Study on a Cascade Utilization of Liquid Natural Gas (LNG) Cold Energy for Power Generation

Liquefied natural gas (LNG) is known as a clean energy source which is widely used in electricity generation and daily living for its friendly environment performance. The global LNG trade has increased rapidly during recent years. Liquid natural gas delivered by sea-ships contains considerable cryogenic exergy which can be utilized for electricity production before its evaporation and introduction into the system of pipelines. Because the need to vaporize LNG offers a thermal sink at a very much lower temperature than seawater, using this thermal sink both power and gas can be produced. So it is possible to recover power from the vaporization of LNG. Based on the exergy analysis of normal Rankine power cycle and LNG gasification characteristics at a different pressure, this paper proposed a cascading power cycle with LNG cold energy recovery, in which a three-tier Rankine cycle system was established to recovery the liquid heat and latent heat of LNG, and the residual sensible heat of LNG vapor can be used to prepare the cold water of central air-conditioning in plant area. The simulating results showed that the cascade power system can improve the LNG cold energy recovery efficiency.