天然气净化用气液聚结滤芯过滤分离机理研究

Considering about problems of coalescence filter for gas-liquid separation on natural gas long-distance pipelines, such as low filtration efficiency, short operating life，high operating cost and so on, a new type of high efficiency and environmental-friendly coalescence filter should be developed as soon as possible. Research at home and abroad mainly focuses on the process of coalescence and the efficiency model in disc-filter medium. According to the previous research of this laboratory, the size of industrial filter element has a prominent effect on filtration performance, and the content of solid particles in natural gas is the key factor affecting operating life. In order to study the performance of nonuniformity in height direction of droplets transportation which is caused by the physical properties of droplet and the structure of filter fibers, Micro computer tomography technology (Micro-CT) is applied to analyze the distribution characteristics of coalesced droplets in filter layers, and analytical means, for example, photomicrography and high speed CCD, are used for micro-perspective research of filter droplet sedimentation in exhaust side area, and the phenomenon of droplets entrainment.Scanning electron microscopy (SEM)is used in the research to determine the structure of solid particles in gas inlet side area and sedimentation in filter layers, and to measure the influence of the solid content on filtration performance and operating life of gas-liquid coalescence filter. The model is established to predict gas-liquid filtration performance and filter operating life by making use of the dimensionless number group including the parameters of droplet properties, physical properties and the structure of fibers. Based on the results above, the technical supportting for developing high efficiency and environmental-friendly coalescence filter can be provided.

天然气长输管道气液分离用聚结滤芯存在过滤效率低、运行寿命短和运行成本高等问题，研发新一代高效环保型聚结滤芯成为亟待解决的工程难题。国内外研究主要集中在圆盘型滤材样品内液滴聚结过程和效率模型。本课题组前期研究发现，工业用滤芯的尺度效应会显著改变过滤性能，而气体中的固体颗粒含量则是影响运行寿命的关键因素。利用微计算机X射线断层扫描技术测定滤层内聚结后的液滴分布形态，应用显微摄影与高速CCD等手段分析滤芯排气侧区域液滴的沉降过程和液滴夹带现象，揭示液滴物性和滤层纤维结构对整根滤芯沿不同高度位置液滴运移过程不均匀性的影响规律。利用扫描电镜等手段测定固体颗粒在滤芯进气侧的粉尘结构和滤层内的沉积过程，深入研究固体粉尘含量对气液聚结滤芯的过滤性能和运行寿命的影响。由液滴物性、纤维物性和滤层结构等参数组成的无量纲准数群，建立气液过滤性能分析和滤芯运行寿命预测模型，为研制高效环保型聚结滤芯提供技术支撑。

本项目以天然气净化用气液聚结滤芯为研究对象，较全面的研究了聚结过滤过程中的液体形态及分布、排液过程、液滴夹带现象、气液固三相过滤以及高压工况下的过滤性能，取得了一些具有重要意义和参考价值的研究成果。. 项目组采用 Micro-CT 技术完成滤芯不同高度位置滤层内液体含量及液滴存在形态特性检测分析，分析了各位置的液滴浓度、粒径分布以及液滴夹带现象，发现了滤芯沿长度方向存在的不均匀特性，并进一步研究了滤芯尺度对过滤性能和和排液过程的影响；研究了滤芯内部沿厚度方向的液滴形态及含量分布特性，考查了液滴与滤材间接触角、滤层结构等参数对滤层内液体存在形态和滤芯性能的影响机理，观测并分析了滤芯排气侧表面液膜气泡破裂动态过程、大直径液滴的重力沉降过程以及小直径液滴夹带过程；采用液滴和固体颗粒交错发尘的方法，研究了固体颗粒和液滴分别对气液过滤过程以及气固过滤过程的影响，分析了固体颗粒和液滴混合浓度比例以及操作参数对分离性能的影响；根据液滴在滤芯内部的分布规律，并结合毛细管理论，建立了滤芯饱和度计算模型。同时，在某天然气压气站内建立了聚结滤芯高压性能检测装置，在高压实际运行工况下对聚结滤芯实际过滤性能进行了评价，结合天然气长输管道聚结滤芯现场测定数据，提出了滤芯运行寿命预测模型。. 本项目的圆满完成，完善了天然气聚结过滤机理的相关理论，对研发新型高效低阻型天然气聚结过滤元件提供了重要理论支撑。