一种吸收塔与脱甲烷塔相结合的乙烷回收改进新流程

An improved ethane recovery process combining absorption column with demethanizing column

随着国内各油田CO_(2)气驱采油技术的应用,油田伴生气中的CO_(2)含量大幅提高,中国乙烷回收装置常对油田伴生气进行乙烷回收。为提高对原料气中CO_(2)的适应性,针对部分干气循环乙烷回收工艺(Recycle Split Vapor Process,RSV)在高含CO_(2)天然气中回收乙烷时存在的系统能耗高、热集成困难、脱甲烷塔塔板中上部易形成CO_(2)固体等问题,提出了一种吸收塔与脱甲烷塔相结合的多回流双塔乙烷回收改进工艺新流程(Recycle Split Vapor Multistage Process,RSVM),并利用Aspen HYSYS软件对RSV流程和RSVM流程进行了模拟对比及适应性分析。研究结果表明:(1)与RSV工艺流程相比,在贫富气2种气质条件下,RSVM工艺流程的主体装置总压缩功分别降低了9.86%和11.18%;(2)当原料气中CO_(2)含量介于2.0%~3.5%时,对于贫富气2种气质,RSVM工艺流程的最小冻堵裕量提高了0.6~8.6℃,且该流程对不同原料气压力的气质适应性强;(3)该流程设置了吸收塔和脱甲烷塔,两塔压力相互独立,吸收塔压力比脱甲烷塔塔压高,提高了塔板上CO_(2)冻堵裕量,降低了外输压缩功率。结论认为,改进后的RSVM工艺流程较RSV工艺流程能更有效控制CO_(2)固体形成,提高乙烷回收率,并能有效降低能耗,新流程可为乙烷回收装置设计和安全平稳运行提供有效的技术支持。

In China,CO_(2) content in oilfield associated gas increases significantly with the application of the recycle CO_(2) flooding technology in oilfields,and ethane recovery device is often used to recover ethane from oilfield associated gas.When the recycle split vapor process(RSV)is used for the recovery of ethane from high CO_(2) content natural gas,it faces the problems of high system energy consumption,difficult thermal integration,and easy formation of CO_(2) solids in the middle and upper parts of the demethanizing column tray.In view of these problems,this paper newly proposes the recycle split vapor multistage process(RSVM)which combines an absorption column with a demethanizing column,to improve the adaptability to CO_(2) in feed gas.In addition,RSV process and RSVM process are simulated and compared by means of Aspen HYSYS software,and their adaptability is analyzed.And the following research results are obtained.First,compared with the RSV process,the RSVM process is 9.86% and 11.18% lower in the total compression work of the main device under the conditions of rich and poor gas,respectively.Second,when the CO_(2) content of the feed gas is in the range of 2.0%-3.5%,the minimum freezing plug margin of the RSVM process for rich and poor gas is increased by 0.6-8.6℃,and this process has strong adaptability to the gas with different feed gas pressures.Third,the RSVM process includes absorption column and demethanizing column,and the pressures of both columns are independent of each other,with the pressure of absorption column higher than that of demethanizing column,which improves the CO_(2) freezing plug margin on the column tray and reduces the compression power of external transmission.In conclusion,compared with RSV process,the improved RSVM process can effectively control the formation of CO_(2) solids,improve the ethane recovery rate,and reduce energy consumption.What's more,the new process can provide an effective technical support for the design and safe and smooth operation of ethane recovery device.