U.S. patent application number 09/136077 was filed with the patent office on 2001-06-07 for apparatus and method for thermal stripping and molecular decomposition for waste streams.
Invention is credited to WAGNER, ANTHONY S..
Application Number | 20010002989 09/136077 |
Document ID | / |
Family ID | 22471180 |
Filed Date | 2001-06-07 |
United States Patent
Application |
20010002989 |
Kind Code |
A1 |
WAGNER, ANTHONY S. |
June 7, 2001 |
APPARATUS AND METHOD FOR THERMAL STRIPPING AND MOLECULAR
DECOMPOSITION FOR WASTE STREAMS
Abstract
An apparatus removes water and organic compounds from waste
streams such as contaminated soils and refinery tailings by a
combination of thermal stripping and molecular decomposition. The
apparatus includes at least one unit having a pipe which is
preferably heated by induction heating and also having a transport
arrangement. The transport arrangement includes a suitable motor
and operates to move the waste stream material through the pipe and
mix the material to provide uniform heat transfer from the heated
pipe. The transport arrangement preferably includes an adjustment
mechanism which allows adjustment of the rate at which material
moves through the pipe for a given motor speed. The adjustment
mechanism also adjusts the mixing provided by the transport
arrangement. Several of the treatment units according to the
invention may be connected in series to form a multistage device.
The initial stages may be operated at temperatures capable of
thermally stripping water and light hydrocarbons from the waste
stream while the later units may be operated at temperatures to
cause remaining organic material to decompose.
Inventors: |
WAGNER, ANTHONY S.; (BEE
CAVES, TX) |
Correspondence
Address: |
RUSSELL D CULBERTSON
1250 CAPITAL OF TEXAS HIGHWAY S
BUILDING ONE SUITE 360
AUSTIN
TX
78746
|
Family ID: |
22471180 |
Appl. No.: |
09/136077 |
Filed: |
August 18, 1998 |
Current U.S.
Class: |
422/232 |
Current CPC
Class: |
B01D 2257/2022 20130101;
F23G 2201/50 20130101; B09C 1/08 20130101; B09B 3/40 20220101; F23G
2209/24 20130101; B09B 3/00 20130101; B09C 1/06 20130101; F23G
2201/40 20130101; B01D 2257/2025 20130101 |
Class at
Publication: |
422/232 |
International
Class: |
B01J 008/02; B01J
035/02; B01J 008/08 |
Claims
1. A thermal stripping and molecular decomposition unit comprising:
(a) a unit body having a substantially cylindrical cavity; (b) a
transport unit mounted within the unit body and having mounted
thereon a plurality of substantially planar transport segments, the
transport unit for transporting material through the unit body from
an inlet end of the unit body to an outlet end of the unit body,
and for mixing the material contained within the unit body; (c) an
adjustment arrangement associated with the transport unit for
adjusting the angle of the transport segments with respect to the
longitudinal axis of the unit body; (d) a feed arrangement at the
inlet end of the unit body; (e) a heater for heating at least the
surface of the cavity of unit body and thereby heating material
contained within the cylindrical cavity of the unit body; and (f) a
discharge arrangement located at the outlet end of the unit
body.
2. The thermal stripping and molecular decomposition unit of claim
1 further comprising: (a) a vent line from the cavity of the unit
body; and (b) a condenser connected to the vent line for condensing
compounds from gases exiting the cavity of the unit body through
the vent line.
3. The thermal stripping and molecular decomposition unit of claim
1 wherein the transport unit comprises: (a) an elongated mounting
cylinder mounted coaxially within the cavity of the unit body for
rotation about the longitudinal axis of the cavity; (b) a plurality
of pairs of mounting rods spaced apart along the length of the
mounting cylinder, each pair of mounting rods including a first
mounting rod extending generally radially from the mounting
cylinder on one side thereof, and a second mounting rod extending
generally radially from the mounting cylinder on the opposite side
of the mounting cylinder, each mounting rod being connected to the
mounting cylinder for rotation about its respective longitudinal
axis, and each mounting rod having one of the transport segments
rigidly connected thereto.
4. The thermal stripping and molecular decomposition unit of claim
3 wherein the adjustment arrangement comprises: (a) mounting rod
control means for simultaneously rotating the mounting rods
extending from one side of the mounting cylinder each about their
respective longitudinal axis and fixing said mounting rods in a
particular angular orientation.
5. The thermal stripping and molecular decomposition unit of claim
3 further comprising: (a) a first scraper connected to a distal end
of each mounting rod extending from one side of the mounting
cylinder and a second scraper connected to a distal end of each
mounting rod extending from the opposite side of the mounting
cylinder.
6. A multistage thermal stripping and molecular decomposition waste
treatment unit comprising: (a) a plurality of unit bodies connected
in series, each unit body have a substantially cylindrical cavity
therein; (b) each unit body having a transport unit mounted in the
respective cavity for transporting material from an inlet end to an
outlet end of the respective unit body; (c) each unit body having a
heater associated therewith for heating at least the surface of the
cylindrical cavity of the respective unit body; (d) each unit body
having a heat sensing and control arrangement at its outlet end,
the respective heat sensing and control arrangement for controlling
at least the operation of the heater associated with the respective
unit body for controlling the temperature at said respective outlet
end; (e) a feed arrangement for feeding waste material into the
inlet end of a first of the unit bodies; (f) an outlet arrangement
at the outlet end of the last unit body in the series of unit
bodies for allowing treated waste material to exit said last unit
body; (g) a transfer arrangement between adjacent unit bodies in
the series of unit bodies for transferring waste material from the
outlet end of one of said adjacent unit bodies to the inlet end of
the other of said adjacent unit bodies; and (h) each unit body
having a vent from the respective cavity for removing gases
released as the waste material within the respective cavity is
heated.
7. The multistage thermal stripping and molecular decomposition
unit of claim 6 further comprising: (a) a condenser connected to
receive gasses from the vent associated with the first unit body in
the series.
8. The multistage thermal stripping and molecular decomposition
unit of claim 6 wherein the transport arrangement associated with
each unit body comprises: (a) an elongated mounting cylinder
mounted coaxially within the cavity of the respective unit body for
rotation about the longitudinal axis of the cavity; (b) a plurality
of pairs of mounting rods spaced apart along the length of the
mounting cylinder, each pair of mounting rods including a first
mounting rod extending generally radially from the mounting
cylinder on one side thereof, and a second mounting rod extending
generally radially from the mounting cylinder on the opposite side
of the mounting cylinder, each mounting rod having a substantially
planar transport segment rigidly connected thereto.
9. The multistage thermal stripping and molecular decomposition
unit of claim 8 wherein the mounting rods are each mounted on the
mounting cylinder for rotation about their respective longitudinal
axis and further comprising: (a) mounting rod control means for
simultaneously rotating the mounting rods extending from one side
of the mounting cylinder and fixing said mounting rods in a fixed
angular orientation.
10. The multistage thermal stripping and molecular decomposition
unit of claim 9 further comprising: (a) a first scraper connected
to a distal end of each mounting rod extending from one side of the
mounting cylinder and a second scraper connected to a distal end of
each mounting rod extending from the opposite side of the mounting
cylinder.
11. A thermal stripping and molecular decomposition method
comprising the steps of: (a) transporting a waste material through
a series of at least two heated pipes, each heated pipe having an
inlet end and an outlet end; (b) controlling the waste material
temperature at the outlet end of the first heated pipe to a first
thermal stripping temperature; (c) removing gasses released from
the waste material as it is heated to the first thermal stripping
temperature in the first heated pipe; (d) controlling the
temperature of the waste material at the outlet end of the last
heated pipe in the series of heated pipes to a thermal
decomposition temperature to release gasses from the waste material
leaving a treated solid material; (e) removing gasses released from
the waste material as it is heated to the thermal decomposition
temperature in the last heated pipe; and (f) removing the treated
solid material from the outlet end of the last heated pipe.
12. The thermal stripping and molecular decomposition method of
claim 11 wherein the series of heated pipes includes three heated
pipes and further comprising the steps of: (a) feeding waste
material exiting the first heated pipe into a second heated pipe
and transporting said waste material to an outlet end of the second
heated pipe; (b) controlling the temperature of the waste material
at the outlet end of the second heated pipe to a second thermal
stripping temperature; (c) removing gasses released from the waste
material as it is heated to the second thermal stripping
temperature in the second heated pipe; and (d) feeding the waste
material exiting the second heated pipe into the last heated pipe
and transporting said waste material to an outlet end of the last
heated pipe.
13. The thermal stripping and molecular decomposition method of
claim 11 wherein the step of controlling the waste material
temperature at the outlet end of at least one heated pipe in the
series of heated pipes is accomplished at least in part by
controlling the rate at which the waste material is transported
through the respective heated pipe.
14. The thermal stripping and molecular decomposition method of
claim 13 wherein the step of controlling the rate at which waste
material is transported through the respective heated pipe is
accomplished by varying the angle of a plurality of transport
segments mounted on a rotating mounting cylinder positioned
coaxially within the respective heated pipe.
Description
TECHNICAL FIELD OF THE INVENTION
[0001] The invention relates to the recovery or removal of organic
compounds from soil, refinery tailings, and the like. The invention
is particularly suited for removing light oils, pesticides, heavy
oils or tar and/or other hazardous chemicals from soil which has
been contaminated with such chemicals.
BACKGROUND OF THE INVENTION
[0002] Soils which have become contaminated with various organic
compounds such as oils or pesticides, for example, must be treated
to remove the contaminating material in order to prevent the
contaminating material from leaching into adjacent areas and ground
water. Certain refinery tailings may also contain harmful organic
compounds with must be removed before the tailings can be
landfilled or otherwise released to the environment.
[0003] Organic compounds may be removed from contaminated soil and
certain refinery tailings and the like by subjecting the
contaminated material to heat. This heat treatment for removing
organic compounds is commonly referred to as "thermal stripping."
Relatively low temperatures cause light oils and other hydrocarbon
contaminants to go into a gaseous phase in which the contaminant
releases from the contaminated material. Heavier oils may be driven
out of the contaminated material in a gaseous phase at higher
treatment temperatures. Even higher temperatures may be used to
break chemical bonds in organic compounds such as pesticides, and
allow the constituent elements or chemicals to release from the
contaminated material. While it has been known to remove organic
compounds from contaminated soil and the like through thermal
stripping, prior thermal stripping processes have not provided
sufficient control to accommodate the many different types of
contaminants which may be present in the contaminated soil.
SUMMARY OF THE INVENTION
[0004] It is an object of the invention to provide an apparatus and
method for removing organic compounds from soil, refinery tailings,
and other similar waste streams. More particularly, it is an object
of the invention to provide an apparatus and method which
facilitates a high degree of control in the removal of organic
contaminants from waste streams such as contaminated soils.
[0005] An apparatus embodying the principles of the invention is
made up of one or more units, the number of units depending upon
the types of contaminants to be removed from the particular waste
stream. Each unit comprises a heated pipe having an inlet end and
an outlet end. The pipe is heated preferably by electrical
induction heating and transfers heat to the waste stream contained
therein. A transport unit is mounted inside the heated pipe for
transporting the waste stream there through and mixing the waste
stream to provide uniform heating in the material. According to the
invention, the transport unit is adjustable so that the rate at
which the waste stream passes through the pipe may be closely
controlled without eliminating the mixing action produced by the
transport unit.
[0006] The transport unit comprises a dual line of substantially
semi-circular transport segments pivotally mounted on opposite
sides of a hollow mounting cylinder. The mounting cylinder itself
is concentrically mounted within the heated pipe for rotation about
its longitudinal axis. A drive unit is associated with the mounting
cylinder for rotating the mounting cylinder about its longitudinal
axis. The uppermost end of a pivotal mounting rod for each segment
is connected to a spring-loaded scraper blade for scraping the
inner wall of the pipe to help mix the material passing through the
pipe and prevent buildup on the pipe walls which could reduce heat
transfer to the waste stream. The lower end of each mounting rod
extends through a bearing into the hollow mounting cylinder and is
operatively connected by a lever arm to a threaded rod that extends
through the mounting cylinder. The lever arm and threaded adjusting
rod cooperate to adjust the angle of each row of transport
segments. For maximum transport at a particular speed setting of
the drive for the transport unit, the angle of each row of segments
is set equal and opposite with the leading edge of one row of
segments being approximately above the trailing edge of the
opposite row of segments. At any one speed, decreasing the angle of
each row of segments with respect to a line perpendicular to the
mounting cylinder will give more mixing and slower transport.
[0007] One unit according to the invention may be used for treating
a waste stream to remove water and low-boiling point organic
compounds by thermal stripping. A plurality of units according to
the invention may be used in series to remove contaminants by both
thermal decomposition and thermal stripping. For example, three
units may be used in series to treat a waste stream comprising a
contaminated soil including water, low-boiling organic compounds,
high-boiling organic compounds, and normally solid compounds such
as pesticides and insecticides. The first unit in the series may be
operated with the exit temperature held at about 100 degrees
centigrade. Water vapor and organic compounds released in the first
unit are preferably vented to a suitable condenser to condense the
water vapor and organic compounds.
[0008] The solids from the outlet of the first unit feeds into the
second unit. The second unit is equipped with a vent line leading
to a condenser to condense the higher-boiling organic compounds for
recycle and the exit temperature may be held at 200 to 300 degrees
centigrade. The solid material discharged from the second unit
feeds into the inlet end of the third unit. The exit temperature of
the third unit may be held at 750 to 950 degrees centigrade to
crack organic compounds remaining in the waste stream. The third
unit in the series is equipped with a vent line and a suitable
scrubber for removing elements such as chlorine and bromine from
the vent gases.
[0009] The process control achieved with the invention makes the
present treatment apparatus and method suitable for treating soils
and the like contaminated with many different types of organic
contaminants. In waste streams containing only light organic
contaminants or organic contaminants plus water, the apparatus
provides thermal stripping to produce a landfillable solids output
while separating the water and lower boiling point organics. The
apparatus according to the invention may also decompose organics
such as insecticides, and remove the resulting constituent elements
or compounds. In waste streams containing organic contaminants plus
metals that must be removed before the solids may be placed in a
landfill, the apparatus according to the invention can be used as a
pretreatment before metal removal. This pretreatment may be
particularly useful where metal removal is to be accomplished by
leaching or by molten metal contact as outlined in U.S. Pat. No.
5,000,101.
[0010] These and other objects, advantages, and features of the
invention will be apparent from the following description of the
preferred embodiments, considered along with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a view in perspective of a single unit embodying
the principles of the invention with a portion of the pipe removed
to show the transport unit.
[0012] FIG. 2 is an end view of a portion of the transport
unit.
[0013] FIG. 3 is an view in perspective showing the lever arm
adjustment mechanism for the transport unit.
[0014] FIG. 4 is a somewhat diagrammatic end view of a portion of
the transport unit.
[0015] FIG. 5 is a diagrammatic representation of a multistage
thermal stripping arrangement embodying the principles of the
invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0016] FIG. 1 shows a single unit 1 embodying the principles of the
invention. The unit 1 includes a heated pipe 2 having a generally
cylindrical inner surface and comprising a top half 2a and a bottom
half 2b. The top half 2a of the heated pipe 2 is shown broken away
in FIG. 1 to show a transport unit within the pipe. The heating
arrangement is also omitted from FIG. 1. The top half 2a in this
illustrated form of the invention is secured to the bottom half 2b
by a suitable longitudinal flange. Those skilled in the art will
appreciate that the pipe may be a unitary piece rather than the
flanged top and bottom halves described with reference to FIG. 1.
Although the single unit 1 may be used both for thermal stripping
and molecular decomposition, a single unit according to the
invention is best used where thermal stripping alone is
desired.
[0017] As shown in FIG. 1, the pipe is sealed at each end with a
flange 17. Feed chute 3 may be used to feed material to be treated
through a star feeder 5 into the pipe. The star feeder 5 helps
reduce the amount of air entering the pipe 2. Solids exit the unit
1 through discharge chute 23 which may empty into any of several
types of containers or as shown in FIG. 5 may discharge into a
similar unit for further treatment. Discharge chute 23 includes a
suitable arrangement for preventing air from entering the pipe.
Although not shown in FIG. 1, each unit preferably also includes a
suitable purging system for purging the pipe 2 of air prior to
operation. A suitable purge system may use an inert gas such as
Nitrogen to displace air from the pipe. Removing air from the pipe
is necessary to prevent the organic materials being released in the
pipe 2 from oxidizing.
[0018] The transport unit housed within the pipe transports
material there through and mixes the material within the pipe. The
transport unit includes a mounting cylinder 11 having multiple,
pivotally mounted transport segments 9. Mounting cylinder 11 is
concentrically mounted within the pipe for rotation about its
longitudinal axis, driven by variable speed drive motor and gearing
arrangement 10. Each transport segment 9 is connected to a pivot
mount rod 21, and the pivot mount rods are each pivotally connected
on a lower end, as shown in more detail in FIG. 4, to the mounting
cylinder 11. Each pivot mount rod 21 is pivotally connected at its
upper end to scraper 19, as also shown in more detail in FIG.
4.
[0019] Referring to FIG. 1, multiple transport segments 7 are
connected to mounting cylinder 11 in the same way as segments 9. To
obtain maximum transport and minimum mixing at a given speed of
motor 10, segments 7 and 9 are adjusted to maximum equal and
opposite angles relative to a plane perpendicular to the mounting
cylinder 11. At a given angle of the transport segments 7 and 9,
the rate at which material is conveyed through the pipe and the
amount of mixing within the pipe is controlled by the speed of the
motor and gearing arrangement 10. The angle of each transport
segment 7 and 9 is adjustment through fittings 13 and 15 as shown
in more detail in FIG. 3. The motor speed, transport segment
angles, and heat of the pipe are preferably automatically
controlled to control thermal stripping and molecular decomposition
within the unit. The control equipment is omitted from the drawings
to avoid obscuring the invention in unnecessary detail. Such
control systems themselves are in any event well within the
knowledge of those skilled in the art.
[0020] Each unit also includes a suitable heating arrangement for
heating the pipe to a desired temperature for transferring heat to
the material being transported through the pipe. The invention
preferably employs a suitable induction heating arrangement shown
in FIG. 5 for heating the pipe, although the invention is not
limited to induction heating. Referring to the fist unit 1 shown in
FIG. 5, the preferred induction heater includes a suitable
induction coil or coils 41 positioned adjacent to the pipe 2 and an
induction heating control unit 41a. The preferred induction heating
arrangement heats the pipe by inducing alternating electromagnetic
fields in the metal from which the pipe is constructed. The
electromagnetic fields produce eddy currents within the pipe
material itself, thereby heating the pipe material internally.
[0021] FIG. 2 shows an end view of mounting cylinder 11 which is
preferably formed from two cylinder halves 11a and 11b connected
together by suitable means such as flange 12. Lever arms 31 are
connected to mounting rods 21 of segments 7 and 9 in bearing
holders 26 as shown in more detail in FIG. 4. Referring to FIGS. 2
and 3, lever arm adjustment fittings 33 are threaded on an
adjustment rod 25 shown in FIG. 3 so that rotation of the
adjustment rod 25 about its longitudinal axis moves the lever arm
31 associated with each transport segment 7 and 9 and adjusts the
angle of the respective transport segment. Adjustment connector 13
is provided at the end of the adjustment rod 25 associated with
transport segments 7 by which the rod may be rotated to adjust the
angle of all segments 7. Adjustment connector 15 is provided at the
end of the adjustment rod 25 associated with transport segments 9
by which the rod may be rotated to adjust the angle of all segments
9.
[0022] FIG. 3 illustrates the interaction of lever arm 31 with
adjustment fitting 33 which is threadably connected with threaded
adjustment rod 25. Threaded adjustment rod 25 is held at both ends
in a suitable bearing 29 mounted at the ends of the mounting
cylinder 11. Rotating adjustment connector 13 rotates rod 25 and
produces an axial displacement of the adjustment fitting 33 along
the rod 25 which in turn moves lever arm 31 through the slotted arm
of fitting 33. This movement of lever arm 31 rotates male fitting
30. As shown in FIG. 4, the rotation of male fitting 30 also
rotates female fitting 32 which is rigidly connected with segment
mounting rod 21.
[0023] As shown in FIG. 1, scraper 19 extends the full length of
the pipe 2. Referring to FIG. 4, scraper 19 connects to all
mounting rods 21 of segments 9 with fitting 18. Spring 20 serves to
press scraper 19 against the inner wall of the pipe. A second
scraper 19 is similarly connected to the mounting rods 21
associated with all segments 7 and functions similarly. Mounting
rod 21 is supported in sleeve bearing 28 which is held in bearing
holder 26. Bearing holder 26 is rigidly connected to mounting
cylinder 11 and is closed with cap 34 that fits closely around rod
21 for form a substantial seal.
[0024] FIG. 5 shows a multistage embodiment of the invention,
including units 1, 42, and 44. Units 42 and 44 are essentially the
same as the single unit 1 described primarily in connection with
FIGS. 1 through 4. However, unit 42 may not require the star feeder
and air blocking outlet chute, and unit 44 may not require the star
feeder. This multistage unit is well suited for waste streams that
may have water, recoverable liquid organic compounds, and hazardous
solid organic compounds. Each stage of the multistage unit may be
individually temperature controlled to remove a different types of
materials from the waste stream.
[0025] Consider the decontamination of a waste stream comprising
soil containing water and contaminated with, oils or other liquid
hydrocarbons, and a solid pesticide. According to the invention,
the waste stream is fed to the first stage, unit 1, through chute 3
and star feeder valve 5 associated with the unit. The temperature
sensor-controller 45 may be set to a first thermal stripping
temperature of about 105 degrees centigrade, controlling induction
heater coils 41 to maintain this temperature. An instrument control
system, not shown, controls the speed of motor 10 and the speed of
star feeder valve 5 to maintain the desired 105 degree centigrade
outlet temperature for unit 1. As shown in FIGS. 1 through 4, the
angle of segments 7 and 9 (FIG. 1) may be adjusted to achieve more
mixing and better heat transfer from the hot wall of unit 1 to the
waste stream. In this example, all water and some oil in the waste
stream goes to a gaseous phase and exits unit 1 through vent line
51 to condenser 50. The liquid condensate from condenser 50 may be
separated in a suitable separator 61 into water and oil output
streams. The multistage unit directs the waste stream exiting unit
1 to the inlet of second stage unit 42. Although the material may
be moved into the second stage unit 42 by any suitable means, the
waste stream is preferably gravity fed into the second stage unit
42. Temperature sensor-controller 47 associated with second stage
unit 42 may be set to control induction coils 43 through induction
unit 43a to maintain the temperature at the outlet end of the
second stage unit at a second thermal stripping temperature of
approximately 250 to 350 degrees centigrade. At these temperatures
heavier oils or other hydrocarbons go into a gaseous phase and exit
the pipe associated with second stage unit 42 through vent line 53.
The exiting hydrocarbons are then condensed in condenser 52 to form
another outlet stream from the multistage unit.
[0026] The waste stream exiting second stage unit 42 is directed to
the inlet of third stage unit 44, again preferably by gravity feed.
At this point the waste stream includes the soil, the contaminating
pesticides, and perhaps other solid organic compounds.
Sensor-controller 49 is set to control the induction unit 46a and
coils 46 to maintain the temperature at the outlet end of the third
stage unit 44 at a decomposition temperature. This temperature may
be at approximately 850 degrees centigrade or some other
temperature to cause the remaining organic materials, and
particularly the contaminating pesticide, to decompose into
constituent compounds or elements. These compounds or elements go
to a gaseous phase at the desired treatment temperature and exit
third stage unit 44 through vent line 55. A suitable scrubber 54,
such as an alkaline scrubber, may be used to remove ions such as
chlorine and bromine before venting to the atmosphere or to further
processing apparatus. The solid material exiting the outlet end of
third stage unit 44 comprises mostly soil and is directed to an
outlet container 48. This solid material may be landfilled or
disposed of in some other suitable manner.
[0027] The above described preferred embodiments are intended to
illustrate the principles of the invention, but not to limit the
scope of the invention. Various other embodiments and modifications
to these preferred embodiments may be made by those skilled in the
art without departing from the scope of the following claims.
* * * * *