Study of the gas phase combustion of hexachlorobenzene, influence of the oxygen concentration Attempt at a global kinetic formulation

摘要

This study describes the high temperature (900-1150℃) degradation of hexachlorobenzene under oxidative atmospheres with a short residence time of 2 s. Three concentrations of oxygen are tested (21, 35 and 50% O_2). The experiments are run in stationary conditions. The combustion of hexachlorobenzene is nearly complete leading to the formation of carbon dioxide and molecular chlorine with a conversion approaching 100% at 1000℃ under 21% of oxygen and at 900℃ with 50% of O_2. The remaining fraction of hexachlorobenzene is close to few ppm, and some halogenated compounds with lighter molecular weight than hexachlorobenzene are present as traces in the exhaust. An attempt at a global kinetic formulation is presented. The kinetic evaluation is performed making the assumption of an overall order of two (one respectively for hexachlorobenzene and oxygen) with an Arrhenius type kinetic rate constant. On this basis, the fitting parameters E_a (activation energy) and A (Arrhenius factor) are calculated for the two limiting concentrations of oxygen, 21 and 50%.