双塔天然气氦气回收工艺设计及(火用)分析

Design and exergy analysis of double-tower natural gas helium recovery process

油田采用的深冷-膜分离联合法提氦工艺存在氦气回收率低、综合能耗高等缺点。提出了一种创新的天然气氦气回收方法,采用双塔提氦,将低温精馏与提氦工艺相结合,特点在于氦气提浓塔和氦气回收塔均采用具有温度梯度的多股进料方式。通过传统(火用)分析发现,该流程冷箱LNG-100(火用)损最大,占总(火用)损的47.48%。通过高级(火用)分析发现,该流程内源(火用)损远大于外源(火用)损,大多数设备的可避免内源(火用)损占比较高,这表明工艺改进应侧重于设备本身的性能改造,而不是工艺结构。改进冷箱LNG-100结构形式,提高压缩机效率,改进空冷器AC-302内部结构以及改善其他设备的工作状况能够有效降低设备(火用)损。塔设备的不可避免内源性(火用)损较大,改造这些设备受到一定的限制,并且塔内会发生精馏反应,使得提高有效能利用变得困难。

The cryogenic-membrane separation combined process used in the oilfield for helium extraction has low helium recovery and high comprehensive energy consumption. An innovative natural gas helium recovery process was proposed, which used double towers to extract helium and combine cryogenic rectification with helium extraction process. Its characteristic is that both helium concentration tower and helium recovery tower adopt multi-feed mode with temperature gradient. Through the traditional exergy analysis, it is found that the exergy loss of the cold box LNG-100 in this process is the largest, accounting for 47.48% of the total exergy loss. Through the advanced exergy analysis, it is found that the avoidable endogenous exergy loss of most equipment accounts for a high proportion, indicating that process improvements should focus on device performance rather than process structure.Improving the structure of cold box LNG-100, the efficiency of compressor, the internal structure of air cooler AC-302 and the working conditions of other equipment can effectively reduce the exergy loss. The inevitable endogenous exergy loss of the tower equipment is large, the transformation of these equipment is limited, and the rectification reaction will occur in the tower, which makes it difficult to improve the effective energy utilization.