The Combustion of Carbon-Tetrachloride in a High Temperature Methane-Air Flame Environment.

Abstract

Stable species concentration and temperature profiles are provided for a series of five CCl$\sb4$/CH$\sb4$/air flames studied on a flat flame burner at atmospheric pressure. A detailed description of the facility used to collect this data is given. This system includes a novel flue gas collection and treatment system. A new gas chromatographic technique used to analyze subatmospheric gas samples is described in detail. This technique utilizes gas syringes for sampling of selected C$\sb1$ and C$\sb2$ hydrocarbons and chlorinated hydrocarbons, as well as fixed gases. Stable species are sampled with aerodynamically cooled quartz microprobes. Temperature measurements are taken with uncoated 0.02 cm type R thermocouple beads. The first three flames comprise a study of the variation of equivalence ratio ($\phi$) at constant atomic chlorine to hydrogen ratio (Cl/H), ($\phi$ = 0.76, 1.02, and 1.17 at Cl/H = 0.3). The first, fourth, and fifth flames comprise a study of the variation of the Cl/H ratio at constant equivalence ratio (Cl/H = 0.073, 0.34, and 0.61 at $\phi$ = 1). Net reaction rate profiles were generated for each flame for CH$\sb4$ and CCl$\sb4$. A mass destruction and removal efficiency (DRE) of near 99.99% was achieved in all five flames. Two types of stable intermediates were observed in several of the flames. Chloroform was seen as the most likely candidate product of incomplete combustion (PIC). No candidate PICs were observed in a fuel rich flame. The increasing importance of recombination reactions to form C$\sb2$ molecules is observed as the Cl/H ratio increases. Saturated hydrocarbons are observed to decrease in stability as the Cl/H increases. A correlation is observed between peak net reaction rate and the overall level of destruction for CH$\sb4$ and CCl$\sb4$. For a constant Cl/H ratio, the fuel rich flame has the highest peak reaction rate for CCl$\sb4$. The highest peak reaction rate for CCl$\sb4$ among the five flames occurs in the flame with the highest Cl/H ratio. An increasing time delay between CO formation and CO$\sb2$ formation was observed as the Cl/H ratio increased. This was due to the chlorine inhibition of CO oxidation.