Preparation and Characterization of Porous Composite Filter Medium by Polytetrafluoroethylene Foam Coating
Abstract The high costs of ceramic and Teflon filter media for hot gas cleaning has limited their industrial applications. This paper presents a foam coating technology that can be used to produce an inexpensive and highly efficient filter for industrial applications. A new apparatus was designed and built that coats porous glass mats with liquid-phase polytetrafluoroethylene (PTFE). The machine generates bubbles, enables the formation of uniform micropores less than 45 μm in diameter, and produces a product with air permeability greater than 5.5 cm3/cm2/sec. The resulting filter was found to be thermally stable up to 270 °C without any visible distortion and was comparable in dust collection efficiency to other commercial filter media. In addition, its de-dusting efficiency was greater than 85%, which is similar to that of other test filter media.
Influence of pleat geometry on filter cleaning in PTFE/glass composite filter
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, α, which stands for the ratio of pleat height to pleat pitch, is 1.48 for optimum operation. When the α 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, α, 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.
Proteins at air-water and oil-water interfaces: static and dynamic aspects.
Abstract Proteins are very surface‐active substances, which means that they readily adsorb onto O/W and A/W interfaces, even if present in very low concentration. They do not yield a very low interfacial tension. Adsorption, conformation in the interface, and the various interfacial properties resulting from their adsorption are briefly reviewed, especially in relation to formation and stability of emulsions and foams. Displacement from the interface by small‐molecule surfactants is also discussed. It is concluded that most effects of adsorbed proteins on the various kinds of physical instability of emulsions and foams are semiquantitatively understood, but that the variation among proteins in the production of small droplets and bubbles during emulsification and foaming, respectively, still largely defies explanation. It makes little sense to classify proteins according to their suitability for emulsification or foaming, because each of the physical properties of these systems may depend in a different w...