The Department of Defense (DoD) and Department of Energy (DOE) need new, cost-effective technologies to comply with the proposed, more stringent Environmental Protection Agency (EPA) standards for particulate matter as small as 2.5 microns (PM2.5) for combination sources such as jet-engine test cells (JETCs), diesel engines, generators, incinerators and steam boilers.

The objective of this project is to develop and test a series of high-efficiency particulate filters based on ceramic-membrane-coated silicon carbide (SiC) monoliths. Specifically, these filters are to have: (1) approximately 99.9% soot removal with low change in pressure (ΔP) for diesel exhaust aftertreatment, up to two orders of magnitude better than current diesel filters; (2) greater than 99.9% particulate removal with modest ΔP for fixed sources (incinerator applications); and (3) greater than 99.99% particulate removal for removal of toxic particulates (chemical and biological agents).

Schematic of Catalyzed Ceramic PM Filter

The project will be carried out in three phases to develop high performance filters that control pollutant emissions from combustion sources. These phases include (1) development and characterization of SiC monolith filters which will be operated in various modes, either for high-efficiency full-particulate- retention, passive catalytic regeneration or backpulse regeneration; (2) scale-up of filter construction, catalyst impregnation methods, and testing; and (3) single filter, slip-stream tests at selected DoD user sites. Three types of filter will be tested. The first is a backpulse-regenerable, compact, ceramic filter capable of reducing particulate concentrations to PM2.5 compliant levels. The second type has an oxidation catalyst deposited on and within the pore structure to simultaneously remove gaseous pollutants such as volatile organic compounds (VOCs) and carbon monoxide (CO). The third filter type has an oxidation catalyst for removal of organic particulate that will be deposited on the surface of the membrane coating. This catalyst will passively regenerate the filter by oxidizing the filtered particulates, thereby eliminating the need for backpulsing. Field tests will be conducted to demonstrate the efficacy of removing particulates, VOCs and CO from selected gas streams.

CeraMem has designed, procured, and installed equipment for the fabrication of prototype full size particulate filters. Membrane coating formulations and procedures as well as passageway cementing procedures were developed and full size filters have been produced with very high fine particulate retention capacity. Membrane-coated filter samples have been produced by this research team which have retentions exceeding 99.999%. This filter will remove particulate matter far in excess of the EPA-proposed standard for the year 2007 of 0.01 g/bhp-hr. CeraMem has developed concepts for a unique configuration of monolith diesel filters. A patent application for these concepts has been prepared and filed with the U.S. Patent and Trademark office.

The proposed filters will bring a unique combination of particulate removal capability, temperature resistance (900°C), and compactness. This very high efficiency and high temperature capability will allow various DoD sources to meet even the most stringent particulate emission regulations. The combination of catalytic oxidation processes addresses the need for filtration to treat organic vapor phase contaminants, CO, and organic particulate contaminants.