Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
REQUIREMENTS AND CONSIDERATIONS FOR CHEMICAL DEMILITARIZATION TECHNOLOGIES 85 to a diffusional limitation, a limitation that would also probably limit the use of microbial organisms or their related large molecule enzymes. The diffusion of heat in solids, liquids, and gases occurs at a much higher rate than molecular diffusion. Thus, the ability of heat to reach and destroy isolated pockets of agent makes heating the process of choice to date for decontaminating residual agent from the surface of solids. Chlorinated Dioxins In addition to providing for the complete destruction of the chemical agent, any alternative process must not inadvertently create other harmful waste products. Of special regulatory concern is the possible production of chlorinated dioxins by recombination of the components produced in the primary agent destruction process. Chlorinated dioxins can be formed in waste gas streams where the temperature is 180 to 400°C and where chlorine and reactive hydrocarbons are present. The reactions take place on the surface of inorganic particulate matter. Salts of iron, copper, and aluminum, as found in fly ash from coal combustion, catalyze this reaction. Subjecting chemical agents to high-temperature pyrolysis or oxygen-deficient combustion will also produce hydrocarbon fragments, which, if not destroyed in an afterburner before cooling to below 400°C, can lead to chlorinated dioxin formation if chlorine is present. The agents GB and VX contain no chlorine; however, HD can be a major source. Nonetheless, because the concentration of allowable chlorinated dioxins is extremely small, even small quantities of chlorine (such as may be present because salt in the air used in oxidation processes) may be sufficient to produce significant quantities of chlorinated dioxin if the proper conditions for the recombination reactions exist. Thus, all processes should be selected and designed to minimize the time spent in the critical 180 to 400°C temperature range and to have subsequent process steps for adequately removing any chlorinated dioxins that are formed. Although the 5X decontamination equilibrium conditions of 1000°F (538°C) for 15 minutes are somewhat above the recombination temperature range, they may allow some synthesis of chlorinated dioxins. More important is that the decontamination of metal parts is inherently a batch process with a substantial heat up time (minutes). Bemuse volatile organic compounds will be released during this heat up period, some chlorinated dioxins may be formed as the heat up progresses through the critical 180 to 400°C temperature range. Further, although subsequent afterburning of any off-gases may destroy these chlorinated dioxins, they might again be produced in the subsequent cooling of the gas if adequate hydrocarbon and catalyst surface still remain
