Re: Terms used in incineration

["superjicb" <superjicb@email.msn.com>]

Shristi,

Volatile Organic Compounds Definitions are given below.  Note that they are
different in Europe than for the USA and as I'm not  sure which you'll be
using I gave both.

In the United States, the criterion for VOC regulation used by the EPA is
"atmospheric lifetime" (greater than 60 days).  The US uses atmospheric
lifetime because using vapor pressure alone only shows how quickly the
chemical evaporates, and does not take into consideration the speed at which
the chemical breaks down in the atmosphere.  For example, it is a chemicals
atmospheric lifetime, or the combination of its rate of evaporation and rate
of decomposition, that determines its ability to form ozone in the
troposphere.  An organic solvent that lasts more than sixty days before
breaking down has already moved out of the troposphere, so it cannot
contribute to tropospheric ozone formation or smog.

The EEC's (Europe's) definition of volatile organic compounds is "any
organic compound having at 293,15 K a vapor pressure of 0.01 kPa or more."
There are two major problems with using vapor pressure alone as a criterion
to regulate tropospheric ozone contribution.  First, it arbitrarily captures
many compounds, that in fact do not contribute to ozone formation in the
lower atmosphere.  Second, using the vapor pressure criterion misses many
VOCs that do contribute to tropospheric ozone formation, like the straight
chain hydrocarbons.  The decision to use a vapor pressure criterion was made
in Europe many years ago, but I've been unable to find its scientific basis.

The US EPA has determined atmospheric lifetimes for organic solvents.
Drying studies are used to predict the time for a compound to evaporate and
enter the troposphere.  This is combined with atmospheric reaction times
from a smog chamber to show the loading caused by a particular substance,
and its contribution to smog production.  The EPA gives VOC exemptions to
products with atmospheric lifetimes greater than sixty days.

Model Comparing Life of some Straight Chain Hydrocarbons

Compound                                             Octane    Decane
Dodecane    Hexadecane
Vapor Pressure kPa                                 1.39        0.12
0.009           0.00005
Vapor Pressure mmHg                           10.44         0.91
0.07            0.0004
Evaporation Time min                                 30           355
4733            852,000
Tropospheric Lifetime days                        1.7            1.2
1.0               0.6
Atmospheric Lifetime Total Days               1.7            1.4
4.3             592.0

Note that dodecane a C-12 paraffin meets the definition of having a vapor
pressure less than 0.01 pKa.  It evaporates very slowly, but reacts rapidly
in the atmosphere. It would not be surprising if some major firms prefer
regulation based solely on vapor pressure, because this will allow some
products which contribute to ozone formation in the troposphere to avoid
regulation.

Atmospheric lifetime is used as the general criterion for setting standards
for ozone contribution in the lower atmosphere.  This is the exact same
approach that was used to determine ozone depletion in the upper atmosphere
(Montreal Protocol), so all countries  already have plenty of experience
with it.  To prevent ozone depletion the atmospheric lifetime of a chemical
must be less than 365 days, while to prevent ozone contribution a chemical's
atmospheric lifetime must be more than 60 days.

Hope this helps,

CB