Load-Wash Testing of Regenerable Sintered Metal and Ceramic Membrane Filter Media

Abstract

Sintered metal and ceramic membrane filtration media have a broad range of applicability due to their mechanical strength, chemical resistance, and their ability to withstand conditions of excessive heat and moisture. Additionally, these media can be cleaned with back pulses of liquid or air. However, these filters are sufficiently more expensive than traditional media, and must last significantly longer in order to be cost effective. Thus, it is necessary to confirm that these filter media maintain efficiency after repeated cleaning. A series of tests has been conducted using ceramic membrane, sintered metal fiber, and powdered sintered metal filter media supplied from three manufacturers to evaluate their performance after repeated loading and washing cycles. The media were loaded to approximately twice their initial differential pressures with a water-insoluble, iron-rich aerosol challenge, and regenerated with a weak acid solution and water. Media were evaluated for pressure drop and filter efficiency changes from one cleaning cycle to the next. Microscopic examination of filter media was also conducted to determine the extent to which particle residues remain after cleaning. Filter efficiencies on the order of 90 to 98% were typical, and the most penetrating particle size was observed to be on the order of 100 nm. The media demonstrated the ability to be effectively cleaned with minimal performance degradation. Although filter efficiencies are reported, the reader should keep in mind that the focus of this study was to evaluate filter media performance after a series of load/wash cycles, and is not intended to be a filter efficiency study.