Process of light hydrocarbons recovery from LNG with cryogenic energy utilized in LNG terminal

In recent years, with the rapid development of large LNG terminals, the research of LNG cryogenic energy utilization is increasingly urgent. C₂⁺ light hydrocarbons, which are resources with high additional values, can be separated from LNG by efficiently utilizing its cryogenic energy. An improved process of light hydrocarbons separation is proposed in this paper: the cold energy of the demethanizer feed is provided to the condenser of the deethanizer for liquefied ethane and C₃⁺, which are easy to be stored and transported. Then, a case study of applying the process was carried out for the rich LNG of a domestic LNG terminal, which indicated that the recovery rate was about 97.5% for C₃⁺, and about 95.78% for ethane. And the economics of the process was studied. The results showed that recovering light hydrocarbons from LNG by this process could gain great profits. This paper also proposed a new calculation method of LNG cryogenic energy utilization rate for the process. It is concluded that LNG cryogenic energy utilization rate is 38.93% with the process used alone. Sensitivity analysis was conducted for the composition, temperature and other parameters of LNG, and the effects of them on the recovery rate of C₃⁺ and ethane and the energy consumption were studied. It provided a guidance for optimal operation of the terminals.