Reducing Hazardous Waste Incinerator Emissions Through Blending: A Study of 1,1,1-Trichloroethane Injection

Abstract

We investigate whether blending liquid hazardous wastes with hydrocarbons such as alkanes can improve the destruction efficiency and reduce the combustion byproduct levels in the post-flame region of a laboratory scale combustor. Outlet species concentrations are measured with an FTTR spectrometer for mixtures of 1,1,1-trichloroethane and 25% (by volume) dodecane or heptane injected as a spray of droplets. We also inject sprays of liquid pure 1,1,1-trichloroethane, gaseous pure 1,1,1-trichloroethane, and gaseous 1,1,1-trichloroethane with 25% (by volume) heptane. Once vaporized, the 1,1,1-trichloroethane decomposes to form CO2 and HCl through the intermediates 1,1-dichloroethylene, phosgene, acetylene, and carbon monoxide. The 1,1,1-trichloroethane/alkane mixtures also form the intermediate ethylene. No significant differences are observed between injecting the compounds as a droplet spray or as a gaseous jet, not an unexpected result as the mixing time of the gas jet is longer than the vaporization time of the droplets. The addition of heptane or dodecane to 1,1,1-trichloroethane produces two principal effects: an increase in ethylene, acetylene and carbon monoxide levels for injection temperatures between 950 to 1040 K, and a decrease in 1,1-dichloroethylene, phosgene, acetylene, and carbon monoxide levels for injection temperatures greater than 1050 K. Reaction of the injected alkane causes the former effect, while the additional heat of combustion of the alkane additives causes the latter.