Industrial Odor Control by Oxidation with Ozone
CARL NEBEL
WILLIAM J. LEHR
HAROLD J. O'NEILL
THOMAS C. MANLEY
Ozone Processes Division
The Welsbach Corporation
Philadelphia, Pennsylvania 19129
INTRODUCTION
Ozone is the most powerful useful oxidant known. It occurs naturally in the upper
atmosphere, at heights of 60,000 to 90,000 feet above sea level, in concentrations of 10 to 12
ppm by volume (1). This ozone layer is of inestimable benefit, as it filters out certain
frequencies of ultra-violet light known to be lethal to all forms of life. At ground level,
however, ozone usually exists in a greatly diluted and completely harmless concentration of
less than one hundredth of part per million. Under smog conditions such as sometimes exist
in places like Los Angeles, the concentration may rise as high as nine-tenths of a part per
million, at which level it can be mildly irritating, though far from toxic. However, such
conditions are exceptional, and represent ozone that is not under control. What we, as
engineers and scientists are concerned with, is ozone that is always under control — in
which connection it should be noted that no known human fatality has ever been caused by
ozone, whether generated by nature or by man.
Like chlorine, fluorine, potassium permanganate, hydrogen peroxide, etc., ozone is an
oxidant; but it differs from other oxidants in some very important ways, such as its potency
and the facility and economy with which it can be generated on-site from air, electricity and
cooling water.
Despite the allegedly novel and superior methods of generating ozone publicized from
time to time, the most practical and economical method employs a glass tube dielectric
around which is produced a corona discharge. The corona discharge converts a portion of
the oxygen in the air feed-gas to ozone. Ozone can be generated directly from ambient air,
or preferably from ambient air that has been filtered, compressed, cooled and dried; the
latter is by far the most consistent and economical process. Packaged ozone generators are
available that include not only the ozonator, but all the electrical gear and air pre-treatment
equipment interconnected, thus requiring minimal installation. Figure 1 shows a flow
diagram for the generation of ozone from air and the accompanying picture shows how
these components are preassembled on a skid frame at the factory.
When ozone leaves the generator, its concentration in the air stream is approximately
1% by weight, or 6,100 ppm by volume. In this state ozone is used commercially for potable
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