U.S. patent application number 14/639984 was filed with the patent office on 2015-09-10 for emission reduction device for a wood heater.
The applicant listed for this patent is Lance Carl Grace, Tyler Mainord Grace. Invention is credited to Lance Carl Grace, Tyler Mainord Grace.
Application Number | 20150253006 14/639984 |
Document ID | / |
Family ID | 54016981 |
Filed Date | 2015-09-10 |
United States Patent
Application |
20150253006 |
Kind Code |
A1 |
Grace; Lance Carl ; et
al. |
September 10, 2015 |
EMISSION REDUCTION DEVICE FOR A WOOD HEATER
Abstract
An inventive apparatus for reducing emissions from a wood heater
comprises (i) two or more volumes of a porous, catalyst-coated
medium and (ii) one or more holders for the catalyst-coated medium.
The one or more holders are structurally arranged to hold the
volumes of the catalyst-coated medium in a specified spatial
arrangement within an exhaust flue of the wood heater. The
catalytic media are sized and shaped so that, in that specified
spatial arrangement, the volumes obstruct substantially all
straight-line paths from a combustion chamber of the wood heater
through the exhaust flue past the volumes of the catalyst-coated
medium. In the specified spatial arrangement, the volumes also
leave unobstructed at least one tortuous exhaust gas flow path from
the combustion chamber through the exhaust flue around and past the
volumes of the catalyst-coated medium.
Inventors: |
Grace; Lance Carl;
(Alamogordo, NM) ; Grace; Tyler Mainord;
(Alamogordo, NM) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Grace; Lance Carl
Grace; Tyler Mainord |
Alamogordo
Alamogordo |
NM
NM |
US
US |
|
|
Family ID: |
54016981 |
Appl. No.: |
14/639984 |
Filed: |
March 5, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61948095 |
Mar 5, 2014 |
|
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|
Current U.S.
Class: |
110/345 ;
110/214; 126/307R |
Current CPC
Class: |
F23B 90/08 20130101;
F23G 7/07 20130101; F24B 1/006 20130101; F24B 5/028 20130101 |
International
Class: |
F23J 15/02 20060101
F23J015/02; F24B 13/00 20060101 F24B013/00; F24B 9/00 20060101
F24B009/00 |
Claims
1. An apparatus for reducing emissions from a wood heater, the
apparatus comprising two or more volumes of a porous,
catalyst-coated medium and one or more holders, wherein: (a) the
one or more holders are structurally arranged to hold the volumes
of the catalyst-coated medium in a specified spatial arrangement
within an exhaust flue of the wood heater; and (b) the volumes of
the catalyst-coated medium are sized and shaped so as to (i)
obstruct, when held by the one or more holders in the specified
spatial arrangement, substantially all straight-line paths from a
combustion chamber of the wood heater through the exhaust flue past
the volumes of the catalyst-coated medium, and (ii) leave
unobstructed, when held by the one or more holders in the specified
spatial arrangement, at least one tortuous exhaust gas flow path
from the combustion chamber through the exhaust flue around and
past the volumes of the catalyst-coated medium.
2. The apparatus of claim 1 further comprising an air inlet tube
with an open inner end arranged to be held by one or more of the
one or more holders in communication with the exhaust flue between
the combustion chamber and the volumes of the catalyst-coated
medium, wherein an open outer end of the air inlet tube is
positioned outside the combustion chamber, at a level below a level
of one or more combustion air inlets into the combustion chamber,
so as to draw ambient air through the air inlet tube into the
exhaust flue during operation of the wood heater.
3. The apparatus of claim 2 wherein the air inlet tube is routed
along an inside or outside surface of the combustion chamber so as
to heat the ambient air drawn into the air inlet tube during
operation of the wood heater.
4. The apparatus of claim 1 further comprising a housing containing
the one or more holders and the volumes of the catalyst-coated
medium, wherein the housing is sized and shaped so as to fit within
the exhaust flue.
5. The apparatus of claim 1 further comprising a housing containing
the one or more holders and the volumes of the catalyst-coated
medium, wherein the housing is structurally arranged so as to be
incorporated as a segment of the exhaust flue.
6. The apparatus of claim 5 further comprising an adapter member
structurally arranged so as to mate a lower end of the housing to
an upper exhaust opening of the wood heater or to mate an upper end
of the housing to the exhaust flue.
7. The apparatus of claim 5 further comprising an air inlet tube
held by the housing so that an open inner end of the air inlet tube
is in communication with the exhaust flue between the combustion
chamber and the volumes of the catalyst-coated medium, wherein an
open outer end of the air inlet tube is positioned outside the
combustion chamber, at a level below a level of one or more
combustion air inlets into the combustion chamber, so as to draw
ambient air through the air inlet tube into the exhaust flue during
operation of the wood heater.
8. The apparatus of claim 1 further comprising a segment of the
exhaust flue, wherein the one or more holders and the volumes of
the catalyst-coated material are mounted within the segment of the
exhaust flue.
9. The apparatus of claim 1 wherein the one or more holders are
formed of the porous, catalyst-coated medium.
10. The apparatus of claim 1 wherein the porous, catalyst-coated
medium comprises a regular or irregular, three-dimensional
latticework of ceramic material forming an open-celled structure
coated with a catalytic material effective to catalyze conversion
of organic particulates or products of incomplete combustion to
water and carbon dioxide.
11. The apparatus of claim 1 wherein the porous, catalyst-coated
medium is coated with a catalytic material that includes one or
more metals or one or more metal oxides.
12. The apparatus of claim 1 wherein the porous, catalyst-coated
medium includes a catalytic material with a light-off temperature
greater than about 350.degree. F.
13. The apparatus of claim 1 wherein the porous, catalyst-coated
medium includes a catalytic material with a light-off temperature
greater than about 500.degree. F.
14. The apparatus of claim 1 wherein: (c) the two or more volumes
of the catalyst-coated medium comprise upper and lower disk-shaped
volumes and a ring-shaped volume; and (d) the specified arrangement
comprises (i) the lower disk-shaped volume being positioned below
and separated by a vertical gap from the ring-shaped volume, (ii)
the upper disk-shaped volume being positioned above and separated
by a vertical gap from the ring-shaped volume; (iii) the upper and
lower disk-shaped volumes being sized so as to form an annular
portion of the tortuous exhaust gas flow path within the exhaust
flue; and (iv) the ring-shaped volume being sized so as to confine
the tortuous exhaust gas flow path to an axial passage through the
ring-shaped volume.
15. The apparatus of claim 1 further comprising an insulator
disposed around a segment of the exhaust flue containing the
volumes of the catalyst-coated material.
16. The apparatus of claim 1 wherein a segment of the exhaust flue
containing the volumes of the catalyst-coated material is
structurally arranged so as to radiate heat into an ambient volume
surrounding the wood heater.
17. A method for reducing emissions from a wood heater, the method
comprising directing exhaust gas from a combustion chamber of the
wood heater through an exhaust flue of the wood heater past two or
more volumes of a porous, catalyst-coated medium, wherein: (a) one
or more holders are structurally arranged to hold the volumes of
the catalyst-coated medium in a specified spatial arrangement
within the exhaust flue; and (b) the volumes of the catalyst-coated
medium are sized and shaped so as to (i) obstruct, when held by the
one or more holders in the specified spatial arrangement,
substantially all straight-line paths from the combustion chamber
through the exhaust flue past the volumes of the catalyst-coated
medium, and (ii) leave unobstructed, when held by the one or more
holders in the specified spatial arrangement, at least one tortuous
exhaust gas flow path from the combustion chamber through the
exhaust flue around and past the volumes of the catalyst-coated
medium.
18. The method of claim 17 wherein: (c) at catalyst temperatures
below a light-off temperature, the porous, catalyst-coated medium
acts as a particle filter to trap and retain organic particulates
and products of incomplete combustion entrained in the exhaust gas,
and the tortuous exhaust gas flow path enables the exhaust gas to
flow through the exhaust flue around and past the volumes of the
catalyst-coated medium even if the catalyst-coated medium is
clogged with the retained organic particulates or products of
incomplete combustion; and (d) at catalyst temperatures above the
light-off temperature, the exhaust gas flows through the volumes of
the catalyst-coated medium.
19. A method for reducing emissions from a wood heater, the method
comprising installing in an exhaust flue of the wood heater two or
more volumes of a porous, catalyst-coated medium and one or more
holders, wherein: (a) the one or more holders are structurally
arranged to hold the volumes of the catalyst-coated medium in a
specified spatial arrangement within the exhaust flue; and (b) the
volumes of the catalyst-coated medium are sized and shaped so as to
(i) obstruct, when held by the one or more holders in the specified
spatial arrangement, substantially all straight-line paths from a
combustion chamber of the wood heater through the exhaust flue past
the volumes of the catalyst-coated medium, and (ii) leave
unobstructed, when held by the one or more holders in the specified
spatial arrangement, at least one tortuous exhaust gas flow path
from the combustion chamber through the exhaust flue around and
past the volumes of the catalyst-coated medium.
20. The method of claim 19 wherein the wood heater is a
pre-existing and previously installed wood heater and the volumes
of the catalyst-coated medium and the holder are retrofitted into
the exhaust flue of the pre-existing and previously installed wood
heater.
Description
BENEFIT CLAIMS TO RELATED APPLICATIONS
[0001] This application claims benefit of U.S. provisional App. No.
61/948,095 filed Mar. 5, 2014 in the names of Lance Carl Grace and
Tyler Mainord Grace entitled "Wood Stove Retrofit Emission Control
Device", said provisional application being hereby incorporated by
reference as if fully set forth herein.
FIELD OF THE INVENTION
[0002] The field of the present invention relates to wood heaters.
In particular, apparatus and methods are described herein for
reducing emissions from a wood heater.
SUMMARY
[0003] An inventive apparatus for reducing emissions from a wood
heater comprises (i) two or more volumes (i.e., pieces) of a
porous, catalyst-coated medium and (ii) one or more holders for the
catalyst-coated medium. The one or more holders are structurally
arranged to hold the volumes of the catalyst-coated medium in a
specified spatial arrangement within an exhaust flue of the wood
heater. The catalytic media are sized and shaped so that, in that
specified spatial arrangement, the volumes obstruct substantially
all straight-line paths from a combustion chamber of the wood
heater through the exhaust flue past the volumes of the
catalyst-coated medium. In the specified spatial arrangement, the
volumes also leave unobstructed at least one tortuous exhaust gas
flow path from the combustion chamber through the exhaust flue
around and past the volumes of the catalyst-coated medium.
[0004] An inventive method for reducing emissions from a wood
heater using the inventive apparatus comprises directing exhaust
gas from the combustion chamber of the wood heater through the
exhaust flue of the wood heater past the two or more volumes of the
porous, catalyst-coated medium.
[0005] An inventive method for reducing emissions from a wood
heater comprises installing in the exhaust flue of the wood heater
the two or more volumes of the porous, catalyst-coated medium and
the one or more holders of the inventive apparatus. The inventive
apparatus can be retrofitted into the exhaust flue of a
pre-existing and previously installed wood heater.
[0006] Objects and advantages pertaining to reducing emissions from
wood heaters may become apparent upon referring to the example
embodiments illustrated in the drawings and disclosed in the
following written description or appended claims.
[0007] This Summary is provided to introduce a selection of
concepts in a simplified form that are further described below in
the Detailed Description. This Summary is not intended to identify
key features or essential features of the claimed subject matter,
nor is it intended to be used as an aid in determining the scope of
the claimed subject matter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIGS. 1A and 1B illustrate schematically a wood heater and
an inventive emission reduction apparatus according to the present
disclosure.
[0009] FIGS. 2 and 3 are schematic cross sectional views of
examples of an inventive emission reduction apparatus on a wood
heater.
[0010] FIGS. 4 and 5 illustrate schematically straight-line and
tortuous flow paths, respectively, through an example of an
inventive emission reduction apparatus.
[0011] FIGS. 6A and 6B illustrate schematically disk- and
ring-shaped volumes, respectively, of a porous, catalyst-coated
medium.
[0012] The embodiments depicted are shown only schematically: all
features may not be shown in full detail or in proper proportion,
certain features or structures may be exaggerated relative to
others for clarity, and the drawings should not be regarded as
being to scale. The embodiments shown are only examples: they
should not be construed as limiting the scope of the present
disclosure or appended claims.
DETAILED DESCRIPTION OF EMBODIMENTS
[0013] For purposes of the present disclosure and appended claims,
the term "wood heater" means, as defined in Title 40 of the Code of
Federal Regulations (CFR) at Chapter I, Subchapter C, Part 60,
Subpart AAA, .sctn.60.531: "an enclosed, wood burning appliance
capable of and intended for space heating or domestic water heating
that meets all of the following criteria: (1) An air-to-fuel ratio
in the combustion chamber averaging less than 35-to-1 as determined
by the test procedure prescribed in .sctn.60.534 performed at an
accredited laboratory; (2) A usable firebox volume of less than
0.57 cubic meters (20 cubic feet); (3) A minimum burn rate of less
than 5 kg/hr (11 lb/hr) as determined by the test procedure
prescribed in .sctn.60.534 performed at an accredited laboratory;
and (4) A maximum weight of 800 kg (1,760 lb). In determining the
weight of an appliance for these purposes, fixtures and devices
that are normally sold separately, such as flue pipe, chimney, and
masonry components that are not an integral part of the appliance
or heat distribution ducting, shall not be included." The term
"wood stove," if appearing anywhere herein, shall be deemed
equivalent to "wood heater."
[0014] An inventive emission reduction device 100 according to the
present disclosure (FIGS. 1A, 1B, and 2-5) can be installed in the
exhaust flue 40 of a pre-existing, previously installed wood heater
10 or of a new wood heater 10. Installation and use with a
previously installed wood heater 10, i.e., via a retrofit, can be
particularly effective for economical reduction of wood heater
emissions, since the entire heater need not be replaced. The cost
reduction of such a retrofit versus a new wood heater makes
adoption of the inventive reduced-emission wood heater technology
more likely. The inventive emission reduction device 100 is
installed in or as part of an exhaust flue of the wood heater 10,
so that exhaust gases from the combustion chamber 20 of the wood
heater are directed through or past a set of two or more pieces of
a porous, catalyst-coated medium 102. Although typically placed
directly on the exhaust outlet 30 from the combustion chamber 20,
the emission reduction device 100 typically is not considered as a
part of the wood heater 10, but rather it should considered as a
portion of the exhaust system 40 of the wood heater 10.
[0015] During periods of operation when exhaust gas passing through
the exhaust flue 40 exceeds a light-off temperature for the given
catalytic material and enough oxygen is available in the exhaust
stream, the catalyst-coated medium 102 converts the organic
particulates and species gas pollution substantially completely
into water vapor and carbon dioxide. At exhaust gas temperatures
below the catalyst light-off temperature, the catalyst-coated
medium 102 acts as a particulate filter to capture and retain
organic particulates (e.g., soot particles) or products of
incomplete combustion. When the exhaust gas temperature later
exceeds the catalyst light-off temperature and enough oxygen is
available in the exhaust stream, the retained organic particulates
or products of incomplete combustion are converted into water vapor
and carbon dioxide. As with any catalytic device that enables
substantially complete combustion, decomposition of organic
particulates and products of incomplete combustion into water and
carbon dioxide is exothermic, so that additional thermal energy is
released by the wood heater, potentially increasing its
efficiency.
[0016] Spatial arrangement of the porous, catalyst-coated medium
102 is such that, even if the medium becomes temporarily totally
blocked or clogged with retained organic particulates or products
of incomplete combustion, exhaust gas from the wood heater can
continue to flow through the exhaust flue 40 past the medium. The
inventive emission reduction device 100, and its constituent
catalyst-coated medium 200, can remain in place throughout all
phases of the fuel burn in the wood heater 10.
[0017] That arrangement is desirable, because, unlike previous
catalytic devices for wood heaters, no action is required on the
part of the user. During an earlier, start-up phase of a fire or a
later, cool-down phase (e.g., just prior to the fire going out),
lower temperatures and lower exhaust flow can lead to clogging of
the catalytic medium. Conventional devices therefore are typically
arranged to be removed from the exhaust flow path during start-up
(by moving or bypassing the catalytic medium), and then replaced in
the exhaust flow path by the user after the wood heater reaches a
sufficiently high operating temperature. There is no suitable
mechanism to ensure that the emission reduction device is used
properly, or even used at all. In contrast, the inventive emission
reduction device 100 is always in place and yet enables the wood
heater to function properly, whether at low or high operating
temperatures. In other words, it is a passive device, and in its
simplest configurations requires neither electrical power nor a
mechanical or electrical control system.
[0018] An inventive apparatus 100 for reducing emissions from a
wood heater 10 comprises (i) two or more volumes (i.e., pieces) of
a porous, catalyst-coated medium (collectively 102; individual
volumes 102a, 102b, etc.), and (ii) one or more holders 104 for the
volumes of the catalyst-coated medium 102. The volumes of the
catalyst-coated medium 102 are also referred to herein as the
catalytic media 102. The one or more holders 104 are structurally
arranged to hold the volumes of the catalyst-coated medium 102 in a
specified spatial arrangement within an exhaust flue 40 of the wood
heater 10. The catalytic media 102 are sized and shaped so that, in
that specified spatial arrangement, the volumes obstruct
substantially all straight-line paths 98 from a combustion chamber
20 of the wood heater through the exhaust flue 40 past the volumes
of the catalyst-coated medium 102. In the specified spatial
arrangement, the catalytic media 102 also leave unobstructed at
least one tortuous exhaust gas flow path 99 from the combustion
chamber 20 through the exhaust flue 40 around and past the volumes
of the catalyst-coated medium 102.
[0019] In some example embodiments, the porous, catalyst-coated
medium 102 comprises a regular or irregular, three-dimensional
latticework of ceramic material forming an open-celled structure
(depicted schematically in FIGS. 6A and 6B; open-celled structure
omitted from the other Figures so as not to clutter the drawings).
The open-cell structure provides a relatively high ratio of surface
area to volume, and that surface area is coated with a catalytic
material effective to catalyze conversion of organic particulates
or products of incomplete combustion to water and carbon dioxide.
The catalytic material in some examples includes one or more metals
(e.g., a transition metal such as nickel, palladium, or platinum)
or one or more metal oxides (e.g., alumina or a zeolite). Specific
examples of suitable catalytic media are disclosed in, inter alia:
[0020] U.S. Pub. No. 2001/0029004 entitled "Apparatus for improving
air quality" published Oct. 11, 2001 in the names of Sparling et
al; [0021] U.S. Pat. No. 6,237,587 entitled "Woodburning fireplace
exhaust catalytic cleaner" issued May 29, 2001 in the names of
Sparling et al; [0022] U.S. Pat. No. 8,622,054 entitled "Methods
and systems for reducing combustion emissions" issued Jan. 7, 2014
in the names of Grace et al; and [0023] PCT Pub. No. WO 2012/027512
entitled "Enhanced emission control for outdoor wood-fired boilers"
published Mar. 1, 2012 in the names of Grace et al. Any suitable
porous, catalyst-coated medium 102 can be employed, including any
of those disclosed in the references listed above, each of which is
hereby incorporated by reference as if fully set forth herein.
Among significant characteristics of such media relevant to the
inventive emission reduction device are: (i) a porous structure
that presents little or no restriction of fluid flow; (ii) a three
dimensional latticework that results in turbulent flow of fluid
through the medium; (iii) large ratio of surface area to volume, on
both microscopic and macroscopic levels; and (iv) resistance to
flame-induced damage. In some examples the catalyst-coated medium
includes a catalytic material with a light-off temperature greater
than about 350.degree. F.; in some of those examples the
catalyst-coated medium includes a catalytic material with a
light-off temperature greater than about 500.degree. F.
[0024] The catalytic media 102 are sized and shaped to fit within
the exhaust flue (or a housing) but do not fill the entire
cross-sectional area of the exhaust flue 40 (or housing 110). The
unfilled portions of the flue cross section allow an unobstructed
exhaust flow path 99 even if the catalytic media 102 are blocked or
clogged. The catalytic media 102 are arranged so that the
respective unfilled portions of the flue cross section do not align
vertically from one volume to the next, so as to obstruct
substantially all straight-line paths 98 from the combustion
chamber 20 through the exhaust flue 40 past the catalytic media
102. The sizes, shapes, and specified arrangement of the catalytic
media 102 achieve a number of goals. By obstructing substantially
all straight-line paths 98 from the combustion chamber 20 through
the exhaust flue 40 past the catalytic media 102, the exhaust gas
will tend to flow through those media under high-temperature
operating conditions, i.e., above the light-off temperature, when
the porous, open-celled structure of the catalytic media 102 is not
clogged by retained particulates or combustion products and
therefore allows nearly free flow of the exhaust gas therethrough
(FIG. 4). Flow of the exhaust gas through the volumes of the
porous, open-celled structure of the catalyst-coated medium 102
enhances the effect of the catalytic material to complete the
combustion of material in the exhaust gas. By providing an
alternative, tortuous flow path 99 around and past the volumes of
the catalytic medium 102 (FIG. 5), exhaust gas can continue to flow
out of the combustion chamber and through the flue even if the
catalytic medium becomes clogged by retained particulates or
combustion products, as may occur under low-temperature conditions
(i.e., below the light-off temperature) that are common during
start-up and cool-down portions of a burn cycle. Those retained
materials can be burned off during a subsequent period of
high-temperature operation (during the same burn cycle or a
subsequent burn cycle). The device is therefore self-cleaning
[0025] The tortuous exhaust flow path 99 can therefore provide
several advantages. First, during low-flow and low-temperature
phases of the fire, when clogging or blockage of the
catalyst-coated medium 102 is possible, such as during the initial
start-up or just before the fire goes out, a sufficient path
remains through which exhaust gas can flow up through the emission
reduction device 100 and the exhaust flue 40 (e.g., a stove pipe or
chimney). Second, during phases of the fire with medium flows and
medium temperature levels, the tortuous path 99 can enable the
catalyst to reach more quickly the light-off temperature or to
remain above the light-off temperature and maintain its catalytic
effect. Third, during high-flow and high-temperature phases of the
fire, the exhaust gas flows directly through all volumes of the
catalyst-coated medium 102 with little pressure restriction to the
flow.
[0026] In one example embodiment, the two or more volumes of the
catalyst-coated medium comprise upper and lower disk-shaped volumes
102a and 102c and a ring-shaped volume 102b (as in FIGS. 2-5, 6A,
and 6B). In this example the specified arrangement of the catalytic
media 102 comprises (i) the lower disk-shaped volume 102c being
positioned below and separated by a vertical gap from the
ring-shaped volume 102b, (ii) the upper disk-shaped volume 102a
being positioned above and separated by a vertical gap from the
ring-shaped volume 102b; (iii) the upper and lower disk-shaped
volumes 102a/102c being sized so as to form an annular portion of
the tortuous exhaust gas flow path 99 within the exhaust flue 40
(or housing 110); and (iv) the ring-shaped volume 102b being sized
so as to confine the tortuous exhaust gas flow path 99 to an axial
passage through the ring-shaped volume 102b. A high-temperature
gasket, comprising any suitable material, can be employed to form
at least a partial seal between the periphery of the ring-shaped
volume 102b and the inner surface of the exhaust flue 40 or housing
110, and can also serve as one of the holders 104. The tortuous
exhaust gas flow path 99 (FIG. 5) includes (i) upward flow through
a lower annular passage around the periphery of the lower
disk-shaped volume 102c, (ii) inward flow between the lower
disk-shaped volume 102c and the ring-shaped volume 102b, (iii)
upward flow through the axial passage of the ring-shaped volume
102b, (iv) outward flow between the ring-shaped volume 102b and the
upper disk-shaped volume 102a, and (v) upward flow through an upper
annular passage around the periphery of the upper disk-shaped
volume 102a. The cross-sectional areas of the annular and axial
passages can be made roughly similar to each other (e.g., within a
factor of two or three). Similarly, the vertical gap between the
ring-shaped volume 102b and the disk-shaped volumes 102a/102c can
be chosen so that inward and outward flow areas at the edges of the
disk-shaped volumes 102a/102c are roughly similar to the areas of
the annular and axial passages (e.g., within a factor of two or
three).
[0027] In one specific example (FIG. 2): the inner diameter of the
(typically cylindrical) exhaust flue 40 or housing 110 is about 6
inches (a standard size for flue pipe); the diameters of the upper
and lower disk-shaped volumes 102a/102c are both about 5 inches;
the outer diameter of the ring-shaped volume 102b is about 6 inches
and its inner diameter is about 3 inches; all three volumes
102a/102b/102c are about 1 inch thick; and the vertical gaps
between the disk-shaped volumes 102a/102c and the ring-shaped
volume 102b between them are both about 0.5 inches. In another
specific example (FIGS. 3-5): the inner diameter of the (typically
cylindrical) housing 110 is about 8 inches (expanded relative to a
standard flue pipe, a standard upper exhaust opening of the wood
heater, or the inner diameter of a secondary air inlet chamber
105a, if present); the diameters of the upper and lower disk-shaped
volumes 102a/102c are both about 53/4 inches; the outer diameter of
the ring-shaped volume 102b is about 8 inches and its inner
diameter is about 5 inches; all three volumes 102a/102b/102c are
about 1 inch thick; and the vertical gaps between the disk-shaped
volumes 102a/102c and the ring-shaped volume 102b between them are
both about 1 inch. If needed or desired, additional disk- and
ring-shaped volumes of the catalyst-coated medium can be employed
in an alternating sequence to provide additional catalytic
capacity.
[0028] Myriad other numbers, sizes, shapes, and spatial arrangement
can be employed for the catalytic media 102. Some examples can
include a set of circular disks with an offset portion removed
(e.g., an angular sector, a circular segment, a smaller offset
circle), with each disk rotated so its missing portion does not
align with the missing portions of adjacent disks. Arranging such a
set of disks in a vertical stack with gaps between them can yield a
spiral or serpentine exhaust gas flow path 99.
[0029] The one or more holders 104 can be formed in any suitable
way and structurally arranged to hold the volumes of the
catalyst-coated medium 102 in the specified arrangement within the
exhaust flue 40 or housing 110. The catalyst coated medium
holder(s) 104 can be fabricated from a variety of substantially
rigid, non-combustible materials including but not limited to: one
or more metal or metal alloys such stainless steel, steel,
titanium, and so on; one or more ceramic materials; or one or more
composite materials such as a continuous fiber ceramic composite
(CFCC). In some examples, two identical or mirror-image members
make up the holder and can be attached to each other either by
screws, nuts and bolts, rivets, welds, or other suitable fasteners.
In other examples, five or more smaller members pieces are used to
hold the catalytic media in the specified arrangement. In the
disks-and-ring example described above, the gasket that can be
employed to seal around the periphery of the ring-shaped volume
102b can also act as a holder 104 by securing the ring-shaped
volume 102b to the inner surface of the housing 110 or exhaust flue
40; additional holders 104 connect the disk-shaped volumes
102a/102c to the ring-shaped volume 102b. In still other examples,
the two or more volumes of the catalyst-coat medium themselves can
also act as the one or more holders. In such as example, the
catalytic media 102 can be fabricated with structural features
(such as posts, tabs, slots, holes, and so forth) that enable them
to be fitted together to form the specified arrangement. In many
examples, the one or more holders 104 typically are attached to or
otherwise engage an inner surface of the exhaust flue 40 or a
dedicated housing 110 to hold the catalytic media in place, and can
in some instances be formed as part of the exhaust flue 40 or
housing 110 (e.g., as an inward-extending flange or rim within the
flue or housing on which the catalytic media might rest).
[0030] In instances when the inventive emission reduction device
100 is installed as part of a new wood heater installation, it can
be desirable to mount the holder(s) 104 and the catalytic media 102
directly within a lower end of the exhaust flue 40, just outside
the combustion chamber 20 of the wood heater. In a retrofit
installation, when the inventive emission reduction device 100 is
installed in the exhaust flue 40 of a pre-existing, previously
installed wood heater 10, it can be advantageous to arrange the
catalytic media 102 and holder(s) 104 in a separate, dedicated
housing 110. Such a housing 110 often would take the form of a
short length of flue pipe similar to that of the exhaust flue 40.
Any suitable materials can be employed to form the housing 110,
including those disclosed above for forming the one or more holders
104. A housing 110 can also be employed in an inventive emission
reduction device that is part of a new wood heater
installation.
[0031] In some examples, the housing 110 can be sized to fit within
the exhaust flue 40; in such an arrangement the housing 110 should
substantially block flow of exhaust gas around the housing 100
within the flue 40, so that substantially all of the exhaust gas
flows through the housing 110 and the emission control device 100.
In other examples, the housing 110 can be arranged to be
incorporated as a segment of the exhaust flue 40; in such an
arrangement the housing 110 is adapted at its lower end to connect
to the exhaust outlet 30 of the combustion chamber 20 and at its
upper end to form a connection with the rest of the exhaust flue
40. In some instance an adapter ring 106 or 107 of some sort might
be needed to mate the upper or lower end of the housing 110 to the
exhaust outlet 30 of the combustion chamber 20 or to the exhaust
flue 40, respectively.
[0032] In many use environments, heat generated by the catalyzed
combustion reactions occurring within the volumes of the
catalyst-coated medium 102 is more than sufficient to maintain the
catalytic material above the light-off temperature. In that
instance, excess heat thus produced can be advantageously radiated
into the ambient surroundings of the wood heater 10 and exhaust
flue 40 as additional heat output of the wood heater 10, thereby
increasing the overall heating efficiency of the wood heater. In
other use environments, an insulated housing 110 (e.g., a segment
of insulated, double-walled flue pipe) can be employed to retain
heat within the housing 110 to maintain the catalytic media 102
above the light-off temperature longer than might otherwise occur
without such insulation. In still other use environments, one or
more heating elements can be employed to heat the catalytic media
102 to remain above the light-off temperature, e.g., using a
suitable temperature sensor and control mechanism.
[0033] In a wood heater, once the fuel is loaded and lit and the
fuel door 12 is closed, combustion air enters through a set of
combustion air inlets 14 suitably arranged about the combustion
chamber 20 to allow ambient air to enter. Those combustion air
inlets 14 are often arranged so as to enable adjustment of the
amount of air that reaches the fire, to control the fire's
intensity. One source of pollution from wood heaters is that, upon
leaving the combustion chamber 20 and entering the exhaust flue 40,
sufficient oxygen may not remain to allow complete combustion in
the exhaust flue of those organic particulates or products of
incomplete combustion that remain entrained in the exhaust gas.
Without sufficient oxygen, even the presence of a catalytic medium
will not allow complete combustion of combustible material in the
exhaust gas. In the inventive emission reduction device 100, a
secondary air inlet tube 105 can be provided to enable additional
ambient air (including oxygen) to be drawn into the exhaust gas and
pass with the exhaust gas past the volumes of the catalyst-coated
medium 102. Such an air inlet tube 105 has an open inner end
arranged to be held within the exhaust flue 40 below the volumes of
the catalyst-coated medium 102, i.e., between the combustion
chamber 20 and the catalytic media 102. In FIG. 2 the open, inner
end is shown as a simple tube ending within the emission reduction
device 100 (e.g., in the lower end of the housing 110, if present).
In FIGS. 3-5 the open inner end of the air inlet tube 105
terminates in an annular chamber or manifold 105a arranged around
the lower end of the emission reduction device 100 (or housing 110,
if present), which has secondary air inlet orifices 105b connecting
the chamber 105a to the interior of the emission reduction device
100.
[0034] An open outer end of the air inlet tube 105 is positioned
outside the combustion chamber 20, at a level below a level of the
combustion air inlets 14 into the combustion chamber 20, so as to
draw ambient air (from around the wood heater 10 or from a
different indoor or outdoor space) through the air inlet tube 105
into the exhaust flue 40 during operation of the wood heater 10. In
some examples, the air inlet tube 105 can be routed along an inside
or outside surface of the combustion chamber 20 so as to heat
ambient air drawn into the air inlet tube 105 during operation. In
some examples, a fan or blower can be employed to increase the flow
of ambient air through the tube 105 into the exhaust flue 40; such
a fan or blower can be coupled to a controller and one or more
sensors in or on the wood heater 10, the exhaust flue 40, or the
inlet tube 105 (e.g., temperature sensor, carbon monoxide sensor,
airflow sensor, or other sensor). In some examples, the air inlet
tube 105 can be shaped and arranged at its open inner end so as to
employ the Venturi effect or other aerodynamic effect to facilitate
air flow through the inlet tube. The open inner end of the air
inlet tube 105 (and any manifold 105a that might be present) can be
held in place by one of the one or more holders 104, by mounting in
or on the housing 110 (if present), by mounting in or on the
exhaust flue 40, or by mounting in the combustion chamber 20 at the
lower end of the exhaust flue 40 (i.e., at the exhaust opening
30).
[0035] An inventive method for reducing emissions from a wood
heater comprises directing exhaust gas from the combustion chamber
20 of the wood heater 10 through the inventive emission reduction
device 100 disclosed above, i.e., through the exhaust flue 40 of
the wood heater past the two or more volumes of the porous,
catalyst-coated medium 102 that are arranged as disclosed above. As
noted above, at catalyst temperatures below a light-off
temperature, the porous, catalyst-coated medium 102 can act as a
particle filter to trap and retain organic particulates and
products of incomplete combustion entrained in the exhaust gas.
Even if the catalytic media 102 are completely clogged under those
conditions, the tortuous exhaust gas flow path 99 enables the
exhaust gas to flow through the exhaust flue 40 around and past the
volumes of the catalyst-coated medium 102. At catalyst temperatures
above the light-off temperature, the exhaust gas flows through the
volumes of the catalyst-coated medium 102 with only negligible
resistance to flow. Particulates or combustion products retained by
the catalytic media during a cooler phase of a fire (e.g., at
start-up, or shortly before going out) can be removed by combustion
during another, hotter phase of that fire or of a subsequent
fire.
[0036] Another inventive method for reducing emissions from a wood
heater 10 comprises installing in the exhaust flue 40 of the wood
heater 10 the inventive emission reduction device 100 disclosed
above, i.e., the two or more volumes of the porous, catalyst-coated
medium 102 and the one or more holders 104, arranged as disclosed
above. The inventive emission reduction device 100 can be installed
as part of a new wood heater 10. Perhaps even more advantageously,
the inventive emission reduction device 100 can be retrofitted into
the exhaust flue 40 of a pre-existing and previously installed wood
heater 10.
[0037] In addition to the preceding, the following examples fall
within the scope of the present disclosure or appended claims:
EXAMPLE 1
[0038] An apparatus for reducing emissions from a wood heater, the
apparatus comprising two or more volumes of a porous,
catalyst-coated medium and one or more holders, wherein: (a) the
one or more holders are structurally arranged to hold the volumes
of the catalyst-coated medium in a specified spatial arrangement
within an exhaust flue of the wood heater; and (b) the volumes of
the catalyst-coated medium are sized and shaped so as to (i)
obstruct, when held by the one or more holders in the specified
spatial arrangement, substantially all straight-line paths from a
combustion chamber of the wood heater through the exhaust flue past
the volumes of the catalyst-coated medium, and (ii) leave
unobstructed, when held by the one or more holders in the specified
spatial arrangement, at least one tortuous exhaust gas flow path
from the combustion chamber through the exhaust flue around and
past the volumes of the catalyst-coated medium.
EXAMPLE 2
[0039] The apparatus of Example 1 further comprising an air inlet
tube with an open inner end arranged to be held by one or more of
the one or more holders in communication with the exhaust flue
between the combustion chamber and the volumes of the
catalyst-coated medium, wherein an open outer end of the air inlet
tube is positioned outside the combustion chamber, at a level below
a level of one or more combustion air inlets into the combustion
chamber, so as to draw ambient air through the air inlet tube into
the exhaust flue during operation of the wood heater.
EXAMPLE 3
[0040] The apparatus of Example 2 wherein the air inlet tube is
routed along an inside or outside surface of the combustion chamber
so as to heat the ambient air drawn into the air inlet tube during
operation of the wood heater.
EXAMPLE 4
[0041] The apparatus of any one of Examples 1 through 3 further
comprising a housing containing the one or more holders and the
volumes of the catalyst-coated medium, wherein the housing is sized
and shaped so as to fit within the exhaust flue.
EXAMPLE 5
[0042] The apparatus of any one of Examples 1 through 3 further
comprising a housing containing the one or more holders and the
volumes of the catalyst-coated medium, wherein the housing is
structurally arranged so as to be incorporated as a segment of the
exhaust flue.
EXAMPLE 6
[0043] The apparatus of Example 5 further comprising an adapter
member structurally arranged so as to mate a lower end of the
housing to an upper exhaust opening of the wood heater or to mate
an upper end of the housing to the exhaust flue.
EXAMPLE 7
[0044] The apparatus of any one of Examples 4 through 6 further
comprising an air inlet tube held by the housing so that an open
inner end of the air inlet tube is in communication with the
exhaust flue between the combustion chamber and the volumes of the
catalyst-coated medium, wherein an open outer end of the air inlet
tube is positioned outside the combustion chamber, at a level below
a level of one or more combustion air inlets into the combustion
chamber, so as to draw ambient air through the air inlet tube into
the exhaust flue during operation of the wood heater.
EXAMPLE 8
[0045] The apparatus of any one of Examples 1 through 3 further
comprising a segment of the exhaust flue, wherein the one or more
holders and the volumes of the catalyst-coated material are mounted
within the segment of the exhaust flue.
EXAMPLE 9
[0046] The apparatus of any one of Examples 1 through 8 wherein the
one or more holders are formed of the porous, catalyst-coated
medium.
EXAMPLE 10
[0047] The apparatus of any one of Examples 1 through 9 wherein the
porous, catalyst-coated medium comprises a regular or irregular,
three-dimensional latticework of ceramic material forming an
open-celled structure coated with a catalytic material effective to
catalyze conversion of organic particulates or products of
incomplete combustion to water and carbon dioxide.
EXAMPLE 11
[0048] The apparatus of any one of Examples 1 through 10 wherein
the porous, catalyst-coated medium is coated with a catalytic
material that includes one or more metals or one or more metal
oxides.
EXAMPLE 12
[0049] The apparatus of any one of Examples 1 through 11 wherein
the porous, catalyst-coated medium includes a catalytic material
with a light-off temperature greater than about 350.degree. F.
EXAMPLE 13
[0050] The apparatus of any one of Examples 1 through 12 wherein
the porous, catalyst-coated medium includes a catalytic material
with a light-off temperature greater than about 500.degree. F.
EXAMPLE 14
[0051] The apparatus of any one of Examples 1 through 13 wherein
the two or more volumes of the catalyst-coated medium comprise
upper and lower disk-shaped volumes and a ring-shaped volume, and
the specified arrangement comprises (i) the lower disk-shaped
volume being positioned below and separated by a vertical gap from
the ring-shaped volume, (ii) the upper disk-shaped volume being
positioned above and separated by a vertical gap from the
ring-shaped volume; (iii) the upper and lower disk-shaped volumes
being sized so as to form an annular portion of the tortuous
exhaust gas flow path within the exhaust flue; and (iv) the
ring-shaped volume being sized so as to confine the tortuous
exhaust gas flow path to an axial passage through the ring-shaped
volume.
EXAMPLE 15
[0052] The apparatus of any one of Examples 1 through 14 further
comprising an insulator disposed around a segment of the exhaust
flue containing the volumes of the catalyst-coated material.
EXAMPLE 16
[0053] The apparatus of any one of Examples 1 through 14 wherein a
segment of the exhaust flue containing the volumes of the
catalyst-coated material is structurally arranged so as to radiate
heat into an ambient volume surrounding the wood heater.
EXAMPLE 17
[0054] A method for reducing emissions from a wood heater using the
apparatus of any one of Examples 1 through 16, the method
comprising directing exhaust gas from the combustion chamber of the
wood heater through the exhaust flue of the wood heater past the
two or more volumes of the porous, catalyst-coated medium.
EXAMPLE 18
[0055] The method of Example 17 wherein: (i) at catalyst
temperatures below a light-off temperature, the porous,
catalyst-coated medium acts as a particle filter to trap and retain
organic particulates and products of incomplete combustion
entrained in the exhaust gas, and the tortuous exhaust gas flow
path enables the exhaust gas to flow through the exhaust flue
around and past the volumes of the catalyst-coated medium even if
the catalyst-coated medium is clogged with the retained organic
particulates or products of incomplete combustion; and (ii) at
catalyst temperatures above the light-off temperature, the exhaust
gas flows through the volumes of the catalyst-coated medium.
EXAMPLE 19
[0056] A method for reducing emissions from a wood heater, the
method comprising installing in the exhaust flue of the wood heater
the two or more volumes of the porous, catalyst-coated medium and
the one or more holders of the apparatus of any one of Examples 1
through 16.
EXAMPLE 20
[0057] The method of Example 19 wherein the wood heater is a
pre-existing and previously installed wood heater and the volumes
of the catalyst-coated medium and the holder are retrofitted into
the exhaust flue of the pre-existing and previously installed wood
heater.
[0058] It is intended that equivalents of the disclosed example
embodiments and methods shall fall within the scope of the present
disclosure or appended claims. It is intended that the disclosed
example embodiments and methods, and equivalents thereof, may be
modified while remaining within the scope of the present disclosure
or appended claims.
[0059] In the foregoing Detailed Description, various features may
be grouped together in several example embodiments for the purpose
of streamlining the disclosure. This method of disclosure is not to
be interpreted as reflecting an intention that any claimed
embodiment requires more features than are expressly recited in the
corresponding claim. Rather, as the appended claims reflect,
inventive subject matter may lie in less than all features of a
single disclosed example embodiment. Thus, the appended claims are
hereby incorporated into the Detailed Description, with each claim
standing on its own as a separate disclosed embodiment. However,
the present disclosure shall also be construed as implicitly
disclosing any embodiment having any suitable set of one or more
disclosed or claimed features (i.e., a set of features that are
neither incompatible nor mutually exclusive) that appear in the
present disclosure or the appended claims, including those sets
that may not be explicitly disclosed herein. In addition, for
purposes of disclosure, each of the appended dependent claims shall
be construed as if written in multiple dependent form and dependent
upon all preceding claims with which it is not inconsistent. It
should be further noted that the scope of the appended claims does
not necessarily encompass the whole of the subject matter disclosed
herein.
[0060] For purposes of the present disclosure and appended claims,
the conjunction "or" is to be construed inclusively (e.g., "a dog
or a cat" would be interpreted as "a dog, or a cat, or both"; e.g.,
"a dog, a cat, or a mouse" would be interpreted as "a dog, or a
cat, or a mouse, or any two, or all three"), unless: (i) it is
explicitly stated otherwise, e.g., by use of "either . . . or,"
"only one of," or similar language; or (ii) two or more of the
listed alternatives are mutually exclusive within the particular
context, in which case "or" would encompass only those combinations
involving non-mutually-exclusive alternatives. For purposes of the
present disclosure and appended claims, the words "comprising,"
"including," "having," and variants thereof, wherever they appear,
shall be construed as open ended terminology, with the same meaning
as if the phrase "at least" were appended after each instance
thereof, unless explicitly stated otherwise.
[0061] In the appended claims, if the provisions of 35 USC
.sctn.112(f) are desired to be invoked in an apparatus claim, then
the word "means" will appear in that apparatus claim. If those
provisions are desired to be invoked in a method claim, the words
"a step for" will appear in that method claim. Conversely, if the
words "means" or "a step for" do not appear in a claim, then the
provisions of 35 USC .sctn.112(f) are not intended to be invoked
for that claim.
[0062] If any one or more disclosures are incorporated herein by
reference and such incorporated disclosures conflict in part or
whole with, or differ in scope from, the present disclosure, then
to the extent of conflict, broader disclosure, or broader
definition of terms, the present disclosure controls. If such
incorporated disclosures conflict in part or whole with one
another, then to the extent of conflict, the later-dated disclosure
controls.
[0063] The Abstract is provided as required as an aid to those
searching for specific subject matter within the patent literature.
However, the Abstract is not intended to imply that any elements,
features, or limitations recited therein are necessarily
encompassed by any particular claim. The scope of subject matter
encompassed by each claim shall be determined by the recitation of
only that claim.
* * * * *