A wide variety of air pollutants may be emitted from many
sources during refinery operations. This chapter discusses briefly
the properties and sources of these pollutants as an introduction
to the detailed descriptions of the methods of control contained in
the following chapters.
The methods employed to control refinery emissions depend on
whether they occur as gases, vapors, aerosols, or dusts. These
states are defined as follows:
Gases are fluids above their boiling points. They have
neither shape .nor volume and tend to expand indefinitely (for
example, methane, nitrous-oxide, and carbon monoxide).
Vapors are fluids which exist like gases in the
atmosphere but at temperatures below their boiling points (for
example. mercaptans and phenolic compounds) .
Aerosols are suspensions of finely divided solid or
liquid particles in air or gas, such as smoke, fumes, and
a. Smoke is a product of the incomplete combustion of
hydrocarbons and other carbonaceous matter consisting of particles
ranging from 0.001 to 1.0 micron in diameter.
b. Fumes consist of solid particles less than 1 micron
in diameter commonly formed by the condensation of vapors of solid
matter after volatilization from the molten state. Fumes may be
generated by sublimation, distillation, calcination, and chemical
reaction whenever such processes create airborne particles.
c. Mists and Fogs consist of particles formed by the
condensation of vapors. In mists, particle sizes range from 40 to
500 microns. In fogs, the particles are less than 40 microns in
diameter. 4. Dusts consist of solid particles blown into the air by
wind, released by other natural forces, or generated by mechanical
processes such as demolition or the crushing, grinding, and
conveying of solids. Usually dusts are coarser than aerosols.
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