Abstract
This work investigates the performance of a supercritical CO2cycle as the bottoming cycle of a commercial gas turbine with 4.7 MW of electric power output. In detail, the partial heating cycle is the layout chosen for the interesting trade-off between heat recovery and cycle efficiency with a limited number of components. Single-stage radial turbomachines are selected according to the theory of similitude. In particular, the compressor is a troublesome turbomachine as it works near the critical point where significant variations of the CO2properties occur. Efficiency values for turbomachinery are not fixed at first glance but result from actual size and running conditions, based on flow rates, enthalpy variations as well as rotational speeds. In addition, a limit is set for the machine Mach numbers in order to avoid heavily loaded turbomachinery. The thermodynamic study of the bottoming cycle is carried out by means of the mass and energy balance equations. A parametric analysis is carried out with particular attention to a number of specific parameters. Considering the power output calculated for the supercritical CO2cycle, economic calculations are also carried out and the related costs compared to those specific of organic Rankine cycles with similar power output.
Highlights
Supercritical CO2 power cycles are an alternative to steam bottoming cycles for natural gas combined cycle applications
This work investigates the performance of a supercritical CO2 cycle as the bottoming cycle of a commercial gas turbine with 4.7 MW of electric power output
Focusing on combined cycle power plants, Cho et al [4] compared the performance of seven Supercritical CO2 (sCO2) cycle layouts as bottoming power systems of the Siemens SGT5-4000F gas turbine unit with that of a steam Rankine cycle in a natural gas combined cycle power plant
Summary
Supercritical CO2 (sCO2) power cycles are an alternative to steam bottoming cycles for natural gas combined cycle applications. A complex cascade sCO2 Brayton cycle among the proposals presented superior efficiency in comparison with the reference steam cycle Another comparison of sCO2 power cycle layouts for waste heat recovery (WHR) from gas turbine was proposed by Kim et al. The authors considered several architectures, where the partial heating cycle appeared to be an interesting solution with high potential for WHR applications Such an architecture combines simple layout and high performance. Another work considering the partial heating cycle as a promising option due to its simple layout and limited number of components is the one carried out by Kim et al [7], who compared the performance of the partial heating cycle (called “split flow” by the authors) against that of the single recuperated cycle for WHR from a 25 MW gas turbine. An assessment of the cost of the technology is proposed and compared with the competing organic Rankine cycle
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