Affect of System Operation on Toxic Air Emissions

Regulatory agencies are becoming more interested in the control of toxic emissions from waste incinerators. Examples of the new regulations include the rules being developed by the U.S. Environmental Protection Agency (EPA) for hazardous waste incinerators and the State of California's recent measure calling for determination of toxic air emissions from a wide variety of equipment including almost all incinerators. This paper examines a technique that can be used to characterize toxic air emissions from waste incinerators. The technique consists of two components: • Pilot scale testing • Theoretical modeling. A series of pilot scale tests were conducted using a rotary kiln simulator to decontaminate soils. The behavior of several toxic metals and organic compounds were observed. The data highlighted the trade off between organics destruction and potential metals emissions. The conditions which maximized organic destruction were found to increase the emissions of certain metals. This finding has important implications in the permitting and operation of hazardous waste incinerators. Theoretical modeling verified the results. A preliminary model has been developed to simulate the behavior of metals in hazardous waste incinerators. This model was used to predict the affect of various operating parameters on metals emissions. The conditions which maximize destruction of organic materials, high temperatures and long residence times, may lead to increased vaporization of volatile metals. These metals condense on particles smaller than 1 micrometer as the exhaust gases are cooled. Particles around 1 micrometer are difficult to capture in flue gas cleaning equipment.