Sizing of heat exchangers and exergoeconomic performance comparison of two supercritical CO2 power cycles driven by flue gas of a steam power plant

This study develops a thermo-fluid model of a sCO2 recompression cycle (sCO2-RC) utilizing boiler flue gas of a reheat regenerative steam power plant (RRSPP) and presents exergoeconomic analysis. Two configurations are considered: Configuration 1 (C1) utilizes the exhaust heat first in an air preheater and next in an intermediate heat exchanger and in Configuration 2 (C2) the order is reversed. Key geometric specifications of the heat exchangers are determined alongside the performance parameters like pressure drop, heat transfer coefficients, etc. The net power output of the sCO2-RC in C2 is found to be 8.32 MW, compared to 2.31 MW in C1. Also, C2 has better thermal and exergy efficiencies of 28.91 % and 38.71 %. Previously, the standalone RRSPP incurred a total cost rate of 5,675.84 $/h against a net power of 205.8 MW. Now, with a surplus power of 2.31 MW and 8.32 MW obtained, respectively, from C1 and C2, the additional total cost rates associated with the combined RRSPP-C1 and RRSPP-C2 are found to be 165.04 $/h and 59.33 $/h, respectively. The RRSPP-C2 produces 2.89 % more power with higher efficiencies and has the lowest levelized cost of energy (LCOE) among the three systems—standalone RRSPP, RRSPP-C1 and RRSPP-C2. Therefore, RRSPP-C2 is recommended for sCO2-RC operation together with the SPP.