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The use of chemical fume
suppressants is a major source reduction
technique- defines
a chemical fume (or mist) suppressant as
any chemical agent that
reduces or suppresses fumes or mists at the
surface of an bath or solution. Chemical
fume suppressants are further defined as
"surface-active" compounds that can be added
directly to a paint stripping bath to
reduce or control misting. Fume suppressants
are classified as being temporary or
permanent. Temporary fume suppressants are
dissipated mainly by the decomposition of
the active chemical components; whereas,
permanent fume suppressants are dissipated
by drag-out of the solution. There are two
basic types of fume suppressants: wetting
agents and foam blankets. The difference
between foam blankets and wetting agents, is
the way in which they reduce emissions. Foam
blankets physically suppress the mists
produced on the surface of baths, while
wetting agents lower the surface chemistry
of
baths to reduce misting.
These differences are explained further in
the following sections. Fume suppressants
(including wetting agents, foam blankets,
and combinations of both wetting agents and
foam ) are manufactured in liquid, powder,
or tablet form. Fume suppressants are used
widely and effectively in and in paint
stripping
operations
. Chemical fume suppressants
inhibit fumes at the source (i.e. the bath)
and reduce emissions ,depending on the type
of product used. Some of the main advantages
of using chemical fume suppressants include:
(1) minimization of solution evaporation
losses; (2) low cost of emission control;
(3) very little energy consumption; and (4)
no solid waste
generation, Limitations in
using chemical fume suppressants include:
(1) some fume suppressants have a tendency
to adhere to work piece (2) foam
blanket-type fume suppressants can entrap
hydrogen gas, which may pose a risk of
explosion Consequently, the main factor
affecting the adequate performance of
chemical fume suppressants is the amount of
suppressant present in the . A bath using
chemical fume suppressants should be
monitored routinely.
Plastic Floating Spheres :Hollow,
floating spheres have been used to reduce
the amount of misting from the surface of
chrome plating tanks. Enough spheres are
added to form a layer that is one or two
spheres thick. Typical sizes range from %”
dia to 2” dia. They are fabricated from
plastics that are resistant to chemical
attack ,such as polypropylene. The use of
these floating spheres :for air pollution
control purposes, and found them to be of
limited use. The effectiveness of this
medium is diminished by the fact that the
evolution of fumes at the work piece tends
to push the spheres away, exposing a portion
of the bath liquid to the air above.
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