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Show INTRODUCTION The primary objective of waste combustion is to permanently dispose of dangerous materials. However, combustion may liberate toxic materials into the environment or produce toxic byproducts. These possibilities have led to public concern over the use of incineration. In response to this concern, regulatory agencies are imposing increasingly strict limitations on the release of toxic materials from waste incinerators. A wide range of toxic materials are potentially emitted from waste combustion systems including: • Toxic metals • Organic constituents of the waste and by-products of combustion • Pathogens • Acid gases All of these pollutants are being addressed in the regulations. Faced with this increased regulatory activity it is vital that methods be developed to evaluate the impact of operating conditions on toxic emissions from combustion equipment. Full-scaling testing is the most direct approach to characterizing the relationship between incinerator operation and toxic emissions. However, there are significant limitations associated with the use of full-scale testing. First, the testing is expensive. A test covering only three or four operating conditions can cost over $1 million. Second, incinerators cannot be operated at conditions which would produce poor combustion. Incinerator operating permits do not allow operation outside of a narrow envelope. In addition, there are significant dangers associated with operating an incinerator outside of its safe operating envelope. However, valuable information may be gathered when incinerators are operated at these undesirable conditions. Third, in full-scale equipment many parameters are closely interrelated. It is not possible to isolate the impact of single parameters on emissions. Finally, it is often desired to evaluate potential emissions from a system which has not yet been constructed. To compensate for the limitations of full-scale testing, a technique was developed which involves the use of small-scale testing and theoretical models. Small-scale testing facilitates detailed analysis of important phenomena over a range of conditions. Modeling is used to plan the small-scale tests and to extrapolate the information gained in small-scale tests to full-scale equipment CASE STUDY Small-scale testing and modeling were used to evaluate the emissions which may result from the destruction of a Superfund waste in a rotary kiln incinerator. The materials were thought to have originated from paint manufacturing. The contaminates were organic compounds which contained significant quantities of heavy metals. Preliminary evaluation of the site and the waste had led to the conclusion that rotary kiln incineration was the most appropriate treatment method for the most heavily contaminated materials. However, because of the presence of significant amounts -2- |
