fuel-rich equivalence ratio (Φ) of 2.8, where Φ is proportional to fuel-air ratio. This electrical efficiency is higher than the standard sCO2 cycle by 6.85%. The maximum power-to-heat ratio of the sequestration-ready FFCTH is 233 at a Φ = 2.8. Even after including the air separation penalty, the electrical efficiency is higher than in previous studies.
Highlights
Over the past few decades, natural gas (NG) production in the USA has increased by 40% [1].NG has been termed a “bridge fuel” between the fossil carbon-intensive electric grid of today and the low fossil carbon grid of the future [2,3,4]
As the Φ increases, more syngas is available in the combustion exhaust leading to larger Gibbs’ free energy released, which in turn leads to less concentration losses and more total power being generated in the flame-assisted fuel cell (FFC)
We evaluated the performance of an integrated FFC system, which is able to provide the heat required by supercritical CO2 (sCO2) cycle
Summary
Over the past few decades, natural gas (NG) production in the USA has increased by 40% [1].NG has been termed a “bridge fuel” between the fossil carbon-intensive electric grid of today and the low fossil carbon grid of the future [2,3,4]. Over the past few decades, natural gas (NG) production in the USA has increased by 40% [1]. Along with less carbon dioxide (CO2 ) emissions per kWh [5,6], switching from coal to NG provides several health benefits. Natural gas power plants emit less sulfur dioxide (SO2 ) [7], nitrogen oxides (NOx ) [2], and primary particulate matter [2] when compared to coal-fired power plants. Emissions of primary particulate matter (PM2.5 and PM10 ) have been linked to human mortality and morbidity [8,9,10,11,12]. Recent regulations have focused attention on reducing emissions and are drivers for a switch from coal to NG power plants [1,13]
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