Abstract:

In long-distance transmission of natural gas, safe operation of compressor units is seriously affected by droplets entrained in natural gas. The characteristics of re-entrainment in gas-liquid filtration process of filter cartridges were investigated using liquid aerosol of di-ethyl-hexyl-sebacate (DEHS). The effects of filter material wettability and filtration velocity on re-entrainment were also evaluated experimentally. Re-entrainment could be observed in the process of filtration as filter cartridges only composed of coalescing layers. More droplets were entrained into the downstream due to re-entrainment and some large particles could be detected at the downstream. Cumulative efficiency decreased at the large particle size at steady state. Re-entrainment was affected by filter material wettability. Compared with non-wettable filter material, re-entrainment was more obvious on the surface of wettable filter material. To improve filtration efficiency, non-wettable filter material were more suitable for producing industrial filter cartridges at the same filtration velocity. As filtration speed increased from 0.1 m·s^-1 to 0.3 m·s^-1, higher filtration velocity led to less re-entrainment, and filtration performance of wettable filter cartridges were improved more significantly than that of non-wettable filter cartridges. Re-entrainment could be eliminated by adding drainage layer to filter cartridges.

Key words: re-entrainment, aerosol, filtration, wettability, filtration velocity, natural gas

摘要：

在天然气长距离输送过程中,天然气夹带的液滴严重影响压缩机组的安全可靠运行。利用所建立的滤芯过滤性能检测装置,以癸二酸二辛酯为实验介质,分析了天然气净化用滤芯气液过滤过程中液滴二次夹带现象的特征,比较了滤材润湿性和过滤速度等参数的影响。结果表明:当滤芯仅由聚结层组成时,滤芯过滤过程中存在液滴二次夹带现象,二次夹带将导致下游气体中液滴数量增多,且有较大液滴出现,稳态阶段滤芯累积效率在大粒径处下降;液滴在滤材表面的润湿性对二次夹带现象具有重要影响,可润湿型滤材表面更易出现液滴二次夹带现象,在相同过滤速度下,若需提高过滤效率,宜选用不可润湿型滤材制作工业滤芯;在0.1～0.3 m·s^-1过滤速度范围内,提高过滤速度可减少液滴二次夹带现象的发生,与不可润湿型滤芯相比,可润湿型滤芯过滤效果的改善更为明显;滤芯增加排液层可有效消除液滴二次夹带现象。

关键词: 二次夹带, 气溶胶, 过滤, 润湿性, 过滤速度, 天然气