PCB's in incineration

[ttweed@wildrockies.org (Tony Tweedale)]

by chance I have just read an extended abstract in the Amer Chem Society's
3/'99 Env Chem Reprints:   'Emissions of PCBs from Combustion Sources'

I'm sure you could get the entire paper and other info from the authors who
all work at the Air Pollution Prevention & Control Div. of the US EPA at
Research Triangle Park, N Carolina (P Lemieux, CW Lee, J Kilgore, J Ryan).
Lemieux is also the author of a couple of the papers cited in the abstract.

Netherlands has the only national PCB inventory.  Municipal waste
combustors apparantly emit little, cement kilns a lot (~60% of total TEq,
ie incl dioxins & furans).  This may be due to differing combustion
environments, incl. stochiometric O2 levels, degree to which the unit
breaks down organochlorine inputs to free chloride or not, etc.--anyone
care to speculate on the reason for the difference?  Apparantly PCB 126,
with the highest TEq (0.1), is the most common dioxin-like PCB.  Full paper
has (will have?) data from 2 USA units, a MWI under good & poor burn
conditions, and open barrel trash burning.

"Evidence seems to indicate PCBs are formed by the same types of reactions
as form PCDD/F"  Ie, 'de novo' synthesis from free chloride, and from
organic precursors (mostly aromatic o at least ring like, I imagine) in
cool (250-700 degC) exit gas zones, both utilizing metals for catalysis on
ash particle surfaces.  De novo apparanntly happens slowly (minutes or
hours), in the captured ash in the ESP or scruber.  I imagine that affects
the partitioning of PCDD/F/PCBs between a landfill and air deposition.  It
implies ash concentrations are much higher than what comes out the stack.
Wheras formation from precursors is rapid, implying most of this source
fractions out the stack.

Tony Tweedale

Causality is a concept not subject to empirical demonstration. -David Hume
(1711-'76)

Temperate but endangered planet.  Enjoys weather, northern lights,
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