低压富气乙烷回收工艺改进

Improvement of ethane recovery process of low pressure rich gas

关键词:  低压富气  乙烷回收  回收率  工艺改进  CO₂冻堵 

Key words:  low pressure rich gas  ethane recovery  recovery rate  process improvement  CO₂ freezing and blocking

摘要:

目的国内油田伴生气乙烷回收均采用液相过冷工艺(LSP),解决该工艺在乙烷回收运行工况中存在的能耗较高、回收率较低的问题。 方法基于LSP工艺流程和气相过冷、气液相混合过冷的原理,提出气液两相过冷改进工艺(GLSP)、原料气分流过冷工艺(FGSP),并进行工艺流程对比分析,重点研究改进工艺的特性和对原料气中CO₂的适应性。 结果①GLSP工艺适用于外输气压力低的油田伴生气乙烷回收,具有乙烷回收率高、CO₂适应性强(CO₂摩尔分数为0.5%~2.5%)等特点；②GLSP工艺流程最优增压压力范围为4.0~4.5 MPa,乙烷回收率不宜超过95%；③在原料气中CO₂含量相同的条件下,随着气质变富,脱甲烷塔控制CO₂冻堵的能力不断增强；④在同一气质条件下,装置总能耗随着原料气中CO₂含量的增加而增大。 结论提出的改进工艺提高了乙烷回收率,确定了最优增压范围,并提高了对原料气中CO₂的适应性,为实际低压富气乙烷回收装置设计提供参考。 

Abstract:

ObjectiveThe domestic oilfield-associated gas ethane recovery adopts liquid subcooled process (LSP) ; the aim of this study is to solve the problems of higher energy consumption and lower recovery rate in the actual operation condition of LSP . Methods Based on the LSP and the principles of gas-phase subcooling and gas-liquid two phases mixed subcooling, two improved processes, gas and liquid subcooled process(GLSP) and feed gas split subcooled process(FGSP), were proposed and analyzed in comparison with each other, focusing on the characteristics and adaptability to CO₂ in the raw gas. ResultsFirstly,the GLSP is suitable for the ethane recovery process of oilfield-associated gas with low outgoing gas pressure. It is characterized by high ethane recovery rate and strong adaptability to CO₂ (CO₂ mole fraction of 0.5%-2.5%). Secondly, the optimal pressurization pressure range of the GLSP is 4.0-4.5 MPa, and the ethane recovery rate should not exceed 95%. Thirdly ,under the same condition of the CO₂ content of raw gas, as the gas becomes richer, the ability of the demethanization tower to control CO₂ freezing and blocking is increasing. Fourthly,under the same gas conditions, the total energy consumption of the plant increases with the increase of CO₂ content in the feed gas. ConclusionsThe proposed improved process has increased the recovery rate of ethane, determined the optimal pressurization range, and improved the adaptability to CO₂ in the raw gas, providing a reference for the design of actual low-pressure rich gas ethane recovery devices.