454 HAZARDOUS WASTE MANAGEMENT
base or acid. This is probably the simplest chemical treat-
ment of those discussed and is widely applicable; care must
be taken, however, to insure that no hazardous precipitates or
dissolved solids forms.Incineration Incineration has been practiced on solid
waste for many years. It has not, however, been as widely
accepted in the United States as in Europe where incin-
eration with heat recovery has been practiced for at least
three decades. Incineration of industrial materials has been
practiced only to a limited extent; first, because it was more
expensive than land disposal, and second, because of a lack
of regulatory guidelines. This has changed because land-
fills are not acceptable or available, costs for landfilling are
becoming extremely high, and regulatory guidance is avail-
able. Equipment for incineration of industrial products has
been, and is available, however, it must be properly designed
and applied.
Incineration is the oxidation of molecules at high tem-
peratures in the presence of oxygen (usually in the form
of air) to form carbon dioxide and water, as well as other
oxygenated products. In addition, products such as hydro-
gen chloride are formed during the oxidation process. The
oxidation, or breakdown, takes place in the gaseous state,
thus requiring vaporization of the material prior to any reac-
tion. The molecules then breakdown into simpler molecules,
with the least stable bonds breaking first. This occurs at rela-
tively lower temperatures and shorter times. It is followed by
the breakdown of the more stable, and then the most stable
bonds to form simple molecules of carbon dioxide, water,
hydrogen chloride, nitrogen oxides, and sulfur oxides, as
may be appropriate.
Thus, the primary considerations for successful oxi-
dation or destruction are adequate time and temperature.
Good air/waste contact is also important. Regulatory guide-
lines require a destruction and removal efficiency (DRE)
of 99.99% thus, time and temperature become all the more
important. For the most refractory compounds, such as
PCB’s, residence times in excess of three seconds and tem-
peratures in excess of 1000°C are required. These tempera-
tures may be reduced in light of special patented processes
utilizing oxidation promoters and/or catalysts. As a result of
the high required DRE, a test burn is required to demonstrate
adequate design.
In addition to time and temperature considerations,
there are other important factors which must be consid-
ered when designing or choosing equipment to incinerate
industrial waste. Most important is adequate emission gas
controls. Where materials which contain metals, chlorides,
or sulfides are to be incinerated, special provisions must be
made to minimize emission of HCl, SO 2 , and metal oxides.
Usually a scrubber is required, followed by a system to
clean up the scrubber-purge water. This system includes
neutralization and precipitation of the sulfur and metal
oxides. In addition, where high temperature incineration
is practiced, control of nitrogen oxides to meet air quality
emissions standards must be considered. These substances
do not present insurmountable technological challenges, asthey have been handled satisfactorily in coal-fired power
plant installations, but they do present added economic and
operating challenges.
Several types of incineration facilities should be con-
sidered. Unfortunately, the standard commercial incinera-
tor utilized or municipal waste will generally not prove
adequate for handling industrial waste loads because the
temperatures and residence times are inadequate. Municipal
incinerators are designed to handle wastes with an energy
content below 8000 Btu/pound, while industrial wastes can
have heating values as high as 24000 Btu/pound. Municipal
incinerators are generally not designed to accept industrial
wastes.
A number of incinerator facilities have been built for
industrial wastes. Small, compact units, utilizing a single
chamber with after-burner, or two-stage, multi-chamber
combustion are available. In general, a single-state unit will
not suffice unless adequate residence time can be assured.
Rotary kiln incinerators are of particular interest for
the disposal of industrial materials. Generally, they are
only applicable for large-scale operations, and can handle
a large variety of feedstocks, including drums, solids and
liquids. Rotary cement kilns have been permitted to accept
certain types of organic hazardous materials as a fuel
supplement.
Of increasing interest for industrial incineration is the
fluid bed incinerator. This has the additional advantage of
being able to handle inorganic residues, such as sodium
sulfate and sodium chloride. These units provide the addi-
tional advantage of long residence time, which may be desir-
able when the waste is complex (e.g., plastics) or has large
organic molecules. On the other hand, gas residence times
are short, and an after-burner or off-gas incinerator is often
required in order to achieve the necessary DRE.
Incineration has been used successfully for the disposal
of heptachlor, DDT, and almost all other commercial chlori-
nated pesticides. Organo-phosphorous insecticides have also
been destroyed, but require a scrubbing system, followed by
a mist eliminator, to recover the phosphorous pentoxide that
is generated.
Some special incineration applications have been imple-
mented. These include:- An ammonia plant effluent containing organics
and steam is oxidized over a catalyst to form CO 2 ,
water and nitrogen; - Hydrazine is destroyed in mobile US Air Force
trailers which can handle 6 gpm of 100% hydra-
zine to 100% water solutions, and maintain an
emission has which contains less than 0.03 pound/
minute of NO x ; - Chlorate-phosphorous mixtures from fireworks
ammunition are destroyed in a special incinerator
which has post-combustion scrubbing to collect
NO x , P 4 O 10 , HCl, SO 2 and metal oxides; - Fluid bed incinerators which handle up to 316 tons
per day of refinery sludge and 56 tons of caustic
are being utilized.
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