ABSTRACT
A pollutant is a substance that affects the health of a biological system directly or indirectly through the environment. With billions of automobiles on the roads, and numerous power plants producing electricity for the energy-starved and increasing population of the world, the levels of combustion pollutants emitted are at ever increasing levels. Combustion from fuels has numerous byproducts, many of which are pollutants (e.g., from car exhaust and power and chemical plants). In small quantities, these pollutants are harmless and pose no threat to the environment. The leading pollutants are carbon oxides (CO
: CO, CO
, etc., called greenhouse gases), nitrogen oxides (NO
: NO, NO
[nitrogen dioxide], etc.), sulfur oxides (SO
: SO
, SO
, etc.), particulate matter having size less than 10
mm (called PM 10) released from coal-fired plants and soot from engines (e.g., diesel), formaldehyde and acetaldehyde, polycyclic aromatic hydrocarbons (PAHs such as primarily naphthalene that are carcinogenic), Hg and unburned hydrocarbons (UHCs; not completely and partially burned/oxidized hydrocarbons [PHCs such as partially combusted C
H
⋅
COOH carboxylic acids, ketones C
H
⋅
CO, aldehydes, and C
H
⋅
CHO] due to low temperature reactions as in lean eddies) mostly due to limited residence time and quenching by walls as in automobile engines. The high NO
and SO
emissions from fossil fuels are caused by the high fuel-bound N and S content in coal. Sources of SO
are fossil fuel power plants (66%), industrial processes (16%), nonutility stationary fuel combustion (14%), and transportation services (4%). Vehicles release large amounts of thermal NO
(because of high temperature) and volatile organic compounds (VOCs; typically, HCs composed of carbon compounds with H/C 2:1 to 0:1). The organic
compounds originate primarily from unburned fuel and lubricating oil. The organic species include sulfur, oxygen, carbon, and nitrogen-containing compounds. There are numerous types of pollutants found in combustion products. Table 17.1 shows typical emission of various pollutants from a 1000 MW plant, whereas the percentages of NO
from various sources are presented in Table 17.2. Total emissions from U.S. power plants alone are 10.6 Mt of SO
, 4 Mt of NO
, 2.5 Gt of CO
, and 45.6 t of mercury [https://www.0101010.org/2004/05/ what-does-2-billion-tons-of-carbon.html]. The SO
and NO
from other sources are 5.1 and 16.4 Mt respectively.
