A novel LNG cryogenic energy utilization method for inlet air cooling to improve the performance of combined cycle

Abstract

A novel liquefied natural gas (LNG) cryogenic energy utilization method for gas turbine inlet air cooling is proposed in this work. In this method, the temperature difference potential between LNG and cooling medium is utilized step by step. The novel cold production process consists of a CO2 Rankine cycle subsystem and a CO2 compression–refrigeration subsystem. A sensitivity analysis is performed to optimize the performance of the proposed novel cold production process. Results show that the cold energy output of the novel process is increased by about 36.5%, compared with that of the conventional cold production process via direct LNG evaporation. The off-design performance of the gas turbine combined cycle under different ambient conditions is also analyzed to identify the effect of the cold production process for inlet air cooling on a combined cycle power plant. The results indicated that by applying the novel cold production method for inlet air cooling, the combined cycle relative power output increment varies from 1.6% to 11.6%, when air humidity changes from 90% to 30%, compared with that without inlet air cooling. The combined cycle relative power and relative efficiency by the novel air cooling is by 0.50–2.47% and 0–0.11%, respectively, higher than that by conventional inlet air cooling. The novel cold production process is beneficial to the augmentation of cold energy output and combined cycle power output. However, there is no significant difference in the combined cycle efficiency between the novel and the conventional power systems.