Effect Of Surface Wettability On Gas-Liquid Coalescence Filtration Performance Of Glass Fiber Filters

In the industrial processes such as natural gas exploitation,transportation and metal cutting,removal of hydrocarbon,lubricating oil and other droplet impurities in gas with high efficiency and low resistance is the key to ensure the gas quality and safe operation of instrument equipment.Coalescence filtration is a commonly used droplet removal method,which mainly uses glass fiber filters.However,due to the oleophilic characteristics of the filter itself,it is easy to cause droplets to form a film on its back or accumulate in the interior,resulting in low efficiency and high resistance.Therefore,some glass fiber filters were manufactured and then treated by surface modification to study the filtration performance of filters with different surface wettability and structural parameters,and an optimization method of wettability gradient combined filters was put forward.Moreover,the mechanisms of filtration performance improvement were analyzed.The research results aim to provide technical support and new ideas for the research and development of highly efficient gas-liquid coalescence filters.For oleophilic filter,with the decrease of fiber surface energy,the jump pressure drop decreases and the channel pressure drop increases,but the filtration efficiency is basically unchanged;For oleophobic filter,with the decrease of fiber surface energy,the filtration efficiency and jump pressure drop increase,while the channel pressure drop decreases.Compared with oleophilic filter,the steady-state pressure drop of oleophobic filter is reduced by 21.6%,and the filtration efficiency of oleophobic filter for small size droplets is increased by 6.7%.The change of fiber surface energy leads to more clean fiber area and lower jump pressure drop in the oleophobic filter,which is the main reason for the improvement of its filtration performance.In order to solve the problem of high pressure drop of oleophobic filters in multi-layer combination,through the gradient combination of filters with different wettability,it is found that the combination method of wettability gradient decrease not only has the filtration efficiency similar to that of oleophobic filter,but also the steady-state pressure drop lower than that of oleophilic filters;Compared with oleophilic filter,its steady-state quality factor for large size droplets is increased by60.7%.Through theoretical analysis and liquid distribution observation,the resistance of the capillary force difference between filter layers to the backward transmission of aerosol droplets,and the absence of obvious jump pressure drop are the main reasons for achieving high efficiency and low resistance.With the increase of the pore size of the filter,the effect of oleophobic modification on the improvement of its filtration performance is more significant;Even if the number of filter layers increases,the oleophobic filters can still maintain a low steady-state pressure drop.The main reason for the above phenomenon is that the air flow channels inside the filter become wider due to the increase of pore size.Meanwhile,by analyzing the filtration performance of the improvement sandwich filters of wettability gradient decrease under large pore size,it is found that the filter treated by this method has the characteristics of high efficiency and low resistance under different pore size.Besides,for the phenomenon of multiple jump pressure drops caused by the increase of gaps in the filter,a thicker filter is prepared to replace multi-layer thinner filters,so as to offset the influence of such factor,and the feasibility is verified.