U.S. patent application number 10/439398 was filed with the patent office on 2004-06-03 for apparatus for waste gasification.
Invention is credited to Pope, Michael G..
Application Number | 20040103831 10/439398 |
Document ID | / |
Family ID | 29550170 |
Filed Date | 2004-06-03 |
United States Patent
Application |
20040103831 |
Kind Code |
A1 |
Pope, Michael G. |
June 3, 2004 |
Apparatus for waste gasification
Abstract
A gasification system that includes a gasification reactor
chamber having perforated conduits or an inner lining that
increases the exposed surface area of waste materials to
gasification conditions, thereby decreasing gasification
temperature, time, and cooling period between subsequent
gasification procedures. After an aspirator withdraws and oxidizes
fuel gas from the reactor chamber, a flare assembly combusts the
mixed fuel gas to provide power or heat to at least one heat
recovery device. The at least one heat recovery device recaptures
thermal energy entrained in the exhaust, thereby reducing exhaust
temperature and eliminating the need for an exhaust stack. An
absorber purifies the exhaust and an extractor removes carbon
dioxide. A portion of the removed carbon dioxide may be used for
industrial purposes or for supporting vegetation. At least a
portion of the remaining exhaust is returned to the reactor chamber
as recycled process gas, thereby completing a closed-loop
system.
Inventors: |
Pope, Michael G.; (North Ft.
Myers, FL) |
Correspondence
Address: |
MCANDREWS HELD & MALLOY, LTD
500 WEST MADISON STREET
SUITE 3400
CHICAGO
IL
60661
|
Family ID: |
29550170 |
Appl. No.: |
10/439398 |
Filed: |
May 16, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60381958 |
May 17, 2002 |
|
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Current U.S.
Class: |
110/341 ;
110/229 |
Current CPC
Class: |
C10J 3/20 20130101; F23G
7/08 20130101; F23M 2900/05004 20130101; F23G 2900/00001 20130101;
C10J 2300/0916 20130101; C10J 3/10 20130101; C10J 2300/1223
20130101; C10J 2300/1807 20130101; C10J 2300/1861 20130101; F23G
5/16 20130101; C10J 3/34 20130101; C10J 2300/1246 20130101; C10J
2300/1696 20130101; F23L 17/00 20130101; F23G 5/027 20130101; C10J
3/723 20130101; F23G 5/006 20130101; F23J 15/025 20130101; C10J
2300/1687 20130101; C10J 2300/1215 20130101; C10J 3/06 20130101;
C10J 2300/0946 20130101; C10J 2300/1284 20130101; F23G 5/46
20130101; C10J 2200/09 20130101 |
Class at
Publication: |
110/341 ;
110/229 |
International
Class: |
F23B 005/00; F23G
007/06 |
Claims
What is claimed:
1. A gasification system comprising: a. a gasification reactor
chamber, the gasification reactor chamber configured to receive and
gasify a plurality of feed stock material to produce a heavy vapor
fuel gas; b. an aspirator assembly operably connected to the
gasification reactor chamber, the aspirator assembly having a gas
siphon assembly and an impeller; c. a flare assembly operably
connected to the aspirator assembly, the flare assembly configured
to receive the mixed gas from the aspirator assembly and to combust
the mixed air; and d. at least one heat recovery device operably
connected to the flare assembly, the at least one heat recovery
device configured to utilize thermal energy produced by the
combustion of the mixed air.
2. The invention of claim 1 wherein the at least one heat recovery
device includes a primary heat recovery device and a secondary heat
recovery device, the primary heat recovery device being operably
attached to the flare assembly, the secondary heat recovery device
being configured to receive exhaust from the primary heat recovery
device.
3. The invention of claim 1 including an absorber, the absorber
being operably connected to at least one of the at least one heat
recovery device, the absorber configured to produce a filtered
gas.
4. The invention of claim 3, including an extractor positioned to
receive the filtered gas, the extractor configured to produce
remove carbon dioxide from the filtered gas and produce a recycled
process gas.
5. The invention of claim 4, including a return air line, the
return air line operably configured to allow for the passage of the
recycled process gas from the extractor to the gasification reactor
chamber.
6. A gasification reactor chamber comprising: a. an interior
chamber, the interior chamber having a top, a bottom, and a
plurality of sidewalls, the interior chamber configured to receive
and gasify a plurality of feed stock material; b. an outer shell,
the outer shell configured to encompass at least a portion of the
plurality of sidewalls and at least a potion of the top of the
interior chamber; c. at least one layer of insulative material, the
at least one layer of insulative material operably positioned
between the plurality of sidewalls and the outer shell; d. at least
one burner, the at least one burner operably connected to the
interior chamber; e. a plurality of process gas inlets operably
connected to the interior chamber, at least two of the plurality of
process gas inlets configured to share a manifold, the manifold
configured to allow the flow of ambient air through the plurality
of process gas inlets; f. at least one vent, the at least one vent
operably connected to the outer shell, the at least one vent
configured to allow the passage of ambient air between the outer
shell and the interior chamber; g. at least one access loading door
operably connected to the gasification chamber; and h. at least one
disposal opening operably connected to the gasification
chamber.
7. The invention of claim 6, wherein the interior chamber has at
least five sidewalls.
8. The invention of claim 6, wherein the plurality of sidewalls
form a cylinder.
9. The invention of claim 6, including at least one perforated
conduit, at least a portion of the perforated conduit being located
inside the interior chamber, the perforated conduit being
configured to transport a gasification process gas to a plurality
of feed stock material.
10. The invention of claim 6, wherein the interior chamber is
operably connected to a return air line, the return air line being
configured to provide a plurality of recycled process gas into the
interior chamber.
11. The invention of claim 6, wherein the interior chamber includes
at least one inclined surface, the at least one inclined surface
having a first portion and a second portion, the first portion
being operably connected to the bottom of the interior chamber, at
least one inclined surface having an inclination from the first
portion towards the second portion, the second portion being
operably connected to at least one of the at least one disposal
opening.
12. A gasification system comprising: a. at least one gasification
reactor chamber, the at least one gasification reactor chamber
configured to receive and gasify a plurality of feed stock material
to produce a heavy vapor fuel gas; b. an extractor assembly, the
extractor assembly configured to extract the heavy vapor fuel gas
from the gasification reactor chamber and to mix the heavy vapor
fuel gas with oxygen to produce a mixed gas; c. a flare assembly
operably connected to the extractor assembly, the flare assembly
comprised of a targeting nozzle, a housing, at least one burner,
and an inlet, the targeting nozzle having a conical funnel
configuration shaped to direct the flow of the mixed gas through
the inlet to a combustion focus point, the at least one burner
positioned to combust the flow of the mixed gas at the combustion
focus point; and d. at least one heat recovery device operably
connected to the flare assembly, the at least one heat recovery
device configured to utilize the combustion of the mixed air.
13. The invention of claim 12, wherein the flare assembly is built
into at least one of the at least one heat recovery device.
14. The invention of claim 12, wherein the combustion of the heavy
vapor fuel gas is used to operate the at least one heat recovery
device.
15. The invention of claim 12, wherein the flare assembly produces
a combusted hot heavy vapor fuel gas, the combusted hot heavy vapor
fuel gas being delivered from the flare assembly to the at least
one heat recovery device, the at least one heat recovery device
configured to utilize the thermal energy entrained in the combusted
hot heavy vapor fuel gas.
16. A gasification reactor chamber for the gasification of a
plurality of feed stock material comprising: a. an interior
chamber, the interior chamber having a top, a bottom, and a
plurality of sidewalls, the interior chamber configured to receive
and gasify a plurality of feed stock material; b. an outer shell,
the outer shell configured to encompass at least a portion the
plurality of sidewalls and at least a portion of the top of the
interior chamber; c. at least one layer of insulative material, the
at least one layer of insulative material operably positioned
between the plurality of sidewalls and the outer shell; d. a
plurality of process gas inlets operably connected to the interior
chamber, at least two of the plurality of process gas inlets
configured to share a manifold, the manifold configured to allow
the flow of a gasification process gas through the plurality of
process gas inlets; e. a perforated grate operably positioned
inside the interior chamber; f. at least one perforated conduit
operably positioned within the interior chamber, the at least one
perforated column configured to expose the gasification process gas
to the surface of the plurality of feed sock material; g. at least
one access loading door operably connected to the gasification
chamber; h. at least one disposal opening operably connected to the
gasification chamber; and i. at least one burner operably connected
to the interior chamber.
17. The invention of claim 16, wherein the at least one perforated
conduit is at least one perforated column.
18. The invention of claim 16, wherein the at least one perforated
conduit is an inner lining.
19. The invention of claim 16, wherein the interior chamber
includes at least one inclined surface, the at least one inclined
surface having a first portion and a second portion, the first
portion being operably connected to the bottom of the interior
chamber, at least one inclined surface having an inclination from
the first portion towards the second portion, the second portion
being operably connected to at least one of the at least one
disposal opening.
20. The invention of claim 16, wherein the plurality of sidewalls
is comprised of at least five sidewalls.
21. The invention of claim 16, wherein the plurality of sidewalls
form a cylinder.
22. A closed-loop municipal solid waste gasification system for the
gasification of a plurality of feed stock material comprising: a. a
gasification reactor chamber; b. an aspirator assembly operably
connected to the gasification chamber, the aspirator assembly
including a conduit coupling, an impeller, and a motor; c. a flare
assembly operably connected to the aspirator assembly, the flare
assembly including at least one burner; d. at least one heat
recovery device operably connected to the flare assembly; e. an
absorber operably connected to the at least one heat recovery
device, the absorber configured to produce a filtered exhaust; f.
an extractor operably connected to the absorber, the extractor
configured to receive and remove a plurality of a carbon dioxide
molecules from the filtered exhaust and to produce a recycled
process gas; and g. a return line operably connected to the
extractor and the gasification chamber, the return line configured
to allow the passage of the recycled process gas from the extractor
to the gasification chamber.
23. The system of claim 22, wherein the at least one heat recovery
device includes a reverse chiller refrigeration system.
24. The system of claim 22, including a geothermal field, the
geothermal field comprised of at least one inlet tube, an induced
draft fan, at least one ventilation tube, and a geothermal loop,
the at least one inlet being operably connected to the at least one
heat recovery device.
25. The system of claim 22, wherein the gasification reactor
chamber is comprised of an interior chamber and an outer shell.
26. The system of claim 25, wherein the interior chamber includes
at least one perforated conduit, the perforated conduit configured
to transport a gasification process gas to the plurality of feed
stock material.
27. The system of claim 25, wherein the interior chamber has at an
inner liner, the inner liner configured to permit the transport of
a gasification process gas to the plurality of feed stock
material.
28. The system of claim 22, wherein the extractor is operably
connected to a greenhouse.
29. The system of claim 22, wherein the flare assembly includes a
targeting nozzle, the targeting nozzle having a conical funnel
configuration, the conical funnel configuration being configured to
restrict the flow of a mixed gas into a combustion focus point.
30. The system of claim 25, wherein the interior chamber has at
least five sidewalls.
31. The system of claim 25, wherein the interior chamber has an
outer surface, the outer surface being operably attached to a
plurality of cooling fins, the plurality of cooling fins being
configured to remove heat from the interior chamber.
32. The system of claim 22, including at least one process gas
inlet, the at least one process gas inlet configured to control the
flow of a gasification process gas into the gasification reactor
chamber.
33. The system of claim 32, whereby a process logic controller is
operably connected to the at least one process gas inlet, the
process logic controller configured to control the flow of the
gasification process gas through the at least one process gas inlet
and into the gasification reactor chamber.
34. The system of claim 22, wherein the extractor is a
greenhouse.
35. The system of claim 22, wherein the extractor is a carbon
dioxide dispersal system.
36. The system of claim 22, wherein the plurality of sidewalls form
a cylinder.
37. The system of claim 22, wherein the absorber is a chilled
radiator.
38. A closed-loop municipal solid waste gasification system
comprising: a. a gasification reactor chamber configured to receive
and gasify a plurality of feed stock material, the gasification
chamber having an interior chamber and an outer chamber, the
interior chamber having an outer surface, the outer surface
including a plurality of cooling fins, the outer chamber having a
plurality of vents; b. at least one layer of insulative material, a
portion of the at least one layer of insulative material being
positioned between the interior chamber and the outer chamber; c.
an aspirator assembly operably connected to the gasification
chamber, the aspirator assembly including a conduit coupling, an
impeller, a motor, and a gas siphon assembly; d. a flare assembly
operably connected to the aspirator assembly, the flare assembly
including at least one burner and a targeting nozzle; e. at least
one heat recovery device operably connected to the flare assembly;
f. an absorber operably connected to the at least one heat recovery
device, the absorber configured to produce a filtered exhaust; and
g. an extractor operably connected to the absorber, the extractor
configured to receive and remove at least a portion of carbon
dioxide molecules from the filtered exhaust and to produce a
recycled process gas.
39. The system of claim 34, including a return line operably
configured to return at least a portion of the recycled process gas
from the extractor to the gasification chamber.
40. The system of claim 38, wherein the at least one heat recovery
device includes a reverse chiller refrigeration system.
41. The system of claim 38, including a geothermal field, the
geothermal field comprised of at least one inlet tube, an induced
draft fan, at least one ventilation tube, and a geothermal loop,
the at least one inlet operably connected to the at least one heat
recovery device.
42. The system of claim 38, wherein the interior chamber includes
at least one perforated conduit, the perforated conduit configured
to transport gasification process gas to the plurality of feed
stock material.
43. The system of claim 38, wherein the interior chamber has at an
inner liner, the inner liner configured to permit the transport of
recycled process gas to the plurality of feed stock material.
44. The system of claim 38, wherein the extractor is operably
connected to a greenhouse.
45. The system of claim 38, wherein the interior chamber has at
least five sidewalls.
46. The system of claim 38, including at least one process gas
inlet, the at least one process gas inlet configured to allow the
flow of a gasification process gas into the interior chamber.
47. The system of claim 46, whereby a process logic controller is
operably connected to the at least one process gas inlet, the
process logic controller configured to control the flow of the
gasification process gas through the at least one process gas inlet
and into the gasification reactor chamber.
48. The system of claim 38, wherein the extractor is a
greenhouse.
49. The system of claim 38, wherein the extractor is a carbon
dioxide dispersal system.
50. The system of claim 38, wherein the interior chamber has a
cylindrical configuration.
51. The system of claim 38, wherein the absorber is a chilled
radiator.
52. A method for the gasification of solid municipal waste
comprising; a. loading a feed stock material into a gasification
reactor chamber; b. gasifying at least a portion of the feed stock
material into a heavy vapor fuel gas; c. extracting the heavy vapor
fuel gas from the gasification reactor chamber; d. mixing the heavy
vapor fuel gas with ambient air to produce a mixed gas; e.
combusting the mixed gas to create a combusted gas; f. recovering
the thermal energy entrained in the combusted gas to create an
ambient temperature exhaust; g. filtering the ambient temperature
exhaust; and h. extracting a carbon dioxide gas from the ambient
temperature exhaust to create a recycled process gas.
53. The method claim of 52, including the step of returning the
recycled process gas to the gasification chamber.
54. The method claim of 52, including venting the extracted carbon
dioxide gas into a greenhouse to produce an oxygen rich gas.
55. The method claim of 54, including venting the oxygen rich gas
into the gasification reactor chamber.
56. The method claim of 52, wherein the recovering step includes
submerging the combusted gas in a geothermal field.
Description
RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 60/381,958, filed May 17, 2002, which is
incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
[0002] Many attempts have been made at creating waste disposal
systems that eliminate or reduce the need to landfill municipal
solid waste ("MSW"). Traditional approaches have included
incineration and pyrolisis. Conventional incineration however is
objectionable because the high burn temperatures in the presence of
oxygen results in the formation of complex pollutants that are
difficult and expensive to control. Furthermore, the vast majority
of incinerated organic material is converted into undesirable
carbon dioxide, which is implicated in global warming, ozone layer
depletion, and the formation of volatile organic compounds. The
incineration process also releases nitrogen oxides that contribute
to smog problems in urban areas. The pyrolisis procedure involves
the conversion of various materials into a glass like residue in an
oxygen depleted, high temperature environment. However, the high
temperature, depleted oxygen environment of pyrolisis creates some
extremely toxic compounds. Furthermore, pyrolisis is an inefficient
method for disposing large volumes of waste materials, and the
residual ash material contains large amounts of carbon.
[0003] Many of the disadvantages of incineration and pyrolisis are
overcome by waste gasification. Waste gasification involves
supplying the minimum amount of oxygen necessary to cause a
thermochemical reaction that releases simple combustible gases at a
controlled temperature, without supplying enough oxygen to cause
combustion. When feed stock materials, such as MSW, that are rich
in energy as measured by British thermal units, are loaded into
gasification reactor chambers, and are exposed to a controlled
temperature, oxygen depleted environment, such solid, sludge, or
liquid feed stock materials are converted into a heavy vapor gas
fuel. Materials that are rich in energy include, but are not
limited to, coal, wood, cardboard, paper, industrial scrap,
plastics, tires, organic wastes, sewage cake, animal waste, and
crop residue, or a combination thereof. The released heavy vapor
fuel gas is then mixed with oxygen and burned. Examples of prior
gasification systems are shown in U.S. Pat. No. 4,941,415, which is
incorporated herein by reference, and U.S. Pat. No. 5,941,184.
[0004] The material remaining after the completion of the
gasification process cycle is composed of incombustible materials,
including metals, glass, and ceramics, along with a fine inert salt
and mineral power residue, and has a greatly reduced volume that is
suitable for remanufacturing into concrete material or land
filling. Furthermore, recyclable materials that do not undergo
phase transition, such as all recycle glass, aluminum, metals,
residual materials and salts, are recoverable after the
gasification process, thereby eliminating the need for pre-sorting
or processing the in-bound feed stock material.
[0005] Conventional prior art gasification systems are multi-step
processes that generally utilize four open-looped process steps.
These four steps typically involve: one or more primary gasifiers;
a central air mixing chamber; a secondary processor for combusting
the produced heavy vapor gas fuel; and final air cleaning systems.
However, conventional gasification systems have proved difficult to
cost-effectively construct. Therefore, a need exists for a
simplified gasification apparatus that is inexpensive to build,
simple to operate, and yet achieves the benefits of producing a gas
fuel from solid waste feed stock materials.
[0006] Furthermore, prior art open-looped systems, such as U.S.
Pat. No. 6,439,135, which is incorporated herein by reference,
utilize exhaust stacks that release hot gases from the final
combustion step into the atmosphere, or use storage tanks to
collect the hot gases for future ancillary purposes, rather than
reclaiming at least a portion of the cleaned air for
re-introduction into the gasification process. Furthermore, such
prior art systems do not teach a gasification system that produces
a relatively pure carbon dioxide for other industrial purposes or
to support the augmentation of vegetation, such as a greenhouse, a
carbon dioxide dispersal system, or an aquaculture bed.
[0007] Current research indicates that increasing the surface area
of feed stock material that is exposed to gasification process gas
significantly improves the production rate of fuel gas from the
feed stock materials. Yet, prior art gasification systems, such as
those illustrated in U.S. Pat. No. 6,439,135 and 5,619,938, utilize
reactor chamber configurations that expose only limited feed stock
surface area to gasification process gas. Such prior art systems
incorporate reactor chamber configurations where only the bottom of
the feed stock at grate level, known as the primary reaction zone,
and the uppermost surface of the feed stock, known as the secondary
reaction zone, are exposed to optimum gasification conditions.
[0008] As a result, gasification of the tons of feed stock material
that is not located at either the primary or secondary zones, such
as that on the sides and center of the reactor chamber, requires
that the temperature and duration of the gasification cycle be
increased. Yet, higher gasification temperatures tend to reduce the
Btu content of the resulting heavy vapor fuel gas. The high
operating temperatures also increase the time required for cooling
the gasification chamber to a temperature suitable for the loading
and disposal of subsequent loads of feed stock materials.
[0009] Furthermore, the costs associated with obtaining and
maintaining the higher gasification temperatures, along with the
cost of fabricating a complex gasification reactor chamber that can
withstand prolonged exposure to high temperatures, also increase.
Current gasification chambers are lined with various clay-based
insulative/refractory materials. These refractory materials
maintain gasification reactor temperatures while also preventing
structural damage to the reactor chamber's steel superstructure and
surface paint from prolonged exposure to excessive heat. Refractory
material is usually applied to the gasification reactor chamber as
pre-cast panels, bricks, or sprayed on as a gunnite-like
application. Such refractory material is affixed to the exterior
steel jacket of the gasification reactor chamber by refractory
hangers, which are heavy metal dowels in the form of hooks. With
typical prior art systems, a 2 to 4 inch layer of ceramic fiber
blanket is usually inserted between the refractory material and the
steel jacket before the refractory layer is installed to offer
additional thermal protection for the exterior steel surfaces of
the gasification reactor chamber.
[0010] Application of refractory material is thus labor intensive,
time consuming, and a significantly expensive step. Additionally,
the weight of the refractory liner necessitates that the steel
vessel be constructed from at least {fraction (1/4)} inch thick hot
rolled A36 steel plate and heavy structurals. This additional
superstructure weight further increases the overall cost of
manufacturing, shipping, and installation.
[0011] An additional problem with the use of refractory material is
the length of time required for cooling the gasification reactor
chamber before it can be re-used to gasify a subsequent load of
MSW. More specifically, a subsequent gasification process typically
cannot begin until the gasification reactor chamber has cooled to
approximately 150 degrees Fahrenheit. Yet, at the end of a process
cycle, the clay refractory material tends to retain heat for a long
period of time. Depending on the particular chemistry of the
refractory material, this retention of heat may require that the
gasification chamber be inoperative for several hours as the
temperature of the chamber, and associated refractory material,
cools down.
[0012] The limited feed stock capacity of prior art gasification
systems often required the construction of multiple gasification
reactor chambers to meet demand requirements. In previous designs,
gasification reactor chambers typically have a rectangular
configuration. As the length of the rectangular sidewalls is
increased to satisfy larger feed stock capacity requirements, the
size of the reactor chamber creates problems associated with
providing sufficient clearance space away from the prolonged high
temperatures of the reactor chamber. This problem typically limits
reactor chambers to configurations that are approximately 20 feet
high, 20 feet wide, 20 feet long. Such a configuration however has
a limited load capacity of approximately 50 tons of feed stock
material. Furthermore, as the size of the rectangular configuration
is increased, problems develop with the side load waste dump
arrangement. More specifically, as the rectangular sidewalls extend
beyond 20 feet, the angle of repose of the trash spilling out of
the garbage truck typically only fills a small portion of the
reactor chamber's near sidewall.
[0013] Because the heavy vapor fuel gas has been produced in an
environment that typically contains no more than 8% oxygen, waste
gasification systems must also increase the level of ambient oxygen
in the gas produced in the gasification reactor chamber to make it
fully flammable. This often requires increasing the oxygen content
of the heavy vapor fuel gas to approximately 15% to 20%.
[0014] Prior art gasification systems increased the oxygen content
of the heavy vapor fuel gas by directing the heavy vapor fuel gas
through air mixing chambers. These mixing chambers are typically
large, cylindrical vessels, with a variety of air induction tubes
attached to multiple blower fans that flood the air mixing chambers
with outside air using air compressors or high velocity fans. Yet
because of the large size of these chambers, they require
substantial fabrication and installation time, and as a result are
expensive. The use of fans and/or air compressors also increases
the initial cost of the system and operating and maintenance
expenses.
[0015] Conventional gasification systems also use cumbersome
techniques for moving fuel gas to the point of combustion. Such
systems often vent, or breech, the fuel gas from the top or at
least one side of the reactor chamber, and direct the vented fuel
gas from the reactor chamber into a secondary gas processor, which
is usually driven by a natural draft current that is created by hot
air in the system rising through an exhaust stack. The fuel gas'
exit from the reactor chamber is controlled by a motor driven
damper assembly that regulates the varying flow of produced fuel
gas from this first process step into ducting that connects the
gasification reactor chamber to the secondary air mixing chamber.
Such systems typically require large diameter piping to draw the
gas off from the gasification chamber. This large piping, and
associated ductwork, increases not only equipment cost, but also
installation expenses.
[0016] A further disadvantage of traditional air draft systems is
that heavy vapor fuel gases have a tendency to linger in the
gasification reactor chamber, and become subject to accidental
combustion, which ultimately lowers the Btu content of the
extracted heavy vapor fuel gas. This problem is exacerbated by the
inconsistency of up-draft air movement in a natural draft system.
Humidity, wind, barometric pressure and outside temperature all
affect the rate of flow through a natural draft system. This
inconsistent flow causes the evacuation of gases from the reactor
chambers to frequently stall, produces negative results in the
process, and adversely effects the total cycle time for the
gasification of the feed stock material.
[0017] Furthermore, the combustion of the heavy vapor fuel gas in a
hot water heater, steam boiler, refrigeration unit, or other
industrial process, produces a relatively high temperature exhaust.
Yet, prior art systems often vent this hot combusted exhaust into
the atmosphere at a temperature between 1200 and 1600 degrees
Fahrenheit, thereby wasting a significant thermal resource that
could be further captured and directly utilized in other heat
dependent applications, thereby preserving natural resources and
providing a cost efficient source for heated gas.
[0018] Hot combusted exhaust that is vented into the atmosphere in
prior art systems via an exhaust stack also often contain large
quantities of carbon dioxide. While carbon dioxide is not currently
regulated as a pollutant from solid waste incinerators, it is
subject to various industrial air quality abatement
initiatives.
[0019] Furthermore, by recapturing the thermal energy that is
entrained in the exhaust for additional attached applications, and
thereby continuing to reduce the ultimate exhaust temperature of
the exhaust gas, the volume of the exhaust decreases. As the volume
of the exhaust gas is reduced, the conveying piping and other gas
handling equipment, along with associated equipment costs, also
decrease.
[0020] It is therefore an object of the present invention to
provide a gasification system capable of gasifying feed stock at a
reduced temperature and time.
[0021] It is another object of the present invention to decrease
the time between subsequent uses of the gasification reactor
chamber.
[0022] It is another object of the present invention to reclaim at
least a portion of the exhaust air for re-consumption in the
gasification process.
[0023] It is a further object of the present invention to provide a
gasification system that produces a high Btu content vapor gas.
[0024] It is another object of the present invention is to provide
an inexpensive to build, simple to operate, gasification system
that provides the benefits of producing a fuel gas from feed stock
material.
[0025] It is another object of the present invention to provide for
improved gas collection that allows for both simpler gasification
reactor chamber configurations and an improved gas flow design that
allows for better final combustion.
[0026] It is another object of the present invention to provide a
gasification system that eliminates the need to rely on multiple
gasification reactor chambers to provide an increased system volume
capacity.
[0027] It is a further objective of the present invention to
capture and sequester carbon dioxide produced by the gasification
system, and to use the sequestered carbon dioxide in a beneficial
manner.
[0028] It is another objective of the present invention to improve
the quality of the final exhaust air from the present invention
sufficiently to re-introduce the recycled process gas into the
gasification system, thereby creating a closed-loop system.
[0029] These and other desirable characteristics of the present
invention will become apparent in view of the present
specification, including the claims and drawings.
BRIEF SUMMARY OF THE INVENTION
[0030] The present invention is directed to a system for the
gasification of a variety of waste streams, including, but not
limited to, agricultural, industrial, and municipal waste streams.
More particularly, the invention relates to a gasification system
that incorporates a self sustaining gasification chamber that has
its own dedicated flare assembly, and which is capable of gasifying
large volumes of feed source material without the need for multiple
gasification chambers. This self-sustaining gasification chamber
and flare assembly are also capable of being used with other
self-sustaining chambers to feed at least one common heat recovery
device. Furthermore, the present invention is a closed-loop system,
which eliminates the need for an exhaust stack, and which recovers
heat entrained in hot exhaust, thereby producing a cooled exhaust
that is subsequently filtered and separated from carbon dioxide,
and which is suitable for re-introduction in the gasification
procedure. Removed carbon dioxide may then be used for other
industrial operations, or may be used to support the augmentation
of vegetation, such as a greenhouse or a carbon dioxide dispersal
system, whereby vegetation converts the carbon dioxide into oxygen
that may also be recaptured for re-introduction in the system of
the present invention.
[0031] In one embodiment of the present invention, the gasification
system is comprised of a gasification reactor chamber, an
aspirator, a flare assembly, at least one heat recovery device, an
absorber, and an extractor.
[0032] MSW is loaded into the gasification reactor chamber for
gasification, whereby the MSW serves as feed stock material. The
reactor chamber is comprised of an interior chamber and an outer
shell. Although the gasification reactor chamber of the present
invention may have a number of shapes, including being rectangular,
square, or cylindrical, the reactor chamber of the preferred
embodiment of the present invention has at least five sidewalls and
includes perforated conduits or an inner liner. The perforate
conduits or inner liner increase the surface area of the feed stock
material that is exposed to optimum gasification conditions,
thereby decreasing both the gasification cycle time and
temperature, while also decreasing the time between additional
gasification procedures on subsequently loaded feed stock material.
The reduction in the gasification temperature also allows for the
fabrication of the gasification chamber from lighter gage material,
and eliminates the need for refractory material, thereby reducing
the weight of the gasification system and the time and expense
associated with its fabrication. Furthermore, gasification
conditions may be controlled by a process logic controller, which
is used to control the gas content and temperature in the interior
chamber.
[0033] An aspirator assembly, through the use of a motor, is used
to create a negative pressure in the interior chamber, thereby
allowing for the smooth and even evacuation of heavy fuel vapor
gas. As the motor blows ambient air into a conduit coupling, a
suction force is created in the conduit coupling and attached
single gas manifold and gas siphon assembly. This suction force
pulls the heavy vapor fuel gas from the interior chamber and into
the conduit coupling. The efficient extraction of heavy vapor fuel
gas afforded by the aspirator assembly also prevents the occurrence
of accidental combustion that may lower the Btu content of the
desired fuel gas.
[0034] The ambient air used by the aspirator to create the suction
force is mixed with the heavy vapor fuel gas in the conduit
coupling, thereby eliminating the need for a separate mixing
chamber. Furthermore, control of the motor and the selected size of
the tubing and conduit allow for finite control of the volume of
gas that moves through, and is mixed by, the aspirator assembly.
The aspirator assembly of the present invention also eliminates the
need for a damper.
[0035] Mixed gas exiting the aspirator then enters a flare
assembly. In the preferred embodiment of the invention, the flare
assembly includes a targeting nozzle that has a conical funnel
configuration. The configuration of the targeting nozzle allows for
additional mixing of the gases, increases the velocity of the mixed
gas so as to provide back pressure in the system, and creates a
focus point for combustion. Back pressure created by the conical
funnel configuration not only aids in the smooth operation of the
at least one common heat recovery device, but allows the system to
incorporate heat recovery devices that have minimum positive input
pressure requirements.
[0036] In the preferred embodiment of the present invention, the
flare assembly is built in, or is a sub-component of, at least one
primary heat recovery device. The combustion of the mixed gas by
the flare assembly is then used to operate or heat the at least one
heat recovery device. Alternatively, hot combusted gas is delivered
from the flare assembly to the at least one common heat recovery
device. In instances in which more than one common heat recovery
device is used, each subsequent heat recovery device further
captures the thermal energy that is entrained in the exhaust until
the temperature of the exhaust has been reduced to a permissible
level for filtering in an absorber. Heat recovery devices include,
but are not limited to, boilers, generators, and reverse chiller
refrigeration loops.
[0037] In an alternative embodiment, the hot exhaust exiting the at
least one heat recovery device may also pass through a geothermal
field, in which the exhaust is directed to a subsurface manifold
that may be located underground or beneath a body of water. Heat
from the exhaust is then used to heat the surrounding ground or
water, and may provide a no-operating cost method for heating such
things as on-site greenhouses and aquaculture beds.
[0038] In another embodiment of the present invention, exhaust from
the last heat recovery device is diverted into a chilling loop. In
the preferred embodiment, the exhaust entering the chilling loop
has a temperature of approximately 30 degrees Fahrenheit. The cold
chill tubes cause the temperature of the through-flowing exhaust
air to cool and the moisture to condense. The condensation removes
virtually all particulate matter, particularly water-soluble
particulate matter, including HCL and SO2, from the exhaust air
stream. The water is then removed in a knock-out trap
[0039] Once the exhaust temperature has been reduced to meet the
intake requirements of an absorber, such as a monolithic lime
absorber, the exhaust gas is filtered for low temperature criteria
pollutants, such as, but not limited to, HCl. The filtered exhaust
then proceeds to an extractor where carbon dioxide is separated
from the remaining filtered exhaust, which is comprised mainly of
oxygen and water vapor. The oxygen and water vapor may then be
re-directed back to the gasification chamber as recycled process
gas for re-use in the gasification system, thus providing a
closed-loop process.
[0040] Carbon dioxide may be captured for other industrial
purposes, or may be vented for the purpose of facilitating the
growth of on-site vegetation, such as a greenhouse. Careful
planning in the selection of plants may create an on-site
vegetative environment that is capable of converting all of the
produced carbon dioxide into oxygen. The converted oxygen may then
be captured for re-introduction in the gasification system of the
present invention.
BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS
[0041] For a more complete understanding of this invention
reference should now be had to the embodiment illustrated in
greater detail in the accompanying drawings and described below by
way of example of the invention.
[0042] FIG. 1 shows a process diagram for a multi-cell gasification
system in accordance with the present invention.
[0043] FIG. 2 shows a variant of the process flow of an embodiment
of the invention.
[0044] FIGS. 3A, 3B, and 3C show exterior views of a gasification
reactor chamber for use with the present invention.
[0045] FIG. 3D shows a perspective view of one embodiment of the
interior chamber of the gasification reactor chamber for use with
the present invention.
[0046] FIG. 3E shows an exterior perspective view of one embodiment
of the interior chamber and an inclined waste disposal
configuration of the gasification reactor chamber for use with the
present invention.
[0047] FIG. 4 shows a flare assembly for use in combusting mixed
gas with the present invention.
[0048] FIG. 5A shows a cross sectional top view of the gasification
reactor chamber made in accordance with one embodiment of the
present invention.
[0049] FIG. 5B shows a perspective cross sectional view of the
gasification reactor chamber made in accordance with one embodiment
of the present invention.
[0050] FIG. 5C shows a perspective cross sectional view of the
gasification reactor chamber including an inner liner in accordance
with one embodiment of the present invention.
[0051] FIG. 5D shows a cross sectional side view outer shell and
interior chamber for the gasification reactor chamber of the
present invention.
[0052] FIG. 6 shows an aspirator assembly for use with the present
invention.
[0053] FIG. 7 shows a cross-sectional view of a conduit coupling
for use with the aspirator assembly shown in FIG. 6.
[0054] FIG. 8 shows the inclusion of a geothermal field in one
embodiment of the present invention.
[0055] FIG. 9 shows a general operational layout of the present
invention.
[0056] FIG. 10 shows an overview of transporting feed stock
material to multiple waste gasification reactor chambers in
accordance with the present invention.
[0057] FIG. 11 shows the use of a greenhouse for absorbing carbon
dioxide in accordance with one embodiment of the present
invention.
[0058] FIG. 12 shows the use of a carbon dioxide dispersal system
in accordance with one embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
Overview
[0059] The complete system of the present invention can be
understood by referring to FIG. 1, which shows a closed-loop waste
gasification system 100. Waste hauling trucks unload feed stock
material either directly into batch waste gasification reactor
chambers 101, 102, 103, as shown in FIG. 9, or unload the feed
stock at a tipping floor area 50, as shown by FIG. 10, whereby a
variety of conveyors 60 transport the feed stock to the
gasification reactor chambers 101, 102, 103. Once in the
gasification reactor chambers 101, 102, 103, the feed stock
material undergoes gasification. Uncombusted heavy vapor fuel gas
driven off in the reactor chambers 101, 102, 103 is evacuated by
aspirator assemblies 229a, 229b, 229c through collection ducts 107,
108, 109 to the dedicated flare assemblies 210a, 210b, 210c.
[0060] Radiant and convection heat generated in the flare
assemblies 210a, 210b, 210c converge, and are absorbed by at least
one heat recovery device, such as a primary heat recovery device
211, which may include, but is not limited to, a steam boiler, heat
exchanger, or any other heat sink. Each flare assembly 229a, 229b,
229c may be operably connected to both a single self-sustaining
gasification reactor chamber 101, 102, 103 and to the primary heat
exchanger 211, as illustrated in FIG. 1, whereby the flare
assemblies 229a, 229b, 229c produce a hot combusted exhaust that is
fed into a primary heat recovery device 211. Alternatively, the
dedicated flare assemblies 210a, 210b, 210c may be a sub-component
of, or built into, a common or a separate primary heat recovery
device 211, whereby, rather than receiving thermal energy in the
form of hot combusted gas, the combustion of heavy vapor fuel gas
is directly used to power or operate the primary heat recovery
device 211.
[0061] As shown in FIG. 9, in the preferred embodiment of the
present invention, the gasification reactor chambers 101, 102, 103
and their dedicated flare assemblies (not shown), the flare
assemblies being similar to the flare assemblies 210a, 210b, 210c
illustrated in FIG. 1, are operably connected to different primary
heat recovery devices. As illustrated, one gasification reactor
chamber 101 provides heavy vapor fuel gas for operating a boiler
111 and hot water heater 110, while other gasification reactor
chambers 102, 103 independently supply heavy vapor fuel gas to
support the operations of a greenhouse 117. Each associated flare
assembly then independently satisfies its combustion requirements
for the attached heat recovery device. Alternatively, as shown in
FIG. 1, the multiple flare assemblies 210a, 210b, 210c may also be
operably connected to a common primary heat recovery device 211,
whereby each individual flare assembly 210a, 210b, 210c
independently combusts heavy vapor fuel gas from its dedicated
reactor chamber 101, 102, 103 in accordance with the designed
combustion requirements of the common primary heat recovery device
211. Furthermore, although FIG. 1 illustrates flare assemblies
210a, 210b, 210c as separate components that are not part of the
primary heat recovery device 211, each flare assembly 210a, 210b,
210c may also be built into, or a subcomponent of, the system's 100
primary heat recovery device 211.
[0062] Additional heat recovery devices, such as a secondary heat
recovery device 212 may also use exhaust from the primary heat
recovery device 211. In one embodiment of the invention, the
secondary heat recovery device 212 is a reverse chiller
refrigeration system, the reverse chiller system being comprised of
an inlet, a radiator, an induced draft fan, a sump, and an outlet.
Hot exhaust is pumped into the radiator from the primary heat
recovery device 211, the momentum for the hot exhaust being
provided by the in-line induced draft fan that is preferably
located on the back out-take side of the radiator loop. In the
preferred embodiment of the present invention, exhaust from the
primary heat recovery device 211 enters the reverse chiller at
approximately 350 degrees Fahrenheit. Water within the radiator
then begins to condense, and continues condensing as the exhaust
gas is reduced in temperature to preferably 70 degrees Fahrenheit.
The rapid cooling of the exhaust from the primary heat recovery
device 211 causes particulates, such as HCl and SO.sub.2, to
condense out of the gas. Accumulated pollutants and condensate are
then collected in a sump at the low point of the radiator and
removed from the system. Cooled exhaust gas will then be piped back
to the gasification reactor via an additional induced draft fan,
and directed to a plurality of cooling fins within the reactor
chambers 101, 102, 103. The cooled exhaust is then used as a
cooling media, which thereby eliminates the need for an exhaust
stack, as required by incineration and pyrolysis operations.
Alternatively, once conditions, such as temperature and oxygen
content, within the reactor chambers 101, 102, 103 reach
predetermined levels, cooled exhaust may be re-introduced into the
gasification chamber through a plurality of process gas inlets and
aid the gasification procedure.
[0063] In the illustrated embodiment, once the at least one heat
recovery device has significantly cooled the exhaust gas, it
becomes possible to avoid any regulated air emissions by diverting
the exhaust to an underground geothermal field 113. Heat from the
exhaust passing through the geothermal field 113 may then heat
surrounding surfaces, such as soil or a body of water, thereby
providing heat to support a number of activities, such as, but not
limited to, a greenhouse 117 or an aquaculture bed.
[0064] The geothermal field 113 is forcibly vented by an induced
draft fan 317 to an absorber 115, such as a monolithic lime or
sodium carbonate absorber, for the removal of at least a portion of
criteria pollutants. For example, if the feed stock material
contained plastics, or other substances which might cause the
formation of either HCl or SO.sub.2, the exhaust leaving the at
least one heat recovery device will be diverted to a passive sodium
carbonate absorber to reduce any potential for excessive levels of
these chemicals in the end recycled process gas product.
[0065] As a final step, at a juncture 148, the filtered gas is
pulled from the system and into an extractor 116 a carbon dioxide
extractor 116 retrieves gaseous carbon dioxide for a carbon dioxide
consumer. Oxygen produced by the consumption of extracted carbon
dioxide, such as the conversion of carbon dioxide into oxygen by
vegetation, may be vented back into the system 100 via a return air
line 118 to provide recycled process gas or a cooling medium for
the gasification reactor chambers 101, 102, 103.
[0066] In another iteration of the design, a greenhouse 117, or
some other agricultural carbon dioxide dispersal system replaces
the carbon dioxide extractor 116. Carbon dioxide is then
sequestered before the balance of the filtered exhaust stream is
returned to the reactor chambers 101, 102, 103 via the return air
line 118 as recycled process gas.
Combustion Loop Detail
[0067] FIG. 2 illustrates additional detail of the gasification
system 100 combustion process loop. Feed stock material is fed into
the gasification chamber 101 through the primary access loading
door 120, as shown in FIG. 3B. The primary access loading door 120
and any other residual removal ports are then sealed, and all
gasification process gas intake ports are closed. The aspirator
assembly 229 then starts reducing the volume of ambient air within
the reactor chamber 101. Following this air purge, which typically
for a system containing 50 tons of feed stock material may take 15
minutes, at least one heater that is near the base of the reactor
chamber 101 is activated. In the preferred embodiment of the
present invention, the heater may include, but is not limited to, a
fuel-fired burner or an electric thermal radiant heat assembly.
[0068] Once the ambient temperature inside the reactor chamber 101
reaches a predetermined temperature, the heater is turned off. For
example, in a system containing 50 tons of mixed feed stock, a
predetermined temperature of 300 degrees Fahrenheit may be reached
in approximately 35 minutes. In the preferred embodiment of the
present invention, a pair of Type K thermocouples is used to
determine whether the average ambient temperature has reached the
predetermined limit. These thermocouples may be positioned in a
variety of locations, such as, but not limited to, below the grate,
around the midsection of the reactor chamber 101, at the top of the
reactor chamber 101, or in conjunction with additional
thermocouples in any combination thereof.
[0069] As the temperature and oxygen level in the reactor chamber
101 reach predetermined levels, a plurality of process gas inlets
located below the grate level of the reactor chamber 101 are slowly
opened. By controlling the flow of process gas, including outside
ambient air and recycled process gas from the extractor, the
plurality of process gas inlets act as valves to keep the average
internal temperature of the reactor chamber 101 within a
predetermined range and prevent the incursion of ambient air, which
may increase the oxygen level of the process air and cause
combustion, from entering into the reactor chamber 101. In the
preferred embodiment of the present invention, this predetermined
temperature range is within approximately 350 and 750 degrees
Fahrenheit, while the oxygen level is 4% to 11% of ambient. These
predetermined levels facilitate the substochiometric combustion
conditions that cause heavy vapor fuel gas to form and rise to the
top of the reactor chamber 101 via convection.
[0070] In the preferred embodiment of the present invention, the
plurality of process gas inlets may be opened by a common electric
motor that is controlled through the use of a process logic
controller. Oxygen and temperature sensors sample the interior
environmental air and relay the information to the process logic
controller. The process logic controller may also be connected to
data recorders and digital display panels in the system control
cabinet. Such sensors may be located in a variety of positions,
including, but not limited to, heavy vapor fuel gas evacuation
ducts in the ceiling of the reactor and in a reinforced stainless
steel cage located on the interior wall of the reactor chamber.
[0071] As the temperature inside the reactor chamber 101 continues
to climb, the ambient oxygen content within the chamber 101 drops.
When the internal temperature and oxygen level reach a
predetermined level, such as, but not limited to, approximately
five percent of ambient oxygen and 350 degrees Fahrenheit, the
aspirator assembly 229 begins extracting heavy vapor fuel gas out
from the reactor chamber 101 through an aspirator assembly 229.
[0072] The aspirator assembly 229 uses impelled ambient air passing
through a conduit coupling to create a negative back pressure in
the reactor chamber 101 and the gas siphon assembly 225. This
negative pressure creates a suction force that draws heavy vapor
fuel gas from the reactor chamber 101 into the gas siphon assembly
225. In the preferred embodiment of the present invention, the gas
siphon assembly 225 extends into and out of the reactor chamber
101, as shown in FIG. 5A. In the preferred embodiment, a portion of
the gas siphon assembly 225 that extends into the reactor chamber
101 is perforated and mounted along the ceiling of the reactor
chamber 101. At least a portion of the gas siphon assembly 225
outside of the reactor chamber 101 is insulated. Besides
withdrawing heavy vapor fuel from the reactor chamber 101, the
aspirator assembly 229 also mixes ambient air with the collected
heavy vapor fuel gas, thereby creating a mixed gas.
[0073] Heavy vapor fuel gas extracted from the reactor chamber 101
will preferably enter the gas siphon assembly 225 at a temperature
of approximately 800 degrees Fahrenheit. However, because the
aspirator assembly 229 mixes the hot heavy vapor fuel gas with
ambient air, the mixed fuel gas released from the aspirator
assembly 229 will preferably have a temperature of approximately
600 degrees Fahrenheit, and is delivered to the flare assembly 210
at a rate of approximately 540 CFM.
[0074] The flare assembly 210 is operably connected to at least one
burner 220 that initiates combustion of the mixed gas. In the
preferred embodiment of the present invention, the at least one
burner 210 consists of, but is not limited to, two 2 inch propane
burners that utilize pilot igniters. Additionally, the combustion
temperatures in the preferred embodiment are operated at
approximately 1600 degrees Fahrenheit.
[0075] In processing 100 tons of MSW in accordance with the present
invention, in which the MSW has a heat value of 4290 Btu/hr, it is
anticipated that the flare temperature will be 1857 degrees
Fahrenheit, and will produce total gas output of 47,903 lb/hr, a
sensible heat content of 25,011,241 Btu/hr (ref. 77 degrees
Fahrenheit), and a latent heat content of 5,337,774 Btu/hr.
[0076] Unlike traditional gasification systems, rather than using
an exhaust stack to vent hot combusted gas into the atmosphere, or
bottle the gas for ancillary operations, heavy vapor fuel is
utilized by at least one heat recovery device. In the preferred
embodiment, a primary heat recovery device 211, a secondary heat
recovery device 212, and a geothermal field 213 recover heat
entrained in the combusted gas.
[0077] In the preferred embodiment, the primary heat recovery
device 211 is configured to operate on the power or heat generated
by the combustion of the heavy vapor fuel gas by the flare assembly
210. In such a design, the flare assembly may be built into, or a
subcomponent of, the primary heat recovery device 211.
Alternatively, hot exhaust produced by the combustion of the heavy
vapor fuel gas by the flare assembly 229 may be delivered to, and
utilized by, the primary heat recovery device 211. Exhaust from the
primary heat recovery device 211 typically has a temperature in the
range of 350 degrees to 500 degrees Fahrenheit.
[0078] The secondary heat recovery device 212 operates on the
combusted exhaust provided by the primary heat recovery device 211.
In the preferred embodiment, the secondary heat recovery device 212
further cools the combusted exhaust to the range of 200 degrees to
300 degrees Fahrenheit.
[0079] In the preferred embodiment, exhausted combusted gas from
the secondary heat recovery device 212 is delivered to the
geothermal field 213, which provides a final cooling stage. An
induced draft fan 214 preferably provides momentum for combusted
gas to pass through the geothermal field 213. The geothermal field
will typically produce a final exhaust temperature of 60 degrees to
80 degrees Fahrenheit, which are approximately ambient conditions.
In one embodiment of the invention, carbon dioxide separation may
be provided at early stage by separator 216 that is operably
connected to the geothermal field 213.
[0080] An absorber 215, such as, but not limited to, a monolithic
lime absorber, then filters critical regulated pollutants, such as
HCl, from the cooled combusted gas. Filtered exhaust exiting the
absorber 215 is typically comprised of water dioxide and carbon
dioxide. A carbon dioxide extractor 116, such as, but not limited
to, a Wittmann carbon dioxide extractor, is employed to remove the
carbon dioxide molecules from the filtered exhaust. In an
alternative embodiment, the extractor 116 is replaced by a
greenhouse 117, or by an agricultural carbon dioxide dispersion
system, whereby carbon dioxide is sequestered from the filtered
exhaust. The remaining filtered gas is then re-directed to the
reactor chambers 101, 102, 103, where it is re-introduced into the
gasification cycle as recycled process gas, and thereby eliminates
the need for an exhaust stack.
[0081] Extracted carbon dioxide gas may be used for other
industrial purposes, or to support vegetation, such as replenishing
the carbon content of soil of an agricultural field by passing
extracted carbon dioxide through a carbon dioxide dispersal system
or venting it into a greenhouse. In an alternative embodiment of
the present invention, oxygen that has been converted from
extracted carbon dioxide may be recaptured and reintroduced into
the gasification chamber as a cooling medium for the chambers 101,
102, 103, or as part of the ambient process gas intake.
Gasification Primary Vessel Detail
[0082] FIGS. 3 and 5 show details of the waste gasification reactor
chamber 101 of the present invention. Depending on the quantity of
required fuel gas, and density of the selected feed stock, the
capacity of the gasification reactor chamber 101 can be configured
to hold a wide range of feed stock material, such as, but not
limited to, as little as one ton or as much as one thousand tons of
feed stock material.
[0083] FIGS. 5A and 5B illustrate the basic configuration of the
gasification reactor chamber 101 of the preferred embodiment. As
shown in FIG. 5A, the gasification reactor chamber 101 incorporates
a double walled configuration, in which the interior chamber 126 is
sleeved inside the outer shell 127. While the interior chamber 126
of the present invention is capable of having a rectangular,
square, or cylindrical configuration, the preferred embodiment of
the present invention has at least five side walls, such as an
octagonal or hexagonal shape, and is a continuously welded
container of {fraction (1/2)} inch thick, 316 or 304 stainless
steel plate or cast iron. In one embodiment of the invention, a
reactor chamber 101 an octagonal reactor chamber that is designed
to hold approximately 50 tons of feed stock material will be
approximately 24 feet tall and 8 feet wide on the sides.
[0084] Additionally, at least one burner 220 is operably connected
to the interior chamber 126, the at least one burner 220 providing
heat to elevate the temperature inside the interior chamber 126. In
the preferred embodiment of the invention, two openings are
positioned beneath grate level, each opening being operably
connected to at least one natural gas or LPG-burner, thermal lance,
electrical resistance heat generator, or other heat generating
device.
[0085] FIG. 5D illustrates a cross sectional side view of the
gasification reactor chamber in accordance with one embodiment of
the present invention. The outer surface of the interior chamber
126 includes a plurality of aluminum convective cooling fins 130
that dissipate heat away from the surface of the interior chamber
126. Between the cooling fins 130 and the interior surface of the
outer shell 127 is at least one layer of insulation 129. The
preferred embodiment of the invention utilizes an insulative jacket
that is comprised of two layers of insulation, with the first layer
77, which covers the cooling fins, being a 2 inch thick blanket of
ceramic fiber. On top of the ceramic fiber is second layer 78, the
second layer being comprised of an 8 inch thick layer of mineral
wool block, which is an inexpensive and durable heat-dissipating
industrial material that is commonly used for covering hot
pipes.
[0086] The preferred embodiment of the invention also includes
vents 131 located on the sides of outer shell 127, as illustrated
in FIG. 5B. Because of the temperature gradient between the cooler
outside ambient air and the elevated temperatures of the
gasification reactor chamber 101, these vents 131 allow for outside
air to rise into the space between the interior chamber 126 and the
outer shell 127, and through the at least one layer of insulation
129, thereby providing cooling air flow through the mineral wool.
In the preferred embodiment of the present invention, such vents
131 could allow for a sustainable external temperature of
approximately 100 degrees Fahrenheit.
[0087] When needed, ambient air and/or recycled process gas is
supplied to the gasification reactor chamber 101. Ambient air may
be provided to the reactor chamber 101 through a plurality of
process gas inlets, as shown in FIGS. 3B, 3C, and 5A. In the
preferred embodiment of the present invention, each wall of the
interior chamber 126 has at least one process gas inlet 112. In the
preferred embodiment of the present invention, each process gas
inlet 112 has a 6 inch diameter. Furthermore, at least two of these
process gas inlets 112 are preferably operably connected to a
common air supply manifold 125. In the preferred embodiment, the
manifolds 125 are comprised of 8 inch diameter tubing that
circumscribes the outside diameter of the interior chamber 126, the
tubing having a first end and a second end, the first end being
connected to a variable speed blower that is located outside of the
reactor chamber 101, and the second end being completely occluded.
Additionally, a damper is preferably operably positioned between
the blower and the manifold, the damper configured to control the
introduction of the limited process gas necessary to maintain the
gasification cycle and to prevent the inclusion of unwanted ambient
air in the interior chamber 126.
[0088] Recycled process gas may be returned to the gasification
reactor chamber 101 via a return air line 118. In the preferred
embodiment of the invention, the recycled process gas may be used
as a cooling media for the reactor chamber 101, in which the
recycled process gas flows between the insulative jacket and the
outer shell 127. Alternatively, the return air line 118 provides a
path for the controlled introduction of the recycled process gas
into the gasification cycle, the return air line being operably
connected to the plurality of process gas inlets 112.
[0089] FIGS. 3A, 3B, and 3C illustrate the outer shell 127 of the
preferred embodiment. The outer shell 127 is preferably constructed
from A36 hot rolled structural shapes and steel sheet, that may be
similar to painted metal ribbed panels, and provides mechanical
support for the loaded reactor vessel. The outer shell 126 may also
provide attachment points for monitoring, ducting, insulation, and
other gasification operating equipment.
[0090] Feed stock is loaded into the reactor chamber 101 through an
access loading door 120, as shown in FIG. 3A, and placed on a grate
70, as illustrated in FIG. 3D. The gasification reactor chamber 101
may also include an additional opening near the floor of the
chamber that is just below the highest edge of the bottom grate,
and which allows for access for maintenance and repairs. In the
preferred embodiment of the present invention, the maintenance
opening is bolted and gasket into place.
[0091] Removal of residual solid waste after gasification is
accomplished through a disposal opening 119, and is preferably lead
away from the reactor chamber 101 via a conveyor 321. The exact
arrangement of the conveyor system is not critical and any
arrangement for conveniently removing solid byproducts is
acceptable as long as the reactor chamber 101 can be sealed off
from outside ambient air during the gasification cycle.
Furthermore, the grate 70, which supports feed stock material
within the reactor chamber 101 may have a sloped configuration that
is designed to facilitate the movement of solid waste product
remaining after the gasification process towards the disposal
opening 119, as illustrated in FIG. 3D.
[0092] FIG. 3E illustrates another embodiment of the present
invention, which includes at least one inclined surface beneath the
grate 70 that tapers inward towards the disposal opening 119, the
disposal opening 119 being located at the base of the reactor
chamber 101. Adjacent to the disposal opening 119 is a slatted
discharge conveyor. The slatted discharge conveyor is preferably
positioned in a trench in the concrete floor and is configured to
receive and remove any remaining debris from the reactor chamber
101 after the completion of the gasification cycle. An air lock at
the exit point of the slatted discharge conveyor is used to
prohibit the unwanted incursion of ambient air into the reactor
chamber 101.
[0093] In the preferred embodiment of the present invention, both
the disposal opening 119 and the primary access loading door 120
are hydraulically activated doors that are formed from {fraction
(1/8)} inch thick type 304 stainless steel, and are insulated with
a ceramic blanket and/or mineral wool fiber. A seal insures an
air-tight fit between the door and the top of the reactor.
[0094] FIGS. 3D and 3E also illustrate the perforated grate 70
within the interior reactor chamber 126, in which the perforated
grate 70 acts as a primary reaction zone. The perforations in the
grate 70 are configured to allow the bottom portion of the feed
stock material to be exposed to gasification process gas.
Furthermore, rather than using a sloped grate 70 that is designed
to facilitate movement of the debris remaining after the completion
of the gasification cycle towards the disposal door 119, as
illustrated in FIG. 3D, the perforations in the grate 70 may be
configured to allow any remaining debris to fall below the grate
for eventual removal from the reactor chamber 101, as illustrated
in FIG. 3E. In such an embodiment, interior chamber includes at
least one inclined surface, the at least one inclined surface 132
having a first portion and a second portion. The first portion of
the inclined surface 132 is operably connected to the bottom of the
interior chamber, and tapers inwards to the second portion. The
second portion is operably positioned in proximity to the disposal
opening 119.
[0095] The present invention increases the primary and secondary
reaction zones through the incorporation of at least one perforated
conduit 75, as illustrated in FIGS. 3D, 3E, and 5A. In the
preferred embodiment, the perforated conduit 75 extends from the
base of the perforated grate 70 towards, but not reaching, the
ceiling of the reactor chamber 101. As illustrated in FIG. 5A, the
at least one perforated conduit 75 is preferably positioned in
proximity to the intersection of the reactor chamber walls, and
extends outwards towards the center of the interior chamber 126.
The plurality of process gas inlets 112 passing through the walls
of the interior chamber 126 are positioned relative to the location
of the at least one perforated conduit 75. The perforated conduit
75 then provides a passageway that permits process gas to travel in
an upward direction along the perforated conduit 75. This
configuration prevents the flow of process gas from being occluded
by feed stock material covering the plurality of process gas inlets
112. These perforations 76 are then configured to allow for the
exposure of additional feed stock surface area to gasification
process gas, with at least a portion of the perforated conduit 75
adding to the total surface area of the primary reaction zone, and
the remaining exposed surface area adding to the total surface area
of the secondary reaction zone. However, the at least one
perforated conduit 75 may be also positioned at a variety of
locations, including, but not limited to, being offset away from
the walls and towards the center of the feed stock, at various
locations along the walls of the reactor chamber 101, through the
center of the feed stock, and all other positions that would be
understood and appreciated by one of ordinary skill in the art. In
the preferred embodiment, the at least one perforated conduit
having a one foot by one foot construction and extends to within
four feet of the top of the interior chamber 126, with the top
being sealed with a solid cap.
[0096] The use of perforated conduits 75 and/or an inner linear 76
also allows the gasification reactor chamber to have a column
configuration that includes at least five sidewalls. This column
configuration and perforated conduits 75 and/or an inner linear 76
configuration eliminates the 50 ton capacity limitation of prior
art gasification reactor chambers. Furthermore, feed stock material
may be top loaded into the column configuration, and therefore
eliminate the repose fill problems associated with side loading a
rectangular reactor chamber configuration, and allows feed stock
material to be top loaded through the use of a conveyor.
[0097] FIG. 5C illustrates an alternative embodiment of the
gasification reactor chamber 101, in which an inner liner 76 is
placed within the interior chamber 126, and preferably is position
so as to leave a gap between the interior sidewalls of the interior
chamber 126 and the inner liner 76, as illustrated in FIGS. 5C and
5D. The inner liner 76, which may be constructed from heavy wire
mesh, has a plurality of perforations that permit the flow of
gasification process gas to the feed stock material. In the
preferred embodiment, the inner liner 76 is a 1 inch by one inch
stainless steel mesh fabricated from {fraction (5/8)} inch
stainless steel wire and positioned 2 to 4 inches away from
interior surface of the interior chamber 126. Process gas is then
able to circulate in and around the feed stock material along the
sides of the inner liner 76, thereby allowing the side surfaces of
the feed stock material to become part of the primary reaction
zone. Additionally, because the inner liner 76 physically contains
the feed stock material, the walls of the interior chamber 126 do
not have any mechanical contact with the feed stock material. This
lack of contact allows the walls of the interior chamber 126 to be
fabricated from substantially thinner material, thereby further
reducing the weight and fabrication expenses of the reactor chamber
101.
[0098] The increased exposure of feed stock material to
gasification process gas significantly increases the sizes of the
primary and secondary zones, which allows for a faster gasification
procedure at lower temperatures. For example, prior art rectangular
reactor chambers that are designed for 50 tons of feed stock
material will typically have a primary reaction zone area of 120
square feet, and an additional 800 square feet of secondary
reaction zone at the uppermost surface of the waste zone, for a
total primary and secondary reaction zone of 920 feet. However, an
octagonal reactor chamber of the present invention that is designed
to hold the same 50 tons of feed stock material, and which includes
eight perforated conduits 75, has a primary reaction zone of 498
feet at the sloped perforated grate 70, plus an additional 384
square feet from at least the lower portion of the perforated
conduits 75, for a total primary reaction zone of 882 square feet.
As the temperature of the reactor chamber 101 stabilizes, an
additional 782 square feet of secondary reaction zone is created,
which is comprised of 384 square feet from at least a portion of
the perforated conduits 75, and 398 square feet from the upper
surface area of the feed stock. The total primary and secondary
reaction zone surface area is therefore 1,664 square feet, roughly
1.78 times that of conventional rectangular reactors.
[0099] The addition of the inner lining 76 to the eight perforated
conduits 75 described in the above-mentioned 50 ton octagonal
reactor chamber increases the surface area of the primary reaction
to 2,002 square feet. When added to the 384 square feet of the
secondary reaction zone, which is created at the top of the feed
stock material, the primary and secondary reaction zones provide a
total feed stock reaction surface area of 2,386 square feet.
Although FIG. 5C illustrates the inner liner 76 being used in
conjunction with at least one perforated conduit 75, the liner may
also be configured to eliminate the need for the perforated
conduits 75, while still preventing the plurality of process gas
inlets from being occluded by feed stock material.
[0100] Because gasification cycle time is a function of surface
exposure to the process gas supply, an increase in the surface area
of the primary and secondary reaction zones represents a
significant reduction in the rate of reaction necessary for
gasification, and thus reduces the cycle time required for a single
charge of feed stock. Thus, for example, the maximum anticipated
volume of heavy vapor fuel gas produced from feed stock material in
the present invention could be reduced to less than 12 hours,
instead of the 18 to 24 hour cycle times of prior art systems. By
decreasing both the time and temperature required for the
gasification of feed stock material, the present invention further
eliminates the need to rely on multiple reactor chambers to meet
system volume capacity requirements.
[0101] Furthermore, this configuration substantially reduces the
external surface temperature of the gasification reactor chamber
101 during operation, thereby making the environment around the
system safer for workers.
[0102] The lower operating temperature within the reactor of the
present invention also improves the ultimate air quality of the
final system exhaust. Constant cooling of the reactor interior
chamber 126 by convection helps stabilize the reactor temperatures
to as low as 750 degrees Fahrenheit. At this temperature level,
there is insufficient thermal energy to create many of the complex
chemical reformation reactions that occur in mass burn
incinerators, some pyrolysis systems, some high temperature
gasifiers, and plasma systems from the various materials that
comprise the feed stock material within the reactor. Depression of
the optimum operating temperature also inhibits the volatilization
of most metals, thus virtually eliminating the metal content in
exhaust air from the total system.
[0103] The simplified single gasification reactor chamber 101 of
the present invention also has significant financial benefits over
large, multi-celled fixed systems, in terms of flexibility,
portability, and economics of installation, operation, and
maintenance. Faster gasification cycles at lower temperatures
permit the gasification reactor chamber 101 to be fabricated from
lighter and less expansive material. In comparison to prior art
systems, the lightness of both the gauge of the material and
insulative layers produces a significant reduction in the overall
weight of the system. This reduction in weight translates into both
lower material and installation expenses. Furthermore, the time
required for fabricating and installing such a system is greatly
reduced by the elimination of refractory materials and associated
refractory hanger installation. The absence of the weight
attributable to refractory material also allows for the use of
lighter structural steel members. Repair and maintenance profiles
for a stainless steel system are far superior to hot rolled steel
structures that are painted. Additionally, the relative small size
of the present invention allows a single gasification system to be
economically and efficiently sited at the location of the fuel
demand, such as the location of the at least one heat recovery
device. These benefits allow a single reactor supplying energy from
this alternative fuel-generating reactor to be economically and
efficiently sited at the location of the fuel demand.
Gas Extraction Details
[0104] FIG. 6 illustrates details of the gas extraction assembly of
the present invention. The extraction scheme includes an aspirator
assembly 229 that replaces the air-mixing chamber of the prior art.
The aspirator assembly 229 is capable of both evenly withdrawing
heavy vapor fuel gas from the interior chamber 126 and completely
mixing impelled ambient air with the extracted oxygen-deficient
heavy vapor fuel gas, thereby creating an oxidized mixed gas. The
aspirator assembly 229 can also provide transport of the mixed gas
over greater distances than conventional methods, thereby making
the whole system more adaptable than current designs, especially
for multiple cell systems.
[0105] A damper assembly, which is the norm in prior art
gasification systems, has been eliminated in the present invention
in favor of employing a variable speed motor 227 as the driving
device for extracting gas from the reactor chamber 101. The motor
227 forces ambient air through a second passageway 228 and into an
impeller 224, which subsequently supplies impelled air through a
passageway 223 and into a conduit coupling 230. In the preferred
embodiment of the invention, a 10 hp motor 227 is mounted
approximately 7 feet above floor level, the motor 229 being
operably connected to a shutoff valve that is located thirty feet
above floor level.
[0106] FIG. 7 illustrates the preferred embodiment of the conduit
coupling 230, which is shown as having a "Y" configuration, but may
have a number of configurations, including a "T" shape, as would be
understood and appreciated by one of ordinary skill in the art. In
the preferred embodiment, the conduit coupling 230 readily
available from an industrial supply source. The conduit coupling
230 is comprised of a first leg 141, a second leg 142, and a stem
143. High velocity impelled air passing along the first leg 141 and
through the stem 143 of the conduit coupling 230 creates a suction
force in the second leg 142, the attached single manifold pipe 226,
and the gas siphon assembly 225, thereby creating a slight negative
pressure in the interior chamber 126. As heavy vapor fuel gas is
produced and rises to the top of the interior chamber 126, the
suction force created in the conduit coupling 230 draws the heavy
vapor fuel gas into the portion of the gas siphon assembly 225 that
extends inside the interior chamber 126, as illustrated in FIG. 5A.
The gas siphon assembly 225 is sized according to the type of feed
stock material and designed for the capacity of the chamber 101. In
the preferred embodiment of the invention, the gas siphon assembly
225 is comprised of 3 inch diameter 316 stainless steel, schedule
40 piping. The pipes are preferably mounted along the ceiling of
interior chamber 126, and terminate at a single manifold pipe 226,
with at least a portion of the piping inside the reactor chamber
101 being perforated so as to permit heavy vapor fuel gas to pass
into the gas siphon assembly 225.
[0107] The suction force created by the aspirator assembly 229
allows for smooth and even extraction of heavy vapor fuel gases
from the interior chamber 126, and increases the quantity of
extracted heavy vapor fuel gas. This even and smooth extraction
provides a number of benefits, including: causing the gasification
process to work with less fluctuation in gas volume removal from
the reactor chamber 101 as the gasification process works its way
through the raw feed stock material; reduces the total primary
gasification process cycle time; and supplies a more homogenous and
regulated flow of heavy vapor fuel gas product to the ultimate
burner system that will combust the gas in the employed heat
recovery strategy of the present invention.
[0108] Once the heavy vapor fuel gas reaches the conduit coupling
230, the influx of the hot heavy vapor fuel gas into the cold
impelled ambient air stream, creates considerable turbulence in the
down-stream pipe 231. This turbulence is more than adequate to
accomplish air mixing, and will add ambient air volume to the heavy
vapor fuel gas that is approximately equal to that produced in
conventional air-mixing chambers.
[0109] The aspirator assembly 229 also overcomes problems
associated with accelerating mixed gas for use in ancillary
systems. In the preferred embodiment, the gas siphon assembly 225,
single manifold pipe 226, passageway 223, conduit coupling 230, and
downstream pipe 231 are constructed from small diameter tubing,
which, in conjunction with the motor 227, increases both the
velocity and turbulence of the passing ambient air and heavy vapor
fuel gas. As compared to the mixing obtained through conventional
prior art methods, the increased velocity and turbulence created by
the present invention significantly contributes to increasing the
mixing of the gases, which improves the completeness of the
combustion event.
[0110] This accelerated velocity may also provide back pressure to
the supply lines, which allows for the proper functioning of
attached heat recovery devices. In some instances, this higher
velocity delivery makes the heat recovery device more efficient.
Additionally, unlike prior art induced draft systems, the increased
mixed gas velocity allows the invention to operate equipment that
requires higher positive gas input pressures, such as common
bottoming cycle electrical power generation turbines, boilers,
carburetors, and other fuel consuming devices that require a given
amount of supply line gas pressure in order to function properly.
Unlike the current invention, prior art designs were typically
unable to satisfy such positive pressure requirements, either
because of the inability to pressurize the gas because of
dependence on a natural draft-driven processes or because of
problems and expense associated with the application of high
temperature, in-line, induced draft fans.
[0111] Furthermore, process efficiency in gasification is directly
related to the ability to control various functions through
equipment sub-sets in the gasification process. For instance,
rather than provide finite control of the oxidation of the fuel
gas, prior art damper assemblies typically guess at the amount of
flow volume moving through the damper valve body. Unlike the prior
art however, the vacuum power and mixing air percentage of the
aspirator assembly 229 of the present invention can undergo a wide
range of adjustment through the modification of the ducting size
for both the evacuated heavy vapor fuel gas and the ambient air
intake line. Further refinements in air mix and flow can be
achieved by varying the speed of the impeller 224. Therefore,
elimination of the damper assembly affords the present invention
finite control over the extraction rate of the heavy vapor fuel gas
from the reactor chamber 101 and the mixing event, and affords
direct control over the exact flow volume through the system.
Additionally, functions of the aspirator assembly 229 may be even
more accurately controlled through the use of process control
logic. These improvements allow for a finite level of process
control which has not been possible in prior art natural draft
systems.
[0112] The gasification reactor chamber described herein simplifies
prior designs and is a significantly less costly assembly,
providing both a smaller space requirement for such equipment and
fewer parts than are represented in prior art systems. The size of
the aspirator assembly 229 may be up to 90% smaller than a
conventional air-mixing chamber, which dramatically decreases
fabrication costs, and installation time. The elimination of a
centralized gas collection duct, which is common to most prior art
waste gasification systems, makes not only the entire configuration
of multiple gasification reactor chambers at a given facility more
flexible, but also makes a multi-cell configuration simpler and
less expensive to operate. Since there is no longer reliance on the
central collection duct, the gasification vessels can be arranged
independently, or along different vertical planes than previous
designs allowed. Furthermore, the flexibility of the present
invention does not suffer from the prior art's cumbersome and
difficult methods of moving the heavy vapor fuel gas from its point
of formation to the point of combustion.
Heavy Vapor Fuel Gas Flare Assembly
[0113] The single flare assembly of the prior art is usually a
cylinder, approximately 6 feet in interior diameter, and is made of
a spun ceramic fiber or refractory casting liner that is position
inside a steel exterior jacket. Piercing the sides of this assembly
along alternating left and right ports are four to eight pilot
igniters. These igniters provide an open flame for the purpose of
facilitating the combustion of the incoming mixed gasses. The
gasification system of U.S. Pat. No. 6,439,135 utilizes a single
flare assembly wherein the heavy vapor fuel gas from multiple
reactor chambers converges for combustion, and in which the
combusted exhaust is typically subsequently vented into the
atmosphere via an exhaust stack. The present invention incorporates
a dedicated flare assembly 210a, 210b, 210c for each reactor
chamber 101, 102, 103, as illustrated in FIG. 1.
[0114] FIG. 4 illustrates the preferred embodiment of the flare
assembly 210. The flare assembly is comprised of a targeting nozzle
243, thermal insulation 241, a housing 240, and at least one burner
220. In the preferred embodiment, the targeting nozzle 243 has a
conical funnel configuration that is constructed from cast ceramic
and is enclosed in a stainless steel housing 240. The conical
funnel configuration of the targeting nozzle 243 is configured to
restrict the incoming flow of mixed gas 239 from the aspirator
assembly 229 into a combustion focus point 242. The conical funnel
design of the targeting nozzle 237 supplements the mixing of the
heavy vapor fuel gas and ambient air received from the aspirator
assembly 229, thereby further improving the combustibility of the
mixed gas 239. Additionally, the conical design of the targeting
nozzle 237 accelerates the velocity of the mixed gas through the
nozzle. Immediately following the nozzle tip 243 is at least one
burner 220 that provides an ignition spark or raw flame to ignite
the incoming mixed gas. In the preferred embodiment, the at least
one burner 220 is comprised of two Maxon Kinemax 2 inch diameter
burners.
[0115] The flare assembly 210 of the present invention has a number
of benefits. The number of igniter burners 220 required to
adequately combust the mixed gas is reduced. Reduction in the
number of igniter burners 220 substantially reduces the consumption
of supplemental fuel by the system. Also, the configuration of the
targeting nozzle 237 offers better control for mixed gas flaring,
and can also be used as an injection point for the processing of
waste oil, paints, or other volatile liquids. The flare assembly
210 is also much smaller than conventional flares. This saves on
fabrication and installation expenses, and reduces the overall size
of the system.
Primary and Secondary Heat Recovery Device
[0116] Unlike traditional gasification systems, rather than use an
exhaust stack to vent the combusted gas into the atmosphere, or
bottle the gas for ancillary operations, heat is recovered from the
flare assembly 210 by at least one heat recovery device. In the
preferred embodiment of the present invention, a primary heat
recovery device 211 utilizes the combustion of the mixed gas,
thereby relying on the fuel content of the heavy vapor fuel gas for
operation. In such a device, the flare assembly may be built into,
or be a sub-component of, the primary heat recovery device 211.
Alternatively, the primary heat recovery device may receive hot
combusted exhaust gas from the flare assembly 210, as illustrated
in FIG. 2. These combusted gases may be directly supplied as the
primary fuel source for powering or heating primary heat recovery
devices 211 such as, but not limited to, hot water heaters,
boilers, refrigeration systems, dryers, omnivorous fuel internal
combustion engines, and turbines. Such use of heavy vapor fuel
gases would provide an alternative to the expense and conservation
issues associated with the production, supply, and consumption of
fossil fuels for powering such above-mentioned devices.
[0117] In the preferred embodiment, exhaust from the primary heat
recovery device 211 typically has a temperature in the range of 350
degrees to 500 degrees Fahrenheit. A secondary heat recovery device
212 may be utilized to further to recapture and reutilize the
thermal energy entrained in the exhaust from the primary heat
recovery device 211, and via subsequent use, provide a further
cooled exhaust that preferably has a temperature in the range of
200 degrees to 300 degrees Fahrenheit.
"Closed-Loop" Geothermal Heat Rejection Field
[0118] In one embodiment of the present invention, the closed-loop
system includes a geothermal field 113 that utilizes the entrained
hot air exhaust from the primary or secondary heat recovery devices
211, 212. The geothermal field 113 provides a very low cost and
maintenance-free system for final thermal energy recovery. This
geothermal field 113 also provides a no-operating cost method of
reducing exhaust temperatures to meet intake requirements of
emission absorbers 115 and carbon dioxide extractors 116.
[0119] FIG. 8 illustrates the operation of one embodiment of the
geothermal field 113. An induced draft fan 317 provides momentum
for intake exhaust 310 from a primary and/or secondary heat
recovery device 211, 211 to flow through both a subsurface manifold
piping system 315 and a geothermal loop 114. The subsurface
manifold piping system 315 may be located underground or beneath a
body of water, and is comprised of inlet piping 316 and ventilation
tubing 318.
[0120] As the hot air exhaust travels through the geothermal loop
114, it loses heat through natural convection to the surrounding
surfaces. The length of the field is adjusted relative to the total
tons of feed stock material being gasified per day. For example,
1,200 feet of piping in a geothermal loop 114 is adequate for
systems up to, and including, 100 tons of feed stock per day, while
a system of 200 tons would require approximately 2,600 feet of
tubing in the field. Furthermore, a manifold piping system 315 that
is comprised of four PVC inlet pipes 316 located six feet below
ground or water, and twelve inch diameter ventilation tubing 318,
can reduce an intake exhaust 310 heat of 500 degrees Fahrenheit to
approximately 200 degrees Fahrenheit.
[0121] When the geothermal loop 114 is placed under a greenhouse
117, it warms surrounding soil, which transfers heat to the
greenhouse. Ventilation fans may then distribute heat throughout
the greenhouse. In winter months, heat provided from the geothermal
field 113 is sufficient to maintain environmental temperatures
within growing limits, with only minimal supplemental heat needed
on the coldest days. This may serve to significantly reduce
wintertime costs of greenhouse operations.
[0122] Furthermore, as previously discussed, the use of a
greenhouse 117, or other vegetative supporting system, also allows
for the option of venting extracted carbon dioxide from the
extractor 116 to the greenhouse via piping 311. Alternatively, as
will be discussed hereinafter, the greenhouse 117 or other
vegetative system, may also replace the extractor 116, and be used
to sequester carbon dioxide out from the filtered exhaust produced
by the absorber 115.
Emission Controls
[0123] While the formation of noxious pollutants such as HCl and
NO.sub.x is greatly reduced in waste gasification processes,
measurable quantities of the pollutants may still persist in the
exhaust stream from time to time. To handle these residual
pollutants, one embodiment of the invention includes an absorber
115, such as, but not limited to, a monolithic lime absorber. An
absorber 115 such as a monolithic lime absorber absorbs HCl
molecules from exhaust gas that is passed through and around it,
thereby reducing the HCl concentration in the gas that is
eventually returned to the chamber reactor 101. Alternatively,
pollutants may be removed by passing the exhaust stream through a
chilled radiator, whereby the pollutants are collected and
condensed in water vapor.
[0124] When the filtered gas leaves the absorber 115, it is
basically comprised of water vapor, oxygen, hydrogen, nitrogen,
carbon dioxide, and minimal trace elements. At juncture 148, as
shown in FIG. 1, the filtered gas is pulled from the system and
into an extractor 116, such as a Wittmann carbon dioxide extractor,
which removes the carbon dioxide molecules from the filtered gas.
In the absence of an extractor 116, the cooled filtered exhaust may
be vented into a greenhouse 117, where vegetation converts the
carbon dioxide of the filtered gas into oxygen. Alternatively, the
filtered gas may be delivered to a carbon dioxide dispersal system,
as previously discussed. The resulting recycled process gas is then
mainly comprised of water vapor and air that is delivered through a
return line 118 and manifold system back to the gasification
reactor chambers 101, 102, 103 for use in the gasification process.
Alternatively, the recycled process gas may be as a cooling media
for the reactor chamber 101.
[0125] The now cooled filtered exhaust also represents a
significant source for clean carbon dioxide. Depending on the size
of the gasification system, carbon dioxide extraction could provide
environmental and economic advantages. For example, should the
gasification system be used to provide energy for a greenhouse
operation, as shown in FIG. 11, piping 311 from the system 100 may
deliver and vent accumulated carbon dioxide for facilitating plant
growth. Properly selected greenhouse plants could easily consume
all of the extracted carbon dioxide in a reasonable time, thereby
allowing the present invention to emit zero carbon dioxide emission
from the disposal of MSW feed stock. Current research indicates
that increasing the Carbon dioxide level in a greenhouse 117 from
ambient to as much as 1,500 ppm can increase the productivity of
tomatoes, green peppers and lettuce by as much as 35%.
Alternatively, as illustrated in FIG. 12, extracted carbon dioxide
may be vented in a carbon dioxide dispersal system 400, in which
carbon dioxide is passed through distribution chambers 410 located
beneath, among other things, porous fill materials 411, filter
fabric 412, topsoil 413, and vegetation 413. In addition to the
vegetation converting the dispersed carbon dioxide into oxygen,
released carbon dioxide also replenishes the carbon content of
soil.
[0126] The foregoing system provides a low cost, closed-loop MSW
gasification system with that allows for complete material recovery
and recycling of metals, glass, minerals and salts. Furthermore,
the present invention may efficiently recapture expended thermal
energy while preventing overt discharge of air, solids, or waste
water from the disposal of solid waste materials.
[0127] While the present invention has been illustrated in some
detail according to the preferred embodiment shown in the foregoing
drawings and descriptions, it will be understood that the invention
is not limited thereto, since modifications may be made by those
skilled in the art, particularly in light of the foregoing
teaching. It is therefore contemplated by the appended claims to
cover such modifications that incorporate those features that come
within the spirit and scope of the invention.
* * * * *