Solids Pyrolysis and Volatiles Secondary Reactions in Hazardous Waste Incineration: Implications for Toxicants Destruction and PIC's Generation

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Abstract
Solids are important contributers to the United States hazardous wastes problem. Hazardous solids include several million tons yearly of residues from industrial processing and treatment of other wastes, and millions to billions of tons of contaminated soils found in numerous, and widely distributed abandoned dump sites. Incineration is an attractive technology for decontaminating hazardous solids, but realization of its potential requires improved public acceptance which can come from better technical understanding. Organic solids fed to an incinerator are thermally decomposed (pyrolyzed, devolatilized) into three products requiring burnout: gases and liquids (volatiles) and a solid residue (char). This paper describes how solids pyrolysis and further, so-called secondary reactions of newly formed volatiles (e.g. cracking, partial oxidation) can contribute to desired and undesired effects within incineration chambers, e.g. high destruction efficiencies for targetted wastes, or generation of undesired by-products. It is shown that incinerator design, operation, and performance monitoring will benefit from better quantitative understanding of devolatilization-related phenomena. Important issues are how solids pyrolysis and volatiles secondary reactions are affected by properties of the raw waste, and by incinerator operating conditions (e.g. temperature, heating rate, treatment time, local oxygen partial pressure). Research methods for obtaining this information are discussed, typical results are illustrated, and research challenges and opportunities in solid wastes pyrolysis are noted.