Energy Integration of LNG Light Hydrocarbon Recovery and Air Separation

Abstract

Liquefied natural gas (LNG) needs to be heated and vaporized before entering the natural gas pipeline network. The traditional seawater heating method not only wastes the cold energy from LNG regasification, but also causes adverse environmental impact, hence the design of cold energy utilization system is necessary. Air separation process is the most common type used in Chinese LNG receiving terminals, and the utilization ratio of LNG cold energy is only about 40 %. The light hydrocarbon separation process is another way to utilize cold energy, which can recover high-value hydrocarbons like ethane from LNG. This paper first presents an integrated process of light hydrocarbon separation and air separation to realize the cascade utilization of LNG cold energy and obtain higher economic benefits. Then, different temperature ranges of LNG regasification for the air separation and light hydrocarbon separation are determined by sensitivity analyses. Results show the utilization ratio of LNG cold energy is increased by 35.77 %. Air separation and light hydrocarbon separation can be easily miniaturized, and they are suitably applied for the LNG receiving terminals.