LNG Regasification Plants Integrated With Low- and High-Temperature Organic Rankine Cycles

Abstract

Abstract The use of natural gas has continuously increased and reached 24.7% of the worldwide primary energy supply in 2020. The same trend applies to Liquefied Natural Gas (LNG), which contributed to 52% of overall natural gas trades in the same year. In this context, the recovery of the cold energy available at LNG receiving terminals during the process of regasification is of a critical importance. This paper addresses the integration of the regasification process with an Organic Rankine Cycle (ORC) in order to exploit the available LNG cold energy, by condensing the organic fluid. In addition, a gas turbine exploits differences between regasification and distribution pressures. The analysis covers different organic fluids and two ORC heating source configurations: a) a low-temperature one, using seawater, and b) a high-temperature one, using exhaust gas. In addition, the integration of a natural gas-fired topping gas turbine, which uses the LNG cold energy by compressor inlet air cooling, was simulated. The performance of a medium size regasification terminal (50 kg/s) was evaluated as a function of both the regasification and the natural gas distribution pressures. Dedicated models have been developed using Aspen Plus software to simulate the regasification process and the integrated topping cycles (Organic Rankine and Brayton), and their mutual energy integrations. The analysis shows that ORC power outputs from 2 MW up to 4.5 MW in case a) and from 6 MW up to 9 MW in case b) can be reached. The topping gas turbine benefits from the inlet air cooling and can add a power output of 35 MW to 40 MW. R125 was the best working fluid for a low-temperature ORC, while R600a showed the best performance for a high-temperature application.