Research on Gas-Liquid Coalescence Filtration Performance of Electrospun Polyacrylonitrile Nanofiber Composite Filters

摘要

Coalescing filters are widely used to remove small droplets from gas streams, while it is increasingly difficult to meet the pollution emission requirements with traditional microfiber filters. Due to a large fiber surface area and small fiber diameter, the nanofiber materials are able to improve the overall filtration performance of filters. Electrospinning is one of the most common and available methods to prepare nanofibers. The work presents a study on the filtration performance of composite nanofiber filters with different properties, aiming to provide a better understanding of the application of nanofibers in the gas-liquid filtration field. A range of solutions with four different concentrations were prepared, with a polymer of Polyacrylonitrile (PAN) and a solvent of N, N-dimethylformamide (DMF). The glass fiber materials were selected as a substrate, on which the nanofibers were collected. Four different voltages were applied for each solution concentration. An additional layer of glass fiber, used as a protective layer, was covered on the prepared nanofiber layer to construct a sandwich. The effects of solution concentration and electrospun voltage on the structure and morphology of nanofibers, as well as filtration performance of composite filters were investigated experimentally A scanning mobility particle sizer (SMPS) was used to measure the aerosol concentrations upstream and downstream of the filters, from which the efficiency was derived. The results showed that the nanofibers prepared with various concentrations possessed different morphologies, where the overlap of two or three fibers occurred for high concentrations while beads were present for low concentrations. When the concentration was 14%, the fiber diameter first decreased, then increased with increasing voltage. It was also found that the solution concentration had a more significant effect on the fiber diameter, compared with the applied voltage. A low solution concentration had a small fiber diameter, leading to a high equilibrium efficiency wim an unremarkable increase in pressure drop.