https://orcid.org/0000-0003-1695-7643
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ABSTRACT
As the bottom cycle of gas turbine waste heat utilization, the S-CO2 cycle can enhance the power output capacity of the system. Based on the energy analysis of the recompression cycle and the partial cooling cycle for gas turbine waste heat utilization, the two cycles are improved from the matching of heat exchange flow of regenerator and heater in this paper. Under the same parameters, compared with the cycle before improvement, increase in heat source utilization rate and net power output of improved cycles is 45.69% and 39.31%, 43.54 MW and 35.43 MW, and the power consumption cost is decreased by 0.6106 $/kWh and 0.6289 $/kWh. However, as part of heat recovery inside the system is replaced by the heat of the heat source, the thermal efficiency is decreased by 10.43% and 8.7%, respectively. Variable parameter study is conducted on the two improved cycles to analyze the cycle characteristics from the perspective of energy, exergy, and economy (3E). The results showed that the improved recompression cycle has a high thermal power conversion capacity, higher system thermal efficiency and exergy efficiency and lower power generation cost, while the improved partial cooling cycle has higher waste heat utilization potential. However, the area of heat exchangers in both cycles tends to increase, which is not conducive to the compactness of the system.
Nomenclature
| Acronyms | = | |
| S-CO2 | = | supercritical carbon dioxide |
| 3E | = | energy exergy and economic |
| TR | = | temperature regenerative heat exchanger |
| HTR | = | high temperature regenerative heat exchanger |
| LTR | = | low temperature regenerative heat exchanger |
| CRF | = | capital recovery coefficient |
| LCOE | = | Levelized cost of energy |
| APR | = | The heat exchanger area per unit power |
| Symbols | = | |
| P | = | pressure (MPa) |
| T | = | tempreature (℃) |
| s | = | entropy (kJ⋅kg−1⋅K−1) |
| Q | = | heat value of syngas (MW) |
| E | = | exergy (kJ) |
| C | = | initial investment of each component |
| ci | = | cost rate of major components |
| A | = | aera of system component |
| yk | = | maintenance coefficient |
| η | = | net cycle efficiency |
| W | = | power output or consumption (MW) |
| m | = | mass flow rate (kg⋅s−1) |
| h | = | enthalpy (kJ⋅kg−1) |
| Δh | = | enthalpy difference (kJ⋅kg−1) |
| ΔT | = | temperature difference (℃) |
| e | = | exergy (kJ⋅kg−1) |
| Subscript | = | |
| 1, 2, 3 … | = | state points of cycle |
| Max | = | theoretical maximum |
| T | = | turbine |
| th | = | thermal |
| sys | = | system |
| s | = | isentropic |
| k | = | interest rate |
| C | = | compressor |
| MC | = | main compressor |
| RC | = | recompressor |
Acknowledgements
The study was supported by the Natural Science Foundation of China (52076079), Natural Science Foundation of Hebei Province, China (Grant No. E2020502013), the Fundamental Research Funds for the Central Universities (2021MS076, 2021MS079).
Disclosure statement
No potential conflict of interest was reported by the author(s).