Evaluation of Gas Turbine Exhaust Heat Recovery Utilizing Composite Supercritical CO2 Cycle

Bottoming cycles are drawing a real interest in a world where resources are becoming scarcer and the environmental footprint of power plants is becoming more controlled. Reduction of flue gas temperature and power generation boost without burning more fuel are certainly very attractive, but how much can really be extracted from a Gas Turbine Unit (GTU) cycle to be converted to a com-bined configuration? The current study presents a continuation of our previous work in which supercritical CO2 (S-CO2) bottoming cycles were con-sidered as an alternative to traditional steam cycles for purposes of waste heat recovery. Prior evaluation regarding the option of com-bined gas and S-CO2 cycles for different gas turbine sizes, gas turbine exhaust gas temperatures and configurations of bottoming cycle type allowed making conclusions about the advisability of the mentioned heat utilization technology and selecting the best em-bodiment of bottoming cycle taking into account heat source fea-tures. In the present paper combinations of different S-CO2 cycles are considered as bottoming parts for a specific middle power gas turbine. Such approach allows combining the advantages of dif-ferent types of S-CO2 cycles to increase the power production utilizing GTU waste heat. Also, a composite cycle approach is proposed to provide a positive effect from the combination of cycles and significantly decrease the number of components com-pared to what it would be for a sequential S-CO2 cycles installation. The comparison of combined gas and supercritical CO2 cycles with traditional combined gas and steam cycles are presented in this paper. The specified comparison was performed in terms of addi-tional power magnitude from the bottoming cycle installation and additional number of components