Section 3. HAZARDOUS AND TOXIC WASTES
TOXIC WASTE DESTRUCTION BY PLASMA PYROLYSIS
T. G. Barton, Associate Professor
Department of Civil Engineering
G. P. Arsenault, Professor
Department of Chemistry and Chemical Engineering
Royal Military College
Kingston, Ontario
Canada K7L 2W3
The known persistence and toxicity of polychlorinated biphenyls (PCB) in the environment resulted in a ban on their use in open systems and their phasing out as transformer
and capacitor fluids. Restrictions on disposal and incineration has led to research into
methods which will achieve destruction efficiencies in excess of 99% without the formation
of hazardous or noxious by-products.
At the Royal Military College (RMC) a testing program has been initiated to demonstrate
the efficacy of plasma arc pyrolysis as a PCB destruction mechanism. Qualitative testing has
shown positive results for the destruction of liquid PCB wastes. Ongoing research has commenced to quantify results and to further test the feasibility of the system for PCB-contam-
inated solid wastes and for commercial-scale operation.
PCB COMPOSITION AND USES
Polychlorinated biphenyl is the name given to a series of aromatic organochlorine homo-
logs and isomers having the chemical composition C! 2H10_nCln. The PCB is a double benzene ring linked by a C-C bond and having 10 possible chlorine substitutions per molecule.
This configuration results in compounds having low water solubilities, low volatilities, and a
high degree of resistance to chemical and thermal degradation. In general, solubility and
volatility decrease with increasing chlorine substitution, whereas resistance to breakdown
increases. A further important property of PCB is a high solubility in organic solvents.
The chemical stability of PCB, coupled with excellent electrical insulating capabilities,
led to extensive use as dielectric fluids in capacitors and transformers. PCB were also used as
hydraulic and heat transfer fluids, as wax and pesticide extenders, in carbonless reproducing
paper, and in other minor applications. After the discovery of the toxic effects of PCB, their
use has been limited to closed systems where release into the environment is minimal.
Commercial production of PCB started in 1929, 48 years after the first reported chemical
synthesis of these compounds. In North America, the sole producer has been Monsanto,
which supplied 99% of the domestic and Canadian requirements. Monsanto marketed a
range of PCB products, trademarked Aroclor, which contained varying mixtures of chloro-
homologs. For example Aroclor 1254, which has an average chlorine content of 54%, contains four homologs in varying amounts.
Total U.S. production to date has been estimated at 1.45 billion pounds, reaching an
annual high of 85 million pounds in 1970. Monsanto's voluntary ban on production for
open system usage in 1970-1971 reduced annual production to 40 million pounds. Production ceased in 1977. Canadian imports have been estimated at 75 million pounds plus an
unknown amount imported in finished electrical goods.
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