Note: Descriptions are shown in the official language in which they were submitted.
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WO 99/28060 PCT/US98/2t861
METHODS AND SYSTEMS FOR BIOREMEDIATING
CONTAMINATED SOIL
HACItGROTJND OF THE INVENTION
The invention relates to methods and systems for
bioremediating contaminated soil, and more particularly
to a methods and systems for volatilizing contaminants
in the soil and effectively and efficiently removing
same therefrom.
Systems for conducting fluid through a soil stack are
known. U.S. 4,139,321 describes a rock channel heat
storage method involving conduit connections provided
within a rock-filled channel. The conduits are used to
conduct fluid through the rock pile to either absorb or
disperse thermal energy. Soviet Patent 837,997 describes
a method for the thermal treatment of embankment soil. A
main hold 3 receives heated combusted gas and directs same
into spiral holes 5 which are vented thraugh valves 8.
U.S. 4,036,285 describes an arrangement to control heat
flow between a member and its environment including
conduit members which conduct heat transfer fluid
underground. Other patents which show devices for
conducting fluid through a soil stack include U.S. Patents
123,384; 2,332,227; 2,332,227; 3,105,134; 3,564,862;
3,935,900; 5,449,113; Soviet Union 600,262; Soviet Union
996,662; Fed. Rep. Germany 2,706,740
Systems for removing contaminants from the ground are
also known. For example, U.S. 4,982,788 removes
contaminants from the ground by circulating air between
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two substantially parallel wells and by removing the
vapors of the organic compounds from the circulated air
using at least one of a condenser and a demister. U.S.
5,011,329 relates to in situ decontamination by injecting
a hot gas into boreholes formed in a contaminated soil
area. A method is also provided in U.S. 5,018,576 for in
situ decontamination of contaminated subsurface areas by
injection of steam into injection wells and withdrawing of
liquids and vapors from the wells under sub-atmospheric
pressure.
Systems have also known for removing contaminants
from soil piles or soil stacks. U.S. 4,973,811 relates
generally to in situ decontamination of soil using radio
frequency induction heating. In U.S. 5,035,537, soil,
porous rock, and similar contaminated materials are
gathered, dispersed uniformly on a horizontal surface, and
treated with an emulsifying agent.
U.S. 5,067,852 relates to a method and apparatus for
removing volatile contaminants from contaminated soil
which has been stacked onto a first vapor-tight liner. A
first set of air distribution pipes disposed within the
soil stack each of which has an opened end, a closed end,
and a plurality of perforations located in the body of the
pipes. An air stream is introduced into the open end of
the distribution pipes and exits the distribution pipes
through the perforations and into the contaminated soil
stack. The air flows from the distribution pipes, through
the contaminated soil, and volatilizes contaminants within
the contaminated soil. The air flow from the distribution
pipes employees a gravel filter medium to prevent the
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perforations in the distribution pipes from clogging. The
volatized vapor created as a result of the induced air flow is
carried by the air flow through the soil, and is exhausted from
the soil. The volatilized vapors exiting the soil stack are
disposed of through an external vapor treatment system. A
second vapor-tight liner is placed over the soil stack to
creating an impervious enclosure between the respective first
and second liners, which are typically formed of a polyethylene
film. In order to avoid melting of the first and/or second
liners, the temperature of the soil stack would have to be
maintained below the melting temperature of the respective
liners.
U.S. 5,213,445 and U.S. 5,340,236 are directed to a similar
process to US '852 except that they provide a recirculating
system which destroys the contaminant phase and returns heated
decontaminated air to the air distributions pipes. The air
heating unit, which is located outside of the soil stack, heats
the air to temperature of between 275 and 300 degrees F.
The above-described methods and systems, have a number of
drawbacks. They are closed loop systems which recirculates a
substantial portion of the heated air after the contaminants are
burned or removed. Recirculation of air through heaters reduces
oxygen in the air stream thereby reducing the effective level of
volatilization. These systems of US '852, US '445 and US '236
make use of a vacuum to encourage contaminants tc> achieve vapor
phase which has proven to be an ineffective apprc>ach for
affecting remediation. As previously stated, the
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temperature of the volatizing air must be maintained below
the melting temperature of the sealing member in order
maintain its structural integrity. The above prior art
systems are designed to move the vaporized contaminants
through the soil stack into the space thereabove
surrounded by the flexible sealing member. Therefore, the
soil cannot be packed down to maintain the~structural
integrity of the soil stack without adversely effecting
the efficiency of the remediation process.
SLJI~ARY OF THE INVENTION
The above-described have been met by the system and
methods of the present invention.
The subject invention is not a closed loop system as
indicated in United States patent Nos. 5,213,445 and
5,067,832. The system and method of this invention also
does not make use of a vacuum to encourage contaminants to
achieve vapor phase. The system and method herein are
designed to treat both volatile and semi-volatile
contaminants as well as a wide variety of soil types
(frozen, very wet, high clay content, etc.) And, unlike
the prior art systems and methods, in the process and
method of this invention, soil can be packed down without
decreasing the efficiency of the system.
More specifically, the present invention is directed
to systems and methods for expurgating contaminants from
contaminated soil removed from a soil site and to systems
and methods for remediating contaminated soil removed from
a soil site. Thus, the subject systems and methods can
comprise forming a multi-layer soil remediation cell
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having a plurality of adjacent layers of contaminated
soil, and a plurality of dual-function perforated pipes
located between the adjacent layers of contaminated soil.
Then, a high temperature air is introduced into the
contaminated soil through the dual-function perforated
pipes. Preferably, the high temperature air is heated to
a temperature of at least about 800 degree F., more
preferably at least about 1000 degree F., and most
preferably at least about 1200 degree F. Extremely high
temperature can also be employed depending on the
temperature limitations of the dual-function perforated
pipes and the covering. Thus, in cases where a dual-
function perforated pipes and covering are used which can
withstand extremely high temperatures, i.e., from 2,000 up
to 3,000 degrees F., a corresponding extremely high
temperature air supply can be employed In this way, the
first function can be imparted to the contaminated soil,
namely, volatilizing the contaminants located within the
contaminated soil thereby producing a contaminated vapor.
This will typically cause the contaminated soil to be
heated to an average temperature of at least about 212
degree F., preferably to an average temperature of at
least about 250 degree F., more preferably to an average
temperature of at least about 300 degree F., and most
preferably to an average temperature of at least about 350
degree F.
Next, the second function of the dual-function
perforated pipes is facilitated, namely, removing the
contaminated vapor from within the multi-layer soil
remediation cell through the dual-function perforated
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pipes. Preferably, this second function is accomplished
by conductively volatilizing the contaminated soil with
the high temperature air, and thereby moving the
contaminated vapors produced into and through the dual-
function perforated pipes (and into and through the
chamber and into an off-gas treatment unit, such as a burn
chamber, as hereinafter described) due to a pressure
differential created by the high temperature air within
the contaminated soil. Tn this systems, it is not the air
moving through the soil which volatilized the contaminants
but rather the conductive heating of the soil. Vapors do
not move through the soil to the top of the soil cell but
rather into the perforated pipes, down the pipes and into
the vapor hold chamber formed between the cell and the
covering, which is preferably.a steel-fabricated building.
When the contaminated vapor is removed from within
the mufti-layer soil remediation cell it substantially
reducing the moisture level in the contaminated soil,
preferably to an average moisture level of less than about
5 ~ by weight, more preferably to an average moisture
level of less than about 2 ~ by weight, and most
preferably to an average moisture level of less than about
I ~ by weight.
A high temperature covering is provide about the
mufti-layer soil remediation cell having an entry opening
at one end of the covering in communication with the dual-
function perforated pipes. The covering is disposed over
the mufti-layer soil remediation cell, a vapor holding
chamber being formed therebetween. An exit opening is
provided at the other end of the covering in communication
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with an off-gas treatment unit. The off-gas treatment unit is
employed for collecting and/or destroying the contaminants in the
contaminated vapors.
The contaminated vapor is released from the dual function
perforated pipes through the entry opening into, and collecting
the contaminated vapor within, the vapor holding chamber. The
system of the present invention can further include me<~ns for
controlling the amount of contaminated vapor that, flows from the
dual-function perforated pipes into the chamber. The collected
contaminated vapor is released from the vapor holding chamber
through the exit opening and passes into the burn chamber.
The system can further include high temperature air supply
pipes within the multi-layer soil remediation ce7_1 for
transferring the high temperature air to the dua7_-funct:ion
perforated pipes. Preferably, the air supply header pipes are
buried within the center. They can also run the length of the
soil cell. Each header pipe can have a pluralit~~ of air supply
connections extending therefrom to both sides of the soil cell.
The system of present invention is typically designed so
that the high temperature air passes within the contaminated
vapors through the exit opening without recirculating t;he high
temperature air to the multi-layer soil remediati.on cell. In
other words, the subject system is preferably configured for a
single-pass remediation operation.
In summary, according to the present invention, there is
provided: a system for remediation of contaminated soil. removed
from a soil site, comprising: a multi-layer soil remeds.ation
cell formed of a plurality of adjacent layers of contaminated
soil, and a plurality of dual-function perforated pipes located
between the adjacent layers of contaminated soil, said dual-
function perforated pipes acting as (a) heating prods for
introducing high temperature air into the contaminated soil for
volatilizing the contaminants located within the contaminated
soil thereby producing a contaminated vapor, and (b) flow
channels for removing said contaminated vapor frcm within said
multi-layer soil remediation cell; a high temperature covering,
located about said multi-layer soil remediation cell, having an
entry opening in communication with said dual-function
perforated pipes, an exit opening in communication with. a burn
chamber, and forming a chamber over said mufti-layer soil
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remediation cell which receives and collects in said chamber
said contaminated vapor which have been released from said dual-
function perforated pipes and passes through said entry opening;
and said burn chamber at least one of collecting and destroying
contaminants in said contaminated vapors which are released from
said storage chamber and passes through said exit opening.
A method for remediating of contaminated soil removed from
a soil site, comprising: forming a mufti-layer soil rernediation
cell having a plurality of adjacent layers of contaminated soil,
and a plurality of dual-function perforated pipes located
between the adjacent layers of contaminated soil, introducing
high temperature air into the contaminated soil through said
dual-function perforated pipes and volatilizing the contaminants
located within the contaminated soil thereby producing a
contaminated vapor; providing a high temperature covering about
said mufti-layer soil remediation cell having an entry opening
in communication with said dual-function perforated pipes, an
exit opening in communication with a burn chamber, and forming a
chamber over said mufti-layer soil remediation cell; removing
said contaminated vapor from within said mufti-layer soil
remediation cell through said dual-function perforated pipes;
releasing said contaminated vapor through said entry opening
into, and collecting said contaminated vapor within, said
chamber; and passing said collected contaminated vapor from said
chamber through said exit opening; and at least one of
collecting and destroying said contaminants in said contaminated
vapors.
A method for expurgating contaminants from contaminated
soil removed from a soil site, comprising: forming a mufti-layer
soil remediation cell having a plurality of adjacent layers of
said contaminated soil, and a plurality of dual-function
perforated pipes located between the adjacent layers of said
contaminated soil, introducing high temperature a.ir into the
contaminated soil through said dual-function perforated pipes
and volatilizing the contaminants located within the
contaminated soil thereby producing a contaminated vapor; and
removing said contaminated vapor from within said. mufti-layer
soil remediation cell through said dual-function perforated
pipes thereby expurgating said contaminants from said
contaminated soil.
7a
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The foregoing and other objects, features and advantages
of the invention will become more readily
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apparent from the following detailed description of a
preferred embodiment which proceeds with reference to the
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic end view of the system 10 of
the present invention.
FIG. 2 is a schematic view of the system 10 of FIG.
1.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
Referring now to Fig. 1, a system denoted "1" is
provided for remediation of contaminated soil removed from
a soil site. System 1 comprises a mufti-layer soil
remediation cell denoted "10" formed of a plurality of
adjacent layers of contaminated soil, and a plurality of
dual-function perforated pipes located between the
adjacent layers of contaminated soil.
System 1 is formed by placing a polymeric liner sheet
11, typically a polyethylene liner, on the ground.
Generally a rectangular work area, such as a 36' x 80'
area, is laid out. A first layer of soil 12 is placed
upon the liner. A layer twelve inches thick can be
employed for this purpose.
Then, air supply pipes 13a, preferably 12" OD, are
placed in the center of the soil layer 12a running the
length of the layer 12a. Dual-function perforated heating
pipes 14a, in the form of 4" steel heating prods, are
connected to the air supply pipes 13.
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A second layer of soil 12b (30" thick) is placed upon the
heating pipes 14a. Another layer of air supply pipes 13b and
heating pipes 14b are placed upon the soil 12b. A third layer
of soil 12c (30" thick) is placed upon the heating pipes 14b.
Another layer of air supply pipes 13c and heating pipes 14c are
placed upon the soil 12c. Finally, a fourth layer of soil 12d
(18" thick) is placed upon the heating pipes 14c. It is
understood that the quantity, size and relative configuration,
etc., of supply pipes 13, heating pipes 14 and soil layers 12
can vary depending on circumstances involved in a given
remediation situation.
A quonset hut-shaped metal building 17 is assembled in 5'
sections and forms a covering for the entire soil cell. The
temperature range of the heated air can reach up to 2500 F.
without compromising the integrity of the sealing member.
Heaters 18 are attached at the inlet end of the air supply
pipes 13a-13c at each soil layer 12a-12d. Heaters 18 which
supply air to the air supply pipes are fueled with fuel oil,
diesel, propane, butane or natural gas. The preferred heaters
18 are the propane burners used for burning alfalfa ("Burners"),
which are numerically denoted as "10", in U.S. 4,644,683 to
Darrell R. Jones ("US '683"). The Burners are pictorially
illustrated in FIGS. 4-9 of US '683 and are specifically
described beginning at column 3, line 6 of US '683. An
exemplary burner is manufactured by Inferno Burner Company of
Clackamas, Oregon. This burner puts out
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300,000 to 1.5 million BTU's, in a CFM range of 1,000 to 6,000,
at a exhaust temperature of 800 to 2500 degree F.
High temperature air is forced into the air supply pipes 13
at temperatures up to 2500 degrees F. at point 21. Air supply
pipes 13 are manufactured from steel (approximately 20 gauge) so
to prevent damage from heavy equipment and/or settling of soil.
An off-gas treatment unit 19 is employed herein to destroy
the contaminants in the contaminated vapor stream. An exemplary
off-gas treatment unit 19 volatizes contaminants which are
preferably drawn into and through a catalytic oxidizer and
destroyed. The off-gas treatment unit 19 is connected to a vent
at the exit 22 of the Quonset hut 17 opposite the heaters.
Generally, a blower, such as a 25-HP, 3-phase, 2.20 volt blower,
draws the contaminated air out of the quonset hut: and through a
15 catalytic converter bank. It is then vented to t:he atmosphere.
The blower is preferably a high-pressure radial blade industrial
blower with a wheel diameter of 25"-30". A typical blower
should be capable of producing 3600-CFM air delivery at 12
inches of static pressure. The catalytic converters ax-e
20 preferably a bank (such as a dozen or more converters) of Walker
Exhaust Catalytic Converter Units (Model No. 15174 for example)
generally arranged in parallel with respect to each other.
This system is designed to allow treatment of soil. cells 25
cubic yards to 1500 cubic yards in volume. The entire system
can be loaded upon a 45 foot flatbed trailer to be transported
from site to site. A remediation system
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which is characterized by its ability to remediate over 5 tons
of soil per hour with less than 7 moving parts.
In operation, as described in FIGS. 1 and 2, heaters 18 are
turned on and air is heated to its supply temperature. The hot
air is introduced at point 18 into hot air supply pipes 13a-c
which in turn feed the hot air to heating pipes :L4a-c,
respectively. As shown in FIG. 1 the hot air exits heating
pipes 14a-c where it is introducing into contaminated coil 15.
Heat and water produce steam which creates high pressure areas
in contaminated soil 15. The contaminated soil :L5 is then
dehydrated by the heated air and forms areas of lower pressure
dehydrated soil 16. The dehydrated soil 16 substantially
surrounds the heating pipes 14a-c. The difference in pressure
between the respective high and low pressure areas forces
contaminated air, depicted as arrows "30", through dehydrated
soil 16 and into the heating pipes 14a-c where it: flows,
depicted as arrows "40", into the space formed between covering
17 and cell 10, where it is forced into the off-gas treatment
unit 20, which is preferably catalytic oxidizer unit.
Having illustrated and described the principles of my
invention in a preferred embodiment thereof, it :should be
readily apparent to those skilled in the art that: the ~_nvention
can be modified in arrangement and detail without: departing from
such principals.
11
