Thermal Destruction of Chlorinated Hydrocarbons by Reductive Pyrolysis∗

Abstract

A rigorous thesmochemical analysis of the pyrolysis of aromatic chlorides shows that destruction efficiencies in excess of 99.999 percent are possible in a reducing atmosphere at temperatures near 1000 K. This process used for the destruction of chlorinated organic om pounds yields non-halogenated hydrocarbons and hydrochloric acid as reaction products. Qualitative batch experiments on chloromethane and polychlorinated biphenyls (PCBs) showed that such efficiencies could be obtained in residence times below 7 minutes at 1273 K. Qualitative continuous flow experiments demonstrated that these efficiencies are actually obtained in residence times less than 1.8 seconds for chloromethane and 4.4 seconds for the PCB mixture Arochlor 1254. A simple kinetic analysis shows that the Aroclor 1254 radicals are produced by the decomposition of hydrocarbon solvents [n-hexane and iso-octane) used to provide the reducing atmosphere. The difference in residence times between batch and continuous flow reactors is explained by temperature gradient effects in batch reactors and the associated heat flux limiting rate phenomenon due to endothermic reaction steps.

A Literature Survey to Identify Potentially Volatile Iodine-Bearing Species Present in Off-Gas Streams

“…Volatilization of iodine from the melter to the MOG system depends on how much iodine might be incorporated in the glass, into particulate matter in the off-gas system (that is eventually captured in scrubber effluents or in particulate filters), and how much is volatilized, forming gaseous species such as I 2 , ICl, HI, HOI, and organic iodides. Because of the relatively high temperatures and estimated low affinity of glass for iodine, it is conservative to assume that, like municipal waste incinerators, inorganic and organic iodides and other halides evolve to the off-gas (Wang et al 2007;Wikström and Marklund 2000) or from pyrolysis (Barton and Mordy 1984;Grossi et al 2007;Hall and Williams 2006;Ravindran et al 1997;Yang et al 2013).…”

Indication of PCDD/F formation through precursor condensation in a full-scale hazardous waste incinerator

“…DDT and hexachlorobenzene, and of certain non-chlorinated hydrocarbons such as cellulose and lignin, which are in principle the main source of precursors in MSW. PCBs and chlorinated pesticides, present in high concentrations in the waste input of the RKI, require longer residence times at elevated temperatures for decomposition than cellulose and lignin [17][18] because the carbon-chlorine bond is much stronger than the carbon-carbon bond. So it is to be expected that in waste incinerators cellulose and lignin are completely thermally destroyed in the furnace and do not yield PCDD/F precursors in the combustion gas.…”

Microwave Plasma Conversion of Volatile Organic Compounds

“…Barat and Bozzelli 14 showed that an overall reaction of the form 15 have shown from thermodynamic arguments that a similar dechlorination in hydrocarbon-rich environments is also possible. These observations suggest that dechlorination may occur under the correct conditions, conditions that may be possible in a microwave plasma.…”