Oxidative pyrolysis of CH₂Cl₂, CHCl₃, and CCl₄‐I: Incineration implications

Abstract

The oxidative pyrolysis of methylene chloride, chloroform, and carbon tetrachloride has been investigated using a micro-bore, fused silica, tubular flow reactor operating under laminar flow conditions coupled to in-line GC-MS detection. Data were obtained over the temperature range 573-1273 K for the following conditions: chlorocarbon/oxygen equivalence ratios of 3.0, chlorocarbon concentrations of 2.7 ? 0.1 x mols/L, gas-phase residence times of 2.0 s, and reactor pressures of 1.15 2 0.05 atm. The parent stability (defined by the temperature required for 99% destruction) was evaluated as:CHpC12: 1028 K, CHC13: 873 K, CCl,: 1153 K Chemically activated recombination of chlorinated C1 radicals are proposed as important pathways to chlorinated ethane and olefin products. The most significant finding from analysis of product distributions containing 2 2 carbon atoms was the observation of ca. 1 mol% yields of higher-molecular-weight perchlorinated aromatic species from the decomposition of chloroform and carbon tetrachloride. Implications with respect to the controlled high-temperature incineration of these chlorinated methanes are briefly discussed.

Use of Pyrolysis GC/MS for Predicting Emission Byproducts from the Incineration of Double-Base Propellant

“…Most bench-scale laboratory experiments have studied waste containing chlorinated compounds (3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14) because of the potential creation of products far more toxic and persistent than the input feed constituents. Results from these experiments illustrate that, when compared to oxygen-rich conditions, PIC generated under oxygen-deficient conditions are more numerous, the molecular weight and the distribution increases, and the maximum yields and temperature stability of the byproducts increase.…”

Postflame reaction chemistry of dichloromethane: variations in equivalence ratio and temperature

“…Recent years have witnessed considerable progress in understanding the combustion chemistry of C 1 and C 2 CHC decomposition using flat flames [5,11,12], isothermal flow reactors [4,[13][14][15][16][17][18], combustion-driven flow reactors [4, 19 -23], and through the development of chemical kinetic mechanisms [13,24]. However, the destruction of CHCs and byproduct formation in postflame conditions is not presently well understood.…”

“…However, the destruction of CHCs and byproduct formation in postflame conditions is not presently well understood. Previous CH 2 Cl 2 flame and flow reactor studies have drawn widely varying conclusions with respect to effects of equivalence ratio: some investigators find that changing equivalence ratio does not vary the chemistry significantly [17], others find that increasing the equivalence ratio increases the amount and number of byproducts [16], and yet others find that increasing the equivalence ratio decreases the amount of byproducts [11,25].…”

“…Most flow reactor studies consider a single equivalence ratio while varying temperature [4,[13][14][15][16][17][18]. No study systematically examines changes in CH 2 Cl 2 destruction and byproduct formation by independently varying equivalence ratio and temperature in postflame conditions.…”

“…They conclude that the number and yield of PICs are greater in pyrolytic conditions. In another study by the same authors [17], the effects of oxygen are evaluated in two flow reactor studies at pyrolytic and oxidative pyrolytic conditions (⌽ ϭ 3.0); similar product yields led the authors to conclude that oxygen does not affect the chemistry, except to reduce the formation of nonperchlorinated products.…”