Page 108 - Fundamentals of Air Pollution

78 6. Sources of Air Pollution

by the vast numbers of private automobiles exceeds that from any other
source.
Control of these personal sources of pollution takes the form of (1) regula-
tion (fireplaces and stoves may be used only when atmospheric mixing
is favorable), (2) change of lifestyle (sell the automobile and ride public
transportation), (3) change from a more polluting to a less polluting source
(convert the furnace to natural gas), or (4) change the form of pollution
(instead of burning leaves, haul them to the city dump). Whatever method
is used for control of pollution from personal sources, it will probably be
difficult and unpopular to enforce. It is difficult to get citizens to believe
that their new, highly advertised, shiny, unpaid-for automobiles are as
serious a pollution problem as the smoking factory stack on the horizon.
It is also a very ineffective argument to point out that the workers at that
factory put more pollution into the air each day by driving their automobiles
to and from work than does the factory with its visible plume of smoke.

II. COMBUSTION

Combustion is the most widely used, and yet one of the least understood,
chemical reactions at our disposal. Combustion is defined as the rapid union
of a substance with oxygen accompanied by the evolution of light and
heat (2).
We use combustion primarily for heat by changing the potential chemical
energy of the fuel to thermal energy. We do this in a fossil fuel-fired power
plant, a home furnace, or an automobile engine. We also use combustion
as a means of destruction for our unwanted materials. We reduce the
volume of a solid waste by burning the combustibles in an incinerator. We
subject combustible gases, with undesirable properties such as odors, to a
high temperature in an afterburner system to convert them to less objection-
able gases.
The simple combustion equations are very familiar:

They produce the products carbon dioxide and water, which are odorless
and invisible.
The problems with the combustion reaction occur because the process
also produces many other products, most of which are termed air pollutants.
These can be carbon monoxide, carbon dioxide, oxides of sulfur, oxides of
nitrogen, smoke, fly ash, metals, metal oxides, metal salts, aldehydes,
ketones, acids, polynudear hydrocarbons, and many others. Only in the
past few decades have combustion engineers become concerned about