The report gives results of bench- and pilot-scale studies of the dust collection characteristics of fabric filters. Techniques for measuring dust deposit porosity as a function of cloth characteristics and filtration velocity on a bench-scale filter have been developed and are described. A method for impregnating and slicing the dust deposit for examination under the electron microscope is also described. For the pulsejet pilot-scale filter, flyash penetration decreased as the dust deposit thickened, increased with increasing filtration velocity, and remained relatively constant for particles down to 0.30 micrometers diameter. Three dust emission mechanisms were investigated, using chemically tagged flyash. Penetration by straight-through dust loss falls off rapidly after cleaning, but later increases. Seepage of dust through the fabric was constant throughout the filtration cycle. Dust lost as pinhole plugs increased after cleaning, but later declined; however, the pinholes may open the way for further emission by the straight-through mechanism. Fabric cleaning was a problem in both the pulsejet and shaker cleaned filters during high velocity operation; redesign of commercial equipment is necessary.

Jan. 1976. "EPA-600/2-76-020." Harvard School of Public Health, Boston, Mass., EPA grant no. R801399-02, program element no. 1AB012, ROAP no. 21ADJ-057. EPA project officer: J.H. Turner. Includes bibliographical references (pages 139-181). For sale by the National Technical Information Service, (Price upon application). 4to.