New cold-level utilization scheme for cascade three-level rankine cycle using the cold energy of liquefied natural gas

Abstract

The topic of this study is the intermediate fluid vaporizer gasification system for a liquefied natural gas floating storage regasification unit. To reduce the loss of heat exchange, the primary distributary cascade three-level Rankine cycle is optimised based on the cascade three-level Rankine cycle that uses the cold energy of liquefied natural gas to generate power. The optimized primary distributary cascade three-level Rankine cycle is then compared with the original cascade three Rankine cycle established under the same conditions. Then, a secondary distributary cascade three-level Rankine cycle is proposed. Results show that under a liquefied natural gas flow of 175 t/h, the primary distributary cascade three-level Rankine cycle system exhibits a maximum net output power of 4130.72 kW and an exergy efficiency of 23.78%, which is higher than that of the typical cascade three-level Rankine cycle. Moreover, the net output power and exergy efficiency of the primary distributary cascade three-level Rankine cycle system increased by 3.71% and by 3.84%, respectively. The secondary distributary cascade three-level Rankine cycle system exhibits a maximum net output power of 4143.75 kW and an exergy efficiency of 23.85%.