Decontamination plant including an indirectly heated desorption system

The present invention is a decontamination plant for removing contaminates from contaminated material. The decontamination plant comprises an outer shell including a cavity therein. A drum formed of heat conductive material is rotatably mounted in the cavity defined by the outer shell so as to form an annular heating chamber between the drum and the outer shell. A plurality of heat sources are positioned to discharge heat into the annular heating chamber. The drum also has an inner surface defining a decontamination chamber. A tube is concentrically supported within the decontamination chamber formed in the drum. The tube has an inlet which is in communication with the annular heating chamber so as to receive flue gases therefrom. The outlet of the tube is positioned to exhaust gases from the drum. The drum is slightly inclined from a material receiving opening to a soil discharge end so as to cause the material which is being decontaminated to progress through the decontamination chamber as the drum rotates. While the material is passing through the decontamination chamber, the material is held in contact with the heating drum and the heated tube so as to heat the material via conduction.

CROSS REFERENCE TO RELATED APPLICATIONS 
Not applicable. 
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
Not applicable. 
BACKGROUND OF THE INVENTION 
A vast amount of hydrocarbon, chlorinated and halogenated solvent 
contaminated soil as well as pesticide and herbicide contaminated soils 
require cleaning up. One method of removing the contaminates from the soil 
is to heat the soil until the contaminates are vaporized. The contaminate 
vapors and the decontaminated soil are then removed from the heating 
chamber and the process is continually repeated until all the soil has 
been decontaminated. 
Rotary dryers and heat exchangers have been used in the past to transfer 
heat from a hot gas, usually the product of combustion, to the sludge or 
granular material which it is desired to heat or dry. These rotary drum 
dryers are generally of two types. Both types employ a horizontal rotating 
drum through which the sludge or granulated material passes. The drum is 
generally slightly inclined from the in-feed end to the out-feed end to 
cause the material being dried to progress down the drum as it rotates. 
Often mounted within the drum are lift flights of various types designed 
to agitate the material passing through the drum and/or to cast the 
material into a falling veil of material where it can interact with gasses 
passing through the drum. One type of drum heater utilizes indirect 
heating wherein a furnace or manifold for hot gases surrounds the central 
portions of the drum, thus heating the exterior of the drum which in turn 
heats the material passing through the interior of the drum by conduction 
and radiation. The other type of drum dryer employs direct heating wherein 
a burner or furnace at one end of the drum introduces hot combustion gases 
into the interior of the drum. The hot combustion gases directly transfer 
heat to dry moisture from the sludge or granular material progressing 
through the drum. The directly fired drum heaters are divided into those 
in which the combustion gases flow in the same direction as the granular 
material passing through the drum, and those in which the combustion gases 
flow in an opposite direction as the granular material which is being 
dried. 
The indirectly heated drum described above is generally inefficient in that 
once the hot combustion gases surround the central drum, such gases are 
then exhausted away from the drum. Or, the hot combustion gases are passed 
through the drum in contact with the material being processed, thus 
defeating a primary purpose of indirect heating. The directly heated drums 
cannot address the processing of contaminated soil because the contaminate 
vapors must not come in contact with the high temperature combustion 
gases. 
What is needed is a more efficient indirectly heated drum. It is to such an 
indirectly heated drum which the present invention is directed. 
BRIEF SUMMARY OF THE INVENTION 
The present invention is a decontamination plant for removing contaminates 
from contaminated material such as soil. Broadly, the decontamination 
plant comprises an outer shell including a first end, a second end and a 
cavity therein. The cavity extends generally from the first end to the 
second end of the outer shell. 
A drum formed of a heat conductive material is provided. The drum is 
rotatably mounted in the cavity defined by the outer shell so as to form 
an annular heating chamber between an exterior surface of the drum and an 
interior surface of the outer shell. The drum also has an inner surface 
defining a decontamination chamber. The decontamination chamber is 
isolated from the annular heating chamber such that contaminate vapors 
will not come in contact with the high temperature combustion gases which 
are present in the annular heating chamber as will be discussed below. The 
drum is also provided with a material receiving opening and a material 
discharging opening in communication with the decontamination chamber. The 
material receiving opening of the drum is disposed a distance beyond the 
first end of the outer shell, and the material discharge opening of the 
drum is also disposed a distance beyond the second end of the outer shell 
such that a portion of the inner surface of the drum, which is located 
generally between the first end and the second end of the outer shell, 
forms a first heat exchange surface. The drum is slightly inclined from 
the material receiving opening to the material discharging opening so as 
to cause the material being decontaminated to progress through the 
decontamination chamber from the material receiving opening to the 
material discharging opening as the drum rotates. 
A tube formed of a heat conductive material is provided. The tube is 
concentrically supported within the decontamination chamber formed in the 
drum. The tube has an inner surface defining an effluent gas discharge 
cavity, and an outer surface defining a second heat exchange surface. The 
tube has an inlet and an outlet in communication with the effluent gas 
discharge cavity. The inlet of the tube communicates with the annular 
heating chamber so as to receive flue gases therefrom, and the outlet is 
positioned to exhaust flue gases from the drum. 
A first set of heat sources are provided in the annular heating chamber. 
The individual heat sources in the first set are spacially disposed about 
the axial length of the annular heating chamber and positioned to 
discharge heat into the annular heating chamber. In one aspect of the 
present invention, a second set of heat sources are also provided in the 
annular heating chamber. The individual heat sources in the second set are 
spacially disposed about the axial length of the annular heating chamber 
and are disposed generally opposite the individual heat sources in the 
first set. 
When the heat sources in the first and second sets are discharging heat 
into the annular heating chamber, the drum is heated by radiation and by 
the heated flue gases flowing about the drum. In response thereto, the 
drum conducts heat to the first heat exchange surface thereof. The heated 
flue gases are then directed through the effluent gas discharge cavity of 
the tube from the inlet to the outlet thereof to heat the tube and thereby 
conduct heat to the second heat exchange surface, whereby material flowing 
through the decontamination chamber is heated conductively when in contact 
with either the first or second heat exchange surfaces. 
Thus, it can be seen that the present invention is an improvement over the 
prior art in that it provides a tube which is concentrically supported 
within the decontamination chamber and which receives heated flue gases 
which have already been in contact with the exterior of the drum and 
directs these flue gases through the tube to heat the second heat exchange 
surface and thereby increase the efficiency of the decontamination plant.

DETAILED DESCRIPTION OF THE INVENTION DEFINITIONS 
The term "indirectly heated" as used herein means a system where heat 
sources such as combustion burners, which generate heat energy for the 
decontamination plant, must be contained in a totally isolated cell such 
that the high temperature combustion or flue gases do not come in direct 
contact with contaminate vapors. 
The term "radiation" as used herein means a direct line of sight function 
requiring an object to directly look at a flame of a burner system in 
order to receive the infrared energy transfer therefrom. 
The term "convection" as used herein means a system which heats one median 
which in turn transfers the heat to another median. The terms "heating by 
conduction" means causing an energy transfer by heating a surface and 
allowing that surface to transfer its energy by physical contact with 
another surface or median. 
The terms "contaminated material" means material which is contaminated with 
chlorinated and halogenated solvents, or pesticides and/or herbicides, or 
any other chemicals or contaminates, such as hydrocarbons. 
The terms "decontaminated material", as used herein means material which is 
substantially free of the contaminates, and does not endanger health. 
The Embodiment of FIGS. 1-5 
Referring now to the drawings, and more particular to FIG. 1, shown therein 
is a schematic, cross-sectional view of a decontamination plant 10 
constructed in accordance with the present invention. 
The decontamination plant 10 is provided with an outer shell 12, a drum 14, 
a tube 16, a first set of heat sources 18 and second set of heat sources 
20. 
The outer shell 12 of the decontamination plant 10 is provided with a first 
end 22, a second end 24, and a cavity 26. The cavity 26 extends generally 
from the first end 22 to the second end 24 thereof. The outer shell 12 may 
have an outer diameter of about eight feet. The outer shell 12 may be 
lined with of 2400.degree. F. rated, six inch thick, high density (twelve 
pounds per cubic feet) ceramic block insulation. 
The drum 14 is formed of a heat conductive material and is rotatably 
mounted in the cavity 26 defined by the outer shell 12 so as to form an 
annular heating chamber 27 in between an exterior surface 28 of the drum 
14 and an interior surface 30 of the outer shell 12. The drum 14 has an 
inner surface 32 defining a decontamination chamber 34. The 
decontamination chamber 34 is isolated from the annular heating chamber 
27. 
The drum 14 has a material receiving opening 36 and a discharge end portion 
38. The material receiving opening 36 and the discharge end portion 38 
communicate with the decontamination chamber 34. The material receiving 
opening 36 is disposed a distance beyond the first end 22 of the outer 
shell 12. The discharge end portion 38 is disposed a distance beyond the 
second end 24 of the outer shell 12. 
The drum 14 is provided with a medial portion 40 which extends generally 
between the first end 22 of the outer shell 12, and the second end 24 of 
the outer shell 12. A first heat exchange surface 42 is formed by the 
inner surface 32 along the medial portion 40 of the drum 14. As will be 
described in more detail below, the drum 14 is slightly inclined from the 
material receiving opening 36 to the discharge end portion 38 so as to 
cause the material being decontaminated to progress through the 
decontamination chamber 34 from the material receiving opening 36 to the 
discharge end portion 38 as the drum 14 rotates. The direction of rotation 
of the drum 14 is indicated in FIG. 2 by an arrow 43. As the material 
progresses through the decontamination chamber 34, such material comes 
into contact with the first heat exchange surface 42 and is thereby heated 
by conduction. The drum 14 may be selectively rotated by four variable 
speed trunion drive systems (not shown) and is rotatably supported by 
conventional trunions 44. 
A first seal 45 is provided between the first end 22 of the outer shell 12 
and the exterior surface 28 of the drum 14. A second seal 46 is provided 
between the second end 24 of the outer shell 12 and the exterior surface 
28 of the drum 14. The first seal 45 and the second seal 46 can be 
multi-stage labyrinth seals which function to seal each end of the annular 
heating chamber 27 to allow the first and second sets of heat sources 18 
and 20 to operate in an internal vacuum. 
The individual heat sources 18 in the first set are spacially disposed 
about the axial length of the annular heating chamber 27 and positioned to 
discharge heat into the annular heating chamber 27. The individual heat 
sources 20 in the second set are also spacially disposed about the axial 
length of the annular heating chamber 27 and positioned to discharge heat 
into the annular heating chamber 27. As best shown in FIG. 2, the 
individual heat sources 18 in the first set are disposed on a side of the 
outer shell 12 about opposite from the individual heat sources 20 in the 
second set. The heat sources 18 and 20 in the first and second sets are 
typically 4.6 mm btuh burners. 
The heat sources 18 in the first set are positioned to inject heat into the 
annular heating chamber 27 in a direction about opposite to the injection 
of heat into the annular heating chamber 27 by the heat sources 20 in the 
second set. The heat sources 18 and 20 in the first and second sets are 
preferably controlled in banks or zones of four heat sources per zone. The 
two zones or eight heat sources 18 in the first set fire opposing the 
other eight heat sources 20 in the second set. This creates a turbine 
effect by utilizing the flame explosion speed (2,000 to 3,000 miles per 
hour) to accelerate and continue to boost the combustion gas speed within 
the annular heating chamber 27 in between the drum 14 and the outer shell 
12 to approximately 1,800 to 2,000 feet per minute. It is this speed and 
turbulence that distributes the heat evenly throughout the drum 14 and 
elevates heat transfer efficiency through the drum 14 to the first heat 
exchange surface 42 to its highest level. The direction of the flue or 
combustion gases in the annular heating chamber 27 is shown in FIG. 2 by 
the arrows 48 and 50. 
The tube 16 is concentrically supported within the decontamination chamber 
34 formed in the drum 14. The tube 16 is generally formed of a heat 
conductive material, such as steel. The tube 16 has an inner surface 56 
defining an effluent gas discharge cavity 58. The tube 16 is also provided 
with an outer surface 60 which defines a second heat exchange surface 62. 
The tube 16 has a pair of inlets 64 and an outlet 66 which communicate 
with the effluent gas discharge cavity 58. The inlets 64 of the tube 16 
communicate with the annular heating chamber 27. The outlet 66 is 
positioned to exhaust the flue gases away from the drum 14. The tube 16 is 
pivotally connected to a stationary stack 68 so that the flue gases can 
exit from the outlet 66 and pass through the stack 68. The flue gases can 
then pass to the atmosphere or be used for any other heat transfer use as 
indicated by an arrow 70. As the flue gases pass through the effluent gas 
discharge cavity 58 formed in the tube 16, such flue gases heat the tube 
16 such that the second heat exchange surface 62 is heated by conduction. 
The heating of the second heat exchange surface 62 provides additional 
heat transfer surface area for heating the material passing through the 
decontamination chamber 34. 
The decontamination plant 10 is also provided with a stationary discharge 
assembly 74. The discharge assembly 74 communicates with the discharge end 
portion 38 of the drum 14. The discharge assembly 74 is provided with a 
first port 76 formed through an upper end 78 thereof, and a second port 80 
formed through a lower end 82 thereof. The first port 76 is adapted to 
selectively discharge contaminates which have been vaporized while passing 
through the decontamination chamber 34 of the decontamination plant 10. 
The vaporized contaminates are drawn through the first port 76 (as 
indicated by an arrow 84) via an exhaust fan (not shown) which maintains a 
vacuum on the decontamination chamber 34 so as to direct all vaporized 
contaminate gases through, for example, a fabric filter bag house (not 
shown) to remove particulates from the vaporized contaminate gases before 
entering a multi-purpose scrubber system for neutralization of contaminate 
vapors if required. 
The second port 80 of the discharge assembly 74 is adapted to selectively 
receive and discharge decontaminated material from the discharge end 
portion 38 of the drum 14, as indicated by an arrow 86. A bin (not shown) 
or any other suitable structure can be positioned adjacent the second port 
80 to receive the decontaminated material therefrom. 
Referring now to FIG. 3, shown therein is a partial, cross-sectional view 
of the decontamination plant 10 taken along the lines 3--3 in FIG. 1. A 
plurality of first lifters 90 are spacially disposed on the inner surface 
32 of the drum 14. The first lifters 90 extend along the axial length of 
the drum 14, generally between the material receiving opening 36 to 
approximately the end of the cavity 26. The lifters 90 veil the material 
being dried across the drum 14 as the drum 14 rotates. 
Referring now to FIG. 4, shown therein is a partial, cross-sectional view 
of the decontamination plant 10 taken along the lines 4--4 depicted in 
FIG. 1. A plurality of substantially Y-shaped second lifters 100 are 
spacially disposed and mounted on the second heat exchange surface 62 of 
the tube 16 substantially as shown. The second lifters 100 serve to 
increase the amount of surface area of the second heat exchange surface 
62, and also to selectively gather and maintain the material passing 
through the decontamination chamber 34 on the second heat exchange surface 
62 so as to enhance the amount of conductive heat transfer from the second 
heat exchange surface 62 to the material. By enhancing the amount of 
conductive heat transfer from the second heat exchange surface 62 to the 
material, the overall efficiency of the decontamination plant 10 is also 
enhanced. As shown in FIG. 4, the second lifters 100 extend along the 
axial length of the tube 16 a distance generally coincident with the 
length of the cavity 26. 
Also shown in FIGS. 4 and 5 are a plurality of spacially disposed third 
lifters 110 mounted on the first heat exchange surface 42 of the drum 14. 
The third lifters 110 extend generally along the axial length of the drum 
14 a distance generally coincident with the length of the cavity 26. Each 
of the third lifters 110 are substantially identical in construction and 
function. Thus, only one of the third lifters 110 will be specifically 
described herein for purposes of clarity. The third lifters 110 are 
provided with a plurality of spacially disposed first supports 112 mounted 
on the first heat exchange surface 42 of the drum 14. The first supports 
112 extend generally away from the first heat exchange surface 42, as 
shown in FIGS. 4 and 5. Each third lifter 110 is also provided with a 
continuous second support 114 mounted on the first heat exchange surface 
42 of the drum 14. A laterally extending and substantially continuous 
third support 116 is mounted on the first supports 112, and the second 
support 114. The first supports 112, the second support 114, and the third 
support 116 cooperate to provide a material receiving cavity 118 which 
receives material through a plurality of material receiving openings 120 
(FIG. 5) defined in between the spacially disposed first supports 112. The 
third lifter 110 is also provided with a forwardly extending portion 124 
formed on or supported by the second support 114. The forwardly extending 
portion 124 extends generally from the third support 116 so as to trap or 
gather a quantity of material onto the third support 116 as the drum 14 
rotates. This causes the quantity of material to be heated by conduction 
via the contact between the quantity of material and the heated forwardly 
extending portion 124 and the heated third support 116. 
In operation, a quantity of material passes through the material receiving 
openings 120 into the material receiving cavity 118 as the drum 14 
rotates. The quantity of material is then held in constant contact with 
the first heat exchange surface 42 until the quantity of material is 
discharged through the material receiving openings 120 by gravity, as best 
shown in FIG. 2. Thus, it can be seen that the third lifters 110 function 
to increase the surface area of the first heat exchange surface 42, and to 
maintain the quantity of material in contact with the first heat exchange 
surface 42 for an enhanced length of time during the rotation of the drum 
14. This enhances the amount of conductive heat transfer from the first 
heat exchange surface 42 to the material and thereby enhances the 
efficiency of the decontamination plant 10. 
Operation 
The operation of the decontamination plant 10 is best shown in FIGS. 1 and 
2. Initially, the heat sources 18 and 20 in the first and second sets are 
selectively actuated to preheat the first and second heat exchange 
surfaces 42 and 62, and to thereby preheat the decontamination chamber 34. 
The direction of movement of the flue gases is indicated in FIG. 1 by the 
arrows 130. The motors (not shown) which rotate the drum 14 are then 
actuated to cause the drum 14 to rotate. Once the drum 14 is rotating, 
contaminated material, such as chlorinated and halogenated soil, is 
introduced through the material receiving opening 36 formed in the drum 14 
as indicated by an arrow 134. As best shown in FIG. 2, the material 
passing through the decontamination chamber 34 from the material receiving 
opening 36 to the discharge end portion 38 of the drum 14 is lifted and 
held against the first and second heat exchange surfaces 42 and 62 by the 
first, second, and third lifters 90, 100, and 110 where conductive heat 
transfer from the first and second heat exchange surfaces 42 and 62 is 
accomplished. The contaminated material is thereby heated for a suitable 
amount of time as the contaminated material passes through the 
decontamination chamber 34. The direction of movement of the material 
passing through the decontamination chamber 34 is indicated by the arrows 
138. The direction of movement of the vaporized contaminates through the 
decontamination chamber 27 is indicated by the arrows 140. When the 
contaminated material is soil, the material can be maintained in the 
decontamination chamber 34 for a predetermined time of about six to twelve 
minutes to heat the material from about 650.degree. F. to about 
950.degree. F. The amount of time that it takes for the contaminated 
material to pass through the decontamination chamber can be varied by 
changing the incline angle of the drum 14 or the speed of the rotation of 
the drum 14. 
A main exhaust fan (not shown) maintains a vacuum on the decontamination 
chamber 34 of the drum 14 to direct all vaporized contaminates through the 
first port 76, as previously discussed. The decontaminated material is 
discharged through the second port 80, as previously discussed. 
The flow of the flue gases relative to the material and vaporized 
contaminants is best shown in FIG. 1. As indicated by the arrows 130, 138 
and 140, the flue gases travel in substantially the same direction as the 
material and vaporized contaminants as the flue gases travel in the 
annular heating chamber 27. However, as the flue gases are exhausted 
through the tube 16, the direction of the travel of same is reversed such 
that the flue gases travel in a direction opposite to the direction of 
travel of the material and vaporized contaminants. 
It should be noted that the drum 14 is subject to heat well above 
1800.degree. F. Therefore, the drum 14 should be fabricated of a material 
capable of withstanding such intense heat. The drum 14 may, for example, 
be constructed of stainless steel. 
Changes may be made in the construction and the operation of the varies 
components, elements, and assemblies described herein and changes may be 
made in the steps or the sequence of steps of the methods described herein 
without departing from the spirit and the scope of the invention as 
defined in the following claims.