Experimental and Numerical Studies of PIC Formation During Chlorocarbon Combustion: Development of a Failure Mode Diagnostic System for Hazardous Waste Incinerators

Abstract

The major concern regarding organic emissions from hazardous waste incineration systems is the formation of products of incomplete combustion (PICs). Previous studies have shed light on the mechanisms of formation and emission of PICs, showing that the formation of these by-products is highly dependent upon the local ratio of fuel and oxidant, and that their amount and composition are sensitive to both turbulent mixing and chemical kinetic constraints. PIC emissions are closely related to the fluctuations in mixture ratio that result from the turbulent mixing process. Experimental and modeling studies are carried out in order to develop a fault diagnostic system for commercial hazardous waste combustors. The experimental facility has been designed to investigate the effects of both mixing and chemical kinetics on product formation. It consists of a Toroidal Jet-Stirred Combustor (TJSC) followed by a Plug Flow Reactor (PFR). An injector positioned at the PFR entrance allows one to inject a selected species directly into the PFR. A mixture of hydrocarbons and chlorocarbons is used as a hazardous waste surrogate. Benzene is injected into the PFR in order to investigate the combined effects of turbulent mixing and chemical kinetic inhibition on PIC emissions. The development of the fault diagnostics is approached by establishing a relationship between the PIC speciation measured in the exhaust and the kinetic and/or mixing failure mode that has led to the emissions. Finally, a numerical simulation of the turbulent reacting flow is attempted by incorporating a highly simplified reaction mechanism in a commercial CFD code. Results for injection of benzene into the PFR are compared to experimental data.