天然气输送管道调压过程的火用分析

Exergy Analysis of the Pressure Reduction Process of Natural Gas Pipeline

长距离高压管输天然气在进入下游管道,要进行降压处理,传统的节流膨胀降压工艺存在着巨大的过程火用损。通过对输气管道调压过程进行火用分析后发现:在完成相同调压任务的情况下,采用透平膨胀机代替节流阀,可显著减少过程火用损、提高系统火用效率,亦可输出功率,产生工艺冷能,具有明显的技术经济效应。考察了进气温度、膨胀比对装置运行工况的影响。提出了回收利用管输天然气调压可用能的工艺流程,以提高能源的利用效率和管网运行的经济性。

The high--pressure natural gas transported by long--distant pipeline has to experience pressure reduction before being supplied into downstream pipeline, such as city gas pipe network. The traditional pressure reduction technology with throttle valve causes tremendous process exergy loss. Consequently, the exergy analysis was launched with regard to the pressure reduction process of natural gas pipeline. It reveals remarkable technical and economical effect by adopting turbo expander to substitute throttle valve when meeting the same pressure reduction requirement, thereby reducing process exergy loss, improving systematical exergy efficiency, as well as delivering power and generating technology cold energy. Besides, the influences of inlet temperature and the ratio of expansion to equipmentsr operating condition are also considered. In order to improve energy efficiency and pipeline operating economy, a new process flow chart is proposed for recovering and utilizing exergy embraced in the pressure reduction process of natural gas pipeline.