Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02574020 2007-01-16
WO 2006/017636 PCT/US2005/027682
GASIFICATION APPARATUS AND METHOD
This application claims priority from U.S. patent application serial number
10/911,386, filed on August 4, 2004.
Background of the Invention
This invention relates to gasification and, more particularly, to a flexible
gasification
apparatus and method that provides combustible gases having high heating
values wllile
avoiding pitfalls of prior attempts at gasification.
Gasification has generally been known for years. In gasification, a
carbonaceous fuel
source is partially combusted to produce a combustible gas, synthesis gas, or
syngas. The
combustible gas is then combusted to produce work. The combustible gases
produced by
gasification may find any number of uses, including but not limited to
supplying heat,
powering a motor, or producing electricity. Gasification provides many
advantages, such as
allowing fuels having relatively low heating values to be used, allowing waste
products to be
used to produce work, and, similarly, reducing the amount of waste material
that must be sent
to landfills. Despite these obvious advantages, gasification has met with only
limited success,
because gasification systems have typically been plagued by a number of
disadvantages or
difficulties. For example, the heating values of gases produced using prior
art systems have
tended to fluctuate to an undesirable degree, particularly when a variety of
fuel sources or fuel
sources of varying compositions have been used. Similarly, it has also proven
difficult to
consistently produce gases having sufficiently high heating values. Separating
particulate
matter from the produced gas has proven problematic. Similarly, it has proven
difficult to
produce sufficiently clean gases having sufficiently low amounts of
particulate matter as well
as sufficiently low amounts of pollutants such as such as sulfur dioxide
(SO2), nitrogen
oxides (NO,t), carbon monoxide (CO), volatile organic compounds (VOC), ammonia
(NH3),
hydrogen chloride (HC1), and other chlorides. Environmentally sound disposal
of wastewater
generated by such systems has also presented difficulties. Further still, the
presence of water
or other liquids in the combustible gas has made it difficult or impossible to
use blowers for
moving the combustible gases without creating undesirable levels of wear and
tear on the
blowers.
1
CA 02574020 2007-01-16
WO 2006/017636 PCT/US2005/027682
Summary of the Invention
It is therefore an object of the present invention to provide a flexible
gasification
apparatus and method that provides combustible gases having high heating
values while
avoiding pitfalls of prior attempts at gasification.
It is a further object of the present invention to provide an apparatus and
method of
the above type that can easily handle a wide variety of carbonaceous fuel
sources or
combinations of fuel sources.
It is a further object of the present invention to provide an apparatus and
method of
the above type that produces a high value heating gas having low amounts of
particulate
matter and otlzer pollutants.
It is a further object of the present invention to provide an apparatus and
method of
the above type that requires little or no wastewater disposal.
It is a still f-urther object of the present invention to provide an apparatus
and method
of the above type that captures a relatively high fraction of the potential
heating value of the
fuel sources.
It is a still furtlier object of the present invention to provide an apparatus
and method
of the above type that safely and cleanly consumes a wide variety of
agricultural and
industrial byproducts, including but not limited to animal waste and wood pulp
sludge.
It is a still further object of the present invention to provide an apparatus
and method
of the above type that is less prone to clogging problems typically associated
with ash
removal.
It is a still further object of the present invention to provide an apparatus
and method
of the above type that may easily process a wide variety of combinations of
solid, semi-solid,
and liquid fuels.
It is a still further object of the present invention to provide an apparatus
and method
of the above type that can safely and efficiently handle and dry relatively
wet combustible
gases.
It is a still further object of the present invention to provide an apparatus
and method
of the above type that uses a rugged, hybrid blower that can safely and
efficiently handle both
dry and relatively wet combustible gases.
Toward the fulfillment of these and other objects and advantages, the system
of the
present invention comprises a combustor, a scrubber, a finisher, and
optionally a recycler. A
2
CA 02574020 2007-01-16
WO 2006/017636 PCT/US2005/027682
carbonaceous fuel is partially combusted in the combustor to generate a
combustible gas. An
improved ash support and removal system reduces clogging and other problems in
the
combustor. The combustible gas passes through the scrubber to remove matter
such as tar
and oil and/or to undergo preliminary catalytic chemical reactions. The
scrubbed gas passes
through a hybrid blower to the finisher. Final catalytic chemical reactions
occur in the
finisher, and wood chips or other filters may also be used in the finisher to
provide a
relatively clean, diy, combustible gas. Wastewater and other waste products
from the
scrubber and finisher may be captured in the recycler and returned to the
combustor.
Brief Description of the Drawings
The above brief description, as well as further objects, features and
advantages of the
present invention will be more fully appreciated by reference to the following
detailed
description of the presently preferred but nonetheless illustrative
embodiments in accordance
with the present invention when taken in conjunction with the accompanying
drawings,
wlierein:
FIG. 1 is a flow diagram of a system for practicing the present invention;
FIG 2 is a side elevation, schematic view of a combustor for practicing the
present
invention;
FIG. 3 is an overhead, schematic view of a blower for practicing the present
invention;
and
FIG. 4 is a side elevation view of an impeller for practicing the present
invention.
Detailed Description of the Preferred Embodiment
Referring to Fig. 1, the reference numeral 10 refers in general to a
gasification system
for practicing the present invention. The system 10 will typically coinprise a
combustor 12, a
sciubber 14, and a finisher 16, and may also include a recycler 18. The system
10 principally
consists of preferably a combustor 12 and a finisher 16, more preferably a
combustor 12, a
scrubber 14, and a finisher 16, and most preferably a combustor 12, a scrubber
14, a finisher
16, and a recycler 18. The combustor 12, scrubber 14, finisher 16, and
recycler 18 may
include any type of reaction vessel.
3
CA 02574020 2007-01-16
WO 2006/017636 PCT/US2005/027682
Referring to Fig. 2, the combustor 12 has an upper, outer wall portion 20 and
a lower
base portion 22. The combustor 12 is preferably open, more preferably closed,
at the top and
is preferably configured as a downdraft combustor, more preferably as an
updraft combustor.
A feed line, conduit, or fuel auger 24 is disposed above the combustor 12 to
provide a
carbonaceous fuel source. Another feed line 26 may also be provided to recycle
material
from other portions of the system 10 as discussed in more detail below.
Additional feed lines
may also be used, for example, to provide different types of solid, semi-
solid, and liquid fuel
sources. An inner wall 28 is disposed within the combustor 12 and is connected
to the
combustor 12 to form an inner chamber 30 and an outer chamber 32. A lower
portion of the
inner wall 28 defines an opening 34. An ash support member 36 is affixed to a
lower portion
of the inner wall 28 by rigid members 38 so that the ash support member 36 is
disposed a
distance below the opening 34. The outer periphery of the ash support member
36 is
relatively free from obstructions about the vast majority of the outer
periphery, providing
relatively open side passageways between the inner wall 28 and the ash support
member 36.
This allows ash to spill from the ash support member 36 preferably over at
least
approximately 80 percent of the outer periphery of the ash support member 36,
more
preferably over at least approximately 90 percent of the outer periphery of
the ash support
member 36, and most preferably over at least approximately 95 percent of the
outer periphery
of the ash support member 36.
A gas injection ring 40 is affixed to the inner wall 28 and is disposed at a
medial point
of the inner chamber 30. Openings 42 in the inner wall 28 provide a flow path
for gas, such
as air or an air and fuel mixture, to pass from a plenum 44 forined by the
ring 40 into the
inner chamber 30. A conduit or gas manifold 46 extends througli the outer wall
20 of the
combustor 12 and is operably connected to the ring 40. The conduit or gas
manifold 46 is
connected to an air source and is preferably connected to a fuel source, such
as a source of
natural gas, liquefied petroleum gas (LPG or LP gas), or propane (C3H8). As
seen in Fig. 1, a
recycle line 48 may also be provided to return a portion of the combustible
gas generated by
the system 10. An igniter 50, such as a spark plug igniter, is preferably
disposed in the
conduit or gas manifold 46 adjacent to the combustor 12, more preferably
disposed inside a
partial shield to prevent particles from bridging the spark plug gap, with
said shield disposed
in the conduit or gas manifold 46 adjacent to the combustor 12. One additional
igniter, partial
shield, and branch of gas manifold 46 may be optionally (and is preferably)
disposed
diametrically opposite igniter 50 to improve combustion uniformity within
combustor 12.
4
CA 02574020 2007-01-16
WO 2006/017636 PCT/US2005/027682
As seen in Fig. 2, a fuel agitator, such as fuel stirring member 52, is
provided in the
inner chamber 30. The fuel stirring member 52 is preferably disposed above the
opening 34
and is more preferably disposed above the ring 40. Similarly, an ash agitator
or combustion
bed stirrer such as ash stirring member or combustion bed stirrer 54 is
provided inside the
combustor 12, below the ring 40 and above the ash support member 36. Another
ash agitator
such as ash stirring member 55 is provided inside the combustor 12 below the
ash support
member 36. Coaxial shafts 56 and 58 extend upward from the stirring members
52, 54, and
55 to or above an upper portion of the combustor 12. Motors 60 and 62 are
operably
connected to the shafts 56 and 58 for rotating the shafts and stirring members
52, 54, and 55.
Hollow shaft 58 is rotated by motor 60 and is preferably connected to both
stirring
members 52 and 54, and more preferably connected to stirring member 52 but not
to stirring
member 54. Solid shaft 56 is rotated by motor 62 and is preferably comlected
to stirring
member 55 but not to stiiTing member 54, but more preferably connected to both
stirring
member 54 and stirring member 55. Stirring members 52, 54, and 55 are most
preferably
attached individually to separate coaxial shafts that are individually rotated
by separate
motors.
The fi-ustoconical, lower base portion 22 of the combustor 12 extends below
the ash
support member 36. An opening is provided at the bottom of the lower base
portion 22 to
allow ash to pass from the combustor 12 to an ash removal system 64, such as
an auger drive
for solids transfer. A conduit 66 is provided through the outer wall of the
combustor 12 in an
upper portion of preferably the outer chamber 32, more preferably the inner
chamber 30 to
provide a path for combustible gases generated within the combustor 12 to pass
from the
combustor 12.
A fuel level sensor 68 is provided in the inner chamber 30, preferably above
the
opening 34, more preferably above the ring 40, and most preferably above the
fuel agitator
52. The fuel level sensor 68 is operably coupled with the feed line or fuel
auger 24 to
automate the process of maintaining fuel at a desired level within the inner
chamber 30. An
ash level sensor 70 is disposed within the combustor 12, preferably below the
opening 34,
more preferably below the ash agitator or combustion bed stirrer 54, and most
preferably
below the ash support member 36. The ash level sensor 70 is operably coupled
with the ash
removal system 64 to automate the process of maintaining ash at a desired
level within the
combustor 12. It is of course understood that the combustor 12 may take any
number of
5
CA 02574020 2007-01-16
WO 2006/017636 PCT/US2005/027682
sizes, shapes, and configurations. It is also understood that the combustor 12
need not be
closed at the top and need not be an updraft combustor 12.
Referring to Fig. 1, conduit 66 connects the combustor 12 with the scrubber
14,
providing a flow path into preferably an upper portion, more preferably a
lower portion of the
scrubber 14. The scrubber 14 preferably contains one or more filters
(including, but not
limited to, ferrous or non-feiTous metals, precious metals, ceramics,
minerals, liquids,
plastics, fibrous or non-fibrous materials, wood chips, organic or inorganic
materials, porous
or non-porous materials, natural or artificial materials, absorbents or
adsorbents,
diatomaceous earth, mixtures or combinations of these and other materials, or
any other filter
known to those skilled in the art). The scrubber 14 more preferably contains
one or more
filters and one or more catalysts (including, but not limited to, ferrous or
non-ferrous metals,
precious metals, ceramics, minerals, liquids, plastics, fibrous or non-fibrous
materials, wood
chips, organic or inorganic materials, porous or non-porous materials, natural
or artificial
materials, absorbents or adsorbents, diatomaceous earth, mixtures or
combinations of these
and other materials, or any other catalyst known to those skilled in the art).
A pump 72 is
preferably provided to pass liquid, for example water with impurities therein,
through a feed
line 74 into a preferably upper portion, more preferably lower portion, of the
scrubber 14 and
preferably through sprayers. A liquid return line 76 is preferably connected
to a lower portion
of the scrubber 14 for returning liquid to the pump 72 for reuse within the
scrubber 14. A
feed line or conduit 78 may also be provided for providing preferably gas from
combustor 12,
more preferably gas and liquids from combustor 12, most preferably gas and
liquids from
combustor 12 and recirculated liquid to scrubber 14. Wash or recirculation
lines 80 may be
provided for intermittent use as described below. Scrubbed gas exits through
conduit 82 that
is disposed at a preferably lower, more preferably upper portion of the
scrubber 14. A skim
line 84 is preferably provided at a lower portion of the scrubber 14, and a
blow down line or
conduit 86 is provided at the bottom of the scrubber 14. A level sensor 88,
such as a float
switch, is preferably disposed in the scrubber 14 for maintaining liquid
levels within the
scrubber 14 at desired levels. It is of course understood that the scrubber 14
may take any
number of shapes, sizes, and configurations, and that any number of different
filter media or
catalysts or different combinations of filter media and catalysts may be used
in scrubber 14.
Conduit 82 passes fiom the scrubber 14 to blowers 90. As best seen in Fig. 3,
the
blowers 90 are heavy duty hybrids that combine desirable features of blowers
designed for
moving gases and pumps designed for moving liquids. Walls fonning the impeller
housing
6
CA 02574020 2007-01-16
WO 2006/017636 PCT/US2005/027682
92 have a wall thickness of preferably approximately 3/4 inch, more preferably
approximately
5/8 inch. A sealing member 94, such as a gasket, is used to create an airtight
and watertight
seal between the walls forming the impeller housing 92. Referring to Fig. 4,
the impeller
blades 96 are preferably straight, but are more preferably curved, and are
thicker than impeller
blades of common blowers designed for moving gases, preferably approximately
50 percent
thicker. Referring back to Fig. 3, a packing gland 98, similar to a packing
gland used in a
water pump, is used to provide a shaft 100 seal. Additional sets of bearings
102 are also
preferably used in connection with the impeller shaft 100. It is preferred to
use at least two
sets of bearings 102. Referring to Fig. 1, conduit 104 passes from the blowers
90 to the
finisher 16, providing a flow path into preferably a lower portion, but more
preferably an
upper portion, of the finisher 16. It is of course understood that the blowers
90 may be
disposed at any number of locations in the system 10 and that the blowers 90
may take any
number of different sizes, shapes, and configurations. It is also understood
that, although not
preferred, conventional blowers may be used.
The finisher 16 preferably contains one or more filters (including, but not
limited to,
ferrous or non-ferrous metals, precious metals, ceramics, minerals, liquids,
plastics, fibrous or
non-fibrous materials, wood chips, organic or inorganic materials, porous or
non-porous
materials, natural or artificial materials, absorbents or adsorbents,
diatomaceous earth,
mixtures or combinations of these and other materials, or any other filter
known to those
skilled in the art). The finisher 16 more preferably contains one or more
filters and one or
more catalysts (including, but not limited to, ferrous or non-ferrous metals,
precious metals,
ceramics, minerals, liquids, plastics, fibrous or non-fibrous materials, wood
chips, organic or
inorganic materials, porous or non-porous materials, natural or artificial
materials, absorbents
or adsorbents, diatomaceous earth, mixtures or combinations of these and other
materials, or
any other catalyst known to those skilled in the art). Conduit 106 passes from
preferably an
upper portion, more preferably a lower portion, of the finisher 16 to provide
a flow path for
the scrubbed and finished combustible gas. Additional conduits 108, 48, and
110 are also
provided for passing the scrubbed, finished combustible gas to flare, to
recycle, and for
further uses. A conduit 112 passes from a lower portion of the finisher 16 for
removing
wastewater and other matter that condenses or is removed from the gas as it
passes through
the finisher 16. It is understood that the finisher 16 may take any number of
shapes, sizes,
and configurations and that any number of different filter media or catalysts
or different
combinations of filter media and catalysts may be used in finisher 16.
7
CA 02574020 2007-01-16
WO 2006/017636 PCT/US2005/027682
Conduits 84, 86, 112, and 114 preferably connect the scrubber 14 and finisher
16 to a
recycler 18, providing a flow path into an upper portion of the recycler 18.
Return line or
conduit 116 preferably passes from a lower portion of the recycler 18 to pump
118, and line
26 preferably passes from pump 118 to combustor 12. A recirculation line 120
is preferably
provided for diverting a portion of the liquid from the return line 26 back to
the recycler 18.
A level sensor 122, such as a float switch, is preferably disposed in the
recycler 18 for
maintaining liquid levels within the recycler 18 at desired levels. It is
understood that the
recycler 18 may take any number of different shapes, sizes, and
configurations.
In operation, feed line or fuel auger 24 provides a solid or semi-solid
carbonaceous
fuel to the combustor 12. As seen in Fig. 2, the solid or semi-solid fuel
drops through the
inner chamber 30, accumulates on the ash support member 36, and builds up
within the inner
chamber 30 to a level above the ring 40 and then above the fuel stirring
member 52. As seen
in Fig. 1, an oxygen source, such as air, is provided preferably via conduit
124, more
preferably via conduit 126 instead, and an alternate fuel source is provided
preferably via
conduit 126, more preferably via conduit 124 instead. Referring to Fig. 2, the
air and
alternate fuel are mixed inside conduit or gas manifold 46, ignited by igniter
50, and pass
through the ring 40 and into the inner chamber 30. The burning air and
alternate fuel mixture
ignites the carbonaceous fuel within the inner chamber 30. As the carbonaceous
fuel sources
pass downward within the inner chainber 30, the carbonaceous fuel sources are
at least
partially combusted to produce, among other materials, ash and a combustible
gas. Fuel
stirring member 52 keeps the different fuel sources blended and reduces or
prevents
channeling, bridging, clumping, voids, and similar problems.
Ash passes through opening 34 and collects on ash support member 36. The ash
stirring member or combustion bed stirrer 54 prevents ash build up by moving
the collecting
ash preferably outward so that the ash spills or passes from the outer
periphery of the ash
support member 36, more preferably moving the collecting ash downward so that
the ash
spills or passes through perforations in ash support member 36, or most
preferably moving
the collecting ash both outward from the outer periphery of ash support member
36 and
downward through perforations in ash support member 36 to fall down to the
lower base
portion 22 of the combustor 12. Other than the ash stirring member or
combustion bed stirrer
54 and support members 38, the area between the opening 34 of the inner wal128
and the top
surface of ash support member 36 is substantially unobstructed to provide a
ready path for ash
removal, free from obstructions and sources of clogging such as grates or mesh
materials. In
8
CA 02574020 2007-01-16
WO 2006/017636 PCT/US2005/027682
that regard, the support members 38 connect the ash support member 36 to the
inner wa1128
in a manner that allows ash to spill from the ash support member 36 preferably
over at least
approximately 70 percent of the outer periphery of the ash support member 36,
more
preferably over at least approximately 80 percent of the outer periphery of
the ash support
member 36, and most preferably over at least approximately 90 percent of the
outer periphery
of the ash support member 36.
Ash that accumulates in the lower base portion 22 of the combustor 12 passes
through
an opening in the bottom of the combustor 12 and is removed by an ash removal
system 64,
such as by an auger or screw drive. The ash auger drive 64 is operably coupled
with ash level
sensor 70 to maintain the ash in the combustor 12 below a desired amount. The
ash removed
from the combustor 12 will typically be a salable product. For example, the
ash might be
suitable for sale as fertilizer, soil stabilizer, filter material, and/or as
an extender for mortar,
concrete, or road material, among other uses.
The fuel level sensor 68 is operably coupled with the solid or semi-solid fuel
feed line
or fuel auger 24 to maintain solid or semi-solid fuel within a desired height
range within the
inner chainber 30. The desired heigl7t range will vary depending upon a number
of factors,
including but not limited to the properties of the solid or semi-solid fuel.
It is typically
desirable to maintain the solid or semi-solid fuel level within the inner
chamber 30 at the
lowest possible level while still maintaining an adequate seal, preferably to
prevent products
of combustion from escaping through the top of the combustor 12 and/or to help
control the
degree of partial combustion within inner chamber 30. The level desired will
vary with
factors such as the density and moisture content of the solid or semi-solid
fuel. For example,
the desired level for a solid or semi-solid fuel comprised primarily of
chicken litter
(including, but not limited to, chicken waste products, absorbents such as
rice hulls or wood
chips, or any combination of these and similar or related materials) will tend
to be higher than
the desired level for a solid or semi-solid fuel comprised primarily of wood
pulp or paper mill
sludge, and the desired level for a solid or semi-solid fuel comprised
primarily of wood pulp
sludge will tend to be higher than the desired level for a solid or semi-solid
fuel comprised
primarily of sanding or wood dust. In a typical operation in which the solid
or semi-solid fuel
is comprised primarily of chicken litter, the level of solid or semi-solid
fuel within the inner
chamber 30 is preferably maintained at a heiglit of approximately 8 inches to
approximately
10 inches above the ring 40. Similarly, in an operation in which the solid or
semi-solid fuel is
comprised primarily of wood pulp sludge, the level of solid or semi-solid fuel
within the inner
9
CA 02574020 2007-01-16
WO 2006/017636 PCT/US2005/027682
chamber 30 is preferably maintained at a height that is only slightly above
the ring 40. Also,
in an operation in which the solid or semi-solid fuel is comprised primarily
of sanding or
wood dust, the level of solid or semi-solid fuel within the inner chamber 30
is preferably
maintained at a height that is approximately even with or slightly below the
ring 40.
The blowers 90 draw gaseous products of combustion preferably downward, more
preferably upward, through the combustor 12 so that they pass through the
opening 34 in the
inner wall 28 and upwardly through preferably the outer chamber 32, more
preferably the
inner chamber 30 before passing tlirough conduit 66. Referring to Fig. 1,
combustible gas
from the combustor 12 enters preferably an upper portion, more preferably a
lower portion, of
the scrubber 14 and passes upward toward conduit 82. Pump 72 circulates
liquid, for
example water with impurities therein, to the scrubber 14. Liquid enters the
scrubber 14
through conduit 74, passes preferably through sprayers, and contacts the
combustible gas.
The liquid cools and scrubs the combustible gas, removing matter from the
combustible gas
including tar, oil, and particulate matter. The liquid level in the scrubber
14 is maintained at a
desired level so that tar, oil, and similar matter may be removed from the
scrubber 14
preferably via the skimmer line 84. Particulate matter and other components
that settle to the
bottom of the scr=ubber 14 are periodically removed via blow down line or
conduit 86. Valves
128 are also opened preferably periodically so that the puinp 72 may circulate
liquid through
wash lines 80 and through conduits 66, 82, and 104 for cleaning. From time to
time, valve
130 may be opened so that the liquid in scrubber 14 may also be drained
through line 86 and
preferably replaced with liquid from line 78. Filters in scrubber 14 primarily
remove liquids
from the gas. Catalysts in scrubber 14 primarily improve the chemical
composition of the
gas.
The scrubbed combustible gas exits the scrubber 14 through line 82, passes
through
blowers 90, and is driven through fmisher 16. As it exits the scrubber 14, the
gas may also be
passed through a filter/knock-out pot, before being passed to the blowers 90.
Wood chips or
other filters in the finisher 16 diy the gas and remove additional amounts of
particulate matter
and other pollutants. Wastewater and other matter that are removed from the
combustible gas
and that are not absorbed by the wood chips or other filters fall to the
bottom of the finisher
16 and are removed via line 112. Filters in finisher 16 primarily remove
liquids from the gas.
Catalysts in finisher 16 primarily improve the chemical composition of the
gas. Scrubbed,
finished combustible gas exits the fmisher 16 via line 106. From there the
combustible gas is
flared via line 108, returned to the reaction chamber via line 48, or sent to
other uses via line
CA 02574020 2007-01-16
WO 2006/017636 PCT/US2005/027682
110. During the initial start-up phase, the combustible gas is flared until it
is determined that
gas is being produced at a desired quantity and quality. Once the start-up
phase is complete,
the combustible gas will primarily be passed via line 110 to produce work or
for further uses
elsewhere. For example, the combustible gas might be combusted to supply heat
to a process
or might be combusted within a motor or turbine to produce work or to generate
electricity.
As additional examples, the combustible gas produced by the system 10 may be
used in
brooder heaters in poultry houses, in internal combustion engines, and in
boilers. In fact, the
combustible gas generated by the present system 10 compares quite favorably
with natural
gas, often being cleaner while having comparable or higher heating values. The
heating
values of the combustible gas produced will vary depending upon a number of
factors, such
as the type, composition, and moisture content of the carbonaceous fuel
provided, but the
heating values of the combustible gas produced will typically be at or near
550 British
Thermal Units (BTUs) per cubic foot. Accordingly, combustible gas produced
using the
present system 10 is a good candidate for use in any situation that currently
uses natural gas,
liquefied petroleum gas (LPG or LP gas), or propane.
Depending upon the properties of the carbonaceous fuels being supplied to the
combustor 12, such as the moisture content, a portion of the combustible gas
may be returned
to the combustor 12 via line 48 to supply additional fuel to aid in the
partial combustion of
the carbonaceous fuel. The combustible gas supplied via line 48 may serve as a
complete or
partial replacement for the alternate fuel source supplied to the combustor
12, preferably via
line 126, more preferably via line 124. Returning the combustible gas to the
reaction
chamber 12 offers a number of advantages. For example, it saves on alternate
fuel costs that
might otherwise be required to maintain the desired combustion in the
combustor 12.
Lines 86, 84, 112, and 114 pass from the scrubber 14 and the finisher 16 to
recycler
18. These lines 86, 84, 112, and 114 pass wastewater, excess liquid from wet
fuel
components, tar, oil, particulate matter, and other removed substances to an
upper portion of
the recycler 18. These components pass from the recycler 18, preferably via
line 116 and
pump 118, via line 26 back to the combustor 12, where they are fed into an
upper portion of
the combustor 12. A portion of these components is preferably diverted via
line 120 and
returned to the recycler 18 to help stir or agitate the contents of the
recycler 18. Returning the
wastewater and other components to the combustor 12 provides a number of
advantages. For
example, the wastewater scavenges additional, residual carbon from the ash as
the liquid is
11
CA 02574020 2007-01-16
WO 2006/017636 PCT/US2005/027682
broken down. This provides for better recovery of the heating value from the
carbonaceous
fuel and eliminates or drastically reduces the need to dispose of wastewater.
The system 10 may be used to process a wide variety of carbonaceous fuels, as
well as
combinations thereof. The spacing between the ash support member 36 and the
opening 34
of the inner wa1128, as well as the relatively unobstructed side openings
there, allow a wide
assortment of solid or semi-solid fuels to be used without fear of clogging.
Possible
carbonaceous fuels include, but are not limited to, materials such as chicken
litter, other
animal waste, municipal solid or semi-solid waste, glued woods (such as
plywood and press
board), paper mill or wood pulp sludge (including sludge with a moisture
content of 65% or
higher), wood or yard waste, agricultural waste, shredded tires, and mixtures
or combinations
of these and other carbonaceous materials. Liquid carbonaceous fuels may also
be added,
including but not limited to waste motor oil and cooking oil. Adding these
liquid
carbonaceous fuels can markedly increase the heating value of the combustible
gas produced.
In one particular embodiment, the system 10 is approximately 6 feet wide,
approximately 10 feet long, and approximately 7.5 feet tall. This particular
embodiment of
system 10 gasifies approximately eighty (80) pounds of chicken litter per
hour, requires no
auxiliary fuel after startup, uses only about three (3) kilowatt-hours of
electricity, produces
over 3.5 million BTUs per hour of combustible gas, and produces only about
four (4) pounds
per hour of mineral ash, generating no other solid waste, no liquid waste, and
no gaseous
waste.
The following emissions test examples illustrate that the gasification system
10 of the
present invention can produce combustible gas that is environmentally friendly
while
processing solid or semi-solid carbonaceous fuels that previously posed
serious landfill
issues.
Example 1
An emissions test was conducted on combustible gas generated by the system 10
while combusting chicken litter. A sample run of 60 minutes in duration was
performed.
Testing was performed in accordance with the methods detailed in 40 Code of
Federal
Regulations (CFR), Part 60, Appendix A. The flow, based on the lowest
recordable flow, had
a velocity of 6.77 feet per second, and the sample collected had a voluine of
41.42 dry
standard cubic feet. The results of the emissions testing are summarized in
Table 1 below.
12
CA 02574020 2007-01-16
WO 2006/017636 PCT/US2005/027682
Table 1
Substance Emissions
lbs/hr
Particulate Matter (based on lowest detectable flow rate) 0.003
VOC as Propane (corrected for moisture) 0.137
Nitrogen Oxides as NOZ 0.001
Carbon Monoxide 0.003
Sulfur Dioxide 0.096
Ammonia 0.033
HCl 0.008
Chloride 0.005
Example 2
An emissions test was conducted on combustible gas generated by the system 10
while combusting paper mill sludge. A sample run of 60 minutes in duration was
performed.
Testing was performed in accordance with the metliods detailed in 40 CFR, Part
60,
Appendix A. The flow, based on the lowest recordable flow, had a velocity of
6.53 feet per
second, and the sample collected had a volume of 40.60 dry standard cubic
feet. The results
of the emissions testing are summarized in Table 2 below.
Table 2
Substance Emissions (lbs/hr)
Particulate Matter (based on lowest detectable flow rate) 0.0014
VOC as Propane (corrected for moisture) 0.014
Nitrogen Oxides as NO2 0.013
Carbon Monoxide 0.051
Sulfur Dioxide 0.017
Other modifications, changes and substitutions are intended in the foregoing,
and in
some instances, some features of the invention will be employed without a
corresponding use
of other features. For example, the configuration of the ash support member 36
may be used
in combination with any number of different gasification systems, regardless
of whether such
systems also use other features of the present invention, and may also find
uses in systems
other than gasification systems. Similarly, the wastewater return features of
the present
13
CA 02574020 2007-01-16
WO 2006/017636 PCT/US2005/027682
invention may be used in combination with any number of different gasification
systems,
regardless of whether such systems also use other features of the present
invention, and may
also find uses in systems other than gasification systems. Further, the wood
chip filtering or
other filters or catalysts of the present invention may be used in combination
with any number
of different gasification systems, regardless of whether such systems also use
other features of
the present invention, and may also find uses in systems other than
gasification systems.
Further still, the hybrid blower 90 design of the present invention may be
used in combination
with any number of different gasification systems, regardless of whether such
systems also
use other features of the present invention, and may also find uses in systems
other than
gasification systems. Of course, quantitative information is included by way
of exainple only
and is not intended as a limitation as to the scope of the invention.
Accordingly, it is
appropriate that the invention be construed broadly and in a manner consistent
with the scope
of the invention disclosed.
14
