LNG接收站冷能用于轻烃回收工艺

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

关键词:  接收站  LNG  冷能利用  天然气  轻烃回收  轻烃分离 

Key words:  terminal  LNG  cryogenic energy utilization  natural gas  light hydrocarbons recovery  light hydrocarbons separation

摘要:

近几年,随着大型LNG接收站的快速发展,LNG冷能利用的研究也日益迫切。利用LNG冷能回收其中高附加值的C⁺₂轻烃则是一种有效的方式。提出了一种利用LNG冷能回收轻烃的改进流程,利用脱甲烷塔进料为脱乙烷塔塔顶冷凝器提供冷量,得到液态乙烷和C⁺₃,方便产品的储运。以国内某LNG接收站的富气为例,模拟计算得到:该流程中C⁺₃收率可达97.5%,乙烷回收率可达95.78%。对装置的经济性进行了分析,结果表明,使用该流程进行轻烃回收效益显著。并提出了LNG冷能用于轻烃回收工艺中冷能利用率的计算方法,得到单独采用该流程的冷能利用率为38.93%。针对LNG组分、温度等参数进行了敏感性分析,考察对C⁺₃收率、乙烷回收率及能耗的影响,可以为接收站的优化运行提供指导。 

Abstract:

In recent years, with the rapid development of large LNG terminals, the research of LNG cryogenic energy utilization is increasingly urgent. C⁺₂ 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 C⁺₃, 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 C⁺₃, 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 C⁺₃ and ethane and the energy consumption were studied. It provided a guidance for optimal operation of the terminals.