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

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 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 the cold energy is utilized, but also a large part of the CO₂ from burning of the vaporized LNG is recovered. 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.