The U.S. Army operates deactivation furnaces to demilitarize spent and expired munitions. These furnaces are subject to the National Emission Standards for Hazardous Air Pollutants (NESHAPS) published by the U.S. Environmental Protection Agency. NESHAPS mandates reduction in lead and mercury emissions among various other volatile and semi-volatile metals and toxic organic compounds. The typical temperature range near the end of the exhaust stream is 422–588 K. The availability of filters capable of capturing particulate emissions, including PM2.5, at these temperatures would reduce the overall costs of operating ceramic baghouses or sorption units and improve the emissions control. With their existing emissions control equipment, it will be difficult for these demilitarization furnaces to meet newer final standards. One of the approaches currently under investigation by the US Army Engineer Research and Development Center is to use high temperature stainless steel filters followed by a high-temperature dry adsorption unit. Custom fabricated stainless steel filters (0.533 m diameter) with nominal pore sizes of 1, 2, 5, and 10 μm, capable of withstanding temperatures up to 922 K, have been evaluated in a laboratory test setup. Filter evaluations yielded data on particle filtration and penetration efficiency, dust-holding capacity and pressure drop. Materials such as perlite and other aluminosilicate materials were also evaluated in the laboratory for sorption of lead and other volatile and semi volatile metals. To enhance the adsorption capacity of perlite, it was treated with a number of chemicals including elemental sulfur, HCl, H2SO4 HNO3, and NaOH. Perlite and treated perlites were evaluated for lead adsorption capacity in the temperature range of 373- 623 K. Sulfuric acid treated perlite showed a maximum adsorption capacity of 4,634 μg Pb/g at 473 K while the untreated perlite gave a value of 1197 μg Pb/g. Results from laboratory studies on these stainless steel filters are being analyzed.
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