78 AIR POLLUTION SOURCES
Part 1. Pollutant Emissions (continued)Pollutant types Sources and abundance Abatement and control- Aldehydes: Aldehydes are one of a group of
organic compound with the general formula R-CHO
which yield acids when oxidized and alcohols when
reduced. They are products of incomplete
combustion of hydrocarbons and other organic
materials.
Formaldehyde and Acrolein-Acetaldehyde cause
irritation to the mucous membranes of the eyes,
nose, and other portions of the upper respiratory
tract. Formaldehyde has also been cited as a potential
human carcinogen.
One of the most popular aldehydes used in the
chemical process industry is formaldehyde.
This is because of its relatively low cost, high
purity, and variety of chemical reactions.
Among its many uses are as an intermediate
in the production of phenolic and amino
resins and also in the production of slow
release fertilizers. Annual worldwide
production capacity now exceeds 12 106
metrics tons (calculated as 37% solution).
In general, aldehydes are produced by the
combustion of fuels in motor vehicles, space
heating, power generation, and in other
combustion activities (such as the incineration
of wastes). In addition aldehydes are formed
in photochemical reactions between nitrogen
oxides and certain hydrocarbons.
Natural sources of aldehydes do not appear to be
important contributors to air pollution. Some
aldehydes are found in fruits and plants.c) Use materials which have a higher
boiling point or are less photo-
chemically active.
d) Use control equipment and
recycling of organic solvents to
reduce emissions.
e) Control by absorption, adsorption
and condensation.
Control methods include more
effective combustion as may be
obtained in direct flame and the use
of catalytic afterburners.- Ethylene: Ethylene (H 2 C = CH 2 ) is the largest
volume organic chemical produced today. Ethylene
is a colorless hydrocarbon gas of the olefin series, it
is generally not toxic to humans or animals, but it is
the only hydrocarbon that has adverse effects on
vegetation at ambient concentrations of 1 ppm or
less. It therefore represents a considerable air
pollution problem, for two reasons: - it is significantly harmful to plants,
Ethylene may form as a by-product of
incomplete combustion of hydrocarbons and
other organic substances. Thus, ethylene has
been found to be one of the components of
automobile and diesel combustion emissions
(exhaust and blow by emissions), incinerator
effluents, and agricultural waste combustion
gases. Ethylene is not normally found in
deposits of petroleum or natural gas.Ethylene poses no peculiar control
problem in these emissions and this
can be controlled by methods
generally used for hydrocarbons.
These methods include combustion
techniques, absorption techniques,
absorption methods, and vapor
recovery systems.TABLE 6
Emissions of Hydrofluorocarbons and Prefluorinated Carbon, 1990 to 1994 Preliminary Estimates
(thousand short tons; molecular basis)Compound GWP 1990 1991 1992 1993 1994HFCs
HFC-23 12,100 6.085 6.206 6.327 2.910 3.075
HFC-125 3,200 0.000 0.000 0.000 0.000 4.211
HFC-134a 1,300 0.551 0.992 1.323 6.526 11.475
HFC-125a 140 0.282 0.292 0.296 1.146 1.687
HFC-227 3,300 0.000 0.000 0.000 0.000 3.946
PFCs
CF 4 6,300 2.701 2.701 2.701 2.695 2.695
C 2 F 6 12,500 0.270 0.270 0.270 0.270 0.270
SF 6 24,900 1.102 1.102 1.102 1.102 1.135
Note(s): Totals presented in this table may not equal the sum of the individual source categories
due to rounding.
Source(s): Inventory of U.S. Greenhouse Gas Emissions and Sinks, 1900–1994. Draft Report, U.S.
Environmental Protection Agency. September 1995.C001_006_r03.indd 78C001_006_r03.indd 78 11/23/2005 9:42:37 AM11/23/2005 9: