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Improvement of Filter Media for Cotton Dust Control

The performance of pile fabrics used as filter media in cotton-mill local-exhaust-ventilation systems was examined.. It was first established that a satisfactory laboratory-test aerosol of cotton dust could be generated from previously collected trash. It was found, as a by-product of this first step, that cotton dust contains few particles smaller than about 0.5 μm. A filtration apparatus was built for measurements at face velocities from 0.5 to 1.0 m/s. Within this range the penetration for these fabrics increased almost linearly with velocity. The particle-size distribution up- and downstream of the fabrics was almost identical, indicating that penetration was either of the "straight through" or of the "pinhole plug" type. The concepts of electrical stimulation of fabric filtration were explored to establish whether this method could be used to improve the performance of cotton-dust filter media. It was observed that an electric field generated by the application of 9 kV to wires on the up stream surface of the fabrics reduced both penetration and cake resistance by approximately 50%. It was also found that certain modifications of the fabric structure can improve filtration efficiency.