EVALUATION OF REGENERABLE FILTER MEDIA

High efficiency particulate air (HEPA) filters employing fibrous glass filtering media are used extensively throughout the DOE complex and are a critical element in treating off gases from waste treatment processes. These filters are capable of lowering particulate matter (PM) emission rates to levels much lower than regulatory thresholds, however, they have definite limits with regard to mass loading capacity and ability to withstand certain upset conditions. The most commonly identified threats to HEPA filter performance are moisture and rapid blinding of filters by smoke. Filtering media of sintered metal or ceramic has been suggested as an alternative for fibrous glass, yet unit cost and operational parameters such as differential pressure across the filters have reduced their deployment as alternatives to HEPA filters. There does seem to be great potential for using these types of filters, however, as protective pre-filters for nuclear grade HEPAs. Regenerable pre-filters do not have to achieve HEPA performance levels and so lower pressure drop units can be developed. Additionally, these filter media have much greater strength and can withstand the rapid blinding of a process upset with out failing structurally. Finally, these filters will not be adversely affected by moisture and can serve to protect the conventional HEPA from becoming wet.