Abstract:

Coalescing filters are used to remove small droplets from air streams. They have numerous industrial applications including natural gas purification, engine crankcase ventilation and compressed air filtration. The evolution of pressure drop, penetration and saturation of oleophilic oil mist filters that distributed in different pore sizes during the process of gas-liquid filtration were examined. The effect of pore size distribution on filtration performance, liquid distribution form and droplet re-entrainment was also evaluated experimentally. The results showed that, when in “channel pressure” stage during the process of gas-liquid filtration, there was significant layering characteristic in the variation curves of pressure drop for filters with pore size distributed increasingly, as well as penetration of droplets above 0.8 μm. There existed a clear difference of steady-state filtration performance between filters with various pore size distribution, which was mainly induced by transfer phenomenon of liquid migration channels inside the filters. By comparing with filters with pore size distributed decreasingly and evenly, it was found that in steady state the filters with pore size distributed increasingly had lower pressure drop, the highest quality factor, less droplet re-entrainment and the highest fractional efficiency for all droplets above 0.8 μm. Therefore, the filters with pore size distributed increasingly were more advantageous for coalescing filter design.

Key words: fibrous filter, filtration, aerosol, coalescence, re-entrainment

摘要：

在天然气净化、大型旋转机械曲轴箱通风和压缩空气过滤等领域，气液聚结过滤器具有广泛的应用。利用滤材过滤性能实验装置，分析了气液过滤过程中不同孔径梯度分布的亲油型滤材的压降、穿透率和饱和度变化，比较了其过滤性能、内部液体分布特性以及对液滴二次夹带现象的影响。结果表明：在气液过滤过程“通道压降”阶段，孔径递增滤材压降和0.8 μm以上液滴穿透率的变化曲线具有明显的分层特征。不同孔径梯度分布滤材的稳态过滤性能存在明显差异，主要原因是滤材内部存在液体运移通道的传递现象。通过与孔径递减和孔径均匀分布滤材的稳态过滤性能对比，发现孔径递增滤材在保证较低压降的同时具有最高的品质因子，有利于减少液滴二次夹带现象的发生，且对0.8 μm以上不同粒径液滴均具有最高的过滤效率，即孔径递增滤材在气液聚结过滤器设计中更具优势。

关键词: 纤维滤材, 过滤, 气溶胶, 聚结, 二次夹带