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3 Controlling Trace Organics with Passive Activated Carbon Filters
Pages 20-30

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From page 20...
... in August 1991 to "polish" reheated flue gas from the scrubber towers. Since then, the design problems listed below have been addressed: 20 plugging of the bed by fine Articulates that penetrated the particulate-control device preceding the filter rapid saturation of the leading edge of the bed with acid gases development of practical, zero-leakage isolation dampers movement of the bed and generation of fine particulates within the bed New standards for emissions of dioxins and mercury for incinerators in several European countries in 1989 and 1990 led to the widespread use of activated carbon filters as a final stage for polishing flue gas (Hartenstein, 1993~.
From page 21...
... No agent has ever been measured in the stack as a consequence, and any release from the furnace into the room air is passed with the air through carbon beds before it is released to the atmosphere. Although the major adsorbable species of the flue gas from chemical agent incinerators have been characterized, the performance of carbon filters on this specific flue gas with its particular SOPCs has not been experimentally determined.
From page 22...
... The chlorinated dioxins and furans measured during trial burns were all at very low concentration levels, and the mustard, if present at all, was below the detection level. The Army and its contractor attempted to characterize carbon-filter adsorption, with special emphasis on these materials experimentally and theoretically (Mitretek Systems, 1997~.2 Carbon beds on incinerators are usually designed to operate for extended periods of time before they become saturated (in the case of the PFS, for more than a year)
From page 23...
... Application to the Incineration of Chemical Agents and Munitions There are two basic problems in determining the adsorption isotherms for a fixed carbon bed (the PFS) with the Army' s baseline incineration system: .
From page 24...
... In these plants, powdered activated carbon was injected into the gas stream and then separated using either an electrostatic precipitator (municipal waste incinerator) or fabric filter (medical waste incinerator)
From page 25...
... As the name implies, the adsorbed materials are assumed to form an "ideal solution" in the solid adsorbent; each component then exerts a vapor pressure proportional to its mole fraction and its single TABLE 3-3 Chlorinated Dioxins Adsorbed on Powdered Activated Carbon Concentration of Dioxin in Gas Phase (ng/dsm3) Concentration of Dioxin on Solids (grams/kg carbon)
From page 26...
... No attempt was made to correct them for temperature, although a much TABLE 3-4 Estimated Carbon Filter Breakthrough Times for Substances of Potential Concern in Stack Gases from the Chemical Agent Disposal Facility Liquid Incineratora Estimated Initial Estimated Breakthrough Estimated Time for Substance Concentration ng/m3 Time as Single Componentb MulticomponentPFS Flue GasC Tetra CDD 0.13 1.5 x 107 years > 5 years Octa CDD 0.24 1.7 x 107 years > 5 years Tetra CDF 0.21 6.8 x 107 years > 5 years Penta CDF 0.088 2.6 x 107 years > 5 years Hexa CDF 0.11 2.2 x 107 years > 5 years Hepta CDF 0.16 1.8 x 107 years > 5 years Bis (2-Ethylhexyl) phthalate 19,000 650 years > 5 years Benzene 90,000 2.4 years 14.2 hours Carbon tetrachloride 35,000 4.1 years 7.1 minutes Chloroform 22,000 2.5 years 5.7 hours Chloromethane 780,000 1.8 years 7.4 minutes cis-1,3-dichloropropene 250,000 1.7 years 1.0 days Methylene chloride 5,900,000 38 days 2.1 hours Vinyl chloride 4,500 1.7 days 9.5 minutes aBed dimension = 214 square feet, 1 foot deep, 3,030 kg of carbon bCalculated based on D-R equation assuming complete saturation of filter at 135F CBased on multicomponent computer model, 135F, 67 percent relative humidity Source: Adapted from Mitretek Systems, 1997.
From page 27...
... . Because more can certainly be adsorbed at the lower temperature, the predicted breakthrough time at 160F would be longer.4 The data in Table 3-3 represent multicomponent adsorption, so the estimated breakthrough time for chlorinated dioxins and furans should be compared with the right-hand column of Table 3-4, "Estimated Breakthrough Time for Multicomponent PFS Flue Gas." Because the estimates are in roughly the same range, they lend some confidence to the calculated results in Table 3-4.
From page 28...
... . In addition, the plant data support the laboratory findings and, thus, reinforce the conclusion derived from theoretical modeling that the PFS carbon bed would effectively remove the compounds of greatest public concern for an extended period of time.
From page 29...
... SUMMARY Carbon filters have been added to many combustion facilities in Europe (see Appendix C) and have proven to be very effective in reducing already low
From page 30...
... Based on these studies, reasonable ranges can be predicted for the quantities of SOPCs adsorbed, and from them a prediction can be made of the useful life of the carbon beds. The calculations suggest that the carbon beds would last for the duration of the munitions destruction programs at both Anniston and Umatilla.


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