Electrospinning is a simple and versatile process to produce polymer nanofibers, which are useful for ultrafine particle filtration. In this study, a polyurethane filter with an average fiber diameter of 150-250 nm was prepared through the electrospinning process and its filtration characteristics were investigated. We found that the electrospun fiber diameter was highly dependent on the polyurethane concentration, electric field, and tip-to-collector distance. As the polyurethane concentration, electric field, and tip-tocollector distance under the same electric field increased, the fiber diameter increased. We also found that the produced filter media had a minimum collection efficiency at particles sizes from 80 to 100 nm, which implies an electrostatic attraction between the filter and the test particles. Furthermore, we observed that interception was a predominant collection mechanism at Peclet numbers higher than 10 in nanofiber filtration for ultrafine particles.Implications: A polyurethane nanofiber filter with excellent mechanical properties was prepared, and the effect of operating conditions on fiber morphology was examined. The filter fabricated by an electrospinning process is charged and has high filtration efficiency due to electrostatic force. Therefore, it can be a good alternative to control hazardous ultrafine particles.
A pleated filter bag is often used to treat exhaust gas in many industrial applications, due to its fairly high dust collection efficiency and relatively low pressure drop. This work deals with the optimum pleating geometries of a pleated filter made with a newly developed PTFE/glass composite filter. It was found that pleating geometries, including pleat height and pleat pitch, directly affect the cleaning efficiency. The design index, a, which stands for the ratio of pleat height to pleat pitch, is 1.48 for optimum operation. When the a value was higher than 1.48, the pressure drop across the pleated filter medium increased, resulting in a decreased cleaning interval due to the difficulty of filter cleaning. Therefore, it is necessary that the optimum pleating geometry should be determined by employing the dimensionless parameter, a, in the design of cartridge filters.Implications: A pleated filter bag is often used to treat exhaust gas in many industrial applications due to its fairly high dust collection efficiency and relatively low pressure drop. The present paper introduces an optimum design configuration to make a pleated filter with newly developed PTFE/glass composite filter media. A dimensionless parameter that is the ratio of pleat height to pleat pitch should be considered to make the best quality pleated filter.
Bag houses are often used to control particulate matters and recover valuable resources in various industries. A bag filter is the most important component in a bag house system, and thus it is important to develop the best-quality filter media and determine the optimum operating conditions of a bag house system. This study focused on particle penetrations under an operating condition of a bag house system, and investigated the relationship between dust clogging and dust penetration as a function of pressure drops across the filter medium. The results showed a minimum collection efficiency of 80% for 0.45 μm particles at the initial stage of filtration, although this quickly recovered and remained over 99.99% with a pressure drop greater than 20 mmH 2 O with a newly developed porous filter (air permeability = 5.78 × 10 −11 m 2 ). Furthermore, the recovery time depended strongly on particle size. While it was inversely proportional to the particle size at the initial stage of filtration, it showed no difference for particles larger than 0.725 μm due to its uniform dust cake as filter cleaning proceeded.
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