中高压富气乙烷回收工艺改进及优化

Improvement and optimization of ethane recovery processes for medium and high pressure rich gas

关键词:  富气  精馏原理  乙烷回收  交互作用  响应面优化

Key words:  rich gas  principle of distillation  ethane recovery process  interaction  response surface optimization

摘要:

针对RSV(recycle split-vapor process)工艺在进行中高压富气乙烷回收时,存在能耗高、流程热集成度低等问题,基于精馏原理,采用改变气源与多级分离的方法提出RSVF(recycle split vapor with liquid flashing process)工艺。再以乙烷回收率和总压缩功耗为响应值,通过灵敏度分析法选出脱甲烷塔压力、低温分离器温度、外输干气回流比、闪蒸温度作为设计变量,采用基于三水平Box-Behnken的响应面法优化工艺参数,对两个模型进行ANOVA法验证。优化后得到的最佳工艺参数为:脱甲烷塔压力2 820 kPa、低温分离器温度-48 ℃、外输干气回流比14.2%、闪蒸温度-40.6 ℃。在天然气处理量为500×10⁴ m³/d的情况下,工艺经济效益增加了1 551万元/年。 

Abstract:

Aiming at the problems of high energy consumption and low process heat integration in the RSV(recycle split-vapor) process in the ethane recovery of medium and high pressure rich gas, based on the principle of distillation, RSVF (recycle split vapor with liquid flashing) process is proposed by changing the gas source and using multi-stage separation. Then taking the ethane recovery rate and the total compression power consumption as the response values, and the demethanizer pressure, the cryogenic separator temperature, the reflux ratio of the external dry gas, and the flashing temperature are selected as the design variables through the sensitivity analysis method. Behnken's response surface method is optimized for the process parameters, and the two models are verified by ANOVA. The optimal process parameters obtained after optimization are as follows:the pressure of the demethanizer is 2 820 kPa, the temperature of the cryogenic separator is -48 ℃, the reflux ratio of the external dry gas is 14.2%, and the flashing temperature is -40.6 ℃. When the natural gas processing capacity is 5×10⁶ m³/d, the economic benefit of the process has increased by 15.51 million yuan per year.