A Transcritical CO2 Rankine Cycle With LNG Cold Energy Utilization and Liquefaction of CO2 in Gas Turbine Exhaust

Abstract

A novel transcritical Rankine cycle is presented in this paper. This cycle adopts CO2 as its working fluid with exhaust from a gas turbine as its heat source and liquefied natural gas (LNG) as its cold sink. With CO2 working transcritically, large temperature difference for the Rankine cycle is realized. Moreover, the CO2 in the gas turbine exhaust is further cooled and liquefied by LNG after transferring heat to the Rankine cycle. In this way, not only is the cold energy utilized but also a large part of the CO2 is recovered from burning of the vaporized LNG. In this paper, the system performance of this transcritical cycle is calculated. The influences of the highest cycle temperature and pressure to system specific work, exergy efficiency, and liquefied CO2 mass flow rate are analyzed. The exergy loss in each of the heat exchangers is also discussed. It turns out that this kind of CO2 cycle is energy-conservative and environment-friendly.