MIXING AND CHEMICAL KINETIC CONSTRAINTS ON PIC PRODUCTION DURING CHLOROCARBON COMBUSTION

The amount and composition of products of incomplete combustion (PICs) in combustion systems is controlled by the complex interactions of turbulent mixing and chemical kinetics. The current paper addresses this problem by focusing on the effects of incomplete turbulent mixing on the extent of reaction and on the distribution of the local equivalence ratio, and investigating the contributions of chlorocarbon inhibition of chemical reaction to the emission of PICs. The experimental facility has been designed to simulate the conditions in actual incinerator systems; it consists of a Toroidal Jet Stirred Reactor (TJSC) followed by a Plug Flow Reactor (PFR). The experimental conditions allow one to investigate the combined effects of turbulent mixing and chemical kinetic inhibition on PIC emissions. To address these issues methyl chloride is injected into a baseline flow of hot products flowing in the PFR. Instantaneous temperature measurement, obtained by application of a laser Rayleigh scattering diagnostic, and stable species concentrations are then measured at various distances from the point of injection. The temperature probability density functions (pdfs) for fuel-lean and fuel-rich conditions show evidence of mixing constraints. Stable species concentration measurements prove that both mixing and chemical kinetic constraints are present in the PFR environment. Detection of aromatic species is interpreted as an effect of the variation of the local value of the equivalence ratio due to imperfect mixing. Finally, in order to model the combined chemical kinetic and mixing constraints and to determine which constraints are responsible for PIC emission, results from a highly simplified turbulent reacting flow model are presented. The model can predict the trend and magnitude of methyl chloride burnout and CO/CO2 ratio. Species, such as aromatic compounds, having a strong nan-linear dependence on the equivalence ratio can provide insights on the mixing history and might serve as diagnostics of failure modes in incinerators.