Note: Descriptions are shown in the official language in which they were submitted.
BACKGROUND OF T~E INVENTION
1. Field of the Invention
This invention relates generally to methods and
apparatus for treating polychlorinated biphenyl contaminated
sludge, such as the sand, mud, or the like, formin~ the bottoms
of PCB contaminated lakes and streams.
2. Back~round Art
Since 1978 the manufacture of polychlorinated
biphenyls (PCBs) has been banned in the united St~tes. These
chemicals have been widely used in the past in transformers,
carbonless carbon paper, hydraulic pumps, caulking compounds~
inks, paints and insect sprays. A tremendous amount of these
chemicals, suspected of causing cancer and birth defects,
have been dumped over a number of years in an entirely reckless
fashion. Commonly these chemicals were dumped in lakes, streams
and waterways where they eventually collected in the bottom
material in considerable concentrations.
Because of the method of dumping these chemicals, a
tremendous mass of material has been contaminated with these
chemicals. In the past, bottom soils or the like contaminated
with these fluids have been treated by attempting to burn or
by burying them. Because of the nature of the materials in
which the PCB contamination is often found, burning is extremely
difficult and burying is often only a stop gap measure.
It ha~ been recognized that thermal decomposition
of polychlorinated organic compounds is possible despite the
very high degree of thermal stability of these compounds.
U.S. Patent 4,140,066 discloses a method of decomposing PCB's
by exposure to heat in a combustion chamber which operates
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with extremely intense turbulance and pulsation under temDer-
atures as low as 850 C. and with residence times as shor~ as
.1 second. However, tne patent provides no method or apparatus
for dealiny with the problem of the treatment of mountainous
amounts of contaminated, wet material having a relatively low
heating value. Thus while the method set forth in the '066
patent may be highly useful in eliminating PCB containing
compounds in relatively small volumes, the process is not
particularly helpful in dealing with contaminations on the
order of tons in the form of residues in sludge.
A variety of techniques for incinerating waste
material are known. The following U.S. patents are exemplary:
4,245,570; 3,858,534; 3,829,558; 3,812,794; 3,716,339; and
3,511,194.
SUMMARY OF THE_INVENTION
It is a primary object of the present invention to
provide an apparatus capable of separating PCB's from an
extremely large quantity of sludge.
It is also an object of the present invention to
provide a method and apparatus for treating contaminated river,
lake, and waterway bottom material in an efficient and econom-
ical way.
These and many other objects and advantages of the
present invention are achieved by a method for treating poly-
chlorinated biphenyl contaminated sludge that includes thesteps of heating the sludge by exposure to hot gas at a temper-
ature of ~50 to 2,500 F., thereby driving the water and poly-
chlorinated biphenyls from the sludge and leaving a dry particu-
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late mass. The PCB material is formed into a gas stream andprepared for burning.
In accordance with another embodiment of the present
invention apparatus for treating polychlorinated biphenyl
contaminated sludge includes a mixing means for mixing the
sludge to be treated. A drying means separates the poly-
chlorinated biphenyls and water from the sludge and includes
means for exposing the sludge to a hot gas stream. Another
means removes the fine particles from a gas stream. A burner
burns the gaseous PCB material. The burner includes means
for injecting ambient air and/or oxygen enriched air trans-
versely into the burner flame at spaced points along its
length.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a schematic layout of the apparatus in
accordance with one embodiment of the present invention;
FIG. 2 is an enlarged cross-sectional view taken
generally along the line 2-2 in FIG. l; and
FIG. 3 is an enlarged~ partial, cross-sectional
view taken generally along the line 3-3 in FIG. 1.
DBTAILED DESCRIPTION OF HE PREFERRED EMBODIMENT
Referring to the drawing wherein like reference
characters are used for like parts throughout the several
views, a PCB contaminated sludge treating apparatus 10, shown
in FIG. 1, includes a mixer 12, a separator 14, a cyclone
separator 16, a bag collector 18, and a furnace 20. Wet or
dry sludge contaminated with PCB's is poured into the apparatus
10 through the mixer 12. The nature o~ the sludge is not
critical, and the device is adapted to operate with sand,
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mud, sewage, organic matter, effluvia and the like, conven-
iently in the form of bottom dredgings.
The mixer 12 is conveniently a conventional
mixer/feeder with a screw feeding mechanism (not shown)
arranged generally horizontally within the mixer 12. As the
sludge is poured into the mixer 12, it is thoroughly mixed
and forwarded into the PCB separator 14. As snown in FIG. 2,
the sludge may be poured in a wet state (including for example
20~ solids) into the separator 14 and quickly dried. Very
hot air is blown inwardly from the bottom of the separator 14
through a wind box 64 and allowed to move upwardly through
the device, drying the sludge with the hot turbulent air. In
addition a burner 15 is provided at the bottom of the separator
15. The air in the separator 14 may be at a temperature of
from 850 F. to 2,500 F.; however, to achieve the full advan-
tages of the present invention an operating range of from
1400 F. to 2,000 F is utilized.
The larger particulate material falls downwardly
through the separator 14 at a rate controlled by the delaying
apparatus 33. The apparatus 33 includes a first frusto-conical
surface 34 angled downwardly so as to direct the particulate
matter to a central position adjacent the shaft 24. The parti-
culate matter falls through the aperture 36 onto the umbrella
38, including a plurality of side by side arms 42. The
umbrella 38 is generally frustoconical in shape but is
directed upwardly so as to receive the particulate matter and
to redirect it outwardly towards ~he periphery of the separator
14. The arms 42 of the frusto-conical umbrella 38 are hingedly
secured at their upper ends to a tube 40 surrounding the shaft
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24. An umbrella angle adjusting mechanism 44 includes a tube
46 which freely encircles the tube 40 and is arranged for
vertical adjustment using a handle 48. A plurality of links
50, connecting the tube 46 to the arms 42 of the umbrella 38,
are hingedly connected to both the tube 46 and the arms 42 to
permit the angle of the arms 42 to be adjusted, as indicated
by the arrows in FIG. 2. The upper surface of each arm 42
includes a plurality of ridges 51 which control the rate of
movement of the particulate matter along the surface of the
arms 42.
Eventually the particulate matter tumbles off of
the edges of the umbrella 38 and collects at the bottom of
the separator 14, eventually flowing outwardly thereof through
the opening 52. From the opening 52 any particulate matter
that contains an excessive PCB concentration is returned by
way of the conveyor channel 54 through the action of the
diverter valve 55 to the mixer 12. The mixer 12 mixes the
dried coarse particulate matter with the incoming wet sludge
and feeds the mixture to the separator 14. The adequately
treated sludge is returned to its source by away of passage
57.
In the separator 14 the finer, dry particulate matter
is propelled upwardly through the spinning product separator
56. The separator 56, rotated in the upper portion of the
separator 14 by a motor 58, includes at least two blades 62.
The fine particulate matter, entrained in the gas flow out of
the separator 14, is propelled upwardly out of the separator
14 through the passage 60. The larger particles are returned
to the separator 14 by the product separator 56.
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The fine particulates and air entrained DC~ materia7
exiting from the separator 14 are conveyed to the conventional
cyclone separator lb whicn separates tne fine particulates
from the gas entraining those particulates. The gas exits
from the cyclone separator 16 through the opening 65 ~hile
the particulates move downwardly through the exit 66. The
yas procee~ing through the opening 65 passes ro a conventional
bag collector 18 ~hat removes any remaining particulates in a
more thorough fashion. The remaining gas is expelled through
the passage 68 wnile any newly recovered particulates fall
downwardly through the passage 70 to join the particulates
collected by the cyclone separator 1~. The PCB effluvia is
then fed to a furnace 20, while particulates are tested for
PCB concentration and, ir a safe PCB level exists, they are
dum~ed. A cnarcoal filter 72 is arranged in the passage 68
to provide a final particulate cleaning step.
The gas flow through the entire system is responsive
to action of the blower 71 while the movement of the separated
particles is responsive to the blower 73. The blower 71 is
powerful enough to maintain a vacuum within the separator 14,
and is conveniently capable of moving about 13,500 SCFM of
hot air.
A suitable multiple fuel burning apparatus for use
as the furnace 20 herein is described in U.S. patents 4,273,527
and 3,174,530 both to Cyril F. Meenan. The furnace 20 is cap-
able of burning unconventional fuels of very low heating value,
at very high temperatures, for example from 3,500 to 5,000F
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As shown in FIG. 3, the Eurnace 20 includes a
plurality of side by side concentric pipes 84, the pipes 84a
conveying wzter, the pipes 84b conveying pressurized air and/or
2 enriched air, the pipes 84c conveying a pressurized combus-
tible fuel gas such as natural gas or natural gas pre-mixea
with 2~ and the pipes 84d conveying the PCB effluvia in the
form of PCBs entrained in gas. The air in the pipes 84b is
conveniently ambient air and/or 2 enriched air. The pipes
84b, 84c, and 84d include a plurality of nozzles 86 arranged
to direct the gas flow out of the pipes radially inwardly in
a circumferential fashion to the center of the generally tubular
combustion chamber 88. Thus, air, natural gas and effluvia
are progressively mixed along the length of the axially directed
burner flame, emanating from the burner 80, conveniently a
natural gas burner, indicated as 90 in FIG. 3. The transversely
or radially injected air and gas mix with the axially applied
burner flame resulting in very thorough and complete combustion
of the PCB's. The water circulating through the pipes 84a is
heated in the process and may be used in the boiler 78 to
produce superheated water or steam. A portion of the hot
flue gases are conducted to the boiler 78 for this purpose.
The hot water or steam produced by the boiler 78 is used for
; operating power generating turbines in a conventional fashion.
A portion of the hot combustion gases from the interior of
the combustion chamber 88 may also be conducted, by way of
the passage 82, to the interior of the separator 14 where
they operate to dry the incoming sludge.
Before any flue gases are released to the environment
from the boiler 78, they are treated by an emissions control
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device 92. The device 92, of conventional form, includes
chemical scrubbers and/or electrostatic precipitators tnat emo~te
any hazardous wastes.
The present device has been found to be nighly
effective in separating PCB's from sludge in the separator 1~
and in subsequently destroying the PCB's such that one percent
or less of the PCB's remain after final processing. Since
all the eY~hausts from each step in the operation or the
apparatus are controlled, these exhausts may be recycled if
it is found that their PCB concentration is too high.
The residence time of the sludge witnin the separator
14 may be controlled by adjusting the angle of the umbrella
38 to control the rate of exhaust of the large particulate
matter from the separator 14. To achieve the full advantages
of the present invention a residence time of the sludge within
the separator 14 on the order of .5 to 2 seconds is used. A
highly advantageous arrangement utilizes air within the
sepa~ator 14 at 1~00 F. with a residence time of tne parti-
culate matter within the roller mill/separator of about .5
seconds. At a temperature of ~0 F. within the separator
14, a residence time of about 10 seconds is required. The
apparatus 10 is capable of processing on the order of 10,000
pounds of sludge per hour~
The foregoing detailed description has been given
for clearness of understanding only and no unnecessary limita-
tions should be understood therefrom as many modifications
will be obvious to those skilled in the art,
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