从天然气中提取乙烷是天然气凝液回收技术发展的新趋势。以提高乙烷回收率和降低能耗为目标,对150×104 m3/d天然气乙烷回收工艺流程开展了研究。研究结果表明,工艺方案均能达到90%以上的乙烷回收率,干气回流工艺方案能够进一步提高乙烷回收率,但是能耗较高,其中气相过冷工艺方案，单位产品能耗最低。对气相过冷工艺方案的主要参数研究表明,随着原料气温度降低和过冷气比例增大,乙烷回收率逐渐增大,单位产品能耗先降低后逐渐升高。提高脱甲烷塔操作压力,单位产品能耗变化较小,但是乙烷回收率逐渐降低。原料气预冷温度-65 ℃,脱甲烷塔操作压力2 100 kPa,过冷气比例25%时,生产粗乙烷气产品151 kmol/h,乙烷回收率95.25%,单位产品能耗173 MJ/kmol。研究结果可为类似工程设计及优化提供参考。

Extracting ethane from natural gas is a new trend in the development of natural gas condensate recovery technology. The study on the 1.5 million m3/d natural gas ethane recovery process was carried out in order to achieve the goals of reducing energy consumption and improving ethane recovery rate. The study results show that all three processes can meet the ethane recovery rate of more than 90%. The Recycle Split-Vapor Process can further increase the ethane recovery rate at the expense of increasing the energy consumption per unit product, and the Gas Subcooled Process has the lowest energy consumption. Study on the main parameters of the Gas Subcooled Process shows that the ethane recovery rate gradually increases as the feed gas temperature goes lower and as the proportion of sub-cooled gas ratio increases. The energy consumption per unit product decreases first and then increases. When the operating pressure of the demethanizer is increased, the energy consumption per unit product does not change significantly, but the ethane recovery rate gradually decreases. When the feed gas is pre-cooled to -65 ℃, with the demethanizer operating pressure at 2 100 kPa and the sub-cooled gas ratio is 25%, the crude ethane gas product is 151 kmol/h, giving an ethane recovery rate of 95.25%, and the energy consumption per unit product is 173 MJ/kmol. This research result can provide a reference for similar engineering design and optimization.